Exploration adit tunneling method based on large-diameter drill hole

Abstract

The invention provides an exploration adit tunneling method based on large-diameter drill holes. The method comprises the steps that lofting is conducted according to the adit axis, and the adit direction and the adit bottom are calibrated; a hole is provided with a movable large-diameter drilling machine platform with a guiding function; combining geological data to pre-judge stratums and partition the stratums; after the hole face is supported, pilot drilling is conducted to the end point through a large drill bit matched with the stratum, and deflection is measured in the whole process; performing grading reaming to a designed hole diameter and correcting deviation; instable sections are recognized in the tunneling process, and immediate supporting is conducted; and cleaning the hole wall and marking the hole depth. The construction precision and safety of adit tunneling can be improved, the construction risk is reduced, and the construction efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of underground engineering exploration and construction technology, and more specifically, to a method for excavating an exploration tunnel based on large-diameter boreholes. Background Technology

[0002] In engineering construction and geological exploration, tunnel boring is a common construction method used to create underground passages or conduct geological exploration. Traditional tunnel boring methods typically employ blasting or mechanical excavation. While blasting is more efficient, it causes significant disturbance to the surrounding rock mass, increasing the risk of geological disasters and posing higher safety risks during construction. Mechanical excavation, although relatively safer, is less efficient in complex geological conditions and requires highly adaptable equipment. Furthermore, both blasting and mechanical excavation methods require frequent monitoring and adjustment of geological conditions during construction, increasing the complexity and cost of the project.

[0003] With the development of geological exploration technology, the application of drilling technology in horizontal tunnel excavation has gradually attracted attention. Drilling technology, by drilling holes into the strata, can effectively reduce disturbance to the surrounding rock mass while improving construction efficiency. However, existing drilling technology still has some limitations in horizontal tunnel excavation. For example, deviation is prone to occur during drilling, making it difficult to guarantee construction accuracy; under complex geological conditions, drilling equipment has poor adaptability, easily leading to problems such as stuck drill bits and drill bit wear; in addition, the post-drilling tunnel wall support measures are not adequate, making it difficult to effectively cope with unstable tunnel sections and increasing construction risks.

[0004] In implementing the embodiments of the present invention, the prior art has at least the following problems or defects: the borehole deviation rate is difficult to control effectively, resulting in insufficient construction accuracy; the drilling equipment has poor adaptability to complex geological conditions, resulting in low construction efficiency and high cost; the tunnel wall support measures are not perfect and cannot effectively cope with unstable tunnel sections, increasing construction risks. Summary of the Invention

[0005] This invention provides a method for excavating an exploration tunnel based on a large-diameter borehole, comprising: Based on the design axis of the horizontal tunnel, measurements were taken and the tunnel orientation and bottom position were marked. A mobile, large-diameter drilling rig platform with leveling and guidance systems is installed at the tunnel entrance; Geological exploration technology is used in conjunction with previous exploration data to predict the geological conditions ahead of the tunnel face and to divide different geological zones. Supporting the tunnel face includes clearing the slope, installing anchor bolts, erecting steel arch support, and spraying concrete. Based on the predicted geological conditions, a large-diameter drill bit was selected and pilot drilling was carried out. The pilot drilling included drilling a guide section at the borehole opening and drilling the main directional hole to the end of the horizontal tunnel, and the borehole deviation rate was monitored in real time during the drilling process. Based on the dominant borehole, the borehole is enlarged in stages to the designed diameter, and the deviation rate is monitored in real time during the enlargement process; During the tunneling process, unstable tunnel sections are identified, and appropriate support methods are selected based on the geological characteristics of these sections. The cave walls were cleaned to make the geological phenomena of the rock layers and structural surfaces on the cave ceiling and walls clearly visible, and the cave depth was marked on the cave walls.

[0006] Furthermore, the step of selecting a large-diameter drill bit and conducting pilot drilling based on predicted geological conditions further includes: Based on the predicted hardness of the formation ahead of the tunnel face, select a drill bit size range suitable for the corresponding hardness of the formation; Multiple high-pressure water jet nozzles are installed on the inner wall of the drill bit; Determine drilling parameters, including adjusting drilling speed, drilling pressure, and rotation speed to a safe range based on formation hardness; After drilling to the initial set length, the drill rod is withdrawn and a steel casing is inserted to form the borehole guide section; Drill the main directional hole along the design axis to the end of the horizontal tunnel, and simultaneously inject mud that stabilizes the borehole wall and carries rock cuttings; The borehole deviation rate is monitored in real time, and the drilling direction is adjusted when the deviation rate exceeds the set threshold.

[0007] Furthermore, in the step of determining the drilling parameters: If a hard rock section is encountered during drilling, the drilling speed should be controlled within the first safe speed range, the drilling pressure within the first pressure range, and the rotation speed within the first rotation speed range. If a soft rock section is encountered during drilling, the drilling speed is controlled within the second safe speed range, which is higher than the first safe speed range; the drilling pressure is controlled within the second pressure range, which is lower than the first pressure range; and the rotation speed is controlled within the second rotation speed range, which is higher than the first rotation speed range. The injected mud is a high-molecular polymer mud. The mud viscosity is controlled within the effective range for stabilizing the borehole wall, the mud density is controlled within the effective range for balancing formation pressure, and the mud recycling rate is maintained above the set level.

[0008] Furthermore, in the step of real-time monitoring of borehole deviation and adjustment of drilling direction: If the skew rate exceeds the set threshold, the drilling direction adjustment mechanism will be activated. After adjustment, continue to monitor the deviation rate. If the deviation rate drops to within the set threshold, maintain the current drilling direction. If the deviation rate still exceeds the set threshold or continues to increase after adjustment, the drilling direction should be adjusted again or continuously until the deviation rate meets the requirements.

[0009] Furthermore, the step of performing graded hole enlargement to the designed hole diameter further includes: Perform the first stage of hole reaming: Use a first-stage hole reamer to enlarge the diameter of the main directional hole to the first target size, and control the first-stage hole reaming speed within a safe range; Perform the second stage of hole reaming: replace the second stage hole reamer with a second stage hole reamer to enlarge the borehole diameter to the designed hole diameter, and control the second stage hole reaming speed within a safe range; During the hole enlargement process, the deviation rate is monitored in real time. When the deviation rate exceeds the set threshold, the correction device is activated to adjust the attitude of the hole enlarger.

[0010] Furthermore, in the step of performing the first-stage hole enlargement: A stepped reamer is used as the first-stage reamer. Real-time monitoring of the reamer's torque and thrust; If the torque exceeds the safe torque range or the thrust exceeds the safe thrust range, reduce the hole reaming speed or suspend hole reaming for inspection.

