JP2021006826A - Surface wave survey analysis method and surface wave survey analyzer - Google Patents

Abstract

To simplify work accompanied by a ground survey by automatically extracting an inflection point of a D-Vrb curve.SOLUTION: In a surface wave survey analyzer for a ground survey system for surveying the ground by detecting a surface wave which is generated around a ground surface by vertically exciting the ground surface, a propagation average speed Vrb(f) and a depth D(f) of the surface wave are calculated by processing output signals of at least two acceleration detectors which are arranged at an excitation site with an interval L, a depth D-propagation average speed Vrb curve is created by repeating processing for calculating the propagation average speed Vrb(f) and the depth D(f), after that, a plurality of inflection points is selected with respect to the created depth D-propagation average speed Vrb curve, and a zone speed between the inflection points is calculated on the basis of the plurality of selected inflection points. In particular, the plurality of inflection points is selected with changes of input signals SA and SB as factors.SELECTED DRAWING: Figure 1

Description

The present invention relates to a surface wave exploration analysis method and a surface wave exploration analysis device for a ground exploration system.

A surface wave exploration method is known as a method of ground exploration. The surface wave exploration method has the property that surface waves (especially Rayleigh waves) that propagate in the ground due to the vibration of the ground propagate faster on harder ground and slowly on softer ground, and the depth of transmission changes when the vibration frequency changes. It takes advantage of the property of changing. In the surface wave exploration method, the speed of surface waves transmitted through the ground by giving a weak vibration to the ground with a vibrator is detected by at least two detectors placed at the vibration site, and these detection signals are used. The propagation condition and velocity of surface waves are analyzed.

A ground exploration device using such a surface wave exploration method is described in Patent Document 1, and will be briefly described below.

The operator installs the exciter at a location requiring ground exploration and at least two accelerometers at intervals on the ground near it. A surface wave is generated around the ground surface by vibrating the ground surface up and down at a vibration frequency with a vibrator. The detection signals from the two acceleration detectors are output as acceleration time series signals A (t) and B (t) through a measuring unit having a signal processing function such as A (Analog) / D (Digital) conversion. An analysis device such as a personal computer is connected to the measurement unit. The analysis device receives acceleration time series signals A (t) and B (t) from the measurement unit as input signals SA and SB, and performs signal processing on the input signals SA and SB based on a predetermined analysis program. , Propagation average velocity Vrb (f) and depth D (f) are calculated. The average propagation velocity is usually indicated by adding a bar indicating the average above Vr indicating the velocity, but here, unless otherwise specified, Vrb without a bar for convenience of notation. It will be shown by.

The operator repeatedly oscillates the oscillating machine while changing the oscillating frequency, so that the analyzer generates a depth D-propagation average velocity Vrb curve (hereinafter, abbreviated as D-Vrb curve). Is displayed on the monitor. The process of generating the D-Vrb curve will be described later.

The operator confirms the D-Vrb curve displayed on the monitor, and selects an inflection point (s) on the D-Vrb curve where it is determined that the physical properties of the ground have changed. The selection of inflection points has been made into a manual, and the operator selection work is performed according to this manual.

After selecting all the inflection points, the section velocity between the inflection points is calculated based on the selected inflection point information. The section speed will also be described later.

Japanese Unexamined Patent Publication No. 2002-341048

Although the selection of inflection points has been made into a manual, it takes skill to select an operator, and considerable experience is required to become a skilled operator. In addition, if the operator changes, it is inevitable that the selection results will vary, and as a result, various calculation results will also vary.

Therefore, an object of the present invention is to make it possible to automate the extraction of the turning point in the D-Vrb curve and to realize the simplification of the work associated with the ground exploration.

Another object of the present invention is to eliminate variations in measurement results due to differences in operators and to improve measurement accuracy.

According to the first aspect of the present invention, it is a surface wave exploration analysis device for a ground exploration system that detects surface waves generated around the ground surface by vibrating the ground surface up and down to perform ground exploration. The surface wave exploration and analysis device transfers the output signals of at least two acceleration detectors arranged at the vibration site at intervals L to the input signal SA via a measuring unit having an A / D conversion function. Received as SB, the received input signals SA and SB are processed to calculate the surface wave propagation average velocity Vrb (f) and depth D (f), and the propagation average velocity Vrb (f) and the depth D. After repeating the process of calculating (f) and generating a depth D-propagation average velocity Vrb curve, a plurality of variation points are selected for the generated depth D-propagation average velocity Vrb curve, and a plurality of selected points are selected. The section velocity between the inflection points is calculated based on the inflection points of, and the surface wave exploration analysis device also factores the selection of the plurality of inflection points by the changes of the input signals SA and SB. A surface wave exploration and analysis apparatus is provided.

In the surface wave method analyzing apparatus according to the first aspect, the input signal SA, the acceleration change amount [Delta] L A per unit frequency relative to _SB, after calculating the [Delta] L _B, calculated acceleration change amount [Delta] L _A and [Delta] L The difference of _B is obtained, the amount of change of this difference per unit frequency is obtained, and the data position where the sign of this amount of change changes from "+" to "-" is extracted for the depth D and the propagation average velocity Vrb. It can be a turning point.

According to the second aspect of the present invention, it is a surface wave exploration analysis method for a ground exploration system that detects surface waves generated around the ground surface by vibrating the ground surface up and down to perform ground exploration. hand,
The output signals of at least two acceleration detectors arranged at the vibration site at intervals L are received as input signals SA and SB via a measuring unit having an A / D conversion function, and the received input signals are received. The process of processing the SA and SB to calculate the propagation average velocity Vrb (f) and the depth D (f) of the surface wave, and calculating the propagation average velocity Vrb (f) and the depth D (f) is repeated. To generate the depth D-propagation average velocity Vrb curve,
Steps to select multiple turning points for the generated depth D-propagation average velocity Vrb curve, and
Including a step of calculating the section velocity between inflection points based on a plurality of selected inflection points.
A surface wave exploration analysis method is provided in which the step of selecting the plurality of bending points is performed by using the changes of the input signals SA and SB as factors.

