| The surface of many opencast mining areas in China is the Quaternary loess layer,which has the characteristics of poor compactness and strong collapsibility.Therefore,when the loess is used as the base of the outer dump,it is not conducive to the stability of the slope,especially after a large amount of rainfall and surface water infiltrates the base,the stability of the slope will be further affected.In addition,the compressed coal under the outer dump of the open-pit mine is usually mined by shaft mining,which makes the stability control of the loess basement dump more difficult.Based on the typical loess basement dump of an open pit mine in Inner Mongolia,this paper studies the stability of the outer dump slope under the influence of flooding and well mining by means of laboratory test,numerical simulation and theoretical calculation.Firstly,considering the influence of different water content and the thickness of weak layer,the variation of slope stability coefficient under different combination conditions is studied;Secondly,combined with the field flooding conditions of the dump,the variation law of the dump slope stability under different well mining process parameters is studied,and the stoping line position of the underground working face is determined;Finally,through field monitoring,the rationality of stoping plan of underground working face is verified.The main research results are as follows:(1)The direct shear tests of loess with different water contents show that the cohesion of loess decreases linearly with the increase of water content,and the internal friction Angle decreases in the form of power function with the increase of water content.(2)The numerical simulation results of loess basement dump slope under different water contents show that the slope displacement increases with the increase of loess basement water content,and the sliding surface changes from "circular arc" to "Lshape".When the water content is higher than 16%,the slope no longer meets the safety requirements.The numerical simulation results under the influence of different thickness of weak bed show that the slope displacement increases with the increase of the thickness of weak bed,and the sliding surface changes from "L-shaped" to "circular arc".When the thickness of weak bed is greater than 0.6 m,the slope no longer meets the safety requirements.(3)According to the empirical formula of the maximum height of waterconducting fracture zone,the feasibility of mining thickness of 30 m was verified.Through numerical calculation,the variation law of slope displacement field,stress field and shear strain in the composite mining of coal 4 and coal 6 is revealed,and the position of stop-mining line in coal 4 and coal 6 face is determined.By using probability integral method,the extremum and range of surface movement and deformation after combined mining of coal face No.4 and coal face No.6 are predicted.(4)According to the field practice,the surface movement and deformation of the control points are monitored.The results show that the total duration of surface movement after mining is about 268 days.Through comparative analysis of the field data,numerical calculation and theoretical calculation results,it is shown that the numerical calculation and theoretical calculation results are close to the field monitoring results,and a good effect has been achieved.This paper provides an important reference for slope stability analysis of loess basement dump under similar working conditions.There are 81 drawings,41 tables and 100 references in this paper. |
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