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The determination of pre-consolidation load and its practical significance
... Meanwhile, Becker et al. [15] and Conte et al. [16] concluded that Casagrande's [17] method, illustrated in Figure 3, is relatively stronger in immunizing the effects of human subjectivity in the determination of pre-consolidation pressure P c . There are three major steps, introduced as follows, in Casagrande's [17] method for the determination of P c . ...
... Meanwhile, Becker et al. [15] and Conte et al. [16] concluded that Casagrande's [17] method, illustrated in Figure 3, is relatively stronger in immunizing the effects of human subjectivity in the determination of pre-consolidation pressure P c . There are three major steps, introduced as follows, in Casagrande's [17] method for the determination of P c . ...
... (2) Draw a horizontal line (I) and a tangent line (II) through this point, and determine the bisecting line (III) of these two lines; (3) Find the straight part in the high pressure range, and extend it so that line IV and line III cross each other. The pressure corresponding to the intersection (point B) of line III and line IV defines Pc. [17]. ...
Ground settlement resulting from consolidation may lead to tilted buildings, cracks in the pavement, damage to underground utilities, etc. Therefore, it is crucial to understand the consolidation behaviors (including primary consolidation and secondary compression) of the soil of the subgrade. There is a large amount of soft clay deposited in Nanjing, located in the Yangtze River Basin. The consolidation behavior of Nanjing soft clay can significantly affect foundation design and the cost of construction. In this study, experimental measurements of the consolidation behavior of Nanjing soft clay were conducted, and parameters (such as pre-consolidation pressure, secondary consolidation index and secondary consolidation ratio) related to consolidation were assessed. The concept of simulated over-consolidation ratio (OCRs) was proposed, and the close relationship between primary consolidation and secondary compression settlement and the OCRs of Nanjing clay was investigated.
... p ′ and σ v ′ stand for pre-consolidation pressure obtained in triaxial and oedometric devices. The subscripts C and B in these denote Casagrande (1936) and Becker et al. (1987) approaches. ...
... The decrease in compression index c c also indicated that the compressibility decreased and stiffness increased as the relative compaction increased. The pre-consolidation pressure was estimated for each compacted isotropic and oedometric sample following Casagrande (1936). In supplement to Casagrande's approach, the method of work proposed by Becker et al. (1987) was also employed to determine the pre-consolidation pressure (Figure 4). ...
... A summary of the pre-consolidation pressure values as determined at different relative degrees of compaction is given in Table 7. It is worthwhile to note here that at the same degree of compaction, the two curves (under isotropic and oedometric compression conditions) which started from identical specific volumes v showed close-ranging pre-consolidation pressures using Casagrande (1936) and Becker et al. (1987) approaches. Looking into the shapes of the compressibility curves, the WKA curves seemed 'flatter' compared to more 'rounded' curves for GKA and MA. ...
... The slope of the VCL is termed compression index, Cc; the slope of the SL is termed swelling index, Cs (A). Determination of precompression stress (σ pc ) according the Casagrande (1936) and Dias Junior and Pierce (1995) methods (B). Adapted from Keller et al. (2011). ...
... However, we held on to both papers if they provided complementary information. For studies that compared several methods to calculate soil precompression stress, we only collected the precompression stress data calculated by the Casagrande (1936) method, which is widely accepted and used as a standard method. ...
... The database comprised eight different methods for calculating precompression stress from the stress-strain curve ( Table 2). The methods described by Dias Junior and Pierce, (1995) and Casagrande (1936) were most commonly used, representing 52 % and 36 % of the data entries, respectively. The method described by Lamandé et al. (2017) showed the lowest number of data entries, but it is also the most recently published method. ...
Precompression stress, compression index, and swelling index are used for characterizing the compressive behavior of soils, and are essential soil properties for establishing decision support tools to reduce the risk of soil compaction. Because measurements are time-consuming, soil compressive properties are often derived through pedotransfer functions. This study aimed to develop a comprehensive database of soil compressive properties with additional information on basic soil properties, site characteristics, and methodological aspects sourced from peer-reviewed literature, and to develop random forest models for predicting precompression stress using various subsets of the database. Our analysis illustrates that soil compressive properties data primarily originate from a limited number of countries. There is a predominance of precompression stress data, while little data on compression index or recompression index are available. Most precompression stress data were derived from the topsoils of conventionally tilled arable fields, which is not compatible with knowledge that subsoil compaction is a serious problem. The data compilation unveiled considerable variations in soil compression test procedures and methods for calculating precompression stress across different studies, and a concentration of data at soil moisture conditions at or above field capacity. The random forest models exhibited unsatisfactory predictive performance although they performed better than previously developed models. Models showed slight improvement in predictive power when the underlying data were restricted to a specific precompression stress calculation method. Although our database offers broader coverage of precompression stress data than previous studies, the lack of standardization in methodological procedures complicates the development of predictive models based on combined datasets. Methodological standardization and/or functions to translate results between methodologies are needed to ensure consistency and enable data comparison, to develop robust models for precompression stress predictions. Moreover, data across a wider range of soil moisture conditions are needed to characterize soil mechanical properties as a function of soil moisture, similar to soil hydraulic functions, and to develop models to predict the parameters of such soil mechanical functions.
