Drilling type tunnel excavation method

Abstract

The invention relates to the technical field of water conservancy projects, and discloses a drilling type tunnel excavation method which comprises a mechanical coring method and a hydraulic splitting method, and the mechanical coring method and the hydraulic splitting method comprise the following steps that S101, surveying and setting out are conducted; step S102, drilling and coring are carried out; step S103, splitting the internal rock mass; and S104, deslagging and circulation are conducted, specifically, a slag climbing machine is used in cooperation with a loading machine to convey the broken rock blocks out of the tunnel, an excavation cycle is completed, and the steps are repeated to conduct step-by-step propelling. According to the mechanical coring and hydraulic splitting method, the coring drilling machine is used for accurately drilling the rock core along the excavation contour line to form the free face, then the hydraulic splitting rod is used for conducting static tensioning crushing on the rock mass, and the surrounding rock loosening and leakage risks can be effectively avoided; and for the section allowed by the conditions, the disturbance of the blasting operation on the surrounding rock is reduced to the greatest extent by adopting the small explosive quantity control blasting method through the technologies of fine drilling of empty holes, layered shock absorption and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydraulic engineering, in particular to a drilling type tunnel excavation method. BACKGROUND

[0002] In the hydraulic engineering system, the successful construction and long-term safe operation of the reservoir greatly depend on its underground structure, especially the water conveyance tunnel and the water diversion tunnel, which bear the functions of water diversion, flood discharge, sand discharge and power generation, etc. Therefore, the excavation construction of these tunnels is not only a process of the whole project, but also a key technical link determining the success or failure of the project. The traditional tunnel excavation methods mainly include the drilling and blasting method and the mechanical tunneling method.

[0003] The applicant found in the implementation of the prior art that, although the drilling and blasting method has high efficiency, the blasting vibration has a great influence on the stability of the surrounding rock, especially in the area adjacent to the reservoir, dam body or existing hydraulic structure, the blasting vibration may cause the surrounding rock to loosen, seepage and even structural safety risk, and although the mechanical tunneling method has small vibration and high forming quality, the equipment cost is high and the adaptability is poor, and for the tunnels with small cross section, short distance or variable geological conditions, the operation cost performance is low. Based on this, the present application designs a drilling type tunnel excavation method to solve the above problems. SUMMARY

[0004] The present application aims to provide a drilling type tunnel excavation method, which solves the problems of high risk of the drilling and blasting method and high cost of the mechanical tunneling method in the background art.

[0005] In order to solve the above technical problems, the present application provides the following technical scheme: A drilling type tunnel excavation method, comprising a mechanical coring and a hydraulic splitting method, the mechanical coring and the hydraulic splitting method comprising the following steps: Step S101, measuring and laying out, using a total station instrument to accurately position and mark the coring points on the excavation contour line.

[0006] Step S102, drilling and coring, using a coring drill with a diameter of 160mm to drill a cylindrical rock core with a depth of about 700mm along the marked contour line in batches, forming a free surface around the periphery of the tunnel.

[0007] Step S103, internal rock mass splitting, the remaining intact rock mass within the contour line is divided into blocks, an automatic water mill drill is used to drill split holes on the divided rock mass, a hydraulic splitting rod is inserted, and the rock mass is cracked along the vertical plane and subjected to horizontal shear fracture at the bottom by the hydraulic tensioning force.

[0008] Step S104, slagging and recycling, using a slagging machine to cooperate with a loader to transport the broken rock out of the tunnel, completing an excavation cycle, and repeating the above steps to gradually advance.

[0009] Preferably, in a tunnel with a cross-sectional dimension of 3.2m × 3.2m, a total of 71 core holes are arranged along the outline; a drilling equipment with one to two drilling machines is used, operated by two workers, and the drilling operation takes about 4.5 hours, with a single cycle advance of 0.7-0.9 meters.

[0010] Preferably, in the internal rock mass splitting step, four splitting holes are drilled for each rock mass to be split.

