I. Core Classification and Application Scenarios of Inclined Shaft Bottom Yards

(1) The Two Basic Types Classified by Mine Car Operation Systems

As the critical hub of an underground mining transportation system, the importance of the inclined shaft bottom yard goes without saying. It not only serves as the vital link connecting the underground mining areas with the hoisting system in the shaft but also acts as the core zone for efficiently transferring ore, waste rock, materials, and equipment. Depending on the specific mine car operation system, the inclined shaft bottom yard is primarily divided into two basic types: the return-type yard and the loop-type yard.

Reversing Yard

This type of yard primarily uses stringing and lifting as its main hoisting method, making it widely applicable in medium- and small-sized metal mines. Its operational feature involves mine cars traveling back and forth on tracks located on both sides of the shaft—specifically, "loaded cars enter, while empty cars return." Typical connection methods for such a reversing yard include sidetracks, overhead bridges, and flat yards. Sidetracks facilitate the smooth transition of mine cars from inclined shafts to flat yards via controlled slopes and curves, while overhead bridges serve as a specialized transfer mechanism, particularly effective when the inclination angle of the inclined shaft exceeds 20 degrees. Meanwhile, flat yards provide the necessary space for parking, dispatching, and performing operations like coupling and uncoupling. By seamlessly integrating the reversing yard with storage tracks, this system ensures efficient vehicle scheduling and management.

Circular Parking Lot

Circular-type yards are generally suitable for large and medium-sized inclined shafts that use skip or belt hoisting systems. The design concept leverages a circular track, allowing empty cars to return via a bypass route, thereby enabling continuous transportation. This type of yard offers the advantage of high transportation efficiency, making it ideal for meeting the high-production demands of large and medium-sized mines. In some major coal mines, where output is substantial and transportation tasks are particularly heavy, implementing a circular-yard system can significantly boost overall efficiency, reduce vehicle waiting times, and lower operational costs.

(II) Key Selection Factors: A Comprehensive Consideration from Equipment Upgrades to Engineering Conditions

When selecting the layout of a bottom-track yard for an inclined shaft, it’s necessary to comprehensively consider multiple factors—factors that are interconnected and collectively influence the choice and design of the yard.

Enhance container type

The type of hoisting equipment is one of the key factors determining the layout of the mine yard. If a string car system is used, its flexibility and adaptability typically make it suitable for a return-type yard. In contrast, if skip or belt conveyors are employed—due to their high lifting capacity and continuous operation—they are better suited for a circular-yard configuration. In some small-scale metal mines, where production volumes are relatively low, adopting a string car system combined with a return-type yard can help reduce investment costs while enhancing operational efficiency. Meanwhile, in large coal mines—with their significantly higher output—using skip hoisting systems paired with a circular-yard design can more effectively meet the demands of intensive production.

Production capacity

Production capacity is one of the key factors in determining the type of yard layout. If a mine has high production capacity, it should opt for a yard design with large throughput, such as a loop-type yard. Conversely, if the production capacity is relatively low, a simpler, return-style yard layout would suffice. In some large-scale mines, where annual output is substantial, adopting a loop-type yard ensures rapid transportation of ore and significantly boosts productivity. Meanwhile, in smaller mines with lower annual output, implementing a return-style yard helps reduce both construction and operational costs.

Inclined Shaft Angle and Rock Stability

The dip angle of the inclined shaft and the stability of the rock significantly influence the connection method and layout of the car shed. When the dip angle of the inclined shaft exceeds 20 degrees, using a suspension bridge as the connecting device can effectively facilitate the transfer of mine cars. Conversely, if the rock stability is poor, appropriate support measures must be implemented to ensure the safety and stability of the car shed. In mines with particularly complex geological conditions, it’s essential to select suitable connection methods and support strategies tailored to the specific circumstances, thereby guaranteeing the smooth operation of the car shed.

Ground production system requirements and the rationality of chamber layout

The requirements of the surface production system and the rationality of chamber layout are also important factors to consider when selecting the type of haulage yard. The arrangement of the haulage yard should align seamlessly with the surface production system, ensuring smooth transportation of ores, waste rock, and other materials to the surface. At the same time, the placement of chambers must be carefully planned to facilitate equipment installation, maintenance, and safe operation by personnel. In some mines, due to varying demands of the surface production system, optimizing the layout of the haulage yard becomes essential for enhancing productivity and reducing operational costs.

