A microseismic positioning method for tunnel excavation

Abstract

The present invention discloses a microseismic positioning method for tunnel excavation, which relates to the technical field of tunnel microseismic positioning. The present invention includes a sensor, a processing unit, and a simulation device. The output end of the sensor is connected to the input end of the processing unit, and the output end of the processing unit is connected to the input end of the simulation device. The positioning method includes the following steps: sensor deployment, dividing the sensors into two groups, namely tunnel cross section A and tunnel cross section C, respectively, with the tunnel excavation surface D and the unexcavated area B in the tunnel, the area between tunnel cross section A and tunnel cross section C as AC, the length of area AC as d1, and the area between tunnel cross section A and excavation surface D as AD. Each group of four sensors is installed in the same tunnel cross section. The present invention simulates hammering and continuously adjusts the position of the detection points, mutually verifies the positioning error between the detection points, and adjusts the weight index of each detection point according to the positioning error.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel microseismic positioning, and in particular to a microseismic positioning method for tunnel excavation. Background Art

[0002] Rockbursts are a common geological disaster during deep engineering excavation or mining. They not only damage underground structures and equipment but also threaten the lives of construction workers. Tunnel excavation in high-stress environments inevitably causes stress concentration or energy accumulation in locations with poor rock mass structure, ultimately leading to rockbursts. Microseismic monitoring, a three-dimensional rock damage monitoring technology, is currently recognized as a reliable means of rockburst early warning. The spatial distribution of microseismic activity clearly corresponds to the location of rockbursts or stress concentration zones, enabling the prediction of rockburst locations and early warning.

[0003] The spatial distribution of microseismic events obtained by the current microseismic monitoring technology has certain errors. The positioning position of each microseismic point monitored deviates from the actual location of the microseismic event. Especially in areas where microseismic events frequently occur, the errors of each microseismic point will affect each other and accumulate, ultimately leading to errors in the prediction of the rockburst location and reducing the credibility of the microseismic monitoring technology results. Therefore, improving the microseismic positioning accuracy of microseismic monitoring technology is a technical problem that technicians in this field need to solve. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a microseismic positioning method for tunnel excavation, which solves the problems raised in the above-mentioned background technology.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: A microseismic positioning method for tunnel excavation, comprising a sensor, a processing unit, and a simulation device, wherein the output end of the sensor is connected to the input end of the processing unit, and the output end of the processing unit is connected to the input end of the simulation device;

[0006] The positioning method includes the following steps:

[0007] Step 1: Sensor deployment. Workers divided the sensors into two groups, namely tunnel cross-section A and tunnel cross-section C. The tunnel excavation surface is D, the unexcavated area is B, the area between tunnel cross-section A and tunnel cross-section C is AC, the length of area AC is d1, and the area between tunnel cross-section A and excavation surface D is AD. Each group of four sensors is installed in the same tunnel cross-section. Sensors in the same group are installed on the spandrels and haunches on both sides of the tunnel cross-section. The installation locations of the sensors are detection points. The detection points of tunnel cross-section A are a1, a2, a3, and a4, and the detection points of tunnel cross-section C are c1, c2, c3, and c4.

[0008] Step 2: Spatial mapping: Workers use mapping tools to measure the tunnel and obtain the tunnel's dimensional information. The mapping tools include an electromagnetic rangefinder and a level. The electromagnetic rangefinder is used to measure the distance and length in the tunnel, and the level is used to measure the height difference in the tunnel. Workers manually input the dimensional information into the processing unit, which establishes a spatial coordinate system in meters. The x-axis of the spatial coordinate system is the tunnel width, the y-axis is the tunnel height, and the z-axis is the tunnel length. The z-axis of the spatial coordinate system coincides with the intersection of the line connecting the detection points of each tunnel cross section. Workers sample the rock in the tunnel and measure the bulk modulus K, shear modulus μ, and rock density ρ of the rock in the tunnel.

[0009] Step 3: Simulate hammering. The staff installs the simulation device in area AC and area AD. The staff manually inputs the position of the simulation device in the spatial coordinate system into the processing unit. The processing unit sends a hammering instruction to the simulation device, and the simulation device hammers the inner surface of the tunnel.

[0010] Step 4: Preliminary positioning. Each time the simulation device hammers the inner surface of the tunnel, the sensor at the detection point obtains vibration information and records the time t. The sensor transmits the vibration information and time t to the processing unit. The processing unit assigns a weight index α to each detection point and initializes it. The weight index α after initialization is unified to 0.125. The processing unit assigns all detection points according to Perform permutations and combinations, determine a micro-seismic point for every three detection points, and calculate the error β between the micro-seismic point and the actual hammering point. The processing unit then divides the detection points into fixed points and moving points, and synchronously adjusts the weight index α of each detection point.

[0011] By simulating hammer strikes and continuously adjusting the positions of detection points, the detection points mutually verify positioning errors, and adjust the weight index of each detection point according to the positioning error, thereby improving the detection accuracy of each detection point and reducing the error of microseismic positioning;

[0012] Step 5: Adjust the detection points. Adjust the installation positions of the detection points with low weight index α and re-execute step 4 to calculate the deployment positions of the remaining detection points. The detection points include fixed points and mobile points. The processing unit outputs the adjusted detection point positions to the display screen for the staff to view. The processing unit is a general-purpose computer. The staff inputs the hammer point of the simulation device through the keyboard and mouse. The display is connected to the general-purpose computer to display the output content of the processing unit for the staff to view;

[0013] Step 6: Deploy sensors again according to the detection points adjusted in step 5 to locate the microseismic points in the tunnel.