In the step of performing a selection of the plurality of inflection points in the second aspect, the input signal SA, the acceleration change amount for each unit frequency relative to SB [Delta] L _A, after calculating the [Delta] L _B, calculated acceleration with obtaining the difference between the amount of change [Delta] L _a and [Delta] L _B, obtains the amount of change per unit frequency of the difference, the sign of this variation is, "+" to "-" depth D data position that changes in the propagation average speed Vrb can be extracted and used as an inflection point.

According to the present invention, it is possible to simplify the work associated with ground exploration by making it possible to automate the extraction of inflection points on the D-Vrb curve.

According to the present invention, it is also possible to eliminate variations in measurement results due to differences in operators and improve measurement accuracy.

It is a figure which showed the structural example of the ground exploration apparatus to which this invention can apply. An example of the frequency band of the electric power applied to the oscillator shown in FIG. 1 (FIG. a) and an example of the D-Vrb curve generated by the analyzer (personal computer) shown in FIG. 1 (FIG. b). It is a figure which showed. An example of the data structure of the D-Vrb curve shown in FIG. 2B, which is stored in the surface wave exploration and analysis apparatus in the present invention, is shown. An example of the data structure of all data stored in the surface wave exploration and analysis apparatus in the present invention is shown. An example of the data structure of FL data stored in the surface wave exploration analysis device in the present invention is shown. It is a figure for demonstrating the calculation example of a section speed.

Before explaining the embodiment of the present invention, the ground exploration apparatus described in Patent Document 1 will be described with reference to FIGS. 1 and 2. This ground exploration device is also applicable to the present invention.

In FIG. 1, the ground exploration device includes at least two acceleration detectors 11A and 11B installed on the ground at the vibration site, and a measuring unit 12 that receives acceleration detection signals from these acceleration detectors 11A and 11B. including. The measurement unit 12 includes a seismograph unit 12-1, an A / D conversion unit 12-2, a communication unit 12-3, and an oscillation unit 12-4. The seismograph unit 12-1 has a built-in low-pass filter circuit and generates an acceleration time series signal from an analog acceleration detection signal. The A / D conversion unit 12-2 is for converting the analog acceleration time series signal from the seismograph unit 12-1 into the digital acceleration time series signals A (t) and B (t), and the input sensitivity. Has an automatic adjustment function. The communication unit 12-3 transmits digital acceleration time series signals A (t) and B (t) to a device connected to the measurement unit 12, for example, a personal computer with a monitor (hereinafter, abbreviated as PC) 13. To do. The PC 13 has a function of receiving acceleration time series signals A (t) and B (t) as input signals SA and SB and processing the input signals SA and SB based on the analysis program software pre-installed in the built-in memory. However, it functions as an analysis device for performing ground analysis. Here, (t) indicates an arbitrary value that changes with time series.

Next, the operation will be described. First, the oscillator 15 and the acceleration detectors 11A and 11B are installed in a straight line at the exploration site. Let L (m) be the distance between the acceleration detectors 11A and 11B. A surface wave is generated around the exciter 15 by vibrating the ground surface in the vertical direction using the exciter 15. The vertical vibration of the surface wave (Rayleigh wave) propagating near the ground surface is detected by the acceleration detectors 11A and 11B. The acceleration detection signals from the acceleration detectors 11A and 11B become analog time-series signals by passing through the low-pass filter circuit of the seismograph unit 12-1, and are input to the A / D conversion unit 12-2. The time-series signals A (t) and B (t) converted to A / D by the A / D conversion unit 12-2 are transferred from the communication unit 12-3 to the PC 13.

In the PC 13, the power spectra _GAA (f), _GBB (f), cross spectrum _GBA (f), transfer function H (f), and coherence function γ of the input signals SA and SB are used based on a predetermined analysis program. ² (f) etc. are calculated. These power spectra _GAA (f), _GBB (f), cross spectrum _GBA (f), transfer function H (f), coherence function γ ² (f) and the like are stored in the built-in hard disk. The PC 13 also obtains the phase difference Δθ (f) between the acceleration detectors 11A and 11B from the transfer function H (f), and subsequently obtains the time difference Δt (f). Here, (f) indicates an arbitrary value that changes along the frequency axis.

Further, the PC 13 obtains the average propagation velocity Vrb (f) and the depth D (f) of the surface wave from the time difference Δt (f) and the interval L between the acceleration detectors 11A and 11B.

The calculation process of the power spectrum _GAA (f), _GBB (f), cross spectrum _GBA (f), transfer function H (f), coherence function γ ² (f), etc. is not the gist of the present invention. Although it is omitted because it is described in Patent Document 1, the average propagation velocity Vrb (m / sec) and the depth D (m) of the surface wave are calculated by the following formulas, respectively.
Vrb = L / Δt (f) = 2π × F × L / −Δθ (f)
D = λ / 2 = Vrb / 2F = π × L / −Δθ (f)
However, F is the frequency of the excitation (excitation) signal, and λ is the wavelength of the acceleration detection signal.

The above calculation is repeated until the desired D-Vrb curve is obtained. That is, the frequency of the excitation signal given to the exciter 15 is changed each time the measurement is performed. That is, the phase difference Δθ (f) of the transfer function H (f), which has an inverse relationship with the propagation velocity of the surface wave, is measured for each frequency. Next, the propagation average velocity Vrb and the depth D are calculated from the relationship between the phase difference and the frequency, and as a result of repeated measurement, a D-Vrb curve is generated and displayed on the monitor.

2 (a) shows the frequency band of the power applied to the exciter 15, the region of the frequency _f 1 ~f _n, where _f 1 ~f _i (band _{B 1), f i ~f k} ( It is divided into three bands, band B ₂ ) and f _{k to} f _n (band B ₃ ). In this case, as shown in FIG. 2 (b), the curve _{C 1} in the D-Vrb surface is measured in the band _{B 1} is, in the measurement of the band _{B 2} curve _{C 2} is the measurement of the band _{B 3} Curves C ₃ are obtained respectively, and these curves C _{1 to} C ₃ are automatically combined and displayed on the monitor.

