A case study and a method of forecasting catastrophic collapses induced by mining activities are described. These "sudden" events are shown to be a result of long-term kinetic processes of defect accumulation in the surrounding rock. The kinetic method has allowed to make a number of successful forecasts of underground excavation collapses in Jezkazgan copper mines (Kazakhstan) in recent years. As is shown, the collapses followed by a vast surface subsidence were caused by the failure of mine pillars. Parameters of the seismic monitoring network used for the forecasting of the catastrophic events are also reported.
In recent decades, man-made geodynamic phenomena are a subject of intensive studies by scientists and engineers. Some catastrophic geodynamic events such as a sudden collapse - caving and, consequently, a vast surface subsidence induced by mining, present a serious danger to modern infrastructure, property and human lives. A considerable body of work devoted to the problem exists in the literature. This paper extends the recent works of the authors, who now apply a statistical rock fracture model based on the kinetic theory to the monitoring of the stability of underground openings. The approach has been applied to the forecasting of subsidence, which happened recently in Jezkazgan copper mines in the Republic o~ Kazakhstan. It should be noted that Urkov (1957) first formulated the kinetic approach to failure processes in solids.
The Jezkazgan deposit of copper ore has been mined since 1942. The deposit is confined to the Jezkazgan area of sedimentary rock that mainly consists of alternating grey and red sandstone layers containing the ore, as well as of aleurolites. The main reserves of copper ore are at depths from 150 m to 450 meters. The thickness of the ore bodies varies from 1.5 m to 30 m. The thickness of some areas of the ore body may reach up to 60 m. The average thickness of the ore body for the entire mine is about 4 to 9 meters. The richest and thickest ore bodies are mined by room-and-pillar technology with the use of heavy mobile mining equipment. At present the mining area contains more than 50 thousand interchamber pillars. The mined out area is partitioned into chambers by 400 chain and harrier pillars. The length of tunnels is more than 1200 km, 540 km of which, relate to the active mining areas. The mines have also about 45 km of shafts for different purposes. The total volume of openings at Jazkazgan mines in 1998 reached 175 millions cubic meters. Thus volume reached 130 millions cubic meters in 2001. The reason for the reduction of the opening volume is the filling of the openings with unconsolidated rock as a result of recent caving. For the past 50 years, subsurface mineral deposits have been removed under a related surface area of 8 sq. km within which a sensitive surface subsidence has been observed. Furthermore, the surface infrastructure has been subjected to the risk of severe damages.