... According to Casagrande (1936), the use of log-transformed stress data in the identification of transition to plastic deformation was suggested by Terzaghi for fine-grained soils. Casagrande (1936) found the procedure to work well for undisturbed clay samples. ...
... According to Casagrande (1936), the use of log-transformed stress data in the identification of transition to plastic deformation was suggested by Terzaghi for fine-grained soils. Casagrande (1936) found the procedure to work well for undisturbed clay samples. Nevertheless, the literature referenced above show that the empirically based interpretation suggested by Casagrande (1936) is iteratively applied for agricultural soils of all textures, for top-as well as subsoils, and for undisturbed as well as remolded soil. ...
... Casagrande (1936) found the procedure to work well for undisturbed clay samples. Nevertheless, the literature referenced above show that the empirically based interpretation suggested by Casagrande (1936) is iteratively applied for agricultural soils of all textures, for top-as well as subsoils, and for undisturbed as well as remolded soil. Keller et al. (2011) demonstrated that the estimates of soil compression properties including Pc and their dependency upon soil density are partly a consequence of the use of log-transformed stress data. ...
Traditionally, soil strength is estimated from uniaxial, confined compression tests by procedures adopted from classical soil mechanics. The heterogeneity of agricultural topsoil calls for an alternative approach. Undisturbed soil cores were collected in the plough layer of 14 soils in arable agriculture. Soil texture ranged from coarse sandy to silty loam soils with a maximum of 20% clay. The samples were drained to either of six matric potentials in the range from -30 to -300 hPa. Uniaxial, confined compression was applied to ~800 kPa with strain-controlled stress application (1 mm min-1). Measured strain was fitted to stress by the Morgan-Mercer-Flodin (MMF) model. The model fitted data remarkably well for all samples. Three fitting parameters of the model reflected physical characteristics of soil reaction to stress. The estimates of soil compressibility calculated from the model at 10 kPa (C10) correlated closely and linearly to the Cs index considered to reflect elastic deformation in classical studies of soil compression tests. Soil bulk density and content of soil organic matter decreased C10 as well as compressibility at 100 (C100) and 400 kPa (C400). A complex pattern in the effects of soil texture and soil moisture on compressibility was revealed. The pattern in strain-stress data is interpreted as a reflection of a gradual transition from elastic to plastic deformation of the mixture of structural units. The MMF model is suggested for interpretation of strain-stress data from uniaxial, confined compression tests. This implies use of stress in a linear scale.
... This methodology resulted in OCRs of 2.5 and 4.8, respectively. However, preconsolidation stress can be difficult to determine when using one-dimensional consolidation tests on fine-grained soils, as demonstrated by the variety of preconsolidation methods available (e.g., Casagrande 1936;Schmertmann 1955;Becker et al. 1987). Due to this inherent uncertainty, the OCRs for the recompression specimens were also calculated from the available static DSS tests and by applying the SHANSEP relationship 0 ′ ⁄ = 0.25 * 0.8 . ...
... one-dimensional consolidation tests and theCasagrande (1936) preconsolidation method ...
... The volume change in sands is dominated by elastic (recoverable) deformation and the volume change in clays is dominated by inelastic (unrecoverable) deformation. The clays in an aquifer system are able to memorize the maximum effective overburden stress that the clays had sustained in its history, which is called pre-consolidation stress [57]. The hydraulic head in the aquifer system corresponding to the pre-consolidation stress is called the pre-consolidation head. ...
... The volume change in sands is dominated by elastic (recoverable) deformation and the volume change in clays is dominated by inelastic (unrecoverable) deformation. The clays in an aquifer system are able to memorize the maximum effective overburden stress that the clays had sustained in its history, which is called preconsolidation stress [57]. The hydraulic head in the aquifer system corresponding to the pre-consolidation stress is called the pre-consolidation head. ...
The South-to-North Water Diversion (SNWD) is a multi-decadal infrastructure project in China aimed at alleviating severe water shortages in north China. It has imposed broad social, economic, environmental, and ecological impacts since 2015, particularly in the Beijing-Tianjin metropolitan area. Sentinel-1A/B Interferometric Synthetic Aperture Radar (InSAR) (2014–2021), Global Positioning System (GPS) (2010–2021), and hydraulic-head data are used to assess the impacts on ongoing land subsidence in Tianjin in this study. Additionally, the Principal Component Analysis (PCA) is employed to highlight primary factors controlling the recent land subsidence. Our results show that the reduced groundwater pumping has slowed down the overall subsidence since 2019 due to SNWD. As of 2021, the subsiding area (>5 mm/year) has reduced to about 5400 km2, approximately 85% of the subsiding area before SNWD; the areas of rapid subsidence (>30 mm/year) and extremely rapid subsidence (>50 mm/year) have reduced to 1300 km2 and 280 km2, respectively, approximately 70% and 60% of the areas before SNWD. Recent subsidence (2016–2021) was primarily contributed by the inelastic compaction of clays in deep aquifers of Aquifers III and IV ranging from approximately 200 to 450 m below the land surface. The ongoing rapid subsidence (>30 mm/year) in Tianjin is limited to border areas adjacent to large industrial cities (e.g., Langfang, Tanshan, Cangzhou) in Hebei Province. Ongoing subsidence will cease when hydraulic heads in the deep Aquifers (IV and V) recover to the new pre-consolidation head, approximately 45 m below the land surface, and subsidence will not be reinitiated as long as the hydraulic heads remain above the new pre-consolidation head. This study reveals the importance of coordinating groundwater and surface water uses at local, regional, and national scales for land subsidence mitigation.
