Experimental Research On Interface Behavior Between Coal Gangue And Clay

The contact surface of soil can be divided into two types: the same soil and the different soil.In practical engineering,the soil often slides along the contact surface of soil.Therefore,the contact surface is considered as a weak surface in stability analysis,and the shear strength index value of soil is reduced and used on the contact surface.This conventional method has neither theoretical basis nor experimental demonstration.Based on the background of the longitudinal cracks in the shoulder position during the reinforcement of embankment in a coal mining subsidence area in Huainan,considering the influence of the strength of the interface between coal gangue and clay as Embankment Filler on the stability of embankment,this paper carries out physical experiment research.According to the test results,the influence of normal pressure and the content of coarse coal gangue on the mechanical properties of the interface is analyzed and studied.Based on Clough's and Duncan's non-linear elastic constitutive models,the parameters of the contact surface model are sorted out,and the curve obtained by the model is fitted with the experimental curve..The ANSYS numerical simulation is used to simulate the direct shear test of the contact surface,and the comparison between the numerical simulation and the physical test results is analyzed,and the reduction relationship between the numerical simulation results and the experimental results is proposed.? It provides a reference for calculating parameters of contact surface in embankment model of mining subsidence area.The main results are as follows:(1)In the reinforcement of embankment in coal mining subsidence area,a calculation model considering the strength of coal gangue-clay interface is put forward for the first time,and the contact surface can be regarded as a thin layer material by means of direct shear test and curve fitting research.In the deformation range of 0~2cm,the difference between maximum shear force obtained by curve fitting and test maximum shear force is 0.40%~9.77%,so the hyperbolic model is used to fit coal gangue.The shear of the interface between stone and clay is suitable.(2)When the normal pressure is between 50 kPa and 300 kPa,the maximum shear stress at the interface increases linearly with the normal stress.In addition,the normal pressure has greater influence on the maximum shear force of the contact surface than the content of coal gangue coarse aggregate,and the influence ranges of the two factors are 18.2%~240%,4.23%~54.55%,respectively.Therefore,the maximum shear stress under 300 kPa normal pressure can be determined to be 71 kPa,which can be used as the upper limit reference value of the design shear strength.(3)The numerical simulation results are consistent with the experimental results,which can be verified and analyzed mutually.The simulation results show that the experimental values of friction angle and shear strength of the contact surface are larger than those of the numerical calculation,while the experimental values of cohesion coincide with those of the numerical calculation.The difference range of shear stress and internal friction angle between numerical simulation and test is 2.5%~21.43% and 15.66%~22.42% respectively.The strength reduction range of contact surface in engineering design can be used as a reference.