Author(s)

E. De Souza & A. P. Dirige

Abstract

In order to maximize the recovery of ore in modern and highly productive mining methods, cemented backfill is normally placed in underground excavations to provide structural support. In order to save on costs, backfill of low cement content is used to fill the mined out excavations. This backfill mass is supported by a sill pillar structure cast from cemented backfill of very high strength. Mining excavations progress under the sill pillar, which must remain stable when exposed and subjected to mine induced stresses. The stability behavior of the sill pillar elements must be carefully studied to provide very effective, safe and economic mining operations. Improper design of these support structures may result in catastrophic fill mass failure, with substantial economic losses. This paper presents a methodology, procedures and engineering standards for backfill design based on three engineering modeling approaches: analytical, centrifuge and numerical modeling. This novel integrated modeling approach represents a powerful design tool in engineering practice. Keywords: underground mining, backfill, sill pillar, centrifuge modeling. 1 Introduction Sill pillars are strong structural elements used to support uncemented or low cement content backfill. Conventional sill pillars are cast from cemented sand backfill materials, often underlain by a timber mat; these structures have to be self-supporting when exposed by undercut mining. Improper design would result in failure of the fill mass, and extensive economic losses associated with loss of production and ore dilution, as well as in safety problems. The traditional stability design of cemented sill pillars is based on experience and on property data from standard static physical model tests such as uniaxial

Keywords

underground mining, backfill, sill pillar, centrifuge modeling.