... Table 3 summarises the yield stress (pci), which indicates the abrupt onset of reduction in soil stiffness and the increase in soil compressibility and their values. These values were determined following the method proposed by Casagrande (1936). At s = 0 kPa (saturated), hydrochar addition increased the pci of the soil by 50%, which was probably due to the use of a high compaction energy needed to prepare the amended specimens to achieve the same initial dry density as the unamended case. ...
... The preconsolidation stress, σ p ′ , is determined using Casagrande's method [41]. It should be pointed out, however, that for the stress levels applied, the consolidation curves in Figure 7 show a predominant elastic behaviour under compression without notable changes in the stiffness response. ...
The shear strength and compression properties of stiff Boom clay from Belgium at a depth of about 16.5 to 28 m were investigated by means of cone penetration and laboratory testing. The latter consisted of index classification, constant rate of strain, triaxial, direct simple shear and unconfined compression tests. The Boom clay samples exhibited strong swelling tendencies. The suction pressure was measured via different procedures and was compared to the expected in situ stress. The undrained shear strength profile determined from cone penetration tests (CPTs) was not compatible with the triaxial and direct simple shear measurements, which gave significantly lower undrained shear strength values. Micro-computed tomography (μCT) scans of the samples showed the presence of pre-existing discontinuities which may cause inconsistencies in the comparison of the laboratory test results with in situ data. The experimental data gathered in this study provide useful information for analyzing the mechanical behaviour of Boom clay at shallow depths considering that most investigations in the literature have been carried out on deep Boom clay deposits.
... However, subsoil stresses are determined primarily by the loads Söhne, 1953). results by Terzaghi, Casagrande (1936) suggested that the intersection of two lines in this semi-log presentation would represent a transition between elastic and plastic regions of soil deformation. This procedure for estimating a soil precompression stress was adapted for agricultural soil mechanics by Horn (1981), and its use in risk assessment was later outlined by Lebert and Horn (1991). ...
Soil compaction is a serious threat to soil functions and ecosystem services. Persistent soil deformation takes place when mechanical stress exceeds soil strength. Risk assessment models typically assume soil to be elastic to a precompression stress level and plastic above this threshold. Currently used procedures for estimating soil precompression stress imply applied stress in a logarithmic form that has been criticized. We performed uniaxial, confined compression tests on 117 soil samples with a well‐defined stress history. Strain and stress were recorded at 200 levels of stress in the range of 0–1 MPa. Soil compressibility was calculated as incremental strain per incremental stress, using stress in arithmetic scale. For a given sample, a local minimum in compressibility appeared close to the preload applied to the sample prior to the compression test. This yield stress is suggested as an expression of soil precompression stress. Not all samples displayed a yield stress. Primarily soil exposed to a high preload did not exhibit a clear stress level with change in compressibility. This indicates that a physically based stress level pointing out a transition to plastic conditions will not exist for all soils. Our observation calls for new concepts in risk assessment. Tests with interpolation between a limited number of data points indicate that the yield stress—if existing—may be detected from classical compression data.
... The void ratio, e, vertical effective stress, 'v, compression curves of the DS and the P-sediment mixtures are reported in Fig. 5a. The yield stress states were determined for each specimen by using the Casagrande's construction and represented by arrows in the figure [21].When P-cement is used (Fig. 5a), the compression curves of the treated soils are stable at higher void ratios than the DS, when subjected to the same vertical effective stress. As well known for sediment-cement mixtures [26], also when MS is added, it is possible to recognise a sub-horizontal branch of high stiffness, a yield stress-state, and a post yield compression behaviour when the treated sediments start to develop larger plastic strains. ...
This article reports some of the results of an experimental research dealing with the reuse of two highly impacting wastes of marine origin, i.e., dredged sediments and mussel shells. Traditionally, commercial cement has been for long used for the mechanical improvement in ex-situ management options of dredged sediments. However, the environmental impact of cement production pushes toward more sustainable binder materials. This study contributes to such a general objective by investigating the effectiveness of shell powder as a partial replacement of cement for the stabilization of dredged sediments. Specifically, the experimental programme involved both traditional cement-based sediment stabilization solutions and original ones where different sediment-shell powder-cement mixtures where prepared and tested. The results of multiscale investigations , including physicochemical and geomechanical tests, indicate a promising potential for mussel shells to reduce compressibility and increase strength properties of sediments, thus contributing to more sustainable waste management practices.
... After the compressibility test, the soil cores were dried at 105 • C. The vertical displacement measured by the consolidometer after the application of each load was used to determine the soil deformation (Def) at the end of the test. The compressibility index (CI) and the precompression stress (PCS) were estimated using Casagrande's method [45]. ...