[0011] Preferably, the mechanical coring and hydraulic fracturing method requires the installation of a support structure, and the installation process of the support structure is as follows: Step Z01: Initially spray a 5cm thick layer of C25F50 concrete and lay a φ8@20cm×20cm steel mesh.

[0012] Step Z02: Erect I14 type steel arch frames with a spacing of 0.5m. Two 1.8m long locking mortar anchor rods are installed at each arch foot of the steel arch frame.

[0013] Step Z03: Spray a 15cm thick layer of C25F50 concrete.

[0014] Step Z04: Construct a 40cm thick C30W6F50 concrete lining.

[0015] Step Z05: Install C22 system mortar anchor bolts, 2.25m in length, 2.05m into the rock, arranged in a quincunx pattern with a spacing of 1.0m between rows.

[0016] Preferably, the steel arch frame is manufactured by cold bending and then trial assembly is performed after processing; the connecting steel plates between the steel arch frames are drilled mechanically, and the holes are cleaned of burrs and steel slag using a grinding wheel.

[0017] Preferably, a complete operation cycle of the mechanical coring and hydraulic fracturing method includes: 1.0 hour for measurement and setting out, 1.0 hour for drilling rig positioning, 4.5 hours for drilling, 0.5 hours for hole cleaning, 1.5 hours for quality inspection, 0.5 hours for splitting the central rock, 1.5 hours for slag removal, and 4.0 hours for surrounding rock support, with a total cycle time of 14.5 hours.

[0018] As can be seen from the above technical solution, the surveying and layout process uses a total station to accurately locate and mark core sampling points on the excavation outline, ensuring the accuracy of the excavation outline. Subsequently, core drilling is carried out, using a Φ160mm diameter core drilling rig to drill cylindrical rock cores to a depth of approximately 700mm along the marked outline. In a tunnel with a cross-sectional size of 3.2m × 3.2m, a total of 71 core sampling holes are arranged along the outline, forming a complete free face around the tunnel perimeter.

[0019] After the outer free face is formed, the internal rock mass splitting stage begins. The remaining intact rock mass within the outline is rationally divided into blocks. Four splitting holes are drilled on each block using an automatic water-jet drill, and then hydraulic splitting rods are inserted. Through the enormous tensile force generated by the hydraulic splitting rods, the rock mass is tensile-fracturing along the predetermined vertical plane, while horizontal shearing fractures occur at the bottom, thus achieving controlled splitting of the rock mass.

[0020] A method for drilling tunnel excavation, including controlled blasting with small explosive charges, comprises the following steps: Step S201: Surface cleaning and hole layout. Clean the excavation face and arrange the slotting holes, auxiliary holes, and peripheral holes according to the design. Step S202: Drilling and inspection. After drilling the blast holes, clean and inspect them. Step S203: Charging and detonation. Strictly control the amount of explosives, complete the blast hole filling and network connection, and detonate after inspection and warning. Step S204: Post-blast slag removal. Conduct a post-blast inspection, lift the warning after confirming safety, and then remove the slag to enter the next cycle.

[0021] Preferably, the low-charge controlled blasting method uses a combination of drilling, tunneling, layered vibration reduction, and peripheral vibration reduction techniques to control the maximum vibration velocity of the tunnel to below 8 mm / s.

[0022] Preferably, the arrangement parameters of the boreholes are as follows: All boreholes have a diameter of 42mm.

[0023] The cut holes are located slightly below the center of the excavation face, with a depth of 3.2m, which is 20cm deeper than other blast holes, and the spacing is 15cm-20cm.

[0024] Auxiliary holes are arranged around the slotted holes at a spacing of 50-70cm and a depth of 3.0m.

[0025] The distance between the opening of the peripheral holes and the outline is 10-20cm, the distance between the bottom holes is 50-70cm, and the depth is 3.0m.

[0026] Preferably, a borehole tunnel excavation method selects different excavation schemes according to the type of surrounding rock: In Class IV surrounding rock sections, the aforementioned mechanical core sampling and hydraulic fracturing methods are used for excavation.

