Construction method for positioning prestressed reinforcement of super-long air pile anti-floating anchor rod

Abstract

The application discloses a positioning construction method for prestressed reinforcement of an ultra-long air pile anti-floating anchor rod, and relates to the technical field of construction methods for anti-floating anchor rods. The anti-floating anchor rod group comprises an anchor rod and a sleeve rod. The construction method comprises the following steps: 1, construction preparation; 2, anchor rod hole forming, the anchoring section of the anchor rod enters the bearing stratum; 3, grout injection, after the grout is prepared, the grout is injected by means of pump pressure in the drill rod; 4, anchor rod hole entering, the anchor rod and the sleeve rod are integrally vertically lowered into the hole; after being lowered to the design elevation, the sleeve rod is reversely rotated and removed; 5, correction and positioning, the RTK system automatically acquires the real-time three-dimensional coordinates of the top of the anchor rod, and compares the real-time three-dimensional coordinates with the design point coordinates; 6, grout supplementing and protection, the grout supplementing process and the anchor rod end part are prevented from being disturbed after the grout supplementing; and 7, end chiseling. The method realizes the effects of non-dewatering construction, material recycling and reuse, high-precision intelligent positioning, simplified construction process, shortened construction period and improved structural anti-floating performance.

Description

Technical Field

[0001] This invention relates to the field of anti-buoyancy anchor construction technology in building engineering, specifically to a method for positioning prestressed steel reinforcement in ultra-long hollow pile anti-buoyancy anchors. Background Technology

[0002] In the construction of anti-buoyancy anchor bolts in the basements of high-rise buildings, many sites have high groundwater levels, making overall dewatering impossible. This results in the anchor bolt construction surface being above the stable groundwater level, leading to ultra-long empty pile segments that can reach 9 meters in length. The unique construction environment of these ultra-long empty pile segments causes many inherent defects in traditional anti-buoyancy anchor bolt construction techniques, seriously affecting construction quality, efficiency, and project economy. Specifically, there are four core technical problems: Technical Problem 1: Dewatering during construction leads to grout loss, compromising anchor bolt anchoring quality. Traditional construction methods typically employ a "dewatering first, construction later" approach to mitigate the impact of groundwater on borehole formation and grouting. However, dewatering continuously disturbs the surrounding soil and water structure, causing the formed cement grout inside the anchor hole to be lost with groundwater, resulting in voids and loosening. This significantly reduces the density of the grout and the bond strength between the anchor bolt and the soil, directly leading to substandard anchor bolt bearing capacity and serious quality risks in the overall anti-buoyancy structure.

[0003] Technical Issue 2: Positioning ultra-long, unsupported piles requires significant material consumption, resulting in substantial waste and poor economic efficiency. For ultra-long, unsupported pile sections (up to 9m), the prestressed steel reinforcement is suspended without effective support, making direct and precise positioning impossible. Traditional methods require the installation of long-distance positioning auxiliary rods matching the length of the unsupported pile. These auxiliary rods are disposable components, non-recyclable after construction, and consume large quantities of high-quality profiles such as precision-rolled threaded steel, leading to extremely high material wastage and significantly increasing construction costs.

[0004] Technical Problem 3: Low positioning accuracy and poor construction efficiency of anchor bolt tops, prone to misalignment. Traditional anchor bolt positioning relies on a crude construction method of manual on-site layout, string alignment, and visual inspection. Errors in manual measurement, layout deviations, and line-of-sight deviations are unavoidable. For batch deployments of anti-buoyancy anchor bolt groups, manual positioning is extremely inefficient and prone to problems such as anchor bolt plane misalignment, excessive verticality, and excessive burial depth deviation, leading to uneven stress on the anchor bolt group and affecting the overall anti-buoyancy system's coordinated load-bearing performance.

[0005] Technical Issue 4: The removal of auxiliary rods in the later stages is cumbersome, requires significant labor, and has a long construction period. Traditional methods of installing long-distance positioning auxiliary rods expose them within the anchor structure after installation, making direct concealment impossible. Removal requires multiple manual processes, including cutting, grinding, and cleaning. This subsequent process is labor-intensive and costly, and the removal process can easily disturb the existing anchor rods and grouting structure, significantly extending the overall construction period and hindering efficient project progress. Summary of the Invention

