A prestressed anchor cable detection device and performance evaluation method

Abstract

The present application relates to geotechnical engineering anchoring structure maintenance technical field, especially in kind, a kind of existing prestressed anchor cable detection device and performance evaluation method, the device includes: inner sleeve and stem, inner sleeve connects anchor head, stem distal end installs counterforce support disc;Detection unit is sheathed in the outer periphery of inner sleeve and is supported in existing anchor pad, for gathering stress and deformation data;Counterforce collar is screw-connected on the outer wall of inner sleeve and is axially adjusted and is resisted to detection unit;And the jacking mechanism is supported between existing anchor pad and counterforce support disc.The present application leads out counterforce space by inner sleeve and coaxial stem, jacking mechanism applies axial force to temporarily release original anchor head stress, counterforce collar is screwed in the state of load preservation and is resisted to detection unit, after unloading jacking mechanism, remaining prestress is transferred to detection unit, and high-precision detection of remaining prestress is realized.System conversion jacking mechanism etc. can be disassembled and reused, and long-term stress monitoring can be realized by retaining detection unit.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering anchorage structure maintenance technology, and in particular to an existing prestressed anchor cable testing device and performance evaluation method. Background Technology

[0002] Prestressed anchor cable reinforcement technology is widely used in slope engineering, deep foundation pit support, underground caverns, and various soil and rock slope projects to ensure stability due to its ability to effectively utilize the strength of deep soil and rock masses. During long-term service, the prestress of prestressed anchor cables is affected by various factors such as material relaxation, ground creep, groundwater corrosion, and changes in external loads, leading to a decrease in their load-bearing capacity. Simultaneously, due to long-term erosion from the harsh underground environment, the anchor cable itself may suffer from corrosion weakening or even cross-sectional damage such as wire breakage. Accurately determining the remaining prestress and cross-sectional damage state of existing prestressed anchor cables and scientifically assessing their long-term performance is crucial for evaluating the long-term safety and stability of slopes and support structures.

[0003] However, during internal discussions, the applicant discovered the following shortcomings in engineering practice when using existing technologies to conduct testing, monitoring, and performance evaluation of existing prestressed anchor cables: 1. After conventional prestressed anchor cables are tensioned and locked during construction, the exposed steel strands are usually cut flat and sealed with anchor concrete or fitted with protective covers. Once the project is operational, there is insufficient exposed length at the anchor cable ends for conventional jacks to clamp and re-tension for testing. Existing testing methods mostly rely on visual inspection or local damage checks, making it difficult to directly determine the actual stress attenuation of the anchor cables over long-term use, which complicates structural safety assessment and early warning.

[0004] 2. Existing prestressed anchor cables are typically composed of multiple strands of steel wire. After long-term service, the stress state and relaxation degree of each strand are often uneven. During the lift-off loading test, it is difficult for each strand to reach the stress equilibrium point synchronously, resulting in a variety of measured load-displacement (Ps) curve shapes: although some curves have inflection points, the actual lift-off point of the working anchor plate often lags significantly behind the true force equilibrium point, causing human interpretation errors; and when the stress of each strand is severely asynchronous, the measured curve often shows a smooth transition without obvious inflection points, causing the traditional inflection point interpretation method to fail and making it impossible to accurately obtain the true remaining prestress of the anchor cable. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing prestressed anchor cable testing methods described in the background art, which cannot directly determine the actual stress attenuation of existing prestressed anchor cables, and to provide an existing prestressed anchor cable testing device and performance evaluation method.

[0006] In a first aspect, the present invention provides an existing prestressed anchor cable testing device, comprising: The inner sleeve and the rod connected to the inner sleeve, the inner sleeve being connected to the anchor head of the existing prestressed anchor cable, and a reaction support plate being installed at the end of the rod away from the anchor head; The detection unit is sleeved on the outer periphery of the inner sleeve and supported on the end face of the existing anchor plate, and is used to collect the stress and deformation data of the existing prestressed anchor cable. A reaction collar, threadedly connected to the outer wall of the inner sleeve, is used to adjustably abut against the detection unit in the axial direction; The lifting mechanism, supported between the existing anchor plate and the reaction support plate, is used to apply axial force to the rod.

[0007] The existing prestressed anchor cable testing device provided by the present invention connects the anchor head of the existing anchor cable through an inner sleeve, and extends the reaction support plate outward from the coaxially arranged rod body, providing sufficient operating and reaction support space for the external jacking mechanism; when the jacking mechanism applies axial force to the rod body, it can slightly lift the working anchor head, temporarily releasing the original working anchor head from the locked stress state, without causing damage to the existing anchoring structure and slope throughout the process; This invention utilizes a reaction collar threaded into the outer wall of the inner sleeve. Under the load-bearing state of the lifting mechanism applying force and unloading, the reaction collar is screwed to move axially and press against the end face of the detection unit. After the lifting mechanism is unloaded, all the remaining prestress of the anchor cable is smoothly transferred between the detection unit and the existing anchor plate. This not only accurately measures the current remaining prestress of the anchor cable but also retains the ability to monitor stress and deformation for a long time after the external lifting fixture is removed. If long-term monitoring is required, only the detection unit needs to be retained and connected to the data acquisition equipment. The lifting mechanism and other components can be completely disassembled, recycled, and reused after system conversion, reducing the cost of use and combining the economy of detection with the practicality of long-term monitoring.

[0008] Preferably, it further includes an outer sleeve, which is fitted around the outer periphery of the detection unit and the reaction ring, and supported between the existing anchor plate and the lifting mechanism; the inner wall of the outer sleeve is in contact with the outer wall of the detection unit.

[0009] A rigid reaction force transmission channel is established between the existing anchor plate and the jacking mechanism by using an outer sleeve, which avoids the jacking mechanism directly damaging the detection unit. At the same time, its inner wall fits and limits the detection unit, which not only prevents the detection unit from being displaced under pressure and subjected to eccentric force, but also axially covers the internal stress components, providing explosion-proof safety protection to prevent components from breaking out under extreme working conditions (such as anchor cable breakage).

[0010] Preferably, the outer sleeve has an operating window, and the outer wall of the reaction collar has multiple insertion holes. Each insertion hole is suitable for inserting a tool that passes through the operating window to rotate and twist the reaction collar so that the reaction collar axially presses against the detection unit.

[0011] By using the cooperation between the operating window of the outer sleeve and the insertion hole on the outer wall of the reaction collar, the operator can use a lever tool to turn and tighten the reaction collar through the window without disassembling the external support under the closed and enclosed load-bearing state. This enables the detection unit to be tightened quickly and conveniently under the lifting and load-bearing state, ensuring the mechanical reliability and operational safety of the system conversion.

[0012] Preferably, the inner sleeve has an internal thread on the inner wall of the end near the anchor head, and the working anchor plate of the existing prestressed anchor cable has an external thread on its outer wall. The inner sleeve is screwed into the working anchor plate through the internal thread.

[0013] The internal thread of the inner sleeve is directly screwed into the external thread of the existing working anchor plate, achieving integrated direct connection assembly under the condition that the original anchor plate has its own thread, making construction simple and efficient.

[0014] Preferably, it further includes a transition anchor plate, which is fixedly installed on the exposed end of the existing prestressed anchor cable; the outer wall of the transition anchor plate is provided with external threads, and the inner wall of the inner sleeve near the transition anchor plate is provided with internal threads, and the inner sleeve is screwed into the external threads of the transition anchor plate through the internal threads.

