Based on the results of integrated geomechanical investigations using analytical methods, methods of laboratory and location experiments and studies, parameters of underground hollows(chambers) and pillars ensuring stability of rock masses accomodating large underground techno-geneous hollows, preservation of terrain and safe operation of engineering installations on it in the zone of mass underworking, as well as safe construction and operation of underground hollows, have been substantiated. Stability of stressed and deformed state of the mining system structural elements in time, and possibility of using hollows (chambers) for the purposes different from mineral resources mining have been noted.
Techno-geneous structures representing- aggregation of extended mine openings with small cross section (S ≤ 15 sq.m), solid (more than 1000 cub.m) openings - chambers (hollows), natural support and protective pillars (natural - rock, ore, - or artificial masses between openings - hollows) are produced in the rock masses, constituting upper portion of the Earth's crust as a result of underground mining of solid mineral resources by systems with open (or temporarily open) worked space. In this connection providing safety of underground mining and operation (construction) of natural and techno-geneous installations on the earth's surface in the area of the worked deposit predetermines a need in preserving stability of rock exposures in mine openings, and rock masses in the bedding leaning over them, and ensuring required strength of pillars or rock masses between the mine openings. It is known that design work preceding mining includes calculations of pillar geometrical parameters, exposure areas and hollow volumes (mine openings and especially chambers) based upon the results of engineering and geological and geo-mechanical conditions of the deposit. But control (supervisions) of the state of rock exposures in the hollows, and pillar deformations in the process of mine construction and operation is not always continuous. Such a control should be ensured to reveal timely pre-critical conditions (i.e. conditions preceding loss of system stability and strength) in the state of the given techno-geneous structure structural elements and undertake appropriate measures in order to maintain their stability and strength at proper level. The necessity and efficiency of such an approach are well illustrated by operational experience of the Korobkovsky iron ore deposit in the field of the Kursk Magnetic Anomaly (Gubkin, Russia). The deposit geological structure includes sedimentary and crystalline complex rocks. The sedimentary complex is represented by the Quaternary, Cretaceous, Jurassic and Devonian age sediments. The complex total capacity is 65 - 150 m. There are some water-bearing levels in the sedimentary rock bedding, and the deposit is considered to be a complicated one by its hydrogeological conditions shows a composite folded structure. These rock masses are broken down by separate disjunctive discontinuities and four systems of cracks filled with rocks of carbonate and silicate composition. This complex is represented by thick divided and mapped ferruginous quartzite beds, and thick dead rock masses (silicified shales, amphibolites, gnessoid granites, quartz porphyres, quartzitic sandstones). Ferruginous quartzite beds being a productive component of the deposit.