Development of a New Gob-Side Entry-Retaining Approach and Its Application

Abstract

Gob-side entry retaining plays an important role in the sustainable exploitation of coal resources and has been widely used in coal mining. However; some disadvantages, such as high labour intensity and low efficiency of wall construction, have gravely restricted the application of this technique. To solve this issue, this paper developed a new gob-side entry retaining approach including a lightweight and high-strength foam concrete and a mortise-and-tenon structure hollow-block wall. The experiment results show that the preparation of foam concrete with a density of 1200 kg/m 3 ; with uniaxial compressive strength greater than 15 MPa, can be realized by the chemical-foaming method. The method is performed by adding silica fume, slag and fly ash to a system of "cement and sand" structure collocation and by optimizing the proportioning of the materials. The density of foam concrete is reduced by 50% relative to that of common concrete which can greatly reduce the weight of the blocks. Compared with the conventional gob-side entry-retaining wall the new wall structure has many advantages. For example, it can improve stability by increasing the width-to-height ratio of the wall and save 44.44% of the material, and at the same time; it can save manpower and improve labour efficiency. Finally, the new approach was tested in the 3203 gob-side entry-retaining working face in a Chinese coal mine and the application effect proves that the new approach is well suited for entry retaining. The wall structure and parameters are reasonable. This work can contribute to the sustainable and efficient exploitation of underground coal resources.

Gob-Side Entry Retained with Soft Roof, Floor, and Seam in Thin Coal Seams: A Case Study

“…In the field construction, the strength of backfill is calculated as 80% of the laboratory test value. Taking 1.3 times the safety factor into account, the theoretical width of the RBB for the 1103 working face for 1 day is calculated as 0.99 m based on Equation (6). Therefore, the RBB width is 1.0 m. The roof is reinforced by Φ17.8 mm × L6300 mm anchor cables, and three rows are set up with a spacing of 800 mm along the roadway.…”

“…GER is beneficial for the sustainable development of the coal mining industry by mining without the coal pillar [1][2][3][4][5] GER maintains the gob boundary roadway behind the roadway behind the working face. The original roadway is retained and used as a roadway adjacent to the working face through effective roadside backfill and road-in support technology (see Figure 1) [6][7][8][9][10]. GER has been widely carried out in many Chinese coal mines due to its advantages [11][12][13][14][15][16].…”

Framework and Application of a Big Data Monitoring System for Mining with a Pillar-Free Self-Forming Roadway

“…The technology for establishing a gob-side retaining roadway without coal pillars has enabled a halving of the driving capacity of mining roadways in the working face and a great improvement in the resource recovery rate. However, that technology often relies on a high-strength roadside filling body to maintain the original mining roadway, requiring the use of a complex filling system and filling technology, thereby limiting its promotion and application [6][7][8][9][10]. In view of the above problems, the team of He Manchao put forward a method for constructing a self-made roadway without the use of coal pillars based on the theory of forming a short-arm beam through roof cutting.…”

Nonlinear Large Deformation Mechanism and Stability Control of Deep Soft Rock Roadway: A Case Study in China

“…Typical tensile bolts are the D bolt, Cone bolt, Roofex bolt, and Constant Resistance Large Deformation bolt [12][13][14][15][16][17][18]. Especially, the Constant Resistance Large Deformation (CRLD) bolt, invented at China University of Mining and Technology Beijing (CUMTB), has the advantages of constant high resistance and large deformation and has been used successfully in some coal mines [17][18][19][20].In recent years, the traditional bolt-mesh-cable support and bolt support for solving the stability problem of surrounding rock in shallow roadways has been shown to have a certain effect, but under complex geological conditions of high stress and mining action, the deformation of surrounding rock in the deep soft rock roadways is seriously large [21][22][23][24][25]. The traditional supporting mechanism theory and traditional support countermeasures cannot effectively reveal and control the large deformation of the surrounding rock in deep roadways [8,26,27].Reasonable support countermeasures should be based on the correct evaluation and analysis of the deformation mechanisms of specific roadways [26].…”

“…In recent years, the traditional bolt-mesh-cable support and bolt support for solving the stability problem of surrounding rock in shallow roadways has been shown to have a certain effect, but under complex geological conditions of high stress and mining action, the deformation of surrounding rock in the deep soft rock roadways is seriously large [21][22][23][24][25]. The traditional supporting mechanism theory and traditional support countermeasures cannot effectively reveal and control the large deformation of the surrounding rock in deep roadways [8,26,27].…”