| With the rapid development of rail transit in China,the development of urban underground space has also entered a new hot stage.The excavation of the foundation will produce additional load and deformation to the existing underlying tunnel,and eventually lead to the deformation of the soil around the tunnel and the crack and damage of the tunnel.It has a great influence on the safe and comfortable operation of the subway.In order to meet the needs of the safity and comfortable operation of the subway,it is very important to control the additional load and deformation caused by the excavation of the foundation above the existing tunnel.At present,there are no relevant regulations on the safe operation of the subway adjacent to the foundation,and the results of the safety evaluation are obtained by the experience method and the qualitative analysis for the displacement of the existing subway.Based on the excavation of a foundation above the section of Chengdu Metro Line 5,this paper,starting with the three aspects of soil loss,excavation unloading and finite element simulation,discusses the influence of the displacement of the surrounding soil and the deformation of the subsurface tunnel under the disturbance of the excavation in order to provide reference for the design and construction of the same kind of engineering..The main contents of this paper are as follows:(1)based on the soil loss is the main factor that causes the displacement field of soil,it simplifies the simplified treatment of soil loss in the bottom uplift of the foundation and the loss of the deformation of the side wall enclosure structure,and briefly describes a method of the change law of the displacement field of the surrounding soil under the soil loss.(2)using the two stage stress method,first of all,the Mindlin solution is used to calculate the additional load of the stress unloading release to the near subsurface tunnel by the stress relief release of the foundation excavation,and then based on the tunnel soil interaction model,the additional load and additional displacement produced by the foundation excavation to the near tunnel are quantitatively reflected.The different factors of tunnel deformation are analyzed by the construction foundation,and finally the sensitivity analysis of different factors of foundation excavation to the deformation and disturbance of tunnel is obtained.(3)the finite element method is used to simulate the engineering precipitation,and the simulation analysis of the deformation of the lower lying tunnel by the dewatering of the foundation pit is obtained.At the same time,the influence of the different reinforcement measures on the deformation of the lower lying tunnel is analyzed,and the reasonable reinforcement measures are taken to control the deformation of the lower lying tunnel. |
