The Surface And Strata Movement Research Induced By Mining Under Final Slope Of Open-pit Iron Mine

Mining under the final slope of open pit always induces serious strata movement.The subsidence,slope sliding and rock falls will happen influenced by the mining underground,slope landform,rock mass structure,etc.Considering joints and joints'strength influence,the physical model experiment and the numerical simulation were used to study the law of surface and strata movement induced by mining under the final slope in this paper,mainly results are as followed:(1)Based on engineering practices of mining under the final slope,the typical types of ground surface and strata failure were summarized,the mainly influence factors were analyzed,and the characteristics of ground surface and strata failure were also summarized.(2)A novel experiment method,which could construct large number of joints and control the joint's strength in physical model,was introduced in this paper.The experiment results show that this method could well reflect the influence of joint and joint's strength on the discountinuities deformation of rock.(3)Three physical model experiments were conducted,which the joints,strength were different.The mining influence transmission law,the displacement distribution of ground surface and strata,and the typical failure models of strata were obrtained by considering the joint and joint's different strength influence.(4)Based on 3 DEC(DEM software),two orthogonal experiments were conducted to study the relationship of the strata movement scope and joint's shear strength parameter(c,?).In the orthogonal experiment,the physical model and the east slope of Yanqianshan Iron Mine were selected as study objects,and the joint's shear strength parameters(c,?)were selected as experiment factors,and the displacement angle was used as evaluation index.(5)Based on the research mentioned above,the law of ground surface and strata movement induced by mining under the final slope are obtained,when the joint and joint's strength are considered:?the higher the joint's shear strength,the slower the mining influence spread,the smaller the mining influence scope,the stronger discontinuities deformation;?the basic failure modes of ground surface and strata movement are deflection deformation,collapse,sliding and overturning,shear moving;?When the joints' strength are low,the overlying rocks of goaf are all collapsed,the movement strata could be divided into sliding or overturning zone,collapse zone,serious disturbed zone,meanwhile,when the joint's strength are relative high,only part of overlying rocks falls,the part rock which is not falls forms subsidence zone;? the movement scope and movement scope enlargement induced by mining depth increasement is more sensitive to joint's friction angle ? than joint's cohesive c,and the scope of strata movement is negative related to joint's strength parameter c and ?,but the scope enlargement is not observably negative or positive related to joint's strength parameter c and ?.