Construction Monitoring And Numerical Simulation For CRD Method Of Subway Tunnels

Mining method due to the low cost, demolition, flexible, and does not interfere with ground transportation and the surrounding environment is widely used in the city subway construction. Tunnel construction will inevitably disturb the undisturbed soil formation, surface moves accordingly in the undisturbed soil to a new equilibrium conversion process. Ground settlement, collapse, resulting in pavement cracks, buildings tilt, underground communication lines, water supply lines, gas pipelines and other cracking damage, which impact on person’s daily life and safety seriously and cause seriously economic losses and social impacts.In this paper, finishing CRD construction method of surface subsidence on-site monitoring results, analysis of the CRD construction method in surface deformation rules and characteristics, combine with sections of the tunnel bored section of the combination of ZhengZhou Sports Center Station Projects. Pointed out that in the CRD four excavation construction method, the upper left and right pilot tunnel excavation produce greater surface subsidence, the settlement produced value accounted for about75%of the total settlement excavation.Using the finite element software for three-dimensional numerical simulation of the CRD construction method in accordance with the actual geological conditions of the project, the tunnel supporting structure, the construction step. Compared software simulation with actual monitoring points surface subsidence value changes, validating the model feasibility. Transform the construction process, the thickness of the grouting, excavation step parameters in the software simulation, and analysis the results based on the original model.(1) the construction process:The original construction process such as:excavation and support of the upper left of the tunnel pilot tunnel、the upper right of the tunnel pilot tunne、the bottom left of the tunnel pilot tunne、the bottom right of the tunnel pilot tunnel, turned into the construction process such as:excavation and support of the upper left of the tunnel pilot tunne、the bottom left of the tunnel pilot tunnel、 the upper right of the tunnel pilot tunnel、the bottom right of the tunnel pilot tunnel. The right upper guide hole and the lower left of the pilot tunnel excavation sequence interchangeable lead to the final settlement of differences in the original construction process of surface subsidence is larger by comparing the surface settlement value of the step sequence.(2) grouting thickness:Comparing the surface measuring point step in the construction of surface subsidence trends by analoging lm,2m,3m different grouting thickness. Surface subsidence values and changes in the thickness of2m is closed to thethickness of3m,in which the soil of the lower part of the tunnel excavation settlement produced larger proportion in the total settlement excavation.(3) excavation step:Comparing the surface measuring points in each construction step surface deposition trends by analoging3m,5m,7m different excavation step. The excavation steps away from the smaller, the smaller the value of surface subsidence within a certain range. Engineering solutions to provide4-6m excavation step away from feasible,7m excavation step contrast3m and5m can be found, the tunnel upper right pilot tunnel excavation Ground Subsidence due to value relatively large differences, other parts caused by the excavation surface settlement value is approaching.(4) The distance between the tunnels:Analoging11m,12m,13m different tunnel distance, contrast surface measuring points in the case of different distance from the settlement of trends. Surface maximum settlement amount decreased with increasing tunnel distance, and the lower rate is smaller. Compared11m with12m and13m tunnel distance, the upper left of the tunnel pilot caused by the excavation adjacent to the tunnel surface subsidence change in quite different. Which is the main cause of the difference between the final settlement.(5) Tunnel depth:Analoging9m,10m,11m,12m depth of the tunnels, compared to the surface maximum settlement. The amount of surface subsidence caused by construction decreased with increasing tunnel depth. According to the comparison results, it is recommended9-11m for the tunnel depth in eastern part of Zhengzhou.