The longwall mining operation, as the core component of mining methods, plays a crucial role throughout the entire mining process. It refers to the comprehensive procedure of extracting ore from prepared and cut-off mine blocks (or mining areas), encompassing several intricate and critical technical steps—such as structural parameter design, layout planning for preparation and cutting operations, and the implementation of specific extraction procedures.

In terms of structural parameter design, the primary basis comes from the geological conditions of the ore body, such as its thickness, dip angle, and stability. These factors directly influence the determination of block dimensions as well as the method used for pillar retention. For instance, for ore bodies with greater thickness and good stability, block sizes can be appropriately increased to enhance mining efficiency. Conversely, in cases where the ore body has a gentler dip angle, extra attention must be paid to the supporting role of the pillars during extraction, helping to prevent safety hazards like roof collapses during the mining process.

The mining preparation and cutting operations involve excavating a series of tunnels—such as shafts, chutes, and cutting slots—to establish both operational spaces and transportation pathways. For instance, a shaft serves as a vertical passage connecting tunnels at different levels, providing convenient access for personnel and equipment while also playing a critical role in ventilation and drainage. Meanwhile, a chute is primarily used for gravity-based ore transportation, efficiently and swiftly conveying mined ore from the working face to the designated transport level. Cutting slots, on the other hand, create free surfaces essential for blasting, enhancing blast effectiveness and ensuring that ore can be smoothly detached from the orebody. The rational arrangement of these mining preparation and cutting structures lays the necessary groundwork for large-scale extraction, forming an indispensable foundation for achieving efficient mining operations.

The primary task of the ore extraction process is to separate and break the ore from the mineral body into a size suitable for transportation, typically achieved through methods such as rock drilling and blasting or mechanical cutting. In practical applications, shallow-hole drilling (with hole diameters less than 50 mm and depths ranging from 3 to 5 meters) is particularly advantageous due to its flexibility and adaptability, making it ideal for mining thin or intricately shaped ore bodies. For instance, in some small-scale mines where ore bodies are relatively thin and irregularly shaped, shallow-hole drilling allows for better control over the mining area, minimizing ore loss and dilution. On the other hand, deep-hole drilling (with hole diameters exceeding 90 mm and depths greater than 15 meters) relies on advanced drilling rigs, enabling highly efficient operations. In large-scale metal mines, deep-hole drilling combined with compaction blasting technology effectively enhances the uniformity of ore fragmentation, significantly boosting mining efficiency. Compaction blasting works by leveraging the mutual compression of rock between adjacent blast holes during detonation, thereby intensifying the blasting effect and ensuring more thorough ore fragmentation.

The ore-handling stage involves transporting crushed ore from the working face to the stage-level transportation level. The primary equipment used for this purpose includes electric scrapers, scraper conveyors, and vibrating discharge machines. Gravity-based transportation is particularly suitable for steeply inclined ore bodies, as it leverages the natural force of gravity to allow the ore to slide down chutes or inclined roadways on its own. This method offers significant advantages, such as low costs and high efficiency. In some non-ferrous metal mines with steeper ore-body dips, adopting gravity-based transportation can substantially reduce both capital investment in transport equipment and ongoing operational expenses. On the other hand, mechanical transportation is more commonly employed in horizontal or gently inclined ore bodies. Equipment like scraper conveyors stands out for its flexibility and efficiency, enabling rapid and reliable delivery of ore to designated locations even in challenging operational environments. However, during mechanical transportation, it’s crucial to manage the rate of oversized chunks, as large ore pieces can easily clog chutes, disrupting transportation efficiency. Moreover, a blockage in the chute not only halts production but may also pose serious safety risks. To prevent such issues, effective measures must be implemented—such as strengthening blasting practices and installing secondary crushing equipment—to minimize the occurrence of oversized chunks and ensure smooth, uninterrupted ore transport operations.

