When developing medium thickness seams with gentle and horizontal bedding the panel system of development is often used. In order to speed up the construction period and quickly put the mine into operation, the deposit is opened by central twin shafts. The mine ventilation scheme at this method of stripping will be central.

At coal and ore mines there are large air leaks, sometimes reaching 70-90% of the fan flow rate. They limit production, create unsatisfactory atmospheric conditions of work, contribute to the accumulation of explosive and harmful gases, increase energy consumption spent on ventilation.

The question of the dependence of local resistance coefficients k on the roughness of the walls of air ducts is one of the little studied issues of practical aerodynamics. Most aerodynamics courses provide values, sometimes very detailed, of coefficients k for a number of local resistances - turns, sudden contractions and expansions, but are not indicated Usually, how to use these coefficients: should they be taken as constant, independent of the roughness of the walls of the air duct, or, conversely, should they be considered variable values, related in some way to the coefficient of friction on the walls of the air duct. The work done by the authors made it possible to clarify the relationship between the coefficients of local resistance k and the coefficients of friction a of air on the walls of the air duct. The previously accepted dependence turned out to be incorrect and must be replaced by another (see article). The turning resistance coefficients given in various courses should be increased for rough concrete fastening by 8-10% and for workings secured with staggered door frames by 25-30%. The correctness of formulas (11) and (12) for other types of local resistance requires verification.