Penetrometers and penetrographers are widely used to measure soil resistance to penetration, but the results are associated with other soil properties (such as bulk density, water content, and particle size distribution). Thus, for an adequate interpretation of results, site-specific studies are necessary to identify which properties are more related to soil resistance. We aimed to measure the resistance to penetration of a Typic Paleudalf under distinct soil uses and to identify soil properties that influence soil resistance. The soil uses in this study included anthropized forest (composed of tree and shrub species), pasture (5-year-old pasture), Eucalyptus 20 (a 20-year-old Eucalyptus saligna stand), and Eucalyptus 4.5 (a 4.5-year-old Eucalyptus saligna under the second rotation). Soil resistance to penetration was measured with an impact penetrometer, and the data were correlated with other physical and mechanical properties of soil, such as the particle size, soil moisture, air permeability, saturated hydraulic conductivity, porosity, bulk density, precompression stress, and compressibility index. We observed that a resistance of 1.3 MPa matches with other soil property values corresponding to soil compaction, and values greater than 1.3 MPa were verified at depths of 0–8 cm for pasture and 8–30 cm for Eucalyptus 4.5. Analyzing all soil uses together, the correlation was significant (p < 0.05) with gravel (r = 0.34), silt (r = −0.32), clay (r = 0.26), gravimetric moisture (r = −0.27), macroporosity (r = 0.24), and soil bulk density at the end of the compressibility test (r = 0.27). The penetrometer is useful for evaluating the physical conditions of soil, but we highlight that soil resistance is influenced by factors such as particle size and soil moisture, as examples. We recommend using a set of soil properties for a better interpretation of penetration resistance data and to support decision-making regarding soil management.
... The Casagrande method (Casagrande, 1936) was utilized in this study to determine the yield stress of soil specimens. As depicted in Fig. 3, the yield stress is influenced by the water content, dry density, and Neogene clay content of the soil, which is consistent with previous findings (Wei et al., 2019;Wang et al., 2020c). ...
Loess formation is widely distributed throughout the world and appears often in the form of a loess and clay mixture. The wetting-induced collapse in such ground conditions is a major concern for protecting tillage land. In this study, we present a simple model for the assessment of wetting-induced collapse in such loess-clay mixtures. Our approach is based on easily accessible oedometer tests by considering the change in dry density, water content, and clay content. Moreover, our model is underpinned by examining the soil structure during wetting deformation with the help of scanning electron microscopy. We demonstrate that the wetting deformation is dictated not only by the physical soil properties but also by its microstructure. Based on the experimental findings, we introduce an index for the yield stress of loess-clay-mixture. We proceed to develop a model for the assessment of collapsibility and show how this model can be used in engineering practice.
... • Preconsolidation pressure (or maximum past pressures) interpreted from the consolidation test results obtained from one-dimensional incremental loading test or constant rate-of-strain consolidation test using the Casagrande (1936) method and the work per unit volume method proposed by Becker, et al. (1987), and overconsolidation ratio (OCR). The histogram of depth below the seafloor of the sets of index and engineering properties in the database is presented in Figure 5a, and the corresponding in situ effective vertical stress for these depths is shown in Figure 5b. ...
In geotechnical earthquake engineering, shear wave velocity (VS) is one of the most important parameters. Several empirical correlations have been developed to estimate VS based on in situ tests, such as P-S logging tests and piezocone penetration tests (PCPTs), and soil properties determined both offshore in a field laboratory and onshore in a geotechnical laboratory. Recently, artificial intelligence (AI), machine learning, and deep learning have been the subject of intense media hype and therefore it was deemed appropriate to develop a deep-learning algorithm (DLA) to predict VS and compare its performance with conventional empirical methods of determining VS. A database of 11 sites in the Bay of Campeche with in situ measurements of VS using P-S logging and 8 clay soil parameters, including in situ measurements of net cone resistance (qnet), water content (w), submerged unit weight (g’), void ratio (eo), undrained shear strength (su), effective overburden pressure (σ′vo), over consolidation ratio (OCR), and plasticity index (Ip), was used to train a DLA and develop empirical equations based on multiple regression analysis (MRA) to predict VS. The accuracy of the results (i.e., how close the predicted VS values are to the in situ measured VS values) illustrates the great potential DLA has to become another class of computational tool to predict VS, and DLA has the advantage that it can be continuously updated as new data become available. The DLA was found to outperform MRA when the three input variables are measurements of qnet, w, and σ′vo and when the eight clay soil parameters are used as input parameters. The results suggest deep learning has the potential to overcome prediction limitations associated with linear or polynomial trends and adjust to discrete variabilities in soil conditions. They also reveal potential applications for deep learning in reducing uncertainty in the characterization of areas with complex soils without drastically increasing the scope of a site investigation.
... Sasanian & Newson, 2014), also when MS is added, it is possible to recognise a sub-horizontal branch of high stiffness, a yield stress state and a post-yield compression behaviour when the treated sediments start to develop large plastic strains. The yield stress states determined by using the Casagrande's construction are represented by the arrows in Fig. 10 (Casagrande, 1936). As detailed in Table 2, regardless of the total percentage of additive used (i.e. 8 or 16%), for 1/4 replacement ratios, the compression behaviour of the mixtures is characterised by higher values of σ′ v , lower recompression (C r ) and swelling index (C s ), and similar compression index (C c ) compared with the control mixtures. ...
