No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Experimental Study on the Piping Erosion Process in Earthen Embankments
Abstract
Experimental results on the piping erosion process in an earthen embankment emplaced in a laboratory flume are reported in this paper along with the details of the experimental set-up and procedures. A mixture of sand, silt, and clay with different compaction rates is used for constructing the embankment. An image processing technique is successfully applied to track the erosion process from both side-looking and bottom-up views. The paper discusses changes in the depth, area, and volume of erosion during the piping phenomenon in a model embankment using a visual technique. The results show that increasing compaction of the construction layers significantly increases the time required for erosion but has little effect on the final-average depth of erosion. The ratio of the average depth of erosion to the average bottom width of piping is close to one at different time intervals. Exponential equations to estimate the depth of erosion, side area of the piping zone, and volume of eroded material are presented. Two approaches are investigated to estimate the volume: the approach based on the processing of images from both the side-view and bottom-view gives more accurate results than that based on processing the side-view.
... They came up with an exponential equation to predict the erosion depth as a function of time and the coefficient of soil erodibility. Sharif et al. (2015) prepared their earthen embankment by using the same procedure and monitored the erosion process by using the same method which was the image processing technique with Elkholy et al. (2015), however, the difference was this time, they had only one soil composition but they applied different numbers of blows during compaction to soil with determined normalized dry densities. The soil composition was the same for all the experiments consisting of 64% sand, 29% silt, and 7% clay, and can be taken into account as a sandy loam soil. ...
... The soil composition was the same for all the experiments consisting of 64% sand, 29% silt, and 7% clay, and can be taken into account as a sandy loam soil. Sharif et al. (2015) developed exponential equations to represent average erosion depth, area of vertical erosion, and volume of erosion with time. Also, they concluded that when the dry density of the soil mixture increases with an increase in the number of compaction blows, the run time is affected considerably which indicates the erosion rate, whereas it has not too much impact on the final average erosion depth. ...
... There are some factors affecting the initiation of piping and breach evolution stated in the literature. The soil erodibility is a basic parameter indicating the time for the embankment failure , and play an important role while estimating the performance of embankment in terms of internal erosion and breach failure (Temple et al. 2005;Elkholy et al. 2015;Sharif et al. 2015). According to Sharif et al. (2015), the hydraulic and mechanical properties of the soil change with internal erosion. ...
From the past to nowadays, earth-fill dams have been built thanks to their
advantages, however, piping is a problem that earth-fill dams can experience and then fail. While there are many studies about the overtopping failures of the dams, there are not too many surveys about dam failures due to piping.
Dams having a height of 0.6 m, a bottom width of 2 m, and a crest width of 0.20
m were built in a channel of 1 m wide, 0.81 m high and 6.14 m long. 3 different
scenarios have been created and the evolution of dam failure resulting from seepage at the dam was recorded by six cameras located at different locations. In the closed system, water was pumped from the lower reservoir to the upper channel. The dam was constructed by using a mixture consisting of 85 % sand and 15 % clay. A circular tunnel with a diameter of 2 cm was created at the middle or corner of the dam according to the scenario and at 6 cm below the dam crest. The breach areas at different time instants at upstream and downstream sides are determined by using the Gauss Area calculation method and by image processing, and then it has been found that methods give close values to each other. Breach discharge and time-varied velocity values were determined by using the continuity equation.
Empirical relations were intended to be derived for the breach flow rate and
empirical relations represented in the literature were trialed by using experimental
findings.
... When investigating the failure of an embankment dam experimentally and numerically, the evolution of the breach caused by the piping is a crucial factor. In the literature, there have been many researches on dam failures, particularly those caused by overtopping, but there have not been as many studies on dam failures caused by piping because it is difficult to investigate erosion and conduct controlled experiments (Chen et al. 2019;Sharif et al. 2015). According to Chen et al. (2019), 3541 dam breach accidents occurred between 1954 and 2018, and more than 30% of them resulted from piping. ...
... According to Chen et al. (2019), 3541 dam breach accidents occurred between 1954 and 2018, and more than 30% of them resulted from piping. Sharif et al. (2015) built dams with varied compaction rates in a laboratory flume and then used image processing techniques to assess depth, area, and volume change due to erosion during the piping progress. Numerous researchers who do numerical studies make simple assumptions about the geometry of the breach and water flow through it. ...
One of the most prominent failure reasons for earth-fill dams is internal erosion resulting from piping. This failure mode may cause irreversible weakened structural integrity, loss of properties, and even loss of lives. Therefore, it is important to understand the breaching process due to piping by providing reliable data for the decision-makers in case of emergency. This study was supported by the Scientific and Technological Research Council of Turkey with project number 119M609 and involves experimental investigation on piping under three different weak zone scenarios to examine the breach process and provide the data for more realistic numerical evaluations. The experiments were conducted in the hydraulic laboratory of Izmir University of Economics and Dokuz Eylul University. The initiation of piping was triggered from seepage in weak layers at the bottom, middle, and upper parts, along the centerline of homogenous earth-fill dams in a rectangular flume. As a result of the experiments, the magnitude of the peak discharges and their durations as well as the eroded breach areas were found to be affected by the locations of the seepage and initial water heads acting on the weak zones. Also, in the experiments, at the beginning of the breaching, initial cascading surface flow resulted in sheet and rill erosion.
... When investigating the failure of an embankment dam experimentally and numerically, the evolution of the breach caused by the piping is a crucial factor. In the literature, there have been many researches on dam failures, particularly those caused by overtopping, but there have not been as many studies on dam failures caused by piping because it is difficult to investigate erosion and conduct controlled experiments (Chen et al., 2019;Greco et al., 2008;Sharif et al., 2015). A two-dimensional depth-averaged (2DH) numerical model was used by Greco et al. (2008) to simulate the development of a breach in an earth-fill dam. ...
... According to Chen et al. (2019), 3541 dam breach accidents occurred between 1954 and 2018, and more than 30% of them resulted from piping. Sharif et al. (2015) built dams with varied compaction rates in a laboratory flume, and then used image processing technique to assess depth, area, and volume change due to erosion during the piping progress. Numerous researchers who do numerical studies make simple assumptions about properties of breach and water flow through it. ...
One of the most significant reasons for earth-fill dam failures is internal erosion resulting from piping. This research was carried out as a part of a project supported financially by the Scientific and Technological Research Council of Turkey (TÜBİTAK). This paper involves the comparison of the experimental findings related to two different scenarios to look into the breach process and to provide the data allowing the realization of more realistic numerical analyses. A circular tunnel of 2 cm diameter located 6 cm below the dam crest was created to induce the seepage. The experiments were conducted at Hydraulics Laboratory of Civil Engineering Department within İzmir University of Economics. The homogeneous earth-fill dams having a height of 0.60 m and a bottom width of 2 m were built in a flume 1.00 m wide, 0.81 m high and 5.44 m long. Some common soil mechanics tests were carried out before the dam was built. The dam bodies were constructed by using a mixture of 15 % clay and 85 % medium sand. High-precision cameras were used to record the temporal development of the breach resulting from the piping. The pump flow rate was measured by a magnetic flowmeter and the flow rate values outgoing from the breach were determined from the continuity equation. Gauss area formula was used to obtain the time-varied values of the breach areas. The temporal changes of water depth in the channel were also recorded. The so obtained experimental findings are presented and commented.
... Research had been undertaken through a combination of laboratory physical modelling, field data collection, field testing, theoretical studies, and numerical simulations. There exist many studies about dam failures especially because of overtopping in the literature, however since it is relatively difficult to observe erosion process and conduct controlled experiments, there are not too much survey about dam failure due to piping [3]- [5]. Chen, Zhong and Shen [4] indicated that between 1954 and 2018, 3541 dam breach accidents occurred and more than 30% of them was due to piping. ...
... Greco, Pontillo, Iervolino and Leopardi [6] simulated the evolution of a breach in an earth-fill dam by means of a two-dimensional depthaveraged (2DH) numerical model, from both the conceptual and the numerical point of view. Sharif, Elkholy, Hanif Chaudhry and Imran [3] constructed a dam 15 cm high in a laboratory flume by using a mixture of sand, silt, and clay with different compaction rates and examined the changes in the depth, area, and volume of erosion during the piping evolution by utilizing an image processing technique. Most of the researchers realizing numerical analyses make some simplified assumptions concerning shape of a breach and discharge of water flowing through the breach. ...
One of the main factors that leads to earth-fill
dam failures is the internal erosion, commonly referred to as
piping. Regarding the geometry of the breach and the
discharge of water flowing through the breach, many
researchers working with numerical analyses in this field
make some simplified assumptions. This study was carried
out as a part of the project supported by the Turkish
Council for Scientific and Technological Research
(TUBITAK) and it includes experimental research with the
goal of supplying the data required to carry out numerical
analysis using more realistic approaches. A dam with a
height of 65 cm, a bottom width of 200 cm and a crest width
of 5 cm was built in a flume 1 m wide, 0.81 m high and 6.14
m long. Before the construction of the dam, some common
soil mechanics tests were carried out. The dam was
constructed by using a mixture consisting of 85 % fine sand
and 15% clay. In order to generate the formation of the
breach, a square shaped rock salt layer of 2 cm side lying
from upstream to downstream was placed at 28 cm from the
bottom of the dam body. The progression of the dam failure
was captured by six cameras located at different locations.
Gauss Area formula was applied to determine the time-varied breach areas at upstream and downstream sides. The
discharge of water through the breach and average flow
velocity were determined by using the continuity equation.
The changes in water depth in the channel were also
recorded. The experimental findings continue to be
compared with numerical results obtained from the
software PLAXIS 3D.
... Such studies have made use of a variety of methods, including physical modeling in the lab, field data collection, field testing, theoretical study, and computer simulations. In the literature, there have been many researches on dam failures, particularly those caused by overtopping, but there have not been as many studies on dam failures caused by piping because it is difficult to investigate erosion and conduct controlled experiments (Chen, Zhong, & Shen, 2019;Greco, Pontillo, Iervolino, & Leopardi, 2008;Sharif, Elkholy, Hanif Chaudhry, & Imran, 2015). A two-dimensional depthaveraged (2DH) numerical model was used by Greco et al. (2008) to simulate the development of a breach in an earth-fill dam. ...
... According to Chen et al. (2019), 3541 dam breach accidents occurred between 1954 and 2018, and more than 30% of them resulted from piping. Sharif et al. (2015) built dams with varied compaction rates in a laboratory flume, and then used image processing technique to assess depth, area, and volume change due to erosion during the piping progress. Numerous researchers who do numerical studies make simple assumptions about properties of breach and water flow through it. ...
One of the most significant reasons for earth-fill dam failures is internal erosion, often known as piping. This research was carried out as part of a project funded by the Scientific and Technological Research Council of Turkey (TÜBİTAK) and it involves an experimental investigation to look into the breach process and provide the data for more realistic numerical evaluations. The experiments were conducted at Hydraulics Laboratory of Civil Engineering Department within İzmir University of Economics. The earthen dam with clay core 0.65 m high, a bottom width of 2 m and a crest width of 0.05 m was built in a flume 1.00 m wide, 0.81 m high and 5.44 m long. Some common soil mechanics tests were also carried out before the dam was built. The dam body was constructed by using a mixture of 15 % clay and 85 % sand. The clay core width was 15 cm at bottom and 1 cm at crest. The weak layer of a cross section of 5x5 cm2 was created by no-compacted soil mixture, and it was placed at 60 cm level from the bottom, along the centerline of the dam. High-precision cameras were used to record the temporal development of the breach resulting from the piping. The pump flow rate was measured by magnetic flowmeter and the flow rate values through the breach were determined from the continuity equation. Gauss Area formula was used to obtain the time-varied values of the total and wetted breach areas. The velocity values were calculated by dividing the flow rates through the breach to the corresponding wetted areas. The temporal changes of water depth in the channel were also recorded. The so obtained experimental findings are presented and commented.
