Full-length expanded-head anchor cable rotary jet grouting reaming rapid construction process

Abstract

The invention discloses a full-length expanded-head anchor cable jet grouting reaming rapid construction process, which comprises the following steps: firstly, equipment is fully prepared and has strong pertinence, and a drill rod, a steel bearing body, a hydraulic extrusion sleeve and other parts act synergistically to ensure stable drilling of an anchor cable; secondly, surveying and setting-out are accurate, and accurate arrangement of anchor cable hole positions and real-time deviation correction of a drilling track are achieved by utilizing equipment such as a total station and a level gauge in combination with a drill rod inclination angle adjusting formula and a directional drilling track design formula; and finally, the staged drilling process is scientific and reasonable, primary drilling and secondary drilling are combined, a reaming method is flexibly selected according to different geological conditions, a hard stratum and a complex space environment are effectively dealt with, the hole forming quality is guaranteed, all links are tightly connected from equipment disassembly to high-pressure rotary guniting fluid back pulling to anchor cable tensioning and locking, and the drilling efficiency is greatly improved. And finally, stable anchoring of the anchor cable under complex geological conditions is achieved, and reliable prestress guarantee is provided for slope or foundation pit supporting.

Description

Technical Field

[0001] The invention relates to the technical field of full-length enlarged head anchor cable construction, and more specifically, to a full-length enlarged head anchor cable rotary spray hole expansion rapid construction process. Background Art

[0002] With the rapid development of urban construction, deep foundation pit support projects have increased one after another, and there are also various forms of support structure systems. Among them, "support piles + prestressed anchor cables" as one of the support forms has been widely adopted due to its simple construction and economic characteristics.

[0003] Support piles are mainly used to withstand lateral thrust. They are used for foundation pit support, slope support and landslide control. They withstand horizontal soil pressure or landslide thrust. Generally, they require higher reinforcement than foundation piles that withstand vertical force, and are often used together with anchor rods.

[0004] Prestressed anchor cable refers to a cable-like support that is anchored inside the rock mass by a prestressed method. It is used to reinforce the slope. The anchor cable is anchored into the rock mass through the holes in the weak structural surface of the rock mass by the anchor head, connecting the sliding body with the stable rock layer, thereby changing the stress state of the slope rock mass and improving the integrity and strength of the unstable rock mass of the slope. Special tensioning devices and machinery are required for the construction of prestressed anchor cables.

[0005] At present, the conventional process flow of prestressed anchor cable construction for deep foundation pit support is: drilling rig in place → drilling to the designed depth → withdrawing and disassembling drill rod section by section → lowering prestressed anchor cable → first grouting → intermittent maintenance → second grouting → tensioning and locking after maintenance to the age. During the construction process, a series of processes such as drilling, lowering anchor cable, grouting, etc. need to be completed step by step in sequence. The construction time is long and therefore does not meet the existing needs. In this regard, we propose a rapid construction process for rotary jet hole expansion with a full-length enlarged head anchor cable. Summary of the invention

[0006] The purpose of the present invention is to provide a rapid construction process for expanding the hole by rotary jetting of a full-length enlarged head anchor cable, so as to solve the problem that the conventional process flow of deep foundation pit support prestressed anchor cable construction in the prior art is as follows: drilling rig in place → drilling holes to the designed depth → withdrawing and disassembling the drill rod section by section → lowering the prestressed anchor cable → first grouting → intermittent curing → second grouting → tensioning and locking after curing to the age, and a series of processes such as hole drilling, lowering the anchor cable, grouting, etc. in the construction process need to be completed step by step in a sequential order, resulting in a long construction time.

