Physical properties of Quaternary sediment and land subsidence life process in Suzhou

Land subsidence is the most critical geological problem in Suzhou area, which influences the development of economy. Based on the analysis of 200 m-drilling core in Shengze, Suzhou, the Quaternary stratum in Suzhou subsidence area is divided into three confined aquifer groups, and the precise columnar section of the borehole is drawn. The variation rules of physical properties of soils and structure with the increasing depth are studied on the basis of a large number of soil sample tests and macro-microstructure analysis. The relationship among compressive deformation of clay layer, microstructure and land subsidence is analyzed. Finally, an evaluation method for soil layer compression is proposed using the indices of Ecl and Esa. The results show that the moisture content, porosity and compressibility of soils get smaller and the microstructure orientation becomes more clearly with the increase of depth. The potential of stratum compression shows a tendency: the upper confining beds of the first and second confined aquifers > the upper confining beds of the third confined aquifer> both top and bottom aquitards of the third confined aquifer. The water-bearing sand layer of the second confined aquifer has a great potential while that of the second confined aquifer has become stable. This research is significant for studying the development mechanism of Quaternary strata in Suzhou land subsidence area and for the assessment of subsidence life process.