The raise bore reamer is the core rock-breaking execution component of the raise boring system, widely applied in vertical and inclined shaft excavation for mining, hydropower, tunnel and underground geotechnical engineering. Different from conventional drilling and reaming tools, the raise bore reamer adopts upward reverse reaming construction technology, relying on mechanical rotation and axial pulling force to achieve full-section rock breaking and shaft forming. This paper systematically elaborates the basic definition, core structure classification, working mechanism, key manufacturing technology, standard operation process, performance optimization strategy and industrial application prospects of raise bore reamers, aiming to provide professional technical reference for the design, selection, maintenance and engineering application of raise boring equipment.
Keywords: raise bore reamer; rock breaking mechanism; shaft excavation; structural optimization; wear resistance technology; underground engineering
Underground vertical shaft engineering is a key infrastructure connecting surface and underground working faces, undertaking critical functions such as ventilation, material transportation, pedestrian passage and slag discharge in mining and hydropower projects. Traditional shaft excavation methods, including manual blasting and mechanical tunneling, have prominent defects such as low construction efficiency, poor operation safety, high labor intensity and poor shaft forming accuracy. With the continuous upgrading of underground engineering mechanization technology, raise boring construction technology has become the mainstream process for modern shaft excavation by virtue of its full mechanization, high efficiency and zero underground manual operation advantages.
As the core rock-breaking tool of the raise boring machine, the raise bore reamer directly determines the construction efficiency, shaft forming quality, equipment energy consumption and service life of the entire raise boring project. The raise boring construction process is divided into two key stages: pilot hole drilling and reverse reaming forming. Firstly, a small-diameter pilot hole is drilled through from the upper working face to the lower working face; then the drill bit is replaced with a matched raise bore reamer, and the reamer is pulled upward by the drill rod while rotating, realizing continuous rock breaking and gradual expansion of the pilot hole to the designed shaft diameter.
Compared with ordinary mechanical reamers used for precision hole finishing, the raise bore reamer belongs to heavy-duty rock-breaking equipment, which needs to bear ultra-large axial tension, strong torsional shear force and severe impact wear in hard rock and complex geological environments. Its structural design, cutter configuration, material performance and assembly process are significantly different from traditional reaming tools. In recent years, with the increasing depth of underground engineering and the complexity of geological conditions, higher requirements have been put forward for the load resistance, rock breaking efficiency, wear resistance and adaptability of raise bore reamers. In-depth research on its working principle and key technologies is of great significance for improving the overall level of raise boring engineering technology.
A raise bore reamer is a large-scale special rotary rock-breaking tool matched with a raise borer. It is installed at the bottom of the through pilot hole, and relies on the upward pulling force and rotary torque provided by the raise borer to crush surrounding rock in a reverse pulling state, so as to expand the small-diameter pilot hole into a large-diameter standard vertical or inclined shaft. It is a special equipment integrating mechanical transmission, rock breaking cutting and wear-resistant protection, and is exclusively used for raise boring reverse reaming construction.
Different from conventional forward drilling tools and precision reaming tools, the raise bore reamer has unique technical characteristics adapted to underground shaft engineering construction, which are summarized as follows:
First, reverse reaming rock breaking mode. The raise bore reamer works in the state of upward pulling and reverse rotation. The rock slag generated by rock breaking falls to the lower working face by gravity, avoiding slag accumulation in the shaft and repeated crushing of rock slag by the cutter, which effectively improves rock breaking efficiency and reduces tool wear. This is the most essential feature distinguishing it from forward drilling tools.
Second, heavy-load impact resistance. The reamer needs to adapt to various complex rock strata such as soft rock, medium-hard rock, hard rock and fractured rock mass. During the working process, it bears composite loads such as large axial tension, alternating torque and random impact force, requiring the tool body and cutters to have excellent structural rigidity and impact toughness.
Third, full-section one-time forming. According to the designed shaft diameter, the reamer adopts a multi-cutter distributed layout, which can realize one-time full-section rock breaking and shaft forming, with smooth shaft wall and high dimensional accuracy, avoiding the secondary trimming process required by traditional blasting construction.
Fourth, mechanized and unmanned operation. The whole reaming process is completed by ground equipment control, no personnel enter the underground shaft operation area, which completely eliminates the safety risks of collapse, falling rocks and gas leakage in shaft construction, and has outstanding safety advantages.
