Integrated mobile vs30 measuring device, design method, and measuring method

Abstract

The application discloses an integrated mobile VS30 measuring device, a design method and a measuring method, belongs to the field of geological exploration, and comprises a mobile seismic source vehicle and a mobile measuring array which is connected with the mobile seismic source vehicle through land streamer traction, wherein the mobile measuring array is composed of multiple node seismic instruments which are uniformly arranged on the land streamer and are in sliding coupling with the ground, and the node seismic instruments are in communication with a master control terminal carried on the mobile seismic source vehicle. The integrated mobile VS30 measuring device, the design method and the measuring method have the advantages that rapid and continuous measurement can be realized through the mobile seismic source vehicle-streamer-node seismic, and the joint inversion of GLM-XGBoost (improving the nonlinear fitting precision) is utilized to guarantee the measurement accuracy and reliability, and the engineering requirements such as urban market ground classification and evaluation can be fully met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geological exploration, and particularly relates to an integrated mobile VS30 measuring device, a design method and a measuring method. BACKGROUND

[0002] VS30 (average shear wave velocity in the top 30 m) is a key parameter for describing site characteristics in earthquake engineering, which refers to the average velocity of shear wave in the vertical direction of the ground surface within the depth of 30 meters. As a core parameter for characterizing the dynamic characteristics of near-surface medium, it can be regarded as a key index for site classification.

[0003] Currently, the acquisition of VS30 mainly relies on three technical routes: static active source surface wave method, micro-oscillation method and borehole seismic method. Among them, the static active source multi-channel surface wave method is a classic method for inverting VS30 by actively exciting surface waves and analyzing their dispersion characteristics. The specific process is as follows: (1) array layout: fixed geophone array is laid at the preset survey line, i.e. vertical component or three-component geophone (sampling rate usually 500-1000 Hz) is connected to the data acquisition system through shielded cable, and the geophone is buried in the ground 5-10 cm to ensure coupling with the ground (to avoid distortion of vibration signal), the inter-channel distance is usually 1-5 m, and the array length is 50-200 m; (2) source excitation: a ramming or drop hammer (hammer weight 50-200 kg) is used to excite the source at one end of the array (or 2-3 inter-channel distances beyond the array), the trigger signal is transmitted to the acquisition system through a dedicated trigger line to realize the time synchronization of source and acquisition; (3) data processing: under the condition of fixed array, 3-5 times of repeated excitation are needed to obtain redundant data, the frequency-wavenumber analysis or multi-channel coherence analysis (coherence threshold usually ≥0.8) is used to generate the dispersion energy diagram, the fundamental mode surface wave phase velocity curve is picked up manually, and the near-surface shear wave velocity profile is inverted based on the layered homogeneous medium model, and finally the VS30 target value is calculated. It can be seen that it has the following defects: (1) large workload and poor adaptability to cities: the equipment layout and recovery need to be completed manually, and it takes 1-2 hours to lay out a 100-meter survey line (including cable laying and geophone burying); and in urban environment, ground obstacles (such as manhole covers and green belts), traffic control (temporary closure of lanes is required) and underground pipelines (preliminary detection is required to avoid cable damage) will further increase the difficulty of operation, resulting in about 30% of the city survey lines needing to adjust the path, greatly prolonging the construction period. (2) low test efficiency and limited advancing speed: limited by "multi-shot excitation + array relocation": single-shot data acquisition (including preparation, excitation and storage) takes 5-10 minutes, and after completing the test of each array, the equipment needs to be relocated to the next survey section, so only 1-2 km of survey line can be completed per day; in addition, about 20% of the shot data is invalid due to urban traffic interference (such as ground vibration caused by vehicle passing), which needs to be re-excited, further reducing the efficiency. (3) low-frequency signal is easily disturbed, and the reliability of dispersion curve picking is low: in urban environment, vehicles, subways and machinery operations can produce 1-10 Hz low-frequency background vibration, which reduces the signal-to-noise ratio (SNR) of the low-frequency band (4-10 Hz, corresponding to 10-30 m depth) of surface wave to below 2 dB (reference document 2 SNR quantification standard), making it difficult to stably identify the energy "ridge line" of the fundamental mode surface wave, and even the energy of high-order surface wave covers the fundamental mode, resulting in an error of more than 15% in the inversion of deep shear wave velocity.(4) Cannot achieve fast continuous mapping: due to the use of "static array + segmented test" mode, the data of each segment of the test line needs to be spliced offline, and the test interval of each segment is ≥30 minutes, which cannot realize continuous mobile collection of long distances (such as urban roads above 5km), and cannot meet the needs of "minute-level result update" of urban and rapid mapping (such as the need for 10 minutes / km mapping efficiency for emergency earthquake assessment).

