JP2952297B2 - Ground measurement analysis judgment system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a ground measurement analysis determination system that determines the layer structure and properties of the ground using surface waves such as Rayleigh waves and Love waves. Things.

[Prior Art] Conventionally, a measurement / analysis determination system for a ground, which determines the layer structure and properties of the ground using a surface wave such as a Rayleigh wave, as shown in FIG. A vertical vibration sensor 2a that receives the vertical component of vibration is placed at a fixed distance D (approximately 1 m) at two points on a straight line separated from the vibrator 1 (the image is about 1 m). ) Separately,
Surface waves generated on the ground by the vibration of the exciter 1 are received by the vertical vibration sensors 2a, and the vertical vibration data of the received surface wave vibrations is analyzed to determine the layer structure of the ground and its properties. It was made.

Now, when vertical vibration (frequency f) is given to the ground to be investigated by the vibration exciter 1, the vertical components of the surface wave vibration generated by the vibration exciter 1 are set at two points on a straight line with a fixed distance D. Are received by the two vertical vibration sensors 2a. When the vibrations are received by the two vertical vibration sensors 2a, first, the time difference ΔT between the waves reaching the vertical vibration sensors 2a is obtained, and the propagation velocity of the surface wave, that is, the phase velocity V is calculated as follows. Obtain from the formula.

V = D / ΔT Next, the wavelength λ of the surface wave is calculated using the phase velocity V obtained by the above equation,
And frequency f by the following equation.

λ = V / f The velocity V obtained by the above equation is the propagation velocity of the surface wave at a depth of 1/2 wavelength (the obtained wavelength λ) from the ground, and the frequency f of the applied vibration can be variously changed. For example, the wavelength λ (V-λ relation diagram, dispersion curve) for each phase velocity V is obtained, and the phase velocity V at each ground depth (1/2 wavelength) is obtained. From the velocity V, it is possible to estimate the density and layer thickness of the ground, that is, the layer structure of the ground and its properties.

[Problems to be Solved by the Invention] However, the characteristics of the ground are grasped by detecting the surface wave (Rayleigh wave) generated by the exciter 1 by the vertical vibration sensor 2a installed at a predetermined distance D. The above-described conventional example has the following problems.

A. The vibration generated by the vertical vibration is
Is a method of detecting only the vertical component of the vibration by using the method. Therefore, the vertical component of the vibration decreases depending on the properties of the ground, the frequency of the vibration generated on the ground, and the distance to the measurement point where the vibration is received ( (See the rotation trajectory of the surface wave shown in FIG. 6), and the measurement analysis becomes inaccurate. In other words, when the vertical component of the vibration at the measurement point is small, the vibration of other components from the vibration source, the running of nearby vehicles, the vibration of machinery, and other noises (noise) enter and the SN ratio (signal) / Noise ratio), it is unclear that the received wave is a surface wave such as a Rayleigh wave, and it is difficult to find the time difference between the waves transmitted between the two vertical vibration sensors.

B. Since the measurement point is located at a short distance of 1 to 2 m from the installation point of the exciter 1, it is not possible to distinguish between body waves such as P waves and S waves and surface waves, and there is a problem in measurement accuracy. is there.

C. Since the predominant vibration mode differs depending on the frequency of the vibration to be generated and the distance from the exciter 1 to the measurement point, the conventional method of receiving and analyzing only the vertical component of the vibration cannot specify the mode.

D. When vertical vibration of the ground is given, body waves such as P wave and S wave, and surface waves such as Rayleigh wave and Love wave are generated, but the wave detected by the vertical vibration sensor 2a must be a surface wave. Confirmation and judgment are not performed at the time of measurement, so the measurement and analysis data are not reliable.In addition, since only vertical vibration is measured by the vertical vibration sensor 2a, confirmation and judgment of surface wave Is impossible to do.

E. The propagation velocity of the surface wave, that is, the phase velocity V is also calculated by measuring the time when the wave generated from the vibration exciter 1 passes through the two vertical vibration sensors 2a and taking the time difference directly. Therefore, if the wave is disturbed by noise or the like, an erroneous result may be obtained.

F. Propagation velocity at each depth in the ground is also determined by an empirical and extremely uncertain method of setting the depth to 1/2 of the wavelength from the dispersion curve. , P-wave velocity, S-wave velocity, layer thickness, etc.) cannot be determined.