[0007] The above technical purpose of the present invention is achieved through the following technical solutions: a full-length enlarged head anchor cable rotary spray hole expansion rapid construction process, comprising the following steps: S1. Equipment preparation: the drilling rig includes a drill rod, a steel bearing body is fixedly arranged on the guide hole of the drill rod, a hydraulic extrusion sleeve is arranged on the steel bearing body, and an anchor cable is arranged on the hydraulic extrusion sleeve; S2. Measurement and layout: according to the design drawings, the plane position and elevation position of the anchor cable hole are determined in the deep foundation pit, and the specific plane position of the anchor cable hole is marked with an iron bar and paint. At the same time, the plane position of the anchor cable hole is installed according to the designed hole position inclination angle. The foundation platform for placing the drilling rig; S3. Primary drilling: after the drilling rig is installed on the foundation platform, the angle of the drill rod is corrected and the anchor cable is compared with the drilling depth, the high-pressure water pump is started to inject water at the first water injection speed, and the drilling rig is started until the drill casing moves forward and the drill rod passes through the steel The bearing body is drilled with the anchor cable; S4. Secondary drilling: During the process of advancing the drill rod and the high-pressure automatic rotating nozzle, according to the pre-determined design position of the anchor hole, when the drill rod and the high-pressure automatic rotating nozzle are close to the design position or reach the design position, they are slowly advanced forward accordingly to expand the aperture at the design position of the anchor hole; S5. Disassembly: When the steel bearing body and the anchor cable are drilled to the design position, the high-pressure rotating nozzle is closed and the steel bearing body and the anchor cable are unloaded; S6. The high-pressure rotary spraying slurry retreats and the drill rod is pulled out: After the steel bearing body and the anchor cable are unloaded, the high-pressure rotating nozzle is reopened and retreated to the outer end of the anchoring section at a low speed and steadily, the high-pressure rotating nozzle is closed and the drill rod is pulled out; S7. Anchor cable tensioning and locking: The anchor cable tensioning can be carried out 14 days after the anchor cable grouting is completed and the grouting body and the crown beam concrete reach 75% of the design strength. The tensioning force is 1.1 times the design tension value. After the tensioning test is qualified, the load is unloaded to the locking value to lock the load.

[0008] By adopting the above technical scheme, firstly, the equipment is fully prepared and highly targeted, and the drill rod, steel bearing body, hydraulic extrusion sleeve and other components work together to ensure stable drilling of the anchor cable; secondly, the measurement and layout are accurate, and the total station, level and MWD wireless inclinometer and other equipment are used, combined with the drill rod inclination angle adjustment formula and directional drilling trajectory design formula, to achieve accurate arrangement of anchor hole positions and real-time correction of drilling trajectory, thereby improving construction accuracy; finally, the staged drilling process is scientific and reasonable, and the first-level drilling is combined with the second-level drilling. The expansion method is flexibly selected according to different geological conditions, effectively coping with hard formations and complex spatial environments, ensuring the quality of the hole, and closely connecting the links from equipment disassembly to high-pressure rotary jet slurry withdrawal and pulling rod, to anchor cable tensioning and locking, to ensure safe and efficient construction, and finally achieving stable anchoring of the anchor cable under complex geological conditions, providing reliable prestressing guarantee for slope or foundation pit support, and improving overall stability and safety.

[0009] The present invention is further configured as follows: each of the anchor cables is composed of 4 bundles of steel strands 3, a steel carrier and a hydraulic extrusion sleeve are fixed on the drill rod, the anchor cable includes a tensioning section, a free section and an anchoring section, the tensioning section, the free section and the anchoring section are different regions of the anchor cable respectively, and the outer edge of the free section is provided with a corrugated tube sleeve.

[0010] By adopting the above technical scheme, the free section of the steel strand can be effectively protected from the influence of the external environment by the corrugated tube casing, such as preventing the corrosion of the steel strand by groundwater, mud, etc., thereby extending the service life of the anchor cable. During the tensioning process, the corrugated tube casing allows the steel strand to freely extend therein, ensuring that the steel strand can fully produce elastic deformation, thereby forming a uniform prestress, and improving the tensioning effect and stability of the anchor cable. The corrugated tube casing can also isolate the free section from the surrounding soil, avoiding the slurry from entering the free section during grouting, thereby ensuring the flexibility of the free section and the smooth progress of the tensioning operation, thereby improving the overall construction quality and working performance of the anchor cable.

[0011] The present invention is further configured such that adjacent anchor cables are laid at a 30° / 35° staggered manner during construction.

[0012] By adopting the above technical solution, the construction method of 30° / 35° staggered placement of adjacent anchor cables can effectively improve the overall stability and safety of slope or foundation pit support. The staggered placement method allows the anchor cables to form a mutually staggered force structure in space, enhances the synergy between the anchor cables, avoids excessive concentration of force on the anchor cables, and thus better disperses and transmits soil pressure, effectively improving the anti-slip and anti-overturning capabilities of the support system. At the same time, it also helps to reduce local stress concentration, reduce the risk of sliding or loosening of the anchor cables due to uneven force, and ensure the stability of the foundation pit during construction and use.

