Strain-rate-dependent stress-strain behavior of overconsolidated Hong Kong marine clay

2000 ◽  
Vol 37 (6) ◽  
pp. 1272-1282 ◽  
Author(s):  
Jun-Gao Zhu ◽  
Jian-Hua Yin
Keyword(s):  
Shear Strength ◽  
Hong Kong ◽  
Strain Rate ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Undrained Shear Strength ◽  
Rate Dependency ◽  
Marine Clay ◽  
Strain Rate Dependency ◽  
Undrained Shear

A total number of 24 consolidated undrained triaxial shear tests on reconsolidated saturated Hong Kong marine clay (HKMC) have been performed in both compression and extension shear states. The specimens were prepared in four different overconsolidation ratios (OCRs) and sheared at three different axial strain rates. The strain-rate dependency of undrained shear strength, pore-water pressure, stress path, and secant Young's modulus are investigated. The influence of OCR on the stress–strain–strength behavior of HKMC is also examined. The results of all tests are presented and interpreted. The interpreted results are compared with the results in the literature. For the HKMC with OCR varying from 1 to 8, the average value of the strain-rate parameter [Formula: see text] 0.15 is 5.5% for compression tests and 8.4% for extension tests. Most interpreted results are conclusive and consistent with the published results, whereas some results are not conclusive. A new parameter for describing the strain-rate dependency of undrained shear strength of overconsolidated soil is introduced.Key words: strain-rate effects, clay, overconsolidated, triaxial, shear strength, pore-water pressure.

scholarly journals Theoretical Equations for the Ratio of Undrained Shear Strength to Vertical Effective Stress for Normally Consolidated Saturated Cohesive Soils

2022 ◽  
Vol 28 (3) ◽  
pp. 241-252
Author(s):  
Sugeng Krisnanto
Keyword(s):  
Shear Strength ◽  
Pore Water ◽  
Effective Stress ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Undrained Shear Strength ◽  
Engineering Practice ◽  
Cohesive Soils ◽  
Vertical Effective Stress ◽  
Undrained Shear

Abstract Two theoretical equations are developed to calculate the ratio of undrained shear strength to the vertical effective stress (the ratio of (su/sv’)) for normally consolidated saturated cohesive soils. The effective stress approach is used as the basis in the development of the theoretical equations. The theoretical equations are developed by relating the total and the effective stress paths. The development of the excess pore-water pressure is quantified using Skempton A and B pore-water pressure parameters. The theoretical equations are developed for two initial stress conditions: (i) an initially hydrostatic condition and (ii) an initially Ko (non-hydrostatic) condition. The performance of the theoretical equations of this study is compared with field and laboratory measurement data obtained from the literature. The close results between the theoretical equations and the measurements show that the theoretical equations of this study can compute the ratio of (su/sv’) well. Using the theoretical equations, the values of the ratio of (su/sv’) commonly used in engineering practice can be explained from the soil mechanics framework. Keywords: Saturated cohesive soils, c/p ratio, normally consolidated soil, undrained shear strength, effective shear strength, theoretical equation. Abstrak Dua persamaan teoritis dikembangkan untuk menghitung rasio kuat geser tak teralirkan dengan tegangan efektif vertikal (rasio (su/sv’)) untuk tanah kohesif jenuh terkonsolidasi normal. Pendekatan tegangan efektif dijadikan dasar dalam pengembangan kedua persamaan teoretis ini. Persamaan teoretis tersebut dikembangkan menghubungkan lintasan tegangan total dan lintasan tegangan efektif. Kenaikan tekanan air pori ekses dikuantifikasi menggunakan parameter tekanan air pori A dan B dari Skempton. Persamaan teoretis dikembangkan untuk dua kondisi tegangan awal: (i) tegangan awal hidrostatik dan (ii) teganan awal Ko (non hidrostatik). Kinerja kedua persamaan teoretis tersebut dibandingkan terhadap data pengukuran lapangan dan pengujian laboratorium yang diperoleh dari literatur. Persamaan teoretis dari studi ini memiliki kinerja yang baik dalam memperhitungan rasio (su/sv’) yang ditunjukkan dengan dekatnya hasil perhitungan menggunakan persamaan teoretis dan hasil pengukuran lapangan maupun pengujan laboratorium. Dengan persamaan teoretis tersebut, nilai rasio (su/sv’) yang biasa digunakan dalam rekayasa praktis bisa dijelaskan secara mekanika tanah. Kata-kata Kunci: Tanah kohesif jenuh, rasio c/p, tanah terkonsolidasi normal, kuat geser tak teralirkan, kuat geser efektif, persamaan teoretis.  