According to structural form, assembly mode and applicable working conditions, raise bore reamers are mainly divided into three types: integral raise reamer, segmented raise reamer and expandable raise reamer. Each type has independent structural characteristics and applicable scenarios, and the overall structure is composed of tool body base, cutting system, wear-resistant protection system and connection assembly system.
The integral raise reamer is an integrated cast or forged structure with an integrated tool body without detachable segments. The overall rigidity is high, the structural stability is strong, and the assembly and disassembly process is simple and efficient. The tool body is uniformly distributed with multiple cutter mounting seats, which are arranged in a spiral or radial equidistant manner to ensure uniform stress in the rock breaking process.
This type of reamer is mostly used for small and medium-diameter shaft construction, with a conventional diameter range of 0.5m to 3m. It is suitable for complete rock strata with stable geology and no large-scale fracture development. Due to the integrated structure, it has strong torsional resistance and small deformation during operation, which can effectively ensure the roundness and straightness of the shaft. However, affected by integral casting and forging process, the volume and weight of large-diameter integral reamers are too large, resulting in inconvenient transportation and hoisting, so it is not applicable to super-large-diameter shaft engineering.
The segmented raise reamer is composed of a central connecting base and multiple detachable cutting segments. All segments are fixedly connected with the central base through high-strength bolts, and the number of segments can be configured according to the diameter specification. Common specifications include 4-segment, 6-segment and 8-segment structures, which are widely used in medium and large-diameter shaft construction with a diameter range of 3m to 6m.
The biggest advantage of the segmented structure is convenient transportation and flexible assembly. Each segment is small in size and light in weight, which can adapt to the narrow underground transportation space of mines and hydropower projects. In addition, when local cutters or segment structures are worn and damaged, only the damaged segments need to be replaced, without overall replacement, which greatly reduces equipment maintenance and use costs. The defect is that the bolt connection part has slight structural gaps, and the overall rigidity is slightly lower than that of the integral structure, so it is not suitable for ultra-hard rock and strongly fractured complex strata.
The expandable raise reamer is a new type of adjustable-diameter reaming tool, which realizes the expansion and contraction of the cutting diameter through the internal mechanical adjusting mechanism. It can complete the construction of shafts with different diameters on the basis of one equipment, and has extremely high construction flexibility. The adjustable diameter range of mainstream expandable reamers covers 2m to 8m, which is suitable for variable-diameter shaft engineering and multi-specification shaft construction scenarios.
The core structure of the expandable reamer includes a central telescopic mechanism, a radial sliding cutter frame and a locking positioning device. By adjusting the telescopic stroke of the internal mechanism, the radial extension distance of the cutter frame is changed, so as to accurately control the reaming diameter. This type of reamer solves the problem of single specification of traditional reamers, and can effectively reduce equipment procurement costs for projects with multiple shaft diameter requirements. However, due to the complex internal adjusting mechanism, the structural stability and impact resistance are limited, and it has higher requirements for daily maintenance and operation accuracy.
Regardless of the structural type, the raise bore reamer mainly includes four core components. First, the tool body base, which is the main stress component of the reamer, bearing tension, torque and impact load, made of high-strength alloy steel through integral forging and heat treatment to ensure structural rigidity and fatigue resistance. Second, the cutting system, composed of multiple rock-breaking cutters, which is the direct rock-breaking component, adopting conical spherical cutters or cylindrical cutters, with high-hardness alloy cutter heads. Third, the wear-resistant protection system, including wear-resistant welding strips and wear-resistant protective plates, which reduces the abrasive wear of the tool body caused by rock slag friction. Fourth, the connection assembly system, including drill rod connecting joints and segment fixing bolts, which ensures the stable connection between the reamer and the drill rod and the overall structural tightness.
The working process of the raise bore reamer is a composite mechanical process of rotary cutting, axial extrusion and impact crushing. Its rock breaking mechanism is different from the single cutting mode of traditional drilling tools, and the rock breaking process can be divided into three stages: contact extrusion, fatigue cracking and slag stripping.
Before the reamer works, the raise borer completes the pilot hole drilling operation to form a through small-diameter hole. The construction equipment is fixed on the upper working face, the drill rod passes through the pilot hole, and the raise bore reamer is installed and locked at the bottom end of the drill rod. After the equipment is debugged, the main engine outputs upward axial pulling force and continuous rotary torque, driving the reamer to rotate and rise slowly.