[0006] The purpose of this invention is to provide a method for positioning prestressed steel reinforcement in anti-buoyancy anchor rods for ultra-long hollow piles. This method solves the technical problems existing in the prior art, such as poor anchoring quality of anchor rods, inability to recycle auxiliary rods, low positioning accuracy of the top of the anchor rods, poor efficiency, and long construction period for cutting and dismantling auxiliary rods later.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for positioning prestressed steel reinforcement in ultra-long hollow pile anti-buoyancy anchor bolts, wherein the anti-buoyancy anchor bolt group includes anchor bolts and sleeve bolts; the construction method includes the following steps: Step 1: Construction preparation, calculating the length, diameter, and spacing of the anchor bolts; Step two, anchor bolt drilling: First, calculate the effective drilling depth to ensure that the anchor bolt's anchoring section stably enters the bearing layer; then, drill the hole using a drilling rig. During the drilling process, measure the hole depth in real time and dynamically adjust the anchor bolt length when the stratum changes. Step 3, grout injection: First, prepare the grout using plain cement grout with a water-cement ratio controlled between 0.5 and 0.55; then, add the corresponding water and cement to the grout mixer for mixing; finally, inject the grout using a pump inside the drill rod. Step 4: Insert the anchor bolt into the hole. Install the sleeve onto the end of the anchor bolt using threads. Lower the anchor bolt and sleeve vertically into the hole as a whole. During the lowering process, use a level and the scale markings on the sleeve to monitor the positioning in real time, ensuring that the lower end of the anchor bolt accurately reaches the design depth, with the deviation controlled within ±50mm. After lowering to the design elevation, rotate the sleeve in the opposite direction to remove it. Step 5, Correction and Positioning: First, perform point calibration of the RTK system, and vertically fix the RTK mobile station centering rod to the exposed end of the top of the anchor rod; the RTK system automatically acquires the real-time three-dimensional coordinates of the top of the anchor rod and compares them with the design layout coordinates; if the plane deviation exceeds the allowable range for construction, the anchor rod position is finely adjusted in time. Step 6, Grouting Protection: After the grouting operation is completed and before the grout has initially set, grouting should be carried out in a timely manner to ensure the fullness of the grouting; during and after the grouting process, prevent the anchor bolt end from being disturbed. Step 7: End chiseling. Before the earthwork excavation work reaches the design elevation, the excess grout at the end of the anchor rod is chiseled to ensure that it is accurately trimmed to the design elevation.

[0008] Preferably, in step one, construction preparation also includes organizing training for all workers, clearly pointing out the key control points in construction; testing the cement's setting time, stability, and 3-day and 28-day compressive strength according to technical requirements; and selecting and deploying drilling rigs.

[0009] Preferably, in step two, for rock formations, a down-the-hole drill rig paired with an eccentric impact drill is used; for silty clay, sandy or soil areas, a long auger drill rig is used for pre-hole drilling paired with high-pressure jet grouting for borehole enlargement; for gravelly or easily collapsed formations, casing drilling is used, with casing being installed while drilling.

[0010] Preferably, in step two, the drilling depth exceeds the designed anchoring section length by 50mm to 100mm.

[0011] Preferably, in step three, the mixing time of the cement slurry in the mortar mixer shall not be less than 2 minutes; when mixing, add a certain amount of water first, then slowly pour in the cement, and use a low-speed mixing mode. After the cement is completely dissolved in the water, increase the mixing speed to the rated speed so that the slurry forms a uniform suspension system. After mixing, let it stand for 30 seconds to allow the air bubbles to be naturally discharged before grouting.

[0012] Preferably, in step four, the lowering termination line is first precisely marked on the sleeve according to the designed total length of the anchor rod and the elevation of the borehole. The lowering position of the anchor rod is determined by measuring the scale markings with a level. Before lowering, the level is set up stably and leveled so that its line of sight is aligned with the initial scale on the sleeve. As the anchor rod is slowly lowered, the observer reads the scale changes on the sleeve in real time through the level. When the termination scale line coincides with the designed elevation line of the borehole, a stop signal is immediately issued.

[0013] Preferably, in step four, high-precision miniature tilt sensors, three-dimensional attitude sensors, and depth displacement sensors are symmetrically deployed on the inner side of the anchor bolt. Throughout the entire process of anchor bolt hoisting and lowering, the high-precision miniature tilt sensors, three-dimensional attitude sensors, and depth displacement sensors continuously collect key parameters such as anchor bolt lowering depth, overall verticality, and three-dimensional tilt angle in real time. The measured data is uploaded in real time to the intelligent monitoring platform and finite element simulation calculation system at the construction site via a wireless transmission module. After receiving the measured data at the site, the finite element simulation calculation system automatically starts the model geometry refinement iterative correction program to optimize and correct the parameters of the standardized theoretical model established in the early stage. The system will replace the theoretical geometric parameters in the model one by one according to the actual buried depth, three-dimensional tilt angle, and overall verticality of the anchor bolt measured at the site, accurately reconstructing the physical geometry, spatial layout coordinates, rod bending shape, and buried depth boundary conditions of a single anchor bolt. At the same time, the contact interface range, contact angle, and coupling boundary parameters between the anchor bolt and the surrounding rock and soil and grouting body are simultaneously corrected.

