I. Mining Methods and the Basic Framework of Development Engineering

(1) Core Components of Mining Methods

Mining methods are systematic technical solutions designed for the efficient extraction of ore from mining units, encompassing four core modules: structural parameter design, development engineering layout, cutting process planning, and mining sequence organization.

The longwall mining unit, often referred to as the "basic operational unit" of mining operations, can be either a panel or a section. The specific mining method employed is essentially a tailored extraction plan designed for this particular "unit." At the heart of this plan lies the structural parameter design, which must be precisely determined based on factors such as orebody thickness, dip angle, and surrounding rock stability. These parameters provide the geometric foundation needed for subsequent engineering work. For instance, when mining thicker orebodies, appropriately increasing the size of the working face can significantly enhance mining efficiency; conversely, if the surrounding rock stability is poor, reducing the spacing between pillars becomes crucial to ensure safe extraction operations.

The mining preparation engineering plays a critical role in creating operational space and establishing the transportation and ventilation systems. It serves as the pivotal link between development and extraction, laying a solid foundation for the subsequent cutting and recovery operations. Meanwhile, the cutting process planning focuses on meticulously shaping ideal free faces and ore-breakage spaces within the mineral body—essentially carving out efficient "passages" that facilitate smooth and streamlined recovery work ahead. Finally, the organization of the recovery procedures involves multiple interrelated steps, including rock drilling, blasting, ventilation, ore removal, and ground pressure management. Each step works in seamless coordination, much like a finely tuned machine, ensuring that ore extraction is both efficient and safe.

(II) Definition and Technical Implications of Mining Preparation Engineering

Mining preparatory engineering refers to the preparatory work carried out on the basis of development projects, involving the excavation of shafts and roadways to delineate mining units, as well as the construction of supporting systems for pedestrian access, transportation, ventilation, and backfilling. Its core tasks include the following aspects:

1. Space Construction

Forming connecting passages that link the mineral body directly to development roadways, such as interlayer connecting drifts or ramps. These passages act like the human body's vascular system, tightly integrating the mineral body with external transportation, ventilation, and other critical systems—ensuring smooth access for personnel, equipment, and materials into the mine, while also enabling timely removal of ore.

2. Functional Integration

Configure functional structures such as ore chutes and ventilation shafts to ensure the continuity of the mining process. Ore chutes are used for the vertical transportation of ore, while ventilation shafts supply fresh air underground and exhaust stale air, creating an optimal working environment for personnel. Additionally, these systems help reduce the concentration of harmful gases generated after blasting, thereby enhancing operational safety.

3. Parameter Optimization

By optimizing tunnel specifications and spacing designs, we can strike a balance between engineering effort and production efficiency, ultimately reducing the mining-to-extraction ratio (the length of preparatory tunnels required per unit of ore mined). Reasonable tunnel dimensions not only meet essential needs such as transportation and ventilation but also minimize unnecessary excavation work. Meanwhile, appropriately spaced tunnels ensure close connectivity among individual mining units, boosting overall extraction efficiency. For instance, when mine conditions permit, slightly increasing tunnel spacing can help cut down on tunneling volume and lower costs—but it’s crucial to still prioritize the convenience of transportation and ventilation, ensuring that short-term gains don’t compromise long-term operational effectiveness.

II. Classification System and Technical Features of Mining Preparation Methods

(1) Core Classification Criteria for Mining Methods

The classification of mining methods is like constructing a towering building—it has a rigorous structure and standardized framework. Based on different technical criteria, these methods are primarily divided into two major categories: one categorized by the relationship between roadways and ore bodies, and the other by the type of transportation equipment used. Each category embodies unique technical principles and application scenarios.

