Effects of Soil Conditions on the Cone Resistance of Lightweight Penetrometers

When exploration depth is shallow or site access is limited, a dynamic lightweight penetrometer is an attractive alternative to large penetrometers. Cone resistance, regardless of the penetration test, is influenced strongly by soil conditions: dry unit weight, overburden stress and water content of the surrounding soil, and fines content. This study explored the effects of these parameters on the cone resistance is in a calibration chamber. A series of tests was conducted in clean sands and mine tailings materials, subjected to different overburden stresses and prepared to different void ratios and degrees of saturation. It was found that dry unit weight and overburden stress significantly increases cone resistance. The effects of water content on cone resistance were more significant in mine tailings materials than in clean sands. An overburden correction factor for a dynamic lightweight penetrometer is proposed based on soil conditions, including fines content. Differences from common correction factors used for large penetrometers were observed, and were attributed to the type of soil and range of overburden stress explored in this study.