Strategy for Improving Precision of Soil Liquefaction Potential

Ilan area is located between the east and the northeastern earthquake regions of Taiwan, which the earthquake occurs quite frequent. Langyang Plain is alluvial plain coupling with fine particles of loose granular soil and high groundwater level, the possibility of soil liquefaction in Ilan area is very high once the earthquake occurs. Therefore, soil liquefaction potential needs to be carefully investigated. In Ilan area the primary soil liquefaction areas was formed with precision is 1/25000 scale. February 6, 2016 Meinung earthquake in the southern Taiwan area brought a lot of liquefaction damages. Therefore, soil liquefaction once again gains people attention. The precision of soil liquefaction potential map is requested to improve to 1/2500 scale. In order to improve the precision of geospatial information effectively, the geological drilling density of 4 holes/km2 are demanded. The drilling method employs the SPT method in general. The soil physical test is taken every 1.5 m or the soil layer change. This study adds about 213 boreholes of geological drilling data in the densely populated areas, low floor houses, old buildings and complex geological conditions of Ilan area. It is believed that we can use the drilling data to know the soil liquefaction potential more accurately. Finally, this study will use SPT-N HBF analysis method to calculate soil liquefaction potential value. The method is a simple evaluation technique to determine the occurrence of soil liquefaction in Taiwan with good accuracy and reliability. The proposed analysis in this study can be used to accomplish more precise soil liquefaction potential with different size earthquake occurs in the region.