scholarly journals Yield stress, volume change, and shear strength behaviour of unsaturated soils: validation of the SFG model

2009 ◽  
Vol 46 (9) ◽  
pp. 1034-1045 ◽  
Author(s):  
Annan Zhou ◽  
Daichao Sheng
Keyword(s):  
Experimental Data ◽  
Shear Strength ◽  
Yield Stress ◽  
Volume Change ◽  
Unsaturated Soils ◽  
Strength Criterion ◽  
Single Equation ◽  
Compacted Soils ◽  
Shear Strength Criterion ◽  
Stress Changes

The model recently presented by Sheng, Fredlund, and Gens, known as the SFG model, provides a consistent explanation of yield stress, shear strength, and volume change behaviour of unsaturated soils as functions of suction. All these functions are based on one single equation that defines the volume change with suction and stress changes. This paper provides a systematic validation of the equation and the derived shear strength criterion against experimental data. The experimental data used include those for samples prepared from slurry soils and compacted soils. It is shown that (i) the method currently used to determine yield stresses of unsaturated soils is incorrect, (ii) volume change behaviour of unsaturated soils can be well predicted by the SFG model, and (iii) shear strength behaviour of unsaturated soils can be represented very well by the criterion in the SFG model.

Capillary water retention curve and shear strength of unsaturated soils

2016 ◽  
Vol 53 (6) ◽  
pp. 974-987 ◽  
Author(s):  
Annan Zhou ◽  
Ruiqiu Huang ◽  
Daichao Sheng
Keyword(s):  
Shear Strength ◽  
Unsaturated Soils ◽  
Water Retention ◽  
Adsorbed Water ◽  
Strength Criterion ◽  
Degree Of Saturation ◽  
Water Retention Curve ◽  
Capillary Water ◽  
Shear Strength Criterion ◽  
Wide Range

This paper proposes a new water retention model for unsaturated soils, which takes into account capillary condensation of adsorbed water. In this model, the degree of saturation of a soil is separated into that based on capillary water and that based on adsorbed water. Through analysis of a partially saturated two-cylinder system, a new shear strength criterion for unsaturated soils is proposed, in which only the degree of saturation based on capillary water contributes to the variation of shear strength with suction. The proposed shear strength criterion is justified against thermodynamic principles and is compared against existing criteria in the literature, which shows that it provides a much improved prediction of the experimental data for a wide range of suction values.

scholarly journals Modelling shear strength of compacted soils

2019 ◽  
Vol 92 ◽  
pp. 15007
Author(s):  
Sam Bulolo ◽  
Eng Choon Leong
Keyword(s):  
Shear Strength ◽  
Unsaturated Soils ◽  
Soil Mechanics ◽  
Published Data ◽  
State Variables ◽  
Compacted Soils ◽  
Earth Structures ◽  
Unsaturated Soil Mechanics ◽  
Coulomb Failure Criterion ◽  
Direct Shear Apparatus

Compacted soils constitute most engineering projects such as earth dams, embankments, pavements, and engineered slopes because of their high shear strength and low compressibility. The shear strength of compacted soils is a key soil parameter in the design of earth structures but it is seldom determined correctly due to their unsaturated state. The shear strength of compacted soils can be better evaluated under the framework of unsaturated soil mechanics. Saturated and unsaturated tests were conducted on compacted specimens using conventional direct shear apparatus under constant water content condition. Tests were conducted at different water contents and net normal stresses. The main objective of this study is to develop a shear strength model for compacted soils. Initial matric suction was measured before the test using the filter paper method. The two-stress state variables together with the extended Mohr-Coulomb failure criterion for unsaturated soils were used to obtain a lower bound model of the shear strength. The model was demonstrated using published data.

scholarly journals A New Shear Strength Criterion for Rock Masses with Non-Persistent Discontinuities Considering the Nonlinear Progressive Failure Process

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4694
Author(s):  
Bowen Zheng ◽  
Shengwen Qi ◽  
Songfeng Guo ◽  
Xiaolin Huang ◽  
Ning Liang ◽  
...  
Keyword(s):  
Shear Strength ◽  
Friction Coefficient ◽  
Progressive Failure ◽  
Strength Criterion ◽  
Rock Masses ◽  
Basic Form ◽  
Shear Strength Criterion ◽  
Nonlinear Shear ◽  
New Criterion ◽  
Internal Friction Coefficient

The shear strength characteristics of rock masses containing non-persistent discontinuities are strongly affected by discontinuities and rock bridges. The linear Jennings criterion cannot reflect the nonlinear mechanical behavior during progressive failure of rock masses with non-persistent discontinuities. In this study, a new nonlinear shear strength criterion was developed. First of all, a series of shear test data about artificial rock mass samples were collected on the basis of the published literatures, and five types of samples were differentiated according to the positions of discontinuities. After that, a new nonlinear shear strength criterion was proposed by introducing two correction coefficients A and B into the basic form of the Jennings criterion, which could correct the weight of the cohesion and the internal friction coefficient of rock bridges respectively. Then, the new criterion was determined by fitting the basic form of the Jennings criterion with the laboratory data. It was found that the parameters A and B had a nonlinear exponential and negative exponential relation with the connectivity rate respectively. It indicated that both the cohesion and the internal friction coefficient estimated by the new criterion were superior to those estimated by the Jennings criterion. Compared with the linear Jennings criterion, the new nonlinear shear strength criterion had a better applicability.

scholarly journals Recent Developments and Limitations of the SFG Model

2016 ◽  
pp. 41-49
Author(s):  
Daichao Sheng
Keyword(s):  
Shear Strength ◽  
Unsaturated Soils ◽  
Water Retention ◽  
Compacted Soils ◽  
Consistent Description ◽  
Strain Behaviour ◽  
Recent Developments ◽  
Density Dependency ◽  
Significant Attention ◽  
Water Retention Behaviour

The SFG model was proposed in attempt to provide a consistent description of the stress-strain behaviour of unsaturated soils, including compacted soils and soils dried from slurry. It differs from existing models mainly through two aspects: a consistent description of volume change, yield stress and shear strength behaviour of unsaturated soils and a smooth and natural transition between saturated and unsaturated states. The model has attracted significant attention since it was first proposed and has been extended to cover coupled hydro-mechanical behaviour, hysteretic water retention behaviour and density-dependency. This paper presents a summary of the latest developments of the model, as well as the aspects that require further refinements.

Sign in / Sign up

Export Citation Format

Share Document