The interpretation of the Lugeon water-test

Introduction The use of water-tests, of gradually increasing elaboration, for establishing the need for, and results of, grouting injections in rock has been discussed frequently (Randall 1923, Fox 1927, Lugeon 1933, Vaughan 1963, Little et. al 1963, Bishop et al. 1963, Fergusson & Lancaster-Jones 1964, Benko 1964, Lancaster-Jones 1967, Snow 1968). By ‘rock’ in this context is meant that part of the Earth's crust in which water circulation is mainly via fractures, joints and other random openings, so that the material cannot be considered as a homogeneous porous medium. Porous sandstones and limestones are included since they also contain joints. Few standard tests have however become accepted; an exception is that named, from it's originator, the Lugeon test. Since first described in 1933 this has been elaborated (Camembert 1964). The problem of extrapolation Although the Lugeon test may serve other purposes, its main object is to determine the ‘Lugeon coefficient’ which by definition is a water absorption measured in litres per metre of test-stage per minute at a pressure of 10 kgs/cm2 (1 MN/m2). At shallow depths or in weak rocks it is not always appropriate to apply such high pressures and the methods used for extrapolating the results of tests at low pressures in order to determine the Lugeon coefficient have been open to question, although Fergusson & Lancaster-Jones ( op. cit ) pointed out that such