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From an engineering perspective, examining the central parallel, central diagonal, and flank diagonal configurations
Central Parallel-Type Ventilation Shaft Arrangement
Concepts and Structural Features
In the central parallel arrangement, the intake shaft and exhaust shaft are centrally located at the center of the mining area, creating a "single shaft with dual shafts" configuration. Fresh airflow descends from the intake shaft to the bottom-level station, then disperses via stage-level transport drifts to reach individual working faces. Meanwhile, exhausted air is collected and discharged through the return shaft. Typically, the distance between the two shafts is maintained at 30–50 meters, and the bottom-level stations are shared, resulting in a compact industrial site layout. This arrangement leverages a centralized ventilation network to ensure rapid airflow circulation; however, the return-style airflow path leads to a circular ventilation pattern that follows the sequence of "intake—working area—return."
Pros and Cons Technical Analysis
Advantages:
- Infrastructure efficiency stands out. : Centralized layout reduces the volume of roadway development work, consolidates industrial sites, shortens the mine construction period, and lowers initial investment costs by approximately 20% to 30%.
- High management convenience : The co-location of the two shafts facilitates centralized installation and maintenance of ventilation equipment, while unified dispatching at the bottom car shed enhances material transportation efficiency.
- Reverse ventilation operation is convenient. : The close-proximity shaft layout enables the reverse ventilation system to respond swiftly, allowing for a rapid switch in airflow direction during emergencies and ensuring enhanced safety.
Drawbacks:
- Shortcomings in ventilation efficiency : Long-distance return airflow leads to increased ventilation resistance (15%-20% higher than diagonal systems), with air leakage rates reaching 12%-15%, making it easy for remote mining areas to experience insufficient airflow.
- Limited Emergency Exits : The closely spaced, centrally arranged shafts create a "single-point safety exit" hazard, increasing the risk of airflow short-circuiting during disasters such as fires.
- Air source quality issues :The air intake shaft is susceptible to industrial-site pollution, and during deep-mining operations, geothermal heat and accumulated gas can compromise the quality of the ventilation source.
Applicable Conditions and Engineering Practices
Applicable Conditions : The longwall face length is less than 4 km, and the orebody dips at an angle greater than 30°; however, fault zones and fracture zones on both sides make it unsuitable to establish shafts there.
Typical scenario : Small-scale mine initial construction, steeply inclined thin ore body mining, and surface-restricted valley terrain mining areas;
Optimization Measures : By renovating the shaft bottom car shed sealing system (reducing the air leakage rate to below 8%) and optimizing the zoned ventilation network, we can enhance ventilation efficiency for medium- and short-distance operations.
Central diagonal ventilation shaft arrangement
- Concepts and Structural Features The central diagonal system employs an asymmetric layout featuring "central intake—side-wing return airflow," which is divided into a two-shaft configuration (single-wing return) and a three-shaft configuration (double-wing return). The intake shaft is located at the center of the mining field, while the return shafts are positioned along the shallow boundaries of one or both wings, creating a "straight-through" ventilation pathway: fresh air flows downward via the central intake shaft, spreads horizontally through the stage-level transport drifts toward the working faces on either side, and then exhausted as stale air through the side-wing return shafts. The three-shaft setup, by adding an additional side-wing return shaft, establishes a bidirectional airflow channel, effectively reducing the ventilation distance on each side.
- Pros and Cons: Technical Analysis – Advantages ：
- Ventilation Performance Optimization :The airflow route, positioned closer to the central parallel layout, is shortened by 30%-40%, reducing ventilation resistance by 25%. Air leakage is controlled within 8%, while airflow in remote mining areas is increased by 15%.
- Enhanced Safety Performance : The side-wing return air shafts are located away from the industrial site, minimizing the impact of contaminated air and noise; additionally, the multi-shaft layout enhances safety exits, bolstering disaster-resistance capabilities.
- Wind Source Quality Assurance :The air intake shaft is located in the central clean zone, while the exhaust shaft is situated away from residential areas, ensuring compliance with environmental protection requirements.
Disadvantages ：
- Initial construction costs are high. :The Mitsui method increases the excavation volume by 20%-25% compared to the two-shaft method, raises initial investment by 15%-20%, and extends the construction period by 3 to 6 months;
- Crossing technology presents significant challenges. When the flank return airway needs to pass through complex geological structures, the initial breakthrough project is prone to risks such as sudden water inrush and collapse.
- Maintenance costs are rising : The dual-return ventilation system requires independent fans and a reverse-air device, leading to a 10%-15% annual increase in equipment operation and maintenance costs.
(III) Applicable Conditions and Engineering Practices
Applicable Conditions : The longwall face extends 4–8 km in length, with orebody dips ranging from 15° to 45°; the side walls feature stable rock formations suitable for shaft development.
