JP2008134070A - Inspection method for pile existing under fundamental structure and its measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection method capable of precisely measuring the position and the diameter of piles, existing under a fundamental structure, and reducing the measuring points tremendously to reduce labor burden and analysis burden in measuring. <P>SOLUTION: On the upper face of a concrete fundamental structure 1, accelerating sensors are set sequentially with the position changed, and frequency analysis is performed for the wave shape, obtained by striking the periphery thereof with a hammer or a steel ball. By detecting the peak positions from the distribution state of the spectrum values in a period or its nearby period in which the response spectrum of the concrete fundamental structure 1 stands out, a plurality of the edge end positions of the pile 2 are specified. The position and the diameter of the pile is determined based on the plurality of edge end positions of the pile. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an investigation method for measuring the position and diameter of a pile existing under a foundation structure by analyzing an elastic shock wave generated by hitting the surface of a concrete foundation structure such as a footing with a hammer or the like, and therefore It relates to a measuring device.

  For example, when reinforcing the foundation of a power transmission tower or when constructing a tunnel or underpass with a shield or propulsion work on the lower ground of an existing structure, a pile extending from the lower surface of the foundation structure into the ground There is a need to investigate the position, pile diameter and pile length. If these blueprints are in place, this information can be easily obtained. However, for old structures, the blueprints are often discarded. It is necessary to investigate the layout and pile diameter of the existing piles by nondestructive inspection.

  When estimating pile arrangement and pile diameter under existing structures, hitherto hitting the top surface of the footing with a hammer to generate an elastic shock wave, and the reflected wave from the bottom of the footing or the pile is detected by an acceleration sensor installed near the hit point. The method of measuring and measuring the frequency of the measured data to determine the presence or absence of piles and the pile diameter has been adopted. This method is called a pile integrity test (hereinafter referred to as PIT test), which was originally a method of investigating pile damage by directly hitting the pile head. It has come to be adopted as a method to investigate the position, pile diameter and pile length. The measurement principle of the PIT test is as follows: (1) The impact emitted from the pile head is reflected at the impedance sudden change part inside the pile body and returns to the pile head; (2) The impedance sudden change inside the pile body where reflection occurs. The part has damage to the tip of the pile, cracks, etc., and there is a sudden change in the cross section of the pile, and (3) the position of the sudden change in impedance can be determined from the time required for the reflected wave to return and the elastic wave velocity. Based on.

  Examples of the use / application of the PIT test include the following Patent Document 1 and Non-Patent Document 2. In the following Patent Document 1, it is a non-destructive investigation method for investigating which part of a foundation slab body has a foundation pile, and the investigation range of the foundation slab body is divided into a plurality of areas, and an accelerometer for each division. , Hit the vicinity with a hammer, analyze the frequency of the elastic wave detected by the accelerometer, and determine whether there is a foundation pile directly under the hit point by whether or not a peak appears at a specific frequency Nondestructive investigation method for investigating the position of the foundation pile based on the above, and nondestructive investigation to investigate the diameter of the foundation pile directly under the pillar from the foundation slab body interposed between the pillar and the foundation pile This method is to take measurement points on a straight line at appropriate intervals from the center point position of the bottom of the column, install an accelerometer at each measurement point, hit the vicinity with a hammer, and detect with the accelerometer Frequency analysis of the elastic wave After determining whether or not there is a foundation pile directly under the impact point, measure the distance between the measurement point that is farthest from the column position and the center point of the column bottom. Thus, a non-destructive investigation method for a foundation pile for measuring the diameter of the foundation pile is disclosed.

In the following Non-Patent Document 2, in order to investigate the presence / absence of the pile under the box culvert, the pile position, and the pile length, a shock wave is used on the transmitting side, and a piezoelectric sensor having sensitivity in the high frequency range is used on the receiving side. A specific frequency range that reflects the most prominently at the tip or crack is selected by the filter function, and the reflected wave position from the sensor position is specified, hitting with a steel hammer in the vicinity of the sensor, and reflected to the exploration waveform When no wave is seen, it is judged that there is no pile, and when a clear reflected wave is obtained from the tip of the pile, it is judged that there is a pile, and the pile length is obtained from the propagation time and propagation speed of the reflected wave It is.
JP 2002-181951 A Toshihiro Horiuchi and three others, “Application example of non-destructive exploration technology to the existing pile survey of construction and promotion part of city gas trunk line”, September 2003, Japan Society of Civil Engineers, 58th Annual Scientific Lecture Summary VI -358, p715-716

