Research On The Morphology And Control Technology Of The Plastic Zone Of The Roadway Surrounding Rock

With the gradual depletion of shallow coal resources,coal mining has been extended to the deeper part,and with it,a series of problems such as large deformation of the roadway envelope rock and support failure have appeared frequently.The formation and expansion of the plastic zone of the surrounding rock is the main reason for the deformation and damage of the roadway surrounding rock structure.Therefore,in this paper,through theoretical analysis,numerical simulation and engineering application,each mechanical parameter’s impact on the plastic zone of the roadway’s surrounding rock is thoroughly investigated,under varied lateral pressure coefficients,the shape of the plastic zone of the highway surrounding rock is investigated,the morphology of the plastic zone is used to study the control technology of the highway around rock.The research results of this paper are as follows:(1)During the process of increasing the lateral pressure coefficient from 1 to 3,the morphology of the plastic zone gradually changes from circular to elliptical,and finally evolves into a "butterfly shape" plastic zone.The cohesion,internal friction angle,primary rock stress,and intermediate principal stress do not change the morphology of the plastic zone,while the cohesiveness and internal friction angle rise,the area of the plastic zone reduces,while the main rock stress increases,the size of the plastic zone grows.The effect of the intermediate principal stress on the plastic zone is not obvious for lateral pressure coefficients of 1 and 1.5,and the effect of the intermediate principal stress on the area of the plastic zone shows a certain interval for a lateral pressure coefficient of 3.When the roadway is shallow,increasing the support force has a certain effect on controlling the expansion of the plastic zone,while when the roadway is deep,the effect of increasing the bearing capacity and controlling the plastic zone of the rock around the road is very small.(2)When the shape of plastic zone is round or oval,uniform support for the roadway can effectively control the deformation of the roadway surrounding rock.When the shape of the plastic zone is "butterfly",the uniform support of the roadway can not inhibit the malignant expansion of the plastic zone butterfly,but after the local grouting support of the roadway,overall,the distribution of the plastic zone has a uniform shape,and the area of the plastic zone and the displacement of the surrounding rock mass have been significantly reduced.(3)With the background of the project of 2354 bottom slab road of Jiahe coal mine,the deformation of the roadway is serious,the top plate sinks obviously and the bottom drum is serious.Based on the theory of butterfly plastic zone,a comprehensive support scheme of "flexible anchor cable + hollow grouting anchor cable + anchor rod + metal mesh + concrete spraying" was designed,and the effectiveness of the scheme was confirmed by displacement monitoring of the roadway.