Model tests on interaction between tunnel-type anchorage and underpass tunnel

In order to study the influences of approaching construction between underpass tunnel and tunnel-type anchorage on the mechanical characteristics as well as the stress characteristics of the underpass tunnel in the bearing stage of the tunnel-type anchorage, taking the project of Baishiyan tunnel Ⅰ under the tunnel-type anchorage of Lüzhijiang bridge of Yuxi-Chuxiong Expressway as the research object, a 1∶100 scaled model test is carried out. The main conclusions are drawn as follows: (1) The settlement of the anchor plug is mainly caused by the excavation of the advanced tunnel of the multi-arch tunnel, and the disturbance by the following tunnel excavation is not obvious. (2) The stress of the surrounding rock between anchorage and tunnel has experienced three development stages: stress concentration, stress transfer and stabilization. The time of abrupt change of the horizontal stress of the surrounding rock is earlier than that of the vertical stress. (3) The bearing effect of the initial support is obvious during tunnel excavation. With the removal of temporary support, the pressure of the surrounding rock borne by the initial support gradually turns to the middle wall. (4) When the cable tension is applied to anchorage, the surrounding rock between anchorage and tunnel will enter the plastic state, and leading to large tensile stress at the spandrel and vault of the tunnel.