CN112925010A - High-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method - Google Patents
High-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method Download PDFInfo
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- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
- G01V1/16—Receiving elements for seismic signals; Arrangements or adaptations of receiving elements
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- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
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- G01V1/36—Effecting static or dynamic corrections on records, e.g. correcting spread; Correlating seismic signals; Eliminating effects of unwanted energy
Abstract
The invention provides a high-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method, which comprises the following steps: from the origin O along the ray vuvkAnd sequentially selecting n exciton points in the direction, wherein the n exciton points are respectively expressed as: s1,S2...Sn(ii) a After the impact seismic source is excited at the origin O ', a delay time tau ' is passed '1Then, at exciton point S1Excitation is carried out; at exciton point S1After excitation, a delay time of τ 'is passed'2Then, at exciton point S2Excitation is carried out; and so on, at exciton point Sn‑1After excitation, a delay time of τ 'is passed'nThen, at exciton point SnExcitation is performed. The invention provides a high-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method, which adopts a dislocation delay superposition technology to realize three-dimensional space scanning of seismic beams and adopts pseudorandom coding superposition to directly aim at transmitting signalsThe noise suppression increases the detection depth of the method, improves the signal-to-noise ratio, and can realize long-distance three-dimensional geological advanced prediction of the front and peripheral areas of the tunnel face.
Description
Technical Field
The invention belongs to the technical field of advanced geological prediction of tunnels, and particularly relates to a high-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method.
Background
With the arrival of the great development period of the traffic construction in China, the construction quantity of engineering projects such as roads, railways and the like is increased dramatically. At present, the center of gravity of the construction of the traffic infrastructure of China gradually shifts to western complex geology and terrain areas, the occupation ratio of tunnel engineering is gradually increased, and the 'more, long, big and deep' becomes the general trend of tunnel development. The greatest risk of the tunnel engineering is caused by geological disasters such as collapse, water burst and mud burst easily caused by geological disasters such as fault broken zones, karst cavities, water-containing bodies and other bad geological bodies in front of and around the tunnel in tunnel construction, which can cause huge threats to the construction safety of the tunnel engineering, particularly the risks of sudden geological disasters of the tunnel engineering under complex geological conditions are very large, once the disasters occur, the construction progress is delayed slightly, and the safety of constructors is threatened seriously. Therefore, advance forecasting of tunnel geology is an essential important link in tunnel construction.
Under the drive of the high-speed development of tunnel geological advanced prediction technology, the traditional detection methods such as advanced drilling detection, advanced pit guiding and the like belong to destructive methods, the workload is large, the time is wasted, the obtained data are only limited in front of the tunnel face, and the requirements of engineering construction efficiency and the requirements of exploring the geological hidden danger in the peripheral range of the tunnel in a complex geological environment are not met. Therefore, the seismic exploration method utilizing the elastic wave reflection principle is better applied and developed in the advance forecasting of tunnel geology, has the characteristics of wide detection range, large depth, convenient and quick operation and the like, and is a geological advance forecasting method mainly applied to tunnel construction at present.
However, the current seismic geological advanced prediction method still has the following problems to be improved urgently:
(1) seismic source optimization
At present, an explosion source or a hammering source is mostly adopted for tunnel earthquake geological advanced prediction, the explosion source needs to be arranged by drilling holes in the side wall of a tunnel, the depth generally needs to be 1.5-2 m, and the explosion source generally adopts an electric detonator and waterproof emulsion explosive. This method is not essentially out of the scope of destructive methods and is therefore inefficient, as shown in figure 1, which is a schematic diagram of the TSP detection principle. Although the hammer seismic source does not need to be punched, the energy is weak, the frequency band range is narrow, the received signal is unclear, and effective information is easy to be annihilated in noise. A comparison of the relevant parameters for the explosive source and the hammering source can be seen in table 1.
