Developments in in situ permeability testing

Abstract

Abstract Assessment of field permeability of soil and rocks can be made using the various techniques outlined in BS 5930, Section 4. Recently, two additional techniques have been used; the slim hole packer testing equipment developed by Soil Mechanics Limited, and the multiple port piezometer Westbay system. This paper describes the equipment and methods used, together with examples of the results obtained. A suite of slim hole packer equipment has been developed to provide testing capability in very low to moderate permeability ground (10 −10 to 10 −5 m s −1 ). Pressures are measured with either a manometer board or transducers and flows monitored using a parafin/water manometer or gapmeters. An on-site computer is used to record and plot test data and calculate permeability results. The Westbay multiple port piezometer system consists of plastic casing, connected with ‘o’-ring seal couplings, installed in a borehole. Casing lengths can be selected so as to divide the borehole into a series of isolated response lengths. The couplings can incorporate monitoring ports for water pressure measurement and groundwater sampling or pumping ports for permeability testing and groundwater. This system has been used to carry out rising head tests by first lowering the water level in the access tube and then recording the change in water level either by using a dipmeter inside the access tube, or via an adjacent monitoring port using a Westbay electronic pressure probe.