AJ Harris and PDJ Watson, School of Civil Engineering, Kingston University. This note was first published in GE’s July 1997 edition.
The test procedure given in BS 1377 Part 7 to determine the residual shear strength of a soil using the Bromhead ring shear apparatus contains a number of procedures that make the test both difficult and time consuming. A test procedure used at Kingston University since the development of the Bromhead ring shear apparatus is therefore proposed. The procedure is in effect a multi-stage test and commonly results in a value for the drained residual shear strength within three working days. The residual shear strength values obtained have been found to be close to those derived from back analyses of slope failures, especially when there is a strong element of bedding control on the location of the slip surface and when the back analysis is not unduly affected by uncertainties in pore pressures and end effects. A review of alternative uses and test procedures for the Bromhead ring shear apparatus is also included.