Use of Standard Penetration Test (SPT) to Determine Raveling Index

In the East-Central Florida region, where there is relatively deeper depth of bedrock than north/west of Florida, cone penetrometer tests (CPTs) have been popularly used for sinkhole geotechnical investigation. From the CPTs, an index known as the raveling index (RI) was developed. This raveling index is used to better understand the status of raveling, thus, quantitatively evaluating the susceptibility of sinkholes. However, standard penetration test (SPT) is still the most common subsurface exploration method in geotechnical engineering practice. In areas of shallow bedrock/limestone or where CPT testing is unavailable, SPT testing is necessary, often the case in West-Central Florida. In this paper, a method for calculating the raveling index in known sinkhole locations using SPTs was developed. An analysis of the RIs calculated using CPTs was performed to compare with those calculated using SPTs. The outcome of this analysis is a preliminary result showing a potential benefit of SPT in sinkhole investigation and also a limited correlation between the RI calculations. Subsequently, there may be a possibility of using SPTs in tandem with CPTs for future projects to be effectively used to investigated for sinkhole risk. This study was applied to various sinkhole locations throughout Central and northern Florida.