Abstract
Abstract In recent years, as a new type of gob-side entry retaining method, roadway automatically formed by roof cutting and pressure releasing (RAFRCPR) has been widely used in China. Under the condition of deep mining, the deformation of the gangue rib of the automatically formed gob-side entry retaining is difficult to control, and it is difficult for the traditional I-shaped steel to provide the needed support. To effectively control the deformation of the gangue rib, a new type of U-shaped retractable gangue prevention structure (URGPS) with high lateral support strength and axial compressible dynamic absorption energy is proposed. Based on the geological conditions of the 21304-working face in the Chengjiao coal mine in Henan, the mechanical characteristics of URGPS and the causes of its local instability are analyzed in detail employing theoretical analysis, laboratory tests, and numerical simulation. A reasonable bolt tightening force, overlap length, and lap combination form of the URGPS are determined according to the actual situation of the project site. Engineering practice shows that a URGPS that was applied to control the deformation of the gangue rib in deep roof-cutting roadway was effective.
Highlights
Coal resources are one of the most important basic energy sources, accounting for about 30% of the world’s total energy consumption
China’s energy supply is dominated by coal, and the energy return on the investment in coal mining is and will continue to be higher than that in oil and gas mining, which indicates that coal is likely to continue to be China’s most important fossil fuel resource in the future [1,2,3]
With the decrease in coal resources and the increase in mining depths, the wastage of coal resources caused by traditional coal pillar mining is becoming increasingly prominent [4,5,6,7]
Summary
Coal resources are one of the most important basic energy sources, accounting for about 30% of the world’s total energy consumption. RAFRCPR adopts bilateral cumulative tensile explosion technology [13] to directionally presplit and cut off the connection between the goaf side roof and the roadway roof in advance and reduce the influence of periodic pressure on the deformation of the roadway roof. Under the condition of deep high-stress mining, the traditional I-shaped steel retaining has a high failure rate, low recovery rate, and poor supporting effect [19,20,21,22]. Chunan [25] conducted a mechanical analysis on the U-shaped steel bracket and pointed out that the load-bearing capacity of the U-shaped steel bracket mainly depends on the overall stability of the bracket itself and analyzed the force changes of the U-shaped steel before and after shrinking. A field test shows that the support structure significantly improves the deformation of the gangue retaining
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