基于台湾集集地震数据的CPT与SPT液化判别方法比较

Comparison of CPT-based and SPT-based liquefaction discrimination methods by Taiwan Chi-Chi earthquake data

利用集集地震静力触探试验(CPT)数据,对基于CPT测试的Robertson液化判别方法和Olsen方法进行了检验,两个方法对液化点判别成功率分别为82.61%和80.43%,对非液化点判别成功率分别为31.82%和44.32%。CPT液化判别方法对液化点判别基本可靠,但对非液化点判别准确性较差。对集集地震标准贯入试验(SPT)数据,美国地震工程研究中心(NCEER)推荐的SPT液化判别方法对液化点和非液化点判别成功率分别达到92.41%和94.35%。SPT方法判别成功率非常高,整体准确性远高于CPT方法。另一方面,CPT的土分类图可以同时反映土的种类与强度,甚至可以对集集地震液化土与非液化土进行区分。对于细粒土的液化初判,CPT土分类图也优于SPT方法中的黏粒含量指标。因此,土分类图是CPT的优势所在。

Using CPT data from the Chi-Chi earthquake, CPT-based liquefaction discrimination methods proposed by Robertson and by Olsen are inspected. The prediction success ratios of the two methods are 82.61% and 80.43% for the liquefied sites, but 31.82% and 44.32% for the non-liquefied sites, respectively. CPT-based methods are reliable for liquefied soils, but not effective for non-liquefied soils. For comparison, the SPT-based liquefaction discrimination method recommended by National Center for Earthquake Engineering Research of USA is tested using data from Chi-Chi earthquake, the prediction success ratio of the procedure is 92.41% and 94.35% for liquefied and non-liquefied sites, respectively. The SPT-based method demonstrates higher prediction success ratio than that CPT-based methods. However, CPT-based soil type chart can reflect soil strength and soil type simultaneously, and can differentiate liquefied soils from non-liquefied soils in Chi-Chi earthquake. Moreover, for the preliminary discrimination of clayey soils liquefaction, CPT-based soil type chart is also better than the clay content which has been always used.