[0015] For existing anchoring conditions where the outer contour of the original working anchor plate is unthreaded (smooth), by adding an external threaded transition anchor plate and using, for example, clamps to lock the exposed end of the steel strand, the inner sleeve can be reliably screwed onto the transition anchor plate. This successfully adapts the unthreaded anchor head into a threaded interface that can be extended and lifted, expanding the versatility and compatibility of the device with various existing anchor head types.

[0016] In a second aspect, the present invention provides a method for evaluating the performance of existing prestressed anchor cables, comprising the following steps: S1. Install the aforementioned existing prestressed anchor detection device at the anchor head of the existing prestressed anchor cable, apply axial force to the rod body through the jacking mechanism to perform jacking loading, and use the detection unit to collect the load and displacement data of the existing prestressed anchor cable in real time to generate the measured load-displacement curve. S2. Based on the morphological characteristics of the measured load-displacement curve generated in S1, calculate the residual load P of the existing prestressed anchor cable. r Unit: kN; S3. Based on the remaining load P r The design locking load P0 (in kN) of the existing prestressed anchor cables, and the tension control force P of the existing prestressed anchor cables. k Unit: kN; Comparison relationship; Graded evaluation of residual load performance of existing prestressed anchor cables. S4. Calculate the measured stiffness coefficient K of existing prestressed anchor cables based on the measured load-displacement curve. iThe unit is kN / mm, and it is based on the measured stiffness coefficient K. i Back-calculation of the total cross-sectional area A of existing prestressed anchor cables sz The unit is mm², and then the cross-sectional damage rate η is calculated to assess the cross-sectional damage of existing prestressed anchor cables.

[0017] Existing assessment methods are typically limited to a single-dimensional analysis of the current residual load or prestress loss level of the anchor cable, failing to detect potential weaknesses in the effective cross-section, such as deep corrosion or wire breakage (for example, an anchor cable with a severely corroded cross-section may still show normal load readings for a short period, easily overlooking the risk of sudden fracture). This invention constructs a dual evaluation system that includes performance grading and cross-sectional damage assessment, deeply integrating "residual load grading assessment" based on measured load-displacement curves with "stiffness-inverse calculation cross-sectional damage assessment." This system not only reveals the current bearing capacity but also quantitatively diagnoses the degree of material damage and deterioration, achieving in-depth health checks and precise early warnings for the entire life cycle of existing anchoring projects. Traditional lift-off detection typically assumes the lift-off point is the force equilibrium point. However, in actual multi-cable anchor projects, uneven stress relaxation among the cables leads to a prolonged lift-off process, resulting in complex and variable load-displacement curves (such as broken lines, arcs, or significant lag between the lift-off point and the equilibrium point). This invention calculates the remaining load P based on the geometric characteristics of the measured load-displacement curve generated by jacking loading. r It avoids physical lag errors such as visual lifting or feeler gauge insertion and removal, and can accurately decouple and extract the real mechanical equilibrium load from complex curves. Without damaging the soil and rock mass and the anchor cable protective layer, this method uses the measured load-displacement curve to obtain the measured stiffness coefficient K during the lift-off loading stage. i And the total cross-sectional area A of the experiment was calculated in reverse. sz The section damage rate η transforms the abstract and hidden degree of corrosion weakening of internal metal sections into an intuitive quantitative indicator, providing scientific and rigorous data support for the reinforcement and treatment decisions of slopes and underground engineering, and improving the efficiency of on-site testing and the reliability of evaluation results.

[0018] Preferably, in S2, when the measured load-displacement curve has an inflection point, data points are selected before and after the inflection point to perform linear fitting to obtain a first fitted line and a second fitted line. The load value corresponding to the intersection of the first fitted line and the second fitted line is determined as the residual load P. r .

[0019] This method selects data points before and after the bend point for linear fitting, using the intersection of the two fitted lines as the final equilibrium point. It utilizes global trend fitting instead of single-point visual inspection, effectively filtering out local measurement errors and minor disturbances. It overcomes the drawbacks of traditional feeler gauge or visual inspection methods, where lag caused by gaps between the working anchor plate and existing anchor plate leads to systematically inflated test values. This method can accurately reconstruct the true residual load P of the anchor cable under the critical state of mechanical equilibrium. r .

[0020] Preferably, in S2, when the measured load-displacement curve is a smooth curve without any bends, the theoretical stiffness coefficient K0 of the existing prestressed anchor cable is calculated, with the unit being kN / mm.

[0021] Where n is the number of steel strands in the existing prestressed anchor cable, E s The elastic modulus of a single steel strand, in kN / mm². 2 A s The cross-sectional area of ​​a single steel strand, in mm², l f The design free length of the existing prestressed anchor cable, in mm; The slope of the tangent along the measured load-displacement curve is calculated segment by segment according to the preset displacement step size and used as the measured stiffness coefficient K. i Unit: kN / mm; A comprehensive comparison of all measured stiffness coefficients K i The measured stiffness coefficient K is selected from the theoretical stiffness coefficient K0. i The interval with the smallest absolute value of the difference from the theoretical stiffness coefficient K0 is determined as the residual load Pr.

[0022] This method calculates the measured stiffness coefficient K segment by segment according to a preset displacement step size. i The load was compared and matched against the theoretical stiffness coefficient K0 as the mechanical benchmark, and the interval load closest to K0 was selected as the residual load P. r It constructs a mathematical and objective calculation model, freeing it from the reliance on intuitive geometric inflection points of curves; it can accurately identify the optimal mechanical critical range in which all steel strands enter the lift-off state, solving the deviation caused by subjective estimation based on human experience under smooth curves, and greatly improving the scientificity and accuracy of residual prestress detection under complex stress conditions.

[0023] Preferably, in S3, P k The calculation formula is:

[0024] Among them, f ptk This refers to the standard value of the tensile strength of steel strand, in MPa and A. dzThe total design cross-sectional area of ​​the existing prestressed anchor cables, in mm². The residual load performance classification assessment of existing prestressed anchor cables includes: When 0.8P0≤P r When <1.1P0, the evaluation level is determined to be Grade A, indicating that the existing prestressed anchor cable has good performance; When 0.5P0≤P r When <0.8P0, the evaluation level is determined to be Grade B, indicating that the existing prestressed anchor cable performance is average; When 0.3P0≤P r When <0.5P0, the evaluation level is determined to be Grade C, indicating that the performance of the existing prestressed anchor cable has deteriorated; When P r When <0.3P0, the assessment level is determined to be D, indicating that the existing prestressed anchor cable has failed; When 1.1P0≤P r <P k At that time, the assessment level was determined to be Grade E, indicating that the existing prestressed anchor cables posed a safety risk; When P r ≥P k At that time, the assessment level was determined to be F, indicating that the existing prestressed anchor cables were in a high-risk state.

[0025] Traditional classification methods often only focus on load attenuation and deterioration, lacking material mechanics verification of abnormal load increases caused by slope deformation and compression; this method will use the measured residual load P r With design locking load P0 and tension control force P k By comparing the data, six levels of AF were defined, clearly indicating the states as "good, average, deteriorated, failed, with safety risks, and high risk," providing an intuitive basis for maintenance decisions.