... There has been a lot of research about dam failures, particularly because of overtopping, in the literature, but there have not been many studies about dam failure due to piping because it's so challenging to observe erosion and perform controlled tests. (Greco et al. 2008;Chen et al. 2019;Sharif et al. 2015). Greco et al. (2008) simulated the evolution of a breach in an earth-fill dam by using a twodimensional depth-averaged (2DH) numerical model. ...
... Chen et al. (2019) indicated that between 1954 and 2018, 3541 dam breach accidents occurred and more than 30% of them were due to piping. Sharif et al. (2015) constructed a dam in a laboratory flume by using a mixture of sand, silt, and clay with different compaction rates and examined the changes in the depth, area, and volume of erosion during the piping evaluation by utilizing an image processing technique. The majority of researchers that perform numerical studies make some simplistic assumptions regarding the characteristics of a breach and the flow of water through it. ...
Internal erosion, also known as piping, is one of the most important causes of earth-fill dam failures. Many researchers dealing with numerical analyses in this area make some simplified assumptions about the shape of the breach and the discharge of water flowing through the breach. This study was conducted in the scope of the project supported financially by the Scientific and Technological Research Council of Turkey and it consists of an experimental study that aims to provide data needed to perform numerical analyses with more realistic approaches. A dam with a height of 0.65 m, a bottom width of 2 m, and a crest width of 0.05 m was built in a flume 0.80 m wide, 0.75 m high, and 18.60 m long. Before the construction of the dam, some common soil mechanics tests were carried out. The dam body was constructed of clay and sand mixture with a clay core 15 cm wide at the bottom and 1 cm wide at the crest. The weak layer with a cross-section of 5x5 cm 2 along the centerline consisted of rock salt. The temporal evolution of the breach resulting from the piping was recorded by means of the high-precision cameras. The flow rate through the breach was measured by a triangular weir located at the channel downstream. Gauss' area formula was applied to determine the time-varied total and wetted areas of the breach at downstream side. The changes in water depth in the channel were also recorded. The so-obtained experimental findings are presented. The experimental findings continue to be compared with the numerical results obtained from the software PLAXIS 3D.
... There has been a lot of research about dam failures, particularly because of overtopping, in the literature, but there have not been many studies about dam failure due to piping because it's so challenging to observe erosion and perform controlled tests. (Greco et al. 2008;Chen et al. 2019;Sharif et al. 2015). Greco et al. (2008) simulated the evolution of a breach in an earth-fill dam by using a twodimensional depth-averaged (2DH) numerical model. ...
... Chen et al. (2019) indicated that between 1954 and 2018, International Conference on Engineering Sciences / November [11][12]2022 299 3541 dam breach accidents occurred and more than 30% of them were due to piping. Sharif et al. (2015) constructed a dam in a laboratory flume by using a mixture of sand, silt, and clay with different compaction rates and examined the changes in the depth, area, and volume of erosion during the piping evaluation by utilizing an image processing technique. The majority of researchers that perform numerical studies make some simplistic assumptions regarding the characteristics of a breach and the flow of water through it. ...
Çirkab suların təmizlənməsində nanotexnologiyanın tətbiqi imkanları
... There has been a lot of research about dam failures, particularly because of overtopping, in the literature, but there have not been many studies about dam failure due to piping because it's so challenging to observe erosion and perform controlled tests. (Greco et al. 2008;Chen et al. 2019;Sharif et al. 2015). Greco et al. (2008) simulated the evolution of a breach in an earth-fill dam by using a twodimensional depth-averaged (2DH) numerical model. ...
... Chen et al. (2019) indicated that between 1954 and 2018, International Conference on Engineering Sciences / November [11][12]2022 299 3541 dam breach accidents occurred and more than 30% of them were due to piping. Sharif et al. (2015) constructed a dam in a laboratory flume by using a mixture of sand, silt, and clay with different compaction rates and examined the changes in the depth, area, and volume of erosion during the piping evaluation by utilizing an image processing technique. The majority of researchers that perform numerical studies make some simplistic assumptions regarding the characteristics of a breach and the flow of water through it. ...
Quantum dots (QDs), which have wide and diverse potential applications, are frequently encountered in
scientific research today. Quantum physics is a fascinating subject for physics undergraduates and many
interdisciplinary students. Combining the theoretical lessons of quantum physics with experimental studies
can make the subject more understandable and interesting for students. The aim of this study is to design an
experiment for undergraduate students. The experiment covers the synthesis and optical characterization of
semiconductor CdTe QDs in aqueous medium. The study consists of two parts, the first part is the synthesis
and growth of CdTe QDs using an analytical technique and the second part is the optical characterization of
these nanoparticles of different sizes. The main scientific and educational aims of this experiment are to
facilitate the understanding of the subject with a less dangerous and practical method compared to others and
to encourage students to research nanoscience and nanotechnology.
... Contact erosion refers to the phenomenon that the fine soil is eroded by seepage flow through the interface between the coarse soil and the fine soil [13,14]. Despite the various types of seepage failure, research has identified that seepage failure stems from soil particle migration along the seepage flow path [15]. As seepage erosion develops progressively in granular soils, hydromechanical characteristics are altered, resulting in an increase in permeability and instability of structures [16]. ...
... Further research with a wider variety of soil types and more advanced visualization technology is encouraged to provide more insights into the mechanisms of the seepage failure process. 15 Geofluids ...
Seepage-induced failure may disable the bearing capacity of foundations in dams and embankments. However, the evolution mechanism of the seepage failure process in granular soils is not well understood. In this paper, a series of laboratory hydraulic tests were performed to investigate the seepage failure process in sandy gravels and fine-grained sands. Seepage behaviors of the hydraulic gradient, seepage flow velocity, and permeability coefficient were observed, and then, the Reynolds number was obtained to describe the seepage regime. By linking the hydraulic gradients with the Reynolds number, the seepage failure process was quantitatively divided into four phases: (i) incubation ( Re < 0.85 ), (ii) formation ( 0.85 ≤ Re ≤ 5 ), (iii) evolution ( 5 < Re ≤ 50 ), and (iv) destruction ( 50 < Re ). The findings of the study identified an approximately linear relationship between the hydraulic gradient and the seepage velocity in the phases of incubation and formation in which the viscous drag effects are not negligible, corroborating Darcy’s view. However, in the phases of evolution and destruction, the hydraulic gradient and the seepage velocity are nonlinearly related, indicating that the inertial force plays a leading role, and the quadratic equation is relevant for the regime transition from laminar flow to turbulent flow. Finally, the mechanism of each phase in the seepage failure process was clarified. Fine content and uniformity coefficient are internal factors that affect the potential of seepage failure, while the seepage force that drives the transport of fine particles is an underlying cause that promotes the development of seepage failure. This study will be quite useful in identifying the limits of applicability of the well-known “Darcy’s law,” in further improving the physical modelling associated with fluid flow through granular soils.
... Research had been undertaken through a combination of laboratory physical modelling, field data collection, field testing, theoretical studies and numerical simulations. There have been many studies about dam failures especially because of overtopping in the literature, however since it is really difficult to observe erosion process and conduct controlled experiments, there are not too much survey about dam failure due to piping [3]- [5]. Chen et al. [4] indicated that between 1954 and 2018, 3541 dam breach accidents occurred and more than 30% of them was due to piping. ...
... They also claimed that the strong unsteadiness of the evolution for a dynamical description of the between flow and sediment, since they may be conveyed under non-equilibrium conditions. Sharif et al. [3] constructed a dam 15 cm high in a laboratory flume by using a mixture of sand, silt, and clay with different compaction rates and examined the changes in the depth, area, and volume of erosion during the piping evaluation by utilizing an image processing technique. Most of the researchers realizing numerical analyses make some simplified assumptions concerning shape of a breach and discharge of water flowing through the breach. ...
Piping is one of the main causes of the earth-fill dam failures. Most of the researchers realizing numerical analyses make some simplified assumptions concerning the shape of the breach and the discharge of water flowing through the breach. The aim of this study is to realize experiments to provide data needed to perform numerical analyses by making more realistic assumptions. The dam having a height of 0.6 m, a bottom width of 2 m and a crest width of 0.20 m is built in a channel 1 m wide, 0.81 m high and 6.14 m long. The evolution of the breach and the discharge through the breach resulting from piping due to seepage at the earth-fill dam bottom was investigated experimentally. The evolution of the dam failure is recorded by six cameras located at different locations. The time-varied of the breach areas at upstream and downstream sides are determined by applying the Gauss Area functions. The discharge of water through the breach and average outflow velocity are determined by using the continuity equation.
... The pick-up, migration, deposition, and clogging of fine particles in porous media are frequently encountered phenomena in different engineering fields [1]. These applications include the injection of zero valence iron (ZVI) particles for environmental remediation [1][2][3][4], grouting [5], the piping failure of earthen dams [6], clogging and particle loss at the interface of the capillary break layer (coarse-grained layer) and moistureretaining layer (fine-grained particles) in a cover system for blocking the ingress of oxygen and meteoric water into waste landfill [7], the clogging of sandstone in methane hydrate exploration [8], the movement of clay particles in rock and soil reducing the efficiency of oil recovery [9][10][11][12][13], the propping of fractures in hydraulic fracking [14,15], and the geological sequestration of CO 2 [16,17]. ZVI particle injection has been proposed to remove heavy metals, organochlorine, and other contaminants in groundwater and soils [1][2][3][4]. ...
... These applications include the injection of zero valence iron (ZVI) particles for environmental remediation [1][2][3][4], grouting [5], the piping failure of earthen dams [6], clogging and particle loss at the interface of the capillary break layer (coarse-grained layer) and moistureretaining layer (fine-grained particles) in a cover system for blocking the ingress of oxygen and meteoric water into waste landfill [7], the clogging of sandstone in methane hydrate exploration [8], the movement of clay particles in rock and soil reducing the efficiency of oil recovery [9][10][11][12][13], the propping of fractures in hydraulic fracking [14,15], and the geological sequestration of CO 2 [16,17]. ZVI particle injection has been proposed to remove heavy metals, organochlorine, and other contaminants in groundwater and soils [1][2][3][4]. However, its field application has been limited because of the short ZVI migration distance due to deposition and particle clogging, i.e., only a few meters from the injection point [18]. ...
The pick-up, migration, deposition, and clogging behaviors of fine particles are ubiquitous in many engineering applications, including contaminant remediation. Deposition and clogging are detrimental to the efficiency of environmental remediation, and their mechanisms are yet to be elucidated. Two-dimensional microfluidic models were developed to simulate the pore structure of porous media with unified particle sizes in this study. Kaolin and bentonite suspensions were introduced to microfluidic chips to observe their particle deposition and clogging behaviors. Interactions between interparticle forces and particle velocity profiles were investigated via computational fluid dynamics and discrete element method simulations. The results showed that (1) only the velocity vector toward the micropillars and drag forces in the reverse direction were prone to deposition; (2) due to the negligible weight of particles, the Stokes number implied that inertia was not the controlling factor causing deposition; and (3) the salinity of the carrying fluid increased the bentonite deposition because of the shrinkage of the diffused electrical double layer and an increase in aggregation force, whereas it had little effect on kaolin deposition.
