Geotechnical engineering investigation method based on drilling seismic source and micro-seismic monitoring technology

Abstract

The invention discloses a geotechnical engineering investigation method based on a drilling seismic source and a micro-seismic monitoring technology, and belongs to the technical field of geotechnical engineering. In order to solve the problems that in geotechnical engineering investigation, a shear wave velocity testing program is complex and low in efficiency, and the real-time hole depth is difficult to accurately measure in the drilling process, a drilling micro-seismic detector is arranged, monitoring is started, drilling source micro-seismic signals are collected and transmitted, original signals are extracted according to extraction intervals, and the drilling source micro-seismic signals are processed. The footage depth and the apparent shear wave velocity are inverted, wave velocity-depth domain scatter mapping and monitoring are carried out, and then whether monitoring needs to be continued or not is judged. Therefore, the stratum shear wave velocity corresponding to the drilling footage depth can be obtained in real time, and the physical and mechanical characteristics of the rock-soil body can be deduced. The stratum changing position in the drilling process can be effectively judged; and the drilling footage depth can be monitored in real time. The method has the advantages that equipment layout and preparation work are simple, abundant elastic wave information can be obtained at the same time, the drilling exploration process can be effectively supervised, and the shear wave velocity test workload can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of geotechnical engineering, and in particular relates to a geotechnical engineering survey method based on drilling source and microseismic monitoring technology. Background Art

[0002] With the development of my country's social economy and the improvement of infrastructure construction level, various projects have higher and higher requirements for construction technology, safety standards and project progress. Drilling, as a traditional means of exploration and detection, urgently needs to be innovated in terms of operation efficiency, accuracy, management model and results utilization. There is a problem that the information management of manual and mechanical survey sites has not yet been realized, resulting in low work efficiency.

[0003] Traditional drilling methods usually measure the current footage position by measuring the drill rod. This method is inefficient and has a high probability of error, making it difficult to accurately determine the position of the stratum change. In addition, when multiple drilling rigs are working at the same time, it is usually difficult for on-site technicians to take care of all the drilling rigs, resulting in a decrease in the quality of field work. There is also the problem that it is difficult to accurately measure the real-time hole depth during the drilling process.

[0004] For shear wave velocity testing of rock and soil, the current industry usually uses a geophone placed in the hole and a manhole at the hole mouth to create a seismic source for testing. This method requires constantly changing the depth of the geophone and performing manual tapping, which is inefficient. There are problems with the shear wave velocity testing procedure in geotechnical engineering surveys, which is complex and inefficient.

[0005] Currently, there is a lack of survey and detection methods for thick fill foundations in the industry, and the accuracy varies. It is usually difficult to accurately judge the spatial distribution and uniformity of thick fill without drilling. Summary of the invention

[0006] In view of the problems that the shear wave velocity testing procedure in geotechnical engineering investigation is complicated and inefficient, and the real-time hole depth is difficult to accurately measure during drilling, the present invention provides a geotechnical engineering investigation method based on drilling source and microseismic monitoring technology.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A geotechnical engineering survey method based on drilling source and microseismic monitoring technology, the method comprising the following steps:

[0009] Step 1: Drilling microseismic detector layout; install and layout drilling microseismic detectors, collectors, drilling rigs and controllers;

[0010] Step 1.1: Geophones are arranged around the borehole, and the number of geophones is not less than 5;

[0011] Step 1.2: There are two ways to arrange the detector: horizontal arrangement and vertical arrangement; where:

[0012] Horizontal layout: The detectors are arranged unequally and asymmetrically around the borehole. The distance between each detector and the borehole is not less than 2 times the depth of the drilling target hole, and the maximum distance is not more than 3 times. The minimum distance between adjacent detectors in the horizontal direction is not less than 1.5 times the depth of the drilling target hole.