[0026] Preferably, in S4, the formula for calculating the cross-sectional damage rate η is:

[0027] Among them, A sz To calculate the total cross-sectional area for the experiment, in mm², A dz K represents the total design cross-sectional area of ​​existing prestressed anchor cables, in mm². i K0 is the measured stiffness coefficient of the existing prestressed anchor cable, in kN / mm; K0 is the theoretical stiffness coefficient of the existing prestressed anchor cable (100), in kN / mm. The cross-sectional damage assessment of existing prestressed anchor cables includes: When η≤10%, the condition of the existing prestressed anchor cable section is judged to be good; When 10% < η ≤ 30%, the condition of the existing prestressed anchor cable section is judged as general. When 30% < η ≤ 40%, the condition of the existing prestressed anchor cable section is judged as deteriorated; When η>40%, the existing prestressed anchor cable section is judged to be in failure.

[0028] By extracting the measured stiffness coefficient K during the lift-off stage i Combined with the design free segment length l f With elastic modulus E s The total cross-sectional area A of the anchor cable can be accurately calculated without excavation or damage. sz The damage rate η was used to transform the hidden metal section loss into a quantifiable mechanical stiffness index; a stepped damage classification system with 10%, 30%, and 40% as the boundaries was defined, overcoming the blindness of the traditional assessment that regards it as safe as long as the load does not drop sharply. It can screen out hidden anchor cables with the risk of sudden brittle fracture due to severe weakening of the effective section earlier and more accurately, providing a scientific and forward-looking opportunity and basis for the reinforcement of slopes and support structures.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a device for detecting existing prestressed anchor cables. An inner sleeve connects to the anchor head of the existing anchor cable, and a reaction support plate extends outward from a coaxially arranged rod, providing ample operating and reaction support space for the external lifting mechanism. When the lifting mechanism applies axial force to the rod, it can slightly lift the working anchor head, temporarily releasing the original locked state of the working anchor head, without causing damage to the existing anchoring structure or slope throughout the process. This device utilizes a reaction collar threaded into the outer wall of the inner sleeve. Under the load-bearing state of the lifting mechanism applying force and unloading, the reaction collar is screwed on. The ring moves axially and presses against the end face of the detection unit; after the lifting mechanism is unloaded, all the remaining prestress of the anchor cable is smoothly transferred between the detection unit and the existing anchor plate. This not only accurately measures the current remaining prestress of the anchor cable, but also retains the ability to monitor stress and deformation for a long time after the external lifting fixture is removed. If long-term monitoring is required, only the detection unit needs to be retained and connected to the data acquisition equipment. The lifting mechanism and other components can be completely disassembled, recycled and reused after the system conversion, reducing the cost of use and combining the economy of detection with the practicality of long-term monitoring.

[0030] 2. This invention provides a method for evaluating the performance of existing prestressed anchor cables, constructing a dual evaluation system that includes performance grading and cross-sectional damage assessment. It deeply integrates "residual load grading assessment" based on measured load-displacement curves with "stiffness-based cross-sectional damage assessment," enabling not only the determination of current bearing capacity but also quantitative diagnosis of material damage and deterioration. This achieves in-depth health checks and precise early warnings for the entire life cycle of existing anchoring projects. This method calculates the residual load P based on the geometric characteristics of the measured load-displacement curves generated by jacking loading. rThis method avoids physical hysteresis errors such as visual lifting or feeler gauge insertion / removal, and can accurately decouple and extract the true mechanical equilibrium load from complex curves. Without damaging the soil and rock mass or the anchor cable protective layer, this method uses the measured load-displacement curve to obtain the measured stiffness coefficient K during the lifting loading stage. i And the total cross-sectional area A of the experiment was calculated in reverse. sz The section damage rate η transforms the abstract and hidden degree of corrosion weakening of internal metal sections into an intuitive quantitative indicator, providing scientific and rigorous data support for the reinforcement and treatment decisions of slopes and underground engineering, and improving the efficiency of on-site testing and the reliability of evaluation results. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the original state of the existing prestressed anchor cable in Example 1.

[0032] Figure 2 This is a schematic diagram of the state after removing the anchor protective cap in Example 1.

[0033] Figure 3 This is a schematic diagram of the installation of the detection unit, inner sleeve, reaction collar, and rod in Example 1.

[0034] Figure 4 This is a schematic diagram of the outer sleeve installation in Example 1.

[0035] Figure 5 This is a schematic diagram of the installation of the lifting mechanism in Example 1.

[0036] Figure 6 This is a schematic diagram of the reaction force collar clamping detection unit in Example 1.

[0037] Figure 7 This is a schematic diagram of existing anchor cable monitoring in Example 1.

[0038] Figure 8 This is a schematic diagram of the original state of the existing prestressed anchor cable in Example 2.

[0039] Figure 9 This is a schematic diagram of the state after removing the anchor protective cap in Example 2.

[0040] Figure 10 This is a schematic diagram of the installation of the transition anchor plate, detection unit, inner sleeve, reaction collar, and rod in Example 2.

[0041] Figure 11 This is a schematic diagram of the outer sleeve installation in Example 2.

[0042] Figure 12 This is a schematic diagram of the installation of the lifting mechanism in Example 2.

[0043] Figure 13This is a schematic diagram of the reaction force collar clamping detection unit in Example 2.

[0044] Figure 14 This is a schematic diagram of existing anchor cable monitoring in Example 2.

[0045] Figure 15 This is a schematic diagram of the measured load-displacement curve with a bend in the angle.

[0046] Figure 16 A schematic diagram illustrating the method for determining the remaining load from measured load-displacement curves with inflection points.

[0047] Figure 17 This is a schematic diagram of the measured load-displacement curve, which is a smooth curve without any sharp inflection points.

[0048] Figure 18 A schematic diagram illustrating the method for determining the remaining load from a measured load-displacement curve that is a smooth curve without any sharp inflection points.

[0049] The markings in the diagram are: 11-inner sleeve, 12-rod body, 13-reaction support plate, 2-detection unit, 3-reaction collar, 31-insertion hole, 4-lifting mechanism, 5-outer sleeve, 51-operation window, 6-transition anchor plate, 7-clamping plate, 8-steel pad, 9-dust cover, 100-existing prestressed anchor cable, 200-existing anchor plate, 300-working anchor plate, 400-anchor protective cap. Detailed Implementation

[0050] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0051] Unless otherwise specified, the use of terms such as "upper," "lower," "left," "right," "center," "inner," and "outer" to indicate orientation or positional relationships in the description of specific embodiments of the present invention is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is typically placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.

[0052] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," and "parallel" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, or parallel, but rather that it can be slightly tilted or have a deviation. For example, "horizontal" merely means that its direction is more horizontal relative to "vertical," not that the structure must be completely horizontal, but that it can be slightly tilted. Alternatively, it can be simplified to mean that the corresponding device / component / element, when set in a "horizontal," "vertical," "suspended," or "parallel" direction, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the present invention.

[0053] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0054] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as 2, 3, 4, 5, 6, 7, 8, or 9, and can even exceed nine.

[0055] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to common connection methods in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0056] Example 1 This embodiment provides an existing prestressed anchor cable testing device, which is mainly used in existing prestressed anchor cable projects that have been tensioned and locked and whose exposed steel strands have been cut in soil and rock reinforcement projects such as slope engineering, deep foundation pit support, underground caverns or tunnels.

[0057] like Figures 1-2As shown, the existing prestressed anchor cable project in this application scenario, in its original working state, includes: an existing prestressed anchor cable 100 inserted into the soil or retaining structure, an existing anchor plate 200 tightly attached to the slope or structural surface, a working anchor plate 300 installed on the outside of the existing anchor plate 200, and an anchor protective cap 400 covering the outside of the working anchor plate 300; wherein, a clamp 7 is installed between the working anchor plate 300 and the existing prestressed anchor cable 100 to lock the prestress of the anchor cable, and as... Figure 2 As shown, the outer periphery of the working anchor plate 300 in this embodiment is formed with external threads (i.e., threaded working anchor plate); after long-term operation of the project, the exposed steel strands usually do not have enough length for the jack to clamp directly.

