A drilling and discharging integrated construction method suitable for high-pressure water-rich soft and hard alternating stratum

Abstract

The application discloses a drilling and drainage integrated construction method suitable for high-pressure water-rich soft and hard alternating stratum, a plurality of outer ring drainage holes are drilled on a tunnel contour of a first layer of soft rock, and a plurality of inner ring drainage holes are drilled on the tunnel contour of the first layer of soft rock and close to the outer ring drainage holes; the inner ring drainage holes are arranged away from the tunnel contour; the drilling method of the outer ring drainage holes and the inner ring drainage holes is as follows: drilling the first layer of soft rock until the first layer of soft rock is completely penetrated, then drilling the first layer of hard rock until the first layer of hard rock is completely penetrated, and then drilling the second layer of soft rock until the second layer of soft rock is completely penetrated, and the drilling is continued until the drainage channels are formed; the method can drain water through the straight hole of the tunnel contour, and can systematically improve and optimize the drilling and hole-forming process and drainage and pressure reduction, so that the demand of the drilling and drainage integrated treatment of the high-pressure water-rich soft and hard alternating stratum is met.

Description

Technical Field

[0001] This invention belongs to the field of advanced drainage and pressure reduction in adverse geological conditions, and particularly relates to an integrated drilling and drainage construction method suitable for high-pressure, water-rich, alternating soft and hard strata. Background Technology

[0002] As tunnel engineering develops towards ultra-deep and ultra-long tunnels, construction projects frequently encounter high-pressure, water-rich, and unevenly hard strata. If pre-emptive water drainage and pressure reduction are not adopted to improve the geological environment, and curtain grouting, pipe roof support, and excavation and sealing are carried out directly, engineering accidents such as water inrush, mudslides, and collapses are very likely to occur during the process, which will seriously affect the progress of the project and threaten personnel safety.

[0003] Currently, most domestic and international methods for advanced water drainage and pressure reduction in complex and unfavorable strata with high pressure, abundant water, and alternating soft and hard surrounding rocks rely on excavation to construct methods such as high-level drainage tunnels, detour tunnels, and side wall vents. These methods involve large-scale construction, high risks, and significantly increased costs. Moreover, similar high-pressure, water-rich, and alternating soft and hard strata require direct treatment during the process. Summary of the Invention

[0004] The purpose of this invention is to provide an integrated drilling and drainage construction method suitable for high-pressure, water-rich, and alternating soft and hard formations, in order to solve the problems of large overall engineering workload, high risk, and soaring costs when dealing with complex and unfavorable formations with high pressure, water-rich, and alternating soft and hard surrounding rocks in existing technologies.

[0005] The present invention adopts the following technical solution: a drilling and drainage integrated construction method suitable for high-pressure water-rich alternating soft and hard strata. When the TBM is continuously excavating, when it reaches the high-pressure water-rich alternating soft and hard strata, the first layer of hard rock in the high-pressure water-rich alternating soft and hard strata is completely excavated, so that the first layer of soft rock in the high-pressure water-rich alternating soft and hard strata is completely exposed. Then, multiple outer ring drainage holes are drilled at intervals along the tunnel outline on the working face of the first layer of soft rock, close to the tunnel outline. In addition, multiple inner ring drainage holes are drilled at intervals on the working face of the first layer of soft rock, close to each of the outer ring drainage holes. Each of the inner ring drainage holes is set away from the tunnel outline.

[0006] The drilling methods for each of the outer and inner ring drainage holes are as follows:

[0007] Drill holes through the first layer of soft rock until the first layer of soft rock is completely penetrated, then drill holes through the first layer of hard rock until the first layer of hard rock is completely penetrated, and continue drilling holes through the second layer of soft rock until the second layer of soft rock is completely penetrated, and so on until each hole forms a drainage channel.

[0008] Among them, the borehole diameter of the first layer of soft rock > the borehole diameter of the first layer of hard rock > the borehole diameter of the second layer of soft rock, and so on.

