Assessment of Liquefaction Potential Index Using Deterministic and Probabilistic Approaches – A Case Study

Abstract

Based on in situ tests results, the deterministic approaches express the soil liquefaction potential in terms of safety factor and the probabilistic approaches define it in terms of probability of liquefaction. The developed methods for soil liquefaction evaluation predict the behavior of a soil element. However, the liquefaction potential index (LPI) evaluates the performance of the entire soil column and allows a measurement of the severity of liquefaction. In this paper, the liquefaction potential is used in conjunction with deterministic approach and reliability based probabilistic approach using SPT and CPT results. A site located to the north of Beirut where the soil investigation consisted of a total of sixteen boreholes with continuous coring and standard penetration test every 1.5 m of depth and thirty-three boreholes with cone penetration test is subjected to liquefaction potential study. Liquefaction potential index (LPI) is calculated at each borehole location from the obtained safety factor or the calculated probability of liquefaction. Spatial distribution of soil liquefaction potential is presented in form of contours maps of the (LPI) values for each considered method. The results show that the evaluation of LPI using the reliability based probabilistic approach and the CPT results is a more conservative method giving larger area with LPI values higher than 15.