[0004] Borehole seismic method is a method of obtaining high-precision shear wave velocity through borehole or interwell seismic testing, which can be directly used for calculating VS30, mainly including three types of testing forms: (1) Borehole testing: In the constructed borehole (depth ≥ 30m, hole diameter 100-150mm), geophones are arranged at an interval of 2-5m (cement coupling or air bag coupling is used to ensure contact with the well wall), the surface uses electric spark or hammer to excite the source, and the first arrival time of the geophone at different depths is recorded. The interlayer travel time difference is used to invert the shear wave velocity of each layer; (2) Interwell testing: Two boreholes with a spacing of 10-50m (both depths ≥ 30m) are constructed, the source is excited at the depth in the shooting hole, and the geophone in the receiving hole records the signal, and the interwell shear wave velocity distribution is inverted through the wave velocity propagation path; (3) CPT shear wave testing: Based on the CPT equipment, a shear wave probe is integrated, and a piezoelectric ceramic source is added to excite shear waves during the probe penetration process (penetration speed 2cm-5cm / s), and the signal is received by the built-in sensor of the probe to obtain shear wave velocity in real time. It can be seen that it has the following defects: (1) Spatial sampling is discrete, high cost and long cycle: borehole construction requires professional equipment and approval process: single-hole construction cost 10,000-20,000 yuan (including drilling, wall fixing, and hole cleaning), and the borehole approval cycle in urban areas is 2-4 weeks; and the spatial sampling interval is usually 2-5m, which cannot reflect the lateral heterogeneity (such as stratum mutation, lens), resulting in poor spatial continuity of VS30 calculation, and it is difficult to meet the continuous evaluation needs of long test lines (such as urban trunk roads).(2) Test error is significant, and is greatly affected by well conditions and strata: well diameter changes (such as 20% expansion of well diameter in loose strata), and well wall water content (water accumulation in well wall of saturated strata leads to poor coupling of geophones) will introduce systematic errors, and the shear wave velocity measurement deviation will be 15%-20%; if the lateral heterogeneity of the underground is obvious (such as stratum change rate >10% / m), the path effect of interwell wave propagation will amplify the profile deviation, and the difference between the inverted VS30 and the actual value will be more than 25%.

[0005] Microtremor method uses environmental background vibration (such as atmospheric disturbance, vehicle vibration, teleseismic signal) to invert VS30, without active source, mainly divided into two types: (1) Horizontal / Vertical Spectral Ratio (HVSR): Using a single three-component seismometer (sampling rate 200-500Hz), 30-60 minutes of environmental vibration signals are recorded at the measuring point, the power spectral ratio of the horizontal component (east-west + north-south) and the vertical component is calculated, the inherent resonance frequency corresponding to the spectral ratio peak is identified, and the VS30 is determined by combining the empirical formula; (2) Small array method: A small array (such as a triangular array, with a side length of 10-50m) is arranged by 4-9 three-component seismometers, time synchronization is realized by satellite time service (or high-stability clock, daily stability ≤1×10 -9 ) to achieve time synchronization, the frequency dispersion curve is estimated by coherent surface wave analysis, and the VS30 is calculated after the shear wave velocity profile is inverted. It can be seen that it has the following defects: (1) The result is not unique, the reliability is low, and the measurement result is highly sensitive to noise field composition: The difference in environmental vibration composition (traffic noise ratio, teleseismic signal intensity) at the same measuring point at different times (such as daytime vs. nighttime) will cause the HVSR spectral ratio peak to shift, and the VS30 calculation deviation will be 15%-20%; and when the microtremor method is used alone, the non-uniqueness of the wave field composition (such as the body wave interference ratio exceeding 30%) and the inversion model (such as the number of layers assumption) will further amplify the error, and the deviation between the VS30 inverted by the microtremor method and the measured value of the borehole is often more than 25%. (2) Relies on external verification and cannot be independently applied: Due to the insufficient reliability of the result, the microtremor method usually needs to be verified by active source methods (such as MASW) or borehole test results, i.e. verification points need to be arranged at both ends of the measuring line or key nodes, which increases the workload by 10%-15%, cannot be used as an independent VS30 measurement method, and limits its application in rapid evaluation scenarios (such as post-disaster emergency). SUMMARY

[0006] The purpose of the present application is to provide an integrated mobile VS30 measurement device, a design method and a measurement method, which solve the above technical problems.

[0007] To achieve the above purpose, the present application provides an integrated mobile VS30 measurement device, which comprises a mobile seismic source vehicle and a mobile measurement array connected with the mobile seismic source vehicle by landstreamer, the mobile measurement array is composed of a plurality of node seismometers uniformly arranged on the landstreamer and slidingly coupled with the ground, the node seismometers are in communication with the master terminal carried on the mobile seismic source vehicle, and are used for performing equal-distance walk-stop excitation by the mobile seismic source vehicle, and after the vibration signals are collected by the plurality of node seismometers during the parking stage, the vibration signals are transmitted to the master terminal for processing and then VS30 is calculated, so as to determine the site type.

[0008] Preferably, the node seismograph is arranged on the sliding coupling assembly, the sliding coupling assembly comprises a clamping structure composed of an upper clamping plate and a lower clamping plate, the upper clamping plate is fixed with the node seismograph at the top end, the land streamer is detachably clamped between the upper clamping plate and the lower clamping plate, and the sliding coupling blocks are arranged at four corners of the lower clamping plate and are in contact with the ground.

[0009] Preferably, the main control terminal comprises a power module, a data acquisition module, a processing module and a display module, the main control terminal is electrically connected with the mobile seismic source vehicle through the vibration sensor triggering module, and the mobile seismic source vehicle is feedback connected with the main control terminal.

[0010] The mobile seismic source vehicle is further integrated with a seismic source triggering sensor, a GNSS timing module and an odometer, the seismic source triggering sensor, the GNSS timing module and the odometer are connected with the data acquisition module and the processing module, and are used for determining the seismic source triggering time and the spatial position of the mobile seismic source vehicle.

[0011] The node seismograph is built-in with a satellite timing module and a wireless transmission module, the node seismograph and the satellite timing module are in communication with the processing module through the wireless transmission module and the data acquisition module in sequence, and the processing module is connected with the display module.

