Research On Subsidence Control Of Shallow Loess Tunnel Underpass Highway

In Zhengxi Passenger Railway construction, plenty of loess tunnels has large section with section area over 170 m2. Additionally, loess, a kind of special soil with unique mechanical property, makes tunnel deformation more hardly to control. Wenxiang Tunnel is a shallow tunnel with more difficulties, shallow buried and underpass a busy highway. So, the construction of Wenxiang Tunnel has an extremely strict settlement restrict. Based on the experimental section research, a thorough study on settlement law have been done and would be use in techniques amelioration to make sure settlement of formal underpass section will get well controlled. The research works in this paper are concluded as follow:(1) Both longitudinal and lateral settlement law caused by tunnel excavation have been summarized to make the research direction clear;(2) In Wenxiang Tunnel, an experimental section before underpass section was set up to do field research on surface settlement, vault settlement, soil body transformation and so on. According to the field data, settlement laws of shallow loess tunnel have been concluded from the final settlement result and would play a basic role in advanced techniques making;(3) By numerical simulation and analysis of on-site research data, the influence factors have been summarized and ameliorate construction techniques and methods also have been made.(4) The settlement law and improved technique are used in the construction and monitoring of underpass section. Through field monitoring, the controlling methods have been evaluated to check their effects in order to provide useful reference to analogous projects.