[0013] The present invention is further configured as follows: the anchor hole depth should be 500 mm longer than the designed length of the anchor, the free section of the anchor is sealed and protected by a bellows casing, and a surplus of 100 mm should be reserved for the length of the tensioning section.

[0014] By adopting the above technical solution, the free section is sealed and protected by a bellows casing, which can prevent the entry of mud, debris, etc. during construction, avoid rust and pollution of the steel strands, and ensure that the free section steel strands can stretch freely during tensioning to form effective prestress; a 100mm surplus is reserved in the tensioning section to meet the operating requirements of the tensioning equipment, ensuring sufficient adjustment space during the tensioning process, making the anchor prestress locking more accurate and reliable, thereby effectively improving the overall stability and durability of the anchor support.

[0015] The present invention is further configured as follows: the thickness of the steel carrier is 10 mm.

[0016] By adopting the above technical solution, its thickness can provide sufficient structural strength to ensure stable bearing of the weight and force of the anchor cable and related equipment during the drilling process, while maintaining good anti-deformation ability under complex geological conditions.

[0017] The present invention is further configured as follows: the length of the hydraulic extrusion sleeve is 50 mm, and the length of the hydraulic extrusion sleeve exposed outside the steel wire rope is not less than 100 mm.

[0018] By adopting the above technical solution, the shorter hydraulic extrusion sleeve can ensure flexible operation during the construction process, and facilitate quick installation and fixation. The longer exposed length of the wire rope provides sufficient adjustment space for the anchor cable, which can better adapt to different construction environments and operation requirements.

[0019] The present invention is further configured as follows: before the secondary drilling, the geology of the drilling position is re-tested again, and the secondary drilling method is determined based on the geological test results. If the geology is a hard stratum or a construction environment that requires large-diameter hole expansion, the first drilling method is used; if the space at the outlet end is small and conventional pull-back hole expansion operations cannot be performed, the second drilling method is used.

[0020] By adopting the above technical solution, if the geology is a hard formation or a construction environment that requires large-diameter hole expansion, the first drilling method is adopted, which can adapt to the high torque and large thrust requirements of the hard formation. By segmented hole expansion and real-time monitoring of the drilling trajectory, the hole expansion process is ensured to be smooth, the risk of blockage in the hole is reduced, and the construction efficiency and hole quality are effectively improved. If the space at the outlet end is small and conventional pull-back hole expansion operations cannot be performed, the second drilling method is adopted, which can provide greater propulsion power and drilling torque, and is suitable for construction in hard rock formations or complex spatial conditions. At the same time, it avoids deviation from the guide hole in soft soil formations to ensure the accuracy and stability of construction.

[0021] The present invention is further configured as follows: the length of the high-pressure pipe connecting the high-pressure grouting pump and the drilling rig for conveying high-pressure injection liquid is less than or equal to 50m.

[0022] By adopting the above technical solution, the length of the high-pressure pipe connecting the high-pressure grouting pump and the drilling rig for conveying high-pressure injection liquid is less than or equal to 50 meters, which can effectively reduce the pressure loss and ensure that the high-pressure injection liquid maintains sufficient pressure during the transportation process, thereby ensuring the effect and quality of the jet hole expansion.

[0023] In summary, the present invention has the following beneficial effects: first, the equipment is fully prepared and highly targeted, and the drill rod, steel bearing body, hydraulic extrusion sleeve and other components work together to ensure stable drilling of the anchor cable; secondly, the measurement and layout are accurate, and the total station, level and MWD wireless inclinometer and other equipment are used, combined with the drill rod inclination angle adjustment formula and the directional drilling trajectory design formula, to achieve accurate arrangement of anchor hole positions and real-time correction of drilling trajectories, thereby improving construction accuracy; finally, the staged drilling process is scientific and reasonable, and the first-level drilling is combined with the second-level drilling. The expansion method is flexibly selected according to different geological conditions, effectively coping with hard formations and complex spatial environments, ensuring the quality of the hole, and from equipment disassembly to high-pressure rotary spraying slurry withdrawal and pulling rod, and then to anchor cable tensioning and locking, each link is closely connected to ensure safe and efficient construction, and finally achieve stable anchoring of the anchor cable under complex geological conditions, provide reliable prestressing guarantee for slope or foundation pit support, and improve overall stability and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the process flow of the rapid construction process of the full-length enlarged head anchor cable rotary spray hole expansion in an embodiment of the present invention;

[0025] Figure 2 is a cross-sectional view of a schematic structural diagram of a full-length enlarged head anchor cable in an embodiment of the present invention;

[0026] Figure 3 is a cross-sectional view of a steel carrier in an embodiment of the present invention;

[0027] Figure 4 It is a structural schematic diagram of the anchor cable, the steel bearing body and the hydraulic extrusion sleeve in an embodiment of the present invention.

