Unified Solution of Passive Earth Pressure for Unsaturated Soils

2012 ◽  
Vol 594-597 ◽  
pp. 430-433 ◽  
Author(s):  
Chang Guang Zhang ◽  
Dong Hui Zhu ◽  
Zhi Gao ◽  
Guang Wei Xue ◽  
Zheng Li
Keyword(s):  
Shear Strength ◽  
Unsaturated Soils ◽  
Earth Pressure ◽  
Matric Suction ◽  
Intermediate Principal Stress ◽  
Strength Theory ◽  
Passive Earth Pressure ◽  
Independent State ◽  
Unified Strength Theory ◽  
State Stress

With two different distributions of matric suction, the unified solution of passive earth pressure for unsaturated soils is obtained, which is based on the unified shear strength for unsaturated soils in terms of two independent state stress variables and could avoid some shortages of Rankine's passive earth pressure. The influence of intermediate principal stress and matric suction on passive earth pressure is discussed. The results show that the passive earth pressure increases significantly with the unified strength theory parameter or matric suction increasing, and does not change more rapidly when matric suction decreases linearly with depths than that is constant.

Estimation of the Passive Earth Pressure with Inclined Cohesive Backfills: The Effect of Intermediate Principal Stress is Considered

2010 ◽  
Vol 168-170 ◽  
pp. 1370-1376
Author(s):  
We Long Yu ◽  
Jian Zhang ◽  
Xiu Hua Sun ◽  
Rui Lin Hu ◽  
Xin Wei
Keyword(s):  
Principal Stress ◽  
Retaining Wall ◽  
Ground Surface ◽  
Earth Pressure ◽  
Intermediate Principal Stress ◽  
Strength Theory ◽  
Passive Earth Pressure ◽  
Unified Strength Theory ◽  
Retaining Structure ◽  
Lateral Earth Pressure

Estimating passive earth pressure accurately is very important when designing retaining wall. Based on the unified strength theory and plane strain assumption, an analytical solution has been developed to determine the passive lateral earth pressure distribution on a retaining structure when the backfill is cohesive and inclined considering the effect of the intermediate principal stress. The solution derived encompasses both Bell’s equation (for cohesive or cohesionless backfill with a horizontal ground surface) and Rankine’s solution (for cohesionless backfill with an inclined ground surface).

scholarly journals Safety Factor of Unsaturated Soil Slopes considering the Intermediate Principal Stress Effect and Different Profiles of Matric Suction

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zhaoxin Li ◽  
Changguang Zhang ◽  
Jingyuan Zhao ◽  
Qing Yan
Keyword(s):  
Shear Strength ◽  
Principal Stress ◽  
Safety Factor ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Matric Suction ◽  
Intermediate Principal Stress ◽  
Stress Effect ◽  
Soil Slopes ◽  
The Stability

Profiles of matric suction are critical for assessing the stability of unsaturated soil slopes, and the strength of unsaturated soils is affected by the intermediate principal stress. This study presents a theoretical formulation of safety factor for infinite unsaturated soil slopes under four different profiles of matric suction using the limit equilibrium method. The unified shear strength equation under plane strain conditions is adopted to capture the effect of intermediate principal stress on the strength of unsaturated soils. The proposed formulation of safety factor is found to have good comparability and broad applicability. The validity of the proposed formulation is demonstrated by comparing its predictions with the results of the extended shear strength method and the finite element method available in the literature. Parametric studies show that the effect of intermediate principal stress on the stability of unsaturated soil slopes is significant; the difference of safety factor among four suction profiles is pronounced, and the safety factor is highest for a linear suction profile. In addition, the safety factor changes with the infiltration depth in two stages, decreases with the slope angle, and increases with effective strength parameters. The results of this study are capable of providing beneficial guidance for optimization designs and disaster preventions of unsaturated soil slopes.

