A near-tunnel large-diameter deep-embedded hard rock low-disturbance hole-forming equipment and construction method

Abstract

The application provides a near-tunnel large-diameter deep-embedded hard rock low-disturbance hole-forming equipment and construction method, which comprises a drill rod connecting mechanism, a damping shock absorption module and an integrated stepped hole expansion drill bit. The drill bit is provided with a leading center pilot core-pulling cylinder and a multi-stage annular stepped hole expansion ring, and the cutting teeth are arranged in a negative rake angle centripetal staggered manner to form a central pressure relief cavity to realize centripetal shear fracture of the rock mass. The damping shock absorption module integrates disc springs, a polyurethane elastic layer, a hydraulic damping cylinder and a high-damping rubber shock absorber to grade dissipate drilling vibration, and the drill bit is provided with a built-in pump suction reverse circulation residue removal system to remove residues in real time. The construction method first lays an isolation hole barrier, and then sequentially implements pilot coring, stepped hole expansion, synchronous residue removal and parameter dynamic regulation and control. The application reduces the radial extrusion stress of the surrounding rock from the source of the rock breaking mechanism, cooperates with multi-stage composite shock absorption and external isolation barrier to synergistically reduce vibration, greatly reduces the disturbance of hard rock hole-forming on the stratum adjacent to the tunnel, and is suitable for hard rock large-diameter pile foundation construction adjacent to an operating tunnel.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering and foundation construction technology, specifically to a method and equipment for drilling large-diameter, deeply embedded, hard rock tunnels with low disturbance. Background Technology

[0002] With the continuous expansion of the simultaneous construction of urban underground spaces and surface structures, a large number of high-rise building and overpass bridge pile foundation construction sites are located adjacent to existing operational tunnels. These pile foundations generally require large diameters and deep embedding in hard rock strata. The ground stress and vibration generated during construction directly affect the tunnel lining, making the disturbance control standards for drilling operations increasingly stringent. When conventional full-face rotary drilling tools are used for hard rock drilling, the cutting force continuously compresses the surrounding rock radially, forming a large-scale, high-amplitude stress wave that propagates outward. This easily causes cracking and structural misalignment in adjacent tunnel linings, making it difficult to meet the safety management requirements for construction near adjacent tunnels.

[0003] Existing staged borehole reaming technology is divided into two categories. One category uses down-the-hole hammers for impact coring before replacing them with rotary drilling tools for reaming. Down-the-hole hammer impact operations generate high-frequency and strong vibrations, which are basically prohibited in near-tunnel scenarios. Moreover, changing the drill bit requires repeated drilling, resulting in low efficiency in deep and hard rock formations. The other category uses rigidly connected ordinary staged borehole reaming drill bits. The drill rod and drill bit lack vibration damping structures, which cannot attenuate drilling vibrations. The cutting teeth still compress the rock mass outward. Optimizing the drill bit shape does not change the rock-breaking stress mode. At the same time, existing technologies only optimize the drill bit body and do not provide supporting stratum isolation measures to block the propagation of stress waves. Vibration and stress will continue to spread to the adjacent tunnel structure, resulting in significant shortcomings in the overall protection effect. Summary of the Invention

[0004] To address the aforementioned technical shortcomings, the purpose of this invention is to provide a low-disturbance drilling equipment and construction method for large-diameter, deep-embedded hard rock tunnels in proximity to tunnels. This method reduces the radial compressive stress of the surrounding rock from the source of the rock-breaking mechanism, and, in conjunction with multi-level composite vibration reduction and external isolation barriers, significantly reduces the ground disturbance caused by hard rock drilling to adjacent tunnels.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A near-tunneling, large-diameter, deep-embedded, hard rock, low-disturbance drilling equipment, connected to a drill rod, includes a drill rod connection mechanism, a damping and vibration reduction module, and a stepped reaming bit connected sequentially from top to bottom. The stepped reaming bit is an integrated structure, including a central pilot core-pulling cylinder and multi-stage annular stepped reaming rings. The central pilot core-pulling cylinder is located at the front end, and PDC teeth are arranged on the lower part of the cylinder wall. The multi-stage annular stepped reaming rings are coaxially sleeved on the outside of the central pilot core-pulling cylinder and arranged axially in stages along the drilling direction. The multi-stage annular stepped reaming rings include an innermost reaming ring, an inner layer reaming ring, and an outer layer reaming ring. The innermost reaming ring is sleeved on the outside of the central pilot core-pulling cylinder, the inner layer reaming ring is sleeved on the outside of the innermost reaming ring, and the outer layer reaming ring is sleeved on the outside of the inner layer reaming ring. The outer edge is evenly distributed with cutting teeth. The cutting teeth have a negative rake angle structure and are arranged asymmetrically and interlaced radially along the multi-level annular stepped reaming ring. The radial projections of the rotational cutting trajectories of adjacent cutting teeth overlap each other. The rake face of the cutting teeth is inclined to the center of the multi-level annular stepped reaming ring. The damping and vibration reduction module includes a disc spring assembly, a high-polymer polyurethane elastic layer, a hydraulic damping cylinder, and a high-damping rubber shock absorber. The lower part of the damping and vibration reduction module is equipped with a spline transmission structure, which includes a spline sleeve and a spline shaft that are splined together. The damping and vibration reduction module transmits torque to the stepped reaming drill bit through the spline transmission structure. The stepped reaming drill bit integrates a pump suction reverse circulation slag discharge system. The pump suction reverse circulation slag discharge system has an axially penetrating slag discharge channel. The slag suction port of the slag discharge channel is located in the transition area between the central pilot core-pulling cylinder and the innermost reaming ring.

