砾性土液化评价方法的通用性和可靠性研究

以2008年汶川地震液化震害调查资料为背景,基于操作性和经济性上具有显著优势的中国动力触探试验(DPT)而提出的砾性土液化评价方法,包括砾性土层液化触发条件以及判别公式(CYY公式),理论上已经得到国内外同行的认可,但其通用性和可靠性尚需检验。以5个国家29个历史地震砾性土场地中美联合勘测为基础,研究DPT技术、砾性土层液化触发条件和CYY公式在不同国家、不同地震和不同场地的适用性和可靠性问题,其中,成都平原14个砾性土场地的勘测与数据处理由中方完成,美国、意大利、新西兰、厄瓜多尔等15个砾性土场地的勘测与数据处理由美方Rollins教授主导完成,均为新的测试检验点。结果表明:中国动力触探标准探头在不同国家、不同砾性土场地上测试具有可行性,可以有效穿透20 m的砾性土场地,动探击数可作为砾性土液化评价的核心指标,同时亦可扩展到砾性土层的力学性能评价;不同国家、不同砾性土液化场地上,均存在不排水或排水不畅的埋藏条件,符合砾性土层液化触发条件要求;对动力触探击数进行锤击能量、有效上覆压力等修正后,CYY公式在不同国家、不同地震、不同砾性土液化场地的判别成功率约96%,具有较高可靠性。以2008年汶川地震砾性土液化为背景、以动力触探锤击数为基本指标的砾性土液化评价方法,具有国际通用的可行性。

Applicability and reliability of CYY formula based on Chinese dynamic penetration test for liquefaction evaluation of gravelly soils

The CYY formula, proposed by Cao, Youd and Yuan in 2013 and based on the field investigations of gravelly soil sites liquefied during the 2008 Wenchuan earthquake using the Chinese dynamic penetration test (DPT), has uncertainty regarding applicability and reliability in practical use. Nevertheless, the DPT has obvious advantages in maneuverability and economy. In order to verify the reliability, accuracy and practicability of the CYY formula, 29 new gravelly soil sites in total, 26 of which are liquefied during 6 different earthquakes including the 1964 Alaska earthquake in America, the 1976 Friuli earthquake in Italy, the 1983 Borah Peak earthquake in America, the 2008 Wenchuan earthquake in China, the 2016 Muisne earthquake in Ecuador, and the 2016 Kaikora earthquake in New Zealand, are selected for China-U S joint borehole drilling and DPT. The field tests at 14 sites in the Chengdu Plain are mainly completed by the Chinese side, and the rest of tests are mainly completed by the US side led by Professor Rollins. The results indicate that the Chinese DPT is feasible in different countries and can effectively penetrate about 20 meters of gravelly soils, and the blow count of DPT can be used as the primary index for predicting the liquefaction of gravelly soils. The 26 selected liquefaction sites consist of soil profiles in undrained conditions