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In the present study, performance of geosynthetic reinforced MSE walls backfilled with locally available marginal lateritic soil at the onset of rainfall infiltration was investigated. Two different types of geosynthetics reinforcements were used. One was a conventional type of geogrids usually used in MSE walls, and the other was composite geogrids. Seepage analysis, stability analysis and strength and deformation analysis were carried out on MSE walls with rainfall simulated for a duration of 3 days. In case of geogrid reinforced soil wall (GR-W), the suction within the backfill was lost completely at the end of 2.176 days of rainfall, whereas suction was maintained even at the end of 3 days of rainfall in walls reinforced with composite geogrids (CGR-W). From the stability analysis, it was observed that the factor of safety of GR-W decreased at the onset of rainfall infiltration with time and reached less than the desirable value of less than 1.5 in 2.125 days of rainfall. The factor of safety of CGR-W was maintained at 1.88 throughout the period of rainfall. The facing deformation in GR-W was found to increase, with a maximum of 3.2 times increase at the end of three days of rainfall. Similarly, there was an increase in maximum tensile load mobilized in the reinforcements in GR-W, whereas in the case of CGR-W, the influence of rainfall was negligible. From the present study, it can be concluded that the presence of composite geogrids improves the overall performance of MSE walls backfilled with marginal lateritic backfills.
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International Journal of Geosynthetics and Ground Engineering (2021) 7:9
https://doi.org/10.1007/s40891-020-00253-8
ORIGINAL PAPER
Performance ofGeosynthetic Reinforced MSE Walls withMarginal
Backfills attheOnset ofRainfall Infiltration
S.Vibha1· P.V.Divya1
Received: 9 August 2020 / Accepted: 26 December 2020 / Published online: 16 January 2021
© The Author(s), under exclusive licence to Springer Nature Switzerland AG part of Springer Nature 2021
Abstract
In the present study, performance of geosynthetic reinforced MSE walls backfilled with locally available marginal lateritic
soil at the onset of rainfall infiltration was investigated. Two different types of geosynthetics reinforcements were used. One
was a conventional type of geogrids usually used in MSE walls, and the other was composite geogrids. Seepage analysis,
stability analysis and strength and deformation analysis were carried out on MSE walls with rainfall simulated for a duration
of 3days. In case of geogrid reinforced soil wall (GR-W), the suction within the backfill was lost completely at the end of
2.176days of rainfall, whereas suction was maintained even at the end of 3days of rainfall in walls reinforced with composite
geogrids (CGR-W). From the stability analysis, it was observed that the factor of safety of GR-W decreased at the onset of
rainfall infiltration with time and reached less than the desirable value of less than 1.5 in 2.125days of rainfall. The factor
of safety of CGR-W was maintained at 1.88 throughout the period of rainfall. The facing deformation in GR-W was found
to increase, with a maximum of 3.2 times increase at the end of three days of rainfall. Similarly, there was an increase in
maximum tensile load mobilized in the reinforcements in GR-W, whereas in the case of CGR-W, the influence of rainfall
was negligible. From the present study, it can be concluded that the presence of composite geogrids improves the overall
performance of MSE walls backfilled with marginal lateritic backfills.
Keywords Geosynthetics· Reinforced soils· MSE wall· Marginal lateritic backfill· Rainfall
Introduction
Mechanically stabilized earth structures (MSE) or reinforced
soil structures have become very popular in enhancing the
stability of soil structures. Often, reinforced soil structures
are used for the construction of approach ways for flyovers
and slope stabilization works. Ideally, freely draining granu-
lar soils such as sand are used as backfill of MSE walls. An
ideal backfill soil ensures proper drainage and load transfer
between the reinforcements and the soil. Reinforced soil
structures require a huge quantity of backfill soil. Backfill
constitutes to about 50–75% of total cost of the wall [1].
FHWA recommends soil with less than 15% fines (pass-
ing through 75µ sieve) and plasticity index less than 6,
as the ideal backfill material for reinforced soil structures
[2]. However, the scarcity of such ideal backfill material
has increased the tendency to use locally available soil in
reinforced soil applications. Any soil which does not meet
the requirements of an ideal backfill material is termed as
marginal backfill soil [3, 4].