[0014] Furthermore, the simulated hammering specifically includes the following steps:

[0015] Step 301: The staff connects the detection points a1, a2, a3, and a4 with the detection points c1, c2, c3, and c4 in sequence, and marks the line segments connecting the detection points as reference lines. a1 and c1 form the first reference line, a2 and c2 form the second reference line, a3 and c3 form the third reference line, and a4 and c4 form the fourth reference line. All four reference lines are parallel to the z-axis of the spatial coordinate system.

[0016] Step 302: Workers sequentially install the simulator on the first, second, third, and fourth reference lines in area AC. After each installation, the simulator strikes the tunnel's inner surface once. The striking point of the simulator is located between tunnel cross sections A and C. This allows for a short transmission distance and a small time difference in vibration information, resulting in high microseismic location accuracy.

[0017] Step 303: The staff sequentially installs the simulator on the first, second, third, and fourth reference lines in the AD area. After each installation, the simulator hammers the tunnel inner surface twice. The hammering point of the simulator is located between the tunnel cross section A and the excavation face D. The vibration information transmission distance is large and the time difference is large, so the positioning accuracy of the microseismic point is low. Therefore, it is necessary to compensate for the error by increasing the number of hammering times.

[0018] Step 304: The staff installs the simulation device at any four positions in the AC area or the AD area except the reference line. After the simulation device is installed, the inner surface of the tunnel is hammered three times. The hammering points of the simulation device are outside the reference line, and the positioning accuracy of the micro-seismic point is lower. Therefore, it is necessary to further increase the number of hammering to compensate for the error. Repeating steps 3 and 4 can screen out the sensor with the highest positioning accuracy, increase the weight index α of the sensor with higher positioning accuracy, and continuously optimize the installation position of the sensor.

[0019] Furthermore, during the initial positioning, the direction θ2 of the microseismic point is obtained by the following steps:

[0020] Step 401: The processing unit randomly selects three detection points from eight detection points. The detection point processing unit obtains vibration information and time t from the sensors at the selected detection points. The processing unit calculates the time difference Δt between any two of the three detection point sensors.

[0021] Step 402: The processing unit selects the minimum value in the time t. The detection point corresponding to the time t with the minimum value is closest to the hammering point. The processing unit marks the closest detection point as the reference point. The processing unit connects the reference point with the other two detection points to obtain two reference lines. The processing unit marks the angle between the two reference lines as the direction range angle θ.

[0022] Step 403: The processing unit calculates the Calculate the direction θ2 of the microseismic point of the reference point. The microseismic point is located in the AC area or the AD area. α1 is the weight index α of the sensor corresponding to the reference point, α2 and α3 are the weight indexes α of the other two detection points, Δt1 is the time difference Δt between the reference point and one of the detection points, Δt2 is the time difference Δt between the reference point and the other detection point, and Δt3 is the time difference Δt between the two detection points. Under the premise of knowing the direction θ2 of the microseismic point, the specific position of the microseismic point is subsequently calculated.

[0023] Furthermore, during the initial positioning, the direction θ2 of the microseismic point is obtained in steps 401 to 403. The position of the microseismic point is obtained by the following steps:

[0024] Step 404: The processing unit calculates the Calculate the propagation velocity v of the P wave generated by microvibration in the tunnel rock. The processing unit uses the formula The distance s1 from the reference point to the hammer point, and the distances s2 and s3 from the two detection points to the hammer point are calculated. α1 is the weight index α of the sensor corresponding to the reference point, α2 and α3 are the weight indexes α of the other two detection points, Δt1 is the time difference Δt between the reference point and one of the detection points, Δt2 is the time difference Δt between the reference point and the other detection point, and Δt3 is the time difference Δt between the two detection points.

[0025] Step 405: The processing unit determines that if the sum of any two of the distances s1, s2, and s3 is equal to d1, then the hammer point is located in the AC region; otherwise, the hammer point is located in the AD region. The processing unit draws a line segment with a distance of s1 starting from the reference point and a direction of θ2. The end of the line segment is the positioning point p1 of the reference point relative to the hammer point. The processing unit draws two line segments with distances of s2 and s3 respectively starting from the two detection points and a direction of θ2. The ends of the two line segments are the positioning points p2 and p3 of the two detection points relative to the hammer point.

[0026] Step 406: The processing unit connects the positioning points p1, p2 and p3 in pairs, and marks the intersection of the vertical lines of the three connected midpoints as the microseismic point. The subsequent calculation of the weight index α requires reselecting three detection points and repeatedly calculating the position and direction θ2 of the microseismic point.

[0027] Furthermore, the sensor weight index α is adjusted as follows:

[0028] Step 407: The processing unit calculates the error β between the micro-seismic point and the hammering point in step 406;

[0029] Step 408: The processing unit The permutation combination selects three detection points in sequence. Every time three detection points are selected, steps 401 to 406 are repeated to obtain a new micro-seismic point. The error β between the new micro-seismic point and the hammering point is calculated. When all permutations and combinations are selected, stop repeating steps 401 to 406;

[0030] Step 409: The processing unit arranges all the errors β obtained in ascending order to obtain a second sequence. The processing unit marks the first three detection points in the second sequence as fixed points and the remaining detection points as moving points. The processing unit increases the weight index α of the detection points marked as fixed points by 0.1. The error β of the three fixed points is the smallest, the position has not changed, and the reference is strong, so the weight index α is greatly increased.

[0031] Furthermore, when installing the sensor, a hole is drilled on the surface of the tunnel rock mass to a depth of 2 meters. The sensor is placed in a steel sleeve. The sensor and the sleeve are screwed together into a whole. The sleeve is placed in the drilled hole and an anchor is used to couple the sleeve and the surrounding rock into a whole. The sensor pigtail is fixed with sound insulation cotton at the opening of the sleeve to initially isolate noise and improve detection accuracy. A sound insulation cover is added to the outermost layer of the sleeve for secondary noise isolation.

