上海黏土压缩指数和回弹指数经验关系

压缩指数Cc和回弹指数Cs是土力学中表征土体变形特性的两个重要参数指标，可通过室内一维固结试验获得。但是试验过程耗时长，因此，很多学者提出了压缩指数Cc与物理指标（尤其是液限wL、天然含水率wn、初始孔隙比e0和塑性指数Ip）的经验关系。通过对比国内外压缩指数经验关系，发现压缩指数与天然含水率和孔隙比关系离散性较小，分别给出了一个统一的经验关系。采用薄壁取土器从上海某一场地取得第②～⑥层土的原状土样进行固结试验，并搜集整理分析已有文献中的试验数据和上海69个场地的岩土勘察数据，给出了上海典型土层压缩指数Cc与wL、wn、e0、Ip的经验关系。同时发现，Cc/n0与Cc以及Cs/n0与Cs（n0为初始孔隙率）之间具有高度的线性关系，从而给出了基于初始孔隙率n0预测上海黏土压缩指数Cc和回弹指数Cs的经验关系。分析了压缩指数和回弹指数的关系，结果表明，上海正常固结黏土Cc/Cs分布在4.8～6.9之间，平均值约为5.8；超固结黏土Cc/Cs分布在3.3～5.2之间，平均值约为4.3。

Empirical correlations of compression index and swelling index for Shanghai clay

Compression index Cc and swelling index Cs are two important deformation parameters in soil mechanics which can be obtained by oedometer tests. However, due to time-consuming of the test, several empirical correlations between compression index and some basic physical parameters (especially liquid limit wL, natural water content wn, initial void ratio e0 and plastic index Ip) have been proposed by many researchers. The empirical relationships of compression index all over the world have been compared and it is found that relationships between compression index and natural water content and void ratio are less discrete. Consequently, the unified correlation equations are given respectively. The oedometer tests have been conducted on specimens from 2nd to 6th soil layers in Shanghai. Samples were retrieved by the thin wall sampler. Consolidation test data available in literatures and geotechnical investigation data from 69 sites in Shanghai were collected and analyzed. Empirical relationships between compression index Cc and wL, wn, e0, Ip of Shanghai clay were given. Meanwhile, it was noted that there were highly linear relationships between Cc /n0 and Cc, Cs /n0 and Cs (n0 is initial porosity). Therefore, empirical formulas for predicting compression index Cc and swelling index Cs of Shanghai clay based on n0 were given. The relationship between compression index and swelling index was also analyzed. The results show that the value of Cc/Cs of Shanghai normally consolidated clay ranges from 4.8 to 6.9, with an average value of 5.8. While the value of Cc /Cs for over-consolidated clay ranges from 3.3 to 5.2, with an average value of 4.3.