II. Key Structural Analysis of Reversing Yards: Centered on String Car Lifting

(1) Siding and Flat Yard: A Typical Connection Scheme for Side-Loaded Cars

1. Sling Lane Structure and Operational Mechanism

The甩车道 is a critical inclined tunnel in the bottom car shed of a decline shaft, serving as the connection between the decline and the flat car shed. Typically branching off from the side wall of the decline, its slope closely mirrors that of the decline itself—usually ranging between 20° and 30°. The primary function of the甩车道 is to facilitate the smooth transition of mine cars from the decline’s track system to the horizontal tracks of the flat car shed. By strategically positioning switches along the lane, it ensures that mine cars can effortlessly move from the decline into the 甩车道 and then smoothly roll onto the flat car shed tracks.

The core structure of a bypass track includes a vertical curve transition section and a car-storing system. The vertical curve transition section is a critical component of the bypass track, as it gradually adjusts the incline angle of the inclined shaft track to the horizontal angle of the flat yard track through a specific radius of curvature. This ensures that mine cars can smoothly change direction during operation, preventing derailments or jolts caused by sudden angular shifts. Meanwhile, the car-storing system—a vital part of the bypass track—comprises empty-car lines and loaded-car lines, which are used to temporarily store loaded cars lifted from the inclined shaft and waiting empty cars ready for lowering. The length and slope of the car-storing lines must be carefully designed in consideration of factors such as the mine’s production capacity, the number of mine cars, and the shunting methods employed, ensuring that mine cars can be safely and efficiently parked and dispatched.

In engineering applications, the advantage of switchback tracks lies in their ability to accommodate varying inclinations of inclined shafts and diverse terrain conditions, while also facilitating the transportation of long materials. However, due to the substantial excavation required for switchback tracks and the relatively high construction complexity, it is essential to carefully consider geological conditions, construction techniques, and safety factors during both the design and implementation phases. Additionally, to ensure the safe operation of mine cars on switchback tracks, it is crucial to strictly control the lifting traction angle—typically keeping it below 10°—to prevent lateral overturning moments that could lead to derailment or tipping accidents.

2. Flat Car Yard: A Direct Transition Plan for Non-Extension Inclined Shafts

The flat yard is a simple and direct connection type of bottom-yard layout for inclined shafts. When the inclined shaft does not need to be extended downward, the flat yard can directly link the shaft tunnel with the bottom-yard facility. The track arrangement in a flat yard is relatively straightforward, typically consisting of a single section of horizontal track combined with turnouts. This allows mine cars to roll directly from the inclined shaft tunnel into the flat yard, where operations such as coupling/uncoupling and shunting can then be carried out smoothly.

The advantage of a flat car yard lies in its simple track layout, ease of construction, and low maintenance costs. Because the track lines in a flat car yard are relatively straight, mine cars maintain high stability during operation, resulting in significantly less wear on the steel cables. Additionally, flat car yards require fewer track switches, which helps reduce both the amount of tunnel excavation work and the cost of support structures—thereby boosting construction efficiency and enhancing economic benefits. For these reasons, flat car yards are well-suited for mines with favorable geological conditions, smaller production scales, or those where further extension of inclined shafts is not necessary.

(2) Suspension Bridge: An Efficient Conversion Device for Deck-to-Vehicle Operations

1. Standard Suspension Bridge: A Basic Design for Single-Phase Operations

The standard suspended bridge is a common device used to connect the inclined shaft with the bottom-level car shed; it typically consists of a bridge deck, supporting structures, and a drive mechanism. When the suspended bridge is lowered, mine cars can pass through it from the top plate of the inclined shaft into the bottom-level car shed. Conversely, when the bridge is raised, mine cars can continue moving up and down along the inclined shaft, effectively meeting transportation needs at different stages.

A notable feature of ordinary suspended bridges is their small engineering requirements, simple construction process, and ease of installation and maintenance. They are well-suited for small-scale mines with inclinations ranging from 20° to 35°, where transportation needs are relatively low due to the modest production volumes. In such settings, ordinary suspended bridges can effectively meet basic transport demands. However, these bridges also have certain limitations: for instance, empty carts need to be manually pushed, resulting in lower shunting efficiency, and they face challenges when transporting long materials. Additionally, to ensure the safe operation of the bridge, it is essential to equip it with dedicated signal chambers and pedestrian walkways, enabling operators to promptly monitor the bridge's status while guaranteeing the safe passage of personnel.