[0028] In the figure: 1. Steel bearing body; 2. Hydraulic extrusion sleeve; 3. Steel strand; 4. Drill rod guide hole; 5. Rotary jet hole expansion aperture; 6. Rotary jet grouting body; 7. Corrugated casing; 8. Anchor section; 9. Free section; 10. Tensioning section. DETAILED DESCRIPTION

[0029] The following is combined with Figure 1 —4 The present invention is described in further detail.

[0030] Example

[0031] like Figure 1 - Figure 4 As shown, a rapid construction process for expanding a hole by using a full-length enlarged head anchor cable through rotary spraying includes the following steps:

[0032] S1. Equipment preparation: The drilling rig includes a drill rod, a steel carrier 1 is fixedly provided on the guide hole of the drill rod, a hydraulic extrusion sleeve 2 is provided on the steel carrier 1, and an anchor cable is provided on the hydraulic extrusion sleeve 2;

[0033] Each anchor cable is composed of 4 bundles of steel strands 33 and is fixed on the drill pipe by a 10mm thick steel carrier 1 and a hydraulic extrusion sleeve 2. The anchor cable includes a tensioning section 10, a free section 9 and an anchoring section 8. The tensioning section 10, the free section 9 and the anchoring section 8 are different areas of the anchor cable respectively. The outer edge of the free section 9 is sleeved with a bellows casing. The anchor cable hole depth should be 500mm longer than the designed length of the anchor cable. The free section 9 anchor cable is sealed and protected by a bellows casing. A surplus of 100mm should be reserved for the length of the tensioning section 10.

[0034] The tensioning section 10 is the portion of the anchor cable outside the hole, which is used for tensioning operation and locking prestress, and has the operation of tensioning equipment. After the grouting strength reaches the design requirement, the anchor cable is prestressed and locked by the tensioning equipment. The free section 9 is the portion of the anchor cable in the hole that is not anchored to the soil, and during the tensioning process, the steel strand 3 of the free section 9 can freely stretch in the corrugated pipe casing, thereby generating elastic deformation to form prestress. The anchoring section 8 is the portion of the anchor cable that is tightly combined with the rock and soil. The prestress of the anchor cable is transferred to the rock and soil through the grouting body, and is formed as a whole with the soil through grouting, so as to ensure that the anchor cable will not slide or loosen under working conditions.

[0035] The adjacent anchor cables are constructed by adopting a 30° / 35° staggered construction method to improve the overall stability and safety of the slope or foundation pit support.

[0036] S2. Measurement and setting out: Determine the plane position and elevation position of the anchor hole in the deep foundation pit according to the design drawings, and use iron rods and paint to mark the specific plane position of the anchor hole. At the same time, the plane position of the anchor hole is installed according to the designed hole position inclination. The foundation platform for placing the drilling rig;

[0037] Use the total station to determine the specific location of the anchor hole, and use the level to measure the elevation of the anchor hole to ensure that the vertical position of the anchor hole meets the design requirements. When determining the location of the anchor hole, at least two operators are required. The operation of the total station requires one person to operate the instrument, including centering, leveling, aiming at the target, reading data, etc., and the other person needs to hold a prism at the anchor hole position to ensure that the prism is aligned with the total station and adjust the position according to the instructions of the instrument. In the subsequent drilling process, the MWD wireless inclinometer technology needs to be used to measure the drilling direction, bevel angle and temperature in real time;

[0038] The specific elevation of the anchor hole obtained by the level also requires attention: the verticality deviation of the anchor (including prestressed anchor cables and anchor steel bars) should not be greater than 5%; the allowable deviation of the hole depth is ±100mm, and the drilling depth should exceed the design length of the anchor by not less than 0.5m; the allowable vertical deviation error of the hole position is ±50mm; the drilling should be carried out according to the position, hole diameter, length and direction shown in the design drawing, and the construction method with little disturbance to the surrounding strata of the drilling hole should be selected, and the drilling should maintain a straight line and a set orientation; before the anchor rod body is placed in the hole or grouting, the rock powder, soil debris and accumulated water in the hole should be cleared; then the specific hole position of the anchor cable is measured with a steel ruler, and the plane position of the hole is determined by accurately measuring the distance.

