Rock anchor engineering tension concentration type anchor cable hidden engineering problem detection method

Abstract

The invention discloses a rock anchor engineering tension concentration type anchor cable hidden engineering problem detection method, which comprises the following steps: aiming at non-uniform length distribution of a free end, adopting graded tension detection, sequentially tensioning each anchor bar, recording elongation and oil pressure readings, calculating the real length of the free end through least square regression, and evaluating the uniformity; aiming at uneven tension distribution, axial force detection based on a strain gauge is adopted, a tool with a notch is designed to lead out a wire, a customized sleeve is arranged between an anchorage device and a working anchor, the strain gauge is pasted and protected, graded tensioning is carried out, micro-strain is collected in real time, axial force of each beam is converted, and the uneven force is quantified. According to the method, synchronous detection of the length of the free end of the anchor cable and tension distribution can be achieved under the condition of a conventional tensioning process, hidden engineering problems are rapidly recognized, and the method has the advantages of being high in detection precision, low in tool cost and high in adaptability.

Description

Technical Field

[0001] This invention belongs to the field of rock anchor engineering construction technology, specifically relating to a method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering. Background Technology

[0002] Existing high-tonnage prestressed anchor cable support technology has many hidden problems that have been overlooked for years. Multi-strand prestressed anchor cable support technology is an important means of maintaining slope stability. Due to the need to apply high prestress, a single anchor cable bundle on site often consists of 3-14 or even more anchor bars. Due to limitations in installation technology and grouting techniques, there are significant differences in the internal grouting anchor sections, resulting in different lengths of the free ends of the anchor cables and affecting the final construction quality. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering, which can simultaneously detect the length of the free end of the anchor cable and the distribution of tension under conventional tensioning process conditions, quickly identify hidden engineering problems, and has high detection accuracy, low tooling cost and strong adaptability.

[0004] The technical solution of this invention is as follows:

[0005] A method for detecting latent engineering problems of anchor cables with concentrated tension in rock anchor engineering includes the following steps:

[0006] Step 1: To address the issue of uneven distribution of the free end length of the anchor bars, conduct graded tensioning tests based on site conditions: determine the testing sequence; prepare hydraulic pumps and single-wire jacks; perform graded tensioning on each anchor bar, record the elongation and hydraulic pressure readings; use the least squares method to fit a linear regression equation to calculate the true length of the free end of the anchor bar, and evaluate the uniformity of distribution.

[0007] Step 2: To address the issue of uneven tension distribution in the anchor bars, axial force detection based on strain gauge monitoring is performed: a custom fixture is designed and fabricated, including creating notches on the anchor to lead out the conductors, and a custom sleeve is added between the custom fixture and the working anchor; the strain gauge bonding location is selected and the bonding and protection process is executed; the test system is arranged, graded tensioning is performed, and micro-strain is recorded in real time; the axial force is calculated based on the strain data, and the uneven stress distribution is quantified.

[0008] Furthermore, in step 1, determining the detection sequence includes: formulating the tensioning sequence based on the anchor cable arrangement sequence, with the tensioning sequence arranged from the center outwards or clockwise.

[0009] Further, in step 1, the graded tensioning includes: based on the design axial tension P of a single anchor cable, each anchor bar is tensioned in 6 stages, with stages of 0.12P, 0.25P, 0.50P, 0.75P, 1.00P, and 1.10P; during each stage of tensioning, the actual elongation value l of the i-th anchor bar at stage k is recorded. ik And the actual oil pressure reading σ np·t .

[0010] Furthermore, in step 1, the formula for calculating the hydraulic pressure reading is:

[0011] σ p·k =PS,

[0012] σ np·k =nσ p·k ,

[0013] In the formula, σ pk σ is the design value of the oil gauge reading for anchor cable tensioning. npk The design value of the anchor cable tensioning oil gauge is denoted by grading coefficient, P is the design axial tension of a single anchor cable, S is the effective area of ​​the jack piston, and n is the tensioning grading coefficient.