[0027] In Class III surrounding rock sections, the aforementioned controlled blasting method was used for excavation.

[0028] As can be seen from the above technical solution, the first step is to clean the surface and lay out the boreholes. After cleaning the excavation face, the slotting holes, auxiliary holes, and peripheral holes are arranged according to the design. Specific parameters are used for the borehole layout: all boreholes have a diameter of 42mm; the slotting holes are located slightly below the center of the excavation face, with a depth of 3.2m, 20cm deeper than other boreholes, and a spacing of 15cm-20cm; auxiliary holes are arranged around the slotting holes, with a spacing of 50-70cm and a depth of 3.0m; the peripheral holes are 10-20cm from the outline line, and the bottom edge holes are spaced 50-70cm apart, with a depth of 3.0m.

[0029] During the charging and detonation phases, precise energy distribution was achieved by strictly controlling the charge amount in each borehole and comprehensively utilizing techniques such as drilling holes, cut-outs, layered vibration reduction, and peripheral vibration reduction. Specifically, optimizing the location and depth of the cut-out holes created favorable open-air conditions for subsequent blasting; the precise arrangement and controlled charging of peripheral holes ensured the smoothness of the excavation profile. During blasting, segmented detonation technology was employed to create a superposition and cancellation effect of blasting vibration waves, strictly controlling the maximum vibration velocity of the tunnel below 8 mm / s.

[0030] The post-blasting treatment phase includes rigorous post-blast inspections, lifting the alert after confirming safety, and then proceeding with muck removal. The entire blasting cycle follows the principle of "short advance and weak blasting." Through scientific blasting parameter design and strict construction control, the impact of blasting vibration on the stability of the surrounding rock is minimized while ensuring excavation efficiency, making it particularly suitable for Class III surrounding rock conditions.

[0031] Compared with the prior art, the beneficial effects achieved by the present invention are: 1. This invention utilizes a mechanical coring and hydraulic fracturing method. A coring drill is used to precisely extract rock cores along the excavation outline to form a free face. Subsequently, a hydraulic fracturing rod is used to statically tension and break the rock mass. This process generates almost no vibration, making it particularly suitable for vibration-sensitive areas and effectively avoiding the risks of surrounding rock loosening and leakage. For sections where conditions permit, the low-charge controlled blasting method employs precise drilling and layered vibration reduction techniques to control the blasting vibration intensity to an extremely low level, minimizing the disturbance to the surrounding rock caused by blasting operations and thus ensuring the long-term stability and safety of the tunnel structure.

[0032] 2. In this invention, the mechanical core sampling process can directly form a precise separation groove along the designed outline, making the excavation cross-section very regular and basically avoiding over-excavation. This not only saves the amount of backfill concrete and reduces support costs, but also creates favorable conditions for subsequent lining construction. For the blasting section, the precise arrangement of blast holes and advanced smooth blasting or pre-splitting blasting technology make the tunnel outline after blasting smooth, with a high half-hole retention rate, reducing damage to the surrounding rock. This also achieves the goals of reducing over-excavation and under-excavation, saving materials, and ensuring project quality.

[0033] 3. In areas with hard rock formations or where blasting is strictly prohibited, the present invention can employ a non-blasting scheme of mechanical core sampling and hydraulic fracturing. In Class III surrounding rock sections where vibration control requirements are relatively relaxed, a more efficient controlled blasting method with small charges can be selected. This flexibility allows the method to cope with complex and varied geological conditions and avoids the limitations of a single construction method. At the same time, the mechanical core sampling and fracturing equipment is usually lighter, more flexible, and has a lower investment cost than large tunneling machines, making it very suitable for small and medium cross-section tunnels, short-distance tunnels, or engineering projects with limited construction sites. Attached Figure Description

