Definition and Core Advantages of Segmented Straight Shafts

Principles of Structural Design

The segmented direct chute well is a specialized type of chute well designed by offsetting the upper and lower openings of each stage by a certain distance, enabling segmented, relay-style transportation. At its core, this design breaks away from the traditional vertical-through structure of conventional direct chute wells, achieving independent operation across multiple stages via spatial misalignment. While retaining the efficient, gravity-driven transport characteristics of straight chutes, it also addresses the critical challenge of coordination in multi-stage mining operations. This innovative design is particularly well-suited for mines with complex geological conditions and those conducting simultaneous production at multiple levels. By implementing staged control, it minimizes the potential impact area of accidents in any single chute, thereby enhancing the overall reliability of the system.

Core Advantage: Segmented Independence and Accident Isolation

Compared to traditional vertical chutes, the greatest advantage of the segmented design lies in "fault isolation." When a particular section of the chute stops operating due to issues such as blockages, wear, or surrounding rock instability, only the gate at that specific segment needs to be closed—allowing the upper and lower sections to continue production via independent chutes, thus avoiding the risk of shutting down the entire system. For instance, after implementing a segmented chute system at a certain metal mine, capacity losses caused by localized chute maintenance were reduced from 20% under the conventional approach to just 5%, significantly enhancing production continuity.

Detailed Explanation of Two Typical Arrangement Forms

Waterfall-style chute: The "ore slide" where inclined chutes pass the load接力

        Structural Features and Operational Mechanisms

In the previous stage, the chute was rigidly connected to the chute in the next stage via an inclined chute, creating a "step-like" transfer channel. After ore descends from the upper-stage chute to its bottom, it is redirected through the inclined chute and enters the lower-stage chute, passing sequentially from one section to the next all the way down to the well’s base—much like water cascading down a waterfall in staged drops. The inclination angle of the inclined chute is typically designed between 45° and 60°, ensuring smooth ore flow while preventing high-speed impacts that could erode the well walls. Field measurements at a certain iron ore mine revealed that, after buffering through the inclined chute, the impact velocity of the ore was reduced by 30% compared to vertical free fall, effectively extending the service life of the chutes.

Applicable Scenarios and Engineering Key Points

Suitable for mines with steeply inclined ore bodies (>60°) and relatively small horizontal spacing between stages. During construction, precise control of the alignment accuracy between the upper and lower skip shafts is essential to ensure a smooth transition at the junctions of the inclined chutes and the shafts, preventing ore blockages. A typical example: A copper mine in Jiangxi adopted a cascaded skip system connected by three inclined chutes, enabling segmented transportation across an elevation difference of 800 meters, with each skip capable of handling up to 4,000 tons per day.

Relay-type chute: A "segmented transfer station" controlled by gates

The chute shafts at each stage are flexibly connected via chute gate systems. Ore from the upper stage is released—either manually or through automated gate control—directly into the chute shaft below. Typically, these gates are powered by pneumatic or hydraulic mechanisms, allowing precise adjustment of the discharge rate. This ensures that simultaneous discharging across multiple stages is avoided, preventing disruptions in underground airflow and potential ore blockages. Practical application at a certain gold mine has demonstrated that integrating PLC systems to coordinate the operation of gates across all stages can boost ore-discharge efficiency by 15%, while simultaneously reducing dust concentrations by 25%.

Suitable for mines requiring flexible allocation of ore flow in multi-stage, independent production processes—particularly ideal for scenarios where ore characteristics vary significantly across different mining and transportation stages. During design, it’s crucial to prioritize optimizing the structural strength of the gate chamber, employing either reinforced concrete lining or steel plate support systems to withstand the impact loads from frequent ore discharges. For instance, a lead-zinc mine in Shandong has installed intelligent weighing sensors within its relay-type chutes, enabling real-time monitoring of ore storage levels at each section and facilitating adaptive control of the gates.

Key technical considerations in engineering applications

Applicable Conditions and Site Selection Principles

        Geological conditions: Prioritize placement in hard, stable rock formations (uniaxial compressive strength > 80 MPa), avoiding fault fracture zones and water-rich layers. When necessary, employ a combined support system of rock bolts and shotcrete.

Geological conditions are the primary consideration for selecting sites for segmented straight shafts. The shaft should ideally be located in hard, stable rock layers with a uniaxial compressive strength exceeding 80 MPa—rocks capable of withstanding the impact loads and ground pressures generated by the long-term descent of ore, thereby ensuring the stability of the shaft walls. For instance, in a certain granite mining area where the rock’s uniaxial compressive strength reaches 100 MPa, the segmented straight shafts installed there have endured years of heavy-duty use, with only minor wear observed on the shaft walls—no significant deformation or collapse has occurred.

