Deformation Characteristics Of Nearly Horizontal Sedimentary Surrounding Rock With Steep Joints In Highway Tunnel

In the construction of the domestic traffic engineering,especially in the centraland western regions of China,as one of the controlling engineering,someconstruction issues has been highlighted,with the tunnel towards long、large section、long span direction,also geological situation has become even more complex.Tunnelexcavation is conducting in rock and soil environment，influenced by rock geologicalstructure, construction methods. Deformation analysis is the key point of safetyconstruction，also is one of the difficult problem in tunnel construction during theexcavation.Rock mass experienced a variety of complex geological tectonism in theformation and developing process，rock physical and mechanical properties is verycomplex and easy to instability、destruction under loads，because a large number ofjoints, cracks and faults in the rock mass structure plane. In tunnel project，thedestruction of surrounding rock usually depends on the nature and distribution of thejoints.The stability of surrounding rock is often controlled by the jointed structuralplane.So,expanding the deformation research of rock mass tunnel which mastered byjoint，we can get the similar experience of tunnel stability analysis which deformationmastered by joint on the hand,on the other hand it can enrich the way of tunnelstability analysis.In this thesis, theoretical analysis, field measurement and numerical simulationhad been used to analysis the process of tunnel excavation to stability at complexgeological conditions，combined field data of shajiaping tunnel, Qinglong to theXingyi highway,from the view of rock stability effected by joint.The relationshipbetween the occurrence of the joints and surrounding rock deformation had been got,then supplemented numerical calculations to verify the reliability of its own rules.Themain conclusions are as follows:（1）The advantage of joints inclination of Shajiaping tunnel was big,which wasthe main controlling factors of tunnel surrounding rock stability.Joints at45°to70°inclination for supporting was the most adverse conditions.The joints angle less than55°, the main affect the surrounding convergence; greater than70°, main affectsettlement influence.（2）The crown settlement and surrounding convergence measured datashowed:the settling time of surrounding rock deformation was about45days at portal section V level surrounding rock，the Ⅴand IV at middle hole was30、25days.Spatialaffection analysis showed：when the tunnel face distance of three times the holediameter,crown settlement and surrounding convergence displacement release ratereached at80%at each section of the portal section;crown settlement andsurrounding convergence displacement release rate reached at90%，when at twice thetunnel diameter at each section of the hole figure；the distance from the working facewas50meters, displacement release rate reached more than90%.（3）Numerical simulation showed that:with the change of inclination,displacement field and stress showed the asymmetric distribution, at45°~60°wasthe most unfavorable bracing case，basically consistent with the measured results ofstatistical analysis.