In FIG. 2B, among the inflection points existing on the D-Vrb curve, the inflection points required for the subsequent calculation of the section speed and the like are indicated by ◯. In the following description, unless otherwise specified, only the inflection points required for the subsequent calculation of the section speed and the like among the inflection points existing on the D-Vrb curve are referred to as inflection points.

In any case, the operator selects the inflection point for the D-Vrb curve as shown in FIG. 2B on the monitor. Selection is done by pointing with a cursor or specifying with a stylus. The inflection point corresponds to the point where the D-Vrb curve changes significantly, but in order to select the velocity of the softest ground part in the measurement range, the left end of the change of the D-Vrb curve, that is, the velocity. The part where Vrb is small is selected as an inflection point.

When the selection of the inflection point is completed, the PC 13 calculates the section speed and the like based on the information of the selected inflection point.

The surface wave exploration analysis device according to the present invention can be realized by a personal computer similar to the PC 13, and can be obtained from the input of the input signals SA and SB (time series signals A (t) and B (t)) to the D-Vrb curve. Up to the generation can be realized by installing the analysis program software having the same function as the analysis program software stored in the PC 13.

Next, the types of data handled in the embodiments of the present invention will be described.

The surface wave exploration analysis device according to the present invention is for a ground exploration system configured by combining at least two acceleration detectors 11A and 11B described with reference to FIG. 1, a measuring unit 12, a power amplifier 14, and a vibrator 15. It can be applied as a surface wave exploration and analysis device. Therefore, in the embodiment of the surface wave exploration analysis device according to the present invention, as described with reference to FIG. 1, the propagation obtained based on the detection signals from the detectors installed at two locations at a constant distance L. Three types of data, the average velocity Vrb, the depth D, and the frequency F of the excitation signal, are stored in the built-in memory as a D-Vrb curve with the extension " ^**. DV".

FIG. 3 shows an example of the data structure of the D-Vrb curve. The data structure of the D-Vrb curve includes a data header part and a data part. Variables such as soft identification number, measurement number, number of data, maximum value of velocity axis at the time of measurement, etc. are stored in the data header section, and the calculation depth D (m), propagation average velocity Vrb (m / sec), etc. are stored in the data section. A variable of frequency (Hz) is stored.

On the other hand, all the data related to the measurement are stored in the built-in memory as all data with the extension " ^** . All".

FIG. 4 shows an example of the data structure of all data. The data structure of all data also consists of a data header part and a data part. Variables such as software identification number, measurement number, number of data, device serial number, etc. are stored in the data header part, and the calculation depth D (m), propagation average velocity Vrb (m / sec), frequency F ( 13 kinds of variables including Hz) are stored.

Next, the automatic inflection point calculation on the D-Vrb curve, which can be said to be a characteristic part of the surface wave exploration analysis method realized by the surface wave exploration analysis apparatus according to the present invention, will be described.

The automatic inflection point calculation in the present invention includes the first automatic inflection point calculation for calculating the inflection point from the amount of change ΔV of the data in the D-Vrb curve and the detection signals from the detectors installed at two places. It is roughly classified into the second automatic inflection point calculation in which the inflection point is calculated by using the change of the time-series signals A (t) and B (t) based on the factor. Both the first and second automatic turning point calculations can be performed by the surface wave exploration and analysis apparatus.

[First automatic inflection point calculation]
The first automatic inflection point calculation is executed after the above-mentioned D-Vrb curve is generated. The first automatic inflection point calculation is an automatic inflection point calculation using the change ΔV of the velocity data in the D-Vrb curve as a factor, and the names are further changed to “calculation R” and “calculation B” depending on the calculation method of the change ΔV. There are four types of calculation methods, "calculation N" and "calculation G".

The D-Vrb curve is based on the DV data of the extension " ^** . DV" stored in the memory as described above. In the DV data with the extension " ^** . DV", two values of the calculation depth D and the propagation average velocity Vrb are stored in descending order of the frequency F of the excitation signal at the time of measurement. The measurement data related to these calculation depths, propagation average velocities, and frequencies are referred to as measurement data DV (D) _i , measurement data DV (V) _i , and measurement data DV (F) _i , and are generally measured data DV (D, V, F). ) _Expressed as _i . Further, i is an integer (i = 1, 2, ...) And indicates the order in which the data is stored.

In "calculation R", the change ΔV is calculated by the first-order difference center) calculation, and the data position (propagation average velocity, calculation depth) at which the sign of the calculation result changes is extracted and used as an inflection point. This will be described in detail below.

"Calculation R" Calculation content Of the measurement data DV (D, V, F) _i of the D-Vrb curve, the first-order difference is calculated for the change ΔV of the measurement data DV (V) _i . During calculation performs calculation of the center differential, according to the conditional expression, to determine the depth D _j, velocity V _j, the frequency F _j about the inflection point data _{FL (D, V, F)} j. Incidentally, the inflection point data _{FL (D, V, F)} j is the depth _{D j,} velocity _{V j,} the frequency _{f j} due inflection point data _{FL (D) j, FL (} V) j, FL (F) j But it is represented.

That is, FL (D) _j = DV (D) _i , FL (V) _j = DV (V) _i , FL (F) _j = DV (F) _i , using i that satisfies the conditional expression described later. Data is extracted from the measurement data DV (D, V, F) _i , and this is referred to as inflection point data FL (D, V, F) _j . Further, j is an integer (j = 1, 2, ...) And indicates a data order in descending order of frequency F.

1.1: Let ΔV _i be the difference between the i + 1st and i-1st values of the velocity data DV (V).
ΔV _i = DV (V) _i-1 -DV (V) _{i + 1}

1.2: After determining the presence or absence of FL (D, V, F) _j and determining the number of data,
Let FL (D, V, F) ₁ = DV (D, V, F) ₁ (determine the starting point and reset).