[0013] Vertical layout: The elevation difference between adjacent geophones in the vertical direction shall not be less than 1 / 100 of the larger horizontal distance between adjacent geophones;

[0014] Step 1.3: Geophone burial method: The burial depth of each geophone from the ground surface is not less than 0.5m, and the bottom is installed on the interface of stable strata. Ensure that the geophone is vertical to the horizontal plane as a whole. The upper part is connected to the cable out of the ground. After backfilling with uniform soil until it is flush with the surrounding ground, the cable is connected to the collector;

[0015] When the bottom of the pit is soil, a tail pin is used, and when the bottom of the pit is rock, a steel plate is used;

[0016] Step 1.4: After the drilling rig is in place and during the installation of the detectors, use measuring equipment to measure the spatial coordinates of each detector and the plane coordinates of the borehole.

[0017] Step 2: Start monitoring; after installation and deployment are completed, start the drilling rig and start drilling, and at the same time turn on the installed equipment for real-time monitoring;

[0018] Step 3: Collect and transmit drilling source microseismic signals; the detector collects the original signal and transmits it to the collector via wired mode, and the collector continuously summarizes the original signal to the controller; wherein the network used by the collector is 4G or WIFI network; the collector can set the sampling frequency, and the sampling frequency is 50Hz to 250Hz;

[0019] Step 4: extracting the original signal according to the extraction interval; operating the controller to set the extraction interval for the original signal, and extracting the original signal with the same current duration as the extraction interval according to the extraction interval; wherein the extraction interval is 1min, 2min, 3min;

[0020] Step 5: Drilling source microseismic signal processing;

[0021] Step 5.1: intercepting the signal: intercepting the extracted signal into multiple groups of signals according to the sampling segment length, and the simultaneous signals of the entire detector sequence are one group; the sampling segment length is 512, 1024, 2048, 4096;

[0022] Step 5.2: Initial filtering: Perform initial filtering on each group of intercepted signals. The filtering method adopts FIR bandpass filtering. The low-pass threshold of the bandpass filtering is set at 2-20Hz and the high-pass threshold is set at 50-100Hz on site. The threshold parameters are selected according to the type of rock and soil bodies mainly involved in the drilling process. If the rock body is mainly rock body, a high value is taken, and if the soil body is mainly soil body, a low value is taken.

[0023] Step 5.3: Autocorrelation judgment: Use the autocorrelation matrix method to solve the autocorrelation coefficient of each detector segment signal in each group of primary filtering signals. If it is greater than the threshold, it is determined to be a valid signal. The threshold value is 0.65~0.95. The threshold is set according to the degree of background noise interference and the required inversion accuracy. A high value is taken when the interference is large and the required accuracy is high.

[0024] Step 5.4: Secondary filtering: Use fast Fourier transform to convert each group of effective signals from time domain signals to frequency domain, and find the corresponding frequency of the maximum amplitude as the main frequency of the signal; the main frequency of the same group of effective signals adopts the average of the main frequencies of the segmented signals of each detector, and the group of filtered signals is subjected to secondary filtering of the main frequency ±1Hz, and the filtering method adopts FIR bandpass filtering.

[0025] Step 5.5: Pick up the arrival time: in each group of time domain secondary filtering signals, pick up the time corresponding to the maximum amplitude of each detection segment signal as the arrival time;

[0026] Step 6: Inversion of footage depth and apparent shear wave velocity;

[0027] Step 6.1: Import basic data: Integrate the arrival times and the corresponding geophone spatial coordinate data obtained in the above steps, and import the integrated data together with the borehole plane coordinates into the optimization calculation program;

[0028] Step 6.2: Target parameter inversion: After the basic data is imported, the double difference positioning method is used to invert the footage depth and apparent shear wave velocity in groups, and the objective function value is iterated to the minimum value using the optimization algorithm. The objective function uses the travel time residual function, and the optimization algorithm uses the particle swarm algorithm.