[0014] Preferably, when the verticality deviation, planar offset, and depth deviation of the anchor bolt are within the allowable range of the specifications, the model is accurately updated based on the measured parameters to ensure that the mechanical calculation boundary conforms to the actual working conditions; when the measured deviation exceeds the controllable threshold, the finite element simulation calculation system immediately issues an early warning, and synchronously feeds back the deviation data and correction suggestions. On-site construction personnel can adjust the hoisting angle, lowering speed, and support positioning method in a timely manner to recalibrate the anchor bolt posture until the parameters meet the standards before completing the final fixation.

[0015] Preferably, in step five, the raw data of the three-dimensional absolute coordinates of the top of each anchor rod measured by RTK are exported in batches. The data is preprocessed and screened to remove abnormal data caused by satellite signal interference and human alignment errors. The compliant measured parameters are imported into the overall anti-buoyancy structure finite element model in batches through the data interface, and the original theoretical design point coordinates are automatically replaced in batches to complete the spatial point reconstruction of all anchor rods in the field. After the model is accurately modeled, mechanical simulation calculation is performed to analyze the impact of position deviation on the coordinated force, load distribution and overall anti-buoyancy bearing capacity of the anchor rod group. Based on the optimal correction displacement and force balance state simulated by the model, the correction direction, correction displacement and fine-tuning construction technology of the substandard anchor rods are determined, and accurate correction is completed without disturbing the surrounding existing anchor rods, soil and rock and grouting structure.

[0016] Preferably, after the correction construction is completed, the coordinates of the points are re-measured using RTK, and the spatial parameters of the anchor bolts are updated by importing them into the finite element model for the second time. At the same time, the boundary conditions of the soil and rock mass, the coupled force boundary of the anchor bolt group, and the force transmission calculation model in the area of ​​the point that exceeds the standard are corrected to eliminate the mechanical calculation error caused by the point deviation.

[0017] This invention addresses the first technical problem: solving the issue of grout loss and poor anchor bolt anchoring quality caused by dewatering during construction. This invention abandons the traditional "dewatering before construction" process, adapting to high-water-level construction conditions without dewatering. It employs a bottom-up grouting process using pump pressure inside the drill rod, combined with pre-setting grouting, which effectively fills the voids inside the anchor hole, preventing grout loss, voids, and loosening defects caused by groundwater erosion. This significantly improves the density of the grout, ensuring the bond strength between the anchor bolt anchoring section and the soil, fundamentally improving the anchor bolt anchoring quality and eliminating safety hazards in the anti-buoyancy structure.

[0018] Addressing the second technical problem: Solving the issue of non-recoverable and wasteful materials associated with ultra-long, empty pile positioning auxiliary rods. This invention replaces traditional disposable positioning auxiliary rods with detachable threaded connecting sleeve rods. After the anchor bolt is positioned and lowered, the sleeve rod can be directly disassembled by reverse rotation. After cleaning and maintenance, the sleeve rod can be reused repeatedly, eliminating the need for large quantities of high-strength threaded steel and other consumables. This completely solves the waste problem of disposable materials in traditional processes, significantly reducing engineering material costs and improving construction economy.

[0019] Addressing the third technical problem: resolving the issues of low positioning accuracy at the top of anchor bolts, poor efficiency of manual layout, and easy deviation of anchor points. This invention abandons the traditional rough manual layout method and combines precise depth control with a rod scale and level, real-time attitude monitoring by sensors, precise RTK three-dimensional coordinate correction, and intelligent correction technology using finite element simulation models. This achieves comprehensive and precise control over the anchor bolt burial depth, verticality, and planar position, with depth deviation controlled within ±50mm and planar deviation controlled within ±20mm. Simultaneously, it can complete anchor bolt position detection and correction in batches, significantly improving positioning construction efficiency, ensuring uniform anchor bolt arrangement and coordinated force distribution, and enhancing the overall stability of the anti-buoyancy structure.

[0020] Addressing technical issue four: Solving the problems of cumbersome post-installation removal procedures, high labor input, and long construction periods associated with auxiliary rods. The sleeve rod used in this invention can be disassembled immediately after the anchor rod is formed, eliminating the need for tedious removal procedures such as cutting, grinding, and cleaning after subsequent earthwork excavation. This significantly simplifies the construction process, reduces labor input and machinery operation costs, avoids disturbance to the formed anchor rod structure during later removal operations, effectively shortens the overall construction period, and is suitable for large-scale, high-standard batch construction scenarios of anti-buoyancy anchor rods.

