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13 pages, 2228 KiB

Open AccessArticle

Cyclic Liquefaction Resistance of an Alluvial Natural Sand: A Comparison between Fully and Partially Saturated Conditions

by Diana Cordeiro, Fausto Molina-Gómez, Cristiana Ferreira, Sara Rios and António Viana da Fonseca

Geotechnics 2022, 2(1), 1-13; https://doi.org/10.3390/geotechnics2010001 - 6 Jan 2022

Cited by 9 | Viewed by 2661

Abstract

Earthquake-induced liquefaction is one of the major causes of building damage as it decreases the strength and stiffness of soil. The liquefaction resistance of soils increases significantly as the degree of saturation decreases, making soil desaturation an effective measure for the mitigation of [...] Read more.

Earthquake-induced liquefaction is one of the major causes of building damage as it decreases the strength and stiffness of soil. The liquefaction resistance of soils increases significantly as the degree of saturation decreases, making soil desaturation an effective measure for the mitigation of this phenomenon. This paper presents a comparative analysis of liquefaction resistance of an alluvial sand from Aveiro (Portugal) under fully and partially saturated conditions. For this purpose, an in situ characterisation based on CPTu and a laboratory series of cyclic triaxial tests were carried out. The cyclic triaxial tests were conducted under undrained conditions on remoulded specimens with different degrees of saturation, including the full saturation. On the other hand, the triaxial apparatus was instrumented with Hall-effect transducers to accurately measure the strains during all testing phases. In addition, it was equipped with piezoelectric transducers to measure seismic waves velocities, namely P-wave velocity, for evaluation of the saturation level of the specimen in parallel with the Skempton’s B parameter. Hence, relations between the B-value, and P-wave velocity and cyclic strength resistance are presented. The number of cycles to trigger liquefaction, considering the pore pressure build-up criterion, is presented for the different degrees of saturation. Results confirmed the increase in liquefaction resistance for lower degrees of saturation in this soil. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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15 pages, 3111 KiB

Open AccessArticle

Strength of Chemically Stabilized Sewage Sludge—Some Inferences from Recent Studies

by Sin Mei Lim, Linqiao He, Siang Huat Goh and Fook Hou Lee

Geotechnics 2021, 1(2), 573-587; https://doi.org/10.3390/geotechnics1020026 - 16 Dec 2021

Viewed by 2287

Abstract

Although there has been a substantial body of research on the chemical stabilization of sewage sludge, most of these results are project-specific and relate mainly to the use of new binders and sewage sludge from specific sources. In this sense, much of the [...] Read more.

Although there has been a substantial body of research on the chemical stabilization of sewage sludge, most of these results are project-specific and relate mainly to the use of new binders and sewage sludge from specific sources. In this sense, much of the work to date is context-specific. At present, there is still no general framework for estimating the strength of the chemically treated sludge. This paper proposes one such general framework, based on data from some recent studies. An in-depth re-interpretation of the data is first conducted, leading to the observation that sludge, which has coarse, hard particulate inclusions, such as sand, premixed into it, gives significantly higher strength. This was attributed to the hard coarse particles that lower the void ratio of treated soil, are much less susceptible to volume collapse under pressure, and contribute to the strength through frictional contacts and interlocking. This motivates the postulation of a general framework, based on the premise that coarse, hard particulate inclusions in the sludge which do not react with the binders can nonetheless contribute to the strength of the treated soil. The overall void ratio, defined as the volume of voids in the cementitious matrix normalised by the overall volume, is proposed as a parameter for quantifying the combined effect of the coarse particulate inclusions and the cementitious matrix. The binder-sludge ratio is another parameter which quantifies the strength of the cementitious matrix, excluding the hard particulate inclusions. Back-analysis of the data suggests that the significance of the binder-sludge ratio may diminish as the content of hard particulate inclusions increases. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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15 pages, 2024 KiB

Open AccessArticle

Microbial-Facilitated Calcium Carbonate Precipitation as a Shallow Stabilization Alternative for Expansive Soil Treatment

by Bhaskar C. S. Chittoori, Tasria Rahman and Malcolm Burbank

Geotechnics 2021, 1(2), 558-572; https://doi.org/10.3390/geotechnics1020025 - 16 Dec 2021

Cited by 8 | Viewed by 3702

Abstract

Expansive soils generally recognized as swell-shrink soils have been a problem for civil infrastructure for a long time. Engineers are in search of sustainable stabilization alternatives to counter these problematic soils. Microbial-induced calcium carbonate precipitation (MICP) is a promising biocementation process that can [...] Read more.

