Properties Of Confined Water In Hangzhou CBD And Engineering Applications

Hangzhou CBD construction is the bridgehead of Hangzhou to implement the policy of "city premises extending east, tourism expansion moving west, exploration along Qiantang River and future development beyond the River", and is also the main sign of Hangzhou city development entering "Qiantang River" from "West Lake era"With the development of Hangzhou CBD, it appeared a lot of engineering established or under construction with more than three layers of basement, the maximum digging deep of whose foundation pit is nearly30m.The confined aquifer at the bottom of Hangzhou CBD site sets on paleochanne of the Qiantang River. The influence of deep confined water on the construction of deep foundation pit engineering is increasingly significant, there have being several deep foundation pit projects threatened by the confined water.Systematically studying the characteristics of confined water in this area, such as water level, distribution, aquifer thickness, flow velocity, flow direction, directly and discharge characteristics, etc, can provide basis for design and construction of similar projects, and can also provide reference for the future construction, therefore, it has important engineering practical significance and theoretical value. This paper made the following work:1、Collected a lot of research achievements of predecessors in palaeochannel confined water of the Qiantang River, expounded the formation process of the paleochannel confined water, the distribution of the aquifer, directly and discharge conditions, as well as the water chemical characteristics and change. In the Supply source analysis, revealed the "shilongshan dormer" supply source for the first time.2、Combined with engineering practice experience and achievement in recent years, focus on the analysis of confined water level dynamic change characteristics in the study area since1997, and predicted the water level dynamic change trend.3、According to the results of confined water single-hole pumping test and group of the well pumping test during the period of construction, we researched the hydraulic conductivity of the confined water.4、Used "three-point method" and "isotope dilution method" to study the flow velocity and flow direction of confined water, summarized the defects of analysis test results and methods.5、Analyzed the cause and incentive of confined water outburst flood, and summarized the method of analysis for confined water foundation pit stability against a sudden surge. Finally, we summarized the construction measures for confined water outburst flood accident caused by ground hole improper handling in the study area.