Reinvestigation of Liquefaction and Nonliquefaction Case Histories from the 1976 Tangshan Earthquake

摘要

A field investigation was carried out to retest liquefaction and nonliquefaction sites from the 1976 Tangshan earthquake in the People's Republic of China (PRC). These sites were carefully investigated in 1978/1979 using standard penetration test (SPT) and cone penetration test (CPT) equipment; however the CPT measurements are obsolete because of the now nonstandard cone that was used at the time. In 2007 a modern cone was mobilized to retest 18 select sites that are particularly valuable because they experienced intense ground shaking, have high fines content, and are classified as nonliquefaction sites. Of the sites reinvestigated and carefully processed, 13 are considered accurate representative case histories that warrant being included in the worldwide CPT database. Two of the sites that were originally documented as exhibiting liquefaction and nonliquefaction have been reassessed as cyclic failure of fine-grained soil and removed from consideration for liquefaction triggering. The most important result of these field investigations are 3 nonliquefaction case histories that experienced intense ground shaking. These 3 case histories reside in a region of the liquefaction-triggering database that is poorly populated and will help constrain the upper bound of future liquefaction-triggering curves.