Abstract:Research purposes: The complicated hydrogeological condition is a great challenge confronted in the construction of Hangzhou subway. Especially,the construction risk caused by the high pressure aquifer along the Qiantang River cannot be ignored. This paper summarizes the features of high pressure aquifer in Hangzhou which has great impacts on the subway construction. The problems of high pressure aquifer in the projects of cross-river tunnel and riverside deep foundation of Hangzhou Metro Line 1 .and the corresponding control measures,are particularly introduced. Additionally,the practical implementation effects are also analyzed. This paper aims to provide the reference to the construction of Hangzhou subway.
Research conclusions: Technical solutions to the problem of high pressure aquifer in the construction of Hangzhou subway are proposed as below:(1)The brine freezing method in conjunction with the mode of tunneling shield reaching the shaft underwater is used to avoid the risk of quicksand and water gushing. (2)The preventive measures against water gushing based on the structure optimization of shield are set, including two inverted one-way restrictors installed in the conveyer and two rings of wire brush seal appended a ring of steel plate brush seal; and the EPDM rubber gasket with water pressure resistance of 0.9MPa is determined to use as waterproof measures of segment joint.(3)The connected aisle under the river is constructed by the subsurface excavation technology and reinforced by a new freezing method,the frost heave and thaw collapse of which is controlled by the deformation of tunnel linings.(4)Combined with the foundation engineering of Jiangling Road station,a complex pressure reduction and dewatering technology is developed, which is to form a complete shut-off waterproof curtain by overlapping a grouting curtain with a certain depth beneath the toe of diaphragm wall. (5)The technical solutions to the problem of high pressure aquifer encountered in the subway construction mentioned in this paper guarantee the successful engineering implementation of Hangzhou Metro Line 1, which can provide valuable experience to the subsequent construction of Hangzhou subway.
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