System and method for monitoring internal vibration of surrounding rock in tunnel time-delay rockburst risk area

Abstract

The invention provides an internal vibration monitoring system and method for surrounding rock in a time-delay type rockburst risk area of a tunnel, and belongs to the field of tunnel engineering.The method comprises the steps that the surrounding rock and a potential time-delay type rockburst risk area are exposed behind a cutterhead, and holes with different radial depths are drilled; installing a vibration sensor in each hole, and plugging each hole by using a plugging material; connecting a signal cable of each vibration sensor in series to an acquisition port of an intelligent sensing gateway server; the axial, radial and vertical vibration speeds and accelerations acquired by each vibration sensor are acquired by adopting an intelligent sensing gateway service; the vibration sensor is fixed in the hole, the coupling degree of the sensor and the surrounding rock is enhanced, it is ensured that the vibration speed and acceleration between the sensor and the surrounding rock are kept consistent, and therefore the monitoring accuracy is improved.

Description

Technical Field

[0001] The present invention belongs to the field of tunnel engineering, and particularly relates to a vibration monitoring system and method for the surrounding rock inside the risk area of time-delay rockburst in tunnels. Background Art

[0002] With the increase in the number of deep-buried tunnels, the burial depths of many deep hard rock projects have successively exceeded one kilometer. As an intelligent tunneling equipment, TBM (Tunnel Boring Machine) has been widely used in deep hard rock tunnels due to its advantages such as fast excavation speed and construction safety. However, rockbursts occur frequently, resulting in serious casualties, equipment damage and construction delays. According to the occurrence time, rockbursts can be divided into instant rockbursts and time-delay rockbursts. Existing research mainly focuses on instant rockbursts, that is, the disasters occurring during the tunnel excavation process. While time-delay rockbursts occur within a period of time after excavation. Under the repeated disturbance of multi-source dynamic forces in deep engineering, the cracks in the surrounding rock continuously accumulate and the strength gradually decreases. When the bearing capacity is less than the tangential stress of the surrounding rock, a time-delay rockburst occurs. Time-delay rockbursts usually occur several months or even 4 - 5 years after excavation, and also occur frequently during the operation of the tunnel. This has brought unprecedented challenges to the construction and operation safety of the tunnel.

[0003] Existing research shows that a series of crack initiation, propagation and penetration usually occur before a rockburst. During this process, the micro-rupture of the rock mass can be captured by microseismic monitoring equipment. If a large number of microseismic rupture events occur in a certain area and no rockburst occurs after exceeding 3 times the tunnel diameter, this area can be regarded as the potential risk area of time-delay rockburst, and this area is more vulnerable to the vibration of the TBM. Therefore, it should be regarded as the key area for vibration monitoring.

[0004] During the TBM construction process, the cutterhead cutting the rock mass will generate continuous and intense vibration propagation in the surrounding rock. At present, vibration monitoring mainly focuses on the TBM structure itself, such as the positions of the main beam, propulsion cylinder and support cylinder, or only focuses on the vibration of the surrounding rock surface in different axial directions. Although the blasting vibration test method for drill-and-blast tunnels has been relatively mature, there is still a lack of systematic and in-depth research on the propagation law and attenuation characteristics of the internal vibration of the surrounding rock in deep-buried TBM tunnels. In addition, a systematic monitoring system for the vibration monitoring method of the surrounding rock inside the TBM tunnel has not been formed. At present, wireless sensors are generally used for TBM vibration monitoring to obtain the vibration velocity and acceleration of the surrounding rock, but it faces a series of problems such as the inability to export data in time, high equipment cost, inability to monitor for a long time (limited by the battery power of wireless sensors), large equipment volume and easy loss. In addition, as a monitoring blind area, there is a lack of effective vibration monitoring methods for the surrounding rock inside the shield. Since this area is closest to the vibration source, that is, the cutterhead, its vibration monitoring is particularly important. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present application proposes a vibration monitoring system and method for the surrounding rock inside the tunnel time-delay rockburst risk area. In the narrow space environment of the TBM tunnel, it can collect the vibration data inside the surrounding rock of the potential time-delay rockburst risk area 24 hours a day, and analyze these data in real time, providing a reference basis for the microseismic monitoring and early warning of time-delay rockburst and the optimization of TBM tunneling parameters.