[0007] Preferably, the multi-stage annular stepped expansion ring gradually increases in diameter along the radial direction. The damping and shock absorption module also includes a spring sleeve. The disc spring assembly is housed inside the spring sleeve. The polymer polyurethane elastic layer is sandwiched between the contact surfaces of the bottom end of the spring sleeve and the top end of the hydraulic damping cylinder, and between the bottom end of the hydraulic damping cylinder and the top end of the high-damping rubber shock absorber. A damping hole is opened inside the hydraulic damping cylinder. The high-damping rubber shock absorber is located below the polymer polyurethane elastic layer.

[0008] Preferably, the slag discharge channel of the pump-suction reverse circulation slag discharge system extends upward through the center hole of the spline shaft and through the drill rod connection mechanism, so as to communicate with the inner cavity of the drill rod when the drill rod connection mechanism is connected to the drill rod; the slag discharge channel is used to communicate with the sand and gravel pump through the inner cavity of the drill rod, so that when the sand and gravel pump is working, a negative pressure is formed in the slag discharge channel for sucking up the rock slag at the bottom of the hole; the damping and shock absorption module is equipped with a multi-parameter sensor, which is used to collect the compression deformation of the damping and shock absorption module and the drill bit torque data.

[0009] Preferably, a Step seal and a Glyd ring are assembled between the piston rod and the cylinder body of the hydraulic damping cylinder; a dustproof ring is assembled on the lower external part of the damping and shock absorption module; the spline transmission structure includes a spline sleeve and a spline shaft, and the spline sleeve and spline shaft mesh with each other to transmit torque while allowing the components to slide axially relative to each other.

[0010] A method for constructing large-diameter, deeply embedded hard rock tunnels in proximity includes the following steps:

[0011] S1. Lower the stepped reaming drill bit and control the drilling pressure so that the central pilot core-pulling cylinder contacts the rock mass to complete the advanced core drilling and form a central pressure relief cavity.

[0012] S2. Keep the drill bit feeding downwards. The multi-stage annular stepped reaming ring cutting teeth contact the rock mass. Relying on the central pressure relief cavity, synchronous stepped centripetal shearing reaming operation is carried out until the target depth is reached.

[0013] S3, steps S1 and S2 are carried out with the pump suction reverse circulation slag discharge system running continuously to pump and discharge the broken rock slag from the bottom of the hole in real time.

[0014] S4. Relying on multi-parameter sensors to collect deformation data of the damping and vibration reduction module in real time, and when the vibration amplitude exceeds the threshold, the drilling pressure is automatically reduced and the drilling speed is adjusted to maintain low-disturbance drilling conditions.

[0015] Preferably, in step S1, the core extraction operation is completed solely by the central pilot core extractor. The multi-stage annular stepped borehole expander ring remains suspended and does not participate in the cutting. After the core extraction is completed, the drill bit is lifted, broken, and the core is removed from the hole. The core extraction operation is repeated to form a central pressure relief cavity that penetrates the entire depth of the pile hole.

[0016] Preferably, in step S2, the cutting teeth of the innermost expanding ring, the inner expanding ring, and the outer expanding ring of the multi-level annular stepped expanding ring are arranged radially in an alternating pattern. The cutting trajectories of adjacent cutting teeth overlap to eliminate rock ridges. The cutting teeth rely on the centripetal inclined structure to guide the rock mass toward the central pressure relief cavity to undergo shearing and collapse. The inner expanding ring preferentially cuts the rock mass, and the outer expanding ring follows up to trim the annular rock ridge.