[0012] The design method of the integrated mobile VS30 measuring device comprises the following steps:

[0013] Sa1, determining a target frequency band f 目标 :

[0014]

[0015] In the formula, c p,min and c p,max respectively represent the minimum surface wave phase velocity and the maximum surface wave phase velocity of the measured site; d min and d max respectively represent the minimum detection depth and the maximum detection depth, and d min = 0 m and d min = 30 m.

[0016] Sa2, calculating a comprehensive environmental evaluation index E:

[0017] E = w1·E disturb +w2·E obs +w3·E flat .

[0018] Among them,

[0019]

[0020] In the formula, w1, w2 and w3 all represent weight coefficients; E disturbrepresents an environmental interference intensity quantitative index; PSD represents an environmental noise power spectral density, and T represents a pre-acquisition time, f s represents a sampling rate, and u(t) represents a noise amplitude at time t; E obs represents an obstacle density quantitative index of a to-be-measured site; N obs represents a total number of obstacles in a survey line; L line represents a survey line length; E flat represents a flatness quantitative index; ΔH max represents a maximum elevation difference of adjacent 10 m survey lines;

[0021] Sa3, based on a target frequency band f 目标 and a comprehensive environmental evaluation index E, determines a shot spacing, a trace spacing, and a fold number.

[0022] Preferably, the shot spacing ΔL in step Sa3 refers to a distance between positions of adjacent two times of seismic source excitation, and an expression thereof is as follows:

[0023]

[0024] In the formula, λ min represents a minimum surface wave wavelength corresponding to the target frequency band, and f 目标-max represents an upper limit of the target frequency band f 目标 ; L 拖缆 represents a length of a land streamer;

[0025] The trace spacing Δx refers to a distance between adjacent two nodal seismic instruments on the land streamer:

[0026]

[0027] The fold number M refers to a number of times of repeated excitation and stacking at a same shot point:

[0028]

[0029] In the formula, SNR 目标 represents a minimum signal-to-noise ratio required for inversion of a dispersion curve; SNR 单次 represents a signal-to-noise ratio of a single excitation; represents a ceiling function.

[0030] A measurement method of the integrated mobile VS30 measurement device includes the following steps:

[0031] Sb1, array initialization: installing nodal seismic instruments on a land streamer according to a set trace spacing, and setting a shot spacing, a fold number, a sampling rate, and a recording length;

[0032] Sb2, isometrically moving excitation: starting to move the mobile seismic source vehicle along the survey line until it stops at a preset inter-shot distance, determining that the shot point is reached, at which time the current mileage coordinate and elevation data are recorded using the odometer;

[0033] Sb3, constructing a short-time static array: after standing for a set time, sending an excitation instruction to the mobile seismic source vehicle using the master terminal, the mobile seismic source vehicle feeding back a trigger signal to the master terminal after executing the excitation instruction, and simultaneously collecting vibration signals using the node seismograph;

[0034] Sb4, repeating step Sb3 to obtain multiple vibration data after a set interval, and stacking the vibration signals;

[0035] Sb5, extracting surface wave characteristics from the stacked signals of step Sb4, generating a dispersion energy graph, and picking a base-order curve or a high-order curve from the dispersion energy graph;

[0036] Sb6, based on the base-order curve or the high-order curve, performing one-dimensional layered shear wave velocity joint inversion using the GLM-XGBoost algorithm to obtain a 0-30m depth shear wave velocity profile and VS30;

[0037] Sb7, starting the mobile seismic source vehicle again, repeating steps Sb2-Sb6 to obtain measurement results of multiple shot points, splicing the measurement results of adjacent two shot points, and performing smoothing processing to generate a two-dimensional shear wave velocity profile along the survey line;

[0038] Sb8, calibrating and comparing the generated two-dimensional shear wave velocity profile using multi-dimensional evaluation indexes and borehole and shallow reflection data, and outputting a calibrated and compared result report.

[0039] Preferably, step Sb4 specifically includes the following steps:

[0040] Sb41, the time-domain signal u K-su (t) as follows:

[0041]

[0042] wherein,

[0043] u i (t) = s(t) + n i (t) ;

[0044] In the formula, u i (t) represents the original time-domain signal of the i-th excitation; s(t) represents the surface wave useful signal; n i (t) represents a random noise signal;

[0045] Sb42, calculate the signal-to-noise ratio SNR of the time-domain signal after superposition of the Kth vibration signal K :

[0046]

[0047] wherein A 面波 represents the peak amplitude of the surface wave signal; A 噪声 represents the peak amplitude of the noise before the surface wave arrives;

[0048] Sb43, determine whether the following condition is met: SNR K <SNR th , if yes, output u K-su (t), otherwise, return to step Sb41, wherein SNR th represents a set signal-to-noise ratio threshold.

[0049] Preferably, step Sb5 specifically comprises the following steps:

[0050] Sb51, signal preprocessing: sequentially performing DC offset, band-pass filtering, inter-channel amplitude equalization, and filter enhancement processing on the superimposed vibration signal u K-su (t), wherein the filter enhancement expression is as follows:

[0051]

[0052] wherein G(f) represents the surface wave energy corresponding to the frequency f; L represents the recording length; and w(t, f) represents a time-varying filter window;

[0053] Sb52, perform frequency-wavenumber analysis on the preprocessed vibration signal u K-su (t) to calculate the phase velocity v p (f) at different frequencies f, and generate a dispersion energy graph:

[0054]

[0055] wherein λ(f) represents the wavelength corresponding to the frequency f; v s represents the shear wave velocity;

[0056] Sb53, determine whether there is a secondary energy ridge in the high-frequency band of the dispersion energy graph, if yes, pick up the high-order branch to obtain a high-order curve; otherwise, pick up the continuous ridge line with the strongest energy in the dispersion energy graph to obtain a base-order curve.

