Abstract: Raise boring drilling, as an efficient and safe underground engineering drilling technology, is widely applied in mine shaft construction, tunnel ventilation hole excavation, and underground pipeline well drilling. In the raise boring process, the stable operation of the drill string and accurate control of borehole trajectory are core prerequisites for ensuring drilling quality, reducing construction risks and improving engineering efficiency. The stabilizer block is a key matching component installed on the drill stabilizer rod of raise boring equipment, which undertakes the core functions of centralizing the drill string, suppressing drilling vibration, correcting borehole deviation and buffering downhole impact load. Affected by complex geological conditions such as broken surrounding rock, uneven rock hardness and downhole high friction, traditional raise boring construction is prone to drill string deflection, hole wall collapse, tool wear and borehole trajectory distortion. The reasonable configuration and high-performance application of stabilizer blocks can effectively solve the above engineering problems, optimize the force state of the downhole drilling system, and improve the overall stability and forming accuracy of raise boring construction. This paper takes the stabilizer block for raise boring drilling as the research object, systematically expounds its structural composition, core working mechanism and mainstream classification, analyzes the key engineering functions in raise boring construction, discusses the practical application difficulties and performance influencing factors in complex drilling conditions, and summarizes the optimization design strategy and future development direction of raise boring stabilizer blocks, so as to provide professional technical reference for the design, selection and field construction application of stabilizer blocks in raise boring engineering.
Introduction
Raise boring drilling technology is a special underground drilling and forming technology, which relies on the raise boring machine to drive the drill string and drill bit to realize upward tunneling from the bottom of the hole. Compared with traditional blasting excavation and manual shaft sinking methods, raise boring drilling has the advantages of high mechanization degree, good construction safety, smooth borehole forming and low disturbance to surrounding rock, and has become the mainstream construction method for vertical and inclined raise engineering in underground mines, hydropower tunnels and municipal underground engineering. Different from conventional downward drilling, raise boring has unique downhole
force characteristics and operating environment: the drill string bears long-term axial tension, torsional shear force and lateral alternating impact force; the downhole closed space leads to poor chip removal and heat dissipation conditions; and the uneven hardness of rock strata and local broken rock mass easily cause unbalanced stress on the drill string, resulting in drilling instability problems.
In the raise boring system, the stabilizer rod is an important part of the bottom hole assembly (BHA), which plays a supporting and transitional role in the drill string. The stabilizer block is the core functional unit assembled on the outer wall of the stabilizer rod, and it is the direct force-bearing component contacting the hole wall rock mass. In the whole drilling process, the stabilizer block can limit the lateral swing of the stabilizer rod and the whole drill string, avoid excessive bending and vibration of the drill string, and constrain the drill bit to advance along the preset trajectory. In the absence of effective stabilizer block support, the drill string is prone to lateral offset and high-frequency whirl vibration under the action of uneven rock breaking resistance, which will lead to serious borehole deviation, irregular hole wall morphology, accelerated wear of drill tools, and even safety accidents such as drill string stuck and hole collapse in severe cases.
With the continuous development of raise boring engineering towards large aperture, deep hole depth and complex geological adaptation, the performance requirements for stabilizer blocks are increasingly stringent. Traditional ordinary stabilizer blocks have prominent problems such as poor wear resistance, low structural rigidity, weak anti-vibration ability and easy deformation in complex broken strata, which can no longer meet the high-precision and high-efficiency construction requirements of modern raise boring engineering. Therefore, it is of great engineering significance to systematically study the structural characteristics, working principle and application performance of raise boring stabilizer blocks, analyze the adaptation law of different types of stabilizer blocks to geological conditions, and explore performance optimization methods. This paper comprehensively analyzes the key technical points of raise boring stabilizer blocks based on field engineering practice and mechanical mechanism, aiming to provide theoretical and practical support for improving the stability and reliability of raise boring drilling construction.