Ground pressure management is a critical component of mining operations, aiming to control the stress distribution in mined-out areas through various methods and ensuring the safety of mining activities. Common ground pressure management techniques include pillar retention, backfill support, or caving of surrounding rock. The open stope method primarily relies on the inherent stability of the ore and rock masses to maintain stope stability; thus, the rational design and placement of pillars are essential in this approach. Pillar dimensions, shapes, and spacing must be precisely calculated based on factors such as the orebody’s stability and mining depth, ensuring that the pillars can effectively support the roof and prevent collapse in the mined-out area. The backfill method involves filling mined-out spaces with either cemented or uncemented materials to create a stable backfill body that supports the surrounding rock. This technique not only helps effectively manage ground pressure and minimize surface subsidence but also enhances the recovery rate of mineral resources. In mines with stringent environmental protection requirements, the backfill method has been widely adopted. Meanwhile, the caving method actively induces the collapse of surrounding rock masses, reducing and redistributing stresses within the stope to achieve a new stress equilibrium. This approach is particularly suitable for unstable orebodies or situations where controlled surface collapse is permissible. However, careful monitoring of the caving range and rate is essential during implementation to safeguard the surrounding environment.

In the entire production process of a mine, the extraction operation occupies an extremely critical position, with its labor consumption and cost accounting for a remarkably high proportion of the mine's overall operations. Specifically, labor input in the extraction phase accounts for as much as 40% to 50% of total workforce usage, meaning that nearly half of the human resources dedicated to daily mining activities are concentrated on extraction tasks. From a cost perspective, extraction costs make up 30% to 50% of the total ore production expenses, underscoring the vital role extraction plays in controlling overall mine costs.

Further analysis delves into the three core processes of mining operations—mining, ore transportation, and ground pressure management—all of which have distinct characteristics in terms of cost structure. Mining costs typically account for 20% to 80% of total extraction expenses, a wide range largely due to significant variations in costs arising from different mining methods and orebody conditions. In mines requiring deep-hole blasting, for instance, the high cost of deep-hole blasting equipment combined with substantial explosives consumption drives mining costs to occupy a disproportionately large share of overall extraction expenses. Meanwhile, ore transportation costs make up 10% to 60% of total extraction expenses, with equipment energy consumption and maintenance costs forming the primary components of this category. As transportation distances increase and equipment ages, both energy consumption and maintenance expenses tend to rise, inevitably boosting ore transportation costs. Finally, ground pressure management costs range from 0% to 30% of total expenses; particularly when the fill-and-mine method is employed, the procurement, transportation, and actual filling operations of backfill materials all demand considerable financial resources, thereby significantly elevating ground pressure management costs within the overall extraction budget.

Different mining methods also influence the cost structure of backfilling operations. Natural support methods, such as the open-stope method, rely primarily on the inherent stability of the ore and surrounding rock to maintain mine stability, which means more precise operations are required during the ore extraction phase to ensure smooth mineral recovery—resulting in the highest proportion of costs attributed to ore extraction. In contrast, artificial support methods like the filling method involve injecting substantial amounts of backfill material into mined-out areas to stabilize the surrounding rock and control ground pressure, thereby significantly increasing expenses related to ground-pressure management.

Improving ore-drawing efficiency is one of the key approaches to reducing mining costs. The widespread adoption of medium-to-deep-hole drilling rigs and intelligent blasting systems has provided strong support for enhancing ore-drawing efficiency. Medium-to-deep-hole drilling rigs are characterized by their fast drilling speed and high precision, significantly boosting the overall efficiency of rock drilling. Meanwhile, intelligent blasting systems enable more accurate blasting outcomes through precise control of blast parameters. By optimizing blast hole layouts and charging parameters, these systems ensure that explosive energy is utilized more effectively, thereby lowering the rate of oversized fragments and reducing secondary crushing costs. Lowering the oversized fragment rate not only minimizes blockages during transportation and hoisting processes but also enhances production efficiency. Additionally, the implementation of electronic detonator millisecond-delay blasting technology allows for precise control over initiation timing and sequence, minimizing blast-induced vibrations that could damage surrounding rock formations while simultaneously improving the quality of ore fragmentation. In several metal mines, after adopting electronic detonator millisecond-delay blasting technology, ore fragmentation has become remarkably more uniform, with the oversized fragment rate dropping by more than 20% and secondary crushing costs declining accordingly.