However, in the case of the inventions described in Patent Document 1 and Non-Patent Document 2, there is the following problem because it is basically a method for determining only the presence or absence of a pile.
(1) Since the peak frequency changes depending on the footing and the thickness of the bottom plate, the accuracy of accurately determining the presence or absence of piles cannot be maintained.
(2) Since the bottom of the footing and bottom plate is laid with crushed stone and then thrown away concrete, the bottom is not necessarily smooth, so the reflected wave may be disturbed. The accuracy of accurately determining the presence or absence of piles cannot be maintained.
(3) Depending on the type of pile, the impedance ratio between the pile and footing or bottom slab increases, so the presence or absence of a pile cannot be accurately determined and may not be applicable.
(4) Since a large number of mesh points are required on the upper surface of the footing or bottom plate, a great deal of labor is required for measurement and analysis.
(5) Since the obtained reflected waveform is analyzed by trial and error to detect the pile position, it takes time to determine the presence or absence of the pile, and quick feedback to the survey site is not possible, and the pile position is not fixed, or Problems such as the need to repeat the measurement until the pile position was obtained sometimes occurred.
(6) Hammers used for measurement vary in material, shape, etc. and need to be used depending on the material and shape of the measurement object, so the degree of dependence on experience is large. Therefore, it is easy to make a difference in measurement accuracy depending on individual skill level.
(7) The pile diameter requires more exploration accuracy than the above-mentioned pile presence / absence measurement, so the measurement accuracy error and measurement labor burden will increase.

  Therefore, the main problem of the present invention is the position of the pile regardless of bad conditions such as footing and bottom plate thickness change, pile type, footing and bottom plate bottom surface, presence of chestnuts, etc., and regardless of individual skill level. In addition to being able to measure the diameter and diameter with high accuracy, the number of measurement points can be greatly reduced, the measurement labor burden and analysis burden can be greatly reduced, and the pile position and pile diameter can be easily identified at the site. An object of the present invention is to provide a method for investigating piles and a measuring device therefor.

In order to solve the above-mentioned problem, the present invention according to claim 1 is an investigation method for measuring the position and pile diameter of a pile existing under a concrete foundation structure,
On the upper surface of the concrete foundation structure, an acceleration sensor is installed while changing the position sequentially, and the waveform obtained by hitting the vicinity with a hammer or a steel ball is subjected to frequency analysis, and the response spectrum of the concrete foundation structure is outstanding. A plurality of edge positions of the piles are detected by detecting peak points from the distribution state of the spectrum values in the period to perform or the vicinity thereof, and the pile position and the pile diameter are obtained based on the edge positions of the plurality of piles. A method for investigating a pile existing under a foundation structure is provided.

  The invention according to claim 1 is an investigation of a pile in which an acceleration sensor is installed on the upper surface of a concrete foundation structure while sequentially changing its position, and the waveform obtained by hitting the vicinity with a hammer or a steel ball is subjected to frequency analysis. In the method, when the acceleration sensor is positioned immediately above the edge of the pile, the elastic shock wave is propagated along the side surface of the pile head embedded in the foundation structure. Based on the knowledge that the diffused reflected wave reflected by the light is less diffused than the part without the pile and a large spectral value can be obtained. According to this knowledge, the waveform data obtained by the acceleration sensor Frequency analysis and detecting the peak point from the distribution state of the spectrum value in the period where the response spectrum of the concrete foundation structure is dominant or in the vicinity period. It is possible to accurately identify the edge position. And if several pile edge end position is calculated | required, it will become possible to obtain | require the position and pile diameter of a pile based on these.

