Anchor rod length measuring method based on free section and reflection characteristics

Abstract

The invention provides an anchor rod length measurement method based on a free section and reflection characteristics, and relates to the technical field of anchor rod measurement. Comprising the steps that a plurality of anchor rod models with different lengths are constructed, and the lengths of the anchor rod models comprise the exposed length and the actual length; the exposed length propagation time and the rod bottom reflection time of each anchor rod are calculated, and a time ratio is obtained through calculation; calculating the rod system wave velocity of each anchor rod according to the rod bottom reflection time and the actual length of each anchor rod; obtaining a rod system wave velocity set relational expression according to the ratio of the rod system wave velocity to the time; obtaining a to-be-measured anchor rod with an unknown length; measuring the exposed length of the anchor rod with the unknown length; the rod system wave velocity of the anchor rod with the unknown length is obtained according to the exposed length of the anchor rod with the unknown length and the rod system wave velocity set relational expression; according to a length calculation formula, the actual length of the anchor rod with the unknown length is determined through the rod system wave velocity. The problem of low anchor rod length detection accuracy caused by the fact that the rod system wave velocity cannot be accurately measured in the prior art is solved.

Description

Technical Field

[0001] The invention relates to the technical field of anchor rod measurement, and in particular to a method for measuring the length of an anchor rod based on a free segment and reflection characteristics. Background Art

[0002] As an important supporting structure, anchor rods are widely used in supporting projects such as tunnels, mines, slopes, and buildings. Corresponding industry standards have been formed in the water conservancy, construction, and railway industries. However, the regulations in the regulations on the rod system wave velocity for calculating the length of the anchor rod are not operational in actual projects. For example, the regulations "Non-destructive Testing Regulations for Anchor Rods in Hydropower and Water Conservancy Projects" (DL / T 5424-2009) stipulate that: when the anchor rod fullness D<30%, or the empty slurry section is concentrated at the hole mouth, the rod system wave velocity is the rod body wave velocity; when the anchor rod fullness 30%≤D<75%, the rod system wave velocity is the average of the rod body wave velocity and the same type of rod system wave velocity; when the anchor rod fullness D≥75%, the rod system wave velocity is the same type of rod system wave velocity. The wave velocity value range of this value-taking method spans a wide range. Under the condition that the wave velocity range is 4.54km / s to 5.18km / s for the rod system (the average wave velocity of the rod system is 3.9km / S), the length of the anchor rod with a design length of 3.5 meters has a length fluctuation range of approximately 3.07 meters to 4.0 meters.

[0003] In the specification "Technical Specification for Nondestructive Testing of Anchor Bolt Anchorage Quality" (JGJ / T 182-2009), it is mentioned that the average wave velocity of the rod system is affected by many factors, and its relationship with density cannot be accurately determined. However, in actual testing work, it should be considered that the rod length detection accuracy is related to the density, which directly affects the safety and stability of the project. In actual testing, the density detection fluctuates greatly, so the wave velocity of the rod system cannot be determined.

[0004] At the same time, when conducting on-site anchor detection, it is often necessary to calibrate the elastic wave velocity of the anchor on-site. In most cases, the conditions for wave velocity calibration are not available on-site, which will ultimately affect the length detection of the anchor. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for measuring the length of an anchor rod based on a free segment and reflection characteristics. The present invention solves the problem in the prior art that the wave velocity of the rod system cannot be accurately measured, resulting in low accuracy in anchor rod length detection.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A method for determining the length of an anchor rod based on free segment and reflection characteristics, comprising:

[0008] Constructing several anchor models with different lengths, wherein the length of the anchor model includes: the exposed length and the actual length;

[0009] Calculate the propagation time of the exposed length of each anchor rod and the reflection time at the bottom of the rod and calculate the time ratio;

[0010] The wave velocity of the rod system of each anchor rod is calculated according to the rod bottom reflection time and the actual length of each anchor rod;

[0011] Obtaining a rod system wave velocity set relational expression according to the rod system wave velocity and the time ratio;

[0012] Obtain the anchor rod of unknown length to be measured;

[0013] Measuring the leakage length of the anchor rod of unknown length;

[0014] Obtaining the rod system wave velocity of the anchor rod of unknown length according to the time ratio of the propagation time of the leakage length of the anchor rod of unknown length to the rod bottom reflection time of the anchor rod of unknown length and the rod system wave velocity set relational expression;

[0015] According to the length calculation formula, the actual length of the anchor rod of unknown length is determined using the rod system wave velocity.

