The classification of mining methods is not arbitrary—it is based on rigorous, scientifically sound principles. At its core lies the method of ground pressure management in mining, a critical element that runs throughout the entire mining operation process and plays a decisive role in ensuring safety, enhancing efficiency, and maximizing economic benefits. Ground pressure management is grounded in the physical and mechanical properties of the ore and rock, such as hardness, strength, and stability—properties that directly determine the structural integrity of the materials during mining. Meanwhile, ground pressure management is closely intertwined with the suitability conditions, design, and parameters of the mining method, as well as the specific extraction techniques employed. Any change in one aspect can have far-reaching consequences, ultimately influencing every facet of mining operations—including safety, efficiency, and economic performance.

Currently, in the mining industry, the widely adopted classification system groups numerous mining methods into three main categories: open-stope mining, stope-filling mining, and caving mining. Each of these three mining methods relies on distinct ground-pressure management strategies, effectively addressing diverse mine geological conditions and specific extraction technology requirements.

The room-and-pillar method, also known as the natural-support mining method, is an extraction technique where the stability of the surrounding rock itself—or, in some cases, a few strategically placed mine pillars or artificial supports—is relied upon to maintain the integrity of the mined-out area during the extraction process. This method is typically suited for ore deposits characterized by relatively stable ore and surrounding rock, allowing for significant exposure surfaces. The basic operational procedure involves first dividing the ore block into "rooms" and "pillars," with priority given to extracting the rooms before moving on to the pillars. During room extraction, the natural load-bearing capacity of both the pillars and the surrounding rock is fully utilized to manage ground pressure, ensuring that the mining space remains continuously open. As for the pillars themselves, their fate—whether they are eventually recovered or left permanently in place as permanent losses—is determined based on factors such as the stability of the ore and surrounding rock, specific mining requirements, and the economic value of the ore.

The Cut-and-Fill Mining Method is suitable for extracting gently inclined, thin-to-medium-thick ore bodies and requires good stability of both the ore and surrounding rock. In practical operations, the working face advances steadily either along the strike or dip direction of the ore body. During the extraction process, to maintain the stability of the mined-out area, interlayered gangue or lean ore within the ore body is deliberately left behind, creating irregular pillars that typically become permanent losses and are no longer recovered. The Cut-and-Fill method can further be subdivided into the conventional Cut-and-Fill method and the pillar-retaining Cut-and-Fill method. In the conventional Cut-and-Fill method, the ore and surrounding rock generally need to achieve at least moderate stability, with the exposed roof area exceeding 200–500 square meters. The ore body should have a dip angle of no more than 30°, and its thickness should remain below 5–7 meters—though most domestic mines currently extract ore bodies measuring 1.5–3.0 meters in thickness, where the ore body’s orientation remains relatively stable. On the other hand, the pillar-retaining Cut-and-Fill method builds upon the conventional approach by incorporating certain features of the pillar-retaining mining technique. Specifically, during extraction, a portion of the ore is temporarily left in place within the working area, forming a stable operational platform. This method boasts smaller development and stope engineering volumes, coupled with excellent ventilation conditions, making it highly adaptable to variations in ore body shape and dip angle. However, it also has certain limitations: the large exposed roof area in the mined-out zones poses significant safety risks, necessitating strict control over the extent of roof exposure to prevent sudden roof collapses.

