Excavation Responses Of Unsymmetrical Loaded Deep Foundation Pit In Complicated Situation

One deep foundation pit in Hefei Metro Line 1 is adjacent to the existed expressway, influenced by the subgrade-induced unsymmetrical load and the vehicle dynamic load together, the geological and environmental situation are complicated. Some literatures indicate that the excavation response of such unsymmetrical loaded deep foundation pit is remarkably different from that of traditional symmetrical loaded deep foundation pit. And, there exists no relevant standards or specifications to make special provisions on the design and construction of this kind of unsymmetrical deep excavation at present. Thus, it has an important practical significance to do the research on the excavation response, find out the diversities between two types of deep foundation pits and then to provide references to the similar case in the future.Based on it, this paper use the methods of literature research, field monitoring, theoretical analysis and numerical simulation to investigate the excavation response of deep foundation pit from the following aspects:(1)Reading relevant literatures at home and abroad in extensive, summing up the research status of the unsymmetrical loaded deep foundation pit, pointing out the existing problems which need to solve on the basis of predecessors’ works.(2)Introducing the design scheme, construction process and the field monitoring scheme in detail, the traffic scheme and emergency plan related to the expressway was introduced as well.(3)Based on the monitoring dates, analyzing the horizontal displacement of fender piles, the horizontal displacement of pile top, the axial force of concrete and steel supports, the ground surface settlement and the deformation of adjacent expressway. Some deformation and bearing laws of supporting structure and expressway are obtained.(4)Summarizing several common constitutive models of the soil in numerical simulation, investigating the control parameters of each model and how to determine them, the constitutive model which is fit for the deep excavation analysis is suggested.(5)Establishing finite element calculation model of deep foundation pit using MIDAS GTS to calculate and analyze the excavation responses, including: the deformation of retaining structure and inner supports, bottom heave, ground surface settlement and subgrade deformation. Same suggestions for similar project are given based on the obtained conclusions.(6)Based on the different calculation methods of vehicle load, establishing finite element model to simulate the excavation responses of foundation pit adjacent to expressway subgrade under the following conditions: 1)taking no account of vehicle load; 2)putting vehicle load equivalent to the uniform load of soil; 3)putting vehicle load equivalent to a belt of wheel load; 4)taking dynamic load of vehicle into consideration additional based on the 3th condition.