[0017] Preferably, before construction, multiple rows of isolation holes are drilled between the pile foundation to be constructed and the adjacent tunnel to form a stress blocking barrier. The isolation holes are laid out along the tunnel direction. After the isolation holes are formed, they are kept in a cavity state. When constructing the isolation holes, a skip-hole drilling sequence is adopted, and low speed and low drilling pressure are used for stable drilling throughout the process. Step S4 forms a triple low-disturbance control system. The first layer relies on the centripetal shearing and crushing mechanism of the cutting teeth to weaken the radial extrusion stress of the surrounding rock. The second layer relies on the damping and vibration reduction module to dissipate the drilling vibration load in stages. The third layer relies on the isolation hole barrier to reflect and attenuate the stress waves and vibration waves propagating outward. The S1 to S4 procedures are executed in a cycle until the design final hole elevation is reached.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] This invention features an integrated stepped borehole reaming drill bit that uses an advanced central pilot core-pulling cylinder to form a central pressure relief cavity. Combined with cutting teeth arranged in a staggered, centripetal pattern with a negative rake angle, it guides the rock mass to shear and collapse toward the center of the borehole. This eliminates the traditional rock-breaking mode of drilling tools that squeeze the surrounding rock outwards, and reduces the radial compressive stress transmitted toward the tunnel from the source of the rock-breaking mechanism.

[0020] This invention is equipped with a four-stage composite structure damping and vibration reduction module, which dissipates vibration loads of different frequency bands in layers through disc spring groups, high-polymer polyurethane elastic layers, hydraulic damping cylinders, and high-damping rubber shock absorbers. The spline transmission structure transmits torque while retaining axial buffer space, thus attenuating the vibration energy generated during drilling from the source of the equipment itself.

[0021] The drill bit integrates a pump-suction reverse circulation slag removal system. The slag inlet is located in the area where rock slag is concentrated and collapsed, which can simultaneously complete rock breaking and continuous slag removal, avoid repeated tool breakage caused by slag accumulation at the bottom of the hole, ensure that the cutting teeth continuously act on the fresh rock surface, and stably maintain low-disturbance cutting conditions.

[0022] The construction method includes the installation of isolation hole barriers, which utilize the cavity to form a wave impedance interface to reflect and attenuate outward propagating stress waves and vibration waves. This, together with the drilling tool's centripetal pressure relief rock breaking and the module's multi-stage vibration reduction, forms a triple disturbance control system, effectively blocking the propagation path of vibration and stress towards the nearby tunnel.

[0023] The damping and vibration reduction module has built-in multi-parameter sensors that can collect deformation and torque data in real time to automatically adjust drilling parameters, so that the equipment can operate continuously in a low-disturbance range, further reducing the dynamic impact of the construction process on the surrounding strata and tunnel structure. Attached Figure Description

[0024] Figure 1 This is a cross-sectional view of the equipment of the present invention;

[0025] Figure 2 for Figure 1 A magnified view of a section at point A in the middle;

[0026] Figure 3 This is a schematic diagram of the cutting tooth displacement of a single-stage expansion ring;

[0027] Figure 4 This is a structural schematic diagram of the damping and vibration reduction module;

[0028] Figure 5 This is a schematic diagram of centripetal shearing;

[0029] Figure 6 This is a schematic diagram showing the location of the isolation holes;

[0030] Figure 7 This is a comparison chart showing the shock absorption effect.

[0031] in:

[0032] 1. Upper connector; 2. Spring sleeve; 3. Disc spring assembly; 4. Hydraulic damping cylinder; 5. High-damping rubber shock absorber; 6. Spline sleeve; 7. Spline shaft; 8. Multi-stage annular stepped expansion ring; 9. Spline connection; 10. Polyurethane elastic layer; 11. Step seal; 12. Glyd ring; 13. Dustproof ring; 14. Slag suction port; 15. Central pilot core-pulling cylinder; 16. Multi-parameter sensor; 17. Spring mandrel; 18. Cutting teeth; 19. Adjacent tunnel; 20. Isolation hole row; 21. Pile foundation to be built; 22. Drill bit; 23. Rock. Detailed Implementation

[0033] The invention will now be further described with reference to the accompanying drawings.

[0034] The low-disturbance drilling equipment provided in this embodiment is particularly suitable for the construction of large-diameter cast-in-place piles that need to be deeply embedded in slightly weathered granite in underground structures close to existing structures.

[0035] I. Detailed Description of Equipment Structure

[0036] like Figure 1 As shown, the low-disturbance drilling equipment provided in this embodiment consists of a stepped reaming drill bit, a damping and shock absorption module, and an upper connector from bottom to top. The upper connector 1 is used to connect with the power head of the drilling rig to transmit axial pressure and rotational torque.

[0037] 1. Stepped reamer bit

[0038] The stepped reaming drill bit, as the rock-breaking execution terminal, includes a central pilot core-pulling cylinder 15 located at the axis and a multi-stage annular stepped reaming ring 8 coaxially sleeved on its outer periphery.

