- 期刊
土壤液化簡易評估法的模式不確定性研究
A STUDY ON MODEL UNCERTAINTIES BETWEEN SPT, CPT, AND VS BASED SIMPLIFIED METHODS FOR LIQUEFACTION EVALUATION
摘要
在缺乏SPT資料或使用SPT-N土壤液化簡易評估法有限制的場合，如離岸海域或砂礫石含量高的場址，工程師僅能改採CPT-_(q_c)或V_S法評估土壤液化潛能。然而這兩者的評估結果常與SPT-N法有明顯差異，本文稱這個差異為「模式不確定性」。本研究利用在臺北盆地13個同時具有跨孔式震測、SPT與CPTU試驗沖積層場址所得之高品質資料，以抗液化安全係數比為指標，比較國際上常見的CPT-_(q_c)法、V_S法與NCEER-SPT法評估結果的差異，繼則以統計估計理論量化各方法間模式不確定性。結果顯示CPT-_(q_c)法、V_S法較SPT法保守，各法間的模式不確定可以常態或對數常態分布量化，供工程師掌握各方法間之相對保守度與離散度。最後以液化潛能指數評估為例，說明此不確定性模式的應用，供耐震設計或製作液化潛勢圖參考應用。
並列摘要
Encountering the sites lacking SPT data or SPT-N methods are restricted to, such as offshore marine areas or sites with high gravel content, engineers merely substitute CPT-_(q_c) or V_S-based simplified methods to evaluate soil liquefaction potential. However, the evaluation results of these two methods often perform inconsistently with those of the SPT-N methods. This research collects the high-quality test data obtained from 13 alluvial sites in the Taipei Basin with simultaneous cross-hole seismic surveys, SPT and CPTU tests at the same site, and compares the evaluation results of the prevalent CPT-_(q_c), V_S and SPT-N methods in the world. This study adopts statistical estimation approaches to quantify the model uncertainty among these methods by using the ratio of safety factor against liquefaction as an indicator. The results show that the CPT-_(q_c) methods and the V_S methods perform more conservatively than the SPT-N methods, and the model uncertainty between the methods can be quantified by normal or log-normal distribution, and helps engineers to grasp the relative conservativeness and dispersion among the methods. Finally, the application of these models to liquefaction potential index evaluation is demonstrated with a real case. The suggested uncertainty models are believed as a reference for seismic design and liquefaction potential map generation.