Field Experimental Study on Mechanical Effect of Invert Construction for Shallow Embedded Underwater Highway Tunnel

Abstract

Field measurements were performed by closely tracking the invert construction states of the Liuyanghe tunnel. Based on measurement data, the mechanical effect of the invert construction was analyzed for the shallow embedded underwater highway tunnel. The research results reveal that (1) to the different parts of the upper-arch, invert excavation causes the increase or decrease of local contact pressure between the initial lining and surrounding rock; (2) the closure of the whole initial lining layer can restrict the development of vault settlement and horizontal convergence of the upper-arch initial lining; (3) the steel frame stress at the invert bottom increases remarkably after digging out the temporary fill on the initial lining; (4) the water pressure behind the initial lining of the invert is increased after concrete pouring; (5) the invert concrete can share the surrounding rock pressure and can be used as safety reserve; and (6) it is reasonable that the distance between the end of the invert concrete and the invert excavation face ranges from 25 m to 35 m.