WO2007137466A1

WO2007137466A1 - A random, nondestructiv and dynamic testing apparatus and method of the stressed state of a roof bolt

Info

Publication number: WO2007137466A1
Application number: PCT/CN2006/003545
Authority: WO
Inventors: Xiexing Miao; Qingfeng Li; Jinhai Xu; Xianbiao Mao; Hao Qin
Original assignee: China University Of Mining And Technology
Priority date: 2006-06-01
Filing date: 2006-12-22
Publication date: 2007-12-06
Also published as: AU2006345338A1; AU2006345338B2; CN101082564A

Abstract

A random, nondestructive and dynamic testing method of the stressed state of a roof bolt includes arranging an exciting force fixture (7) on external end of the roof bolt (1) which is anchored in the rock, and mounting an accelerometer (5) on a fixing nut (6) of the external end of the roof bolt (1), connecting an intelligent and dynamic collecting tester (8) to the accelerometer (5), applying a force to the exciting force fixture (7) and making the roof bolt vibrate transversely, collecting accelerating signals of the vibration by the accelerometer (5) and transmitting to the intelligent and dynamic tester (8), transferring the received accelerating analog signals to digital signals and storing by the intelligent and dynamic tester (8), inputting the data finally to a computer and processing, then the pre-stress testing when the roof bolt is initially installed and the load testing of working state are accomplished.

Description

Random and non-destructive dynamic detection technology for bolt stress state

TECHNICAL FIELD The present invention relates to a random non-destructive dynamic detection technology for a state of stress applied to a bolt, and is particularly suitable for on-line monitoring of mine, tunnel, slope prestressed anchor, and anchor cable use state, and is also applicable to mines, tunnels, and slope anchors. , online monitoring of the state of use of the anchor cable. BACKGROUND OF THE INVENTION Bolt support is widely used in the reinforcement and support of underground roadways and surrounding rock of slopes, especially the bolt support is widely used in coal mines. At present, the total footage of the annual roadway of state-owned coal mines in China is over 10 million meters. The amount of bolts used for support is more than 40 million. How many anchors in the 40 million anchors can strengthen the underground roadway and the surrounding rock of the slope, no one can answer. In fact, the tensile stresses of different anchors or bolts that are close to each other will vary depending on the nature of the surrounding rock and the quality of the construction, and the same anchor will be due to the redistribution or geological movement of the stress during the mining process. The stress in the service will also change during the service period. If the support strength is weak, the surrounding rock is not safe. If the support strength is too high, material waste will be caused. Therefore, it is necessary to monitor the stress state in the anchor in real time. .

At present, there are two main methods for monitoring the safety and stability of the anchor. One monitoring method is to use a deep-hole multi-point displacement meter, a displacement convergence meter, a roof separation indicator, etc. for displacement monitoring. Displacement is a cumulative effect of force, so this monitoring is delayed in time and has poor timeliness. Another method of monitoring is to use force extraction, force-measuring bolts, pull gauges, steel chords, hydraulic pillow dynamometers, etc. for force detection. Torque pull force can only be estimated by testing the torque when the bolt is installed, and its accuracy is low. The force measurement of the force-measuring anchor is to measure the stress state of the anchor rod in the surrounding rock through the special anchor rod with the strain gauge attached, and it is impossible to monitor the force of any ordinary bolt. The steel string meter and the hydraulic pillow dynamometer measure the force between the surrounding rock and the pallet, and measure the stress state of the bolt according to the frequency of the steel string meter or the pressure of the hydraulic pillow after the bolt is stressed. It is also impossible to perform force monitoring on any one of the anchors. The two types of force detection methods, such as force-measuring anchor and pull-out meter, can only perform point detection, and can not perform surface inspection. The pull-out measurement force is to use the hydraulic jack to perform the pull-out test to determine the anchor rod. The solid force (maximum load carrying capacity), the force state of the bolt cannot be detected, and the detection method is laborious and time consuming. More importantly, the detection means has a strong disturbance to the roadway reinforced by the anchor rod, and reduces The reinforcement effect of the anchor on the surrounding rock is limited to individual sampling. SUMMARY OF THE INVENTION Technical Problem: An object of the present invention is to provide a convenient, fast, and effective random non-destructive power detection technology for a state in which a bolt and a cable are stressed.

Technical Solution: The random non-destructive power detecting device of the anchor state of the present invention comprises a computer data processing system, and further comprises an exciting force fastening device disposed on the exposed end of the anchor rod, and is fastened at the exposed end of the anchor rod An acceleration sensor on the nut is connected with a signal acquisition intelligent measuring instrument on the acceleration sensor; the exciting force fastening device is a shape steel, and the shape steel is provided with a hole that can be put on the anchor rod, and is also provided There is a screw hole at right angles to the bore.

