CN109541025B

CN109541025B - Time domain superposition surface wave detection method based on pseudo-random signal

Info

Publication number: CN109541025B
Application number: CN201811416305.5A
Authority: CN
Inventors: 姜文龙; 马若龙; 谢向文; 郭玉松; 刘现锋; 毋光荣
Original assignee: Yellow River Engineering Consulting Co Ltd
Current assignee: Yellow River Engineering Consulting Co Ltd
Priority date: 2018-11-26
Filing date: 2018-11-26
Publication date: 2021-03-23
Anticipated expiration: 2038-11-26
Also published as: CN109541025A

Abstract

The invention discloses a time domain superposition surface wave detection method based on a pseudorandom signal, which comprises the following steps of 1, acquiring the pseudorandom signal, wherein the acquired pseudorandom signal has directivity, and the pseudorandom signal is distributed in a full frequency band or within a frequency band range of 1Hz-1000 Hz; the pseudo-random signal is obtained by the mode of vibration noise of an automobile, the mode of vibration noise of river flow with the flow velocity more than 2m/s or the mode of vibration noise of artificial loading; step 2, carrying out t-p transformation on the obtained pseudo-random signal to obtain a signal of a time-speed domain; and 3, superposing the obtained time-velocity domain signals in a time-velocity domain, namely performing Fourier transform in the time domain, converting the time domain into a frequency domain, and obtaining frequency-velocity domain signals. The invention has the advantages of high detection precision, good consistency, high precision and capability of being used as an effective test means for detection, and the errors of the speed obtained by testing at different times at the same point are less than 10 percent.

Description

Time domain superposition surface wave detection method based on pseudo-random signal

Technical Field

The invention relates to engineering investigation and engineering quality nondestructive inspection, in particular to a time domain superposition surface wave detection method based on a pseudorandom signal.

Background

In engineering investigation and engineering quality nondestructive testing, the wave velocity is an important and stable parameter, the characterization of the geological structure and the characterization of the target body characteristics are less affected by external interference, and the obtained signal is stable, so that the method is an important detection and detection means. Particularly, in nondestructive testing of engineering quality, if the speed of the relevant engineering is not changed greatly due to factors such as external climate and environment, the speed is stable, and therefore, the evaluation of the engineering quality by using the speed is also an important testing technology, such as evaluation of backfill grouting quality by using the improvement of the speed.

The surface wave is an important means for obtaining the velocity distribution in a certain depth underground without damage through the ground, and the current common methods are hammering transient surface wave detection and natural source surface wave detection, but both have certain problems and are not enough to meet the related requirements on the detection at present.

In the aspect of transient surface waves, common explosives are not applied to surface wave detection any more, the effective depth of a hammering surface wave detection technology is generally smaller than 30m, particularly the effective depth in a soil layer is generally smaller than 20m, and a related frequency dispersion spectrum is wide, so that the depth speed pickup is very unstable, and the application in engineering is greatly limited.

In the aspect of the natural source surface wave technology, although the detection depth is large, the arrangement of an observation system is complex, three-dimensional arrangement is generally required, and the arrangement has extremely high requirement on coordinates, slow arrangement time and high requirement on observation time. The natural source surface wave detection of one point is generally more than 1h, and the arrangement is not satisfactory in most fields. If the quasi-linear arrangement mode and other modes are adopted, certain errors exist in the acquiring speed in theory and practice, and the technology cannot be popularized in a large scale in the practical engineering investigation and quality detection application process.

Disclosure of Invention

The invention aims to provide a time domain superposition surface wave detection method based on a pseudo-random signal.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention discloses a time domain superposition surface wave detection method based on a pseudo-random signal, which comprises the following steps:

step 1, acquiring a pseudorandom signal, wherein the acquired pseudorandom signal must have directionality, and the pseudorandom signal is distributed in a full frequency band or the frequency band range is within 1Hz-1000 Hz; the pseudo-random signal is obtained by the mode of vibration noise of an automobile, the mode of vibration noise of river flow with the flow velocity more than 2m/s or the mode of vibration noise of artificial loading;

step 2, carrying out t-p transformation on the obtained pseudo-random signal to obtain a signal of a time-speed domain;

and 3, superposing the obtained time-velocity domain signals in a time-velocity domain, namely performing Fourier transform in the time domain, converting the time domain into a frequency domain, and obtaining frequency-velocity domain signals.

The flow velocity is more than 2m/s, and the vibration noise of the river flow is between 0.5Hz and 50 Hz.

The advantages of the invention are embodied in the following aspects:

(1) the comprehensive advantages of the detection efficiency and the detection depth are great: in the aspect of traditional detection work, certain contradiction generally exists between the detection depth and the detection efficiency. For example, the hammering transient surface wave technology has high detection efficiency but shallow detection depth, and the natural source surface wave has large detection depth but very low detection efficiency, but the invention better solves the contradiction.