... field through a dual random lattice method. Saliba et al. (2019) involves a variety of erosion processes over time (Sharif et al. 2015;Robbins et al. 2018a;2018b), 117 which contradicts the assumption of a constant amplification factor. Moreover, other experimental 118 studies show that this factor is related to several features of foundation material such as soil type 119 (Shen et al. 2013), grain size distribution (Shen et al. 2013), soil fabric ) and the 120 stress state condition (Chang and Zhang 2012). ...
... scale experiments have been conducted(Sharif et al. 2015;Robbins 2016;Robbins et al. 2018a;248 2018b; Douglas et al. 2019). Robbins (2016) conducted horizontal flume test experiment on a 249 uniform coarse sand with mean grain size distribution, , and coefficient of uniformity, and 1.31, respectively. ...
The progression length at various stages of backward erosion piping (BEP) in levee systems can serve as a key engineering demand parameter for reliability and risk assessments. The main goal of this study is to put forward a reliable and computationally efficient technique for predicting the progression length during BEP. Many existing modeling approaches for predicting progression lengths of BEP are either computationally expensive or consider a constant, time-independent amplification factor for the permeability coefficient. In contrast, the model developed here considers the underlying physical phenomena to properly capture the amplification of the permeability coefficient during the progression of BEP. The proposed model is derived considering the rolling threshold condition, which is obtained from the moment equilibrium of erodible particles. This modeling approach with time-varying permeability coefficients has been implemented in FLAC3D, and the derived BEP paths are validated for three flume experiments. The impact of material properties including porosity, tortuosity, and coefficient of uniformity on the amplification factor are investigated. These analyses show that the permeability amplification factor and the progression length increase with low rates at the initial stages of piping. Following the formation of the piping path, they both increase at a generally greater rate over time.
... At present, the measurement methods in geotechnical laboratory experimental studies are of two main classes: contact measurement method and non-contact measurement method White et al. 2001;White et al. 2003). For example, in terms of the contact measurement method, grid lines are widely used as measuring instruments to measure the landslide dam topography in laboratory flume experiments (Awal et al. 2009;Jiang et al. 2017;Niu et al. 2012;Sharif et al. 2015;Yang et al. 2015). Despite being a simple and effective approach, the measured results from this approach are relatively inaccurate. ...
... For example, Awal et al. (2009) 0.5 m on the sidewall of a channel with a width of 0.4 m and a length of 12 m to mark the evolution characteristics of the landslide dam topography. Sharif et al. (2015) studied the topography evolution characteristics of the erosion failure of a landslide dam in a flume with a length, width, and height of 6.1 m, 0.45 m, and 0.25 m, respectively, using a grid line with a spacing of 50 mm. Jiang et al. (2017) studied the process of dam failure by a grid line with an interval of 50 mm in a flume with a length, width, and height of 6 m, 0.3 m, and 0.4 m, respectively. ...
Topography is a crucial characteristic reflecting the stability status of a landslide dam. The methods for measuring landslide dam topography in a laboratory-scale test study are currently operator dependent, time-consuming, or only applicable to the measurement of the two-dimensional section. In this paper, a laboratory-scale photogrammetric method based on the structure from motion (SfM) technique was proposed to measure the three-dimensional (3D) topography of a landslide dam. The SfM technique, which is a revolutionary, low-cost, user-friendly computer vision technique, was employed for reconstructing a landslide dam 3D computer model. A scientific method to determine the topography parameters of a landslide dam was put forward. Meanwhile, two materials with different particle sizes were used to simulate the formation process of the landslide dam in the laboratory-scale. Then, the measurement results of the two materials were compared. Five parameters of a landslide dam topography with 100 parallel measurement results for each parameter were obtained. The results show that the SfM technique could build a high-quality 3D point cloud in a laboratory scale. The proposed method of determining the topography parameters of a landslide dam was useful and has low measurement uncertainty. The material type affected the sparse density of the point cloud and then affected the measurement uncertainty of landslide dam topography parameters. The measurement uncertainty of the gravel-type landslide dam was significantly higher than that of the sand-type landslide dam. This research contributes to promoting the application of a photogrammetric method based on the SfM technique in geotechnical engineering laboratory-scale tests.
... An important requirement is maintaining a constant reservoir head during the breaching process (Sharif et al., 2015) that is, representing the worst-case scenario simulation. For this purpose, a 0.3 m wide side spillway was located 1.5 m upstream of the model dam (see Figure 1). ...
... The experimental conditions described are similar to Overtopping erosion of model earthen dams analysed using digital imageprocessing method Zomorodian, Ataee Noghab, Zolghadr and O'Kelly Offprint provided courtesy of www.icevirtuallibrary.com Author copy for personal use, not for distribution those employed by Sharif et al. (2015). A control valve regulated the targeted constant reservoir inflow rate of 1.5 l/s for all tests, verified using a flowmeter device. ...
Overtopping erosion is one of the main factors responsible for the destruction of earthen structures due to floods. Considering the shortage of existing studies and the need for further research to properly understand the processes leading to breaching failure, this study investigates the effect of compaction level (dry density) on the overtopping erosion response of model compacted silty sand dams using a laboratory flume apparatus. From side-view video recordings of the homogeneous earthen dam cross-section, digital image-processing techniques are employed to track and forensically analyse and interpret the initiation and progression of the erosion edge. The results indicate that the overall pattern of initiation and development of overtopping erosion depends on the compaction level, with greater compactive effort (higher shear strength of soil) reducing its progression speed, thereby increasing the time period for the erosion edge to reach the dam’s upstream crest (tB) and breaching failure. Artificial neural network and response surface methodology (RSM) approaches are investigated for estimating the experimental tB values, with the RSM-derived third-order polynomial found to produce good predictions for the three compaction levels investigated. Finally, recommendations are given for further research, including employing the experimental set-up presented for investigating other types of dam failure.
... The most common cause of failures, as seen in the flooding in South Carolina, are overtopping, seepage, internal erosion and piping, and slope instability or a combination (Tabrizi et al., 2017). Although, the ASCE/EWRI Task Committee on dam and Levee Breaching reports that overtopping is the most common cause of embankment failure, piping or internal erosion is the most detrimental (Costa, 1985;Sharif et al., 2015). It is often cited as the most destructive among dam safety professionals because it is progressive and can rapidly lead to failure of the dam. ...
... It is often cited as the most destructive among dam safety professionals because it is progressive and can rapidly lead to failure of the dam. Approximately 28% of all dam failures are due to piping (Costa, 1985;Sharif et al., 2015). Piping produces a widening hole through the embankment because of internal erosion. ...
The structural integrity of earthen dams in the natural habitat of wildlife is commonly affected by invasive animal burrowed into the embankment. The effects may be observed on the phreatic line, pore water pressures and seepage rate through the dam. This study investigates the effects of previously reported wildlife activities on two failed dams in the Midlands of South Carolina. Dam sites were visited to collect soil samples for geotechnical testing, measure the geometry, and make observations for animal presence. The dams are determined to have burrows by gophers and ant colonies from the inspection reports and site observations. To characterize the soils, geotechnical tests are conducted for grain size distribution, permeability, porosity, and liquid limit. The finite-element method is used to simulate the two-dimensional steady-state seepage at dams with isotropic and homogeneous soil assumption. A saturated/unsaturated soil model is used and Modified Kovacs and Mualem methods are utilized for the estimation of the volumetric water content function and hydraulic conductivity function, respectively. Pore water pressures, hydraulic gradients and seepage velocity are compared for intact and deteriorated structures to investigate the effects of animal activity. The results show that the animal burrows negatively impact the seepage behavior of the dams by affecting the pore water pressures, seepage rate, hydraulic gradients, and seepage velocities.
... The results showed standard deviations ranging from 0.005 m to 0.037 m, with coefficients of variation ranging from 1.4% to 10.9%. Sharif Yusuf et al. [120] conducted repeatability tests on four embankment dams by comparing the non-dimensional depth versus time curves of quasi-identical experiments. Dezert et al. [23] evaluated the repeatability of large-scale rockfill dam breaching tests, reporting larger differences in standard deviations among tests. ...
The breaching of embankments have devastating consequences for the economic, human, cultural, and environmental assets. One of the most widely used approaches for understanding the characteristics of embankment breaching is through laboratory and field-scale experiments. Despite the advancements in instrumentation and measurement techniques of embankment breaching experiments, there is a lack of comprehensive documentation. In this review, the advancements and state-of-the-art instrumentation and measurement techniques employed in overtopping-induced embankment breaching of laboratory and field-scale experiments are discussed. The key parameters commonly measured in experimental modeling are breach morphological changes, reservoir and flow depth, velocity, breach outflow, and pore water pressure. Instrumentation for breach morphological change detection, including mechanical, photography, photogrammetry, electronic sensors, and laser technologies, are reviewed. The various flow velocity measuring techniques, such as Particle Tracking Velocimetry (PTV), Particle Imaging Velocimetry (PIV), acoustic, and radar-based techniques, are discussed. Instrumentation for water level, flow rate, and pore pressure measurements are also briefly documented. The challenges and constraints encountered during embankment breaching experiments are discussed. The review further suggests future perspectives in improving the accuracy of breach detection, velocity, and pore pressure measurement techniques. Additionally, improving scale effects by incorporating geotechnical factors is also recommended.
... As river water flows out along a pipeline and carries out sediment particles, it can damage the embankment structure and eventually ultimately lead to its collapse. With reference to the piping simulation experimental methods in previous studies (Beek et al., 2012;Bersan et al., 2018;Sharif et al., 2015), similar simulation methods were adopted. In each experiment, to simulate real piping, a portable electric pump was used to extract water from approximately 30 cm below the river surface as experimental water to ensure that the piping effluent temperature was the same as the river water temperature (Figure 4). ...
With flooding events expected to increase in both intensity and frequency in the future due to climate change, ensuring the safety of river embankments is vital to withstand flood disasters. Piping is one of the most harmful river embankment hazards in the flood season, and recent advances in unmanned aerial vehicles (UAVs) and deep learning‐based object detection have enabled efficient and automated hazard detection. In this study, a novel approach that integrates a UAV with deep learning‐based object detection and edge computing was proposed for rapid and automatic piping detection. First, a total of 104 field simulation experiments were conducted across 12 different sites in flood‐prone areas to fill gaps in the high‐quality data set, and the UAV thermal infrared and visible data sets of river embankment piping were produced, including various times (forenoon, afternoon, and night), weather conditions (clear‐sky, cloudy, and rainy), locations (bare land, paddy, grassland, and pond) and flight altitudes (10, 20, and 30 m). Second, the deep learning‐based object detection model was selected and trained on the thermal infrared and visible data sets. The well‐trained infrared and visible models have detection precisions of 92.7% and 70.4%, respectively, with recalls of 84.9% and 69.7%. Furthermore, both models exhibited great resistance to interference from several types of aquatic vegetation and could effectively detect piping on rainy days. The integration of a UAV and edge computing enabled real‐time detection of piping. The proposed method enhances hazard detection efficiency, contributing to intelligent emergency embankment management.
... 이는 이방성구조물과 성토재의 경계부가 침투에 취약한 조건인 것과 관계가 있다 (Noh and Lee, 2014 (Coleman et al., 2002;Chahar, 2004;Kumar and Sreeja, 2012;Van Beek et al., 2014;Sharif et al., 2015;Rotunno et al., 2017) ...
... Their results revealed that the initiation and development of the erosion by overtopping depended on the soil compaction level. [11] investigated the piping erosion process in an earthen embankment by creating a hole at the bottom of the dam to initiate the piping. The soil mixture used in these experiments consisted of 64% medium sand, 29% silt and 7% clay. ...
