Prevention of gas emanation and securing of stability by grouting in the surrounding of a backfilled vertical mine pit


In the Ostrava-Karvina mining area arise specific problems – methane emanations to the surface from abandoned mining works - interconnected with stopping of mining activities in the Ostrava basin. This results in formation of explosive concentrations of CH4 in the surrounding backfilled mine pits. The whole area is very densely built up by urban buildings and industrial plants.
Within termination of the mining activity a long-term stabilization of mine pit openings was performed in order to stop uncontrolled dropping of mine pit fill and control the release of mine gas (CH4). Mine gases are discharged through piping into the atmosphere in order to prevent migration of gas into the surrounding at the surface and thus potential migration into existing buildings. Due to gas tightness of polyurethane resins for CH4, GEOPUR 082/ 230 systems were applied for stabilization of mine pit openings Vilém, Jindřich, Josef and Muglinovská.

Grouting of mine pit opening Vilém.

Opening of this mine pit is located in current railway track by the former Mine Dul Zarubek. The railway track is placed on an approx. 3 m thick fill material from mine dump material.
An annular ring of 5,8 m diameter, approx. 1,9 m wide was grouted into the depth of 8 m below surface level. This ring forms a geo-composite formed from the mine dump material and polyurethane resin applied into the soil through grouting steel pipes (50/42 mm) pushed into the depth of 8 m.
After finishing the grouting a covering slab of 50 cm thickness reinforced with welded latticing. A steel piping Dn 600 mm was installed for the purposes of mine pit fill control and a Dn 300 mm piping for the purposes of ventilation into the slab. A sprayed on polyurethane layer protects the surface of the concrete slab.
This alternative solution was cheaper compared to the original design (costs are lower by 20 - 30 %). A total of 21 000 kg of Geopur polyurethane grouting resins.