The present study contributes to develop a novel eco-friendly solution for the mechanical stabilisation of dredged marine sediments by using mussel shells, i.e., another highly impacting waste of marine origin, in partial replacement of cements. Which are the underlying chemo-mechanical interactions affecting the evolution of such mixtures? Can the mussel shells replace cement without compromising useful geomechanical and geochemical properties of the stabilized sediments? Can such mixtures still be modelled as soils when it comes to their geotechnical design and analysis? The paper answers these questions by assessing the mechanical performance of the mixtures formed by sediments stabilised with three types of cement and a mussel shell powder and comparing it with that of the same sediments when treated with cement only. Multiple beneficial effects of the use of mussel shell powder, as peculiar source of calcium carbonate for its biogenic origin, have been demonstrated: it acts as a void filler, enhances the electrolytic exchanges between sediment and cement, and increases the contact area between the mineral particles promoting the chemical hydration reactions. As a result, for fixed replacement ratios, the original mixtures still exhibit soil-like behaviour consistent with traditional geomechanics and even better performances than the control mixtures.
... For approximately 60% of the dataset, the results of the consolidation tests were manually validated using the graphical method described by Casagrande (1936). Estimates of Cc obtained through graphical methods and values obtained from automated reporting software had a Pearson's correlation coefficient of 0.98; therefore, automated values were utilized for this study. ...
... Overall, higher compaction water contents allow the specimens to maintain larger suctions during the compaction. Based on Casagrande's [35] method, the yield stresses determined from the compression curves are presented in Figure 8. At a given testing water content of 14.7% (W1), 17.4% (W2), and 39.7% (W3), the yield stress decreases by 50.5%, 49.6%, and 18.5%, respectively, with the compaction water content increasing from 12.4% to 19.0%. ...
Compacted loess is widely used as a construction material in engineering practices. The compaction dry density and compaction water content have significant effects on the hydromechanical behavior of compacted loess, thereby influencing the serviceability and safety of engineering structures. The former was widely studied in previous studies, while the latter is rarely known. In this study, the water retention, compression, and collapse behavior of compacted loess at different compaction water contents are investigated through pressure plate and oedometer tests. Microstructure analysis was carried out for insight analysis of the test results. The air entry value and yield stress of compacted loess decreased by 64% and 50%, respectively, with the compaction water content increasing from 12.4% to 19.0%. This is due to the fact that the number of clods increases with increasing the compaction water content, leading to many large-sized pores (i.e., diameter > 1,000 μm) and weaker soil skeletons. The influence of compaction water content on the water retention and compression behavior of loess is more pronounced at lower compaction dry densities and lower testing water contents, respectively. In addition, the specimen shows smaller collapse indexes at higher compaction water contents, mainly because of the larger deformation induced by the initial compression.
... Yield stress value for each sample was determined by three methods (i.e. Casagrande, 1936, Tavenas et al., 1979, and Şenol et al., 2005. As depicted in the presented histograms, the differences are significant and in some cases exceed 100%. ...
Stress history acquired by any cohesive soil influences, to a large extent, three groups of fundamental properties indispensable in geotechnical design i.e. state of soil, shear strength, and stiffness characteristics. The basic stress history parameter (from which other parameters are derived) determined directly from laboratory tests is a preconsolidation stress σ′ p . Since the first method proposed by Casagrande in 1936, value σ′ p is determined in the oedometer test as a border between overconsolidated (OC) and normally consolidated (NC) zones. Approach based on division between predominantly elastic, (recoverable) strain, and plastic (irrecoverable) strain is a main principle of several methods of σ′ p determination, which have been proposed over the past eighty-six years.
Accumulated experiences have revealed that any laboratory procedure based on the oedometer test does not provide realistic value of preconsolidation stress, especially in heavy preconsolidated soils. The major reason for that results from the fact that the mechanism responsible for natural overconsolidation is more complicated than mechanical preloading. Therefore, there is a necessity to reevaluate effectiveness of standard methods and look for another solution of evaluation yield stress σ′ Y in natural soils.
This article presents the comparison between σ′ Y determined for various soils with use of standard methods based on conventional oedometer test and yield stress determined on the basis of alternative procedures. The latter are represented by various approaches as e.g. based on SHANSEP procedure or initial shear modulus and others. The most promising among these alternative methods is a new concept based on dilatancy phenomenon that takes place during shearing of a dense soil. The parameter reflecting stress history is derived from pore pressure response and is based on characteristic values of Skempton's parameter A record. Consistency of data concerning stress history parameters profile obtained for deep subsoil on the basis of various methods is shown for comparison.
... The elastic deformation occurs when the preconsolidation stress in the aquifer system is not exceeded. The preconsolidation stress is the maximum vertical effective stress that the subsoil has suffered due to its own weight or external loading (Casagrande 1936). The preconsolidation stress is influenced by several factors such as environmental conditions, hydrology, secondary compression, chemical alteration, variation in overburden pressure, sedimentation rate, sediment age, and tectonic conditions (e.g., Brumund et al. 1976). ...
