Analysis And Regular Study On Ground Surface Subsidence Induced By Shield Construction

As China’s economic development, to alleviate the problem of urban road traffic problems, the construction of urban subway quantity is more and more. Due to the complexity of the environment inside the city construction, the choice of construction method, shield construction method with less impact on the surrounding environment and has been more and more widely used. But the construction process will inevitably cause the surface subsidence, surface settlement affects not only the construction safety, meanwhile, affect the safety of roads, buildings, etc. In this thesis, combined with 3 shield project tenders of Beijing Changping Line Phase II project, analysis the surface subsidence caused by different models of EPBS across different soil. First analyze the measured surface subsidence date, at the same time, summarized the relationship between the shield construction parameters and the surface subsidence. Then using finite element software Midas GTS simulated 3 shield tunnel, analysis of the simulated date, and comparing with the measured date. Drew the following conclusions:(1)Shield tunneling through different soil layer, the horizontal sedimentation tank approximately obey the normal distribution. With great external factors, the subsidence trough will shift. When the simulation parameters value to the actual engineering, the simulation well reflected surface subsidence rule.(2)The surface subsidence associated with the soil of shield crossing.As shield through the pebble layer, the surface subsidence is-16.2mm,and while shield through the silty clay layer, the surface subsidence is about-8.5mm.(3)The surface subsidence trough has distinct stages in the process of formation, which can be divided into three phase,each stage of the surface subsidence: at before arrival of the shield machine phase surface subsidence account for 5-10% of the total, surface subsidence account for 60-70% during the shield machine advancing, and the other phase account 20-35%.But through the different layers, changing of the subsidence rate are obviously different at the first two stage.(4)The soil settlement decreases gradually with the increase of tunnel buried depth, and spatial effect is obvious.If shield tunnel overburden soil layer count thicker pebble, soil disturbance range extension.(5) Construction parameters, grouting quantity and grouting pressure impact on surface subsidence is more obvious. Thrust is smaller influence on changes of the surface subsidence.