Hydraulic Compresiosn of Shaft Backfill at the Backfill/Rock Interace

Abstract

Based on theoretical considerations, this paper shows that the horizontal pressure acting on the backfill/rock interface of a vertical shaft can be quite small due to the shearing resistance developed between the compressible backfill and the rock surface. A laboratory program was then carried out to measure the horizontal pressures in two model shafts and the experimental data were compared with the theoretical results. In addition, hydraulic compression experiments were performed on backfill specimens compacted in an apparatus specially designed for these tests. The practical implications of the laboratory findings on the design of shaft backfills are discussed.