2.Basic Structure and Working Principle of Raise Boring Stabilizer Block
2.1 Basic Structural Composition
The stabilizer block for raise boring is a special wear-resistant and stabilizing component fixedly installed on the outer circumferential surface of the drill stabilizer rod. It is processed and manufactured with high-strength wear-resistant alloy steel as the base material, and matched with surface strengthening and anti-wear treatment processes. The overall structure is compact and highly matched with the stabilizer rod, which can adapt to the narrow downhole working space of raise boring. The complete stabilizer block assembly mainly includes three core parts: base matrix, wear-resistant working layer and fixed limit structure, and each part undertakes independent structural and functional tasks.
The base matrix is the main force-bearing structure of the stabilizer block, which is integrally forged with high-strength alloy steel with good toughness and structural rigidity. Its core function is to bear the lateral extrusion force, impact load and torsional force transmitted by the hole wall rock mass, and stably transmit the load to the stabilizer rod and the whole drill string system. The matrix has high structural strength and fatigue resistance, which can avoid structural fracture and plastic deformation under long-term alternating load in deep hole drilling. The overall size of the matrix is designed according to the standard aperture of raise boring and the outer diameter of the stabilizer rod, ensuring accurate assembly gap and structural coordination.
The wear-resistant working layer is the outer contact part of the stabilizer block and directly contacts with the hole wall rock mass. It is prepared by surfacing hard alloy, inlaying wear-resistant blocks or integral hardening treatment. In the process of raise boring, the drill string rotates continuously, and the stabilizer block rubs and impacts with the rock wall for a long time. The high-hardness wear-resistant layer can effectively resist rock abrasion and impact damage, reduce the radial wear of the stabilizer block, and maintain the long-term dimensional stability of the stabilizing structure. At the same time, the surface of the wear-resistant layer adopts a streamlined or ribbed structure design, which can reduce the friction resistance between the block and the hole wall, and facilitate the discharge of downhole rock chips.
The fixed limit structure includes positioning clamping grooves and anti-loosening bolts, which are used to fix the stabilizer block on the outer wall of the stabilizer rod stably. Different from the integral stabilizer structure of conventional drilling tools, the split stabilizer block for raise boring is independently replaceable. The limit structure can effectively prevent the block from rotating, shifting or falling off relative to the stabilizer rod during high-speed rotation and up-and-down lifting of the drill string, ensuring the overall structural stability of the stabilizing system in the whole drilling cycle.
2.2 Core Working Principle
The working principle of the raise boring stabilizer block is based on the mechanical support centralization and vibration damping stabilization mechanism. In the raise boring drilling system, the drill string is a long flexible slender rod structure. Under the action of rock breaking resistance, self-weight tension and downhole fluid disturbance, the drill string is easy to produce lateral bending deformation and periodic vibration. The stabilizer block installed on the stabilizer rod forms a multi-point support structure between the drill string and the hole wall, which fundamentally changes the stress state of the flexible drill string and realizes trajectory constraint and vibration suppression.
First, centralization and deviation correction principle. In the process of upward tunneling of the raise boring drill bit, when the drill bit encounters rock strata with uneven hardness or local structural defects, the rock breaking resistance on each side of the drill bit is unbalanced, which will produce lateral deflection torque to push the drill string to offset to one side. At this time, the outer contour of the stabilizer block closely fits the hole wall, and the hole wall provides reverse supporting reaction force for the stabilizer block. This supporting force can balance the unbalanced deflection torque of the drill string, limit the lateral offset of the stabilizer rod and drill string, constrain the drill bit to advance along the preset central axis of the borehole, and realize active correction of borehole trajectory, effectively reducing the generation of borehole deviation.
