Application of flat dilatometer test for undrained shear strength evaluation in soft soils: Case study in Cai Mep, Vietnam

Abstract

Undrained shear strength (Su) is one of the most critical parameters in the design and improvement of soft soil foundations. This paper presents the results of a study on the application of the flat dilatometer test (DMT) to determine the Suof soft soils in the Cai Mep area, Ba Ria -Vung Tau Province, Vietnam. DMT tests were conducted at four survey locations, in parallel with unconsolidated undrained triaxial tests (UU), field vane shear tests (FVT), and piezocone penetration tests (CPTu),to evaluate the reliability and calibration potential of empirical expressions used to estimate Sufrom DMT results. The findings indicate that the empirical formulas proposed by Marchetti (1980) and Lutenegger & Kabir (1988) yield small deviations are consistent with reference test results (UU and FVT) in soft to very soft clay. The formula by Roque et al. (1988) is only suitable for highly plastic clays (Is> 0.85), but produces significant errors in soils with lower plasticity. Meanwhile, the expression by Kamei shows large discrepancies and is not applicable to the soft soil conditions in the study area. The study confirms the applicability of the DMT in soft ground conditions in the Cai Mep region and provides an experimental basis for broader geotechnical survey applications