Method for testing compactness and stress of anchor rod

Abstract

The invention discloses a method for testing the compactness and stress of an anchor rod. The method comprises the following steps: constructing an experimental model for testing the compactness and stress of the anchor rod; performing nondestructive testing on the experimental model by using an anchor rod nondestructive testing system, and calculating the compactness of the anchor rod according to a waveform time-distance graph transmitted by the obtained excitation waves in the anchor rod; carrying out multiple anchor rod drawing experiments and anchor rod nondestructive testing experiments on the experimental model to respectively obtain anchoring surrounding rock body parameters, anchoring quality parameters and anchor rod stress states; and the analysis anchoring force is calculated according to the anchoring surrounding rock parameters and the anchoring quality parameters. According to the method, a nondestructive testing result and a result obtained by an anchor rod drawing force experiment are mutually verified by constructing an experimental model for testing the compactness and the stress of the anchor rod, and a calculation rule of the anchor rod drawing force is summarized, so that mathematical calculation is performed, the working efficiency is improved, and reliable data are provided for tunnels, geotechnical engineering supports and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of tunnel and geotechnical engineering test equipment, and particularly relates to a method for testing anchoring density and anchoring force of an anchor rod. 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 bonding force between the anchor rod body and the anchoring cementitious body, the bonding force 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 and soil body. In tunnel and geotechnical engineering, the anchor rod is widely used in engineering structures such as slope reinforcement, foundation pit support, tunnel lining, etc. Accurate measurement of the pullout force of the anchor rod is of great significance to the evaluation of the anchoring effect of the anchor rod and the safety of the project.

[0003] Traditional anchor rod pullout force tests are often carried out on the construction site, and there are problems such as complex test environment, great interference from external factors, etc. Moreover, there is a lack of convenient and accurate experimental models specially designed for scientific research and teaching or small-scale experimental research. Secondly, the anchor rod pullout force test is a destructive test, which will cause damage to the anchor rod that has been constructed on site, and may affect the stability of the surrounding rock or structure, which has a certain risk.

[0004] The existing anchoring force test equipment has the problems of low efficiency and difficulty in carrying, and the data collection in the test process is discontinuous, which is not conducive to accurate monitoring and analysis of the anchoring force. SUMMARY

[0005] In view of the above problems in the prior art, the method for testing anchoring density and anchoring force of an anchor rod provided by the application solves the problems of low efficiency, low precision and high cost of the existing test method.

[0006] In order to achieve the above-mentioned purposes, the technical scheme adopted by the application is as follows: a method for testing anchoring density and anchoring force of an anchor rod, comprising: constructing an experimental model for testing anchoring density and anchoring force of an anchor rod; using an anchor rod nondestructive testing system to perform nondestructive testing on the experimental model, and obtaining a waveform time interval diagram of the excitation wave transmitted in the anchor rod; calculating the anchoring density of the anchor rod according to the waveform time interval diagram of the excitation wave transmitted in the anchor rod; performing multiple anchor rod pullout tests and anchor rod nondestructive testing experiments using the experimental model, and obtaining anchoring surrounding rock body parameters, anchoring quality parameters and anchoring force states of the anchor rod, respectively; calculating the analytical anchoring force according to the anchoring surrounding rock body parameters and the anchoring quality parameters.

[0007] Further, the specific method for constructing an experimental model for testing anchoring density and anchoring force of an anchor rod is as follows: The experimental box is made of metal material; Two angle-adjustable steel base plates are arranged on one side of the outer part of the experimental box body; The experimental box is filled with simulated rock-soil, and a reserved groove with the same size as the anchor rod drilling hole is reserved during the filling; Five measuring points are arranged along the longitudinal direction of the anchor rod surface, and four strain gauges are attached to the periphery of each measuring point at equal angles, and each strain gauge is independently connected to a strain meter; The anchor rod with the attached strain gauges is wrapped with anchoring medium and then placed in the reserved groove; The second filling of simulated rock-soil is performed until the anchoring medium wrapping the anchor rod is completely buried; A weight is placed on the simulated rock-soil; The experimental model is completed.

[0008] Further, the specific method for obtaining the waveform-time distance diagram of the excitation wave transmitted in the anchor rod is as follows: The anchor rod nondestructive testing system is connected to the experimental model, and the data acquisition module is connected to the control system and the anchor rod nondestructive testing system; the anchor rod nondestructive testing system comprises an anchor rod nondestructive testing instrument and a super-magnetic-induced energy transmitter; The super-magnetic-induced energy transmitter is started to emit the excitation wave at the first end of the free section of the anchor rod; The anchor rod nondestructive testing instrument receives the excitation wave signal transmitted by the anchor rod; The data acquisition module and the control system collect, amplify, filter and read the excitation wave signal received by the anchor rod nondestructive testing instrument to obtain the waveform-time distance diagram of the excitation wave transmitted in the anchor rod.

