Application Of Risk Management And Control In The Subway Station Foundation Pit Of Unsymmetrical Pressure

With the rapid development of civilization in China, the advent of traffic jam comes into being. In order to solve the urban traffic pressure, subway construction is being operated extensively in the recent years. However, there exist many challenging problems for the subway construction, such as deep depth, large scale, close spacing, limited term, risky geological conditions and hidden dangers. It is required to decrease the occur of construction accidents to the greatest extent meanwhile accomplish the project in good quality, which can be solved by the application of risk analysis theories.Most subway station is built in the function of foundation pits that are environmentally complicated, highly expensive and long construction term. In addition, many uncertain factors exist during the construction procedure. Recently, the accidents of foundation pit instability have occurred repeatedly in subway projects nationwide, which brought about serious consequences. Hence, because the deep foundation pit construction can be describe as a highly risky project, it is crucial to operate risk evaluation and management in deep foundation constructions of subway.The main researches studied in this paper are listed below.(1) Through summarizing the domestic and abroad research statuses, the methodologies of various risk evaluations and level determinations are studied from the aspects of theory and practice. Aimed at the objective project, the risk evaluation method for unsymmetrical pressure foundation pits is put forward preliminarily.(2) Based on Wuhe Station Project, the numerical method of quantitative study is adopted for analyzing the influence degrees of different unsymmetrical pressure depth on foundation pit envelop structures, which can provide data support for evaluation of unsymmetrical pressure risk resource.(3) Based on Minzhi Station, composite risk evaluation method is used to assess the probability of each risk event as well as the consequences with the calculation of each risk factor weight.(4) The risk levels are confirmed and then the risk control and management measures are raised so as to guarantee the construction safety of subway foundation pit in the situation of symmetrical pressure.The research conclusions achieved are expounded as follows.(1) Various risk evaluation methods are utilized comprehensively to provide rational basis for the risk administrators.(2) The deformations and stress characteristics of foundation pit envelop structures differ while the unsymmetrical pressure depths and supporting styles vary. As mentioned, this situations bring about difficulties on the program calculation and risks on the construction. The unsymmetrical load is a significant risk resource as to unsymmetrical pressure foundation pit, so the risk management and control should be reinforced.(3) According to the evaluation results, total risk values and each construction section risk value are figured out in foundation pit excavation construction of Minzhi Station.(4) The risks of monitoring failure, roadbed and rail deformation by excavation and fault immovable pipeline construction are relatively high, which call for effective actions for avoiding and reinforced surveying.(5) On the basis of evaluation, the response risk management and control measures are put forward for the works of program, construction and monitor etc. for rational decisions, in order to hit the target of minimum administration cost.