[0032] The sensor is the OF-MMS fiber optic accelerometer of the all-fiber microseismic monitoring system. The sensor has a voltage sensitivity of 40V / g, an observation frequency band of 20Hz-5kHz, and adopts 16-bit sampling accuracy and a maximum sampling frequency of 32KHz.

[0033] Furthermore, the simulation device is a JAY-7117 model hammer test device, which includes a base, a frame fixedly connected to one side of the base surface, a movable shaft provided on the side of the base surface close to the frame, a hammer handle rotatably connected to the base surface through the movable shaft, a hammer head fixedly connected to the end of the hammer handle, a spring fixedly connected between the side of the hammer handle and the base, an electromagnetic lock installed on the top of the frame, and the electromagnetic lock matches the hammer head.

[0034] Furthermore, when installing the simulation device, the base is fixed to the inner surface of the tunnel by screws, and the electromagnetic lock adsorbs and fixes the hammer head to the frame. At this time, the hammer handle is perpendicular to the inner surface of the tunnel;

[0035] When the simulation device hammers, the processing unit sends a hammering command to the electromagnetic lock, and the electromagnetic lock releases the hammer head. The hammer head is pulled by the spring and moves in a circular motion with the movable axis as the center to hammer the inner surface of the tunnel.

[0036] Furthermore, the bulk modulus K, shear modulus μ, and rock density ρ of the rock in the tunnel are obtained by the following steps:

[0037] Step 201: Obtain rock samples from tunnel cross section A, tunnel cross section C, and excavation face D, respectively. The samples are standard cylinders with a height of L.

[0038] Step 202: Use the water displacement method to measure the rock density ρy of the rock sample. Completely immerse the rock sample in a graduated cylinder filled with water, record the volume Vy of the water overflowing from the graduated cylinder, and weigh the rock sample to obtain the mass m. According to the formula The rock density ρy is obtained, and the bulk modulus Ky of the rock sample is measured by hydrostatic pressure test. A uniform hydrostatic pressure Pw is applied to the rock sample. At this time, the rock only changes in volume but not in shape. According to the formula The bulk modulus Ky of the rock sample is obtained, Vy is the volume of the rock sample, ΔV is the deformation of the rock sample after being subjected to hydrostatic pressure, and the shear modulus μy of the rock sample is measured by a torsion test. A torque F is applied to the rock sample to cause shear deformation and a torsion angle J. The formula The relationship between torque and torsion angle is measured to calculate the shear modulus μy;

[0039] Step 203: The processing unit calculates the average value Kp of the bulk modulus Ky of the three rock samples of tunnel cross-section A, tunnel cross-section C and tunnel face D, calculates the average value μp of the shear modulus μy of the three rock samples of tunnel cross-section A, tunnel cross-section C and tunnel face D, and calculates the average value ρp of the rock density ρy of the three rock samples of tunnel cross-section A, tunnel cross-section C and tunnel face D. The average values ​​of the bulk modulus Kp, shear modulus μp and rock density ρp of the rock samples are marked as the bulk modulus K, shear modulus μ and rock density ρ of the rock in the tunnel.

[0040] Furthermore, adjusting the detection point specifically includes the following steps:

[0041] Step 501: The processing unit determines whether the detection points marked as fixed points are on the same side of the tunnel. For example, detection points a4, a2, and c4 are on the same side of the tunnel, while detection points a4, c4, and c3 are not on the same side of the tunnel.

[0042] Step 502: If the three fixed points are located on the same side of the tunnel, the processing unit connects the three fixed points to form a closed triangle, places one of the mobile points between two fixed points in the same tunnel cross section, and places the mobile point at the midpoint of the line connecting the two fixed points. The other four mobile points are placed in groups of two, with each group being placed between two fixed points in different tunnel cross sections, and the two mobile points being evenly distributed on the line connecting the two fixed points.

[0043] Step 503: If the three fixed points are not located on the same side of the tunnel, the processing unit symmetrically mirrors the single fixed point located on the different side to the other side of the tunnel, with the symmetry plane being the vertical plane of the central axis of the tunnel. The processing unit repeats step 502 to determine the distribution positions of the five moving points;

[0044] Step 504: The processing unit converts all moving points into Perform permutations and combinations, repeat step 4, determine a micro-seismic point for every three detection points, and the processing unit calculates the error β between the micro-seismic point and the actual hammering point; when When all permutations and combinations are selected, stop and repeat step 4.

[0045] Step 505: The processing unit arranges all the errors β obtained in step 504 in ascending order to obtain a third sequence. The processing unit marks the first three moving points in the third sequence as fixed points, and marks the remaining detection points as moving points. The processing unit increases the weight index α of the detection points marked as fixed points by 0.05. The three detection points that have changed from moving points to fixed points have a medium reference value after changing their positions once, and their weight index α is slightly increased.

[0046] Step 506: The processing unit places the remaining moving points between any two fixed points on the same side of the tunnel. The placement position of the moving point is located at the midpoint of the line connecting the two fixed points. The processing unit reduces the weight index α of the two detection points marked as moving points by 0.02. The two moving points have changed positions twice and have a low reference value, so the weight index α is reduced.

[0047] The present invention has the following beneficial effects:

[0048] By simulating hammer strikes and continuously adjusting the positions of detection points, the detection points mutually verify positioning errors, and adjust the weight index of each detection point according to the positioning error, thereby improving the detection accuracy of each detection point and reducing the error of microseismic positioning.

[0049] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. 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 creative work.

