Analysis Of Construction And Impact To Surrounding Buildings Of Top-down Method On Qingdao Underground Street

With the acceleration of urbanization in our county, some problems appeared in many cities,such as:city land tension, people living in cramped,and many other issues.The development and utilization of underground space provides a very rich space resources for urban development, also has important social benefits. Meanwhile, the underground space development and utilization has also brought deep excavation more strict requirements. Foundation pit are not only to ensure strength requirements of supporting structure, but also to meet the requirements of the deformation control to ensure the security of the existing buildings, underground pipelines and roads. However, due to the theoretical study of underground works started late, in addition to the underground engineering involved in considerable factors , the design of underground structure theory are far from perfect, so the question for this research is particularly necessary.On the basis of commercial street project in College Road, Qingdao Licang District , using the finite element analysis software Midas/ gts, this paper researthed top-down method construction process by the way of three-dimensional numerical simulation, and then find the impact of the structure itself and surrounding buildings during construction process, to provide some reference for the similar projects . Main contents and the results are as follows:(1)This paper introduced the diaphragm wall, intermediate support columns, pile–continuous wall structure and some other key technologies about top-down method in detail.(2)The basic theory of FEM, the calculation theory of initial field stress, the calculation theory of soil excavation, the simulation theory of excavation process and constitutive models of geotechnical material are introduced in detail.(3)The selection of soil parameters, the model domain boundary constraints and model region selection, and the division of construction process in numerical simulation are researched in detail.(4)The paper researthed and analysised some performance in detail about the displacement of site surface, horizontal displacement ,of piles,vertical displacement of underground structures column, vertical displacement, settlement difference of foundation and horizontal displacement about the columns of ground structure and some other phenomenons during the construction process of top-down method The results showed that: the soil excavation within foundation pit caused the soil around the foundation pit relatively large movement toward the foundation pit. during the construction process of top-down method, the floor can play the supporting role well, which can slow the impact to the ground. The same building can cause different settlement difference when they have different distance to the foundation pit ,the more nearer ,the more bigger. the buildings on both sides of foundation pit inclines toward the foundation pit during the construction process of top-down method.