[0014] Furthermore, in step 1, the formula for calculating the actual length of the free end is:

[0015] L n·t =l ik ε,

[0016] ε=A·σ np·t EA c ,

[0017] In the formula, L n·t ε is the true length of the free end of the anchor bar, ε is the average strain of the anchor bar, A is the effective area of ​​the jack piston, and σ is the average strain of the anchor bar. np·t The anchor stress is calculated from hydraulic pressure at the t-th tension stage, where E is the elastic modulus of steel, and A is the stress. c Given the cross-sectional area of ​​the anchor bar, determine the relationship between L and L using the least squares method. n·t and σ np·t The linear regression equation is used to determine the true length of the anchor bar.

[0018] Furthermore, in step 2, the tooling design and fabrication includes: creating a notch on the anchor by pyrotechnic welding; and adding a custom sleeve, the length of which is calculated using the following formula:

[0019] l = 1.1l k +20,

[0020] In the formula, l is the custom sleeve length, l k To determine the elongation of the anchor bars;

[0021] The inner diameter of the sleeve is greater than the distance between the farthest ends of the outer contours of the adjacent anchor bars, and the inner diameter of the sleeve is less than the maximum diameter of the tooling.

[0022] Furthermore, in step 2, the strain gauge attachment position is specifically selected as follows: located inside the tangent between the anchor bar and the custom sleeve.

[0023] Furthermore, in step 2, the strain gauge pasting and protection process specifically includes: rust removal, degreasing, coarse grinding, fine grinding, wet cleaning, dry cleaning, pasting, waterproof protection, ultraviolet baking, secondary protection, and wire lead-out.

[0024] Furthermore, in step 2, the experimental system arrangement specifically includes: installing customized tooling, customized sleeves, working anchors, limiters, through-hole jacks, multi-strand anchor cables, strain gauges, and lead wires; using traditional tensioning technology for graded tensioning, the data acquisition instrument records micro-strain in real time and calculates the axial force; the formula for calculating the axial force is:

[0025] F = E·A c ·ε,

[0026] Where F is the axial force, E is the elastic modulus of steel, and A c Let ε be the cross-sectional area of ​​the anchor bar, and ε be the average strain of the anchor bar.

[0027] Furthermore, it also includes data processing and evaluation: the collected data are fitted with linear regression using the least squares method; the evaluation index is the length uniformity coefficient, including the standard deviation and the mean; and the stress non-uniformity index, including the maximum stress and the minimum stress.

[0028] The beneficial effects of this invention are:

[0029] 1. Achieve low-cost on-site testing and improve engineering economy: This invention relies on existing common equipment such as hydraulic pumps, single-wire tensioning jacks and strain gauges, and can be implemented with simple modifications (such as anchor burning notches and customized sleeves). There is no need to introduce expensive special instruments or make significant adjustments to the construction process. This significantly reduces the testing cost and is suitable for large slope, tunnel or water conservancy project sites with limited budgets, promoting the widespread application of rock anchor support technology.

[0030] 2. Avoiding eccentricity and anchor damage, improving detection reliability: This invention effectively minimizes eccentric loads and local stress concentrations during the tensioning process by formulating a scientific tensioning sequence (such as from the center outwards or clockwise) and a graded tensioning strategy (0.12P to 1.10P levels), ensuring the stability of the anchoring material and avoiding the propagation of hidden cracks. This not only improves the accuracy of data acquisition (such as the reliability of elongation and micro-strain) but also protects the integrity of the anchor cable structure and reduces the risk of secondary engineering.

[0031] 3. Quantifying feedback on hidden problems to promote construction quality assurance: This invention uses the least squares method to fit linear regression, calculates the true length of the free end and the axial force distribution, and introduces evaluation indicators (such as length uniformity coefficient: standard deviation / mean value; stress unevenness index: maximum stress / minimum stress) to achieve accurate quantification and real-time feedback of hidden problems. This helps to identify defects caused by differences in installation process or grouting in a timely manner, improve the uniformity of anchor cable prestress, and thus ensure the long-term stability of the project.

