01 Core Definition and Key Parameters of the Tilted Silo

Essential Characteristics and Functional Positioning

The inclined chute is a critical channel in mine transportation systems, arranged at an angle. Its most distinctive feature is that the shaft extends downward at an inclination greater than 60°, effectively creating a "natural slide" for ore to transport by gravity. Unlike vertical chutes, the inclined design significantly reduces the falling speed and minimizes the impact load at the bottom of the shaft by lengthening the ore’s travel path—making it the preferred solution for alleviating transportation pressure in deep mines. In practical applications, the inclined chute leverages its unique structural advantages to efficiently and reliably convey ore extracted from the mining face to the next operational stage. For instance, at a large-scale metal mine where the ore body lies deep underground and the geological conditions are highly complex, using a vertical chute would result in excessive impact forces at the bottom of the shaft, frequently damaging the shaft structure and driving up maintenance costs. However, after switching to an inclined chute, the ore’s rolling speed was effectively slowed down, virtually eliminating the problem of bottom-of-shaft damage. As a result, both the mine’s production efficiency and overall safety have been significantly enhanced.

Core Technical Parameter Analysis

Inclination Design: The angle must be strictly greater than 60° to ensure that the gravitational component of the ore overcomes frictional resistance, enabling smooth sliding. At the same time, avoid excessively steep angles that could lead to increased impact forces; instead, precise calculations should be made based on parameters such as ore size and moisture content. For instance, in a certain iron ore mine, the initial design set the inclination angle at 65° for the inclined chute. However, during actual operation, it was observed that when the ore had higher moisture content, some chunks experienced poor sliding or even blockages. After thorough mechanical analysis and field testing, the inclination angle was adjusted to 70°, resulting in smoother ore flow and a significant boost in production efficiency. This clearly demonstrates that inclination design requires a comprehensive consideration of multiple factors to guarantee the stable operation of the chute.

Rock layer suitability: The structure must be placed within hard rock layers or ore bodies characterized by high strength (uniaxial compressive strength > 80 MPa) and good integrity (joint spacing > 1.5 m), while avoiding fault fracture zones to ensure long-term stability. During the construction of a certain copper mine, insufficient preliminary geological exploration led to the placement of an inclined chute shaft in a rock layer with relatively well-developed joints. After commissioning, continuous impacts from ore flow gradually caused issues such as spalling and collapse along the shaft walls, severely disrupting normal mining operations. As a result, significant manpower and resources had to be diverted later to reinforce and repair the chute shaft—and ultimately, a new site was selected for its construction. This case serves as a stark reminder that rock layer suitability is critical to the stability of inclined chute shafts, underscoring the need for meticulous geological investigation and analysis throughout the design and construction phases.

02 Advantage Analysis: Dual Optimization of Efficiency and Cost

Buffering and Shock Absorption: The Flexible Resolution of Dynamic Loads

In the ore transportation process, the inclined chute ingeniously leverages the long-distance rolling effect of the inclined shaft to effectively convert the kinetic energy of falling ore. When ore moves from the mining face through a branching inclined chute into the main inclined shaft, it continues to roll along the shaft wall throughout its descent. During this process, the kinetic energy generated by the ore's fall is gradually transformed into frictional thermal energy along the shaft walls. For instance, in a large-scale metal mine with a depth reaching up to 300 meters, using a vertical chute would result in the ore hitting the bottom of the shaft at an astonishing speed of 15–20 m/s, generating immense impact forces that severely damage the shaft’s bottom structure. As a result, the mine’s bottom cushioning systems and support structures frequently suffer extensive wear and tear, requiring major repairs or replacements on average once every month—draining significant manpower, resources, and financial investments. However, after switching to an inclined chute system, precise mechanical calculations and on-site testing ensured that the ore’s rolling path within the inclined shaft was significantly extended, allowing for better velocity control. Consequently, the ore’s impact speed at the bottom of the shaft was reduced to 8–12 m/s, slashing the peak impact force by 30%–50% compared to the vertical chute design. This remarkable reduction not only alleviates the stress placed on the shaft’s bottom structure but also dramatically extends the service life of the mine’s bottom cushioning and support systems—from requiring monthly maintenance previously to only needing repairs every six months. This improvement has markedly enhanced the stability and reliability of the mine’s transportation system, minimizing downtime caused by equipment repairs and providing robust support for the mine’s sustained, high-efficiency operations.

