Compressibility of Compacted Weathered Basalt Soil

Onjaku土是玄武岩的风化产物，分布于佐贺县东北部的乌瓦坝地区。Onjaku土主要由埃洛石和绿泥石作为粘土矿物组成，按日本标准土壤分类属于粘性土。这种土的一般特征是土壤颗粒的比重大，粘粒含量小，含水率高，干密度小，约为1g/cm~3。以及浸水后土体的沉降行为。当土样压实到最适含水率以下时，土体的压缩特性发生变化，发生膨胀或沉降；当土样压实到最适含水率以上，饱和度大于85%左右时，土样的压缩性保持不变，不会发生沉降。

Onjaku Soil, the weathering product of basalt, is distributed in Uwaba area, north eastern part of Saga Prefecture. Onjaku soil which consist mainly of halloysite and chlorite as clay mineral is classified as clay soil according to Japanese Standard Soil Classification. The general features of this soil are great specific gravity of soil particles, high water content for small clay fraction percentage, and small dried density of around lg/cm^3.The present paper investigates the compressibility of compacted Onjaku soil. and its settlement behavior due to water immersion. The characteristics of soil compressibility, due to water immersion, changed for soil samples compacted below optimum water content, and expansion or settlement occurred, while the soil compressibilty remained unchanged and no settlement occurred for soil samples compacted above optimum water content, with saturation degree greater than around 85%.