Traditional electric raking operations are less efficient and involve high labor intensity. Introducing new equipment such as trackless loaders and automated loading-and-unloading systems can effectively replace conventional electric raking methods. Trackless loaders stand out for their flexibility and efficiency, enabling rapid transportation of ore to designated locations even in complex mining environments. Meanwhile, automated loading systems streamline the entire process—automatically loading, transporting, and unloading ore—significantly boosting overall transportation efficiency. For large-scale underground mines, digital twin-based intelligent equipment scheduling technology allows real-time monitoring and smart coordination of transport vehicles. By continuously collecting and analyzing data on equipment status and location, the system can automatically adjust vehicle routes and task assignments according to production needs, thereby reducing idle running rates by 15% to 20%. In one major underground mine, after implementing this digital twin-driven intelligent scheduling technology, the idle running rate of transport equipment dropped from the original 30% to below 10%, while transportation efficiency improved by more than 30%.

Numerical simulation techniques, such as the FLAC3D software, enable precise modeling of stress distribution and deformation patterns within mining areas. Based on these simulation results, engineers can accurately design pillar dimensions and backfill strength, ensuring neither excessive nor insufficient support. Over-supporting not only drives up support costs but also increases the risk of ground pressure-related hazards, while inadequate support heightens the likelihood of such disasters. For deep, high-stress ore bodies, the caving method combined with microseismic monitoring technology proves to be an effective approach for managing ground pressure. Microseismic monitoring continuously tracks microseismic activities in the surrounding rock mass; by analyzing these events, engineers can promptly identify potential failure zones, allowing them to dynamically adjust the pace of rock caving and, in turn, mitigate both ground pressure risks and support costs. In several deep-mining operations, the implementation of the caving method alongside microseismic monitoring has led to a more than 50% reduction in ground pressure incidents and a roughly 30% decrease in support expenses.

The room-and-pillar method is primarily suited for medium-to-thick ore bodies with stable surrounding rock. During the mining process, it relies on retaining pillars to support the mined-out areas, thereby ensuring the safe continuation of extraction operations. The room-and-pillar method and the sublevel caving method are typical techniques employed in this mining approach.

In the room-and-pillar method, mining rooms and pillars are arranged in a regular pattern. The dimensions of the mining rooms are typically determined based on the stability of the ore body and the capacity of the mining equipment. Generally, the length of a mining room ranges from 40 to 60 meters, while its width spans 8 to 20 meters. During the extraction process, mining rooms are first mined out, leaving behind pillars that serve to support the roof. This method offers several advantages: it requires minimal preparatory work, features a straightforward extraction process, provides excellent ventilation conditions, facilitates mechanized operations, and achieves relatively high productivity with substantial face production capacity. However, it also has notable drawbacks—significant ore loss occurs in the pillars—and as mining depth increases, the stability of the roof may be compromised to some extent.

The sublevel caving method divides the ore block into several sublevels along the vertical direction, with stopes and pillars arranged horizontally within each sublevel. During mining, medium-to-deep hole drilling and blasting are used to break the ore, and the fragmented ore is then transported out through the bottom structure. This method is particularly suitable for ore bodies with significant thickness and where both the ore and surrounding rock maintain good stability. Its advantages include fully leveraging the high efficiency of medium-to-deep hole drilling, thereby enhancing ore extraction efficiency while simultaneously reducing the volume of preparatory mining work. However, in practical applications, it is essential to carefully control the sublevel height and blast-hole parameters to ensure optimal blasting performance and stable conditions in the mining area.

