CPTU and DMT for estimating soil unit weight of Lake Bonneville clay

Abstract

This paper discusses the use of piezecone penetration test (CPTU) and flat-plate dilatometer (DMT) for estimating the soil unit weight of the Lake Bonneville clay in Salt Lake City, Utah. Soil unit weight is required when calculating net cone resistance, normalized cone resistance, pore pressure ratio, and normalized friction ratio from CPTU results, and horizontal stress index from DMT results. To improve the predictive performances of existing correlations additional analysis were carried out. This is accomplished by correlating CPTU and DMT parameters with results obtained from high quality undisturbed sampling using Multiple Linear Regression (MLR) analyses to develop correlations for soil unit weight. MLR analyses showed that the both CPTU and DMT can reasonably estimate the soil unit weight of the relatively soft, Lake Bonneville clay deposits with CPTU giving slightly higher predictive performance. Proposed correlations emerged for estimation of total unit weight in terms of net cone resistance and sleeve friction from CPTU results and P1 value of DMT. By obtaining reliable estimates of soil unit weight directly from CPTU and DMT results, geotechnical consultants in the Salt Lake Valley would gain benefit for efficient post-processing of the both CPTU and DMT data.