As the present invention according to claim 2, an investigation method for measuring the position and pile diameter of a pile existing under a concrete foundation structure,
It is obtained by placing an acceleration sensor on the top surface of a concrete foundation structure in an area where there is no pile on the bottom surface of the concrete foundation structure, and hitting the vicinity with multiple types of hammers or steel balls with different masses. Frequency analysis of the obtained waveform, and a first procedure in which the peak period obtained in common is used as the period of interest;
A second procedure for setting a survey line on the concrete foundation structure;
Set measurement points at appropriate intervals along the survey line, install an acceleration sensor at each measurement point in sequence, analyze the frequency of the waveform obtained by hitting the vicinity with a hammer or a steel ball, and analyze the period of interest. A third procedure for detecting a peak point from the distribution state of the spectrum value and identifying two edge positions of the pile;
Set a second survey line in a direction passing through the two points specified as the edge position of the pile and intersecting the survey line, and set a survey point at an appropriate interval along the second survey line, Install an acceleration sensor at each measurement point in sequence, analyze the frequency of the waveform obtained by hitting the vicinity with a hammer or steel ball, detect the peak point from the distribution state of the spectrum value in the period of interest, A fourth procedure for identifying one or two end positions;
A method for investigating a pile existing under a foundation structure comprising a fifth procedure for geometrically calculating a pile position and a pile diameter from three to four points specified as edge positions of the pile Is provided.

  According to the second aspect of the invention, a first procedure for specifying a period of interest corresponding to a period in which the response spectrum of the foundation structure is dominant, a second procedure for setting a survey line on the foundation structure, and along the survey line A third procedure for specifying two edge positions of the pile at the position, and a third procedure for specifying the edge positions 1 or 2 of the pile at a position along the second measurement line set to intersect the measurement line. This is a fifth procedure for geometrically calculating the pile position and the pile diameter based on the procedure and the edge position of the pile obtained from 3 to 4 points.

  In the above first procedure, by specifying the period of interest (period in which the response spectrum is dominant) used for detecting the edge of the pile, the spectrum value is clearly expressed, so trial and error in the analysis can be reduced. In the 3rd and 4th steps, by focusing on the response intensity (spectrum value) of the reflected wave in the period of interest, the footing and bottom plate thickness change, pile type, footing and bottom plate bottom surface, presence of chestnut The edge position of the pile can be measured with high accuracy regardless of the unfavorable conditions such as the above and irrespective of the individual skill level. In addition, since the edge positions of the piles are found on two intersecting survey lines, the number of measurement points can be greatly reduced, and the measurement labor burden and analysis burden can be greatly reduced. Since the edge position of the pile can be specified locally, it is possible to prevent rework.

  As the present invention according to claim 3, there is provided a method for investigating a pile existing under a foundation structure according to claim 1, wherein a hammer or a steel ball to be used is selected in the first procedure.

  According to the third aspect of the present invention, in the first procedure, a hammer or a steel ball in which a peak of a spectral value is clearly expressed to some extent is selected, and the use of an inappropriate hammer or steel ball is used. Decrease in accuracy and rework can be prevented.

  As a fourth aspect of the present invention, an impact tool made of a hammer or a steel ball, an acceleration sensor, an amplifier that amplifies a waveform signal from the acceleration sensor, an A / D converter that converts an analog waveform signal into a digital waveform signal, and The frequency analysis is performed on the digital waveform signal to obtain the spectrum value, and the period in which the response spectrum is dominant or the vicinity thereof, or the spectrum value in the period of interest, the horizontal axis is the measurement position, and the vertical axis is the spectrum. The measuring apparatus for the investigation method of the pile which exists under the foundation structure in any one of Claims 1-3 which consists of a computer which has a function to display as a value.

  As described in detail above, according to the present invention, the piles and bottom plate thickness changes and pile types, footings and bottom plate bottom surface irregularities, such as the presence of chestnuts, and regardless of individual skill level, piles As a result, the position and the diameter of the sensor can be measured with high accuracy, the number of measurement points can be greatly reduced, and the measurement labor and analysis burden can be greatly reduced. Furthermore, it becomes possible to easily specify the pile position, pile diameter, etc. at the site.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Measurement principle]
The measurement principle of the investigation method of the pile existing under the foundation structure according to the present invention will be described in detail with reference to FIG.

  In the present invention, on the upper surface of a concrete foundation structure 1 having piles 2 and 2 on the lower surface side, the acceleration sensor 3 is installed while changing the position sequentially, and the waveform obtained by hitting the vicinity with a hammer or a steel ball. When the frequency analysis is performed and the distribution state of the spectrum value (horizontal axis: station position, vertical axis: spectrum value) in the period in which the response spectrum of the concrete foundation structure 1 is dominant or in the vicinity thereof is verified, the edge of the pile 2 It is noted that a peak point is detected at a measurement point corresponding to the end position.