In the working process, the cutters on the reamer are in close contact with the rock wall of the pilot hole. Under the action of axial pulling force, the cutters produce extrusion pressure on the rock mass; under the action of rotary torque, the cutters produce shear cutting force on the rock mass. The composite force of extrusion and shear acts on the rock mass, making the rock produce stress concentration and local plastic deformation. With the continuous operation of the equipment, the rock stress exceeds the ultimate strength of the rock mass, resulting in micro-cracks, and the cracks expand and penetrate to form broken rock blocks.
The broken rock slag falls to the lower working face by its own gravity, realizing automatic slag discharge without manual slag cleaning. The reamer continuously rises and cuts circularly until it penetrates from the lower working face to the upper working face, completing the one-time forming of the whole shaft.
The rock-breaking cutters of the raise bore reamer adopt a multi-cutter staggered layout. Different cutters bear different rock-breaking tasks: the outer cutters are responsible for main cutting and diameter forming, bearing large shear force and impact load; the middle cutters assist in crushing rock mass and optimizing rock breaking uniformity; the central cutters trim the hole wall to ensure the smoothness of the shaft wall.
For medium and soft rock strata, the cutter mainly relies on shear cutting to break rock, with high cutting efficiency and small tool wear. For hard rock and dense rock strata, the extrusion crushing effect is dominant. The cutter continuously impacts and extrudes the rock mass, making the rock mass produce fatigue damage and layered peeling, so as to realize efficient rock breaking. For fractured rock mass, the staggered cutter layout can avoid stress concentration caused by rock mass cracks, reduce the vibration impact of the reamer, and improve the stability of the reaming process.
In the working state, the raise bore reamer is in a complex alternating stress field. The axial tension is uniformly distributed on the tool body, the torsional shear stress is concentrated on the cutter mounting seat and the tool body surface, and the impact stress is randomly generated with rock breaking. Long-term alternating load action is easy to cause fatigue wear and local crack damage of the cutter and tool body.
The main wear forms of the reamer include abrasive wear and impact wear. The rock slag rubs against the tool body and cutters for a long time to form abrasive wear; the instantaneous impact between the cutter and hard rock mass causes impact wear and even cutter tooth breakage. Therefore, the structural design and material selection of the reamer need to balance hardness and toughness, which not only ensures the high hardness of the cutter head to resist abrasive wear, but also ensures the toughness of the tool body to resist impact damage.
The tool body of the raise bore reamer is mainly made of high-strength low-alloy structural steel, which has excellent tensile strength, yield strength and fatigue resistance after integral forging and quenching and tempering heat treatment. The surface of the tool body is treated with wear-resistant surfacing to form a high-hardness wear-resistant layer, which effectively improves the anti-wear ability of the tool body and prolongs the service life.
The rock-breaking cutter is the core vulnerable part, and the cutter head adopts ultra-fine grain cemented carbide material. This material has high hardness, high wear resistance and good impact toughness, which can adapt to long-term high-load rock breaking operation. The cutter body is made of alloy steel with good plasticity and toughness, which avoids cutter body fracture caused by impact load, and realizes the perfect matching of hardness and toughness of the whole cutter.
In order to improve the rock breaking efficiency and structural stability of the reamer, modern finite element analysis technology is adopted to optimize the structural parameters. By simulating the stress distribution and vibration law of the reamer under different working conditions, the layout angle, spacing and number of cutters are optimized. The spiral staggered cutter layout is adopted to make the rock breaking force uniform in the circumferential direction, reduce the vibration amplitude of the equipment, and avoid eccentric wear of the reamer.
At the same time, the transition fillet optimization design is carried out for the stress concentration parts such as the cutter mounting seat and the tool body connection part, which eliminates the structural dead angle of stress concentration, improves the overall structural fatigue resistance, and reduces the failure rate of tool body cracking. The segmented reamer optimizes the bolt connection structure and adopts high-precision positioning and anti-loosening design to ensure the structural tightness and rigidity during operation.
The manufacturing process of the raise bore reamer directly determines its service performance. The tool body adopts integral forging process to ensure the internal metal fiber continuity, avoid internal defects such as air holes and sand holes, and improve the overall mechanical properties. The cutter mounting hole adopts precision machining technology to ensure the matching accuracy between the cutter and the tool body, reduce assembly gaps, and avoid cutter vibration and abnormal wear during operation.
