Key Takeaways & Executive Findings
- •• The N00 mining approach significantly reduces entry roof settlement compared to the conventional 121 approach, enhancing entry stability and safety. • By incorporating roof cutting and NPR cable support, the N00 approach optimizes the mining and entry formation process, reducing the settlement phase and improving roof steadiness. • The N00 approach lowers hydraulic support pressure in the mining panel, mitigating severe mining pressure manifestations and improving operational safety. • Field monitoring confirms the effectiveness of the N00 approach in protecting both entries and mining panels, offering a promising alternative for coal mining.
Abstract
Addressing the issues of significant entry settlement and severe mining pressure manifestations in the conventional 121 approach, an innovative N00 approach is proposed. By comparing the mining process and entry formation process of different approaches, the characteristics of entry roof settlement evolution under different approaches are obtained. The N00 approach, which incorporates roof cutting and NPR cable support, optimizes the mining and entry formation process to reduce the settlement phase of entry roof, decreases the settlement of entry roof, and enhances the steadiness of entry roof. The N00 approach modifies the entry roof structure through roof cutting and establishes a hydraulic support load mechanics model for the mining panel to derive the theoretical load pressure formula for the N00 approach’s hydraulic support. Compared with the conventional 121 approach, the pressure on the N00 approach’s hydraulic support is reduced. Empirical data obtained through field monitoring demonstrate that the N00 approach has reduced the roof settlement of the entry and weakened the mining pressure manifestation at the mining panel, achieving the goal of protecting the entry and mining panel.
1. Introduction
An escalation in the output and utilization of coal frequently serves as an indicator of an expanding economy [1]. China has witnessed a substantial augmentation in its raw coal production, rising from 1.384 billion metric tons in the year 2000 to a substantial 4.71 billion metric tons by the year 2023, marking an impressive 2.40-fold enhancement. The rapid growth in raw coal production and coal consumption has driven the rapid development of China’s economy [2−5]. The main mining approach currently used in China is the 121 approach, which requires the advance excavation of two entries for the mining of one mining panel, and one protective coal pillar must be left between adjacent mining panels [6]. The 121 approach has made significant contributions to China’s coal industry. However, with the increase in coal production, problems in the production process of the conventional 121 approach have become increasingly prominent, and severe safety challenges are faced during mining [7].
The conventional 121 approach, which involves the retention of protective coal pillars, is susceptible to the concentration of stress within these pillars [8, 9], causing hidden safety hazards in the entries, and insufficient roof support leads to severe settlement of the entries roof [10, 11]. In addition, the mining panel exhibits severe mining pressure manifestations and high hydraulic support pressure [12, 13]. These factors collectively impinge upon the safety and efficiency of the mining panel’s operational productivity. In response to the aforementioned challenges, backfill is one of the main control means in the mining process of the 121 approach [14, 15]. In addition, with a large number of studies on mining approaches and entry support [16, 17], the authors’ research team has researched and proposed the 110 approach [18−21], which uses roof cutting and NPR cable support, eliminates the requirement for coal pillars traditionally situated between adjacent mining panels, averting incidents that may arise from the stress concentration of coal pillars, optimizes the stress distribution, attenuates the settlement of the entry roof, and augments the overall steadiness of the entry. However, although the 110 approach solves the problem of entry steadiness, it still requires the prior excavation of entries before the mining panel is mined, and most entry accidents occur during the excavation of the entries. To solve this problem, the authors’ research team further proposed the N00 approach [22 −24], which, on the basis of roof cutting and NPR cable support, chang
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ZHANG Jun, HE Man-chao, WANG Ya-jun, YANG Gang, HOU Shi-lin, CHEN Yu-wen, KANG Xu-hui, SHI Zhen, FU Qiang, DU Fu-kang (2025). An innovative N00 mining approach for protecting entries and mining panels. Journal of Central South University. https://doi.org/10.1007/s11771-025-6074-4
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Frequently Asked Questions
What is the N00 mining approach?
The N00 mining approach is an innovative method that incorporates roof cutting and NPR cable support to optimize the mining and entry formation process, reducing entry roof settlement and enhancing stability, thereby protecting entries and mining panels.
How does the N00 approach compare to the conventional 121 approach?
Compared to the conventional 121 approach, the N00 approach reduces the pressure on hydraulic support, decreases entry roof settlement, and weakens mining pressure manifestations, improving safety and efficiency.
What are the key benefits of the N00 approach?
Key benefits include reduced entry roof settlement, enhanced entry steadiness, lower hydraulic support pressure, and improved protection of both entries and mining panels, as demonstrated by field monitoring.
What is the role of roof cutting in the N00 approach?
Roof cutting modifies the entry roof structure, which helps in reducing the settlement phase and overall settlement of the entry roof, contributing to the stability and safety of the mining operation.
What is the significance of NPR cable support in the N00 approach?
NPR cable support provides additional reinforcement to the entry roof, enhancing its steadiness and preventing severe settlement, which is crucial for maintaining safe mining conditions.
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