[0016] Preferably, the process of making the anchor model includes:

[0017] Put an anchor rod of known length into a PVC or PE pipe, and seal the bottom of the PVC or PE pipe with a plastic cover to obtain a first model;

[0018] Pour fine stone concrete mortar into the initial model and tap it to obtain a second model;

[0019] The second model is cured to obtain an anchor model.

[0020] Preferably, the relationship between the beam wave velocity is expressed as:

[0021] V = A*k+B;

[0022] Among them, V is the wave velocity of the rod system, A is the first fitting parameter, B is the second fitting parameter, and k is the time ratio.

[0023] Preferably, the length calculation formula is expressed as:

[0024] L = T * V / 2;

[0025] Where T is the rod bottom reflection time.

[0026] Preferably, the calculation expression of the exposed length propagation time is:

[0027] T1 = Lx0 / V0;

[0028] Among them, T1 is the propagation time of the exposed length, Lx0 is the leakage length, and V0 is the elastic wave velocity of the impact signal in the leakage section.

[0029] Preferably, the elastic wave velocity of the impact signal is 5.18 km / S.

[0030] The present invention discloses the following technical effects:

[0031] The present invention provides a method for determining the length of an anchor rod based on free segment and reflection characteristics, comprising: constructing several anchor rod models of different lengths, wherein the length of the anchor rod model includes: an exposed length and an actual length; calculating the exposed length propagation time and the rod bottom reflection time of each anchor rod and calculating the time ratio; calculating the rod system wave velocity of each anchor rod according to the rod bottom reflection time and the actual length of each anchor rod; obtaining a rod system wave velocity set relationship according to the rod system wave velocity and the time ratio; obtaining an anchor rod of unknown length to be measured; measuring the exposed length of the anchor rod of unknown length; obtaining the rod system wave velocity of the anchor rod of unknown length according to the exposed length of the anchor rod of unknown length and the rod system wave velocity set relationship; determining the actual length of the anchor rod of unknown length using the rod system wave velocity according to the length calculation formula. The present invention combines the established relationship between the exposed length reflection time of the anchor rod and the rod bottom reflection time ratio and the rod system wave velocity to provide a method for determining the rod system wave velocity in on-site anchor rod detection. By establishing anchor models of different lengths and calculating the propagation time of the exposed length and the reflection time at the bottom of the rod, the actual length of the anchor can be estimated more accurately, thus improving the reliability of the measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0033] Figure 1 A flow chart of a method for determining the length of an anchor rod based on free segment and reflection characteristics provided by an embodiment of the present invention;

[0034] Figure 2 A test waveform diagram provided by an embodiment of the present invention;

[0035] Figure 3 A schematic diagram of the relationship between the pole system wave velocity V, the free section propagation time and the pole bottom reflection ratio K provided in an embodiment of the present invention;

[0036] Figure 4 A schematic diagram of waveform acquisition of anchor rods provided in an embodiment of the present invention;

[0037] Figure 5 A schematic diagram of anchor rod length detection provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] like Figure 1 As shown, the present invention provides a method for measuring the length of an anchor rod based on free segment and reflection characteristics, comprising:

[0041] Step 100: constructing several anchor models of different lengths, wherein the length of the anchor model includes: a leaked length and an actual length;

[0042] Step 200: Calculate the exposed length propagation time and the rod bottom reflection time of each anchor rod and calculate the time ratio;

[0043] Step 300: Calculating the wave velocity of each anchor rod according to the rod bottom reflection time and the actual length of each anchor rod;

[0044] Step 400: obtaining a rod system wave velocity set relational expression according to the rod system wave velocity and the time ratio;

[0045] Step 500: obtaining an anchor rod of unknown length to be measured;

[0046] Step 600: measuring the leakage length of the anchor rod of unknown length;

[0047] Step 700: Obtaining the rod system wave velocity of the anchor rod of unknown length according to the time ratio of the propagation time of the leakage length of the anchor rod of unknown length to the rod bottom reflection time of the anchor rod of unknown length and the rod system wave velocity set relational expression;

[0048] Step 800: According to the length calculation formula, the actual length of the anchor rod of unknown length is determined using the rod system wave velocity.

