Method for measuring wave velocity of rock mass on site based on blasting vibration test

Abstract

The invention discloses a blasting vibration test-based rock mass wave velocity field measurement method, which is applied to a blasting operation area, is consistent with a tunnel blasting propulsion direction, does not need to independently open up a test area, and can obtain rock mass vibration data of a measurement point corresponding to a vibration measurement instrument after blasting only by arranging the vibration measurement instrument on an excavated tunnel bottom plate. According to the method, the rock mass average wave velocity can be rapidly and accurately calculated by combining the pre-measured error time of the vibration measurement instrument, the limitation of the arrangement distance of the vibration measurement instrument is broken through, the measurement range is remarkably expanded, the cost and difficulty of rock mass wave velocity measurement are effectively reduced, wave velocity measurement is completed under the condition that the original property of the rock mass is kept, and the rock mass average wave velocity is calculated. The actual rock mass condition of the blasting construction area is fed back in time, high adaptability to different rock mass properties is achieved, a scientific basis is provided for engineering design and construction, and safety and efficiency of construction are guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering, and particularly to a method for on-site determination of rock mass wave velocity based on blasting vibration testing. Background Art

[0002] During the blasting construction process of a tunnel, the rock mass wave parameters play a key role in the propagation and attenuation of blasting seismic waves. The rock mass wave parameters include wave velocity, wave impedance, attenuation coefficient, frequency characteristics, etc. These parameters directly determine the transmission efficiency of blasting energy, the vibration intensity of surrounding rock, and the stress condition of structures, thus affecting construction safety and engineering quality.

[0003] The average wave velocity of the rock mass occupies a core position among these rock mass wave parameters. By measuring the average wave velocity of the rock mass, the integrity of the rock mass can be quickly evaluated, the rock mass strength can be inferred, and the hydrogeological properties of the rock mass can be reflected, providing an important basis for engineering design, construction safety, and disaster prevention and control.

[0004] Existing methods for measuring rock mass wave velocity include single-hole method, cross-hole method, surface wave method, ultrasonic method, and vibration method. Although each has its own advantages, when used at the blasting construction site of a tunnel, there are often many limitations, including high measurement cost, complex operation, low spatial resolution, limited test accuracy, etc. It is difficult to quickly give the average wave velocity of the rock mass in the construction area during the blasting construction process of the tunnel, and it cannot play the role of timely feedback and guiding subsequent construction. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for on-site determination of rock mass wave velocity based on blasting vibration testing for the problems existing in the prior art.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A method for on-site determination of rock mass wave velocity based on blasting vibration testing includes the following steps:

[0008] Detect the error time of each vibration measuring instrument , where n is the serial number;

[0009] According to the requirements of tunnel blasting construction, drill holes on the tunnel excavation face and load explosives into the holes;

[0010] Arrange a plurality of the vibration measuring instruments on the tunnel floor, and the vibration measuring instruments are respectively located at different blast center distances, and measure the distance S between adjacent vibration measuring instruments n(n-1) ;

[0011] According to the existing blasting parameters, conduct blasting according to the setting of the initiation network. When the vibration frequency monitored by the vibration measuring instrument exceeds the threshold value, the vibration signal will start to be recorded;

[0012] Analyze the vibration signals recorded by each of the vibration measuring instruments to obtain the peak recording time T of each of the vibration measuring instruments n ;

[0013] Calculate the average wave velocity of the rock mass in the construction area , .

[0014] In the present invention, charge blasting is carried out in the blast holes in the construction area, and the vibration signals generated by the blasting are used to measure the average wave velocity of the rock mass. Based on the measured average wave velocity of the rock mass, the dynamic parameters of the rock mass are further determined. These parameters are crucial for accurately evaluating the dynamic response and stability of the rock mass under the action of blasting loads, thereby ensuring higher accuracy and reliability in the safety evaluation of the construction area.