[0009] Further, the specific method for calculating the anchor rod compactness according to the waveform-time distance diagram of the excitation wave transmitted in the anchor rod is as follows: The first wave signal, 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 are identified according to the waveform-time distance diagram of the excitation wave transmitted in the anchor rod 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; the excitation wave speed in the free anchor rod is determined; the anchoring section wave speed is calculated according to the length of the free section of the anchor rod, the length of the anchoring section of the anchor rod, the tail-end reflection time of the free section of the anchor rod, the tail-end reflection time of the anchoring section of the anchor rod and the excitation wave speed in the free anchor rod; the position and size of the anchoring defect of the anchor rod and the amplitude of the bottom reflection wave are analyzed according to the waveform-time distance diagram of the excitation wave transmitted in the anchor rod; and the anchoring section wave speed, the position and size of the anchoring defect of the anchor rod and the amplitude of the bottom reflection wave are comprehensively considered to determine the compactness of the anchor rod.

[0010] Further, the specific method for obtaining the anchoring quality parameter is as follows: The maximum amplitudes of the first wave signal and the tail-end reflection signal of the anchoring section of the anchor rod in the waveform-time distance diagram of the excitation wave transmitted in the anchor rod obtained in each anchor rod nondestructive testing experiment are identified; According to the wave velocity of the anchoring section, the anchoring density of the anchor rod, and the ratio of the maximum wave amplitude of the tail end reflection signal to the maximum wave amplitude of the first wave signal of the anchor rod, the anchoring quality parameter is calculated.

[0011] Further, the anchor rod pull-out experiment is performed using a pull-out force loading system, which includes an electric hydraulic jack, an anchor rod pull-out instrument, a steel counterforce frame, an anchor cable load cell, and a rod end displacement meter.

[0012] Further, the specific method for performing the anchor rod pull-out experiment using the pull-out force loading system is as follows: The anchor cable load cell and the rod end displacement meter are installed at the first end of the free section of the anchor rod; the anchor rod pull-out instrument is connected to the electric hydraulic jack; the steel counterforce frame is placed behind the electric hydraulic jack; the electric hydraulic jack is used to apply a pull-out force to the anchor rod; the anchor rod pull-out force, the axial force data of the anchor cable load cell, and the displacement data of the rod end displacement meter are recorded each time the pull-out force is applied until the anchoring system is destroyed.

[0013] Further, the specific method for obtaining the anchoring surrounding rock mass parameter is as follows: The pull-out resistance of the anchor rod is obtained by analyzing the anchor rod pull-out experiment results, thereby obtaining the anchoring force under the experimental conditions; According to the mathematical relationship between the anchoring force under the experimental conditions obtained from multiple anchor rod pull-out experiments and the theoretically estimated anchoring force, the anchoring surrounding rock mass parameter is summarized.

[0014] Further, the mathematical relationship between the anchoring force under the experimental conditions and the theoretically estimated anchoring force is as follows:

[0015]

[0016] wherein, is the anchoring force under the experimental conditions, is the anchoring surrounding rock mass parameter, is the theoretically estimated anchoring force; is the anchoring quality parameter, is the bond stress between the anchoring medium and the anchoring surrounding rock, is the circular constant, is the diameter of the anchor rod anchoring body, is the anchoring length.

[0017] Further, the analytical anchoring force calculation formula is as follows:

[0018] wherein, is the analytical anchoring force, is the anchoring surrounding rock mass parameter summarized after multiple anchor rod pull-out experiments, It is the anchoring quality parameter summarized after multiple anchor rod non-destructive testing experiments.