[Means for Solving the Problems] According to the present invention, when a surface wave such as a Rayleigh wave propagates in a horizontal multilayered ground layer, the phase velocity (propagation velocity) changes depending on the wavelength (dispersion), and By detecting and combining the horizontal and vertical components of the particle motion of the ground surface due to the transmission of vibration, it is possible to draw the rotation trajectory of the surface particle motion, and the fact that this rotation trajectory differs depending on the frequency. It provides a system that analyzes and determines the layer structure of the ground and its properties, etc., using the characteristics.In addition to installing an exciter on the ground to be investigated, At the point, a vertical vibration sensor that receives the vertical component of vibration and a horizontal vibration sensor that receives the horizontal component are installed in pairs at the same position, and the vertical component of the surface wave vibration generated on the ground by the vertical vibration of the exciter and The horizontal sensor is provided at the same position with a vibration sensor. Simultaneous reception is repeated at different frequencies, and the received vertical and horizontal vibration data are analyzed to determine the layer structure of the ground and its properties. A determination means is provided, wherein the data analysis determination means obtains from the horizontal vibration data received by the horizontal vibration sensor which is a pair with the vertical component wave obtained from the vertical vibration data received by the vertical vibration sensor. The frequency component corresponding to the exciter is extracted when confirming that the wave received by the rotation locus of the ground soil particles by the vibration propagation obtained by synthesizing the obtained horizontal component wave is a surface wave, Based on the phase difference of this frequency component, the time difference of the wave reaching the vibration sensor is obtained, the phase velocity is obtained, the wavelength is obtained, and the operation of obtaining the phase difference, the time difference, the phase velocity, and the wavelength of the wave are repeated. Performing seek dispersion curve, and performs determination of the layer structure and properties of the ground by the inverse analysis based the dispersion curve on the theory of Haskell.

[Operation] The present invention provides a system for analysis and determination, in which an exciter is installed on the ground to be investigated,
At a plurality of points on a straight line distant from the exciter, a vertical vibration sensor that receives a vertical component of vibration and a horizontal vibration sensor that receives a horizontal component are installed in pairs at the same position. A pair of vibration sensors that have the vertical and horizontal components of the surface wave vibrations generated on the ground at the same position.Repeated simultaneous reception at different frequencies, and analyze the received vertical and horizontal vibration data to A data analysis determining means for determining a layer structure and its properties is provided. In the data analysis determining means, a horizontal component paired with a vertical component wave obtained from vertical vibration data received by a vertical vibration sensor is provided. When confirming that the wave received by the rotation trajectory of the ground soil particles due to the vibration propagation obtained by combining the horizontal component wave obtained from the horizontal vibration data received by the vibration sensor is a surface wave The frequency component corresponding to the exciter is extracted, the time difference of the wave arriving at the vibration sensor is obtained based on the phase difference of the frequency component, the phase speed is obtained, and the wavelength is obtained.These phase difference, time difference, phase speed, The dispersion curve is obtained by repeatedly performing the operation for obtaining the wavelength of the wave, and the layer structure and properties of the ground are determined by inverse analysis based on Haskell's theory. Thus, the analysis and determination of the layer structure of the ground and its properties can be performed reliably and accurately.

Embodiment FIG. 1 and FIG. 2 show an embodiment of the present invention.
A vibration exciter 1 installed on the surface of the ground to be investigated vibrates vertically or horizontally with respect to the ground, and a signal generated by a signal generator (function generator) 5 (frequency f is several Hz to It is driven by a signal obtained by amplifying a standing wave such as a sine wave of several hundred Hz or a random wave) by the power amplifier 6. Note that the vibration in this case includes a shocking vibration.

2a is a vertical vibration sensor that receives the vertical component of vibration (surface waves that propagated through the ground), 2b is a horizontal vibration sensor that receives the horizontal component of vibration, and both vibration sensors 2a and 2b are speedometers.
It is formed by an accelerometer or the like, and is arranged at the same position (equidistant from the exciter 1) as a pair of sensors at points A and B on a straight line. Here, the distance D between A and B where the pair of vibration sensors 2a and 2b are installed, and the distance L between the exciter 1 and the center of the two points A and B are determined by the vibration generated as described later. Is appropriately selected and changed according to the frequency f, the type of the ground, and the like. Note that the vertical vibration sensor 2a and the horizontal vibration sensor 2b are not separately provided as described above, but may be integrated.

Reference numeral 7 denotes a signal amplifier for amplifying the detection signal output from each of the vibration sensors 2a and 2b, and the amplified detection signal is transmitted to an A / D converter (interface) 8 to a data analysis / judgment means 3 comprising a microcomputer. Has been entered.