[0058] like Figures 3-7 As shown, the existing prestressed anchor cable testing device provided in this embodiment includes: The inner sleeve 11 and the rod 12 connected to the inner sleeve 11 are connected to the anchor head of the existing prestressed anchor cable 100. The rod 12 is equipped with a reaction support plate 13 at the end away from the anchor head.

[0059] Specifically, the inner sleeve 11 has a hollow cylindrical structure. The inner wall of the end of the inner sleeve 11 near the anchor head is formed with internal threads. Correspondingly, the outer wall of the working anchor plate 300 of the existing prestressed anchor cable 100 is machined with external threads. The inner sleeve 11 is coaxially screwed into the external threads of the working anchor plate 300 through the internal threads, realizing the direct assembly and connection of the existing working anchor plate 300. The inner wall of the other end of the inner sleeve 11 away from the anchor head is coaxially threaded into the near end of the rod body 12. The far end of the rod body 12 away from the anchor head extends outward and is equipped with a reaction support plate 13 (such as a threaded connection). The inner sleeve 11 and the rod body 12 not only provide assembly and operation space for the peripheral detection unit 2 and lifting mechanism 4, but also, under the condition of no exposed steel strand excess length, coaxially lead outward the tension axis of the existing prestressed anchor cable 100 and extend it to the reaction support plate 13, forming a complete force transmission channel.

[0060] The detection unit 2 is sleeved on the outer periphery of the inner sleeve 11 and supported on the end face of the existing anchor plate 200. It is used to collect the stress and deformation data of the existing prestressed anchor cable 100.

[0061] The detection unit 2 has a hollow annular structure and is fitted around the outer periphery of the inner sleeve 11. The inner end face of the detection unit 2 is tightly fitted and supported on the outer end face of the existing anchor plate 200. The detection unit 2 is mainly used to collect real-time stress and deformation data of the existing prestressed anchor cable 100 during the loading process and subsequent service. Specifically, the detection unit 2 integrates a through-hole pressure sensor and a displacement sensor, and is electrically connected to external data acquisition and control instruments. It can accurately measure the magnitude of axial force and axial displacement, and can collect, display, and automatically store pressure and elongation data during long-term monitoring. When installing the detection unit 2, it is necessary to ensure good alignment, strictly controlling the installation tilt within 0.5° and the eccentricity within 0.5mm to ensure uniform stress and accurate data acquisition.

[0062] The reaction collar 3 is threaded to the outer wall of the inner sleeve 11. The reaction collar 3 is used to adjustably abut against the detection unit 2 in the axial direction. The outer end of the reaction collar 3 faces outward, and its inner end face faces the outer end face of the detection unit 2. By screwing the reaction collar 3, it can be moved axially along the outer wall of the inner sleeve 11, thereby adjusting its abutment against the outer end face of the detection unit 2 in the axial direction.

[0063] The lifting mechanism 4 (e.g., a perforated jack) is supported between the existing anchor plate 200 and the reaction support plate 13, and is used to apply axial force to the rod 12. When the lifting mechanism 4 is working, its extended end pushes the reaction support plate 13, which in turn pulls the threaded working anchor plate 300 outward through the rod 12 and the inner sleeve 11, causing a small displacement (e.g., 0.5~1.0mm), thereby temporarily relieving the original working anchor plate 300 from the pressure on the existing anchor plate 200. The perforated jack in this embodiment can also be equipped with integrated pressure sensors and displacement sensors, which, together with control instruments or software, can collect, display and automatically store pressure and elongation data during the tensioning process in real time.

[0064] During use, when the lifting mechanism 4 applies axial force for lifting, the inner sleeve 11 pulls the working anchor plate 300 outward (away from the existing anchor plate 200) to generate a slight axial displacement. At this time, the reaction ring 3 moves outward synchronously with the inner sleeve 11, so that a small axial adjustment gap is formed between the reaction ring 3 and the detection unit 2. When the lifting load is in place, the working anchor plate 300 is completely unloaded and in the load-bearing state, the reaction ring 3 is rotated, driving the reaction ring 3 to move along the outer wall of the inner sleeve 11 toward the detection unit 2 until the inner end face of the reaction ring 3 tightly abuts the outer end face of the detection unit 2. Then the pressure of the lifting mechanism 4 is released and removed, and all the tension of the existing prestressed anchor cable 100 is smoothly transmitted back to the detection unit 2 and the existing anchor plate 200 through the inner sleeve 11 and the reaction ring 3, thus successfully completing the conversion of the force system.

[0065] It should be noted that the existing prestressed anchor cable testing device in this embodiment has both single-time testing and long-term monitoring functions, and can be flexibly configured according to project requirements in actual engineering applications: Single test condition: If it is only necessary to test the current remaining bearing capacity and performance status of the existing prestressed anchor cable 100, after the lifting mechanism 4 is loaded to the point where the anchor head is lifted and complete load-displacement data is obtained, the lifting mechanism 4 is slowly unloaded (the unloading rate is controlled at 10~20kN / min) so that the original working anchor plate 300 re-presses the existing anchor plate 200; the lifting mechanism 4, rod 12, outer sleeve 5, reaction support plate 13, reaction collar 3, detection unit 2 and inner sleeve 11 can all be disassembled, removed and recycled for reuse, and finally the anchor protective cap 400 is reinstalled so that the existing prestressed anchor cable 100 is restored to its original stress state.

[0066] Long-term monitoring conditions: such as Figure 7 As shown, if the work site needs to retain the long-term health monitoring function for the anchor cable stress state, then under the load-bearing state where the lifting mechanism 4 applies force to completely unload the working anchor plate 300, tighten the reaction collar 3 to make it press against the outer end face of the detection unit 2; then slowly release the pressure of the lifting mechanism 4 (unloading rate controlled at 10~20kN / min). At this time, all the remaining prestress of the existing prestressed anchor cable 100 is transferred to the detection unit 2 through the inner sleeve 11 and the reaction collar 3, and is jointly borne and continuously sensed by the detection unit 2 and the existing anchor plate 200. Prestress measurement; finally, only the external lifting mechanism 4, outer sleeve 5, reaction support plate 13 and rod 12 need to be removed, and the dust cover 9 (with anti-rust grease or anti-rust agent applied) needs to be screwed or clipped onto the end of the inner sleeve 11 away from the anchor head to form a sealed protection for the inner cavity of the inner sleeve 11 and the internal anchor connection. The detection unit 2 is connected to the external data acquisition unit (the acquisition parameters can be set to automatically acquire and store data once every 1 hour), so that in-situ monitoring and early warning of the whole life cycle can be achieved without changing the stress balance of the existing structure.

[0067] The existing prestressed anchor cable testing device provided in this embodiment connects the anchor head of the existing anchor cable through the inner sleeve 11, and the reaction support plate 13 is extended outward from the coaxially arranged rod 12, providing sufficient operating and reaction support space for the external lifting mechanism 4; when the lifting mechanism 4 applies axial force to the rod 12, it can slightly lift the working anchor head, temporarily releasing the original working anchor head from the locked stress state, without causing damage to the existing anchoring structure and slope throughout the process.