[0021] Additional benefits: This invention integrates intelligent sensing and monitoring, finite element simulation iterative correction, and RTK high-precision positioning technology to achieve dynamic monitoring, deviation warning, and intelligent correction throughout the entire anchor bolt construction process. It can accurately reconstruct the actual force boundary of the anchor bolt, eliminate mechanical calculation errors caused by construction deviations, ensure the coordinated force balance of the anchor bolt group, and significantly improve the standardization and intelligence level of ultra-long hollow pile anti-buoyancy anchor bolt construction. It also enhances construction safety and engineering applicability, and can be adapted to various complex strata and high water level ultra-long hollow pile construction conditions. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the construction process of the present invention; Figure 2 This is a schematic diagram showing the connection state between the anchor rod and the sleeve rod of the present invention; In the diagram: 1. Anchor bolt; 2. Sleeve bolt. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings: like Figure 1 and Figure 2 The diagram illustrates a method for positioning prestressed steel reinforcement in ultra-long hollow pile anti-buoyancy anchor bolts. The anti-buoyancy anchor bolt group includes anchor bolts 1 and sleeve bolts 2. Anchor bolts 1 have threaded connections at their ends, and sleeve bolts 2 are threadedly connected to these connections. A limiting plate is installed on the anchor bolt 1, with the distance from the limiting plate to the other end of the anchor bolt 1 being the designed length. During installation, the sleeve bolt 2 is positioned when it rests against the end of the limiting plate, ensuring the accuracy of the depth below the anchor bolt 1.

[0024] The construction method includes the following steps: Step 1: Construction preparation. Calculate the length, diameter, and spacing of anchor bolt 1. Organize training for all workers, clearly outlining key control points during construction. Perform cement setting time, stability, and 3-day and 28-day compressive strength tests according to technical requirements. Select and deploy the drilling rig. Conduct safety education and training for all personnel involved in the operation, focusing on risk prevention measures at the construction site, especially safety regulations for drilling rig operation, precautions for temporary power supply, protective requirements for working at heights, and key aspects of pressure control during grouting. These points should be repeatedly emphasized to improve the safety awareness of all personnel.

[0025] Step two: Drilling of anchor bolt 1. First, calculate the effective drilling depth to ensure that the anchoring section of anchor bolt 1 stably enters the bearing layer. Then, drill the hole using a drilling rig. During the drilling process, measure the hole depth in real time, and dynamically adjust the length of anchor bolt 1 when the stratum changes. The drilling depth exceeds the designed anchoring section length by 50mm to 100mm; this excess depth is for sediment treatment space.

[0026] For rock formations, down-the-hole drills are used in combination with eccentric impact drills. With the help of high-pressure air for slag removal, the drilling speed is fast and the integrity of the borehole wall is guaranteed. It is especially suitable for hard formations such as moderately and strongly weathered granite.

[0027] For areas with silty clay, weak sand layers, or soil layers, a long spiral drilling rig is used for pilot hole preparation combined with high-pressure jet grouting for hole enlargement. This process can effectively improve construction efficiency while reducing mud pollution. Some improved long spiral drilling rigs are also equipped with air supply and dust suppression structures, which are in line with the concept of green construction.

[0028] For gravelly or easily collapsed formations, casing drilling is used, where casing is installed while drilling. This effectively avoids borehole collapse. In addition, factors such as drilling efficiency, site conditions, terrain, and economics must also be considered. For example, in confined spaces, lightweight equipment with flexible transport should be prioritized, while large-scale construction requires balancing the equipment's continuous operating capacity with cost control.

[0029] The drilling depth must adhere to the precise control principle of "one measurement per hole". Before construction, it is necessary to comprehensively review the elevation differences of the foundation structure, especially for independent columns, strip foundations and other parts, whose base elevation often differs from that of the large-area base slab. The effective drilling depth must be calculated for each hole in conjunction with the foundation drawing to ensure that the anchoring section of anchor rod 1 can stably enter the bearing layer required by the design.

[0030] In practice, the actual elevation of the foundation slab is used as the benchmark, and the designed anchorage length is superimposed, with a certain amount of space reserved for sediment treatment. During the drilling process, the hole depth can be manually checked using a measuring rope with a weight, and geological logging can be used to verify stratigraphic changes. If weak interlayers or abnormal geological conditions are found that do not conform to the exploration report, it is necessary to communicate with the design unit in a timely manner and dynamically adjust the anchor length to avoid insufficient anchorage force due to geological deviations.

[0031] Step three, grout injection. First, prepare the grout using plain cement grout made with PO 42.5 ordinary Portland cement. The water-cement ratio should be controlled within the range of 0.5 to 0.55. This ratio ensures grout fluidity and facilitates grouting operations while effectively balancing grout strength and shrinkage, preventing insufficient strength or shrinkage cracking later due to an excessively high water-cement ratio. During preparation, the cement must be re-inspected beforehand to ensure it is free of lumps and moisture; expired or substandard cement is strictly prohibited to guarantee grout quality from the source. Then, add the corresponding amount of water and cement to the grout mixer and mix. Finally, grout is injected using a pump pump inside the drill pipe.

