Determination of the in situ modulus of the rockmass by the use of backfill measurements

Abstract

In situ measurements and numerical modelling based on elastic theory showed that backfill stresses are considerably higher than originally thought. This has led to a change in understanding of rockmass behaviour. After describing previous work on the behaviour of the rockmass, this paper discusses possible reasons for the high stresses measured in backfill, and identifies the rockmass mechanisms possible generating these stresses. It is concluded that the joints and the geological stratigraphy can lead to increased elastic convergence, and that the elastic behaviour of the rockmass is also partly responsible for the increased closure measured in backfill. The use of an in situ modulus is suggested as an interim solution until a new computer model that allows for joints, different layers, and inelastic closures becomes available.