基于不同原位试验的土壤液化判别模型保守性评估

Assessment of model bias of SPT,Vs and CPT-based liquefaction models

基于现场原位试验和地震液化案例库建立的液化判别模型是一种常见的场地液化判别方法。然而,场地液化判别模型存在着准确性因测试手段而异的问题,即判别模型存在偏差;同时基于同一原位试验建立的液化判别模型的准确性因地震场地而异,即存在地震场地变异性。为评估基于SPT,V_(s)和CPT建立的液化判别模型的保守性特点,研究汇编了同时含有3种原位试验的地震液化案例库,分别含88,176,107个案例,涉及6次地震事件和场地。根据汇编的案例库采用贝叶斯分层建模法(BHM)标定了SPT-Youd模型、V_(s)-AS模型和CPT-RW模型的偏差系数,建立了分地震场地的液化判别模型。结果表明:CPT-RW模型的场地液化判别结果最为保守,SPT-Youd模型存在高估多个地震场地的抗液化能力而偏于危险的情况,V_(s)-AS模型的保守性则介于两者之间;基于汇编的CPT案例库,运用BHM法分地震场地建立的液化判别模型能够有效地修正CPT-RW模型的保守性,且不同地震场地的修正程度不同。研究工作可在工程师采用多种原位试验结果评估同一场地的液化势时提供有效的先验信息。

The liquefaction models established through the in-situ tests and liquefaction case histories are widely adopted in the liquefaction evaluation of a site.However,it is reported that the model accuracy varies with the in-situ test methods(i.e.,model bias),as well as the earthquake sites(i.e.,seismic site variability).To assess the model bias of SPT-Youd model,V_(s)-AS model and CPT-RW model,a database of liquefaction case histories containing all these three in-situ tests is compiled firstly,containing 88,176 and 107 cases,respectively,and involving sites from six seismic events.Based on the compiled database,the Bayesian hierarchical modeling(BHM)method is adopted to correct the model bias of the three models,and liquefaction models for each of the seismic sites are established.It is found that the CPT-RW model is the most conservative model,and the liquefaction resistance calculated by the SPT-Youd model is overestimated in several seismic sites,and the conservatism of the V_(s)-AS model is between them according to the complied database.Using the complied CPT database,the seismic site-specific liquefaction models established by the BHM method can effectively correct the conservatism of the original CPT-RW model,and the levels of correction vary from one seismic site to another.This study provides effective priori information for engineers to assess the liquefaction potential of a site using multiple in-situ tests.