| November,15,2008witnessed a major accident of foundation-pit subsidence in Xianghu Station of Hangzhou Metro Line1, causing21dead, which was called the most serious accident in metro history of China by engineer circles. This accident has sparked a heated discussion among the industry and the mass about whether Hangzhou is suitable for constructing the metro. Reflecting and summarizing the lessons of Accident in November,15, Hangzhou Metro constructors take a series of measures to control the construction risk with a view to making concerted efforts for Harmonious Metro, Safe Metro.Based on the summarization of experiences and lessons from Hangzhou Metro Line1and taking some practices as examples, this paper is aimed at studying how to control the construction risk in Hangzhou Metro Line1under special geological conditions and complex environmental conditions, which gives reference for the same kind demolitionin in future.To begin with, it is well known that Hangzhou has experienced the consequences brought by several transgression, regression and alluvium. With the analysis of effects, this paper introduces the formation history of quaternary stratigraphic configuration in Hangzhou, tracing the cause of special geological condition about Hangzhou Metro. In addition, according to the railway route planning of Hangzhou Metro Line1, the geological characteristics in the east, west, center and Jiangnan city are analysed respectively. Considering the characteristic of geological condition and surrounding environment, this paper distinguishes major construction risks and the factors of construction risks and at the same time evaluates them.Secondly, this paper combines the construction character of Hangzhou Metro Line No.1and addresses the control measures to major construction risks. On foundation-pit construction risk, the risk-controlling solutions have been presented in respect of the quality of outer protective structure, dewatering, soil stabilization and excavation measures and so on. On shield construction risk, what have been presented is the risk-controlling measures regarding shield initiation and arrival, the freezing construction of connecting passage, methane poisoning and explosion. When it comes to other construction risks, it mainly refers to the risk control concerning pipeline, building structures and shaping tunnels.Thirdly, manifold measures have been adopted in terms of construction risk by optimizing scheme to avoid it, by developing QC activity to mitigate it, and by building the remote monitoring and management system to control it, by which the risk can be controlled in every aspect, through many channels and a variey of ways. Apart from these, this paper combines with the specific cases to explain how to diversify and reduce the risks during the metro construction and how to minimize the economic loss caused by the construction risk through construction insurance claim.Lastly, this paper introduces the emergency plan establishment in Hangzhou Metro Line1and presents preventive and emergency actions against great risk imposed on subway construction. |
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