[0057] Preferably, step Sb6 specifically comprises the following steps:

[0058] Sb61, based on the regional geological data of the to-be-measured field, construct a one-dimensional layered shear wave velocity initial model;

[0059] Joint inversion using Sb62 and GLM-XGBoost algorithms;

[0060] Sb621, GLM inversion: with phase velocity v p (f) represents the observations, and the following linear prediction model is constructed:

[0061] v p (f)=β0+β1V s,1 +β2V s,2 +...+β j V s,j +...+β n V s,n +ε;

[0062] In the formula, β0 represents the intercept; β j b represents the shear wave velocity at the j-th layer. s,j The coefficient, and

[0063] Represents the variance of the coefficients. ε represents the error term, and ε ~ N(0,σ) 2 ), σ 2 The variance is σ ~ Exp(λ = 1); n represents the total number of layers.

[0064] Then, MCMC simulation was used to perform posterior distribution sampling and convergence determination, and the posterior mean of shear wave velocity for each layer was obtained from the converged MCMC samples. And the corresponding 95% confidence interval;

[0065] Sb622, XGBoost inversion: using GLM inversion results Using the initial input values, the frequency-phase velocity-layer thickness relationship is analyzed using the XGBoost algorithm. The nonlinear relationship is fitted to output the optimized shear wave velocity v for each layer. optimal,j ;

[0066] Wherein, the input feature matrix X of the XGBoost algorithm is... t represents the standardized thickness of the j-th layer; j Indicates the characteristics of propagation time, and h j The output label represents the thickness of the j-th layer; the output label is the theoretical phase velocity corresponding to each frequency point. objective function as follows:

[0067]

[0068] In the formula, denotes a fitting loss term, l(·) denotes a loss function, and v k,p (f) denotes the observed phase velocity at the kth frequency point, N denotes the number of effective frequency points; denotes a regularization term, η denotes a leaf node number penalty coefficient of the decision tree, denotes a leaf node weight L2 penalty coefficient, ω g denotes the weight of the gth leaf node, G denotes the total number of leaf nodes; denotes a Bayesian prior constraint term, ζ denotes a constraint strength coefficient, denotes the standard deviation of v s,j ;

[0069] Sb623, taking the posterior mean value of the GLM corresponding 95% confidence interval as an uncertainty constraint, the output of the XGBoost optimal,j as the optimal solution, to generate a 0-30m shear wave velocity profile;

[0070] Sb624, calculating VS30V S30 :

[0071]

[0072] Therefore, the present application adopts the above-mentioned integrated mobile VS30 measurement device, design method and measurement method, which has the beneficial effects of:

[0073] 1. Greatly improving the measurement efficiency: using an integrated mobile array, cooperating with the walking-stop type excitation-segmented static imaging-rolling splicing process, without the cumbersome cable laying and geophone burying of traditional static testing, a hundred-meter measurement line can complete array deployment within 10-20 minutes, realize minute-level continuous updating of VS30 results, and the single-day detection advancing speed is 3-5 times higher than that of the static MASW method, while avoiding the interference of ground obstacles and traffic control in urban environment on the test, solving the core pain points of traditional methods such as complex layout, low efficiency and difficulty in continuous mapping;

[0074] 2. Ensuring measurement accuracy and reliability: improving accuracy through GLM-XGBoost joint inversion: Bayesian GLM quantifies the uncertainty of layered shear wave velocity (outputs 95% confidence interval), avoiding the risk of a single numerical value; XGBoost captures the nonlinear relationship between frequency, phase velocity and layer thickness, making the phase velocity fitting determination coefficient ≥0.78, which is 15%-20% higher than the traditional linear inversion accuracy; at the same time, it is matched with borehole data calibration (making the relative error of VS30 ≤8%), ensuring that the results not only conform to the data law, but also do not violate the geological and physical common sense.

[0075] 3、Parameter adjustment is flexible, and core parameters such as shot interval, trace interval and stacking times can be adjusted according to the requirements of the test scene, for example, reducing the trace interval to improve the shallow resolution of the complex urban road section, increasing the shot interval to improve the detection efficiency in the open field, and breaking through the limitations of fixed traditional test parameters and poor scene adaptability;

[0076] 4、The output results meet the engineering requirements and directly serve the site evaluation. The final output includes a two-dimensional shear wave velocity profile, site classification results (according to the VS30 interval corresponding to A-E site) and a 95% confidence interval, which provides high-precision data and clear classification for urban site classification, seismic amplification effect evaluation and seismic design, reduces the subsequent data processing steps and shortens the engineering design cycle.

[0077] The technical solutions of the present application will be further described in detail below with the help of the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0078] Figure 1 Figure 1 is a structural schematic diagram of the integrated mobile VS30 measurement device of the present application;

[0079] Figure 2 Figure 2 is an operation example diagram of the experimental example of the present application;

[0080] Figure 3 Figure 3 is a single-shot result diagram of the experimental example of the present application, wherein (a) is a single-shot record profile diagram, and (b) is a single-shot fundamental mode wave dispersion diagram;

[0081] Figure 4 Figure 4 is a joint inversion schematic diagram of the experimental example of the present application, wherein (a) is a one-dimensional initial model diagram, (b) is a fitting schematic diagram of the dispersion curve pickup value and the GLM-XGBoost model, and (c) is a root mean square error convergence curve diagram in the inversion process;

[0082] Figure 5 Figure 5 is a two-dimensional shear wave velocity profile diagram of the experimental example of the present application.

