1976年唐山大地震CPT液化数据库检验

1976年唐山大地震引发了范围广、灾害重的液化震害。铁道部科学研究院等单位于1977、1978年对液化场地进行了单桥静力触探测试。但单桥静力触探在数据指标方面存在缺陷，与国际标准不接轨。中国地震局工程力学研究所与东南大学等单位于2007年对上述唐山地区部分测点再次进行了孔压静力触探（CPTU）测试。本文通过对比2次静力触探数据，利用Robertson土质分类图，进行新孔压静力触探数据土类分层检验，将土类检验结果与单桥静力触探测试时钻孔柱状图进行对比，发现大部分测点土层土类均能较好对应，现场测试力学指标沿深度变化趋势较相符，仅剔除了错误点T2、T3。对所有测点选定液化层，分别建立基于单桥静力触探测试比贯入阻力p_s和基于孔压静力触探测试锥尖阻力q_c的液化数据库。利用基于静力触探测试（CPT）的我国规范液化判别方法检验了2个数据库，发现对单桥静力触探测试的数据库液化判别效果好，而对孔压静力触探测试的数据库液化判别效果较差，说明经过30年的时间，土层液化可能已发生较大改变。因此，基于孔压静力触探测试的液化数据库可靠性较低，基于该数据库对液化判别方法进行改进意义较小。

Inspection on CPT-based Liquefaction Database from 1976 Tangshan Earthquake

The 1976 Tangshan earthquake resulted in widespread liquefaction. China academy of railway sciences and other institutes conducted single bridge probe CPT test on these liquefied and non-liquefied sites in 1977—1978. However, the single bridge CPT measured only specific penetration resistance, and is not conformity with international standards. Institute of Engineering Mechanics, CEA and Southeast University retested 18 sites using piezocone penetration test (CPTU) in 2007. By comparing two CPT profiles, and comparing soil types obtained from Robertson CPT-based soil behavior-type chart with borings in first test, it is found that soil layers fit reasonably well for most of sites, and in-situ indicators also change same trend along depth for most of sites, finally only two error sites(T2, T3) were excluded. Critical layers were selected for all sites, a database of p_s-based liquefaction case histories and another database of q_c-based liquefaction case histories were constructed. Two databases were tested by CPT-based Chinese code methods, liquefaction discrimination result for the first database is good, while liquefaction discrimination result for the second database is poor, which shows that potential of soil liquefaction had changed significantly after 30 years. Therefore, the liquefaction database based on CPTU test has low reliability, and has little help for future improvement of liquefaction discrimination methods.