杭州地铁2号线过江区间地下水流速流向测试分析

Measurement and Analysis of Velocity and Flow Direction of Water in River-crossing Section of Line 2 of Hangzhou Metro

研究目的:地下水流速和流向会影响地铁工程冻结法施工效果。地铁过江区间水文地质条件复杂,应进行地下水的流速流向测试和分析。在杭州地铁2号线过江区间勘察过程中,采用同位素单孔稀释法完成三个钻孔(南岸1个,北岸2个)中地下水流速流向的测定,得出钱塘江两岸潜水和承压水的水平流速、水平流向和垂向流速测试成果。研究结论:(1)钱塘江两岸地下水均无明显的垂向流存在;(2)潜水和承压水的水平流速均远小于5 m/d;(3)钱塘江两岸地下水的流速和流向对杭州地铁2号线过江区间工程冻结法施工影响小;(4)在无邻近工程施工(如降水)影响的情况下,杭州城区地下水流速总体缓慢,一般不会影响地铁工程或市政隧道工程的冻结法施工,建议工程勘察不再进行地下水流速流向测定。

Research purposes： The velocity and flow direction of groundwater will affect the effect of metro engineering with freezing method. It is necessary to measure and analyze the velocity and flow direction of the groundwater in river - crossing section due to the complex hydrogeologieal conditions in this area. In the process of detailed geological survey for the river - crossing section of the Line 2 of Hangzhou metro, the determinations of the velocity and flow direction of the groundwater flow in three boreholes （ one in the south bank and another two in the north bank） were made with single hole dilution method to know the horizontal velocity , horizontal flow direction and vertical velocity of the phreatic water and artesian water on both banks of the Qiantang River. Research conclusions ： （ 1 ） There is no obvious vertical velocity of the groundwater flow on both banks of the Qiantang River. （2） The horizontal velocities of phreatic water and artesian water are far less than 5m/d. （3） The groundwater＇s velocity and flow direction on both banks of the Qiantang River have a little influence on the construction of the river - crossing section of Line 2 of Hangzhou metro with freezing method. （4） In the case of no influence by nearby engineering construction （ such as precipitation） , the velocity of the groundwater in the Hangzhou area is generally slow with little influence on the construction of the metro engineering or municipal tunnel project with freezing method. So it is proposed it is unnecessary to do the determination of the velocity and flow direction of the groundwater during the engineering investigation in future.