True Shear Parameters of Saturated Clays

1973 ◽  
Vol 10 (4) ◽  
pp. 652-663
Author(s):  
A. Sridharan ◽  
S. Narasimha Rao
Keyword(s):  
Stress Level ◽  
Pore Water Pressure ◽  
Initial Conditions ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Compression Tests ◽  
Strength Parameters ◽  
Test Procedures ◽  
Stress History ◽  
Triaxial Compression Tests

Ever since Hvorslev proposed a failure criterion incorporating intrinsic parameters, several test procedures have come into practice to determine these ‘true’ strength parameters. Several consolidated undrained triaxial compression tests with pore water pressure measurement were conducted on both montmorillonite and kaolinite clays and the results were analyzed using different existing methods. All the methods through which the data were analyzed fail to assign any unique true strength parameters. Even a particular method yields different values depending upon the initial conditions (stress history, water content) of the sample and stress level during testing. It has been reasoned that these variations are due to the probable differences in fabric between the samples which are involved in various methods. There seems to be a unique linear relationship between tan [Formula: see text] and Cc/pe irrespective of the sample state, stress level, and stress history in both undisturbed and remolded conditions for all the procedures adopted.

scholarly journals Semi-empirical elastic–thermoviscoplastic model for clay

2016 ◽  
Vol 53 (10) ◽  
pp. 1583-1599 ◽  
Author(s):  
David Kurz ◽  
Jitendra Sharma ◽  
Marolo Alfaro ◽  
Jim Graham
Keyword(s):  
Stress Level ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Compression Tests ◽  
One Dimensional ◽  
Load Duration ◽  
Compression Creep ◽  
Overconsolidated Clays ◽  
Semi Empirical ◽  
Triaxial Compression Tests

Clays exhibit creep in compression and shear. In one-dimensional compression, creep is commonly known as “secondary compression” even though it is also a significant component of deformations resulting from shear straining. It reflects viscous behaviour in clays and therefore depends on load duration, stress level, the ratio of shear stress to compression stress, strain rate, and temperature. Research described in the paper partitions strains into elastic (recoverable) and plastic (nonrecoverable) components. The plastic component includes viscous strains defined by a creep rate coefficient ψ that varies with plasticity index and temperature (T), but not with stress level or overconsolidation ratio (OCR). Earlier elastic–viscoplastic (EVP) models have been modified so that ψ = ψ(T) in a new elastic–thermoviscoplastic (ETVP) model. The paper provides a sensitivity analysis of simulated results from undrained (CIŪ) triaxial compression tests for normally consolidated and lightly overconsolidated clays. Axial strain rates range from 0.15%/day to 15%/day, and temperatures from 28 to 100 °C.

Static response of fly ash columnar improved ground

2001 ◽  
Vol 38 (2) ◽  
pp. 276-286 ◽  
Author(s):  
A Porbaha ◽  
T BS Pradhan ◽  
T Kishida
Keyword(s):  
Fly Ash ◽  
Stress Concentration ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Area Ratio ◽  
Stress Redistribution ◽  
Soft Ground ◽  
Compression Tests ◽  
Composite Ground

This study presents the results of a series of monotonic undrained triaxial compression tests on clay specimens improved by columnar reinforcement. The process of loading and stress redistribution of a fly ash – clay specimen (FCS), in comparison with a sand–clay specimen (SCS), is examined in terms of stress–strain characteristics, generation of excess pore-water pressure, effective and total earth pressures, development of stress concentration, and the normalized undrained shear strength of the improved soil. It was found, predictably, that the deviator stress of the composite specimens was influenced by the consolidation stress, replacement area ratio, and properties of the column material. The stress concentration at the top of the composite ground which depends on the loading stage reaches a peak after the consolidation state and is reduced due to stress redistribution between the column and the soft ground. In terms of improvement effects, the mean shear strengths of FCS and SCS relative to the clay specimen are three and seven times greater, respectively, for a replacement area ratio of 49%.Key words: composite ground, fly ash, soil improvement, soft ground, triaxial test.

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.