On the contrary, if the skip shaft passes through fault fracture zones or water-rich strata, it will face significant risks. Fault fracture zones have poor rock integrity and are highly susceptible to loosening and collapse under ore impacts, potentially leading to blockages or even collapses of the skip shaft. Meanwhile, water-rich strata may trigger underground debris flows, further compromising the structural integrity of the skip shaft. When it’s impossible to avoid these unfavorable geological areas, a combined support approach using rock bolts and shotcrete is essential. Rock bolts can be anchored deep into stable rock layers, providing strong anchoring forces that integrate fractured rocks with the surrounding stable mass into a cohesive whole. Shotcrete, on the other hand, effectively seals the well walls, preventing rock weathering and spalling while enhancing the overall structural stability. For instance, a certain metal mine successfully ensured the safe operation of its skip shaft in a section crossing a fracture zone by densely installing rock bolts at 0.5-meter intervals and applying 15-centimeter-thick shotcrete, significantly reinforcing the shaft’s stability.

Phase Matching: The horizontal spacing between upper and lower phases should be maintained at 15 to 30 meters, which not only reduces the construction volume of inclined chutes or gate chambers but also prevents excessive misalignment that could lead to decreased transportation efficiency.

Properly controlling the horizontal spacing between upper and lower stages is crucial for maximizing the efficiency of segmented straight decline shafts. If the spacing is too small, although the construction of inclined chutes or gate chambers becomes easier, it becomes difficult to fully leverage the advantages of segmental independence. Conversely, if the spacing is too large, it not only increases the length of the inclined chutes or the number of gate chambers, dramatically boosting the project’s workload, but also extends the ore transportation routes, thereby reducing overall transport efficiency.

Generally speaking, a horizontal spacing of 15 to 30 meters is ideal. Take the cascade chute system as an example—this spacing ensures that the length of the inclined chute remains within a reasonable range. It not only allows gravity to efficiently facilitate the smooth transfer of ore but also prevents the ore from descending too quickly due to an excessively long chute, thereby reducing wear and tear. At a certain lead-zinc mine, optimizing the horizontal spacing at each stage to around 20 meters lowered the construction cost of the inclined chutes by 25% compared to the original design. At the same time, ore transportation efficiency improved by 12%, achieving a win-win outcome in both economic benefits and operational performance.

System Coordination: It is essential to precisely align with transportation roadways and ore-discharging chambers at each stage. We recommend using 3D laser scanning technology for spatial positioning, ensuring that the interface errors between segments remain below 10 cm.

As a critical node in the mine transportation system, the segmented straight-through shaft must work closely with transportation drifts at each stage and the ore-discharging chambers to ensure smooth operation of the entire process. Precise alignment is the foundation for achieving this coordination—any significant deviation in interface positioning could lead to inefficient ore transfer or even trigger blockage incidents.

Employing 3D laser scanning technology can effectively enhance docking accuracy. This technology enables the rapid and precise acquisition of three-dimensional data for underground spaces, providing a reliable foundation for the design and construction of skip shafts and related chambers. During the construction process, scanned data is used in real time to monitor the positions of each segmental interface, allowing for timely adjustments to address any deviations and ensuring that interface errors remain within 10 cm. For instance, during the construction of a large-scale copper mine’s segmented straight skip shaft, 3D laser scanning technology was instrumental in identifying and correcting multiple interface misalignments ahead of schedule. As a result, after the skip shaft went into operation, ore-handling efficiency significantly improved, while the failure rate dropped by 30%, strongly supporting the mine’s ability to maintain highly efficient production.

Key Points in Underground Chamber Structural Design

        Unloading chute chamber: A buffer layer (such as waste rock or rubber padding) must be installed to reduce the impact of unloading materials, thereby minimizing wear on the upper opening of the chute. Additionally, a grizzly screen device—featuring screening holes 1.2 times the size of the largest ore pieces—should be equipped to prevent oversized chunks from causing blockages.

The ore discharge chamber is the entry point where ore enters the chute, enduring high-intensity unloading impacts over extended periods. Therefore, a well-designed structure is crucial. Installing buffer layers is an effective way to reduce impact-induced wear; common materials for these buffers include waste rock and rubber linings. Waste rock pads leverage their naturally loose structure to absorb the impact energy from falling ore, while being easy to source and cost-effective. On the other hand, rubber linings offer excellent elasticity and abrasion resistance, providing even more effective shock absorption and significantly extending the service life of the chute. At one iron mine, a 0.5-meter-thick layer of waste rock was laid in the discharge chamber, and measurement data showed that the wear rate at the chute’s upper opening decreased by 40% compared to conditions before the installation.

