| With the rapid development of urban underground space,comprehensive pipe gallery is widely used in transportation,municipal engineering and other types of projects.As an important infrastructure investment project in China's 13 th five year plan,it develops rapidly with the construction speed of nearly 2000 km per year.By the end of 2020,it is expected to reach a large scale of 10000 km,and China will become a real comprehensive pipe gallery country.However,in the context of the booming construction of the comprehensive pipe gallery,the unreasonable design of the foundation of the pipe gallery causes the collapse of the foundation pit of the pipe gallery,the structural cracking and seepage damage,the damage of the surrounding environment and other phenomena frequently.At present,the isolated foundation design often aims at the bearing capacity requirements or settlement control of the structure,and few researches involve the foundation design based on the principle of the safety of the whole process of the pipe gallery project.In this paper,based on a pipe gallery project in the east station area of Jinan City,the burst failure occurs many times in the excavation stage of foundation pit,the failure accident is analyzed,and on the basis of the pressure balance method,several positive factors are considered to propose a more practical method for the determination of the burst resistance.Considering the surge stability of the foundation pit and the bearing capacity of the foundation,the design method of the foundation pit considering the surge stability of the foundation pit is proposed.According to this method,the optimal design of the foundation of the project is carried out.The three-dimensional finite element numerical model is established to analyze and confirm,and the stress law of the pipe gallery structure and the stratum in the construction process is studied,and the reasonable design parameters of the pipe gallery foundation are proposed.The main research contents and achievements are as follows:(1)Combined with a pipe gallery foundation pit in Jinan City,based on the classical pressure balance method,the shear strength of the soil,the size effect of the foundation pit and the reinforcement of the pit bottom are studied in depth.The determination method of the critical reinforcement thickness is established by considering the above positive factors.And combined with the field situation,the deformation form,accident causes and measures offoundation pit surge are analyzed.(2)Combined with several engineering examples,the risk,deformation characteristics and reinforcement measures of foundation settlement of pipe gallery are analyzed.On this basis,the objective and method of foundation design of pipe gallery are studied.(3)Aiming at the safety and economy of the whole process of the pipe gallery project,and taking the foundation settlement value and the project cost as the control index,and considering the surge stability during the excavation period of the pipe gallery foundation pit and the requirements of the foundation bearing capacity during the construction and operation period,the design method of the pipe gallery foundation considering the surge stability of the foundation pit is proposed finally.The method is used to optimize the design of a pipe gallery foundation in Jinan.(4)Based on the method of finite element numerical simulation,the construction simulation analysis of a pipe gallery project in Jinan is carried out,including:(1)The results show that the scheme can not only avoid the burst damage in the excavation stage of the pipe gallery,but also reduce the cost of the project;(2)The deformation law of structure and stratum in each stage of pipe gallery construction in confined water stratum is studied;(3)The influence of different cushion thickness and reinforcement range on the pipe gallery project is discussed in order to determine the reasonable parameters of foundation reinforcement. |
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