JPH03289587A - Apparatus and method for investigating position of boundary surface of horizontal strata of soil - Google Patents

Abstract

PURPOSE:To easily and accurately estimate the position of the boundary surfaces of horizontal strata of soil by extracting a curve high in correlation as the reflected wave from the boundary surfaces of horizontal strata of soil and extracting the calculated change point of a section dielectric constant. CONSTITUTION:A pulse wave having wide-band frequency is generated from a pulse generator 1 to be transmitted to a transmission antenna 2. The electromagnetic wave sent out as a result is reflected from the boundary surfaces BD1, BD2 of horizontal strata of soil and the other unnecessary reflecting body NN. The reflected waves are received by a receiving antenna 3 while the receiving antenna 3 is allowed to run and the interval between the transmission antenna 2 and the receiving antenna 3 is changed by a definite distance. Next, the received reflected waves are sampled and only inflection points are extracted by an extraction circuit 4. The extracted inflection points are constituted as a plurality of point groups by an operation part 5 and the change point of a section dielectric constant is determined as the boundary surfaces of the horizontal strata of soil to be displayed on a dummy cross section display part 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exploration method and apparatus for estimating the position of a horizontal stratum boundary surface of soil using electromagnetic waves.

[Conventional technology]

Conventionally, two methods have been proposed for estimating the position of the horizontal stratum boundary surface of soil using electromagnetic waves. The steps of this method are shown in (i) and (ii) below.

(i) Measurement method using an integrated transmitting and receiving antenna ∎ Carry out test digging and actually measure the position of the horizontal stratum boundary surface of the soil at the test digging location.

■The integrated transmitting and receiving antenna will be run from near the test excavation.

(2) An electromagnetic wave is sent out from the transmitter of the integrated transmitter/receiver antenna, and the receiver receives the reflected waves of the electromagnetic wave at regular intervals of travel distance, and measures the propagation time.

■Determine the permittivity of each layer based on the test excavation results and the propagation time of electromagnetic waves from the integrated transmitting and receiving antenna near the test excavation.

Apply the dielectric constant estimated in ■■ to exploration locations other than the vicinity of the test excavation, convert it to the overlay of the strata boundary surface, and estimate the horizontal stratum boundary surface position of the soil.

(ff) Measurement method using separate transmitting/receiving antenna ■ Fix one of the separate transmitting/receiving antennas and run the other.

■ Send electromagnetic waves from a transmitting antenna and receive the reflected waves of the electromagnetic waves.The receiving antenna and the transmitting antenna are separated by a certain distance, and the receiving antenna is received while changing the spacing between the transmitting and receiving antennas, and the reflected wave propagation time of the electromagnetic waves is measured. .

■Measured reflected waves Assume that a continuous flow of waveforms with large amplitude values is reflection from a reflective object underground.

■Select a continuous waveform flow that matches the curve assumed to be the horizontal strata boundary surface of the soil from among multiple continuous waveform flows with assumed large amplitude values.

■Calculate and estimate the soil cover at the horizontal stratum boundary surface position from the curvature of the curve selected above.

[Problem to be solved by the invention]

However, the measurement method (i) using an integrated transmitting and receiving antenna has a problem in that it requires some kind of excavation work such as test digging, and is not efficient.

In addition, measurement method (ii) using separate transmitting and receiving antennas does not require excavation work, but it is difficult to extract boundary surfaces other than reflected waves that appear with strong amplitude values, and because unnecessary reflected waves are mixed in, horizontal strata of the soil It is difficult to select a continuous waveform flow that matches the curve when it is assumed to be a boundary surface, and even if it is possible to select it, the weight of the curve determined from multiple point groups varies, making it difficult to select all curves in the same way. There was a problem with accuracy because it was impossible to compare soil cover based on curvature, considering that it was a horizontal stratum boundary surface of soil.

The present invention has been made in view of these points, and an object of the present invention is to provide a method and apparatus that can easily and accurately estimate the position of a horizontal stratum boundary surface of soil.