[0068] By threading a reaction collar 3 onto the outer wall of the inner sleeve 11, and under the load-bearing state of the lifting mechanism 4 applying force and unloading, the reaction collar 3 is screwed to move it axially and press against the end face of the detection unit 2. After the lifting mechanism 4 is unloaded, all the remaining prestress of the anchor cable is smoothly transferred between the detection unit 2 and the existing anchor plate 200. This not only accurately measures the current remaining prestress of the anchor cable, but also retains the ability to monitor stress and deformation for a long time after the external lifting fixture is removed. If long-term monitoring is required, only the detection unit 2 needs to be retained and connected to the data acquisition equipment. The lifting mechanism 4 and the rod 12 and other components can be completely disassembled, recycled and reused after the system conversion, reducing the cost of use and combining the economy of detection with the practicality of long-term monitoring.

[0069] In this embodiment or other embodiments, such as Figures 4-6 As shown, the existing prestressed anchor cable testing device also includes an outer sleeve 5, which is sleeved on the outer periphery of the testing unit 2 and the reaction ring 3, and supported between the existing anchor plate 200 and the lifting mechanism 4; the inner wall of the outer sleeve 5 is in contact with the outer wall of the testing unit 2.

[0070] A rigid reaction force transmission channel is established between the existing anchor plate 200 and the lifting mechanism 4 through the outer sleeve 5, so as to avoid the lifting mechanism 4 directly damaging the detection unit 2; at the same time, its inner wall fits and limits the detection unit 2, which not only prevents the detection unit 2 from being displaced by pressure and subjected to eccentric force, but also axially covers the internal stress components, and plays a role in preventing the components from breaking out under extreme working conditions (such as anchor cable breakage).

[0071] like Figure 4 and Figure 5 As shown, the outer wall of the outer sleeve 5 is provided with a lifting lug (with a lifting hole). Similarly, the outer wall of the jacking mechanism 4 is also provided with a matching lifting hole. In the case of working in the air at high altitudes on slopes or deep foundation pits, the outer sleeve 5 and the jacking mechanism 4 can be fixed by an external crane or lifting sling through the lifting hole, which reduces the difficulty of centering and the intensity of construction labor in high-altitude suspended operations.

[0072] In this embodiment or other embodiments, such as Figures 4-6As shown, the outer sleeve 5 has at least one operating window 51 (operating through hole) circumferentially; correspondingly, the outer peripheral wall of the reaction ring 3 has multiple insertion holes 31 (such as radial blind holes or grooves) evenly spaced circumferentially. Under the condition that the lifting mechanism 4 applies axial tension to slightly lift the working anchor plate 300 and maintains a constant lifting force, the operator does not need to disassemble the outer sleeve 5 or the lifting mechanism 4. Instead, they can directly use a special lever or pin tool to insert it into any insertion hole 31 through the operating window 51 to rotate the reaction ring 3. As the reaction ring 3 rotates, it is inserted into different insertion holes 31 in sequence for step-by-step continuous rotation, thereby driving the reaction ring 3 to move along the external thread of the inner sleeve 11 toward the existing anchor plate 200 until its end face firmly abuts against the outer end face of the detection unit 2.

[0073] By cooperating with the operating window 51 of the outer sleeve 5 and the insertion hole 31 on the outer wall of the reaction collar 3, the operator can use a lever tool to turn and twist the reaction collar 3 through the window without disassembling the external support under the closed and covered load-bearing state. This enables the detection unit 2 to be quickly and conveniently tightened under the lifting and load-bearing state, ensuring the mechanical reliability and operational safety of the system conversion.

[0074] Example 2 This embodiment provides another existing prestressed anchor cable detection device, whose structural principle, detection and monitoring working mechanism are basically the same as those in Embodiment 1. The main difference is that this embodiment is used to adapt to the working conditions of existing working anchor plates with no threads on the outer periphery (i.e., smooth working anchor plates).

[0075] like Figures 8 to 9 As shown, in the original working state, the existing prestressed anchor cable project includes the existing prestressed anchor cable 100, the existing anchor plate 200, the unthreaded working anchor plate 300 and the outer anchor protective cap 400. The steel strand is anchored in the working anchor plate 300 through the clamp 7. The outer wall of the working anchor plate 300 is smooth and cannot be directly screwed to the inner sleeve 11.

[0076] like Figures 10 to 14 As shown, the existing prestressed anchor cable testing device in this embodiment adds a transition assembly component based on Embodiment 1: After removing the anchor protective cap 400 and cleaning the exposed end, the transition anchor plate 6 is fitted onto the exposed steel strand end of the existing prestressed anchor cable 100, and a clamping plate 7 is installed in the tapered hole of the transition anchor plate 6 to lock the exposed steel strand inside the transition anchor plate 6. A steel pad 8 can also be pressed on the end face of the clamping plate 7 away from the existing anchor plate 200 to ensure that the force is even and uniform. The outer peripheral wall of the transition anchor plate 6 is machined with external threads.

[0077] The inner sleeve 11 has a hollow cylindrical structure. The inner wall of the inner sleeve 11 near the anchor head is machined with internal threads. The inner sleeve 11 is coaxially screwed to the external threads of the transition anchor plate 6 through the internal threads. The hollow inner cavity of the inner sleeve 11 forms an installation cavity suitable for accommodating the clamping plate 7 and the steel pad 8. The other end of the inner sleeve 11 is coaxially connected to the rod body 12, and the far end of the rod body 12 is equipped with a reaction support plate 13.

[0078] like Figures 10 to 14 As shown, the detection unit 2 is supported on the end face of the existing anchor plate 200 and sleeved on the outer periphery of the inner sleeve 11. The reaction ring 3 is threadedly connected to the outer wall of the inner sleeve 11. The outer sleeve 5 is sleeved on the outer periphery and its inner wall is in contact with the outer wall of the detection unit 2. The lifting mechanism 4 is supported between the outer sleeve 5 and the reaction support plate 13.

[0079] When using: The lifting mechanism 4 is activated to apply axial tension to the rod 12. The tension is transmitted to the existing prestressed anchor cable 100 through the rod 12, inner sleeve 11, transition anchor plate 6 and wedge 7, which in turn pulls the smooth working anchor plate 300 to produce a slight lifting, releasing the original anchoring stress state. The detection unit 2 collects load and deformation data in real time.

[0080] like Figures 12 to 14 As shown, if long-term in-situ monitoring is required, under the jacking and load-bearing state, the operating tool is inserted through the operating window 51 into the socket 31 to move the reaction collar 3 and tighten the reaction collar 3 so that it is axially and tightly pressed against the outer end face of the detection unit 2; then the jacking mechanism 4, the reaction support plate 13 and the rod 12 are unloaded and removed, and a dust cover 9 is installed at the end of the inner sleeve 11. The prestress is completely transferred to the detection unit 2, realizing the conversion from single detection to long-term monitoring.

[0081] For existing anchoring conditions where the outer contour of the original working anchor plate 300 is unthreaded (smooth), by adding an external threaded transition anchor plate 6 and using, for example, a clamp 7 to lock the exposed end steel strand, the inner sleeve 11 can be reliably screwed onto the transition anchor plate 6. This successfully transforms the unthreaded anchor head into a threaded interface that can be extended and lifted, expanding the versatility and compatibility of the device with various existing engineering anchor head types.

[0082] Example 3 This embodiment provides a method for evaluating the performance of existing prestressed anchor cables, including the following steps: S1. Install the existing prestressed anchor detection device provided in Example 1 or Example 2 at the anchor head of the existing prestressed anchor 100, apply axial force to the rod 12 through the lifting mechanism 4 to perform lifting loading, and use the detection unit 2 to collect the load and displacement data of the existing prestressed anchor 100 in real time to generate the measured load-displacement curve.

