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Abstract

The technology for gob-side entry retaining in steep coal seams is still in the development stage. The

analysis results of the caving structure of main roof, low influence of gateway’s stability because of long

filling distance and weak dynamic effect of the gateway, and the low stress redistribution environment

indicate that using this technology in steep coal seams has significant advantages. Moreover, to reinforce

the waste rock and the soft floor and to better guard against the impact of the waste rock during natural

filling, a rock blocking device and grouting reinforcement method were invented, and theoretical calculations

result show that the blocking device has high safety factor. In addition, we also developed a set of

hydraulic support devices for use in the strengthening support zone. Furthermore, because the retaining

gateway was a systematic project, the selection of the size and shape of the gateway cross section and its

support method during the initial driving stage is a key step. Thus, first, a section the size of bottom width

and roof height of a new gateway was determined to meet any related requirements. Then, according

to the cross sections of 75 statistical gateways and the support technique, it chosen a trapezoidal cross

section when the dip of the coal seam is 35° < α ≤ 45°, a special and an inclined arch cross section when

45° < α ≤ 55°. Eventually, a support system of bolts and cables combined with steel mesh and steel belts

was provided. The support system used optimized material and improved parameters, can enhanced the

self-bearing ability of the surrounding coal and rock masses.

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Authors and Affiliations

Hongyun Yang
Shugang Cao
Guisong Zhou
Yuan Zhao
Guodong Li
Yong Li
Yingchong Fan
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Abstract

Cumulative blasts are an important controlled blasting method used to control the propagation of cracks in the predetermined direction. However, traditional cumulative blasts are associated with long processing times and poor blasting effects. A simple blasting technology called bilateral cumulative tensile explosion (BCTE) is proposed in this paper. There are two application types where BCTE is used. The first application is used to control the stability of high-stress roadways in both Wangzhuang mine 6208 tailgate and Hongqinghe mine 3-1103 tailgate. The second application is used to replace the backfill body in gob-side entry retaining (GER) in Chengjiao mine 21404 panel, Jinfeng mine 011810 panel and Zhongxing mine 1200 panel. The first application type reveals that BCTE can significantly reduce the deformation of the surrounding rock and reduce the associated maintenance cost of the roadways. Whereas the second application type, the roadway deformations are smaller, the process is simpler, and the production costs are lower, which further promotes GER and is of significance towards conserving resources.
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Authors and Affiliations

Jun Yang
1
ORCID: ORCID
Binhui Liu
1
ORCID: ORCID
Wenhui Bian
1
ORCID: ORCID
Kuikui Chen
1
ORCID: ORCID
Hongyu Wang
1
ORCID: ORCID
Chen Cao
2
ORCID: ORCID

  1. China University of Mining and Technology, State Key Laboratory for Geomechanics and Deep Underground Engineering, Beijing 100083, China
  2. University of Wollongong, Mining & Environment Engineering, School of Civil, Wollongong, NSW 2522, Australia
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Abstract

There are many problems associated with the surrounding rocks of the gob-side entry retaining by roof cutting (GERRC) as they are difficult to stabilise in deep mines. The following needs to be studied to understand the problems such as the pressure relief mechanism, evolution law of the surrounding-rock stress and the key technologies of GERRC in deep mines. Cracks are formed by advanced directional blasting to sever the path of stress transmission from the roof of the goaf to the roof of the entry and reduce the lateral cantilever length of the roof. Therefore the surrounding-rock stress and roof structure are optimised. The broken and expanded gangue formed by the collapse of the strata in the range of roof cutting fills the mining space adequately, which avoids a rapid pressure increase caused by the roof breaking impact and slows down the movement of overlying strata. The deformation of the deep surrounding rocks is transformed from “abrupt” to “slow”, and the surrounding-rock deformation of the retained entry in deep mines is significantly reduced. The average pressure and periodic pressure of the supports near the blasting line can be reduced by the blasting cracks to a certain extent, mainly due to the reduction of the length of the immediate roof cantilever and the effective load of the main roof. The combined support technologies for GERRC in deep mines were proposed, and field tests were performed. The monitoring results show that the coordinated control system can effectively control the deformation of deep rock masses, and all indexes can meet the requirements of the next working face after the retained entry is stabilised.
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Authors and Affiliations

Shangyuan Chen
1
ORCID: ORCID
Qian Lv
1
ORCID: ORCID
Yue Yuan
2
ORCID: ORCID

  1. School of Civil and Architectural Engineering, Anyang Institute of Technology, Anyang, Henan 455000, China
  2. Work Safety Key Lab on Prevention and Control of Gas and Roof Disasters for Southern Coal Mines, Hunan University of Science and Technology, Xiangtan Hunan 411201, China

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