Abstract
In order to explore the distribution law of stress field under the mining mode of gob-side entry retaining by roof cutting without pillar (GERRCP) under goaf, based on the engineering background of 8102 and 9101 working faces in Xiashanmao coal mine, the stress field distribution of GERRCP and traditional remaining pillar was studied by means of theoretical analysis and numerical simulation. The simulation results showed that: (1) in the front of the working face, the vertical peak stress of non-pillar mining was smaller than that of the remaining pillar mining, and it could effectively control stress concentration in surrounding rock of the mining roadway; the trend of horizontal stress distribution of the two was the same, and the area, span and peak stress of stress the rise zone were the largest in large pillar mining and the minimum in non-pillar mining. (2) On the left side of the working face, the vertical stress presented increasing-decreasing characteristics under non-pillar mining mode and saddle-shaped distribution characteristics under the remaining pillar mining mode respectively. Among them, the peak stress was the smallest under non-pillar mining, and compared with the mining of the large pillar and small pillar, non-pillar mining decreased by 12–21% and 3–10% respectively. The position of peak stress of the former was closer to the mining roadway, indicating that the width of the plastic zone of the surrounding rock of the non-pillar mining was smaller and bearing capacity was higher. In the mining of the large and small pillar, the horizontal stress formed a high stress concentration in the pillar and 9102 working face respectively. In non-pillar mining, the horizontal stress concentration appeared in solid coal, but the concentration area was small.
Highlights
In the 1960s and 1970s, longwall mining technology developed rapidly, and the “masonry beam theory” was put forward, forming the “121” construction method of longwall mining [1]
Its core can be summarized as four steps: strengthening, cutting, protecting and closing, that is: (1) adopt the constant-resistance large-deformation anchor cable (CRLDAC) to actively strengthen the supporting roadway roof according to the designed supporting parameters (Figure 4a); (2) the energy-gathered pre-cracking blasting hole shall be constructed at a certain distance in advance of the working face, and the bidirectional energy-gathered pre-cracking blasting shall be carried out according to the parameters determined by the blasting test to form a slit on the roof at the side of the goaf (Figure 4b); (3) after mining at the working face, the sliding and yielding gangue support structure and the constant pressure retractable support equipment are adopted behind the working face to strengthen the support in time
For the non-pillar mining, (a) ditto; (b) two mining roadways of the 9101 working face were excavated at one time, and the calculation was made to the model balance; (c) pre-cracking roof cutting was conducted firstly
Summary
In the 1960s and 1970s, longwall mining technology developed rapidly, and the “masonry beam theory” was put forward, forming the “121” construction method of longwall mining [1]. Domestic and foreign experts and scholars have conducted a lot of studies on the distribution law of a stress field in lower coal seam when mining close distance coal seam, and achieved fruitful results. The above experts and scholars have achieved fruitful results in research on the distribution structure of roof under goaf, were carried out by means of theoretical analysis, similarity simulation law of a stress field when mining near-group coal seam. In order to explore the of thedistribution roof structure of through theoretical analysis, and establishes a three-dimensional law of three-dimensional stress field of GERRCP in the near-group coal seam mining, this paper takes Xiashanmao coalon mine an engineering background, establishes the mechanical numerical calculation model based the as finite difference program. The numerical simulation results are validatedEntry by field experiments
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