Expansive soils generally recognized as swell-shrink soils have been a problem for civil infrastructure for a long time. Engineers are in search of sustainable stabilization alternatives to counter these problematic soils. Microbial-induced calcium carbonate precipitation (MICP) is a promising biocementation process that can improve the properties of expansive soil through calcium carbonate precipitation. Past research has shown promise for the use of MICP in mitigating swelling distress from expansive soils. In this research, MICP via biostimulation was attempted by mixing enrichment and cementation solutions with soils in an effort to develop a new alternative to shallow chemical stabilization. Three soils with varying clay contents (30%, 40%, and 70%) and plasticity characteristics were selected, and soils were treated by mixing with enrichment solutions followed by cementation solutions. Five different mellowing periods, three different curing periods, and two types of cementation solutions were studied to optimize the method. Treatment effectiveness was evaluated using unconfined compression tests, calcium carbonate tests, and free swell index tests. Results showed that an increase in the mellowing period beyond two days was not beneficial for any of the three soils tested in this research. It was determined that the best improvement was observed at two days of mellowing and seven days of curing. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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24 pages, 1665 KiB

Open AccessArticle

Modeling of Seismic Energy Dissipation of Rocking Foundations Using Nonparametric Machine Learning Algorithms

by Sivapalan Gajan

Geotechnics 2021, 1(2), 534-557; https://doi.org/10.3390/geotechnics1020024 - 12 Dec 2021

Cited by 6 | Viewed by 2754

Abstract

The objective of this study is to develop data-driven predictive models for seismic energy dissipation of rocking shallow foundations during earthquake loading using multiple machine learning (ML) algorithms and experimental data from a rocking foundations database. Three nonlinear, nonparametric ML algorithms are considered: [...] Read more.

The objective of this study is to develop data-driven predictive models for seismic energy dissipation of rocking shallow foundations during earthquake loading using multiple machine learning (ML) algorithms and experimental data from a rocking foundations database. Three nonlinear, nonparametric ML algorithms are considered: k-nearest neighbors regression (KNN), support vector regression (SVR) and decision tree regression (DTR). The input features to ML algorithms include critical contact area ratio, slenderness ratio and rocking coefficient of rocking system, and peak ground acceleration and Arias intensity of earthquake motion. A randomly split pair of training and testing datasets is used for initial evaluation of the models and hyperparameter tuning. Repeated k-fold cross validation technique is used to further evaluate the performance of ML models in terms of bias and variance using mean absolute percentage error. It is found that all three ML models perform better than multivariate linear regression model, and that both KNN and SVR models consistently outperform DTR model. On average, the accuracy of KNN model is about 16% higher than that of SVR model, while the variance of SVR model is about 27% smaller than that of KNN model, making them both excellent candidates for modeling the problem considered. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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17 pages, 34877 KiB

Open AccessArticle

Novel Methods for the Computation of Small-Strain Damping Ratios of Soils from Cyclic Torsional Shear and Free-Vibration Decay Testing

by Zhongze Xu, Yumeng Tao and Lizeth Hernandez

Geotechnics 2021, 1(2), 330-346; https://doi.org/10.3390/geotechnics1020016 - 21 Oct 2021

Cited by 2 | Viewed by 5304

Abstract

This paper illustrates two novel methods for computing the small-strain hysteretic material damping ratio, λ_min, of soils from the cyclic torsional shear (TS) and computing the small-strain viscous material damping ratio, D_min, from the free-vibration decay (FVD) testing. Both [...] Read more.

