IMPACT CONTROL OF ENTRANCE AND EXIT OF SUBWAYS CONSTRUCTED WITH PIPE-JACKING METHOD ON EXISTING INTERVAL TUNNELS
The construction of subway entrance and exit with pipe-jacking method has an apparent impact on exist-ing interval tunnel. Based on the elaboration of tunnel protection measures,a three-dimensional finite element analy-sis model is established. This paper studies the distribution characteristics of horizontal and vertical displacement of interval tunnels during the construction stages of launching shaft,receiving shaft,and pipe jacking. The changing law of roadbed settlement and tunnel horizontal displacement are analyzed in details. The results show that the road-bed settlement near subway station is mainly uplift and the roadbed settlement far from subway station is settlement. The impact of pipe jacking excavation on interval tunnels is greater than that of working shaft excavation,and pipe jacking excavation is a key stage. The significant change range of horizontal convergence for the near and far tunnels is about 5 and 3 times of tunnel diameters. Under those targeted protection measures,the displacement of interval tunnels meets the control standards.