Additionally, the grizzly screen is a critical safeguard against oversized ore pieces entering the chute and causing blockages. The size of the grizzly screen’s openings should be carefully designed based on the maximum ore block dimension—typically 1.2 times the size of the largest block—ensuring both smooth passage of qualified ore while effectively intercepting excessively large chunks. At one copper mine, a grizzly with 30-centimeter openings (matching a maximum ore block size of approximately 25 cm) has been successfully implemented, effectively preventing chute blockages caused by oversized ore and maintaining uninterrupted production.

The ore-discharging gate chamber must have spatial dimensions that accommodate equipment installation and maintenance requirements. The single-sided pedestrian walkway should be at least 1.2 meters wide and stand at least 2.5 meters high, while also incorporating ventilation and dust removal ducts to enhance the working environment. Actual measurements from a certain copper mine show that a properly designed gate chamber can reduce equipment maintenance time by up to 40%.

The ore-discharge gate chamber, serving as the core component for controlling ore flow, directly influences the convenience and safety of both equipment operation and personnel handling. Ample space is essential for equipment installation and maintenance: a single-sided walkway must be at least 1.2 meters wide to ensure safe passage during equipment operation and facilitate routine inspections; meanwhile, a minimum height of 2.5 meters is required to accommodate the lifting, installation, and dismantling of large-scale machinery, thereby enhancing maintenance efficiency. At one copper mine, optimizing the gate chamber's spatial design expanded the originally narrow passageway to 1.5 meters wide and increased the height to 2.8 meters. As a result, equipment maintenance time was reduced from 8 hours per session to just 4.8 hours, significantly cutting down on production downtime caused by maintenance activities.

Meanwhile, the ore-discharging process generates significant amounts of dust, severely impacting the health of workers and the ventilation conditions underground. Installing ventilation and dust-control ducts can promptly remove dusty air, effectively reducing dust concentrations. By strategically placing ventilation openings on the ceiling or sidewalls of the chamber and connecting them to the mine's main ventilation system—combined with mist-based dust suppression equipment—workers' environments can be significantly improved. Field measurements have shown that, after implementing these ventilation and dust-control measures, dust concentrations inside the chamber can be reduced by more than 80%, creating safe and healthy working conditions for personnel.

Gate System Maintenance Strategy

Establish a dual mechanism of "regular inspections + condition monitoring": 1. Daily Maintenance: Inspect the gate sealing performance and lubrication status of the drive system during each shift, and record the opening/closing times as well as any unusual noises. 2. Regular Overhauls: Conduct quarterly structural stress tests on the gate, and replace the wear-resistant lining plates annually—recommended to be made from high-molecular polyethylene material, which extends the service life by more than twice compared to traditional steel.

The gate system is a critical control component of the segmented straight shaft well, and its stable operation directly affects the well’s normal production. Establishing a dual mechanism of "regular inspections + condition monitoring" enables comprehensive maintenance of the gate system, allowing for the timely detection and resolution of potential faults.

Daily maintenance is the foundational work that ensures the short-term stable operation of the gate system. Before each shift begins, operators must inspect the sealing performance of the gates to confirm there are no mineral leaks, preventing ore from escaping and causing resource waste as well as environmental pollution. At the same time, they should check the lubrication status of the drive system, promptly replenishing oil to minimize component wear and ensure smooth operation. Recording the opening and closing times, along with any unusual sounds, serves as crucial data for analyzing equipment performance. If the operator notices unusually prolonged opening/closing times or detects abnormal noises, it may indicate potential issues such as jamming or loose components, prompting an immediate shutdown for thorough inspection and troubleshooting.

Regular maintenance involves in-depth inspection and upkeep of the gate system from a long-term operational perspective. Gate structural stress is tested quarterly using non-destructive testing techniques such as ultrasonic flaw detection and strain gauge measurements, allowing engineers to assess stress distribution in critical areas. This proactive approach helps identify structural damage caused by prolonged stress, preventing sudden fractures or failures. Additionally, wear-resistant liners are replaced annually; switching to high-performance polyethylene material can significantly extend their service life. For instance, after one mine replaced its conventional steel liners with polyethylene ones, the liners’ lifespan increased dramatically—from the original 6 months to over 18 months. This improvement not only reduced equipment maintenance costs and downtime but also ensured the continuous, stable operation of the shaft.

Pros and Cons Comparison & Application Scenario Recommendations

Core Advantages and Limitations

Segmented straight-shaft wells demonstrate unique advantages in mine transportation, while also coming with certain limitations. A thorough analysis of these characteristics can help facilitate informed decision-making in practical applications.

