基于电阻率CPTU的饱和砂土液化势评价研究

饱和砂土的液化是地基基础震害的主要原因之一，对饱和砂土的液化势进行有效的评估是非常重要的。由于获得无扰动试样的困难和成本限制，原位测试方法通常用于砂土液化势的评价。目前出现了许多基于静力触探的液化评估方法，然而还没有出现哪一种方法最可靠的结论，高风险项目中通常采用多种方法进行综合评估，而新的液化评估方法的研究是非常有意义的。以宿迁—新沂高速公路建设为工程背景，采用电阻率孔压静力触探（RCPTU）对饱和粉质砂土进行了土层电阻率测试。首先，分析了归一化锥尖阻力与电阻率的关系，对建立电阻率液化评估方法具有指导意义。其次，以Robertson修正方法给出的周期阻力比为参考值，研究了联合电阻率和土类指数的周期阻力比计算方法，并研究了薄黏土层和过渡层对本文所提出电阻率方法的影响。结果表明，采用电阻率和土类指数能够对饱和砂土的液化势进行有效评估，然而应用于薄黏土层和过渡层时会低估土的周期阻力比。

Evaluation of liquefaction potential of saturated sands based on piezocome penetration tests on resistivity

The liquefaction of saturated soils is a major concern for the earthquake damage of foundation, and its effective evaluation is rather important. Because of the difficulty and cost constraint of obtaining high-quality undisturbed samples, in-situ testing is commonly applied to evaluate the potential of soil liquefaction. At present, numerous methods based on the cone penetration test (CPT) have been developed, but none of them has been accepted to be the most reliable one. In high risk projects, a comprehensive evaluation based on various methods is usually adopted, and thus the research on new method to evaluate the liquefaction is still necessary. The resistivity of saturated silts and sands is measured using resistivity piezocone penetration tests for the construction of Suqian-Xinyi expressway. First, the relationship between normalized cone tip resistance and resistivity is analyzed and can contribute to the evaluation of soil liquefaction based on resistivity. Second, the study on combination of resistivity and soil behavior type index to directly calculate the cycle resistance ratio (CRR) is conducted with the CRR from Robertson modified liquefaction evaluation model as a reference. The influence of thin cohesive layers and transition zones is also analyzed. It is shown that the resistivity and soil behavior type index can be used for effective evaluation of liquefaction potential of saturated soils. The accuracy of the proposed method is distinct when the cone passes soil interface since the vertical resolution of resistivity is directly proportional to the distance between outer electrodes. Otherwise, the proposed method is not suitable to thin clay layers and transition zones as it may underestimate CRR.