[0039] Drill pipe inclination angle adjustment formula:

[0040] ∠ 总 =arctan(H / L)±∠ 地 +C

[0041] ∠ 总 is the drilling angle after the drill rod is adjusted, H is the vertical depth of the drill hole, L is the drilling length, ∠ 地 is the angle adjusted according to geological conditions, and C is the drilling angle adjustment caused by temperature changes.

[0042] Use the on-site geological survey report to understand the rock or soil properties in the construction area. For soft rock or unstable strata, 地 The value may be smaller, generally 9°-10°, to reduce the deviation during drilling; for hard rock or stable formations, ∠ 地 The value needs to be appropriately increased, generally 13°-14°, to adapt to the stability of the formation, and test drilling is required before construction to measure the actual deflection of the drilling trajectory and adjust the ∠ 地 value to ensure that the drilling trajectory meets the design requirements.

[0043] Before construction, the vertical depth and drilling length of the borehole are determined according to the design drawings and geological conditions, and the theoretical inclination angle is calculated using the formula. According to the geological exploration data, ∠ 地 The specific value of the drilling angle is determined by the drilling angle. For example, a smaller inclination angle may be required in soft rock formations, while a larger inclination angle may be required in hard rock formations. In addition, temperature changes will affect the physical properties of the drill pipe. The drilling angle adjustment caused by temperature changes is usually fine-tuned according to the temperature changes on site, generally ranging from ±0.1° to ±0.3°. If the temperature change on the construction site exceeds 10°C, the fine-tuning range may need to be expanded to between ±0.1° and ±0.5°. Finally, during the drilling process, the MWD wireless inclinometer is used to measure the inclination angle of the drill pipe in real time, and the drilling direction of the drilling rig is adjusted according to the measurement results.

[0044] The specific operation process of the drill pipe inclination angle adjustment formula is to determine the values ​​of H and L according to the design requirements, calculate the theoretical inclination angle arctan (H / L), and determine ∠ 地 The specific value of , and the temperature change on site needs to be considered, the C value is estimated, and the calculated ∠ 总 Input the drilling rig control system to adjust the initial inclination of the drill pipe.

[0045] During the drilling process, the MWD wireless inclinometer is used to monitor the inclination of the drill pipe in real time, and the drill pipe angle is dynamically adjusted according to the measurement results.

[0046] Calculation formula for directional drilling trajectory design:

[0047] L=H / si nα

[0048] L is the drilling length and H is the vertical depth of the borehole.

[0049] During the construction process, when the drilling length is long, it is usually necessary to drill in sections. After each section, the actual drilling length and inclination are measured to check whether they meet the design requirements. If a deviation is found between the actual trajectory and the designed trajectory during the drilling process, the deviation can be corrected by adjusting the inclination of the drill rod or the drilling length.

[0050] The specific operation process of the drill rod inclination angle adjustment formula is as follows: during the drilling process, the drilling length L is dynamically adjusted according to the actual measured inclination angle α to ensure that the borehole reaches the designed depth. Every 20 meters of drilling, the actual trajectory is measured using an inclinometer to check the drilling length and inclination, and correction is performed when necessary.

[0051] S3. Primary drilling: After the drilling rig is installed on the foundation platform, the angle of the drill rod is corrected and the anchor cable is compared with the drilling depth. The high-pressure water pump is started to inject water at a first water injection speed, and the drilling rig is started until the drill bit casing moves forward and the drill rod is drilled through the steel carrier 1 with the anchor cable;

[0052] The drill rod is drilled through the steel carrier 1 with the anchor cable, the anchor cable is fixed to the steel carrier 1 through the hydraulic extrusion sleeve 2, the steel carrier 1 is fixed to the drill rod through the drill rod guide hole 4, and the drill rod is drilled through the steel carrier 1 with the anchor cable.

[0053] Preferably, the length of the hydraulic extrusion sleeve 2 is 50 mm, and the length of the steel wire rope exposed outside the hydraulic extrusion sleeve 2 is not less than 100 mm.