[0029] Step 7: Depth-velocity domain scatter plotting and monitoring;

[0030] Step 7.1: Based on the footage depth and apparent shear wave velocity results obtained by inversion of each group of arrival times in the above steps, a scatter plot is drawn with depth as the vertical axis and wave velocity as the horizontal axis;

[0031] Step 7.2: Use the fitting algorithm to fit the scattered center point on the graph, and obtain the footage depth and apparent shear wave velocity corresponding to the center point as the final inversion result of the extracted signal; the fitting algorithm adopts the K-means clustering algorithm.

[0032] Step 7.3: Plot the final inversion result on the real-time monitoring diagram in the depth-velocity domain to obtain the drilling source microseismic inversion footage depth and the apparent shear wave velocity of the corresponding depth formation within the current extraction interval;

[0033] Step 7.4: During the monitoring process, determine whether to continue monitoring based on the actual situation such as the monitoring purpose, drilling process and on-site conditions. If monitoring needs to be continued, the process returns to step 4, otherwise the process proceeds to step 8;

[0034] Step 7.5: Obtain one footage depth-apparent shear wave velocity inversion result at each sampling interval. As the drilling rig continues to drill, the formation apparent shear wave velocity stratification information from shallow to deep and the real-time drilling rig footage depth are gradually formed, realizing real-time monitoring of footage depth and apparent shear wave velocity;

[0035] Step 8: End monitoring. When the current drilling footage is completed, stop monitoring and turn off the device, or end monitoring automatically as needed.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] (1) It can save the cost of traditional shear wave velocity testing;

[0038] (2) The location of the drilling stratum change can be accurately determined on site, saving workload for later work;

[0039] (3) It can monitor the drilling depth in real time, accurately calculate the actual workload, and improve the work efficiency of on-site technicians;

[0040] (4) Currently, there is a lack of exploration and detection methods for thick fill foundations in the industry. The present invention can use a drilling source to explore and detect thick fill foundations within a depth range.

[0041] The present invention can be widely used in various geotechnical engineering surveys in conjunction with drilling methods. It can accurately and in real time determine the drilling footage depth, and can also provide the layer position and apparent shear wave velocity of the rock and soil body, qualitatively and preliminarily quantitatively determine the physical and mechanical properties of the rock and soil body within the survey range, and can use the drilling source to survey and detect thick fill foundations within the depth range. It not only saves the engineering cost of shear wave velocity testing, but also has a more accurate understanding of the rock and soil body in the survey area, thereby improving the credibility of the survey results and the economic benefits of the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a flow chart of the present invention;

[0043] Figure 2 This is the detector layout diagram;

[0044] Figure 3 How to install the detector and collector;

[0045] Figure 4 It is the monitoring result of drilling source depth-wave velocity domain. DETAILED DESCRIPTION

[0046] In order to gain a deeper understanding of the present invention, we will provide a comprehensive and detailed description of the present invention. However, the present invention has multiple implementations and is not limited to the specific examples listed herein. The presentation of these examples is intended to deepen the comprehensive understanding of the disclosure of the present invention.

[0047] A geotechnical engineering survey method based on drilling source and microseismic monitoring technology, the method comprising the following steps:

[0048] Step 1: Drilling microseismic detector layout; install and layout drilling microseismic detectors, collectors, drilling rigs and controllers;

[0049] Step 1.1: Geophones are arranged around the borehole, and the number of geophones is not less than 5;

[0050] Step 1.2: There are two ways to arrange the detector: horizontal arrangement and vertical arrangement; where:

[0051] Horizontal layout: The detectors are arranged unequally and asymmetrically around the borehole. The distance between each detector and the borehole is not less than 2 times the depth of the drilling target hole, and the maximum distance is not more than 3 times. The minimum distance between adjacent detectors in the horizontal direction is not less than 1.5 times the depth of the drilling target hole.