[0083] REFERENCE NUMERALS

[0084] 1, mobile seismic source vehicle; 2, node seismograph; 3, land streamer; 4, upper clamp plate; 5, lower clamp plate; 6, sliding coupling block. DETAILED DESCRIPTION

[0085] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0086] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as a process, method, system, product, or server that includes a series of steps or units, not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or device.

[0087] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0088] like Figure 1 As shown, the integrated mobile VS30 measurement device includes a mobile seismic source vehicle 1 and a mobile measurement array connected to the mobile seismic source vehicle 1 by a land tow cable 3. The mobile measurement array consists of multiple nodal seismographs uniformly arranged on the land tow cable 3 and slidingly coupled to the ground. The nodal seismographs 2 communicate with the main control terminal mounted on the mobile seismic source vehicle 1. They are used to perform constant-mileage stop-and-go excitation using the mobile seismic source vehicle 1, and after collecting vibration signals using multiple nodal seismographs during the stopping phase, they are transmitted to the main control terminal for processing and VS30 calculation to determine the site type.

[0089] The nodal seismograph 2 is mounted on the sliding coupling assembly, which includes a clamping structure consisting of an upper clamping plate 4 and a lower clamping plate 5 that are fastened together. The nodal seismograph 2 is fixed at the top of the upper clamping plate 4. The land tow cable 3 is detachably clamped between the upper clamping plate 4 and the lower clamping plate 5. Sliding coupling blocks 6 are provided at the four corners of the lower clamping plate 5, and the sliding coupling blocks 6 are in contact with the ground.

[0090] The master terminal comprises a power module, a data acquisition module, a processing module and a display module, the master terminal is electrically connected with the mobile seismic source vehicle 1 through a vibration sensor triggering module, the mobile seismic source vehicle 1 is feedback connected with the master terminal; the mobile seismic source vehicle 1 is further integrated with a seismic source triggering sensor, a GNSS timing module and an odometer, the seismic source triggering sensor, the GNSS timing module and the odometer are connected with the processing module through the data acquisition module, and are used for determining the seismic source triggering time and the spatial position of the mobile seismic source vehicle 1; the node seismograph 2 is internally provided with a satellite timing module and a wireless transmission module, the node seismograph 2 and the satellite timing module are in communication with the processing module through the wireless transmission module and the data acquisition module in sequence, and the processing module is connected with the display module.

[0091] It should be noted that the above electronic components are all mature products on the market, and the embodiment only needs to connect them according to the instructions after purchasing, and does not improve them, so the circuit connection structure and principle will not be described here.

[0092] The design method of the integrated mobile VS30 measuring device comprises the following steps:

[0093] Sa1, determine the target frequency band f 目标 :

[0094]

[0095] In the formula, c p,min and c p,max respectively represent the minimum surface wave phase velocity and the maximum surface wave phase velocity of the measured site; d min and d max respectively represent the minimum detection depth and the maximum detection depth, and d min = 0m, d min = 30m;

[0096] Sa2, calculate the comprehensive environmental evaluation index E:

[0097] E = w1·E disturb +w2·E obs +w3·E flat ;

[0098] Among them,

[0099]

[0100] In the formula, w1, w2 and w3 all represent weight coefficients; E disturb represents the environmental interference intensity quantitative index; PSD represents the environmental noise power spectral density, and T represents the pre-acquisition time, f sdenotes the sampling rate, u(t) denotes the noise amplitude at time t; E obs denotes the obstacle density quantitative index of the measured site; N obs denotes the total number of obstacles in the survey line; L line denotes the length of the survey line; E flat denotes the flatness quantitative index; ΔH max denotes the maximum elevation difference of adjacent 10m survey lines;

[0101] Sa3, based on the target frequency band f 目标 and the comprehensive environmental evaluation index E, determine the shot spacing, trace spacing and fold number.

[0102] The shot spacing ΔL in step Sa3 refers to the distance between the positions of adjacent two seismic source excitations, and its expression is as follows:

[0103]

[0104] In the formula, λ min denotes the minimum surface wave wavelength corresponding to the target frequency band, and f 目标-max denotes the upper limit of the target frequency band f 目标 ; L 拖缆 denotes the length of the land streamer;

[0105] The trace spacing Δx refers to the distance between adjacent two nodal geophones on the land streamer:

[0106]

[0107] The fold number M refers to the number of repeated excitations and stacking at the same shot point:

[0108]

[0109] In the formula, SNR 目标 denotes the minimum signal-to-noise ratio required for inversion of the dispersion curve; SNR 单次 denotes the signal-to-noise ratio of single excitation; denotes the upward rounding function.

