Field and numerical investigations on the lower coal seam entry failure analysis under the remnant pillar

Zhang, Zizheng; Deng, Min; Wang, Xiangyu; Yu, Wenxin; Zhang, Fei; Dao, Viet Doan

doi:10.1016/j.engfailanal.2020.104638

Cited by 67 publications

(45 citation statements)

References 23 publications

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“…A comprehensive analysis of the average distance between the upper and lower coal seams, overburden thickness, rock mechanical parameters, stress transfer angle, and other parameters revealed that the optimal staggered distance minimized the peak stress of the lower coal pillar after mining of the upper coal pillar (In the Mohr‐Coulomb elastic‐plastic constitutive condition, the stress in the goaf could be effectively transferred downward through the coal pillars 9,46 ). Meanwhile, the lower coal working face and pillar could effectively avoid the staggered distance between the upper and the lower coal pillars in the stress concentration area of the upper coal seam.…”

Section: Numerical Simulation and Different Staggered Distance Schemementioning

confidence: 99%

Optimization of staggered distance of coal pillars in multiseam mining: Theoretical analysis and numerical simulation

Sun

Cheng³

2020

Energy Science & Engineering

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Aimed at solving problems related to water retention and loss reduction in multiseam mining, a mechanical model of staggered distance mining was established. First, elastic and plastic slip line field theories were used to calculate the reasonable staggered distance expressions of multiseam mining. The staggered distance schemes of multiseam mining were optimized using the numerical simulation software FLAC3D. By performing an experiment comparing similar materials, the influence on water retention and loss reduction by optimal and unfavorable staggered distance schemes in multiseam mining was explored. The results showed that the σzz curve was distributed in the shape of a “peak” of the staggering distance coal pillars, the Z displacement curve was a “Л,” and the surface subsidence curve was a “W.” Each of these displayed the rule of “decrease then increase.” In staggered distance multiseam mining, the optimal staggered distance value for coal seam Nos. 2 and 3 was 40 m, while the most unfavorable staggered distance value was 0 m. The corresponding subsidence coefficients of the optimal staggered distance values were 0.29, 0.23, and 0.19, under the condition of keeping the optimal staggered distance value for coal seam Nos. 1 and 2 unchanged. These results could be beneficial in reduction of surface subsidence and may also have specific practical engineering significance.

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Section: Numerical Simulation and Different Staggered Distance Schemementioning

confidence: 99%

Optimization of staggered distance of coal pillars in multiseam mining: Theoretical analysis and numerical simulation

Sun

Cheng³

2020

Energy Science & Engineering

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“…Zhang proposed a GER case with supercritical retained entry width in the thick coal seam (4.0 m) of Liujiazhuang Coal Mine (Zhang et al 2019). Zhang proposed a GER case in the medium-thick coal seam (2.8 m) of Xinyuan Coal Mine (Zhang et al 2020). Therefore, GER engineering applications have developed from thin coal seam and medium-thick coal seam to thick coal seam mining.…”

Section: Literature Review Of Ger-rfmentioning

confidence: 99%

“…The filling area near the roadway is often in the state of no support or simple temporary support, that is, the support strength of the area to be filled is low, which is called "lagging unsupported roof" (see Fig.1). Zhang and Zheng firstly proposed that roof stability in the filling area is one of the key factors for the success of GER Zhang et al 2020;Zhang et al 2012). The length of the lagging unsupported roof in GER-RF is mainly composed of the cyclic filling length and the width of the pedestrian passage behind the support.…”

Section: Literature Review Of Ger-rfmentioning

confidence: 99%

Determination of cyclic filling length in gob-side entry retained with roadside filling and its application

Zhang

Bai

et al. 2020

Preprint

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Gob-side entry retained with roadside filling (GER-RF) plays a key role in achieving coal mining without pillar and improving the coal resource recovery rate. Since there are few reports on the cyclic filling length of GER-RF, a method based on the stress difference method is proposed to determine the cyclic filling length of GER-RF. Firstly, a stability analysis mechanics model of the immediate roof above roadside filling area in GER was established, then the relationship between the roof stress distribution and the unsupported roof length was obtained by the stress difference method. According to the roof stability above roadside filling area based on the relationship between the roof stress and its tensile strength, the maximum unsupported roof length and rational cyclic filling length of GER-RF. Combined with the geological conditions of the 1103 thin coal seam working face of Heilong Coal Mine and the geological conditions of the 1301 thick coal seam working face of Licun Coal Mine, this suggested method was applied to determine that the rational cyclic filling lengths of GER-RF were 2.4 m and 3.2 m, respectively. Field trial tests show that the suggested method can effectively control the surrounding rock deformation along with rational road-in support and roadside support, and improve the filling and construction speed.

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“…Protective pillar around the gob provides a safe and stable production environment for the roadway and decreases disturbance to the roadway from high external stress. An improper protective pillar design can cause frequent roof sagging, pillar rib bulging, and severe coal bump to occur in a roadway, which will eventually cause the collapse of the surrounding rock structure [2,3]. erefore, protective pillar width design is a necessity for maintaining the stability of the surrounding rock.…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of the Width Design of a Protective Pillar in High‐Stress Roadway: A Case Study

et al. 2021

Advances in Civil Engineering

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The width design of protective pillars is an important factor affecting the stability of high-stress roadways. In this study, a novel numerical modeling approach was developed to investigate the relationship between protective pillar width and roadway stability. With the 20 m protective pillar width adopted in the field test, large deformation of roadways and serious damage to surrounding rocks occurred. According to the case study at the Wangzhuang coal mine in China, the stress changes and energy density distribution characteristics in protective pillars with various widths were analysed by numerical simulation. The modeling results indicate that, with a 20 m wide protective pillar, the peak vertical stress and energy density in the pillar are 18.5 MPa and 563.7 kJ/m3, respectively. The phenomena of stress concentration and energy accumulation were clearly observed in the simulation results, and the roadway is in a state of high stress. Under the condition of a 10 m wide protective pillar, the peak vertical stress and energy density are shifted from the pillar to roadway virgin coal region, with peak values of 9.5 MPa and 208.3 kJ/m3, respectively. The decrease in vertical stress and energy density improves the stability of the protective pillar, resulting in the roadway being in a state of low stress. Field monitoring suggested that the proposed 10 m protective pillar width can effectively control the large deformation of the surrounding rock and reduce coal bump risk. The novel numerical modeling approach and design principle of protective pillars presented in this paper can provide useful references for application in similar coal mines.

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Field and numerical investigations on the lower coal seam entry failure analysis under the remnant pillar

Cited by 67 publications

References 23 publications

Optimization of staggered distance of coal pillars in multiseam mining: Theoretical analysis and numerical simulation

Optimization of staggered distance of coal pillars in multiseam mining: Theoretical analysis and numerical simulation

Determination of cyclic filling length in gob-side entry retained with roadside filling and its application

Numerical Analysis of the Width Design of a Protective Pillar in High‐Stress Roadway: A Case Study

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