JP6994785B2 - Surface wave exploration analysis method and surface wave exploration analysis device - Google Patents

Description

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

The surface wave exploration method is known as one 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 in harder ground and slowly in 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 the surface wave that propagates in the ground by giving a weak vibration to the ground with a vibrator is detected by at least two detectors installed at the vibration site, and these detection signals are used. The propagation situation 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 oscillator at a location that requires 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 shown by adding a bar indicating the average on Vr indicating the velocity, but here, unless otherwise specified, Vrb without a bar for convenience of notation. It shall be indicated 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 a point on the D-Vrb curve where it is determined that the physical properties of the ground have changed as inflection points (plural). 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 speed 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 is manualized, the operator selection work requires skill, and considerable experience is required before becoming 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 inflection points in the D-Vrb curve and to realize the simplification of the work associated with the ground exploration.

The present invention also aims 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 and performs ground exploration. The surface wave exploration and analysis device receives the output signals of at least two acceleration detectors arranged at the vibration site at intervals L via the measurement unit having an A / D conversion function, and the input signal SA. The input signals SA and SB received as 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. 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 speed between the variation points is calculated based on the variation points of, and the surface wave exploration analysis device also factores the selection of the plurality of variation points by the changes of the input signals SA and SB. A surface wave exploration and analysis device is provided, which is characterized by performing as a surface wave exploration and analysis device.

In the surface wave exploration and analysis apparatus according to the first aspect described above, the acceleration changes _ΔLA and _ΔLB for each unit frequency are calculated for the input signals SA and SB, and then the calculated acceleration changes _ΔLA and ΔL are calculated. The difference of _B 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 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 and performs 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 SA and SB to calculate the average propagation velocity Vrb (f) and the depth D (f) of the surface wave, and calculating the average propagation velocity Vrb (f) and the depth D (f) is repeated. And the step 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 the step of calculating the interval velocity between the inflection points based on the selected inflection points.
A surface wave exploration analysis method is provided in which 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 selecting the plurality of inflection points in the second aspect described above, the acceleration changes _ΔLA and _ΔLB for each unit frequency are calculated for the input signals SA and SB, and then the calculated acceleration is calculated. Find the difference between the amount of change ΔLA _A and _ΔLB , and find the amount of change per unit frequency of this difference. Vrb can be extracted and used as an inflection point.

According to the present invention, it is possible to realize the simplification of the work associated with the ground exploration by making it possible to automate the extraction of the inflection point in the D-Vrb curve.

According to the present invention, it is 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 is applied. 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 analysis device in the present invention, is shown. An example of the data structure of all data stored in the surface wave exploration analysis device 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. 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. By vibrating the ground surface in the vertical direction using the exciter 15, a surface wave is generated around the exciter 15. The acceleration detectors 11A and 11B detect the vertical vibration of the surface wave (Rayleigh wave) propagating near the ground surface. 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) A / D-converted 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. In the PC 13, the phase difference Δθ (f) between the acceleration detectors 11A and 11B is obtained from the transfer function H (f), and then the time difference Δt (f) is obtained. Here, (f) indicates an arbitrary value that changes along the frequency axis.

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

The calculation process of the above power spectra _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 equations, 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 oscillator 15 is changed each time the measurement is performed. That is, the phase difference Δθ (f) of the transfer function H (f), which has a reciprocal 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.

FIG. 2A shows the frequency band of the electric power applied to the oscillator 15, and the region of the frequencies f ₁ to f _n , in this case f ₁ to _fi (band B ₁ ), f _i to 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. 2B, the curve C1 is _on the D _- Vrb surface in the measurement in the band _B1 , the curve _C2 is in the measurement in the band B2, and the curve _C2 is in the measurement in the band B3. 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 in the D-Vrb curve, the inflection points required for the subsequent calculation of the section speed and the like are indicated by circles. In the following description, unless otherwise specified, only the inflection points required for the subsequent calculation of the section speed and the like are referred to as inflection points among the inflection points existing in the D-Vrb curve.

