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.

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.

scholarly journals The undrained shear strength anisotropy of four Jurassic to Eocene stiff clays

Géotechnique ◽  
2017 ◽  
Vol 67 (8) ◽  
pp. 653-671 ◽  
Author(s):  
A. M. Brosse ◽  
R. J. Jardine ◽  
S. Nishimura
Keyword(s):  
Shear Strength ◽  
Undrained Shear Strength ◽  
Strength Anisotropy ◽  
Stiff Clays ◽  
Undrained Shear

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.

scholarly journals Evaluation of Undrained Shear Strength of Miocene Clay from the Weight Sounding Test (WST)

2017 ◽  
Vol 62 (2) ◽  
pp. 367-384
Author(s):  
Sebastian Olesiak
Keyword(s):  
Shear Strength ◽  
Field Testing ◽  
Field Investigation ◽  
Undrained Shear Strength ◽  
Cohesive Soils ◽  
Strength Parameters ◽  
Additional Measurement ◽  
Carpathian Foredeep ◽  
Innovative Solution ◽  
Undrained Shear

Abstract Soil strength parameters needed for the calculation of bearing capacity and stability are increasingly determined from field testing. This paper presents a method to determine the undrained shear strength cuWST of the soil, based on the Weight Sounding Test (WST). The innovative solution which allows for a significant reduction of equipment needed for geotechnical field investigation is presented. The proposed method is based on an additional measurement of the torque during testing. It then becomes possible to estimate the undrained shear strength, cuWST of the soil, using the correlation given in this paper. The research results presented in this paper were carried out on selected cohesive soils, Miocene clays from the Carpathian Foredeep.

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