The room-and-pillar mining method is primarily used for extracting horizontal or gently inclined ore bodies. In the mining area, ore blocks are divided into regular rooms and pillars. When reclaiming the ore rooms, carefully designed continuous or intermittent pillars are left intact to provide stable support for the roof strata. Depending on the thickness of the ore body, different extraction techniques can be employed: - For ore bodies thinner than 3 meters, the entire layer can be extracted in one go. - When the thickness ranges from 3 to 5 meters, the ore must be mined in two separate layers. - For ore bodies between 5 and 8 meters thick, the lower layer is first extracted, followed by the upper layer after roof caving. Electric loaders are typically used to remove the ore. - In cases where the ore body is 8 to 20 meters thick, shallow-hole drilling is utilized to cut shafts and roof-cutting drifts. A reserved pillar is left in the roof area, and this pillar is advanced ahead of the main extraction process by 5 to 7 meters. Subsequently, deep-hole blasting with a drill rig is carried out to break up the ore, which is then removed using trackless mining equipment. This method boasts a high degree of mechanization, enabling substantial production capacity while minimizing preparatory work and simplifying the extraction process. It also offers excellent ventilation conditions, making it well-suited for automated operations and resulting in relatively high productivity and large-scale mining capacity. However, the method does come with a relatively higher ore loss rate associated with the pillars, and the stability of the roof remains a concern. Therefore, optimizing the spacing and cross-sectional dimensions of the pillars is essential to reduce ore losses and enhance overall mining safety.

The cut-and-fill mining method is specifically designed for extracting steeply inclined, thin ore veins. It requires the surrounding rock and ore to possess double stability, while the ore itself must be free from caking or spontaneous combustion tendencies. During the mining process, workers directly operate above the exposed face of the stope, on top of the previously left ore pillars, employing a bottom-up, layered extraction approach. Each time ore is mined, about one-third of it is released by gravity, while the remaining portion remains temporarily in the stope, serving as a working platform for subsequent upward mining operations. Once the entire stope has been fully extracted, the ore initially reserved within the stope is finally discharged. This method boasts a relatively simple structural design and straightforward production process, making it easy to manage. Additionally, it leverages the natural weight of the ore for controlled discharge, significantly reducing the amount of preparatory work required. However, it also has certain drawbacks: for instance, it tends to result in substantial ore loss and dilution, as the ore undergoes multiple transfers and temporary storage during the mining process, increasing the risk of both loss and degradation. Moreover, this method imposes strict requirements on the properties of the ore—it is not suitable for all types of ore—and demands extra precautions during mining to prevent risks such as ore caking or spontaneous combustion. Cut-and-fill mining is particularly well-suited for extracting non-cohesive ores like tungsten and tin.

The sublevel caving method further divides each stage into several sublevels—typically 3 to 5—in each of which mining rooms and pillars are arranged separately. Sublevels essentially serve as the basic units for extraction, and the mining processes within each sublevel are generally similar. The ore extracted from each sublevel is transported out through the sublevel stope drifts, either via chutes or directly along inclined ramps leading to underground stockpiles. This method usually does not leave interpillar pillars; instead, continuous mining is carried out within each sublevel, often utilizing self-propelled equipment for extraction. If pillars are left between sublevels or within the mining rooms, they are typically recovered immediately after the room-by-room extraction is completed, followed by timely backfilling of the resulting voids. In this method, nearly all mining operations take place in tunnels and chambers with relatively small exposed surfaces, ensuring good safety conditions. Moreover, since each sublevel functions as an independent extraction unit, the method offers high flexibility. However, this approach requires substantial preparatory work due to the presence of pillars, which can hinder ore recovery and increase the volume of preparatory tasks. As a result, while it enhances operational flexibility, it may also slightly reduce overall mining efficiency.

The stope-and-pillar method uses an entire mining stage as the extraction unit, employing either deep or medium-deep holes for ore breaking. Depending on the arrangement of blast holes, it can be further divided into the Horizontal Deep-Hole Stope-and-Pillar Method and the Vertical Deep-Hole Stope-and-Pillar Method. In the Horizontal Deep-Hole method, undercutting must be performed at the bottom of the stope; horizontal fan-shaped deep holes are drilled from the drilling chambers to break ore directly into the undercut space at the stope floor. Meanwhile, the Vertical Deep-Hole method not only involves undercutting but also requires the excavation of cutting slots. Here, the working face is vertical, and the broken ore naturally falls by gravity to the stope floor, gradually expanding the mined-out area. This method demands that the orebody maintain strong integrity, making it suitable for large-scale, mechanized mining of medium-to-thick orebodies—enabling highly efficient extraction operations. However, it also places relatively high demands on both mining techniques and equipment.