[0034] Fig. 1 This is a flowchart of the mechanical coring and hydraulic fracturing method of the present invention; Fig. 2 This is a flowchart of the controlled blasting method with small charge quantity of the present invention; Fig. 3 This is a flowchart illustrating the installation of the support structure of the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] Please see Figs. 1-3 In this embodiment of the invention, a method for drilling tunnel excavation includes mechanical core sampling and hydraulic fracturing. The mechanical core sampling and hydraulic fracturing method includes the following steps: Step S101: Surveying and setting out. Use a total station to accurately locate and mark core sampling points on the excavation outline. Step S102: Core drilling. Use a φ160mm diameter core drill to drill cylindrical rock cores to a depth of approximately 700mm along the marked outline, forming the free face around the tunnel. Step S103: Internal rock mass splitting. Divide the remaining intact rock mass within the outline into blocks. Use an automatic water-cooled drill to drill splitting holes in the blocks, insert hydraulic splitting rods, and use hydraulic tension to cause the rock mass to split along the vertical plane and undergo horizontal shear fracture at the bottom. Step S104: Muck removal and circulation. Use a muck crawler in conjunction with a loader to transport the broken rock blocks out of the tunnel, completing one excavation cycle, and repeat the above steps to advance step by step.

[0038] In a tunnel with a cross-sectional dimension of 3.2m×3.2m, a total of 71 core holes are arranged along the outline. A drilling rig with one to two drilling machines is used, operated by two workers. The drilling operation takes about 4.5 hours, with a single cycle advance of 0.7-0.9 meters.

[0039] In the internal rock mass splitting process, four splitting holes are drilled for each rock mass to be split.

[0040] Mechanical coring and hydraulic fracturing methods require the installation of a support structure. The installation process for the support structure is as follows: Step Z01: Apply a 5cm thick layer of C25F50 concrete and lay a φ8@20cm×20cm steel mesh. Step Z02: Erect I14 type steel arch frames with a spacing of 0.5m, and install two 1.8m long locking mortar anchors at each arch foot. Step Z03: Apply a 15cm thick layer of C25F50 concrete. Step Z04: Construct a 40cm thick layer of C30W6F50 concrete lining. Step Z05: Install C22 system mortar anchors, 2.25m long, with a rock penetration depth of 2.05m, arranged in a quincunx pattern with a spacing of 1.0m between rows.

[0041] The steel arch frame is manufactured using the cold bending method and then trial-assembled after processing. The connecting steel plates between the steel arch frames are drilled mechanically, and the holes are cleaned of burrs and steel slag using a grinding wheel.

[0042] A complete work cycle of mechanical coring and hydraulic fracturing includes: 1.0 hour for surveying and setting out, 1.0 hour for drilling rig positioning, 4.5 hours for drilling, 0.5 hours for hole cleaning, 1.5 hours for quality inspection, 0.5 hours for splitting the central rock, 1.5 hours for slag removal, and 4.0 hours for surrounding rock support, with a total cycle time of 14.5 hours.

[0043] The working principle of this invention is as follows: First, through the surveying and setting-out process, a total station is used to accurately locate and mark the core sampling points on the excavation outline to ensure the accuracy of the excavation outline. Then, core drilling is carried out, using a Φ160mm diameter core drilling rig to drill cylindrical rock cores to a depth of approximately 700mm along the marked outline in batches. In a tunnel with a cross-sectional size of 3.2m × 3.2m, a total of 71 core sampling holes are arranged along the outline, forming a complete free face around the tunnel perimeter.

[0044] After the outer free face is formed, the internal rock mass splitting stage begins. The remaining intact rock mass within the outline is rationally divided into blocks. Four splitting holes are drilled in each block using an automatic water-jet drill, and then hydraulic splitting rods are inserted. The enormous tensile force generated by the hydraulic splitting rods causes the rock mass to fracture along the predetermined vertical plane, while horizontal shearing fractures occur at the bottom, thus achieving controlled splitting of the rock mass.

