Optimum Of Top-down Construction Patterns In Soil-rock Dualistic Area

The Deep foundation pit engineering is a more complex project involves more subject and theories , and it is also a developing systemic theory engineering. Along with the development progress of urban construction, the city space becomes less, the buildings and traffic facilities continuously transferred to the underground space. The depth and the area of the excavation of deep foundation pit increasing fast. Those asked for higher request of deep foundation construction both on design and construction method. The space around the big pit is very nervous and the architectural environment is complicated, at the same time, people became more concern about the building environmental problems in the construction process, the top down construction method is demand to salve those problems .The top-down construction method is suitable for such excavation which is large, deep, surrounded by complicated surroundings.Because the superiority of top-down construction method, it is first applied and started for research and practice in soft soil area in China, like Shanghai, Guangzhou, etc. So, various parameters of top down construction method both in practice experience and theoretical research were suitable for soft soil foundation. But Qingdao is a typical"soil-rock"Dualistic Structure, the foundation bearing capacity is larger than the soft area. In Qingdao , there aren't standard parameters to referred to the top down construction method. In this paper ,a lot of analysis and study were done about Qingdao DongHaiLu underground defend engineering , by comparing numerical simulation results and construction monitoring data, a system standard parameters apply to"soil-rock"Dualistic Structure area was proposed. It can also provide experience for the traditional top down construction method .At the same time; a new construction method will be proposed to improve top-down construction method. According to numerical simulation results to identify the feasibility of the new jump-later excavation manner, and calculates the limited excavation depth in "earth rock" dual by jump-layer method.Through the above research, this paper will presents a complete set of parameters of top down construction method which is applicable to Qingdao, as a representative of the"soil-rock"Dualistic Structure area. According to numerical simulation, the feasibility of jump-layer construction can be identified to provide theoretical basis and guidance of deep foundation pits in the engineering practice of Qingdao later, and it also help to improve the design level and construction level, and offer valuable experience for such projects.