International Journal of Geomechanics

Calculation of volume changes by constitutive models for soils and correct transition from contraction to dilation is important for prediction of undrained conditions under which developing pore water pressures may result in instability or in increased stability. Partly drained conditions involving imposed volume changes occur under many field-loading conditions, and prediction of the correct soil response is important for analysis of geotechnical structures. The effects of imposed volume changes on the instability of granular materials are studied in experiments on a fine sand in which water is forced into or out of the sand specimen during shearing. The effects on stress–strain behavior and stability are recorded and discussed. The conditions of imposed volume changes are then simulated with a single hardening constitutive model and compared with the experimental results. It is shown that the model can predict the corresponding loading paths and sand behavior as well as the resulting stable and unstable conditions.

Considering foam’s expansive characteristics and using programming language, the level set method was used to simulate the polymer injection process that forms a thin wall; the influencing factors of the wall formation were studied for injection pressure, expansion ratio, and gel time. The polymer injection–wall-formation process was verified using a modeling test, and its molding effect was proven using a field test. The results show that the polymer injection technique can quickly form a thin wall, and it is feasible to use the level set method to simulate the polymer injection filling process and display the grout interface more accurately.

Static and seismic passive earth pressure coefficients for the general case of an inclined wall and a sloping cohesionless backfill were computed by using finite-element lower-bound limit analysis based on second-order cone programming (SOCP). The comparison with the best existing upper-bound solution and the widely accepted solution obtained by the method of stress characteristics has shown that the present lower-bound solutions can provide a safe estimate of the passive earth pressures. Therefore, combining present results and upper-bound solutions can bracket the true value of passive earth pressures. In addition, design tables are presented that allow geotechnical engineers to easily use the present results in practice.

An experimental study of the thermal damage properties of mudstone at high temperature can serve as a reference for problems in rock mechanics under high temperature, such as in oil exploration, geothermal resource development, and nuclear waste treatment. In this study, a uniaxial compression test of mudstone was conducted using the MTS 810 electrohydraulic servo system and MTS 652.02 high-temperature furnace under different temperatures ranging from 25 to 800°C to analyze the thermal damage properties of mudstone at high temperature. The main results of the study are as follows: the ductility of mudstone is improved under the effect of high temperature, and the failure mechanism exhibits a transition trend from brittleness to ductility; the elastic modulus increases from normal temperature to 400°C and then decreases rapidly when the temperature is over 400°C; and by defining the damage by tangent deformation modulus and combining the test data from uniaxial compression tests of mudstone at high temperature, the damage evolution rules of mudstone at high temperatures are obtained.

The paper presents vertical pressure values occurring under the center line of uniformly loaded laboratory model tests of a surface strip footing on a sand bed. The vertical pressure distribution in medium dense sand was measured using miniature pressure sensors. The experimental measures obtained from the model test program have been compared with values obtained from earlier theories. Tests were performed in plane strain conditions. Finally, the results obtained from experiments and theoretically obtained values were discussed. The results indicated that the distribution of pressure was not the same for every load level. It was found that the pressure distributions fit Westergaard distribution better at lower loads. They approach the pressure predicted by an earlier study as the applied loads reach bearing capacity values.

The discrete-element method (DEM) is an important tool for understanding the underlying microscale processes that influence macroscale behavior. For quasi-static simulations, numerically imaginary input parameters such as strain rate and damping constant can have significant influence on the resulting shear behavior, especially after the peak strength condition is attained. Consistent results require small unbalance forces among the particles, expressed as an unbalanced resultant force index. The unbalanced resultant force index is roughly proportional to the strain increment and inversely proportional to the average ratio of the particle overlaps and diameters and the ratio of the mean stress and the normal spring constant.

Determining the vertical stresses within underground mine stopes is necessary for designing the barricades that block the drives during filling. This paper discusses two different procedures that can be used for determining the vertical stress profile, which give different values of stresses. The difference is attributed to fixing the bottom of the stope, implying zero displacement in any direction. The reasons are discussed, and it is suggested that the method commonly used in numerical modeling (Method 2) is not necessarily the better of the two. The alternate method (Method 1) models the field situation better when the loadings at the bottom during filling are required, mimics the laboratory model tests, and gives the same stress profile for all stopes with any aspect ratio. The findings are applicable to backfilled trenches as well.