[0083] Specifically, before formally conducting the on-site assessment, design and as-built data of existing prestressed anchor cable projects can be collected (including steel strand specifications, number of strands n, and elastic modulus E). s Standard value of tensile strength f ptk The cross-sectional area A of a single steel strand s Design locking load P0, design free length l f Including parameters such as the original construction pull-out test data), and inspecting the work site and anchor head appearance, confirming that the outer contour is undamaged (if there is damage, the test is terminated), install the existing prestressed anchor detection device provided in Example 1 (for threaded anchor plates) or Example 2 (for smooth anchor plates) at the anchor head of the existing prestressed anchor cable 100; start the jacking mechanism 4, and slowly and steadily apply axial tension to the rod body 12 through the perforated jack (the jacking loading rate is controlled at 1~2kN / min), and push the reaction support plate 13 to apply lifting force to the anchor head; during the loading process, collect the force data and axial deformation displacement data of the existing prestressed anchor cable 100 under various loads in real time and synchronously, and draw and generate continuous and complete measured load-displacement (Ps) curves in the background system. When a small design allowable gap (e.g., 0.5~1mm) is observed between the working anchor plate 300 and the existing anchor plate 200, it indicates that the original working anchor has been lifted and unloaded and the loading stops.

[0084] S2. Based on the morphological characteristics of the measured load-displacement curve generated in S1, calculate the residual load P of the existing prestressed anchor cable 100. r (Unit: kN).

[0085] In the jacking test, an existing prestressed anchor cable 100 is usually composed of multiple strands of steel strands. After long-term service, the stress state and relaxation degree of each strand of steel strands are often uneven, causing the strands to reach the stress equilibrium point asynchronously during the loading and lifting process. This results in different morphological characteristics of the measured load-displacement curves. Based on the geometric characteristics of the measured curves in the field, the following strategy is adopted to calculate the remaining load P. r : When the measured load-displacement curve has an inflection point, data points are selected before and after the inflection point to perform linear fitting, resulting in a first fitted line and a second fitted line. The load value corresponding to the intersection of the first and second fitted lines is determined as the residual load P. r .

[0086] Specifically, such as Figure 15 As shown, the measured load-displacement curve consists of segments OA, AB, and BC. Inflection point B is the critical point of stress equilibrium. The working anchor plate 300 is simultaneously subjected to P r And the load P is applied by two forces acting in opposite directions.

[0087] When the lifting load P < P r At that time, the working anchor plate 300 remained stable, and the slope of the curve was relatively steep (section AB). When P>P r Afterwards, the working anchor plate 300 was lifted, and the slope of the curve became gentler (section BC).

[0088] When the displacement of the working anchor plate 300 relative to the existing anchor plate 200 reaches the design allowable lift-off judgment value, the existing anchor plate 200 is completely lifted off. The load at this point is called the lift-off load, and therefore the corresponding point on the measured load-displacement curve is called the lift-off point. Figure 15 As shown in the image below (▲).

[0089] When P>P r At this time, a gap or lifting phenomenon usually does not immediately appear between the working anchor plate 300 and the existing anchor plate 200; that is, the lifting point ▲ often lags behind the equilibrium point. B Selecting loads B Fit two stiffness coefficient straight lines to the data before and after the point; the load value corresponding to the intersection of the lines is the residual load. P r .

[0090] To eliminate human reading errors and hysteresis effects, 3-5 sets of measured data points were selected before and after the inflection point B of the bend angle for linear fitting, generating a first fitted line and a second fitted line respectively. The load value corresponding to the intersection of the extensions of the first and second fitted lines was directly determined as the residual load P of the existing prestressed anchor cable 100. r .

[0091] Specifically, such as Figure 16 As shown, the measured load-displacement curve has an inflection point and a lift-off point ( Figure 16 (As shown in ▲) The load is 274kN, and the inflection point B can be initially determined as the equilibrium point, at which time the load is 238kN. The curve is not very straight. Using 3-5 sets of data before and after point B, a first and second fitted straight line are generated. The intersection of the two lines is taken as the final equilibrium point, and the remaining load P can be obtained. r =252kN, which is more accurate than 238kN. If the design locking load P0 is 300kN, according to the residual load performance classification assessment of the existing prestressed anchor cable 100 described later, 0.8P0 < P r <1.1P0, the anchor cable has good performance.

[0092] This method selects data points before and after the bend point for linear fitting, using the intersection of the two fitted lines as the final equilibrium point. It utilizes global trend fitting instead of single-point visual inspection, effectively filtering out local measurement errors and minor disturbances. It overcomes the drawbacks of traditional feeler gauge or visual inspection methods, where the lag between the working anchor plate 300mm and the existing anchor plate leads to systematically inflated test values. This method can accurately reconstruct the true residual load P of the anchor cable under the critical state of mechanical equilibrium. r .

[0093] When the stress on each bundle of steel strands is severely uneven, each bundle of steel strands reaches the stress equilibrium point in batches and multiple times, resulting in the measured load-displacement curve showing a smooth and continuous arc transition without intuitive geometric angles, and the traditional inflection point method fails.

[0094] like Figure 17 As shown, calculate the theoretical stiffness coefficient K0 (unit: kN / mm) of the existing prestressed anchor cable 100:

[0095] Where n is the number of steel strands in the existing prestressed anchor cable 100, E s The elastic modulus of a single steel strand (unit: kN / mm²) 2 A s The cross-sectional area of ​​a single steel strand (in mm²), l f The design free section length (in mm) of the existing prestressed anchor cable 100.

[0096] Calculate the slope of the tangent line (the ratio of load increment to displacement increment) segment by segment along the measured load-displacement curve at a preset displacement step size (e.g., a preset displacement step size of 2 mm) to obtain a series of measured stiffness coefficients K. i (e.g., K1, K2, K3...K) n (Unit: kN / mm).

[0097] like Figure 18 As shown, the measured stiffness coefficients K are compared and analyzed. i The measured stiffness coefficient K is selected from the theoretical stiffness coefficient K0. i The interval corresponding to the smallest absolute value of the difference between the load and the theoretical stiffness coefficient K0 is determined as the residual load Pr of the existing prestressed anchor cable 100.

[0098] Specifically, such as Figure 18 As shown, the measured load-displacement curve is a smooth curve without any sharp inflection points, and the lift-off point ( Figure 18 (As shown in ▲) The load is 268kN, but before this, the measured load-displacement curve is smooth, continuous, and approximately arc-shaped, with the slope between each two points gradually decreasing. i The value is decreasing. Calculate K segment by segment. iThe values ​​are calculated as follows: K0 = 9.1 kN / mm, K1 = 15.6 kN / mm, K2 = 10.2 kN / mm, K3 = 8.5 kN / mm, and K4 = 6.8 kN / mm. K3 is closest to K0, therefore the load corresponding to segment K3 is determined to be the residual load P. r =254kN. If the design locking load P0 is 300kN, then 0.8P0 < P r <1.1P0, the anchor cable has good performance.

[0099] This method calculates the measured stiffness coefficient K segment by segment according to a preset displacement step size. i The load was compared and matched against the theoretical stiffness coefficient K0 as the mechanical benchmark, and the interval load closest to K0 was selected as the residual load P. r It constructs a mathematical and objective calculation model, freeing it from the reliance on intuitive geometric inflection points of curves; it can accurately identify the optimal mechanical critical range in which all steel strands enter the lift-off state, solving the deviation caused by subjective estimation based on human experience under smooth curves, and greatly improving the scientificity and accuracy of residual prestress detection under complex stress conditions.