The data analysis judging means 3 is composed of a search CPU 3a and an inverse analysis CPU 3b. The signal generated by the signal generator 5 by the search CPU 3a, the amplification of the power amplifier 6 and the signal imager 7 Etc. are D / A converters (interfaces)
9 and is controlled by a signal generator 5
, The switching of the frequency f, the switching of the signal amplification degree in the power amplifier 3 and the detection amplifier 6, and the like can be automatically performed. Also, reverse analysis CPU 3b
The analysis determination result calculated by the data analysis determination means 3
The information is displayed on a CRT built in the printer, and can be printed out by the printer 10 as needed.

The operation of the embodiment has been described above. First, the exciter 1, two pairs of vertical vibration sensors 2a and horizontal vibration sensors 2b
Are set at predetermined measurement positions. Here, the exciter 1
The distance L between the center of the two pairs of vibration sensors 2a and 2b is determined by calculating the waveform of the surface wave theoretically obtained on the measurement ground, a waveform close to the rotation locus (described later), and several meters to several tens of meters. Change in range. The distance D (A) between the two pairs of vibration sensors 2a and 2b
−distance between points B) is set in a range of several M according to the change in the wavelength λ of the surface wave to be measured.

In addition, to several measurement points that change in the range of several meters to several tens of meters,
The vibration sensors 2a, 2b are installed in pairs in advance, and the outputs of the respective vibration sensors 2a, 2b are input to the search CPU 3a via the signal amplifier 7, and the search CPU 3a controls the signal amplifier 7 to specify the signals. The vibration sensors 2a and 2b installed at the measurement points can be selectively taken in, and the measurement analysis in which the distance L between the exciter 1 and the vibration sensors 2a and 2b is changed is automatically continued. It may be performed.

Next, the exciter 1 having a constant mass is vertically vibrated by a signal (for example, a sine wave) of the frequency f generated by the signal generator 2. In this case, the frequency f is changed stepwise within a range of several Hz to several hundred Hz to measure. Instead of the vertical vibration by the vibrator 1, vibration may be performed by horizontal vibration or vibration by vertical vibration and horizontal vibration. In this case, the vibration mode can be more easily specified. And may be able to measure other modes of vibration.

Next, by the vertical vibration sensor 2a and the horizontal vibration sensor 2b installed at a fixed distance L, each position A,
The vertical and horizontal components of the surface wave vibration at B are received.
The signals received simultaneously by the two vibration sensors 2a and 2b at each point are respectively amplified by the signal amplifier 7, and the A / D converter 8 converts the analog amount into a digital amount.
Sent to U3a.

The vibration data at each frequency f sent to the data analysis determination means 3 as described above is stored in the search CPU 3a and the reverse analysis C
It is stored in the PU 3b and analyzed and analyzed in accordance with the flow procedure shown in FIG. The analyzed and analyzed results such as the measured waveform data, the dispersion curve, and the cross spectrum are displayed on the CRT of the data analysis determination means 3 and immediately printed by a printer (including an XY plotter) 10. Be out.

As described above, when the measurement at one measurement point is completed, the distance L between the vibration exciter 1 and each of the vibration sensors 2a and 2b is changed, and the same measurement operation is repeated by moving to another measurement point. Do it.

Hereinafter, the measurement, analysis, and determination operations will be described with reference to the flowchart shown in FIG. Now, the vertical component signals (A) of the vibrations received by the vibration sensors 2a and 2b at the points A and B, respectively.
v, Bv) and the horizontal component signals (Ah, Bh) are amplified by the signal amplifier 7, A / D converted, and sent to the exploration CUP 3 a as vibration data for analysis (flow,,).

Next, the exploration CPU 3a checks the vibration of the detected vibration waveform, and if the vibration is small and unsatisfactory in the analysis of the following flow, the amplification degree of the signal amplifier 7 is further increased and the detection signal is detected. And amplify (flow).

Next, FFT (calculation by fast Fourier transform) is performed (flow), cross spectrum, coherence, etc. are obtained on the frequency of the obtained data, and the vibration data obtained by A / D conversion is acquired by the exciter 1. A check (flow) is performed to determine whether the frequency corresponds to the generated frequency f. If the frequency f does not correspond to the frequency f, the flow returns to the flow, another vibration data is fetched, and the above flow is performed. Extract the ingredients. In this case, an upper limit value is set for the number of repetitions of the acquisition of the vibration data (flow-
1) If a corresponding result is not obtained even after performing a certain number of times, the above processing is performed by changing the frequency f (flow-1). In the above-described flow, the rotation trajectory of the ground surface particle motion is observed in order to confirm that the extracted frequency component wave is a surface wave such as a Rayleigh wave.

