This paper focuses on the effects of particle size distribution on shear strength of accumulation soil. A series of direct shear box tests and triaxial tests were performed to characterize the shear strength of the accumulation soil. Results from the direct shear tests indicate that the range of the angle of shearing resistance of the accumulation soil is 33.5–54.6°, and those from the triaxial tests indicate that the angle is 37.2–50.7°. The basic properties of the soil, such as median particle diameter, coefficient of uniformity, and gravel content, were used to analyze the effects. The angle of shearing resistance is generally increasing with increasing median particle diameter and gravel content and decreasing with increasing coefficient of uniformity.

The influence of water on the mechanical properties of rock is vital for determining the rock stability when subjected to changes of water conditions. In this paper, a series of uniaxial compression tests were conducted to investigate effects of cyclic wetting and drying on the mechanical properties of sandstone and mudstone collected from Chongqing city, China. The results showed that both elastic modulus and uniaxial compressive strength of sandstone and mudstone were reduced by wetting and drying cycles, and that the degradation rate of the two mechanic parameters of mudstone was always larger than sandstone. The parameters, including water adsorption, degradation degree of elastic modulus, degradation degree of uniaxial compressive strength, increase with the increase of the wetting-drying cycles (N). The relationship between these three parameters and the value of N + 1 could be well fitted by logarithmic curves. The average degradation degree was also used to describe the degradation of per time wetting-drying cycles. It is found that the average degradation degree of elastic modulus and uniaxial compressive strength decrease with the increase of wetting-drying cycles. Moreover, the relationships between the mechanical properties and the porosity are presented, which can be fitted by linear curves. In the cyclic wetting-drying process, the elastic modulus and the uniaxial compressive strength decreased with the porosity increasing, and the degradation rates of sandstone mechanic parameters were higher than those of mudstone.

This paper describes the development of a modified instrument used to measure the anisotropic hydraulic conductivity of coarse soils. Then, based on this modified instrument, horizontal and vertical hydraulic conductivities and critical hydraulic gradients of a crushed sandstone–mudstone particle mixture are measured. Using this data, we investigate the effects of particle size on the anisotropic hydraulic conductivity. The testing results indicate that the anisotropic hydraulic conductivity coefficient, which is defined as the logarithm value of the ratio of the horizontal hydraulic conductivity to the vertical conductivity, ranges from 0.079 to 0.358. This means the horizontal hydraulic conductivity is 1.20 to 2.28 times to that of the vertical conductivity. The anisotropic coefficient decreases as the uniformity coefficient increases. Meanwhile, the critical hydraulic gradient increases with an increase in fine particle content.