Second, vibration damping and stability enhancement principle. Raise boring drilling will produce continuous rock breaking impact and drill string rotation excitation, inducing high-frequency vibration and low-frequency whirl of the drill string. The rigid contact between the stabilizer block and the hole wall can increase the lateral support stiffness of the drill string system, restrain the high-frequency vibration amplitude of the drill string, and consume the vibration energy generated by drilling through the friction and extrusion between the block and the rock wall. For low-frequency whirl caused by flexible deformation of the drill string, the multi-block distributed support structure of the stabilizer block can break the resonance condition of the drill string, avoid continuous whirl vibration, and ensure the smooth and stable operation of the drilling system.
Third, load balancing and protection principle. In complex broken rock strata, the hole wall is uneven, and the local drill string is prone to stress concentration. The stabilizer block can disperse the local concentrated load of the drill string, make the lateral stress of the stabilizer rod uniformly distributed, avoid local bending fatigue damage of the drill string, and protect the stabilizer rod and drill pipe from excessive wear and deformation. At the same time, the stabilizer block bears most of the friction and impact load between the drill string and the hole wall, which acts as a sacrificial wear-resistant component, effectively protecting the core structure of the stabilizer rod and reducing the maintenance cost of downhole drilling tools.
3.Classification and Structural Characteristics of Raise Boring Stabilizer Blocks
According to the structural form, assembly mode and adaptive geological conditions, raise boring stabilizer blocks can be divided into three mainstream types: integral rib stabilizer block, split block stabilizer block and spiral wear-resistant stabilizer block. Different types of stabilizer blocks have unique structural advantages and applicable scenarios, which can meet the drilling stabilization requirements of different borehole diameters, rock hardness and formation complexity.
3.1 Integral Rib Stabilizer Block
The integral rib stabilizer block is an integrated forming structure, which is forged and processed as a whole with the base and the wear-resistant rib, without split assembly structure. The overall structural rigidity is high, and there is no hidden danger of loose assembly and local falling off. The outer wall is uniformly provided with 3 to 6 symmetrical stabilizing ribs, and the rib surface is subjected to high-frequency quenching and hard alloy surfacing treatment, with extremely high wear resistance and impact resistance. This type of stabilizer block is mostly used in medium and hard rock strata with complete hole walls and stable geological conditions, and is suitable for conventional vertical raise boring construction.
The prominent advantages of the integral rib stabilizer block are stable structural performance, strong load-bearing capacity and good centralizing effect. The symmetrical rib layout can realize uniform contact with the hole wall in all directions, effectively avoid unilateral stress concentration of the drill string, and maintain the linear stability of the borehole trajectory. In terms of defects, the integral structure has poor adaptability to irregular hole walls. When encountering local collapse and uneven rock walls, the stress of individual ribs is excessive, which is easy to cause local wear and damage. In addition, the integral block cannot be partially replaced after wear, and the whole component needs to be replaced, resulting in relatively high use cost.
3.2 Split Block Stabilizer Block
The split stabilizer block is a modular assembled structure, which is composed of multiple independent single small blocks fixed on the outer wall of the stabilizer rod through positioning grooves and anti-loosening bolts. Each small block is an independent wear-resistant unit with small volume and flexible assembly. According to the actual aperture and formation conditions, the number and spacing of blocks can be adjusted flexibly, which has strong engineering adaptability. This type of stabilizer block is the most widely used in current raise boring engineering, especially suitable for complex strata with broken surrounding rock and uneven hole walls.
The core advantage of the split stabilizer block is convenient maintenance and low replacement cost. After long-term drilling wear, only the severely worn single block needs to be replaced, without disassembling the overall stabilizer rod, which greatly improves the maintenance efficiency of downhole tools and reduces the engineering cost. At the same time, the gap between the split blocks can form a rock chip discharge channel, which is conducive to the timely discharge of downhole rock chips, avoiding the accumulation of rock chips to cause jamming and wear of drilling tools. The disadvantage is that the assembly gap exists between the blocks, and the overall structural rigidity is slightly lower than that of the integral structure, so it is not suitable for ultra-hard rock drilling with strong impact load.
