Design approach for squeezing ground

Abstract

Many mines experience squeezing ground conditions due to orebodies located in weak rock masses. Often, the conditions leading to squeezing ground are not recognised or underestimated at the feasibility stage, leading to significant difficulties in mining the deposit, high costs and lost resources. There are a number of processes to determine the potential existence and degree of squeezing ground. Feasibility study to determine the rock mass behaviour will significantly reduce the risks associated with mining such deposits. In many cases, it is not possible to prevent squeezing occurring; however, good planning at the feasibility stage can provide the means to control the ground to allow economical extraction. The aim of this paper is to present an approach to maintain access development in squeezing ground identified during the feasibility study. Much is written about squeezing ground, but mainly about how to solve a problem that has already occurred (Potvin & Hadjigeorgiou 2008; Sandy et al. 2007). The aim of this paper is to give guidance for planning and management solutions for a deposit that will likely encounter squeezing ground conditions. The paper will also discuss operational requirements that need to be considered at the pre-production stage. The paper reviews ground control schemes aimed at controlling movement before and during stoping. It is based on experiences and research conducted at mines experiencing squeezing ground conditions and reviews considerations in design and monitoring to mitigate outcomes associated with squeezing rock masses. 2 Defining squeezing ground A number of definitions of squeezing ground are available. Potvin and Hadjigeorgiou (2008) listed a number of definitions as part of the Australian Centre for Geomechanics Squeezing Ground Task Force. Several of these are shown in Section 2.1. Section 2.2 describes how to recognise rock mass conditions that may lead to squeezing ground.

Monitoring and controls for sublevel caving in an anisotropic rock mass

“…SLC mine design as a contributing factor for caving controls is considered due the potential impact of the pillar between levels on tunnel squeezing and deformity, and brow competency. Varden & Woods (2015) outlined that the pillar between levels in a mine design to mitigate tunnel squeezing and deformity is to be a minimum 15 m. In the Venus south cave the level spacing of 25 m intervals and the high rates of unravelling and squeezing of drives within the UM at the tunnelling level suggest that other factors such as the lead-lag and mining advance direction are controls that might be specific to rock mass strength. In a heterogenous system the rule must be applied for the lowest common denominator of strength capability.…”

Ground support design for weak rock mass: quantifying time-dependent closure in squeezing ground

“…The authors would like to acknowledge previous research conducted on squeezing ground, and the interested reader is referred to other publications, including Hoek (1998), Potvin & Hadjigeorgiou (2008), Hadjigeorgiou & Karampinos (2017) and Varden & Woods (2015).…”

Support and reinforcement damage initiation and design adjustments in a deep mine environment Case study: Cuiabá Mine, Minas Gerais, Brazil

“…It is common not to recognize or to underestimate the conditions leading to squeezing ground during the feasibility stage of a project, which then causes significant difficulties in mining the deposit, higher costs and lost resources Varden et al(2015). Field observations of the mechanism, associated with the geological-geotechnical characterization, monitoring, numerical modeling as well as support damage analysis can assist in understanding the problem as well as to define actions to solve it.…”