[0006] In a first aspect, the present application proposes a vibration monitoring system for the surrounding rock inside the tunnel time-delay rockburst risk area, including: multiple vibration sensors and an intelligent sensing gateway server;

[0007] The multiple vibration sensors are respectively connected to the intelligent sensing gateway server through signal cables;

[0008] The multiple vibration sensors are arranged in holes with different radial depths in the potential time-delay rockburst risk area behind the tunnel boring machine face, and are used to collect the axial, radial, and vertical vibration velocities and accelerations caused by the excavation of the tunnel boring machine, and send the vibration velocities and accelerations to the intelligent sensing gateway server;

[0009] The intelligent sensing gateway server is used to receive the vibration velocities and accelerations transmitted by the multiple vibration sensors.

[0010] In a second aspect, the present application proposes a vibration monitoring method for the surrounding rock inside the tunnel time-delay rockburst risk area, which is implemented by using the vibration monitoring system for the surrounding rock inside the tunnel time-delay rockburst risk area described in the first aspect, and includes:

[0011] Based on the potential time-delay rockburst risk area behind the tunnel boring machine face determined by microseismic rupture events, determine the positions of the vibration sensors and various different radial depths;

[0012] According to the determined positions of the vibration sensors and various different radial depths, drill holes with different radial depths in the exposed surrounding rock behind the cutter head and the potential time-delay rockburst risk area;

[0013] Install vibration sensors in each hole and seal each hole with a sealing material;

[0014] Connect the signal cables of each vibration sensor in series to the acquisition port of the intelligent sensing gateway server;

[0015] Use the intelligent sensing gateway server to collect the axial, radial, and vertical vibration velocities and accelerations collected by each vibration sensor;

[0016] According to the axial, radial, and vertical vibration velocities and accelerations, draw the frequency-domain curves of the vibration velocities and accelerations to realize the monitoring of the vibration;

[0017] After the monitoring is completed, the vibration sensors are retrieved.

[0018] The potential time-delay rockburst risk area is the area where microseismic fracture events gather more than 3 times the tunnel diameter behind the tunnel face.

[0019] The multiple different radial depths include: the tunnel wall, the starting position of the excavation damaged zone, the ultimate depth of the excavation damaged zone, and the depth beyond the excavation damaged zone.

[0020] Determining the positions for arranging the vibration sensors includes: setting a hole every 5 meters between the axial starting point and the ending point of the potential time-delay rockburst risk area, and setting a hole on the surrounding rock exposed between the cutter head and the shield of the tunnel boring machine.

[0021] Determining the positions for arranging the vibration sensors also includes: arranging vibration sensors at the cutter head and the shoe where the tunnel boring machine resonates with the surrounding rock.

[0022] Sealing each hole with the sealing material includes: injecting the sealing material made by mixing quick-setting powder and water in a ratio of 5:3 into the hole and solidifying for the first preset time.

[0023] For the signal cables, the processing method includes: tying the signal cables outside the hole to the nearest wire mesh and rock bolts.

[0024] After the monitoring is completed, retrieving the vibration sensors includes: injecting a dissolving agent into the hole, standing for the second preset time to dissolve the sealing material, and taking out the sensor with a vibration sensor retrieval rod.

[0025] Advantageous effects:

[0026] This application proposes a vibration monitoring system and method for the surrounding rock inside the tunnel time-delay rockburst risk area. Fixing the vibration sensors in the holes enhances the coupling degree between the sensors and the surrounding rock, ensuring that the vibration velocity and acceleration between the sensors and the rock are consistent, thereby improving the accuracy of monitoring. The vibration sensors can be flexibly arranged at different radial depths, independent of the influence of on-site construction. This flexibility ensures the effectiveness and accuracy of monitoring. The vibration sensors can be retrieved and reused, which has economic benefits and sustainability. This can effectively reduce project costs and reduce resource waste. Description of the Drawings

[0027] Figure 1 Flowchart of a vibration monitoring method for the surrounding rock inside the tunnel time-delay rockburst risk area in an embodiment of this application;

[0028] Figure 2 Layout diagram of micro triaxial vibration sensors in the potential time-delay rockburst risk area in an embodiment of this application;

[0029] Figure 3 Schematic diagram of the miniature triaxial vibration sensor in the potential time-delay type rockburst risk area of the embodiment of the present application at different radial depths inside the surrounding rock;