Engineering Economics: Lean Layout of the Tunnel Network

Inclined chutes offer unique advantages in engineering layout, enabling a streamlined arrangement of tunnel networks and thereby delivering significant economic benefits to the project. In actual mining operations, ore bodies often exhibit complex and varied occurrences, but inclined chutes can be cleverly aligned along the natural dip direction of the ore body or rock strata. For instance, in a certain metal mine, the ore body is inclined at an angle of approximately 45° to 55°. Initially, the design called for vertical chutes, requiring transportation drifts at each stage to be driven perpendicular to the ore-body strike, connecting the vertical chutes directly to the mining areas. This approach resulted in excessively long transportation drifts, substantial excavation volumes, and heightened construction challenges. However, by adopting the inclined chute design, the chutes were positioned parallel to the ore-body dip, allowing transportation drifts to intersect the chutes at an angle instead. As a result, the length of the transportation drifts across all stages was dramatically reduced. According to precise measurements and calculations, the inclined chute design shortened the transportation drift lengths by 15% to 25% compared to the vertical-chute approach, while also cutting down the overall excavation volume accordingly. Moreover, the shorter drift lengths translated into significantly lower support costs. Statistics show that after implementing the inclined chute system, this metal mine achieved savings of 1,200 cubic meters in tunnel excavation, reduced construction time by 45 days, and lowered overall costs by 18%. Not only did this approach save the mine substantial capital expenditures, but it also accelerated the project timeline, enabling the mine to ramp up production more swiftly and reap earlier economic returns.

03 Challenges and Responses: Wear Mechanisms and Protection Strategies

The "Three-Dimensional Impact" of Wear and Damage

During the operation of an inclined chute, the complex interaction between ore and the chute wall is a key factor leading to wear and damage. Since the ore does not follow a single, uniform motion pattern within the inclined shaft but instead exhibits a combination of sliding, rolling, and bouncing movements, different sections of the chute experience distinct wear characteristics, resulting in what is known as a "three-dimensional impact" failure mode.

In the bottom plate area, ore continuously collides with the baseplate under the influence of gravity and its own inertia, resulting in severe impact abrasion. According to relevant data statistics and on-site measurements, in medium-sized mines, when the ore throughput reaches a certain level, the wear rate of the bottom plate typically ranges from 0.8 to 1.2 mm per 10,000 tons. Although this wear amount may seem minor at first glance, it steadily accumulates over the long-term ore transportation process, gradually weakening the structural integrity of the bottom plate. For instance, after three years of operation—during which the inclined chute in a particular mine had processed 5 million tons of ore—a detailed inspection revealed that localized wear on the bottom plate had already exceeded 300 mm in depth. In some areas, even noticeable depressions and pitting had emerged, severely compromising the chute's normal functionality.

The sidewalls of the chute are primarily affected by lateral impacts and shear forces caused by ore collisions. As ore rolls or bounces inside the shaft, it occasionally collides with the two sidewalls, generating lateral forces that induce shear stress on the井壁. Over time, these repeated side impacts significantly increase the risk of fracture development in the sidewall rocks—by as much as 30%. For instance, in an inclined chute at a certain metal mine, geological radar surveys conducted just one year after operation revealed that the originally intact rock structure of the sidewalls had already begun to develop numerous fine cracks. In some areas, these cracks had widened to 5–10 mm, severely compromising the structural integrity of the井壁 and creating potential hazards for future incidents such as roof falls or collapses.

Meanwhile, the impact pressure exerted on the roof of the ore storage section in the skip shaft cannot be ignored. As ore continuously descends from the upper levels, the roof endures tremendous shock forces. To ensure the stability of the roof, it must possess an impact-resistant strength exceeding that of C30 concrete. However, in actual production, some mines have experienced cracking and spalling in their roof structures due to either improper roof support designs or inadequate material selection under the frequent impact of falling ore. For instance, at one particular mine, after using ordinary concrete for roof support in the skip shaft's ore storage section, multiple cracks appeared within just six months, with several concrete blocks even detaching—posing a serious threat to the safe operation of the skip shaft. Moreover, the wear-and-tear damage occurring in these various areas interacts with each other, creating multi-directional stress concentration zones inside the skip shaft and further accelerating the overall deterioration of the structure.

A Full Lifecycle Protection System

Facing the complex wear issues of inclined chutes, it is crucial to establish a full-lifecycle protection system that covers every stage—from structural design to operational monitoring—aiming to comprehensively enhance the durability and safety of these chutes.