[0032] The mixing time of cement slurry in the mortar mixer shall not be less than 2 minutes. When mixing, add a certain amount of water first, then slowly pour in the cement, and use a low-speed mixing mode. After the cement is completely dissolved in the water, increase the mixing speed to the rated speed so that the slurry forms a uniform suspension system. After mixing, let it stand for 30 seconds to allow the air bubbles to be released naturally before grouting.

[0033] Using pressure to propel grout from bottom to top to fill the anchor hole effectively removes air and residual soil, avoiding the problem of a full upper section and voids at the bottom that often occurs with traditional borehole grouting. During grouting, the pump pressure must be controlled and kept stable between 0.3 and 0.5 MPa. Too low a pressure will prevent grout from penetrating the borehole wall, while too high a pressure may cause borehole collapse or grout overflow and waste. The drill rod lifting speed must be synchronized with the grouting speed, always keeping the bottom of the drill rod submerged below the grout surface to prevent air from entering and forming a grout gap.

[0034] Grouting operations must be carried out continuously without interruption. If interruption occurs due to equipment failure or other special reasons, the drill rod must be immediately raised to the borehole opening, residual grout inside the drill rod cleaned, and then drilled back down to the bottom of the hole. Grouting should begin again from the bottom of the hole to ensure the continuity of the grouting. The grout should follow the principle of "stirring and using immediately." The grout, after being stirred, must be injected into the hole within 30 minutes. If left for too long, the grout will gradually lose its fluidity or even begin to set, which will not only cause grouting pipe blockage but also significantly reduce the strength of the grout. Backup mixing equipment and grouting pumps must be available at the construction site to deal with unexpected failures and ensure the continuity of operations.

[0035] During construction, grout test blocks must be prepared according to specifications, with no fewer than 6 blocks per set. Test blocks should be randomly sampled and prepared at the grouting site, and vibrated to simulate on-site grouting conditions. The frequency of test block preparation must be strictly adhered to: if fewer than 30 anchor rods are constructed per day, at least one set must be prepared daily; if more than 30 anchor rods are constructed per day, one additional set must be prepared for every 30 anchor rods constructed cumulatively. After 28 days of curing, the test blocks must undergo compressive strength testing. The test results must meet design requirements. If any strength fails to meet the requirements, non-destructive testing or load-bearing capacity testing must be immediately conducted on the corresponding batch of anchor rods to identify potential quality issues and ensure that the anchoring performance of each anchor rod meets the standards.

[0036] Step 4: Insert anchor rod 1 into the hole and install sleeve rod 2 onto the end of anchor rod 1 via thread. Lower anchor rod 1 and sleeve rod 2 vertically into the hole as a whole. During the lowering process, use a level and the scale markings on sleeve rod 2 to monitor the positioning in real time, ensuring that the lower end of anchor rod 1 accurately reaches the design depth with a deviation controlled within ±50mm. After lowering to the design elevation, rotate sleeve rod 2 in the opposite direction to remove it.

[0037] First, accurately mark the lowering termination line on the sleeve rod 2 according to the designed total length of the anchor rod 1 and the elevation of the borehole. Determine the lowering position of the anchor rod 1 by measuring the scale mark with a level. Before lowering, set up the level steadily and level it so that its line of sight is aligned with the initial scale on the sleeve rod 2. As the anchor rod 1 is slowly lowered, the observer reads the scale changes on the sleeve rod 2 in real time through the level. When the termination scale line coincides with the designed elevation line of the borehole, immediately issue a stop signal.

[0038] Specifically, after anchor bolt 1 is manufactured, it is smoothly lifted and lowered using a small-diameter long auger drill hook or a crane. During lifting, the force should be evenly distributed at multiple points to avoid bending and deformation of the bolt. If the bolt is found to be tilted or deviated during the lowering process, the lifting angle should be adjusted in time. If necessary, the bolt should be slightly lifted and lowered again until the positioning requirements are met.

[0039] During the separation of sleeve rod 2 from anchor rod 1, the auxiliary components must be kept stable to prevent displacement of the positioned anchor rod 1 due to excessive rotational force. The removed sleeve rod 2 should be promptly cleaned of surface dirt and impurities, and the thread wear should be checked. After confirming its integrity, it should be stored uniformly for future reuse.

[0040] Step 5, Correction and Positioning: First, perform point calibration of the RTK system, and vertically fix the centering rod of the RTK mobile station to the exposed end of the top of the anchor rod 1; the RTK system automatically acquires the real-time three-dimensional coordinates of the top of the anchor rod 1 and compares them with the design layout coordinates; if the plane deviation exceeds the allowable range for construction, the position of the anchor rod 1 is finely adjusted in time; the RTK system uses existing products.