[0049] Furthermore, the process of making the anchor model includes:

[0050] Put an anchor rod of known length into a PVC or PE pipe, and seal the bottom of the PVC or PE pipe with a plastic cover to obtain a first model;

[0051] Pour fine stone concrete mortar into the initial model and tap it to obtain a second model;

[0052] The second model is cured to obtain an anchor model.

[0053] Furthermore, the relationship between the wave velocity of the rod system is expressed as follows:

[0054] V = A*k+B;

[0055] Among them, V is the wave velocity of the rod system, A is the first fitting parameter, B is the second fitting parameter, and k is the time ratio.

[0056] Furthermore, the length calculation formula is expressed as:

[0057] L = T * V / 2;

[0058] Where T is the rod bottom reflection time.

[0059] Furthermore, the calculation expression of the exposed length propagation time is:

[0060] T1 = Lx0 / V0;

[0061] Among them, T1 is the propagation time of the exposed length, Lx0 is the leakage length, and V0 is the elastic wave velocity of the impact signal in the leakage section.

[0062] Specifically, the specific construction method of the model and the length measurement method in the length determination method are as follows:

[0063] (1) making anchor rod models of different lengths and different exposed lengths, wherein the anchor rod model comprises an anchor rod made of threaded steel with a diameter of not less than 10 mm, placed in a PVC or PE pipe with an inner diameter of not more than 90 mm, and the bottom of the pipe is sealed with a plastic cover;

[0064] (2) inserting the threaded steel bar into the PVC or PE pipe, and pouring fine stone concrete mortar, and vibrating and compacting the inside of the pipe by knocking or other means;

[0065] (3) curing the anchor model for no less than 7 days;

[0066] (4) Using a dedicated non-destructive testing instrument to perform vibration and other processes on each anchor model to achieve detection, record the exposed length Lx0 and actual length Lx1 of each anchor, and test and analyze the rod bottom reflection time Tx through the non-destructive testing instrument;

[0067] (5) Analyze and calculate the ratio k of the propagation time (Lx0 / V0) of the exposed length of each anchor rod to the reflection time at the bottom of the rod, where V0 is the propagation speed of the elastic wave velocity of the impact signal in the leakage section in the free threaded steel bar;

[0068] (6) Calculate the wave velocity Vx of each anchor by combining the reflection time at the bottom of each anchor and the actual length of the anchor;

[0069] (7) The wave velocity of each anchor is counted, and the relationship between the wave velocity set Vx and the ratio k is fitted to obtain the relationship: wave velocity V = A*k + B, where A and B are fitting parameters;

[0070] (8) using the nondestructive testing equipment to collect the exposed length and the reflection time of the bottom of the anchor rod of unknown length, calculating the ratio K1 of the propagation time of the exposed part and the reflection time of the bottom of the anchor rod, and combining the relationship to obtain the wave velocity V1 of the anchor rod;

[0071] (9) Using the rod system wave velocity V1 to detect and calculate the length of the anchor rod model;

[0072] Repeat steps (8) and (9) to detect the next anchor rod.

[0073] Furthermore, the elastic wave velocity of the impact signal is 5.18 km / S.

[0074] Specifically, the elastic wave velocity of the impact signal is collected by a sensor, and the sensor for collecting the signal is located at the top or side of the anchor rod, and the axis of the sensor is parallel to or on the same extension line as the anchor rod; the sensor for collecting the signal is coupled to the anchor rod through a special coupling method, and the coupling methods include magnetic attraction, manual pressing, etc., and the coupling agent uses a material such as vaseline that excludes air from the bonding surface.

[0075] Signal excitation methods include hammering and automatic excitation device knocking.

[0076] Furthermore, the present invention is used to test the length of anchor rods constructed as required in a high-speed tunnel in Guangyuan, Sichuan. The anchor rods are threaded steel anchor rods, the length of the anchor rods is 25m, the design length of the anchor rods is 3.5m, and the exposed length is 6cm. Before the test, anchor rod models with different exposed lengths and different lengths were made, and the relationship between the rod system wave velocity and the ratio of the propagation time of the exposed length of the anchor rod to the total time of the rod body was established. The rod system wave velocity of the anchor rod is determined in combination with the parameters of the object to be tested, and the wave velocity is used to detect the length of the anchor rod.

