Penetration test parameters and their correlations for different USCS classes of soil from selected locations of Bangladesh

Both the standard penetration test (SPT) and the cone penetration test (CPT) measures the tip resistance; the CPT, however, takes some other data like sleeve friction and porewater pressure. In principle, there exists a considerable difference between these two considering their penetration modes. Twenty four (24) SPT-CPT proximity locations were considered to find the relations of soil parameters and profiles for various Unified Soil Classification System (USCS) classes of alluvial soil deposits at a selected location of Bangladesh. Five classes of soil like sand and silty sand (SM), silt of low plasticity (ML), silt of high plasticity (MH), clay of low plasticity (CL) and clay of high plasticity (CH) were found at the site. Strong statistical correlations were found to exist between the field SPT value, and CPT cone resistance and the sleeve friction for SM and CH types of soil. For ML, MH and CL classes of soil moderate linear correlations were found. Thus, if the parameter(s) of one of the two methods is available the other could be estimated. Isometrics of soil profile was constructed considering both SPT data, and CPT classifications chart proposed by previous investigators. Present study reveals that both CPT and SPT provide comparable soil profile for sandy soil. However, as many minor soil classifications are proposed in CPT charts as against limited soil classes in SPT, a consensus soil profile could not be achieved; the principal difference being while CPT chart shows a clay soil, SPT interprets it as silty soil, and vice versa.