DISCUSSION ON THE ENGINEERING GEOLOGICAL STRATIFICATION OF THE SOFT SOIL DEPOSITED IN DEEP-INCISED VALLEY IN QIANTANG RIVER OF HANGZHOU BAY

The Hangzhou Bay is located in the north plain area of Zhejiang Province, also the deep-incised valley of Qian Tang river located, and it can be know that the depth and thickness of Holocene Sediments are of special nature.The shallow silty clay in this area is divided into the Holocene transgression in the ③2 layer of Fuyang transgression and the deep silty clay is divided into the Late Pleistocene in the ④2 layer of Hangzhou transgression in the engineering field. Through comparative study, the stratification method does not match the research results of the sedimentary and sedimentary sequences of soft soil in the area. With determination of the stratigraphic deposition time by determining the formation of 14C, and the sedimentary sequence of the of the deep-incised valley of Qian Tang River by some geological scholars, thenit can be concluded that the deep silt clay layer was formed about ten thousand years ago which we called the Fuyang transgression period, and it should belong to the ③2 layer of the Holocene. The particularity of this area should be considered in the specification, the two soft soil layers in Holocene are divided into ③2 layer and ③3 layer.