In any case, the operator selects the inflection point for the D-Vrb curve as shown in FIG. 2 (b) on the monitor. Selection is done by pointing with a cursor or by specifying with a stylus. The inflection point corresponds to the place 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 and analysis apparatus according to the present invention is for a ground exploration system configured by combining at least two acceleration detectors 11A and 11B described in FIG. 1, a measuring unit 12, a power amplifier 14, and a oscillator 15. It can be applied as a surface wave exploration and analysis device. Therefore, in the embodiment of the surface wave exploration and analysis apparatus 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 certain distance L. Three types of data, the average speed Vrb, the depth D, and the frequency F of the excitation signal, are stored in the built-in memory as a D-Vrb curve having 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 speed axis at the time of measurement are stored in the data header part, and calculation depth D (m), propagation average speed Vrb (m / sec), etc. in the data part. 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 in 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 device according to the present invention, will be described.

The automatic inflection point calculation in the present invention is based on 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 inflection point calculations can be performed by the surface wave exploration analysis device.

[First automatic inflection calculation]
The first automatic inflection point calculation is performed 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 speed, 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 The first-order difference is calculated for the change ΔV of the measurement data DV (V) _i in the measurement data DV (D, V, F) _i of the D-Vrb curve. At the time of calculation, the center difference is calculated, and the inflection point data FL (D, V, F) _j with respect to the depth D _j , the velocity V _j , and the frequency F _j is determined by the conditional expression. The inflection point data FL (D, V, F) _j is the inflection point data FL (D) _j , FL (V) _j , FL (F) _j according to the depth D _j , the velocity V _j , and the frequency 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,
FL (D, V, F) ₁ = DV (D, V, F) ₁ (determination of the first point and resetting).

1.3: Under the conditions of ΔV _i and ΔV _{i + 2} , the position where the sign of the value of the first-order difference changes from minus to plus (zero cross point) 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.
For the selection of conditional expressions 1 to 3, basically conditional expression 2 shall be used, 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. (Adjusting the number of automatic inflection data and intervals)
Conditional expression 4: For the depth Ds (arbitrarily 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".
Abs (FL (D) _j-1- DV (D) _i ) ≥ D_DE is satisfied for the optional deletion (depth) level D_DE. 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 points where the Vrb curve changes significantly and the leftmost change point can be selected as inflection point data FL (D) _j , FL (V) _j , and FL (F) _j .

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 velocity 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 referred to as inflection point data FL (D, V, F) _j .

2.1: Let Δ2Vi 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

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.
For the selection of conditional expressions 1 to 3, basically conditional expression 2 shall be used, 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. (Adjusting the number of automatic inflection data and intervals)
Conditional expression 4: For the depth Ds (arbitrarily 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".
Abs (FL (D) _j-1- DV (D) _i ) ≥ D_DE is satisfied for the optional deletion (depth) level D_DE. 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 , which 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 points where the Vrb curve changes significantly and the leftmost change point can be selected as inflection point data FL (D) _j , FL (V) _j , and FL (F) _j .

For "calculation N", the change ΔV is calculated by "R" / "B" calculation, and the data position (propagation average speed, calculation depth) at which the sign of the calculation result changes is extracted and used as the 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 of 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 and the second-order difference is forward-calculated, and the inflection point data FL (D, V, F) _j is calculated by 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 referred to as inflection 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 value of the first-order difference changes from minus to plus (zero cross point) is extracted, and the depth and the average propagation 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.
For the selection of conditional expressions 1 to 3, basically conditional expression 1 shall be used, and the same conditional expression shall be applied at the same site.

