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1

Study on pressure relief mechanism of hydraulic support in working face under directional roof crack

Zhang Jun, Liu Jianning, Wang Yajun, Yang Gang, Hou Shilin, Wang Yuanjun, He Manchao, Yang Jun

Archives of Mining Sciences

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2023

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Vol. 68, no. 1

103--123

EN

When mining coal from the working face, the main roof withstands the overlying strata. The main roof’s first weighting and periodic weighting may cause accidents, such as crushing the working face hydraulic supports. A mechanical model of the main roof was constructed, and the contributing factors of first and periodic weights on the main roof were examined in order to prevent such accidents. The thickness of the main roof was found as the most contributory factor to the main roof’s stability. Therefore, a new directional roof crack (DRC) technique is proposed, which produces directional cracks in the main roof through directional blasting and makes part of it collapse in advance so as to reduce the thickness and relieve the first and periodic weighting. To verify the effectiveness of DRC, the mechanism of DRC was analysed. A mechanical model of the hydraulic support was constructed, and the DRC techniques were tested on-site. Field experiments with a complete set of monitoring schemes showed that, with DRC technology, the roof periodic weighting interval decreased by 35.36%, and the hydraulic support pressure decreased by 17.56%. The theoretical analysis was consistent with the measured results. Therefore, the DRC technology is feasible and effective to ensure mining safety at the working face.

2

Air Pollution Regulations in China: A Policy Simulation Approach with Evolutionary Game

Chu Zhaopeng, Bian Chen, Yang Jun

Problemy Ekorozwoju

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2022

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Vol. 17, nr 1

222--233

EN

In the institutional context of China’s political centralization and fiscal decentralization, this study explores the environmental regulations that make the central and local governments join efforts in air pollution control. Policy simulations in an evolutionary game show that the best approach is to internalize environmental costs and benefits in local governments’ objective function. The effectiveness of several policy instruments is examined individually and jointly, including administrative inspection, transfer payment, and environmental taxes. It is shown that in case environmental consequences are not internalized, appropriate application of policy instruments can incentivize goal-oriented local governments to choose the socially optimal strategy.

PL

W kontekście instytucjonalnym chińskiej centralizacji politycznej i decentralizacji fiskalnej, niniejsze badanie analizuje regulacje środowiskowe, które zmuszają rządy centralne i lokalne do wspólnych wysiłków na rzecz kontroli zanieczyszczenia powietrza. Symulacje polityki w grze ewolucyjnej pokazują, że najlepszym podejściem jest internalizacja kosztów i korzyści środowiskowych w funkcji celu samorządu. Skuteczność kilku instrumentów polityki jest badana indywidualnie i wspólnie, w tym kontroli administracyjnej, płatności transferowych i podatków ekologicznych. Wykazano, że w przypadku braku internalizacji konsekwencji środowiskowych, odpowiednie zastosowanie instrumentów polityki może zmotywować zorientowane na cel samorządy lokalne do wyboru społecznie optymalnej strategii.

3

Application cumulative tensile explosions for roof cutting in Chinese underground coal mines

Yang Jun, Liu Binhui, Bian Wenhui, Chen Kuikui, Wang Hongyu, Cao Chen

Archives of Mining Sciences

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2021

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Vol. 66, no. 3

421--435

EN

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.

4

Study on intensive design and control of chamber group under the condition of weak surrounding rock

Yang Jun, Hou Shilin, Zhou Kaifang, Qiao Bowen, Wang Hongyu, Wei Qinglong

Mining Science

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2019

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Vol. 26

223--240

EN

In order to study the design and stability control of deep soft rock chamber group, taking ninth coal mine of Hebi Coal Power Co., Ltd. as the engineering background, The main problem in normal design is analyzed with the combined method of FLAC3D numerical simulation and field engineering test. and then puts forward targeted control measures and carries out field application. The results show that, compared with the conventional design, the intensive design can reduce the stress concentration degree and plastic zone range of the surrounding rock, as well as reduce the quantities. Compared with conventional supporting schemes, the surrounding rock deformation greatly reduces by more than 82% after adopting bolting and shotcreting with wire mesh + anchor cable + floor anchor supporting. Among them, the floor heave control has obvious effect, and the decreasing amplitude reaches more than 93%. The field application shows that the surrounding rock deformation of the main chamber is within the allowable range, and the chamber control effect is good. Therefore, the research results can provide reference for the design and control of similar chamber groups.