Typical scenario : Medium-sized mines with large-scale mining operations, medium-gas-level mines, and coalfields with a low propensity for spontaneous combustion;
Optimization Measures : Adopting a transitional scheme of "central intake shaft + single-wing return shaft" (initially a two-shaft system), which will be expanded into a three-shaft system as mining depth increases, balancing initial investment with long-term ventilation needs.
Side-wing diagonal ventilation shaft arrangement
Concepts and Structural Features
The diagonal layout with side-entry shafts positions the intake and return shafts on opposite wings of the mining field, creating a fully diagonal arrangement such as "intake on the left wing—return on the right" or "intake on the right wing—return on the left." Fresh airflow enters through the intake shaft on one wing, traveling longitudinally across the entire mining field via stage-level transport drifts, while stale air is exhausted via the return shaft on the other wing, forming a straightforward ventilation pathway. This layout eliminates the need for centrally concentrated shafts, reduces the necessity for maintaining protective pillars, and enhances the overall integrity of ore-body extraction.
Pros and Cons: Technical Analysis – Advantages:
- Exceptional ventilation efficiency : The straight-line airflow path is the shortest (more than 50% shorter than the central parallel type), resulting in minimal ventilation resistance and a leakage rate of less than 5%. It is particularly well-suited for long-advancing mine fields.
- Outstanding safety performance : The dual shafts are arranged on two separate wings, creating independent safety exits. In case of a fire, this design allows for zoned isolation and ventilation, enhancing fire safety by 30% while also facilitating the dilution and dispersion of gas.
- Resource Utilization Optimization : Reducing the central safety pillar increases the ore recovery rate by 5%–8%, making it ideal for mining high-value ore bodies.
Drawbacks:
- Initial breakthrough is challenging. : The two wing shafts must be constructed simultaneously; however, discrepancies in progress are likely to occur when passing through different geological layers, requiring a breakthrough accuracy of up to ±0.5 meters.
- Increased transportation costs : The separate placement of the intake and return air shafts on either side results in a 10%-15% increase in material transportation routes, thereby boosting auxiliary underground transport efforts.
- High management complexity : The dual-well independent ventilation system requires real-time coordination to maintain balanced air pressure, making it highly dependent on an automated monitoring system.
Applicable Conditions and Engineering Practices
Applicable Conditions : The longwall face extends over 8 km, with orebody dips of less than 30°, and the ground on both sides is open and features stable rock strata.
Typical scenario : Large-scale mine with long-distance extraction, high-gas or easily self-combustible coal seams, and mining areas with no significant surface topographical constraints;
Optimization Measures : The "Intelligent Wind Pressure Balancing System" dynamically adjusts the rotational speeds of the dual-wing fans, while combining drone inspections to assess the geological stability around the shafts, ensuring reliable long-distance ventilation.
- Layout Comparison and Selection Recommendations Different ventilation shaft arrangement methods show significant differences in technical and economic indicators. To optimize the ventilation system, it is essential to conduct a scientific selection tailored to the actual conditions of the mine. Below is a comparison of ventilation shaft arrangements based on the length of the mining field (Table 1):
| Comparison Metrics | Central Parallel Style | Central Diagonal Type | Side-wing diagonal layout |
| Well-Field Strike Length | <4km | 4-8km | > 8km |
| Ventilation Route Characteristics | Return-style, long-distance | Straight-through, medium distance | Straight-through, short-distance |
| Initial investment | Low (100% baseline) | Medium (120%-130%) | High (150%-180%) |
| Safety Exit Advantages | Single Centralization | Central + Side Dual Outlets | Two independent wings with dual outlets |
| Applicable Disaster Types | Low gas content, non-combustible | Moderate gas content, low spontaneous combustion | High-gas, easily combustible |
Here are the selection recommendations:
1. Short-access mine : Prioritize the central parallel layout due to its low initial investment, high infrastructure efficiency, and ease of centralized management—making it ideal for mines with a shaft field length of less than 4 km.
2. Medium-to-long-term approach to the mine : The central diagonal layout is recommended, as it offers a balanced ventilation route that effectively balances ventilation efficiency with construction costs, making it suitable for mines with shaft field lengths ranging from 4 to 8 km.
3. Chang heads to the high-risk mine :The diagonal flank layout is the preferred solution, offering high ventilation efficiency and outstanding safety performance. It effectively addresses complex mining environments characterized by high gas concentrations and spontaneous combustion risks, making it ideal for mines with a field length exceeding 8 km. The selection of the ventilation shaft arrangement must carefully balance various factors, including geological conditions, mining scale, and safety requirements, to achieve multi-objective optimization. In practical applications, digital ventilation simulation tools—such as Ventsim modeling—can be employed to simulate airflow patterns and pressure drop distributions across different design options, providing a clear visual representation of ventilation performance. This approach not only supports informed decision-making during scheme comparisons but also enables the implementation of "one mine, one tailored solution" for precise, site-specific designs.