[Failure to solve the problem]

In order to achieve such an object, the present invention provides an apparatus for detecting the position of horizontal stratum boundary surfaces in soil, which includes a transmitting section and a receiving section that are separated from each other, and the transmitting section includes a pulse generator having a wide frequency band; It is equipped with a transmitting antenna that sends the signal from this pulse generator to the earth's surface as an electromagnetic wave, and the receiving section has a
The receiving antenna changes the distance from the transmitting antenna at regular intervals and captures the reflected waves of the electromagnetic waves sent out from the transmitting antenna, and the reflected waves captured by the receiving antenna are sampled to find the zero-crossing point or inflection point of the electromagnetic waves. The extraction circuit to be extracted and the zero-crossing points or inflection points extracted by this extraction circuit are configured as a plurality of continuous point groups, and each configured point group is a calculation unit that calculates the interval permittivity and soil cover between the curves with high correlation by comparing the curves that occur in the case, using a group of points with high correlation as reflected waves from the horizontal strata boundary surface of the soil;
The present invention includes a pseudo cross-section display section that determines the change point of the calculated section permittivity as the actual horizontal strata boundary surface of the soil and displays the soil cover.

In addition, the method for detecting the position of horizontal stratum boundary surfaces in soil according to the present invention involves transmitting electromagnetic waves with a wide band frequency into the ground from a transmitting antenna, moving the receiving antenna away from the transmitting antenna at regular intervals, and connecting the transmitting antenna and the receiving antenna. Receive reflected waves while changing the interval, extract zero-crossing points or inflection points of the received reflected waves, and configure the extracted zero-crossing points or inflection points as a group of multiple points with continuity. Each point group is compared with the curve that would occur in the case of a reflected wave from the horizontal stratum boundary surface of the soil, and the point group with a high correlation is regarded as the reflected wave from the horizontal stratum boundary surface of the soil, and the section between the curves with a high correlation is The permittivity and soil cover are calculated, and the change point of the calculated section permittivity is determined to be the horizontal stratum boundary surface of the actual soil, and the soil cover is displayed.

[Effect]

The present invention extracts only zero-crossing points or inflection points from a measured waveform in a method of searching by changing the distance between a transmitting antenna and a receiving antenna, and makes the extracted zero-crossing points or inflection points continuous. Each point group is configured as a plurality of point groups, and a group of points with a higher correlation is compared to a curve generated in the case of reflected waves from the horizontal stratum boundary surface of the soil. Separate the curves as waves, calculate the interval permittivity and soil cover between the highly correlated curves, determine the change point of the calculated interval permittivity as the actual horizontal stratum boundary surface of the soil, and display the earth cover. This results in
Even if the amplitude value of the horizontal stratum boundary surface of the soil is small, or even if unnecessary reflected waves are mixed in and it is difficult to fit the curve that occurs in the case of reflected waves from the horizontal stratum boundary surface of the soil, the phase of the fitted curve is By comparing the relationship coefficients, the weight of the curve can be determined, and the position of the horizontal stratum boundary surface of the soil can be easily estimated with high accuracy.

〔Example〕

Next, examples of the present invention will be described. Note that the embodiments are merely illustrative, and it goes without saying that various changes and improvements can be made without departing from the scope of the present invention.

FIG. 1 is a block system diagram showing an embodiment of an apparatus for detecting the horizontal stratum boundary position of soil according to the present invention. In the figure, (a) shows a transmitting section, and (b) shows a receiving section.

In the transmitting section shown in FIG. 1(a), 1 is a pulse generator having a wide frequency band, and 2 is a transmitting antenna that transmits the pulses of the pulse generator 1 as electromagnetic waves into the ground.

In the receiving section of FIG. 1(b), 3 is a receiving antenna for receiving electromagnetic waves reflected from the horizontal stratum boundary surface of soil and other reflective objects, 4 is a receiving antenna for sampling the electromagnetic waves received by the receiving antenna 3, An extraction circuit extracts a zero-crossing point or an inflection point of a sampled electromagnetic wave, and 5 is an arithmetic unit. The calculation unit 5 configures the zero-crossing points or inflection points extracted from the extraction circuit 4 as a plurality of continuous point groups, and calculates the case where each of the configured point groups is a reflected wave from a horizontal stratum boundary surface of soil. The point group with high correlation is regarded as the reflected wave from the horizontal stratum boundary surface of the soil, and the interval permittivity and soil cover between the curves with high correlation are calculated. Reference numeral 6 denotes a pseudo cross-section display section that determines the point of change in the section permittivity calculated by the calculation section 5 as the position of the actual horizontal strata boundary surface of the soil and displays the soil cover.