[0045] After the rock mass is split, muck removal is carried out. A muck-climbing machine, in conjunction with a loader, transports the broken rock blocks out of the tunnel, completing one excavation cycle. The entire work cycle is divided into the following time allocations: surveying and setting out 1.0 hour, drilling rig positioning 1.0 hour, drilling 4.5 hours, hole cleaning 0.5 hours, quality inspection 1.5 hours, splitting the central rock 0.5 hours, and muck removal 1.5 hours, for a total cycle time of 14.5 hours. This method, through precise control of the excavation contour and graded splitting, minimizes disturbance to the surrounding rock and is particularly suitable for construction in Class IV surrounding rock sections where vibration control is critical.

[0046] Example 2

[0047] Please see Figs. 1-3 In this embodiment of the invention, a borehole tunnel excavation method includes a small-charge controlled blasting method, comprising the following steps: Step S201, surface cleaning and hole layout: cleaning the excavation face and arranging slotted holes, auxiliary holes, and peripheral holes according to the design; Step S202, drilling and inspection: after drilling the blast holes, cleaning and inspecting the holes; Step S203, charging and detonation: strictly controlling the charge amount, completing the blast hole filling and network connection, and detonating after inspection and warning; Step S204, post-blast muck removal: performing a post-blast inspection, lifting the warning after confirming safety, and then removing the muck to enter the next cycle.

[0048] The controlled blasting method with small charge can control the maximum vibration velocity of the tunnel to below 8 mm / s by comprehensively using drilling, caving, layered vibration reduction and peripheral vibration reduction techniques.

[0049] The layout parameters of the blast holes are as follows: all blast holes have a diameter of 42mm; the cut holes are located slightly below the center of the excavation face, with a depth of 3.2m, which is 20cm deeper than other blast holes, and a spacing of 15cm-20cm; auxiliary holes are arranged around the cut holes, with a spacing of 50-70cm and a depth of 3.0m; the openings of the peripheral holes are 10-20cm from the outline, and the bottom edge holes are 50-70cm apart, with a depth of 3.0m.

[0050] A borehole tunnel excavation method selects different excavation schemes according to the surrounding rock type: in Class IV surrounding rock sections, mechanical core sampling and hydraulic splitting methods are used for excavation; in Class III surrounding rock sections, small-charge controlled blasting method is used for excavation.

[0051] The working principle of this invention is as follows: First, surface cleaning and hole layout are carried out. After cleaning the excavation face, the slotting holes, auxiliary holes, and peripheral holes are arranged according to the design. The arrangement of the blasting holes adopts specific parameters: all blasting holes have a diameter of 42mm. The slotting holes are arranged in the lower center of the excavation face, with a depth of 3.2m, which is 20cm deeper than other blasting holes, and the spacing is controlled between 15cm and 20cm. The auxiliary holes are arranged around the slotting holes, with a spacing of 50-70cm and a depth of 3.0m. The peripheral holes are 10-20cm from the outline line, and the bottom edge holes are 50-70cm apart, with a depth of 3.0m.

[0052] During the charging and detonation phases, precise energy distribution was achieved by strictly controlling the charge amount in each borehole and comprehensively utilizing techniques such as drilling holes, cut-outs, layered vibration reduction, and peripheral vibration reduction. Specifically, optimizing the location and depth of the cut-out holes created favorable open-air conditions for subsequent blasting; the precise arrangement and controlled charging of peripheral holes ensured the smoothness of the excavation profile. During blasting, segmented detonation technology was employed to create a superposition and cancellation effect of blasting vibration waves, strictly controlling the maximum vibration velocity of the tunnel below 8 mm / s.

[0053] The post-blasting treatment phase includes rigorous post-blast inspections, lifting the alert after confirming safety, and then proceeding with muck removal. The entire blasting cycle follows the principle of "short advance and weak blasting." Through scientific blasting parameter design and strict construction control, the impact of blasting vibration on the stability of the surrounding rock is minimized while ensuring excavation efficiency, making it particularly suitable for Class III surrounding rock conditions.