Unified Solution of Coulomb’s Active Earth Pressure for Unsaturated Soils without Crack

2012 ◽  
Vol 170-173 ◽  
pp. 755-761 ◽  
Author(s):  
Wen Biao Liang ◽  
Jun Hai Zhao ◽  
Yan Li ◽  
Chang Guang Zhang ◽  
Su Wang
Keyword(s):  
Principal Stress ◽  
Unsaturated Soils ◽  
Retaining Wall ◽  
Research Result ◽  
Earth Pressure ◽  
Friction Angle ◽  
Matric Suction ◽  
Intermediate Principal Stress ◽  
Active Earth Pressure ◽  
Soil Pressure

Based on the unified solution of shear strength in terms of double stress state variables for unsaturated soils, whilst considering the effect of the intermediate principal stress rationally, the unified solution of Coulomb’s active earth pressure for unsaturated soils without cracks is developed. Comparability of the solution is analyzed and influencing characteristic of each factor is obtained. The research result indicates that: the intermediate principal stress and matric suction have obvious impacts on Coulomb’s active earth pressure for unsaturated soils; Coulomb’s active earth pressure has been decreasing until zero with the increase of unified strength theory parameter and matric suction; Coulomb’s active earth pressure increases with the increase of grading angle of retaining wall and slop angle of backfill, but decreases with the increase of matric suction, effective internal friction angle and matric suction angle, while external friction angle has no obvious influence. The proposed unified solution of Coulomb’s active earth pressure enjoys a wider application, and unified solution of Rankine’s active earth pressure is just the special case. The results are of great significance to soil pressure determination such as slope and foundation pit, and to retaining structures design.

Calculation of Earth Pressure on Straight Ditch Buried Rigid Pipe

2013 ◽  
Vol 438-439 ◽  
pp. 824-828
Author(s):  
Qing Liu ◽  
Wei Ding ◽  
Jian Bo Cui ◽  
Yan Xiao ◽  
Xue Qiang Zhao
Keyword(s):  
Shear Strength ◽  
Optimization Design ◽  
Earth Pressure ◽  
Calculation Model ◽  
Intermediate Principal Stress ◽  
Strength Theory ◽  
Soil Pressure ◽  
Top Soil ◽  
Pressure Calculation ◽  
New Formula

Based on the unified twin shear strength theory, a new earth pressure formula is deduced for the straight groove buried rigid pipes, with a straight slip plane soil pressure calculation model established. Compared with traditional earth pressure calculation method, the new formula which considers influence of intermediate principal stress on the pipeline earth pressure can obtain the result which is much closer to the actual pipeline stress situation. The results determined from the proposed formula with an engineering example show the influence law of slot width and the thickness of the overburden on tube top soil pressure. The conclusions have some guidance significance for optimization design of pipeline engineering.

A relationship describing the shear strength of unsaturated soils

1999 ◽  
Vol 36 (2) ◽  
pp. 363-368 ◽  
Author(s):  
Daud W Rassam ◽  
David J Williams
Keyword(s):  
Shear Strength ◽  
Soil Water ◽  
Nonlinear Regression ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Three Dimensional ◽  
Matric Suction ◽  
Linear Increase ◽  
Soil Water Characteristic Curve ◽  
Stress Dependent

A relationship describing the shear-strength profile of a desiccating soil deposit is essential for the purpose of analysis, especially when a numerical method is adopted where each zone in a discretised grid is assigned an elevation-dependent shear-strength value. The matric-suction profile of a desiccating soil deposit is nonlinear. Up to the air-entry value, an increase in matric suction is associated with a linear increase in shear strength. Beyond air entry, as the soil starts to desaturate, a nonlinear increase in shear strength occurs. The soil-water characteristic curve is stress dependent, as is the shear-strength gain as matric suction increases. In this paper, a three-dimensional, nonlinear regression analysis showed that a power-additive function is suitable to describe the variation of the shear strength of unsaturated soils with matric suction. The proposed function incorporates the effect of normal stress on the contribution of matric suction to the shear strength.Key words: air-entry value, matric suction, nonlinear regression, soil-water characteristic curve, tailings, unsaturated shear strength.

scholarly journals Ultimate Bearing Capacity of Strip Foundations in Unsaturated Soils considering the Intermediate Principal Stress Effect

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Qing Yan ◽  
Junhai Zhao ◽  
Changguang Zhang ◽  
Jintai Wang
Keyword(s):  
Bearing Capacity ◽  
Principal Stress ◽  
Unsaturated Soils ◽  
Matric Suction ◽  
Ultimate Bearing Capacity ◽  
Intermediate Principal Stress ◽  
Shallow Foundations ◽  
Hyperbolic Function ◽  
Stress Effect ◽  
Intermediate Principal Stress Effect

