Method for testing wave velocity and anchoring quality of anchor rod system

Abstract

The invention discloses a method for testing the rod system wave velocity and anchoring quality of an anchor rod, and the method comprises the steps: building an experimental model for testing the rod system wave velocity of the anchor rod, and testing the rod system wave velocity of the anchor rod wrapped by different anchoring media through the experimental model; the influence of different anchoring media on the anchor rod system wave velocity is analyzed through multiple experiments, and the curvilinear relation between the different anchoring media and the anchor rod system wave velocity and the anchoring quality is established; and evaluating the anchoring quality by measuring the rod system wave velocity of the anchor rod by using the curve relationship. According to the method, engineering scenes under different working conditions are simulated, the anchoring section wave velocity of an anchor rod anchoring system can be more comprehensively recognized, meanwhile, the anchoring quality is rapidly evaluated by measuring the anchor rod system wave velocity in actual engineering, problems in the construction process are found and corrected in time, the anchoring quality problem is avoided, and the construction efficiency is improved. The method has remarkable anchoring engineering quality identification and scientific research values.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of anchor rod determination, and particularly relates to a method for testing anchor rod system wave velocity and anchoring quality. BACKGROUND

[0002] As an important supporting structure, the anchoring quality and efficiency of the anchor rod mainly depend on the strength of the anchor rod body, the adhesion between the anchor rod body and the anchoring cementitious body, the adhesion between the anchoring cementitious body and the anchor hole wall, and the improvement of the physical values of the inner friction angle and cohesion of the anchoring cementitious body to the near-domain rock-soil body of the anchor hole. The nondestructive testing of the anchor rod is one of the most common technical means for detecting the anchoring quality, and the anchor rod wave velocity is used to identify the key parameters of the anchoring quality such as the length of the anchor rod, the integrity and continuity of the anchoring cementitious body, and the strength thereof.

[0003] In actual anchoring construction and detection, due to the single and / or comprehensive effects of subjective and objective factors such as inaccurate drilling depth, underground water and / or drilling water, water sensitivity of rock-soil body, incomplete cleaning of the anchor rod body, incomplete hole cleaning and / or underground water backflow, improper grouting parameters, grouting interruption, and turbulent impact of the slurry in the extremely small space due to the excessively high pressure, the length of the anchor rod body is insufficient, the adhesion between the anchoring cementitious body and the anchor rod body and / or the anchor hole wall is insufficient, and even the anchoring cementitious body is discontinuous, and the mud occupies the position of the anchoring cementitious body. The conventional nondestructive testing technology of the anchor rod does not have the identification ability of the setting mud and the anchoring cementitious body, and does not identify the reinforcement effect of the anchoring grouting on the near-domain rock-soil body of the anchor hole, resulting in low accuracy of the anchoring quality determination. Therefore, there is an urgent need for a more accurate, efficient and accurate determination method. SUMMARY

[0004] In view of the above problems in the prior art, the method for testing the anchor rod system wave velocity and the anchoring quality provided by the application solves the problems of complex operation and inaccurate measurement of the anchor rod wave velocity in the prior art.

[0005] In order to achieve the above-mentioned purposes, the technical scheme adopted by the application is as follows: a method for testing the anchor rod system wave velocity and the anchoring quality, comprising: constructing an experimental model for testing the anchor rod system wave velocity; using the experimental model for testing the anchor rod system wave velocity to measure the anchor rod system wave velocity wrapped by different anchoring media; analyzing the influence of different anchoring media on the anchor rod system wave velocity through multiple experiments, and establishing a curve relationship between different anchoring media and the anchor rod system wave velocity and the anchoring quality; using the established curve relationship to evaluate the anchoring quality according to the anchor rod system wave velocity.

[0006] Further, the specific method for constructing the experimental model for testing the anchor rod system wave velocity is as follows: an experimental box is made of metal materials; Fill the experimental box with simulated rock-soil, and reserve a reserved slot with the same size as the anchor hole during filling; Put the anchor rod with a known length into the reserved slot after wrapping it with different anchoring media; Fill the simulated rock-soil for the second time until the anchoring medium wrapping the anchor rod is completely buried; Place a heavy object above the simulated rock-soil; Connect the non-destructive testing instrument with the head of the free section of the anchor rod to complete the production of the experimental model.