1. Classified by the relationship between roadways and ore bodies

Intravascular Precision Sampling

The main roadways are like roots embedded deep within the ore body, closely adhering to its structure. This approach is particularly suited for scenarios where the ore body is thick and the surrounding rock lacks stability—much like driving sturdy pillars directly into solid bedrock when working in loose, unstable soil, ensuring greater structural integrity. For instance, the vein-inclined ramps extend along the orientation of the ore body, providing a convenient pathway for mining equipment; meanwhile, the vein shafts act as vertical "blades," piercing straight through the ore body to connect different horizontal levels. This design proves highly efficient in transporting ore from thick, extensive deposits down to the main transport tunnels during extraction.

Extravascular Sampling Calibration

The roadway, designed with a "hands-off" approach, is strategically placed within the surrounding rock of the ore body. The primary benefit of this method is that it minimizes disruption to the integrity of the ore body—much like carefully unwrapping a gift without damaging its contents. Additionally, it creates ideal conditions for the smooth passage of mechanized equipment, with ample space allowing machines to maneuver effortlessly. In the extraction of medium-to-thick ore bodies, off-vein mining preparation has become the mainstream solution. For instance, in several large-scale metal mines, off-vein ramp systems and segmented level drifts are employed to connect individual mining areas, thereby establishing an efficient transportation network.

Joint Mining and Preparation

Skillfully integrating in-mine and out-of-mine roadways is like perfectly fitting together the pieces of a complex puzzle. When mining intricate ore bodies, this approach ensures both optimal resource utilization and enhanced engineering safety. For instance, in mines with irregular ore-body shapes and significant thickness variations, one can first establish the primary transportation and ventilation systems using out-of-mine roadways, then precisely excavate the ore body via in-mine roadways. This method not only guarantees efficient extraction but also minimizes resource waste.

2. Categorized by Type of Transportation Equipment

Track-based mining

Suitable for narrow-gauge railway transportation, its track cross-section is relatively small—almost as if the rails were custom-made for compact trains. In some small-scale mines or areas with limited extraction conditions, rail-based mining operations continue to play a vital role, thanks to their low costs and simple equipment. By laying tracks and connecting mine cars with motorized locomotives, this system efficiently facilitates the transport of ore.

Trackless Mining and Preparation

Adapted to equipment such as loaders and trucks, the mine tunnels must meet both the turning radius requirements of these "big machines" and stringent ventilation standards to ensure smooth operation. Trackless equipment boasts exceptional maneuverability, allowing for rapid relocation between different mining areas—significantly boosting overall extraction efficiency. In modern large-scale mines, trackless mining techniques are widely adopted: massive loaders directly scoop and load ore within the mining face, then transport it swiftly through spacious tunnels to designated unloading points.

(II) Advantages of Off-Wellbore Precision Drilling Technology and Its Applicable Scenarios

As an important member of mining surveying methods, Pulse External Surveying stands out among numerous mining scenarios thanks to its unique technical advantages.

By positioning the main transport and ventilation roadways in the hanging wall or footwall surrounding rock of the orebody, the off-mine access method cleverly avoids the direct impact of mining activities on these tunnels, significantly enhancing the reliability of the entire mining system—almost as if a robust armor has been donned around the transport and ventilation networks.

Its core advantages lie in several key areas: In terms of safety, the surrounding rock typically exhibits greater stability than the ore body itself, which not only reduces tunnel support costs but also significantly minimizes safety risks such as roof collapses, thereby providing a much safer working environment for personnel. In terms of flexibility, it allows for continuous operation by trackless equipment, supporting the excavation of large-section tunnels—essentially creating a wide "highway" for machinery to move swiftly and efficiently, dramatically boosting mining productivity. As for adaptability, the off-vein mining method is well-suited for veins ranging from thin to medium-thick (3–15 meters in thickness), particularly in ore bodies with complex mineral-rock boundaries. This approach is especially prevalent in the extraction of high-value metal ores. For instance, in the mining of certain gold and silver deposits, off-vein mining enables maximum recovery of ore resources while ensuring safety, minimizing damage to the ore body, and ultimately enhancing overall resource utilization.