The random non-destructive power detecting method for the state of stress of the anchor of the present invention is to install an exciting force fastening device on the exposed end of the anchor bolt anchored in the rock (coal) body, and install an acceleration sensor on the fastening nut of the exposed end of the bolt Connect the signal acquisition intelligent measuring instrument to the acceleration sensor; apply force to the exciting force fastening device to cause the anchor to vibrate, collect the vibration acceleration of the anchor through the acceleration sensor provided on the fastening nut, and collect the acceleration of the anchor The acceleration signal is transmitted to the intelligent motion measuring instrument. The intelligent motion measuring instrument converts the received acceleration analog signal into an acceleration digital signal and stores it, and inputs the collected data into a computer for arithmetic processing, and selects the 5th order frequency before the anchor vibration. Calculate the prestress or working load of the bolt, calculate the prestress or working load of the bolt, and compare the calculated prestress or working load of the anchor 1 with the design value of the anchor anchor force. The force state of the measured anchor.

Advantageous Effects: The random non-destructive power detection technology of the stress state of the anchor rod of the invention is most suitable for online monitoring of the state of use of the bolt and the wrong cable of the mine, and is also applicable to the online monitoring of the use state of the anchor bolt of the tunnel and the slope. An excitation force fastening device and an acceleration sensor connected to the signal acquisition intelligent motion tester are mounted on the exposed end of the anchor cable anchored in the rock (coal) body, and the anchor is applied by applying force to the excitation force fastening device The anchor cable generates lateral vibration, and the signal is transmitted to the intelligent motion measuring instrument through the acceleration sensor. The intelligent motion measuring instrument converts the received acceleration signal into a digital signal and stores it, and finally completes the anchor through computer data processing. 00 Pre-stress at the initial installation of the anchor cable and load detection during the working state, the whole process of the entire force is monitored online, non-destructive, comprehensive, and can be used for non-destructive dynamic testing of any one of the anchors, as long as the anchor The exposed end of the anchor cable knocks, no need to install any additional device when the anchor cable is constructed, the operation is simple, the use is convenient, fast, easy to carry, the effect is good, and has wide practicality. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are schematic structural views of a random non-destructive power detecting device for the state of stress of the anchor of the present invention.

In the figure: 1-Bolt, 2-resin, 3-coal, 4-tray, 5-acceleration sensor, 6 - fastening nut, 7-exciting force fastening device, 8-intelligent dynamic measuring instrument. detailed description

An embodiment of the present invention will be further described below with reference to the accompanying drawings:

The random non-destructive power detecting device for the stress state of the anchor rod of the invention is mainly composed of an acceleration sensor 5, an exciting force fastening device 7, an intelligent motion measuring device 8 and a computer data processing system, and the exciting force fastening device 7 is fixed at the anchor The exposed end of the rod, the acceleration sensor 5 is closely attached to the fastening nut 6 of the exposed end of the anchor through the magnetic seat, and the signal acquisition intelligent measuring instrument 8 is connected to the acceleration sensor 5 through the transmission line. The accelerometer 5 adopts the Bzl05 type acceleration sensor produced by Rand Technology Co., Ltd.; the intelligent dynamic measuring instrument 8 adopts the JL-MG type intelligent motion measuring instrument produced by Changsheng Engineering Testing Technology Development Co., Ltd., and the exciting force fastening device 7 is A square steel, the square steel is provided with a hole for inserting on the anchor rod, and a screw hole is formed at a right angle to the hole to facilitate the fixing of the square steel by screws.

The random non-destructive power detecting method for the state of stress of the anchor rod of the present invention is to install the exciting force fastening device 7 on the exposed end of the anchor rod 1 anchored by the resin 2 in the coal body 3, and the exposed end of the anchor rod 1 is close to the tray 4 The acceleration nut 5 is mounted on the fastening nut 5, and the acceleration sensor 5 is connected with the signal acquisition intelligent measuring instrument 8; the striking force fastening device 7 fixed on the exposed end of the anchor 1 is struck, so that the anchor 1 generates a The slight lateral vibration, the acceleration vibration of the anchor 1 is collected by the acceleration sensor 5 mounted on the fastening nut 6, and the acceleration signal collected by the acceleration sensor 5 is transmitted to the intelligent measuring instrument 8 through the transmission line, and the intelligent measuring instrument 8 Convert the received acceleration analog signal into an acceleration digital signal and store it, and finally All the collected data is input into the computer for arithmetic processing, and the vibration frequency and echo time of the acceleration wave of the force-bearing anchor 1 are obtained, and the pre-stress or working load of the anchor 1 is calculated, and the calculated anchor 1 is calculated. The prestressed or working load is compared with the bolt anchoring force design value to determine the force state of the measured anchor. The specific implementation steps are as follows - a. First, the excitation force fastening device 7 is installed on the exposed end of the anchor 1 to connect the 5 end of the B _Z 105 type acceleration sensor to the side of the fastening nut on the exposed end of the anchor, one end and JL-MG type intelligent measuring instrument 8 is connected, as shown in Figure 1;