Filling mining is an extraction method in which the mined-out areas are gradually backfilled with filling materials as the working face advances during the mining process. In practical operations, support structures are sometimes used in conjunction with the filling materials to maintain the stability of the mined-out zones. The primary purpose of filling these voids is to manage ground pressure effectively by leveraging the resulting fill mass, thereby controlling rock bursts and surface subsidence, and creating safe and convenient conditions for continued mining activities. It is also occasionally employed to prevent spontaneous combustion fires in ores that have a tendency to self-ignite.

The single-layer filling method is suitable for gently dipping, thin ore bodies. In this method, mining operations are conducted along the full-length, wall-like retreat face of the ore block, advancing sequentially across the entire thickness of the ore body in the strike direction. As the working face progresses, mined-out areas are systematically treated using either hydraulic or cemented filling techniques to effectively control roof caving. Take the Xiangtan Manganese Mine in Hunan Province as an example. This mine extracts gently dipping, thin ore bodies characterized by stable ore that is prone to spontaneous combustion. Meanwhile, the roof rock is unstable, and the overlying area contains a water-bearing aquifer, making caving unacceptable. The stability of the floor, however, allows for safe extraction. During the mining process, each ore block measures 30–40 meters in dip length and extends 60–80 meters along the strike. Key parameters include a controlled roof distance of 2.4 meters, a filling distance of 2.4 meters, and a hanging roof distance of 4.8 meters. Shallow-hole sublevel caving is employed, with ZJP-13 electric winches used to haul the ore out of the mine. Simultaneously, timber supports are installed as mining advances. Once the working face has advanced 1.8 meters along the strike, filling operations begin at a rate of 2.4 meters. Before filling, the site must be cleared, filling pipelines installed, sand gates constructed, and sand curtains hung to ensure proper material flow. Hydraulic filling is carried out intermittently from bottom to top, against the dip direction, while staged removal of pillars and backfill materials follows. Under conditions where roof rock instability prohibits caving, the single-layer filling method proves to be an effective approach for extracting gently dipping, thin ore bodies. It offers advantages such as high recovery rates and low dilution but also suffers from drawbacks like relatively low mining efficiency and significant consumption of timber supports.

The upward layer-by-layer filling method can further be divided into the upward horizontal layer-by-layer filling method and the upward inclined layer-by-layer filling method. In the upward horizontal layer-by-layer filling method, the ore block is typically first divided into mining rooms and ore pillars. The mining of the rooms proceeds in the first step, followed by the extraction of the ore pillars in the second step. When mining the rooms, a bottom-up, horizontal layer-by-layer approach is adopted. As the working face advances, each layer is sequentially filled to backfill the mined-out areas, while leaving sufficient space for continued upward mining operations. The backfilled material not only helps stabilize the surrounding rock on both sides but also serves as a stable working platform for subsequent mining activities. The collapsed ore naturally lands on the surface of the backfill, where it can then be mechanically transported via chutes directly into the drawbings. When the mining reaches the topmost layer of the room, roof-closing filling must be carried out. Meanwhile, the ore pillars are extracted only after several mining rooms have been fully depleted or once the entire stage has been completely mined out. The structural parameters of the ore blocks under this method vary depending on the thickness of the ore body. Specifically: when the ore body is less than 10–15 meters thick, the long axis of the mining room is aligned along the strike direction, with room lengths ranging from 30 to 60 meters. However, when the ore body exceeds 10–15 meters in thickness, the mining rooms are arranged perpendicular to the strike direction. In such cases, the room length is usually kept within 50 meters, while the room width is set at 8–10 meters, leaving an inter-pillar width of 6–8 meters. The roof pillar is designed to be 4–5 meters thick, and the floor pillar stands 5 meters high. The overall stage height is maintained between 30 and 60 meters. To minimize ore loss, concrete floor pillars can be used instead of traditional ore-based floor pillars. This method offers versatile and flexible mining plans, features a straightforward design, simplifies mining and cutting operations, results in low cut-to-ore ratios, and effectively prevents both over-mining and under-mining. It also enables selective mining practices, leading to minimal ore loss and dilution rates. Additionally, the method demonstrates strong adaptability to variations in ore body geometry and supports high levels of mechanization, thereby delivering substantial production capacity in the mining area. However, since workers operate directly beneath the exposed roof, safety conditions remain relatively poor, placing stringent demands on roof management and maintenance practices.

