Acoustic emission sensor

Abstract

The invention discloses an acoustic emission sensor which comprises an acoustic emission probe, a probe installation mechanism and a transmitting mechanism, wherein the acoustic emission probe is arranged in a probe sleeve, and the acoustic emission probe is in clearance fit with an inner wall of the probe sleeve; a first spring and second springs are arranged between a shell and the probe sleeve; the first spring is arranged in a frame body of the shell, and the first spring is fixedly connected with an end cover on the probe sleeve, and is in a tension state or free state; the two second springs respectively sleeve guide rods in two spring sleeves, and the two second springs are in contact with stopping plates arranged in inner holes of the spring sleeves, and are in a compressed state. According to the acoustic emission sensor disclosed by the invention, the probe installation mechanism solves the problem that an acoustic emission probe cannot be effectively installed and coupled through controllable extension and retraction of the first spring and the second springs which are arranged between the shell and the probe sleeve; thus, reliability of monitoring and predicting mine rock (body) stability and rock burst dynamic disasters is enhanced.

Description

technical field [0001] The invention belongs to the technical field of rock (body) engineering safety monitoring in engineering construction, and relates to an acoustic emission sensor. Background technique [0002] Rock (body) deformation and damage during engineering construction, especially rockburst dynamic disasters, will directly endanger the safety of the project and even cause catastrophic effects. Therefore, effective monitoring and monitoring of rock (body) stability and rockburst dynamic disasters Forecasting is one of the important contents of engineering safety construction. At present, as an important means of non-destructive monitoring, acoustic emission is used in the monitoring and forecasting of rock (body) stability and rockburst dynamic disasters in engineering construction. [0003] During the excavation and construction of surrounding rocks in underground engineering, in order to accurately predict the possible deformation and damage of surrounding roc...

AI Technical Summary

Problems solved by technology

[0005] (1) At the engineering site, the acoustic emission probe is directly placed in the borehole, relying on the residual liquid medium (such as water) in the borehole as the medium for signal transmission between the rock mass and the acoustic emission probe, the acoustic emission probe will receive The detection signal is transmitted to the ground monitoring system through cables; however, this method has the following disadvantages: ① This implementation is only suitable for drilling holes with a downward direction, and for drilling holes that are completely horizontal or upward at a certain angle, it is difficult to store Even for the downward drilling, the rock mass around the drilling still needs to be relatively intact, so as to avoid the loss or seepage of the transmission medium from the borehole cracks, and ensure that the AE probe is always in the transmission medium, but the actual site However, it is difficult to meet this requirement, which affects the monitoring effect; ②Although the liquid between the rock mass and the acoustic emission probe can be used as the coupling medium for signal transmission, the density of the liquid is generally relatively low, and its signal transmission effect is not as good as that of the acoustic emission probe directly. The detection signal received by the transmitter probe in effective contact with the rock wall

[0006] (2) In order to ensure effective coupling between the acoustic emission probe placed in the borehole and the borehole wall, cement can also be poured into the borehole at the engineering site so that the acoustic emission probe and the rock wall are poured as a whole. Although this method It can solve the problem of effective transmission of detection signals, but there are still the following defects: ①The acoustic emission probe after casting is not recyclable, resulting in high monitoring costs; adjustment, only to re-drill and install new acoustic emission probes, which not only leads to high monitoring costs, but also leads to prolongation of the project progress and even delays in the construction period; The grouting effect of the installation part of the acoustic emission probe is difficult to guarantee, and there may be situations where the installation part of the acoustic emission probe cannot be effectively grouted, resulting in no effective coupling between the acoustic emission probe and the rock wall and no monitoring signal; Deeper, the greater the total shrinkage and deformation of the poured cement after solidification, the signal transmission cable of the acoustic emission probe bonded to the cement will bear tension due to the shrinkage and deformation of the cement, resulting in ineffective signal transmission; ④ During the excavation process Explosive blasting may cause the grouting surface and the rock wall surface to relax, resulting in a decrease in the effectiveness of monitoring signal transmission; ⑤The inside of the borehole is usually relatively humid, and it takes a long period for the grout to solidify after pouring, which will prolong the construction period; and the installation The process is time-consuming and laborious, requiring a series of professional grouting equipment and grouting personnel, which further increases the cost of monitoring

[0007] (3) Another implementation method is to use a simple fixed installation device to fix the acoustic emission probe inside the device, and then use a rigid non-movable metal transmission rod to send the fixing device to the installation site, and use pressure to push the acoustic emission probe to the top of the device. After it comes out, it is in contact with the rock wall of the borehole to achieve fixation. Its advantage is that it realizes the contact between the acoustic emission probe and the rock wall in the case of non-grouting, but there are still the following disadvantages: The distance between the walls is very close, so the fixed installation device and the drilling hole must have a concentric structure, and the hole wall needs to be smooth, but these requirements are difficult to guarantee in actual construction; ② Due to the large size of the fixed installation device, it is only suitable for Large drilling holes lead to higher drilling costs; ③The entire transmission rod and installation device are inserted into the drilling hole through force and rigidity, which not only has high friction, it is easy to wear out the cable or the acoustic emission probe, and it is easy to It is stuck in the drill hole and cannot be sent to the place where it needs to be installed; ④ Since the fixed installation device is rigidly inserted into the drill hole through external force, the installation process is not only time-consuming and laborious, but also the work efficiency is extremely low; ⑤ Due to the The hole wall is a cylindrical surface, while the end face of the acoustic emission probe is a plane. How to ensure that the end face of the acoustic emission probe is effectively coupled with the borehole wall is also a difficult problem to be solved in practical applications

[0008] Based on the disadvantages and defects in the above-mentioned various implementation methods, the application and promotion of acoustic emission detection in the monitoring of rock (body) stability and rockburst dynamic disasters is limited to a certain extent.

[0009] Therefore, how to install the acoustic emission probe in the borehole conveniently and effectively, and how to effectively couple the installed acoustic emission probe with the hole wall is still a difficult point in field monitoring and research at present, and there is a lack of relevant testing methods and technical support

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