[0054] After the first-level drilling is completed, it is necessary to check the wear of the drill rod and drill bit to ensure that the equipment is in good condition. In addition, the angle and position of the drill rod need to be rechecked multiple times according to the design requirements to ensure that the drill rod is consistent with the design trajectory of the second-level drilling. If the hole diameter needs to be enlarged, replace it with an expansion drill bit suitable for the second-level drilling, or adjust the hole diameter of the adjustable diameter drill bit. Finally, adjust the drilling pressure, speed and mud parameters of the drilling rig to meet the construction requirements of the second-level drilling.

[0055] After the first-level drilling is completed, first remove the drill bit and replace it with a hole-reaming drill tool suitable for the second-level drilling. Adjust the drill rod and equipment to ensure that the drill rod is firmly connected, and install a hollow stabilizer to ensure the stability of the drill tool. Start the drilling rig, use high-pressure mud to drive the power drill tool, and use the screw motor to drive the hole reamer to rotate forward to expand the hole. During the hole expansion process, it is necessary to reasonably control the drilling pressure and speed according to the formation conditions and equipment capabilities to ensure the hole expansion efficiency and hole wall stability. At the same time, pay attention to the smooth circulation of mud, discharge drill cuttings in time, and avoid blockage in the hole. After each hole expansion, check the hole diameter and hole wall quality. If necessary, adjust the mud formula or increase the number of hole washing times to ensure the quality of the hole.

[0056] After completing step S3, it is necessary to check the wear of the drill rod and drill bit to ensure that the equipment is in good condition, check the angle and position of the drill rod to ensure that it is consistent with the designed trajectory of the secondary drilling, and if the hole diameter needs to be enlarged, it is also necessary to adjust the hole diameter of the drill bit or replace the reaming drill bit.

[0057] S4. Secondary drilling: During the process of advancing the drill rod and the high-pressure automatic rotating nozzle, according to the pre-determined design position of the anchor hole, when the drill rod and the high-pressure automatic rotating nozzle approach the design position or reach the design position, they advance forward slowly accordingly to achieve the enlarged hole diameter at the design position of the anchor hole;

[0058] Before secondary drilling, the geology of the drilling location needs to be re-tested. The secondary drilling method is determined based on the geological test results. If the geology is hard or a large-diameter hole expansion is required, the first drilling method is used. If the exit space is small and conventional pull-back expansion operations cannot be performed, the second drilling method is used.

[0059] The first drilling method is used in hard formations or construction environments that require large-diameter hole expansion. The torque and axial tension of the drilling rig are appropriate, but attention should be paid to the control of torque and tension during construction in hard formations. After the first-level drilling construction is completed, remove the guide drill bit, replace it with a reverse hole expansion drill bit and a swivel joint, connect the hole expansion drill bit to the pullback drill rod through the swivel joint, use the drilling rig to pull back and rotate the drill rod, so that the hole expansion drill bit cuts the hole wall during the pullback process, gradually expanding the hole diameter. According to the formation conditions and the drilling rig capacity, reasonably adjust the drilling pressure and speed to ensure a smooth hole expansion process and maintain The mud circulation is smooth to ensure that the drill cuttings are discharged in time and reduce the risk of blockage in the hole. For long-distance or large-diameter hole expansion, the segmented hole expansion method is adopted. The hole diameter and hole wall quality are checked after each section of hole expansion. During the hole expansion process, the drilling trajectory and equipment operation status are monitored in real time. The drill rod angle or hole expansion parameters are adjusted when necessary. The drive head is strictly prohibited from reversing during the hole expansion process to prevent damage to the drill tool. In hard formations, the hole expansion speed should be appropriately reduced to avoid excessive impact on the drill tool. After the hole expansion is completed, the residue in the hole needs to be cleaned to ensure that the hole wall is smooth and reduce the resistance to subsequent construction.

[0060] When constructing in hard formations, a lower rotation speed and a higher drilling pressure are required. When drilling into hard rock, the rotation speed can be controlled at 40-60r / min, and the drilling pressure is adjusted according to the hardness of the formation. During the construction process, torque monitoring equipment should be equipped to monitor the drill bit torque in real time to avoid exceeding the maximum output torque of the equipment. When the torque approaches the limit of the equipment, the drilling pressure should be appropriately reduced or the rotation speed should be increased to prevent excessive wear of the drill bit or damage to the equipment. During the hole expansion process, the slow advancement and slow rotation modes should be maintained. The pulling force is generally controlled at 8-9MPa, and the maximum torque does not exceed 13MPa.

