Liquefaction Susceptibility in the Northern Provinces of Thailand

Problem statement: There are quite a few active faults recently found in the western and northern parts of Thailand, which could possibly induce earthquakes of magnitude (M_L) of 5.5-6.5. Although seismic design code has been enforced in the area since 1980, the fundamental knowledge on dynamic soil behavior has not been extensively attained. Approach: Collection of existing borehole information in the targeted areas to form a typical subsoil profile. This borehole information, together with analytical result obtained from logistic regression based on worldwide liquefaction database was used to conduct an effective stress analysis. Result: Literature reviews of the existing boreholes from the two largest provinces in the north, Chiang-Mai and Chiang-Rai, revealed that the areas were underlain by layers of loose to medium dense sand found at shallow depths. The corrected SPT N-value of those sand layers varies in the range of 5-20. A simple tool correlating the liquefaction probability, which correlated excess pore water pressure and peak ground acceleration, was proposed for the studied areas. Conclusion: The proposed correlation provided preliminary tool to evaluate risk of the shallow foundation from partial liquefaction in the two northern provinces of Thailand.