[0041] Specifically, after anchor bolt 1 is inserted into the hole, top alignment and positioning using RTK is a crucial verification step to ensure that the planar position of anchor bolt 1 accurately meets the design requirements. This process is not adjusted after anchor bolt 1 is fully lowered, but rather during the lowering process or after it is in place. RTK is used to measure the top coordinates of anchor bolt 1 in real time to verify its matching degree with the design coordinates, thereby achieving dynamic calibration.

[0042] After anchor bolt 1 is slowly inserted into the borehole using hoisting equipment, the RTK mobile station centering rod is vertically fixed to the exposed top end of anchor bolt 1, ensuring a stable connection and vertical orientation. At this point, the RTK system should have completed the preliminary point calibration, successfully converting the WGS-84 coordinates to the local coordinate system used in the project, such as Beijing 54 or an independent coordinate system, to ensure that the measurement benchmark is consistent with the design drawings. The RTK system automatically acquires the real-time three-dimensional coordinates (X, Y, H) of the top of the anchor bolt and compares them with the design layout coordinates. If the planar deviation exceeds the allowable construction range, usually controlled within ±20mm, the position of anchor bolt 1 needs to be finely adjusted in a timely manner. This can be done through auxiliary supports or guide frames to correct the deviation and ensure its final positioning accuracy.

[0043] It is worth noting that during RTK measurements, it is essential to ensure a good satellite signal and avoid operating in areas with dense reinforced concrete or near tall obstacles to prevent multipath effects from affecting accuracy. Furthermore, to reduce human error, RTK equipment with tilt compensation should be used, and electronic bubble calibration and magnetometer alignment should be performed before measurement to improve the reliability of single-point measurements.

[0044] Step 6, Grouting Protection: After the grouting operation is completed and before the grout has initially set, timely grouting operation should be carried out to ensure the fullness of the grouting; during and after the grouting process, prevent the end of anchor bolt 1 from being disturbed.

[0045] Determining the grouting volume is not an arbitrary process, but rather requires comprehensive consideration of the specific geological conditions and the actual situation during the first grouting. Throughout the grouting process, it is essential to ensure continuous grouting operations without interruption to guarantee optimal grouting results.

[0046] Step 7: End Chipping. Before reaching the design elevation during earthwork excavation, the excess grout at the end of anchor rod 1 is chipped away to ensure precise alignment to the design elevation. During the chipping process, unnecessary damage to anchor rod 1 and other surrounding structures is avoided, thus laying a solid foundation for the smooth progress of the entire project.

[0047] In a preferred embodiment, in step four, the anchor rod 1 is a hollow structure, and high-precision miniature tilt sensors, three-dimensional attitude sensors and depth displacement sensors are symmetrically arranged on the inner side of the anchor rod 1; this measurement system is independent of the physical measurement method mentioned above and does not affect each other.

[0048] Throughout the entire process of hoisting and lowering anchor bolt 1, high-precision miniature tilt sensors, three-dimensional attitude sensors, and depth displacement sensors continuously and in real time collect key parameters such as the lowering depth, overall verticality, and three-dimensional tilt angle of anchor bolt 1. The measured data is simultaneously uploaded to the intelligent monitoring platform and finite element simulation calculation system at the construction site via a wireless transmission module. After receiving the measured data from the site, the finite element simulation calculation system automatically starts the preset model geometry refinement and iterative correction program to optimize and correct the parameters of the standardized theoretical model established in the early stage. The system will replace the theoretical geometric parameters in the model one by one according to the actual burial depth, three-dimensional tilt angle, and overall verticality of anchor bolt 1 measured on site, accurately reconstructing the physical geometry, spatial layout coordinates, bending shape of the bolt body, and burial depth boundary conditions of a single anchor bolt 1. At the same time, the contact interface range, contact angle, and coupling boundary parameters between anchor bolt 1 and the surrounding rock and soil and grouting body are simultaneously corrected.

[0049] When the verticality deviation, plane offset, and depth deviation of anchor bolt 1 are within the allowable range of the specifications, the model is accurately updated based on the measured parameters to ensure that the mechanical calculation boundary conforms to the actual working conditions. When the measured deviation exceeds the controllable threshold, the finite element simulation calculation system immediately issues an early warning and synchronously feeds back the deviation data and correction suggestions. On-site construction personnel can adjust the hoisting angle, lowering speed, and support positioning method in a timely manner to recalibrate the attitude of anchor bolt 1 until the parameters meet the standards before completing the final fixation.

