上海莲花路浅部土层超固结特性试验研究

Experimental Study of Overconsolidation Behavior of the Upper Shanghai Clays in Lianhua Road

对上海②～⑥层原状土样进行了一系列室内试验，得到了整个浅层土基本物理参数，并由标准固结和三轴试验综合分析了上海浅部土层超固结度（OCR）的分布规律．研究认为上海浅层黏土天然含水率、初始孔隙比、液塑限、液性指数与塑性指数沿深度具有与OcR相反的变化规律．上海浅部土层的弱结构性导致一维压缩曲线无明显拐点，引用Becket能量法得到：②层土的OCR最大，达到8．0左右。之后急剧减小；③、④和⑤层土的OCR=1．15～1．40；⑥层土的OCR〉2．0．三轴排水试验结果体现了浅部各土层超固结性的差异，与标准固结试验的结果基本一致．这种固结试验与三轴试验相结合的研究方法为进一步准确得到原位土体尤其是弱结构性土的应力历史提供了新柏途径。

A series of laboratory tests were conducted of intacted samples of the 2nd to 6 th Shanghai clays to investigate fundamental physical properties of successive upper clay layers in Shanghai, and overconsoli- dation behaviors were studied through a series of standard oedometer tests and triaxial consolidated drained compression tests. Natural water content, initial void ratio, liquid/plastic limit and liquid/plastic index were found to have similar trends of variations with depth change. Due to gentle curvature of the compres- sion curve over the preconsolidation pressure range, the work method proposed by Becker was cited to ob- tain the yield pressure in oedometer test, which showed that the overconsolidated ratio（OCR） of the 2nd and 6th layers were larger than 2, while those of the 3rd and 4th were about 1.15, and that of the 5th were closed to 1.40. Different characteristics of stress-strain curves in drained triaxial tests of the 2nd to 6th Shanghai clays reflect the distribution of OCR obtained in the oedometer test. The unite study method composed by oedometer and triaxial tests will contribute to further understanding of the overconsolidated behaviour of soft clays with weak structure.