In the open-pit mining method, the ore-caving stage primarily relies on deep-hole blasting. This blasting technique enables large-scale rock fragmentation, significantly boosting mining efficiency. Deep-hole blasting requires the use of specialized drilling equipment, such as drill rigs, to ensure the precision and quality of the blast holes. When selecting blasting parameters, factors like the characteristics of the ore body, the dimensions of the mining chambers, and the hardness of the rock must be carefully considered, aiming to optimize blasting performance while minimizing the occurrence of oversized fragments.

The ore transportation process commonly employs either scraper conveyors or electric rakes. Scraper conveyors are characterized by their flexibility and high efficiency, enabling them to swiftly move ore to designated locations even in complex mining environments. Electric rakes, on the other hand, are well-suited for shorter mine rooms with gentler slopes; they feature a simple design and easy operation, though their transportation efficiency is relatively lower. In practical applications, it’s essential to select the appropriate transport equipment based on the specific conditions of the mining site, thereby enhancing transportation efficiency while reducing costs.

Ground pressure management is a critical component of the open stope mining method, primarily relying on the stability analysis of ore pillars. Before mining begins, it’s essential to accurately calculate the load-bearing capacity of the pillars using methods such as numerical simulations, and then rationally determine their dimensions, shapes, and spacing. During the mining process, close attention must be paid to the exposed area and duration of the mined-out zones, ensuring that excessive exposure or prolonged exposure does not trigger sudden roof collapses. If any signs of deformation or failure in the ore pillars are detected, immediate reinforcement measures should be implemented—such as adding support pillars or injecting grout—to maintain the safety of the mining area.

The fill mining method is primarily suited for unstable ore bodies or mining areas with stringent environmental protection requirements. The extraction process in this method typically proceeds step by step: first, the initial extraction area is mined out, followed by backfilling operations. Once the backfill material has achieved sufficient strength, the second-stage pillar is then extracted.

In the ore extraction stage, the upward horizontal slicing and shallow-hole drilling method is commonly employed. This drilling approach effectively controls the mining area, minimizes disturbance to the surrounding rock, and helps reduce ore loss and dilution. In practice, the depth, spacing, and angle of blast holes are carefully determined based on the thickness of the ore body and the hardness of the rock. For thinner ore bodies, a single-pass full-thickness extraction method can be used; whereas for thicker ore bodies, layered mining is required, with each layer typically maintained at a thickness of 2 to 3 meters.

The ore transportation process combines both mechanical and manual methods. Within the mining area, small loaders or electric winches are used to transport ore directly into chutes, which then carry the material down to the stage-level transportation levels. For certain corners or areas where mechanical transport is impractical, manual handling is employed instead. During transportation, it's crucial to carefully manage the ore particle size, ensuring that large chunks don't clog the chutes.

Ground pressure management is the core of the backfill mining method, primarily achieved by allowing the backfill material to work synergistically with the ore pillars to bear the load. The quality of the backfill directly influences the effectiveness of ground pressure control, making it essential to optimize the mix ratio of backfill materials. For instance, in tailings-based cemented backfilling, the strength of the backfill typically needs to be maintained within the range of 2–5 MPa to ensure it can effectively support the surrounding rock mass. During the backfilling process, strict control over the quality, mix ratio, and construction techniques of the backfill material is crucial, guaranteeing uniformity and compactness of the backfill body. Additionally, real-time monitoring of the backfill’s strength is required, enabling timely adjustments to backfill parameters based on the monitoring results. By implementing sound ground pressure management practices, it’s possible to effectively control deformation and displacement in the mining area, ensuring safe extraction operations while keeping the ore dilution rate below 10%.

The caving mining method is suitable for loose ore bodies that allow surface subsidence, as well as steeply inclined, thick-and-large ore deposits. At the heart of this method is the use of collapsed surrounding rock to form a natural overburden, with ore extraction carried out through a bottom-level structure.