[0050] In step five, the raw data of the three-dimensional absolute coordinates of the top of each anchor rod 1 measured by RTK are exported in batches. The data is preprocessed and screened to remove abnormal data caused by satellite signal interference and human alignment errors. The compliant measured parameters are imported into the overall anti-buoyancy structure finite element model in batches through the data interface, and the original theoretical design point coordinates are automatically replaced in batches to complete the spatial point reconstruction of all anchor rods 1 in the field. After the model is accurately modeled, mechanical simulation calculation is performed to analyze the impact of position deviation on the coordinated force, load distribution and overall anti-buoyancy bearing capacity of the anchor rod group 1. Based on the optimal correction displacement and force balance state simulated by the model, the correction direction, correction displacement amount and fine-tuning construction technology of the substandard anchor rods 1 are determined, and the accurate correction is completed without disturbing the surrounding existing anchor rods 1, soil and rock and grouting structure.

[0051] After the correction work was completed, the coordinates of the points were re-measured using RTK, and the spatial parameters of anchor 1 were updated by importing them into the finite element model for the second time. The boundary conditions of the soil and rock mass in the area of ​​the point that exceeded the standard, the coupled force boundary of the anchor 1 group, and the force transmission calculation model were corrected simultaneously to eliminate the mechanical calculation error caused by the point deviation.

[0052] The above embodiments are merely illustrative of the concept and implementation of the present invention and are not intended to limit it. Under the concept of the present invention, technical solutions without substantial changes are still within the scope of protection.

Claims

1. A method for positioning prestressed steel reinforcement in ultra-long hollow pile anti-buoyancy anchor rods, characterized in that: The anti-buoyancy anchor group (1) includes anchors (1) and sleeves (2); the construction method includes the following steps: Step 1, construction preparation, calculate the length, diameter and spacing of the anchor rods (1); Step 2: Drilling of anchor rod (1) First, calculate the effective drilling depth so that the anchoring section of anchor rod (1) can stably enter the bearing layer; then drill the hole using a drilling machine. During the drilling process, measure the hole depth in real time and dynamically adjust the length of anchor rod (1) when the stratum changes. Step 3, grout injection: First, prepare the grout using plain cement grout with a water-cement ratio controlled between 0.5 and 0.55; then, add the corresponding water and cement to the grout mixer for mixing; finally, inject the grout using a pump inside the drill rod. Step 4: Insert the anchor rod (1) into the hole and install the sleeve rod (2) on the end of the anchor rod (1) by thread. Lower the anchor rod (1) and sleeve rod (2) vertically into the hole as a whole. During the lowering process, use a level instrument in conjunction with the scale markings on the sleeve rod (2) to monitor the positioning in real time, ensuring that the lower end of the anchor rod (1) accurately reaches the design depth, with the deviation controlled within ±50mm. After lowering to the design elevation, rotate the sleeve rod (2) in the opposite direction to remove it. Step 5, Correction and Positioning: First, perform point correction of the RTK system and vertically fix the centering rod of the RTK mobile station to the exposed end of the top of the anchor rod (1); The RTK system automatically obtains the real-time three-dimensional coordinates of the top of the anchor rod (1) and compares them with the design layout coordinates; If the plane deviation exceeds the allowable range of construction, the position of the anchor rod (1) is finely adjusted in time. Step 6, Grouting Protection: After the grouting operation is completed and before the grout has initially set, grouting should be carried out in a timely manner to ensure the fullness of the grouting; during the grouting process and after grouting, prevent the end of the anchor rod (1) from being disturbed; Step 7, end chiseling: Before the earthwork excavation operation reaches the design elevation, the excess grout part of the anchor rod (1) is chiseled to ensure that it is accurately trimmed to the design elevation.

2. The method for positioning prestressed steel reinforcement of ultra-long hollow pile anti-buoyancy anchor rod according to claim 1, characterized in that: In step one, construction preparation also includes organizing training for all workers, clearly pointing out the key control points in construction; testing the cement's setting time, stability, and 3-day and 28-day compressive strength according to technical requirements; and selecting and deploying drilling rigs.

3. The method for positioning prestressed steel reinforcement of ultra-long hollow pile anti-buoyancy anchor rod according to claim 1 or 2, characterized in that: In step two, for rock formations, a down-the-hole drill rig with an eccentric impact drill is used; for silty clay, sandy or soil areas, a long auger drill rig with high-pressure jet grouting is used for pre-hole drilling; for gravelly or easily collapsed formations, casing drilling is used, with casing being installed while drilling.

4. The method for positioning prestressed steel reinforcement of ultra-long hollow pile anti-buoyancy anchor rod according to claim 3, characterized in that: In step two, the drilling depth exceeds the designed anchoring section length by 50mm to 100mm.