[0077] The manufactured anchor rods are maintained according to regulations and tested using non-destructive testing equipment. The test waveform is shown in the figure below. Figure 2The exposed length was recorded and the reflection time of the bottom of each anchor was tested and analyzed. The analysis results are shown in Table 1. The relationship between the wave velocity V of the rod system and the ratio K of the free section length to the rod body length was established as shown in Figure 3 .

[0078] Table 1 is a table showing the test analysis results, as shown below:

[0079] Table 1 Test analysis results

[0080]

[0081]

[0082] Furthermore, through fitting, the relationship between the rod system wave velocity V and K is:

[0083] V = 0.9772K + 4.2167;

[0084] Based on this relationship, the wave velocity of the anchor rod tested on site is determined. The exposed length of the anchor rod is 6 cm, and the propagation velocity of the exposed part is 5.18 km / s. The test waveform is shown in Figure 4 .

[0085] According to the detected waveform, the reflection time of the rod bottom is 1.627ms, and the K value of the anchor rod and the wave velocity V of the rod system are calculated.

[0086] K=0.06*2 / 5.18=0.00142ms;

[0087] V=0.9772*0.00142+4.2167=4.219km / s;

[0088] The length of the anchor rod is calculated using the wave velocity of the rod system, and the waveform is analyzed and calculated as follows: Figure 5 . After calculation, the length of the anchor rod is 3.416m. According to the regulations "Non-destructive Testing Regulations for Anchor Rods in Hydropower and Water Conservancy Projects" (DL / T5424-2009) and "Technical Regulations for Non-destructive Testing of Anchor Rod Anchoring Quality" (JGJ / T 182-2009), the length of the anchor rod is qualified.

[0089] By comparing with the design value and actual value of the anchor rod, the wave velocity of the rod system determined by this technology and the detected length result are consistent with the actual value.

[0090] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0091] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for measuring anchor rod length based on free segment and reflection characteristics, characterized in that: include: Constructing several anchor models with different lengths, wherein the length of the anchor model includes: the exposed length and the actual length; Calculate the propagation time of the exposed length of each anchor rod and the reflection time at the bottom of the rod and calculate the time ratio; The wave velocity of the rod system of each anchor rod is calculated according to the rod bottom reflection time and the actual length of each anchor rod; Obtaining a rod system wave velocity set relational expression according to the rod system wave velocity and the time ratio; Obtain the anchor rod of unknown length to be measured; Measuring the leakage length of the anchor rod of unknown length; Obtaining the rod system wave velocity of the anchor rod of unknown length according to the time ratio of the propagation time of the leakage length of the anchor rod of unknown length to the rod bottom reflection time of the anchor rod of unknown length and the rod system wave velocity set relational expression; According to the length calculation formula, the actual length of the anchor rod of unknown length is determined using the rod system wave velocity.

2. The method for determining the length of an anchor rod based on free segment and reflection characteristics according to claim 1, characterized in that: The manufacturing process of the anchor model includes: Put an anchor rod of known length into a PVC or PE pipe, and seal the bottom of the PVC or PE pipe with a plastic cover to obtain a first model; Pour fine stone concrete mortar into the initial model and tap it to obtain a second model; The second model is cured to obtain an anchor model.

3. The method for determining the length of an anchor rod based on free segment and reflection characteristics according to claim 1, characterized in that: The relationship between the wave velocity of the rod system is expressed as: V = A*k+B; Among them, V is the wave velocity of the rod system, A is the first fitting parameter, B is the second fitting parameter, and k is the time ratio.

4. The method for determining the length of an anchor rod based on free segment and reflection characteristics according to claim 3, characterized in that: The expression of the length calculation formula is: L = T * V / 2; Where T is the rod bottom reflection time.

5. The method for determining the length of an anchor rod based on free segment and reflection characteristics according to claim 1, characterized in that: The calculation expression of the exposed length propagation time is: T1 = Lx0 / V0; Among them, T1 is the propagation time of the exposed length, Lx0 is the leakage length, and V0 is the elastic wave velocity of the impact signal in the leakage section.

6. The method for determining the length of an anchor rod based on free segment and reflection characteristics according to claim 1, characterized in that: The elastic wave velocity of the impact signal is 5.18 km / S.

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