III. Key Technologies and Engineering Practices for Off-Wellbore Data Acquisition

(1) Principles for Layout of Off-Mine Surveying and Control Engineering

1. Tunnel Positioning

In off-vein mining, the precise positioning of roadways is both fundamental and critical. Typically, main transport tunnels and ventilation drifts are laid out in the surrounding rock, 5 to 8 meters away from the ore body, running parallel to it. This specific distance is not chosen arbitrarily but is carefully determined after considering multiple factors. On one hand, a 5- to 8-meter gap effectively shields the roadways from blast-induced vibrations during ore extraction, ensuring their structural stability. At the same time, it helps reduce the overall excavation workload to some extent, thereby lowering costs. For instance, in a certain copper mine, a 5-meter-off-vein inclined ramp was designed on the lower side of the ore body. During subsequent mining operations, this ramp remained largely unaffected by the ore-body blasts, reliably supporting safe equipment transportation and personnel movement while significantly cutting down on the expenses associated with frequent ramp maintenance.

2. Hierarchical Contact Roadway Design

The layered connecting drift serves as the "link" that connects each layer to the main transportation and ventilation systems, and its design directly impacts the efficiency of mining operations. Generally, layered connecting drifts are arranged at intervals corresponding to the layer height (typically 3–5 meters). In terms of length, keeping them within 10 meters is generally ideal. Shorter connecting drifts help reduce ventilation resistance, boosting ventilation efficiency, while also minimizing the time required for equipment and personnel to traverse these passages—thus enabling a streamlined workflow characterized by "short connections and high efficiency."

3. Slurry Well System

The chute mine plays a critical role in ore transportation. Typically, the diameter of the chute mine is designed to be between 2 and 2.4 meters—this size ensures smooth ore discharge while also preventing damage caused by oversized diameters that might result in ore impacting the井壁 (well wall). A single chute mine can handle up to 300,000 tons of ore, demonstrating its robust transportation capacity. To further enhance equipment efficiency, the design of an accompanying reversing chamber has become essential. The reversing chamber provides ample turning space for equipment like scraper conveyors, enabling them to quickly and safely unload ore, reducing idle time and significantly boosting overall mining efficiency.

(II) Innovative Application of Return-Type Mining Access Ramp

Addressing the issue of traditionally high vein-extraction-to-mining ratios (often exceeding 15 m/kt), the new retrograde ramp technology has effectively enhanced mining economics through a series of optimizations.

1. Structural Design

During the construction of the return ramp under the mining area, this design breaks away from the traditional combination of "segmented level drifts combined with interlayer connecting drifts." Instead, a connecting drift is established every time the mining height advances by one layer (3–5 meters), directly penetrating the orebody. For instance, at a certain mine, the conventional mining preparation method would require extensive segmented level drifts and interlayer connecting drifts. However, by adopting the return ramp design, the overall engineering workload has been reduced by more than 30%. This not only lowers excavation costs but also significantly shortens the construction period for mining preparation, enabling the mine to move into the recovery phase much faster.

2. Mechanized Adaptation

The slope design for the return-type ramp is set between 10% and 15%, a range carefully determined based on the performance characteristics of the 3m³ loader, ensuring it meets the demands for efficient operation. Compared to traditional rail-based transportation, using loaders on this type of ramp boosts mining efficiency by up to two times. Loaders can directly scoop ore within the mining area and swiftly transport it via the ramp to the designated unloading point, significantly enhancing overall ore-handling productivity.

3. Collaborative Filling Process

After the layered mining is completed, a filling retaining wall will be installed at the entrance of the connecting drift to facilitate upward filling operations. Once the shear strength of the filled material reaches 1 MPa, it can safely support the next layer of mining activities. The application of this technology has significantly reduced the curing period for the fill body, enhancing the continuity of mining operations. In a certain gold mine, after implementing this technique, the recovery cycle for each layer was shortened by 3 to 5 days, leading to an overall improvement in mining efficiency.

