Study On The Evolution Law Of Tunnel Collapse In Jointed Rock By Discrete Element Method

Over the last ten years,traffic congestion has increasingly become one of the most prominent diseases of the big cities.In order to ease the traffic pressure,major cities has competed to develop underground space,which intensified the construction of the tunnel.The situation in the tunnel project is more complicated,especially in the joint development of the tunnel excavation,which has brought great difficulties and risks to the construction.Judging from the investigation of most of the tunnel accidents,the failure of jointed rock mass is from the beginning of the extension of the discontinuous surface,which is the large deformation and displacement.Therefore,exploring the mechanical properties of jointed rock mass is of great help to the practical engineering.Firstly,this article is based on the laboratory tests of fresh sandstone strength deformation characteristics and artificial prefabricated shear resistance strength,and studies the different joint angles facing deformation characteristics of fresh sandstone strength.Then uses particle flow numerical simulation software PFC2 D on the fresh sandstone three axial compression test,direct shear joint simulation test and three axial compression the joint test of different angle of sandstone,sandstone and a fresh artificial prefabricated joint macro meso relationship between parameters.Finally by simulating the excavation process of the joint formation of deep buried tunnel,the article studies the effects of different joint angles and the deformation characteristics of tunnel surrounding rock,and qualitatively analyses the effect after the excavation of the lining.Specifically as follows:(1)This article develops a series of laboratory tests,then gains mechanical properties of intact sandstone through the rock routine triaxial compression test,which provide the basis for the analysis of joints on the mechanical properties of intact sandstone;the article gains the mechanical characteristics of joint surface through the plane of rock direct shear test,which provides the basis for the analysis of joint existence of deep buried tunnel excavation deformation of the surrounding rock;the article gains sandstone deformation and damage law under the condition of different joint angle through different joint angle sandstone triaxial compression test,which provides the basis for analysis of the different joint angles and stratum after the excavation of tunnel surrounding rock deformation evolution.(2)This article carries out a series of numerical simulation test with the particle flow numerical simulation software PFC2 D,and simulates the laboratory tests,then build corresponding relationship between a fresh sandstone and artificial prefabricated joints surface micro to macro view of strength and deformation parameters.(3)Based on the results of laboratory tests,the tunnel excavation process in jointed rocks were simulated,the deformation evolution law of surrounding rock shows that tunnel collapse happens when deformation is large.It is found that the collapse positions are different in different jointed angle,the deformation in surrounding rocks were analyzed in meso level to explain the macro behaviors.The characteristics of surrounding rocks with tunnel lining support were simulated,it is proved that lining could reduce the deformation significantly to help tunnel safety.