[0009] The beneficial effects of this invention are:

[0010] This invention can drain water from straight holes at the working face, systematically improve and optimize the drilling and hole-forming process, and reduce water pressure, thereby meeting the needs of integrated drilling and drainage treatment of high-pressure, water-rich, and unevenly hard formations.

[0011] This invention enables the direct release of high-pressure fracture water in the formation, which not only solves the prominent problems of conventional drainage methods in poor formations with high quality and efficiency, but also further realizes the integrated operation of long-distance straight hole drilling and drainage, greatly reducing construction costs and time.

[0012] This invention allows for timely changes in the drilling process based on changes in the surrounding rock, meeting the requirements for strong adaptability to the formation. Furthermore, it dynamically adjusts construction parameters in real time during the drilling process to ensure high-efficiency drilling.

[0013] In the drilling process, if soft rock is encountered, a drainage steel pipe is lowered; if alternating soft and hard zones are encountered, a drainage cone-shaped screen pipe is lowered to provide strong support to the borehole wall and ensure the long-term stability and effectiveness of the drainage holes at the working face.

[0014] This invention changes the drilling process each time the surrounding rock changes during drilling, while appropriately reducing the diameter of the next section of the hole to ensure the feasibility of the process. At the same time, it significantly reduces stress concentration in the transition hole and disturbance and damage to the formation.

[0015] The hole-forming process of this invention enables a single hole to reach 50-60m, and the presence of the drainage conical screen pipe with drainage holes promotes the concentration of water from the surrounding rock fissures and its discharge along the hole, greatly improving the drainage efficiency. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the drainage steel perforated pipe used in this invention;

[0017] Figure 2 This is a schematic diagram of the structure of the drainage cone-shaped screen pipe used in this invention;

[0018] Figure 3 This is a schematic diagram of the structure of the variable diameter drill bit used in this invention;

[0019] Figure 4 This is a schematic diagram of the drilling layout at the working face in this invention;

[0020] Figure 5 This is a cross-sectional view of the construction of the present invention;

[0021] Figure 6 This is a schematic diagram of the borehole layout according to an embodiment of the present invention. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0023] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "multiple" means two or more.

[0024] This invention discloses an integrated drilling and drainage construction method suitable for high-pressure, water-rich, alternating soft and hard formations, such as... Figure 4 and Figure 5 As shown, during the continuous excavation of the TBM, when the high-pressure, water-rich, alternating soft and hard strata are reached, the first layer of hard rock in the high-pressure, water-rich, alternating soft and hard strata is completely excavated, exposing the first layer of soft rock in the high-pressure, water-rich, alternating soft and hard strata. Then, multiple outer ring drainage holes are drilled at intervals along the tunnel outline on the working face of the first layer of soft rock, near the location of each of the outer ring drainage holes. In addition, multiple inner ring drainage holes are drilled at intervals on the working face of the first layer of soft rock, near the location of each of the outer ring drainage holes. Each of the inner ring drainage holes is located away from the tunnel outline.

[0025] The drilling methods for each of the outer and inner ring drainage holes are as follows:

[0026] Drill holes through the first layer of soft rock until the first layer of soft rock is completely penetrated, then drill holes through the first layer of hard rock until the first layer of hard rock is completely penetrated, and continue drilling holes through the second layer of soft rock until the second layer of soft rock is completely penetrated, and so on until each hole forms a drainage channel.

[0027] Among them, the borehole diameter of the first layer of soft rock > the borehole diameter of the first layer of hard rock > the borehole diameter of the second layer of soft rock, and so on.

[0028] Prior to drilling, on-site operations were primarily conducted using the "Seismic Wave Reflection Method (TSP) + Transient Electromagnetic Method (TEM)," supplemented by "Ground Ground Radar (GPR) local identification and advanced horizontal drilling verification" for detailed implementation. Subsequently, through comparison and mutual verification of various analytical data, the engineering geological parameters were clearly identified, including the distribution boundaries of soft / hard strata, the physical and mechanical properties of the surrounding rock, hydrogeological parameters, and structural surface characteristics.