[0011] Furthermore, in the step of performing the second-stage hole enlargement: A cylindrical reamer is used as the second-stage reamer, and the inner wall of the cylindrical reamer is uniformly distributed with carbide cutting teeth. Real-time monitoring of the temperature of the expander; If the temperature exceeds the safe temperature threshold, the hole enlargement process will be paused and cooled down. The hole enlargement will resume once the temperature drops below the safe range.

[0012] Furthermore, in the step of real-time monitoring of the skew rate and adjustment of the reamer's posture during the hole reaming process: A high-precision guidance system is used for positioning and deviation monitoring; If the skew rate exceeds the set threshold, the hydraulic correction device will be activated to adjust the attitude of the reamer. After adjustment, continue to monitor the skew rate. If the skew rate drops to within the set threshold, maintain the current reamer posture. If the skew rate still exceeds the set threshold or continues to increase after adjustment, adjust the hole expander posture again or continuously until the skew rate meets the requirements.

[0013] Furthermore, the step of identifying unstable tunnel sections and selecting support methods based on geological characteristics further includes: Identify the fractured zone area: If a fractured zone area is identified, grouting reinforcement is selected for support. The grouting reinforcement includes grouting within a set range outside the excavation outline. Identify sections prone to rockfall or collapse: If sections prone to rockfall or collapse are identified, steel arch support is selected for support. The steel arch support includes erecting arches connected by connectors and laying protective netting between the arches and the tunnel wall.

[0014] Furthermore, in the step of selecting the grouting reinforcement method for support, cement-water glass dual-liquid grout is used as the grouting material; In the step of selecting the steel arch support method for support, the arch frame is processed using threaded steel bars. The arch frame is composed of segmented components connected by connecting sleeves. The arch frames are connected by connecting bars to form a stable support structure. A machine-woven galvanized protective net is laid between the arch frame and the tunnel wall, and the arch frame is treated with anti-corrosion to ensure durability.

[0015] The embodiments of the present invention have at least the following beneficial effects: 1. By deploying a mobile, large-diameter drilling rig platform with leveling and guidance systems at the tunnel entrance, and combining this with geological exploration technology to predict geological conditions, precise positioning and guidance of the borehole can be achieved, effectively reducing borehole deviation rate, improving construction accuracy, and solving the problem of difficult-to-control borehole deviation under complex geological conditions using traditional drilling technology, thus ensuring the construction quality and safety of horizontal tunnel excavation.

[0016] 2. During pilot drilling, drilling parameters are adjusted according to different geological conditions, and borehole deviation is monitored in real time. This allows for flexible handling of hard and soft rock sections, optimizing drilling efficiency, reducing drill bit wear and equipment failure. At the same time, by injecting polymer mud to stabilize the borehole wall and carry rock cuttings, the formation pressure is effectively balanced. This solves the problems of poor adaptability, low construction efficiency, and high cost of existing drilling equipment under complex geological conditions, and improves the overall construction efficiency and economy of horizontal tunnel excavation.

[0017] 3. During the tunneling process, unstable tunnel sections are identified, and appropriate support methods, such as grouting reinforcement or steel arch support, are selected based on geological characteristics. At the same time, the tunnel walls are cleaned and marked. This can effectively cope with unstable geological conditions, ensure the stability of the tunnel walls, and clearly present geological phenomena. It solves the problem that the existing tunnel wall support measures are not perfect and cannot effectively cope with unstable tunnel sections, reduces construction risks, and improves the construction safety and reliability of horizontal tunnel excavation. Attached Figure Description

[0018] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of the invention are illustrated in the drawings by way of example and not limitation, wherein: Figure 1This is a flowchart illustrating an exploration tunnel excavation method based on large-diameter boreholes, provided in an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] like Figure 1 As shown, this application proposes a method for excavating an exploration tunnel based on a large-diameter borehole, comprising the following steps: S1. Conduct surveying and layout according to the design axis of the horizontal tunnel, and mark the tunnel direction and the position of the tunnel bottom; S2. A mobile, large-diameter drilling rig platform with leveling and guiding functions is installed at the tunnel entrance; S3. Use geological exploration technology combined with previous exploration data to predict the geological conditions ahead of the tunnel face and divide different geological areas; S4. Support the tunnel face, including clearing the slope, installing anchor bolts, erecting steel arch support and spraying concrete; S5. Based on the predicted geological conditions, select a large-diameter drill bit and carry out pilot drilling. The pilot drilling includes drilling a guide section at the borehole opening and drilling the main directional hole to the end of the horizontal tunnel, and monitoring the borehole deviation rate in real time during the drilling process. S6. Based on the main directional hole, perform graded hole enlargement to the designed hole diameter, and monitor the deviation rate in real time during the hole enlargement process; S7. During the tunneling process, identify unstable tunnel sections and select appropriate support methods based on the geological characteristics of the unstable tunnel sections. S8. Clean the formed cave walls to make the geological phenomena of the rock layers and structural surfaces on the cave top and two walls clearly visible, and mark the cave depth on the cave wall surface.

[0021] This application integrates geological prediction, directional drilling, staged borehole enlargement, and dynamic support technologies to form a highly efficient and precise method for horizontal tunnel excavation. This method controls borehole accuracy through real-time monitoring and correction, reduces surrounding rock disturbance by combining staged borehole enlargement, and dynamically selects support methods based on geological characteristics. It systematically solves the problems of construction deviation, low efficiency, and insufficient support in traditional methods.

[0022] Specifically, the first step is to measure and lay out the tunnel according to its design axis, marking the tunnel direction and bottom position to determine the excavation direction. A mobile, large-diameter drilling rig platform with leveling and guidance systems is then deployed at the tunnel entrance to provide a stable foundation for subsequent drilling operations. Geological exploration technology, combined with previous exploration data, is used to predict the geological conditions ahead of the tunnel face, dividing the area into different geological zones to provide a basis for adjusting drilling parameters and selecting support methods.

[0023] The tunnel face was supported, including slope clearing, installation of anchor bolts, erection of steel arch supports, and shotcreting to ensure tunnel stability. Based on the predicted geological conditions, a suitable large-diameter drill bit was selected, and pilot drilling was carried out. Pilot drilling included drilling a guide section at the tunnel entrance and drilling the main directional hole to the end of the horizontal tunnel. The borehole deviation rate was monitored in real time during drilling to ensure drilling accuracy.

[0024] Based on the dominant directional borehole, the borehole is enlarged in stages to the designed diameter, with the deviation rate monitored in real time during the enlargement process. Staged enlargement can gradually correct deviation errors while reducing the torque load of each enlargement operation. During tunneling, unstable sections are identified, and appropriate support methods are selected based on the geological characteristics of these sections to ensure construction safety.

[0025] Finally, the cave walls were cleaned to make the geological phenomena of the rock strata and structural surfaces on the cave ceiling and walls clearly visible, and the cave depth was marked on the cave walls to facilitate subsequent geological exploration work.