[0052] Vertical layout: The elevation difference between adjacent geophones in the vertical direction shall not be less than 1 / 100 of the larger horizontal distance between adjacent geophones;

[0053] Step 1.3: Geophone burial method: The burial depth of each geophone from the ground surface is not less than 0.5m, and the bottom is installed on the interface of stable strata. Ensure that the geophone is vertical to the horizontal plane as a whole. The upper part is connected to the cable out of the ground. After backfilling with uniform soil until it is flush with the surrounding ground, the cable is connected to the collector;

[0054] When the bottom of the pit is soil, a tail pin is used; when the bottom of the pit is rock, a steel plate is used; see the attached Figure 3 .

[0055] Step 1.4: After the drilling rig is in place and during the installation of the detectors, use measuring equipment to measure the spatial coordinates of each detector and the plane coordinates of the borehole.

[0056] A geotechnical engineering survey project for a mine industrial site. The surface soil of the project area is an interlayer of Quaternary sandy silt and silty clay, with a thickness of about 20m, and the lower part is an interlayer of Permian strongly weathered to moderately weathered mudstone and sandstone. The site is relatively flat as a whole, with little ups and downs, and belongs to the river terrace landform.

[0057] The target hole depth of one of the boreholes under the raw coal silo is 30m. Five detectors are installed around the borehole. The horizontal distances between each detector and the borehole are 60m, 65m, 72m, 75m and 81m respectively. The distance between adjacent detectors is 69.5-94.6m. The elevation difference between adjacent detectors in the vertical direction is 0.8-1.0m. The buried depth of the detector from the ground is not less than 0.5m. The bottom is inserted into the soil with a tail pin, and the detector as a whole is made vertical to the horizontal plane.

[0058] Use RTK to measure the detector's spatial coordinates and the borehole's plane coordinates. Then connect one end of the cable to the detector and bring the other end out of the ground. Backfill the detector pit with soil and connect the other end of the cable to the collector.

[0059] Step 2: Start monitoring; after installation and deployment are completed, start the drilling rig and start drilling, and at the same time turn on the installed equipment for real-time monitoring;

[0060] After the drilling rig is in place, turn on the collector and operator, connect them to the 4G network, create a new monitoring task, notify the drilling rig to start drilling, and then start monitoring.

[0061] Step 3: Collect and transmit drilling source microseismic signals; the detector collects the original signal and transmits it to the collector via wired mode, and the collector continuously summarizes the original signal to the controller; wherein the network used by the collector is 4G or WIFI network; the collector can set the sampling frequency, and the sampling frequency is 50Hz to 250Hz;

[0062] After starting monitoring, set the sampling frequency to 100Hz. The detector collects the original signal in real time and transmits it to the collector via wired mode. The collector continuously aggregates the original signal to the controller via 4G or WIFI network.

[0063] Step 4: extracting the original signal according to the extraction interval; operating the controller to set the extraction interval for the original signal, and extracting the original signal with the same current duration as the extraction interval according to the extraction interval; wherein the extraction interval is 1min, 2min, 3min;

[0064] The operator sets the extraction interval to 1 minute, that is, the original signal with a current duration of 1 minute is extracted every 1 minute;

[0065] Step 5: Drilling source microseismic signal processing;

[0066] Step 5.1: intercepting the signal: intercepting the extracted signal into multiple groups of signals according to the sampling segment length, and the simultaneous signals of the entire detector sequence are one group; the sampling segment length is 512, 1024, 2048, 4096;

[0067] The operator sets the sampling segment length to 1024. Based on the sampling frequency of 100 Hz, the segment length of 1024 means that the intercepted signal duration is about 10.24 s, that is, the 1-minute extracted signal will be intercepted into 6 groups, and each group of intercepted signals contains the segmented signals of 5 detectors at the same time.

[0068] Step 5.2: Initial filtering: Perform initial filtering on each group of intercepted signals. The filtering method adopts FIR bandpass filtering. The low-pass threshold of the bandpass filtering is set at 2-20Hz and the high-pass threshold is set at 50-100Hz on site. The threshold parameters are selected according to the type of rock and soil bodies mainly involved in the drilling process. If the rock body is mainly rock body, a high value is taken, and if the soil body is mainly soil body, a low value is taken.