[0051] Figure 1 A schematic diagram of the construction of a microseismic positioning method for tunnel excavation according to the present invention;

[0052] Figure 2 This is a schematic diagram of the arrangement and combination of step 4 in a specific embodiment of the present invention;

[0053] Figure 3 This is a system block diagram of a microseismic positioning method for tunnel excavation according to the present invention;

[0054] Figure 4 Schematic diagram of the structure of the simulation device of the present invention.

[0055] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0056] In the figure: 1-base, 2-frame, 3-movable shaft, 4-hammer handle, 5-hammer head, 6-electromagnetic lock, 7-spring. DETAILED DESCRIPTION

[0057] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making any creative efforts shall fall within the scope of protection of the present invention.

[0058] The present invention provides a technical solution: a microseismic positioning method for tunnel excavation, such as Figure 3 As shown, it includes a sensor, a processing unit and a simulation device, the output end of the sensor is connected to the input end of the processing unit, and the output end of the processing unit is connected to the input end of the simulation device;

[0059] The positioning method includes the following steps:

[0060] Step 1: If Figure 1 As shown, for sensor deployment, the staff divided the sensors into two groups, namely tunnel cross-section A and tunnel cross-section C, the tunnel excavation surface in the tunnel is D, the unexcavated area is B, the area between tunnel cross-section A and tunnel cross-section C is AC, the length of area AC is d1, and the area between tunnel cross-section A and excavation surface D is AD. Each group of four sensors is installed in the same tunnel cross-section. The sensors in the same group are installed on the spandrels and waists on both sides of the tunnel cross-section. The installation positions of the sensors are detection points. The detection points of tunnel cross-section A are a1, a2, a3 and a4, and the detection points of tunnel cross-section C are c1, c2, c3 and c4.

[0061] Step 2: Spatial mapping: Workers use mapping tools to measure the tunnel and obtain the tunnel's dimensional information. The mapping tools include an electromagnetic rangefinder and a level. The electromagnetic rangefinder is used to measure the distance and length in the tunnel, and the level is used to measure the height difference in the tunnel. Workers manually input the dimensional information into the processing unit, which establishes a spatial coordinate system in meters. The x-axis of the spatial coordinate system is the tunnel width, the y-axis is the tunnel height, and the z-axis is the tunnel length. The z-axis of the spatial coordinate system coincides with the intersection of the line connecting the detection points of each tunnel cross section. Workers sample the rock in the tunnel and measure the bulk modulus K, shear modulus μ, and rock density ρ of the rock in the tunnel.

[0062] Step 3: Simulate hammering. The staff installs the simulation device in area AC and area AD. The staff manually inputs the position of the simulation device in the spatial coordinate system into the processing unit. The processing unit sends a hammering instruction to the simulation device, and the simulation device hammers the inner surface of the tunnel.

[0063] Step 4: Preliminary positioning. Each time the simulation device hammers the inner surface of the tunnel, the sensor at the detection point obtains vibration information and records the time t. The sensor transmits the vibration information and time t to the processing unit. The processing unit assigns a weight index α to each detection point and initializes it. The weight index α after initialization is unified to 0.125. The processing unit assigns all detection points according to Perform permutations and combinations, determine a micro-seismic point for every three detection points, and calculate the error β between the micro-seismic point and the actual hammering point. The processing unit then divides the detection points into fixed points and moving points, and synchronously adjusts the weight index α of each detection point.

[0064] Step 5: Adjust the detection points. Adjust the installation positions of the detection points with low weight index α and re-execute step 4 to calculate the deployment positions of the remaining detection points. The detection points include fixed points and mobile points. The processing unit outputs the adjusted detection point positions to the display screen for the staff to view. The processing unit is a general-purpose computer. The staff inputs the hammer point of the simulation device through the keyboard and mouse. The display is connected to the general-purpose computer to display the output content of the processing unit for the staff to view;

[0065] Step 6: Deploy sensors again according to the detection points adjusted in step 5 to locate the microseismic points in the tunnel.

[0066] The simulated hammering process specifically includes the following steps:

[0067] Step 301: The staff connects the detection points a1, a2, a3, and a4 with the detection points c1, c2, c3, and c4 in sequence, and marks the line segments connecting the detection points as reference lines. a1 and c1 form the first reference line, a2 and c2 form the second reference line, a3 and c3 form the third reference line, and a4 and c4 form the fourth reference line. All four reference lines are parallel to the z-axis of the spatial coordinate system.

[0068] Step 302: Workers sequentially install the simulator on the first, second, third, and fourth reference lines in area AC. After each installation, the simulator strikes the tunnel's inner surface once. The striking point of the simulator is located between tunnel cross sections A and C. This allows for a short transmission distance and a small time difference in vibration information, resulting in high microseismic location accuracy.

[0069] Step 303: The staff sequentially installs the simulator on the first, second, third, and fourth reference lines in the AD area. After each installation, the simulator hammers the tunnel inner surface twice. The hammering point of the simulator is located between the tunnel cross section A and the excavation face D. The vibration information transmission distance is large and the time difference is large, so the positioning accuracy of the microseismic point is low. Therefore, it is necessary to compensate for the error by increasing the number of hammering times.

[0070] Step 304: The staff installs the simulation device at any four positions in the AC area or the AD area except the reference line. After the simulation device is installed, the inner surface of the tunnel is hammered three times. The hammering points of the simulation device are outside the reference line, and the positioning accuracy of the micro-seismic point is lower. Therefore, it is necessary to further increase the number of hammering to compensate for the error. Repeating steps 3 and 4 can screen out the sensor with the highest positioning accuracy, increase the weight index α of the sensor with higher positioning accuracy, and continuously optimize the installation position of the sensor.