The role of rainfall in triggering the failures in geotech-
nical structures is widely recognized. The pores in soil are
partially filled with water and remains unsaturated in the
region above the ground water table [5]. Rainwater infil-
tration and associated fluctuations in the pore water pres-
sure and shear strength are influenced by the unsaturated
soil properties. The stability of residual soil slopes during
rainwater infiltration is greatly influenced by the mechani-
cal and hydraulic behavior of unsaturated soils [69]. In the
case of unsaturated soils, both volumetric water content and
the co-efficient of permeability are significantly affected by
the combined changes in matric suction and void ratio [10].
Unlike saturated soils, the stress state in unsaturated soils are
expressed in terms of two independent stress state variables,
net normal stress (σua) and matric suction (ua−uw) [11].
The shear strength of unsaturated soil is given by extended
Mohr–Coulomb criteria [12] as shown in Eq.1:
* P. V. Divya
divyapv@iitpkd.ac.in; divya.pv.nair@gmail.com
1 Department ofCivil Engineering, Indian Institute
ofTechnology Palakkad, Palakkad, Kerala, India
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... This geosynthetic material is a geocomposite of a geogrid combined to a nonwoven geotextile. Many authors demonstrated the efficiency of this type of reinforcement to dissipate pore water pressure developed inside the reinforced zone (Portelinha et al., 2013, Bui Van et al. 2017, Portelinha and Zornberg, 2017, Yang et al., 2018, Razeghi et al., 2019, Bhattacherjee and Viswanadham 2019, Albino et al., 2020, Vibha and Divya, 2021, Yoo et al. 2022. Meanwhile, some of these authors the adverse capillary break effect on unsaturated soil-geosynthetic interfaces, halting the wetting front, and leading to positive PWP accumulated at the interface between the soil and the underlying geotextile. ...
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Geosynthetic-reinforced soil (GRS) walls using marginal soils can operate under unsaturated conditions depending on climate conditions and drainage inside the reinforced zone. Geocomposite reinforcements have been suggested to act as internal drainage layers, but their hydraulic behavior can also be strongly affected by climate conditions. Numerical analyses were conducted to observe the impact of four distinct tropical climate conditions (arid, semi-arid, humid subtropical and humid tropical) on suction profiles and stability of reinforced soil walls constructed using geogrid and geocomposite reinforcements. The climate simulation involved the incorporation of a soil-atmosphere interaction on water balance and on the unsaturated transient infiltration. Results indicate the GRS walls can operate under relatively high suction levels under arid climates in which cumulative evaporation overcomes infiltration. Any climate that has rainy seasons with consecutive rainfalls with intensities close to the infiltration capacity of soil and/or monthly cumulative precipitation higher than 200 mm/day led to critical conditions in terms of soil water saturation and stability. Under unsaturated conditions of soil, the drainage effectiveness of geocomposites is significantly reduced and adverse capillary break effects become critical.
... The geosynthetic has been considered as a premium geotechnical engineering material to build reinforcements [22,23]. The geotextile tube made of geotextile sheets can also be used for soil strengthening [24][25][26]. Tubes can be filled with tailings slurry through the hydraulic transport process [27]. After the slurry is consolidated, the geotextile tubes are accumulated to form a dam or other types of geotechnical structures. ...
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Geotextile tubes are one of the emerging and promising technologies to build fine-grain tailings dams. In this study, shaking table model tests are conducted to evaluate the seismic performance as characterized by horizontal acceleration and displacement of the tailings dam subject to horizontal peak ground accelerations (HPGAs). The test results indicate that the tailings dam is sustainable, whereas the whole dam tends to slide forward. Test results reveal a W-pattern variation of acceleration amplification coefficient (A m) at the same elevation despite different HPGA, whereas A m on the geotextile tubes exhibits minimal changes with increasing HPGA. A m inside the dam is highly variable in terms of the elevation and the specific position. The maximum vertical displacement occurs at the top of the geotextile tubes as the side of the geotextile tubes tilting upward. The highest horizontal displacement is observed in the middle section of the geotextile tubes, resulting in an overall convex deformation pattern. Two reinforcement schemes are proposed accordingly including strengthening the drainage and installing the anti-slide piles. The dynamic behaviors of the tailings dam subject to earthquakes from this study can serve as guidance for seismic design and technology promotion.
... In addition, the use of internal drainage materials (e.g. nonwoven geotextiles, geocomposites, sand cushions, chimney sand drains) are reported to be useful to keep high levels of soil suction and increase factors of safety of geosynthetic reinforced slopes (Balakrishnan and Viswanadham, 2019;Razeghi et al., 2019;Vibha and Divya, 2021). Hence, there arises the necessity to investigate the mechanical response of GMSE walls as rainwater infiltration progress into the reinforced zone, quantifying loads and strains related to suction induced by various rainfall intensities and patterns. ...