[0039] The central pilot core-pulling cylinder 15 is located at the very front of the drill bit. Its body is made of high-strength, wear-resistant alloy steel, with PDC teeth evenly distributed along the lower part of the cylinder wall. The hardness of the PDC teeth is far higher than that of the carbide tips of cutting teeth. During drilling, it maintains excellent cutting smoothness and sharpness, allowing it to cut into the formation in a smoother manner, closer to milling. Furthermore, compared to cutting teeth, the PDC teeth not only reduce vibration but also significantly improve drilling efficiency and reduce tool wear. The central pilot core-pulling cylinder 15 has an outer diameter of 0.8m and a core-pulling length of 1.0m, enabling it to preferentially cut into the rock mass under low drill pressure conditions, forming a central cylindrical pressure-relief cavity with a diameter of 0.8m. The formation of this central cavity provides a crucial free surface for subsequent borehole reaming, transforming the surrounding rock from a triaxial compression state to a biaxial stress state, significantly reducing the energy required for rock breaking, and simultaneously preventing the radial propagation of cutting stress to the surrounding rock.

[0040] The multi-stage annular stepped expansion rings 8 are arranged axially in stages according to the principle of the inner ring leading and the outer ring lagging. The diameter of each expansion ring increases progressively, with the first stage having a diameter of 1.3m, the second stage 1.6m, and the third stage 2.0m, ultimately reaching the designed pile diameter. Figure 2 , Figure 3 As shown, cutting teeth are evenly distributed on the outer edge of each level of the borehole reamer ring, arranged in a radially staggered overlapping pattern. The cutting teeth are installed with a negative rake angle (typically -5° to -15°), and are tilted towards the borehole center (centripetal angle set at 10°~20°), ensuring that the principal component of the cutting force always points towards the central cavity. Under the combined action of drill pressure and torque, the cutting teeth apply force to the rock mass in a centripetal oblique cutting manner, inducing tensile-shear composite failure of the rock along the radial central free plane, achieving a controlled rock-breaking mechanism of centripetal shear. Compared with traditional full-face drilling, this mechanism effectively eliminates the radial compression effect on the surrounding rock of the borehole wall, fundamentally ensuring the structural safety of the adjacent tunnel.

[0041] 2. Damping and vibration reduction module

[0042] like Figure 1 , Figure 4 As shown, the damping and vibration reduction module is located between the upper joint 1 and the stepped reaming drill bit, undertaking multiple functions such as axial load transmission, torque transmission, and vibration energy dissipation. This module adopts a four-stage composite dissipation structure:

[0043] The first stage is the disc spring assembly 3, which is composed of multiple disc spring plates conforming to GB / T1972-2005 standard, assembled in a composite manner. It is coaxially fitted onto the outside of the spring spindle 17 and housed as a whole within the inner cavity of the spring sleeve 2. Its upper end is in contact with the lower surface of the upper connector 1, and its lower end is in contact with the upper surface of the high-polymer polyurethane elastic layer 10, forming a stable axial force transmission path. As the main load-bearing element, the disc spring system mainly bears the entire weight of the drill pipe and drill bit, as well as the static drilling pressure during drilling, so that the subsequent hydraulic damping cylinder 4 and high-damping rubber shock absorber only need to bear the dynamic vibration load, significantly reducing their workload.

[0044] The second stage is a high-polymer polyurethane elastic layer 10, serving as a dedicated high-frequency micro-vibration dissipation unit for the entire damping and vibration reduction module. It is a solid annular sheet structure manufactured using a molding process, coaxially sandwiched between the lower end face of the disc spring assembly 3 and the upper end cover of the hydraulic damping cylinder 4, and between the lower end face of the hydraulic damping cylinder 4 and the upper end face of the high-damping rubber shock absorber 5. The upper and lower surfaces are tightly fitted to the metal end faces, forming a gapless force transmission interface. Its core function is to absorb the residual vibration filtered by the first-stage disc spring assembly 3. Utilizing the unique viscoelastic internal friction effect of polyurethane material, it specifically absorbs and dissipates the 100~5000Hz high-frequency micro-amplitude vibrations generated during hard rock drilling, blocking the propagation path of high-frequency vibration waves to the drill pipe and the upper drilling rig. Simultaneously, it provides uniform load distribution and flexible buffer protection for the hydraulic damping cylinder.

[0045] The third stage is the hydraulic damping cylinder 4, which serves as the core dissipation unit for low-to-medium frequency large-amplitude vibrations in the entire damping and vibration reduction module. It adopts a single-acting piston-type fully sealed structure, coaxially connected between the lower part of the polymer polyurethane elastic layer 10 and the upper part of the high-damping rubber shock absorber 5. The upper end of the cylinder body is tightly bonded to the polyurethane layer via a precision-machined flange, while the lower end is rigidly connected to the upper surface of the high-damping rubber shock absorber via a high-strength adhesive. The piston rod and cylinder body are firmly sealed together using a Step seal 11 and a Gale ring 12, ensuring long-term sealing under high-speed reciprocating motion and effectively preventing oil leakage into the piston's side chambers, thus guaranteeing the stability of the damping force. Its core function is to specifically dissipate the 1-100Hz low-to-medium frequency, large-amplitude vibrations generated during hard rock drilling. These vibrations are the primary cause of overall drilling rig vibration, drill rod fatigue fracture, and large deformation and misalignment of the tunnel lining. It utilizes the velocity-dependent viscous damping force generated by hydraulic oil flowing through a precision damping orifice to efficiently convert large-amplitude vibration mechanical energy into heat energy and dissipate it quickly through the cylinder.

