Study On Instability Mode Of Layered Slope In Jianshan Phosphate Mine

Because of the layered characteristics of rock structure, the failure mechanism and instability mode of layered slope is different from other slope. In the past mining activities, affected by engineering excavation disturbance and exogenic force, Jianshan phosphate rock slopes show different degrees of deformation and failure in different mining stages, slope stability has become a potential safety hazards in mines. In this paper, taking Jianshan phosphate layered slope as the object of study, paying attention to open-pit mining technology condition and analysis of mechanical properties of rock mass, combined with the analysis of the stability of engineering rock mass, the slope dynamic evolution test and numerical analysis method to carry out an in-depth study on slope deformation and failure mechanism and instability mode, and puts forward the countermeasures to control the stability of slope. Through field investigation, theoretical analysis and experimental study, the main research results obtained are as follows:(1) Combined with conditions of Jianshan open-pit mine, divide the rock mass, analyze random structure surface characters on engineering rock mass by use of the survey line, point out position of dominant structural plane of rock mass that affects on slope stability. Based on the classification of engineering rock mass, evaluate integrity and structural characteristics of engineering rock mass through testing technique on rock sonic wave and rock block index RBI, determine the range of disturbance of the reserved slope rock and coefficient of disturbance D. With the help of the generalized Hoek-Brown criterion to estimate the mechanical parameters of rock slope, carry out the in-situ direct shear testing on the key rock slope, comprehensively determine the macroscopic rock mechanics parameters of slope.(2) Based on classification feature of the layered slope engineering, analyze the deformation mechanism of layered slope and potential failure mode of different slope structures and lithologic features. Analyze the stress state of the slope rock mass and evolution, deformation mode of layered slope on Jianshan phosphate rock is slip-bending-shear failure, and the potential sliding surface is a combination that upper part is plane and lower part is arc surface.(3) Analyze sliding-bending stress mechanism of layered slope, aiming at the nonlinear characteristic of deformation of slope rock mass, apply catastrophe theory in systems science to disaster analysis of buckling deformation of layered slope, build the cusp catastrophe model of layered rock board system, reproduce the catastrophe process of gradient force leading to mutation of system state of the slope.(4) Based on geological environment of slope in studying area, use the technique of physical model test,build slope excavation model with dip angle45or50in side slope and excavation model with changeable dip angle, combined with analysis on slope displacement and variation of displacement vector field. The deformation and failure mode of slope excavation is that upper body is bedding slip, lower body produces bending deformation with slip and extrusion. When the deformation exceeds the limit bearing capacity of rock, the slope tends to destruct along the path with the bending deformation of maximum curvature, the potential sliding surface is that upper slip surface is parallel to the free surface, lower shear plane is similar to arc.(5) Numerically analyze open-pit mining of Jianshan layered slope, excavation of slope leads to redistribution of stress in rock mass, the slope emergence a new "stress balance area", and activate the original control on slope stability of adverse factors, relaxation from the excavation of rock stress and change of stress field in rock mass result in deformation. The excavation of rock slope makes resistance between the sliding force decreasing, the relative movement between the layers increasing. The upper part of slope rock mass tends to sliding downward along the level, the lower part of the slope with the extrusion from the upper produces bending deformation from lateral free surface, cutted by developed structural surfaces, rock mass with bending deformation is anomaly broken, which is beneficial to that the shear plane goes through completely. Slip surface and the shear plane of slope is fully connected, makes the overall slope produce slip-bending-shear failure, slope slip surface is a combination with upper slip surface parallel to the free surface, lower shear plane similar to arc.(6) On the basis of the mining condition in the deep, propose the stability controlling countermeasures of top unloading, bottom dumping in on Jianshan phosphate rock slope, realize safe, efficient production of mine.