3.3 Spiral Wear-Resistant Stabilizer Block
The spiral stabilizer block adopts a spiral continuous rib structure design, and the stabilizing ribs are arranged in a spiral shape along the axial direction of the stabilizer rod. The spiral structure is consistent with the rotation direction of the drill string, which can produce a certain lifting and guiding effect on downhole rock chips during the rotation of the drill string, significantly improving the chip removal efficiency of raise boring. The surface of the spiral rib is thickly paved with hard alloy wear-resistant points, which has excellent anti-wear and anti-scouring performance, and is specially suitable for deep-hole raise boring construction with large chip output and poor chip removal conditions.
In terms of stabilization performance, the spiral continuous contact structure can maintain continuous contact with the hole wall during the rotation of the drill string, avoid intermittent support failure, and effectively suppress the rotary vibration and trajectory jitter of the drill string. For inclined raise boring construction, the spiral stabilizer block can rely on the spiral structure to balance the lateral sliding force of the drill string, improve the anti-deviation ability of inclined boreholes, and solve the problem of easy trajectory drift in inclined raise construction. The limitation is that the spiral structure has large contact friction with the hole wall, which will increase the drilling torque to a certain extent, and is not suitable for soft and easily collapsed rock strata.
4.Key Engineering Functions of Stabilizer Block in Raise Boring Construction
4.1 Precise Control of Borehole Trajectory and Suppression of Borehole Deviation
Borehole deviation is one of the most common quality problems in raise boring construction. Affected by in-situ stress, rock stratum inclination and uneven rock hardness, the drill bit is prone to directional deviation during upward tunneling, resulting in excessive borehole deviation, which affects the later use function of the raise and even leads to engineering scrapping. The stabilizer block is the core component to control the borehole trajectory of raise boring. Through the rigid support and constraint effect between the block and the hole wall, it limits the free deflection of the drill string and drill bit, forces the drill bit to advance along the preset central axis, and realizes active control of borehole deviation.
In the whole drilling process, the stabilizer block forms a stable centralizing support system together with the stabilizer rod and drill bit. When the drill bit tends to deviate, the supporting reaction force of the hole wall on the stabilizer block will generate reverse correction torque, offset the deviation trend of the drill bit, and ensure the straightness of the borehole. Engineering practice shows that the reasonable configuration of high-performance stabilizer blocks can control the borehole deviation of raise boring within 0.5% of the hole depth, which meets the high-precision construction standard of mine ventilation raises and pipeline raises, and greatly improves the one-time forming qualification rate of boreholes.
4.2 Suppression of Drill String Vibration and Improvement of Drilling Stability
The drill string of raise boring belongs to a long-span flexible structure. During high-speed rotation and rock breaking, it is easy to produce complex vibration forms such as transverse vibration, torsional vibration and whirl vibration. Excessive vibration will lead to unstable rock breaking of the drill bit, reduced drilling efficiency, and accelerated fatigue damage of drill string components. The stabilizer block can significantly improve the overall stiffness of the bottom hole drill string assembly, constrain the vibration amplitude of the drill string, and avoid resonance failure of the drilling system.
The multi-point contact support formed by the stabilizer block and the hole wall can effectively limit the transverse displacement of the drill string, consume the vibration energy generated by rock breaking and rotation, and reduce the high-frequency jitter of the drill bit. For the low-frequency whirl vibration easily occurring in deep-hole raise boring, the stabilizing constraint of the stabilizer block can break the vibration excitation cycle, inhibit the continuous development of whirl, and keep the drill string running in a stable state. Stable drilling state can ensure uniform rock breaking of the drill bit, reduce the impact damage of the drill bit, and effectively extend the service life of drilling tools.
4.3 Protection of Downhole Drilling Tools and Reduction of Construction Loss
In the absence of stabilizer block protection, the stabilizer rod and drill pipe will directly contact and rub with the hole wall rock mass. The hard rock and broken rock debris will cause serious abrasive wear and impact damage to the drill string components, resulting in frequent replacement of drilling tools and increased construction cost. As a sacrificial wear-resistant component, the stabilizer block bears most of the friction, impact and extrusion load between the drill string and the hole wall, which effectively protects the stabilizer rod, drill pipe and drill bit from excessive wear and damage.