Next, a method for measuring the horizontal stratum boundary surface position of soil using the apparatus shown in FIG. 1 will be explained with reference to FIGS. 3 to 9, which show the results obtained using the actual soil layer shown in FIG. 2.

In Figure 2, SUF is the ground surface and LAI.

LA2 is for example mountain sand, Kanto loam stratum, BDIBD2
is a horizontal strata boundary surface, and NN is an unnecessary reflective object.

i) A pulse wave having a wide band frequency is generated from the pulse generator 1 shown in FIG. 2, and transmitted from the transmitting antenna 2 shown in the same figure.

ii) As a result, the emitted electromagnetic waves are transmitted to the horizontal strata boundary surfaces BDI, BD2 and other unnecessary reflectors NN of the soil shown in Figure 2.
reflected by.

iii) The reflected wave is received by the receiving antenna 3 shown in FIG. 2 while the receiving antenna 3 shown in FIG.

iv) Next, in the extraction circuit 4 shown in Fig. 2, the received reflected waves are sampled on the coordinate axes of the electromagnetic wave propagation time and the transmitting/receiving antenna interval as shown in Fig. 3, and only the inflection points are extracted as shown in Fig. 4. do.

■ to ■ in Figure 3 show the reflection propagation time of electromagnetic waves on the vertical axis and the amplitude intensity of electromagnetic waves on the horizontal axis, and display the respective reflected waveforms when the transmitting/receiving antenna interval is widened at regular intervals from Om. It is something.

The circles in FIG. 4 indicate inflection points where the amplitude intensity in FIG. 3 changes from a positive direction to a negative direction or from a negative direction to a positive direction.

■) The calculation unit 5 in Fig. 2 configures the inflection points extracted in iv) as a plurality of continuous point groups, and each configured point group is used as a reflection wave from the horizontal stratum boundary surface of the soil. In comparison with the curves that occur in the case of , the point group with high correlation is treated as the horizontal strata interface wave of the soil, and the interval permittivity and soil cover between the curves with high correlation are calculated.

An example of processing performed in the calculation unit 5 in FIG. 2 will be shown below.

(a) In the extraction circuit 4 of FIG. 2, the inflection points extracted as shown in FIG. 4 are squared on the coordinate axes of the electromagnetic wave propagation time and the transmitting/receiving antenna interval, respectively, and displayed as shown in FIG. The circle mark in FIG. 5 indicates the electromagnetic wave propagation time at the inflection point in FIG. 4 and the square of the transmitting/receiving antenna interval, respectively, on the same coordinate axes as in FIG. 4.

('b) From among the point group of inflection points displayed in Fig. 5, multiple point groups that seem to have continuity as shown in Fig. 6 are estimated as ■, ■, ~, @. Then, in order to approximate on a straight line, a starting point and an ending point a, b, . . . , n are given to each point group, and approximate straight lines A, B, .

In Figure 6, . is one of the point groups that are considered to have continuity, and given the starting point a=O・ and the ending point a→・,
The approximate straight line A has just been determined. Furthermore, the next point group (2) of O, which is thought to have continuity, is estimated, a starting point a=+. and an ending point a=O. are given, and an approximate straight line B is determined. Approximate straight lines A, B, ~, from the point group ■, ■, ~■, which seem to have sequential continuity in this way.
N is determined, and ◎ corresponds to point group ■.

(C) Let the approximate straight lines A, B, ~, N determined in (b) determine the matching or shortest point group ■', ■', ~, ■' on the electromagnetic wave propagation time axis as shown in Figure 7, Furthermore, each determined point group ■′, ■′, ~, ■′
, the lines iA', B', .

