Structure characteristics and mechanical properties of kaolinite soils. II. Effects of structure on mechanical properties

2006 ◽  
Vol 43 (6) ◽  
pp. 601-617 ◽  
Author(s):  
Y -H Wang ◽  
W -K Siu
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Shear Modulus ◽  
Critical State ◽  
Soil Structure ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Undrained Shear Strength ◽  
Interparticle Forces ◽  
Undrained Shear

This paper reports the effects of structure on the mechanical responses of kaolinite with known and controlled fabric associations. The dynamic properties and strength were assessed by resonant column tests and undrained triaxial compression tests, respectively. The experimental results demonstrate that interparticle forces and associated fabric arrangements influence the volumetric change under isotropic compression. Soils with different structures have individual consolidation lines, and the merging trend is not readily seen under an isotropic confinement up to 250 kPa. The dynamic properties of kaolinite were found to be intimately related to the soil structure. Stronger interparticle forces or higher degrees of flocculated structure lead to a greater small-strain shear modulus, Gmax, and a lower associated damping ratio, Dmin. The soil structure has no apparent influence on the critical-state friction angle (ϕ′c = 27.5°), which suggests that the critical stress ratio does not depend on interparticle forces. The undrained shear strength of kaolinite is controlled by its initial packing density rather than by any interparticle attractive forces, and yet the influence of the structure on the effective stress path is obvious.Key words: interparticle forces, shear modulus, damping ratio, stress–strain behavior, undrained shear strength, critical state.

UNDRAINED SHEAR STRENGTH OF K0 CONSOLIDATED SOFT CLAYS UNDER TRIAXIAL AND PLANE STRAIN CONDITIONS

2014 ◽  
Vol 06 (03) ◽  
pp. 1450032 ◽  
Author(s):  
QIUSHENG WANG ◽  
XIULI DU ◽  
QIUMING GONG
Keyword(s):  
Shear Strength ◽  
Plane Strain ◽  
Yield Surface ◽  
Critical State ◽  
Volumetric Strain ◽  
Stress Path ◽  
Undrained Shear Strength ◽  
Triaxial Tests ◽  
Soft Clays ◽  
Undrained Shear

Theoretical formulas for predicting the undrained shear strength of K0 consolidated soft clays under the stress path related to triaxial and plane strain tests are presented within the framework of critical state soil mechanics. An inclined elliptical yield surface is adopted to take account of the initial anisotropic stress state. The undrained strength is determined by combining the undrained stress path in the volumetric stress–strain space and the initial yield surface in the deviator-mean stress space. The derived mathematical expressions are functions of the critical state frictional angle, the plastic volumetric strain ratio and the overconsolidation ratio, which can be simplified into the solutions for isotropically consolidated clays under triaxial tests or under plane strain tests. The results calculated by using the theoretical formulas obtained in this paper are in good agreement with the available collected test results. It indicates that these new formulas are applicable to triaxial and plane strain tests on normally and lightly to moderately overconsolidated soft clays.

Mechanisms controlling the undrained shear strength behaviour of clays

1999 ◽  
Vol 36 (6) ◽  
pp. 1030-1038 ◽  
Author(s):  
A Sridharan ◽  
K Prakash
Keyword(s):  
Shear Strength ◽  
Double Layer ◽  
Clay Mineralogy ◽  
Shear Resistance ◽  
Undrained Shear Strength ◽  
Interparticle Forces ◽  
Physico Chemical ◽  
Viscous Shear ◽  
Undrained Conditions ◽  
Undrained Shear

The undrained shear strength behaviour of kaolinitic soils is shown to be quite opposite to that observed for montmorillonitic soils under different physico-chemical environments. The mechanism controlling the undrained shear strength behaviour of soils is a function of clay mineralogy of the soils. The present investigation proposes two mechanisms to explain the contradictory behaviour of kaolinitic and montmorillonitic soils under undrained conditions. The undrained shear strength of kaolinitic soils is a result of the net attractive forces and the mode of particle arrangement as governed by the interparticle forces, whereas that of montmorillonitic soils can be attributed to the viscous shear resistance of the double-layer water. The validity of the proposed mechanisms is confirmed by the results of the present investigation and those in the literature.

scholarly journals Undrained shear strength of Lisbon Miocene clay: a reappraisal based on triaxial and pressuremeter test results

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Mafalda Lopes Laranjo ◽  
Manuel Matos Fernandes
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Physical And Mechanical Properties ◽  
Undrained Shear Strength ◽  
Triaxial Tests ◽  
Relevant Parameter ◽  
List Type ◽  
Test Results ◽  
Overconsolidated Clays ◽  
Undrained Shear

