JP2002181951A - Method for non-destructively inspecting foundation pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grasp the conditions of existing foundation piles in a state where an existing structure exists. SOLUTION: The range of inspection is subdivided in a mesh shape in such a way as to maintain any given constant shape over a range in which the grasping of the location of a foundation pipe 5 is desired with a foundation slab main body 2 is present. Accelerometers 1 are arranged at the points of intersection in the set mesh, and a light hammer 10 is used to hit the foundation slab main body 2 close to the accelerometers 1. Frequency analysis is performed on waveforms detected by the accelerometers 1. In the case that some frequency components are conspicuously detected, it is determined that the foundation pile 5 is not present under the foundation slab main body 2. These operations are repeated on every mesh to determine the presence or absence of the foundation pile 5 within the range of inspection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The condition (position,
The present invention relates to a non-destructive investigation method for foundation piles for investigating a diameter and the like in a non-destructive state.

[0002]

2. Description of the Related Art Conventional nondestructive investigation is a method of estimating an underground structure from the propagation speed of an artificially generated elastic wave (seismic wave). The part must be exposed.

[0003]

In a situation where an existing structure exists, a conventional non-destructive inspection using an elastic wave is based on the fact that a reflected wave is generated due to a cross-sectional change between the foundation slab body and the head of the foundation pile. However, the waves returning from the tip of the foundation pile became weak and were buried in the noise due to the reflected waves, so the waveforms were not clear and the investigation could not be performed until after the structure was dismantled.

In the renovation and renewal work of existing structures, the existence of existing foundation piles often hinders construction, and the cost and design method of handling existing foundation piles depends on whether they can be reused or not. different. For this reason,
It is important to grasp the condition of the foundation pile at an early stage before construction starts.

According to the present invention, it is determined whether or not a foundation pile exists below a strike point based on the frequency components included in a waveform measured by striking the foundation slab body.
It aims to provide a non-destructive method for investigating foundation piles.

[0006]

According to the first aspect of the present invention,
A non-destructive inspection method for investigating whether a foundation pile is located directly below which part of a foundation slab body, dividing the investigation range of the foundation slab body into a plurality, installing an accelerometer for each section, The vicinity is hit with a hammer, the elastic wave detected by the accelerometer is subjected to frequency analysis, and whether or not a peak appears at a specific frequency, based on determining the presence or absence of the foundation pile immediately below the impact point, It is characterized by investigating the location.

According to a second aspect of the present invention, there is provided a non-destructive method for investigating a diameter of a foundation pile immediately below a column from a foundation slab body interposed between the column and the foundation pile. Take measurement points on a straight line at an appropriate interval from the center point position, install an accelerometer for each measurement point, hit the vicinity with a hammer, analyze the frequency of the elastic wave detected by the accelerometer, After judging the presence or absence of a foundation pile immediately below the impact point based on whether or not a peak appears at a specific frequency, the distance between the center point of the column bottom and the measurement point determined to have the foundation pile at the farthest position from the column position It is characterized by measuring the diameter of the foundation pile by measuring.

[0008]

FIG. 1 is a sectional view showing a non-destructive inspection for exploring the position of a foundation pile. Reference numeral 1 denotes an accelerometer, 2 denotes a base slab body, and 5 denotes a base pile. As shown in the figure, the existing base slab body 2 is
A wave is generated by hitting using 0, and the presence or absence of the foundation pile position is determined by analyzing the frequency component of this waveform.

There are three types of waveforms generated when the basic slab body 2 is hit, namely, a direct wave 6, a reflected wave 7, and a transmitted wave 8. The direct wave 6 is a wave that does not pass through the inside of the basic slab body 2 by hitting the basic slab body 2, is generated on the surface, and is directly captured by the accelerometer 1,
This is a waveform that needs to be removed in the nondestructive investigation in the present invention.

The reflected wave 7 is transmitted from the surface 3 of the base slab by hitting the base slab body 2, and transmits through the base slab body 2, and the bottom surface 4 of the base slab is struck.
This is a waveform that is captured by the accelerometer 1 after being reflected by. If there is no skeleton at the bottom of the base slab body 2, the reflected wave is almost totally reflected on the surface 3 and the bottom surface 4 of the base slab,
Multiple reflections 9 will occur.

The transmitted wave 8 is a wave which is incident on the surface 3 of the basic slab by hitting the basic slab main body 2 when a skeleton such as the basic pile 5 is present below the basic slab main body 2. After passing through the inside of the foundation slab body 2, the waveform is transmitted through the skeleton such as the foundation pile 5 without being reflected on the bottom surface of the foundation slab body 2.

Next, a method for determining the presence or absence of the foundation pile 5 in the present invention will be described. The presence or absence of the foundation pile 5 in the lower part of the foundation slab main body 2 is determined using the reflected wave 7 in the waveforms described above.

[0013] As shown in FIG.
The survey range is subdivided into, for example, a mesh 12 that maintains an arbitrary constant shape in a range in which the position of the foundation pile 5 is to be grasped in the state where the stake exists. Next, the accelerometer 1 is set on, for example, an intersection of the set mesh 12 and the base slab body 2 near the accelerometer 1 is hit by utilizing the light hammer 10.