[0030] Figure 4 Installation schematic diagram of the miniature triaxial vibration sensor of the embodiment of the present application;

[0031] Figure 5 Schematic diagram of the layout of monitoring points inside the cutter head of the embodiment of the present application;

[0032] Figure 6 Schematic diagram of the remote monitoring and acquisition system of the embodiment of the present application;

[0033] Wherein: 1 - tunnel; 2 - miniature triaxial vibration sensor; 3 - surrounding rock; 4 - sealing material; 5 - solder ring; 6 - signal cable; 7 - cutter head; 8 - shield; 9 - cutter head monitoring point, 10 - intelligent sensing gateway server, 11 - TBM operation room, 12 - potential time-delay type rockburst risk area, 13 - microseismic fracture event. Detailed implementation manners

[0034] The following further describes in detail the specific implementation manners of the present application in conjunction with the drawings and embodiments.

[0035] The present application provides a vibration monitoring system and method for the surrounding rock inside a tunnel in a time-delay type rockburst risk area. In the time-delay type rockburst risk area behind the TBM working face, miniature triaxial vibration sensors are arranged at different depths inside the surrounding rock. The three-direction vibration velocity and acceleration characteristics at different cross-section positions and different depths are measured on-site. The vibration sensors at different depths and the intelligent sensing gateway server form a vibration data acquisition system, and each vibration sensor can collect the vibration velocity and acceleration in three directions: axial (X direction), radial (Y direction), and vertical (Z direction) caused by TBM excavation.

[0036] Embodiment 1:

[0037] This embodiment provides a vibration monitoring system for the surrounding rock inside a tunnel in a time-delay type rockburst risk area, as shown in Figure 2 、 Figure 4 、 Figure 5 , including: multiple vibration sensors, intelligent sensing gateway server 10;

[0038] The multiple vibration sensors are respectively connected to the intelligent sensing gateway server 10 through signal cables 6;

[0039] The multiple vibration sensors are arranged in holes at different radial depths in the potential time-delay type rockburst risk area 12 behind the tunnel boring machine face, and are used to collect the axial, radial and vertical vibration velocities and accelerations caused by the excavation of the tunnel boring machine, and send the vibration velocities and accelerations to the intelligent sensing gateway server 10;

[0040] The intelligent sensing gateway server 10 is used to receive the vibration velocities and accelerations transmitted by the multiple vibration sensors.

[0041] In this embodiment, the multiple vibration sensors are respectively connected to the intelligent sensing gateway server 10 through signal cables 6, and the intelligent sensing gateway server 10 is connected to mobile phones, computers, tablets, etc. respectively by wireless communication, such as Figure 6 shown, which avoids the disadvantages of generally using wireless sensors in TBM vibration monitoring, can export vibration data in time, reduces the cost of equipment, extends the monitoring time, and avoids a series of problems such as large equipment volume and loss.

[0042] In this embodiment, the vibration sensor adopts a micro triaxial vibration sensor 2, which is small in size, firm and beautiful, and is suitable for various harsh working conditions. When installing, no large equipment is required, only a hand-held electric drill is needed, and holes can be easily drilled at any position in the tunnel 1 to ensure the rapid installation of the vibration sensor. The data of the micro triaxial vibration sensor 2 can be directly transmitted to the intelligent sensing gateway server 10 through the signal cable 6, and the vibration monitoring data on site can be viewed in real time through software. This monitoring method can be carried out continuously without worrying about the power problem. Once abnormal data is found, the system will promptly feedback to the on-site management personnel to ensure the safety of construction personnel and equipment. The micro triaxial vibration sensor 2 can be flexibly arranged at different radial depths, independent of the influence of on-site construction. This flexibility ensures the effectiveness and accuracy of monitoring.