[0026] By monitoring and adjusting drilling parameters in real time, combined with staged borehole enlargement and targeted support, this method can effectively control borehole deviation, improve construction accuracy, adapt to complex geological conditions, and ensure construction safety and efficiency.

[0027] Surveying and setting out refers to determining the location and direction of the tunnel entrance based on the tunnel's design axis. This can be done using a total station or GPS positioning technology for on-site marking. Its purpose is to ensure the excavation direction aligns with the design axis and prevent construction deviation. A mobile large-diameter drilling rig platform refers to a drilling rig support device equipped with leveling and guidance systems. Specifically, hydraulic outriggers can be used to adjust the platform's levelness, and a laser guidance system can be integrated. Its purpose is to improve borehole positioning accuracy and construction stability. Geological exploration technology combined with preliminary exploration data involves obtaining geological information ahead of the tunnel face using ground-penetrating radar or seismic wave detection equipment and comparing it with existing exploration data. Its purpose is to identify different geological areas in advance, guiding drill bit selection and adjustment of construction parameters.

[0028] Supporting the tunnel face refers to reinforcing the slope at the tunnel entrance. This includes clearing loose rock, installing anchor bolts to fix the steel arch frame, and sealing the surface with shotcrete. Its purpose is to prevent tunnel entrance collapse and enhance structural stability. Pilot drilling involves drilling a main directional hole along the design axis using a large-diameter drill bit. This includes installing a steel casing in the guide section at the borehole entrance and circulating mud for slag removal. Its purpose is to create a precise guiding channel and provide a benchmark for subsequent borehole reaming. Real-time monitoring of borehole deviation rate involves detecting the borehole axis offset using a borehole trajectory measuring instrument or inertial navigation system. Its purpose is to correct deviations promptly and ensure the borehole direction meets design requirements. Staged reaming involves gradually increasing the borehole diameter to the design tunnel diameter using different sized reamers. Its purpose is to reduce the difficulty of each reaming operation and minimize disturbance to the surrounding rock. Identifying unstable tunnel sections and selecting support methods involves identifying fracture zones or easily collapsible areas through geological sketching or monitoring equipment. Its purpose is to dynamically adjust support strategies to address different geological risks. Cleaning the tunnel walls and marking the tunnel depth refers to using a high-pressure water gun to wash the rock surface and mark the mileage information, which is used to facilitate geological logging and construction quality inspection.

[0029] As a preferred embodiment, the solution of this application is specifically implemented as follows: During the exploration and excavation of the horizontal tunnel, the first step is to conduct surveying and setting out according to the design drawings, using a total station and level to accurately determine the tunnel orientation and bottom position. A large-diameter drilling rig platform is then set up at the tunnel entrance, equipped with a hydraulic leveling system and a high-precision guidance system.

[0030] Using ground-penetrating radar (GPR) detection technology combined with drilling data, the geological conditions ahead of the tunnel face were predicted and divided into different geological zones, including sandstone, mudstone, and fractured zones. Support was provided for the tunnel face, loose rock blocks on the slope were cleared, 2-meter-long anchor bolts were installed, H-shaped steel arch supports were erected, and 10-centimeter-thick concrete was sprayed.

[0031] Based on the anticipated geological conditions, a PDC composite drill bit suitable for medium-hard rock was selected for pilot drilling. A 5-meter-long guide section was drilled first, and a steel casing was inserted and fixed in place. Drilling continued to the main directional hole to the end of the horizontal tunnel. During drilling, polymer mud was injected, and a gyroscope was used to monitor the borehole deviation rate in real time.

[0032] Based on the dominant borehole orientation, a staged reaming process is performed. The first stage uses a stepped reamer to enlarge the borehole diameter to 70% of the designed diameter, and the second stage uses a cylindrical reamer to enlarge it to the designed diameter. During the reaming process, the deviation rate is continuously monitored, and a hydraulic correction device is activated to adjust the reamer's posture if necessary.

[0033] During tunneling, unstable sections such as fractured zones are identified. For fractured zones, cement-water glass dual-liquid grouting is used for reinforcement. For sections prone to rockfall or collapse, steel arch supports are used, and protective netting is laid.

[0034] Finally, high-pressure water guns were used to clean the formed cave walls, exposing the rock strata, and the cave depth was marked every 10 meters on the cave walls.

[0035] This application further proposes a scheme including the following steps: selecting a drill bit size range suitable for the corresponding hardness of the formation ahead of the tunnel face based on the predicted hardness of the formation; setting multiple high-pressure water jet nozzles on the inner wall of the drill bit; determining drilling parameters, including adjusting the drilling speed, drilling pressure, and rotation speed to a safe range according to the formation hardness; after drilling to the initial set length, withdrawing the drill rod and inserting a steel casing to form a borehole guide section; drilling the main directional hole along the designed axis to the end of the horizontal tunnel, simultaneously injecting mud that stabilizes the borehole wall and carries rock cuttings; monitoring the borehole deviation rate in real time, and adjusting the drilling direction when the deviation rate exceeds the set threshold.

[0036] The selection of drill bit size is based on the formation hardness; small-diameter drill bits are used in hard rock sections, and large-diameter drill bits are used in soft rock sections, ensuring a balance between drilling efficiency and drill bit life. High-pressure water jet nozzles are arranged in a ring array along the inner wall of the drill bit, with the jet direction forming an angle with the drill bit's rotation direction, used to break up uncut rock in the central area of ​​the drill bit. Drilling parameters are adjusted dynamically by acquiring real-time formation feedback data, adjusting the rotation speed and drilling pressure accordingly: low rotation speed and high drilling pressure are used in hard rock sections, and high rotation speed and low drilling pressure are used in soft rock sections. Guide ribs are welded to the outer wall of the steel casing at the wellhead, forming a mechanical engagement with the borehole wall. The injected mud is a bentonite-based slurry with a viscosity controlled at 30-45 seconds and a density maintained at 1.2-1.4 g / cm³. 3 The recycling rate is no less than 80%. The skew monitoring adopts a composite measurement system of gyroscope and laser ranging. When the skew rate exceeds 0.5%, the hydraulic correction mechanism is activated.

[0037] Specifically, in hard rock formations, the drill bit size is selected in the range of Φ200-250mm, the drilling speed is controlled at 0.5-1.2m / h, the drilling pressure is maintained at 8-12MPa, and the rotation speed is adjusted to 60-80rpm. High-pressure water jets are injected at a pressure of 15-20MPa to effectively break the hard rock mass not cut by the drill bit center. After the steel casing is inserted, the guide ribs form a mechanical guiding structure with the borehole wall to ensure the accuracy of the subsequent drilling axis. The mud injection system uses dual pumps to alternately supply mud to maintain the pressure balance in the borehole and prevent borehole collapse. When the monitoring system detects borehole axis deviation, the hydraulic correction mechanism adjusts the drill pipe advance angle, with each adjustment not exceeding 0.3 degrees, until the deviation returns to the allowable range. In soft rock formations, the drill bit size is increased to Φ300-350mm, the drilling speed is increased to 2-4m / h, the drilling pressure is reduced to 4-6MPa, and the rotation speed is increased to 100-120rpm. Simultaneously, the mud viscosity is appropriately reduced to 25-30 seconds to enhance cuttings removal. This approach, through the organic combination of parameter optimization and process control, achieves a drilling efficiency increase of over 30% and a deviation control accuracy improvement to within 0.3%.