Multivariate Adaptive Regression Spline and Least Square Support Vector Machine for Prediction of Undrained Shear Strength of Clay

2012 ◽  
Vol 3 (2) ◽  
pp. 33-42 ◽  
Author(s):  
Pijush Samui ◽  
Pradeep Kurup
Keyword(s):  
Support Vector Machine ◽  
Shear Strength ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Undrained Shear Strength ◽  
Least Square ◽  
Support Vector ◽  
Regression Spline ◽  
Adaptive Regression ◽  
Undrained Shear

This study adopts Multivariate Adaptive Regression Spline (MARS) and Least Square Support Vector Machine (LSSVM) for prediction of undrained shear strength (su) of clay, based Cone Penetration Test (CPT) data. Corrected cone resistance (qt), vertical total stress (sv), hydrostatic pore pressure (u0), pore water pressure at the cone tip (u1), and pore water pressure just above the cone base (u2) are used as input parameters for building the MARS and LSSVM models. The developed MARS and LSSVM models give simple equations for prediction of su. A comparative study between MARS and LSSSM is presented. The results confirm that the developed MARS and LSSVM models are robust for prediction of su.

scholarly journals Post-Cyclic Mechanical Behaviors of Undisturbed Soft Clay with Different Degrees of Reconsolidation

2021 ◽  
Vol 11 (16) ◽  
pp. 7612
Author(s):  
Yuan Lu ◽  
Jian Chen ◽  
Juehao Huang ◽  
Libo Feng ◽  
Song Yu ◽  
...  
Keyword(s):  
Shear Strength ◽  
Cyclic Loading ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Undrained Shear Strength ◽  
Excess Pore Water Pressure ◽  
Undrained Shear ◽  
Excess Pore

Soft soil is often subjected to cyclic loading such as that imposed during storms, under traffic, or in an earthquake. Furthermore, the cyclic-loading-induced excess pore water pressure can be partially dissipated after cyclic loading. Thus, different reconsolidation processes should be considered. A series of static and dynamic triaxial tests were conducted on undisturbed soft soil to determine the post-cyclic mechanical behavior thereof, such as the variation of undrained shear strength, the development of excess pore water pressure, and the evolution of effective stress path. The effects of consolidated confining pressure, cyclic stress ratio, and degree of reconsolidation were analyzed. Results show that the trend of all stress–strain curves is similar under different conditions. The effect of the degree of reconsolidation is such that, with increasing the degree of reconsolidation, the shear strength is enhanced. Meanwhile, compared with undrained shear strength without cyclic loading, the shear strength after cyclic loading with full reconsolidation is increased. These factors also have a significant effect on the undrained shear strength: the greater both the confining pressure and cyclic stress ratio are, the higher the undrained shear strength. A positive excess pore water pressure is always observed during post-cyclic shearing process, irrespective of different factors. The S-shaped effective stress paths under different test conditions are observed and cross the critical state line. The microstructures of undisturbed soil and post-cyclic specimens with different degrees of reconsolidation were quantitatively investigated. Besides that, the degree of influence of different factors on the post-cyclic undrained strength was analyzed. Based on the test results, the undrained shear strength with cyclic load-history was well predicted by existing models.

