Applicability of Ball Penetration Test to Soft Clay in the Narkdong River Delta, South Korea

Abstract

Ball penetration test (BPT), in association with different field tests such as CPTU, field vane test (FVT), seismic dilatometer test (SDMT), was carried out at an investigation site in the Nakdong River delta, Busan, S. Korea. The main objectives of the BPT were to evaluate the ball factor (thus the undrained shear strength, Su) and sensitivity of the soft clay at the site. As the BPT was first applied to the delta, four different ball sizes were used to examine the behavior of the test compared with the conventional CPTU. It was found from the study that ball factors, unlike the cone factors, are independent on rigidity index (Ir). The ball factors obtained from different ball sizes are quite similar to each other and slightly smaller than those obtained from theoretical solutions. The sensitivity of the test soil was found smaller than the ratio of initial penetration resistance to the remolded penetration resistance (qball,ini/qball,rem). However, no clear correlation was obtained for the test soil.