Hong Jian Liao

Test and Numerical Analysis of the Constitutive Relation of a Diatomaceous Soft Rock

A kind of diatomaceous soft rock and its constitutive model are studied in this article. Based on Yin and Grahams (1999) 3-D elastic viscoplastic constitutive model, the formulation under a triaxial stress state is established, and it is used to simulate the time-dependent stress-strain behavior and effective stress path of consolidated undrained triaxial tests of both normally consolidated and overconsolidated soft rock. The comparison between the model predictions and measured results shows that their agreement is good. This demonstrates that the constitutive equation established here can be used to simulate the time-dependent stress-strain behavior of the soft rock under triaxial stress condition.

Stability Analysis of a High Slope Along a Loess Plateau Based on Field Investigation and Numerical Analysis

In this paper, a landslide along a high loess plateau is studied by the method of field investigation, laboratory test and numerical analysis. First, the environmental factors that induce the landslide of the high loess slope are investigated. Second, an elastoplastic constitutive model based on the unified strength theory (UST) was established and implemented in a three-dimensional finite difference code FLAC3D. Based on the information from field investigation and the results of laboratory test, three-dimensional stability analysis of the high loess slope is analyzed using the FLAC3D code and UST model. The influence of the ground water level variation and the seepage flow on the slope stability is analyzed. The calculation results of the ground water level variation suggest that the slope reaches an equilibrium state after a certain amount of deformation is yielded. However, the displacement increased significantly and the failure of the high loess slope occurred suddenly when the seepage flow is taken into account. The analysis results of this paper indicated that it is necessary to reduce the reclamation and irrigation along the boundary of the loess plateau, and the stability of the high loess slope along the loess plateau could be ensured.

An experimental study on the shear strength of undisturbed loess

Advances in Unsaturated Soil, Seepage, and Environmental Geotechnics, Shanghai, 6-8 June 2006

Effects of the time-dependent behavior on strain softening of diatomaceous soft rock

This paper is concerned with a new concept of modeling the strain softening behavior of diatomaceous soft rocks based on the laboratory investigation. An approximate solution was described for a stress-strain-time relation taking into account strain softening phenomenon. The treatment of the post-peak behavior in the calculation is discussed and comparisons of the experimental observations of normally consolidated specimens with results of numerically simulated undrained triaxial tests are given. The strain rate effect and strain softening behaviors are controlled by the time dependent stress strain relation.

Numerical Simulation of Pressure Grouting in Soil Nail Pull-Out Tests

Soil nailing is a widely used technique for stabilizing slopes and excavations. In all current design methods, the nail-soil interface shear strength, that is, the pull-out resistance of a soil nail is an important parameter which controls the design and safety assessment of the soil nailing system. The pressure grouting is a cost effective method for increasing the soil nail pull-out resistance and in turn improving the performance of the nailed structure. In this paper, a three dimensional (3-D) finite element (FE) model for pull-out tests is established and verified by comparing simulated results with measured data. This model is then used to simulate the effect of grouting pressure on the soil nail pull-out resistance.

Analysis of Soil-Structure Interaction with Finite Element Method

Analysis of dynamic behavior of soil-structure interaction (SSI) is a complicated problem due to the complexities of soil behaviors and dynamic analysis. It is difficult to solve SSI with analytical methods. However, numerical methods with highly developed computer technique are efficient. Based on the advanced nonlinear finite element analysis software MSC.Marc, SSI on loess ground is studied. An approach for the application of MSC.Marc in SSI analysis is presented and an example is given. Hyperbolic soil constitutive relationship and viscous boundary conditions are adopted in the soil model. Moreover, contact between the embedded columns and the adjacent soil is considered. Response spectrum analysis of the result is carried out. Some conclusions about the seismic response of soil-structure system under different soil stiffness and different soil-layer thickness conditions are given. A new way of analyzing SSI for loess ground is provided.

Application of Fracture Mechanics to Arch Dam Analysis

The authors present a procedure for the analysis of the stability and propagation of cracks in arch dams based on linear elastic fracture mechanics. A finite element method was used to calculate the stress intensity factors(KⅠ, KⅡ and KⅢ) of crack in the concrete arch dam, and fracture analysis for arch dams was carried out, which based on the criterion of three-dimensional mixed mode fracture of concrete from the experiment. The analysis method can be applied to evaluate the safety of the arch dam and improve the design for arch dam.

Influence of Intermediate Principal Stress on the Bearing Capacity of Strip and Circular Footings

AbstractStudies of the bearing capacity of footings usually do 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. This paper focuses on a numerical study using the finite-difference code Fast Lagrangian Analysis of Continua (FLAC) and the united strength theory (UST) to investigate the influence of the intermediate principal stress on the bearing capacity of strip and circular footings. A series of numerical solutions are presented to determine the vertical bearing capacity of strip and circular footings using an elastic–perfectly plastic constitutive model following UST and the associative flow rule. First, the bearing capacity of flexible and strip footings according to UST and other criteria are compared. Second, three bearing capacity factors (Nc, Nq, and Nγ) are evaluated for strip and circular footings subjected to centered vertical loads with r...

Probabilistic Strength-Reduction Stability Analysis of Slopes Accounting for 2-D Spatial Variation

Using the elasto-plastic constitutive model and strength reduction technique, the stability of slopes is analyzed by a finite difference numerical package FLAC version 7.0. Shear strain increment is used to identify the failure zone. Unlike the conventional investigation taking the soil strengths as constant parameters, this study deals with random variables of soil strengths by using first order reliability method (FORM). In particular, two-dimensional (2-D) spatial variation unique to soil strengths is investigated in the reliability analysis.

Experimental Study on Shear Strength Characteristics and Stress-Strain Relationship of Loess

This paper mainly concerns the non-linear strength characteristics of the loess. A series of consolidated undrained triaxial tests(CU test) and consolidated drained triaxial tests (CD test) of normal consolidation and over consolidation loess specimens are carried out by using the normal triaxial apparatus of strain control. The stress-strain relationship curves and strength characteristics of loess are investigated and analyzed. The results show that the stress-strain relationship obtained by CU tests appears strain softening, while the stress-strain relationship for CD tests appears strain hardening. Different failure modes have different stress-strain relationships. Furthermore, the results also show that the peak strength, residual strength and residual strength ratio change with the different confining pressure. Based on the triaxial shear tests of normal consolidated loess, the influences of over-consolidated loess on the stress-strain relationships and strength characteristic are discussed. Several conclusions obtained in this paper can be referenced for the loess experimental study.