This paper illustrates two novel methods for computing the small-strain hysteretic material damping ratio, λ_min, of soils from the cyclic torsional shear (TS) and computing the small-strain viscous material damping ratio, D_min, from the free-vibration decay (FVD) testing. Both λ_min and D_min are challenging to measure, due to the significant level of ambient noise at small strains (<10⁻⁴%). A two-step method is proposed combining the Fourier Transform and a phase-based data fitting method for torsional shear testing, and this method can effectively eliminate the ambient noise at small strains. A Hilbert Transform-based method is proposed for the free-vibration decay testing in order to achieve a more accurate measurement of the viscous material damping ratio, D, at different strain levels, especially at small strains. The improved λ_min and D_min at small strains are compared to data available in the literature. The two novel methods are shown to be accurate in computing the small-strain damping ratios. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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17 pages, 4374 KiB

Open AccessArticle

The Mechanical Response of a Silty Sand Stabilized with Colloidal Silica

by Antigoni Vranna and Theodora Tika

Geotechnics 2021, 1(2), 243-259; https://doi.org/10.3390/geotechnics1020013 - 28 Sep 2021

Cited by 5 | Viewed by 2726

Abstract

This paper presents a laboratory investigation into the mechanical response of a silty sand, with a fines content of 10%, stabilized with colloidal silica (CS). To this end, a series of unconfined compression tests as well as monotonic and cyclic triaxial tests was [...] Read more.

This paper presents a laboratory investigation into the mechanical response of a silty sand, with a fines content of 10%, stabilized with colloidal silica (CS). To this end, a series of unconfined compression tests as well as monotonic and cyclic triaxial tests was performed on a silty sand, comprising a mixture of a clean sand and a silty sand, stabilized with two concentrations of CS. The effect of various parameters on the behaviour of the stabilized silty sand was studied, such as CS concentration, soil density, and the presence of fines. The test results were compared with the corresponding of the untreated silty sand as well as the parent clean sand. It is shown that stabilization, even at the lowest CS = 6% concentration studied, significantly improves the undrained shear strength as well as the liquefaction resistance of the stabilized silty sand. Both the monotonic and cyclic response of the stabilized soil are only slightly affected by density. Furthermore, cyclic straining up to at least 5% of double-amplitude axial strain does not influence the undrained shear strength of the stabilized silty sand. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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24 pages, 6524 KiB

Open AccessArticle

Laboratory-Based Correlation between Liquefaction Resistance and Shear Wave Velocity of Sand with Fines

by Anthi I. Papadopoulou and Theodora M. Tika

Geotechnics 2021, 1(2), 219-242; https://doi.org/10.3390/geotechnics1020012 - 26 Sep 2021

Cited by 3 | Viewed by 4072

Abstract

This paper presents the results of a laboratory investigation into the effect of non-plastic fines on the correlation between liquefaction resistance and the shear wave velocity of sand. For this purpose, undrained stress-controlled cyclic triaxial and bender element tests were performed on clean [...] Read more.

This paper presents the results of a laboratory investigation into the effect of non-plastic fines on the correlation between liquefaction resistance and the shear wave velocity of sand. For this purpose, undrained stress-controlled cyclic triaxial and bender element tests were performed on clean sand and its mixtures with non-plastic silt. It is shown that the correlation between liquefaction resistance and shear wave velocity depends on fines content and confining effective stress. Based on the test results, correlation curves between field liquefaction resistance and overburden stress corrected shear wave velocity for sand containing various contents of fines are derived. These curves are compared to other previously proposed by field and laboratory studies. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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24 pages, 5665 KiB

Open AccessArticle

On the Dilatancy of Fine-Grained Soils

by Merita Tafili, Carlos Grandas Tavera, Theodoros Triantafyllidis and Torsten Wichtmann

Geotechnics 2021, 1(1), 192-215; https://doi.org/10.3390/geotechnics1010010 - 31 Aug 2021

Cited by 8 | Viewed by 4962

Abstract

A new evaluation method for the dilatancy of fine-grained soils based on monotonic and cyclic undrained triaxial tests has been established using two elasticity approaches: isotropic and transverse isotropic hypoelasticity. The evaluation of two clays, Kaolin and Lower Rhine Clay, with the new [...] Read more.