At the same time, the stable support of the stabilizer block can avoid local stress concentration of the drill string, reduce the alternating fatigue load of the drill pipe during rotation, and prevent drilling safety accidents such as drill pipe fracture and tool falling caused by long-term fatigue damage. In broken and complex strata, the stabilizer block can also play a certain role in supporting the loose hole wall, reducing the risk of local hole collapse and drill string sticking, and improving the safety and continuity of raise boring construction.
4.4 Optimization of Chip Removal Environment and Improvement of Drilling Efficiency
Raise boring belongs to upward tunneling construction, and rock chips are easy to accumulate at the bottom of the hole, resulting in poor chip removal, which will seriously affect rock breaking efficiency and even cause repeated grinding of rock chips and tool jamming. The structural gap and spiral guide structure of the stabilizer block can form a smooth chip removal channel between the drill string and the hole wall. With the rotation and lifting of the drill string, the stabilizer block drives the downhole fluid and rock chips to flow upward, accelerating the discharge of rock chips.
Good chip removal conditions can ensure that the drill bit always contacts fresh rock strata, avoid the reduction of rock breaking efficiency caused by rock chip accumulation, and improve the overall drilling speed. At the same time, timely discharge of rock chips can reduce the abrasive wear of rock chips on drilling tools, reduce the number of tool lifting and replacement, and effectively shorten the construction cycle and improve the economic benefits of engineering construction.
5.Practical Application Difficulties and Performance Influencing Factors
5.1 Main Application Difficulties in Complex Strata
In the construction of raise boring in broken loose strata, fractured rock mass and soft-hard interbedded strata, the stabilizer block faces prominent application difficulties. First, the hole wall of broken strata is unstable and easy to collapse locally, resulting in insufficient effective support of the stabilizer block, reduced centralizing effect, and easy drift of borehole trajectory. Second, the broken rock debris has strong abrasion, which causes rapid wear of the wear-resistant layer of the stabilizer block, leads to the failure of the stabilizing structure in advance, and increases the frequency of tool replacement. Third, the soft-hard interbedded strata make the drill string bear alternating unbalanced load, which causes alternating impact on the stabilizer block, easily leads to fatigue cracking and falling off of the wear-resistant layer, and affects the stability of the drilling system.
In deep-hole and large-aperture raise boring construction, the drilling depth is large, the self-weight tension of the drill string is high, the downhole pressure and temperature are increased, and the vibration and deformation of the drill string are more obvious. The traditional stabilizer block has insufficient structural rigidity and poor fatigue resistance, which is easy to produce plastic deformation and structural failure under long-term deep-hole alternating load, resulting in drilling instability and increased construction risks.
5.2 Key Performance Influencing Factors
The first factor is material performance. The base material strength, toughness and wear-resistant layer hardness of the stabilizer block directly determine its service life and stabilizing effect. If the base material has insufficient toughness, it is easy to crack under impact load; if the hardness of the wear-resistant layer is too low, the wear speed is fast, which cannot meet the long-term drilling requirements. The second factor is structural design. The rib height, spacing, symmetry and spiral angle of the stabilizer block affect the centralizing accuracy, vibration damping effect and chip removal efficiency. Unreasonable structural parameters will lead to poor support effect and increased drilling resistance.
The third factor is assembly accuracy. The matching gap between the stabilizer block and the stabilizer rod and the anti-loosening performance of the limit structure affect the overall structural stability. Excessive assembly gap will cause the block to shake during operation, reduce the stabilization effect, and even cause block falling accidents. The fourth factor is matching construction parameters. Unreasonable drilling speed, propulsion pressure and torque parameters will increase the impact and wear of the stabilizer block, accelerate structural failure, and affect the overall construction quality and efficiency.