[0054] Example 3

[0055] Please see Figs. 1-3This paper provides a specific embodiment of a mechanical coring and hydraulic fracturing method applied to the section from chainage 0+161.64 to 0+151.64, which is classified as Class IV surrounding rock. The tunnel has a diameter of 3.2 meters and a length of 10 meters. First, surveying and setting out were conducted, using a total station to accurately mark the drilling locations on the construction site, ensuring deviations were within acceptable limits. Then, the coring rig was transported to the drilling points, its horizontal and vertical alignment was adjusted, and the equipment was secured with expansion bolts. The coring rig used a 160 mm diameter drill bit to collect cores in batches along the tunnel outline, forming a free face. This free face required drilling 71 holes, each approximately 700 mm deep. A single-to-two drilling rig was used, operated by two workers, one operating the equipment and the other assisting. During drilling, the cooling water valve was opened to ensure a cooling water supply. The drilling rig was started and pressurized slowly, with pressure and speed adjusted to maintain stable drilling. After drilling was completed, the debris inside the holes was cleaned, and the hole wall quality was inspected. The total drilling time was approximately 4.5 hours, with a drilling depth of 0.7 to 0.9 meters. Next, the rock was segmented. Four splitting holes were drilled at the excavation face, and multiple hydraulic rock splitters were inserted. Hydraulic force was used to split the rock, causing it to fracture along the vertical plane and undergo horizontal shearing. After splitting, a muck-climbing machine in conjunction with a loader was used to remove the rock from the tunnel, and the remaining material was manually cleaned up. The entire cycle included 1.0 hour for surveying and setting out, 1.0 hour for drilling rig positioning, 4.5 hours for drilling, 0.5 hours for hole cleaning, 1.5 hours for quality inspection, 0.5 hours for splitting the central rock, 1.5 hours for muck removal, and 4.0 hours for surrounding rock support, for a total cycle time of 14.5 hours. The support structure uses C25F50 shotcrete, 5 cm thick, with φ8 mm reinforcing steel mesh spaced 20 cm x 20 cm apart. I14 steel arch frames are spaced 0.5 m apart, with a 15 cm thick C25F50 shotcrete layer and a 40 cm thick C30W6F50 concrete lining. C22 system mortar anchors, 2.25 m long and 2.05 m deep into the rock, are installed in a staggered pattern with a 1.0 m spacing between rows. The steel arch frames use I14 I-beams, with two 22 anchor bolts (1.8 m long) at each arch foot. The connecting steel plates are double-sided welded to the I-beams, with a weld height of at least 8 mm. The steel arch frames are connected by 22 steel bars on the inner side of the upper flange. The steel arch frames are fabricated using a cold-bending method and trial-assembled. The connecting steel plates are mechanically drilled. Through cyclical operations, the excavation progress target is gradually achieved.

