Stress path during pressuremeter test and link between shear modulus and Menard pressuremeter modulus in unsaturated fine soils

This paper presents a study of the pressuremeter test and the results that can be obtained from this test. Hostun's fine sand was chosen as the material upon which to perform the experimental study of the pressuremeter. Numerical simulations of the pressuremeter tests have been made with the commercially available PLAXIS software. The numerical results have been compared with the experimental ones. The variation of the parameters resulting from an applied surcharge was studied experimentally and numerically. Finally, the relationship between the magnitude of the deformation and the pressuremeter modulus was analyzed.Key words: sand, pressuremeter, triaxial, pressure, modulus, deformation, numerical simulation.

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A finite element study of the pressuremeter test in sand using a nonlinear elastic plastic model

Canadian Geotechnical Journal ◽

10.1139/t93-029 ◽

1993 ◽

Vol 30 (2) ◽

pp. 348-362 ◽

Cited By ~ 99

Author(s):

Martin Fahey ◽

John P. Carter

Keyword(s):

Finite Element ◽

Shear Modulus ◽

Hyperbolic Model ◽

Type Model ◽

Model Parameters ◽

Nonlinear Behaviour ◽

Stress Strain ◽

Pressuremeter Test ◽

Strain Behaviour ◽

Highly Nonlinear

The stress–strain behaviour of sands is highly nonlinear, even at stresses well below the peak strength of the sand. The hyperbolic model is a reasonable conceptual model for representing the stress–strain behaviour of sand, but some empirical curve fitting is required to obtain a more realistic model for calculation purposes. This can readily be performed for reconstituted samples of sand using laboratory tests. Recent evidence shows that the stiffness of natural sands is often much greater than that of the same sand when reconstituted at the same density and stress state in the laboratory, and it is therefore necessary to use in situ testing methods to determine the stress–strain behaviour of such sands. In this paper, the finite element method is used to simulate pressuremeter tests in a soil modelled using a hyperbolic-type model. It concentrates on the behaviour in unload-reload loops, which are often included in pressuremeter tests to measure shear modulus. The effect on the whole unload-reload loop of varying some of the model parameters is examined. The results are compared with a high-quality pressuremeter test in sand. It is concluded that, though the results to date are encouraging, some further experimental work is required to verify some of the features of the model. Key words : pressuremeter test, hyperbolic model, nonlinear behaviour, initial shear modulus, sand behaviour.

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Stiffness of lightly cemented sand under multiaxial loading

E3S Web of Conferences ◽

10.1051/e3sconf/20199211008 ◽

2019 ◽

Vol 92 ◽

pp. 11008

Author(s):

Marina Bellaver Corte ◽

Erdin Ibraim ◽

Lucas Festugato ◽

Andrea Diambra ◽

Nilo Cesar Consoli

Keyword(s):

Shear Modulus ◽

Young’S Modulus ◽

Young's Modulus ◽

Stress Path ◽

Silica Sand ◽

Triaxial Tests ◽

Cemented Sand ◽

Content Ratio ◽

Hollow Cylinder Torsional Apparatus ◽

Set Up

This paper presents experimental triaxial tests conducted on two lightly cemented sand samples on the set-up conditions of a Hollow Cylinder Torsional Apparatus (HCTA). The laboratory study has been carried out on an angular to sub-angular silica sand reinforced with Portland cement of high early strength. The samples have identical porosity/volumetric cement content ratio, η/Civ, values. The Young's modulus and shear modulus were measured by the application of a series of small unload-reload cycles at different investigation points along the triaxial stress path up to about 50% of the maximum deviatoric stress. At these investigation points, additional series of unload-reload cycles of higher amplitudes were also applied and the stiffness moduli assessed using local instrumentation. While the peak strength seems to be controlled by the density of the sand matrix, as extensive bond cementation damages occur at peak and pre-peak stages, the Young's modulus and shear modulus normalised by the void ratio function show the effect of the cementation ratio with higher values for the sample with higher cementation ratio.

