Salt leaching of marine clay and its effect to the sensitivity with ground water pumping

为了阐明萨嘎平原阿里亚克粘土地层(海相层)的盐溶机理及其与岩土性质的独特关系，通过测定粘土中的氧化还原相(ORP)和贝壳残留物的栖息地，建立了该地层的沉积环境。结果是在以下假设的基础上得出的：(1)人工抽水引起地层的盐淋滤；(2)最初，海水影响下沉积了高孔隙率的海相粘土(Ariake粘土)；(3)当地的Ariake粘土经过几十年的人工抽水，形成了高敏感性和高压缩性。该报告包括：1.阿里亚克粘土地层沉积环境及其敏感性研究；2.包括更新世沉积在内的地下水位调查…3.天然示踪法研究地下水循环；4.基于孔径分布测量考虑海相粘土的压缩特性。通过这些研究对象，可以获得各种信息。阿里亚克粘土地层可分为正常层和淋滤层。同样，可以从粘土中盐分浓度的角度对哈绥克组(非海相层)进行分类。根据这一分类，可以清楚地了解该地层的岩土性质。受地下水位季节变化的影响，地层中的孔压分布在表层没有发生变化，但在更深处发生了变化。可以认为，萨嘎低洼地区盐分浓度的分布不仅受人工抽水的影响，还受河流复杂性态的影响。胶结效应是理解其高灵敏度、高可压缩性时应考虑的重要因素之一。较少

In order to clarify the salt leaching mechanism of The Ariake Clay Formation (marine layer) in Saga plain and the unique relationship between the phenomenon and its geotechnical properties, the depositional environment of the formation was established by measuring Oxidization-Reduction-Phase(ORP) and analysis of habitat of shell remains in the clay. The result was made with the following assumptions ; (1)Groundwater flow with artificial pumping caused salt leaching of the formation ; (2)Initially, the marine clay(Ariake clay) deposited with high void ratio influenced by sea water ; (3)High sensitivity and high compressibility of local Ariake clay had been resulted from artificial pumping for dozens of years.Based on the above assumptions, 4 subjects have been established and investigated in this study. The report consists of ; 1. Study on depositional environment of The Ariake Clay Formation and its sensitivity ; 2. Investigation of groundwater level including the Pleistocene deposits … More ; 3. Research on groundwater circulation using natural tracer method ; 4. Consideration of compression properties of marine clay based on the pore size distribution measurement. Through these subjects, various information could be obtained.The Ariake Clay Formation can be classified into normal layer and leached one. Likewise, The Hasuike Formation(non-marine layer) can be classified from the viewpoint of salt concentration in the clay. Based on this classification, geotechnical properties of the formation could be clearly understood. Pore pressure distribution in the formation has not changed at the surface, but changed at deeper depth affected by the change in groundwater level with season. It can be considered that the distribution of salt concentration in the formation is not only affected by artificial pumping, but also by the complicated river behavior in Saga lowland area. Cementation effect is one of the important factors that should be considered in the understanding of its high sensitivity, high compressibility. Less