Article
A laboratory testing that simulates the mechanisms of a geosynthetic-reinforced layer was used to assess the impact of rainwater infiltration on reinforcement loads and strains in mechanically stabilized earth (MSE) walls. The testing device allows measuring loads transferred from a backfill soil subjected simultaneously to surcharge loading and controlled irrigation. Load-strain responses of geosynthetic-reinforced layers constructed with three different geosynthetics under a moderate rainfall are related to suction captured along the depth of reinforced layers. Results show infiltration leading to increases on strains and tensile loads mobilized by reinforcements. Rates of increases of both parameters were found to be dependent of global suction, geosynthetic stiffness and hydraulic properties. In addition, increases in water content at soil-geotextile interfaces due to capillary breaks also had a significant effect on mobilized loads. The loss of interaction due to the interface wetting was observed to affect the stress transference from soil to geosynthetic reinforcement. An approach suggested for calculation of lateral earth pressures in unsaturated GMSE walls under working stress conditions and subjected to rainfall infiltration demonstrated a reasonable agreement with experimental data.
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Chapter
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Chapter
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Conference Paper
Major part of Kerala is covered with lateritic soil. Lateritic soils, in general, can withstand high stress under unsaturated conditions. However, during rainfall infiltration, there is a tendency that the lateritic soil may undergo large and sudden deformation. In the recent past, Kerala experienced heavy rainfall induced distress. Associated with the rainfall event, a series of landslides and formation of cavities and subsidence of ground were observed in many parts of Kerala. Mechanically stabilised earth (MSE) structures such as reinforced soil walls and slopes can be used in landslide mitigation; especially in slide repair using the slide mass as the backfill. In the present study, soil was collected from a nearby site where landslide has occurred due to heavy rainfall. Experimental studies were conducted to study the collapse potential of the soil. An attempt was also made herein to investigate the deformation behaviour of geosynthetic reinforced soil slope resting on foundation soil subjected to rainfall induced subsidence.
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This paper presents a comprehensive failure investigation of a geosynthetic-reinforced soil (GRS) slope subjected to rainfall. The investigated slope is a 26-m high, four-tier, geogrid-reinforced structure backfilled with low plasticity silty clay that contains more than 60% of fines. The GRS slope first exhibited excessive deformation after typhoons and heavy rainfall from 2010 to 2012. The slope collapsed in 2013 due to two sequential typhoon events with a total accumulated rainfall of more than 600 mm. The slope failed in a compound failure mode in which the failure surface partially cut through the reinforced zone and partially passed along the interface between the weathered sandstone and intact shale. By using the recorded rainfall, site geology, and measured soil and reinforcement parameters, a series of coupled hydro-mechanical finite element analyses were performed on the basis of the unsaturated soil mechanics to examine the failure mechanism and factors triggering the slope failure. The numerical results indicated that the slope failure occurred due to the development of positive porewater pressure within the reinforced zone and retained weather sandstone layer. Observations and lessons learned from this case history are discussed and remedial measures to improve the overall slope stability are proposed and evaluated.
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Mechanically stabilized earth (MSE) walls reinforced by geogrids and geotextiles have seen a tremendous growth over the past thirty years. However, along with this growth has come numerous failures consisting of excessive deformation and, in some cases, actual collapse. Of the 82-cases in the authors data base, improper drainage control was the cause in 68% of them. As a result, this paper is focused on both internal drainage issues within the reinforced soil mass within the reinforced soil mass (46%) and external drainage issues around the soil mass (22%). After a brief introduction of the technology some elements of traditional design will be presented. The issue of proper versus improper methods of drainage control will then form the core of the paper. A summary and recommendations section aimed at preventing drainage problems in the future will conclude the paper.
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IntroductionVolume-Mass Constitutive RelationsEquations for SWCCRegression Analysis on SWCC EquationsHysteresis, Initialization, and Interpretation of SWCCPham and Fredlund (2011) Equation for Entire SWCCGitirana and Fredlund (2004) SWCCMeasurement of SWCC Using Pressure Plate DevicesSingle-Specimen Pressure Plate Devices for Geotechnical EngineeringVacuum Desiccators for High SuctionsUse of Chilled-Mirror or Dew-Point Method Estimation of SWCCTwo-Point Method of Estimating SWCCCorrelation of Fitting Parameters to Soil PropertiesApplication of SWCCGuidelines and Recommendations for Engineering Practice