[0046] The fourth stage is the high-damping rubber shock absorber 5, which serves as the final residual vibration dissipation unit and resonance suppression core of the entire four-stage damping system. It adopts a shear-compression composite structure and is coaxially connected in series between the lower end face of the hydraulic damping cylinder 4 and the upper end face of the spline sleeve 6. The upper and lower end faces are rigidly connected to metal flanges via high-strength adhesive, forming a gapless, non-slip force transmission interface. Its core function is to receive the full-frequency residual vibration energy filtered by the first three damping units, utilizing the unique hysteresis dissipation effect and intramolecular friction characteristics of high-damping rubber to ultimately attenuate all residual vibrations in the 1~10000Hz range.

[0047] 3. Pump-suction reverse circulation slag discharge system

[0048] The stepped reaming drill bit integrates a pump-suction reverse circulation slag removal system. The slag removal channel runs axially along the drill bit and connects to the upper drill pipe cavity. The slag suction port 14 is precisely positioned in the annular transition area between the central pilot core-pulling cylinder 15 and the first-stage reaming ring; this area is the primary rock-breaking zone with a high concentration of rock debris. A high-power sand pump is installed at the borehole opening. During drilling, the sand pump is activated to create a continuous negative pressure within the drill pipe cavity. Driven by the pressure difference between atmospheric pressure and the negative pressure within the drill pipe, the circulating fluid at the borehole opening carries the rock debris and accelerates into the slag removal channel through the suction port 14. The mixture of rock debris and liquid rises along the drill pipe cavity at a flow rate of 3-5 m / s and is continuously pumped to the surface mud purification system. The surface system performs solid-liquid separation of the slag, and the purified mud is returned to the borehole opening for reuse, achieving green construction. The pump-suction reverse circulation slag removal system enables simultaneous rock breaking and slag removal, effectively avoiding slag accumulation at the bottom of the hole and repeated crushing of rock cuttings, ensuring that the cutting teeth always act on the fresh rock surface, and significantly improving drilling efficiency and hole quality.

[0049] Regarding the torque transmission path, the lower part of the module transmits torque through a splined sleeve 6 and a splined shaft 7 via a splined connection 9. This splined connection can transmit large torques while allowing axial relative sliding, ensuring the proper functioning of the damping and vibration reduction module's axial vibration reduction function. The module also includes a multi-parameter sensor 16 for real-time monitoring of parameters such as the compression deformation of the vibration reduction module and the drill bit torque, providing a basis for dynamic control of drilling parameters.

[0050] Regarding the drilling rig's sealing, the lower part of the module employs a combined sealing scheme of Step Seal 11, Glyd ring 12, and dustproof ring 13. This scheme achieves the dual goals of preventing internal leakage and external contamination. Even under the high water pressure conditions of deep hole drilling, it ensures zero leakage of drilling mud inside the drill pipe while preventing external rock debris from damaging internal transmission components, thus guaranteeing continuous and stable operation of the drilling rig under harsh geological conditions.

[0051] II. Detailed Description of Construction Methods

[0052] Based on the above equipment, the low-disturbance hole-forming construction method provided by the present invention includes the following steps:

[0053] S0, Construction of isolation hole array

[0054] like Figure 5As shown, the construction of isolation boreholes is an active vibration isolation technology. Its core is to form a physical barrier between the pile foundation 21 to be constructed and the adjacent tunnel 19 through drilling, thereby blocking or weakening the vibration stress waves generated during pile foundation construction. Specifically, the isolation boreholes 20 are drilled using a fully hydraulic core drilling rig, employing a rotary cutting method to minimize vibration and impact. The diameter of the isolation holes is set at 200mm, and the isolation boreholes 20 are positioned 1 meter from the outer wall of the tunnel structure. The center-to-center spacing of the holes is set at 1.5 times the hole diameter to ensure sufficient stability of the soil columns formed between the holes, while simultaneously creating a continuous, low-stiffness isolation zone. During the drilling process, to avoid stress concentration and cumulative disturbance to the soil, a skip-hole construction sequence is adopted, drilling parameters are strictly controlled, and low-speed, low-feed pressure drilling is used for smooth operation. After drilling, the cavity state within the hole is maintained, where the vibration isolation effect of the air medium is optimal.

