| At present,it is difficult for my country’s urban road traffic to adapt to the needs of urban renewal.In order to build a modern urban traffic system with "external connections and internal smoothness",speed up the filling of urban infrastructure shortcomings,and make every effort to smooth the traffic microcirculation.Ways to broaden the urban road network are particularly important.Bridge-tunnel connection engineering refers to a complex combination of existing structures in tunnels,bridges,surrounding rock at the entrance of the tunnel,and connecting sections.Due to the mutual influence between the structures,the mechanical behavior of the connecting section is more complicated.At present,most of the analysis is that the bridge-to-tunnel or the single impact of the tunnel to the bridge has been completed in mountainous areas.However,the construction of the connecting section of the tunnel in the complex environment of the city has the safety impact on the surrounding existing structures,and the small-distance tunnel opening of the connecting section The method of digging and the reasonable distance of staggering have not yet been discussed.Therefore,this article is based on the construction of the tunnel connecting the Leijiapo overpass and tunnel in Chongqing.According to the actual site environment,the safety assessment of the existing structures in the bridge-tunnel connecting section of the project is carried out,and the tunnel excavation problem of the connecting section is established at the same time.Corresponding numerical model,and apply car load to the connecting section for mechanical analysis.The main work is as follows:(1)Summarize the current research and engineering application of bridge-tunnel connections at home and abroad,and summarize its main characteristics and adaptability conditions.Subsequently,based on the actual project of Leijiapo,the mechanism of damage to the existing structures around was discussed.Using MIDAS GTS,a three-dimensional numerical calculation model of the bridge-tunnel connecting section was established.According to the reinforcement measures taken by the proposed project,the safety evaluation of the pile-slab retaining wall,existing viaduct piers and highway of the connecting section was carried out.(2)At the junction of the bridge and the tunnel,three different excavation methods are adopted for the tunnel entrance section to simulate the mechanical behavior characteristics of the part of the bridge connecting the tunnel,the existing structure and the surrounding rock and soil.Compare and select different construction schemes from the perspective of economy and technology,and optimize the excavation method of the tunnel entrance section at the junction.(3)A numerical model of the excavation of the two tunnels staggered at different distances is established,and the obtained results of vault settlement,bottom uplift,plastic zone of surrounding rock,and supporting force are compared,and the reasonable distance of the two tunnels longitudinal staggered excavation is analyzed.(4)Based on the finite element model,the vehicle load is applied to the bridge-tunnel connection section according to the change of vehicle speed.Compare the displacement and deformation difference of each structure under the load of the vehicle,and obtain the relationship between the speed change and the settlement of the structure.(5)Monitor the Leijiapo project,analyze the safety impact of the Leijiapo bridge-tunnel connecting section construction on the existing structures through the measured data,and compare the measured data with the numerical simulation results.It is concluded that the structure meets the safety requirements,which proves the effectiveness of the reinforcement measures and the optimized excavation method of the tunnel entrance section. |
