Doctor of Philosophy
Chris H Cramer
An investigation of the impact of shear strength and thickness of non-liquefiable soil layers on the surface manifestation of liquefaction based on finite difference numerical methods and to investigate the liquefaction potential of the West Tennessee area was performed by (1) analyzing liquefaction potential of Lake, Dyer, Lauderdale, and Tipton Counties, which are in West Tennessee and within or near the New Madrid Seismic Zone, based on the liquefaction potential indices of LPI and LPIISH methods; (2) developing a numerical model to perform liquefaction analysis ; (3) validating the developed numerical model in FLAC based on the evaluation of New Zealand data and observations; (4) performing sensitivity analysis of the overall FLAC model to shear strength and thickness of non-liquefiable soil layers; (5) adjusting the LPIISH procedure to incorporate the effects of shear strength and thickness of non-liquifiable soil layers based on the numerical model and sensitivity results; (6) performing liquefaction potential analysis of West Tennessee based on the LPIISH. A comparison of the LPI- and LPIISH-based Liquefaction Probability Curves (LPCs) for the probability of LPI and LPIISH exceeding 5, which provides the probability that liquefaction surface manifestation can occur based on the threshold of 5, revealed that the probability of liquefaction surface manifestation provided by the LPIISH method is significantly lower than the probability of liquefaction surface manifestation provided by the LPC based on the LPI method, mainly at higher ratios of PGA/MSF, i.e., more intense earthquake scenarios for the West Tennessee Area. The results of this study indicate two primary reasons that the LPI-based LPC predicts a higher probability of liquefaction surface manifestation than the LPIISH-based LPC. First, the LPIISH method includes the impact of non-liquefiable layers on liquefaction surface manifestation by incorporating a limiting non-liquefiable layer thickness whereby surficial manifestation is not expected to puncture through the non-liquefiable layer regardless of the thickness of the underlying liquefiable layer while LPI does not consider the impact of non-liquefiable soil layers. Second, LPIISH incorporates a power-law depth weighting function that provides for shallower liquefiable layers to contribute more to surficial manifestation than deeper layers. Therefore, because the weighting function between the two methods is based on different statistical methods, the contribution of soil layers to liquefaction surface manifestation is different between LPI and LPIISH methods. Additionally, the results of the numerical analysis of this study using FLAC software show that liquefaction surface manifestation occurrence is very sensitive to the thickness and shear strength of upper non-liquefiable soil layers. The LPIISH method is adjusted in this study by considering the impact of shear strength and thickness of upper non-liquefiable layers and a new LPC is developed for the West Tennessee area. By comparing the adjusted LPIISH-based LPC with LPIISH and LPI-based LPCs in this study, it is shown that the adjusted LPIISH-based LPC predicts a liquefaction probability significantly different than LPI and LPIISH-based LPCs.
Dissertation or thesis originally submitted to ProQuest
Tohidi, Hamed, "Evaluation of Surficial Non-Liquefiable Soil Layer Impacts on Liquefaction Surface Manifestation of the West Tennessee Area Based on Finite Difference Methods" (2022). Electronic Theses and Dissertations. 3194.