Search

It rains rarely in the northwest of arid and semi-arid regions. The roadbed is not saturated and the internal moisture changes dynamically. The moisture content of the roadbed has a great influence on the roadbed strength significantly. The roadbed moisture status is the key factor to design and evaluate the bearing capacity of the subgrade bed. Model test in the research was used in the research. The self-developed subgrade bed dynamic moisture model test is introduced. The precipitation intensity, the rain interval, the subgrade bed compaction and other factors on the impact of moisture were considered. Studies have shown that embankment slope measuring point reaches saturation after the precipitation firstly. The roadbed internal parts and the downwards parts are followed then. The water content of each measuring point rises firstly and then shows a stable trend. The subgrade bed moisture lags seriously. It does not change for a long time after raining. And with the changing, it would not restore to normal level in a long time. The slope permeability coefficient and permeability coefficient of silty clay was got, which is useful for engineering applications and numerical experiments.

The mechanical parameters of the rock masses are scale dependent because of the existence of the discontinuities. The self-similarity of the discontinuities makes the application of fractal theory in the description of the rock mass structure possible. The novel point in this study is that the structure representative elementary volume (SREV) of rock mass is proposed. Rock mass structures were obtained through the two-dimensional discontinuity network simulation results, from which ten pieces of square rock mass specimens were chosen. The side lengths of the specimens were increased in turn from 1m to 10m. And the fractal dimension of each specimen with different sizes was calculated by the box-counting principal of the fractal geometry. The fractal dimensions of the rack mass structures became larger with their side lengths increasing, and finally stable. And the SREV of the rock mass was determined based on the variation rule of the fractal dimensions. Further, the relation between the structure representative elementary volume (SREV) and mechanical parameter representative elementary volume (REV) was qualitatively analyzed from the strength differences between the discontinuities and intact rock. And the conclusion was inferred that the size of the SREV was the upper limit of mechanical parameter REV. Meanwhile, the conclusion was verified by the results of the finite element method. This study can provided a referring value for the estimation of the mechanical parameter REV in future.

Zhangjiaba-Enshi 500kV Transmission Line is a backbone network in the West to East Power Transmission Project of China, which passes through the factory area of Chongqing Sanxing Iron Mine Factory. According to solving the additional stress on foundation rock produced by tower load based on the Boussinesq theory and the redistribution of surrounding rock stress resulting from iron mining computed by using the calculation formula for redistribution stress on circular chamber in rock mass, this paper analyzes and demonstrates the impact of Zhangjiaba-Enshi Line N327 tower footing pressure mine on mining within the range of mining scheme, and determines that there is no mutual impact between the Zhangjiaba-Enshi Line N327 tower and exploitation of Sanxing ore horizon.