The grouting of low permeability soils in dam foundations
Creators: name: Brett, DM
Publisher: name: University of Tasmania
Year: 2024

description: In 1979 the author was appointed by his employers, Consulting Engineers, Gutteridge Haskins and Davey Pty Ltd as project engineer for the site investigation phase of a feasibility study into the management of fresh Water resources and contaminated water at the proposed Worsley Alumina Refinery in the Darling Range of Western Australia. He subsequently became project manager for the design phase of the $40 million \Water Management System\" for which Gutteridge Haskins and Davey were responsible. His total involvement with the project was completed when he was seconded to the Project Managers Raymond Engineers Australia Pty Ltd as an on-site technical consultant. The Worsley \"Water Management System\" comprised three 'large dams' as defined by the International Committee on Large Dams (ICOLD) over twenty kilometres of diversion channels various hydraulic structures lined water storage basins tailings disposal areas and various seepage collection systems. A particular feature of the project was a multi-backup environmental protection system to control water contaminated by caustic soda and other chemicals used on the site. The first level of protection involved the construction of a storage reservoir called the Refinery Catchment Lake to the highest practical degree of water tightness. Part of the design for this reservoir comprised the incorporation of a grout curtain beneath the earth fill embankment in the thick weathered in-situ laterite soils. Field testing confirmed that only low viscosity chemical grout could effectively reduce the already low permeability of the foundation Chemical grouting of soils is a relatively recent engineering development and whilst a certain amount of experience has been gained particularly over the past twenty five years the procedures to be used are far from being precisely defined. Practical field testing at the Refinery Catchment Lake Dam Site indicated potential problems with some grouting procedures used at other sites in the past. These procedures related principally to the grout pressures and injection volumes used with evidence that excessive hydraulic fracturing of the low permeability soil was counter productive to the overall aim of economically reducing permeability. The thesis describes the design of the Refinery Catchment Lake Dam reviews the history and theory of chemical grouting and discusses some relevant case histories. It then describes the development of a practical technique used to inject cement/bentonite grout and a phenoplast grout Geoseal MQ4 into the dam foundations to achieve the design requirements. The thesis was prepared following post-construction research by the author to deepen his knowledge on the general subject of chemical grouting. The thesis was written in the belief that the work carried out at the Refinery Catchment Lake Dam was unique in terms of the attempted reduction of already low permeability. It is believed that in documenting a major field operation the thesis makes a positive contribution to the increase in knowledge of low permeability soil grouting techniques and points to areas where additional academic research is required."