TABLE 1 comparison of parameters for explosive and hammering sources
| Explosive source | Hammering seismic source | |
| Effective frequency band range | ＜1000Hz | ＜200Hz |
| Effective depth of investigation | ～150m | ＜50m |
| Seismic source delay error | 0.1～2ms | Is free of |
In addition, in a tunnel environment, space limitation causes that the traditional seismic geological advanced forecasting method is too single in the aspect of data acquisition mode compared with ground seismic exploration, so that the method generally has the defects of low resolution, serious energy attenuation, incapability of identifying water-containing bodies, incapability of performing qualitative judgment on faults and broken zones and the like.
(2) Influence of noise
The tunnel environment inevitably brings a great deal of noise interference, and the influence of the noise on the advance prediction of earthquake geology mainly lies in: 1) the judgment of the first arrival time of the seismic waves is influenced, and the final analysis of the whole geological advanced prediction result is further influenced; 2) the accuracy of velocity analysis is directly reduced, and meanwhile, the quality of seismic migration imaging is also influenced, so that misjudgment on the position and range of the unfavorable geological body is caused. Therefore, suppression of noise in seismic geological advanced prediction signal processing has been a hot spot and a focus of research of worldwide scholars.
The currently commonly used seismic geological advanced prediction signal denoising method mainly focuses on denoising a received signal, namely, recording a signal waveform and then performing denoising processing, such as high-frequency filtering, f-k (frequency-wave number) filtering, wavelet transformation, S transformation, Hilbert transformation and the like, and few researches on directly denoising a transmitted signal are performed.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a high-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method, which can effectively solve the problems.
The technical scheme adopted by the invention is as follows:
the invention provides a high-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method, which comprises the following steps:
Wherein, a three-component detector is respectively arranged at the vault center point position, the tunnel arch waist left side position and the tunnel arch waist right side position of the acquisition section; therefore, the three-component detectors are arranged in a three-dimensional observation mode;
at an arbitrary u-th trigger profile DM u1,2,.. w, three excitation points are selected, which are respectively: excitation point No. 1P u12 nd excitation point Pu2And 3 rd excitation point Pu3(ii) a Wherein the 1 st excitation point Pu1Is the dome center point excitation point, 2 nd excitation point Pu2The excitation point at the left side of the arch waist, the 3 rd excitation point Pu3Is the excitation point on the right side of the arch waist; three excitation points are arranged in a three-dimensional observation mode; u-th trigger profile DMuIs denoted as the v-th excitation point Puv，v＝1,2,3；
Arranging a seismic impact seismic source at each excitation point;
step 4, according to the 1 st trigger section DM 12 nd trigger profile DM2,., Wth trigger profile DMwAnd for an arbitrary u-th trigger profile DMuFrom the 1 st excitation point P u12 nd excitation point Pu2And 3 rd excitation point Pu3Sequentially exciting the excitation points of each trigger section by adopting an earthquake impact source, scattering and reflecting the excited source wavelets by an underground medium, detecting by a three-component detector of the acquisition section, and uploading to a master station;
wherein for an arbitrary u-th trigger profile DMuExcitation point of (v) PuvThe method comprises the following steps of exciting through a seismic impact seismic source:
step 4.1, at excitation Point PuvConstructing a plane rectangular coordinate system XOZ facing to the top of the tunnel, wherein an origin O is at an excitation point PuvA location; the X axis is parallel to the axial direction of the tunnel and points to the palm surface direction; the Z axis is as follows: u-th trigger profile DMuAt the excitationPoint PuvThe tangential direction of the position points to the top direction of the tunnel;
in the XOZ plane according to the excitation point PuvDetermining the angle of the focus source energy required by the azimuth relation between the target and the tunnel abnormal body detection target
Enabling the direction of the energy of the focus seismic source to point to a detection target of the tunnel abnormal body; wherein k is 1, 2.., b; namely: b angles needed to focus the source energy can be determined
Then, in the XOZ plane, a ray v is taken through the origin OuvkLet a ray vuvkAt an angle equal to the angle of the X-axis
Wherein the ray vuvkNamely, the array combined rays which need to form an equivalent phased array seismic source on the XOZ plane;