Piping and overtopping are the most important causes of earth-fill dam failure. Such dams may erode under seepage, causing a reduction in the structural strength. The aim of this study was to investigate the temporal evolution of the breach and flow rate from the breach resulting from the piping in earth-fill dams. The experiments were carried out at Hydraulics Laboratory of Civil Engineering Department within İzmir University of Economics. The dam was constructed by using a mixture consisting of 85 % sand and 15 % fine (low plasticity clay). In the first scenario a circular tunnel with a diameter of 2 cm was created along the centreline at 6 cm below the dam crest whereas in the second one it was located at the upper edge. Six cameras at different locations recorded the evolution of the progress of the breach formation. The pump flow rate was measured by magnetic flow meter, and the continuity equation was used to calculate the flow rate values from the breach. The time-varied values of the total breach areas were determined using the Gauss Area formula. The image processing method was also applied in the determination of the breach areas. The time-dependent changes of water depth in the channel were also recorded. The obtained experimental findings are presented and commented, together with the universal dimensionless curves. The failure of the dams occurred mainly because of the headcut erosion developed from downstream to upstream. When breaching started, the orifice flow was converted to open channel flow where breach bottom behaved like a broad crested weir. In the second scenario, the rigid lateral side considerably influenced the flow rate and the development of the breach. The peak flow rate corresponding to the first scenario was found approximately 2.3 times greater than that of the second one. The maximum values of all the breach parameters were reached earlier in the case of the seepage along the centerline. The ratios between the values corresponding to the first and the second scenarios were found as 3.25 and 1.75 for maximum breach areas at downstream and at upstream sides, respectively. These ratios were 2.44 and 1.37 for the average breach widths at downstream and upstream sides, respectively. A very good agreement was found between the area values obtained from Gauss area method and image processing technique, in both scenarios. This fact demonstrated that either of these two approaches can be used to determine the time-dependent breach areas. These experimental findings provide the opportunities for the calibration and validation of the numerical models used in the relevant numerical investigations. This study also offers guidance for the strategies concerning emergency action plans related to the failure of homogeneous earth-fill dams when the piping starts at upper part of the homogeneous earth-fill dams.
... On the other hand, the simulation predicts a higher erodibility coefficient compared to the EFA experiment. It is worth noting that the erodibility of granular soils is affected by various factors such as soil grain size, density, void ratio, and particle shape (Briaud 2015;Sharif et al. 2015;Guo et al. 2018). The overestimation of erosion rate and erodibility coefficient in the simulation can be attributed to three key factors reasons: (a) the greater void ratio e in the simulation (i.e., e = 0.69 vs. 0.58), (b) the use of spherical particle shape in the simulation versus the angular particle shape of the sand tested in Ham et al. (2016), and (c) the interlocking effect due to the preconsolidation stress applied during specimen preparation in the experimental setup. ...
This study introduces a numerical modeling approach that couples the computational fluid dynamics (CFD) with the discrete element method (DEM) to simulate grain-scale soil erosion processes induced by water flows. In this modeling framework, CFD simulates fluid flows by solving the volume-averaged Navier–Stokes equations, and uses the k–ω turbulent model for turbulent flows. Simultaneously, DEM computes the displacement of solid particles by incorporating the fluid–particle interactions driven by fluid flows while adhering to Newton’s laws of motion. These interactions encompass drag force, buoyancy force, pressure-gradient force, and viscous force exerted by fluid flows and acting on the particles. The coupled CFD–DEM modeling adeptly replicates soil erosion processes, demonstrating good alignment with results obtained from laboratory erosion function apparatus tests. In particular, the DEM facilitates the estimation of shear stress acting on the soil surface based on fluid–particle interaction forces, which has been roughly approximated by empirical or semi-empirical models. This study underscores the capability of coupled CFD–DEM in providing valuable insights into the grain-scale behavior of soil particles subjected to fluid flows, with the potential for extension to address soil erosion and fines migration.
... Numerous researchers have investigated barrier dam-related issues. Predominant barrier dam stability assessment methods include simulation experiment analysis (Carrivick et al. 2011;Chen et al. 2015;Sharif et al. 2015;Shi et al. 2015Shi et al. , 2022bWang et al. 2016a;Zhou et al. 2019bZhou et al. , a, 2021Wu et al. 2020;Ruan et al. 2021;Peng et al. 2021), numerical calculation and analysis (Cundall and Strack 1979;Hu et al. 2011;Shan and Zhao 2014;Wang et al. 2016b;Zhong et al. 2018;Zhou et al. 2019a;Zhao et al. 2019;Takayama et al. 2021), and statistical analysis. The first two methods necessitate obtaining detailed data on material composition, structural characteristics, and barrier dam geometry. ...
Barrier dams are major natural disasters that frequently occur in mountainous areas and have a high probability of destabilizing and failing within a short period. Catastrophic dam failures cause significant economic and ecological damage to downstream areas. Therefore, rapid and accurate assessment of barrier dam stability is crucial for effective emergency rescue efforts. A database was constructed with 1,738 barrier dam cases from 49 countries and regions. A machine learning algorithm was employed for barrier dam stability assessment, and the Sparrow Search Algorithm (SSA) was used to optimize the Gradient Boosting Decision Tree, Random forest, and Extreme Gradient Boosting (XGBoost) respectively. Then, 192 cases with detailed data were selected for training, validation, and comparison of model performance. Among the methods tested, the SSA-XGBoost model performed the best. In addition, the feature importance values of the input parameters were also analyzed. The dam height emerged as the most important factor, with a significantly higher importance value compared to other features. Based on this, 50 barrier dam cases with detailed information were randomly selected for stability assessment, and the results were compared with those of several classical methods. The results indicate that the SSA-XGBoost algorithm can more accurately judge the stability of barrier dams. The absolute accuracy, conservative accuracy, and misjudgment rates were 86%, 94%, and 6%, respectively. These findings demonstrate that the assessment method proposed in this study is reliable and can provide some practical references for the emergency rescue of barrier dams.
... There are some laboratory flume overtopping earthfill dam break experiments, over the sand-constructed dam body (Tingsanchali and Chinnarasri 2001;Zhang et al. 2009;Msadala 2016). Some studies, although constructed earthfill dam body, they just concentrated on the breaching process (Morris et al. 2007;Greco et al. 2008;Sharif et al. 2015). Only recently, Taskaya et al. (2023) investigated sedimentary flow movement over smooth and rough downstream areas due to overtopping earthfill dam breaks. ...
... Soil erosion by wind and water causes enormous global ecological and economic damage, and soil erosion has tangible and intangible impacts (Marzen et al., 2015). Worldwide water erosion occurs in a variety of forms, viz., splash, sheet, interrill, rill, gully, and side erosion (Poesen, 2011;Sharif et al., 2015;Sun et al., 2021;Yang et al., 2021;Li et al., 2022). Meanwhile, splash erosion has received particular attention as the initial stage of soil erosion (Nelson and Sommers, 1982;Hu et al., 2018) and is caused by the impact of raindrops on the soil surface, leading to the movement of soil particles and the destruction of soil structure (Ellison, 1947;Valette et al., 2006). ...
The present study investigated the interaction of wind and rain (WDR) on splash and interril erosions under laboratory conditions. The corresponding experiments were carried out with rainfall intensity of 50 mm h − 1 with a duration of 30 min under no-wind control conditions and two wind velocities viz., 3 and 6 m s − 1 at a slope of 12%. The study was conducted on sandy-loam soil from summer rangelands of the Northern Alborz Mountain in Iran. The soil collected was transported to the Rainfall and Erosion Simulation Laboratory. The prepared 6 × 1 m-plots were concurrent with the simulation of the WDR. Moreover, three splash cups were used to measure splash erosion, and each cup was placed on the soil surface at distances of 1.5, 3.0, and 4.5 m from the plot outlet. The results displayed the significant effects of wind (P < 0.01) on runoff generation and soil erosion components. Therefore, the mean runoff and runoff coefficient decreased while increasing wind velocity increased sediment concentration and soil loss. The mean runoff volume and coefficient were 103.48, 94.62, and 88.82 L and 94.43, 87.23, and 81.62 % at wind velocities of 0, 3, and 6 m s − 1 , respectively. In addition, the mean soil loss and sediment concentration were 414.94, 1057.47, and 1375.48 g; and 31.35, 156.31, and 303.75 g L − 1 ; at 0, 3, and 6 m s − 1 wind velocities, respectively. Besides, the mean net splash increased significantly with increasing wind velocity, from 9.58, 14.93, and 18.63 g, respectively, as wind velocity changed from 0 to 3 and then 6 m s − 1. It has been proven that WDR soil erosion was higher than no-wind rain. This research could increase soil managers' awareness of solution strategies.
... Greco, Pontillo, Iervolino , & Leopardi (2008) used a two-dimensional depth-averaged (2DH) numerical model to simulate the evolution of a breach in an earth-fill dam. Sharif, Elkholy, Hanif Chaudhry, & Imran (2015) constructed a dam in a laboratory flume by using a mixture of sand, silt, and clay with different compaction rates and examined the changes in the depth, area, and volume of erosion during the piping evaluation by utilizing an image processing technique. Most of the researchers realizing numerical analyses make some simplified assumptions concerning shape of a breach and discharge of water flowing through the breach. ...
Piping is one of the main problems which threatens stability of earth-fill dams. Realistic approaches are needed for breach mechanism as well as breach geometry and flow. The aim of this study is to realize experiments to provide data needed to perform numerical analyses by making more realistic assumptions. Dam having a height of 0.6 m, a bottom width of 2 m and a crest width of 0.20 m is built in a channel of 1 m wide, 0.81 m high and 6.14 m long. Evolution of dam failure resulting from seepage at upper corner of the dam is recorded by six cameras located at different locations. The time-varied of breach areas at upstream and downstream sides are determined by applying the Gauss Area functions. Discharge of water through the breach and average outflow velocity are determined by using the continuity equation.
... Greco et al. (2008) used a two-dimensional depth-averaged (2DH) numerical model to simulate the evolution of a breach in an earth-fill dam. Sharif et al. (2015) constructed a dam in a laboratory flume by using a mixture of sand, silt, and clay with different compaction rates and examined the changes in the depth, area, and volume of erosion during the piping evaluation by utilizing an image processing technique. Most of the researchers realizing numerical analyses make some simplified assumptions concerning shape of a breach and discharge of water flowing through the breach. ...
Internal erosion, also known as piping, is one of the most important causes of earth-fill dam breaks. Many researchers dealing with numerical analyses in this area make some simplified assumptions about the shape of the breach and the discharge of water flowing through the breach. This study was conducted in the scope of the project supported financially by the Scientific and Technological Research Council of Turkey and it consists of experimental study which aims to provide data needed to perform numerical analyses with more realistic approaches. A dam with a height of 0.6 m, a bottom width of 2 m and a crest width of 0.20 m was built in a flume 1 m wide, 0.81 m high and 6.14 m long. Before the construction of the dam, some common soil mechanics tests were carried out. The dam was constructed by using a mixture consisting of 85 % sand and 15 % clay. A circular tunnel with a diameter of 2 cm was created along the centerline at 6 cm below the dam crest. In the closed system, water was pumped from the lower reservoir to the upper channel. Six cameras located at different locations recorded the evolution of the dam failure. Gauss Area formula was applied to determine the time-varied of the breach areas at upstream and downstream sides. The discharge of water through the breach and average flow velocity were determined by using the continuity equation. The changes in water depth in the channel were also recorded.
