Study on Strength of Shanghai Marine Clay by True Triaxial Test

2012 ◽  
Author(s):  
Jia-ren Sheng ◽  
Chao-jun Wu ◽  
Guan-lin Ye ◽  
Jian-hua Wang
Keyword(s):  
Soft Soil ◽  
Three Dimensional ◽  
Stress Path ◽  
Failure Criteria ◽  
Yangtze River Delta ◽  
Triaxial Tests ◽  
True Triaxial Test ◽  
Marine Clay ◽  
Undisturbed Soil ◽  
True Triaxial

Shanghai locates on the east tip of Yangtze River Delta facing the East China Sea. Shanghai marine clay owns some particular properties. However, the report on the mechanical properties of Shanghai marine clay is rather rare. The three-dimensional strength and deformation characteristics of soft soil are dependent on the stress conditions. In this study, a series of isotropic consolidated drained true triaxial tests are carried out with an automatically controlled mixed rigid-flexible boundary true triaxial apparatus. Undisturbed soil sample is prepared by the block sampling method. 5 drained tests with stress path in the same π plane along different Lode angles are performed. Tests results show that the intermediate stress has large influence on the yielding and failure of Shanghai marine clay. Three dimensional strength of Shanghai marine clay generally obeys the SMP failure criteria.

scholarly journals Comparative Analysis of Common Strength Criteria of Soil Materials

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4302
Author(s):  
Ping Xu ◽  
Zhijun Sun ◽  
Shengjun Shao ◽  
Lingyun Fang
Keyword(s):  
Failure Criterion ◽  
Triaxial Test ◽  
Three Dimensional ◽  
Strength Criterion ◽  
Failure Criteria ◽  
Theory And Practice ◽  
Engineering Practice ◽  
Test Results ◽  
True Triaxial Test ◽  
True Triaxial

In this paper, the common failure criteria of existing soil materials, such as the Mohr–Coulomb criterion, Drucker–Prager criterion, Lade–Duncan criterion, Matsuoka–Nakai criterion andAC-SMP criterion are systematically discussed, and the applicability of these criteria is quantitatively analyzed through the true triaxial test results of loess, so as to provide reference for the accurate selection of specific criteria in engineering practice. The failure criteria are classified from several aspects, such as whether the influence of the intermediate principal stress and the change of spatial moving plane are considered, analyzed and discussed, respectively. According to the true triaxial test results of undisturbed loess, the difference of strength criterion between the three-dimensional failure plane and p-q plane is analyzed, and based on the true triaxial test data of undisturbed loess, the error analysis of each failure criterion is carried out. The results show that the AC-SMP criterion is in good agreement with the test results, and can accurately evaluate the true triaxial test of loess. For different soil materials or different stress states, it is necessary to select appropriate failure criteria. This study shows how to choose the corresponding failure criterion under specific circumstances, so as to better satisfy the theory and practice and provide reference for engineering.

Anisotropic Behavior of Geomaterial under Three-Dimensional Stress States

2010 ◽  
Vol 160-162 ◽  
pp. 1425-1431
Author(s):  
Kun Yong Zhang ◽  
Yan Gang Zhang ◽  
Chi Wang
Keyword(s):  
Stress State ◽  
Principal Stress ◽  
Three Dimensional ◽  
Complex Stress State ◽  
Triaxial Tests ◽  
Induced Anisotropy ◽  
Principal Stresses ◽  
True Triaxial ◽  
Stress Effects ◽  
Stress Induced Anisotropy

Most soil constitutive models were developed based on the traditional triaxial tests with isotropic assumption, in which the load is applied as the major principal stress direction and the other two principal stresses are symmetric. When such isotropic models are applied to practical analysis, stress induced anisotropy under complex stress state and the middle principal stress effects are often neglected, thus there are many disagreements between the calculated results and the infield testing data. To simulate the practical loading process, true triaxial tests were carried out on geomaterial under three-dimensional stress state. It was found that the stress induced anisotropy effects are remarkable and the middle principal stress effects are obvious because of the initial three-dimensional stress state. Such kind of stress-induced anisotropy could have important impact on the numerical analysis results and should be taken into consideration when developing the constitutive model.

Study on Microstructure Changes of Soft Clay in the Peal River Delt under Dynamic Load

2014 ◽  
Vol 894 ◽  
pp. 238-244
Author(s):  
Shi Hua Liang ◽  
Lang Zhang ◽  
Yong Jian Liu ◽  
Na Fu
Keyword(s):  
Dynamic Load ◽  
Soft Soil ◽  
Soft Clay ◽  
Microscopic Theory ◽  
Average Diameter ◽  
Test System ◽  
True Triaxial Test ◽  
True Triaxial ◽  
Shape Coefficient ◽  
Microstructure Parameters

The characteristics and distribution of pores in soil are the key factors in the determination of the physical and mechanical characteristics of soft soil. Using static-dynamic true triaxial test system of modified SPAX-2000 and scanning electron microscope (SEM), the microstructure images of soft clay in the Peal River Delt are studied. By analyzing these microstructure images, eight microstructure parameters including number of pore, total area, classification of area, total perimeter, average diameter, roundness, shape coefficient and anisotropy have been obtained. The changes of microstructure parameters are analyzed ,before and after applying dynamic load . The results show that the change of microstructure parameters has certain rules. This study is help to provide microscopic theory basis for static-dynamic drainage consolidation method to treatment soft ground engineering design.

