Standard Penetration Test in Engineering Geological Site Investigations – A Review

Abstract

Prior to the construction of engineering structures, site investigation is required in order to determine the suitability of the site for the intended structure. The results of the investigation furnish information on the engineering properties of earth materials and groundwater conditions of the site.During the field exploration phase, in situ engineering field tests are carried out. These include standard penetration tests (SPT), vane shear tests (VST), cone penetration tests (CPT), flat plate dilatometer tests (DMT) and pressure meter tests (PMT). These tests give results that are used to characterize the strength and deformation properties of earth materials. The SPT as used in engineering geological site investigation is reviewed in this paper with emphasis on its significance in engineering geological site investigations. The equipment used is the cable percussion drilling rig and its accessories made up of split-spoon sampler, hammer, and drill rods. The SPT is performed by driving the split spoon sampler into the ground by a drop of hammer of mass 64 kg falling from a predetermined height. The hammer blow counts, disturbed and undisturbed soil samples collected during the test are processed and interpreted. The interpreted results are used to estimate the relative density, shear strength of soils and the bearing capacity. Based on these estimates, recommendations for foundation design and construction of civil engineering structures can be made.