The key difference between the upward-inclined slicing method and the upward-horizontal slicing method lies in their mining approach: the former employs inclined slicing for extraction, with ore and backfill materials primarily moved within the stope by gravity. Therefore, it can only utilize dry-type backfilling. In this method, each ore block serves as the unit of extraction, with backfill material fed from the filling shaft directly onto the inclined working face, where it spreads naturally under its own weight. After laying down support planks, ore is then dropped into the shaft—again relying on gravity. The entire mining process is divided into three distinct stages: first, the triangular base area is mined to create the inclined working face; next, the regular inclined working face is extracted; and finally, the top portion of the triangle-shaped ore body is removed. As the mechanization level of the upward-horizontal slicing method continues to advance, the inherent advantages of using gravity to transport both ore and backfill materials are gradually becoming less pronounced. Moreover, this method comes with stringent operational requirements—it demands that the orebody maintain a well-defined, regular shape and must be medium- to thick-sized, with an inclination angle exceeding 60° to 70°. Importantly, it cannot be applied to hydraulic or cemented backfilling systems.

The downward layered filling method is suitable for mining ore bodies that are highly unstable—either the ore itself or the surrounding rock—and which contain high-grade or high-value non-ferrous or rare metal deposits. The essence of this mining technique lies in layer-by-layer extraction from top to bottom, followed by step-by-step backfilling. Each extraction layer is carried out under the protection of an artificial false roof constructed above the previous layer. Extraction layers can be either horizontal or inclined at angles ranging from 4°–10° or 10°–15° relative to the horizontal plane. Inclined layers are primarily designed to support the immediate roof while also facilitating ore transportation; however, drilling and support operations are less convenient compared to horizontal layers. For instance, at the Garpenberg lead-zinc mine in Sweden, the ore body dips at approximately 70° with a thickness of 20 meters. The ore is soft yet boasts exceptionally high grade. Here, each extraction layer is set at a height of 4 meters, with drifts measuring 4.5 to 5 meters in width. Two-jig drill rigs are used to drill blast holes, each 38 mm in diameter and up to 2.7 meters deep. After blasting, the extracted ore is loaded into 2.6 m³ front-end loaders, which then transport it via dump trucks directly to the stope chute. Immediately following the completion of drift excavation, backfilling commences. Tailings are first processed on the surface: after desliming through hydrocyclones and dewatering via cylindrical vacuum filters, they are mixed with cement and water in a twin-shaft blade mixer to form a slurry. This prepared filling material is subsequently pumped underground using a dual-cylinder plunger pump. Before backfilling begins, a 30-cm-thick layer of crushed ore is left at the floor of the drift, topped with plastic sheeting, and further covered by a metal mesh. The lower portion of the drift is initially filled with a mixture having a cement-to-sand ratio of 1:4, reaching a height of 1.6 meters, while the remaining space is backfilled with a cement-sand mix at a ratio of 1:8. Notably, the two adjacent extraction layers intersect perpendicularly, with the upper layer’s backfill acting like a crossbeam supporting the lower drift, thereby ensuring optimal operational safety. This downward layered filling method effectively addresses the challenging issue of safe extraction in extremely unstable ore bodies, though it comes with relatively higher costs.