[0110] The measurement method of the integrated mobile VS30 measurement device comprises the following steps:

[0111] Sb1, array initialization: install nodal geophones on the land streamer according to the set trace spacing, and set the shot spacing, fold number, sampling rate and recording length;

[0112] Sb2, equidistant moving excitation: start the mobile seismic source vehicle to move along the survey line until it stops at the preset shot spacing, determine that the shot point is reached, and at this time, use the odometer to record the current mileage coordinate and elevation data;

[0113] Sb3, constructing a short-time static array: after the setting time, the main control terminal sends a firing instruction to the mobile seismic source vehicle, and the mobile seismic source vehicle feeds back a trigger signal to the main control terminal after executing the firing instruction, and a node seismograph is used to collect vibration signals;

[0114] Sb4, repeating step Sb3 after a set interval to obtain a plurality of vibration data, and stacking the vibration signals;

[0115] Step Sb4 specifically includes the following steps:

[0116] Sb41, the time domain signal u K-su (t) is as follows:

[0117]

[0118] wherein,

[0119] u i (t)=s(t)+n i (t);

[0120] In the formula, n i (t) represents the original time domain signal of the i-th excitation; s(t) represents the surface wave useful signal; n i (t) represents a random noise signal;

[0121] Sb42, calculating the signal-to-noise ratio SNR of the time domain signal after the K-th vibration signal stacking K :

[0122]

[0123] In the formula, A 面波 represents the peak amplitude of the surface wave signal; A 噪声 represents the peak amplitude of the noise before the surface wave arrives;

[0124] Sb43, judging whether the following condition is met: SNR K <SNR th , if met, output u K-su (t), otherwise, return to step Sb41, wherein SNR th represents a set signal-to-noise ratio threshold.

[0125] Sb5, performing surface wave feature extraction on the signal stacked in step Sb4 to generate a dispersion energy graph, and then performing curve picking on the dispersion energy graph to generate a fundamental curve or a high-order curve;

[0126] Step Sb5 specifically includes the following steps:

[0127] Sb51, signal preprocessing: on the superimposed vibration signal u K-su (t) sequentially performing DC offset, band-pass filtering, inter-channel amplitude equalization and filter enhancement processing, wherein the filter enhancement expression is as follows:

[0128]

[0129] In the formula, G(f) represents the surface wave energy corresponding to the frequency f; L represents the recording length; w(t, f) represents a time-varying filter window;

[0130] Sb52, on the pre-processed vibration signal u K-su (t) performing frequency-wavenumber analysis to calculate the phase velocity v p (f) at different frequencies f to generate a dispersion energy map:

[0131]

[0132] In the formula, λ(f) represents the wavelength corresponding to the frequency f; v s represents the shear wave velocity;

[0133] Sb53, judging whether there is a secondary energy ridge in the high frequency band of the dispersion energy map, if there is, picking up a high-order branch to obtain a high-order curve; otherwise, picking up a continuous ridge line with the strongest energy in the dispersion energy map to obtain a base-order curve.

[0134] Sb6, based on the base-order curve or the high-order curve, using the GLM-XGBoost algorithm for one-dimensional layered shear wave velocity joint inversion to obtain a shear wave velocity profile at a depth of 0-30m and VS30;

[0135] Step Sb6 specifically includes the following steps:

[0136] Sb61, based on regional geological data of the to-be-measured field, constructing a one-dimensional layered shear wave velocity initial model;

[0137] Sb62, GLM-XGBoost algorithm joint inversion;

[0138] Sb621, GLM inversion: taking the phase velocity v p (f) as an observation quantity, constructing the following linear prediction model:

[0139] v p (f)=β0+β1V s,1 +β2V s,2 +...+β j V s,j +...+β n V s,n +ε;

[0140] In the formula, β0 represents the intercept; β j b represents the shear wave velocity of the j-th layer. s,j The coefficient, and

[0141] Represents the variance of the coefficients. ε represents the error term, and ε ~ N(0,σ) 2 ), σ 2 The variance is σ ~ Exp(λ = 1); n represents the total number of layers.

[0142] Then, MCMC simulation was used to perform posterior distribution sampling and convergence determination, and the posterior mean of shear wave velocity for each layer was obtained from the converged MCMC samples. And the corresponding 95% confidence interval;

[0143] Sb622, XGBoost inversion: using GLM inversion results Using the initial input values, the frequency-phase velocity-layer thickness relationship is analyzed using the XGBoost algorithm. The nonlinear relationship is fitted to output the optimized shear wave velocity v for each layer. optimal,j ;

[0144] Wherein, the input feature matrix X of the XGBoost algorithm is... t represents the standardized thickness of the j-th layer; j Indicates the characteristics of propagation time, and h j The output label represents the thickness of the j-th layer; the output label is the theoretical phase velocity corresponding to each frequency point. objective function as follows:

[0145]

[0146] In the formula, Let l represent the fitting loss term, l(·) represent the loss function, and v k,p (f) represents the observed phase velocity at the k-th frequency point, and N represents the number of effective frequency points; Let η represent the regularization term, and let η represent the penalty coefficient for the number of leaf nodes in the decision tree. ω represents the L2 penalty coefficient for the leaf node weights. g This represents the weight of the g-th leaf node, where G represents the total number of leaf nodes; Let ζ represent the Bayesian prior constraint term, and let ζ represent the constraint strength coefficient. Indicates v s,j Standard deviation;

[0147] Sb623, Take the posterior mean of GLM. The corresponding 95% confidence interval as an uncertainty constraint, v optimal,j As the optimal solution, a 0-30m shear wave velocity profile is generated;

[0148] Sb624, calculating VS30V S30 :

[0149]

[0150] Sb7, starting the mobile seismic source vehicle again, repeating steps Sb2-Sb6 to obtain measurement results of multiple shot points, splicing the measurement results of adjacent two shot points, and performing smoothing processing to generate a two-dimensional shear wave velocity profile along the survey line;

[0151] Sb8, using the multi-dimensional evaluation index and the borehole and shallow reflection data to calibrate and compare the generated two-dimensional shear wave velocity profile, and outputting a calibrated and compared result report.