Compared with the traditional hammering transient surface wave detection, for example, in a soil layer with approximate transverse wave velocity of about 150m/s-300m/s, the effective detection depth of the conventional hammering transient surface wave is generally less than 20m, and the effective detection depth of the invention is between 60m and 70 m. In the relevant rock strata, the relevant detection depth can exceed hundreds of meters according to the arrangement size, but the working efficiency is not reduced too much.

Compared with the natural source surface wave technology with larger detection depth, the invention obviously improves the observation efficiency. If the observation error of a natural source is smaller, three-dimensional arrangement needs to be arranged, the acquisition time of one point is about 20min, and the observation time of the next point after arrangement is about 1h, and the three-dimensional arrangement is not suitable in most mountainous regions and other regions, so that the practical engineering significance is not great.

(2) The detection precision is high, and the uniformity is good: generally, transient surface waves are affected by excitation energy, and the related dispersion axis is too wide, so that the picking precision of the speed is not high overall. The natural source surface wave is greatly influenced by the direction of the wave, the natural source surface wave is acquired twice at the same place, and if obvious wave propagation direction difference exists, certain errors possibly exist in the speed. The invention effectively avoids the problem, and the speed obtained by testing at different times has errors less than 10 percent at the same point, has high precision and can be used as an effective testing means for detection.

Drawings

FIG. 1 is a schematic diagram of time domain superposition of pseudorandom sources in accordance with an embodiment of the present invention.

Detailed Description

The following describes embodiments of the present invention in detail with reference to the drawings, which are implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific operation procedures are provided, but the scope of the present invention is not limited to the following embodiments.

The invention discloses a time domain superposition surface wave detection method based on a pseudorandom signal, which is carried out according to the following steps:

in step 1, fig. 1 (1), to obtain a pseudo-random signal, the signal must be directional, and preferably has a full frequency band distribution or a frequency band range between 1Hz and 1000 Hz. The pseudo-random signals are obtained in various manners, such as vibration noise of an automobile (such as low-frequency vibration noise provided by vibration of a large number of heavy trucks in Shenzhen's forepoling, and utilized in the great deep harbor avenues, the frequency is 0.5Hz-50 Hz), vibration noise of a river with a large flow rate (generally the flow rate is greater than 2 m/s) (such as Ji geophysical prospecting in the summer of Xinjiang, the flow rate of the river is generally greater than 3m/s due to the influence of a reservoir, and certain vibration is easily formed due to stones around the river, and the related vibration frequency is 3Hz-50 Hz), and vibration noise of artificial loading (such as engineering of a new banker reservoir, Jinan yellow puncture, Fumi, Sandy and the like), and broadband vibration signals of 1Hz-1000Hz are obtained by adopting artificial continuous impact seismic sources. However, this noise must be directional, otherwise the speed of acquisition is unreliable and the detection results are prone to false anomalies. Since the noise loading is not completely random, it is called a pseudo-random signal.

Step 2, as shown in fig. 1 (2), performing t-p transformation and the like to obtain a time-velocity (slowness) domain signal, where the time-velocity domain signal of one vibration shown in the block of fig. 1 (2) is consistent with the signal obtained by the conventional hammering transient surface wave detection, as shown in fig. 1 (3). The invention is characterized in that a plurality of signals are obtained, and the vibration directions of the signals are consistent, namely the speed consistency is high, so that the signals can be effectively superposed in a time domain.

And 3, superposing the signals in a time-velocity domain, namely performing Fourier transform in the time domain, and converting the time domain into a frequency domain to obtain the frequency-velocity domain signals shown in (4) of fig. 1.

Single vibration of a pseudo-random source can carry certain high-frequency information, and the interval between random vibrations carries effective low-frequency signal information, namely a low-frequency interpolation signal; due to the high and low frequency full coverage, the full coverage of the detection depth can be effectively realized, so that the detection depth is effectively improved; and the superposition in time, external interference factors (such as external noise interference of single hammering) become smaller in principle, the speed is more stable, and therefore the precision is higher.

Claims

1. A time domain superposition surface wave detection method based on a pseudo-random signal is characterized in that: the method comprises the following steps:

step 1, acquiring a pseudorandom signal, wherein the acquired pseudorandom signal must have directionality, and the pseudorandom signal is distributed in a full frequency band; the pseudo-random signal is obtained by the mode of vibration noise of an automobile, the mode of vibration noise of river flow with the flow velocity more than 2m/s or the mode of vibration noise of artificial loading; the frequency of the relevant vibration noise is between 0.5Hz and 50 Hz;