6.Optimization Design and Future Development Trend
6.1 Optimization Design Strategy for Stabilizer Blocks
Aiming at the application defects of traditional stabilizer blocks in raise boring engineering, targeted optimization design can be carried out from material upgrading, structural optimization and process improvement. In terms of materials, high-strength alloy steel with better toughness and fatigue resistance is selected as the base material, and ultra-high hardness hard alloy composite surfacing technology is adopted for the wear-resistant layer to improve wear resistance and impact resistance, adapt to complex and harsh downhole environments, and extend the service life of the block.
In terms of structure, according to different geological conditions, adaptive structural optimization is carried out. For broken strata, a widened arc contact structure is adopted to increase the contact area with the hole wall, improve the support stability, and avoid local stress concentration. For deep-hole large-aperture drilling, an integral reinforced rib structure is used to improve the overall structural rigidity and anti-deformation ability. For inclined raise boring, a low-resistance spiral symmetrical structure is optimized to balance lateral force and improve trajectory control accuracy.
In terms of assembly technology, the positioning clamping groove structure is optimized to improve the assembly matching accuracy, and a double anti-loosening structure of bolt locking and positioning limit is adopted to eliminate the hidden danger of block loosening and falling off. At the same time, modular standardized design is realized to improve the universality and interchangeability of stabilizer blocks, reduce the types of spare parts, and improve the efficiency of on-site maintenance and replacement.
6.2 Future Development Trend
First, intelligent and wearable adaptive development. With the continuous improvement of intelligent drilling technology, the future stabilizer block will integrate micro-sensing monitoring units, which can monitor the wear degree, stress state and vibration parameters of the block in real time, realize online fault early warning, and provide data support for intelligent adjustment of drilling parameters. At the same time, combined with bionic wear-resistant structure and self-lubricating materials, the adaptive wear-resistant and low-resistance performance of the block in complex strata is improved.
Second, high integration and multifunctional development. The new generation of stabilizer blocks will break the single stabilization function, integrate the functions of trajectory correction, vibration damping, chip removal guidance and hole wall protection, form a multifunctional integrated stabilizing component, further simplify the structure of the downhole drilling assembly, and improve the overall operation efficiency and stability of the raise boring system.
Third, green and efficient low-resistance development. Optimize the fluid dynamics structure of the stabilizer block, reduce drilling friction and torque loss, reduce drilling energy consumption, and realize energy-saving and efficient drilling construction. At the same time, improve the material utilization rate and structural durability, reduce the frequency of component replacement, reduce engineering waste, and meet the green construction requirements of modern underground engineering.
7.Conclusion
The stabilizer block is an indispensable core functional component of the raise boring drilling system, which is installed on the drill stabilizer rod and plays a key role in borehole trajectory control, drill string vibration suppression, drilling tool protection and efficient chip removal. Different from stabilizer blocks in general mechanical and power systems, the raise boring stabilizer block has the structural characteristics of high wear resistance, high impact resistance and modular assembly, and faces complex and harsh downhole working conditions such as rock friction, impact load and narrow space. Its structural performance and matching application effect directly determine the construction quality, safety and efficiency of raise boring engineering.
This paper systematically analyzes the structural composition, working mechanism and classification characteristics of raise boring stabilizer blocks, expounds the core engineering functions in raise boring construction, summarizes the practical application difficulties in complex geological conditions and key performance influencing factors, and puts forward targeted optimization design strategies and future development trends. At present, with the continuous expansion of the application scope of raise boring technology in underground engineering, the technical requirements for high-performance stabilizer blocks are constantly improving. Subsequent research and engineering applications should focus on material performance upgrading, structural adaptive optimization and intelligent function expansion, to further improve the stability, durability and engineering adaptability of stabilizer blocks, provide strong technical support for the high-quality, efficient and safe construction of modern raise boring engineering, and promote the mechanization and intelligent upgrading of underground drilling engineering.