The increased need for water resources in urban sprawls and intense droughts has forced more aggressive groundwater extraction resulting in numerous urban areas undergoing land subsidence. In most cases, only some large metropolitan areas have been well-characterized for subsidence. However, there is no existing country-wide assessment of urban areas, population, and households exposed to this process. This research showcases a methodology to systematically evaluate urban localities with land subsidence higher than − 2.8 cm/year throughout Mexico. We used Interferometric Synthetic Aperture Radar (InSAR) tools with a dataset of 4611 scenes from European Space Agency’s Sentinel-1 A/B SAR sensors acquired from descending orbits from September 2018 through October 2019. This dataset was processed at a supercomputer using InSAR Scientific Computing Environment and the Miami InSAR Time Series software in Python software. The quality and calibration of the resulting velocity maps are assessed through a large-scale comparison with observations from 100 continuous GPS sites throughout Mexico. Our results show that an urban area of 3797 km², 6.9 million households, and 17% of the total population in Mexico is exposed to subsidence velocities of faster than − 2.8 cm/year, in more than 853 urban localities within 29 land subsidence regions. We also confirm previous global potential estimations of subsidence occurrence in low relief areas over unconsolidated deposits and where groundwater aquifers are under stress. The presented research demonstrates the capabilities for surveying urban areas exposed to land subsidence at a country-scale level by combining Sentinel-1 velocities with spatial national census data.
Supplementary Information
The online version contains supplementary material available at 10.1007/s11069-023-06259-5.
... Moreover, the use of adsorbents does not seem to influence the one-dimensional compression behaviour: when either AC or BC are added, the compression curves are almost the same as those of specimens stabilised by cement only. For the treated sediment specimens, the vertical effective stress at yield (Casagrande, 1936) is about σ'y = 500-600 kPa. The average recompression, Cr, and compression indexes, Cc, are about 0.01 and 0.8, respectively. ...
The paper deals with an innovative approach to the management of contaminated sites, where geotechnical engineering bridges the gap between site characterisation and addresses for remedial strategies. Such approach has been successfully applied to one of the most critical industrial sites in Europe, which is the marine site of the Mar Piccolo in Taranto (Italy), also declared 'at high risk of environmental crisis' by the national government. The high degree of pollution that has been recorded in the clayey sediments at the sea bottom was found to affect the water quality and promote bioaccumulation of pollutants in fishes and mussels. These findings triggered a governmental investigation campaign to define sustainable remediation actions for the environmental risk mitigation. The site characterisation involved experts from geotechnical engineering, geological, sedimentological, mineralogical, hydraulic engineering, hydrological, chemical, geochemical, biological research fields, who cooperated to gather a new insight into the origin, distribution, mobility and fate of the contaminants within the basin and to define an original Conceptual Design Site Model (CDSM). The present contribution highlights some aspects of such holistic approach, from selected results from the multidisciplinary characterisation of the sediments to some addresses on remedial strategies and few considerations about solidification/stabilisation solutions for polluted sediments after dredging.
... The yield stress phase (50 to 110 kPa) was evaluated from the void ratio (e) versus effective vertical pressure (log r v ) compression curves for the reconstituted soil specimens. These yield stresses (r y ) were estimated from the e vs. log r v plots using the Casagrande method (Casagrande, 1936), as discussed in a related study (Owino et al., 2022a), to create the boundary conditions for the yield phases employed in this study. The observed approximate constant values of c v revealed that the creep effects should be carefully considered when working with basalt fiber-reinforced and RHAstabilized expansive soils. ...
... In MSL oedometer tests the compression index (Cc), swelling index ( graph from 6 -24 hours during each load increment since the primary consolidation was found to be completed within the first 5 -6 hours. The generation of the apparent preconsolidation stress ( 4 ) was determined using the Casagrande (1936) method. ...
The ever-growing climate problem has created a drive to ensure a sustainable future
can be achieved by meeting the net zero carbon emissions requirement by 2050.
Within the UK there has been an increase in record temperatures being experienced
particularly since the turn of the millennium. The UK is now experiencing
temperatures which are rising above 40°C and are set to continue over the next
century. Therefore, it is crucial to understand why thermo-mechanical behaviour of
clays is understood, as the increase in temperature causes an increase number of
geomechanical problems. In addition, the temperature fluctuations surrounding
energy geo-structures (ground source heating & thermo-piles) must be understood.
The study aims to assess the impact of temperature, ranging between 20 and 55 °C,
on the time- and rate-dependent behaviour of London Clay. As the London clay unit
lies within the warmest part of the UK and within a high urban development, it is vital we understand the impact temperature can play on this geological unit.
The thesis reports an extensive experimental program on the primary and secondary consolidation, stress relaxation, and rate-dependency. A series of conventional multi-staged loading (MSL) oedometer tests, and temperature-controlled constant rate of strain (CRS) oedometer tests were carried out on saturated and unsaturated reconstituted London clay (unit B) specimens, collected from the Bank Station project upgrade in London, UK.
... The accuracy of the microtensiometers ranges from − 600 hPa up to + 600 hPa. The precompression stress (Pc) was derived according to the method of Casagrande (1936). Beside others, total pore volume, bulk density (ρ t ) as well as the air capacity were determined for each structured soil cylinder (236 cm 3 ) prior and after the final stress (400 kPa) application. ...
... Once the precompression is exceeded, deformation is greater with increasing applied stress and the soil does not bounce back when the stress is removed. This expression of soil strength is somewhat idealized and originates in civil engineering soil mechanics (Casagrande, 1936) where it was introduced to characterize the reversible (elastic) and persistent (plastic) strain of homogenized clay during slow consolidation. Because the precompression stress represents the strength of a soil, we call it the precompression strength. ...