2. Suspension Bridge-Type Diversion Lane: An Upgraded Solution Adaptable to Multiple Conditions

The suspended bridge-style bypass track is a new type of connecting device that combines the functions of a suspension bridge and a bypass track. Through its ingenious design, it enables efficient transportation of both loaded and empty vehicles. In this system, loaded vehicles descend directly into the bottom-level yard via the suspension bridge from the inclined shaft roof, while empty vehicles are lowered through bypass tracks along the side walls. This innovative design effectively addresses the challenges associated with transporting long materials using conventional suspension bridges, while also enhancing the convenience of shunting operations.

The advantage of the suspended bridge-type transfer track is its ability to adapt to various operating conditions, making it suitable for multi-level operations in medium- and small-sized mines. While ensuring transportation efficiency, it also reduces the risk of mine cars derailing, minimizes wire rope wear, and enhances the safety and reliability of material transport. However, due to the relatively complex structure of the suspended bridge-type transfer track, construction is more challenging and demands higher technical expertise and extensive construction experience. Therefore, careful consideration of both site conditions and technical requirements is essential during the process of wider implementation and promotion.

3. Vertical and Horizontal Differential Suspension Bridge: Optimized Design for Self-Propelled Transport

The height-difference suspension bridge is an optimized solution designed specifically for gravity-assisted transportation. It features a dual-suspension-bridge structure, with separate tracks for empty and loaded vehicles, and utilizes crossover switches within inclined shafts to seamlessly switch between the two lines. In this system, both empty and loaded vehicles can rely on their own gravitational force to move autonomously, significantly reducing shunting time and boosting overall transportation efficiency.

The core advantage of a differential-height suspended bridge is that both empty and loaded mine cars can smoothly coast along the track on their own. This not only reduces energy consumption during transportation, lowering operational costs, but also enhances the automation level of the transport system. Meanwhile, since the speed of the mine cars remains relatively stable during self-coasting, the risk of derailment is minimized, and the wear on the steel cables is significantly reduced, further improving the safety and reliability of transportation. During construction, it’s essential to precisely design the bridge’s height difference and the layout of the track switches, ensuring that both empty and loaded cars can seamlessly engage in self-coasting and smoothly switch between tracks. The differential-height suspended bridge is one of the preferred solutions for medium- and small-sized mines aiming to boost transportation efficiency.

III. Core Points of Engineering Design: Balancing Safety with Cost-Effectiveness

(1) Chamber Layout and Functional Integration

As an essential component of the bottom-yard car shed in inclined shafts, the rational layout and functional integration of chambers are critical to the efficient operation of the entire yard. Around the shaft, a series of chambers with diverse functions must be constructed to meet various production needs.

The signal chamber serves as the control center for yard operations, responsible for managing the raising and lowering of the drawbridge as well as coordinating vehicle traffic. Equipped with advanced signaling control systems, operators can monitor vehicles' real-time status through this system and precisely issue various signal commands, ensuring the drawbridge rises or lowers at the right moment while allowing vehicles to enter and exit the yard safely and in an orderly manner. In some modern mines, the signal chamber has even achieved automated control, significantly enhancing both scheduling efficiency and accuracy.

Pedestrian walkways are critical facilities that ensure the safety of personnel, and their design must comply with relevant safety standards and regulations. The width, height, and lighting conditions of pedestrian walkways all need to meet the requirements for smooth passage, while also incorporating essential protective features—such as handrails and guardrails—to prevent accidents during movement. In some large-scale mines, pedestrian walkways are further integrated with other safety systems, creating a comprehensive evacuation network that guarantees people can swiftly and safely escape in emergency situations.

The car-storage tunnel chamber is designed for the segregated storage of empty and loaded vehicles, and its capacity and layout must be carefully planned according to the mine’s production scale and transportation requirements. The length of the car-storage tunnel should adequately accommodate a specific number of vehicles while also ensuring convenient and safe access for both entering and exiting. Inside the car-storage tunnel, auxiliary facilities such as wheel chocks and vehicle-handling machines are typically installed to facilitate efficient vehicle scheduling and management.