(III) Comparative Analysis of Sampling Accuracy Between Extravascular and Intravascular Methods

1. Tunnel Maintenance Costs

The roadways mined outside the vein are located within the surrounding rock, which generally exhibits high stability and experiences minimal direct impact from mining activities, resulting in low support requirements and a potential reduction of maintenance costs by 30% to 50%. In contrast, the roadways mined inside the vein are situated within the ore body itself, which tends to fracture easily due to blasting and other extraction processes. This necessitates frequent support and reinforcement, leading to increased investments in labor, materials, and equipment.

2. Degree of mechanization

Pit-exit alignment can create spacious, continuous operating spaces for trackless equipment, easily accommodating their turning and passage needs. This allows loaders, trucks, and other equipment to operate efficiently, significantly boosting overall mining productivity. In contrast, pit-in alignment is constrained by the orebody’s shape and spatial limitations—narrow tunnel cross-sections and insufficient turning radii severely restrict the movement of trackless machinery. As a result, operators often have to rely on smaller, less maneuverable equipment, which ultimately hampers mining efficiency.

3. Ore Loss Rate

Pit-wall mining causes minimal disturbance to the ore body, allowing precise control of mining boundaries and resulting in a low ore loss rate, typically between 5% and 8%. In contrast, room-and-pillar mining, where roadways are laid directly within the ore body, often leads to ore dilution and significant losses during extraction, with loss rates ranging from 8% to 12%.

4. Applicable Ore Body Thickness

Pit-extrapolated mining is suitable for ore bodies with thicknesses ranging from 3 to 30 meters, allowing flexible adjustments to the layout of mining roadways based on the specific ore body thickness. Pit-intruded mining, when applied to ore bodies thinner than 5 meters, can reduce the amount of roadway excavation required outside the vein. In extremely thick ore bodies, pit-intruded roadways can be used for zonal mining; however, this method is less effective for medium-to-thick ore bodies.

5. Typical Engineering Cases

The Jinchuan nickel mine and Fan'kou lead-zinc mine employ off-vein mining methods, achieving efficient and safe extraction while enhancing resource utilization and boosting economic returns. Meanwhile, Yunnan Phosphate's gently inclined ore bodies utilize in-vein mining techniques, fully leveraging the internal space of the ore bodies and significantly reducing extraction costs.

IV. Optimization Directions for Off-Pipeline Data Acquisition Projects

(1) Integration of Intelligent Technologies

1. 3D Modeling

By leveraging professional mine modeling software such as DIMINE, it is possible to accurately construct 3D models of ore bodies and surrounding rocks based on geological exploration data. In this model, engineers can clearly visualize the ore body’s shape, orientation, and its relationship with the surrounding rock—essentially presenting the entire internal structure of the mine in a直观 way. Through detailed analysis of the model, the spatial layout of off-vein mining roadways can be comprehensively optimized. For instance, when planning transportation tunnels, engineers can avoid areas with complex geological structures and instead opt for locations where the surrounding rock maintains high stability, thereby reducing construction challenges and lowering maintenance costs. Meanwhile, by simulating various layout options and systematically comparing their respective advantages and disadvantages, the most optimal solution can be selected, effectively minimizing the risk of three-dimensional intersection conflicts and significantly enhancing the overall efficiency of the mining preparation process.

2. Device Interconnection

Achieving full wireless signal coverage on the ramp provides the foundational conditions for the intelligent operation of equipment such as mining loaders. By equipping these loaders with positioning devices and data transmission modules, operators can instantly access real-time information about the loaders' location, operational status, and other critical details—data that is then relayed to the central dispatch system. Leveraging this real-time data, combined with the mine’s production schedule and the specific operational needs of each working area, the central dispatch system automatically coordinates the loaders’ movements. For instance, when a particular mining area requires ore transportation, the system will autonomously calculate the most efficient route and assign the nearest, best-conditioned loader to carry out the task. This approach eliminates unnecessary, unguided operations and empty trips, boosting equipment utilization by more than 15% and significantly enhancing overall ore transportation efficiency.