[0032] 4. High versatility and scalability, applicable to multiple engineering scenarios: This invention is applicable to prestressed anchor cables with 3-14 or more bundles, compatible with traditional tensioning processes, requires no special environmental adaptation, and is easy to promote (such as slope support, tunnel surrounding rock reinforcement, or hydraulic dam stability). Its innovation lies in combining on-site conditions with low-invasive monitoring (such as strain gauge protection process), providing a standardized testing paradigm for rock anchor engineering, and promoting technological progress in the industry.

[0033] 5. Enhanced engineering safety and sustainability: This invention can prevent structural failure caused by stress loss by detecting hidden problems at an early stage, reduce the risk of accidents, and promote the sustainable development of rock anchor support. At the same time, it supports the combination of numerical simulation to verify field data, further optimize design parameters, and improve the overall lifespan of the project. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the detection of the free segment length distribution of anchor bars in a method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to the present invention.

[0035] Figure 2 This is a schematic diagram of the grading and tensioning of anchor bars in a method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering, according to the present invention.

[0036] Figure 3 This is a schematic diagram of the anchor cable arrangement and numbering for a method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to the present invention.

[0037] Figure 4 This is a schematic diagram of the tension distribution detection method for a method of detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to the present invention.

[0038] Figure 5 This is a schematic diagram of a customized tooling for a method of detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to the present invention.

[0039] Figure 6 This is a schematic diagram of strain gauge patching for a method of detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to the present invention.

[0040] Figure 7This is a schematic diagram of the anchor bar length distribution detection test equipment for a method of detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to the present invention.

[0041] Figure 8 This is a flowchart illustrating a method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering, according to the present invention.

[0042] Figure 9 This is a flowchart of a method for detecting the length distribution of the free end of an anchor cable, which is a method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to the present invention.

[0043] Figure 10 This is a flowchart of the anchor cable tension distribution detection method, which is part of the present invention, for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering.

[0044] In the diagram: 1-Single wire harness jack; 2-Anchor bar; 11-Custom tooling; 12-Custom sleeve; 13-Working anchor; 14-Limiter; 15-Through-core jack; 16-Multi-wire harness anchor cable; 17-Strain gauge; 18-Leading wire; 19-Tangent section. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0046] Example 1: As Figure 1-7 As shown, a system employing the method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to this application includes a free end length distribution detection system and a tension distribution detection system. The free end length distribution detection system includes a single-wire jack 1 and an anchor bar 2. The single-wire jack 1 directly clamps the free end of the anchor bar 2 through its clamping end to achieve hydraulic tensioning. The connection method is mechanical clamping to ensure that the tension force is evenly transmitted to the anchor bar 2. During the staged tensioning process, the jack 1 applies axial tension and records the elongation and hydraulic pressure reading of the anchor bar 2. This connection avoids eccentricity and quantifies the free end length distribution.