A new evaluation method for the dilatancy of fine-grained soils based on monotonic and cyclic undrained triaxial tests has been established using two elasticity approaches: isotropic and transverse isotropic hypoelasticity. The evaluation of two clays, Kaolin and Lower Rhine Clay, with the new method also shows that the dilatancy of fine-grained soils is dependent on the stress ratio, the void ratio, and the straining direction along with the intrinsic material parameters. Similar to sand, we can observe a Phase Transformation Line beyond which further shearing induces a volume increase. A generalization of the Taylor dilatancy rule from direct shear to multiaxial space is established, and an extension accounting for the behaviour of soft soils is proposed. We formulate a simple hypoplastic constitutive relation with a modified flow rule that reproduces the observed dilatant as well as contractant behaviour. Some simulations of monotonic as well as cyclic tests prove the accurate performance of the proposed dilatancy relation. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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20 pages, 10130 KiB

Open AccessArticle

Compositional Features and Swelling Potential of Two Weak Rock Types Affecting Their Slake Durability

by Lena Selen, Krishna Kanta Panthi, Mai Britt Mørk and Bjørn Eske Sørensen

Geotechnics 2021, 1(1), 172-191; https://doi.org/10.3390/geotechnics1010009 - 24 Aug 2021

Cited by 2 | Viewed by 2715

Abstract

Weak and weathered rocks are well known for their sensitivity to changes in moisture content. Degrading behavior is common in weak rocks with moisture-sensitive mineral components and present numerous stability problems. The slake durability is a measure of the resistance to weakening and [...] Read more.

Weak and weathered rocks are well known for their sensitivity to changes in moisture content. Degrading behavior is common in weak rocks with moisture-sensitive mineral components and present numerous stability problems. The slake durability is a measure of the resistance to weakening and disintegration of rock materials which quantitatively distinguishes durable from non-durable rock materials. Several rock material parameters interact on the process of disintegration when exposed to cyclic moisture changes, whereby the content of clay is believed to play a major role. This manuscript evaluates the overall material composition of flysch and serpentinite rocks cored from the wall of the shotcrete-lined headrace tunnel of a hydropower project, including minerals, structure, porosity, the presence of micro-discontinuities, and swelling potential, and links these properties to the slake durability. Further, the different methods used to assess compositional features affecting the durability of weak rocks are evaluated and discussed. The manuscript argues that the mineralogical composition and microstructures present in the intact rock and the content of moisture-sensitive constituents, as swelling clays, control the long-term durability of weak rock material. It is demonstrated that XRD assessments are not sufficient to detect the content of brucite and swelling components, and that methods as thin section and SEM analyses should be carried out in the assessment of weak and weathered rock mass. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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20 pages, 6396 KiB

Open AccessArticle

Numerical Study of the Behavior of Back-to-Back Mechanically Stabilized Earth Walls

by Seyed Hamid Lajevardi, Khashayar Malekmohammadi and Daniel Dias

Geotechnics 2021, 1(1), 18-37; https://doi.org/10.3390/geotechnics1010002 - 19 Apr 2021

Cited by 2 | Viewed by 3144

Abstract

Back-to-back mechanically stabilized earth (MSE) walls can sustain significant loadings and deformations due to the interaction mechanisms which occur between the backfill material and reinforcement elements. These walls are commonly used in embankments approaching bridges, ramps, and railways. The performance of a reinforced [...] Read more.

Back-to-back mechanically stabilized earth (MSE) walls can sustain significant loadings and deformations due to the interaction mechanisms which occur between the backfill material and reinforcement elements. These walls are commonly used in embankments approaching bridges, ramps, and railways. The performance of a reinforced wall depends on numerous factors, including those defining the soil, the reinforcement, and the soil/reinforcement interaction behavior. The focus of this study is to investigate the behavior of back-to-back mechanically stabilized earth walls considering synthetic and metallic strips. A two-dimensional finite difference numerical modeling is considered. The role of the soil friction angle, the distance of the reinforcement elements, the walls’ width to height ratio, and the quality of the soil material are investigated in a parametric study. Their effects on the critical failure surface, shear displacements, wall displacements, and tensile forces on the reinforcements are presented. The interaction between back-to-back reinforced walls strongly depends on the distance between walls and modifies the critical failure surface location. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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Review