The stope backfilling method is primarily characterized by its drift-based mining approach, with upward and downward drifts constructed alternately. During the mining process, high-concentration cemented backfill material is used in conjunction to maintain the stability of the mine walls. The patent titled "A Medium-to-Deep Hole Drift Backfill Mining Method and Backfilling Device," filed by China Coal No.71 Engineering Corporation Limited, introduces a mesh component that effectively connects the solidified tailings or cement mortar, preventing cracks and subsequent collapse after solidification. This innovation significantly enhances the internal stability of the mined-out areas post-backfilling. Additionally, the patent "A Construction Process for Drift-Type Backfill Retaining Walls," submitted by Baiyin Colored Metal Group Co., Ltd., features a straightforward construction process, shortens the project timeline, and boasts high drainage and backfilling efficiency. The retaining wall can be fully installed and allowed to set within just one day, making it easy to inspect and verify the backfilling quality. This method also reduces costs and offers excellent load-bearing capacity. Moreover, some of the backfill pipelines can even be recovered, making it particularly beneficial for mines requiring rapid completion of drift backfilling operations to ensure uninterrupted production continuity. The drift backfilling method is well-suited for a wide range of complex orebody conditions, effectively boosting the overall recovery rate of mineral resources.

The selective mining and backfilling method is primarily designed for thin veins or multi-variety ore bodies. When the vein thickness falls below 0.3 to 0.4 meters, workers are unable to operate directly within the orebody. In such cases, it becomes necessary to separately extract the ore and surrounding rock, ensuring that the mined-out area reaches the minimum working thickness required for safe operations—typically 0.8 to 0.9 meters. The extracted ore is transported out of the mine, while the excavated surrounding rock is used to backfill the mined-out spaces, creating favorable conditions for advancing further upward. This method combines selective mining through wall-cutting techniques with waste-rock backfilling, significantly reducing dilution rates. It is particularly well-suited for the extraction of rare metal ores, enabling maximum recovery of valuable resources and minimizing waste—a crucial approach for sustainable mining practices.

The backfilling method involves implementing either cemented or non-cemented backfilling in one go after the mining room has been fully extracted. This approach creates artificial pillars that combine the high-efficiency mining advantages of the open-stope method with the stability provided by backfilling. In practical applications, if the pillars are not intended for recovery and will remain as permanent losses, non-cemented backfilling can be used to fill the mined-out areas. However, when the backfill material in a particular block needs to serve as an access passage for adjacent blocks, the bottom section—approximately 10 meters deep—should be filled with a higher-grade cemented mixture featuring a greater ratio of fly ash to sand. For instance, the Kidd Creek mine overseas utilizes large-scale sulfide ores as its primary ore type. The mining chambers measure 79 feet wide, 98 feet long, and 299 feet high, with each sublevel standing 98 feet tall. Pillar dimensions range between 70 and 98 feet, while transport drifts are spaced 397 feet apart. This mine employs the open-stope backfilling method, which has proven highly effective in enhancing overall production capacity and significantly reducing ore loss and dilution.

In recent years, backfilling technology has seen continuous innovation in both processes and materials. In terms of filling materials, the reuse of waste products such as tailings and industrial slag not only reduces filling costs but also minimizes environmental impact. Meanwhile, the adoption of pipeline transportation for high-concentration backfill slurries and optimized cementation ratios have significantly enhanced the strength and stability of the backfilled material. Additionally, advanced monitoring technologies enable real-time tracking of the backfill’s condition and the stability of mined-out areas, providing miners with a more reliable safety assurance. As technology continues to advance, the application of the backfilling method is steadily expanding—particularly in deep-metal mines and regions with stringent surface protection requirements—making it an essential tool for achieving sustainable, efficient mining practices.

The caving mining method is an extraction technique where the surrounding rock collapses simultaneously as mining operations advance, thereby filling the mined-out areas. This method uses an entire ore block as the mining unit, employing a top-to-bottom approach within a single stage. A key feature of this method is the discharge of ore directly beneath the overlying strata. The caving method is suitable when surface collapse is permissible and the orebody consists of thick, steeply inclined or vertical high-grade deposits with unstable ore or surrounding rock, coupled with high mining intensity. While this method offers advantages such as high production efficiency, enhanced operational safety, and flexible production processes, it also suffers from significant ore loss and dilution, making it unsuitable for extracting high-grade, high-value ores.

