Types of Support Systems in Underground Mines

Underground mining operations present unique challenges that require robust support systems to ensure the safety of miners and the stability of the mine workings. I have conducted extensive research and practical studies on various support systems used in underground mines. In this article, I will discuss different types of support systems commonly employed in the mining industry, providing explanations and examples to enhance understanding.

Wood Support Systems

Wood support systems have a long-standing history in the mining industry and continue to be widely used. The versatility, accessibility, and processing ease of wood make it a preferred material for support applications. Typically, wood support systems involve the use of timber posts, beams, and lagging. These components are strategically installed to reinforce the mine openings and provide structural stability. Wood support systems are particularly prevalent in small-scale and shallow mines.

Advantages:

• Versatility: Wood can be easily processed and shaped in various ways, allowing it to adapt to different shapes and sizes in mine cavities.
• Accessibility: Wood is generally readily available and easy to transport and install in mine sites. This enables quick implementation of support systems and ensures rapid mine safety.
• Workability: Wood can be easily worked by mining personnel. It can be cut, shaped, and assembled to the required dimensions. This allows miners to efficiently install wood support systems.
• Cost-effectiveness: Wood material is often less expensive compared to other support materials. This is one of the reasons why wood support systems are preferred in small-scale and shallow mines.
• Audible Warning: One unique characteristic of wood support systems is that they produce sound when they start to break or crack under load. This audible warning provides an early indication of potential instability, allowing miners to take necessary precautions and evacuate the area if needed.

Disadvantages:

• Limited Durability: Wood material has lower strength compared to other support materials. Therefore, wood support systems are more commonly used in smaller and shallower mines. For deeper and wider mines that require heavier-duty support, steel or concrete support systems may be more suitable.
• Risk of Moisture and Decay: Wood is susceptible to moisture and decay. Prolonged exposure can cause wood support systems to deteriorate and lose their durability. Regular maintenance and moisture control measures should be implemented.
• Fire Hazard: Wood material is more susceptible to fire compared to other support materials. Enhanced fire prevention measures should be taken in mines, and special measures should be implemented to increase the fire resistance of wood support systems.
• Limited Applicability: Wood support systems may have more limitations when used in larger and deeper mines. Steel or concrete support systems can handle heavier loads and withstand more challenging mine conditions.

Example: In a small gold mine, timber posts are strategically placed along the mine tunnels to support the roof and prevent collapses. Horizontal timber beams are then installed to distribute the load and further strengthen the structure.

Steel Support Systems

Steel support systems are another common type employed in underground mines. Steel’s high strength, durability, and workability make it a preferred choice for demanding mining conditions. Steel support systems typically consist of steel posts, steel profile sheets, and wire meshes. These components are designed to reinforce the roof and walls of the mine workings. Steel support systems are often utilized in deeper and wider mines that require heavier-duty support.

Advantages:

• High Strength: Steel possesses exceptional strength, allowing it to withstand significant loads and pressures in underground mines. This high strength provides enhanced stability and support to mine openings.
• Durability: Steel is highly durable and resistant to wear, corrosion, and deterioration. It can withstand harsh mining environments, including exposure to moisture, chemicals, and high-stress conditions. This durability ensures the long-term stability of the support system.
• Workability: Steel is a malleable material that can be easily shaped, cut, and welded to meet specific design requirements. This flexibility enables the customization of steel support systems to fit different mine geometries and conditions.
• Versatility: Steel support systems offer versatility in terms of their design and application. They can be adapted to different mine layouts, including varying roof heights, spans, and wall conditions. This adaptability makes steel support systems suitable for a wide range of mining scenarios.

Disadvantages:

• Cost: Steel support systems are generally more expensive compared to other support materials, such as wood. The higher cost is primarily due to the materials, manufacturing processes, and installation requirements associated with steel support systems.
• Complex Installation: Installing steel support systems can be more complex and time-consuming compared to other support types. It often requires specialized equipment, skilled labor, and meticulous planning. This complexity can increase the overall project timeline and costs.
• Weight and Handling: Steel components are heavier than materials like wood or concrete. Handling and transporting steel support systems require appropriate equipment and careful consideration of logistics. This additional weight can also affect the overall stability and load-bearing capacity of the mine structure.
• Potential for Corrosion: Although steel is generally corrosion-resistant, exposure to certain environmental conditions, such as high humidity or aggressive chemical agents, can lead to corrosion. Proper coating and maintenance measures should be implemented to protect the steel support system from corrosion and ensure its long-term effectiveness.

Example: In a large-scale underground coal mine, steel roof bolts are extensively used to provide immediate roof support. These long steel rods are inserted into pre-drilled holes and anchored to the roof strata, effectively preventing roof falls.

Concrete Support Systems

Concrete support systems play a crucial role in underground mines, especially in challenging ground conditions. Concrete’s high compressive strength, durability, and fire resistance make it a reliable material for support applications. Concrete support systems typically involve the use of concrete pillars, shotcrete, reinforced concrete roofs, and walls. These elements provide structural support and enhance the overall stability of the mine workings.