[0007] Further, the non-destructive testing instrument comprises a vibration excitation device, a vibration pickup device, and a data acquisition and processing system; The vibration excitation device is connected to one side of the head of the free section of the anchor rod, and the vibration pickup device is connected to the other side of the head of the free section of the anchor rod; the data acquisition and processing system is connected to the output end of the vibration pickup device.

[0008] Further, the specific method for measuring the wave velocity of the anchor rod wrapped with different anchoring media by using the experimental model for testing the wave velocity of the anchor rod is as follows: Collect the waveform graph by using the experimental model for testing the wave velocity of the anchor rod to obtain the waveform time-distance graph of the excitation sound wave transmitted in the anchor rod; Identify the tail-end reflection signal of the free section of the anchor rod and the tail-end reflection signal of the anchoring section of the anchor rod according to the waveform time-distance graph to obtain the tail-end reflection time of the free section of the anchor rod and the tail-end reflection time of the anchoring section of the anchor rod; Measure the excitation sound wave velocity in the free section of the anchor rod; Measure the length of the free section of the anchor rod and the length of the anchoring section of the anchor rod; Calculate the wave velocity of the anchor rod according to the length of the anchoring section of the anchor rod, the tail-end reflection time of the free section of the anchor rod, and the tail-end reflection time of the anchoring section of the anchor rod.

[0009] Further, the specific method for collecting the waveform graph is as follows: Start the vibration excitation device to generate excitation forces with different frequencies and intensities, receive the sound wave reflection signals transmitted by the anchor rod by the vibration pickup device, and collect, amplify, filter, and read the graph of the sound wave reflection signals received by the vibration pickup device by the data acquisition and processing system to obtain the waveform time-distance graph of the excitation sound wave transmitted in the anchor rod.

[0010] Further, the calculation expression of the length of the free section of the anchor rod is as follows:

[0011] wherein, L is the length of the free section of the anchor rod, V is the excitation sound wave velocity in the free section of the anchor rod, T is the tail-end reflection time of the free section of the anchor rod.

[0012] Further, the calculation expression of the anchor rod anchoring segment length is:

[0013] wherein, is the anchor rod anchoring segment length, is the total length of the anchor rod.

[0014] Further, the calculation expression of the anchor rod rod system wave speed is:

[0015] wherein, is the anchor rod rod system wave speed, is the tail end reflection time of the anchor rod anchoring segment.

[0016] The beneficial effects of the present application are: 1. By making an experimental model for testing the anchor rod rod system wave speed, various working conditions, different geological conditions and even surrounding rock loads can be simulated. By changing the experimental conditions in the model, the different external influences on the anchor rod in different geological environments can be accurately studied, and more accurate changes in the anchor rod rod system wave speed can be obtained, and the stress condition of the anchor rod can be further analyzed, thereby providing more accurate and convincing experimental basis for developing anchor rods suitable for deep underground engineering.

[0017] 2. By wrapping the anchor rod with a known length with different anchoring media and placing it in the reserved slot, different anchoring media can be simulated, and the relationship between the anchoring medium and the anchor rod rod system wave speed can be more accurately studied, and the anchor rod wave speed can be more accurately predicted and determined, so that the use of anchoring media can be adjusted according to the actual situation during construction, the construction process is optimized, and the stability and bearing capacity of the anchor rod under different conditions are ensured.

[0018] 3. By measuring the anchor rod rod system wave speed under different simulated anchor rods and different simulated working conditions, the variation law of the anchor rod wave speed can be deeply studied, which provides a data basis and reference for non-destructive testing of anchor rods, improves the accuracy and reliability of non-destructive testing of anchor rods, and at the same time provides reliable detection data and technical support for tunnel primary support anchor rod anchoring engineering.