Structural Reinforcement: When it comes to enhancing structural durability, employing cast steel wear-resistant liners is an effective solution specifically designed to address the high-intensity abrasion experienced by the baseplate. These cast steel wear-resistant liners boast exceptional hardness—measuring at least HRC55—which enables them to withstand the continuous impact and friction from ore over extended periods. For instance, in a large-scale iron ore mine’s inclined chute system, after implementing these cast steel wear-resistant liners, the baseplate’s wear rate was significantly reduced. Comparative monitoring revealed that prior to their installation, the baseplate suffered annual wear depths of approximately 15–20 mm. However, after adopting the liners, the wear depth was effectively controlled within just 3–5 mm, substantially extending the baseplate’s service life and cutting down on maintenance frequency.

The anchor-net-shotcrete combined support technique plays a critical role in protecting the two sidewalls. By strategically arranging anchors at a spacing of 1.0m × 1.2m, the rock in the wellbore walls is securely anchored together, significantly enhancing the overall integrity of the rock mass. Meanwhile, spraying a 150mm-thick layer of concrete not only fills the surface cracks in the rock but also creates a robust protective barrier, effectively resisting lateral impacts and shear forces from the ore. After implementing this combined support system in an inclined chute at a certain copper mine, the development of cracks along the sidewalls was effectively controlled. Over the subsequent three years of operation, no significant spalling occurred, ensuring the stable and reliable functioning of the chute.

Intelligent Monitoring: The intelligent monitoring system serves as the "smart brain" of the full-lifecycle protection framework. By integrating vibration sensors and a video surveillance system, it enables real-time control over the operational status of the chute. The vibration sensors precisely detect the vibration signals generated when ore impacts the chute walls—when the vibration amplitude exceeds 8g, the system immediately triggers an alarm, alerting staff to promptly investigate any abnormalities. In a real-world application at a particular mine, the vibration sensors successfully identified an unusual impact caused by a large piece of ore becoming lodged in the chute. Upon receiving the alert, workers swiftly implemented corrective measures, preventing a potential chute blockage and safeguarding the chute walls from damage.

By integrating AI algorithms, the intelligent monitoring system can also perform in-depth analysis of the collected data to predict wear cycles. By establishing a wear model that incorporates factors such as ore properties, transportation volume, and impact frequency, the system accurately forecasts wear conditions at different sections of the chute. For instance, a certain mine leveraged AI algorithms to analyze historical data and successfully predicted that the chute floor would reach its wear limit within the next three months. As a result, the mine promptly scheduled liner plate replacements, effectively preventing safety incidents caused by excessive wear on the floor and ensuring continuous production operations.

04 Key Structural and Layout Principles

Collaborative Design of Functional Chambers

The ore unloading chamber serves as the entry point where ore is transferred into the chute system, and its rational design directly influences the operational efficiency and safety of the entire chute system. To effectively mitigate the impact force generated during ore unloading, a buffer pit with a depth of 1.5 to 2.0 meters should be installed within the chamber. This buffer pit acts like a "flexible spring," providing excellent cushioning between the ore and the chamber structure. For instance, at a large-scale mine, before the installation of the buffer pit, the intense impact forces during ore unloading frequently caused damage to the chamber floor and retaining walls, requiring major repairs every two months on average—and consuming significant manpower and resources. However, after implementing the buffer pit, on-site monitoring and data analysis revealed that the impact stress on the retaining walls was reduced by 40% to 50%. As a result, the repair cycle extended to once every six months, significantly enhancing the stability and service life of the ore unloading chamber.

When designing the size of the ore discharge opening, it is essential to strictly adhere to 3 to 5 times the maximum ore block size. For instance, if the largest ore blocks allowed to pass through during mining are 800 mm in diameter, the clear width of the discharge opening should be no less than 2.4 meters. This ensures that ore can smoothly enter the chute, preventing blockages from occurring. In actual production, one mine initially underestimated the ore block size, resulting in a discharge opening that was too small. Consequently, large ore chunks frequently became stuck at the discharge point during transportation, causing frequent interruptions in operations. Not only was production efficiency severely impacted, but additional handling costs were also incurred as a result. It wasn’t until the discharge opening was later widened and properly redesigned that the issue was finally resolved.

Additionally, to further enhance the wear resistance of the ore-discharging chamber, the retaining walls must be constructed using high-strength, wear-resistant materials—such as wear-resistant concrete infused with special alloy components—which offer 2 to 3 times greater durability compared to ordinary concrete. This advanced material effectively withstands the impact and friction caused by ore particles, significantly reducing wear on the retaining walls and ensuring the long-term, stable operation of the ore-discharging chamber.