Tensile Strain-Rate Dependency of Pore Water Pressure and Failure Strength of Soil

2014 ◽  
Vol 13 (5) ◽  
pp. vzj2013.06.0098 ◽  
Author(s):  
Paul D. Hallett ◽  
Thomas Baumgartl ◽  
Jonathan P.K. Seville ◽  
Rainer Horn ◽  
Anthony R. Dexter
Keyword(s):  
Strain Rate ◽  
Pore Water ◽  
Tensile Strain ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Failure Strength ◽  
Rate Dependency ◽  
Strain Rate Dependency

scholarly journals Interpretation of undrained shear strength observed in confined triaxial compression tests on compacted clay

2021 ◽  
Author(s):  
Chee K. Wong ◽  
Martin Lun ◽  
Ron C.K. Wong
Keyword(s):  
Shear Strength ◽  
Unsaturated Soil ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Undrained Shear Strength ◽  
Compacted Clay ◽  
Compression Tests ◽  
Basic Model ◽  
Triaxial Compression Tests ◽  
Undrained Shear

This paper presents an interpretation technique to quantify the effects of compaction state and matric suction on the undrained shear strength of compacted clay under confined undrained triaxial compression. This novel technique is based on the mathematical frameworks of SHANSEP (Stress History and Normalized Soil Engineering Property) method for saturated soil and BBM (Barcelona Basic model) for unsaturated soil. Test data of compacted Calgary till were analyzed and interpreted using the proposed technique. The interpretation technique is very useful in delineating the relative impacts of the factors on the behavioral trends in measured undrained shear strength. It was found that in addition to the initial compacted void ratio and suction, soil structure and failure mode exert significant influence on the undrained shear strength of compacted clay. This technique is attractive to engineering practitioners because the confined undrained compression tests (with no pore air and water pressure measurement) are much simpler and less time consuming compared to rigorous laboratory tests on unsaturated soil.

Finite element modeling of partially embedded pipelines in clay seabed using Coupled Eulerian–Lagrangian method

2015 ◽  
Vol 52 (1) ◽  
pp. 58-72 ◽  
Author(s):  
Sujan Dutta ◽  
Bipul Hawlader ◽  
Ryan Phillips
Keyword(s):  
Finite Element ◽  
Shear Strength ◽  
Strain Rate ◽  
Deep Water ◽  
Strain Softening ◽  
Mesh Size ◽  
Undrained Shear Strength ◽  
Band Formation ◽  
Offshore Pipelines ◽  
Undrained Shear

Vertical seabed penetration and lateral movement of deep-water offshore pipelines are simulated using the Coupled Eulerian–Lagrangian (CEL) approach in Abaqus finite element (FE) software. Abaqus CEL has been used in some previous studies to simulate large-deformation behavior of offshore pipelines; however, the effects of strain rate and strain-softening on undrained shear strength (su) have not been considered. In this study, the effects of these factors are critically examined. The available built-in models in Abaqus CEL cannot account for these factors directly, especially the strain rate; therefore, the development of user subroutines is required. In the present study, a simple but realistic soil constitutive model (published by Zhou and Randolph in 2007) that considers the effects of strain rate and strain-softening on su is implemented in Abaqus CEL. The effects of FE mesh size and shear band formation on penetration resistance are discussed based on a comprehensive FE simulation. Lateral analyses are performed for “light” and “heavy” pipes in clay seabed having a linearly increasing undrained shear strength profile for smooth and rough pipe–soil interface conditions. The FE results are compared with previous theoretical, numerical, and centrifuge test results. Based on the present FE analyses, it is shown that, similar to the remeshing and interpolation techniques with small strain (RITSS) technique developed at the The University of Western Australia, the Abaqus CEL can successfully simulate the response of partially embedded pipelines in deep-water clay seabed, provided strain rate and softening dependent clay models are implemented. A methodology to implement such a model using Abaqus user subroutine is also presented.

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