[0061] Segmented hole expansion: the borehole is divided into several sections according to design requirements and geological conditions. The length of each section is usually determined according to equipment capacity and construction needs. During the hole expansion process, the hole expansion operation is carried out section by section. After each section is completed, the hole diameter and hole wall quality are checked to ensure that they meet the design requirements.

[0062] The second drilling method is used when the exit space is small and conventional pull-back expansion operations cannot be performed. In hard rock formations or construction conditions that require high torque and high thrust, the second drilling method can provide greater propulsion power and drilling torque. After the first-level drilling construction is completed, remove the guide drill bit and replace it with a forward expansion drill tool, including an expander, a mud motor, a stabilizer, etc. The expansion drill tool is connected to the drilling rig through the drill pipe, and the stability and sealing of the drill pipe are ensured. Start the mud pump, deliver high-pressure mud through the drill pipe, drive the mud motor to rotate, and drive the expander to expand forward. According to the design requirements, expand the hole step by step to the required aperture. During the expansion process, the drilling pressure and speed need to be controlled to ensure the expansion efficiency and hole wall stability. The second drilling method is easy to deviate from the guide hole in soft soil formations, so it is not recommended to use it in soft soil formations. During the expansion process, the mud performance needs to be strictly controlled to ensure that the mud has good carrying capacity and wall protection effect. The expansion drill tool needs to select a suitable type according to the formation conditions, such as a cone type, roller type or composite expander.

[0063] S5. Disassembly: When the steel carrier 1 and the anchor cable are drilled to the designed position, the high-pressure rotary nozzle is closed to unload the steel carrier 1 and the anchor cable.

[0064] S6. Retract the high-pressure rotary spray slurry and pull out the drill rod: After the steel carrier 1 and the anchor cable are unloaded, reopen the high-pressure rotary spray head and retreat steadily at a low speed to the outer end of the anchoring section 8, then close the high-pressure rotary spray head and pull out the drill rod.

[0065] S7. Anchor cable tensioning and locking: Anchor cable tensioning can be carried out 14 days after anchor cable grouting is completed and the grouting body and crown beam concrete reach 75% of the design strength. The tensioning force is 1.1 times the design tension value. After the tensioning test is passed, the load is unloaded to the locking value to lock the load.

[0066] According to the design requirements of the construction drawings and the type of anchor cable, the removal scope of the anchor cable should be clearly defined, including the location and length of the anchor cable and whether it needs to be completely or only partially removed. Before removal, the prestress in the anchor cable should be gradually released, and the prestress should be released slowly to avoid sudden release that may cause structural vibration or damage. Use hydraulic shears, cutting tools or pliers to remove the fixing parts of the anchor cable. If the anchor cable adopts a detachable core design, the anchor cable and the fixing parts can be released by mechanical pulling or chemical methods. For conventional anchor cables, they can be cut off with cutting tools and then removed section by section. For detachable core anchor cables, such as "U"-shaped detachable core anchor cables, the steel strand (3) can be pulled out of the rod body by mechanical strong pulling. For hot-melt detachable core anchor cables, the hot-melt anchor can be heated by electricity, and the steel strand (3) can be pulled out after the core removal is completed.

[0067] The diameter of the free hole section 9 is φ180 mm, and the diameter of the anchoring section 8 is expanded to φ500 mm.

[0068] The high-pressure jet hole expansion can use cement slurry. When the cement slurry hole expansion process is adopted, the hole should be expanded up and down at least twice. The water-cement ratio of the cement slurry is 1.0-1.5. During the supplementary injection process, the hole mouth returns to the slurry, and the injection pressure needs to be increased. If leakage occurs, the nozzle aperture needs to be reduced or an accelerator needs to be added. The injection pressure of the high-pressure jet hole expansion is not less than 20Mpa, the nozzle feed speed is 10-25cm / min, and the nozzle speed is 5-15r / min. The length of the high-pressure pipe connecting the high-pressure grouting pump and the drilling rig for conveying high-pressure injection liquid is less than or equal to 50m.