[0071] During the initial positioning, the direction θ2 of the microseismic point is obtained by the following steps:

[0072] Step 401: Figure 2 As shown, the processing unit randomly selects three detection points from the eight detection points, namely a1, c1 and c2. The processing unit obtains vibration information and time t from the selected detection point sensors. Time t includes t1, t2 and t3, t1 is the time t of detection point a1, t2 is the time t of detection point c1, and t3 is the time t of detection point c2. The processing unit calculates the time difference Δt between any two of the three detection point sensors. The time difference Δt includes Δt1, Δt2 and Δt3. Time difference Δt1 is the time difference Δt between detection point a1 and detection point c1, time difference Δt2 is the time difference Δt between detection point a1 and detection point c2, and time difference Δt3 is the time difference Δt between detection point c2 and detection point c1.

[0073] Step 402: The processing unit selects the minimum value in time t, assuming that t1 is the minimum value among t1, t2, and t3. The detection point corresponding to the time t with the minimum value is closest to the hammer point. The processing unit marks the closest detection point a1 as the reference point. The processing unit connects the reference point with the other two detection points c1 and c2 to obtain two reference lines, namely the reference line connecting detection point a1 and detection point c1, and the reference line connecting detection point a1 and detection point c2. The processing unit marks the intersection angle of the two reference lines as the direction range angle θ;

[0074] Step 403: The processing unit calculates the Calculate the direction θ2 of the microseismic point of the reference point a1. The microseismic point is located in the AC area or the AD area. α1 is the weight index α of the sensor corresponding to the reference point a1, α2 and α3 are the weight indexes α of the other two detection points respectively, Δt1 is the time difference Δt between the reference point and one of the detection points, Δt2 is the time difference Δt between the reference point and the other detection point, Δt3 is the time difference Δt between the two detection points, α2 is the weight index α of the sensor corresponding to the detection point c1, and α3 is the weight index α of the sensor corresponding to the detection point c2. Under the premise that the direction θ2 of the microseismic point is known, the specific position of the microseismic point is subsequently calculated.

[0075] During the initial positioning, steps 401 to 403 obtain the direction θ2 of the microseismic point. The position of the microseismic point is obtained by the following steps:

[0076] Step 404: The processing unit calculates the Calculate the propagation speed v of the P wave generated by micro-vibration in the tunnel rock. The sensor mainly obtains the vibration information of the P wave propagation. Here, the propagation speed v of the P wave represents the propagation speed of the micro-vibration in the tunnel. The processing unit uses the formula Calculate the distance s1 from the reference point to the hammer point, the distances s2 and s3 from the two detection points to the hammer point, the distance s2 from the detection point c1 to the hammer point, and the distance s3 from the detection point c2 to the hammer point. α1 is the weight index α of the sensor corresponding to the reference point a1, α2 and α3 are the weight indexes α of the other two detection points, Δt1 is the time difference Δt between the reference point and one of the detection points, Δt2 is the time difference Δt between the reference point and the other detection point, Δt3 is the time difference Δt between the two detection points, α2 is the weight index α of the sensor corresponding to the detection point c1, and α3 is the weight index α of the sensor corresponding to the detection point c2.

[0077] Step 405: The processing unit determines that if the sum of any two of the distances s1, s2, and s3 is equal to d1, then the hammer point is located in the AC region; otherwise, the hammer point is located in the AD region. The processing unit draws a line segment with a distance of s1 starting from the reference point and a direction of θ2. The end of the line segment is the positioning point p1 of the reference point relative to the hammer point. The processing unit draws two line segments with distances of s2 and s3 respectively starting from the two detection points and a direction of θ2. The ends of the two line segments are the positioning points p2 and p3 of the two detection points relative to the hammer point, respectively. p2 is the positioning point of the detection point c1 relative to the hammer point, and p3 is the positioning point of the detection point c2 relative to the hammer point.

[0078] Step 406: The processing unit connects the positioning points p1, p2 and p3 in pairs, and marks the intersection of the vertical lines of the three connected midpoints as the microseismic point. The subsequent calculation of the weight index α requires reselecting three detection points and repeatedly calculating the position and direction θ2 of the microseismic point.

[0079] The sensor weight index α is adjusted as follows:

[0080] Step 407: The processing unit calculates the error β between the micro-seismic point and the hammering point in step 406;

[0081] Step 408: The processing unit The permutation combination selects three detection points in sequence. Every time three detection points are selected, steps 401 to 406 are repeated to obtain a new micro-seismic point. The error β between the new micro-seismic point and the hammering point is calculated. When all permutations and combinations are selected, stop repeating steps 401 to 406;

[0082] Step 409: The processing unit arranges all the errors β obtained in ascending order to obtain a second sequence. The processing unit marks the first three detection points in the second sequence as fixed points and the remaining detection points as moving points. The processing unit increases the weight index α of the detection points marked as fixed points by 0.1. The error β of the three fixed points is the smallest, the position has not changed, and the reference is strong, so the weight index α is greatly increased.

[0083] When installing the sensor, a hole is drilled on the surface of the tunnel rock mass to a depth of 2 meters. The sensor is placed in a steel sleeve. The sensor and the sleeve are screwed together into a whole. The sleeve is placed in the drilled hole and an anchor is used to couple the sleeve and the surrounding rock into a whole. The sensor pigtail is fixed with sound insulation cotton at the opening of the sleeve to initially isolate noise and improve detection accuracy. A sound insulation cover is added to the outermost layer of the sleeve for secondary noise isolation.

[0084] The sensor is the OF-MMS fiber optic accelerometer of the all-fiber microseismic monitoring system. The sensor has a voltage sensitivity of 40V / g, an observation frequency band of 20Hz-5kHz, and adopts 16-bit sampling accuracy and a maximum sampling frequency of 32KHz.

