Study On Macro-meso Mechanical Characteristics With Its Excavation Stability Analysis And Control Of Rock Slope

Many open-pit mines with high-steep slope face challenges of deteriorating of rock mass and complex mining-induced stress environment during the mining excavating.Mechanical behavior and stability analysis of rock slope under excavation process are the research focus in geotechnical engineering,which have great scientific and engineering significance.This dissertation was financially supported by the Key Program of National Nature Science Foundation of China "Study on Stability of High and Steep Slope in Deep Open-pit Mine"(No.51034001).According to the mining boundary extending program in Shuichang Iron Mine,literature review,field test,laboratory experiment,numerical simulation and theoretical analysis were carried out to research the excavation of II area in north mining slope.Based on the comprehensive knowledge of rock mechanics,elastic-plastic mechanics,finite difference method and discrete element method,the mechanical behaviors and excavation stability of rock slope were studied from continuous to discontinuous and macro to mesoscopic perspective.The results of this research are as follows:(1)The rock parameters,in-situ stress and joint distribution rule of the rock slope by rock mechanical experiments,in-situ stress measurement and joints field survey were obtained.(2)By using of Particle Flow Code(PFC)method,the correlation between macro-parameters and micro-parameters was discussed through single-factor analysis and orthogonal test analysis.And the sensitivity sorting of each meso-parameter was determined.A prediction model and method to determine the meso-parameters were built by means of MATLAB neural network.Afterwards,the meso-parameters of granitization granite were calibrated.In addition,the optimal inner scale ratio for the research was obtained.(3)With granitization granite as the research object,the macroscopic failure features of rock were analyzed by experimental research,including uniaxial and triaxial compression experiments and unloading tests.The mesoscopic behaviours of rock failure using the PFC numerical tests under different compression pressure were analyzed from the aspects of energy evolution,micro crack propagation and failure modes.The microcrack number was defined as the damage variable to describe the unloading deformation modulus and poisson ratio.And finally,the unloading yield constitutive equation was proposed.(4)The mechanisms of deformation modulus deterioration under excavation process and its significance in numerical simulation were studied.A quantitative relationship between deterioration factor A and reduction percentage of confining pressure was established,and was embed to the FLAC3D to build the excavation degradation model of engineering rock mass,which can be successfully used to analysis the stability of the excavation slope.A fuzzy comprehensive evaluation model by optimizing the RMR method was proposed.Afterward,the slope rock mass quality intelligent evaluation system was established.(5)Combining with the Synthetic Rock Mass(SRM)technology and the joints field survey,a numerical model of jointed rock mass in the PFC was built.Then,the size of REV in this research was determined,and the meso-parameters of the joint model were optimized.On this basis,the meso-mechanism and process of slope instability were revealed through simulating of slope excavation.Based on the tension-shear composite failure criterion,the stability of slope was analyzed by the mesoscopic strength reduction method.According to the numerical analysis results and situations of slope,a dynamic feedback system for slope stability control was established.The influence of mining sequence on slope stability was analyzed,and the controlling suggestions of slope stability were proposed.