[0056] Example 4

[0057] Please see Figs. 1-3This paper provides a specific embodiment of controlled blasting using a small-charge method, applied to the section from chainage 0+151.64 to 0+121.64 meters, which is Class III surrounding rock and has a length of 30 meters. First, surface cleaning is performed, followed by bench drilling. The blasting design employs controlled blasting, optimizing the construction plan and comprehensively utilizing drilling, slotting, layered vibration reduction, and peripheral vibration reduction technologies to strictly control the blasting velocity, ensuring a maximum velocity of less than 8 mm / s. Slotting holes are located slightly below the center of the excavation face, 20 cm deeper than other blasting holes. Side and top holes are arranged along the outline of the excavation section, with the bottom extending 10 cm beyond the design outline. The opening of the bottom and side holes is 15 cm above the designed floor level, and the bottom reaches 10-20 cm below the floor level. The slotting hole diameter is 42 mm, with a depth of 3.2 meters in Class III surrounding rock, and a spacing of 15-20 cm. Auxiliary holes are arranged around the cut holes at intervals of 50-70 cm, with a diameter of 42 mm and a depth of 3 meters in Class III surrounding rock. The peripheral holes are positioned 10-20 cm from the edge plate, while the bottom holes are spaced 50-70 cm apart, with a diameter of 42 mm and a depth of 3 meters in Class III surrounding rock. After drilling, blowdown and inspection are performed, followed by charging, strictly controlling the charge quantity and adhering to the principles of short advances and weak blasting. After the blast holes are plugged, network connection and inspection are carried out, a warning zone is established, and post-blast inspection and de-escalation are conducted. Slag is removed using a muck-climbing machine in conjunction with a loader to transport the slag to a designated spoil heap for proper stacking. The entire process includes surface cleaning, step-by-step drilling, drilling, blowdown, inspection, charging, blast hole plugging, network connection, network inspection, warning, de-escalation, post-blast inspection, de-escalation, and slag removal, all performed in a cyclical manner. The support structure uses C25F50 shotcrete with a thickness of 5 cm, reinforced with φ8 mm steel wire mesh spaced at 20 cm x 20 cm intervals, and I14 steel arch frames spaced 1.0 meter apart. The shotcrete thickness is 15 cm, and the C30W6F50 concrete lining is 40 cm thick. C22 system mortar anchors, 2.25 meters long and 2.05 meters embedded in the rock, are installed in a staggered pattern with a spacing of 1.0 meter between rows. By strictly controlling blasting parameters and vibration velocity, tunnel safety is ensured, and the excavation work is completed step by step.

[0058] Working Principle: Two differentiated technical approaches—mechanical core sampling and hydraulic fracturing, and controlled blasting with small charges—achieve precise, low-disturbance excavation of the tunnel rock mass. Both methods aim to maximize the self-supporting capacity of the surrounding rock while ensuring construction efficiency, making them particularly suitable for sections sensitive to vibration or with special geological conditions. The mechanical coring and hydraulic fracturing method begins with high-precision surveying and setting out, establishing a precise contour for subsequent operations. Next, a large-diameter coring rig is used to drill dense cylindrical rock cores along the contour line. This essentially creates a continuous stress-relief groove, creating a regular free surface for the internal rock mass. Subsequently, the intact internal rock mass is segmented, and a hydraulic fracturing rod is used to apply significant hydraulic tension in pre-drilled holes. This process cleverly utilizes the mechanical property that the tensile strength of rock is much lower than its compressive strength, allowing the rock mass to be smoothly split in a predetermined direction rather than through violent explosions. This significantly reduces disturbance and damage to the surrounding rock. The entire operation cycle is tightly scheduled, highlighting the applicability of this method under specific conditions.

[0059] The controlled blasting method, using small charges, operates on the principle of "precise control." First, the layout of the blast holes is meticulously designed based on blasting theory, including cut holes, auxiliary holes, and peripheral holes. Millisecond delay detonation technology is used to detonate the explosive charges sequentially at precisely calculated, extremely short time intervals. By comprehensively employing measures such as drilling holes, creating free faces through cuts, layered vibration reduction, and peripheral vibration reduction, the seismic wave energy and vibration velocity generated by the blast are strictly limited within safe limits.

[0060] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for excavating a borehole tunnel, characterized in that, This includes mechanical coring and hydraulic fracturing methods, wherein the mechanical coring and hydraulic fracturing methods include the following steps: Step S101: Measure and set out the line. Use a total station to accurately locate and mark the core sampling points on the excavation outline. Step S102, core drilling: Using a core drilling rig with a diameter of φ160mm, cylindrical rock cores with a depth of about 700mm are drilled in batches along the marked outline to form the free surface on the outer perimeter of the tunnel. Step S103: Internal rock mass splitting. The remaining intact rock mass within the outline is divided into blocks. Splitting holes are drilled on the blocks using an automatic water-jetting drill. A hydraulic splitting rod is inserted, and the rock mass is pulled along the vertical plane and undergoes bottom horizontal shear fracture through hydraulic tension. Step S104, muck removal and circulation: Use a muck crawler in conjunction with a loader to transport the broken rock blocks out of the tunnel, completing one excavation cycle, and repeat the above steps to advance step by step.

