Application of the dilatometer test for estimating undrained shear strength of Busan New Port clay

The dilatometer test (DMT) is an economical and fast tool that evaluates the stratigraphy and properties of soil. In this study, a series of DMTs, field vane tests (FVTs), and K₀ consolidated-undrained triaxial compression (CK₀UC) tests were performed to develop an empirical correlation for the undrained shear strength (s_u) of clayey soils from the Busan New Port site. The stress-normalized mobilized s_u(μ_su/σv′) for both laboratory tests and FVTs is determined to be around 0.22, which is consistent with previous studies. The exponent m for overconsolidation ratio (OCR), which is in the relation of _su/σv′=S·OCR^m, is determined to be 0.83 by using the SHANSEP technique. Two different methods of estimating s_u are reviewed to make use of either the horizontal stress index (K_D) or the bearing factor (N_c). Because the DMT results indicate that the N_c is linearly proportional to the material index (I_D), representing the characteristics of soil, the empirical s_u estimating formula with I_D is newly suggested in this study. According to the values for the mean absolute percentage error (MAPE), the empirical correlation with I_D shows a slightly better accuracy than that using K_D. However, a comparison between the values for the s_u that are measured and estimated by using two different methods shows good agreement in general.