The reasonable determination of ultimate bearing capacity is crucial to an optimal design of shallow foundations. Soils surrounding shallow foundations are commonly located above the water table and are thus in an unsaturated state. The intermediate principal stress has an improving effect on the unsaturated soil strength. In this study, the ultimate bearing capacity formulation of strip foundations in unsaturated soils is presented by using Terzaghi’s theory. The unified shear strength equation of unsaturated soils under a plane strain condition is utilized to capture the intermediate principal stress effect. Furthermore, two profiles of matric suction are considered and a hyperbolic function of the friction angle related to matric suction (φb) is adopted to describe strength nonlinearity. The validity of this study is demonstrated by comparing it with model tests and a theoretical solution reported in the literature. Finally, parameter studies are conducted to investigate the effects of intermediate principal stress, matric suction, and base roughness on the ultimate bearing capacity of strip foundations. Besides, the effect of strength nonlinearity is discussed with two methods representing the angle φb.

Study on the Bearing Capacity of Slime Friction Pile Based on the Double-Sheared Theory

2013 ◽  
Vol 353-356 ◽  
pp. 1005-1010
Author(s):  
Xiang Qiu Wang ◽  
Wen Tao Yang
Keyword(s):  
Bearing Capacity ◽  
Strength Criterion ◽  
Intermediate Principal Stress ◽  
Resistance Force ◽  
Strength Theory ◽  
Unified Strength Theory ◽  
Friction Resistance ◽  
Double Shear ◽  
Friction Pile ◽  
Lateral Friction

The bearing capacity of slime friction pile based on the Mohr-Coulombs strength criterion couldnt make full use of the potential strengths ability of rock-soil. But the double shear unified strength theory can depict really the bearing characteristics of rock-soil because it can consider the effect of intermediate principal stress comprehensively. On this condition, based on the Mindlins displacement solution and the double shear unified strength theory, a calculated formula of bearing capacity was proposed for the slime friction pile, and then the distribution regularities of lateral friction-resistance force for the slime friction pile were discussed.

Modeling the unsaturated soil zone in slope stability analysis

2014 ◽  
Vol 51 (12) ◽  
pp. 1384-1398 ◽  
Author(s):  
L. L. Zhang ◽  
Delwyn G. Fredlund ◽  
Murray D. Fredlund ◽  
G. Ward Wilson
Keyword(s):  
Shear Strength ◽  
Stability Analysis ◽  
Slope Stability ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Matric Suction ◽  
Slope Stability Analysis ◽  
Engineering Practice ◽  
Rate Of Increase ◽  
Nonlinear Shear

The linear form of the extended Mohr–Coulomb shear strength equation uses a [Formula: see text] parameter to quantify the rate of increase in shear strength relative to matric suction. When the [Formula: see text] value is unknown, a [Formula: see text] equal to 15° is sometimes used in the slope stability study to assess the influence of matric suction on the stability of a slope. In many cases, however, a [Formula: see text] value of zero is used, signifying that the effect of matric suction is ignored. Experiment results have shown that the relationship between the shear strength of an unsaturated soil and matric suction is nonlinear. Several semi-empirical estimation equations have been proposed relating the unsaturated shear strength to the soil-water characteristic curve. In this paper, the results of a study using two-dimensional slope stability analysis along with an estimated nonlinear shear strength equations is presented. The effects of using an estimated nonlinear shear strength equation for the unsaturated soils are illustrated using three example problems. Several recommendations are made for engineering practice based on the results of the example problems. If the air-entry value (AEV) of a soil is smaller than 1 kPa, the effect of matric suction on the calculated factor of safety is trivial and the [Formula: see text] value can be assumed to be zero. If the AEV of a soil is between 1 and 20 kPa, the nonlinear equations of unsaturated shear strength should be adopted. For soils with an AEV value between 20 and 200 kPa, an assumed [Formula: see text] value of 15° provides a reasonable estimation of the effects of unsaturated shear strength in most cases. For soils with an AEV greater than 200 kPa, [Formula: see text] can generally be assumed to be equal to the effective angle of internal friction, [Formula: see text], in applications where geotechnical structures have matric suctions around 100 kPa.

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