[0069] Since the borehole is mainly composed of Quaternary sandy silt and silty clay interlayers, the low-pass threshold of the bandpass filter is set to 5Hz and the high-pass threshold is set to 60Hz on site. After entering the bedrock, the low-pass threshold of the bandpass filter is set to 15Hz and the high-pass threshold is set to 80Hz.

[0070] The six groups of intercepted signals are initially filtered using FIR bandpass filtering to filter out surface waves and on-site construction vibration interference;

[0071] Step 5.3: Autocorrelation discrimination: Use the autocorrelation matrix method to solve the autocorrelation coefficient of each detector segment signal in each group of primary filtering signals. If it is greater than the threshold, it is determined to be a valid signal. The threshold value is 0.65-0.95. The threshold is set according to the degree of background noise interference and the required inversion accuracy. A high value is selected when the interference is large and the required accuracy is high;

[0072] Considering that there is no cross-construction on site and no other interference sources on the site, the autocorrelation threshold is selected as 0.90 to ensure high inversion accuracy.

[0073] The autocorrelation matrix method is used to solve the autocorrelation coefficients of the six groups of primary filtering signals. Those greater than the threshold of 0.90 are determined as valid signals, which are screened out and prepared for secondary filtering.

[0074] After identification, 4 of the 6 groups of initial filtering signals are greater than the threshold value of 0.90, so they are determined to be valid signals;

[0075] Step 5.4: Secondary filtering: Use fast Fourier transform to transform each group of valid signals from time domain signals to frequency domain, and find the corresponding frequency of the maximum amplitude as the signal main frequency; the main frequency of the same group of valid signals adopts the average of the main frequencies of the segmented signals of each detector, and the group of filtered signals is subjected to secondary filtering of the main frequency ±1Hz, and the filtering method adopts FIR bandpass filtering;

[0076] Fast Fourier transform is used to transform the four groups of effective signals that meet the autocorrelation judgment from time domain signals to frequency domain, and the frequency corresponding to the maximum amplitude is found as the main frequency of the signal;

[0077] The four groups of effective signals can obtain a total of four groups of detector segment signal main frequencies, each group containing five detector segment signal main frequencies.

[0078] Taking the group as the unit, the average of the main frequency of each detector segment signal is taken as the secondary filtering center frequency, and its ±1Hz is used for secondary filtering, and the filtering method adopts FIR bandpass filtering.

[0079] Through the above process, a total of 4 groups of secondary filtering signals are obtained.

[0080] Step 5.5: Pick up the arrival time: in each group of time domain secondary filtering signals, pick up the time corresponding to the maximum amplitude of each detection segment signal as the arrival time;

[0081] Among the four groups of time domain secondary filtering signals, the time corresponding to the maximum amplitude of each detection segment signal is picked up as the arrival time. A total of four groups of arrival times can be obtained from the four groups of secondary filtering signals, and each group contains five arrival times.

[0082] Step 6: Inversion of footage depth and apparent shear wave velocity;

[0083] Step 6.1: Import basic data: Integrate the arrival times and the corresponding geophone spatial coordinate data obtained in the above steps, and import the integrated data together with the borehole plane coordinates into the optimization calculation program;

[0084] The four groups of arrival times obtained in the above steps and their corresponding detector spatial coordinates and other data are integrated, and the integrated data together with the borehole plane coordinates are sequentially imported into the optimization calculation program in groups;

[0085] Step 6.2: Target parameter inversion: After the basic data is imported, the double difference positioning method is used to invert the footage depth and apparent shear wave velocity in groups, and the objective function value is iterated to the minimum value using the optimization algorithm. The objective function uses the travel time residual function, and the optimization algorithm uses the particle swarm algorithm.