Jump to: Research

59 pages, 5350 KiB

Open AccessReview

Transient Two-Phase Flow in Porous Media: A Literature Review and Engineering Application in Geotechnics

by Guanxi Yan, Zi Li, Sergio Andres Galindo Torres, Alexander Scheuermann and Ling Li

Geotechnics 2022, 2(1), 32-90; https://doi.org/10.3390/geotechnics2010003 - 11 Jan 2022

Cited by 34 | Viewed by 7321

Abstract

This work reviews the transient two-phase flow in porous media with engineering applications in Geotechnics. It initially overviews constitutive relationships, conventional theories, and experiments. Then, corresponding limitations are discussed according to conflicting observations and multiphase interfacial dynamics. Based on those findings, the dynamic [...] Read more.

This work reviews the transient two-phase flow in porous media with engineering applications in Geotechnics. It initially overviews constitutive relationships, conventional theories, and experiments. Then, corresponding limitations are discussed according to conflicting observations and multiphase interfacial dynamics. Based on those findings, the dynamic nonequilibrium effects were so defined, which could also be abbreviated as dynamic/transient effects. Four advanced theories have already been developed to resolve these effects. This review collects them and discusses their pros and cons. In addition, this work further reviews the state-of-art in terms of experimental methods, influential factors in dynamic/transient effects, and modelling performance, as well as micromodel and numerical methods at pore-scale. Last, the corresponding geotechnical applications are reviewed, discussing their applicability in effective stress, shear strength, and deformation. Finally, the entire review is briefed to identify research gaps in Geotechnics. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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42 pages, 15913 KiB

Open AccessReview

Investigating Sand Production Phenomena: An Appraisal of Past and Emerging Laboratory Experiments and Analytical Models

by Kenneth Imo-Imo Israel Eshiet and Yong Sheng

Geotechnics 2021, 1(2), 492-533; https://doi.org/10.3390/geotechnics1020023 - 7 Dec 2021

Cited by 1 | Viewed by 3173

Abstract

This paper provides an in-depth review of research developments on a common phenomenon in oil and gas exploration: sand production. Due to its significant impact to reservoir productivity and production efficiency, sand production has been widely researched in recent years. This paper focused [...] Read more.

This paper provides an in-depth review of research developments on a common phenomenon in oil and gas exploration: sand production. Due to its significant impact to reservoir productivity and production efficiency, sand production has been widely researched in recent years. This paper focused on the review of historical progress in experimental and analytical studies which helped to understand the nature of the sanding mechanism and identify conditions that favour the process. Collation of the experimental data and analytical solutions and formulations enabled the authors to comment on effectiveness and also limitations of the existing experimental protocols and analytical models. Sand production models were then grouped into categories based on initiation of sanding, rate and amount of sanding as well as the failure criterion incorporated in their formulation so that it will be more convenient for future researchers to identify and adopt an appropriate model for their own research. The review also confirms that there are still some aspects of sand production requiring further investigation, and maybe a hybrid approach combining experimental, analytical and numerical methods could be the best solution for future explorations. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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25 pages, 3444 KiB

Open AccessReview

Results of Application of Artificial Neural Networks in Predicting Geo-Mechanical Properties of Stabilised Clays—A Review

by Jeremiah J. Jeremiah, Samuel J. Abbey, Colin A. Booth and Anil Kashyap

Geotechnics 2021, 1(1), 147-171; https://doi.org/10.3390/geotechnics1010008 - 17 Aug 2021

Cited by 25 | Viewed by 4030

Abstract

This study presents a literature review on the use of artificial neural networks in the prediction of geo-mechanical properties of stabilised clays. In this paper, the application of ANNs in a geotechnical analysis of clay stabilised with cement, lime, geopolymers and by-product cementitious [...] Read more.