[0043] Embodiment 2:

[0044] This embodiment provides a method for monitoring the internal vibration of the surrounding rock in the time-delay type rockburst risk area of the tunnel, which is implemented by using the internal vibration monitoring system of the surrounding rock in the time-delay type rockburst risk area of the tunnel described in the first aspect, as Figure 1 shown, including:

[0045] Step S1: According to the potential time-delay type rockburst risk area 12 determined by the microseismic rupture event 13 behind the tunnel boring machine face, determine the positions and multiple different radial depths for arranging the vibration sensors;

[0046] In this embodiment, based on the existing microseismic monitoring means, if there are more microseismic rupture events 13 in a certain area and no immediate rockburst occurs within the range of three times the tunnel diameter from the face, it can be determined that this area is a potential time-delay type rockburst risk area, as Figure 2As shown. According to the scope of the excavation damage zone of the TBM, the following are determined Figure 3 Four depths as shown: a, the tunnel wall; b, the starting position of the excavation damage zone; c, the ultimate depth of the excavation damage zone; d, the depth beyond the excavation damage zone.

[0047] Step S2: According to the determined positions of the vibration sensors and various different radial depths, drill holes with different radial depths in the exposed surrounding rock 3 and the potential delayed rockburst risk area 12 behind the cutter head 7;

[0048] At the axial starting point to the ending point of the potential delayed rockburst risk area 12 as determined as Figure 2 shown, drill holes with different depths every 5 meters. The diameter of the drill holes is between 70 mm and 100 mm. According to the position where microseismic energy accumulates, the drill hole depth is set to be between 1 m and 3 m. At the same time, drill holes with different radial depths in the exposed surrounding rock 3 behind the cutter head 7 (including inside the shield 8 and behind the shield 8) for vibration monitoring; place a micro triaxial vibration sensor 2 in the drilled hole in the exposed surrounding rock 3 between the cutter head 7 and the shield 8. Arrange vibration sensors at the cutter head 7 and the thrust shoes where the TBM resonates with the surrounding rock 3 to compare with the vibration data measured inside the surrounding rock 3.

[0049] Step S3: Install a vibration sensor in each hole and seal each hole with a plugging material 4;

[0050] In this embodiment, install a micro triaxial vibration sensor 2 in each hole, as Figure 4 shown, and calibrate the zero point of the sensor. Subsequently, inject a quick-setting powder and water into the drill hole to make a plugging material 4 by stirring in a ratio of 5:3, and wait for it to solidify to ensure that it cannot be pulled out. This can ensure that the vibration velocity and acceleration collected by the sensor are consistent with the vibration velocity and acceleration propagated by the surrounding rock 3. Next, carry out on-site percussion tests to test the sensitivity of the sensor to signals, and a total of two groups of experiments are conducted. Percuss the surrounding rock 3 20 times in each group. The percussion point of the first group is located at the central part (12 o'clock position) of the potential delayed rockburst area, and the percussion point of the second group is located 10 meters in front of the potential delayed rockburst area (12 o'clock position), and use the vibration sensor to receive the percussion signal.

[0051] Step S4: Connect the signal cables 6 of each vibration sensor in series to the acquisition port of the intelligent sensing gateway server 10;

[0052] In this embodiment, use a wire stripper to strip the insulation layer of the signal cable exposed outside the hole by 1-2 cm to expose the copper wire. Slip the prepared solder ring 5 onto the signal cable 6 of the sensor, then align the two copper wires and tightly twist them together. Move the solder ring 5 to the center position of the cable connection, and use a hot air gun to heat the solder ring 5 until it completely melts and shrinks. This process is cycled in sequence to ensure that the signal cables 6 of multiple sensors are combined into one, reducing the number of cables, making the wiring neater, occupying less space, and not affecting the construction of on-site personnel. The solder ring 5 will shrink after heating, firmly connecting the two cables and enhancing the stability of the joint. Tie the signal cable 6 outside the hole to the nearby anchor net and anchor rod, and tidy up the excess signal wires and place them in the corner to prevent cable damage and reduce interference with on-site construction. Finally, connect the combined cable to the intelligent sensing gateway server 10 to achieve the integration and data transmission of the sensor network.

[0053] Step S5: Use the intelligent sensing gateway server to collect the axial, radial, and vertical vibration velocities and accelerations collected by each vibration sensor;

[0054] In this embodiment, insert the power cord of the voltage stabilizer into the power socket, then turn on the power switch of the voltage stabilizer and confirm that the indicator light is on normally. Then, connect the power cord of the intelligent sensing gateway server 10 to the output terminal of the voltage stabilizer and start the intelligent sensing gateway server 10, where the voltage stabilizer provides stable power for the intelligent sensing gateway server 10. Then, remotely set the acquisition parameters of the sensor through the mobile phone APP, and set acquisition parameters such as acquisition time, acquisition segments, and trigger levels.