  FIG. 1 is a structural cross-sectional view of a concrete concrete structure 1 (hereinafter also referred to as footing) of a steel tower having piles 2 and 2 on the lower surface. (A) is the elasticity at a position where no pile 2 exists. Shock wave reflection status, (b) shows the elastic shock wave reflection status at the position where the pile 2 exists, and (c) shows the elastic shock wave reflection status at the edge position of the pile 2 according to the present invention. .

  When the pile 2 of (a) does not exist, the elastic shock wave is repeatedly reflected at a period corresponding to the thickness D of the footing 1 while being diffused and attenuated at the time of reflection. When the pile 2 of (b) exists, the reflection and transmittance of the elastic wave are determined according to the impedance ratio between the foundation concrete 1 and the pile 2. That is, when the impedance ratio is large, the reflectance is large and the transmittance is small. When the impedance ratio is small, the reflectance is small and the transmittance is large. Part of the elastic shock wave generated on the upper surface of the footing 1 is reflected by the pile head and repeatedly reflected with diffusion and attenuation. The elastic shock wave transmitted to the pile 2 is diffused on the peripheral surface of the pile 2 and the boundary surface of the tip. The reflection is repeated with attenuation.

  In contrast to (b) and (b), in the case of the edge position of the pile 2 in (c), the head of the pile 2 is embedded in the footing 1 for a certain length, so Diffusion after being transmitted along the side of the head and reflected by the bottom surface of the footing 1 is suppressed by the embedded portion of the pile 2, so that the attenuation due to the diffusion of the reflected wave is smaller than the other portions, and the acceleration sensor The signal strength received by 3 is greater than in the cases (a) and (b).

  Therefore, paying attention to the period in which the response spectrum of footing 1 is dominant or its neighboring period so that the spectrum value becomes clear, the edge position of the pile 2 is determined by detecting the peak point from the distribution state of the spectrum value in that period. It becomes possible to specify.

〔measuring device〕
As shown in FIG. 2, the measuring device used in the method for investigating a pile existing under a foundation structure according to the present invention includes an impact tool 4 made of a hammer or a steel ball, an acceleration sensor 3, and an acceleration sensor 3. The amplifier 5 that amplifies the waveform signal of A, the A / D converter 6 that converts the analog waveform signal into the digital waveform signal, frequency analysis is performed on the digital waveform signal to obtain a spectrum value, and the concrete foundation structure The computer 7 has a function of displaying a spectrum value in a period in which the response spectrum is dominant or a period in the vicinity thereof (attention period) as a measurement position on the horizontal axis and a spectrum value on the vertical axis.

  The computer 7 includes an interface 8 for connecting to an external device, a CPU 9, a main memory 10, a large-capacity memory 11, a touch display panel (monitor) 12, and a keyboard 13, and is a portable notebook. Use the type.

〔Measurement procedure〕
Hereinafter, the method for investigating a pile according to the present invention will be described in detail in accordance with the measurement procedure shown in FIG. 3 and based on the specific work procedure.

(1) Selection of hammer or steel ball and identification of period of interest As preparations before measuring pile position and pile diameter, first the hammer or steel ball hitting tool 4 is selected and the response spectrum of the concrete foundation structure is outstanding. Specify the period. For the hammer or steel ball striking tool 4, a plurality of types having different masses or materials are prepared in advance, and an acceleration sensor is used in a region that is the upper surface of the foundation structure and does not have the pile 2 on the lower surface. 3 is installed, and the vicinity thereof is hit with the plurality of types of hitting tools 4, and the reflected wave is measured by the acceleration sensor 3. If the waveform data is adjusted, such as noise removal using a digital filter, amplification corresponding to the passage of time, correction of variation in striking force, etc., the obtained waveform data is subjected to FFT (high speed). (Fourier transform) analysis is performed to obtain a spectrum diagram for each of the impacting tools 4, as shown in FIG.

  In the example of FIG. 4, spectrum diagrams are drawn for three types of steel balls, but it can be seen that the cycle in which the maximum peak value of the spectrum value occurs varies depending on the mass of the steel ball, but the response spectrum of footing 1 is A common peak appears in the period of excellence (736 μs), and this period is specified as the period of interest. In addition, as for the steel balls used for the measurement, a steel ball whose period of interest is easy to distinguish (a peak is clear and other peaks are not close) is selected. In the illustrated example, it is desirable to select an intermediate striking tool 4 (steel ball <medium>).

