砂土液化标贯判别法在天津地区适用性分析

Analysis of Applicability of Standard Penetration Test Method for Evaluating Sand Liquefaction Potential in Tianjin

针对天津地区典型的饱和粉土液化判别现状以及抗震设防标准大幅调整的情况,进行标贯判别法的适用性分析。通过收集大量工程钻孔数据,结合唐山地震震后调查研究结果,对比分析国内三种规范标贯法的液化判别效果;并结合Seed简化法对明显液化区、非液化区数据进行液化回判成功率对比。研究结果表明,在Ⅶ度(0.15g)和Ⅷ度(0.20g)条件下,现行《建筑抗震设计规范》(2010版)法在天津地区液化判别的安全度最高,在液化区的判定成功率最高,但在非液化区的误判率也很高,且判定的液化程度等级与实际液化情况相比明显偏重;地标《岩土工程勘察规范》法在液化区的判定成功率较高,与现行抗规2010版接近,但对非液化区的误判率降低比较明显,判定液化程度等级与实际情况吻合性较好,既保证了安全度,又体现出了一定的经济性,对天津地区粉土液化的适用性更好。

With reference to the evaluations of the typical saturated silt liquefaction potential in the Tianjin area,along with an adjustment in the seismic fortification criterion,in this paper,we discuss the applicability of the standard penetration test method for evaluating soil liquefaction.We collected a great volume of engineering drilling data and investigation results pertaining to the1976 Tangshan earthquake,compared and analyzed the evaluation results of three methods used in the seismic design codes of China.The results show that the method in the Code for Seismic Design of Buildings（GB50011-2010）has the highest degree of safety in evaluating the liquefaction potential in the Tianjin area at seismic fortification intensities of 7degrees（0.15g）and8degrees（0.20g）.This method＇s accuracy ratio is highest in liquefied areas,but its misjudgment ratio in non-liquefied areas is also high,and the degree of liquefaction determined by this method is more severe than the facts.The accuracy ratio of the method used in the local Code for Investigation of Geotechnical Engineering in liquefied areas is also high,close to that of the current seismic design code,but its misjudgment ratio in non-liquefied areas is relatively reduced compared to the previous method.The degree of liquefaction determined by this method is in good agreement with the facts,which will not only ensure safety,but also reflect a certain degree of economy,making it more suitable for evaluating the silt liquefaction potential in the Tianjin area.