Study On Influencing Factors And Stability Evaluation Method Of Slope Excavation In Deep Pit Mine

Open-pit mining accounts for a very large proportion in the mining methods of various mineral resources.According to statistics,about 80% of the mining of metallurgical mines in China use open-pit mining methods,and the resulting landslide hazard of mines becomes One of the key issues that scholars are concerned about.Therefore,under the influence of continuous excavation unloading and external disturbances,how to maintain the stability of the slope while balancing the maximum economic benefits,not only has a certain research value in the academic field,but also in the actual mine side.Slope mining and prevention also have important engineering significance.In this paper,the deep concave mine slope formed by open-pit mining in Jinchuan Group quartz mine,Jinchang City,Gansu Province,is taken as the research object.The stress field,displacement field,plastic area and the evolution law of stability coefficient in the process of mining slope excavation under the design conditions are analyzed by using Midas GTS NX finite element software,Then,based on the design conditions,two parameters,step slope angle and height,which have great influence on slope stability and production efficiency,are selected to study the evolution of stress field,displacement field and stability under different excavation parameters.According to the evolution law,based on the orthogonal test design principle,16 groups of test schemes are set up through the orthogonal table,and the stability results are calculated respectively.At the same time,in order to simplify the follow-up optimization process,a BP neural network is designed with the excavation parameters as input vector and the overall slope angle and stability coefficient as output vector through the neural network toolbox of MATLAB.Then combined with the simulation rule,orthogonal test scheme and BP neural network under different working conditions,the optimized excavation parameters combination of slope is obtained.On the basis of the above research,two kinds of dynamic loading displacement response ratio models are constructed by using the dynamic loading displacement response ratio theory,and the evolution law of dynamic loading displacement response ratio of the optimal excavation scheme and the actual excavation scheme of the slope is analyzed in combination with the field measured data.At the same time,the strength reduction method and the limit equilibrium M-P method in Midas GTS and geo studio are used to calculate them respectively.The correlation between the slope stability coefficient and the dynamic loading displacement response ratio parameter is analyzed to explore the rationality and feasibility of using the parameter to predict and evaluate the mine slope stability.The main conclusions of this paper are as follows:(1)During the excavation process of the deep concave mine slope,the choice of the step slope angle and the step height of the step has a significant influence on the stability and production cost.Under the condition of certain slope height,with the gradual increase of the whole slope angle,the overall stability of the slope decreases gradually,and the sensitivity of the upper step to the slope angle with a larger angle is relatively less than that of the lower step;under the condition of a certain slope angle,with the gradual increase of slope height,the performance of slope height is consistent with that of angle.At the same time,in the process of changing the two parameters from workingslope condition 1 to working condition 4,the overall stability of the slope shows a decreasing trend.Although the force of some steps tends to be beneficial to the stability of the steps,the amplitude is small.By comparison,it can be found that the influence of the gradual increase of step height on the overall stability of the slope is greater than that of the step slope angle.Considering slope stability and production cost,it is suggested that the angle of bench slope should be between working condition 3 and working condition 4,and the slope height of bench should be between working condition 1 and working condition 2.At the same time,in the respective range of each step,the slope angle and the slope height of the upper bench can be suitably increased,and the slope angle and the slope height of the lower bench can be reduced.(2)According to the variation of stress field and displacement field and stability coefficient during slope excavation,combined with orthogonal experimental design and BP neural network in Matlab,the excavation parameters of mine slope are optimized and optimized.After the excavation parameter scheme,the slope angles and slope heights of the seven steps from 1826 to 1816 m steps to 1744 to 1732 m steps are: 69.5°,71.5°,73.5°,75.5°,77.5°,78.5°,80.5°.14.0m,26.0m,14.0m,14.0m,15.0m,15.0m,16.0m.(3)Based on the principle of dynamic load-increasing displacement response ratio and the criterion of instability,the dynamic load-increasing displacement response ratio model of slope is constructed by taking the horizontal stress and displacement as the unloading load-increasing and corresponding response during slope excavation.The excavation scheme optimized in the previous paper is used as a slope model.Through numerical simulation,the simulation results of the measured points located at the shear outlet are brought into the model,and the slope stability coefficient is calculated at the same time.Through the study of its evolution law,it is found that there is a good negative correlation between the response ratio parameters and the stability coefficient in the process of slope excavation,and the dynamic load-added displacement response ratio parameters do not exceed the early warning value.It can be seen that the dynamic load-added displacement response ratio parameters can better predict and evaluate the slope stability.(4)Based on the actual excavation in the field,the slope model is established,which takes the excavation volume of the slope as the dynamic load increment,and takes the measured horizontal displacement data of the 4-C monitoring point and the 2-C monitoring point near the shear outlet as the response quantity.The dynamic load increment displacement response ratio model is calculated,and its stability coefficient is calculated.By analyzing its change law,it is also found that the response ratio parameters of the model are the same as those of the The stability coefficient has a good negative correlation in the process of slope excavation,and when the 4-C occurs small-scale collapse,the response ratio curve changes abruptly,but the response ratio curve of the stability coefficient and the 2-C near the shear outlet does not exceed the warning value,so it does not affect the overall stability of the slope,and there is no large-scale landslide on site.At the same time,the dynamic load displacement response ratio model is easy to obtain because of the parameters,which can be easily applied to the actual slope stability evaluation and prevention.