With finite difference code Flac3D, the stability of loess slope with hidden hole at different locations has been evaluated. Failure mechanism of loess slope is also studied. Under plane strain conditions, the results of numerical simulation show that the existence of hidden hole has a direct impact on the stability of the loess slope, and sometimes decreases the safety factor. The failure of hidden hole also directly affects on the overall destruction of slope. Consequently, at the stage of loess slope design, it is necessary to carefully evaluate the stability of loess slope with hidden hole. Particularly, it is important to consider the influence of stability by the position of hidden hole in loess slope.

High speed camera system is used to record crack propagation on rock surface during the lab rocburst experiment. This paper presents the specific analytical method of crack propagation with high speed images. Crack propagation types and directions are briefly described, and the lengths, growth rate and fractal dimension of cracks are calculated. The results show that the crack grows mainly along the horizontal line on the unloading surface, at a low speed before rockburst and reaches a very high speed abruptly near the burst point. The fractal dimensions demonstrated that the crack turns to be rough when rockburst happens. The study on the crack propagation is benefit to the understanding on the mechanism of rockburst.

By the use of the experimental system of Impact Rockburst, which was designed by State Key Laboratory for GeoMechanics and Deep Underground Engineering, the stress concentration for orifices in a cubic gypsum specimen subjected to static and dynamic combination loads was studied. The different triaxial precompression was loaded on gypsum specimen, then the dynamic cyclic loading is exerted in the direction of σ1, while the constant stress is exerted in σ2 and σ3. For the stress strain curve, the data of force and displacement were collected by the servo control system in real time. By the strain gauge near the orifices, the strain was recorded by the dynamic strain collecting device, that result in the orifices stress was obtained. In addition, the phenomenon of inner wall of the orifices was real-time photographed. Based on elastic theory and dynamic stress concentration theory, we calculated the stress near the orifices, which keep pace with the results of test.

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