After the completion of processing and assembly, all reamers need to undergo strict quality inspection, including dimensional accuracy detection, hardness detection, ultrasonic flaw detection and load simulation test, to ensure that all performance indicators meet the engineering use standards, and eliminate unqualified products from the source.
Raise bore reamers are widely used in vertical and inclined shaft excavation of various underground engineering. In the mining industry, it is used for ventilation shafts, skip shafts, cable shafts and emergency escape shaft construction, which can efficiently complete the excavation of deep vertical shafts and solve the safety and efficiency problems of traditional mining shaft construction. In hydropower engineering, it is applied to the construction of water diversion shafts, tailwater shafts and ventilation shafts of underground powerhouses, with high shaft forming accuracy and good wall flatness, reducing the later concrete lining engineering volume.
In addition, it is also used in tunnel emergency shaft construction, geotechnical engineering deep hole forming and underground storage shaft engineering. With the continuous development of underground space development technology, the application scope of raise bore reamers is further expanding to large-diameter, ultra-deep and complex geological shaft engineering.
Standardized operation and scientific maintenance are key to ensuring the efficient operation and long service life of the raise bore reamer. Before construction, it is necessary to check the integrity of the reamer structure, the fastening degree of the cutter and the wear-resistant layer, confirm that the connecting bolt is not loose and the cutter is not damaged, and carry out trial operation and debugging.
During the construction process, the construction parameters should be reasonably matched according to the geological conditions. For hard rock strata, appropriately reduce the rotating speed and pulling speed to avoid excessive impact load causing cutter damage; for soft rock and fractured strata, increase the rotating speed appropriately to improve rock breaking efficiency and prevent rock slag accumulation. Real-time monitor the equipment torque, tension and vibration data, and stop the machine in time for inspection in case of abnormal parameters.
After the completion of construction, clean the rock slag and dirt on the surface of the reamer, check the wear degree of the cutter and wear-resistant layer, replace the severely worn cutter in time, and repair the local wear-resistant layer by surfacing. Regularly carry out structural flaw detection on the reamer tool body to eliminate potential structural safety hazards. Scientific maintenance can effectively reduce the failure rate of equipment and extend the service life of the reamer by more than 30%.
With the continuous progress of underground engineering mechanization, intelligence and green construction technology, the raise bore reamer industry is developing towards high efficiency, intelligence, wear resistance and multi-adaptation. First, intelligent optimization. Combined with sensor monitoring and big data analysis technology, the intelligent reamer with real-time wear monitoring, stress feedback and automatic parameter adjustment is developed to realize adaptive rock breaking under different geological conditions.
Second, new material application. The application of new high-wear-resistant, high-toughness composite materials further improves the impact resistance and wear resistance of the reamer, reduces the frequency of tool replacement, and improves the continuous construction capacity of the equipment. Third, multi-functional integration. The integrated design of rock breaking, hole wall trimming and slag guiding is realized to further improve the shaft forming quality and construction efficiency.
Fourth, green and low-consumption development. Through structural optimization and parameter matching, the energy consumption of rock breaking is reduced, the vibration and noise in the construction process are reduced, and the green construction level of underground engineering is improved. In the future, with the deepening of deep earth resource development and underground space utilization, raise bore reamer technology will be further innovated and upgraded, becoming an indispensable core equipment in modern underground engineering construction.
As the core rock-breaking tool of raise boring construction technology, the raise bore reamer determines the core indicators of shaft construction efficiency, forming quality and construction safety. This paper systematically analyzes the structural classification, working mechanism, key manufacturing technology, engineering application and development trend of raise bore reamers. The integral, segmented and expandable reamers have their own advantages and applicable scenarios, and the reverse reaming rock breaking mode has significant technical advantages such as high efficiency, safety and environmental protection.
At present, with the increasing complexity of underground engineering geological conditions, the performance optimization of raise bore reamers needs to focus on material innovation, structural optimization and intelligent upgrading. Through standardized operation and refined maintenance, the service performance and service life of the equipment can be effectively improved. In the future, the continuous innovation of raise bore reamer technology will provide strong technical support for the efficient, safe and intelligent construction of deep underground engineering, and have broad engineering application and market development prospects.
