Prezzi, M., Scheilz, S., Salgado, R., & Siddiki, N. Z. (2014). Development of SPT-torque test correlations for glacial till (Joint Transportation Research Program Publication No. FHWA/IN/JTRP-2014/05). West Lafayette, IN: Purdue University. http://dx.doi.org/10.5703/1288284315499
Torque tests, which are performed immediately after a standard penetration test (SPT), have grown in popularity since its conception in Brazil during the early 1990s. Purdue University developed the first automated torqueing hardware prototype in 2010. SPT, SPT-Torque and cone penetration test (CPT) field testing were performed in glacial till soils at four different sites in northern Indiana and one site in southern Indiana. Index tests were performed for the soil samples collected at each of these sites. Relationships between the torque ratio (the measured torque divided by the corrected SPT blow count) vs. soil type, and unit side resistance vs. normalized SPT blow count (N1,60) and normalized CPT cone resistance (qc,1) were explored for these soils. For saturated clay soils, development of a relationship between unit side resistance and undrained shear strength was also attempted. Reliable correlations based on the torque ratio were not achieved based on the data collected for all the different soils tested. However, reasonably high coefficients of determination were obtained for the normalized equations developed for clays and saturated non-plastic silt. Low coefficients of determination were obtained for saturated and unsaturated sandy soils. The low coefficients of determination values are attributed to the small population dataset for sandy soils and the difficulty of adequately determining the degree of saturation for unsaturated non-plastic soil types due to the soil structure destruction with sampling. Overall, it was found that the relationships are strong for clay and saturated non-plastic silt and it is recommended that further data be collected to continue to strengthen all relationships, especially those for sand and unsaturated non-plastic silt.
SPT, torque, SPT-T, glacial till, field testing, correlations, udrained shear strength, side resistance
Joint Transportation Research Program
Indiana Department of Transportation
West Lafayette, Indiana
Date of this Version