[0038] As a preferred embodiment, the solution of this application is specifically implemented as follows: Based on the predicted hardness of the formation ahead of the tunnel face, select a drill bit size range suitable for the corresponding hardness of the formation. For example, an 800mm diameter drill bit can be selected for soft rock formations, a 600mm diameter drill bit for medium-hard rock formations, and a 400mm diameter drill bit for hard rock formations.

[0039] Multiple high-pressure water jet nozzles are installed on the inner wall of the drill bit. Specifically, eight high-pressure water jet nozzles can be evenly arranged on the inner wall of the drill bit, with an nozzle outlet diameter of 2 mm and a jet pressure of 20 MPa.

[0040] Determine drilling parameters, including adjusting drilling speed, drill pressure, and rotation speed to safe ranges based on formation hardness. Specifically, for soft rock formations, control the drilling speed at 2-3 m / h, drill pressure at 100-150 kN, and rotation speed at 60-80 r / min; for medium-hard rock formations, control the drilling speed at 1-2 m / h, drill pressure at 150-200 kN, and rotation speed at 40-60 r / min; and for hard rock formations, control the drilling speed at 0.5-1 m / h, drill pressure at 200-250 kN, and rotation speed at 20-40 r / min.

[0041] After drilling to the initial set length, the drill rod is withdrawn and a steel casing is inserted to form the borehole guide section. The initial set length can be 5m, the outer diameter of the steel casing matches the borehole diameter, and the wall thickness is 10mm.

[0042] Drill the main directional borehole along the designed axis to the end of the horizontal tunnel, simultaneously injecting drilling mud that stabilizes the borehole wall and carries rock cuttings. Therefore, polymer-modified drilling mud can be used, with a mud density controlled at 1.1-1.3 g / cm³. 3 The viscosity is controlled at 30-50s.

[0043] The borehole deviation rate is monitored in real time, and the drilling direction is adjusted when the deviation rate exceeds a set threshold. Specifically, a gyroscope inclinometer can be used for real-time monitoring, and when the deviation rate exceeds 1%, a hydraulic correction device is activated to adjust the drilling direction.

[0044] This application further proposes that when determining drilling parameters, if a hard rock section is encountered during drilling or in the actual process, the drilling speed should be controlled within a first safe speed range, the drilling pressure within a first pressure range, and the rotational speed within a first rotational speed range; if a soft rock section is encountered during drilling or in the actual process, the drilling speed should be controlled within a second safe speed range higher than the first safe speed range, the drilling pressure within a second pressure range lower than the first pressure range, and the rotational speed within a second rotational speed range higher than the first rotational speed range; and polymer mud should be injected to control the mud viscosity within an effective range for stabilizing the borehole wall, the mud density within an effective range for balancing formation pressure, and to maintain the mud recycling rate above a set level.

[0045] The first safe speed range limits the drilling speed in hard rock sections to prevent drill bit overheating or excessive wear; the first pressure range and the first rotation speed range ensure stable cutting in hard rock. The second safe speed range increases efficiency by increasing the drilling speed in soft rock sections; the second pressure range reduces the risk of soft rock deformation by decreasing drilling pressure; and the second rotation speed range optimizes chip removal by increasing rotation speed. The polymer mud enhances borehole support by adjusting viscosity, balances formation pressure by adjusting density to prevent borehole collapse, and maintains recycling rate to reduce mud waste.

[0046] Specifically, in hard rock drilling, a combination of lower drilling speed, higher drill pressure, and moderate rotation speed reduces drill bit impact damage and extends its service life. In soft rock drilling, a higher drilling speed, lower drill pressure, and higher rotation speed are used to prevent the drill bit from getting stuck in the rock formation and causing deviation, while also accelerating the removal of cuttings. The viscosity of the polymer mud is determined experimentally to a critical value to ensure the formation of an effective mud film on the borehole wall; the density is calculated based on formation pressure and dynamically adjusted to match the pressure at different depths; the mud circulation system is equipped with a filtration device, and mud performance is monitored in real time, with recycling and purification achieving high recycling rates. This scheme, through differentiated parameter settings and mud performance optimization, balances drilling efficiency and borehole stability under different formation conditions, reducing equipment wear and construction risks.

[0047] As a preferred embodiment, the solution of this application is specifically implemented as follows: When determining drilling parameters, adjustments should be made based on the predicted or actual formation types encountered during drilling. For hard rock sections, the drilling speed should be controlled within the range of 0.5-1.5 m / h, the drilling pressure within the range of 200-300 kN, and the rotation speed within the range of 30-50 rpm. For soft rock sections, the drilling speed should be increased to the range of 2-3 m / h, the drilling pressure reduced to the range of 100-150 kN, and the rotation speed increased to the range of 60-80 rpm.

[0048] The injected drilling mud is made of high-molecular polymer. The mud viscosity is controlled within the range of 30-50 seconds per quart to ensure effective borehole wall stabilization. The mud density is controlled within the range of 1.1-1.3 g / cm³ to balance formation pressure. Through a mud circulation system and solids control equipment, the mud recycling rate is maintained at over 85%.

[0049] This application further proposes a technical solution that activates a drilling direction adjustment mechanism when the deviation rate exceeds a set threshold, and continues to monitor the deviation rate after adjustment. If the deviation rate drops to within the set threshold, the current drilling direction is maintained. If the deviation rate still exceeds the threshold or continues to increase after adjustment, the drilling direction is adjusted again or continuously until the requirements are met.

[0050] The drilling direction adjustment mechanism uses a hydraulic drive to control the drill rod angle offset. This device includes four symmetrically distributed hydraulic cylinders, and the drill bit attitude is adjusted by regulating the pressure difference between the cylinders. During the adjustment process, the guidance system collects three-dimensional coordinate data at set intervals and calculates the real-time deviation angle and direction using an algorithm. When the deviation rate exceeds a threshold, the control system automatically generates a correction command, and the hydraulic cylinders adjust their pressure parameters accordingly. After adjustment, the guidance system continues to monitor the deviation data of subsequent drilling sections. If the data at three consecutive monitoring points are all below the threshold, the correction is considered successful. If the deviation rate does not decrease after adjustment or continues to increase, the system will recalculate the correction amount and perform a second adjustment until the deviation rate stabilizes within the allowable range.

