Abstract
Abstract The design of room-and-pillar mines relies on the correct estimation of the safety indicator of the underground structures formed by the excavation of drifts. Thus, the study of the geomechanical behavior is of vital importance. The mathematical models play an important role in the identification of problematic areas and allows different configurations to be tested in a safe manner. This article presents the development and application of a flexible and automatic routine to quantify the safety of room-and-pillar mines in terms of the safety factor of pillar and room convergence. The commercial software package FLAC3D was used to implement a computation routine in FISH language that can automatically represent the main characteristics of the geomechanical conditions, lithology and geometric features of a room-and-pillar project in a fast and accurate manner. A case study was performed on a manganese ore mine in order to demonstrate the capabilities of the developed routine.
Highlights
Room-and-pillar (R&P) mining is a method of extracting the material of a series of crossing rooms to leave behind pillars of ore
As the conditions of the depth of the current mining panel of the manganese layer, lithology above the target level, quality of blasting with explosives (D = 0.8), and intact rock strength are known, the resistance parameters to be used in the numerical model may be estimated based on Hoek et al.’s formulation
A three-dimensional numerical model was developed with innovative characteristics, including excellent flexibility and geomechanical and geometric adaptability to different scenarios, to consider the variability of the operational and geomechanical conditions for a manganese ore mine
Summary
Room-and-pillar (R&P) mining is a method of extracting the material of a series of crossing rooms (i.e. horizontal linear openings) to leave behind pillars of ore. When the rock mass can be considered highly competent, pillars are usually much smaller than the rooms and the weakest rock mass between the roof, ore layer, and floor will command the opening instability. According to Idris et al (2015), a pillar can be defined as the in situ rock mass between two or more underground openings. Pillars can be composed entirely of ore or ore and waste when the ore body has a small thickness relative to the excavation height. In some cases, this type of mining may need ground support systems such as cable bolting or confinement ribs. The optimum size of pillars that guarantees stable rooms depends on the active load on the pillar and its strength and stiffness as well as on the carrying capacity and stiffness of the roof rock mass
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