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Single-Unit Hydraulic Prop and Hinged Roof Beam Support Arrangement—Heijinggang Broadcast
In ordinary mechanized coal mining operations (commonly referred to as "Pucai") in coal mines, face support is the core component that ensures both safe production and efficient extraction. It not only needs to withstand the pressure from the roof strata and prevent roof collapses but also provides a stable working space for the operation of mining equipment and the movement of personnel. Among various support methods, the combination of single hydraulic props and articulated roof beams has become the mainstream approach for Pucai faces. The arrangement of this system, along with the design of end-head supports, directly influences the overall effectiveness of the support structure. This article will systematically review the key principles underlying this technical framework.
I. The Core Supporting Elements of the Fully Mechanized Mining Face: Single-Unit Hydraulic Props and Hinged Roof Beams
Single hydraulic props, with their advantages of high supporting capacity and stable initial support force, have become the primary load-bearing components in fully mechanized mining faces. Meanwhile, hinged roof beams utilize a mortise-and-tenon structure to achieve continuous connections among multiple beams, allowing them to flexibly adapt to undulations in the roof plate. Together, these two elements form a "point pillar + continuous beam" support system, which effectively distributes roof pressure while preventing localized roof caving. In practical applications, the layout of this system is typically categorized into two main dimensions: one based on the "relative relationship between cantilevered roof beams and supports," and the other based on the "characteristics of roof beam arrangement."
II. Two Core Arrangement Methods for Single-Unit Hydraulic Props and Hinged Roof Beams
(1) According to the relationship between the cantilever top beam and the support pillars: normal cantilever vs. inverted cantilever
The core difference between the two arrangement methods lies in the orientation of the cantilevered end of the roof beam, which directly determines the emphasis placed on supporting the coal wall and the side of the goaf area.
The positive cantilever arrangement features the cantilevered end of the roof beam facing the coal wall on the working face side, while individual support pillars are positioned at the end of the roof beam closer to the gob area. This structural design offers a key advantage: the cantilevered end provides timely support for the newly exposed roof (in the freshly mined area right in front of the coal wall), significantly reducing the duration during which the roof remains unsupported. Additionally, by positioning the pillars away from the coal wall, interference with the mining machine during operation is effectively avoided. This setup is particularly well-suited for working faces where the roof remains relatively intact and the coal wall is less prone to rib spalling, making it the most widely adopted configuration today.
Inverted cantilever arrangement: The cantilevered end of the roof beam faces toward the gob side, while the supporting pillars are positioned closer to the coal face. Its primary function is to reinforce the coal wall through the "pillar close to the coal face" design, effectively preventing rib spalling—especially in loose and soft coal seams. At the same time, the cantilevered end can extend over the edge of the gob, reducing the risk of fractured roof material from the gob entering the working face. However, it’s important to note that, with this setup, the pillars are placed close to the coal face, requiring sufficient clearance for mining equipment to pass through. This arrangement is typically employed in working faces where coal wall stability is poor and rib spalling is a significant concern.
(2) By Top Beam Arrangement Characteristics: Straight-Beam Type vs. Staggered-Beam Type
The arrangement of roof beams determines the continuity and uniformity of the support system, and should be selected based on the degree of roof fracturing as well as the working face parameters.
Qilang-style arrangement: All articulated roof beams are neatly aligned at their ends along the working face’s direction (advancement direction), while individual support pillars are also arranged in a straight line perpendicular to the roof beams. This layout offers several advantages: it ensures uniform support strength and clear load distribution, standardizes the installation and removal procedures for both roof beams and pillars, making it easier for workers to perform tasks swiftly. Additionally, the seamless roof coverage effectively prevents localized roof caving. This arrangement is ideally suited for scenarios where the working face length remains stable, and the roof pressure is evenly distributed and intact—such as in longwall mining operations involving medium-to-thick coal seams or gently inclined coal beds.