For large-scale mine shafts, it is also necessary to integrate critical chambers such as pump rooms and substations. The pump room is responsible for draining accumulated water from underground, ensuring safe and efficient operations in the mine; meanwhile, the substation provides essential power support for all production equipment throughout the mine. When arranging these chambers, careful consideration must be given to the spacing between them and their ventilation design, to prevent interference caused by equipment operation. Both the pump room and substation should maintain a safe distance from one another, while effective ventilation measures should be implemented to guarantee adequate air circulation and ensure the smooth functioning of the equipment. Additionally, fireproofing, waterproofing, and moisture-proofing measures must be taken for the chambers to enhance their safety and reliability.

(2) Tilt Angle Matching and Equipment Selection

Suspension Bridge Application Threshold

The dip angle of an inclined shaft is a critical factor influencing the selection of equipment for the bottom-of-shaft car shed and its operational efficiency. When the shaft inclination exceeds 20°, overhead bridges are preferably used as connecting devices, effectively preventing excessive wear on the sidings caused by the steep gradient. This is because overhead bridges operate smoothly, minimizing the impact forces experienced by mine cars as they traverse the bridge, thereby reducing wear on tracks and equipment. In mines with particularly steep inclines, the adoption of overhead bridges has significantly extended the service life of tracks and dramatically lowered maintenance costs.

However, when the incline angle of the inclined shaft exceeds 30°, it becomes essential to rigorously calculate the self-sliding gradient of the mine cars to ensure that empty cars can move smoothly under gravity. This is because, at steep inclines, the speed of a mine car’s self-sliding increases significantly. If the self-sliding gradient is not properly designed, it could lead to dangerous situations such as loss of control or derailment. In practical engineering applications, the self-sliding gradient is typically calculated precisely based on factors like the type and load capacity of the mine car, as well as the friction coefficient of the track. Additionally, appropriate safety measures—such as installing car stoppers or speed-limiting devices—are implemented to guarantee the safe and smooth operation of empty cars.

Enhance equipment matching

When selecting hoisting equipment, it is essential to match it appropriately based on the layout of the mine yard and the specific transportation requirements. In cases where series-hoisting systems are paired with return-type mine yards, the design of the storage track length becomes critically important. The length of the storage track should be carefully determined by considering factors such as the tonnage of the mine cars, the number of cars lifted in each cycle, and the frequency of lifting operations—ensuring that the storage track can adequately accommodate vehicle parking and scheduling needs. If the storage track is too short, it may lead to vehicle congestion, thereby reducing hoisting efficiency; conversely, if the track is excessively long, it will increase both capital investment and maintenance costs.

In cases where the hoisting system is equipped with a ring-type yard for skip operations, the efficiency of the connection between the loading chamber and the belt conveyor directly affects the overall production capacity of the transportation system. The design of the loading chamber should enable quick and precise loading of skips, while also ensuring seamless coordination with the belt conveyor system to guarantee that ore is transported to the surface promptly and efficiently. In some large-scale mines, the adoption of automated loading equipment and advanced belt conveyor control systems has significantly enhanced the efficiency of the loading chamber-belt conveyor interface, enabling continuous and rapid ore transportation.

(III) Construction and Maintenance Cost Control

During the construction and operation of the bottom yard in inclined shafts, construction costs and maintenance expenses are key factors that require careful consideration. The bypass track and suspension bridge, as two common connection methods, each have distinct characteristics in terms of construction and maintenance costs.

The excavation work for the bypass track is relatively extensive, as it requires cutting an inclined tunnel along the side wall of the inclined shaft, along with the complex tasks of laying tracks and installing switches. However, once completed, the bypass track demands relatively simple long-term maintenance. Due to its structurally stable design, wear and tear on tracks and equipment are minimal, resulting in lower maintenance effort and costs. In mines with favorable rock conditions, utilizing a bypass track can fully leverage its advantages—though initial investment may be higher, it ultimately helps reduce operational expenses over the long term.

Initially, suspension bridges have relatively low costs because their structure is comparatively simple, construction is less challenging, and they require fewer materials and equipment. However, suspension bridges demand regular maintenance of their mechanical components to ensure safe and reliable operation. The mechanical systems of a suspension bridge include the bridge deck, supporting structures, drive mechanisms, and other parts, all of which can suffer from wear and corrosion over time. Therefore, these elements must undergo periodic inspections, upkeep, and replacement as needed. In some smaller mines, where funding is limited, opting for a suspension bridge can help reduce upfront investment—but it also requires enhanced maintenance and management practices to keep the structure functioning properly.