This study presents a literature review on the use of artificial neural networks in the prediction of geo-mechanical properties of stabilised clays. In this paper, the application of ANNs in a geotechnical analysis of clay stabilised with cement, lime, geopolymers and by-product cementitious materials has been evaluated. The chemical treatment of expansive clays will involve the development of optimum binder mix proportions or the improvement of a specific soil property using additives. These procedures often generate large data requiring regression analysis in order to correlate experimental data and model the performance of the soil in the field. These analyses involve large datasets and tedious mathematical procedures to correlate the variables and develop required models using traditional regression analysis. The findings from this study show that ANNs are becoming well known in dealing with the problem of mathematical modelling involving nonlinear functions due to their robust data analysis and correlation capabilities and have been successfully applied to the stabilisation of clays with high performance. The study also shows that the supervised ANN model is well adapted to dealing with stabilisation of clays with high performance as indicated by high R² and low MAE, RMSE and MSE values. The Levenberg–Marquardt algorithm is effective in shortening the convergence time during model training. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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19 pages, 2135 KiB

Open AccessReview

3-D Rock Mass Strength Criteria—A Review of the Current Status

by Pinnaduwa H. S. W. Kulatilake

Geotechnics 2021, 1(1), 128-146; https://doi.org/10.3390/geotechnics1010007 - 8 Aug 2021

Cited by 2 | Viewed by 3192

Abstract

The presence of complex discontinuity patterns, the inherent statistical nature of their geometrical parameters, the uncertainties involved in the estimation of the discontinuity geometrical and geo-mechanical properties and complex three dimensional (3-D) in-situ stress make the accurate prediction of rock mass strength a [...] Read more.

The presence of complex discontinuity patterns, the inherent statistical nature of their geometrical parameters, the uncertainties involved in the estimation of the discontinuity geometrical and geo-mechanical properties and complex three dimensional (3-D) in-situ stress make the accurate prediction of rock mass strength a difficult task. It has been a great challenge for the rock mechanics and rock engineering professions to develop a rock mass strength criterion in three dimensions that incorporates the effect of the minor and intermediate principal stresses and captures the scale dependent and anisotropic properties resulting from the discontinuity geometry parameters, such as the number of discontinuity sets, 3-D discontinuity intensity, and the distributions of the discontinuity orientation and size. Rock mechanics and rock engineering researchers have dealt with this topic for more than 55 years. The paper provides a critical review of the current state of the art regarding 3-D jointed rock mass strength criteria. The shortcomings of several rock mass strength criteria are discussed. The historic development of rock mass strength criteria that incorporate the effect of the minor and intermediate principal stresses and capture the scale dependent and anisotropic properties is presented. The most advanced 3-D rock mass strength criteria currently available in the literature are presented, including suggested future improvements. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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33 pages, 7100 KiB

Open AccessReview

by António Viana da Fonseca, Diana Cordeiro and Fausto Molina-Gómez

Geotechnics 2021, 1(1), 95-127; https://doi.org/10.3390/geotechnics1010006 - 29 Jul 2021

Cited by 26 | Viewed by 5847

Abstract

The critical state theory is a robust conceptual framework for the characterisation of soil behaviour. In the laboratory, triaxial tests are used to assess the critical state locus. In the last decades, the equipment and testing procedures for soil characterisation, within the critical [...] Read more.

The critical state theory is a robust conceptual framework for the characterisation of soil behaviour. In the laboratory, triaxial tests are used to assess the critical state locus. In the last decades, the equipment and testing procedures for soil characterisation, within the critical state framework, have advanced to obtain accurate and reliable results. This review paper summarises and describes a series of recommended laboratory procedures to assess the critical state locus in cohesionless soils. For this purpose, results obtained in the laboratory from different cohesionless soils and triaxial equipment configurations are compiled, analysed and discussed in detail. The procedures presented in this paper reinforce the use of triaxial cells with lubricated end platens and an embedded connection piston into the top-cap, together with the verification of the full saturation condition and the measurement end-of-test water content—preferable using the soil freezing technique. The experimental evidence and comparison between equipment configurations provide relevant insights about the laboratory procedures for obtaining a reliable characterisation of the critical state locus of cohesionless geomaterials. All the procedures recommended herein can be easily implemented in academic and commercial geotechnical laboratories. Full article

(This article belongs to the Special Issue Fundamental Challenges for Civil Infrastructures in Problematic and Unsaturated Soils, Breakthroughs, and Opportunities)

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