[0015] Preferably, the method for detecting the error time of the vibration measuring instrument is as follows :

[0016] Set an artificial seismic source, with the artificial seismic source as the center, and arrange the vibration measuring instruments around the artificial seismic source

[0017] Start the artificial seismic source, and the vibration measuring instruments will record vibration signals

[0018] Analyze the vibration signals recorded by each of the vibration measuring instruments, record the peak recording time of any one of the vibration measuring instruments as T0, and record the peak recording times of the remaining vibration measuring instruments as T n ;

[0019] Calculate the error time of each of the vibration measuring instruments , .

[0020] Since the distances from the blast center of each vibration measuring instrument are different, the trigger times of each vibration measuring instrument are also different, resulting in differences in the starting times of the measured data. In order to obtain the time difference between adjacent measuring points for acquiring vibration signals, it cannot be directly obtained by taking the difference of the times corresponding to the test data, but it is necessary to use the difference between the true times corresponding to when the instruments are triggered, on the basis of considering the errors caused by the time differences in triggering and storing data between the instruments, to obtain the time difference between adjacent measuring points for acquiring vibration signals.

[0021] By measuring and calculating the error time between the vibration measuring instruments, and combining the vibration waveform data measured by each of the vibration measuring instruments, correct the times when the vibration wave peaks appear at each measuring point, and then calculate the time difference between adjacent measuring points for acquiring vibration signals, breaking through the distance limitation of the arrangement of the vibration measuring instruments, and significantly expanding the measurement range of the wave velocity of the rock mass.

[0022] Preferably, the vibration measuring instruments and the artificial seismic source are on the same horizontal plane.

[0023] The distance between any of the vibration measuring instruments and the artificial seismic source is the same, and the distance between adjacent vibration measuring instruments is the same.

[0024] By arranging the vibration measuring instruments at equal distances from the artificial seismic source, it is ensured that each vibration measuring instrument can simultaneously receive the vibration signals transmitted from the artificial seismic source. Through the processing of the waveform files, the error time between the vibration measuring instruments can be calculated, and the accuracy can reach 0.001 ms, thus providing a reliable guarantee for the accurate calculation of the rock mass wave velocity in the subsequent process.

[0025] Preferably, after the blasting is completed, safety inspections and ventilation for smoke dispersion are carried out. After confirming safety, the vibration measuring instruments are turned off and recovered, and the vibration signals recorded by the vibration measuring instruments are read.

[0026] By closely combining with the blasting excavation operation in actual construction, only the layout and data processing of the vibration measuring instruments are required. The equipment is portable and easy to operate, without the need to separately open a test area or drill blast holes for testing, effectively reducing the cost and difficulty of calculating the rock mass wave velocity.

[0027] Preferably, a vibration waveform diagram is generated from the vibration signals recorded by the vibration measuring instruments. The earliest occurring wave peak is found in the vibration waveform diagram, and the time corresponding to the earliest occurring wave peak plus the time for starting vibration correction is recorded as the wave peak recording time of the vibration measuring instrument.

[0028] Preferably, the vibration measuring instrument is a vibration sensor, and the vibration measuring instrument is arranged along the axis direction of the tunnel.

[0029] The distance between adjacent vibration measuring instruments is 10 - 30 m.

[0030] The distance between the vibration measuring instrument and the tunnel excavation face is not less than 10 m.

[0031] The number of vibration measuring instruments arranged on the tunnel floor is not less than 8.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] (1) Before measuring the average wave velocity of the rock mass, the method provided by the present invention ensures that each vibration measuring instrument can simultaneously receive the vibration signals transmitted from the seismic source by arranging the vibration measuring instruments at equal distances from the seismic source. Through the processing of the waveform files, the error time between the instruments can be calculated, and the accuracy can reach 0.001 ms, thus providing a reliable guarantee for the accurate calculation of the rock mass wave velocity in the subsequent process.

[0034] (2) The method provided by the present invention calculates the error time between each instrument and corrects the time when the vibration peak appears at each measuring point in combination with the vibration waveform data measured by each vibration measuring instrument. Then, the time difference of the vibration signal obtained by adjacent measuring points is calculated, thus breaking through the distance limitation of the arrangement of vibration measuring instruments and significantly expanding the measurement range of rock wave velocity.