Abstract Undrained shear strength plays a fundamental role on the behaviour of clays. In overconsolidated clays, this parameter is largely influenced by test conditions, namely consolidation stress. “Prazeres Clay” is a Miocene overconsolidated formation, that can be found in a significant part of Lisbon area. Over the last decades a number of very relevant constructions have generated a large database for physical and mechanical properties of Miocene clays. Included in a broader study at the Faculty of Engineering of Porto University about Miocene clay’s physical and mechanical properties, existing data was gathered, treated and critically analysed, in order to establish a useful framework for geotechnical designers. This paper presents the results obtained for undrained shear strength, obtained from triaxial tests and Ménard Pressuremeter tests. It addresses the main difficulties associated with test’s interpretation and presents a discussion on how theoretical values relate to experimental ones. The paper proposes a range of variation for Prazeres Clay’ undrained shear strength based on a significant amount of test results, that is considered to be useful for geotechnical design. Article Highlights Undrained Shear strength is a relevant parameter for clays, and is usually derived from triaxial tests For overconsolidated clays, this parameter is highly dependent on preconsolidation stress, and on its relation to in situ stress. Based on a significant set of data, the paper presents a simple methodology for estimating this parameter

scholarly journals Site Investigations of the Lacustrine Clay in Taihu Lake, China, Using Self-Boring Pressuremeter Test

Sensors ◽  
2021 ◽  
Vol 21 (18) ◽  
pp. 6026
Author(s):  
Bin Wang ◽  
Kang Liu ◽  
Yong Wang ◽  
Quan Jiang
Keyword(s):  
Shear Strength ◽  
Shear Modulus ◽  
Normal Distribution ◽  
Taihu Lake ◽  
Undrained Shear Strength ◽  
Plasticity Index ◽  
Lake Area ◽  
Site Investigations ◽  
Lacustrine Clay ◽  
Undrained Shear

Site investigations of the soils are considered very important for evaluation of the site conditions, as well as the design and construction for the project built in it. Taihu tunnel is thus far the longest tunnel constructed in the lake in China, with an entire length of over 10 km. However, due to the very insufficient site data obtained for the lacustrine clay in the Taihu lake area, a series of self-boring pressuremeter (SBPM) field tests was therefore carried out. Undrained shear strengths were deduced from the SBPM test, with the results showing generally higher than those obtained from the laboratory tests, which may be attributed to the disturbance to the soil mass during the sampling process. Degradation characteristics of the soil shear modulus (Gs) were mainly investigated, via a thorough comparison between different soil layers, and generally, the shear modulus would cease its decreasing trends and become stable when the shear strain reaches over 1%. Meanwhile, it was found that a linear relationship between the plasticity index and the shear modulus, and between the decay rate of the shear modulus and the plasticity index as well, could be developed. Further statistical analysis over the undrained shear strength and shear modulus distribution of the soils shows that the undrained shear strength of the soils follows a normal distribution, while the shear modulus follows a log-normal distribution. More importantly, the spatial correlation length of the shear modulus is found much smaller than that of the undrained strength.

The influence of constitutive models on self-boring pressuremeter interpretation in clay

1995 ◽  
Vol 32 (3) ◽  
pp. 420-427 ◽  
Author(s):  
Christropher Nigel Pye
Keyword(s):  
Shear Strength ◽  
Shear Modulus ◽  
Constitutive Models ◽  
Undrained Shear Strength ◽  
Systematic Difference ◽  
Stiff Clays ◽  
Perfectly Plastic ◽  
Lift Off ◽  
Elastic Perfectly Plastic ◽  
Undrained Shear

A comparison of the elastic-perfectly plastic (EPP) and hyperbolic (HB) theories for interpreting loading and unloading parts of self-boring pressuremeter (SBP) tests in clay is presented. Computer-aided modelling (CAM) is used to analyze 60 SBP tests in clay to obtain shear modulus (G), undrained shear strength (Su), and in situ total horizontal geostatic stress (σHo). It is shown that the technique of CAM is consistent, repeatable, and simple to use. For all tests analyzed by both models the inferred horizontal geostatic stresses are identical and comparable to "lift-off" measurements. A small systematic difference is found between the two models for the undrained shear strength of soft and stiff clays. The shear modulus valves derived from the EPP model are unrelated to the true modulus of the soil. There is, however, a semiempirical relationship between the HB model and pressuremeter unload–reload (UR) shear modulus. Key words : clay, self-boring pressuremeter, elastic-perfectly plastic, hyperbolic.

scholarly journals Evaluation of Dynamic Properties of Sodium-Alginate-Reinforced Soil Using A Resonant-Column Test

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2743
Author(s):  
Seongnoh Ahn ◽  
Jae-Eun Ryou ◽  
Kwangkuk Ahn ◽  
Changho Lee ◽  
Jun-Dae Lee ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Sodium Alginate ◽  
Shear Failure ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Reinforced Soil ◽  
Resonant Column ◽  
Column Test ◽  
Alginate Solution ◽  
Resonant Column Test

Ground reinforcement is a method used to reduce the damage caused by earthquakes. Usually, cement-based reinforcement methods are used because they are inexpensive and show excellent performance. Recently, however, reinforcement methods using eco-friendly materials have been proposed due to environmental issues. In this study, the cement reinforcement method and the biopolymer reinforcement method using sodium alginate were compared. The dynamic properties of the reinforced ground, including shear modulus and damping ratio, were measured through a resonant-column test. Also, the viscosity of sodium alginate solution, which is a non-Newtonian fluid, was also explored and found to increase with concentration. The maximum shear modulus and minimum damping ratio increased, and the linear range of the shear modulus curve decreased, when cement and sodium alginate solution were mixed. Addition of biopolymer showed similar reinforcing effect in a lesser amount of additive compared to the cement-reinforced ground, but the effect decreased above a certain viscosity because the biopolymer solution was not homogeneously distributed. This was examined through a shear-failure-mode test.

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