step 4.2, follow ray v from origin OuvkAnd sequentially selecting n exciton points in the direction, wherein the n exciton points are respectively expressed as: s1,S2,...,Sn(ii) a Wherein the exciton spot S1A distance d from the origin O1Exciton spot S2To the exciton spot S1A distance of d2And so on, the exciton point S is excitednTo the exciton spot Sn-1A distance of dn(ii) a Thus, for an arbitrary exciton spot S i1,2, n, with a corresponding movement distance di；
After the impact seismic source is excited at the origin O ', a delay time tau ' is passed '1Then, at exciton point S1Excitation is carried out; at exciton point S1After excitation, a delay time of τ 'is passed'2Then, at exciton point S2Excitation is carried out; and so on, at exciton point Sn-1After excitation, a delay time of τ 'is passed'nThen, at exciton point SnExcitation is carried out; thus, for arbitrary exciton spotsS i1,2, n, which is relative to the previous neighboring exciton point Si-1Is τ'i；
Wherein the exciton spot SiRelative to the previous adjacent exciton spot Si-1Of delay time τ'iIs determined by:
step 4.2.1, determining an azimuth angle theta' of the seismic source energy to be focused according to the azimuth relation between the XOZ plane and the tunnel abnormal body detection target; wherein, theta' is an included angle between the energy direction of the main beam of the seismic source and the XOZ plane;
step 4.2.2, according to the following formula, the delay calculation time tau between adjacent impact seismic sources is calculatedi：
Wherein:
k is the wave number;
f is the frequency of the impact seismic source;
viis the wave velocity;
step 4.2.3, aiming at the interference of noise, introducing a dynamic seismic source coding strategy while applying delay superposition to an equivalent phased array artificial seismic impact seismic source, thereby finally realizing the high-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method for directly decoupling and denoising a transmitting signal;
in particular, due to the random delay Δ τiAn impulse source superposition greater than 1/(4 λ) will cause the waveform of the equivalent phased array impulse source to be distorted, thus given the range of variation of Δ τ: 0 is less than or equal to | delta tau i1/(4 lambda) is less than or equal to | l; wherein λ is the wavelength of the impact seismic source;
at 0 ≦ Δ τiRandomly selecting random delay delta tau within the range of less than or equal to 1/(4 lambda)iAnd removing the random delay delta tauiCorrelation between them, obtaining a correlation-free Delta tau1,Δτ2,...,Δτn；
Step 4.2.4, calculating the time tau according to the delay obtained in step 4.2.2iAnd a step of4.2.3 random delay DeltatauiObtaining an exciton point S according to the following formulaiRelative to the previous adjacent exciton spot Si-1Of delay time τ'i：
τ′i＝τi+Δτi
Step 4.3, for each excitation point PuvIn the determination of the ray vuvkAfter that, the impact seismic source is excited at the origin O, and a delay time tau 'is passed'1Distance d of movement1Thereby moving to the exciton spot S1At exciton point S1Excitation; then, a delay time τ 'elapses'2Distance d of movement2Thereby moving to the exciton spot S2At exciton point S2Excitation; and so on, at exciton point Sn-1Excitation; then, a delay time τ 'elapses'nThen, move by a distance dnThereby moving to the exciton spot SnAt exciton point SnExcitation;
thereby in the ray vuvkSeismic wavelets with the same frequency and waveform are generated at different positions of the excitation sub-points, an equivalent phased array seismic source is formed after superposition, the equivalent phased array seismic source is used as excitation to carry out three-dimensional geological advanced prediction, and the larger detection depth and the higher detection precision are obtained.
Preferably, in step 4.2.3, a correlation-free Δ τ is obtained by the following method1,Δτ2,...,Δτn：
Randomly sampling the random delay variable delta tau for n times, and sequentially obtaining random sampling values as follows: x1,1,X1,2,...,X1,n；X1,1,X1,2,...,X1,nForm vector X ═ X1,1,X1,2,...,X1,n)T(ii) a Wherein, the superscript T represents the rank of the matrix;
let Z1,nIs a 1 x n vector with all elements 1;
calculating T according to the following formula0＝(Δτ1,Δτ2,...,Δτn)T
Wherein: d is an intermediate matrix;
thus obtaining a.DELTA.tau without correlation1,Δτ2,...,Δτn。
The high-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method provided by the invention has the following advantages:
the invention provides a high-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method, which adopts a staggered delay superposition technology to realize three-dimensional space scanning of seismic beams, adopts pseudo-random coding superposition to directly suppress noise of a transmitting signal, increases the detection depth of the method, improves the signal-to-noise ratio, and can realize long-distance three-dimensional geological advanced prediction of the front and peripheral areas of a tunnel face.
