Abstract
The necessity of development and improvement of methods and means for the protection of preparatory roadways, in particular, protective structures, was proved on the basis of ordinary rock with binding surfaces. Analysis of the results of the study on the use of protective structures of ordinary rock and bounding surfaces was performed. It has shown the feasibility of reinforcing rock structures to ensure operational conditions for the protected roadways. Such structures include rubble strips reinforced with partitions made of metal mesh. To determine their efficiency and reinforcement parameters, studies were performed using provisions of structural mechanics, soil mechanics, and bulk media, as well as physical modeling using natural materials. According to the results obtained in the performed studies, the efficiency of reinforcement of rubble strips with a metal grid was proved and a procedure for calculation of reinforcement parameters that need to be considered in designing the above structures was developed. Such parameters include width and height of the strip, class of reinforcement, its diameter and tensile strength, size of the grid cells, angle of internal friction of rocks, and diameter of maximum rock pieces in the strip. It was established that reinforcement of the rubble strip by partitions made of metal meshes can reduce the width of the strip and volume of the rock fill by 1.33…2.66 times without losing the structure rigidity. To do this, the condition of reinforcement strength in grids must be met. It consists of comparing its tensile strength with maximum stresses in the partition. These stresses are determined by the magnitude of the load on the rubble strip from the roof rocks, the diameter of the reinforcement, and the maximum rock pieces, as well as relative extensional strain in reinforcement.
Highlights
With an increase in depth of mining operations in conditions of coal mines, the problem of ensuring the operational condition of preparatory roadways is becoming increasingly difficult
Preparatory roadways behind walls are mostly protected in a massif and coal pillars [7]
Pillars are destroyed at high external loads and are unable to ensure the operational condition of roadways [8, 9] and safe excavation conditions for miners [10, 11]
Summary
With an increase in depth of mining operations in conditions of coal mines, the problem of ensuring the operational condition of preparatory roadways is becoming increasingly difficult. There are cases when leaving pillars to protect roadways is unacceptable because of significant losses of minerals [12,13,14] or the tendency of coal to self-ignite [15, 16] In such cases, technologies are used when artificial structures made of wood [13, 17], concrete [18], ordinary rock [19, 20], etc. It was proved that rubble strips are cheaper than other means, practically feasible in the mechanization of their erection and the initial costs are compensated by reducing the cost of maintenance of roadways and cost of rock disposal [21] These structures have their own disadvantages including large amounts of rock, a high proportion of manual labor in its movement and laying, low load-bearing capacity, and significant pliability. Studies on the efficiency and parameters of reinforcement for rubble strips are relevant
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