[0019] The beneficial effects of the present invention are as follows: by constructing an experimental model for testing the density and stress of anchor rods, the non-destructive testing results are combined with the results obtained from the anchor rod pull-out force experiment, and the density of the anchor rod and its stress are analyzed at the same time, the corresponding relationship between the non-destructive testing of the anchor rod and the anchor rod pull-out force is established, and the calculation law of the anchor rod pull-out force is summarized, so that mathematical deduction can be directly performed, which not only reduces the testing cost, but also reduces the experimental risk, improves work efficiency, and provides reliable data for projects such as geotechnical tunnel engineering support. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the process of the present invention; Figure 2 For the reserved slot subjective map; Figure 3 This is the layout diagram of the anchor strain gauge; Figure 4 This is the main view of the experimental model before the second simulated rock and soil filling; Figure 5 This is the top view of the experimental model before the second simulated rock and soil filling; Figure 6 This is a schematic diagram of the anchor nondestructive testing device; Figure 7 This is a detailed view of the free end of the anchor nondestructive testing device; Figure 8 This is the side view of the anchor pulling experimental device; Figure 9 Schematic diagram of the pulling force change process during the anchor pulling experiment. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0022] like Figure 1 As shown, in one embodiment of the present invention, a method for testing the density and stress of an anchor rod provided by the present invention includes the following steps: S1. Construct an experimental model for testing anchor density and anchor stress; The specific and method are: using high-strength metal material to make the experimental box, so that it has enough rigidity and stability; two adjustable angle steel pads are arranged on one side of the test box body, which can fix anchor rods of different diameters and lengths, so that they can be buried in the simulated rock soil at the set position and angle; fill the experimental box with simulated rock soil (you can choose different types of sand, clay or their mixture to simulate different geological conditions), as shown in Figure 2 , when filling, reserve a reserved groove with the same size as the anchor rod drilling hole, and the distance between the reserved groove and the box wall is appropriately larger, so as to ensure that the contact condition between the anchor rod body and the surrounding rock is close to the real situation when testing the pulling force, the diameter of the reserved groove is the same as the anchoring body, and the length is slightly longer than the anchoring length, so as to simulate the drilling environment of the anchor rod; as shown in Figure 3 , five measuring points are arranged equidistantly along the longitudinal direction of the anchor rod, and four strain gauges are pasted equiangularly around each measuring point, each strain gauge is independently connected with a strain gauge and is well marked, so as to accurately collect and distinguish the subsequent data; the anchor rod with strain gauges is wrapped with anchoring medium (different anchoring media can be used according to different needs) and then put into the reserved groove, as shown in Figure 4 、 Figure 5 , (the anchor rod in the box is wrapped with anchoring medium, so it is called anchoring section, that is, the anchoring section of the anchor rod; the anchor rod outside the box is not wrapped with anchoring medium, which is called free section); carry out the second filling of simulated rock soil until the anchoring medium wrapped with the anchor rod is completely buried; pile up weights on the simulated rock soil to simulate the surrounding rock load; complete the production of the experimental model.

[0023] S2, as shown in Figure 6 , use the anchor rod nondestructive testing system to carry out nondestructive testing on the experimental model, and obtain the waveform time-distance diagram of the excitation wave transmitted in the anchor rod: Connect the anchor rod nondestructive testing system with the experimental model; connect the data acquisition module with the control system and the anchor rod nondestructive testing system (the anchor rod nondestructive testing system includes an anchor rod nondestructive testing instrument and a super magnetostrictive transducer emitter); as shown in Figure 7 , start the super magnetostrictive transducer emitter to emit excitation wave at the first end of the anchor rod free section; receive the excitation wave signal transmitted by the anchor rod by the anchor rod nondestructive testing instrument; collect, amplify, filter and read the diagram of the excitation wave signal received by the anchor rod nondestructive testing instrument through the data acquisition module and the control system, and obtain the waveform time-distance diagram of the excitation wave transmitted in the anchor rod.

[0024] S3, calculate the anchor rod density according to the waveform time-distance diagram of the excitation wave transmitted in the anchor rod: According to the wave shape time-distance diagram of the excitation wave transmitted in the anchor rod, the first wave signal, 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 are identified, and 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 are obtained; the excitation wave velocity in the free anchor rod is measured; according to the length of the free section of the anchor rod, the length of the anchoring section of the anchor rod, the tail end reflection time of the free section of the anchor rod, the tail end reflection time of the anchoring section of the anchor rod and the excitation wave velocity in the free anchor rod, the anchoring section wave velocity is calculated; according to the wave shape time-distance diagram of the excitation wave transmitted in the anchor rod, the position and size of the anchoring defect of the anchor rod and the amplitude of the bottom reflection wave are analyzed; the anchoring section wave velocity, the position and size of the anchoring defect of the anchor rod and the amplitude of the bottom reflection wave are comprehensively determined to determine the compactness of the anchor rod.

[0025] S4, a plurality of anchor rod pull-out experiments and anchor rod nondestructive testing experiments are performed by using the experimental model, and the anchoring surrounding rock body parameters, anchoring quality parameters and stress state of the anchor rod are obtained.