[0069] The nozzle should rotate evenly, be lifted or lowered evenly, and perform high-pressure jet expansion from top to bottom or from bottom to top. The overlap length of the jet pipe when lifted or lowered in sections shall not be less than 100 mm.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A rapid construction process for expanding the hole by rotary spraying of full-length enlarged head anchor cable, characterized in that: The following steps are involved: S1. Equipment preparation: The drilling rig includes a drill rod, a steel carrier (1) is fixedly provided on the guide hole of the drill rod, a hydraulic extrusion sleeve (2) is provided on the steel carrier (1), and an anchor cable is provided on the hydraulic extrusion sleeve (2); S2. Measurement and setting out: Determine the plane position and elevation position of the anchor hole in the deep foundation pit according to the design drawings, and use iron rods and paint to mark the specific plane position of the anchor hole. At the same time, the plane position of the anchor hole is installed according to the designed hole position inclination. The foundation platform for placing the drilling rig; S3. Primary drilling: After the drilling rig is installed on the foundation platform, the angle of the drill rod is corrected and the anchor cable is compared with the drilling depth, the high-pressure water pump is started to inject water at a first water injection speed, and the drilling rig is started until the drill bit casing moves forward and the drill rod is drilled through the steel carrier (1) with the anchor cable; S4. Secondary drilling: During the process of advancing the drill rod and the high-pressure automatic rotating nozzle, according to the pre-determined design position of the anchor hole, when the drill rod and the high-pressure automatic rotating nozzle approach the design position or reach the design position, they advance forward slowly accordingly to achieve the enlarged hole diameter at the design position of the anchor hole; S5. Disassembly of the steel carrier (1) and the anchor cable: When the steel carrier (1) and the anchor cable are drilled to the designed position, the high-pressure rotary nozzle is closed to unload the steel carrier (1) and the anchor cable; S6. The high-pressure rotary spraying slurry is retreated and the drill pipe is pulled out: After the steel carrier (1) and the anchor cable are unloaded, the high-pressure rotary spray head is reopened and the low-speed stable retreat is made to the outer end of the anchoring section (8), and then the high-pressure rotary spray head is closed and the drill pipe is pulled out; S7. Anchor cable tensioning and locking: Anchor cable tensioning can be carried out 14 days after anchor cable grouting is completed and the grouting body and crown beam concrete reach 75% of the design strength. The tensioning force is 1.1 times the design tension value. After the tensioning test is passed, the load is unloaded to the locking value to lock the load.

2. According to claim 1, a rapid construction process for expanding the hole by rotary spraying of a full-length enlarged head anchor cable is characterized in that: Each anchor cable is composed of four bundles of steel strands (3), a steel carrier (1) and a hydraulic extrusion sleeve (2) are fixed on the drill rod, and the anchor cable comprises a tensioning section (10), a free section (9) and an anchoring section (8), wherein the tensioning section (10), the free section (9) and the anchoring section (8) are different regions of the anchor cable, respectively, and the outer edge of the free section (9) is sleeved with a corrugated tube sleeve.

3. A rapid construction process for expanding the hole by rotary spraying of full-length enlarged head anchor cable according to claim 2, characterized in that: When constructing adjacent anchor cables, a 30° / 35° staggered arrangement is adopted.

4. A rapid construction process for expanding the hole by rotary spraying of full-length enlarged head anchor cable according to claim 3, characterized in that: The anchor hole depth should be 500 mm longer than the designed length of the anchor. The free section (9) of the anchor should be sealed and protected by a corrugated tube casing. A surplus of 100 mm should be reserved for the length of the tensioning section (10).

5. The rapid construction process for expanding the hole by rotary spraying of full-length enlarged head anchor cable according to claim 3 is characterized in that: The steel carrier (1) has a thickness of 10 mm.

6. The rapid construction process for expanding the hole by rotary spraying of full-length enlarged head anchor cable according to claim 1 is characterized in that: The length of the hydraulic extrusion sleeve (2) is 50 mm, and the length of the steel wire rope exposed outside the hydraulic extrusion sleeve (2) is not less than 100 mm.

7. The rapid construction process for expanding the hole by rotary spraying of full-length enlarged head anchor cable according to claim 1 is characterized in that: Before the secondary drilling, the geology of the drilling location is re-tested again, and the secondary drilling method is determined based on the geological test results. If the geology is a hard stratum or the construction environment requires large-diameter hole expansion, the first drilling method is used. If the space at the exit end is small and conventional pull-back hole expansion operations cannot be performed, the second drilling method is used.

8. The rapid construction process for expanding the hole by rotary spraying of full-length enlarged head anchor cable according to claim 1 is characterized in that: The length of the high-pressure pipe connecting the high-pressure grouting pump and the drilling rig for conveying high-pressure injection liquid is less than or equal to 50m.

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