Site investigation for the active layer during thawing period is necessary to ensure the ground stability in cold region. For the thawed active layer, the strength of the ground is dependent on the characteristics of soil particles rather than ice amount. The objective of this study is to evaluate the effect of particle size and particle distribution on the strength of soils. The dynamic cone penetrometer instru-mented with strain gauges and accelerometer is developed to investigate the active layer in the field. The dynamic cone penetration index (DCPI) is measured for the strength characterization. Furthermore, the dynamic cone resistance is estimated using the transferred energy at the cone tip. The soil samples at 4 different depths are gathered after the dynamic cone penetration test. The particle size at 60% finer (D60) and coefficient of uniformity (Cu) of soil samples are estimated for the comparison with the dynamic pen-etration index and dynamic cone resistance. Experimental results show that the dynamic cone penetration index increases, and dynamic cone resistance decreases as both particle size and coefficient of uniformity increase. In addition, the dynamic cone resistance is more reliable than dynamic cone penetration index because the transferred energy is considered. This study suggests that the particle characteristics affect the strength of the soils in active layer, and the dynamic cone resistance can be used as an effective tool for the ground investigation.
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