[0026] The specific method for obtaining the anchoring quality parameters is: The maximum amplitudes of the first wave signal and the tail end reflection signal of the anchoring section of the anchor rod in the wave shape time-distance diagram of the excitation wave transmitted in the anchor rod obtained by each anchor rod nondestructive testing experiment are identified; the anchoring quality parameters are calculated according to the anchoring section wave velocity, the compactness of the anchor rod and the ratio of the maximum amplitude of the tail end reflection signal of the anchoring section of the anchor rod to the maximum amplitude of the first wave signal.

[0027] The specific method for obtaining the anchoring surrounding rock body parameters is: The pull-out force of the anchor rod is obtained by analyzing the results of the anchor rod pull-out experiment, so that the anchoring force under the experimental condition is obtained; according to the mathematical relationship between the anchoring force under the experimental condition obtained by a plurality of anchor rod pull-out experiments and the theoretically estimated anchoring force, the anchoring surrounding rock body parameters are summarized.

[0028] As shown in Figure 8 , the anchor rod pull-out experiment is performed by using the pull-out force loading system, and the pull-out force loading system includes an electric hydraulic jack, an anchor rod pull-out instrument, a steel counterforce frame, an anchor cable force measuring ring and a rod end displacement meter.

[0029] The specific method for performing the anchor rod pull-out experiment by using the pull-out force loading system is: The anchor cable force measuring ring and the rod end displacement meter are installed at the first end of the free section of the anchor rod; the anchor rod pull-out instrument is connected with the electric hydraulic jack; the steel counterforce frame is placed behind the electric hydraulic jack to ensure the linearity and stability of the pull-out force direction; the pull-out force is applied to the anchor rod by the electric hydraulic jack; the anchor rod pull-out force, the axial force data of the anchor cable force measuring ring and the displacement data of the rod end displacement meter are recorded when the pull-out force is applied each time, until the anchoring system is damaged, so that the complete pull-out force data change process is obtained, as shown in Figure 9 . At the same time, the stress state of different measuring points on the anchoring section of the anchor rod can be obtained by reading the corresponding data of the strain gauges installed on the anchor rod.

[0030] The mathematical relationship between the anchoring force under experimental conditions and the theoretically estimated anchoring force is:

[0031]

[0032] wherein, is the anchoring force under experimental conditions, is the anchoring surrounding rock mass parameter, is the theoretically estimated anchoring force; is the anchoring quality parameter, is the bonding stress between the anchoring medium and the anchoring surrounding rock, is the circular constant, is the diameter of the anchoring body, is the anchoring length.

[0033] S5, the analytical anchoring force under experimental conditions is calculated according to the anchoring surrounding rock mass parameter and the anchoring quality parameter.

[0034] The calculation formula of the analytical anchoring force is:

[0035] wherein is the analytical anchoring force, is the anchoring surrounding rock mass parameter summarized after multiple anchoring rod pulling experiments, is the anchoring quality parameter summarized after multiple anchoring rod nondestructive testing experiments.

[0036] The present application combines the nondestructive testing results with the results obtained by the anchoring rod pulling force experiment by constructing an experimental model for testing the anchoring rod density and the anchoring rod stress, analyzes the anchoring rod density and its stress, establishes the corresponding relationship between the anchoring rod nondestructive testing and the anchoring rod pulling force, summarizes the calculation rule of the anchoring rod pulling force, and thus directly performs mathematical calculation, which not only reduces the testing cost, but also reduces the experimental risk and improves the work efficiency, and provides reliable data for tunnel and geotechnical engineering support engineering.

Claims

1. A method for testing the density and stress of an anchor rod, characterized in that: include: Construct an experimental model for testing anchor density and anchor stress; The experimental model was non-destructively tested using the anchor bolt non-destructive testing system to obtain the waveform time-distance diagram of the excitation wave transmitted in the anchor bolt; The density of the anchor bolt is calculated based on the waveform time-distance diagram of the excitation wave transmitted in the anchor bolt; The experimental model was used to conduct multiple anchor pull-out tests and anchor non-destructive testing tests to obtain the anchoring surrounding rock parameters, anchoring quality parameters, and anchor stress state. The analytical anchoring force is calculated based on the anchoring surrounding rock mass parameters and anchoring quality parameters.

2. A method for testing anchor density and anchor stress according to claim 1, characterized in that: The specific method for constructing an experimental model for testing anchor density and anchor stress is as follows: Use metal materials to make the experimental box; Two steel plates with adjustable angles are installed on one side of the outside of the test chamber; Fill the experimental box with simulated rock and soil, and reserve a reserved groove equal to the size of the anchor hole when filling; Five measuring points are arranged longitudinally along the surface of the anchor rod, and four strain gauges are pasted at equal angles around each measuring point. Each strain gauge is independently connected to a strain meter. Wrap the anchor rod with the strain gauge with anchoring medium and place it 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; Complete the production of the experimental model.