7 in Fig. 7 is the point group ■' that coincides with or is the shortest point group on the electromagnetic wave propagation time axis with the approximate straight line liA in Fig. 6, and from this point group ■', the reflected wave from the horizontal stratum boundary surface of the soil is calculated by the least squares method. A straight line A' is determined based on the assumption that Furthermore, the straight line B', which is assumed to be a reflected wave from the horizontal strata boundary surface of the soil, is determined by the least squares method from the following point group ■'.In this way, the point group ■', ■', ~
, ■', straight lines A', B', . . . , N' are determined.

Note that ◎ corresponds to point @'.

(d) Straight lines A', B', ~, N' and point group ■'■'
, ~, and ○', and calculate the interval permittivity and earth cover between the straight lines from the slope and vertical axis intercept of only those lines with high correlation, as shown in FIG.

○ connected by solid lines in Figure 8 is a point group ■′■′, ~, ■′
Correlation coefficients of , ○ connected by thick lines indicate interval permittivity of only those with high correlation coefficients, and ○ connected by solid lines indicate overburden of only those with high correlation coefficients.

vi) The point of change in the section permittivity calculated in v) is determined to be the horizontal strata boundary surface of the soil, and is displayed as shown in FIG. 9 on the pseudo section display section 6 of FIG. 2.

Although the above description of the operation has been made only for the inflection point, the same effects as those for the inflection point can be achieved with the same device and the same operation for the zero cross point.

FIG. 10 is a flowchart showing the procedure of the above-mentioned measuring method. In the figure, first, an electromagnetic wave is transmitted from the transmitting antenna 2 (see FIG. 1) (step 11), a reflected wave is received by the receiving antenna 3 (step 12), and the received reflected wave is sampled (step 13). Next, step 14) to extract zero-crossing points or inflection points, and step 15) to extract multiple consecutive point groups of zero-crossing points and inflection points. Step 16) to fit the curves, step 17) to calculate each correlation coefficient, and step 18 to extract hypothetical curves whose correlation coefficients are above a certain value.
), Calculate the interval permittivity and soil cover between the extracted hypothetical curves (Step 19), Determine the change point of the interval permittivity as the horizontal strata boundary (Step 20), Display the pseudo cross section of the horizontal strata boundary ( Step 21).

Using this method, the horizontal stratum boundary surface of soil can be estimated without any excavation work, and by extracting only the zero-crossing points or inflection points of continuous waveforms, horizontal strata of soil with small amplitude values can be estimated. It can also be captured at a stratum boundary surface, and even if it is difficult to select a curve that matches the curve that would occur in the case of a reflected wave from a horizontal stratum boundary surface due to the inclusion of unnecessary reflected waves, it is possible to capture the The weight of the point group can be compared by comparing the correlation coefficient with the curve that occurs when the wave is reflected from the horizontal stratum boundary surface of the soil. By extracting, calculating the interval permittivity and soil cover between curves with high correlation, and extracting the points of change in the calculated interval permittivity, it is possible to easily and accurately estimate the position of the horizontal stratum boundary surface of the soil.

〔Effect of the invention〕

As explained above, the present invention sends electromagnetic waves with a wide band frequency from the transmitting antenna underground, moves the receiving antenna away from the transmitting antenna at regular intervals, and collects reflected waves while changing the distance between the transmitting antenna and the receiving antenna. Receive and extract the zero crossing point or inflection point of the received reflected wave,
The extracted zero-crossing points or inflection points are configured as a plurality of continuous point groups, and each configured point group is compared with a curve that occurs in the case of a reflected wave from the horizontal strata boundary surface of soil, and the correlation is calculated. The high point group is the reflected wave from the horizontal stratum boundary surface of the soil, and the interval permittivity between the curves with high correlation,
By calculating the soil cover and determining the change point of the calculated interval permittivity as the actual horizontal stratum boundary surface of the soil and displaying the soil cover, the horizontal stratum boundary surface of the soil can be determined without any excavation work. By estimating the position and extracting only the zero-crossing points or inflection points of a continuous waveform, it is possible to capture even horizontal strata boundary waves of soil with small amplitude values.