2. The method for drilling tunnel excavation according to claim 1, characterized in that: In a tunnel with a cross-sectional dimension of 3.2m×3.2m, a total of 71 core holes are arranged along the outline. A drilling rig with one to two drilling machines is used, operated by two workers. The drilling operation takes 4.5 hours, and the single-cycle advance is 0.7-0.9 meters.

3. The method for drilling tunnel excavation according to claim 1, characterized in that: In the internal rock mass splitting step, four splitting holes are drilled for each rock mass to be split.

4. The method for drilling tunnel excavation according to claim 1, characterized in that: The mechanical coring and hydraulic fracturing methods require the installation of a support structure. The installation process of the support structure is as follows: Step Z01: Initially spray 5cm thick C25F50 concrete and lay φ8@20cm×20cm steel mesh; Step Z02: Erect I14 type steel arch frames with a spacing of 0.5m. Two 1.8m long locking mortar anchor rods are installed at each arch foot of the steel arch frame. Step Z03: Spray a 15cm thick layer of C25F50 concrete. Step Z04: Construct a 40cm thick C30W6F50 concrete lining; Step Z05: Install C22 system mortar anchor bolts, 2.25m in length, 2.05m into the rock, arranged in a quincunx pattern with a spacing of 1.0m between rows.

5. The method for drilling tunnel excavation according to claim 4, characterized in that, The steel arch frame is manufactured by cold bending and then trial assembly is carried out after processing. The connecting steel plates between the steel arch frames are drilled mechanically, and the holes are cleaned of burrs and steel slag using a grinding wheel.

6. The method for drilling tunnel excavation according to claim 1, characterized in that, A complete work cycle of the mechanical coring and hydraulic fracturing method includes: 1.0 hour for measurement and setting out, 1.0 hour for drilling rig positioning, 4.5 hours for drilling, 0.5 hours for hole cleaning, 1.5 hours for quality inspection, 0.5 hours for splitting the central rock, 1.5 hours for slag removal, and 4.0 hours for surrounding rock support, with a total cycle time of 14.5 hours.

7. The method for drilling tunnel excavation according to claim 1, characterized in that, This includes controlled blasting with small charges, comprising the following steps: Step S201: Surface cleaning and hole layout. Clean the excavation surface and arrange the slotting holes, auxiliary holes and peripheral holes according to the design. Step S202, Drilling and Inspection: After drilling the blast holes, clean and inspect the holes. Step S203, charging and detonation: strictly control the amount of explosive, complete the filling of the blast hole and the network connection, and detonate after inspection and warning. Step S204: After the explosion, slag is removed, a post-explosion inspection is conducted, and the warning is lifted after confirming safety. Then, the slag is removed, and the cycle begins.

8. The method for drilling tunnel excavation according to claim 7, characterized in that: The low-charge controlled blasting method, by comprehensively utilizing drilling, excavation, layered vibration reduction, and peripheral vibration reduction techniques, controls the maximum vibration velocity of the tunnel to below 8 mm / s.

9. A method for excavating a bored tunnel according to claim 7, characterized in that, The arrangement parameters of the boreholes are as follows: All borehole diameters are 42mm; The cut holes are located slightly below the center of the excavation face, with a depth of 3.2m, which is 20cm deeper than other blast holes, and the spacing is 15cm-20cm. Auxiliary holes are arranged around the slotted holes at a spacing of 50-70cm and a depth of 3.0m; The distance between the opening of the peripheral holes and the outline is 10-20cm, the distance between the bottom holes is 50-70cm, and the depth is 3.0m.

10. A method for excavating a bored tunnel according to claim 1, characterized in that, Different excavation schemes are selected based on the type of surrounding rock: In Class IV surrounding rock sections, excavation is carried out using the mechanical core sampling and hydraulic fracturing methods as described in any one of claims 1 to 6; In Class III surrounding rock sections, excavation is carried out using the small-charge controlled blasting method as described in any one of claims 7 to 9.

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