Drawings
Fig. 1 is a schematic diagram of a TSP detection principle provided in the prior art;
FIG. 2 is a schematic diagram of the arrangement principle of the high-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method provided by the invention;
FIG. 3 is a schematic plan view of a three-dimensional directional seismic source principle;
FIG. 4 is a schematic cross-sectional view of a three-dimensional directional seismic source
FIG. 5 is a diagram of the effect of seismic source superposition for different phase differences;
FIG. 6 is a diagram of the effect of seismic source superposition for different phase differences;
FIG. 7 is a diagram of the effect of seismic source superposition for different phase differences;
FIG. 8 is a diagram of the effect of seismic source superposition for different phase differences;
FIG. 9 is a diagram of the denoising effect of an encoding phased array impact seismic source;
FIG. 10 is a diagram of the denoising effect of an encoding phased array impact seismic source;
FIG. 11 is a diagram of the denoising effect of an encoding phased array impact seismic source.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The seismic source excitation method based on the phased array technology provided by the invention realizes three-dimensional space scanning of seismic beams by adopting a staggered delay superposition technology, realizes suppression of noise directly aiming at a transmitted signal by adopting pseudo-random coding superposition, increases the detection depth of the method, improves the signal-to-noise ratio, can realize long-distance three-dimensional geological advanced prediction on the front and peripheral areas of a tunnel face, forms high-resolution three-dimensional imaging of a geological abnormal body, and provides technical support for optimization of a construction scheme and guarantee of construction safety.
Referring to fig. 2, the invention provides a high-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method, which comprises the following steps:
For example, a collection section is arranged at the position 40m away from the tunnel face of the tunnel; and (3) arranging trigger sections at a position 5m away from the acquisition section near the tunnel face of the tunnel, arranging the trigger sections in a three-dimensional observation mode, arranging one trigger section at intervals of 3m, and arranging the last trigger section at a distance of 3-5 m from the tunnel face.
Wherein, a three-component detector is respectively arranged at the vault center point position, the tunnel arch waist left side position and the tunnel arch waist right side position of the acquisition section; therefore, the three-component detectors are arranged in a three-dimensional observation mode;
at an arbitrary u-th trigger profile DM u1,2,.. w, three excitation points are selected, which are respectively: excitation point No. 1P u12 nd excitation point Pu2And 3 rd excitation point Pu3(ii) a Wherein, 1 st laserHair point Pu1Is the dome center point excitation point, 2 nd excitation point Pu2The excitation point at the left side of the arch waist, the 3 rd excitation point Pu3Is the excitation point on the right side of the arch waist; three excitation points are arranged in a three-dimensional observation mode; u-th trigger profile DMuIs denoted as the v-th excitation point Puv，v＝1,2,3；
Arranging a seismic impact seismic source at each excitation point;
that is, the invention uses artificial earthquake impact seismic sources as trigger points to excite each trigger section, each trigger section excitation point is 3 points, the excitation points are distributed on both sides of the tunnel arch and the center point of the arch crown, the seismic source wavelet is scattered and reflected by underground medium, the response signal is measured on the tunnel wall, recorded by the acquisition station and then uploaded to the master station.