... A two-dimensional problem of soil contact erosion based on a soil dam was considered in the work [138]. To describe 27 the filtration processes, the author uses the Laplace equation, which complements the boundary conditions. ...
... For convenience, the erosion path is commonly designed to be straight in existing experiments to study the hydraulic properties and mechanical properties [11,[46][47][48][49]. For example, Hanson et al. [46] and Ali et al. [47] placed the continuous steel pipe through the physical earthen dam model for simulating the internal erosion process, and then pulled the steel pipe out to initiate internal erosion. ...
Internal erosion is widely perceived as contributing to the failure of earthen dams. To reduce the failure risk, timely monitoring of internal erosion is an effective method in observing their internal structure evolution. A set of earthen dam model experiments were conducted. Under an applied voltage, the response potential differences (PD) at the slope of the dam models were collected before and after the impoundment of the upstream reservoir. The discrepancy among the four dam models, the influence of soil moisture content on PD, and the impact of internal erosion on PD were studied. The results show that it is acceptable to employ different dam models to simulate the development of internal erosion, although the discrepancy among the models is inevitable. The moisture content of the soil significantly affects the PD response to applied voltage. The PD increases with an increase in soil moisture content until the soil is saturated. The change in PD is correlated with the development of internal erosion. With the progression of internal erosion, the starting position for the steep increase in PD distribution continues to move toward the dam toe. In addition, the electrode stability is noted to have an effect on measured PD, which requires further studies to be clarified. This study sets the stage for the PD-based monitoring method in observing the evolution of internal erosion in earthen dams.
... Pour étudier le phénomène d'érosion interne au laboratoire, plusieurs dispositifs expérimentaux ont été développé [16,[125][126][127][128]. ...
Résumé
L’érosion interne est définie comme la migration de particules initiées par les forces d’écoulement au sein d’un ouvrage hydraulique ou sa fondation. Ce processus peut affecter la stabilité des digues, de barrages en remblai ou les talus naturels. Les études expérimentales présentes dans la littérature se concentrent principalement sur l’identification des gradients hydrauliques critiques pour l’initiation de l’érosion, et sur l’analyse de la courbe granulométrique des sols érodables pour définir des critères permettant de quantifier le potentiel d’érosion d’un sol donné. Cependant, il existe peu d’études sur l’effet de l’érosion sur le comportement mécanique des sols. Dans cette étude, on s’intéresse dans un premier temps à l’effet de l’érosion interne sur les paramètres de résistance au cisaillement des sols sableux. Des essais de cisaillement direct ont été effectués à l’aide d’un dispositif (boîte de Casagrande) modifié sur des sols avant et après érosion interne. Les résultats de cette étude ont montré que l’érosion affecte considérablement la résistance au cisaillement des sols étudiés. On s’intéresse dans un deuxième temps à la modélisation de l’érosion interne, un modèle mathématique avec une loi d’érosion modifiée, basée sur la diffusion de la porosité du milieu, est proposé et résolu numériquement par la méthode des éléments finis. L’effet de l’érosion interne sur la stabilité au glissement a été étudié à travers une co-simulation éléments finis-équilibre limite, en calculant la variation du facteur de sécurité en fonction du temps. Les résultats ont montré que l’érosion interne entraine une réduction de la valeur du facteur de sécurité de 16% de sa valeur initiale, et peut conduire à la rupture de l’ouvrage.
Mots clés : Erosion interne, Résistance au cisaillement, Stabilité, digues, Barrages en remblai, Talus naturels, Modélisation.
Abstract
Internal erosion is defined as the migration of particles initiated by flow forces within a hydraulic structure or its foundation. This process can affect the stability of dikes, embankment dams or natural slopes. The experimental studies present in the literature focus mainly on the identification of critical hydraulic gradients for erosion initiation, and on the analysis of the particle size distribution of erodible soils to define criteria to quantify the erosion potential of a given soil. However, there are few studies on the effect of erosion on the mechanical behavior of soils. In this study, the effect of internal erosion on the shear strength parameters of sandy soils is first investigated. Direct shear tests were performed using a modified Casagrande box on soils before and after internal erosion. The results of this study showed that erosion significantly affects the shear strength of the studied soils. In a second time, we are interested in the modelling of the internal erosion, a mathematical model with a modified erosion law, based on the diffusion of the porosity of the medium, is proposed and solved numerically by the finite element method. The effect of internal erosion on sliding stability was studied through a finite element-limit equilibrium co-simulation, by calculating the variation of the safety factor over time. The results showed that internal erosion leads to a reduction of the safety factor value by 16% of its initial value, and can lead to the failure of the structure
Key words: Internal erosion, Shear strength, Stability, Dikes, Embankment dam, Natural slopes, Modeling.
ملخص
يُعرَّف التآكل الداخلي بأنه تنقل الجسيمات الناتجة عن قوى التدفق داخل هيكل هيدروليكي أو أساسه. يمكن أن تؤثر هذه العملية على استقرار السدود أو المنحدرات الطبيعية. تركز الدراسات التجريبية المقترحة من قبل الباحثين بشكل أساسي على تحديد التدرجات الهيدروليكية الحرجة لبدء التآكل ، وعلى تحليل منحنى حجم الجسيمات للتربة القابلة للتآكل لتحديد المعايير التي تسمح بتحديد إمكانية التآكل لتربة معينة. ومع ذلك ، هناك القليل من الدراسات حول تأثير التآكل الداخلي على السلوك الميكانيكي للتربة. في هذه الدراسة تم دراسة تأثير التآكل الداخلي على تغيرات مقاومة القص للتربة الرملية. تم إجراء اختبارات القص المباشر باستخدام علبة كازاغروند المعدلة على التربة قبل وبعد التآكل الداخلي. أظهرت نتائج هذه الدراسة أن الانجراف يؤثر بشكل كبير على مقاومة القص للتربة المدروسة. من جهة أخرى ، صببنا اهتمامنا الى نمذجة التآكل الداخلي و قد تم اقتراح نموذج رياضي مع قانون تآكل معدل ، بناءً على انتشار مسامية الوسط ، وحلها عدديًا بطريقة العناصر المحدودة. تمت دراسة تأثير التآكل الداخلي على ثبات االمنحدرات من خلال محاكاة مشتركة بين حد التوازن و العناصر المحدود ، عن طريق حساب التباين في عامل الأمان بمرور الوقت. أظهرت النتائج أن التآكل الداخلي يؤدي إلى انخفاض قيمة عامل الأمان بنسبة 16٪ من قيمته الأولية ، ويمكن أن يؤدي إلى انهيار الهيكل.
الكلمات المفتاحية: التآكل الداخلي ، مقاومة القص ، الثبات ، السدود الترابية ، المنحدرات الطبيعية ، النمذجة.
... During the hydraulic process, however, the PSD is constantly affected by the hydraulic velocity and seepage direction of the flowing liquid; which causes skeletal particles to be unable to prevent finer particle transport, thus causing ineffective filter assessment Wan and Fell, 2008). At present, it is also difficult to determine how the PSD changes in the hydraulic process because the internal erosion mechanism remains poorly understood owing to the complex hydraulic process and limited detection methods (Sharif et al., 2015). ...
Soil particle size distribution (PSD) is critical for assessing the potential for internal instability of sand–gravel soils, mainly because particle migration in sand–gravel soils owing to seepage forces affects almost all soil hydraulic properties during internal erosion processes. Therefore, a reliable PSD analysis is essential for revealing the mechanism of particle migration and internal instability of sand–gravel soils. At present, however, PSD is commonly calculated by manual interpretation methods and cannot be continuously and nondestructively analyzed during internal erosion processes. Those methods are lacking, however, in that it results in a failure to continuously determine the internal erosion condition. In this paper, a new approach with the ability to continuously predict the PSD changes in sand–gravel mixtures is introduced based on one-dimensional laboratory suffusion tests in a non-destructive nuclear magnetic resonance (NMR) system over a range of suffusion times. The results show that pore expansion and particle migration are an interactive process that controls suffusion development in sand–gravel mixtures. The proposed method is verified through experimental data measured by sieve analysis, and has potential to retrieve PSD information at different suffusion times.
... The seepage process mainly consists of three stages according to the material behavior: 1) first visible/initial movement of particles, 2) heave progression to form the seepage path, 3) total heave. Numerous types of experimental methods could be found to study the erosion of soils, as the flume test [3][4][5], rotating cylinder test [6][7][8][9], hole erosion test [10,11] and jet erosion test [6,12]. The rotating cylinder test is a widely used method, due to its smaller sample volume, the ability to adequately control the stress state and the available measurements of the rate of erosion. ...
Increases in seepage force reduce the effective stress of particles and result in the erosion of particles, producing heave failure and piping. Sheet piles/cutoff walls are often employed in dams to control the seepage. In this study, a computational fluid dynamics solver involving two fluid phases was developed and coupled with discrete element method software to simulate the piping process around a sheet pile/cutoff wall. Binary-sized particles were selected to study the impact of fine particles on the mechanisms of seepage. The seepage phenomenon mainly appeared among fine particles located in the downstream side, with the peak magnitudes of drag force and displacement occurring around the retaining wall. Based on the particle-scale observations, the impact of seepage produced a looser condition for the region concentrated around the retaining wall and resulted in an anisotropic condition in the soil skeleton. The results indicate that heave behavior occurs when the drag force located adjacent to the boundary on the downstream side is larger than the corresponding weight of the bulk soil.
... Simultaneously, the breach gradually moves upward. The rate of this transfer is a function of the dam material properties (Coleman et al. 2002;Temple and Hanson 2005;Orendorff et al. 2011;Hakimzadeh et al. 2014;Kakinuma and Shimizu 2014;Sharif et al. 2015;Müller et al. 2016;Elalfy et al. 2018b). ...
In this research, physical modeling of nonhomogeneous earth dams with clay cores was performed. The effects of dam slope, dimensions, and geometrical shape of the core, as well as the materials used for the core and body, on the breaching process and corresponding output hydrographs were studied. The breaching processes of each experiment were recorded using three digital cameras, and both quantitative and qualitative results were extracted. A decrease in the dam slope decreases the peak outflow, and the corresponding output hydrograph has a lower peak discharge and longer occurrence time. In addition, results show that the cohesion of materials is a prominent factor in the breaching of the core, and with a more cohesive core, the peak outflow and occurrence time considerably increase (by approximately 40% and up to 50%, respectively). For core materials with lower cohesion, erosion of the core and body occurs simultaneously, and consequently, the breach formation process is similar to a homogeneous dam. Finally, the hydrographs of dams with various practical core shapes show that the construction of an inclined core will increase the peak outflow up to 55% and weaken the dam behavior during overtopping. In these experiments, the trapezoidal cores presented the best results.
... It has been found that the pipe channel has the cross-section of an arch, with a rectangle at the bottom and a semicircle at the top. Because direct observation cannot reveal the enlargement process of the pipe in the dam, Sharif et al. (2015) conducted a flume test by initially placing a pipe at the side of the plexiglass wall. They utilized two SONY HDR-XR 160 high-definition video cameras to record the enlargement of the pipe and an image processing technique to analyze the results. ...