The single-layer caving method is suitable for mining layered ore bodies with unstable roof rocks, a thickness of less than 3 meters, and an inclination angle below 30°. During the mining process, the inter-stage ore layers are divided into individual blocks, and extraction advances along the strike direction across the full thickness of the ore body. As the working face moves forward, supporting pillars are recovered, while the roof rock above the mined-out area is collapsed and used to backfill the voids. Depending on the specific characteristics of the working face, this method can be further categorized into longwall, shortwall, and drift types. The longwall method features a working face length equal to the entire block’s diagonal length, making both preparatory work and face layout straightforward. It boasts high production capacity, excellent labor efficiency, minimal ore loss and dilution, and superior ventilation. However, its primary support materials are wood-based, leading to significant timber consumption, heavy labor intensity in support tasks, and complex roof management. In contrast, the shortwall method is better suited for situations where roof stability is poor. Here, segmented roadways are driven between stages along the strike direction, effectively reducing the size of each working face. While this approach offers greater flexibility and adaptability, it results in lower overall production capacity and reduced labor productivity compared to the longwall method. Finally, the drift method is ideal for cases where ore stability is extremely poor. In this scenario, the ore block is divided into segments using either segmented roadways or inclined shafts, which then serve as the working faces for advancing extraction.

The sublevel caving method is suitable for steeply inclined ore bodies where both the ore and surrounding rock are unstable, the ore body is extremely thick, and the ore grade does not offer high economic value. This method involves mining in layers from top to bottom, with each mining unit defined by a specific extraction drift. Mining is carried out under false roof support; once a layer is fully extracted, a flat layer of backing boards is laid at the bottom, supporting pillars are removed, and the roof is then allowed to collapse naturally. This method boasts low ore loss and dilution rates, enabling in-situ mineral processing directly at the extraction face. It also demonstrates excellent adaptability to various ore body shapes. However, it has significant drawbacks: it consumes large amounts of timber, suffers from poor ventilation conditions, poses a fire hazard, and has relatively low production capacity. For instance, in a particular mine, the sublevel caving method was employed, with extraction areas arranged continuously along the strike of the ore body, each spanning 50 meters in length. The width of each area matched the horizontal thickness of the ore body, while the height remained consistent with the height of the intermediate levels. Importantly, no pillar or stope pillars were left between upper and lower levels, nor were any inter-stope pillars retained between adjacent extraction areas—instead, mining proceeded continuously downward in distinct layers. During the extraction process, shallow-hole drills were used to create shallow blast holes for ore fragmentation, and electric-powered ore loaders were employed to remove the broken material. Simultaneously, as mining progressed, supports were promptly installed to reinforce connecting passageways between layers, as well as the level drifts and extraction roadways themselves. When extracting the topmost layer, it was essential to lay wooden beams and metal mesh false roofs on the layer’s baseplate before allowing the roof to collapse, ensuring the safety of subsequent mining operations.

The cut-and-fill method with a bottom pillar is suitable for steeply inclined ore bodies that are at least 5 meters thick, with an inclination of no less than 10 meters, where the hanging wall rock is relatively unstable while the footwall remains moderately stable or better. The ore grade should be at least medium, and the ore value shouldn’t be high. This method involves mining in descending, segmented stages, with each segment equipped with specialized bottom structures—such as electric rakers—for ore extraction. Its advantages include flexibility, broad applicability, high production capacity, simple mining equipment, and excellent ventilation conditions. However, its drawbacks include significant ore loss and dilution, as well as substantial preparatory and cutting work. In practical applications, it’s essential to carefully select the appropriate ore-drawing method—such as planar, vertical, or inclined drawing—to minimize ore loss and dilution. For instance, Zhongtiaoshan Nonferrous Metals Company has successfully implemented inclined ore-drawing techniques in cut-and-fill operations with bottom pillars, particularly for thick and large-scale ore bodies. By running multiple parallel cross-cut raking drifts within the stope and adopting an inclined drawing approach, they control the discharge rate from each funnel. This ensures that the collapsed ore forms a slope with an angle greater than 30° within the stope, effectively maintaining the inclined contact between ore and waste rock and thereby reducing both ore loss and dilution rates.