step 4, according to the 1 st trigger section DM 12 nd trigger profile DM2,., Wth trigger profile DMwAnd for an arbitrary u-th trigger profile DMuFrom the 1 st excitation point P u12 nd excitation point Pu2And 3 rd excitation point Pu3Sequentially exciting the excitation points of each trigger section by adopting an earthquake impact source, scattering and reflecting the excited source wavelets by an underground medium, detecting by a three-component detector of the acquisition section, and uploading to a master station;
wherein for an arbitrary u-th trigger profile DMuExcitation point of (v) PuvThe method comprises the following steps of exciting through a seismic impact seismic source:
step 4.1, at excitation Point PuvConstructing a plane rectangular coordinate system XOZ facing to the top of the tunnel, wherein an origin O is at an excitation point PuvA location; the X axis is parallel to the axial direction of the tunnel and points to the palm surface direction; the Z axis is as follows: u-th trigger profile DMuAt excitation point PuvTangential to the positionThe direction is pointed to the top direction of the tunnel;
in the XOZ plane according to the excitation point PuvDetermining the angle of the focus source energy required by the azimuth relation between the target and the tunnel abnormal body detection target
Enabling the direction of the energy of the focus seismic source to point to a detection target of the tunnel abnormal body; wherein k is 1, 2.., b; namely: b angles needed to focus the source energy can be determined
Then, referring to fig. 3, a schematic plan view of a principle of a three-dimensional directional seismic source is shown; referring to fig. 4, a schematic cross-sectional view of a three-dimensional directional seismic source is shown. In the XOZ plane, a ray v is taken through the origin OuvkLet a ray vuvkAt an angle equal to the angle of the X-axis
Wherein the ray vuvkNamely, the array combined rays which need to form an equivalent phased array seismic source on the XOZ plane;
step 4.2, follow ray v from origin OuvkAnd sequentially selecting n exciton points in the direction, wherein the n exciton points are respectively expressed as: s1,S2,...,Sn(ii) a Wherein the exciton spot S1A distance d from the origin O1Exciton spot S2To the exciton spot S1A distance of d2And so on, the exciton point S is excitednTo the exciton spot Sn-1A distance of dn(ii) a Thus, for an arbitrary exciton spot S i1,2, n, with a corresponding movement distance di；
After the impact seismic source is excited at the origin O ', a delay time tau ' is passed '1Then, at exciton point S1Excitation is carried out; at exciton point S1After excitation, a delay time of τ 'is passed'2Then, at exciton point S2Excitation is carried out; and so on, at exciton point Sn-1After excitation, a delay time of τ 'is passed'nThen, at exciton point SnExcitation is carried out; thus, for an arbitrary exciton spot S i1,2, n, which is relative to the previous neighboring exciton point Si-1Is τ'i；
Wherein the exciton spot SiRelative to the previous adjacent exciton spot Si-1Of delay time τ'iIs determined by:
step 4.2.1, determining an azimuth angle theta' of the seismic source energy to be focused according to the azimuth relation between the XOZ plane and the tunnel abnormal body detection target; wherein, theta' is an included angle between the energy direction of the main beam of the seismic source and the XOZ plane;
step 4.2.2, according to the following formula, the delay calculation time tau between adjacent impact seismic sources is calculatedi：
Wherein:
k is the wave number;
f is the frequency of the impact seismic source;
viis the wave velocity;
the derivation process of the above equation is:
the direction of the main beam capability of the phased array seismic source can be changed by changing the phase difference of adjacent impact seismic sources, and if the main beam of the seismic source is strongest in the theta' direction, the following steps are required:
kdicosθ′+β＝0
according to the time difference relation between the phase delay and the impact seismic source, beta is 2 pi f tauiThe following can be obtained:
if the zero phase delay superposition (i.e. β is 0) is adopted at this time, the direction of energy enhancement of the main beam of the seismic wave is fixed to be 90 ° (perpendicular to the ZX plane).
Step 4.2.3, aiming at the interference of noise, introducing a dynamic seismic source coding strategy while applying delay superposition to an equivalent phased array artificial seismic impact seismic source, thereby finally realizing the high-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method for directly decoupling and denoising a transmitting signal;
in particular, due to the random delay Δ τiAn impulse source superposition greater than 1/(4 λ) will cause the waveform of the equivalent phased array impulse source to be distorted, thus given the range of variation of Δ τ: 0 is less than or equal to | delta tau i1/(4 lambda) is less than or equal to | l; wherein λ is the wavelength of the impact seismic source;
at 0 ≦ Δ τiRandomly selecting random delay delta tau within the range of less than or equal to 1/(4 lambda)iAnd removing the random delay delta tauiCorrelation between them, obtaining a correlation-free Delta tau1,Δτ2,...,Δτn；
That is, in the present invention, the random delay Δ τ is1,Δτ2,...,ΔτnAre different so as to avoid noise superposition.