[0047] The tension distribution detection system includes: a custom-made tooling 11, a custom-made sleeve 12, a working anchor 13, a limiter 14, a through-hole jack 15, a multi-strand anchor cable 16, a strain gauge 17, a lead wire 18, and a tangent section 19. The multi-strand anchor cable 16 (composed of multiple anchor bars) passes through the central channel of the through-hole jack 15. The front end of the jack 15 is connected to the limiter 14, which is further fixed to the rear end of the working anchor 13. The connection method is a through-hole fitting to ensure that the anchor cable 16 is axially aligned during tensioning. The through-hole jack 15 applies tension, and the displacement is limited by the limiter 14. The working anchor 13 serves as the anchor point and bears the overall stress. The front end of the working anchor 13 is connected to the custom-made sleeve 12, and the outer end of the custom-made sleeve 12 is fixed to the custom-made tooling 11. The connection method is a socket-type embedding. The sleeve 12 provides displacement space for the strain gauge (length not less than 1.1 times the design elongation plus 20mm). The custom tooling 11 bears the tensile force through a notch formed by acetylene welding and leads out the wire (the custom tooling 11 is made of high-strength steel, cylindrical in shape, and has multiple anchor bar holes inside, corresponding to the number of multiple wire bundle anchor cables, for example, 14 holes, to ensure uniform distribution of axial tensile force). The anchor bars of the anchor cable 16 pass through these components to form a continuous force chain. The strain gauge 17 is pasted at the tangent part 19 (inner side position, to avoid friction failure) between the anchor bar and the custom sleeve 12 and is fixed with a special adhesive. One end of the lead wire 18 is welded to the strain gauge 17, and the other end is led out from the notch of the custom tooling 11 and connected to an external acquisition instrument. The connection method is electrical welding and mechanical protection to ensure stable signal transmission.

[0048] Example 2: Figure 8-10 As shown, a method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering includes the following steps:

[0049] Step 1: To address the issue of uneven distribution of the free end length of the anchor bars, conduct graded tensioning tests based on site conditions: determine the testing sequence; prepare a hydraulic pump and a single-wire jack 1; perform graded tensioning on each anchor bar, record the elongation and hydraulic pressure readings; use the least squares method to fit a linear regression equation to calculate the true length of the free end of the anchor bar 2, and evaluate the uniformity of distribution;

[0050] Step 2: To address the issue of uneven tension distribution in the anchor bars, axial force detection based on strain gauge monitoring is performed: A custom fixture 11 is designed and fabricated, including forming a notch on the anchor to lead out the conductor 18, and a custom sleeve 12 is added between the custom fixture 11 and the working anchor 13; the bonding position of the strain gauge 17 is selected and the bonding and protection process is executed; the test system is arranged, graded tensioning is performed and micro-strain is recorded in real time; the axial force is calculated based on the strain data, and the uneven stress distribution is quantified.

[0051] Preferably, in step 1, determining the detection sequence includes: formulating a tensioning sequence based on the anchor cable arrangement sequence, wherein the tensioning sequence is arranged from the center outwards or clockwise.

[0052] Preferably, in step 1, the graded tensioning includes: based on the design axial tension P of a single anchor cable, each anchor bar is tensioned in 6 stages, with stages of 0.12P, 0.25P, 0.50P, 0.75P, 1.00P, and 1.10P; during each stage of tensioning, the actual elongation value l of the i-th anchor bar at the k-th stage is recorded. ik And the actual oil pressure reading σ np·t .

[0053] Preferably, in step 1, the formula for calculating the hydraulic pressure reading is:

[0054] σ p·k =PS,

[0055] σ np·k =nσ p·k ,

[0056] In the formula, σ pk σ is the design value of the oil gauge reading for anchor cable tensioning. npk The design value of the anchor cable tensioning oil gauge is denoted by grading coefficient, P is the design axial tension of a single anchor cable, S is the effective area of ​​the jack piston, and n is the tensioning grading coefficient.

[0057] Preferably, in step 1, the formula for calculating the actual length of the free end of the anchor bar 2 is:

[0058] L n·t =l ik ε,

[0059] ε=A·σ np·t EA c ,

[0060] In the formula, L n·t ε is the true length of the free end of the anchor bar, ε is the average strain of the anchor bar, A is the effective area of ​​the jack piston, and σ is the average strain of the anchor bar. np·t The anchor stress is calculated from hydraulic pressure at the t-th tension stage, where E is the elastic modulus of steel, and A is the stress. c Given the cross-sectional area of ​​the anchor bar, determine the relationship between L and L using the least squares method. n·t and σ np·t The linear regression equation is used to determine the true length of the anchor bar.

