Research On The Effects Of Tunnel Cross Passage Excavation On Surface Settlement And Tunnel Displacement

With the rapid development of China’s social and economic, and the level of urbanization, the city’s transportation capacity requirements are also increasing. Ur-ban subway construction is undoubtedly an important measure to ease the traffic pressure. From a security perspective, it is needed to set up a cross passage between the two tunnels in the design of the urban subway. Because the cross passage exca-vation destroyed the stability of the original main tunnels and the soil, and the im-proper operation in the construction process of the cross passage will be a big risk to the whole project.Based on the cross passage which was located between Hongpu station and Jiubao station of Hangzhou Metro Line1, and by means of the analysis of the meas-ured data and numerical simulation, the comparison of measured data and simulation data, and parameter sensitivity analysis, this dissertation studied the effects of tunnel cross passage excavation on surface settlement and tunnel displacement. It also veri-fied the reliability of the numerical simulation. Conclusions were as follows:(1)Lateral surface settlement curve caused by cross passage excavation was a U-shaped. A relatively large range of settlement was basically located within the range of16meters from the axis of the cross passage.(2) Overall, the settlement of the tunnel in which the steel segment was re-moved first was more than the other one. From another perspective, the settlement of the tunnel is mainly generated in the soil excavation stage. And the tunnel settlement curves which were caused in different operating conditions were U-shaped.(3)The horizontal deformation of the tunnel segments caused by cross passage excavation turned towards the direction of outside the tunnel. The maximum defor-mation position of the tunnel is located in a place connected with the cross passage. And the horizontal deformation of the tunnel in which the steel segment was re-moved first was more than the other one. (4) By changing the value of the elastic modulus of the soil, reinforced area, the soil cover thickness, the cross span of the cross passage, we could know that as the elastic modulus of the soil as well as reinforced area increased, it was possible to ef-fectively improve the self-supporting capacity of the soil. For example, when the elastic modulus increased to40Mpa, the maximum lateral surface settlement was41.11%less than the unreinforced one. And for the changes of he soil cover thick-ness and the cross span of the cross passage, surface settlement and tunnel displace-ment would show different change rules.