[0019] 4. By establishing the curve relationship between different anchoring media and anchor rod rod system wave speed and anchoring quality, the anchoring quality can be quickly evaluated by measuring the anchor rod rod system wave speed in actual engineering, which provides a scientific basis for the safe operation of the project, timely discovers and corrects problems in the construction process, avoids safety problems, and has important engineering practice and scientific research value. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the flowchart of the method of the present application; Figure 2The reserved slot schematic diagram of the experimental model for testing the wave speed of the anchor rod system; Figure 3 The front view of the experimental box before the second simulation of the filling of the rock-soil; Figure 4 The top view of the experimental box before the second simulation of the filling of the rock-soil; Figure 5 The front view of the experimental box after the second simulation of the filling of the rock-soil; Figure 6 The detail view of the free section of the anchor rod; Figure 7 The side view of the experimental model for testing the wave speed of the anchor rod system; Figure 8 The relationship curve between the cement slurry ratio provided by the embodiment and the wave speed of the anchor rod system and the anchoring quality. DETAILED DESCRIPTION

[0021] The specific embodiments of the present application are described below to facilitate the understanding of the present application for those skilled in the art, but it should be clear that the present application is not limited to the scope of the specific embodiments, and for those skilled in the art, as long as various changes are within the spirit and scope of the present application defined and determined by the appended claims, all the inventions utilizing the concept of the present application are within the scope of protection.

[0022] As shown in Figure 1 , in one embodiment of the present application, a method for testing the wave speed of the anchor rod system and the anchoring quality comprises the following steps: S1, constructing an experimental model for testing the wave speed of the anchor rod system: An iron plate (or other metal materials with sufficient rigidity and stability) with appropriate length size (can accommodate most size anchor rods for experiments) is welded into an experimental box; The simulated rock-soil is filled in the experimental box, and the simulated rock-soil can be used for different types of original rock, sand, clay or their mixture to simulate different geological conditions; When filling the simulated rock-soil, a reserved slot with appropriate spacing equal to the size of the anchor rod drilling hole is reserved to ensure that the rod bodies do not affect each other when testing the wave speed of the anchor rod, and the steel wire and the padstone are fixed in the reserved slot in the experimental box to ensure the stability of the position and prevent movement or shaking during the experiment, as shown in Figure 2 ; The anchor rod with a known length is wrapped with different anchoring media (various surrounding rock, cement slurry, etc. for simulating different anchoring media; when simulating an empty rod, a PVC pipe can be used to cover, and foam plastic is used to fill the inside to prevent subsequent soil contact with the anchor rod or cement slurry entering the simulated empty rod), and then placed in the reserved slot, as shown in Figure 3 , Figure 4As shown, the part of the test box body wrapped with anchoring medium is called anchoring section of anchor rod or anchoring section, and the part of the test box body not wrapped with anchoring medium is called free section of anchor rod; when wrapping the anchor rod, multiple different anchoring medium sections can be selected to wrap the same anchor rod at the same time.

[0023] The second simulation of rock-soil filling is performed until the anchoring medium wrapped with the anchor rod is completely buried, as shown in Figure 5 A weight is placed on the simulated rock-soil to simulate the surrounding rock load; The nondestructive testing instrument is connected with the free section of the anchor rod, and the experimental model is completed, as shown in Figure 7

[0024] The nondestructive testing instrument includes an excitation device, a vibration pickup device and a data acquisition and processing system, as shown in Figure 6 The excitation hammer head of the excitation device is connected with one side of the first end of the free section of the anchor rod (i.e. the exposed section of the anchor rod shown in the figure), and the vibration pickup head in the vibration pickup device is connected with the other side of the first end of the free section of the anchor rod; the data acquisition and processing system is connected with the output end of the vibration pickup device.

[0025] S2, the wave speed of the anchor rod system wrapped with different anchoring media is measured by using the experimental model for testing the wave speed of the anchor rod system: S2-1, the wave form graph is collected by using the experimental model for testing the wave speed of the anchor rod system to obtain the wave curve of the anchor rod body vibration. The specific method is as follows: the excitation device is started to generate excitation force with different frequencies and intensities acting on one end of the anchor rod, the sound wave reflection signal transmitted by the other end of the anchor rod is received by the vibration pickup device, the sound wave reflection signal received by the vibration pickup device is collected, amplified, filtered and read by the data acquisition and processing system, and the wave form time-distance graph of the excitation sound wave transmitted in the anchor rod is obtained. The data acquisition and processing system also has data storage and transmission functions, can store the measurement data in the local hard disk, and can transmit the measurement data to external devices such as computers or tablet computers through wireless or wired ways, so as to facilitate further analysis and processing of the data.

