gobs

Depending on the distance from the longwall front and gates change of air flow character in gobs is presented.

In Table 4 characteristic value for air stream velocity in gobs depending on value of destratification resistance of rocks are presented.

Analysis of obtained results clearly indicates that increase of value of destratification resistance of rocks causes an increase of volumetric air stream incoming into gobs and flowing also through caving zone.

Lower value of destratification resistance of roof rocks forming goaf with caving causes decreased of their permeability and decreased velocity and greater pressure differences of air in gobs. In a case of greater values of destratification resistance of rocks one can observe opposite phenomenon.

one can conclude that gobs created by roof rocks with different values of destratification resistance create different conditions for air flowing through these gobs.

In which : [q.sub.y] is the force of overlying rocks on the roofing of upper coal stratum; [Q.sub.1] and [Q.sub.3] are respectively the weight of natural arch springing for each coal stratum; [Q.sub.2] is the weight of waste rocks in the gobs of upper coal stratum; Q is the weight of complete rock stratum between the two coal strata in the range of excavation of close distance coal strata; n is the number of working faces in the range of excavation of coal strata; q is the load of lower coal stratum flooring on the natural arch springing.

Incorporate Equations 7 and 8, the load of lower coal stratum flooring on the coal pillars in the gobs can be calculated as:

The weight of waste rocks in the natural arch of the gobs of lower coal stratum acts directly on the coal stratum flooring.

In which [q.sub.c] is the average load of the flooring of the gobs of lower coal stratum.

For misaligned independent natural arch structure of close distance coal strata, the loading condition of the natural arch of the gobs of lower coal stratum is similar to the case of aligned independent structure.