3.4: FL _j is tentatively determined by DV _i that 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: Of FL (D, V, F) _j , using the frequency F, FL (F) _j = DV (F) _i and FL (F) _{j + 1} = DV (F) _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 value of the second-order difference changes from minus to plus (zero cross point) is extracted, and the depth and the average propagation velocity at that position are extracted.
To summarize the calculation N calculation so far, 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 vacancy of 3.0 m or more, the range vacant by 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.
For the selection of conditional expressions 1 to 3, basically conditional expression 2 shall be used, 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. (Adjusting the number of automatic inflection data and intervals)
Conditional expression 4: For the depth Ds (arbitrarily 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".
Abs (FL (D) _j-1- DV (D) _i ) ≥ D_DE is satisfied for the optional deletion (depth) level D_DE. 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 points where the Vrb curve changes significantly and the leftmost change point can be selected as inflection point data FL (D) _j , FL (V) _j , and FL (F) _j .

“Calculation G” simultaneously confirms the data change ΔD (change in the depth direction) in addition to the data change ΔV (change in 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. do.

"Calculation G" Calculation content D-Vrb curve data DV (D, V, F) In _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: The amount of change ΔD_V _i of the data DV (D, V, F) _i of the D-Vrb curve depending on the i-1st and i-th values of the velocity V and the depth D is calculated by the following formula (1). do.

However, _{ΔD_V i} is the velocity and the amount of change in depth, Di is the _i -th depth data, V _i is the i-th velocity data, i is an integer (i = 1, 2, ...), And VT is at the time of measurement. It is the set maximum speed value, and in 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_Di} 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 roughness is set by the following mathematical formula (3).

4.4: The variable GRL is set as a value indicating the degree of coarseness 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. (Adjusting the number of automatic inflection data and intervals)
Conditional expression 2: For the depth Ds (arbitrarily 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".
Abs (FL (D) _j-1- DV (D) _i ) ≥ D_DE is satisfied for the optional deletion (depth) level D_DE.
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 condition of 4.5 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 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 points where the Vrb curve changes significantly and the leftmost change point can be selected as inflection point data FL (D) _j , FL (V) _j , and FL (F) _j .

[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. It is an inflection calculation. As described with reference to FIG. 4, the input signals from the acceleration detectors 11A and 11B are recorded in the "all data" as values with respect to the frequency at which the measurement was performed. For the input signals SA and SB of Ach and Bch from the acceleration detectors 11A and 11B, the acceleration change amounts _ΔLA and _ΔLB for each unit frequency are obtained, and _ΔLA between the two acceleration detectors 11A and 11B. Also, the difference between ΔLB and _ΔLB is obtained. 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.

Calculation contents of the second automatic inflection point calculation 5.1: Acceleration change amount _ΔLA , ΔLB for each unit frequency with respect to the input signals SA and SB of each of Ach and Bch by the two acceleration detectors 11A and _11B . And further, the difference between _ΔLA and _ΔLB between the two acceleration detectors 11A and 11B is obtained. The amount of change in this difference per unit frequency is obtained, and the inflection point data FL (D, V, F) _j is calculated.

That is, a conditional expression based on the acceleration change amounts _{ΔLA A} and ΔLB is provided, and FL (D) _j = DV (D) _i , FL (V) _j = DV using DV (F) _i satisfying this conditional expression. (V) _i , FL (F) _j = DV (F) _i is extracted from the measurement data DV (D, V, F) _i , and this is the variation 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: At the time of measurement by 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 formulas (4) and (5), and the decibel values _LAVa and _LBVa are obtained. do.

However, _LAVa is the vibration acceleration of Ach (db), SA is the acceleration of Ach (gal), _LBVa is the vibration acceleration of _Bch (db), and SB is the acceleration of _Bch (gal), all of which are for each frequency. It is the maximum value of the vibration acceleration of.

_SA and SB have extensions ^** recorded in the memory at the time of measurement in the same manner as the measurement data DV ( _D , V, F) _i . It is stored in the all data of "all". The extension " ^** . DV "D-Vrb curve and extension" ^** . The all data of "all" stores all the values related to the measurement for the same frequency change. Therefore, _{SA and SB, or LAVa and LBVa are the} measurement data DV (D, V, F) Similar to _i , the order is expressed 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 _{LAVa (i)} and _{LAVa (i-1} ) at a certain point and one point before and after that point are used. ₎ , _{LAVa (i + 1)} and vibration acceleration _{LBVa (i)} , _{LBVa (i-1)} , _{LBVa (i + 1)} are averaged.