1.3: Based on the conditions of ΔV _i and ΔV _{i + 2} , the position (zero cross point) where the sign of the value of the first-order difference changes from minus to plus is extracted.
Conditional expression 1: (ΔV _i ≧ 0 ∩ ΔV _{i + 1} <0) ∪ (ΔV _i > 0 ∩ ΔV _{i + 1} ≦ 0)
Select i (i ≧ 2) that satisfies the conditional expression 1.
Conditional expression 2: (ΔV _i ≤ 0 ∩ ΔV _{i + 1} > 0) ∪ (ΔV _i <0 ∩ ΔV _{i + 1} ≥ 0)
Select i (i ≧ 2) that satisfies the conditional expression 2.
Conditional expression 3: Select i (i ≧ 2) that satisfies conditional expression 1 or conditional expression 1.
Conditional expression 1 to 3 shall be selected by using conditional expression 2 basically, and the same conditional expression shall be applied at the same site.

1.4: Substitute the selected i to obtain DV _i . It is confirmed whether or not the following three conditions are satisfied for this value. (Adjustment of the number of automatic inflection point data and interval)
Conditional expression 4: For the depth Ds (optionally given) that determines the automatic inflection point
DV (D) _i ≤ k × Ds is satisfied. However, k is an arbitrary value and is usually set to "1.1".
For the optional deletion (depth) level D_DE, abs (FL (D) _j-1- DV (D) _i ) ≥ D_DE is satisfied. However, D_DE is an arbitrary value and is usually set to "0.1".
Abs (FL (V) _j-1- DV (V) _i ) ≥ V_DE is satisfied for the deletion (speed) level V_DE given arbitrarily. However, V_DE is an arbitrary value and is usually set to "4.0".

1.5: FL _j is determined by DV _i satisfying the condition of 1.4 above.
FL (D) _j = DV (D) _i , FL (V) _j = DV (V) _i , FL (F) _j = DV (F) _i

As described above, according to "Calculation R", D as shown by ○ in FIG. 2B, similar to the selection of the inflection point that the operator has performed on the D-Vrb curve so far. The inflection point data FL (D) _j , FL (V) _j , and FL (F) _j can be selected as the points where the −Vrb curve changes significantly and the leftmost change point is changed.

In "calculation B", the change ΔV of the velocity is calculated by the second-order difference (forward) calculation, and the data position (propagation average velocity, calculation depth) at which the sign of the calculation result changes is extracted and used as an inflection point. This will be described in detail below.

"Calculation B" Calculation content The second-order difference is calculated for the change in speed V in the data DV (D, V, F) _i of the D-Vrb curve. At the time of calculation, the forward difference is calculated, and the inflection point data FL (D, V, F) _j is calculated by the conditional expression.

That is, FL (D) _j = DV (D) _i , FL (V) _j = DV (V) _i , FL (F) _j = DV (F) _i , using i that satisfies the conditional expression described later. Data is extracted from the measurement data DV (D, V, F) _i , and this is used as the turning point data FL (D, V, F) _j .

2.1: i-2-th speed data DV (V), according to (i-1) -th and i-th rate value, the second difference to Deruta2V _i.
Δ2V _i = DV (V) _i-2 -2DV (V) _i-1 + DV (V) _i

2.2: Check the presence or absence of FL (D, V, F) _j , check the number of data, and then
FL (D, V, F) ₁ = DV (D, V, F) ₁
(Determining the starting point and resetting).

2.3: Under the conditions of Δ2V _i and Δ2V _{i + 2} , the position (zero cross point) where the sign of the value of the first-order difference changes from minus to plus is extracted.
Conditional expression 1: (Δ2V _i ≧ 0 ∩ Δ2V _{i + 1} <0) ∪ (Δ2V _i > 0 ∩ Δ2V _{i + 1} ≦ 0)
Select i (i ≧ 2) that satisfies the conditional expression.
Conditional expression 2: (Δ2V _i ≤ 0 ∩ Δ2 V _{i + 1} > 0) ∪ (Δ2V _i <0 ∩ Δ2V _{i + 1} ≥ 0)
Select i (i ≧ 2) that satisfies the conditional expression.
Conditional expression 3: Select i (i ≧ 2) that satisfies conditional expression 1 or conditional expression 2.
Conditional expression 1 to 3 shall be selected by using conditional expression 2 basically, and the same conditional expression shall be applied at the same site.

2.4: Substitute the selected i to obtain DV _i . It is confirmed whether or not the following three conditions are satisfied for this value. (Adjustment of the number of automatic inflection point data and interval)
Conditional expression 4: For the depth Ds (optionally given) that determines the automatic inflection point
DV (D) _i ≤ k × Ds is satisfied. However, k is an arbitrary value and is usually set to "1.1".
For the optional deletion (depth) level D_DE, abs (FL (D) _j-1- DV (D) _i ) ≥ D_DE is satisfied. However, D_DE is an arbitrary value and is usually set to "0.1".
Abs (FL (V) _j-1- DV (V) _i ) ≥ V_DE is satisfied for the deletion (speed) level V_DE given arbitrarily. However, V_DE is an arbitrary value and is usually set to "4.0".

2.5: FL _j is determined by DV _{i that} satisfies the condition of 2.4 above.
FL (D) _j = DV (D) _i , FL (V) _j = DV (V) _i , FL (F) _j = DV (F) _i

As described above, according to "Calculation B", D as shown by ◯ in FIG. 2B, similar to the selection of the inflection point that the operator has performed on the D-Vrb curve so far. The inflection point data FL (D) _j , FL (V) _j , and FL (F) _j can be selected as the points where the −Vrb curve changes significantly and the leftmost change point is changed.

For "calculation N", the change ΔV is calculated by "R" / "B" calculation, and the data position (propagation average velocity, calculation depth) at which the sign of the calculation result changes is extracted and used as an inflection point. This will be described in detail below.

"Calculation N" Calculation content The first-order difference and second-order difference are calculated for the change in velocity V in the data DV (D, V, F) _i of the D-Vrb curve. At the time of calculation, the first-order difference is neutral, the second-order difference is forward-calculated, and the inflection point data FL (D, V, F) _j is calculated based on the results of both calculations and the conditional expression.

That is, FL (D) _j = DV (D) _i , FL (V) _j = DV (V) _i , FL (F) _j = DV (F) _i , using i that satisfies the conditional expression described later. Data is extracted from the measurement data DV (D, V, F) _i , and this is used as the turning point data FL (D, V, F) _j .

