Use of Borehole Shear Test to Obtain Shear Strength Data Comparison to Direct Shear Test

Abstract

The knowledge of shear strength geotechnical parameters, cohesion and friction angle, is necessary for many engineering works and slope stability analysis. Traditionally, the Direct Shear Test (DST) in the laboratory is used to determine these parameters. However, recently, the use of the Borehole Shear Test (BST) in Brazil is being evaluated to supplement or substitute for DST. The Geotechnical Mapping Laboratory of Federal University of Santa Catarina (LAMGEO-UFSC) is conducting research comparing DST and BST data which proposes to validate BST use in projects that demand a huge number of shear strength tests. Laboratory and field tests were performed to compare the parameters of shear strength of granite, migmatite, granulite, granitoid, gneiss and rhyolite residual soils from the Brazilian states of Santa Catarina and Rio de Janeiro. According to the obtained data, it was found that the failure envelope of soil samples analyzed from the same soil area (in wet states and in the same drainage and normal stress conditions) showed satisfactory correlations. The shear strength values obtained by DST and BST were similar, but the differences in the soil effective cohesion intercept parameter were more significant. Thus, BST field tests compare well with DST data with near perfect correlation.