Analysis And Research On Excavation And Support Of Gongbei Tunnel

A double-deck highway tunnel, buried very shallowly, is constructed in the softsoils with a super section. Based on the tunnel, the paper studies the excavationmethod, the temporary support，the initial support, the secondary lining with ANSYSsystematically, and meanwhile makes an analysis on the bearing capacity andstability of the tertiary lining.The paper makes a brief induction of the research and development of theshallowly buried tunnel with a super cross-section and sums up the method ofcalculating the rock pressure first. Then it introduces the temporary support，theinitial support, the secondary lining and the tertiary lining and makes a discussion onimprovement of the fore poling and initial support,it concluded that:(1)It has done a temporary support beam when tunnel excavation, calculated bythe analysis, the axial force of the vertical support is increasing from top to bottomand vertical temporary support is larger than transverse temporary support, it shouldbe used vertical support than the lateral support strength, stiffness.(2)Horizontal and vertical temporary support should bear certain moments,especially connecting nodes of temporary support bear large moments.it must attachimportance to the accuracy strength and rigidity of the connection node during theconstruction, to prevent the node opening during support in the flexural, impact of theconstruction safety(3)With tunneling steps carried soil plastic zone is also to the deep development.After the fourth step of the excavation, except near the anchor of tunnel roofsurrounding and the vertical support, were involved in the tension zone, and the areaaffected by tension zone becomes larger, so in tunnel construction it should pay closeattention to the fourth level excavation, preventive measures well done in advance.Strength of the tertiary lining is calculated during construction and operation byANSYS. Link between the medial plate and the side wall is studied and suggestion onthe construction and design of the tertiary lining is proposed. At last, the paper makes a conclusion of the design and construction of thetunnel and provides suggestion on the design and research of the tunnel with a supercross-section which is buried shallowly in the city ground. For tunnel across the citydense buildings and the politically sensitive area, if it cannot close groundtransportation, using double excavation of the tunnel structure is feasible. Due to theinfluence of ground transportation, coupled tunneling itself span big, depth is small,poor geological conditions, formation damage caused by the tunnel excavation maycause surface subsidence and even roof fall, so taking strong advance supportprotection measures are necessary before tunneling excavation. Use advance pipecurtain method can minimize ground subsidence, mitigate the effects groundtransportation to and tunneling excavation.It can be widely used. While act in concertwith cave freezing and grouting, can ensure safety during construction. It also pointsout further research questions:The numerical simulation, based on the design and construction, is a reflection ofthe mechanical behavior of the tunnel and is aimed to provide some references to thesimilar projects.