[0029] Based on advanced geological forecasts, drilling parameters and support schemes are dynamically adjusted, and the tunneling direction and borehole trajectory are optimized in real time to ensure efficient drilling and structural stability in complex strata. Combined with surrounding rock deformation monitoring data, initial support is implemented promptly, and the combined support system of anchor pipes and steel arches is strengthened to enhance overall deformation resistance.

[0030] Drilling in the surrounding rock requires dynamic adjustments to the process based on geological forecasts, water output, and changes in rock cuttings. For similar formations, the same borehole diameter is maintained. When the formation changes, the drill bit blades are hydraulically controlled to achieve a slow diameter change. Corresponding drainage cone screens are used to protect the wall in the diameter change section to ensure borehole quality, stress balance, and stable seepage, thereby enabling long-distance penetration of the formation for water drainage.

[0031] The schematic diagram of the opening layout on the working face in this invention is shown below. Figure 4 As shown, each working face adopts a combination of annular and radial perforation patterns to construct a three-dimensional spatial drainage network, which directly drains and reduces pressure in the water-rich area in front of the working face.

[0032] Before drilling each single hole, a complete set of multiple anti-outburst devices must be strictly installed. First, hemp fiber, cement, and anchoring agent are used to place the borehole pipe on the working face surface. Then, matching bolts are used to connect the borehole flange → double gate high-pressure blowout preventer → rotary blowout preventer → zero-pressure relief tee manifold in sequence. Finally, a pressure test of no less than 1.5 times the stable water pressure is carried out on the anti-outburst device. If there is no water leakage at the borehole and the entire device is firm and stable after 30 minutes, the device can be confirmed to have risk control capability.

[0033] Once the drainage channel is formed, it is divided into three necessary pressure reduction and control stages according to the overall water discharge and pressure reduction standards: the initial water discharge stage, the intermediate rock stabilization stage, and the later standard attainment stage.

[0034] When encountering soft rock formations that are muddy or fragmented, a dual-tube coordinated hydraulic impact drilling process is adopted. In this case, the inner tube and the inner drill rely on the hydraulic device to impact and break the surrounding rock at high frequency; while the outer tube or casing and the outer drill are responsible for enlarging the hole wall, rotating and cutting the soft rock to form a space that can accommodate the casing and simultaneously lowering it. This process is repeated until the predetermined depth is reached, then the inner tube drill rod is withdrawn, the drainage steel pipe is lowered along the casing, the casing is slowly pulled out, and a stable drainage channel is formed.

[0035] When drilling into soft rock, casing drilling is used, and after removing the drill rod, a drainage steel perforated pipe is inserted to protect the borehole. Figure 1 As shown.

[0036] If the current layer is soft rock and the next layer is hard rock, and the boundary between the soft and hard rock is greater than 50cm, a transitional diameter hole is drilled in the boundary between the soft and hard rock; the diameter of the transitional diameter hole gradually decreases from the soft rock to the hard rock; the drilling method for the transitional diameter hole is as follows: Figure 3 As shown, a transition hole is opened using a reducing drill bit. After removing the reducing drill bit, a drain cone screen is placed inside the transition hole to protect it. Figure 2 As shown.

[0037] Preferably, the borehole diameter of the first layer of soft rock is ≥200cm, and the borehole diameter of the last borehole is ≥50cm regardless of whether the last borehole is in hard rock or soft rock.

[0038] Preferably, the total length of multiple drilling operations is ≤60m.

[0039] Preferably, the borehole diameters between adjacent soft and hard rocks differ by 30-40 mm.

[0040] Preferably, if encountering weakly weathered or strongly weathered hard rock strata, the hole is drilled directly without inserting a drainage steel pipe, and a high-frequency shallow hole hammer drilling process is adopted. Based on the down-the-hole hammer and diamond drill rod, the down-the-hole hammer impacts the hard rock at high frequency, and the resulting strong axial force forces the hard rock to break, while driving the hammer to carry rock cuttings in the hole.