[0100] S3. Based on the remaining load P r The design locking load P0 (in kN) of the existing prestressed anchor cable 100 and the tension control force P of the existing prestressed anchor cable 100 are compared with those of the existing prestressed anchor cable 100. k (Unit: kN) Comparison relationship, and conduct residual load performance classification assessment of existing prestressed anchor cable 100.

[0101] Furthermore, P k The calculation formula is:

[0102] Among them, f ptk A represents the standard value of the tensile strength of steel strand (in MPa). dz The total design cross-sectional area (in mm², A) of the existing prestressed anchor cable 100. dz =n A s ).

[0103] The residual load performance classification assessment of the existing prestressed anchor cable 100 includes: When 0.8P0≤P r When the value is less than 1.1P0, the evaluation level is determined to be Grade A, indicating that the existing prestressed anchor cable 100 has good performance and can continue to be used normally.

[0104] When 0.5P0≤P r When the value is less than 0.8P0, the evaluation level is determined to be Grade B. The performance of the existing prestressed anchor cable 100 is generally poor, indicating that the prestress has relaxed to a certain extent. It can continue to be observed and used.

[0105] When 0.3P0≤P r When the value is less than 0.5P0, the assessment level is determined to be Grade C. The performance of the existing prestressed anchor cable 100 deteriorates, indicating that the prestress has significantly decreased. It is advisable to take measures such as supplementary tensioning or structural reinforcement.

[0106] When P r When the value is less than 0.3P0, the assessment level is determined to be D, indicating that the existing prestressed anchor cable has failed 100%, which means that the anchor cable has basically lost its anchoring function and should be dealt with and reinforced as soon as possible.

[0107] When 1.1P0≤P r <P k At that time, the assessment level was determined to be Grade E, indicating that the existing prestressed anchor cable 100 posed a safety risk. This indicated that the anchor cable was overloaded due to ground creep or slope deformation, and that monitoring should be strengthened and corresponding protective measures should be taken.

[0108] When P r ≥P k At that time, the assessment level was determined to be F, indicating that the existing prestressed anchor cable 100 was in a high-risk state, which means that the stress on the anchor cable has approached or exceeded the material strength limit, and there is a high risk of sudden breakage. Emergency unloading or emergency risk mitigation measures need to be taken immediately.

[0109] Traditional classification methods often only focus on load attenuation and deterioration, lacking material mechanics verification of abnormal load increases caused by slope deformation and compression; this method will use the measured residual load P r With design locking load P0 and tension control force P k By comparing the data, six levels of AF were defined, clearly indicating the states as "good, average, deteriorated, failed, with safety risks, and high risk," providing an intuitive basis for maintenance decisions.

[0110] S4. Calculate the measured stiffness coefficient K of the existing prestressed anchor cable 100 based on the measured load-displacement curve. i (Unit: kN / mm), and based on the measured stiffness coefficient K i Back-calculation of the total cross-sectional area A of the existing prestressed anchor cable 100. sz (Unit: mm²), then calculate the cross-sectional damage rate η (unit: %), and conduct a cross-sectional damage assessment of the existing prestressed anchor cable 100.

[0111] Furthermore, the formula for calculating the cross-sectional damage rate η is as follows:

[0112] Among them, A sz To calculate the total cross-sectional area (in mm²) for the experiment, A dz K represents the total design cross-sectional area (mm²) of the existing prestressed anchor cable 100. iK0 is the measured stiffness coefficient (in kN / mm) of the existing prestressed anchor cable 100, and K0 is the theoretical stiffness coefficient (in kN / mm) of the existing prestressed anchor cable 100. K0 can be calculated using the following formula:

[0113] Where n is the number of steel strands in the existing prestressed anchor cable 100, E s The elastic modulus of a single steel strand (unit: kN / mm²) 2 A s The cross-sectional area of ​​a single steel strand (in mm²), l f The design free section length (in mm) of the existing prestressed anchor cable 100.

[0114] The cross-sectional damage assessment of the existing prestressed anchor cable 100 includes: When η≤10%, the condition of the existing prestressed anchor cable 100 section is judged to be good, indicating that the material body is basically free of rust and broken wires and can continue to be used.

[0115] When 10% < η ≤ 30%, the condition of the existing prestressed anchor cable 100 section is judged as general, indicating that there is slight section damage, and it can continue to be observed and used.

[0116] When 30% < η ≤ 40%, the condition of the existing prestressed anchor cable 100 section is judged as deteriorated, indicating that the section is significantly weakened and reinforcement measures should be taken.

[0117] When η>40%, the existing prestressed anchor cable section 100 is judged to be in failure, indicating that the effective load-bearing section is severely damaged, and the anchor cable should be scrapped and replaced or the structure should be reinforced as soon as possible.

[0118] Specifically, such as Figure 18 As shown above, K3 is closest to K0, therefore the load corresponding to segment K3 is determined to be the residual load P. r =254kN. K3 is 8.5kN / mm, E s =195kN / mm 2 nA s =700mm 2 , l f =15000mm, the damage rate of the anchor cable section is calculated as follows.

[0119]

[0120]

[0121] Therefore, the anchor cable section damage rate is low, the anchor cable performance is good, and the anchor cable can continue to be used based on comprehensive judgment.

[0122] By extracting the measured stiffness coefficient K during the lift-off stage i Combined with the design free segment length l f With elastic modulus E s The total cross-sectional area A of the anchor cable can be accurately calculated without excavation or damage. sz The damage rate η was used to transform the hidden metal section loss into a quantifiable mechanical stiffness index; a stepped damage classification system with 10%, 30%, and 40% as the boundaries was defined, overcoming the blindness of the traditional assessment that regards it as safe as long as the load does not drop sharply. It can screen out hidden anchor cables with the risk of sudden brittle fracture due to severe weakening of the effective section earlier and more accurately, providing a scientific and forward-looking opportunity and basis for the reinforcement of slopes and support structures.

[0123] Existing assessment methods are typically limited to a single-dimensional analysis of the current residual load or prestress loss level of the anchor cable, failing to detect potential weaknesses in the effective cross-section, such as deep corrosion or wire breakage (for example, an anchor cable with severely corroded and weakened cross-section may still show normal load readings for a short period, easily overlooking the risk of sudden fracture). This embodiment constructs a dual evaluation system that includes performance grading and cross-sectional damage assessment, deeply integrating "residual load grading assessment" based on measured load-displacement curves with "stiffness-based cross-sectional damage assessment." This not only reveals the current bearing capacity but also quantitatively diagnoses the degree of material damage and deterioration, achieving in-depth health checks and precise early warnings for the entire life cycle of existing anchoring projects.

[0124] Traditional lift-off testing typically assumes the lift-off point is the force equilibrium point. However, in actual multi-cable anchoring projects, uneven stress relaxation among the cables leads to a prolonged lift-off process, resulting in complex and variable load-displacement curves (such as broken lines, arcs, or significant lag between the lift-off point and the equilibrium point). This method calculates the remaining load P based on the geometric characteristics of the measured load-displacement curve generated by jacking loading. r It avoids physical lag errors such as visual estimation or feeler gauge insertion and removal, and can accurately decouple and extract the real mechanical equilibrium load from complex curves.