[0026] S2-2, the anchor rod free section tail end reflection signal and the anchor rod anchoring section tail end reflection signal are identified according to the wave form time-distance graph of the excitation sound wave transmitted in the anchor rod, and the anchor rod free section tail end reflection time and the anchor rod anchoring section tail end reflection time are obtained; S2-3, the excitation sound wave wave speed in the anchor rod free section is measured; S2-4, the length of the anchor rod free section and the length of the anchor rod anchoring section are calculated according to the anchor rod free section tail end reflection time, the anchor rod anchoring section tail end reflection time and the excitation sound wave wave speed in the anchor rod free section; The calculation expression of the length of the anchor rod free section is as follows:

[0027] wherein,​​ is the length of the free section of the anchor rod, is the elastic stress wave velocity in the free section of the anchor rod, is the reflection time at the tail end of the free section of the anchor rod.

[0028] The calculation expression of the length of the anchoring section of the anchor rod is:

[0029] wherein, is the length of the anchoring section of the anchor rod, is the total length of the anchor rod.

[0030] S2-5, the wave velocity of the anchor rod is calculated according to the length of the free section of the anchor rod and the length of the anchoring section of the anchor rod, and the calculation expression is:

[0031] wherein, is the wave velocity of the anchor rod, is the reflection time at the tail end of the anchoring section of the anchor rod.

[0032] According to steps S2-1 to S2-5, the wave velocity of the anchor rod in different media is accurately determined. By measuring the wave velocity of the anchor rod under different simulated anchor rods and different simulated working conditions, the variation law of the wave velocity of the anchor rod can be further studied, which provides a data basis and reference for nondestructive testing of the anchor rod, improves the accuracy and reliability of the nondestructive testing of the anchor rod, and at the same time, provides reliable detection data and technical support for the anchoring engineering of the initial support anchor rod of the tunnel.

[0033] S3, the influence of different anchoring media on the wave velocity of the anchor rod is analyzed through multiple experiments, and the curve relationship between different anchoring media and the wave velocity of the anchor rod and the anchoring quality is established.

[0034] The wave velocity of the anchor rod and the bonding strength between the anchor rod and the anchoring agent are related. The better the anchoring quality is, the higher the bonding strength is, and the closer the wave velocity of the anchor rod is to the wave velocity of the anchoring medium; while the worse the anchoring quality is or the anchor rod has no bonding at all, the wave velocity of the anchor rod is close to or equal to the wave velocity of the free section of the anchor rod.

[0035] In this embodiment, the cement slurry as the anchoring medium is taken as the research object, and the relationship curve between the proportion of the cement slurry and the wave velocity of the anchor rod and the anchoring quality is obtained through multiple experiments, as shown in Figure 8 .

[0036] S4, the anchoring quality is evaluated according to the wave velocity of the anchor rod by using the established curve relationship.

[0037] from Figure 8It can be known that, in the case of known wave velocity of anchor rod system, the corresponding anchoring medium proportion and anchoring quality can be obtained accurately and quickly, and according to the curve relationship, the appropriate anchoring medium and anchor rod material combination can be selected in the engineering implementation process, so as to achieve the expected anchoring quality. For high humidity environment, selecting more suitable anchoring medium can ensure the long-term stability of the anchor rod.

[0038] Secondly, in actual engineering (such as tunnel support, slope reinforcement and other engineering), the anchoring quality can be found out in time according to the wave velocity detection result, and remedial measures such as re-anchoring or increasing the number of anchor rods can be taken to avoid engineering accidents and ensure engineering safety.

[0039] In summary, the application can simulate various working conditions, different geological conditions and even surrounding rock load, and by changing the experimental conditions in the model, the different external influences on the anchor rod in different geological environments can be accurately studied, the more accurate change of the wave velocity of the anchor rod system is obtained, and the stress condition of the anchor rod is further analyzed, so that more accurate and convincing experimental basis for developing anchor rod design suitable for deep underground engineering is provided.