[0086] After the basic data is imported, the double difference positioning method is used to invert the footage depth and apparent shear wave velocity in groups. The objective function uses the travel time residual function, and its formula is as follows:

[0087]

[0088]

[0089] Where: is the theoretical calculation travel time (s); x0, y0 are the plane coordinates of the drilling source (m); z0 is the footage depth (m); i ,y i 、z i is the spatial coordinate of each detector (m); N is the number of detectors; TS0 is the estimated earthquake occurrence time (s); v m is the apparent shear wave velocity (m / s); is the actual observed time (s); R(x0,y0,z0,v m ) is the travel time residual;

[0090] After calculation, 4 sets of arrival times, geophone spatial coordinates, and borehole plane coordinates can obtain 4 footage depth-apparent shear wave velocity inversion results;

[0091] Step 7: Depth-velocity domain scatter plotting and monitoring;

[0092] Step 7.1: Based on the footage depth and apparent shear wave velocity results obtained by inversion of each group of arrival times in the above steps, a scatter plot is drawn with depth as the vertical axis and wave velocity as the horizontal axis;

[0093] Step 7.2: Use the fitting algorithm to fit the scattered center point on the graph, and obtain the footage depth and apparent shear wave velocity corresponding to the center point as the final inversion result of the extracted signal; the fitting algorithm adopts the K-means clustering algorithm.

[0094] Step 7.3: Plot the final inversion result on the real-time monitoring diagram in the depth-velocity domain to obtain the drilling source microseismic inversion footage depth and the apparent shear wave velocity of the corresponding depth formation within the current extraction interval;

[0095] Step 7.4: During the monitoring process, determine whether to continue monitoring based on the actual situation such as the monitoring purpose, drilling process and on-site conditions. If monitoring needs to be continued, the process returns to step 4, otherwise the process proceeds to step 8;

[0096] Step 7.5: Obtain one footage depth-apparent shear wave velocity inversion result at each sampling interval. As the drilling rig continues to drill, the formation apparent shear wave velocity stratification information from shallow to deep and the real-time drilling rig footage depth are gradually formed, realizing real-time monitoring of footage depth and apparent shear wave velocity;

[0097] After the above steps, a total of 4 footage depth-apparent shear wave velocity inversion results are obtained. With depth as the vertical axis and wave velocity as the horizontal axis, the 4 footage depth-apparent shear wave velocity inversion results are plotted as a scatter plot.

[0098] The K-means algorithm is used to fit the scattered center points on the graph, and the footage depth and apparent shear wave velocity corresponding to the center point are obtained as the final inversion results of the extracted signal.

[0099] The final inversion results are plotted on the real-time monitoring diagram in the depth-velocity domain to obtain the drilling source microseismic inversion footage depth and the apparent shear wave velocity of the corresponding depth formation within the current extraction interval.

[0100] In order to fully monitor the real-time footage depth of the borehole and the distribution of apparent shear wave velocity in the formation within the borehole, continuous monitoring is selected until the drilling footage reaches the final hole depth of 30m, so as to achieve real-time monitoring of footage depth and apparent shear wave velocity;

[0101] Step 8: End monitoring. When the current drilling footage is completed, stop monitoring and turn off the equipment, or end monitoring automatically as needed;

[0102] The monitoring lasted for 4.5 hours in the morning and 3 hours in the afternoon, for a total of 7.5 hours. The inversion results of the footage depth and apparent shear wave velocity were obtained every 1 minute. As the drilling rig continued to drill, the apparent shear wave velocity stratification information of the formation from shallow to deep 0 to 30 meters and the real-time drilling rig footage depth were gradually formed.

[0103] When the penetration depth reaches 30m, the drilling rig stops drilling, the controller stops monitoring and then shuts down all equipment, thus ending the monitoring work of the borehole.

[0104] Figure 4 This is the drilling source-wave velocity and domain monitoring result of the current borehole in this drilling work. As shown in the figure, the drilling depth of the borehole is 30m, of which 0-20m is the Quaternary sandy silt and silty clay interlayer, and the apparent shear wave velocity in the figure is 168-423m / s; 20-30m is the Permian strongly weathered to moderately weathered mudstone and sandstone interlayer, and the apparent shear wave velocity in the figure is 525-697m / s. Based on this, the apparent shear wave velocity of each layer from shallow to deep in the strata around the borehole was obtained.