b. Turn on the intelligent measuring instrument 8, enter the parameter setting column, input the length and diameter of the measured anchor, set the high-pass filter to 10, the low-pass filter to 2000Hz, and the wave speed to 3500m/s~5100 m/s, 釆The sample interval is 6 s;

c. Horizontally tapping the excitation force fastening device 7 3~5 times, the tapping force is controlled at about 2kg, and the acceleration wave and echo collection of each tapping is transmitted to the intelligent motion measuring instrument 8 by the Bzl05 type acceleration sensor 5. , the acceleration signal is converted into a digital signal by the smart measuring instrument 8 and stored;

d. Input all the collected data from the instrument into the computer, select one of the two similar waveforms in the measured waveform, and read the time difference between the incident wave and the in-phase reflected wave in the waveform to calculate The length of the un-anchor section of the anchor; e. Calculate the top five of the non-prestressed anchor using equation (1): f _{n =} ⁽ " + ^ ^{) 2} jg

21 m

The vibration frequency of the order; (f) = -^∑ (t,)cos(2^/S )

f. Use equation (2): 3⁄4 ( _{0 </} ^ ^:) to calculate b(f) = ~∑x(t _k )s^kf/SF)

iV _k= Q

The continuous Fourier transform value at a frequency of 0.5 Hz at 0 to 900 Hz is plotted, and the amplitude spectrum map is drawn. The peak value of the spectrogram and the first 5 frequency values of the non-prestressed anchor are used to obtain the measured prestressed anchor. A certain frequency value of the first 5th order frequency of the rod. g. Use formula (3): N _n ⁽ " ^{+ 2} to calculate the anchor

(η + β ₂ ) ² I ¹

Working load, the calculated prestress or working load of the bolt and the anchoring force of the anchor Comparing the design values, it is finally determined whether the measured anchor is within the safe range. If the measured working load of the anchor is greater than the design value of the anchoring force, it is unsafe, and anchor bolting is needed to ensure the bolt support engineering. Safe to use; If the measured working load of the bolt is less than the design value of the anchoring force, it is safe, no need to add a bolt.

In the above formula: is the first main vibration frequency; 2 is the frequency order; is the non-prestressed frequency coefficient; β 2 is the prestressed frequency coefficient; _ is the length of the unanchor segment; the elastic modulus of the anchor; Moment of inertia; mass per unit length of the bolt; ^ is the sampling frequency; is the number of points of the sample; is the time series of the acceleration signal;

Claims

Claim

1. A random non-destructive power detecting device for a state of stress of a bolt, comprising a computer data processing system, characterized in that it further comprises an exciting force fastening device (7) provided on the exposed end of the anchor rod (1), The acceleration sensor (5) on the exposed end of the bolt is fastened to the nut (6), and the signal acquisition intelligent measuring instrument (8) is connected to the acceleration sensor (5).

2. The random non-destructive power detecting device for a state of stress of a bolt according to claim 1, wherein: the exciting force fastening device (7) is a steel, and the steel is provided with a wearable The hole sleeved on the anchor rod is also provided with a screw hole at right angles to the aperture.

3. A random non-destructive dynamic testing method for the stress state of the anchor, characterized in that: an exciting force fastening device (7) is mounted on the exposed end of the anchor (1) anchored in the rock (coal) body, and the anchor is

(1) The acceleration sensor (5) is attached to the fastening nut (6) of the exposed end, and the signal acquisition intelligent measuring instrument (8) is connected to the acceleration sensor (5); the force is applied to the exciting force fastening device (7), The anchor rod is vibrated, and the acceleration vibration of the anchor rod is collected by an acceleration sensor (5) provided on the fastening nut (6), and the acceleration signal collected by the acceleration sensor (5) is transmitted to the intelligent motion measuring instrument (8), intelligently moving The measuring instrument (8) converts the received acceleration analog signal into an acceleration digital signal and stores it, and inputs the collected data into a computer for arithmetic processing, and selects any frequency and acceleration wave back in the 5th order frequency before the anchor vibration. The wave time, calculate the prestress or working load of the bolt, compare the calculated prestress or working load of the bolt (1) with the design value of the anchor anchor force, and finally determine the force of the measured anchor. status.