Numerical Simulation of Breakwaters for Land Reclamation

2009 ◽  
Author(s):  
Jian-Min Zhang ◽  
Jianhong Zhang ◽  
Gang Wang ◽  
Yang Chen
Keyword(s):  
Land Reclamation ◽  
Southern China ◽  
Soft Soil ◽  
Three Dimensional ◽  
Marine Clay ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Reclamation Project ◽  
The Moment ◽  
Three Dimensional Finite Element

This paper highlights some practical considerations of soil structure interactions in the design of the breakwater for a land reclamation project at Da Ya Bay, Southern China sea, through three-dimensional finite element analysis. A pile-breakwater-foundation system is evaluated during its construction and after construction has been completed. The maximum deflections and moments of the piles take place in the soft marine clay underneath the breakwater. The deformation of the soft soil imposes great impact on the slender pile. Based on the study, it is considered inadequate to solely increase the density and stiffness of the piles, as it will not effectively reduce the deformation of the foundation as well as the moment of the pile. On the contrary, the increased stiffness results in significant increase of the stresses in the pile. Consequently, the deformation of pile should be evaluated in terms of interactions between soil and pile. Improvement of the soft marine clay is also of great importance.

An Analysis of the Strength of Anisotropic Granular Assemblies via Discrete Methods

2014 ◽  
Vol 553 ◽  
pp. 525-530
Author(s):  
Sergio Andres Galindo-Torres ◽  
Dorival Pedroso ◽  
David Williams ◽  
Hans Mühlhaus
Keyword(s):  
Shear Strength ◽  
Granular Media ◽  
Three Dimensional ◽  
Spherical Particles ◽  
Triaxial Tests ◽  
True Triaxial ◽  
Polyhedral Particles ◽  
Granular Assemblies ◽  
Mean Pressure ◽  
Confining Pressures

This paper presents a study on the macroscopic strength characteristics of granular assemblies with three-dimensional complex-shaped particles. Different assemblies are considered, with both isotropic and anisotropic particle geometries. The study is conducted using the Discrete Element Method (DEM), with so-called sphero-polyhedral particles, and simulations of mechanical true triaxial tests for a range of Lode angles and confining pressures. The observed mathematical failure envelopes are investigated in the Haigh-Westergaard stress space, as well as on the deviatoric-mean pressure plane. It is verified that the DEM with non-spherical particles produces results that are qualitatively similar to experimental data and previous numerical results obtained with spherical elements. The simulations reproduce quite well the shear strength of assemblies of granular media, such as higher strength during compression than during extension. In contrast, by introducing anisotropy at the particle level, the shear strength parameters are greatly affected, and an isotropic failure criterion is no longer valid. It is observed that the strength of the anisotropic assembly depends on the direction of loading, as observed for real soils.

Assessment of the Mechanical Behaviour of Granular Media by DEM-Based True Triaxial Tests

2016 ◽  
Vol 846 ◽  
pp. 428-433
Author(s):  
J. Cabrejos-Hurtado ◽  
S. Galindo Torres ◽  
D.M. Pedroso
Keyword(s):  
Numerical Simulation ◽  
Mechanical Behaviour ◽  
Granular Media ◽  
Triaxial Tests ◽  
Granular Soils ◽  
True Triaxial Test ◽  
Virtual Sample ◽  
True Triaxial ◽  
Toyoura Sand ◽  
True Triaxial Tests

This study presents the numerical simulation of a true triaxial test by means of the discrete element method (DEM). Experimental results performed on Toyoura sand are employed as reference and the calibration methodology is explained. Physical aspects of the real soil, such as the grain size distribution and the relative density, are considered during the generation of the virtual sample. It is shown that the main aspects of the macro-mechanical behaviour of granular soils during compression loading can be fairly represented by the idealised simulations with particles.

Unified Three-Dimensional Revision of Modified Cam Clay Model

2007 ◽  
Vol 340-341 ◽  
pp. 1267-1272
Author(s):  
Hang Zhou Li ◽  
Hong Jian Liao ◽  
Kyoji Sassa ◽  
Gong Hui Wang
Keyword(s):  
Three Dimensional ◽  
Yield Function ◽  
Triaxial Tests ◽  
Strength Theory ◽  
Unified Strength Theory ◽  
True Triaxial ◽  
Proposed Model ◽  
Modified Cam Clay ◽  
Stress States ◽  
Cam Clay

According to unified strength parameters obtained from unified strength theory, the slope of critical state line is modified to reflect critical states of different geomaterials under general stress states. Yield function that can consider the effect of the third deviatoricic invariant is proposed, and an elasto-plastic constitutive model is established by adopting non-associated flow rules; furthermore, methods of overcoming singular points on the yield surface are discussed. The proposed model is verified by true triaxial tests of clay, and results show that the model can well predict stress-strain relationships.