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

L _{BVa (i)} = L _{BVa (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 the hit points of the vibration acceleration data, the acceleration change amounts ΔLA _A and _ΔLB for each unit frequency are obtained by the following mathematical formulas (8) and (9).

However, _ΔLA and _ΔLB are the amount of change in the vibration acceleration data of Ach and Bch per 1 Hz, DV (F) _i is the i-th frequency of the measurement data DV, and _{LAVa (i)} and _{LBVa (i)} are extended. The i-th vibration acceleration (db) of Ach and Bch stored in the child “ ^** . All” is shown.

5.4: The difference ΔΔL in 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)

The mathematical formulas (10) and (15) show the calculation contents at the time of 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, and formulas (14) and (15) are when averaging a certain point and 5 points before and after it. The calculation contents are shown respectively. The 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: For the difference ΔΔL of the change amount of the vibration acceleration data obtained in 5.4 above, the change amount ΔΔΔL for each unit frequency is obtained by the following mathematical formula (16).

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, 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 which the operator has performed for 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 consists of a data header part and a data part. Variables such as soft identification number, measurement number, and number of data are stored in the data header part, and the calculation depth D (m), propagation average speed V (m / s), and frequency F (Hz) at the inflection point are stored in the data part. ) Is recorded.

The average propagation 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. Calculated based on the average propagation velocity V _{j + 1} and the calculation depth D _{j + 1} at the inflection point.

In this 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 details of the calculation of the second section speed will be described below.

Section speed calculation details The section speed _Vrj is calculated from the obtained inflection point data using the following section speed calculation formulas (1-1) to (1-3). 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 average propagation 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 (using section velocity calculation formulas (1-3), (1-2) and the following multiple conditional formulas)

6.6: Third section velocity calculation method (using 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 the 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 divided 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 (2)

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 while changing the excitation frequency f, 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 measurement unit having an A / D conversion function. Received, the received input signals SA and SB are processed , the propagation average velocity Vrb (f) and the depth D (f) of the surface wave are calculated for each excitation frequency f, and the propagation average velocity Vrb (f) is calculated. ) And the process of calculating the depth D (f) 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. The section speed between the inflection points is calculated based on the selected inflection points.
The surface wave exploration and analysis apparatus calculates the acceleration changes ΔLA _A and ΔLB for each unit frequency of the excitation frequency f with respect to the input signals SA and SB, and then calculates the acceleration changes _{ΔLA A} and _ΔLB . Along with obtaining the difference, the amount of change in the excitation frequency f of the difference per unit frequency is obtained, and the data position where the sign of the amount of change changes from "+" to "-" is extracted for the depth D and the propagation average speed Vrb. A surface wave exploration and analysis device characterized by selecting the turning point . It is a surface wave exploration analysis method for a geological exploration system that detects surface waves generated around the ground surface by vibrating the ground surface up and down while changing the excitation frequency f, and performs 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. SA and SB are processed to calculate the propagation average velocity Vrb (f) and the depth D (f) of the surface wave for each excitation frequency f, and the propagation average velocity Vrb (f) and the depth D (f). The step of generating the depth D-propagation average velocity Vrb curve by repeating the process of calculating and
A step of selecting multiple inflection points for the generated depth D-propagation average velocity Vrb curve, and
Including the step of calculating the interval velocity between the inflection points based on the selected inflection points.
In the step of selecting the plurality of inflection points, the acceleration change amounts ΔLA and ΔLB for each unit frequency of the excitation frequency f are calculated for the input signals SA and SB, _and then _the calculated acceleration change amount is calculated. The _difference between ΔLA and ΔLB _is obtained, and the amount of change in the excitation frequency f of this difference per unit frequency is obtained. A surface wave exploration analysis method characterized in that the inflection point is selected by extracting the propagation average velocity Vrb .

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