Based on model tests of earthen dam breach due to piping failure, a numerical model was developed. A key difference from previous research is the assumption that the cross-section of the pipe channel is an arch, with a rectangle at the bottom and a semicircle at the top before the collapse of the pipe roof, rather than a rectangular or circular cross-section. A shear stress-based erosion rate formula was utilized, and the arched pipe tunnel was assumed to enlarge along its length and width until the overlying soil could no longer maintain stability. Orifice flow and open channel flow were adopted to calculate the breach flow discharge for pressure and free surface flows, respectively. The collapse of the pipe roof was determined by comparing the weight of the overlying soil and the cohesion of the soil on the two sidewalls of the pipe. After the collapse, overtopping failure dominated, and the limit equilibrium method was adopted to estimate the stability of the breach slope when the water flow overtopped. In addition, incomplete and base erosion, as well as one- and two-sided breaches were taken into account. The USDA-ARS-HERU model test P1, with detailed measured data, was used as a case study, and two artificially filled earthen dam failure cases were studied to verify the model. Feedback analysis demonstrates that the proposed model can provide satisfactory results for modeling the breach flow discharge and breach development process. Sensitivity analysis shows that the soil erodibility and initial piping position significantly affect the prediction of the breach flow discharge. Furthermore, a comparison with a well-known numerical model shows that the proposed model performs better than the NWS BREACH model. Keywords: Earthen dam, Piping failure, Overtopping failure, Breach flow, Numerical modeling, Sensitivity analysis
Earth-fill dams have been constructed for decades by compacting natural soil materials near the dam site. Piping is of the most important causes of their failure.
In the scope of this thesis, 2 m in length homogenous earth-fill dams were constructed in a rectangular flume in the laboratory of the Izmir University of Economics. The experimental and numerical investigations on a breach by generating piping were realized with different weak zone scenarios. Three experiments were performed by placing a weak layer cross-section 5x5 cm2 at the dam bottom center. One scenario was performed by locating a weak layer of 2x2 cm2, 28 cm above the bottom.
Temporal breach areas and the breach-wetted areas are evaluated on scaled screenshots by using Gauss’s area formulation. The Temporal breach discharges were calculated from the continuity equation.
Furthermore, finite element analyses on the breaching of homogenous earth-fill dams in different scenarios were performed by comparing the hydraulic gradient with the critical value. In addition to the bottom and middle scenarios, two upper scenarios were also modeled. The water depths were used for each scenario to represent the experimental conditions, and some approaches were made for the weak zones. To simulate the breach mechanism with different loops, a python algorithm was integrated with the Jupyter console. As a result of the simulations, it has been observed that the findings obtained by simulations were in accord with the experimental studies, and the dams were exposed to backward piping starting from downstream towards upstream.
Özet: Borulanma toprak dolgu barajların stabilitesini tehdit eden önemli ve karmaşık bir problemdir. Günümüzde borulanmanın karmaşık özellikleri nedeniyle erozyon sürecini tarif edecek genel bir formül mevcut değildir. Bu çalışma kapsamında, toprak baraj gövdesinin üst köşesindeki sızma nedeniyle oluşan borulanmanın gelişimi deneysel olarak araştırılmıştır. Bu amaç çerçevesinde, 1 m genişliğinde, 0.81 m yüksekliğinde ve 6.14 m uzunluğunda bir kanal içine, % 85 kum ve % 15 kil karışımı kullanılarak hazırlanan, 0.6 m yüksekliğinde, 2 m taban genişliğinde ve 0.20 m kret genişliğinde bir baraj inşa edilmiştir. Baraj haznesindeki su seviyesi seviye ölçer sensoru ile sabit tutulmuştur. Kanala gelen suyun debisi manyetik debimetre ile ölçülmüştür. Gediğin zamana bağlı olarak gelişimi uzaktan da izlenilebilen gelişmiş kameralar ile kaydedilmiştir. Erozyon sürecini izlemek için görüntü işleme tekniği uygulanmıştır ve gedik tabanının erozyonu ve düşey erozyon alanı incelenmiştir. Görüntü işleme tekniği ile elde edilen alan sonuçları Gauss alan hesabı yöntemi kullanılarak hesaplanan alan değerleri ile karşılaştırılmıştır. Ortalama erozyon derinliği, düşey erozyon alanı ve yaklaşık gedik hacmi hesaplanmış, daha sonra literatürde sunulan ampirik denklemler elde edilen deneysel bulgular ile test edilmiştir.
Abstract: Piping is a significant and complex problem which threatens the stability of the earth-fill dams. Currently, there is no general formula to describe the erosion process due to the complex characteristics of piping. In the scope of this study, the development of piping due to seepage in the upper corner of the earth-fill dam body was investigated experimentally. A dam consisting of 85% sand and 15% clay with a height of 0.6 m, a bottom width of 2 m and a crest width of 0.20 m was built in a flume 1 m wide, 0.81 m high and 6.14 m long. The water level was kept constant by an electronic sensor. The flow rate was measured by a magnetic flowmeter. The temporal evolution of the breach has been recorded with advanced cameras that can also be viewed remotely. Image processing technique was applied to monitor the erosion process, and then the bottom erosion line of the breach and the vertical erosion area were determined. The area values achieved by image processing technique was compared with those calculated by Gauss area calculation method. Average depth of erosion, vertical erosion area and approximate breach volumes were calculated, and then the experimental findings were compared with numerical results obtained from the empirical equations available in the literature.
One of the principal side effects of wildland fire extreme events is mass soil erosion event of the soil and slopes denuded by the fire. These soil erosion events may be devastating and extreme in their own rights, damaging critical infrastructure downslope or downstream of the fire burn scars. While there are many variables influencing the severity of post fire erosion, the amounts of soil erosion are largely dependent on the water content of the soil at the time of the fire coupled with the fire intensity. Fires that are lower intensity or soils that are "wet" at time of burning have significantly less damage to root structures of grasses and other plants while showing lessened soil erosion potential. Fires that are higher intensity or on dry soils have higher damages to root structures and increased soil erosion potential. In this laboratory study, a single clayey sand soil material common to the ground surface across the Black Hills of South Dakota and Wyoming is studied for erosion potential after burning in a controlled container burn. This material is varied by initial water content and burned at a soil surface temperature of 800 Celsius for 75 minutes, a temperature-time continuum consistent with severe wildland fire. Burning is used rather than kilns to preserve the same atmospheric conditions as in the field fire event. A laboratory soil-erosion device is then used to measure soil erosion potential across a range of fluid velocities and soil slopes. The results of this study show that the initial water content of the soil at the time of fire is a key parameter in understanding soil erosion potential post-fire. While not a complete study on time-temperature-water content across many soil types, this pilot research shows promise for future models and mapping tools. These future tools will enable planners to target resources for post wildfire erosion mitigation based on surficial soil water content at the time of the fire.
This manuscript presents the results of research conducted in the context of the assessment of Flood Protection Infrastructure (FPI) against the progressive evolution of internal damage caused by erosion mechanisms, with emphasis on Backward Erosion Piping (BEP) induced failures. A novel approach, encompassing both deterministic physics-based numerical simulations and probabilistic data-based techniques, is presented and validated through experimental data obtained at multiple length scales. The deterministic simulations are used to train a multilayer machine learning model that is capable of quantifying the state of the infrastructure in quasi-real-time and is inherently capable of accepting live data from embedded and remote sensors. The significant reduction in computational cost obtained through the adoption of ML techniques allows for the investigation of the hyperparameters space in an efficient fashion, allowing for meaningful sensitivity analyses and physics discovery. The results of a projected real-life case study are reported, where a selected FPI system is simulated at the system scale ( m) over a period of one year, and conclusions are drawn on the capabilities of the proposed model.
The purpose of this study is to conduct hole erosion tests (HETs) to better understand the progression of concentrated leaks in compacted soils. While samples with high levels of compaction have been extensively tested for their erosion characteristics in the literature, soils at lower compaction levels have not yet been extensively assessed. This study aims to better understand the internal erosion behaviours of low-compacted soils during the progression of concentrated leaks. To this end, compaction tests are performed on various mixtures of Sydney sand and kaolin clay samples at different compaction moisture contents (i.e. moisture content at the time of compaction) and compaction efforts. Optimum moisture contents for different compaction efforts are subsequently determined. Samples for the HET are then prepared at various compaction densities and moisture contents to obtain their rate of erosion due to concentrated leaks. Results from testing show that if appropriate moisture contents are used, low-compacted samples do not necessarily show higher erodibility potential. The results can help in the determination of the most cost-effective, yet stable, materials for use in practice, for example in the core of embankment dams.
The aim of this study is to develop a method to simulate the behaviors of clayey gravel during water erosion by using computational fluid dynamics–discrete element method. The fluid phase was solved using the “fixed coarse-grid” scheme based on Navier–Stokes equations, and the solid phase was described by an assemblage of discontinuous particles in the Particle Flow Code in three dimensions (PFC3D) modeling framework. A fictitious clay method was introduced, in which the suffosion of clay matrix was translated to the strength degradation of bond according to a degradation law. The degradation law was embedded into PFC3D by the development of additional code in the Python language. The method was first validated by comparing with experimental results. Then, a parametric study was carried out to investigate the influence of three different factors, particle-size distribution (PSD), soil porosity, and pressure gradient, on the erosion behavior of soil. Results show that the proposed model offers a promising method to predict the erosion behavior of clay soil at the particle level. The numerical results generally match the empirical criteria, for example, it demonstrates that the initiation of the erosion process is significantly influenced by material properties (PSD, porosity) and loading condition (hydraulic gradient), and also reveals clearly defined critical levels for the three parameters, below which through-piping cannot be expected.
Loss of fine particles or suffusion in soils induced by seepage is an important problem that may cause dam or dike failures. This paper aims to study the evolution mechanisms of suffusion in gap-graded sandy gravels using coupled computational fluid dynamics and discrete-element method (CFD-DEM). In the simulation, five groups of sandy gravel including four groups of gap-graded sandy gravel and a benchmark linearly graded sandy gravel were studied. Changes in flow rate, evolution of porosity in different layers, and spatial and temporal redistributions of particles in the samples during suffusion under upward seepage were studied. Simulation results show that when the fine particle content is the same, the total fine erosion ratio is larger when the stability index (H/F)min of the gap-graded sandy gravel is lower. The porosities of five layers of the gap-graded sandy gravel change continuously with infiltration time. A slight decrease in the fine grain content appears in the upper layers, while a sharp reduction in the fine grain content occurs in the bottom layer. The study provides a mechanics basis for the prediction and prevention of suffusion in gap-graded sandy gravels.
Test results on the suffusion of sand-rock mixtures (SRMs) in one-dimensional laboratory seepage tests are reported with details regarding the experimental setup and procedures. The nuclear magnetic resonance (NMR) systems were successfully applied to track fine-particle migration through pores and detect the pore size distribution of SRMs during suffusion. This article discussed the changes of pore size distribution and fine-particle migration and its effect on the suffusion mechanism at 0, 15, 30, 60, 90, and 120 min under the critical hydraulic gradient. Then, the mesostructural changes of mixtures—such as pore distribution, curvature coefficient, and pore fractal dimension—were analyzed to reveal the suffusion mechanism, and an original suffusion evaluation model was proposed. The results showed that the pore connectivity and fine-particle migrations as two controlling factors for suffusion are an interactive process. Furthermore, the pore size range was narrowed and mostly concentrated in large pores with an increase of pore volume, resulting in fine-particle migration and structural deterioration. Moreover, the suffusion evaluation model was divided into four stages by the mesostructural parameters variation.
This article presents a novel multiscale modeling approach to simulate the evolution of the backward erosion piping (BEP) process in flood protection systems (FPSs). A multiphase description of the BEP phenomenon is proposed for the numerical solution at the local scale and validated by means of full‐scale experimental results available in the literature. Results of the local scale simulations are used as the training set for a multilayer machine learning (ML) model to bridge the information between the local and system scales. Accuracy of the trained ML algorithms is demonstrated by comparing results obtained from detailed physics‐based numerical models. The novelty of the proposed methodology lies in its capability of real‐time predictions of the overall response at the system scale. A case study is presented where a portion of the Nashville Metro Levee System is analyzed over the span of a year, to assess the likelihood of BEP in the infrastructure. The capability of the model to accept water height data obtained from field measurements is exploited in the numerical simulations.