[0041] Preferably, the distance between each outer ring drainage hole and the tunnel outline is 1-1.5m, and the distance between each inner ring drainage hole and its corresponding outer ring drainage hole is also 1-1.5m. The outer ring drainage holes and inner ring drainage holes are arranged alternately, such as... Figure 4 As shown. Example

[0042] like Figure 4 As shown, a network-style overall layout of "planar arrangement + vertical layering" is adopted. The planar arrangement follows a "ring + radial" perforation pattern, with a spacing of 1.5m between each perforation, an elevation angle of 10-20°, and a length of 50-60m per perforation. The vertical arrangement is designed for multiple aquifers within the altered mud and sand surrounding rock, using a "double-ring" perforation pattern where the outer ring perforations are primarily for drainage and secondarily for pressure reduction, while the inner ring perforations are primarily for pressure reduction and secondarily for drainage.

[0043] like Figure 6As shown, the variable diameter drilling design follows this progression: "First layer soft rock borehole diameter (1st opening 216mm) → Variable diameter transition section (216mm→178mm) → First layer hard rock borehole diameter (2nd opening 178mm) → Variable diameter transition section (178mm→152mm) → Second layer soft rock borehole diameter (3rd opening 152mm) → Variable diameter transition section (152mm→126mm) → Second layer hard rock borehole diameter (4th opening 126mm) → Variable diameter transition section (126mm→108mm) → Third layer soft rock borehole diameter (5th opening 108mm) → Variable diameter transition section (108mm→76mm) → Third layer hard rock borehole diameter (6th opening 76mm)". Each variable diameter transition section is designed with a drainage conical screen to prevent stress concentration and borehole collapse, further achieving the multi-stage variable diameter effect.

[0044] To balance the stability between the discharge volume / velocity and the formation, and to prevent a sudden increase in effective formation stress from causing uncontrollable deformation of the surrounding rock, the on-site stepped depressurization standard is detailed in Table 1.

[0045] Table 1. Standards for the Stages of On-site Water Drainage and Pressure Reduction

[0046]

[0047] Anti-surge design:

[0048] Single-hole anti-surge structure design: strictly install double gate high-pressure blowout preventer + rotary blowout preventer + three-way drain manifold, and reserve pressure relief bypass channel in advance.

[0049] If a sudden surge occurs in a weak area at the working face, under controllable conditions, ultrafine cement-water glass dual-liquid grout will be injected within a 3m radius around the surge drainage hole to quickly form a water-stop curtain.

[0050] Main equipment selection: The core parameters of the selected hydraulic geological drilling rig must meet the requirements of high torque (19~22kN.m), strong force (55kN), high impact frequency (1800~2300) and impact force (>1000N.m); the casing, drainage steel pipe, drainage screen pipe and other components of each model must meet the mechanical performance requirements described in the above instruction manual.

[0051] Construction of straight hole drainage at the working face

[0052] Advanced geological prediction: The main method is "Seismic reflection method (TSP) + transient electromagnetic method (TEM)," combined with "Ground ground radar (GPR) local identification and advanced horizontal drilling verification" to carry out the determination of engineering geological parameters in a refined manner.

[0053] Precise borehole positioning: The borehole coordinates are calibrated using a total station (repeated calculations are performed to ensure that the borehole coordinate error is <5cm and the position deviation is <1°), and the borehole trajectory is corrected in real time using a drilling rig to ensure that the borehole axis is orthogonal to the target geological body.

[0054] Anti-outburst device in place: Before drilling each hole, an anti-outburst device must be installed at the hole opening. After passing the inspection, drilling and hole formation and water drainage operations can be carried out by passing through the anti-outburst device.

[0055] Variable diameter drilling with wall support: The drilling process is divided into multiple "sections" of variable diameter hole formation. When encountering a variable diameter transition section, a variable diameter drill bit is used to slowly form the hole. During this process, when encountering soft rock / rock with frequent alternation between soft and hard rock / transition sections, various types of drainage steel flower pipes and drainage cone screens need to be lowered simultaneously to provide strong support for the hole wall. Hard rock sections do not require support (hard rock has strong self-stabilizing ability).