5. The method for positioning prestressed steel reinforcement of ultra-long hollow pile anti-buoyancy anchor rod according to claim 1 or 4, characterized in that: In step three, the cement slurry must be mixed in the mortar mixer for no less than 2 minutes. When mixing, add a certain amount of water first, then slowly pour in the cement, using a low-speed mixing mode. After the cement is completely dissolved in the water, increase the mixing speed to the rated speed so that the slurry forms a uniform suspension system. After mixing, let it stand for 30 seconds to allow the air bubbles to be naturally expelled before grouting.

6. The method for positioning prestressed steel reinforcement of ultra-long hollow pile anti-buoyancy anchor rod according to claim 1, characterized in that: In step four, the lowering termination line is first marked on the sleeve rod (2) according to the designed total length of the anchor rod (1) and the elevation of the borehole. The lowering position of the anchor rod (1) is determined by measuring the scale mark with a level. Before lowering, the level is set up and leveled so that its line of sight is aligned with the initial scale on the sleeve rod (2). As the anchor rod (1) is slowly lowered, the observer reads the scale change on the sleeve rod (2) in real time through the level. When the termination scale line coincides with the designed elevation line of the borehole, a stop signal is immediately issued.

7. The method for positioning prestressed steel reinforcement of ultra-long hollow pile anti-buoyancy anchor rod according to claim 6, characterized in that: In step four, high-precision miniature tilt sensors, three-dimensional attitude sensors, and depth displacement sensors are symmetrically arranged on the inner side of the anchor rod (1). During the entire process of hoisting and lowering the anchor rod (1), the high-precision miniature tilt sensors, three-dimensional attitude sensors, and depth displacement sensors continuously collect key parameters such as the lowering depth, overall verticality, and three-dimensional tilt angle of the anchor rod (1) in real time. The measured data are uploaded to the intelligent monitoring platform and finite element simulation calculation system at the construction site in real time through the wireless transmission module. After receiving the measured data at the site, the finite element simulation calculation system automatically starts the model geometry refinement iterative correction program to optimize and correct the parameters of the standardized theoretical model established in the early stage in all aspects. The system will replace the theoretical geometric parameters in the model one by one with the actual buried depth, three-dimensional tilt angle and overall verticality of the anchor rod (1) measured on site, and accurately reconstruct the physical geometry, spatial layout coordinates, rod bending shape and buried depth boundary conditions of a single anchor rod (1); at the same time, it will simultaneously correct the contact interface range, contact angle and coupling boundary parameters between the anchor rod (1) and the surrounding rock and soil and grouting body.

8. The method for positioning prestressed steel reinforcement of ultra-long hollow pile anti-buoyancy anchor rod according to claim 7, characterized in that: When the verticality deviation, plane offset, and depth deviation of the anchor rod (1) are within the allowable range of the specification, the model is accurately updated based on the measured parameters to ensure that the mechanical calculation boundary conforms to the actual working conditions. When the measured deviation exceeds the controllable threshold, the finite element simulation calculation system immediately issues an early warning and synchronously feeds back the deviation data and correction suggestions. On-site construction personnel can adjust the hoisting angle, lowering speed, and support positioning method in a timely manner to recalibrate the attitude of the anchor rod (1) until the parameters meet the standard before completing the final fixation.

9. The method for positioning prestressed steel reinforcement of ultra-long hollow pile anti-buoyancy anchor rod according to claim 8, characterized in that: In step five, the raw data of the three-dimensional absolute coordinates of the top of each anchor rod (1) measured by RTK are exported in batches. The data is preprocessed and screened to remove abnormal data caused by satellite signal interference and manual alignment error. The compliant measured parameters are imported into the overall anti-buoyancy structure finite element model in batches through the data interface. The original theoretical design point coordinates are automatically replaced in batches to complete the spatial point reconstruction of all anchor rods (1) in the field. After the model is accurately modeled, mechanical simulation is performed to analyze the influence of position deviation on the coordinated force, load distribution and overall anti-buoyancy bearing capacity of the anchor rod (1) group. According to the optimal correction displacement and force balance state simulated by the model, the correction direction, correction displacement and fine-tuning construction technology of the substandard anchor rod (1) are determined. Accurate correction is completed without disturbing the surrounding formed anchor rods (1), soil and rock and grouting structure.

10. The method for positioning prestressed steel reinforcement of ultra-long hollow pile anti-buoyancy anchor rod according to claim 9, characterized in that: After the correction construction is completed, the coordinates of the points are re-measured by RTK, and the spatial parameters of the anchor rod (1) are updated by importing the finite element model for the second time. The boundary conditions of the soil and rock mass, the coupled force boundary of the anchor rod (1) group and the force transmission calculation model of the area of ​​the point exceeding the standard are corrected simultaneously to eliminate the mechanical calculation error caused by the point deviation.

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