The problem of dam failures is of great importance as it has devastating impact upon humankind and the environment. This review highlights the hydraulic failure of earthen dams and embankments, emphasizing on the piping and overtopping phenomena. Piping failures are mostly attributed to the uncontrolled seepage or the absence of suitable zonation of materials and filters in earthen dams. The overtopping process is a complex unsteady, nonhomogeneous, nonlinear three-dimensional problem, which has not yet been methodically studied from a theoretical perspective. With the advancement of time and technology, different mathematical, analytical and numerical models, aptly supported by physical modeling, has led to the better understanding of these phenomena. Although these approaches have facilitated the evaluation of seepage and deformation in the earthen dams and embankments, still several critical issues need to be addressed. This review highlights the gap areas and possible future scopes related to the hydraulic failures of dams.
Internal erosion, also known as piping, is one of the major causes of earth dam failures. Piping occurs when flowing water transports soil particles out of the structure of the dam creating a hole within the embankment. According to the U.S. Department of the Interior Bureau of Reclamation almost 30% of dam failures are due to piping. Lebanon, a developing country, also has its share of dam failure. Recently, two earth dams failed in Laqlouq area, Lebanon, due to erosion causing a massive inundation. No systematic studies have been conducted to provide better insight on piping evolution/failure in Lebanon. Plaxis 2D, a commercial finite element software, was used to model one of the sustained earth dams in Laqlouq area. The aim of this study is to show the piping evolution using an iterative approach within the body of the structure. Soil properties (i.e., permeability, strength, density) were determined in the laboratory using ASTM standard methods. Disturbed soil samples were collected from the earth dam. 2D model of the dam was created and the initiation of piping was determined based on the hydraulic gradient “i” versus the critical hydraulic gradient “icr”. Piping was identified at the location where the hydraulic gradient was greater than the critical hydraulic gradient. Findings showed that the current dam is susceptible to internal erosion, triggering the formation of a pipe and failure.
This manuscript provides a novel random lattice model to simulate the progressive degradation of soil embankments induced by the backward erosion piping (BEP) phenomenon. The progressive evolution of the piping process is described by expressing apparent diffusivity of the soil as a function of the local hydraulic gradient. In order to accurately compute local field gradients, a dual lattice approach that evaluates the response on both Delaunay and Voronoi nodes is formulated. The response computed at the Delaunay nodes is then employed to augment field gradient computation on the Voronoi grid. The proposed dual lattice model is numerically verified and validated by comparing numerical results with BEP experiments available in the literature.
The issues of landslide dam and dam break are the focus of current research. Landslide dam is remarkably different from man-made earth-rockfill dam because of its special formation process,inhomogeneous material composition,complex internal structure and various geometrical shapes. Currently,there is still lack of in-depth research in the analysis of entire lifecycle and the reliable method to assess rapidly the stability of landslide dam. On the basis of systematical reviews of the forming conditions,stability analysis methods,overtopping and piping collapse mechanisms,dam break floods and geological disaster chain of landslide dams,a database which contains 1 328 cases of landslide dams is built according to the bibliography compilation. Then,the triggering factors,causes,volumes distribution,morphological characteristics and lifetime of landslide dams,and the relationships between them are analyzed. According to the principle of logistic regression,a prediction model with three parameters,the length and width of landslide dam and the reservoir capacity of barrier lake,is established,and a method to rapidly evaluate the stability of landslide dam is proposed. Finally,from the perspective of disaster chain,the main problems existing in current research and the future key development directions of the whole process of river-blocking disaster are pointed out. The research results indicate that the volumes,lifetime and stability of landslide dam are closely related to the triggering factors and causes of landslide dam. The three-parameter rapid assessment method predicts the stability of landslide dam accurately. The process simulation of the whole lifecycle and development of disaster warning system for landslide dam are the key development directions in the future.
Piping is considered as an important failure mechanism for water retaining structures in the Netherlands. A recently performed study on the safety of Dutch levees raised some doubts with respect to the validity of the current calculation model. A large research program has therefore started to investigate the process of piping in more detail. After laboratory experiments and desk studies, the model was validated in a full-scale experiment (seepage length 15 m). This paper describes the piping process as observed in this experiment. Different phases were found: seepage, retrograde erosion, widening of the channel and failure. Once sand craters were formed, stabilization of sand transport was not observed, although quantities of transported sand were very low. Ongoing erosion resulted in a piping channel from the downstream to the upstream side in a few days. Widening of the channel due to continued erosion finally resulted in significant deformation and failure of the levee.
The mechanical characteristics of earth dams and levees, such as settlement, permeability, and strength, can be affected by internal erosion in the forms of piping and suffusion. This paper reports a preliminary experimental study on the changing mechanical characteristics (permeability, consolidation) with the progression of suffusion of a sandy soil. The internal erosion tests are conducted using a triaxial apparatus. The pedestal of the triaxial cell is modified to allow seepage and eroded soil particles to exit the specimen into an effluent tank. The seepage is induced in the specimen by controlled constant hydraulic gradient. The eroded soils are collected in the effluent tank so that the erosion rate and extent can be measured. Variations of the specimen's permeability and volume during the erosion are recorded. With approximately 5.5% fines in the sand, the test suggests that suffusion can occur and cause soil settlement. Suffusion of finer particles may also clog the downstream soil layer and results in permeability reduction. Suffusion and volume reduction gradually diminish relatively quickly to an un-measurable level after 4hr of seepage through the soil under a hydraulic gradient of approximately 20.
The piping flow erosion process, involving the enlargment of a continuous tunnel between upstream and downstream, is a major cause of water retaining structures. Such a pipe can be imputed to roots or burrows. The coefficient of erosion must be known in order to estimate the remaining time to failure and to downstream flood. The Hole Erosion test is a laboratory experiment especially suited to estimate a priori this geotechnical parameter. We propose therefore simplified expressions for the remaining time to breaching accounting for this erosion parameter. We established that the radius evolution of the pipe follows a two-parameters scaling law. The first parameter is the critical stress. The second parameter is the characteristic time of piping erosion, which is a function of the initial hydraulic gradient and the coefficient of erosion. We establish here new mechanically based relations for water retaining structures. The time to failure and the peak flow are related to the two basic parameters of piping failure: the coefficient of erosion, and the maximum pipe diameter prior to roof collapse and breaching. Orders of magnitude of the coefficient of erosion and the erosion rate are finally inferred from 18 case studies.
Within hydraulic earth structures (dikes, levees, or dams), internal seepage flows can generate the entrainment of the soil grains. Grain transportation affects both particle size distributions and porosity, and changes the mechanical and hydraulic characteristics of the earth's structure. The occurrence of failures in new earth structures due to internal erosion demonstrates the urgency of improving our knowledge of these phenomena of erosion. With this intention, a new experimental device has been developed that can apply hydraulic stresses to reconstituted consolidated cohesive soils without cracks in order to characterize the erosion evolution processes that might be present. A parametric study was conducted to examine the influence of three critical parameters on clay and sand erosion mechanisms. When the hydraulic gradient was low, it was concluded that the erosion of the structure's clay fraction was due to suffusion. When the hydraulic gradient increased, it was concluded that the sand fraction erosion initiation was due to backward erosion. The extent of the erosion was dependent on the clay content. The study underlines the complexity of confinement stress effects on both erosion phenomena.
The failure of natural dam may occur with a variety of failure modes
which includes overtopping, seepage or piping, sudden sliding etc.
Natural dams may fail due to seepage or piping because they have not
undergone systematic compaction and they may have high porosities.
In-depth knowledge of the mechanism of the dam failures by seepage or
piping and measured data are still lacking. Extensive laboratory
experiments are carried out to study enlargement of the pipe due to
internal erosion and resulting outflow hydrographs by varying size of
initial pipe, lake water level, lake water volume, slope and location of
the pipe. This paper highlights limitations of simplified models used to
predict outflow hydrograph due to piping failure of the dam based on
experimental results and provides data set for the validation of
numerical model. Experimental results show that the initial size, slope
and location of pipes have significant effects on magnitude and
occurrence time of peak discharge.
Research conducted over the past few years has led to a greater understanding of the overall breach process of overtopped
embankment dams. This increased understanding allows the development of computational models that better reflect the complex physical action observed during embankment dam breach. One approach to quantification of the complex erosive action associated with an embankment breach is to link simplified component models such that the dominant processes are properly represented for the various stages or phases of the overall breach process. Application of this approach has resulted in the development of a SIMplified Breach Analysis computer model (SIMBA) that is capable of reproducing the key features of breaches observed at various scales in the indoor and outdoor laboratory. In its present form, the model addresses only homogeneous embankment conditions. The model is presently research oriented, but work is underway to incorporate it into a dam overtopping analysis routine for application to field conditions. This application model is structured to allow consideration of non-homogeneous conditions and associated alternate failure scenarios
in future versions. This report describes the SIMBA model and the underlying component models in terms of the observed breach processes for earth embankments and spillways. The interrelation of the various failure stages or phases represented by the component models is discussed. A companion report discusses the ability of the model to reproduce the results of embankment breach tests.
A soil parameter is developed based on concepts from local scour studies of non-cohesive and cohesive soils and the results of a site-specific submerged jet testing device. Submerged jet test results on four soils with a range of physical conditions are analyzed. The submerged jet had a nozzle diameter of 13 mm, and was set at a jet height of 0.22 m prior to testing the soil. The soils were tested over a range of jet velocities at the nozzle of 166 cm/s to 731 cm/s. The results indicate that erosion, expressed as the depth of scour divided by time, in the site-specific submerged jet testing device may be related to the jet velocity, a time function, and a soil parameter (jet index, Ji). The jet index is intended to provide a common method of expressing erosion resistance, to assist those who work with different soils and soil conditions for measurement and design, and possibly to develop performance and prediction relationships for earthen spillways.
Internal erosion involves selective loss of fine particles within the matrix of coarse soil particles under seepage flow, which affects the hydraulic and mechanical behavior of the soil. In this research, extensive laboratory internal erosion tests were conducted under complex stress states following three stress paths: isotropic, drained triaxial compression, and triaxial extension stress paths. These tests were designed to investigate the initiation and development of internal erosion and the effect of stress state on critical hydraulic gradients. The entire erosion process can be divided into four phases: stable, initiation, development, and failure. Accordingly, three critical gradients termed as initiation, skeleton-deformation, and failure hydraulic gradients, can be defined. These critical gradients correspond to the onset of erosion of the fine particles filling the large pores of the skeleton, the buckling of the strong force chains formed by the coarse particles, and the soil failure, re-spectively. The initiation gradient under compression stress conditions generally increases with the shear stress ratio first and then decreases when the stress conditions approach failure. The tests under isotropic stress conditions show the largest initiation and skeleton-deformation gradients at the same porosity. DOI: 10.1061/(ASCE)GT.1943-5606.0000871. © 2013 American Society of Civil Engineers.
