Method for reducing compressed air losses when driving underground cavities supported by compressed air

In a method of reducing compressed air losses in a mining cavity formation when progressively driving underground cavities which are supported by compressed air, said method including the step of sealing part of an advancing cavity having an inner cavity surface exposed by mining and adding a viscous medium as a sealant layer applied in a step-wise manner according to advance of the cavity and also that the sealant layer does not add to the strength of the formation after breaking away the earth;

• the improvement therewith which comprises the steps of:
• using viscous medium having a plastic viscosity of up to about 30 cp and having an apparent viscosity of up to about 50 cp;
• combining said viscous medium with a propellant to form a mixture;
• applying said mixture, in the form of a spray mist which is directed toward said exposed part of said inner cavity surface, in such a way that said mist penetrates the substratum without significantly destroying said exposed surface part;
• moving said viscous medium continuously during advance of the underground cavity formation;
• and
• applying viscous medium in a renewed manner in sections corresponding to the advance.