Taking the Ricker wavelet as an example, the encoded impact source wavelet can be represented as:
en＝[1-2(πf0(t-Δτ))2]exp(-(πf0(t-Δτ))2)
wherein: t is the time of the source wavelet, f0Is the seismic source dominant frequency.
Calculating the Pearson product moment correlation coefficient of the random time delay of each wavelet of the phased array impact seismic source:
wherein:
Fig. 5, 6, 7 and 8 are diagrams of the superposition effect of the seismic sources with different phase differences;
as a specific implementation, a correlation-free Δ τ is obtained by the following method1,Δτ2,...,Δτn：
Randomly sampling the random delay variable delta tau for n times, and sequentially obtaining random sampling values as follows: x1,1,X1,2,...,X1,n；X1,1,X1,2,...,X1,nForm vector X ═ X1,1,X1,2,...,X1,n)T(ii) a Wherein, the superscript T represents the rank of the matrix;
let Z1,nIs a 1 x n vector with all elements 1;
calculating T according to the following formula0＝(Δτ1,Δτ2,...,Δτn)T
Wherein: d is an intermediate matrix;
thus obtaining a.DELTA.tau without correlation1,Δτ2,...,Δτn。
Step 4.2.4, calculating the time tau according to the delay obtained in step 4.2.2iAnd the random delay delta tau obtained in step 4.2.3iObtaining an exciton point S according to the following formulaiRelative to the previous adjacent exciton spot Si-1Of delay time τ'i：
τ′i＝τi+Δτi
Step 4.3, for each excitation point PuvIn the determination of the ray vuvkAfter that, the impact seismic source is excited at the origin O, and a delay time tau 'is passed'1Distance d of movement1Thereby moving to the exciton spot S1At exciton point S1Excitation; then, a delay time τ 'elapses'2Distance d of movement2Thereby moving to the exciton spot S2At exciton point S2Excitation; and so on, at exciton point Sn-1Excitation; however, the device is not suitable for use in a kitchenAfter that, a delay time τ 'elapses'nThen, move by a distance dnThereby moving to the exciton spot SnAt exciton point SnExcitation;
thereby in the ray vuvkSeismic wavelets with the same frequency and waveform are generated at different positions of the excitation sub-points, an equivalent phased array seismic source is formed after superposition, the equivalent phased array seismic source is used as excitation to carry out three-dimensional geological advanced prediction, and the larger detection depth and the higher detection precision are obtained.
Fig. 9, fig. 10 and fig. 11 are diagrams of denoising effects of coding phased array impact seismic sources;
the method adopts a time delay superposition method to control the energy focusing direction of an equivalent phased array seismic source, so as to form scanning observation of a three-dimensional space; changing the ray vuvkAngles in ZX plane, i.e. changing angles
The equivalent phased array seismic source scanning measurement of energy focusing in any direction in the three-dimensional space can be realized.
Suppose in a linear observation system, along ray vuvkWith n exciton spots S1,S2,...,SnEach exciton has m tracks of record, the exciton point SiAnd the jth signal rijThe expression of (t) is:
rij(t),(i＝1,2…,n；j＝1,2,…,m)
after the seismic wave is oriented by the time delay superposition technology, the j-th seismic signal Rj(t) can be expressed as:
from the above equation, the energy of the j-th channel signal is enhanced in a certain direction. According to the formula, all the track signals after orientation can be obtained, and therefore, the oriented seismic wave record with energy enhancement in one direction is obtained.
And analyzing the sampled data through a host control terminal, and acquiring the position and scale of the poor geologic body in front of the tunnel face to realize three-dimensional imaging tunnel geology advanced prediction.
The invention provides a high-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method, which has the following advantages:
1) the detection method is convenient to operate and visual in result.