Erosion rates of unsaturated compacted Na‐montmorillonite clays are measured under a range of tractive stresses from surface flows in a rectangular flume. The degree of saturation of compacted samples ranges from 0.52–0.97. The Na‐montmorillonite (Volclay bentonite) is mixed with ground silica to obtain samples with various percentages of clay. Samples of 100, 70, 40, and 10% clay content by dry weight are tested. Samples are compacted under 700 Pa into sample containers with 160‐cm2 surface area and are subjected to flowing water in the flume. The results of the study show that the erosion rate of Na‐montmorillonite soil samples increases when clay content decreases and is independent of compaction water content. The relationship between erosion rate and tractive stress is linear for all Na‐montmorillonite samples. For the range of water content tested, an empirical relationship is developed to estimate the erosion rate of compacted Na‐montmorillonite clays as a function of percent clay content and tractive stress.
A process called “piping”, which often occurs in water-retaining structures (earth-dams, dykes, levees), involving the formation and progression of a continuous tunnel between the upstream and downstream sides, is one of the main cause of structure failure. Starting with the diphasic flow volume equations and the jump equations including the erosion processes, a simplified one-dimensional model for two-phase piping flow erosion was developed. The numerical simulation based on constant input and output pressures showed that the particle concentration can be a significant factor at the very beginning of the process, resulting in the enlargement of the hole at the exit. However, it was concluded that this influence is a secondary factor: the dilute flow assumption, which considerably simplifies the description, is relevant here. To cite this article: D. Lachouette et al., C. R. Mecanique 336 (2008).
The purpose of this paper is to assess the difference between surface and internal erosion processes using results from flow pump tests. Samples of 70% Ottawa sand + 30% kaolinite mixture were used with distilled water and NaCl solutions as permeants. Two kinds of tests were conducted, a surface erosion test where the permeant was pumped through a cylindrical hole of 7-mm diameter and an internal erosion test where the permeant was pumped through intact compacted samples in compaction permeameters. A simple capillary tube model was used to estimate the critical shear stresses needed to cause erosion in surface erosion experiments. It was found that although surface erosion critical shear stresses were exceeded in the intact soil samples, particle clogging in the pores and redeposition of eroded particles prevented mobilization of particles into the effluent stream. Erosion rates estimated using surface erosion parameters were significantly greater than those observed in internal erosion experiments. The results suggest that the fate of eroded particles, including particle redeposition and pore clogging, may govern the internal erosion process far more than the surface erodibility of the soil.
The IMPACT project addressed the assessment and reduction of risks from extreme flooding caused by natural events or the failure of dams and flood defence structures. It was funded by the European Commission (EC) and started in November 2001 and lasted for 3 years. The project framework was divided into five work packages. Three of these addressed specific flood processes (WP2–WP4), whilst the fourth and the fifth considered the uncertainty associated with these processes (WP5) and techniques to monitor behaviour of embankments and collect field data (WP6). This document gives an overview of the field and laboratory experiments undertaken as a part of Work Package 2 (WP2): Breach Formation under the IMPACT project.
Computer programs developed for dam safety analyses are limited by the accuracy of the input data for the geometric and temporal dam breach characteristics. Data on a number of historical dam failures were collected and analyzed and graphical relationships for predicting breach characteristics were developed for erosion type breaches. The data provides a basis for selecting a breach shape and calculating the breach size and the time for breach development. A relationship is also developed for estimating peak outflows from dam failures. This relationship can be used to verify the methodology and the results of dam safety studies.
The slot erosion test and the hole erosion test have been developed to study the erosion characteristics of soil in cracks in embankment dams. The erosion characteristics are described by the erosion rate index, which measures the rate of erosion, and the critical shear stress, which represents the minimum shear stress when erosion starts. Values of the erosion rate index span from 0 to 6, indicating that soils can differ in their rates of erosion by up to 106 times. The rate of erosion is shown to be dependent on the soil fines and clay sized content, plasticity, and dispersivity; compaction water content, density and degree of saturation; and clay mineralogy, and possibly the presence of cementing materials such as iron oxides. Coarse-grained, noncohesive soils, in general, erode more rapidly and have lower critical shear stresses than fine-grained soils. Knowledge of the erosion characteristics of the soil in the core of an embankment dam aids in the assessment of the likelihood of dam failure due to piping erosion.
The current design practice for filters in earth and rock fill dams is an outgrowth of a well known concept proposed by Terzaghi. The main effect of amplifications that investigators have added to the Terzaghi criteria is to permit the use of widely graded sand-gravel mixtures as filter materials. The use of these criteria without consideration of the erodibility characteristics of the core material and crack potential of the filter has caused near failure and total failure of several dams. A new method is presented for quantifying the erodibility of soils based on the use of critical shear stress, TC, developed due to hydraulic flow in the cracked zone of a dam. The limitation of the classification proposed for evaluating erosion from a knowledge of Atterberg limits of soils is considered. A direct correlation between the critical shear stress required to cause erosion and the piping failure of several dams whose filters were designed under the Terzaghi criteria, is presented. Core fines with TC values less than 4dynes/cm2 have been shown to be one of the contributing factors causing piping failure of dams. The need to correctly quantify erodibility and to carry out filtration tests using the eroded fines and proposed filter material is recommended for the safe design of protective filters. Research is necessary to determine the percent of fines less than #200 sieve size needed in a filter in order that it will retain fines which have been eroded and also so that it will not sustain a transverse crack.
The erosion of clayey soils is a complex phenomenon that includes various types of erosive actions. A tentative classification of erosion processes is proposed. This paper concentrates on the scour resistance of solid clays. Available prediction methods are reviewed. Generally they propose relationships between physical or mechanical parameters and the critical hydraulic shear stress, c, that defines a boundary between "no erosion" and "erosion". It became apparent that the physicochemical parameters of both the clay and the eroding water control the erosion process. However, subsequent studies on these parameters have yet to yield reliable predictions of natural clay erodibility from indirect measurements. An erosion testing program was therefore performed on three Quebec clays with the improved rotating cylinder technique. In this test, intact or remolded samples can be tested, physicochemical parameters can be controlled, and the hydraulic shear stress and the erosion rate ė can be adequately determined. A relatively complete and accurate graph of ė versus , including ė values for values lower than critical can be established. Previous and present research underline the need to exert a strict control of all clay and water parameters, including that of sample preparation, in order to adequately simulate a field problem. Key words: erosion, clay, scour resistance, physicochemical properties, rotating cylinder test.
The methods developed to predict the action of eroding fluid on cohesive soils lead to contradictory predictions. Most of them are questionable since they ignore the physicochemical parameters that seem to control the erosion process. In order to study the scour resistance of intact or remolded cohesive soils, a rotating cylinder technique allowing for the control of essential parameters was recently improved by the authors. Intact or remolded samples can be used. The water quality is controlled in order to respect the in situ physicochemical conditions. The shear stress transmitted by water to the clay surface is directly and accurately derived. The dry weight of eroded material per unit time and unit area, for given conditions, is also directly and adequately measured. The influence of water quality, or of any treatment of the clay, may be quantitatively analyzed. Key words: erosion, scour, clay, rotating cylinder, viscometry, physical chemistry, river channels.
The paper describes the results of a statistical analysis of failures and accidents of embankment dams, specifically concentrating on those incidents involving piping and slope instability. The compilation of dam incidents includes details on the characteristics of the dams, including dam zoning, filters, core soil types, compaction, foundation cutoff, and foundation geology. An assessment of the characteristics of the world population of dams was also carried out. By comparing the characteristics of the dams which have experienced failures and accidents to those of the population of dams, it was possible to assess the relative influence of particular factors on the likelihood of piping and slope instability.Key words: dams, failures, piping, instability database.
A piping model based on Darcy's law is developed. An analysis of data pertaining to different soil particle sizes and varying porosity shows that the choice of the permeability function is critical for the piping model. The permeability relations, which depend only on the grain size, are of limited value.
Current methods available for testing the piping potential of soils in dams (pinhole test, hole erosion test, and slot erosion test) are limited to cohesive soils that maintain an open hole within the sample. These tests do not adequately simulate conditions within a zoned embankment, where zones of non-cohesive materials are present under relatively high confining stresses. A new apparatus, called true triaxial piping test apparatus or TTPTA, was developed for testing a wider variety of soils under a wider range of confining stresses, hydraulic gradients, and pore pressures than current tests allow. The TTPTA is capable of applying a range of confining stresses along three mutually perpendicular axes in a true triaxial test apparatus. Pore pressures are also controlled through regulated inlet and outlet pressures. The test determines the critical hydraulic gradient and, more importantly, the critical hydraulic velocity at which piping is initiated in non-cohesive soils. Detailed descriptions of the test apparatus and test method are presented, as are initial test results using TTPTA. Three sets of initial tests were conducted using uniform sand to (1) assess the repeatability of test results, (2) evaluate how the rate of change of inflow impacts the critical discharge rate at which piping is initiated, and (3) evaluate how the angle of seepage affects the critical velocity for piping initiation. These initial tests were conducted to evaluate the method and to help set test parameters for future testing. It is found that the TTPTA is capable of yielding fairly consistent results with 10 % scatter in repeat tests. The seepage angle tests demonstrate that the angle between seepage flow direction and the direction of gravity is an important factor to consider when evaluating piping potential. The rate of change in seepage also has a minor influence on test results, but a change in flow rate of 5 (mL/min)/min could produce reliable results. Based on the results, the hydraulic gradient is found to be a less reliable indicator of piping potential than the hydraulic velocity for non-cohesive soils. The TTPTA is capable of simulating conditions within small to medium sized embankments.
Erodibility characteristics of embankment materials
- G J Hanson
- T L Wahl
- D Temple
- D Hunt
- R Tejral
Hanson, G. J., Wahl, T. L., Temple, D., Hunt, D., and Tejral, R. (2010).
"Erodibility characteristics of embankment materials." ASDSO 2010
Annual Conf., Seattle.
Analysis of crack erosion in dam cores: The crack erosion test Em
- E Maranha Das Neves
Maranha das Neves, E. (1989). "Analysis of crack erosion in dam cores:
The crack erosion test Em." De Mello Volume: Attribute to Prof. Dr.
Victor F. B. de Mello, Sao Paulo, Brazil, 284-298.
Physical modeling of breach formation: Large scale field tests
- K A Vaskinn
- A Løvoll
- K Höeg
- M Morris
- G Hanson
- M A Hassan
- Phoenix
- C Wan
- R Fell
Vaskinn, K. A., Løvoll, A., Höeg, K., Morris, M., Hanson, G., and Hassan,
M. A. (2004). "Physical modeling of breach formation: Large scale field
tests." Dam Safety, Association of State Dam Safety Officials, Phoenix.
Wan, C., and Fell, R. (2004). "Investigation of rate of erosion of soils in
embankment dams." J. Geotech. Geoenviron. Eng., 10.1061/(ASCE)
1090-0241(2004)130:4(373), 373-380.
Discussion of "breaching characteristics of dam failures
- M Houston
Houston, M. (1985). "Discussion of "breaching characteristics of dam failures" by Thomas C. Macdonald and Jennifer Langridge-Monopolis
(May, 1984)." J. Hydraul. Eng., 10.1061/(ASCE)0733-9429(1985)
111:7(1125), 1125-1129.
The Teton dam failure: A retrospective review
- H B Seed
- J M Duncan
Seed, H. B., and Duncan, J. M. (1981). "The Teton dam failure: A retrospective review." Proc., 10th Int. Conf. on Soil Mechanics and Foundation Engineering, Balkema, Rotterdam, Netherlands, 219-238.
Geological Survey Open-File Rep
- J E Costa
Physical modeling of breach formation: Large scale field tests.” Dam Safety Association of State Dam Safety Officials Phoenix
- K A Vaskinn
- A Løvoll
- K Höeg
- M Morris
- G Hanson
- M A Hassan