In addition, even if it is difficult to select a curve that matches the curve that occurs in the case of reflected waves from the horizontal stratum boundary surface of soil due to the inclusion of unnecessary reflected waves, it is possible to In contrast to the curve that occurs in the case of reflected waves from
By comparing the correlation coefficients, the weights of point groups can be compared, and curves with high correlation are extracted as reflected waves from the horizontal stratum boundary surface of the soil, and the interval permittivity and soil cover between the curves with high correlation are calculated. By extracting the points of change in the calculated interval permittivity, it is possible to easily and accurately estimate the position of the horizontal strata boundary surface of the soil.

[Brief explanation of drawings]

Fig. 1 is a block system diagram showing an embodiment of an apparatus for searching for the horizontal stratum boundary position of soil according to the present invention, and Fig. 2 shows an embodiment of the search method according to the present invention, and shows the soil layers actually explored. Fig. 3 is a graph showing the sampling wave of the observation signal, Fig. 4 is a graph showing the extraction of inflection points from the sampling wave, and Fig. 5 is a graph showing the inflection point with electromagnetic wave propagation time and transmission/reception. Figure 6 is a graph displaying the antenna spacing squared on the coordinate axes, and shows a situation where a straight line approximated to a group of points with continuity of inflection points is given by specifying the starting point and ending point. The graph shown in Fig. 7 is the 6th
A graph showing the situation in which a group of points that match the straight line given in the figure or are the shortest on the vertical axis are selected, and the straight line is fitted using the best squares method, assuming that all the points are horizontal strata boundary surfaces underground. Figure 8 is the same as Figure 7. A graph showing the results of calculating the correlation coefficient of the straight line group fitted by , and calculating the interval permittivity and soil cover of objects with high correlation coefficients. Figure 9 shows the change points of the interval permittivity calculated in Figure 8. 10 is a flowchart for explaining an embodiment of the method for searching for the horizontal stratum boundary position of soil according to the present invention. It is. 1...Pulse generator, 2...Transmission antenna, 3...
- Receiving antenna, 4... Extraction circuit, 5... Arithmetic unit,
6...Pseudo cross section display section, SUF...Ground surface, LAl
, LA2...Geological stratum, BDl, BD2...Horizontal stratum boundary surface, NN...Unnecessary reflective object.

Claims (2)

[Claims] (1) A transmitting section and a receiving section are provided which are separated from each other, and the transmitting section is provided with a pulse generator having a wide frequency band and a transmitting antenna that transmits a signal from the pulse generator to the ground surface as an electromagnetic wave. , the receiving section changes the distance from the transmitting antenna at regular intervals, and includes a receiving antenna that captures reflected waves of electromagnetic waves sent out from the transmitting antenna, and samples the reflected waves captured by the receiving antenna, and An extraction circuit extracts zero-crossing points or inflection points of electromagnetic waves, and the zero-crossing points or inflection points extracted by this extraction circuit are configured as a plurality of continuous point groups, and each configured point group is A calculation unit that compares the curves that occur in the case of reflected waves from horizontal stratum boundary surfaces, uses points with high correlation as reflected waves from horizontal stratum boundary surfaces of soil, and calculates the interval permittivity and earth cover between curves with high correlation. and a pseudo cross section display section that determines the point of change of the calculated interval permittivity as the actual horizontal stratum boundary surface of the soil and displays the soil cover. (2) Send electromagnetic waves with a wide band frequency underground from the transmitting antenna, move the receiving antenna away from the transmitting antenna at regular intervals, and receive the reflected waves while changing the distance between the transmitting antenna and the receiving antenna. The zero-crossing points or inflection points of the reflected waves are extracted, the extracted zero-crossing points or inflection points are configured as a plurality of points with continuity, and each configured point group is connected to the horizontal strata boundary surface of the soil. Contrast this with the curve that occurs when the reflected wave from A method for detecting the position of a horizontal stratum boundary surface of soil, characterized by determining a point of change in permittivity as the actual horizontal stratum boundary surface of soil and displaying the soil cover.