Abstract:

In order to study the evolution characteristics of the fracture plane of the anti-dip rock slope with the steep and gently dipping structural plane under the condition of its own weight. Taking the toppling deformation form of right abutment of Miaowei Hydropower Station as the geological prototype, the centrifugal model test was carried out by presetting non-penetrating cracks of the rock strata in different parts of the slope body to simulate the evolution characteristics of the fracture surface of the anti-dip rock slope under the condition of its own weight. The researches have demonstrated that: (1) The failure of anti-dip rock slopes with steep and gently dipping structural planes are marked by the formation of fracture surfaces, which are divided into three stages: in the initial period (0–40g, g is the acceleration of gravity), it refers to the stage of partial fracturation which takes partial fracturation and stratum forwarding on the trailing edge as the major failure characteristics with less position changes in slope plane. In the middle period (40g–80g), it refers to the formation stage of major fracture plane which can be formed in the deep structural plane of slope through expansion and connection in a top-down approach. Position changes in slope nearly account for 3/4 of total position changes. In the later period (80g–120g), it refers to the formation stage of multi-stage fracture plane whose main formation feature is the stress redistribution of fracture strata within the slope. Position changes in slope basically remain unchanged. (2) The fracture of rock bridge between structural planes is transient, but the formation of fracture plane is a gradual development process which is mainly controlled by steep-inclined structural planes. The strain at the crevice of the main fracture plane is the greatest and the stress mode is the most complex. And the fracture strain at the secondary fracture plane takes the second place. Based on fracture mechanics, the fracture criteria of the rock compression-shear and unbalanced force formula for rock stratum have been simplified. It is revealed that the unbalanced force of the rock stratum at the main fracture surface decreases from 1/3 of the slope height to the bottom and top of the slope. The formation of fracture surface is mainly affected by the ratio of the intensity factor of shear stress to normal stress, the length of rock structure plane and the crack rate.

Key words: anti-dip layered slope, centrifuge test, crack propagation, fracture of rock bridge, fracture surface formation