[0051] Specifically, the guidance system uses a combination of gyroscope and laser rangefinder for positioning, collecting data once every set drilling length. When the deviation rate exceeds a threshold, the hydraulic drive adjusts the drill rod angle once per second, with each adjustment dynamically calculated based on the degree of deviation. For example, when the horizontal deviation reaches a set threshold, the system automatically increases the pressure of the corresponding hydraulic cylinder, causing the drill bit to shift in the opposite direction. If the monitoring data is below the threshold for three consecutive times after adjustment, the correction stops and the current parameters are maintained. If the first monitoring data still exceeds the threshold after adjustment, the system immediately initiates a second adjustment and uses incremental correction in subsequent monitoring until the deviation rate is completely under control. This process is automated through a closed-loop control system, ensuring that the borehole trajectory always extends along the designed axis.

[0052] As a preferred embodiment, the solution of this application is specifically implemented as follows: For real-time monitoring of borehole deviation, a high-precision gyroscope inclinometer is used for measurement. The inclinometer is installed at the bottom of the drill string, and the borehole inclination and azimuth are measured every 5 meters. The measurement data is transmitted to the ground control system via a data cable, where it is processed and displayed in real-time by a computer.

[0053] The deviation rate threshold is set to 2%. When the deviation rate exceeds 2%, the drilling direction adjustment mechanism is automatically triggered. The adjustment mechanism includes a controllable eccentric sleeve and a hydraulic thruster. The controllable eccentric sleeve is mounted on the drill string and changes the center of gravity of the drill string by rotation. The hydraulic thruster is mounted on the drill rig base and can apply lateral force to the drill pipe.

[0054] After activating the adjustment mechanism, first rotate the controllable eccentric sleeve to shift the drill bit's center of gravity towards the direction requiring correction. Then, activate the hydraulic thruster to apply lateral force to the drill pipe, guiding the drill bit to deflect in the target direction. During the adjustment process, continuously monitor changes in the skew rate.

[0055] After adjustment, continue drilling and monitor the deviation rate. If the deviation rate drops to below 2%, maintain the current drilling direction. If the deviation rate still exceeds 2% or continues to increase after adjustment, repeat the above adjustment process. Each adjustment should be spaced at least 10 meters of drilling distance apart to fully observe the adjustment effect.

[0056] If the deviation rate still cannot be controlled within 2% after multiple adjustments, drilling should be stopped, and the drill bit and geological conditions should be analyzed. If necessary, the drill bit should be replaced or the drilling parameters should be adjusted before continuing construction.

[0057] This application further proposes a first-stage reaming process: using a first-stage reamer to enlarge the main directional hole diameter to the first target size, and controlling the first-stage reaming speed within a safe range; a second-stage reaming process: replacing the first-stage reamer with a second-stage reamer to enlarge the hole diameter to the designed hole diameter, and controlling the second-stage reaming speed within a safe range; and real-time monitoring of the deviation rate during the reaming process, and when the deviation rate exceeds a set threshold, activating a correction device to adjust the reamer's posture.

[0058] The first-stage reamer employs a stepped structure, reducing the load per reaming cycle through staged cutting. The second-stage reamer uses a cylindrical structure with evenly distributed carbide cutting teeth on its inner wall to improve reaming efficiency. Different safety ranges are set for reaming speeds based on the reamer type to prevent equipment overload due to excessive speed. The alignment correction device adjusts the reamer's posture hydraulically, combining real-time positioning data from a high-precision guide system to achieve dynamic alignment correction.

[0059] Specifically, in the first stage of reaming, the stepped reamer performs initial reaming at a lower speed to reduce the instantaneous impact on the rock mass. Simultaneously, the equipment status is assessed by monitoring torque and thrust; if safety thresholds are exceeded, the speed is reduced or the process is paused for inspection. In the second stage, the cylindrical reamer completes the final reaming at a higher efficiency, but temperature control is necessary to prevent overheating and failure of the cutting teeth. During both stages of reaming, the guiding system continuously collects deviation data. When the deviation rate exceeds a threshold, the hydraulic correction device adjusts the reamer angle to correct the trajectory. For example, the first-stage reaming speed is controlled at 0.5 to 1.2 meters per minute, and the second-stage speed is controlled at 0.3 to 0.8 meters per minute. This combination of staged reaming and dynamic correction reduces the equipment load per reaming cycle while ensuring the axial accuracy of the final tunnel diameter.

[0060] As a preferred embodiment, the solution of this application is specifically implemented as follows: The first stage of reaming involves using a first-stage reamer to enlarge the main directional hole diameter to the first target size, controlling the reaming speed within a safe range. Specifically, a stepped reamer is used as the first-stage reamer, comprising multiple reaming sections with gradually increasing diameters. During the reaming process, the torque and thrust of the reamer are monitored in real time. If the torque exceeds the safe torque range or the thrust exceeds the safe thrust range, the reaming speed is reduced or reaming is paused for inspection.

[0061] Second-stage reaming: A second-stage reamer is installed to enlarge the borehole diameter to the designed diameter, controlling the reaming speed within a safe range. A cylindrical reamer is used as the second-stage reamer, with carbide cutting teeth evenly distributed on its inner wall. During reaming, the reamer's temperature is monitored in real time. If the temperature exceeds the safe threshold, reaming is paused for cooling. Reaming resumes once the temperature has dropped below the safe range.

[0062] During the reaming process, the skew rate is monitored in real time. When the skew rate exceeds a set threshold, a correction device is activated to adjust the reamer's posture. Furthermore, a high-precision guiding system is used for positioning and skew monitoring. When the skew rate exceeds the set threshold, a hydraulic correction device is activated to adjust the reamer's posture. After adjustment, the skew rate continues to be monitored. When the skew rate drops below the set threshold, the current reamer posture is maintained. If the skew rate still exceeds the set threshold or continues to increase after adjustment, the reamer posture is adjusted again or continuously until the skew rate meets the requirements.

[0063] This application further proposes the following steps for performing the first stage of hole reaming: using a stepped hole reamer as the first stage hole reamer; monitoring the torque and thrust of the hole reamer in real time; if the torque exceeds the safe torque range or the thrust exceeds the safe thrust range, reducing the hole reaming speed or pausing hole reaming for inspection.

[0064] The stepped reamer employs a multi-stage cutting tooth distribution structure, with the diameter of the front cutting teeth being smaller than that of the rear cutting teeth, forming a stepped reaming path. Torque and thrust are collected in real time by sensors installed at the rear of the reamer, and the sensors transmit the data to the control unit. The safe torque and safe thrust ranges are preset according to the reamer model and formation hardness; for example, the safe torque threshold is set to 200-500 N·m, and the safe thrust threshold is set to 50-100 kN. When the torque or thrust exceeds the threshold, the control unit sends a command to the hydraulic system to reduce the reamer's advance speed. If the parameters continue to exceed the limits, a shutdown command is triggered, and the operator inspects the reamer's cutting tooth wear or any formation abnormalities.