[0061] Preferably, in step 2, the tooling design and fabrication includes: forming a notch on the anchor by burning it with acetylene welding; adding a custom sleeve 12, the length of which is calculated using the following formula:

[0062] l = 1.1l k +20,

[0063] In the formula, l is the custom sleeve length, l k To determine the elongation of the anchor bars;

[0064] The inner diameter of the custom sleeve 12 is greater than the distance between the farthest ends of the outer contours of the adjacent anchor bars 2, and the inner diameter of the custom sleeve 12 is less than the maximum diameter of the custom tooling 11.

[0065] Preferably, in step 2, the strain gauge 17 is selected to be attached at a location inside the tangent between the anchor bar 2 and the custom sleeve 12.

[0066] Preferably, in step 2, the strain gauge 17 pasting and protection process specifically includes: rust removal, degreasing, coarse grinding, fine grinding, wet cleaning, dry cleaning, pasting, waterproof protection, ultraviolet baking, secondary protection, and wire lead-out;

[0067] The on-site anchor bars differ from experimental conditions and are affected by the environment, exhibiting characteristics of rust and oiliness. A special rust remover and degreaser should be used for initial cleaning of the anchor bar surface. Then, use a file to grind the anchor bar area where the strain gauge will be attached, creating a rectangular platform whose length and width are evenly less than twice the length and width of the strain gauge substrate. After the platform is formed, use 1000-grit sandpaper to finely grind the platform to ensure it is clean and tidy. Then, use alcohol wipes and dry wipes to cyclically wipe the platform area to ensure it is clean and dry. Use a special strain gauge adhesive to fix the strain gauge to the platform surface, pressing with PTFE paper for 1 minute to ensure full adhesion. Use a special waterproof silicone sealant to fully cover the strain gauge surface for waterproof protection. Under outdoor conditions, to ensure the survival rate of the strain gauge, use a UV lamp to thoroughly heat the waterproof silicone sealant for 3 hours. After confirming solidification and hardening, use insulating glue to fully wrap it for secondary protection. After the conductor protection is completed, the anchor cable should be led out from the notch in the custom-made tooling for external data acquisition monitoring.

[0068] Preferably, in step 2, the experimental system arrangement specifically includes: installing a customized fixture 11, a customized sleeve 12, a working anchor 13, a limiter 14, a through-hole jack 15, a multi-wire anchor cable 16, strain gauges 17, and lead-out wires 18; using a traditional tensioning process for graded tensioning, the data acquisition instrument records micro-strain in real time and calculates the axial force; the formula for calculating the axial force is:

[0069] F = E·A c ·ε,

[0070] Where F is the axial force, E is the elastic modulus of steel, and A c Let ε be the cross-sectional area of ​​the anchor bar, and ε be the average strain of the anchor bar.

[0071] Preferably, it also includes data processing and evaluation: using the least squares method to fit linear regression to the collected data; the evaluation index is the length uniformity coefficient, including: standard deviation and mean; and the stress non-uniformity index, including: maximum stress and minimum stress.

Claims

1. A method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering, characterized in that, Includes the following steps: Step 1: To address the uneven distribution of the free end length of the anchor bars, a graded tensioning test based on the site conditions is conducted: Determine the test sequence; Prepare a hydraulic pump and a single-wire jack (1); Tension each anchor bar (2) in stages, record the elongation and oil pressure readings; Use the least squares method to fit the linear regression equation to calculate the true length of the free end of the anchor bar, and evaluate the uniformity of the distribution; Step 2: To address the issue of uneven tension distribution in the anchor bars, axial force detection based on strain gauge monitoring is performed: a custom fixture (11) is designed and fabricated, including forming a notch on the anchor to lead out the wire, and a custom sleeve (12) is added between the custom fixture (11) and the working anchor (13); the location for pasting the strain gauge (17) is selected and the pasting and protection process is executed; the test system is arranged, graded tensioning is performed, and micro-strain is recorded in real time; Axial force is calculated based on strain data, and the uneven distribution of stress is quantified.

