Scalp-and-Replacement of Oversize Particles: Laboratory Permeameter Testing

Abstract

Abstract A reanalysis is made of 24 rigid-wall permeameter tests on eight widely-graded sand-gravel mixtures, using empirical methods that post-date the original study by Jones in 1955. The reanalysis is conducted to better understand the consequences of the scalp-and-replacement method of removing oversize particles in laboratory permeameter testing. A necessary requirement of the scalp-and-replacement method is that the porosity, hydraulic conductivity, and susceptibility of the test gradation to internal instability be largely unchanged. The reanalysis provides a framework for such considerations and serves to identify the consequences of excessive scalping such as increased porosity and hydraulic conductivity. The results show that scalp-and-replacement to 35 % of the gradation curve imparts no significant change to the porosity and hydraulic conductivity of an internally stable gradation.