[0055] S1, Initial Pilot Cut-in

[0056] The initial pilot entry is the primary core process of this invention and the physical basis for achieving low-disturbance rock breaking in hard rock. The rotary drilling rig lowers the drill bit to the bottom of the hole. Initially, only the central pilot core-pulling cylinder 15 contacts the rock surface, while the multi-stage annular reaming rings 8 are suspended. Under a low-pressure, high-speed drilling condition (50-80 kN drill pressure and 15-25 rpm rotation speed), the central pilot core-pulling cylinder 15 is driven for core drilling. After drilling to the set core-pulling depth of 1.0 m, drilling is stopped, and the drill string is raised. The cylindrical rock core is broken using the friction between the inner wall of the central pilot core-pulling cylinder and the rock core, or by using an auxiliary core-breaking device. After core breaking, the drill string is raised at a constant speed of 0.3-0.5 m / s to avoid sudden stops and accelerations that could cause the rock core to fall out. Once the drill bit is pulled out of the borehole, it is moved to the core-unloading area, where a special core-unloading tool is used to push the rock core out of the central pilot core-pulling cylinder. Repeat the drilling, core extraction, and core sampling cycles until a through-hole with a diameter of 0.8m is formed throughout the entire depth of the pile hole.

[0057] S2, Centripetal shearing staged hole expansion

[0058] The drill bit 22 is lowered back to the bottom of the hole, ensuring full contact between the cutting teeth of the multi-stage annular stepped reamer 8 and the surrounding rock mass of the central cavity. The drilling pressure is then increased to 120-150 kN, while the rotation speed is maintained at approximately 15 rpm. To prevent the formation of unbreakable hard rock ridges between adjacent cutting teeth, which could lead to tooth root shear failure, the cutting teeth 18 on the multi-stage stepped reamer 8 are arranged in a radially staggered overlapping pattern. The overlap width of the cutting trajectories of adjacent cutting teeth is 5-15 mm. This ensures that during drilling, the rock 23 is divided into extremely narrow annular protrusions by the cutting teeth, allowing for brittle shear failure even under very low axial drilling pressure, thus preventing direct contact between the rock ridges and the drill bit body and tooth roots. Simultaneously, to address the issue of the cutting teeth's centripetal inclination potentially causing external compression of the hole wall, the geometric angles of the cutting teeth 18 are designed collaboratively. For example... Figure 3 As shown, the rake face of the cutting teeth gradually tilts towards the hole axis (centripetal angle from 0° to 15°) to guide rock cuttings to slide towards the inner free surface. Due to the stepped design of the drill bit, the first-stage annular reaming ring leads the outer ring axially. Its negative rake angle cutting teeth first cut into the rock mass. Under torque, the cutting teeth do not impact the rock wall perpendicularly, but rather cut obliquely at a centripetal angle of 10° to 15°. This mechanical mechanism forces the cracks inside the rock to extend towards the free central cavity, and the rock 20 collapses directly inward under shear force, rather than squeezing the surrounding rock outward. Subsequently, the second and third stages follow, gradually enlarging the hole diameter to the designed pile diameter of 2.0m. At this time, the outer ring cutting teeth also utilize the pressure relief space provided by the inner ring to trim and enlarge the remaining annular rock ridge. Because the various levels of the expanding rings are arranged in a stepped manner along the axial direction, with the inner ring leading the outer ring in cutting, each level of cutting teeth has an independent free surface, avoiding simultaneous compression of the rock wall across the entire cross section, thereby minimizing radial disturbance.

[0059] S3, Full-process reverse circulation slag removal

[0060] Simultaneously with the borehole reaming process, the reverse circulation slag removal system is activated. A high-power sand pump (≥75kW) is started, and a vacuum pump or jet device is used to create a negative pressure environment within the sand pump and drill pipe cavity. The vacuum gauge reading must be monitored to ensure the system vacuum remains stable between -0.06MPa and -0.08MPa. When a sufficient negative pressure difference is achieved within the drill pipe cavity, the flushing fluid at the borehole opening, under atmospheric pressure, carries the rock cuttings from the drill bit and is forcefully drawn into the slag removal channel from the slag suction port 14 at the bottom of the drill bit. Observe the water outlet pipe; when the discharged liquid changes from pure liquid to slag-containing fluid, and no obvious bubbles are ejected, it indicates that the reverse circulation system is operating smoothly and has good airtightness. Thanks to the centripetal shearing rock-breaking mechanism, the rock mainly collapses towards the central cavity, which perfectly aligns with the flow direction of the reverse circulation slag removal. The rock cuttings generated are drawn into the slag removal channel from the slag suction inlet along with the circulating fluid and continuously pumped out of the borehole through the drill pipe cavity. Slag removal and borehole enlargement are carried out simultaneously to ensure that the bottom of the borehole remains clean at all times, eliminate secondary crushing and abnormal wear of cutting teeth caused by rock slag accumulation, and ensure borehole efficiency and borehole wall forming quality.

[0061] S4, Dynamic Control

[0062] Throughout the entire construction process, key parameters such as drilling torque, rotational speed, thrust, and compression deformation of the damping module are collected in real time using multi-parameter sensors 16. The control system judges these parameters according to the preset optimized operating condition range: when a sudden increase in torque or an abnormal increase in the deformation of the damping module is detected, it is determined that the cutting condition has deteriorated or the vibration has exceeded the standard. The system automatically fine-tunes to reduce drilling pressure or adjust the rotational speed, so that the drilling state returns to a stable range with high cutting efficiency and low vibration response. Through this closed-loop control mechanism, the synergistic optimization of efficient rock breaking and low-disturbance control in hard rock is achieved.