2) The method obtains the equivalent phased array seismic sources and excites the equivalent phased array seismic sources to synthesize seismic waves by arranging a plurality of manual impact seismic sources on the side wall of the tunnel, the main beam direction of the seismic waves is controllable, reflected waves are generated after geological abnormality occurs, and the reflected waves are received by a plurality of three-component detectors arranged on the side wall of the tunnel to carry out three-dimensional imaging on geological conditions in front of tunnel construction and around the tunnel construction so as to realize accurate advanced prediction.
3) The method can effectively overcome the problems of weak received signals and shallow detection distance of the traditional geological advanced prediction, and realizes the ultra-long-distance geological prediction through energy focusing.
4) According to the method, the suppression of noise is realized through the shocker seismic source coding technology, so that the speed analysis result is more accurate, the three-dimensional imaging result is clearer, the geological forecast interpretation is more accurate, and the tunnel construction safety is guaranteed.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements should also be considered within the scope of the present invention.
Claims (2)
1. A high-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method is characterized by comprising the following steps:
step 1, in front of the tunnel face, according to the direction gradually approaching the tunnel face, parallel selecting the acquisition section and the 1 st trigger section DM in turn12 nd trigger profile DM2,., Wth trigger profile DMw；
Wherein, a three-component detector is respectively arranged at the vault center point position, the tunnel arch waist left side position and the tunnel arch waist right side position of the acquisition section; therefore, the three-component detectors are arranged in a three-dimensional observation mode;
at an arbitrary u-th trigger profile DMu1,2,.. w, three excitation points are selected, which are respectively: excitation point No. 1Pu12 nd excitation point Pu2And 3 rd excitation point Pu3(ii) a Wherein the 1 st excitation point Pu1Is the dome center point excitation point, 2 nd excitation point Pu2The excitation point at the left side of the arch waist, the 3 rd excitation point Pu3Is the excitation point on the right side of the arch waist; three excitation points are arranged in a three-dimensional observation mode; u-th trigger profile DMuIs denoted as the v-th excitation point Puv，v＝1,2,3；
Arranging a seismic impact seismic source at each excitation point;
step 2, each seismic impact seismic source and each three-component detector are wirelessly connected to a master station; each seismic impact seismic source is wirelessly connected with each three-component detector;
step 3, determining a tunnel abnormal body detection target;
step 4, according to the 1 st trigger section DM12 nd trigger profile DM2,., Wth trigger profile DMwAnd for an arbitrary u-th trigger profile DMuFrom the 1 st excitation point Pu12 nd excitation point Pu2And 3 rd excitation point Pu3Sequentially exciting the excitation points of each trigger section by adopting an earthquake impact source, scattering and reflecting the excited source wavelets by an underground medium, detecting by a three-component detector of the acquisition section, and uploading to a master station;
wherein for an arbitrary u-th trigger profile DMuExcitation point of (v) PuvThe method comprises the following steps of exciting through a seismic impact seismic source:
step 4.1, at excitation Point PuvConstructing a plane rectangular coordinate system XOZ facing to the top of the tunnel, wherein an origin O is at an excitation point PuvA location; the X axis is parallel to the axial direction of the tunnel and points to the palm surface direction; the Z axis is as follows: u-th trigger profile DMuAt excitation point PuvThe tangential direction of the position points to the top direction of the tunnel;
in the XOZ plane according to the excitation point PuvDetermining the angle of the focus source energy required by the azimuth relation between the target and the tunnel abnormal body detection target
Enabling the direction of the energy of the focus seismic source to point to a detection target of the tunnel abnormal body; wherein k is 1, 2.., b; namely: b angles needed to focus the source energy can be determined
Then, in the XOZ plane, a ray v is taken through the origin OuvkLet a ray vuvkAt an angle equal to the angle of the X-axis
Wherein the ray vuvkNamely, the array combined rays which need to form an equivalent phased array seismic source on the XOZ plane;