[0085] Among them, such as Figure 4 As shown, the simulation device is a JAY-7117 model hammer test device, which includes a base 1, a frame 2 fixedly connected to one side of the surface of the base 1, a movable shaft 3 is provided on the surface of the base 1 close to the frame 2, a hammer handle 4 is rotatably connected to the surface of the base 1 through the movable shaft 3, a hammer head 5 is fixedly connected to the end of the hammer handle 4, a spring 7 is fixedly connected between the side of the hammer handle 4 and the base 1, and an electromagnetic lock 6 is installed on the top of the frame 2, and the electromagnetic lock 6 matches the hammer head 5.

[0086] When installing the simulation device, the base 1 is fixed to the inner surface of the tunnel by screws, and the electromagnetic lock 6 adsorbs and fixes the hammer head 5 on the frame 2. At this time, the hammer handle 4 is perpendicular to the inner surface of the tunnel;

[0087] When the simulation device hammers, the processing unit sends a hammering instruction to the electromagnetic lock 6, and the electromagnetic lock 6 releases the hammer head 5. The hammer head 5 is pulled by the spring 7, and the hammer head 5 makes a circular motion with the movable shaft 3 as the center to hammer the inner surface of the tunnel.

[0088] The bulk modulus K, shear modulus μ, and rock density ρ of the rock in the tunnel are obtained by the following steps:

[0089] Step 201: Obtain rock samples from tunnel cross section A, tunnel cross section C, and excavation face D, respectively. The samples are standard cylinders with a height of L.

[0090] Step 202: Use the water displacement method to measure the rock density ρy of the rock sample. Completely immerse the rock sample in a graduated cylinder filled with water, record the volume Vy of the water overflowing from the graduated cylinder, and weigh the rock sample to obtain the mass m. According to the formula The rock density ρy is obtained, and the bulk modulus Ky of the rock sample is measured by hydrostatic pressure test. A uniform hydrostatic pressure Pw is applied to the rock sample. At this time, the rock only changes in volume but not in shape. According to the formula The bulk modulus Ky of the rock sample is obtained, Vy is the volume of the rock sample, ΔV is the deformation of the rock sample after being subjected to hydrostatic pressure, and the shear modulus μy of the rock sample is measured by a torsion test. A torque F is applied to the rock sample to cause shear deformation and a torsion angle J. The formula The relationship between torque and torsion angle is measured to calculate the shear modulus μy;

[0091] Step 203: The processing unit calculates the average value Kp of the bulk modulus Ky of the three rock samples of tunnel cross-section A, tunnel cross-section C and tunnel face D, calculates the average value μp of the shear modulus μy of the three rock samples of tunnel cross-section A, tunnel cross-section C and tunnel face D, and calculates the average value ρp of the rock density ρy of the three rock samples of tunnel cross-section A, tunnel cross-section C and tunnel face D. The average values ​​of the bulk modulus Kp, shear modulus μp and rock density ρp of the rock samples are marked as the bulk modulus K, shear modulus μ and rock density ρ of the rock in the tunnel.

[0092] Adjusting the detection point specifically includes the following steps:

[0093] Step 501: The processing unit determines whether the detection points marked as fixed points are on the same side of the tunnel. For example, detection points a4, a2, and c4 are on the same side of the tunnel, while detection points a4, c4, and c3 are not on the same side of the tunnel.

[0094] Step 502: If the three fixed points are located on the same side of the tunnel, the processing unit connects the three fixed points to form a closed triangle, places one of the mobile points between two fixed points in the same tunnel cross section, and places the mobile point at the midpoint of the line connecting the two fixed points. The other four mobile points are placed in groups of two, with each group being placed between two fixed points in different tunnel cross sections, and the two mobile points being evenly distributed on the line connecting the two fixed points.

[0095] Step 503: If the three fixed points are not located on the same side of the tunnel, the processing unit symmetrically mirrors the single fixed point located on the different side to the other side of the tunnel, with the symmetry plane being the vertical plane of the central axis of the tunnel. The processing unit repeats step 502 to determine the distribution positions of the five moving points;

[0096] Step 504: The processing unit converts all moving points into Perform permutations and combinations, repeat step 4, determine a micro-seismic point for every three detection points, and the processing unit calculates the error β between the micro-seismic point and the actual hammering point; when C 3 5. When all permutations and combinations are selected, stop and repeat step 4.

[0097] Step 505: The processing unit arranges all the errors β obtained in step 504 in ascending order to obtain a third sequence. The processing unit marks the first three moving points in the third sequence as fixed points, and marks the remaining detection points as moving points. The processing unit increases the weight index α of the detection points marked as fixed points by 0.05. The three detection points that have changed from moving points to fixed points have a medium reference value after changing their positions once, and their weight index α is slightly increased.

[0098] Step 506: The processing unit places the remaining moving points between any two fixed points on the same side of the tunnel. The placement position of the moving point is located at the midpoint of the line connecting the two fixed points. The processing unit reduces the weight index α of the two detection points marked as moving points by 0.02. The two moving points have changed positions twice and have a low reference value, so the weight index α is reduced.