[0065] Specifically, in the stepped reamer, during drilling, the front cutting teeth first contact the borehole wall for pre-cutting, and the rear cutting teeth then complete the reaming. This structure can disperse cutting resistance and reduce sudden changes in instantaneous load. The torque and thrust monitoring system collects data in real time to determine whether the reamer is operating normally. When the torque exceeds 500 N·m or the thrust exceeds 100 kN, the reaming speed is automatically reduced from 20 cm / min to 5 cm / min. If the parameters still exceed the threshold after the speed reduction, the reaming operation is completely stopped, and the presence of hard rock interlayers or reamer jamming is checked. This process, through a graded response mechanism, maintains construction continuity to the maximum extent while ensuring equipment safety.

[0066] As a preferred embodiment, the solution of this application is specifically implemented as follows: During the first stage of reaming, a stepped reamer is used. The stepped reamer consists of multiple stages of reaming blades, each with a progressively increasing diameter, forming a stepped structure. The torque and thrust of the reamer are monitored in real time during the reaming process. Torque is measured by a torque sensor mounted on the reamer spindle, and thrust is calculated using a pressure sensor in the drilling rig's hydraulic system.

[0067] If the monitored torque or thrust exceeds the safe torque or thrust range, appropriate measures will be taken. Specifically, when the torque exceeds the safe torque range, the reaming speed will be reduced from 2 m / h to 1 m / h. If the torque still exceeds the limit after reducing the speed, the reaming operation will be suspended, and the reamer will be removed for inspection. The inspection will include checking for wear on the reaming blades and for rock cuttings accumulation.

[0068] Similarly, when the thrust exceeds the safe thrust range, first reduce the reaming speed. If the thrust still exceeds the limit after reducing the speed, stop reaming and remove the reamer for inspection. The inspection should focus on whether the front end of the reamer encounters hard rock layers or whether there is rock cuttings blocking it.

[0069] This application further proposes the use of a cylindrical reamer in the second stage of hole reaming. The inner wall of the cylindrical reamer is uniformly distributed with carbide cutting teeth. The temperature of the reamer is monitored in real time. If the temperature exceeds the safe temperature threshold, hole reaming is paused and cooled. Hole reaming is resumed after the temperature drops below the safe range.

[0070] The cylindrical reamer features a cylindrical structure with evenly distributed cutting teeth along its inner wall, forming a continuous cutting surface. The cemented carbide material exhibits high wear resistance. Temperature monitoring is achieved through a temperature sensor embedded within the reamer, with sensor data transmitted to the control system in real time. The safe temperature threshold is set based on the heat resistance of the reamer material and the operating conditions of the cutting teeth. Cooling is achieved using an external circulating water cooling system, which lowers the temperature through internal cooling channels within the reamer.

[0071] Specifically, during the rotary propulsion process of the cylindrical reamer, the carbide cutting teeth contact the rock strata to generate a cutting action. The evenly distributed cutting teeth reduce local stress concentration. A temperature sensor collects the reamer's operating temperature in real time. When the temperature exceeds a set threshold, the control system automatically stops the reamer. Cooling water circulates through the reamer's internal pipes, quickly removing accumulated heat. Once the temperature returns to a safe range, the control system restarts the reaming operation. This process achieves dynamic temperature regulation through closed-loop control, preventing cutting tooth oxidation failure or structural deformation caused by high temperatures, and ensuring the reamer's continuous and stable operation under complex geological conditions.

[0072] As a preferred embodiment, the solution of this application is specifically implemented as follows: During the second stage of reaming, a cylindrical reamer is used. The inner wall of this reamer is uniformly lined with carbide cutting teeth. The temperature of the reamer is monitored in real time during the reaming process. If the temperature exceeds the safe temperature threshold, the reaming operation is paused for cooling. The reaming operation resumes once the temperature has dropped below the safe range.

[0073] Specifically, the cylindrical reamer is made of high-strength alloy steel, with multiple rows of carbide cutting teeth evenly arranged on its inner wall. A temperature sensor is installed on the reamer and connected to the ground control system to transmit temperature data in real time. The safe temperature threshold is set at 200℃. When the detected temperature exceeds 200℃, the control system automatically stops the reaming operation and activates the cooling system. The cooling system cools the reamer with high-pressure water while simultaneously using circulating drilling mud to remove heat. When the temperature drops below 150℃, the system sends a signal indicating that operation can resume; after operator confirmation, the reaming operation is restarted.

[0074] This application further proposes to use a high-precision guidance system for positioning and deviation monitoring; if the deviation rate exceeds the set threshold, the hydraulic correction device is activated to adjust the attitude of the reamer; after adjustment, the deviation rate is monitored again, and if the deviation rate drops to within the set threshold, the current attitude of the reamer is maintained; if the deviation rate still exceeds the set threshold or continues to increase after adjustment, the attitude of the reamer is adjusted again or continuously until the deviation rate meets the requirements.

[0075] The high-precision guidance system can be configured as a laser positioning module or an inertial navigation module, with positioning accuracy controlled within ±0.1 degrees. The hydraulic correction device includes at least two symmetrically distributed hydraulic cylinders, with the cylinder stroke forming an angle of 15-30 degrees with the reamer axis. During the adjustment of the reamer's attitude, the extension and retraction of the hydraulic cylinders are controlled by a proportional valve, and the adjustment amount is fed back in real time by a displacement sensor. The threshold value is set according to the hole diameter; for example, when the hole diameter is 3 meters, the deflection rate threshold is set to 0.5%.

[0076] Specifically, during the staged reaming process, the high-precision guiding system continuously collects the three-dimensional coordinate data of the reamer and calculates the deviation angle between the actual trajectory and the design axis. When the deviation rate exceeds 0.5%, the control system sends a pulse signal to the hydraulic correction device, driving the corresponding hydraulic cylinder to extend and retract at a speed of 2-5 mm per second, changing the force distribution at the front support point of the reamer, thereby adjusting its direction of travel. During the adjustment process, the guiding system updates the deviation rate data every 10 seconds. If the data drops below 0.5%, the hydraulic cylinder maintains its current stroke; if the data still exceeds the standard, another set of hydraulic cylinders is automatically selected for secondary adjustment based on the deviation direction until the deviation data meets the standard. This process is achieved through a closed-loop control algorithm, with the adjustment response time controlled within 30 seconds, ensuring that the deviation of the reaming axis does not exceed the design allowable range.

[0077] As a preferred embodiment, the specific implementation of this application is as follows: During the staged reaming construction of a horizontal tunnel, a high-precision guiding system is used to position and monitor the attitude of the reamer. The high-precision guiding system consists of a combination of a fiber optic gyroscope and a laser rangefinder, which collects the azimuth, tilt, and position coordinate data of the reamer in real time. When the monitoring system determines that the skew rate exceeds a threshold, multiple adjustable hydraulic cylinders in the hydraulic correction device adjust the pitch and horizontal deflection angles of the reamer according to control commands. After adjustment, monitoring data continues to be collected. If the skew rate falls back to within the threshold, the current hydraulic cylinder pressure parameters are maintained; if the skew rate still exceeds the threshold or continues to rise, the cylinder adjustment amount is recalculated through the closed-loop control system, and the correction action is executed again until the skew rate meets the requirements.

