Subsidence Mechanism and Stability Assessment Methods for Partial Extraction Mines for Sustainable Development of Mining Cities—A Review

Abstract

Abstract:Partial extraction methods such as underground strip pillar mining or room-and-pillar mining are widely adopted techniques to control ground subsidence. However, pillar failure in partial extraction mines may introduce violent secondary ground collapses. The stability of partial extraction mines dictates the safety of ground surface structures and the environmental health state of the surrounding mining areas. To reuse mining subsidence lands, it is necessary to evaluate the stability of the land through mine subsidence assessments. This paper summarizes current pillar stability assessment methods and their limitations, and the rock mechanics associated with the stability of abandoned mines. The effects of multiple factors that affect mine stability are discussed in detail; special attention has been extended to discuss the weathering effects associated with infused water and spontaneous combustion, as these are some key reasons for pillar strength degradation in abandoned mines. The mechanism of mine collapse and the corresponding post-mining disasters are also summarized. Finally, suggestions and strategies to improve current mine stability assessment methods are proposed based on the perspective of subsidence control.

Mine Size Effects on Coal Pillar Stress and Their Application for Partial Extraction

“…Underground mining activities can result in severe ground subsidence and damage man-made structures (buildings, railways, or other infrastructure) on the surface [1][2][3][4][5]. Mining subsidence is an important factor that restricts the sustainable development of mining cities [5].…”

“…Underground mining activities can result in severe ground subsidence and damage man-made structures (buildings, railways, or other infrastructure) on the surface [1][2][3][4][5]. Mining subsidence is an important factor that restricts the sustainable development of mining cities [5]. To reduce mining subsidence and protect surface and ground structures, partial extraction methods such as strip pillar mining or room-and-pillar mining are widely adopted [5][6][7].…”

“…Mining subsidence is an important factor that restricts the sustainable development of mining cities [5]. To reduce mining subsidence and protect surface and ground structures, partial extraction methods such as strip pillar mining or room-and-pillar mining are widely adopted [5][6][7]. Figure 1 shows typical layouts of room-and-pillar mining and strip pillar mining techniques.…”

“…The stress calculation for room-and-pillar mining is a three-dimensional problem because both the pillar length and the pillar width are relatively small (Figure 1a), whereas the stress calculation for strip pillar mining can be simplified to a two-dimensional problem because the pillar length is usually far longer than the pillar width ( Figure 1b). In coal mine design and pillar stability evaluation, the pillar stress is usually determined by using TAT (tributary area theory), PAT (pressure arch theory), or numerical simulations [5,[10][11][12][13][14][15][16]. TAT assumes that the overburden load will be evenly distributed among coal pillars, and the overburden load above the mined room is equally shared by neighboring pillars [5].…”

“…In coal mine design and pillar stability evaluation, the pillar stress is usually determined by using TAT (tributary area theory), PAT (pressure arch theory), or numerical simulations [5,[10][11][12][13][14][15][16]. TAT assumes that the overburden load will be evenly distributed among coal pillars, and the overburden load above the mined room is equally shared by neighboring pillars [5]. On the other hand, PAT assumes that a pressure arch will form between large barrier pillars and carry most of overburden weight, the abutment angle is utilized to describe the shape of the pressure arch [5,15].…”