피에조콘관입시험으로부터 구한 시화지역 해성점토층의 피에조콘 계수와 과압밀비

Abstract

Piezocone penetration test (CPTu) has widely been known as one of very promising in situ test methods available at offshore regions as well as onshore. Cone penetration in clayey soils is generally treated as undrained because a rate of penetration is traditionally 2cm/sec. Therefore, the CPTu results may be highly linked to undrained shear strength (su). Estimation of undrained shear strength of clayey soils including marine clays from CPTu requires piezocone factors, which are generally derived using empirical correlations. However, previous studies on the empirical piezocone factors are site-specific and in some cases need engineering characteristics, which should be obtained from additional laboratory tests. Overconsolidation ratio (OCR) of soils is one of factors that affect strength characteristics, stress-strain behavior, and soil compressibility. OCR can generally be obtained from conventional oedometer test. Many attempts have been tried to evaluate OCR from CPTu, based on the theoretical and/or empirical methods. In this study, empirical cone factors were evaluated by comparing 6 CPTu results at Shihwa region in Korea with reference su values obtained from field vane test (FVT). From previous CPTu results of other regions in Korea as well as the results herein, the correlations between piezocone factor, NkT and CPTu results were examined and three simplified evaluation methods of su using only CPTu results were presented. Furthermore, the most appropriate evaluation method of OCR applicable to Shihwa region was also investigated by correlating the OCR values obtained from oedometer test with various piezocone parameters.