Tests of Rock Bands With Limited Suppleness

Physical simulation of integrated protective structures

“…1). According to the results of previous laboratory and analytical studies the parameters of this technology have been determined [21,22]. But a small number of parameters which varied in a limited range have been considered in laboratory models.…”

“…Previously, it was found out that walls should contain two bags in a row laid perpendicular to each other along the height of the protective structure [21], but by changing the rock width between these walls, it is possible to change their bearing capacity and yielding strength, as well as affect the stability of the working. The rock wall width can be calculated by the equation [22]:…”

“…where h is height of the structure, m; σ y is stress over the protective structure caused by the weight of the rocks held by the structure, MPa; f is coefficient of rock friction within the structure against the material of its shell; ϕ is angle of internal friction of rocks, degrees; b Р is stress occurring when ordinary rocks contact the bag wall, MPa. The integrated structure involves erection of walls made of bags and rock packs, but from the equation (1) it follows that at σ y = b Р the rock pack is not required, and this construction will be similar to the method of protecting by rock walls [21,24]. In the case when σ y > b Р , it will be insufficient to make use of rock pack only, so it is necessary to fill space between them with ordinary rocks, i.e.…”

“…at γ m /γ f = 1 and l m /l f = 0.04g m = 0.04g f . Thus, at depth of 1000 m, assuming that the working contour stress can exceed 2 times the stress in virgin ground [22], the g m should be 2 MPa, and taking into account the bearing surface area, the load intensity should be 180 kN. Therefore, the boundary load was 200 kN.…”

“…Technological scheme of lining the final part of the longwall face and erecting the integrated protective rock structure[22].…”