[0078] This application further proposes a step for real-time monitoring of the skew rate and adjustment of the reamer's attitude during the reaming process, including: using a high-precision guiding system for positioning and skew monitoring; if the skew rate exceeds a set threshold, activating a hydraulic correction device to adjust the reamer's attitude; continuing to monitor the skew rate after adjustment, and maintaining the current reamer attitude if the skew rate drops to within the set threshold; if the skew rate still exceeds the set threshold or continues to increase after adjustment, adjusting the reamer's attitude again or continuously until the skew rate meets the requirements.

[0079] The high-precision guidance system can utilize a gyroscope and laser positioning composite system, with positioning accuracy controlled within ±5mm. The skew monitoring frequency is set to collect data once per second. The hydraulic correction device comprises four symmetrically arranged hydraulic cylinders, each with a stroke adjustment accuracy of 0.1mm, enabling attitude adjustment within a ±2° range of the borehole expander's axis angle. The set threshold is set to 0.5% of the borehole diameter; when the skew exceeds this value, the correction action is triggered. After adjustment, the monitoring cycle is shortened to collect data once every 0.5 seconds; successful correction is determined when three consecutive monitoring data points are below the threshold.

[0080] Specifically, the high-precision guiding system collects the spatial coordinate data of the reamer in real time and calculates the offset between the actual axis and the design axis. When the offset exceeds 0.5% of the hole diameter, the control system sends an adjustment command to the hydraulic correction device. Four sets of hydraulic cylinders differentially extend and retract according to the offset direction, changing the spatial position of the front support point of the reamer, thereby correcting the drilling axis angle. During the adjustment process, the guiding system continuously monitors the trend of offset changes. If the offset still shows an upward trend after a single adjustment, a continuous adjustment mode is activated, performing progressive correction at a frequency of twice per second. This process is achieved through a closed-loop control algorithm, ultimately stabilizing the skew rate within the allowable range and ensuring that the hole reaming accuracy meets the design requirement of ±1.5% of the hole diameter.

[0081] As a preferred embodiment, the specific implementation of this application is as follows: Within the excavated tunnel section, the fractured zone area is identified by ground-penetrating radar scanning. When the rock fracture index exceeds the critical value, grouting holes are arranged in a quincunx pattern within a 0.8-meter radius outside the excavation outline, with a hole spacing of 1.2 meters and a hole depth of 3 meters. Seamless steel pipes with an outer diameter of 42 mm are used for grouting, with grout outlet holes spaced 30 cm apart on the pipe wall. The grouting material is a two-component grout prepared from 42.5 grade ordinary silicate cement and water glass at a volume ratio of 1:0.3, and the grouting pressure is controlled within the range of 1.5-2.0 MPa. The grouting operation adopts a segmented retreating process, with each grouting segment not exceeding 50 cm in length. After grouting, the grouting holes are sealed. For tunnel sections where structural surfaces are detected and the rock quality index is below 40, HRB400 grade threaded steel bars are used to fabricate arch frame units with a radius of 60 cm. The units are longitudinally connected by steel sleeves connected by M24 bolts, with a circumferential spacing of 80 cm. A 5-cm-diameter machine-woven galvanized steel wire mesh is laid between the arch frame and the tunnel wall, with an overlap length of not less than 10cm, and is fixed to the arch frame using U-shaped clips. The surface of the arch frame is coated with a 200-micron-thick epoxy zinc-rich primer and polyurethane topcoat composite anti-corrosion layer.

[0082] This application further proposes using cement-water glass dual-liquid grout as the grouting material; using threaded steel bars to process the arch frame, the arch frame being connected by segmented components through connecting sleeves, the arch frames being connected by connecting bars to form a stable support structure, laying machine-woven galvanized protective netting between the arch frame and the tunnel wall, and performing anti-corrosion treatment on the arch frame to ensure durability.

[0083] The volume ratio of cement to water glass is controlled within the range of 1:0.3 to 1:0.5, utilizing the setting-promoting properties of water glass to allow the slurry to solidify rapidly within the fractured zone; the yield strength of the threaded steel bars is not less than 335 MPa, and they are processed into arc-shaped segmented components through cold bending, with segment lengths set at 1.5-2.0 meters; the connecting sleeve adopts an internal thread structure, forming a mechanical engagement with the external thread machined at the end of the steel bar; the diameter of the connecting bars is set at 12-16 mm, and they are arranged at 0.8-1.2 meters circumferentially along the arch frame; the mesh size of the machine-woven galvanized protective net is 50×50 mm, and the wire diameter is 2.8 mm; the anti-corrosion treatment adopts a hot-dip galvanizing process, with a zinc layer thickness of not less than 80 micrometers.

[0084] Specifically, during grouting in the fractured zone, a dual-liquid grout is injected into rock fissures within a 1.5-meter radius outside the excavation outline through grouting pipes. The cement grout and water glass react chemically in a mixer, forming a gel that fills the fissures within 30-60 seconds. When fabricating the steel arch frame, threaded steel bars are cold-bent on a hydraulic bending machine to avoid strength loss caused by hot working. During installation, segmented arch frames are screwed together and fixed using connecting sleeves, with adjacent arch frames welded together to form a spatial grid structure. A protective net is fixed to the outside of the arch frame using U-shaped clips, maintaining a 50-mm gap from the rock surface. Hot-dip galvanizing creates a dense alloy layer on the arch frame surface, providing corrosion resistance for over 15 years in the humid tunnel environment. This solution achieves a synergistic effect of rapid reinforcement of the fractured zone and long-term support from the steel arch frame through optimized material properties and innovative structural connections.

[0085] As a preferred embodiment, the specific implementation of this application is as follows: During grouting reinforcement, a two-component grout is used, formed by mixing silicate cement grout and water glass solution in a specific volume ratio. The modulus of the water glass solution is controlled within a set range. The two grouts are injected into the fractured zone area through a dual-channel grouting pipe. After mixing in the hole, the two grouts gel and solidify. During steel arch support, the arch frame is made of hot-rolled threaded steel bars cold-bent into arc-shaped components. Each arc-shaped component has external threads at its ends and is connected by steel sleeves with internal threads. Adjacent arch frames are connected by horizontal welding using straight threaded steel bars as connecting reinforcement. A machine-woven galvanized steel wire mesh with a aperture not exceeding a set value is laid between the arch frame and the tunnel wall. The galvanized layer thickness meets relevant standard requirements. After installation, an epoxy zinc-rich primer and a polyurethane topcoat are sprayed onto the arch frame surface to form a composite anti-corrosion layer.