Geogrid-Reinforced Pile-Supported Railway Embankments

2005 ◽  
Vol 1936 (1) ◽  
pp. 221-229 ◽  
Author(s):  
Jie Huang ◽  
Jie Han ◽  
James G. Collin
Keyword(s):  
Load Transfer ◽  
Soft Soil ◽  
Three Dimensional ◽  
Field Measurements ◽  
Failure Criteria ◽  
Organic Soils ◽  
Lagrangian Analysis ◽  
Modeling And Analysis ◽  
Axial Forces ◽  
Lateral Displacements

Piles or columns have been used successfully in combination with geosynthetics to support embankments over soft soil. The inclusion of geosynthetic reinforcement over piles enhances load transfer from soil to piles, reduces total and differential settlements, and increases slope stability. It creates a more economical alternative than that without the geosynthetic. An existing geosynthetic-reinforced pile-supported embankment in Berlin was selected for numerical modeling and analysis. This embankment was constructed to support railways over deep deposits of peat and soft organic soils. Precast piles and caps were installed with a load transfer platform formed by three layers of geogrid and granular materials installed between the piles and the embankment fill. Instrumentation was installed to monitor the settlements of the embankment and the strains in the geogrid layers over time. A finite difference method, incorporated in the fast Lagrangian analysis of continua three-dimensional software, was used to model this embankment. In the numerical analysis, piles were modeled with pile elements, and caps were modeled as an elastic material. Geogrid elements built in the software were used to represent the geogrid reinforcement. Embankment fill, soft soil, firm soil, and platform fill material were modeled as linearly elastic perfectly plastic materials with Mohr–Coulomb failure criteria. The embankment was built by a number of lifts to simulate its construction. Numerical results and comparisons with field measurements on the vertical and lateral displacements, the tension along the reinforcement, and the axial forces and moments on piles are presented.

Unified hardening (UH) model for overconsolidated unsaturated soils

2014 ◽  
Vol 51 (7) ◽  
pp. 810-821 ◽  
Author(s):  
Y.P. Yao ◽  
L. Niu ◽  
W.J. Cui
Keyword(s):  
Unsaturated Soils ◽  
Path Dependence ◽  
Three Dimensional ◽  
Constitutive Models ◽  
Stress Path ◽  
Triaxial Tests ◽  
Additional Material ◽  
Basic Model ◽  
Proposed Model ◽  
Unsaturated Clays

Naturally deposited clays are often unsaturated and overconsolidated. Within the frameworks of the Barcelona Basic model (BBM) for normally consolidated unsaturated clays and the unified hardening (UH) model for overconsolidated saturated clays, a three-dimensional constitutive model for overconsolidated unsaturated clays is proposed in this paper. This model can be reduced to the original UH model for overconsolidated saturated clays when suction becomes zero and the BBM when the overconsolidated behaviour disappears. Compared with existing constitutive models for unsaturated clays, the influence of a high overconsolidation ratio (OCR) on wetting deformation can be adequately described. Also, many other characteristics of overconsolidated unsaturated clays can be modelled, including strain-hardening, softening, shear dilatancy, and stress path–dependence behaviour. Compared with the BBM, the proposed model requires no additional material parameter. The validity of the UH model for overconsolidated unsaturated clays has been confirmed by data from two groups of wetting tests performed by the authors and previous triaxial tests in the literature.

scholarly journals A Simple Three-Dimensional Failure Criterion for Jointed Rock Masses under True Triaxial Compression

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Yaohui Gao ◽  
Chunsheng Zhang ◽  
Zhaofeng Wang ◽  
Jun Chen
Keyword(s):  
Failure Criterion ◽  
Triaxial Compression ◽  
Three Dimensional ◽  
Friction Angle ◽  
Failure Criteria ◽  
Jointed Rock ◽  
Rock Masses ◽  
True Triaxial ◽  
Jointed Rock Masses ◽  
Triaxial Strength

The joint configuration and the intermediate principal stress have a significant influence on the strength of rock masses in underground engineering. A simple three-dimensional failure criterion is developed in this study to predict the true triaxial strength of jointed rock masses. The proposed failure criterion in the deviatoric and meridian planes adopts the elliptic and hyperbolic forms to approximate the Willam–Warnke and Mohr–Coulomb failure criterion, respectively. The four parameters in the proposed failure criterion have close relationships with the cohesion and the internal friction angle and can be linked with the joint inclination angle using a cosine function. Two suits of true triaxial strength data are collected to validate the correctness of the proposed failure criterion. Compared with other failure criteria, the proposed failure criterion is more reasonable and acceptable to describe the strength of jointed rock masses.

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