2. The method for detecting hidden engineering problems of concentrated anchor cables in rock anchor engineering according to claim 1, characterized in that, In step 1, determining the testing sequence includes: formulating the tensioning sequence based on the anchor cable arrangement sequence, with the tensioning sequence arranged from the center outwards or clockwise.

3. The method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to claim 1, characterized in that, In step 1, the graded tensioning includes: based on the design axial tension P of a single anchor cable, each anchor bar (2) is tensioned in 6 levels, with levels of 0.12P, 0.25P, 0.50P, 0.75P, 1.00P, and 1.10P; during each level of tensioning, the actual elongation value l of the i-th anchor bar at the k-th level is recorded. ik And the actual oil pressure reading σ np·t .

4. The method for detecting hidden engineering problems of tension-concentrated anchor cables in rock anchor engineering according to claim 1, characterized in that, In step 1, the formula for calculating the oil pressure reading is: σ p·k =PS, s np·k =nσ p·k , In the formula, σ pk σ is the design value of the oil gauge reading for anchor cable tensioning. npk The design value of the anchor cable tensioning oil gauge is denoted by grading coefficient, P is the design axial tension of a single anchor cable, S is the effective area of ​​the jack piston, and n is the tensioning grading coefficient.

5. The method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to claim 1, characterized in that, In step 1, the formula for calculating the actual length of the free end of the anchor bar (2) is as follows: L n·t =l ik eh, ε=A·σ np·t YES c , In the formula, L n·t ε is the true length of the free end of the anchor bar, ε is the average strain of the anchor bar, A is the effective area of ​​the jack piston, and σ is the average strain of the anchor bar. np·t The anchor stress is calculated from hydraulic pressure at the t-th tension stage, where E is the elastic modulus of steel, and A is the stress. c Given the cross-sectional area of ​​the anchor bar, determine the relationship between L and L using the least squares method. n·t and σ np·t The linear regression equation is used to determine the true length of the anchor bar.

6. The method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to claim 1, characterized in that, In step 2, the tooling design and fabrication include: forming a notch on the anchor by burning it with acetylene welding; adding a custom sleeve (11), the length of which is calculated using the following formula: l＝1.1l k +20， In the formula, l is the custom sleeve length, l k To determine the elongation of the anchor bars; The inner diameter of the custom sleeve (12) is greater than the distance between the farthest ends of the outer contours of the adjacent anchor bars (2), and the inner diameter of the custom sleeve (12) is less than the maximum diameter of the custom tooling (11).

7. The method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to claim 1, characterized in that, In step 2, the specific location for attaching the strain gauge (17) is as follows: it is located inside the tangent between the anchor bar (2) and the custom sleeve (12).

8. The method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to claim 1, characterized in that, In step 2, the strain gauge (17) pasting and protection process specifically includes: rust removal, degreasing, coarse grinding, fine grinding, wet cleaning, dry cleaning, pasting, waterproof protection, ultraviolet baking, secondary protection and wire lead-out.

9. The method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to claim 1, characterized in that, In step 2, the experimental system arrangement specifically includes: installing customized tooling (11), customized sleeve (12), working anchor (13), limiter (14), through-hole jack (15), multi-wire anchor cable (16), strain gauge (17), and lead wire (18); using traditional tensioning technology for graded tensioning, the data acquisition instrument records micro-strain in real time and calculates the axial force; the formula for calculating the axial force is: F=E·A c ·e, Where F is the axial force, E is the elastic modulus of steel, and A c Let ε be the cross-sectional area of ​​the anchor bar, and ε be the average strain of the anchor bar.

10. The method for detecting hidden engineering problems of anchor cables with concentrated tension in rock anchor engineering according to claim 1, characterized in that, It also includes data processing and evaluation: using the least squares method to fit linear regression to the collected data; The evaluation indicators are the length uniformity coefficient, including the standard deviation and the mean; and the stress non-uniformity index, including the maximum stress and the minimum stress.

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