(II) Green Mining Adaptation

1. Filling material utilization

In some gold mining practices, using off-vein roadways as structural supports for backfill materials has yielded remarkable results. Traditionally, off-vein roadway support relies on materials like concrete, which not only incurs high costs but also has certain environmental impacts. However, by replacing part of the roadway support with tailings-based cemented backfill, miners have managed to reduce concrete usage, cut down expenses, and simultaneously achieve resource recovery from tailings—effectively alleviating the environmental pressure caused by tailings disposal. Moreover, the backfill material integrates seamlessly with the surrounding rock of the roadway, creating a unified load-bearing structure that enhances roadway stability and ensures the safety of mining operations.

2. Waste Rock Emission Reduction

By precisely designing the location and dimensions of off-mine access roadways, it’s possible to minimize unnecessary excavation work, thereby reducing the amount of waste rock generated during mining. In some mines, the introduction of advanced surveying technologies and geological modeling software has enabled precise analysis of orebody characteristics, allowing for rational planning of roadway layouts. As a result, waste rock generation has been cut by 20% to 30%. Additionally, by equipping underground facilities with waste-rock crushing stations, the generated waste rock can be crushed on-site and subsequently used to backfill underground mined-out areas. This approach not only turns waste rock into a valuable resource but also significantly cuts costs associated with transporting waste rock to the surface—reducing both operational expenses and the environmental impact on surface ecosystems. Moreover, it lowers overall lifting costs by 20%, enhancing both the economic and environmental sustainability of mining operations.

(III) Enhanced Adaptability to Complex Conditions

Addressing the challenging issue of mining steeply inclined, thin ore bodies (dip angle > 50°, thickness < 4m), the innovative "off-vein skip shaft + in-vein electric winch chamber" combined solution holds significant importance. In a real-world application at a particular mine, deploying pedestrian ventilation shafts outside the vein provided workers with a safe and convenient access route, while simultaneously ensuring smooth underground ventilation. This effectively removed harmful gases generated after blasting, significantly improving the working environment and reducing safety risks. Meanwhile, short-distance electric winch tunnels installed within the vein successfully tackled the difficulty of extracting ore from confined spaces. The electric winch allowed for flexible operation in the narrow vein environment, efficiently hauling fragmented ore toward the skip shaft—thus enabling highly efficient ore transportation. Compared to the conventional pillar-and-floor method, this approach reduced dilution by 10% and boosted ore recovery rates, offering fresh insights and methodologies for mining similar ore bodies under comparable conditions.

V. Conclusion and Engineering Value

In the mining of medium-to-thick ore bodies, out-of-pit stope mining has demonstrated exceptional practical value, thanks to its unique technical advantages and proven engineering outcomes. By adopting a rational drift layout that avoids the complex geological conditions within the ore body, this method not only reduces drift maintenance costs but also creates favorable conditions for mechanized operations, significantly boosting mining efficiency. Compared to in-pit stope mining, it excels in key indicators such as ore loss rate and degree of mechanization, making it particularly well-suited for extracting ore bodies ranging from 3 to 30 meters in thickness.

In terms of integrating intelligent technologies, the Pulse External Mining Method has achieved optimized roadway layouts and automated equipment scheduling through 3D modeling and equipment interconnectivity, significantly boosting equipment utilization and overall mining efficiency. In the context of green mining adaptation, this method leverages backfill materials to support roadways and minimize waste rock discharge, enabling efficient resource utilization while effectively safeguarding the environment. Additionally, for mining operations under complex geological conditions, the innovative extraction approach has proven effective in reducing dilution rates and enhancing resource recovery rates.