Advantages:

• High Compressive Strength: Concrete exhibits excellent compressive strength, allowing it to withstand heavy loads and pressures in underground mining environments. This strength provides a solid foundation for reinforcing mine openings and stabilizing the surrounding rock mass.
• Durability: Concrete is highly durable and resistant to wear, weathering, and chemical degradation. It can withstand harsh mining conditions, including exposure to moisture, chemicals, and abrasive materials. This durability ensures the long-term stability and effectiveness of the support system.
• Fire Resistance: Concrete is inherently fire-resistant, offering an important safety advantage in underground mines. In the event of a fire, concrete support systems can provide a barrier against the spread of flames and heat, helping to protect personnel and infrastructure.
• Flexibility in Design: Concrete support systems offer flexibility in terms of design and application. They can be tailored to accommodate various mine geometries, including different roof heights, spans, and wall conditions. This adaptability allows for customized solutions that meet specific mining requirements.

Disadvantages:

• Construction Time: Building concrete support systems can be time-consuming due to the curing time required for concrete to reach its full strength. The need for proper formwork, pouring, and curing processes can prolong the construction schedule, affecting overall project timelines.
• Initial Cost: Concrete support systems often involve higher initial costs compared to other support materials. The cost is influenced by factors such as the quantity of concrete needed, formwork requirements, and labor expenses. However, it’s important to consider the long-term durability and performance benefits that concrete provides.
• Weight and Handling: Concrete components are heavy, which can pose challenges during transportation and installation. Adequate equipment and planning are necessary to handle and position concrete elements safely and efficiently. The weight of the concrete also affects the load-bearing capacity of the mine structure.
• Limited Flexibility: Unlike steel or wood, concrete is a rigid material that lacks the same level of flexibility. This limited flexibility can present challenges when dealing with ground movements or dynamic mining conditions. Additional measures, such as incorporating expansion joints, may be required to accommodate any potential movement.

Example: In a deep underground copper mine, concrete pillars are strategically installed to support the massive weight of the overlying strata. Additionally, shotcrete is sprayed onto unstable rock surfaces to provide immediate support and prevent rock bursts.

Resin Support Systems

Resin support systems have gained popularity in recent years due to their effectiveness in stabilizing fragile rock formations. Resins are specialized polymer-based materials with high strength, rapid curing, and chemical resistance properties. Resin support systems typically involve injecting resins into boreholes, which interact with the rock mass, spreading and hardening to improve its stability.

Advantages:

• High Strength: Resins used in support systems exhibit high tensile and shear strength, allowing them to reinforce weak rock formations effectively. They can provide structural support by bonding fractured or loose rock surfaces together, increasing the overall stability of the rock mass.
• Rapid Curing: Resins typically have fast curing times, allowing for quick installation and minimal disruption to mining operations. Rapid curing enables a faster return to full productivity in the supported areas.
• Chemical Resistance: Resins possess excellent resistance to chemicals and corrosive substances, making them suitable for use in various mining environments. They can withstand exposure to water, acids, and other harsh substances commonly encountered in underground mines.
• Flexibility and Adaptability: Resin support systems offer flexibility in terms of application and adaptability to various rock formations. They can be injected into boreholes, which allows for precise and targeted reinforcement in specific areas of the mine. This flexibility allows for customization and optimization of the support system based on the geological conditions.

Disadvantages:

• Dependency on Rock Condition: The effectiveness of resin support systems is highly dependent on the condition of the rock mass. Fragile or heavily fractured rock formations may require additional preparatory work or alternative support systems. A thorough understanding of the geological conditions is crucial for the successful implementation of resin support systems.
• Expertise and Equipment Requirements: Proper installation of resin support systems requires specialized knowledge, equipment, and trained personnel. The injection process must be carefully monitored to ensure the correct amount and distribution of resin within the rock mass. This expertise and equipment can increase the overall project cost.
• Long-Term Performance: The long-term performance of resin support systems can vary depending on factors such as temperature fluctuations, moisture content, and chemical interactions within the mine environment. Regular monitoring and maintenance are essential to ensure ongoing effectiveness and stability.
• Cost: Resin support systems can be relatively expensive compared to other support materials due to the specialized nature of the resins and the equipment required for installation. The cost of resin materials, drilling, and injection equipment should be considered in the project budget.

Example: In a narrow vein gold mine with weak and fractured rock walls, resin bolts are employed. These bolts consist of a resin cartridge inserted into a borehole, which, when activated, expands and hardens, reinforcing the surrounding rock and preventing wall collapses.

As a mining professional, I emphasize the importance of selecting appropriate support systems in underground mines to ensure the safety of miners and the stability of mine workings. Wood, steel, concrete, and resin support systems offer unique advantages and are selected based on the mine’s characteristics, depth, and service conditions. The examples provided in this article illustrate the practical applications of different support systems in real mining scenarios. However, it is essential to stay abreast of technological advancements, as the mining industry continuously evolves, leading to further innovations in support systems.