Next, in the CUP3a for exploration, 2 of the extracted frequency components
By combining the two waves, that is, the wave of the vertical component and the wave of the horizontal component, as shown in FIG. 5 and displaying them vertically or horizontally on the screen of the CRT or the printer 10, the rotation trajectory of the ground surface particle motion is obtained. (Rotation direction and vertical / horizontal vibration ratio) are drawn and observed, and it is determined whether or not the received vibration wave is a surface.

The rotation trajectories shown in FIGS. 6 (a) to 6 (d) depict the movement of a wave in a plane in which the wave propagates perpendicular to the ground when the frequency f and the distance D are changed, such as a Rayleigh wave P wave, S generated by vibration
It is not observed in other vibration propagation waves such as waves. In the drawing, R indicates reverse rotation. In this case, in a flow described later, it is determined whether or not the surface wave is a surface wave such as a Rayleigh wave by comparing with a rotational locus theoretically obtained (FIG. 6 (e)). Returning to the flow, another vibration data is taken in and the above flow is performed.

FIG. 3 is a flowchart of the subroutine sub-1. First, the phase difference φ of the vibration data of the frequency f extracted in the flow is calculated (flow-1).
ΔT = (φ / 2π) · (1 / f), both vibration sensors at points A and B
Calculate the wave time difference ΔT arriving at 2a and 2b (flow-
2). Further, the phase velocity V is obtained from the equation V = D / ΔT (flow-3), and the wavelength λ is obtained from the equation λ = V / f (flow-4).

Next, V is measured for a specific frequency f and the wavelength λ
Is calculated, a dispersion curve (phase velocity V-wavelength λ) as shown in FIG. 7 is obtained (−5), and one point of the dispersion curve is obtained.

Note that the calculation for obtaining V and λ in the above-mentioned flow of −1 or less is performed by calculating the aspect ratio from the horizontal component (horizontal) and the vertical component (vertical) of the extracted vibration data of the frequency f, and the major axis of the rotation locus synthesized. Detect and select the wave in the direction,
Further, it may be performed for each of the horizontal component and the vertical component, and may be performed by selecting a component having a clear waveform from the horizontal component and the vertical component. In addition, in this way, by obtaining the phase velocities of both the horizontal and vertical components and the rotation trajectories of a plurality of points, it is possible to confirm the degree of correspondence of whether or not the calculation results performed for each of them match, and furthermore, to obtain a plurality of orders. Since there is a possibility that the vibration mode can be measured and determined at the same time, the analysis and determination of the layer structure of the ground and its properties can be reliably performed.

By repeating the above process while changing the frequency f (flow-1), a dispersion curve (V-λ) shown in FIG. 7 is obtained, and data such as a waveform, a dispersion curve, and a rotation locus are accumulated.

When the measurement when the distance between the exciter 1 and the vibration sensors 2a and 2b is L is completed as described above, an inverse analysis based on Haskell's theory is performed on the obtained dispersion curve, and the ground Determine the layer structure and its properties.

The dispersion curve in the horizontal multilayer structure is given by the following equation according to Haskell's theory.

c = F (f: h ₁ , ρ ₁ , α ₁ , β ₁ , h ₂ , ρ ₂ α ₂ , β ₂ ,..., hn, ρn, αn, βn) f... frequency hm. (Thick number n is the lowermost layer) ρm: density at m-th layer αm: P-wave velocity at m-th layer βm: S-wave velocity at m-th layer V: variable I: measurement Number of data i: Subscript of measurement data J: Number of variables j: Subscript of variable V: Variable vector dV: Variable correction amount D: Variable correction vector P: Partial differential The matrix C of I rows and J columns to be performed... I The number of residual vectors is I, and the measured phase velocity at a certain frequency f ₁ is
_Assuming that c _ei and the theoretical phase velocity are c _i = F (f ₁ :...), the parameter is changed so as to minimize S represented by the following equation S = (c _ei −c _i ) = minimum (optimum ) Can be obtained by performing an inverse analysis.

Next, as shown in FIG. 7, the accumulated dispersion curve and rotation trajectory (including the rotation direction of the trajectory) are compared, and data such as a measured dispersion curve and a rotation trajectory to be analyzed below are fixed. In this case, if it is difficult to fix the data, the flow shifts to the flow and the measurement distance L is changed.

