APPLICATION OF CLASSICAL STRESS WAVE PROPAGATION THEORY FOR THE ANALYSIS OF THE STANDARD PENETRATION TEST

Abstract

Standard Penetration Test is widely used as a simple and convenient test for estimating soil properties. But till 19719 it was used to be treated at par with other static or quasi-static penetration test and there has been very little carefully controlled (except the one by Gibbs and Holtz at U.S.-B.R. soil mech, lab.) studies on the effect of. different testing variables related to soil characteristics and mechanical systems on the test results. Schmertmann (1971) carried out perhaps the first experimental investigation of the dynamic behaviour involved when SPT sampler penetrates the soil in response. to the stress wave generated by the hammer blow. This established the possibility of applicability of one dimensional stress wave equation to analyse the dynamics of SPT rather than treating it at par with static or quasi-static penetration test. Standard Penetration Test was carried out with accele-ration pick-ups mounted on the rod to get the velocity of propagation of wave generated by the shearing of soil as the 'sampler penetrates under each hammer blow. Thus the tests carried out yeilded N-value and dynamic shear modulus, G, for a soil layer. Tests were performed on a almost uniform local silty sand to a depth of about 8.2 metre at an interval of 0.5 m to 1 m.