Pre- and post-cyclic behavior of mixed clayey soils

2009 ◽  
Vol 46 (2) ◽  
pp. 115-128 ◽  
Author(s):  
Abbas Soroush ◽  
Hossein Soltani-Jigheh
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Cyclic Strain ◽  
Cyclic Behavior ◽  
Clayey Soils ◽  
Compression Tests ◽  
Soil Structures ◽  
Number Of Cycles ◽  
Cyclic Strain Amplitude

Soil structures are often comprised or supported by soils that are mixtures of cohesive and granular geomaterials. These soils are termed as intermediate or mixed soils and are widely found in natural deposits and man-made soil structures. The objective of this paper is to study the behavior of mixed clayey soils under monotonic, cyclic, and post-cyclic monotonic loading, with the main focus on the last of these three. For this purpose, a number of strain-controlled monotonic, cyclic, and post-cyclic triaxial compression tests were carried out on “clay–sand” and “clay–gravel” mixtures in undrained conditions. The effects of sand (or gravel) contents, number of cycles, cyclic strain amplitude, consolidation pressure, and grain size on the mechanical behavior of the mixtures are evaluated. The major findings from the laboratory study are: (i) the addition of granular materials to the clayey soils increases excess pore-water pressure during strain-controlled monotonic undrained shearing and cyclic loading and (ii) during post-cyclic monotonic shearing, mixed clayey soils behave similarly to overconsolidated soils; the higher the granular material is, the higher the overconsolidation ratio would be. Based on the research results, an algorithm for estimating post-cyclic mechanical parameters of mixed clayey soils, without conducting cyclic and post-cyclic tests, is suggested.

scholarly journals Change of soil mechanical properties due to triaxial sample size

2019 ◽  
Author(s):  
Šarūnas Skuodis ◽  
Neringa Dirgėlienė ◽  
Ieva Lekstutytė
Keyword(s):  
Shear Strength ◽  
Sample Size ◽  
Triaxial Compression ◽  
Specimen Size ◽  
Compression Tests ◽  
Shear Strength Parameters ◽  
Strength Parameters ◽  
Soil Shear Strength ◽  
Confining Pressures ◽  
Triaxial Compression Tests

Triaxial test is widely used to determine the behaviour and strength parameters of soil. Several consolidated drained triaxial compression tests were performed on two specimen sizes of sand and clay. This article investigate and compares the influence of specimen size and scale effect on the soil shear strength. The tests results show that the shear strength parameters are influenced by the clay specimen size. The results indicate that the effect of triaxial clay sample size is more significant with higher confining pressures. The second type of tests carried out on sand samples shows that sample size doesn‘t influence the results of the shear strength. Author’s show that clay analyses can be significantly affected by the choice of the specimen size used to determine shear strength parameters.

Cyclic Response and Instability Analysis of Seabed With Cohesionless Soils Due to Surging Waves

2021 ◽  
Author(s):  
Amin Rafiei ◽  
M. A. Gabr ◽  
M. S. Rahman ◽  
Majid Ghayoomi
Keyword(s):  
Finite Element ◽  
Pore Pressure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Soil Liquefaction ◽  
Cyclic Behavior ◽  
Cohesionless Soil ◽  
Compression Tests ◽  
Element Analysis

Abstract Surface waves may generate significant loadings on the seabed destabilizing sediments and the supporting marine structures. This threat is more pronounced in shallower water depths where the cyclic wave loading may induce residual pore water pressure in sediments triggering soil liquefaction. In this paper, a coupled numerical framework is presented to evaluate the interaction of waves and horizontal seabed considering nonlinear cyclic behavior of the cohesionless soil. A simple experimental model is employed for concurrent simulation of nonlinear buildup of pore pressure and deformation of saturated sand subjected to the cyclic loadings. The model (in elemental scale) is incorporated into a finite element code to solve the interaction of wave and seabed. Poro-elastoplastic response of the seabed is obtained by modifying the Biot’s coupled flow-and-deformation equations by adding equivalent nodal force terms associated with residual deformations of the soil. Potential flow theory is adopted for the fluid domain to model wave-induced pressure and flow fields. The governing equations and boundary conditions are solved using finite element analysis in time domain. The numerical framework is verified against results of cyclic triaxial compression tests and analytical solutions. Parametric studies are conducted to evaluate the effects of wave characteristics on triggering the residual liquefaction. The numerical results indicate good agreements with experimental measures. The results also show that for large waves, the progressive buildup of pore pressure in sediments may become high enough, leading to residual liquefaction. The details of the numerical model and the potential of residual liquefaction within the seabed soil are discussed.