The pillarless sublevel caving method is suitable for mining roadways with stable conditions, as well as steeply or gently inclined thick ore bodies. It can be used to remove intercalated gangue from the ore or to grade the mined material. In this method, both the sublevel drilling and blasting, as well as ore extraction, are carried out entirely within the mining roadway, ensuring high safety and a simple stope structure. It is particularly well-suited for large-scale trackless equipment operations, boasts a high degree of mechanization, requires minimal preparatory mining work, delivers high labor productivity, and keeps costs low while maintaining safe working conditions. However, this method also has certain drawbacks, such as challenging ventilation in the mining roadways and relatively high ore losses and dilution. China's metal mines began adopting the pillarless sublevel caving method in 1965, and it quickly gained widespread use. Today, this technique accounts for approximately 70% of the total ore production in underground iron mines across the country. That said, the method still faces an ore loss rate of around 20% and a dilution rate ranging from 20% to 30%. To address these challenges in practical applications, it is essential to optimize mining designs and carefully plan preparatory mining operations, thereby effectively reducing both ore losses and dilution.

The stage caving method is divided into stage forced caving and stage natural caving. Stage forced caving is suitable for ore bodies that are thick, large in size, uniformly shaped, steeply inclined, low in value, and characterized by non-caking, non-spontaneous combustion, and non-oxidized ore. In this method, the mining height equals the full height of the stope, resulting in minimal preparatory works, high labor productivity, low costs, and enhanced operational safety. However, it demands strict control over production and ore-drawing techniques, leading to a higher percentage of large fragments and greater ore loss. Stage natural caving, on the other hand, is ideal for ore bodies whose lower portions can naturally collapse under their own weight after being undercut. This method shares the same applicability conditions as stage forced caving. For instance, the Tongkuangyu Mine has long relied on natural caving for ore extraction; yet, this approach has also triggered issues such as ground pressure-related damage, necessitating the implementation of appropriate mitigation measures to ensure safe and sustainable mine operations.

The application of the caving method is subject to strict prerequisites. First, the surface must be capable of subsidence—this is the fundamental condition for implementing the caving method. If buildings, transportation infrastructure, or other critical facilities are present on the surface and any collapse would pose a risk to these structures, then the caving method cannot be used. Second, the thickness and dip angle of the orebody must meet the requirement that the collapsed rock layers can effectively cover the mined-out area. Generally speaking, the caving method is most suitable for steeply inclined orebodies with a thickness of at least 5 meters, and for gently inclined orebodies with a thickness of at least 10 meters.

In terms of engineering control, establishing a comprehensive ground pressure monitoring system is crucial. By continuously tracking changes in ground pressure in real time, it becomes possible to promptly assess the stability of surrounding rock masses and proactively predict potential secondary hazards such as landslides or surface collapses. For instance, in several mines, advanced sensor technologies are employed to monitor parameters like stress and displacement in the rock mass surrounding the mining areas. As soon as anomalies are detected, immediate countermeasures are implemented—such as reinforcing support structures or adjusting the sequence of mining operations. Meanwhile, during the construction process, it’s essential to rationally optimize the sequence of rockfall and blasting parameters. Based on the geological conditions of the ore body and specific mining requirements, a scientifically sound sequence for rockfall should be carefully planned to ensure that the collapse of surrounding rock occurs uniformly and steadily. When selecting blasting parameters, factors like ore hardness and rock mass structure must be thoroughly considered. This approach not only guarantees that the blasting meets the demands of efficient extraction but also minimizes damage to the surrounding rock, striking a balance between resource recovery rates and mining costs. Ultimately, this strategy enables safe and highly productive mining operations.

In the field of mining engineering, selecting an appropriate mining method is by no means a simple or arbitrary decision—it is a complex process that requires careful consideration of numerous factors and adherence to rigorous engineering logic. This decision directly impacts critical aspects such as mine safety, operational efficiency, resource recovery, and economic profitability; indeed, even the slightest oversight in any step could lead to severe consequences.

