苏州第四纪沉积物物理性质与地面沉降生命过程分析

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

地面沉降是苏州地区当前面临的最大地质灾害,影响了该地区经济的发展。在苏州盛泽200 m钻孔岩芯分析的基础上,对苏州沉降区第四纪地层进行了含水层组划分,共分成3个承压含水层组,并精细化地绘制出了钻孔岩芯柱状图;在大量土样土工试验和宏-微观结构分析的基础上,掌握了200 m钻孔土样的物理性质和结构随深度的变化规律,详细分析了黏土层压缩变形、微观结构与地面沉降的关系;最后,根据各土层沉积物的平均孔隙比指标,提出了用孔隙比率指标Ecl和Esa来评价土层压缩潜力的方法。研究结果表明:随着深度的增加,土层含水率、孔隙比和压缩性变小,微观结构颗粒定向性越明显;第Ⅰ、Ⅱ承压含水层隔水顶板压缩潜力>第Ⅲ承压含水层隔水顶板>第Ⅲ承压含水层顶部及底部弱透水层;第Ⅱ承压含水砂层压缩潜力较大,而第Ⅲ承压含水砂层的固结压密已趋稳定。研究成果对于掌握苏州沉降区第四纪地层地面沉降的发生发展机理和生命过程的评价具有重要意义。

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.