[0063] Repeat steps S1 to S4 until the drilling reaches the designed final hole depth, thus completing the drilling construction of the large-diameter deep-embedded hard rock pile foundation.

[0064] III. Explanation of the Centripetal Shear Mechanism

[0065] Figure 6This invention illustrates the pilot pressure relief and centripetal shear rock breaking mechanism. Its core lies in constructing a dual-protection system of source control and propagation path vibration isolation. Unlike traditional methods that compress and compact rock masses, this invention first uses a central pilot core-extraction cylinder to drill a complete rock core with a diameter of 0.8m to 1.0m at the center of the pile location, forming a central cavity. This cavity disrupts the triaxial force balance of the original rock mass, providing a stable inner free surface for subsequent borehole enlargement operations. According to the principle of the line of least resistance in rock mechanics, rock fracturing will preferentially proceed towards this cavity of least resistance, rather than compressing outwards towards the tunnel side. The existence of the cavity also causes diffraction and attenuation of the radial stress field around the pile hole, significantly reducing the effective stress peak transmitted to the adjacent tunnel. Simultaneously, the damping and vibration reduction module absorbs and dissipates the vibration energy inevitably generated during drilling in stages, further isolating the vibration from propagation to the drilling rig and the strata, achieving dual low-disturbance protection through source control and path vibration isolation.

[0066] IV. Comparison of Shock Absorption Effects

[0067] Figure 7 The demonstration showed a dynamic comparison of vibration amplitude between traditional rotary drilling rigs, low-disturbance drilling rigs, and the latter combined with a specific construction method during an 8-second continuous operation. The traditional rotary drilling rig exhibited the most dramatic vibration amplitude fluctuations, consistently maintaining a value of 1100 mm / s. 2 Up to 1600mm / s 2 The high-level range exhibits obvious periodic impact characteristics, with high peak values ​​and slow decay. In contrast, simply using low-disturbance drilling equipment can reduce the overall vibration amplitude to 700 mm / s. 2 Up to 1050 mm / s 2 While the range is within acceptable limits, noticeable fluctuations still exist. However, when using low-disturbance drilling equipment and methods, the vibration amplitude exhibits extremely strong stability, remaining essentially suppressed to within 500 mm / s throughout the entire process. 2 Up to 750mm / s 2 The low level and minimal fluctuations clearly demonstrate that low-disturbance drilling technology and its supporting construction methods have significant vibration reduction effects, effectively mitigating dynamic impacts during drilling and greatly improving the stability of the operation.

Claims

1. A near-tunnel, large-diameter, deep-embedded, hard rock drilling equipment with low disturbance, connected to a drill rod, characterized in that... The system includes a drill rod connection mechanism, a damping and vibration reduction module, and a stepped reaming drill bit, connected sequentially from top to bottom. The stepped reaming drill bit is an integrated structure, comprising a central pilot core-pulling cylinder and multi-stage annular stepped reaming rings. The central pilot core-pulling cylinder is located at the front end, with PDC teeth arranged on the lower part of its cylinder wall. The multi-stage annular stepped reaming rings are coaxially fitted onto the outside of the central pilot core-pulling cylinder and arranged axially in stages along the drilling direction. Each multi-stage annular stepped reaming ring includes an innermost reaming ring, an inner layer reaming ring, and an outer layer reaming ring. The innermost reaming ring is fitted onto the outside of the central pilot core-pulling cylinder, the inner layer reaming ring is fitted onto the outside of the innermost reaming ring, and the outer layer reaming ring is fitted onto the outside of the inner layer reaming ring. Cutting teeth are arranged on the outer edges of the innermost reaming ring, the inner layer reaming ring, and the outer layer reaming ring. The drill bit has a negative rake angle structure and is arranged asymmetrically and interlaced radially along a multi-level annular stepped reaming ring. The radial projections of the rotational cutting trajectories of adjacent cutting teeth overlap, and the rake face of the cutting teeth is inclined to the center of the multi-level annular stepped reaming ring. The damping and vibration reduction module includes a disc spring assembly, a high-polymer polyurethane elastic layer, a hydraulic damping cylinder, and a high-damping rubber shock absorber. The lower part of the damping and vibration reduction module is equipped with a spline drive structure, which includes a spline sleeve and a spline shaft that are splined together. The damping and vibration reduction module transmits torque to the stepped reaming drill bit through the spline drive structure. The stepped reaming drill bit integrates a pump suction reverse circulation slag removal system. The pump suction reverse circulation slag removal system has an axially penetrating slag removal channel. The slag suction port of the slag removal channel is located in the transition area between the central pilot core-pulling cylinder and the innermost reaming ring.