Here, the layer thickness, density, V _P (P wave velocity),
Assuming Vs (S-wave velocity), a theoretical Rayleigh wave dispersion curve for the assumed ground is obtained, and the ground structure is optimized such that the calculated theoretical dispersion curve matches the dispersion curve obtained by measurement. By the operation analysis of the inverse analysis program,
The stratified S-wave velocity is calculated.

Note that the dispersion curve, waveform, and rotation trajectory obtained by the measurement are compared with the theoretical dispersion curve, waveform, and rotation trajectory obtained at the above-described inverse analysis (which are obtained simultaneously when the theoretical dispersion curve is obtained). If it is determined that the measurement and analysis are normal and accurate, the flow proceeds to the determination of the layer structure of the ground and its properties. On the other hand, if it is not normal, the flow is executed.

Next, the distance L is changed, the vibration sensors 2a, 2b are moved to the next measurement point, and the above-mentioned flow is performed. If the flow is satisfied by measurement, calculation, and analysis at a certain distance L, the layer structure of the ground and its properties (density, P-wave velocity, S-wave velocity, layer thickness, etc.) are determined. In FIG. 7, the dispersion curve obtained by the measurement is indicated by a dot, and the dispersion curve obtained by the reverse analysis is indicated by a solid line.

[Effects of the Invention] The present invention provides a system for analysis and determination, in which an exciter is installed on the ground to be investigated, and vibrations are applied to a plurality of points on a straight line distant from the exciter. A vertical vibration sensor that receives the vertical component and a horizontal vibration sensor that receives the horizontal component are installed in pairs at the same position, and the vertical and horizontal components of the surface wave vibration generated on the ground by the vertical vibration of the exciter are placed at the same position. In the pair of vibration sensors provided in the above, the simultaneous reception is changed with changing the frequency, and the data analysis determination means for analyzing the received vertical and horizontal vibration data to determine the layer structure of the ground and its properties is provided. Wherein the data analysis determination means includes a vertical component wave obtained from the vertical vibration data received by the vertical vibration sensor and a horizontal component obtained from the horizontal vibration data received by the horizontal vibration sensor which is a pair. When confirming that the wave received by the rotation locus of the ground soil particles due to vibration propagation obtained by synthesizing the component wave with the component wave is a surface wave, the frequency component corresponding to the exciter is extracted, and this frequency component is extracted. The time difference between the waves reaching the vibration sensor and the phase velocity are obtained based on the phase difference, and the wavelength is obtained.The dispersion curve is obtained by repeating the operation of obtaining the phase difference, the time difference, the phase velocity, and the wavelength of the wave. Because the dispersion curve is determined by the inverse analysis based on Haskell's theory, the layer structure and properties of the ground can be determined, so that a system that determines the dispersion curve in real time while confirming the surface wave can be realized. In addition, there is an effect that analysis and determination of the characteristics and the like can be performed reliably and accurately.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention, FIG. 2 is a block circuit diagram of the same, FIGS. 3 to 7 are operation explanatory diagrams of the same, and FIG. 8 is a schematic configuration diagram of a conventional example. is there. 1 is an exciter, 2a is a vertical vibration sensor, 2b is a horizontal vibration sensor, and 3 is a data analysis determination means.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References Research Report of the Saitama Prefectural Pollution Center No.15 (1988) Tatsuro Muraoka “Soil Investigation Method Using Surface Waves”

Claims (1)

(57) [Claims] An exciter is installed on the ground to be investigated, and a vertical vibration sensor for receiving a vertical component of vibration and a horizontal for receiving a horizontal component at a plurality of points on a straight line distant from the exciter. A pair of vibration sensors installed at the same position with a pair of vibration sensors installed at the same position, and the vertical component and the horizontal component of the surface wave vibration generated on the ground due to the vertical vibration of the exciter,
Simultaneous reception is repeated at different frequencies, and the received vertical and horizontal vibration data is analyzed to provide data analysis determination means for determining the layer structure of the ground and its properties. The vibration obtained by combining the vertical component wave obtained from the vertical vibration data received by the vertical vibration sensor with the horizontal component wave obtained from the horizontal vibration data received by the paired horizontal vibration sensor When confirming that the wave received by the rotation locus of the ground soil particles due to propagation is a surface wave, the frequency component corresponding to the exciter is extracted, and reaches the vibration sensor based on the phase difference of the frequency component. Obtain the wavelength for which the phase velocity is obtained while obtaining the time difference of the wave, and obtain the dispersion curve by repeatedly performing the operation for obtaining the phase difference, the time difference, the phase velocity, and the wavelength of the wave. Ground measurement analysis determination system, characterized in that the inverse analysis based on the theory of skeletal judging the layer structure and properties of the ground.