[0035] (3) The method provided by the present invention can be closely integrated with the blasting and excavation operations in actual construction. It only requires the arrangement and data processing of vibration measuring instruments. The equipment is portable and easy to operate. There is no need to open up a separate test area or drill blastholes for testing. Instead, the measurement is completed with the help of blasting during tunnel excavation, which effectively reduces the cost and difficulty of rock mass wave velocity measurement.

[0036] (4) The method provided by the present invention is applied to the area where blasting operation is about to be carried out. It is consistent with the direction of the tunnel blasting cycle advancement and makes full use of the flow operation organization of the excavation working face. Therefore, the calculated average wave velocity of the rock mass can timely feedback the rock mass condition in the blasting construction area, thereby effectively guiding the subsequent construction and improving the construction efficiency and safety.

[0037] (5) The method provided by the present invention has high adaptability to different rock properties. No matter whether it is a relatively intact rock mass or a rock mass with developed joints and fissures, the rock mass wave velocity can be measured while maintaining its original properties as much as possible, which is closer to its true value. This enables the measurement results to more accurately guide the excavation and blasting in subsequent construction, provide a scientific basis for engineering design and construction, and ensure the safety and efficiency of the construction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the process of the present invention;

[0039] Figure 2 The present invention is a test arrangement diagram for detecting the error time of the vibration measuring instrument;

[0040] Figure 3 This is a test arrangement diagram for measuring the average wave velocity of rock mass in tunnel blasting according to the present invention;

[0041] In the figure: 1. Artificial seismic source; 2. Vibration measuring instrument; 3. Tunnel blasting hole; 4. Tunnel. DETAILED DESCRIPTION

[0042] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings 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.

[0043] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "middle", "upper", "lower", "left", "right", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0044] As Figures 1 to 3 shown, the specific solutions of the embodiments are as follows:

[0045] A method for on-site determination of rock mass wave velocity based on blasting vibration testing includes the following steps:

[0046] S1: Detect the error time of each vibration measuring instrument 2 , where n is the serial number, the vibration measuring instrument 2 is a vibration sensor, and the artificial seismic source 1 is a pneumatic hammer. Since a total of eight vibration measuring instruments 2 are used in this embodiment, the value range of n is 1 to 8. The specific detection method is as follows:

[0047] S1.1: Set the artificial seismic source 1, with the artificial seismic source 1 as the center, the vibration measuring instruments 2 are arranged around the artificial seismic source 1. The vibration measuring instruments 2 and the artificial seismic source 1 are placed on the same horizontal plane, and the distance between any vibration measuring instrument 2 and the artificial seismic source 1 is 1 m, and the distance between adjacent vibration measuring instruments 2 is the same.

[0048] S1.2: Start the artificial seismic source 1, and the vibration measuring instruments 2 will record the vibration signals;

[0049] S1.3: Analyze the vibration signals recorded by each vibration measuring instrument 2, record the wave peak recording time of the vibration measuring instrument 2 with the serial number 1 as T0, and record the wave peak recording times of the remaining vibration measuring instruments 2 as T n ;

[0050] S1.4: Calculate the error time of each vibration measuring instrument 2 , .

[0051] To ensure the accuracy of the results, a total of four repeated tests are carried out, and the average value of the error times measured in the four tests is taken to obtain the error time of each vibration measuring instrument 2 , and the measurement results of each vibration measuring instrument 2 and the calculated error time are shown in Table 1.

[0052] The unit format of the wave peak recording time is hour / minute / second. For example, 9:19:36.856 means 9 hours 19 minutes 36.856 seconds.

[0053] Table 1 Measurement results of vibration measuring instrument 2 and calculated error time

[0054]

[0055] S2: According to the requirements of the blasting construction of the tunnel 4, drill the tunnel blasting holes 3 on the excavation face of the tunnel 4. Weigh the explosive accurately according to the blasting design requirements to ensure that the charge amount meets the design standard. Load the explosive into the holes, paying attention to the loading position and height to ensure uniform and firm loading.

[0056] Select suitable plugging materials such as clay and water bags, and plug according to the design requirements. Ensure tight plugging during plugging to prevent gas leakage, and at the same time avoid adverse effects of the plugging materials on the blasting effect.

