Settlement Law of Overlying Plug Body Caused by Close Construction of Underpass Tunnel Anchorage

To study the influences of the underpass tunnel proximity construction on the settlement of overlying suspension bridge tunnel anchor plug body, taking the Baishiyan tunnel Ⅰ under the tunnel anchorage of Lyuzhijiang bridge of Yuxi-Chuxiong Expressway as an example, model test and numerical analysis methods are used to analyze the deformation evolution characteristics of surrounding rock during the proximity construction, investigate the influence distance between plug body and tunnel and the burial depth of tunnel on the settlement of the plug body. The results show that: The settlement of plug body mainly occurs during the advance tunneling of the tunnel. The settlement of plug body and tunnel arch and disturbance area increase with the decrease of surrounding rock grade, the decrease of distance between plug body and tunnel and the increase of buried depth. The settlement of tunnel arch and the bottom settlement of plug body are the most sensitive to the change of tunnel buried depth, the least sensitive to the distance between plug body and tunnel. The change of the distance between plug body and tunnel has little effect on the settlement of tunnel arch, but has a greater effect on the settlement of plug body. The research results can provide important reference for the construction design and stability control of tunnel-type anchorage and underpass tunnel.