scholarly journals Effect of Intermediate Principal Stress on the Bearing Capacity of Footings in Soft Rock

Coatings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1019
Author(s):  
Zongyuan Ma ◽  
Faning Dang ◽  
Hongjian Liao
Keyword(s):  
Constitutive Model ◽  
Bearing Capacity ◽  
Strain Hardening ◽  
Principal Stress ◽  
Numerical Solutions ◽  
Soft Rock ◽  
Intermediate Principal Stress ◽  
Rock Foundation ◽  
Unified Strength Theory ◽  
Bearing Capacity Factor

The bearing capacity for footings is a fundamental scientific problem in civil engineering. The evaluation of the bearing capacity of footings usually does not take into account the effect of the intermediate principal stress. In practice, the intermediate principal stress has certain influences on the strength of geomaterials (e.g., rock and soil) or concrete. In this paper, a series of numerical solutions are presented to evaluate the bearing capacity of footings in a soft rock foundation via a two-dimensional finite difference code (FLAC) with a strain hardening/softening constitutive model based on the unified strength theory (UST). The values of the bearing capacity factor Nc and Nγ for strip, circular and square footings in a soft rock foundation were evaluated using the strain hardening/softening constitutive model. The effect of the intermediate principal stress on the bearing capacity of strip, circular and square footings in a soft rock foundation was analyzed. The results of the numerical computation show that the intermediate principal stress has a significant influence on the bearing capacity and failure mechanisms of a soft rock medium. The influence of the intermediate principal stress on the peak and residual values of the bearing capacity for a strip footing is much greater than for circular and square footings. Research works for the reasonable estimation of the bearing capacity of footings in soft rock are facilitated by this study.

A Nonlinear Constitutive Model for Soil under Complex Stress State

2013 ◽  
Vol 535-536 ◽  
pp. 561-564 ◽  
Author(s):  
Hang Zhou Li ◽  
Hong Jian Liao ◽  
Bo Han ◽  
Li Song
Keyword(s):  
Constitutive Model ◽  
Principal Stress ◽  
Friction Angle ◽  
Complex Stress ◽  
Complex Stress State ◽  
Intermediate Principal Stress ◽  
Strength Theory ◽  
Unified Strength Theory ◽  
Strain Behavior ◽  
Chang Model

It is fundamental to predict the stress-strain behavior of soils to control the stability of the geotechnical engineering. A Duncan-Chang constitutive model is analyzed and found that it ignores the effect of the intermediate principal stress. A unified strength theory is investigated and revised. The lode parameter is introduced into the unified strength theory. The unified friction angle and cohesion which may reflect the influence of the intermediate principal stress and verified by the polyaxial tests are obtained. The compressive strength revised from the unified strength theory is used to replace the Mohr-Coulomb criterion and introduced into the Duncan-Chang model. A modified constitutive model is proposed, which is verified by the plane strain tests. The result shows that the modified constitutive can reflect the effect of the intermediate principal stress, and the Duncan-Chang model is a special case of the modified model when b=0.

The Development and Implementation of Improved Duncan-Chang Constitutive Model in ABAQUS

2011 ◽  
Vol 99-100 ◽  
pp. 965-971
Author(s):  
Zhi Ping Dai ◽  
Cheng Zhao ◽  
Chun Feng Zhao
Keyword(s):  
Constitutive Model ◽  
Principal Stress ◽  
Deformation Behavior ◽  
Fine Sand ◽  
Intermediate Principal Stress ◽  
Strength Theory ◽  
Unified Strength Theory ◽  
Dense Sand ◽  
Improved Model ◽  
Chang Model

As it ignorance the effect of intermediate principal stress, traditional Duncan - Chang model has limitation when applied into geotechnical engineering. It was improved through incorporating the effect of intermediate principal stress based on unified strength theory. Under the help of customized modification platform in ABAQUS, the applicability and stability of the improved model and the reliability of subroutine were validated through simulation of several examples. The results show the improved model can better reflect the deformation behavior of soil through taking the influence of intermediate principal stress into consideration. The improved model in paper can be applied into dense sand, fine sand and clay.

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.

scholarly journals Analysis of Three-Dimensional Damage Constitutive Model of Frozen Sand Based on the Influence of Intermediate Principal Stress and Temperature

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Shilong Ma ◽  
Zhaoming Yao ◽  
Shuang Liu ◽  
Xuan Pan
Keyword(s):  
Constitutive Model ◽  
Weibull Distribution ◽  
Principal Stress ◽  
Three Dimensional ◽  
Intermediate Principal Stress ◽  
Frozen Soil ◽  
Stress Coefficient ◽  
Frozen Sand ◽  
Distribution Parameters ◽  
Damage Constitutive Model

To study the mechanical properties of frozen soil, it is necessary to understand the damage characteristics of frozen soil. Four types of three-dimensional indoor tests of frozen sand were carried out at −5°C, −10°C, and −15°C to study the mechanical damage properties. These include different stress path tests with the principal stress coefficients of 0, 0.25, 0.5, and 0.75 while analyzing the entire failure process. First, the three-dimensional compression test of frozen sand was studied to analyze the influence of temperature and intermediate principal stress coefficient on the large principal stress of frozen soil. The damage cost of frozen sand under the influence of different temperatures and intermediate principal stress coefficients was also established. Second, using the characteristics of discreteness and randomness of the distribution of the microelements inside the frozen soil and assuming that the failure of the microelement of the frozen soil obeys the Weibull distribution, the Drucker–Prager strength criterion was used as the statistical distribution variable of the microelement of the frozen soil based on the strain equivalence hypothesis, statistical theory, and continuous damage mechanics. This allows for a constitutive model of frozen sand damage under the three-dimensional stress state to be established. Finally, the model parameter values through low-temperature three-dimensional test data were able to be determined. This model allows for the physical meaning of Weibull distribution parameters F0 and m to be analyzed, and the distribution parameters with temperature and intermediate principal stress coefficient can be modified to obtain a modified frozen sand damage constitutive model. The results show that the modified damage constitutive model can simulate the entire process curve of the large principal stress-strain of frozen sand. It shows that the large principal stress of frozen sand increases with the increase of temperature and intermediate principal stress coefficient. Concurrently, the frozen sand damage constitutive model proposed in this paper can describe the deformation behavior of frozen soil under different temperature and stress paths and can be adapted to various other sediment types.

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