3.1: Let ΔV _i be the difference between the (i-1) th and (i + 1) th velocity V values of the velocity data DV (V).
ΔV _i = DV (V) _i-1 -DV (V) _{i + 1}

3.2: Check for the presence or absence of inflection point data FL (D, V, F) _j , check the number of data, and then
FL (D, V, F) ₁ = DV (D, V, F) ₁
(Determining the starting point and resetting).

3.3: Under the conditions of the difference ΔV _i and ΔV _{i + 2} , the position where the sign of the first-order difference value changes from minus to plus (zero cross point) is extracted, and the depth and propagation average velocity at that position are extracted. ..
Conditional expression 1: (ΔV _i ≧ 0 ∩ ΔV _{i + 1} <0) ∪ (ΔV _i > 0 ∩ ΔV _{i + 1} ≦ 0)
Select i (i ≧ 2) that satisfies the conditional expression.
Conditional expression 2: (ΔV _i ≤ 0 ∩ ΔV _{i + 1} > 0) ∪ (ΔV _i <0 ∩ ΔV _{i + 1} ≥ 0)
Select i (i ≧ 2) that satisfies the conditional expression.
Conditional expression 3: Select i (i ≧ 2) that satisfies conditional expression 1 or conditional expression 2.
Conditional expression 1 to the selection of conditional expression 3 shall basically use conditional expression 1, and the same conditional expression shall be applied at the same site.

3.4: FL _j is tentatively determined by DV _i , which satisfies the condition of 3.3 above.
FL (D) _j = DV (D) _i , FL (V) _j = DV (V) _i , FL (F) _j = DV (F) _i

3.5: With respect to the depth D of the inflection point data FL (D, V, F) _j obtained in 3.4 above and the arbitrarily set maximum layer thickness DT_L.
FL (D) _{j + 1 −} FL (D) _j <extract j that satisfies DT_L. However, DT_L is an arbitrary value and is usually set to "3.0".

3.6: FL (D, V, F) of the _j, the using frequency _{F, FL (F) j =} DV (F) i and _{FL (F) j + 1 =} DV (F) i i Is extracted, and each is Si and Ei.

3.7: Let Δ2V _{i be the} second-order difference due to the i-2nd, i-1st, and i-th velocity values of the velocity data DV (V).
Δ2V _i = DV (V) _i-2 -2DV (V) _i-1 + DV (V) _i
However, i is an integer from Si to Ei.

3.8: Under the conditions of Δ2V _i and Δ2V _{i + 2} , the position where the sign of the second-order difference value changes from minus to plus (zero cross point) is extracted, and the depth and propagation average velocity at that position are extracted.
To summarize the calculation N calculation up to this point, first, the temporary inflection points are extracted by the calculation based on the first-order difference, and then the difference in the depth of each point of the temporary inflection points is determined by the above 3.5. It is determined whether or not it is within 3.0 (m). If there is a gap of 3.0 m or more, the range free of 3.0 m or more is extracted, and the second-order difference is calculated again for this range.
Conditional expression 1: (Δ2V _i ≧ 0 ∩ Δ2V _{i + 1} <0) ∪ (Δ2V _i > 0 ∩ Δ2V _{i + 1} ≦ 0)
Select i (i ≧ 2) that satisfies the conditional expression.
Conditional expression 2: (Δ2V _i ≤ 0 ∩ Δ2 V _{i + 1} > 0) ∪ (Δ2V _i <0 ∩ Δ2V _{i + 1} ≥ 0)
Select i (i ≧ 2) that satisfies the conditional expression.
Conditional expression 3: Select i (i ≧ 2) that satisfies conditional expression 1 or conditional expression 2.
Conditional expression 1 to 3 shall be selected by using conditional expression 2 basically, and the same conditional expression shall be applied at the same site.

3.9: Substitute the selected i to obtain DV _i . It is confirmed whether or not the following three conditions are satisfied for this value. (Adjustment of the number of automatic inflection point data and interval)
Conditional expression 4: For the depth Ds (optionally given) that determines the automatic inflection point
DV (D) _i ≤ k × Ds is satisfied. However, k is an arbitrary value and is usually set to "1.1".
For the optional deletion (depth) level D_DE, abs (FL (D) _j-1- DV (D) _i ) ≥ D_DE is satisfied. However, D_DE is an arbitrary value and is usually set to "0.1".
Abs (FL (V) _j-1- DV (V) _i ) ≥ V_DE is satisfied for the deletion (speed) level V_DE given arbitrarily. However, V_DE is an arbitrary value and is usually set to "4.0".

3.10: FL _jj is determined by DV _{i that} satisfies the condition of 3.9 above.
FL (D) _jj = DV (D) _i , FL (V) _jj = DV (V) _i , FL (F) _jj = DV (F) _i

3.11: FL _jj is added to FL _j obtained in 3.4 above to obtain inflection point data FL (D, V, F) _j .

As described above, according to "Calculation N", D as shown by ◯ in FIG. 2B, similar to the selection of the inflection point that the operator has performed on the D-Vrb curve so far. The inflection point data FL (D) _j , FL (V) _j , and FL (F) _j can be selected as the points where the −Vrb curve changes significantly and the leftmost change point is changed.

“Calculation G” simultaneously confirms the data change ΔD (change in the depth direction) in addition to the data change ΔV (change in the propagation average velocity value) in the D-Vrb curve. From these values, the degree of data density TG is calculated, and the data position (propagation average speed, calculation depth) where the value of data density TG exceeds the preset value GR _level is extracted and used as the inflection point. To do.

"Calculation G" Calculation content D-Vrb curve data DV (D, V, F) _i , the change of velocity V and the change of depth D are arranged, and the inflection point depends on the degree of density of the data. Calculate the data FL (D, V, F) _j .

That is, FL (D) _j = DV (D) _i , FL (V) _j = DV (V) _i , FL (F) _j = DV (F) _i , using i that satisfies the conditional expression described later. Data is extracted from the measurement data DV (D, V, F) _i , and this is referred to as inflection point data FL (D, V, F) _j .