Its core advantage lies first and foremost in the high reliability achieved through the independent operation of each segment. When an unexpected incident occurs in one particular stage—such as a blockage or collapse of the shaft wall—thanks to the relative independence of each segment, the gate at the malfunctioning section can be swiftly closed, ensuring that production in other stages remains unaffected. For instance, at a large copper mine, when a localized chute was temporarily blocked by falling rocks, timely isolation of the faulty segment allowed the remaining sections to continue operating normally. This proactive measure effectively prevented a daily production loss of approximately 1,500 tons, thereby maintaining the mine's overall production capacity and stability.

Segmented straight chutes can also better adapt to complex geological conditions. In areas with intricate geological structures, dividing the chute into segments reduces the depth of each individual segment, thereby minimizing risks associated with long-distance passage through unfavorable strata—such as surrounding rock deformation and water inrush—that could threaten chute stability. At the same time, this design facilitates separate mining and transportation processes, allowing for flexible control over the discharge of ores with varying grades and from different zones. This, in turn, enhances resource utilization. For instance, in mines where multiple mineral types coexist, operators can leverage the gate systems in relay-style chutes to precisely manage the flow of distinct ore types, ensuring that the diverse raw material requirements of the beneficiation plant are effectively met.

However, the limitations of segmented straight chutes cannot be overlooked. Their gate systems are a major factor contributing to increased costs and management challenges. Each segment of the chute must be equipped with a discharge gate, along with its associated drive and control mechanisms, significantly boosting both equipment procurement and installation expenses. Moreover, this setup leads to a substantial rise in the workload and costs associated with subsequent maintenance and repairs. According to statistics, compared to traditional straight chutes, segmented straight chutes involve an equipment investment that is approximately 20% to 30% higher, while annual maintenance costs increase by around 35%.

The complex chamber structure also presents a significant challenge. To accommodate the gates and facilitate ore transfer, additional unloading chambers and ore-discharge gate chambers must be excavated, increasing the tunneling workload by 20% to 30% compared to traditional chutes—resulting in higher construction difficulty and extended project timelines. Moreover, operating and managing the segmented straight chutes demands highly skilled workers, as operators need to master the coordinated control techniques for gates at each section, precisely adjusting the discharge rate and flow to maintain stable ore movement and prevent blockages. Consequently, this raises both personnel training costs and management complexity.

Scene Matching Suggestions

Based on the characteristics of segmented straight-shaft wells, their applicability varies across different mining scenarios.

In multi-stage metal mines with an annual output exceeding 500,000 tons—particularly those featuring long ore bodies and complex geological structures (such as multiple fault zones)—segmented straight shafts offer significant advantages and should be prioritized. These mines typically operate on a large scale, with high demands for coordinated, multi-stage production. The segmented, independent design of these shafts effectively ensures uninterrupted operations while minimizing the impact of geological risks. For instance, at a major lead-zinc mine in Yunnan Province, where the ore body stretches over 3,000 meters along its strike and crosses several fault zones, the implementation of segmented straight shafts successfully addressed the challenges of multi-stage transportation. As a result, production efficiency improved by more than 20%, and the accident rate was reduced by 30%.

However, in single-stage mining operations—where multi-stage coordinated transportation is not required—the complex structure and high cost advantages of segmented direct chutes are difficult to realize. On the contrary, they may lead to unnecessary construction and operational expenses. Therefore, this design is not recommended. For mines with high clay content in ore (>15%), the clay-rich material tends to stick easily to gates and chute walls, causing gate jams and chute blockages that disrupt the system’s normal operation. As such, caution is also advised when considering this type of design. In these scenarios, if a segmented design is absolutely necessary, it is strongly recommended to prioritize the waterfall-style, gateless design instead. This approach leverages inclined chutes to naturally transfer ore, significantly reducing the risk of failures caused by gates and ensuring smooth, uninterrupted chute operation.

Conclusion

The segmented straight shaft addresses the logistical challenges of multi-stage mining transportation through innovative structural design. Its "segmented control and fault isolation" design philosophy provides an efficient solution for deep-well mining and the development of complex ore bodies. Although it presents the challenge of higher maintenance complexity, its advantages in enhancing production continuity and reducing safety risks make it a key choice for modernizing and智能化 transforming mines. In practical applications, it is essential to carefully select either a cascaded or relay-style arrangement based on the mine's geological conditions, production scale, and level of automation, while integrating intelligent monitoring systems to fully unlock the engineering value of the segmented straight shaft.