... The general consolidation curves for the tested soils are presented in Fig. 10 in terms of void ratio versus applied stress. The yield stress refers to the minimum stress at which the clay starts to show excessive deformation without further increase in load, as described in Casagrande's method (Casagrande 1936). This parameter is a measure of strong values that can be used in the design. ...
Light structures, roads, and pavements in semi-arid regions suffer from frequent damage due to expansive subsurface soils subjected to frequent wetting and drying. This research presents the distribution and characterization of expansive soil in a major semi-arid region. The characterization includes investigating the mineralogy and physical properties using X-ray diffraction and geotechnical testing methods. The mineralogical study is a key factor and is utilized to interpret and understand the geotechnical behavior of these soils. The X-ray diffraction showed that the mineralogy of clay is significantly variable for zones with different geological backgrounds. The influence of the minerals on the geotechnical properties of clay from different zones is viewed and reported. Non-sharp peaks above the background intensities were reported as a common feature within the zones of smectite clay minerals. The highly plastic clays showed clear peaks of minerals known for their high expansivity. The influence of high-intensity peaks of some clay minerals within the low ranges of 2θ may cause adjacent expansive mineral peaks not to appear. The flocculation of clays rich in expansive minerals and the cementitious bond between particles influence the magnitude of swelling and shrinkage in clays.
... Fig. 3 shows the 1D consolidation test results for two specimens, one from each Shelby tube. The maximum preconsolidation stresses were determined to be 320 kPa and 260 kPa using the Casagrande (1936) method for tubes B-211 SH-7 and B-212 SH-8, respectively. The preconsolidation stresses using the dissipated strain energy method modified by Wang and Frost (2011) were larger and were determined to be 404 kPa and 310 kPa, respectively. ...
... MPa by following the load pattern given in Table 3 The end of primary compression displacement ( ) was calculated by drawing axial deformation vs. logarithm of the time plot as suggested by Casagrande (1963). ...
The response of sandy soils under monotonic loading depends on size, shape and mineralogy of particles, fabric, stress, and density states of mixtures. Researchers around the world have studied their local sands and calibrated their responses (e.g., Toyoura sand-Japan, Ottawa sand-Canada, Sacramento sand-US, Sydney sand-Australia, etc.). However, there are not many studies that have focused on regional sands from Turkey. This research study aims to introduce a local sand, Kızılırmak sand, to literature as a "standard sand" from Turkey. For this purpose, shear and volumetric straining responses of Kızılırmak sand samples were investigated by a series of consolidated undrained monotonic triaxial and oedometer tests. Specimens with relative densities of 35-45-60-75 and 80 %, were prepared by wet tamping method and consolidated under 50 kPa, 100 kPa, 200 kPa and 400 kPa cell pressures, followed by undrained shearing. Test results were presented by four-way plots, which enable the individual variations of axial load, cell pressure, pore water pressure, and axial deformation along with the progress of the stress paths relative to failure envelopes. On the basis of test results, linear and nonlinear elastic-perfectly plastic constitutive modeling parameters, including but not limited to stress and relative-density dependent modulus and effective stress based angles of shearing resistance, were estimated. Due to its angular nature, Kızılırmak sands' angles of shearing resistance values of 35.4˚-42.8° were observed, which are closer to the upper limits of available literature. Triaxial modulus values fall in the range of ~10 and ~160 MPa and are concluded to be in conformance with available literature.
Similarly, samples with varying relative densities, prepared by air pluviation method, were tested in a conventional oedometer device under stresses starting from ~17 kPa increasing up to ~33.5 MPa. During tests, unloading and reloading cycles were performed. Based on these test results, particle crushing-induced yield stresses of Kızılırmak sands along with their Cc, Calpha values were estimated as ~2.1-4.0 MPa, ~2×10-3-1×10-2, and ~1×10-5–1×10-3, respectively. It was concluded that Kızılırmak sand exhibited Type B volumetric compression response as defined by Mesri and Vardhanabhuti (2009). Additionally, test results were also assessed within critical state framework. Critical state framework soil parameters of angle of steady state shearing resistances, slope of the critical state line and the critical state void ratio at 1 kPa values were estimated as 39.4˚, 0.070, and 0.975. Initial dividing line, defining the boundary between strain hardening and softening responses, is determined specific for Kızılırmak sand.
Predicting the stress–strain behavior of unsaturated soils is essential for determining yield stress. This paper explores a new method for determining the yield stress of unsaturated soils from the lateral pressure curve. A series of earth pressure at rest (K0) ondometer tests were conducted on unsaturated Yangqin silt clay. Lateral stress was obtained under different saturations and compactness. The relationship curves between lateral and vertical net stress were drawn for each condition. An obvious turning point was observed in the curve, which can be used to determine the yield stress. The oedometer tests were conducted, and the Casagrande and the bilogarithmic methods were used for comparison purposes. The difference between the proposed and traditional methods was less than 17 %. The initial saturation and compactness influence on the yield stress was discussed. The yield stress increased with the decrease in saturation and increases in compactness, which is consistent with that of the classic method. The test results and comparison prove the rationality of the proposed method. No coordinate transformation is required in the proposed method, which is more convenient for data processing. It can be used to determine the yield stress of unsaturated soils from another perspective.