但し、ΔＤ＿Ｖ_ｉは速度、深度の変化量、Ｄ_ｉはｉ番目の深度データ、Ｖ_ｉはｉ番目の速度データ、ｉは整数（ｉ＝１，２，・・・）、Ｖ_Ｔは計測時に設定した最大速度値であり、自動計算に際しては、この最大速度値より小さい速度データについて処理を行う。同様に、Ｄ_Ｔは計測時に設定した最大深度値であり、自動計算に際しては、この最大深度値より小さい深度データについて処理を行う。 4.1: D-Vrb curve data DV (D, V, F) _i is calculated by the following mathematical formula (1) as the amount of change ΔD_V _i depending on the i-1st and i-th values of velocity V and depth D. To do.

However, Derutadi_V _i is the speed, the amount of change in depth, _{D i} is the i-th depth data, _{V i} is the i-th speed data, i is an integer (i = 1,2, ···), V T is the time of measurement It is the set maximum speed value, and in the automatic calculation, processing is performed for speed data smaller than this maximum speed value. Similarly, _DT is the maximum depth value set at the time of measurement, and in the automatic calculation, processing is performed on depth data smaller than this maximum depth value.

但し、Ｔ＿Ｄ_ｉは平均化に関する係数で、Ｔ＿Ｄ_１＝０、ＥＭは計算のための設定値（１〜９の整数で、通常４とする）である。 4.2: The coefficient T_D _i related to data averaging is set by the following mathematical formula (2).

However, T_D _i is a coefficient related to averaging, T_D ₁ = 0, and EM is a set value for calculation (an integer of 1 to 9, usually 4).

4.3: The variable TG _i indicating the degree of data density is set by the following mathematical formula (3).

4.4: The variable GRL is set as a value indicating the degree of coarse density of the data, the conditions of the variable GRL and the variable TG _i are set, and i (i ≧ 2) satisfying the conditions is selected. However, the variable GRL is a value indicating the degree of coarse density of the data, and takes a value of 0.1 to 1.5, usually 0.5.
Conditional expression 1: | TG _i | ≧ GRL
Select i (i ≧ 2) that satisfies the conditional expression.

4.5: Substitute the selected i to obtain DV _i . It is confirmed whether or not the following three conditions are satisfied for this value. (Adjustment of the number of automatic inflection point data and interval)
Conditional expression 2: For the depth Ds (optionally given) that determines the automatic inflection point
DV (D) _i ≤ k × Ds is satisfied. However, k is an arbitrary value and is usually set to "1.1".
For the optional deletion (depth) level D_DE, abs (FL (D) _j-1- DV (D) _i ) ≥ D_DE is satisfied.
Abs (FL (V) _j-1- DV (V) _i ) ≥ V_DE is satisfied for the deletion (speed) level V_DE given arbitrarily.

4.6: FL _j is determined by DV _i satisfying the above 4.5 condition.
FL (D) _j = DV (D) _i , FL (V) _j = DV (V) _i , FL (F) _j = DV (F) _i

As described above, according to "Calculation G", D as shown by ◯ in FIG. 2B, similar to the selection of the inflection point that the operator has performed on the D-Vrb curve so far. The inflection point data FL (D) _j , FL (V) _j , and FL (F) _j can be selected as the points where the −Vrb curve changes significantly and the leftmost change point is changed.

[Second automatic inflection point calculation]
The second automatic inflection point calculation is executed by receiving the time-series signals A (t) and B (t) from the measurement unit 12 described above as the input signals SA and SB. That is, the second automatic inflection point calculation is an automatic inflection based on the change of the input signals SA and SB in which the detection signals from the acceleration detectors 11A and 11B installed at the two locations are input via the measuring unit 12. Inflection point calculation. As described with reference to FIG. 4, the input signals from the acceleration detectors 11A and 11B are recorded in "all data" as values with respect to the frequency at which the measurement was performed. Acceleration detector 11A, Ach from 11B, Bch respective input signals SA, against SB, acceleration change amount [Delta] L _A per unit frequency, obtains the [Delta] L _B, two additional acceleration detectors 11A, [Delta] L between 11B _A as well as obtaining a difference of ΔL _B. The amount of change in this difference per unit frequency is obtained, and the inflection point is the data position where the sign of this amount of change changes from "+" to "-". The calculation contents of the second automatic inflection point calculation will be described in detail below.

Second calculation contents of automatic inflection point calculator 5.1: two acceleration detectors 11A, Ach by 11B, Bch respective input signals SA, against SB, acceleration change amount [Delta] L _A per unit frequency, [Delta] L _B the calculated, two additional acceleration detectors 11A, obtains a difference [Delta] L _a and [Delta] L _B between 11B. The amount of change in this difference per unit frequency is obtained, and the inflection point data FL (D, V, F) _j is calculated.

In other words, the conditional expression based on the acceleration change amount [Delta] L _A and [Delta] L _B provided with DV _{(F) i} which satisfies this _{condition, FL (D) j = DV} (D) i, FL (V) j = DV (V) _i , FL (F) _j = DV (F) _i is extracted from the measurement data DV (D, V, F) _i , and this is extracted from the inflection point data FL (D, V, F). ) _{Let j} .

但し、Ｌ_ＡＶａはＡｃｈの振動加速度（ｄｂ）、Ｓ_ＡはＡｃｈの加速度（ｇａｌ）、Ｌ_ＢＶａはＢｃｈの振動加速度（ｄｂ）、Ｓ_ＢはＢｃｈの加速度（ｇａｌ）であり、いずれも周波数毎の振動加速度の最大値である。 5.2: When measuring with the acceleration detectors 11A and 11B, the maximum acceleration value for each frequency obtained by each of Ach and _Bch is converted by the following mathematical formulas (4) and (5), and the decibel values _LAVa and _LBVa are obtained. To do.

_{However, L AVa} is vibration acceleration (db), _{S A} is the Ach acceleration Ach _{(gal), L BVa} the vibration acceleration of the Bch (db), _{S B} is the Bch acceleration (gal), both each frequency It is the maximum value of the vibration acceleration of.