In the ore-drawing stage, large-diameter deep-hole blasting is typically employed. This method enables large-scale rock fragmentation, significantly boosting mining efficiency. Before blasting, it's essential to precisely design the arrangement of blast holes and determine the appropriate blasting parameters, taking into account the orebody's occurrence conditions, the characteristics of the surrounding rock, and the features of the underlying structure. To further enhance blasting effectiveness and reduce the percentage of oversized fragments, techniques such as millisecond-delay blasting and squeeze blasting can also be utilized.

The ore handling process primarily relies on gravity or vibrating ore dischargers. In gravity-based discharge, the ore slides naturally downward—guided by its own weight—through a funnel and chute system directly onto the stage-level transportation platform. This method is particularly suitable for ore bodies with steep dip angles and ores that exhibit good flowability. However, for ore bodies where the ore has poor flow characteristics, vibrating ore dischargers are employed to ensure smooth movement of the material through the funnel and chute system via vibrational action. During the handling process, it’s crucial to carefully regulate the discharge rate to prevent excessive speed, which could lead to increased ore loss and grade dilution.

Ground pressure management is crucial in the caving mining method, with its core focus on controlling the sequence and rate of ore extraction. A well-planned extraction sequence and speed ensure that the collapsed surrounding rock evenly covers the mined-out areas, forming a stable overburden layer that effectively controls ground pressure. During the extraction process, it’s essential to closely monitor both the amount of ore extracted and changes in ore grade, adjusting the termination of extraction based on the cutoff grade. For instance, in the staged caving method, the precision of the cutoff grade control must reach ±2% to guarantee optimal ore recovery rates and quality. Additionally, real-time monitoring systems should be employed to track ground pressure variations within the mining area. If any ground pressure anomalies are detected, the extraction sequence and speed should be promptly adjusted, accompanied by immediate implementation of appropriate ground pressure control measures—such as reinforcing support structures or modifying the extent of caving—to ensure the safety of mining operations.

Driven by the wave of intelligentization, mining equipment is accelerating its upgrade toward smarter and more automated operations. Take the rock drilling jumbo as an example—this next-generation machine integrates laser positioning and an automatic compensation system. Thanks to this innovative technology, drilling deviations can now be precisely controlled within 5 cm. In real-world operations, the laser positioning system acts like a pair of highly accurate "eyes," quickly and precisely identifying the exact drilling locations. Meanwhile, the automatic compensation system dynamically adjusts drilling parameters in real time, taking into account factors such as rock hardness and geological conditions, thereby ensuring both drilling accuracy and quality. Such high-precision drilling not only enhances blasting efficiency but also minimizes ore loss and dilution caused by drilling inaccuracies.

The loader has also achieved a smart leap forward, equipped with an inertial navigation system and a remote control module. The inertial navigation module enables real-time tracking of the loader's position and orientation, ensuring it can autonomously follow its pre-programmed route—even in complex tunnel environments. Meanwhile, the remote control module offers operators a safer and more convenient way to manage the machine, allowing them to operate the loader precisely from a control room safely removed from hazardous areas, significantly reducing operational risks. In several underground mines, operators have successfully used remote-controlled loaders to complete high-risk ore transportation tasks, boosting productivity while keeping workers safe.

In terms of ground pressure monitoring, the application of distributed fiber-optic sensing technology has enabled highly accurate, real-time monitoring of surrounding rock deformation. This technology leverages the inherent sensing capabilities of optical fibers to continuously capture even minute changes in the surrounding rock, with precision as high as 0.1 mm. Think of distributed fiber-optic sensing as an invisible monitoring network seamlessly covering the surrounding rock in mining areas—enabling early detection of subtle deformations. Whenever abnormal deformation occurs, the system instantly triggers an alert, providing precise data to support timely decisions on dynamic reinforcement measures. For instance, at a certain metal mine, distributed fiber-optic sensors detected an emerging risk of potential deformation in the surrounding rock of a specific mining area. Thanks to the real-time monitoring data, mine personnel promptly implemented appropriate support measures, effectively preventing what could have been a serious ground pressure-related disaster.