In engineering practice, it is necessary to conduct a comprehensive comparison and selection, taking into account factors such as the mine's service life and rock stability. For mines with shorter service lives and poorer rock stability, prioritizing suspended bridges can help reduce both the cost and complexity of roadway support. Conversely, for mines with longer service lives and better rock stability, adopting skip hoists can lower equipment investment and long-term operating expenses. In one small-scale mine, where the service life was relatively short and rock stability poor, the use of suspended bridges not only minimized initial capital outlay but also significantly cut down on the labor and costs associated with roadway support. Meanwhile, in a larger mine—with its extended service life and superior rock stability—switching to skip hoists, though requiring a higher upfront investment, ultimately led to reduced equipment maintenance costs and lower overall operational expenses over time. By carefully evaluating and selecting the most suitable connection method, it’s possible to effectively control construction and maintenance costs, thereby enhancing the mine’s economic profitability.

IV. Case Study Analysis: Selecting the Optimal Solution for Different Well Types

(1) Small Metal Mines: Economical Application of Simple Suspension Bridges

In a small-scale metal mine with a designed production capacity of 90,000 t/year, classified as a low-gas mine with stable strata conditions, the mine employs an inclined shaft development method featuring a shaft inclination angle of 22°. During the extraction of the C8 coal seam, the mine faces challenges related to multi-level transportation. To address this issue, the mine has implemented a conventional suspended bridge system to connect the intermediate-level car yards.

The application of a conventional suspension bridge has brought numerous benefits to this mine. Thanks to its relatively simple structure and shorter construction period, the bridge can be quickly put into operation, effectively meeting the mine's production schedule needs. Moreover, the ease of maintenance for a conventional suspension bridge significantly reduces operational costs and management challenges, making it an ideal choice for smaller mines that may have limited financial resources and technical expertise. At the bridge’s leveling point, a signal chamber has been installed, enabling centralized control over both the bridge and vehicles—thus enhancing the safety and reliability of material transportation. While the manual cart system used in lowering materials offers comparatively lower efficiency, it still adequately supports the production scale and transportation demands of this small-scale mine. Overall, this solution clearly demonstrates the economic viability and practicality of conventional suspension bridges in small mining operations, providing valuable insights for designing similar underground car parks in other mines.

(II) Medium-Sized Inclined Shaft Project: Efficient Implementation of the Suspension Bridge-Type Diverging Track

A medium-sized mine features a decline shaft with a 25° inclination angle. In the design of the bottom-level car shed, an overhead bridge-type reversing track system was adopted. The implementation of this solution has significantly improved the mine's transportation efficiency.

In this scheme, loaded vehicles enter the main shaft's heavy-vehicle track directly via the overhead bridge, while empty cars are allowed to roll freely onto the sidetrack and then be shunted to the marshalling yard. This design reduces single-car shunting time by 40%, significantly boosting vehicle turnover efficiency. The dual-track layout effectively prevents blockages of long materials during transportation, ensuring smooth operations. By optimizing the track layout and selecting appropriate equipment, the方案 fully leverages the advantages of the overhead-bridge sidetrack system, enhancing the overall efficiency of the transportation system and meeting the medium-sized mine's demands for transport capacity. This case demonstrates that, in medium-scale inclined-shaft projects, the overhead-bridge sidetrack system is an efficient and reliable choice, providing strong support for safe production and highly effective mine operations.

V. Conclusion: Optimizing Shaft Bottom Yard Design with Systems Thinking

The design of a decline shaft bottom car shed is fundamentally a systems engineering endeavor aimed at "enhancing efficiency, ensuring safety, and controlling costs." From the flexibility and adaptability of return-type sheds to the high efficiency and compactness of loop-type designs, and from the side-wall connections in skip hoisting lanes to the ceiling transitions in overhead bridge layouts—each solution must align closely with the specific conditions of the mine. In engineering practice, the optimal balance between technical feasibility and economic viability should be achieved, taking into account the characteristics of lifting equipment, the geological conditions of the ore body, and long-term production plans, thereby laying a solid foundation for the efficient operation of the mine.