[0055] Step S6: According to the axial, radial, and vertical vibration velocities and accelerations, draw the vibration velocity and acceleration frequency domain curves to achieve vibration monitoring;

[0056] In this embodiment, remotely view the vibration data in real time through software, and process the collected data. Use the fast Fourier transform (FFT) to convert the time-domain signal into a frequency-domain signal, so as to obtain the vibration velocity and acceleration frequency domain curves collected by the vibration sensors in three directions in each hole. This method can better study the frequency domain characteristics of the vibration data and analyze the vibration data in real time. If the vibration data is significantly abnormal during a certain period, the system will promptly feedback to the on-site management personnel. The management personnel can adjust the tunneling parameters of the TBM, such as reducing the thrust, penetration, torque, and tunneling speed, etc., to reduce the amplitude A and frequency f of the vibration, thereby reducing the possibility of rock burst occurring in the potential time-delay type rock burst risk area 12 and achieving effective prevention and control.

[0057] Step S7: After the monitoring is completed, recover the vibration sensors.

[0058] In this embodiment, after the vibration monitoring is completed, a gypsum dissolving agent is poured into the hole to evenly cover the surface of the gypsum. As the dissolving agent penetrates, the gypsum gradually softens. Then, a recovery rod is used to gently stir to help the dissolving agent fully react with the gypsum. After a period of time, the gypsum becomes soft and loose. Then, the vibration sensor is smoothly taken out using the recovery rod. The recovery rod is a hook-shaped metal rod with a metal hook at the front end, so that the vibration sensor can be firmly fixed in the hook for convenient removal together.

[0059] In addition, vibration monitoring needs to be carried out on the cutter head 7 and the surrounding rock 3 inside the exposed area between the cutter head 7 and the shield 8, as Figure 5 shown. The cutter head 7 is the main vibration source of the TBM, and its vibration monitoring is particularly important. As a TBM structure that resonates with the surrounding rock 3, monitoring the vibration of the cutter head 7 can help reveal the attenuation law of vibration waves in the surrounding rock 3, thereby providing important data support and safety guarantee for construction.

[0060] The surrounding rock 3 between the cutter head 7 and the shield 8 is a monitoring blind area, and existing TBM vibration monitoring methods do not cover it. This is mainly because the internal operation space of the cutter head 7 is narrow, and vibration monitoring equipment is prone to being lost or damaged. In addition, existing monitoring equipment is usually large in size and cannot provide a suitable installation space in this area. The equipment used in this monitoring method can be installed in the surrounding rock 3 inside the cutter head 7. In this embodiment, it is installed at the cutter head monitoring point 9, and the specific installation method is carried out according to steps S1, S2, S3, S4, S5, S6, and S7. As the TBM advances, the micro triaxial vibration sensor 2 will gradually be covered by the shield 8 to achieve vibration monitoring of the surrounding rock 3 inside the shield 8. Since this sensor is far from other vibration sensors, an additional intelligent sensing gateway server 10 needs to be arranged to supply power to it separately. Another intelligent sensing gateway server 10 can be placed in the TBM operation room 11.

[0061] The thrust shoes, as the supporting structure of the TBM, are closely attached to the side wall of the surrounding rock 3 of the already excavated tunnel 1 and bear the vibration transmitted from the cutter head 7. Therefore, monitoring the vibration of the thrust shoe part is of great significance. This data can be compared with the vibration data inside the surrounding rock 3 to analyze the vibration characteristics and propagation law, and provide a basis for optimizing the tunneling parameters (thrust, torque, penetration rate) of the TBM.

[0062] The micro triaxial vibration sensors 2 at each position and the intelligent sensing gateway server 10 are constructed into a vibration remote monitoring and acquisition platform, as Figure 6 shown. The vibration velocity and acceleration in three directions collected by each sensor are transmitted to the intelligent sensing gateway server 10 through the signal cable 6. Subsequently, these data are remotely processed by a computer. If any abnormal situation is found, the system will promptly notify the on-site personnel to adjust the tunneling parameters of the TBM. This monitoring method provides an effective guarantee for the safety of personnel and equipment.

[0063] Each embodiment in this application is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other, and the key point of each embodiment is to illustrate the differences from other embodiments.