[0105] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. Although the illustrative specific embodiments of the present invention are described above to facilitate the understanding of the present invention by the technical personnel in the field, it should be clear that the present invention is not limited to the scope of the specific embodiments. For the ordinary technical personnel in the field, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A geotechnical engineering investigation method based on drilling source and microseismic monitoring technology, characterized in that: The method comprises the following steps: Step 1: Drilling microseismic detector layout; install and layout drilling microseismic detectors, collectors, drilling rigs and controllers; Step 2: Start monitoring; after installation and deployment are completed, start the drilling rig and start drilling, and at the same time turn on the installed equipment for real-time monitoring; Step 3: Collect and transmit drilling source microseismic signals; the geophone collects the original signal and transmits it to the collector via wired mode, and the collector continuously summarizes the original signal to the controller; Step 4: extract the original signal according to the extraction interval; operate the controller to set the extraction interval for the original signal, and extract the original signal whose current duration is the same as the extraction interval according to the extraction interval; Step 5: Drilling source microseismic signal processing; Step 6: Inversion of footage depth and apparent shear wave velocity; Step 7: Depth-velocity domain scatter plotting and monitoring; Step 8: End monitoring.

2. A geotechnical engineering investigation method based on drilling source and microseismic monitoring technology according to claim 1, characterized in that: Step 1: Drilling microseismic geophone deployment; installing and deploying drilling microseismic geophones, collectors, drilling rigs and controllers; the specific operations are: Step 1.1: Geophones are arranged around the borehole, and the number of geophones is not less than 5; Step 1.2: There are two ways to arrange the detector: horizontal arrangement and vertical arrangement; where: Horizontal layout: The detectors are arranged unequally and asymmetrically around the borehole. The distance between each detector and the borehole is not less than 2 times the depth of the drilling target hole, and the maximum distance is not more than 3 times. The minimum distance between adjacent detectors in the horizontal direction is not less than 1.5 times the depth of the drilling target hole. Vertical layout: The elevation difference between adjacent geophones in the vertical direction shall not be less than 1 / 100 of the larger horizontal distance between adjacent geophones; Step 1.3: Geophone burial method: The burial depth of each geophone from the ground surface is not less than 0.5m, and the bottom is installed on the stable stratum interface. Ensure that the geophone is vertical to the horizontal plane. The upper part is connected to the cable out of the ground. After backfilling with soil until it is flush with the surrounding ground, the cable is connected to the collector; When the bottom of the pit is soil, a tail pin is used, and when the bottom of the pit is rock, a steel plate is used; Step 1.4: After the drilling rig is in place and during the installation of the detectors, use measuring equipment to measure the spatial coordinates of each detector and the plane coordinates of the borehole.

3. The geotechnical engineering investigation method based on drilling source and microseismic monitoring technology according to claim 2 is characterized in that: The step 3: collects and transmits the microseismic signal of the drilling source; the detector collects the original signal and transmits it to the collector via a wired method, and the collector continuously summarizes the original signal to the controller; wherein the network used by the collector is a 4G or WIFI network; the collector can set the sampling frequency, and the sampling frequency is 50Hz to 250Hz.

4. A geotechnical engineering investigation method based on drilling source and microseismic monitoring technology according to claim 3, characterized in that: The step 4: extracting the original signal according to the extraction interval; operating the controller to set the extraction interval for the original signal, and extracting the original signal whose current duration is the same as the extraction interval according to the extraction interval; wherein the extraction interval is 1min, 2min, and 3min.