[0086] Through the above technical solutions, this application effectively solves the problem of insufficient reinforcement effect of existing support measures on fractured zones. The cement-water glass dual-liquid grout achieves rapid reinforcement of fractured rock mass through controllable setting time. The prefabricated structure formed by the threaded steel bar arch frame and connecting sleeve improves the overall rigidity of the support system. The combined application of machine-woven galvanized protective netting and anti-corrosion coating significantly extends the service life of the support structure in humid environments and avoids the risk of support failure caused by steel bar corrosion in traditional support.

[0087] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for excavating an exploration tunnel based on large-diameter boreholes, characterized in that, Includes the following steps: Based on the design axis of the horizontal tunnel, measurements were taken and the tunnel orientation and bottom position were marked. A mobile, large-diameter drilling rig platform with leveling and guidance systems is installed at the tunnel entrance; Geological exploration technology is used in conjunction with previous exploration data to predict the geological conditions ahead of the tunnel face and to divide different geological zones. Supporting the tunnel face includes clearing the slope, installing anchor bolts, erecting steel arch support, and spraying concrete. Based on the predicted geological conditions, a large-diameter drill bit was selected and pilot drilling was carried out. The pilot drilling included drilling a guide section at the borehole opening and drilling the main directional hole to the end of the horizontal tunnel, and the borehole deviation rate was monitored in real time during the drilling process. Based on the dominant borehole, the borehole is enlarged in stages to the designed diameter, and the deviation rate is monitored in real time during the enlargement process; During the tunneling process, unstable tunnel sections are identified, and appropriate support methods are selected based on the geological characteristics of these sections. The cave walls were cleaned to make the geological phenomena of the rock layers and structural surfaces on the cave ceiling and walls clearly visible, and the cave depth was marked on the cave walls.

2. The method according to claim 1, characterized in that, The step of selecting a large-diameter drill bit and conducting pilot drilling based on predicted geological conditions further includes: Based on the predicted hardness of the formation ahead of the tunnel face, select a drill bit size range suitable for the corresponding hardness of the formation; Multiple high-pressure water jet nozzles are installed on the inner wall of the drill bit; Determine drilling parameters, including adjusting drilling speed, drilling pressure, and rotation speed to a safe range based on formation hardness; After drilling to the initial set length, the drill rod is withdrawn and a steel casing is inserted to form the borehole guide section; Drill the main directional hole along the design axis to the end of the horizontal tunnel, and simultaneously inject mud that stabilizes the borehole wall and carries rock cuttings; The borehole deviation rate is monitored in real time, and the drilling direction is adjusted when the deviation rate exceeds the set threshold.

3. The method according to claim 2, characterized in that, In the step of determining drilling parameters: If a hard rock section is encountered during drilling, the drilling speed should be controlled within the first safe speed range, the drilling pressure within the first pressure range, and the rotation speed within the first rotation speed range. If a soft rock section is encountered during drilling, the drilling speed is controlled within the second safe speed range, which is higher than the first safe speed range; the drilling pressure is controlled within the second pressure range, which is lower than the first pressure range; and the rotation speed is controlled within the second rotation speed range, which is higher than the first rotation speed range. The injected mud is a high-molecular polymer mud. The mud viscosity is controlled within the effective range for stabilizing the borehole wall, the mud density is controlled within the effective range for balancing formation pressure, and the mud recycling rate is maintained above the set level.

4. The method according to claim 2, characterized in that, In the step of real-time monitoring of borehole deviation and adjustment of drilling direction: If the skew rate exceeds the set threshold, the drilling direction adjustment mechanism will be activated. After adjustment, continue to monitor the deviation rate. If the deviation rate drops to within the set threshold, maintain the current drilling direction. If the deviation rate still exceeds the set threshold or continues to increase after adjustment, the drilling direction should be adjusted again or continuously until the deviation rate meets the requirements.

5. The method according to claim 1, characterized in that, The step of reaming the hole in stages to the designed diameter further includes: Perform the first stage of hole reaming: Use a first-stage hole reamer to enlarge the diameter of the main directional hole to the first target size, and control the first-stage hole reaming speed within a safe range; Perform the second stage of hole reaming: replace the second stage hole reamer with a second stage hole reamer to enlarge the borehole diameter to the designed hole diameter, and control the second stage hole reaming speed within a safe range; During the hole enlargement process, the deviation rate is monitored in real time. When the deviation rate exceeds the set threshold, the correction device is activated to adjust the attitude of the hole enlarger.

6. The method according to claim 5, characterized in that, In the step of performing the first stage of hole enlargement: A stepped reamer is used as the first-stage reamer. Real-time monitoring of the reamer's torque and thrust; If the torque exceeds the safe torque range or the thrust exceeds the safe thrust range, reduce the hole reaming speed or suspend hole reaming for inspection.

7. The method according to claim 5, characterized in that, In the step of performing the second-stage hole enlargement: A cylindrical reamer is used as the second-stage reamer, and the inner wall of the cylindrical reamer is uniformly distributed with carbide cutting teeth. Real-time monitoring of the temperature of the expander; If the temperature exceeds the safe temperature threshold, the hole enlargement process will be paused and cooled down. The hole enlargement will resume once the temperature drops below the safe range.

8. The method according to claim 5, characterized in that, In the step of real-time monitoring of the skew rate and adjusting the attitude of the reamer during the hole reaming process: A high-precision guidance system is used for positioning and deviation monitoring; If the skew rate exceeds the set threshold, the hydraulic correction device will be activated to adjust the attitude of the reamer. After adjustment, continue to monitor the skew rate. If the skew rate drops to within the set threshold, maintain the current reamer posture. If the skew rate still exceeds the set threshold or continues to increase after adjustment, adjust the hole expander posture again or continuously until the skew rate meets the requirements.

9. The method according to claim 1, characterized in that, The step of identifying unstable tunnel sections and selecting support methods based on geological characteristics further includes: Identify the fractured zone area: If a fractured zone area is identified, grouting reinforcement is selected for support. The grouting reinforcement includes grouting within a set range outside the excavation outline. Identify sections prone to rockfall or collapse: If sections prone to rockfall or collapse are identified, steel arch support is selected for support. The steel arch support includes erecting arches connected by connectors and laying protective netting between the arches and the tunnel wall.

10. The method according to claim 9, characterized in that: In the step of selecting the grouting reinforcement method for support, cement-water glass dual-liquid grout is used as the grouting material. In the step of selecting the steel arch support method for support, the arch frame is processed using threaded steel bars. The arch frame is composed of segmented components connected by connecting sleeves. The arch frames are connected by connecting bars to form a stable support structure. A machine-woven galvanized protective net is laid between the arch frame and the tunnel wall, and the arch frame is treated with anti-corrosion to ensure durability.

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