The geological conditions of the ore body serve as the fundamental basis for selecting an appropriate mining method. The stability of the ore body directly determines the requirements for support systems and ground pressure management during the mining process. For ore bodies with good stability, the open-stope mining method is a more suitable choice, as it fully leverages the inherent strength of the ore and rock to maintain the stability of the mined-out areas, thereby reducing support costs and enhancing mining efficiency. On the other hand, for unstable ore bodies, filling or caving mining methods may be more appropriate, as they help control ground pressure by either backfilling or allowing controlled collapse of the surrounding rock, ensuring safe and secure operations.

The thickness and dip angle of ore bodies also significantly influence the selection of mining methods. For gently inclined, thin ore bodies, methods like the room-and-pillar or cut-and-fill mining techniques are more suitable, as they can effectively accommodate the ore body's shape and orientation, enabling efficient extraction. In contrast, for steeply inclined, thick and large ore bodies, methods such as sublevel caving or block caving are preferred, leveraging the natural weight of the ore to facilitate mineral discharge and boost production capacity.

Economic and technical indicators are indispensable factors to consider when selecting an mining method. Cost control is crucial to mine operations, as different mining methods vary significantly in terms of equipment purchase costs, material consumption, labor input, and other expenses. For instance, open-pit mining typically incurs lower costs but is limited by the depth of ore deposits and topographical conditions; in contrast, underground mining, though more expensive, allows access to deeper mineral resources. Therefore, when choosing a mining method, it’s essential to comprehensively assess the specific conditions of the mine and carefully weigh the trade-offs between cost and profitability.

Resource recovery rate is one of the key indicators for evaluating the effectiveness of mining methods. High-value precious metal ores or rare metal ores typically require mining methods with high recovery rates, such as backfill mining, to maximize resource recovery and minimize waste. Meanwhile, for low-grade ores, miners can opt for lower-cost mining methods—while still maintaining an acceptable recovery rate—in order to enhance economic efficiency.

Environmental protection requirements are also playing an increasingly important role in modern mining. As public awareness of environmental issues continues to grow, higher standards are being set for minimizing the environmental impact of mining operations. Surface protection is one of the key aspects of environmental sustainability; for mines located near critical structures, ecological reserves, or densely populated areas, it’s essential to adopt mining methods that cause minimal disturbance to the surface—such as backfilling techniques—to prevent land subsidence and ecological damage.

Waste rock management is also a crucial aspect of environmental protection requirements. Traditional mining methods often generate large amounts of waste rock, placing significant pressure on the environment. Therefore, when selecting mining techniques, it's essential to consider how waste rock will be handled—aiming to minimize its generation and, whenever possible, turning waste rock into valuable resources through recycling and reuse.

To achieve precise selection of mining methods, modern mines widely employ digital modeling and rock mechanics analysis techniques. Digital modeling enables the simulation and analysis of orebody geological conditions and the mining process, helping to predict the effectiveness of various mining methods and providing a scientific basis for decision-making. Meanwhile, rock mechanics analysis allows for an in-depth study of the mechanical properties of ore rocks, assesses the stability of mining areas, and optimizes ground pressure management strategies.

For example, in the mining operations of a particular mine, digital modeling and rock mechanics analysis were used to simulate and compare three mining methods: open stope mining, backfilling mining, and caving mining. The results showed that, given the orebody conditions of this mine, while backfilling mining is more costly, it effectively controls ground pressure, ensures surface safety, and achieves a higher resource recovery rate. On the other hand, caving mining, though less expensive, leads to greater ore loss and dilution, and also has a noticeable impact on the surface environment. Although open stope mining boasts high extraction efficiency, it poses significant safety risks in areas where the orebody is unstable. After carefully weighing all these factors, backfilling mining was ultimately chosen as the primary method for this mine.

Selecting an appropriate mining method is a comprehensive and systematic engineering decision-making process that requires careful consideration of various factors, including the geological conditions of the ore body, economic and technical indicators, as well as environmental protection requirements. By adopting scientifically sound and rational methods, combined with cutting-edge technological approaches, we can achieve safe, efficient, and environmentally friendly mining operations—laying a solid foundation for the sustainable development of the mining industry.