The Ore Discharge Gate Chamber: The ore discharge gate chamber is a critical component that controls the flow of ore from the draw shaft. Its equipment selection and structural design play a decisive role in determining both the efficiency and safety of ore discharge. Today, hydraulic vibrating ore dischargers have become the mainstream choice in modern mines, thanks to their exceptional handling capacity—typically ranging from 500 to 1,000 tons per hour—which perfectly meets the production demands of large-scale mining operations. For instance, at a large-scale metal mine producing up to 8,000 tons of ore daily, the selected hydraulic vibrating ore discharger consistently delivers an average output of 600 to 700 tons per hour during actual operation. With its stable and reliable performance, this equipment ensures the mine maintains highly efficient production levels.

To address potential ore blockage issues during the discharge process, the ore discharge gate chamber must be equipped with advanced anti-blocking devices. For instance, a certain mine has implemented an intelligent anti-blocking system that uses multiple sensors installed around the discharge opening to continuously monitor the flow status of the ore. If the system detects abnormal ore flow rates or signs of blockage, it immediately activates a vibration-based clearing mechanism, using high-frequency vibrations to restore smooth ore movement and prevent clogging from occurring. In practical applications, this anti-blocking device has demonstrated an effectiveness rate of over 95%, significantly reducing downtime caused by blockages and enhancing both the controllability and continuity of the ore-discharge process.

At the same time, the spatial layout of the ore-discharging gate chamber also requires careful design, taking full consideration of equipment installation, maintenance, and sufficient operational space for personnel. A well-planned spatial arrangement can enhance equipment efficiency, reduce the likelihood of malfunctions, and provide strong support for the mine's continuous and stable production.

Key Points for Geological Suitability Assessment

Rock mechanics testing is a fundamental step in evaluating the geological suitability of inclined chutes. By obtaining rock parameters through a series of specialized tests, this process provides crucial data for the design and construction of the chutes. Among these parameters, the Rock Mass Integrity Index (RMI) serves as a key indicator of the overall structural integrity of the rock mass, with a requirement that RMI > 0.7. This means the rock contains few discontinuities such as joints or fractures, ensuring excellent overall stability. During preliminary exploration at a certain mine, rock mass integrity index tests were conducted at multiple potential chute locations. Unfortunately, one particular site yielded an RMI as low as 0.6. After thorough geological analysis and assessment, it was determined that this location was unsuitable for constructing an inclined chute. Subsequently, construction proceeded in areas where the RMI exceeded 0.7, and the resulting chutes have performed exceptionally well in operation—showing no incidents such as shaft wall collapses caused by inadequate rock integrity.

Water absorption rate (<1.5%) is also an important parameter, as it reflects the rock's ability to absorb moisture. Excessively high water absorption can lead to a reduction in rock strength under water exposure, increasing the risk of chute damage. For instance, at one mine, rigorous testing of rock water absorption was conducted during the selection of chute locations. It was discovered that in certain areas, the water absorption exceeded 1.5%. Over time, these areas—subjected continuously to groundwater and dust-control sprinkling—experienced a noticeable decline in rock strength, with varying degrees of softening observed. In contrast, chutes built in areas where the water absorption remained below 1.5% maintained stable rock strength, effectively withstanding the impact and friction from ore materials.

The number of freeze-thaw cycles (greater than 50) is a specific requirement tailored for mines located in cold regions. In cold environments, moisture within rocks repeatedly freezes and thaws, causing destructive forces that weaken the rock structure. If the rock fails to withstand an adequate number of freeze-thaw cycles, prolonged exposure to these conditions can lead to cracks, spalling, and other forms of damage—posing serious risks to the safety of the skip shaft. Before constructing an inclined skip shaft at a northern mine, researchers conducted freeze-thaw cycle tests on the selected rock samples, ensuring that the chosen material could endure more than 50 cycles without degradation. After several winters of rigorous testing, the shaft walls remained intact, with no signs of freeze-thaw-induced damage compromising the structure's safety.

Numerical simulation verification: Numerical simulation verification leverages advanced computer technology to virtually replicate the operational behavior of inclined chutes under various conditions, enabling optimization of the design and ensuring the chute's safety and stability. Currently, simulating with FLAC³D software is a widely adopted method, as it accurately models the movement trajectories of ore within the chute and analyzes the interactions between the ore and the chute walls. During the design process of an inclined chute at a particular mine, FLAC³D software was employed to conduct simulation analyses for chutes with different inclination angles and varying locations of slope-change points. The simulations revealed that the original design featured an improperly positioned slope-change point, causing ore to form an impact dead zone as it passed through this section. As a result, localized areas of the chute wall experienced excessively high impact forces, posing significant safety risks.

