RE-INVESTIGATING SAND LIQUEFACTION CASE HISTORIES FROM THE TANGSHAN EARTHQUAKE USING MULTI-FUNCTIONAL SEISMIC CONE PENETRATION TESTS
TONG Liyuan1,TU Qizhu2,LIU Songyu1,DU Guangyin1
(1. Institute of Geotechnical Engineering,Southeast University,Nanjing,Jiangsu 210096,China;
2. China Railway Fourth Survey and Design Institute Group Co.,Ltd.,Wuhan,Hubei 430063,China)
Abstract:Due to the limitations of investigating instruments and liquefaction evaluation methods after the 1976 Tangshan earthquake,it is very useful to perform the re-investigations at liquefaction and non-liquefaction sites nowadays. The multifunctional seismic piezocone penetration test(SCPTu) method was used for this work. The nearly continuous profiles of tip resistance,sleeve friction,pore water pressure,and shear wave velocity were obtained. The liquefaction potential of testing sites was evaluated by comparing the SCPTu measurements,the indoor experiments and historical investigation data. Several popular CPTu-based liquefaction evaluation methods at home and abroad were analyzed particularly. Results from Chinese Standard method,Robertson deterministic method and Moss probabilistic method indicate that most of the testing sites that liquefied during the 1976 Tangshan earthquake will liquefy again. The CPTu-based Robertson deterministic method and the Moss probabilistic method based on Bayesian theory show respective advantages and disadvantages. Both of them have reasonably comprehensive calculation procedures. The Robertson deterministic method has special advantage in predicting vertical settlement and lateral large deformation,while the Moss probabilistic method can present the liquefaction probability for every site and serve for the seismic evaluation and engineering design. However,due to the slow development of SCPTu technique in China,kinds of current international CPTu-based liquefaction evaluation methods are seldom used,which require further study after technology have been breakthrough in future.
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