Research On Analysis Method Of Slope Stability And The Optimization Of Treatment Technique For Large-scale Bedding Slope

Baiyun Obo east mine is the main rare earth mine for Baotou steel group or even for the whole country. With the increasement of mining height, slumping accidents frequently occured, especially in zone B, where the volume cf slide body is the biggest and the deformation is the most active. From the slope state exposed, the slope will be affected by several cross faults for a long time, and the rock mass is very fragile. However, this area is the throat channel for mining and transport, where has been adopted a series of reinforcement measures in recent years. All the reinforcement projects affected by internal rock rupture have appeared different degree of deformation. Besides, along with the excavation of deep slope and the intersection of each fault, a huge potential slide slope body will form in this region. Whether the existing reinforcing scheme can ensure the safety of deep slope or not needs to be solved immediately.Taking the project of The real-time dynamic monitoring and early warning system for slope stability of Baiyun Obo mine’ as the back ground, the typical section B-B’of bedding slope in zone B was focused in this study. In order to solve the existing problems of stability analysis and treatment technique, the user defined constitutive model was conducted through the measured displacement in zone B, and the improved study of strength reduction method was also realized based on this constitutive model. After obtaining more reliable safety factors of slope, the optimized treatment technique was put forward in this study. Main contents of this thesis are as follows:(1) Based on the criterion of generalized nonlinear unified strength, the program code of criterion of generalized nonlinear unified strength was written by Visual C++. By adjusting the intermediate stress parameter b, different dynamic link library files were generated. Combined with the platform of User Defined Model in Flac3D, numerical simulation of different nonlinear strength criterions were realized in this study.(2) Based on the inversion technique of BP neural network, taking the displacements of monitoring points as the input vector, selecting the physical and mechanical parameters and the intermediate stress parameter b as the output vector, the BP neural network system was built according to the numerical simulating samples. After bringing the measured displacement into the system, physical and mechanical parameters of rock mass and the intermediate stress parameter b that can suit the actual working condition were obtained by inversion. And the user defined model was built based on the theory of generalized nonlinear unified strength, which was verified to be more suitable for the actual working condition compared with other constitutive models in this study.(3) Starting from the differences of slope rock mass parameters in ultimate state, different reduction limits were set for different parameters to realize the improved strength reduction. Based on this improved method, the stability evaluation of slope rock mass was studied, and the stability sensitivity sequence of the rock mass slope and the key rock mass were also determined.(4) Based on the user defined constitutive model proposed in this study, the numerical simulation was finished in accordance with the reinforcement measures for the excavation of deep slope. It was found that a massive landslide was likely to be happened if the past reinforcement measures would be still used in future. And further treatment measures must be taken.(5) Combined with the the stability sensitivity sequence of the rock mass slope, the primary scheme of ’anchored-tunnel+grouting+prestressed anchor cable+rib-concrete wall’was determined. It was verified by calculation that the big massive landslide can be avoided after the primary scheme was taken, but the minimum value of safety factor during the whole process was still lower than the limit value of safety factor for this slope. So the optimized schemes of ’anchored-tunnel+prestressed anchor cables with system layout’ and ’advanced grouting+anchoring integrally’ were proposed from the aspects of ’reducing the blasting work of anchored-tunnel’ and ’elevating the strength of rock mass as soon as possible’. After verification, a better result can be obtained, and the slope will be more stable.