Time-dependent compaction in caving rock

Abstract

This paper reports a literature view of one possible cause of time-dependent cave growth: the time-dependent compaction of caved rock following cessation of mining. It is widely suggested in literature that particle breakage and reorientation is the dominant candidate (Terzaghi 1960; McDowell & Bolton 1998). Evidence of this mechanism from the field and laboratory are provided. In Oldecop & Alonso (2007) experiments a universal model was derived relating the rate of time-dependent compaction with 3 key governing parameters: 1) stress intensity, 2) fracture toughness and 3) relative humidity. It was discovered that the rate of crack growth increases with saturation level and when the stress intensity approaches to the fracture toughness. Taking into account the time-dependent breakage, a new estimation method to predict the compaction settlement in caved rock is suggested. The review and estimation method presented here demonstrate that time-dependent compaction of caved rock could be significant enough to explain the time-dependent growth of caves after cessation of draw. © 2011 ARMA, American Rock Mechanics Association.