Recovery Technology of Bottom Coal in the Gob-Side Entry of Thick Coal Seam Based on Floor Heave Induced by Narrow Coal Pillar

Abstract

<jats:p>To improve the resource recovery efficiency of mining face in thick coal seams, the correlation between deformation failure of bottom coal in the gob-side entry and coal pillar width was analyzed by theoretical analysis, numerical calculation, and similar simulation experiments. The results showed that, when the coal pillar was strong, with the decrease of pillar width, the failure depth of the bottom coal in the gob-side entry and floor heave increased. The deformation failure depth of the bottom coal in the entry was inversely related to the width of the coal pillar. The bottom coal was further fractured and dispersed under the action of tension, shear, and extrusion in the process of floor heave. Based on the floor heave induced by the narrow coal pillar, a recovery technique of the bottom coal with thick coal seams in the gob-side entry was developed. The width of the narrow pillar to be reserved was obtained by theoretical calculation and revised by numerical simulation; ultimately, the reasonable width was determined. Under the complex stress of the narrow pillar, the bottom coal in the gob-side entry was fully heaved, cracked, and separated. To realize the comprehensive mechanization and resource recovery of bottom coal, a matching mining excavator loader, transfer conveyor, and retractable belt conveyor were selected to transport the crushed bottom coal in the entry. This method has been successfully applied to the return airway of working face 8407 in the No. 5 Coal Mine of Yangquan Coal Group with remarkable economic and social benefits.</jats:p>

The Effect of Selected Factors on Floor Upheaval in Roadways—In Situ Testing

“…This form of floor upheaval is described in papers e.g., by [7,11,14,17,18]. To prevent this phenomenon a combined support system with concrete slab is bolted to the floor [18,19]. Shearing takes place in headings driven in strong rocks and with strong stratified floors, where the upheaval occurs in the form of a threshold in a discontinuous manner (Figure 3b).…”

“…Observations of roadways show that if the floor rocks are weak and have lower strength parameters than the rocks in the side walls of the excavation, the floor upheaval occurs in the form of extrusion, bending and swelling of the floor layers (Figure 3a). This form of floor upheaval is described in papers e.g., by [7,11,14,17,18]. To prevent this phenomenon a combined support system with concrete slab is bolted to the floor [18,19].…”

“…This form of floor upheaval is described in papers e.g., by [7,11,14,17,18]. To prevent this phenomenon a combined support system with concrete slab is bolted to the floor [18,19].…”

Loading Performance of a Novel Shearer Drum Applied to Thin Coal Seams

“…Coal is an important, globally relevant energy source to support industrial production and development and mining it safely and efficiently has been studied extensively [1,2]. As the key equipment in the longwall mining coalface, the shearer's cutting and traction performance has been investigated [3,4].…”

Deterioration of Coal Microstructure under Discontinuous Cyclic Loading Based on Nuclear Magnetic Resonance

“…As a typical mining layout form that saves coal resources, improves the resource recovery rate, and simplifies mining and excavation replacement, gob (after the coal is mined, the original working face position is called the gob)-side entry (GSE) has been used extensively in Chinese coal mining roadways [1,2]. The development of the surrounding rock joints and fissures of the GSE is affected by factors such as multiple mining at the working face, advanced support pressure and other factors, and is often accompanied by engineering disasters, such as the collapse of slabs of coal pillars on the side of the goaf [3,4]. The small coal pillar is an important part of the surrounding rock of GSE, and its stability affects the roadway stability directly.…”