Claims

1. A method for testing the wave velocity and anchoring quality of an anchor rod system, characterized in that: include: Construct an experimental model to test the wave velocity of the anchor rod system; The wave velocity of anchor rods wrapped with different anchoring media is measured using an experimental model for testing the wave velocity of anchor rods. Through multiple experiments, we analyzed the effects of different anchoring media on the wave velocity of the anchor rod system, and established a curve relationship between different anchoring media, the wave velocity of the anchor rod system and the anchoring quality. The established curve relationship is used to evaluate the anchoring quality based on the wave velocity of the anchor rod system.

2. A method for testing the wave velocity and anchoring quality of an anchor rod system according to claim 1, characterized in that: The specific method for constructing the experimental model for testing the wave velocity of the anchor rod system is as follows: Use metal materials to make the experimental box; Fill the experimental box with simulated rock and soil, and reserve a reserved groove equal to the size of the anchor hole when filling; Anchor rods of known length are wrapped with different anchoring media and placed in the reserved groove; Carry out the second simulated rock and soil filling until the anchoring medium wrapping the anchor rod is completely buried; Pile heavy objects on top of the simulated rock and soil; Connect the nondestructive testing instrument to the head end of the free section of the anchor rod to complete the production of the experimental model.

3. A method for testing the wave velocity and anchoring quality of an anchor rod system according to claim 2, characterized in that: The nondestructive testing instrument includes a vibration excitation device, a vibration pickup device and a data acquisition and processing system; The excitation device is connected to one side of the head end of the anchor rod free section, and the vibration pickup device is connected to the other side of the head end of the anchor rod free section; the data acquisition and processing system is connected to the output end of the vibration pickup device.

4. A method for testing the wave velocity and anchoring quality of an anchor rod system according to claim 2, characterized in that: The specific method for measuring the wave velocity of anchor rods wrapped with different anchoring media using the experimental model for testing the wave velocity of anchor rods is as follows: The experimental model for testing the wave velocity of the anchor rod system is used to collect waveforms and obtain the waveform time-distance diagram of the excitation sound wave transmitted in the anchor rod; According to the waveform time-distance diagram, the reflection signal of the tail end of the free section of the anchor rod and the reflection signal of the tail end of the anchor rod anchoring section are identified, and the reflection time of the tail end of the free section of the anchor rod and the reflection time of the tail end of the anchor rod anchoring section are obtained; Determine the velocity of the exciting sound wave in the free section of the anchor bolt; Determine the length of the free section and the anchoring section of the anchor rod; The wave velocity of the anchor rod system is calculated based on the length of the anchor rod anchoring section, the reflection time of the tail end of the anchor rod free section and the reflection time of the tail end of the anchor rod anchoring section.

5. A method for testing the wave velocity and anchoring quality of an anchor rod system according to claim 4, characterized in that: The specific method for waveform acquisition is: The excitation device is started to generate excitation forces of different frequencies and intensities. The vibration pickup device receives the acoustic wave reflection signal transmitted by the anchor rod. The acoustic wave reflection signal received by the vibration pickup device is collected, amplified, filtered, and processed by the data acquisition and processing system to obtain a waveform time-distance diagram of the excitation sound wave transmitted in the anchor rod.

6. A method for testing the wave velocity and anchoring quality of an anchor rod system according to claim 3, characterized in that: The calculation expression of the free section length of the anchor rod is: in, is the free length of the anchor rod, is the velocity of the exciting acoustic wave in the free section of the anchor, is the reflection time at the tail end of the free segment of the anchor.

7. A method for testing the wave velocity and anchoring quality of an anchor rod system according to claim 3, characterized in that: The calculation expression of the anchor bolt anchoring section length is: in, is the length of the anchor bolt anchoring section, is the total length of the anchor rod.

8. A method for testing the wave velocity and anchoring quality of an anchor rod system according to claim 3, characterized in that: The calculation expression of the wave velocity of the anchor rod system is: in, is the wave velocity of the anchor rod system, is the reflection time at the tail end of the anchoring section.

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