[0125] Without damaging the soil and rock mass and the anchor cable protective layer, this method uses the measured load-displacement curve to obtain the measured stiffness coefficient K during the lift-off loading stage. i And the total cross-sectional area A of the experiment was calculated in reverse. sz The section damage rate η transforms the abstract and hidden degree of corrosion weakening of internal metal sections into an intuitive quantitative indicator, providing scientific and rigorous data support for the reinforcement and treatment decisions of slopes and underground engineering, and improving the efficiency of on-site testing and the reliability of evaluation results.

[0126] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An existing prestressed anchor cable testing device, characterized in that, include: The inner sleeve (11) and the rod (12) connected to the inner sleeve (11) are connected to the anchor head of the existing prestressed anchor cable (100). The rod (12) is equipped with a reaction support plate (13) at one end away from the anchor head. The detection unit (2) is sleeved on the outer periphery of the inner sleeve (11) and supported on the end face of the existing anchor plate (200) for collecting the stress and deformation data of the existing prestressed anchor cable (100). The reaction collar (3) is threaded to the outer wall of the inner sleeve (11) and is used to adjustably abut against the detection unit (2) in the axial direction. The lifting mechanism (4) is supported between the existing anchor plate (200) and the reaction support plate (13) and is used to apply axial force to the rod (12).

2. The existing prestressed anchor cable testing device according to claim 1, characterized in that, It also includes an outer sleeve (5), which is fitted around the outer periphery of the detection unit (2) and the reaction ring (3) and supported between the existing anchor plate (200) and the lifting mechanism (4); the inner wall of the outer sleeve (5) is in contact with the outer wall of the detection unit (2).

3. The existing prestressed anchor cable testing device according to claim 2, characterized in that, The outer sleeve (5) has an operation window (51), and the outer wall of the reaction collar (3) has multiple insertion holes (31). Each insertion hole (31) is suitable for inserting a tool that passes through the operation window (51) to rotate and twist the reaction collar (3) so that the reaction collar (3) axially abuts against the detection unit (2).

4. The existing prestressed anchor cable testing device according to claim 1, characterized in that, The inner sleeve (11) has an internal thread on the inner wall near the anchor head, and the working anchor plate (300) of the existing prestressed anchor cable (100) has an external thread on the outer wall. The inner sleeve (11) is screwed into the working anchor plate (300) through the internal thread.

5. The existing prestressed anchor cable testing device according to claim 1, characterized in that, It also includes a transition anchor plate (6), which is fixedly installed on the exposed end of the existing prestressed anchor cable (100); the outer wall of the transition anchor plate (6) is provided with an external thread, and the inner wall of the inner sleeve (11) near the transition anchor plate (6) is provided with an internal thread. The inner sleeve (11) is screwed into the external thread of the transition anchor plate (6) through the internal thread.

6. A method for evaluating the performance of existing prestressed anchor cables, characterized in that, Includes the following steps: S1. Install the existing prestressed anchor detection device according to any one of claims 1-5 at the anchor head of the existing prestressed anchor (100), apply axial force to the rod (12) through the lifting mechanism (4) to lift and load, and use the detection unit (2) to collect the load and displacement data of the existing prestressed anchor (100) in real time to generate the measured load-displacement curve. S2. Based on the morphological characteristics of the measured load-displacement curve generated in S1, calculate the residual load P of the existing prestressed anchor cable (100). r Unit: kN; S3. Based on the remaining load P r The design locking load P0 of the existing prestressed anchor cable (100), in kN, and the tension control force P of the existing prestressed anchor cable (100). k Unit: kN; Comparison relationship: Residual load performance classification assessment of existing prestressed anchor cables (100); S4. Calculate the measured stiffness coefficient K of the existing prestressed anchor cable (100) based on the measured load-displacement curve. i The unit is kN / mm, and it is based on the measured stiffness coefficient K. i The total cross-sectional area A of the existing prestressed anchor cable (100) was calculated by back-calculation test. sz The unit is mm², and then the section damage rate η is calculated to evaluate the section damage of the existing prestressed anchor cable (100).

7. The method for evaluating the performance of existing prestressed anchor cables according to claim 6, characterized in that, In S2, when the measured load-displacement curve has an inflection point, data points are selected before and after the inflection point to perform linear fitting, resulting in a first fitted line and a second fitted line. The load value corresponding to the intersection of the first and second fitted lines is determined as the residual load P. r .

8. The method for evaluating the performance of existing prestressed anchor cables according to claim 6, characterized in that, In S2, when the measured load-displacement curve is a smooth curve without any bends, calculate the theoretical stiffness coefficient K0 of the existing prestressed anchor cable (100), in kN / mm. Where n is the number of steel strands in the existing prestressed anchor cable (100), E s The elastic modulus of a single steel strand, in kN / mm². 2 A s The cross-sectional area of ​​a single steel strand, in mm², l f The design free section length of the existing prestressed anchor cable (100) is in mm; The slope of the tangent along the measured load-displacement curve is calculated segment by segment according to the preset displacement step size and used as the measured stiffness coefficient K. i Unit: kN / mm; A comprehensive comparison of all measured stiffness coefficients K i The measured stiffness coefficient K is selected from the theoretical stiffness coefficient K0. i The interval with the smallest absolute value of the difference from the theoretical stiffness coefficient K0 is determined as the residual load Pr.

9. The method for evaluating the performance of existing prestressed anchor cables according to claim 6, characterized in that, In S3, P k The calculation formula is: Among them, f ptk This refers to the standard value of the tensile strength of steel strand, in MPa (amperes per inch). dz The total design cross-sectional area of ​​the existing prestressed anchor cable (100) is expressed in mm². The residual load performance classification assessment of existing prestressed anchor cables (100) includes: When 0.8P0≤P r When <1.1P0, the evaluation level is determined to be Grade A, indicating that the existing prestressed anchor cable (100) has good performance; When 0.5P0≤P r When <0.8P0, the evaluation level is determined to be B, indicating that the performance of the existing prestressed anchor cable (100) is generally average. When 0.3P0≤P r When <0.5P0, the evaluation level is determined to be C, indicating that the performance of the existing prestressed anchor cable (100) has deteriorated; When P r When <0.3P0, the assessment level is judged as D, and the existing prestressed anchor cable (100) has failed; When 1.1P0≤P r <P k At that time, the assessment level was determined to be Grade E, indicating that the existing prestressed anchor cable (100) posed a safety risk; When P r ≥P k At that time, the assessment level was determined to be F, and the existing prestressed anchor cable (100) was in a high-risk state.

10. The method for evaluating the performance of existing prestressed anchor cables according to claim 6, characterized in that, In S4, the formula for calculating the cross-sectional damage rate η is: Among them, A sz To calculate the total cross-sectional area for the experiment, in mm², A dz K represents the total design cross-sectional area of ​​the existing prestressed anchor cable (100), in mm². i K0 is the measured stiffness coefficient of the existing prestressed anchor cable (100), in kN / mm; K0 is the theoretical stiffness coefficient of the existing prestressed anchor cable (100), in kN / mm. The cross-sectional damage assessment of the existing prestressed anchor cable (100) includes: When η≤10%, the condition of the existing prestressed anchor cable (100) section is judged to be good; When 10% < η ≤ 30%, the condition of the existing prestressed anchor cable (100) section is judged as general; When 30% < η ≤ 40%, the condition of the existing prestressed anchor cable (100) section is judged to be deteriorated; When η>40%, the existing prestressed anchor cable (100) section is judged to be in failure.

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