3. A method for testing anchor density and anchor stress according to claim 2, characterized in that: The specific method for obtaining the waveform time-distance diagram of the excitation wave transmitted in the anchor is: Connecting the anchor nondestructive testing system to the experimental model; connecting the data acquisition module to the control system and the anchor nondestructive testing system; the anchor nondestructive testing system includes an anchor nondestructive testing instrument and a giant magnetostrictive transducer transmitter; Start the giant magnetostrictive transducer transmitter to emit the excitation wave at the head end of the free section of the anchor rod; The anchor nondestructive testing instrument receives the excitation wave signal transmitted by the anchor; The excitation wave signal received by the anchor rod nondestructive testing instrument is collected, amplified, filtered, and processed through the data acquisition module and the control system to obtain the waveform time-distance diagram of the excitation wave transmitted in the anchor rod.

4. A method for testing anchor density and anchor stress according to claim 3, characterized in that: The specific method for calculating the density of the anchor bolt based on the waveform time-distance diagram of the excitation wave transmitted in the anchor bolt is: According to the waveform time-distance diagram of the excitation wave transmitted in the anchor rod, the first wave signal, 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 to obtain 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; the excitation wave velocity in the free anchor rod is measured; the anchoring section velocity is calculated based on the free section length of the anchor rod, the anchoring section length of the anchor rod, the reflection time of the tail end of the free section of the anchor rod, the reflection time of the tail end of the anchor rod anchoring section and the excitation wave velocity in the free anchor rod; the position and size of the anchoring defect of the anchor rod and the amplitude of the reflection wave at the bottom of the rod are analyzed according to the waveform time-distance diagram of the excitation wave transmitted in the anchor rod; the density of the anchor rod is determined by comprehensively considering the anchoring section velocity, the position and size of the anchoring defect of the anchor rod and the amplitude of the reflection wave at the bottom of the rod.

5. A method for testing anchor density and anchor stress according to claim 4, characterized in that: The specific method for obtaining anchoring quality parameters is: Identify the maximum amplitude of the first wave signal and the reflected signal at the end of the anchoring section of the anchor obtained from each anchor nondestructive testing experiment; The anchoring quality parameters are calculated based on the wave velocity of the anchoring section, the density of the anchor rod, and the ratio of the maximum amplitude of the reflected signal at the tail end of the anchor rod to the maximum amplitude of the first wave signal.

6. A method for testing anchor density and anchor stress according to claim 5, characterized in that: The anchor pulling test is carried out using a pulling force loading system, which includes an electric hydraulic jack, an anchor pulling instrument, a steel reaction frame, an anchor force ring and a rod end displacement meter.

7. A method for testing anchor density and anchor stress according to claim 6, characterized in that: The specific method of using the pull-out force loading system to conduct anchor pull-out tests is as follows: Install the anchor cable force ring and the rod end displacement meter at the head end of the free section of the anchor rod; connect the anchor rod puller to the electric hydraulic jack; place the steel reaction frame behind the electric hydraulic jack; apply tension to the anchor rod through the electric hydraulic jack; record the anchor rod pull-out force, the axial force data of the anchor cable force ring and the displacement data of the rod end displacement meter each time tension is applied until the anchor system is destroyed.

8. A method for testing anchor density and anchor stress according to claim 7, characterized in that: The specific method for obtaining the parameters of the anchored surrounding rock mass is: By analyzing the anchor pull-out test results, the pull-out resistance of the anchor is obtained, and thus the anchoring force under the experimental conditions is obtained; Based on the mathematical relationship between the anchoring force under experimental conditions obtained from multiple anchor pull-out tests and the theoretically estimated anchoring force, the anchoring surrounding rock mass parameters are summarized.

9. A method for testing anchor density and anchor stress according to claim 8, characterized in that: The mathematical relationship between the anchoring force under experimental conditions and the theoretically estimated anchoring force is: in, is the anchoring force under experimental conditions, is the anchoring rock mass parameter, is the theoretically estimated anchoring force; is the anchoring quality parameter, is the bonding stress between the anchoring medium and the surrounding rock, is pi, is the diameter of the anchor bolt, is the anchoring length.

10. A method for testing anchor density and anchor stress according to claim 9, characterized in that: The calculation formula of the analytical anchoring force is: in To analyze the anchoring force, These are the anchoring surrounding rock parameters obtained after multiple anchor pull-out experiments. It is the anchoring quality parameter summarized after multiple anchor rod non-destructive testing experiments.

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