| The deformation, strength and stability of the high steep rock slope are controlled by the structure planes and distribution as well as the stress fields. Most of the slide zones in high steep rock slopes comprise of rock bridges whose strength is relatively high. These rock bridges have key influence on the stability of the slopes. These kinds of slopes are called partly locked slope. At the moment, many such partly locked slopes are widely distributed over the mining and geotechnical engineering areas. The damage of this kind of slopes has characters of both evolving progressivity and arising on a sudden. Therefore, stability analysis and damage prevention for these slopes are a big challenge. To make deep study on this subject is necessary and useful.In this paper, the mechanism of locked patch in the partly locked slopes was studied on the basis of establishing geotechnical model, experimental tests, theoretical and numerical analysis under the background of Aoshan open pit mine of Nanshan Mining Co., Ltd. From the view point of energy the progressive evolving and sudden damage of the partly locked slopes, i.e. "slipe-lock-slipe" was analyzed. A methodology for dealing with the safety factor of partly locked slopes was also established. Moreover, the stress distribution, damage evolution, stability analysis as well as the warning model were studied during the process of reclaiming residual ores. The main contents of the study are as follows:(1) A geometric mechanical model of Aoshan open pit was established through field exploration, fitting and reconstruction of 3D joint networks. It was found that the rock mass at the top was softer and looser than in that in the bottom, so the slope has the structure to reserve the residue energy from the upper rock mass in the post-peak stage. Meanwhile, stress rotation and unloading area were produced owing to the F1 fault, which is distributed through the southern area. The concentration of stress in the slope is distinct and thus, Aoshan open pit can be treated as partly locked slope.(2) Direct shear test was carried out with artificial rock specimens. The test results of shear strength and crack propagation mode of the locked-up rock specimens with different conditions of cracking penetration, normal stress, rock bridge arrangement and joint inclinations were analyzed using direct shear tests. According to the results, the strength of rock mass and fracture propagation were obviously influenced by the attitude of joint and rock bridge. A highly phased damage evolution was observed and the penetration of fracture around rock bridge means the loss of rock strength. The instantaneous release of residual energy along the shear direction is the principal mechanism of the abrupt failure of locked-up rocks.(3) A generalized model for partly locked slope was established. Moreover, dynamic failure criterion and energy evolution formula based on energy concentration and release, were also put forward. A quantitative study was carried out on the progressive and dynamic failure process of partly locked slopes. The methodology for calculating the safety factor of the partly locked slope was proposed and the influencing factors were also discussed.(4) A 3D damage evolving model and analysis program of jointed rock mass were established on the basis of effective stress and fracture mechanics. Based on Rosenblueth theory, the 3D random damage zone during its residual ore recovery in different stages were analyzed in Aoshan deep open pit. The results can reveal the principal mode for the changes from jointed rock slope to partly locked slope.(5) According to the character of partly locked slopes, a new type multipoint extensometer was developed, a space-time warning model for slopes considering the damage evolution was also established based on displacement back analysis theory, using 3DEC code and the BP neural network platform. The damage evolution mode of the partly locked slopes was finally analyzed for prediction. |
PDF Full Text Request