[0152] In this embodiment, the multi-dimensional evaluation index includes a root mean square error and a coherence.

[0153] Experimental example

[0154] Table 1 site classification

[0155] Site category VS30 range (m / s) Typical ground Class A >800 Hard rock Class B 360-800 Harder rock / dense sand Class C 180-360 Medium dense sand / clay Class D 120-180 Loose sand / soft clay Class E <120 Very soft clay / liquefiable strata

[0156] As Figure 2 shown, the test application described in the present application was performed on a soil road with a length of about 120m. In this experimental example, the following parameters were set: a trace interval of 1m, a shot interval of 60m, a shot stacking of 2 times per point, a sampling rate of 1000Hz, and a recording length of 1.5s. A single-shot record profile as Figure 3 shown was obtained, with a minimum offset of 5m, a trace interval of 1m, and a streamer arrangement length of about 60m. A group of Rayleigh wave signals with relatively strong amplitude and fan-shaped spreading with distance was observed. The obtained fundamental Rayleigh wave dispersion curve frequency range was about 4-30Hz. After joint inversion as Figure 4 shown, a shear wave velocity profile in the depth range of 0-30m was calculated as Figure 5 shown. The calculated VS30 at each survey point along the survey line was about 210m / s-240m / s, and according to the current site classification standard, the soil site classification of the survey area was determined to be class C.

[0157] It should be pointed out finally that the above examples are only used to illustrate the technical solutions of the present application but not to limit it, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can still be modified or replaced equivalently, and these modifications or equivalent replacements should not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. Design method of integrated mobile VS30 measuring device, wherein, An integrated mobile VS30 measurement device includes a mobile seismic source vehicle and a mobile measurement array connected to the mobile seismic source vehicle via a land tow cable. The mobile measurement array consists of multiple nodal seismographs uniformly arranged on the land tow cable and slidingly coupled to the ground. The nodal seismographs communicate with a main control terminal mounted on the mobile seismic source vehicle. The device is used for constant-mileage stop-and-go excitation using the mobile seismic source vehicle. During the stopping phase, vibration signals are collected by multiple nodal seismographs and transmitted to the main control terminal for processing to calculate VS30, thereby determining the site type. The device is characterized by the following design method: Sa1, Determine the target frequency band : ； In the formula, and These represent the minimum and maximum surface wave phase velocities of the test site, respectively. and These represent the minimum and maximum detection depths, respectively. , ; Sa2, Calculate the comprehensive environmental assessment index : ； in, ； ； ； In the formula, , and All represent weighting coefficients; Indicators representing quantitative indicators of environmental disturbance intensity; Represents the power spectral density of ambient noise, and , Indicates the pre-collection time. Indicates the sampling rate. express The noise amplitude at any given moment; A quantitative index representing the obstacle density of the test site; Indicates the total number of obstacles within the survey line; Indicates the length of the survey line; This represents a quantitative indicator of flatness. This indicates the maximum elevation difference between adjacent 10m survey lines; Sa3, based on target frequency band and comprehensive environmental assessment indicators Determine the shot spacing, track spacing, and number of stacking operations.

2. The design method of the integrated mobile VS30 measuring device according to claim 1, characterized in that: The nodal seismograph is mounted on the sliding coupling assembly, which includes a clamping structure consisting of an upper clamping plate and a lower clamping plate that are fastened together. The nodal seismograph is fixed at the top of the upper clamping plate. A land tow cable is detachably clamped between the upper and lower clamping plates. Sliding coupling blocks are provided at the four corners of the lower clamping plate, and the sliding coupling blocks are in contact with the ground.

3. The design method of the integrated mobile VS30 measuring device according to claim 1, characterized in that: The main control terminal includes a power module, a data acquisition module, a processing module, and a display module. The main control terminal is electrically connected to the mobile seismic source vehicle via a vibration sensor trigger module, and the mobile seismic source vehicle is connected to the main control terminal via feedback. The mobile seismic source vehicle also integrates a seismic source triggering sensor, a GNSS timing module, and an odometer. The seismic source triggering sensor, GNSS timing module, and odometer are all connected to the data acquisition module and the processing module to determine the seismic source triggering time and spatial location of the mobile seismic source vehicle. The nodal seismograph has a built-in satellite timing module and a wireless transmission module. Both the nodal seismograph and the satellite timing module communicate with the processing module via the wireless transmission module and the data acquisition module, respectively. The processing module is connected to the display module.

4. The design method of the integrated mobile VS30 measuring device according to claim 1, characterized in that: The gun spacing mentioned in step Sa3 This refers to the distance between two adjacent earthquake source locations, and its expression is as follows: ； In the formula, This represents the minimum surface wave wavelength corresponding to the target frequency band, and , Indicates the target frequency band The upper limit; Indicates the length of the land-based tow cable; Lane spacing The distance between two adjacent nodal seismographs on a land-based towed cable: ； Stacking times The number of times the same shot is fired repeatedly and the results are superimposed: ； In the formula, This represents the minimum signal-to-noise ratio required to retrieve the dispersion curve; This represents the signal-to-noise ratio of a single excitation; This represents the function for rounding up.