[0099] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A microseismic positioning method for tunnel excavation, comprising a sensor, a processing unit, and a simulation device, wherein the output of the sensor is connected to the input of the processing unit, and the output of the processing unit is connected to the input of the simulation device; characterized in that: The following steps are involved: Step 1: Sensor deployment. Divide the sensors into two groups, namely tunnel cross-section A and tunnel cross-section C. The tunnel excavation surface is D, the unexcavated area is B, the area between tunnel cross-section A and tunnel cross-section C is AC, the length of area AC is d1, and the area between tunnel cross-section A and excavation surface D is AD. Each group of four sensors is installed in the same tunnel cross-section. The sensors in the same group are installed on the spandrels and haunches on both sides of the tunnel cross-section. The installation locations of the sensors are detection points. The detection points of tunnel cross-section A are a1, a2, a3, and a4, and the detection points of tunnel cross-section C are c1, c2, c3, and c4. Step 2: Spatial mapping: Use mapping tools to measure the tunnel to obtain tunnel dimensional information. This dimensional information is input into the processing unit to establish a spatial coordinate system. The x-axis of the spatial coordinate system is the tunnel width, the y-axis is the tunnel height, and the z-axis is the tunnel length. The z-axis of the spatial coordinate system coincides with the intersection of the line connecting the detection points of each tunnel cross section. Workers sample the rock in the tunnel and measure the bulk modulus K, shear modulus μ, and rock density ρ of the rock in the tunnel. Step 3: Simulate hammering. Install the simulation device in area AC and area AD. Input the position of the simulation device in the spatial coordinate system to the processing unit. The processing unit sends a hammering instruction to the simulation device, and the simulation device hammers the inner surface of the tunnel. Step 4: Preliminary positioning. Each time the simulation device hammers the inner surface of the tunnel, the sensor at the detection point obtains vibration information and records the time t. The sensor transmits the vibration information and time t to the processing unit. The processing unit assigns a weight index α to each detection point and initializes it. All detection points are calculated according to C8. 3 Perform permutations and combinations, determine a microseismic point for every three detection points, calculate the error β between the microseismic point and the hammering point, screen the detection points into fixed points and moving points, and synchronously adjust the weight index α of each detection point; Step 5: Adjust the detection points. Adjust the installation positions of the detection points with low weight index α. Re-execute step 4 to calculate the deployment positions of the remaining detection points. The detection points include fixed points and mobile points. Output the adjusted detection point positions to the display screen. Step 6: Deploy sensors again according to the detection points adjusted in step 5 to locate the microseismic points in the tunnel.

2. A microseismic positioning method for tunnel excavation according to claim 1, characterized in that: The simulated hammering process specifically includes the following steps: Step 301: The staff connects the detection points a1, a2, a3, and a4 with the detection points c1, c2, c3, and c4 in sequence, and marks the line segments connecting the detection points as reference lines. a1 and c1 form the first reference line, a2 and c2 form the second reference line, a3 and c3 form the third reference line, and a4 and c4 form the fourth reference line. All four reference lines are parallel to the z-axis of the spatial coordinate system. Step 302: The staff installs the simulation device in the first reference line, the second reference line, the third reference line, and the fourth reference line in the AC area in sequence. After each installation, the simulation device hammers the inner surface of the tunnel once. Step 303: The staff installs the simulation device in the first reference line, the second reference line, the third reference line, and the fourth reference line in the AD area in sequence. After each installation, the simulation device hammers the inner surface of the tunnel twice. Step 304: The staff installs the simulation device at any four locations in the AC area or the AD area except the reference line. After the simulation device is installed, the staff hammers the inner surface of the tunnel three times.

3. The microseismic positioning method for tunnel excavation according to claim 1, characterized in that: During the initial positioning, the direction θ2 of the microseismic point is obtained by the following steps: Step 401: The processing unit randomly selects three detection points from the detection points, obtains vibration information and time t from the selected detection points, and calculates the time difference Δt between any two of the three detection points; Step 402: The processing unit selects the minimum value in the time t. The detection point corresponding to the time t with the minimum value is closest to the hammer point. The closest detection point is marked as the reference point. The reference point is connected with the other two detection points to obtain two reference lines. The angle between the two reference lines is marked as the direction range angle θ. Step 403: According to the formula Calculate the direction θ2 of the microseismic point of the reference point. The microseismic point is located in the AC area or the AD area. α1 is the weight index α of the sensor corresponding to the reference point, α2 and α3 are the weight indexes α of the other two detection points, Δt1 is the time difference Δt between the reference point and one of the detection points, Δt2 is the time difference Δt between the reference point and the other detection point, and Δt3 is the time difference Δt between the two detection points. Under the premise of knowing the direction θ2 of the microseismic point, the specific position of the microseismic point is subsequently calculated.

4. The microseismic positioning method for tunnel excavation according to claim 3, characterized in that: During the initial positioning, steps 401 to 403 obtain the direction θ2 of the microseismic point. The position of the microseismic point is obtained by the following steps: Step 404: According to the formula Calculate the propagation velocity v of the P wave generated by microvibration in the tunnel rock, according to the formula The distance s1 from the reference point to the hammer point, and the distances s2 and s3 from the two detection points to the hammer point are calculated. α1 is the weight index α of the sensor corresponding to the reference point, α2 and α3 are the weight indexes α of the other two detection points, Δt1 is the time difference Δt between the reference point and one of the detection points, Δt2 is the time difference Δt between the reference point and the other detection point, and Δt3 is the time difference Δt between the two detection points. Step 405: If the sum of any two of the distances s1, s2, and s3 is equal to d1, the impact point is located in the AC region. Otherwise, the impact point is located in the AD region. A line segment with a distance of s1 is drawn with the reference point as the starting point and a direction of θ2. The end of the line segment is the positioning point p1 of the reference point relative to the impact point. Two line segments with distances of s2 and s3 are drawn with the two detection points as the starting points and a direction of θ2. The ends of the two line segments are the positioning points p2 and p3 of the two detection points relative to the impact point, respectively. Step 406: Connect the positioning points p1, p2 and p3 in pairs, and mark the intersection of the three connected midpoints as the microseismic point. The subsequent calculation of the weight index α requires reselecting three detection points and repeatedly calculating the position and direction θ2 of the microseismic point.