5. A geotechnical engineering investigation method based on drilling source and microseismic monitoring technology according to claim 4, characterized in that: The specific operations of step 5: drilling source microseismic signal processing are: Step 5.1: intercepting the signal: intercepting the extracted signal into multiple groups of signals according to the sampling segment length, and the simultaneous signals of the entire detector sequence are one group; the sampling segment length is 512, 1024, 2048, 4096; Step 5.2: Initial filtering: Perform initial filtering on each group of intercepted signals. The filtering method adopts FIR bandpass filtering. The low-pass threshold of the bandpass filtering is set at 2-20Hz and the high-pass threshold is set at 50-100Hz on site. The threshold parameters are selected according to the type of rock and soil bodies mainly involved in the drilling process. If the rock body is mainly rock body, a high value is taken, and if the soil body is mainly soil body, a low value is taken. Step 5.3: Autocorrelation discrimination: Use the autocorrelation matrix method to solve the autocorrelation coefficient of each detector segment signal in each group of primary filtering signals. If it is greater than the threshold, it is determined to be a valid signal. The threshold value is 0.65-0.

95. The threshold is set according to the degree of background noise interference and the required inversion accuracy. A high value is selected when the interference is large and the required accuracy is high; Step 5.4: Secondary filtering: Use fast Fourier transform to transform each group of valid signals from time domain signals to frequency domain, and find the corresponding frequency of the maximum amplitude as the signal main frequency; the main frequency of the same group of valid signals adopts the average of the main frequencies of the segmented signals of each detector, and the group of filtered signals is subjected to secondary filtering of the main frequency ±1Hz, and the filtering method adopts FIR bandpass filtering; Step 5.5: Pick up the arrival time: In each group of time domain secondary filtering signals, pick up the time corresponding to the maximum amplitude of each detection segment signal as the arrival time.

6. A geotechnical engineering investigation method based on drilling source and microseismic monitoring technology according to claim 5, characterized in that: The specific operation of step 6: inversion of footage depth and apparent shear wave velocity is: Step 6.1: Import basic data: Integrate the arrival times and the corresponding geophone spatial coordinate data obtained in the above steps, and import the integrated data together with the borehole plane coordinates into the optimization calculation program; Step 6.2: Target parameter inversion: After the basic data is imported, the double difference positioning method is used to invert the footage depth and apparent shear wave velocity in groups, and the objective function value is iterated to the minimum value using the optimization algorithm. The objective function uses the travel time residual function, and the optimization algorithm uses the particle swarm algorithm.

7. A geotechnical engineering investigation method based on drilling source and microseismic monitoring technology according to claim 6, characterized in that: The specific operations of step 7: depth-wave velocity domain scatter plotting and monitoring are as follows: Step 7.1: Based on the footage depth and apparent shear wave velocity results obtained by inversion of each group of arrival times in the above steps, a scatter plot is drawn with depth as the vertical axis and wave velocity as the horizontal axis; Step 7.2: Use the fitting algorithm to fit the scattered center point on the graph, and obtain the footage depth and apparent shear wave velocity corresponding to the center point as the final inversion result of the extracted signal; the fitting algorithm adopts the K-means clustering algorithm; Step 7.3: Plot the final inversion result on the real-time monitoring diagram in the depth-velocity domain to obtain the drilling source microseismic inversion footage depth and the apparent shear wave velocity of the corresponding depth formation within the current extraction interval; Step 7.4: During the monitoring process, determine whether to continue monitoring based on the actual situation. If it is necessary to continue monitoring, the process returns to step 4, otherwise the process proceeds to step 8; Step 7.5: Obtain the footage depth-apparent shear wave velocity inversion result once per sampling interval. As the drilling rig continues to drill, the formation apparent shear wave velocity stratification information from shallow to deep and the real-time drilling rig footage depth are gradually formed, realizing real-time monitoring of footage depth and apparent shear wave velocity.

8. The geotechnical engineering investigation method based on drilling source and microseismic monitoring technology according to claim 7, characterized in that: The specific operation of step 8: ending the monitoring is: when the current drilling footage ends, stop monitoring and turn off the equipment, or end the monitoring automatically as needed.

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