[0057] Connect the detonators or detonating cords of each hole to the initiation network according to the initiation sequence and time interval of the blasting design. Check whether the connection of the networking line is firm and conductive to ensure the reliability of the initiation network.

[0058] S3: Arrange several vibration measuring instruments 2 on the floor of the tunnel 4. The vibration measuring instruments 2 are arranged along the axis direction of the tunnel 4, and the vibration measuring instruments 2 are located at different blast center distances respectively. The measured distances between each vibration measuring instrument 2 and the face are 10m, 30m, 50m, 60m, 80m, 90m, 100m and 130m respectively, and the distance S n(n-1) between adjacent vibration measuring instruments 2 is 20m.

[0059] The blast center distance refers to the distance between the explosion point and the tunnel center in the blasting operation.

[0060] Unify the settings of parameters such as the trigger level, acquisition frequency, and acquisition method of each vibration measuring instrument 2 to ensure that the parameters of all instruments are consistent. The trigger level setting should be adjusted according to the expected vibration signal intensity to avoid abnormal triggering of the instrument due to too strong or too weak signals.

[0061] The acquisition frequency should be selected according to the test requirements and instrument performance to ensure that the details of the vibration signal can be accurately recorded. The acquisition method (such as continuous acquisition, trigger acquisition, etc.) should be set according to the test plan to ensure that complete vibration data can be obtained.

[0062] Set the instrument to the automatic acquisition mode and enter the state to be measured. Check the power supply, storage and other states of the instrument to ensure that the instrument can work normally during the blasting process.

[0063] S4: Set up a warning area according to the requirements of the blasting safety regulations to ensure that there are no personnel and equipment in the warning area. Set obvious warning signs at the boundary of the warning area, arrange special personnel to be responsible for the warning work, and notify the surrounding personnel to evacuate the warning area through means such as broadcasting and whistles.

[0064] After confirming the safety of the warning area, the blasting commander gives the detonation order. After receiving the detonation order, the detonator personnel carry out blasting according to the existing blasting parameters and the setup of the detonation network. When the vibration measuring instrument 2 detects that the vibration frequency exceeds the threshold, it will start recording the vibration signal;

[0065] After detonation, ventilation is carried out to disperse the smoke, ensuring the discharge of harmful gases within the blasting area. The ventilation time should be determined according to the blasting scale and ventilation conditions, usually not less than 15 minutes. Then, a safety inspection is carried out to check the blasting effect and confirm whether there are misfires or unexploded cartridges.

[0066] After ensuring there are no safety hazards, turn off and retrieve the vibration measuring instrument 2, and read the vibration signal recorded by the vibration measuring instrument 2.

[0067] S5: Analyze the vibration signals recorded by each vibration measuring instrument 2, generate a vibration waveform diagram through the vibration signals recorded by the vibration measuring instrument 2. Since the waveform data may contain noise, interference signals, etc., it is necessary to preprocess the waveform data using analysis software.

[0068] During the preprocessing process, the analysis software performs cross-correlation processing on the waveform data of multiple vibration cycles recorded by the vibration measuring instrument 2 to determine the relative delay time of each vibration cycle. Then, singular points are removed through the 3-sigma criterion, and the standard system delay time is calculated, which is the time for the starting vibration time correction in Table 2.

[0069] The wave crest recording time refers to the time point when the vibration signal reaches the maximum amplitude (wave crest). The wave crest is a local maximum point of the vibration signal, usually indicating the concentrated release of vibration energy.

[0070] Find the earliest wave crest in the vibration waveform diagram, add the time for the starting vibration time correction to the time corresponding to the earliest wave crest, and record it as the wave crest recording time T1~T8 of the vibration measuring instrument 2. Among them, the triggering time recorded in Table 2 is the time corresponding to the earliest wave crest, and the unit format is hour / minute / second. For example, 14:51:35.757 means 14 hours 51 minutes 35.757 seconds.

[0071] S6: Calculate the average wave velocity of the rock mass in the construction area , .

[0072] Table 2 also records the distances from the blasting center of each vibration measuring instrument 2, the error time, and the wave velocities of the rock mass measured separately by each vibration measuring instrument 2. The calculation result of the average wave velocity of the rock mass obtained according to step S6 is also located in Table 2.