5. The microseismic positioning method for tunnel excavation according to claim 4, characterized in that: The steps to adjust the sensor weight index α are as follows: Step 407: Calculate the error β between the micro-seismic point and the hammering point in step 406; Step 408: According to C8 3 Three detection points are selected in sequence through permutation and combination. Every time three detection points are selected, steps 401 to 406 are repeated to obtain a new micro-seismic point. The error β between the new micro-seismic point and the hammering point is calculated. When C8 3 When all permutations and combinations are selected, stop repeating steps 401 to 406; Step 409: Arrange all the errors β obtained in ascending order to obtain a second sequence, mark the first three detection points in the second sequence as fixed points, mark the remaining detection points as moving points, and increase the weight index α of the detection points marked as fixed points by 0.

1.

6. The microseismic positioning method for tunnel excavation according to claim 1, characterized in that: When installing the sensor, drill a hole on the tunnel rock surface, place the sensor in the sleeve, screw the sensor and the sleeve together, place the sleeve in the hole, use an anchor to couple the sleeve and the surrounding rock together, fix the sensor pigtail with sound insulation cotton at the sleeve opening to initially isolate noise and improve detection accuracy, and add a sound insulation cover to the outermost layer of the sleeve. The sensor is a fiber optic accelerometer with a voltage sensitivity of 40V / g, an observation frequency band of 20Hz-5kHz, and a sampling accuracy of 16 bits and a sampling frequency of 32KHz.

7. The microseismic positioning method for tunnel excavation according to claim 1, characterized in that: The simulation device comprises a base (1), a frame (2) is fixedly connected to one side of the surface of the base (1), a movable shaft (3) is provided on the side of the surface of the base (1) close to the frame (2), a hammer handle (4) is rotatably connected to the surface of the base (1) through the movable shaft (3), a hammer head (5) is fixedly connected to the end of the hammer handle (4), a spring (7) is fixedly connected between the side of the hammer handle (4) and the base (1), and an electromagnetic lock (6) is installed on the top of the frame (2), and the electromagnetic lock (6) matches the hammer head (5).

8. The microseismic positioning method for tunnel excavation according to claim 1, characterized in that: When installing the simulation device, the base (1) is fixed to the inner surface of the tunnel by screws, and the electromagnetic lock (6) adsorbs and fixes the hammer head (5) on the frame (2), and the hammer handle (4) is perpendicular to the inner surface of the tunnel; When the simulation device hammers, the processing unit sends a hammering instruction to the electromagnetic lock (6), the electromagnetic lock (6) releases the hammer head (5), and the hammer head (5) is subjected to the pulling force of the spring (7). The hammer head (5) performs a circular motion with the movable shaft (3) as the center of the circle to hammer the inner surface of the tunnel.

9. The microseismic positioning method for tunnel excavation according to claim 1, characterized in that: The bulk modulus K, shear modulus μ, and rock density ρ of the rock in the tunnel are obtained by the following steps: Step 201: Obtain rock samples from tunnel cross section A, tunnel cross section C, and excavation face D, respectively. The samples are standard cylinders with a height of L. Step 202: measuring the rock density ρy of the rock sample using a water displacement method, measuring the bulk modulus Ky of the rock sample using a hydrostatic pressure test, and measuring the shear modulus μy of the rock sample using a torsion test; Step 203: Calculate the average value Kp of the bulk modulus Ky of the three rock samples of tunnel cross section A, tunnel cross section C, and tunnel face D; calculate the average value μp of the shear modulus μy of the three rock samples of tunnel cross section A, tunnel cross section C, and tunnel face D; calculate the average value ρp of the rock density ρy of the three rock samples of tunnel cross section A, tunnel cross section C, and tunnel face D; and mark the average values ​​of the bulk modulus Kp, shear modulus μp, and rock density ρp of the rock samples as the bulk modulus K, shear modulus μ, and rock density ρ of the rock in the tunnel.

10. The microseismic positioning method for tunnel excavation according to claim 1, characterized in that: Adjusting the detection point specifically includes the following steps: Step 501: Determine whether the detection points marked as fixed points are on the same side of the tunnel; Step 502: If the three fixed points are located on the same side of the tunnel, connect the three fixed points to form a closed triangle. Place one of the mobile points between two fixed points in the same tunnel cross section, with the mobile point located at the midpoint of the line connecting the two fixed points. The other four mobile points are placed in groups of two, with each group being placed between two fixed points in different tunnel cross sections, with the two mobile points evenly distributed on the line connecting the two fixed points. Step 503: If the three fixed points are not located on the same side of the tunnel, the single fixed point located on the different side is symmetrically mirrored to the other side of the tunnel, with the symmetry plane being the vertical plane of the central axis of the tunnel. Repeat step 502 to determine the distribution positions of the five moving points. Step 504: All moving points are moved according to C 3 5. Perform permutations and combinations, repeat step 4, determine a micro-seismic point for every three detection points, and calculate the error β between the micro-seismic point and the hammering point; when C 3 5. When all permutations and combinations are selected, stop and repeat step 4. Step 505: Arrange all the errors β obtained in step 504 in ascending order to obtain a third sequence, mark the first three moving points in the third sequence as fixed points, mark the remaining detection points as moving points, and increase the weight index α of the detection points marked as fixed points by 0.05; Step 506: Place the remaining moving points between any two fixed points on the same side of the tunnel. The placement position of the moving point is located at the midpoint of the line connecting the two fixed points. Reduce the weight index α of the two detection points marked as moving points by 0.02.

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