By leveraging digital twin technology, a virtual model of the mining operation has been constructed, offering a fresh perspective and innovative approach to process collaboration and optimization. Digital twin technology involves creating a dynamic, digital replica of a physical entity through advanced digitization methods, enabling real-time data exchange and coordinated operations between the virtual and physical models. In mining operations, this technology can simulate the coupled effects across the entire workflow—such as ore falling, material transportation, and ground pressure management—allowing operators to identify potential process conflicts in advance. During the simulation, by analyzing factors like equipment trajectories and blasting vibrations, it becomes possible to pinpoint issues such as overlapping equipment paths or blast-induced vibrations impacting transport routes, thereby facilitating the proactive development of optimized solutions.

Discrete Event Simulation (DES) technology plays a crucial role in optimizing equipment scheduling across multiple mining sites. By using DES, operators can simulate and analyze equipment operations in multi-site scenarios, enabling them to rationally plan the sequence of equipment usage and task execution times based on production requirements and equipment conditions. This approach ultimately boosts overall production efficiency. For instance, at a large-scale mine, implementing DES technology for optimizing equipment scheduling across multiple sites led to a 12%-18% improvement in overall productivity, significantly enhanced equipment utilization rates, and concurrently reduced production costs.

Under the guidance of the green development concept, backfilling operations have actively integrated green technologies, paving the way for sustainable development. The widespread adoption of low-toxicity emulsified explosives and column-free blasting technology has effectively reduced emissions of harmful gases during blasting. Low-toxicity emulsified explosives boast stable explosive performance and minimal production of harmful gases, enabling reliable blasting outcomes while significantly minimizing environmental pollution. Meanwhile, the column-free blasting technique, by optimizing blasting processes, has cut down on the use of detonating cords, further reducing the generation of hazardous gases. In several mines, after implementing low-toxicity emulsified explosives combined with column-free blasting technology, emissions of harmful gases have been slashed by more than 30%, markedly improving the overall working environment at these sites.

The research, development, and application of the full-tailings high-concentration filling technology have significantly boosted the utilization rate of tailings. By optimizing the particle gradation of tailings and enhancing the rheological properties of the slurry, this technology enables stable transportation with a solid-liquid ratio as high as 70%–85%, achieving a tailings utilization rate exceeding 90%. Not only does this high-concentration filling process alleviate the pressure of tailings storage on the surface environment, but it also provides an effective solution for mine ground-pressure management. At a certain non-ferrous metal mine, after implementing the full-tailings high-concentration filling technology, tailings were fully utilized, leading to a substantial reduction in the amount of tailings piled up on the surface—and simultaneously improving the overall stability of the mining areas.

The pilot "Mining-Backfilling-Transportation" integrated intelligent system implemented in a metal mine has achieved zero waste discharge and energy recycling throughout the mining process. By leveraging smart control and management, the system seamlessly integrates the three key stages—mining, backfilling, and transportation—enabling efficient resource utilization while minimizing waste emissions. During mining, waste rock and tailings are directly reused to fill mined-out areas, significantly cutting down on waste disposal. Meanwhile, optimized transportation routes and equipment scheduling have enabled energy to be recycled effectively, thereby reducing overall energy consumption. In a pilot project at a specific metal mine, the application of this integrated intelligent system has slashed waste emissions by more than 80% and cut energy consumption by approximately 20%, delivering remarkable economic and environmental benefits.

As the "core battlefield" of mining engineering, the rationality of backfilling operations and their ability to control costs directly determine a mine's economic efficiency and safety levels. From traditional rock drilling and blasting to intelligent, unmanned operations, the evolution of backfilling techniques has always revolved around the goals of "efficiency, safety, and sustainability." Looking ahead, as demands for deep-mining operations and the development of complex ore bodies continue to rise, it will be essential to further strengthen multidisciplinary integration—leveraging precise process design, smart equipment deployment, and dynamic cost management—to continuously enhance the core competitiveness of backfilling operations.