Based on the simulation results, the location of the wellbore slope transition point was optimized and adjusted. The revised design was subsequently re-verified through further simulations, revealing smoother ore movement trajectories, the elimination of impact dead zones, and a more uniform distribution of impact forces acting on the wellbore walls—effectively reducing the risk of wall damage. During actual construction and operation, the optimized design was implemented as planned, resulting in stable chute performance without any incidents such as wellbore wall damage caused by ore impacts. This clearly demonstrates the critical importance and high effectiveness of numerical simulation verification in the design of inclined chutes.

05 Engineering Practices and Selection Recommendations

Typical Application Scenarios

Inclined chute shafts offer significant advantages under specific mining conditions, particularly well-suited for steeply inclined ore bodies (with dip angles exceeding 45°). In such mines, where the ore body dips at a steep angle, inclined chute shafts can better align with the natural geometry of the deposit, enabling efficient ore transportation. For instance, the Jiamu copper-polymetallic mine in Tibet features an inclined chute shaft that reaches a depth of 320 meters with a dip angle of 65°, handling an annual transport volume as high as 3 million tons. Thanks to the steep dip of the ore body, the use of inclined chute shafts allows the ore to flow naturally downward under gravity, significantly reducing energy consumption and equipment wear during transportation. Meanwhile, the shaft’s depth and dip angle have been carefully designed to meet the demands of large-scale mining operations, ensuring stable and reliable ore transport.

For the mining of high-hardness ores (with a Pugh coefficient f > 12), inclined chutes have also demonstrated excellent adaptability. High-hardness ores cause significant wear on chutes during transportation, but the long-distance rolling effect of inclined chutes effectively disperses the impact force of the ore, thereby reducing wear on the chute bottom. For instance, in the extraction of a certain quartz-vein-type gold deposit—where the ore’s Pugh coefficient reached 15—the adoption of inclined chutes, combined with rational structural design and protective measures, successfully addressed the issue of severe wear caused by the high-hardness ore, ensuring the long-term stable operation of the chute system.

In mines employing multi-stage collaborative mining, inclined chutes can efficiently gather and transport ore from different stages. By incorporating branch inclined chutes, ore from each stage can seamlessly flow into the main chute, enabling centralized transportation. This approach not only enhances transportation efficiency but also reduces the investment in and operational costs of transportation equipment. For instance, a large-scale lead-zinc mine utilized inclined chutes during its multi-stage extraction process to uniformly convey ore from various stages directly to the beneficiation plant, thereby achieving highly efficient and coordinated production across the entire mine operation.

Selection Decision Matrix

In mining engineering, the selection of chute types is crucial, directly impacting the mine's production efficiency, cost control, and safe operations. Below is a comparative analysis of the applicable conditions for inclined chutes versus vertical and segmented chutes across various performance indicators, providing clear guidelines for engineering decision-making.

When the ore has a large size and high hardness—such as ore pieces larger than 500mm with high brittleness—the inclined chute can effectively reduce the impact of ore on the chute itself by utilizing long-distance rolling and buffering, making it well-suited for transporting this type of ore. On the other hand, for ores smaller than 300mm or those that are easily crushed, vertical or segmented chutes, due to their structural characteristics, are better equipped to handle the transportation needs of small or fragile ore pieces, thereby minimizing the risk of ore breakage and blockages.

When it comes to rock stability, inclined chutes must be placed in hard, intact rock formations (RQD > 85%) to withstand the impact and abrasion caused by ore. Meanwhile, moderately stable rock formations (RQD = 60%-85%) are better suited for vertical or segmented chutes, as these chute designs can maintain stability in medium-strength rock layers through appropriate support measures.

Transportation drop is also an important factor to consider when selecting equipment. When the transportation drop exceeds 150 meters, inclined chutes can effectively reduce the impact force of ore falling by leveraging their sloped shaft structure, thereby ensuring safe transportation. However, for transportation drops below 100 meters, the structural advantages of vertical or segmented chutes can be better utilized, resulting in relatively lower construction and maintenance costs.

Construction convenience is equally important and cannot be overlooked. Tilted chutes are ideally suited for natural alignment along rock layers, allowing full utilization of terrain conditions while minimizing construction challenges and reducing the overall project workload. Meanwhile, in vertical or terraced landscapes, vertical or segmented chutes prove more convenient to construct, better adapting to the unique features of the terrain.

As the "slope artery" of mine transportation, the core value of the inclined chute lies in achieving a balanced approach to efficiency enhancement and risk control through the deep integration of its tilt angle design with geological suitability.