S _A and _{S B,} the measurement data _{DV (D, V, F)} i and recorded extension ^** into memory at the measurement as well. It is stored in the all data of "all". The extension " ^** . The D-Vrb curve of "DV" and the extension " ^** . all data all "stores the same frequency change all the values of the measurement. Therefore, _{S A} and _{S B} or _{L AVa} and _{L BVa,} the measurement data DV (D, V, similar to _{F) i,} represents the order by using an integer i (i = 1,2, ···) .

Ｌ_{ＡＶａ（i）}＝Ｌ_{ＡＶａ（i）}‘ （６’）

Ｌ_{ＢＶａ（i）}＝Ｌ_{ＢＶａ（i）}‘ （７’） Finally, according to the following mathematical formulas (6), (6'), (7), and (7'), the vibration accelerations of three points, one point and one point before and after it, _{LAVa (i)} , _{LAVa (i-1). )} , _{LAVa (i + 1)} and vibration acceleration _{LBVa (i)} , _{LBVa (i-1)} , _{LBVa (i + 1)} are averaged.

L _{AVa (i)} = L _{AVa (i)} '(6')

_{LBVa (i)} = _{LBVa (i)} '(7')

但し、ΔＬ_Ａ、ΔＬ_ＢはＡｃｈ、Ｂｃｈの振動加速度データの１Ｈｚ当たりの変化量、ＤＶ（Ｆ）_iは計測データＤＶのi番目の周波数、Ｌ_{ＡＶａ（i）}、Ｌ_{ＢＶａ（i）}は拡張子“^＊＊．ａｌｌ”に格納されているＡｃｈ、Ｂｃｈのi番目の振動加速度（ｄｂ）を示す。 5.3: for all strike the vibration acceleration data, the following equation (8), determine the acceleration change amount [Delta] L _A, [Delta] L _B per unit frequency (9).

However, ΔL _A, ΔL _B is Ach, the amount of change per 1Hz vibration acceleration data Bch, DV (F) _i is the i-th frequency of the measurement data _{DV, L AVa (i),} L BVa (i) is extended The i-th vibration acceleration (db) of Ach and Bch stored in the child “ ^{**. All} ” is shown.

5.4: The difference ΔΔL of the amount of change in the vibration acceleration data of each of Ach and Bch obtained in 5.3 above is obtained.
ΔΔL = ΔL _A −ΔL _B
However, ΔΔL is the difference between the amount of change in the vibration acceleration data of Ach and the amount of change in the vibration acceleration data of Bch per 1 Hz.

上記の数式（１０）〜数式（１４）に共通して、以下の数式（１５）が適用される。
ΔΔＬ_（i）＝ΔΔＬ’_（i） （１５） Finally, the following mathematical formulas (10) to (14) are used to average a certain point and 1 to 5 points before and after the change amount of the vibration acceleration data 1 to 5 times. It is desirable to adjust the content of averaging while checking the content of automatic discrimination of the boundary surface.

The following mathematical formula (15) is applied in common to the above mathematical formulas (10) to (14).
ΔΔL _(i) = ΔΔL' _(i) (15)

Formulas (10) and (15) show the calculation contents when averaging a certain point and one point before and after it. Similarly, formulas (11) and (15) are the calculation contents when averaging a certain point and two points before and after it, and formulas (12) and (15) are when averaging a certain point and three points before and after it. Calculation contents, formulas (13) and (15) are calculation contents when averaging a certain point and 4 points before and after it, and formulas (14) and (15) are when averaging a certain point and 5 points before and after it. The calculation contents are shown respectively. Formulas (10) to (14) can be repeated, but the upper limit is 5 times.

但し、ＤＶ（Ｆ）_iは計測データＤＶのi番目の周波数、ΔΔΔＬはΔΔＬデータの１Ｈｚ当たりの変化量、ΔΔＬ_（i）はΔΔＬデータのi番目の値である。 5.5: The amount of change ΔΔΔL for each unit frequency is obtained by the following mathematical formula (16) with respect to the difference ΔΔL of the amount of change in the vibration acceleration data obtained in 5.4 above.

However, DV (F) _i is the i-th frequency of the measurement data DV, ΔΔΔL is the amount of change per 1 Hz of the ΔΔL data, and ΔΔL _(i) is the i-th value of the ΔΔL data.

5.6: The boundary surface is discriminated from the ΔΔΔL data obtained in 5.5 above.
k = ΔΔΔL _{(i) and} kk = ΔΔΔL _{(i + 1)}
FL (D, V, FL (D, V,) for i satisfying the conditions (k × kk <0 and kk <k) (where k indicates the i-th value of the ΔΔΔL data and kk indicates the (i + 1) th value of the ΔΔΔL data). f) Determine _j .
FL (F) _j = DV (F) _i
FL (D) _j = DV (D) _i
FL (V) _j = DV (V) _i

As described above, according to the "second automatic inflection point calculation", in the same manner as the selection of the inflection point that the operator has performed on the D-Vrb curve so far, FIG. As shown by, the inflection point data FL (D) _j , FL (V) _j , and FL (F) _j can be selected as the inflection point data where the D-Vrb curve changes significantly and the leftmost change point is changed.

The first and second automatic inflection point calculations have been described above, but in both of the above-mentioned first and second automatic inflection point calculations, as described in FIG. 3, the selection result of the inflection point Has an extension of " ^** . FL" and saves it as FL data.

FIG. 5 shows an example of the data structure of FL data stored in the surface wave exploration analysis device. The data structure of FL data also includes a data header part and a data part. Variables such as the software identification number, measurement number, and number of data are stored in the data header section, and the data section contains the calculation depth D (m) at the inflection point, the propagation average velocity V (m / s), and the frequency F (Hz). ) Is recorded.

The propagation average velocity Vrb recorded in the FL data refers to the velocity value at which the entire ground vibrates from the ground surface to the calculated depth D. Here, the velocity structure in the depth direction can be calculated by calculating the velocity value in each range in the depth direction divided by the inflection point as the section velocity.

FIG. 6 is a diagram for explaining a calculation example of the section speed. As shown in FIG. 6A, when the inflection point is extracted from the D-Vrb curve, the ground of the first, second, third, and fourth layers is assumed from the ground surface.