Misaligned beam arrangement: The ends of adjacent hinged roof beams are arranged in an alternating, interlocking pattern (resembling a "locking" structure), and the supporting pillars are also staggered according to the positions of the roof beams. Its core advantage lies in "staggered support"—by having the roof beams overlap and cover the fractures in the roof plate, it significantly reduces the risk of coal spillage when the roof breaks. Meanwhile, the staggered arrangement of pillars creates "distributed stress points," enabling the system to better accommodate localized undulations or uneven pressure on the roof. However, this method is relatively complex to implement, requiring precise control over the spacing between roof beams, and is typically used in working faces where the roof is prone to breaking or features localized geological structures, such as small faults.
III. Key Stage: Three Typical Forms of Working Face End Support
The face end—where the working face meets the return roadway—is a weak link in the support system. This area experiences concentrated roof pressure (due to the combined influence of both the working face and return roadway stresses), while also needing to accommodate space requirements for coal transportation, pedestrian traffic, and equipment movement. Therefore, a targeted support design is essential. Currently, the three main types of face-end support systems are:
1. Monolithic pillar + hinged top beam support
This is the most basic type of end-head support, directly utilizing the "pillar + roof beam" combination already in place for the main working face. By reducing the spacing between pillars—typically by 20%–30% compared to the main working face—the load-bearing capacity at the end head is significantly enhanced. Its advantages include a simple structure, flexible assembly and disassembly, and low cost, as it doesn’t require any additional specialized equipment. However, the support strength is limited, making it suitable only for longwall faces with relatively low end-head pressures and slower advancing speeds (≤2 meters per day), such as those working in thin coal seams or small-scale mines.
2. 4-5 pairs of extended beams + monolithic support pillars for stepped heading roof support
To address the issue of "continuous support at the end headings," this system employs extended, hinged roof beams measuring 1.8 to 2.4 meters in length—50% to 80% longer than standard roof beams—which are paired and combined with single hydraulic props to form a "cantilevered canopy" structure. At its core lies the principle of "step-by-step movement": four to five pairs of these extended beams are divided into two groups. While one group supports the roof, the other advances by retracting the supporting props and moving the roof beams forward—a process known as "stepping." The two groups alternate their operations, ensuring that the end heading maintains continuous support at all times. This approach delivers high support strength and is well-suited for scenarios requiring rapid advancing speeds (2–3 meters per day), while also accommodating the transportation space along the roadway. It is currently the preferred solution for medium-pressure end headings.
3. Basic Support Structure + Walking-Style Step-and-Lift Roof Support
For scenarios involving concentrated end-head pressures—such as in deep mining operations or working faces with thick coal seams—this support system builds upon the "stepped roof beam" design by adding "basic supports" that align precisely with the main working face area (e.g., reinforced single hydraulic props paired with double-hinged roof beams). The basic supports handle routine support tasks in the conventional end-head region, while the stepped roof beams focus on reinforcing the "stress concentration zone" where the entryway meets the working face, creating a "double-layered protective barrier." This approach offers significant advantages, including strong load-bearing capacity (capable of supporting roof pressures ≥300 kN per prop) and excellent adaptability to complex geological conditions. However, it comes at a higher cost and is typically employed in large-scale mines, high-gas environments, or deep-level longwall mining operations.
IV. Principles for Selecting Support Systems in Fully Mechanized Mining Faces
The rationality of the support scheme directly determines mining safety and efficiency; therefore, three core principles must be followed when making your selection:
Roof condition takes priority: For intact roofs, prefer the "positive cantilever + flush-beam" system; for fractured roofs, choose the "offset-beam" system; and for coal seams prone to rib spalling, opt for the "inverted cantilever" method.
Match mining parameters: Workfaces advancing at high speed should prioritize using "step-by-step roof support," while slower-moving workfaces can opt for "standard single units + roof beams."
Balancing safety and efficiency: While ensuring the roof support strength (initial jacking force ≥ 50 kN per pillar), prioritize designs that are easy to assemble and disassemble, thereby minimizing the impact of support operations on the coal mining cycle.
