Soil depth and soil–bedrock interface location are critical indices for land use classification and slope stability analysis. To evaluate soil depth in hillslope environments, the portable cone penetration test (PCPT) is an
extensively applied method for calculating penetration resistance (Nh) based on the number of knocks required for
penetration. In this study, we developed a portable dynamic cone penetration test (PDCPT) based on a conventional
PCPT design. The PDCPT features a knocking engine instead of the knocking weight of the PCPT. The penetration
resistance (Npd) detected by the PDCPT is expressed based on the time of knocks required for penetration. We used an
experimental device containing layers with varying levels of hardness to evaluate the PDCPT and PCPT and discovered
a strong correlation between the vertical distributions of penetration resistance measured using both tests. The relationship of these two values for penetration resistance can be expressed through the following linear regression: Npd =0.0197 × Nh. The results of field tests indicated that both the PDCPT and PCPT successfully detected the spatial distribution of penetration resistance and depths of the soil–bedrock interface in a simple environment with an obvious distinction between soil and bedrock layers. By contrast, in a complex environment with heterogeneously geological structures, only the PDCPT was able to analyze deeper structures and detect vertically or horizontally discontinuous layers within weathered bedrock layers. The findings of this study demonstrated that compared with the PCPT, the PDCPT with portability greatly reduced the survey duration and was able to detect deeper geological structures within weathered bedrock layers. Thus, the PDCPT is a more efficient method for use in hillslope environments.
Keywords: Discontinuous layer, equipment development, soil depth, soil–bedrock interface.