Influence Of Non-persistent Joint On The Plastic Zone Of The Tunnel Surrounding Rock Mass

The deformation of tunnel surrounding rock is one of the key and difficult problems in tunnel engineering field recent years.Surrounding rock of tunnel are mostly compound,well developed joint,soft and which will be thin sheets and fragmental when hammering.In the process of design,construction,and supporting engineering,the engineering stability directly depends on the strength,deformating,damage and fracture of excavated surrounding rock.And the existence of the joint greatly affected the strength and deforma-tion characteristics of surrounding rock.So aiming at analyzing the influence of different characteristics joints in rock to plastic zone is a worthy subject.Aiming at deformation problems appeared in the process of tunnel construction,the paper takes deeply buried tunnel project as the research object.By using engineering geological data,simplified geological model,and Phase2D simulation by finite element method,the paper simulates the change rule of tunnel surrounding rock plastic zone’s stress,displacement and the yield range under no joint conditions and different geometric features of the penetration joints.First,determining the scope of the excavation of stress release to 4 times of tunnel diameter.Secondly,through the surround yield failure units of tunnel in proportion to the total net unit value,determining the area of plastic zone joint spacing increases first and then decreases.Decreases with increasing length of joints rock bridge,it is determined ultimately that the joint spacing is 1.5m,the length of rock bridge is 0.5m,and the angle is 15 degrees.Finally,based on stress reduction and analyzing displacement around tunnel,it will be determined the arrange of supporting force around tunnel at containing joints and without joints respectively.Without joints:no unit yields when supporting force range is Q=3.5MN/m~2-12.5 MN/m~2 and supporting force is Q=0.8MN/m~2that displacement is under security line.Containing joints:no unit yields when supporting force range is Q=5MN/m~2-12.5 MN/m~2 and supporting force is Q=0.9MN/m~2 that displacement is under security line.The paper gives suggestive value in order to provides theoretical reference to analysis and evaluation of surrounding rock stability and take reasonable supporting measures late period.