step 4.2, follow ray v from origin OuvkAnd sequentially selecting n exciton points in the direction, wherein the n exciton points are respectively expressed as: s1,S2,...,Sn(ii) a Wherein the exciton spot S1A distance d from the origin O1Exciton spot S2To the exciton spot S1A distance of d2And so on, the exciton point S is excitednTo the exciton spot Sn-1A distance of dn(ii) a Thus, for an arbitrary exciton spot Si1,2, n, with a corresponding movement distance di；
After the impact seismic source is excited at the origin O ', a delay time tau ' is passed '1Then, at exciton point S1Excitation is carried out; at exciton point S1After excitation, a delay time of τ 'is passed'2Then, at exciton point S2Excitation is carried out; and so on, at exciton point Sn-1After excitation, a delay time of τ 'is passed'nThen, at exciton point SnExcitation is carried out; thus, for an arbitrary exciton spot Si1,2, n, relative to the previous phaseAdjacent exciton spot Si-1Is τ'i；
Wherein the exciton spot SiRelative to the previous adjacent exciton spot Si-1Of delay time τ'iIs determined by:
step 4.2.1, determining an azimuth angle theta' of the seismic source energy to be focused according to the azimuth relation between the XOZ plane and the tunnel abnormal body detection target; wherein, theta' is an included angle between the energy direction of the main beam of the seismic source and the XOZ plane;
step 4.2.2, according to the following formula, the delay calculation time tau between adjacent impact seismic sources is calculatedi：
Wherein:
k is the wave number;
f is the frequency of the impact seismic source;
viis the wave velocity;
step 4.2.3, aiming at the interference of noise, introducing a dynamic seismic source coding strategy while applying delay superposition to an equivalent phased array artificial seismic impact seismic source, thereby finally realizing the high-precision phased array elastic wave tunnel three-dimensional geological advanced prediction method for directly decoupling and denoising a transmitting signal;
in particular, due to the random delay Δ τiAn impulse source superposition greater than 1/(4 λ) will cause the waveform of the equivalent phased array impulse source to be distorted, thus given the range of variation of Δ τ: 0 is less than or equal to | delta taui1/(4 lambda) is less than or equal to | l; wherein λ is the wavelength of the impact seismic source;
at 0 ≦ Δ τiRandomly selecting random delay delta tau within the range of less than or equal to 1/(4 lambda)iAnd removing the random delay delta tauiCorrelation between them, obtaining a correlation-free Delta tau1,Δτ2,...,Δτn；
Step 4.2.4, calculating the time tau according to the delay obtained in step 4.2.2iAnd the random delay delta tau obtained in step 4.2.3iAccording to the following formula,obtaining an exciton point SiRelative to the previous adjacent exciton spot Si-1Of delay time τ'i：
τ′i＝τi+Δτi
Step 4.3, for each excitation point PuvIn the determination of the ray vuvkAfter that, the impact seismic source is excited at the origin O, and a delay time tau 'is passed'1Distance d of movement1Thereby moving to the exciton spot S1At exciton point S1Excitation; then, a delay time τ 'elapses'2Distance d of movement2Thereby moving to the exciton spot S2At exciton point S2Excitation; and so on, at exciton point Sn-1Excitation; then, a delay time τ 'elapses'nThen, move by a distance dnThereby moving to the exciton spot SnAt exciton point SnExcitation;
thereby in the ray vuvkSeismic wavelets with the same frequency and waveform are generated at different positions of the excitation sub-points, an equivalent phased array seismic source is formed after superposition, the equivalent phased array seismic source is used as excitation to carry out three-dimensional geological advanced prediction, and the larger detection depth and the higher detection precision are obtained.
2. The method for the three-dimensional geological advanced prediction of the high-precision phased array elastic wave tunnel according to claim 1, characterized in that in step 4.2.3, the uncorrelated Δ τ is obtained by the following method1,Δτ2,...,Δτn：
Randomly sampling the random delay variable delta tau for n times, and sequentially obtaining random sampling values as follows: x1,1,X1,2,...,X1,n；X1,1,X1,2,...,X1,nForm vector X ═ X1,1,X1,2,...,X1,n)T(ii) a Wherein, the superscript T represents the rank of the matrix;
let Z1,nIs a 1 x n vector with all elements 1;
calculating T according to the following formula0＝(Δτ1,Δτ2,...,Δτn)T
Wherein: d is an intermediate matrix;
thus obtaining a.DELTA.tau without correlation1,Δτ2,...,Δτn。
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