2. The near-tunneling equipment for large-diameter, deep-embedded hard rock with low disturbance as described in claim 1, characterized in that, The multi-stage annular stepped expansion ring gradually increases in diameter along the radial direction. The damping and shock absorption module also includes a spring sleeve. The disc spring assembly is housed inside the spring sleeve. Polyurethane elastic layers are sandwiched between the contact surfaces of the bottom end of the spring sleeve and the top end of the hydraulic damping cylinder, and between the bottom end of the hydraulic damping cylinder and the top end of the high-damping rubber shock absorber. Damping holes are opened inside the hydraulic damping cylinder. The high-damping rubber shock absorber is located below the polyurethane elastic layers.

3. The near-tunneling equipment for large-diameter, deep-embedded hard rock with low disturbance as described in claim 2, characterized in that... The slag discharge channel of the pump-suction reverse circulation slag discharge system extends upward through the center hole of the spline shaft and through the drill rod connection mechanism, so as to communicate with the inner cavity of the drill rod when the drill rod connection mechanism is connected to the drill rod; the slag discharge channel is used to communicate with the sand and gravel pump through the inner cavity of the drill rod, so that when the sand and gravel pump is working, a negative pressure is formed in the slag discharge channel for sucking up the rock slag at the bottom of the hole; the damping and vibration reduction module is equipped with a multi-parameter sensor, which is used to collect the compression deformation of the damping and vibration reduction module and the drill bit torque data.

4. The near-tunneling equipment for large-diameter, deep-embedded hard rock with low disturbance as described in claim 3, characterized in that, The piston rod of the hydraulic damping cylinder is fitted with a Step seal and a Glyd ring between it and the cylinder body; the spline sleeve and spline shaft mesh with each other to transmit torque while allowing the components to slide relative to each other axially.

5. A method for constructing large-diameter, deeply embedded hard rock tunnels in close proximity, based on the equipment described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Lower the stepped reaming drill bit and control the drilling pressure so that the central pilot core-pulling cylinder contacts the rock mass to complete the advanced core drilling and form a central pressure relief cavity. S2. Keep the stepped reaming drill bit feeding downwards. The cutting teeth of the multi-stage annular stepped reaming ring contact the rock mass. Relying on the central pressure relief cavity, synchronous stepped centripetal shearing reaming operation is carried out until the target depth is reached. S3, steps S1 and S2 are carried out with the pump suction reverse circulation slag discharge system running continuously to pump and discharge the broken rock slag from the bottom of the hole in real time. S4. Relying on multi-parameter sensors to collect deformation data of the damping and vibration reduction module in real time, and when the vibration amplitude exceeds the threshold, the drilling pressure is automatically reduced and the drilling speed is adjusted to maintain low-disturbance drilling conditions.

6. The method for constructing a large-diameter, deeply embedded hard rock tunnel in close proximity as described in claim 5, characterized in that, Step S1 relies solely on the central pilot core-pulling cylinder to complete the core extraction operation. The multi-stage annular stepped borehole expander ring remains suspended and does not participate in cutting. After core extraction is completed, the stepped borehole expander bit is lifted, broken off, and the core rock inside the hole is removed. The core extraction operation is repeated to form a central pressure relief cavity that penetrates the entire depth of the pile hole.

7. The method for constructing a large-diameter, deeply embedded hard rock tunnel in close proximity as described in claim 6, characterized in that, In step S2, the cutting teeth of the innermost, inner, and outermost expanding rings of the multi-level annular stepped expanding rings are arranged radially in an alternating pattern. The cutting trajectories of adjacent cutting teeth overlap to eliminate rock ridges. The cutting teeth rely on the centripetal inclined structure to guide the rock mass toward the central pressure relief cavity to undergo shearing and collapse. The inner expanding rings preferentially cut the rock mass, while the outer expanding rings follow up to trim the annular rock ridges.

8. The method for constructing a large-diameter, deeply embedded hard rock tunnel in close proximity as described in claim 7, characterized in that, Before construction, multiple rows of isolation holes are drilled between the pile foundation to be constructed and the adjacent tunnel to form a stress blocking barrier. The isolation holes are laid out along the tunnel direction. After the isolation holes are formed, they are kept in a cavity state. When constructing the isolation holes, a skip-hole drilling sequence is adopted, and low speed and low drilling pressure are used for smooth drilling throughout the process. Step S4 forms a triple low-disturbance control system. The first layer relies on the centripetal shearing and crushing mechanism of the cutting teeth to weaken the radial compressive stress of the surrounding rock. The second layer relies on the damping and vibration reduction module to dissipate the drilling vibration load in stages. The third layer relies on the isolation hole barrier to reflect and attenuate the stress waves and vibration waves propagating outward. The S1 to S4 procedures are executed in a cycle until the design final hole elevation is reached.

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