The development practice of Fuling shale gas field in Jiaoshiba area shows that the large-scale production capacity of shale gas in the Longmaxi Formation has not yet been fully established. One of the main reasons is that the mechanical properties of shale under high-temperature and high-pressure conditions greatly inhibit the hydraulic fracturing degree of the rock.
Excessive soil compaction is a major cause of environmental problems and reduced agricultural soil productivity. Soil conditions can affect soil compressive characteristics. The application of organic materials reduces soil susceptibility to compaction. However, the direct effect of incorporated organic matter and interactions among soil conditions and incorporated organic materials on soil compressive characteristics are poorly understood. In this study, uniaxial compressive experiments were conducted to determine the compression curves of repacked brown earth from Northeast China. The effect of variable levels of incorporated corn straw (20, 40, 60, 80, and 100 g kg ⁻¹ ) and soil conditions (moisture content 0.14, 0.18, and 0.22 g g ⁻¹ , and bulk density 1.20, 1.30, 1.45, and 1.60 g cm ⁻³ ) on the compressive characteristics were investigated. The results showed that compressive characteristics were directly affected by soil conditions and corn straw‐derived organic matter ( p < 0.01). Compressive characteristics were also significantly influenced by the interaction between soil conditions and corn straw‐derived organic matter ( p < 0.01). By constructing a Entropy Weight Method (EWM) Technique for Order Preference by Similarity to Ideal Solution model (EWM‐TOPSIS), the conflicting indicators of soil resistance was comprehensively evaluated. The evaluation results indicated that moisture content at 0.14 g g ⁻¹ , bulk density at 1.30 g cm ⁻³ and corn straw‐derived organic matter at 34 g kg ⁻¹ was the optimal mode for soil resistance in our experiment. The results suggested that the interaction of soil conditions and incorporated organic matter should be considered to evaluate the susceptibility to compaction in the fields accurately.
Experimental Study of yield surface of saturated silty tailings
Description
First publication of its kind in 25 years, this 900-page volume serves as an engineer’s guide for triaxial testing. Subjects include: equipment, test methods, and test interpretation and errors, and new test varieties.
The creep behavior of the frozen soil-structure interface as the research point in this paper subjected to mechanism theory principles of water-thermal coupling cycle was exhibited. There are mainly three situations, one is pile uplifting in the freezing heave period owing to frost heave force, then soil melt, and the pile would keep stable which the skin friction supported the pile at interface, three is both cases acting as stated above, the positive frozen cohesive is not enough to support the pile in frozen soil combined the negative friction at the same time. The frost heave with creep effect analysis was given the mainly concern. The emphasis of the frost heave phenomenon considering inner shear behavior under different geometric parameters in Freezing-Thawing cycle pointed that creep effect of the soil-pile interface played a domain role in the total deformation of interface due to common source of the settlement and uplift in cold regions.
It reveals that the actual strain rate was sensitive at deeper soil layer by layer towards ground, according to the good agreement between the relaxation data and secondary creep conditions. The best fit regression was occurred in the period of approximate 65 th day to 200 th day accordingly. The strain mainly presents promoted when the temperature are below-2℃ in freezing transmission period, while it shows reduction trend with water content increase to ice-rich soil.
It is taken for that with flow rate varying with stress conditions which exceed a yield stress level. And it shown the relationship of stress and strain at various depths with diminished lay-up character distribution. The numerical calculated result was shown that the high cohesion concentration zone be in the position of-2m depths of pile.
And the mechanism model can be described by Kelvin-Voigt model, with validating by experimental simulation and published literature. Above all, it can be seen the temperature and moisture were the most significant effects for interface frost heave, which is indicated by the shear creep response analyzing. The combination of factors closely associated with the cohesion leading the pile continuously uplifting. The creep effect worked on the interface separated by three stage of primary creep stage, secondary creep stage and tertiary creep stage in frozen and thawing period by different cohesion force. So the characteristics of creep combined the Kelvin Voigt model was presented in this paper.
Abstract
Evidence of ageing has been reported in natural deposits of sedimentary clays, dredged sediments, and in clay-rich oil sands tailings, and such time-dependent behaviour has been
observed to influence their long-term settlement and strength development characteristics. The ageing phenomenon can, therefore, have important implications for the reclamation of such
deposits. This research investigated ageing in polymer-amended tailings and Leda clay monitoring relatively small (10 cm high) laboratory samples for over 100 days. Both tailings and
natural clay were found to develop increased strength, sensitivity, and higher pre-consolidation pressure and reduced compressibility. The correlation between fall cone shear strengths and preconsolidation pressures was strong for both the natural clay and the clayey tailings, though this ratio was different in the tailings and the clay. The Leda clay appeared to reabsorb some of its bleed water, which was found to be due to the transition of some free water to absorbed water after 80 days. Using a concept developed from ageing experiments in artificial clays, it was found that shear strengths measured after an “early equilibrium state” correlated strongly with shear strengths measured near the end of ageing. This is promising for quantifying the potential for ageing on compressibility without having to resort to year-long experiments.
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