(2) Setting of survey line Next, as shown in FIG. 5, the survey line 14 is set on the upper surface of the footing 1. In setting the survey line 14, the pile position is predicted in advance in consideration of the ground type, the terrain state, the footing shape, and the like. In the illustrated example, the measurement line 14 is set along the direction of 45 degrees from the corner of the footing 1.

(3) First-stage pile edge specific measurement Next, measurement points are set at appropriate intervals along the survey line 14, and the acceleration sensor 3 is sequentially installed at each of these measurement points. ) Is subjected to frequency analysis, the peak point is detected from the distribution state of the spectrum value in the period of interest, and two edge positions of the pile 2 are specified.

  The waveform data measured by the acceleration sensor 3 is stored in the large-capacity memory 11 of the computer 7, and these waveform data are called into the main memory 10, and as shown in FIG. After adjustment of waveform data such as amplification corresponding to the passage of time and correction of variation in impact force, FFT (Fast Fourier Transform) analysis is performed on the adjusted waveform data, as shown in FIG. As shown in the figure, a distribution state graph of spectrum values in the period of interest is created (the horizontal axis is the measurement position and the vertical axis is the spectrum value). As can be seen from FIG. 6, the spectral value shows a peak at the edge position e of the pile 2, and the peak position can be identified as the edge position of the pile 2. In addition, regarding the measurement point interval, it is possible to accurately measure the pile diameter by setting the measurement pitch finely at the edge position of the pile 2.

  In addition, it is estimated that the reason that the spectrum value is large on the end side of the region L is that the end surface of the footing 1 suppresses diffusion in the side surface direction. Further, no significant difference was observed in the spectrum value between the region L where the pile 2 was not present and the region p where the pile 2 was present.

(4) Edge-specific measurement of pile in the second stage If two edge positions (e, e) of pile 2 are specified, then the edge position between two points e, e passes and A second survey line 15 is set in a direction intersecting the survey line, a survey point is set at an appropriate interval along the second survey line 15, and the acceleration sensor 3 is sequentially installed at each of these survey points. Frequency analysis of the waveform obtained by hitting with the hitting tool 4 selected in 1), and the peak position from the distribution state graph of the spectrum value in the period of interest (the horizontal axis is the measurement position and the vertical axis is the spectrum value) Is detected and two edge positions (one point) or two points (e ′, e ′) of the pile 2 are specified.

(5) Calculation of pile position and pile diameter from 3 to 4 pile edge positions Geometric from (3 to) 4 points (e, e, e ', e') specified as edge positions of pile 2 The position and diameter of the pile 2 are calculated scientifically.

(6) Others If the pile position and the pile diameter of one pile 2 among the plurality of piles 2, 2... Existing on the lower surface side of the footing 1 are determined, the remaining pile positions are the same from the footing side edge. Since it can be presumed that it is located, a survey line 16 is set at a position along the side of the footing 1 through the center of the pile, and measurement points are set along the survey line 16 at appropriate intervals. The acceleration sensor 3 is sequentially installed at the point, and the vicinity of the acceleration sensor 3 is subjected to frequency analysis on the waveform obtained by hitting with the hitting tool 4 selected in (1), and the distribution state graph of the spectrum value in the period of interest (the horizontal axis is The position of the peak point is detected from the measurement position and the vertical axis is the spectrum value), and the two edge positions (e, e) of the pile 2 are specified. Since it is known that the survey line 16 passes through the center of the pile, it is not necessary to set the intersecting survey line, and only the survey line 16 is sufficient.