[0064] The protection scope of this application is not limited to the above embodiments. Obviously, those skilled in the art can make various changes and deformations to the present disclosure without departing from the scope and spirit of the present disclosure. If these changes and deformations fall within the scope of the claims of the present disclosure and their equivalent technologies, the intention of the present disclosure also includes these changes and deformations.

Claims

1. A tunnel time-lag type rockburst risk zone surrounding rock internal vibration monitoring system, characterized in that: include: Multiple vibration sensors, intelligent sensor gateway server; The multiple vibration sensors are respectively connected to the intelligent sensor gateway server through signal cables; The multiple vibration sensors are arranged in holes of different radial depths in a potential time-lag rockburst risk zone behind the tunnel boring machine face, and are used to collect axial, radial and vertical vibration velocities and accelerations caused by tunnel boring machine excavation, and send the vibration velocities and accelerations to the intelligent sensor gateway server; The intelligent sensor gateway server is used to receive vibration speed and acceleration transmitted by multiple vibration sensors.

2. A method for monitoring internal vibration of surrounding rocks in a tunnel time-lag rockburst risk zone, implemented by using a system for monitoring internal vibration of surrounding rocks in a tunnel time-lag rockburst risk zone as claimed in claim 1, characterized in that: include: Based on the potential time-delay rockburst risk area behind the tunnel boring machine face determined by microseismic rupture events, the location and multiple radial depths of vibration sensors are determined; Based on the determined location of the vibration sensor and various radial depths, the surrounding rock and potential time-delay rockburst risk areas are exposed behind the cutterhead and holes of different radial depths are drilled; Install a vibration sensor in each hole and seal each hole with a sealing material; Connect the signal cable of each vibration sensor in series to the acquisition port of the intelligent sensor gateway server; The intelligent sensor gateway server is used to collect the axial, radial and vertical vibration velocity and acceleration collected by each vibration sensor; According to the axial, radial and vertical vibration velocities and accelerations, vibration velocity and acceleration frequency domain curves are drawn to realize vibration monitoring; After the monitoring is completed, the vibration sensor is recovered.

3. A method for monitoring internal vibration of surrounding rock in a tunnel time-lag rockburst risk zone according to claim 2, characterized in that: The potential time-lag rockburst risk area is the area where microseismic rupture events are concentrated, which is more than 3 times the tunnel diameter behind the tunnel face.

4. A method for monitoring internal vibration of surrounding rock in a tunnel time-lag rockburst risk zone according to claim 2, characterized in that: The various radial depths include: the tunnel wall, the starting position of the excavation damage zone, the limit depth of the excavation damage zone, and the depth beyond the excavation damage zone.

5. The method for monitoring internal vibration of surrounding rock in a tunnel time-lag rockburst risk zone according to claim 2, characterized in that: The method of determining the position of arranging the vibration sensor includes: setting a hole every 5 meters between the axial starting point and the end point of the potential time-lag rock burst risk zone, and setting a hole on the surrounding rock exposed between the cutter head and the shield of the tunnel boring machine.

6. A method for monitoring internal vibration of surrounding rock in a tunnel time-lag rockburst risk zone according to claim 2, characterized in that: The step of determining the position for arranging the vibration sensor further includes arranging the vibration sensor at the cutter head and the gripper shoe of the tunnel boring machine where the vibration sensor resonates with the surrounding rock.

7. The method for monitoring internal vibration of surrounding rock in a tunnel time-lag rockburst risk zone according to claim 2, characterized in that: The method of using the plugging material to plug each hole includes: injecting the plugging material prepared by mixing quick-setting powder and water in a ratio of 5:3 into the hole and solidifying it for a first preset time.

8. The method for monitoring internal vibration of surrounding rock in a tunnel time-lag rockburst risk zone according to claim 2, characterized in that: The signal cable processing method includes: tying the signal cable outside the hole to the nearest anchor net and anchor rod.

9. The method for monitoring internal vibration of surrounding rock in a tunnel time-lag rockburst risk zone according to claim 2, characterized in that: After the monitoring is completed, the vibration sensor is recovered, including: injecting a dissolving agent into the hole, standing for a second preset time to allow the plugging material to dissolve, and taking out the sensor using a vibration sensor recovery rod.

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