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Anisotropic stress state and small strain stiffness in granular materials: RC experiments and DEM simulations

Meccanica ◽

10.1007/s11012-020-01229-8 ◽

2020 ◽

Vol 55 (10) ◽

pp. 1869-1883

Author(s):

Meisam Goudarzy ◽

Vanessa Magnanimo ◽

Diethard König ◽

Tom Schanz

Keyword(s):

Shear Modulus ◽

Coordination Number ◽

Triaxial Compression ◽

Analytical Description ◽

Stress Path ◽

Small Strain ◽

Micro Structure ◽

Direct Function ◽

Anisotropic Stress ◽

Small Strain Stiffness

Abstract The paper combines experimental and numerical analyses to study the relation between small strain stiffness and micro-structure of an idealized granular material under isotropic and anisotropic stress conditions. Results from the resonant column device on glass ballotini show that the relation between the maximum shear modulus and anisotropic stress components strongly depends on the applied stress path. Discrete element simulations (DEM) are performed to investigate the material behaviour along isotropic compression, triaxial compression and constant $$\hbox {K}_0$$ K 0 deformation. The DEM analysis reveals that each stress path is associated with a characteristic evolution of the coordination number, i.e., the average number of contacts per particle. In turn, the maximum shear modulus is found to be a direct function of the coordination number. In order to include the micro-structure interpretation in the analytical description, a modified version of Hardin’s relation is proposed as a function of coordination number, void ratio and mean pressure.

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Small-Strain Shear Modulus of Calcareous Sand under Anisotropic Consolidation

Canadian Geotechnical Journal ◽

10.1139/cgj-2021-0329 ◽

2021 ◽

Author(s):

Jinquan Shi ◽

Yang Xiao ◽

Jian Hu ◽

Huanran Wu ◽

Hanlong Liu ◽

...

Keyword(s):

Shear Modulus ◽

Void Ratio ◽

Preparation Method ◽

Stress Path ◽

Small Strain ◽

Sample Preparation Method ◽

Calcareous Sand ◽

Small Strain Shear Modulus ◽

Stiffness Anisotropy ◽

Anisotropic Consolidation

In this study, the small strain shear modulus of a calcareous sand was investigated by conducting bender element tests on both horizontal and vertical planes. The effects of sample preparation method, stress path and stress history on the developing of void ratio, the parameters in the modified Hardin equation and the stiffness anisotropy were examined. The test results show that the moist tamping samples have the least void ratio variation among the five samples. The void ratio recovery in σ'h = 100 kPa tests is higher than that in the σ'v = 100 kPa tests. The samples prepared in dry state have lower stiffness than those prepared in moisture state, which is not influenced by the anisotropic stress state. The stiffness anisotropy induced by the sample preparation method is significant under anisotropic consolidation. In σ'h = 100 kPa tests, the stiffness ratios at the end of the unloading stage are lower than the initial values at the loading stage, which is not found in the σ'v = 100 kPa tests, meaning that the stress history and stress path could affect the stiffness anisotropy and cover the impact of fabric anisotropy.

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The measurements of soil parameters relevant to tunnelling in clays

Canadian Geotechnical Journal ◽

10.1139/t85-049 ◽

1985 ◽

Vol 22 (3) ◽

pp. 375-391 ◽

Cited By ~ 9

Author(s):

Robert M. C. Ng ◽

K. Y. Lo

Keyword(s):

Shear Modulus ◽

Deformation Modulus ◽

Stress Path ◽

Triaxial Tests ◽

Soil Parameters ◽

Silty Clay ◽

Elastic Parameters ◽

Soft Clays ◽

Anisotropic Elastic ◽

Stress States

A comprehensive laboratory program was carried out on specimens trimmed from 152 mm diameter piston samples of a soft silty clay and a varved clay at a tunnel site in Thunder Bay. Results of conventional triaxial tests as well as special tests for the determination of anisotropic elastic parameters, simple shear tests, and stress path tests are presented.Results indicate that the unloading moduli are about twice the loading moduli, the Poisson's ratios in unloading are about three times those in loading, but the independent shear modulus is relatively unaffected. While the modulus is sensitive to mode of consolidation, drainage, and direction of stress path, the stress states at failure of all the different types of tests fall close to a single envelope for compression and extension. The choice of soil parameters for the analysis of deformation in tunnelling in soft clays is discussed. Key words: clay, tunnelling, stress path, deformation modulus, shear modulus, anisotropic elastic parameters, failure envelope.

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