5. A measurement method for an integrated mobile VS30 measuring device, characterized in that: Includes the following steps: Sb1, Array initialization: Install nodal seismometers on the land tow cable according to the set trace spacing, and set the shot spacing, stacking times, sampling rate and recording length; Sb2, Equidistant Moving Excitation: Start the mobile seismic source vehicle and move it along the survey line until the preset shot spacing is reached and then stop. Determine that the shot point has been reached. At this time, use the odometer to record the current mileage coordinates and elevation data. Sb3. Construct a short-time static array: After a set static time, the main control terminal sends an excitation command to the mobile seismic source vehicle. After the mobile seismic source vehicle executes the excitation command, it sends a trigger signal back to the main control terminal. At the same time, the nodal seismometer collects vibration signals. Sb4. Repeat step Sb3 after a set time interval to obtain multiple vibration data, and then superimpose the vibration signals. Sb5. Extract surface wave features from the superimposed signal in step Sb4 to generate a dispersion energy map, and then perform curve picking on the dispersion energy map to generate a basic or higher-order curve. Sb6. Based on the basic or higher-order curves, the GLM-XGBoost algorithm is used to perform one-dimensional layered shear wave velocity joint inversion to obtain the shear wave velocity profile at a depth of 0-30m and VS30. Sb7. Restart the mobile seismic source vehicle and repeat steps Sb2-Sb6 to obtain measurement results from multiple shot points. Then, stitch together the measurement results from two adjacent shot points and perform smoothing to generate a two-dimensional shear wave velocity profile along the survey line. Sb8. The generated two-dimensional shear wave velocity profile is calibrated and compared using multi-dimensional evaluation indicators and borehole and shallow reflection data, and a calibration and comparison result report is output.

6. The measurement method of the integrated mobile VS30 measuring device according to claim 5, characterized in that: Step Sb4 specifically includes the following steps: Sb41, No. Time-domain signal after superposition of secondary vibration signals as follows: ； in, ； In the formula, Indicates the first The original time-domain signal that was excited; Indicates the useful signal of the surface wave; Indicates random noise signal; Sb42, Calculate the first Signal-to-noise ratio of the time-domain signal after superposition of secondary vibration signals : ； In the formula, Indicates the peak amplitude of the surface wave signal; This represents the peak noise amplitude before the surface wave arrives; Sb43. Determine whether the following conditions are met: If satisfied, output Otherwise, return to step Sb41, where, This indicates that the signal-to-noise ratio threshold is set.

7. The measurement method of the integrated mobile VS30 measuring device according to claim 6, characterized in that: Step Sb5 specifically includes the following steps: Sb51, Signal Preprocessing: Preprocessing the superimposed vibration signal The following steps are performed sequentially: DC offset, bandpass filtering, inter-channel amplitude equalization, and filter enhancement. The filter enhancement expression is as follows: ； In the formula, Represents frequency The corresponding surface wave energy; Indicates the record length; Indicates the time-varying filter window; Sb52, regarding the pre-processed vibration signal Perform frequency-wavenumber analysis to calculate different frequencies Phase velocity below Generate a dispersion energy map: ； In the formula, Represents frequency The corresponding wavelength; Indicates the shear wave velocity; Sb53. Determine whether there is a secondary energy ridge in the high-frequency band of the dispersion energy map. If so, pick the higher-order branch to obtain the higher-order curve; otherwise, pick the continuous ridge line with the strongest energy in the dispersion energy map to obtain the basic-order curve.

8. The measurement method of the integrated mobile VS30 measuring device according to claim 7, characterized in that: Step Sb6 specifically includes the following steps: Sb61. Based on the geological data of the site to be tested, a one-dimensional layered shear wave velocity initial model is constructed. Joint inversion using Sb62 and GLM-XGBoost algorithms; Sb621, GLM inversion: using phase velocity For the observations, the following linear prediction model is constructed: ； In the formula, Indicates the intercept; Indicates the first Layer shear wave velocity The coefficient, and , Represents the variance of the coefficients. ; Indicates the error term, and , Indicates the error variance. ; Indicates the total number of floors; Then, MCMC simulation was used to perform posterior distribution sampling and convergence determination, and the posterior mean of shear wave velocity for each layer was obtained from the converged MCMC samples. And the corresponding 95% confidence interval; Sb622, XGBoost inversion: using GLM inversion results Using the initial input values, the frequency-phase velocity-layer thickness relationship is analyzed using the XGBoost algorithm. The nonlinear relationship is fitted to output the optimized shear wave velocity for each layer. ; The input feature matrix of the XGBoost algorithm , Indicates the first The thickness after layer standardization; Indicates the characteristics of propagation time, and , Indicates the first The layer thickness; the output label is the theoretical phase velocity corresponding to each frequency point. Objective function as follows: ； In the formula, Represents the fitting loss term. Denotes the loss function, and , Indicates the first Observed phase velocity at each frequency point Indicates the number of valid frequency points; Represents the regularization term. The penalty coefficient represents the number of leaf nodes in the decision tree. This represents the L2 penalty coefficient for the leaf node weights. Indicates the first The weight of each leaf node, Indicates the total number of leaf nodes; This represents the Bayesian prior constraints. Indicates the constraint strength coefficient. express Standard deviation; Sb623, Take the posterior mean of GLM. The corresponding 95% confidence interval serves as an uncertainty constraint, and the XGBoost output... As the optimal solution, a 0-30m shear wave velocity profile is generated; Sb624, Calculate VS30 : 。

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