Ground behavior and liquefaction analyses in central Taiwan-Wufeng: Fid-Bau Portal

Ground behavior and liquefaction analyses in central Taiwan-Wufeng

Chu, Bin-Lin / Hsu, Sung-Chi / Chang, Yi-Ming

AbstractThe 921 Chi-Chi earthquake (Mw=7.6) in 1999 caused extensive ground failures in the central part of Taiwan. Severe damages due to soil liquefaction and ground softening occurred widespread in Wufeng. Various phenomena such as sand boils, settlement, horizontal translation of a building, and lateral spreading associated with liquefaction and ground softening were observed in Wufeng and documented. The locations of soil liquefaction, settlement, and no observed ground failures in Wufeng were also identified, investigated, and analyzed after the earthquake. The areas of sand boils and lateral spreading are mainly located beside the creeks and match the regions of present and old river channels pretty well. In situ soil profiles and material properties of Wufeng are obtained based on 25 borings and six cone penetrometer (CPT) soundings before and after the earthquake. Results of aftershocks and data obtained from Nantou Township are compiled in the analyses to delineate the boundary of liquefaction and nonliquefaction. Data of standard penetration tests (SPT), CPT, and shear wave velocity are selected and the empirical methods recommended by an NCEER workshop were employed to evaluate the liquefaction resistance of soils. The results are also compared with the performance functions obtained through artificial neural network modeling. The SPT-based performance function has better prediction on the cases of nonliquefaction than other empirical methods do. Impacts of fines content (FC) (both nonplastic and plastic) on liquefaction resistance are also found to be profound. For SPT cases, an empirical boundary is suggested for soils with fines content larger than 35%.