[0073] Table 2 Measurement results of each vibration measuring instrument 2 and the calculated average wave velocity of the rock mass

[0074]

[0075] In summary, the method of the present invention skillfully integrates the normal tunneling 4 blasting construction process, can quickly and conveniently measure the rock wave velocity of the project area, neither affects the construction progress nor requires accurate determination of the initiation point position, thus avoiding the errors that may be introduced during the on-site drilling and charging processes. This method provides reliable rock material parameters for subsequent analysis of the dynamic response of rock masses under dynamic loads such as blasting loads and seismic loads, and effectively guarantees the construction safety and project quality.

[0076] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for on-site determination of the wave velocity of rock mass based on blasting vibration test, characterized in that, It includes the following steps: Detect the error time of each vibration measuring instrument , where n is the serial number; According to the requirements of tunnel blasting construction, drill holes on the tunnel excavation face and load explosives into the holes; Arrange a number of the vibration measuring instruments on the tunnel floor, where the vibration measuring instruments are respectively located at different distances from the blast center, and measure the distance S between adjacent vibration measuring instruments n(n-1) ; According to the existing blasting parameters, conduct blasting according to the setting of the initiation network. When the vibration frequency monitored by the vibration measuring instrument exceeds the threshold, the vibration signal will start to be recorded; Analyze the vibration signals recorded by each of the vibration measuring instruments to obtain the peak recording time T of each of the vibration measuring instruments n ; Calculate the average wave velocity of the rock mass in the construction area , .

2. The method for on-site determination of rock mass wave velocity based on blasting vibration test according to claim 1, characterized in that, Detect the error time of the vibration measuring instrument The method is as follows: Set up an artificial seismic source, with the artificial seismic source as the center, and arrange the vibration measuring instruments around the artificial seismic source; Start the artificial seismic source, and the vibration measuring instrument will record the vibration signal; Analyze the vibration signals recorded by each of the vibration measuring instruments. Denote the wave peak recording moment of any one of the vibration measuring instruments as T0, and denote the wave peak recording moments of the remaining vibration measuring instruments as T n ; Calculate the error time of each of the vibration measuring instruments , .

3. The method for on-site determination of rock mass wave velocity based on blasting vibration test according to claim 2, characterized in that, The vibration measuring instrument and the artificial seismic source are on the same horizontal plane.

4. A method for on-site determination of rock mass wave velocity based on blasting vibration test according to claim 2, characterized in that, The distance between any vibration measuring instrument and the artificial seismic source is the same, and the distance between adjacent vibration measuring instruments is the same.

5. The method for on-site determination of rock mass wave velocity based on blasting vibration test according to claim 1, wherein After the blasting is completed, conduct safety inspections and ventilation to disperse the smoke. After confirming safety, turn off and recover the vibration measuring instrument, and read the vibration signal recorded by the vibration measuring instrument.

6. The method for on-site determination of rock mass wave velocity based on blasting vibration test according to claim 1, characterized in that, Generate a vibration waveform diagram through the vibration signal recorded by the vibration measuring instrument. Find the earliest peak in the vibration waveform diagram, and add the time of the start vibration time correction to the time corresponding to the earliest peak, which is recorded as the peak recording time of the vibration measuring instrument.

7. A method for on-site determination of rock mass wave velocity based on blasting vibration test according to claim 1, characterized in that, The vibration measuring instrument is a vibration sensor, and the vibration measuring instrument is arranged along the tunnel axis direction.

8. The method for on-site determination of rock mass wave velocity based on blasting vibration test according to claim 1, characterized in that The distance between adjacent vibration measuring instruments is 10 - 30m.

9. The method for on-site determination of rock mass wave velocity based on blasting vibration test according to claim 1, characterized in that, The distance between the vibration measuring instrument and the tunnel excavation face is not less than 10m.

10. A method for on-site determination of rock mass wave velocity based on blasting vibration test according to claim 1, characterized in that, The number of vibration measuring instruments arranged on the tunnel floor is not less than 8.

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