Regarding the calculation of the section velocity, for example, in the case of the second layer shown in FIG. 2 (b), the propagation average velocity V _{j at} the upper inflection point of the second layer, the calculation depth D _j , and the lower layer of the second layer. It is calculated by the average propagation velocity V _{j + 1 at the} inflection point and the calculation depth D _{j + 1} .

In the present embodiment, four types of calculation formulas for calculating the section speed are prepared as section speed calculation formulas (1-1), (1-2), and (1-3). The velocity structure of the ground at the exploration site is obtained by using a combination of these calculation formulas and a conditional formula. The calculation contents of the second section speed will be described in detail below.

Section speed calculation details The section speed _Vrj is calculated from the obtained inflection point data using the section speed calculation formulas (1-1) to (1-3) below. Here, in order to distinguish between the average propagation velocity and the interval velocity, the notation used in the explanation so far is changed, the interval velocity is expressed as _Vrj, and the average propagation velocity is indicated by _{adding a} bar above V. However, it will be called a V-bar.

但し、Ｖ_ｊバーはＦＬデータのｊ番目の伝搬平均速度、Ｄ_ｊはＦＬデータのｊ番目の深度、jは整数（ｊ＝１，２，・・・）である。 6.1: Section velocity calculation formula (1-1)

However, the V _j bar is the j-th propagation average velocity of the FL data, D _j is the j-th depth of the FL data, and j is an integer (j = 1, 2, ...).

6.2: Section velocity calculation formula (1-2)

6.3: Section velocity calculation formula (1-3)

但し、ρＶは伝搬平均速度Ｖｒｂに対する補正値であり、後述する数式（１２−８）において、補正後の値CVが算出される。 6.4: First section velocity calculation method (using the section velocity calculation formula (1-1) and the following multiple conditional formulas)

However, ρV is a correction value for the propagation average velocity Vrb, and the corrected value CV is calculated in the mathematical formula (12-8) described later.

但し、下記の条件式（１２−１１）の場合、区間速度計算式（１−２）を用いる。

However, in the case of the following conditional expression (12-11), the section velocity calculation formula (1-2) is used.

但し、下記の条件式（１２−１３）の場合、区間速度計算式（１−２）を用いる。

However, in the case of the following conditional expression (12-13), the section velocity calculation formula (1-2) is used.

6.5: Second section velocity calculation method (uses section velocity calculation formulas (1-3) and (1-2) and the following multiple conditional formulas)

6.6: Third section velocity calculation method (uses section velocity calculation formulas (1-1) and (1-2) and the following multiple conditional formulas)

以上のようにして、地表面から第１層、第２層、・・・、第j層の各層の地盤の区間速度が算定される。 6.7: Fourth section velocity calculation method (using section velocity calculation formula (1-3))

As described above, the section velocity of the ground of each of the first layer, the second layer, ..., The jth layer is calculated from the ground surface.

As described above, according to the embodiment of the present invention, since a plurality of inflection points in the D-Vrb curve can be automatically extracted, it is possible to realize simplification of the work associated with the ground exploration. In addition, it is possible to eliminate variations in measurement results due to differences in operators and improve measurement accuracy. Then, the velocity structure in the depth direction of the exploration ground can be calculated by calculating the section velocity in each layer of the plurality of ground layers in the depth direction classified by the extracted inflection points.

The surface wave exploration analysis device and the surface wave exploration analysis method according to the present invention are suitable for application to ground exploration.

11A, 11B Acceleration detector 12 Measuring unit 13 Personal computer

Claims (4)

It is a surface wave exploration analysis device for a ground exploration system that detects surface waves generated around it by vibrating the ground surface up and down and performs ground exploration.
The surface wave exploration and analysis device uses the output signals of at least two acceleration detectors arranged at the vibration site at intervals L as input signals SA and SB via a measuring unit having an A / D conversion function. Received, the received input signals SA and SB are processed to calculate the average propagation velocity Vrb (f) and the depth D (f) of the surface wave, and the average propagation velocity Vrb (f) and the depth D (f). ) And are repeated to generate a depth D-propagation average velocity Vrb curve, and then a plurality of inflection points are selected for the generated depth D-propagation average velocity Vrb curve, and a plurality of selected inflection points are selected. It calculates the section speed between inflection points based on the inflection points.
The surface wave exploration and analysis device is also characterized in that the selection of the plurality of inflection points is performed by factoring the changes in the input signals SA and SB. The surface wave probe analyzer, the input signal SA, the acceleration change amount [Delta] L A per unit frequency relative to _SB, after calculating the [Delta] L _B, together with obtaining the difference of the calculated acceleration variation [Delta] L _A and [Delta] L _B, The feature is that the amount of change of this difference per unit frequency is obtained, and the data position where the sign of this amount of change changes from "+" to "-" is extracted for the depth D and the propagation average velocity Vrb to be a turning point. The surface wave exploration and analysis apparatus according to claim 1. It is a surface wave exploration analysis method for a ground exploration system that detects surface waves generated around the surface by vibrating the ground surface up and down to perform ground exploration.
The output signals of at least two acceleration detectors arranged at the vibration site at intervals L are received as input signals SA and SB via a measuring unit having an A / D conversion function, and the received input signals are received. The process of processing the SA and SB to calculate the propagation average velocity Vrb (f) and the depth D (f) of the surface wave, and calculating the propagation average velocity Vrb (f) and the depth D (f) is repeated. To generate the depth D-propagation average velocity Vrb curve,
A step of selecting multiple inflection points for the generated depth D-propagation average velocity Vrb curve, and
Including a step of calculating the section velocity between inflection points based on a plurality of selected inflection points.
A surface wave exploration analysis method characterized in that the step of selecting the plurality of inflection points is performed by factoring the changes of the input signals SA and SB. In the step of performing a selection of the plurality of inflection points, the input signal SA, the acceleration change amount for each unit frequency relative to SB [Delta] L _A, after calculating the [Delta] L _B, calculated acceleration change amount [Delta] L _A and [Delta] L _B The difference is obtained, and the amount of change of this difference per unit frequency is obtained, and the data position where the sign of this amount of change changes from "+" to "-" is extracted for the depth D and the propagation average speed Vrb, and the variation is performed. The surface wave exploration analysis method according to claim 3, wherein the point is used.

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