[0056] Long-distance dewatering: The effective advance length of a single hole on site can be ensured to be within the range of 50 to 60m. The drainage holes on the surface of each protective pipe provide multiple drainage channels, realizing formation dewatering and pressure reduction on a large scale and with high efficiency, ensuring that the single hole drainage efficiency is >95%.

[0057] Real-time on-site monitoring and dynamic adjustment:

[0058] Monitor the total discharge volume and single-hole discharge volume of each working face to ensure that each value does not exceed the design limit (single-hole discharge volume limit ≤ 200L / min, total discharge volume of the working face ≤ 25L / (s.50m)). If the discharge volume limit is exceeded, the corresponding discharge hole gate valve should be closed or partially closed in time to prevent the surrounding rock from settling significantly in a short period of time.

[0059] Local reinforcement and adjustment of drainage holes: This mainly involves the tunnel face with abnormal TSP and TEM sections, abnormally small overall drainage volume, and abnormalities such as deviation, collapse, and blockage of most drainage holes. It is necessary to carry out "secondary" drainage optimization through densification and optimization of hole depth and angle.

[0060] When the measured water pressure of the surrounding rock remains stable at or below 0.8 MPa for a long period, subsequent construction procedures such as curtain grouting reinforcement and advanced pipe roof support can be considered to accelerate the overall construction progress.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A drilling and discharging integrated construction method suitable for high-pressure water-rich soft and hard alternating strata, characterized in that, As the TBM continues to advance, when it reaches the high-pressure, water-rich, alternating soft and hard strata, the hard rock facing the high-pressure, water-rich, alternating soft and hard strata is completely excavated and laid, so that the first layer of soft rock in the high-pressure, water-rich, alternating soft and hard strata is fully exposed. Then, multiple outer ring drainage holes are drilled at intervals along the tunnel outline on the face of the first layer of soft rock near the tunnel outline. Furthermore, multiple inner ring drainage holes are drilled at intervals on the face of the first layer of soft rock, near the outer ring drainage holes; each inner ring drainage hole is located away from the tunnel outline. The drilling methods for each of the outer and inner ring drainage holes are as follows: Drill holes through the first layer of soft rock until the first layer of soft rock is completely penetrated, then drill holes through the first layer of hard rock until the first layer of hard rock is completely penetrated, and continue drilling holes through the second layer of soft rock until the second layer of soft rock is completely penetrated, and so on until each hole forms a drainage channel. Among them, the borehole diameter of the first layer of soft rock > the borehole diameter of the first layer of hard rock > the borehole diameter of the second layer of soft rock, and so on. If the current layer is soft rock and the next layer is hard rock, and the boundary between the soft rock and the hard rock is greater than 50cm, a transitional variable diameter hole is drilled in the boundary between the soft rock and the hard rock; the diameter of the transitional variable diameter hole gradually decreases from the soft rock to the hard rock. The method for drilling the transition diameter hole is as follows: use a diameter-changing drill bit to open the transition diameter hole, and after removing the diameter-changing drill bit, insert a drainage cone screen pipe into the transition diameter hole to protect it.

2. The drilling and drainage integrated construction method for high-pressure, water-rich, alternating soft and hard formations according to claim 1, characterized in that, in, When drilling into soft rock, casing drilling is used, and after the drill rod is removed, a drainage steel pipe is inserted to protect the borehole.

3. The drilling and drainage integrated construction method for high-pressure, water-rich, alternating soft and hard formations as described in claim 1, characterized in that, The borehole diameter in the first layer of soft rock is ≥200cm, and the borehole diameter in the last borehole is ≥50cm, regardless of whether the last borehole is in hard rock or soft rock.

4. The drilling and drainage integrated construction method for high-pressure, water-rich, alternating soft and hard formations according to claim 1, characterized in that, The total length of multiple drilling operations is ≤60m.

5. The drilling and drainage integrated construction method for high-pressure, water-rich, alternating soft and hard formations according to claim 1, characterized in that, The borehole diameters between adjacent soft and hard rocks differ by 30-40 mm.

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