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.

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.

Modeling piezocone cone penetration (CPTU) parameters of clays as a multivariate normal distribution

2014 ◽  
Vol 51 (1) ◽  
pp. 77-91 ◽  
Author(s):  
Jianye Ching ◽  
Kok-Kwang Phoon ◽  
Chih-Hao Chen
Keyword(s):  
Shear Strength ◽  
Normal Distribution ◽  
Multivariate Normal Distribution ◽  
Undrained Shear Strength ◽  
Soil Parameters ◽  
Multivariate Normal ◽  
Cone Penetration ◽  
Overconsolidation Ratio ◽  
Data Points ◽  
Undrained Shear

This study examines the possibility of modeling piezocone cone penetration (CPTU) cone tip resistance, excessive pore pressure behind the cone, undrained shear strength, and overconsolidation ratio of lightly overconsolidated clays as a multivariate normal distribution. This is part of a continuing study to develop a multivariate distribution that could be used to simulate common soil parameters at a clay site. This study compiles a large database consisting of 535 data points in which the CPTU parameters, undrained shear strength, and overconsolidation ratio are simultaneously measured in close proximity. A multivariate normal distribution is then used to capture the correlations between soil parameters of interest and to derive useful equations for Bayesian inference. This constructed multivariate normal distribution and equations are further validated by another independent database consisting of 594 data points as well as by empirical equations proposed in literature. The most useful outcome of this study is to provide a systematic and analytical method for updating the distributions of the normalized undrained shear strength and the overconsolidation ratio in the presence of CPTU parameters.

scholarly journals Modeling parameters of structured clays as a multivariate normal distribution

2012 ◽  
Vol 49 (5) ◽  
pp. 522-545 ◽  
Author(s):  
Jianye Ching ◽  
Kok-Kwang Phoon
Keyword(s):  
Shear Strength ◽  
Probability Distribution ◽  
Normal Distribution ◽  
Multivariate Normal Distribution ◽  
Undrained Shear Strength ◽  
Multivariate Distribution ◽  
Soil Parameters ◽  
Multivariate Normal ◽  
Multivariate Probability Distribution ◽  
Undrained Shear

This study explores the possibility of modeling liquidity index, undrained shear strength, remolded undrained shear strength, preconsolidation stress, and vertical effective stress of structured clays (sensitive or quick clays) as a multivariate normal distribution. The literature is replete with correlation equations between two soil parameters. Consistent synthesis of more than two soil parameters through construction of a multivariate probability distribution function is rare, despite obvious practical usefulness of such an approach. This study compiles a large database of structured clays to construct the multivariate probability distribution among the aforementioned five soil parameters. This multivariate distribution is then used to simulate the correlations between soil parameters of interest and to derive useful equations for Bayesian inference. This constructed multivariate distribution and equations are further validated by another independent database of structured clays as well as by empirical equations proposed in the literature.

Halloysite behaving badly: geomechanics and slope behaviour of halloysite-rich soils

Clay Minerals ◽  
2016 ◽  
Vol 51 (3) ◽  
pp. 517-528 ◽  
Author(s):  
Vicki Moon
Keyword(s):  
Shear Strength ◽  
Bulk Density ◽  
High Mobility ◽  
Undrained Shear Strength ◽  
Field Conditions ◽  
High Peak ◽  
Plasticity Index ◽  
Undrained Shear

AbstractHalloysite-rich soils derived fromin situweathering of volcanic materials support steep stable slopes, but commonly fail under triggers of earthquakes or rainfall. Resulting landslides are slideflow processes, ranging from small translational slides to larger rotational failures with scarps characteristic of sensitive soils. Remoulding of failed materials results in high-mobility flows with apparent friction angles of 10–16°. The materials characteristically have high peak-friction angles (∼25– 37°), low cohesion (∼12–60 kN m−2) and plasticity ( plasticity index ∼10–48%), and low dry bulk density (∼480–1,080 kg m−3) with small pores due to the small size of the halloysite minerals. They remain saturated under most field conditions, with liquidity indexes frequently >1. Remoulded materials have limited cohesion (<5 kN m−2) and variable residual friction angles (15°–35°). Halloysite mineral morphology affects the rheology of remoulded suspensions: tubular minerals have greater viscosity and undrained shear strength than spherical morphologies.

A statistical evaluation of some engineering properties of eastern Canadian clays

1990 ◽  
Vol 27 (3) ◽  
pp. 373-386 ◽  
Author(s):  
Étienne J. Windisch ◽  
Raymond N. Yong
Keyword(s):  
Shear Strength ◽  
Statistical Evaluation ◽  
Undrained Shear Strength ◽  
Plasticity Index ◽  
Engineering Properties ◽  
Plastic Limit ◽  
Liquidity Index ◽  
Marine Clays ◽  
Undrained Shear

Statistics for data collected on eastern Canadian clays (Champlain, Goldthwait, Tyrrell, and Laflamme marine clays and Barlow–Ojibway lacustrine clays) are computed and analyzed. These clays are divided into three groups: eastern Canadian marine clays, Champlain clays (as an important part of the first group), and Barlow–Ojibway lacustrine clays. The analysis reveals significant differences between eastern Canadian clays and Scandinavian clays. Some relationships proposed in the literature and based on plasticity index, liquidity index, and plastic limit are found to be inapplicable to eastern Canadian clays. On the basis of a proposed method for estimating the undrained shear strength of normally consolidated eastern Canadian marine clays, the overconsolidation ratio is found to be equal to the ratio of the in situ undrained shear strength to the estimated normally consolidated undrained shear strength. Key words: undrained shear strength, plasticity index, liquidity index, plastic limit, statistical evaluation, over-consolidation ratio, lacustrian clays.

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