Experimental Research of Fine Sandstone Strength and Deformation Characteristics under Different Confining and Hydraulic Pressure

2013 ◽  
Vol 353-356 ◽  
pp. 562-570 ◽  
Author(s):  
Zai Bin Liu
Keyword(s):  
Rock Strength ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Hydraulic Pressure ◽  
Compression Tests ◽  
Exponential Relationship ◽  
Sandstone Rock ◽  
Strength And Deformation

In order to study sandstone rock strength and deformation parameters under pore water pressure conditions, triaxial compression tests of different hydraulic pressure were executed. Fitting equations of fine sandstone confining pressure and hydraulic pressure coupling effects were established. This research show that fine sandstone rock strength increases with confining pressure increases. Rock mass strength and cohesion have negative exponential relationship with hydraulic pressure. When the hydraulic pressure is 3MPa, elasticity and confining pressure fit to logarithmic relationship. Fine sandstone Elasticity modulus decreases with hydraulic pressure increases. Poisson’s ration and hydraulic pressure fit to linear relationship.

scholarly journals Consolidated Undrained Triaxial Compression Tests and Strength Criterion of Solidified Dredged Materials

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Jianwen Ding ◽  
Xusong Feng ◽  
Yupeng Cao ◽  
Sen Qian ◽  
Feng Ji
Keyword(s):  
Shear Strength ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Strength Criterion ◽  
Undrained Shear Strength ◽  
Compression Tests ◽  
Dredged Materials ◽  
Strength Evolution ◽  
Triaxial Compression Tests ◽  
Undrained Shear

Consolidated undrained triaxial compression tests were performed to investigate the shear strength behavior of the solidified dredged materials (SDM). The variation law of deviator stress and excess pore water pressure with the increase of the applied confining pressure was investigated. It is found that the shear strength envelope is consisted of two lines, and there exists a transitional stress on the intersection point. The undrained shear strength develops slightly with the increase of applied normal stress in the preyield state. However, the undrained shear strength increases significantly in the postyield state, and the strength envelope is nearly a straight line with the extension through the origin. Based on the triaxial test data and the binary medium model, a strength criterion considering strength evolution mechanism is proposed and the relevant parameters of the strength criterion were discussed. Comparisons of the predicted results and experimental data demonstrate that the proposed strength criterion can properly describe the strength evolution rules of the SDM.

scholarly journals Evolution of Strength Parameters for Sandstone Specimens during Triaxial Compression Tests

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xiang Ding ◽  
Na Chen ◽  
Fan Zhang ◽  
Guangqing Zhang
Keyword(s):  
Stress Tensor ◽  
Triaxial Compression ◽  
Cohesive Strength ◽  
Compression Tests ◽  
Strength Parameters ◽  
Frictional Strength ◽  
Coulomb Criterion ◽  
First Time ◽  
Triaxial Compression Tests ◽  
Deviatoric Stress Tensor

Despite the lack of test data of the coefficient of pressure sensitivity α and the shearing cohesion k, the Drucker–Prager criterion is commonly applied for numerical analyses of geotechnical engineering. To bridge the gap between the wide application and insufficient knowledge of strength parameters of the Drucker–Prager criterion, this study presents experimentally calibrated strength parameters of this criterion for the first time. This paper proposes a new method to measure α and k in the Drucker–Prager criterion. The square root of the second invariant of the deviatoric stress tensor J 2 is linearly fitted with the first invariant of the stress tensor I 1 in the stress space. The parameters φ and c in the Mohr–Coulomb criterion and α and k in the Drucker–Prager criterion are calibrated to the same set of triaxial compression tests of sandstones. With these testing results, five pairs of conversion formulae (which are most commonly used in the literature) are examined and the most appropriate pair of conversion formulae is identified. With parameters indicating cohesive strength (c and k) and parameters indicating frictional strength ( φ and α ), the evolutions of different strength components are compared with those in the cohesion-weakening friction-strengthening model. With an increase in plastic deformation, the cohesive strength parameters c and k firstly increase to a peak value and then decrease. The frictional strength parameters φ and α gradually increase at a decreasing rate after the initial yield point.

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