[Other examples]
(1) In the above embodiment, the foundation structure in which the piles 2 and 2 exist under the footing of the steel tower foundation is targeted. However, the present invention can be similarly applied to an underground structure such as a box culvert. is there.
(2) This measurement method focuses on the fact that elastic shock waves are less diffused at the edge position of the pile 2, so the type of the pile 2 is not limited. It can be applied to cast-in-place concrete piles, ready-made concrete piles and steel piles.
(3) The thickness of the footing 1 can be calculated backward from the target period in the procedure of (1) selecting the hammer or steel ball and specifying the target period (period in which the response spectrum is excellent) in the above-described embodiment.
(4) By the way, when calculating the number of measurement points, in this measurement, in order to detect the position of the first pile 2, the hammer was selected 3 times, the pile edge detection was 2 lines and 24 points. 27 measurements will be performed, and the second to fourth pile arrangement will be 39 times, 13 average points per line, and 66 measurements in total. On the other hand, if it is assumed that a grid-like station with a pitch of 10cm is set in the range of 1.0m square per pile of the first edge pile as in the conventional method, the number of stations is 121 times. The remaining three are assumed to be capable of exploring the pile position with 1/3 of the first number of measurement points, measuring 121 times, for a total of 242 measurements. As a result, the number of times of measurement of the present invention is about 27% (66/242), which is considered to be a method with excellent speediness and economy.

It is a figure for demonstrating the measurement principle of the pile investigation method which concerns on this invention. It is a block diagram which shows the structure of a measuring apparatus. It is a flowchart which shows the procedure of the pile investigation method which concerns on this invention. It is a spectrum figure which shows the specific point of selection of a hammer or a steel ball, and an attention cycle (period where a response spectrum is excellent). It is a footing top view which shows the survey line setting point of the pile investigation method which concerns on this invention, a measurement point, and a measurement result. It is a distribution state graph (spectral position on the horizontal axis and spectral value on the vertical axis) of spectral values in the period of interest. It is a flowchart which shows the analysis procedure in the computer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Concrete foundation structure (footing), 2 ... Pile, 3 ... Acceleration sensor, 4 ... Impact tool, 5 ... Amplifier, 6 ... A / D converter, 7 ... Computer, e'e '... Pile edge position, 14 ~ 16 ... Survey line

Claims (4)

An investigation method for measuring the position and diameter of a pile existing under a concrete foundation structure,
On the upper surface of the concrete foundation structure, an acceleration sensor is installed while changing the position sequentially, and the waveform obtained by hitting the vicinity with a hammer or a steel ball is subjected to frequency analysis, and the response spectrum of the concrete foundation structure is outstanding. A plurality of edge positions of the piles are detected by detecting peak points from the distribution state of the spectrum values in the period to perform or the vicinity thereof, and the pile position and the pile diameter are obtained based on the edge positions of the plurality of piles. A method for investigating piles existing under a foundation structure. An investigation method for measuring the position and diameter of a pile existing under a concrete foundation structure,
It is obtained by placing an acceleration sensor on the top surface of a concrete foundation structure in an area where there is no pile on the bottom surface of the concrete foundation structure, and hitting the vicinity with multiple types of hammers or steel balls with different masses. Frequency analysis of the obtained waveform, and a first procedure in which the peak period obtained in common is used as the period of interest;
A second procedure for setting a survey line on the concrete foundation structure;
Set measurement points at appropriate intervals along the survey line, install an acceleration sensor at each measurement point in sequence, analyze the frequency of the waveform obtained by hitting the vicinity with a hammer or a steel ball, and analyze the period of interest. A third procedure for detecting a peak point from the distribution state of the spectrum value and identifying two edge positions of the pile;
Set a second survey line in a direction passing through the two points specified as the edge position of the pile and intersecting the survey line, and set a survey point at an appropriate interval along the second survey line, Install an acceleration sensor at each measurement point in sequence, analyze the frequency of the waveform obtained by hitting the vicinity with a hammer or steel ball, detect the peak point from the distribution state of the spectrum value in the period of interest, A fourth procedure for identifying one or two end positions;
A method for investigating a pile existing under a foundation structure comprising a fifth procedure for geometrically calculating a pile position and a pile diameter from three to four points specified as edge positions of the pile .   The method for investigating a pile existing under a foundation structure according to claim 1, wherein a hammer or a steel ball to be used is selected in the first procedure.   A hammer or a steel ball hitting tool, an acceleration sensor, an amplifier that amplifies the waveform signal from the acceleration sensor, an A / D converter that converts an analog waveform signal into a digital waveform signal, and a frequency analysis for the digital waveform signal And a computer having a function of obtaining a spectrum value and displaying a period in which the response spectrum is dominant or a period near the period or a spectrum value in the period of interest as a measurement position on the horizontal axis and a spectrum value on the vertical axis The measuring apparatus for the investigation method of the pile which exists under the foundation structure in any one of Claims 1-3 characterized by these.

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