Among the waveforms generated by the impact, the accelerometer 1 measures the direct wave 6 and the reflected wave 7,
Except for the direct wave 6 and the portion that is considered to have a large effect, the other reflected wave 7 is analyzed for each frequency component by Fourier analysis or the like (FIG. 3). Since the reflected wave 7 enters from the surface 3 of the base slab and is reflected by the bottom surface 4 of the base slab, the reflected wave 7 reaches the accelerometer 1 every time when the base slab 2 reciprocates one time. The frequency component of the waveform measured by the accelerometer 1 can be expressed by equation (1).

F = c / 2H (1) c: Wave velocity H: Slab thickness

If the foundation pile 5 does not exist below the foundation slab body 2, the reflected wave 7 causes multiple reflections 9, so that the frequency component represented by the equation (1) is outstanding. Also, when the foundation pile 5 is present below the foundation slab body 2, the reflected wave 7 is not totally reflected,
Since the transmitted wave 8 penetrating into the foundation pile is generated, the reflected wave 7
Immediately becomes weak, and the frequency component shown in the equation (1) does not become outstanding. (FIG. 4)

From these measurement results, it is determined that there is no foundation pile 5 when a peak appears at a frequency caused by multiple reflections 9 in the basic slab body 2 and that there is no foundation pile 5 when no peak appears. . These operations are repeated for all the meshes 12, and the foundation pile 5
Is determined.

In addition, the existing pillar 13 exists and the foundation pile 5
A method for measuring the diameter of the foundation pile 5 in a situation where the position is known will be described. On a straight line passing through the center point of the bottom surface of the pillar 13,
Several measurement points 11 are determined at intervals of several to 10 cm from the position of the column 13, the accelerometer 1 is installed on the measurement point 11, and the vicinity thereof is hit with a light hammer 10. (Fig. 5)

As described above, the presence or absence of the foundation pile 5 is determined based on whether or not a prominent peak appears at the frequency caused by the multiple reflection 9 in the foundation slab body 2 with respect to the frequency component of the obtained waveform. . The approximate diameter of the foundation pile 5 is calculated by measuring the distance between the measurement point determined to have the foundation pile 5 and the center point of the bottom surface of the column 13. (FIG. 6)

Although the light hammer 10 is used for hitting the base slab body 2, the present invention is not limited to this.

As a method of removing the direct waves 6, a light hammer 10 is used when the basic slab body 2 is hit.
Alternatively, a method of separately obtaining an input waveform using an impact hammer and subtracting the input waveform from a measurement wave may be considered.

According to the above-described configuration, it is possible to grasp the condition of the existing foundation pile 5 in a state where the foundation slab 2 and the like are present, and to reflect the situation on the design and construction plan of the repair and renewal work. Becomes

[0023]

According to the non-destructive inspection method of claim 1, the non-destructive inspection method for investigating which part of the foundation slab body is directly below the foundation pile is provided. It is divided into a plurality of parts, an accelerometer is installed for each section, the vicinity is hit with a hammer, the elastic wave detected by the accelerometer is subjected to frequency analysis, and whether or not a peak appears at a specific frequency is determined. From investigating the position of the foundation pile based on judging the presence or absence of the foundation pile immediately below the point,
It is possible to grasp the position of the foundation pile even in the presence of structures such as the foundation slab with simple equipment, and reflect it in the design and construction plan of renovation, renewal, etc. at an early stage before construction starts This contributes to shortening the construction period and reducing construction costs.

According to a second aspect of the present invention, there is provided a non-destructive inspection method for investigating a diameter of a foundation pile immediately below a column from a base slab body interposed between the column and the foundation pile. ,
Taking measurement points on a straight line at appropriate intervals from the center point position of the bottom surface of the column, installing an accelerometer at each measurement point, hitting the vicinity with a hammer, and changing the elastic wave detected by the accelerometer to frequency Analyze and determine the presence or absence of a foundation pile immediately below the strike point based on whether or not a peak appears at a specific frequency.Then, the measurement point determined to have a foundation pile farthest from the column position and the center point of the column bottom By measuring the distance from the base pile, the diameter of the foundation pile is measured, and as described above, it can be reflected in the design and construction plan of repair and renewal at an early stage before the start of construction, shortening the construction period, It is effective in reducing construction costs.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a situation of a non-destructive inspection for exploring a position of a foundation pile.

FIG. 2 is a plan view showing a situation of a non-destructive inspection for exploring a foundation pile position.

FIG. 3 is a graph showing an example of a measured waveform and a portion used for determination.

FIG. 4 is a graph showing an example of measured multiple reflection frequencies.

FIG. 5 is a plan view showing a situation of a non-destructive inspection for exploring a foundation pile diameter.

FIG. 6 is a graph showing an example of measured multiple reflection frequencies.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Accelerometer 2 Basic slab main body 3 Surface of basic slab main body 4 Base bottom of basic slab main body 5 Foundation pile 6 Direct wave 7 Reflected wave 8 Transmitted wave 9 Multiple reflection 10 Light hammer 11 Measurement point 12 Mesh 13 Column

Claims (2)

[Claims] 1. A non-destructive inspection method for inspecting a portion of a foundation slab body directly below a portion of a foundation slab, wherein an investigation range of the foundation slab body is divided into a plurality of sections, and an accelerometer is provided for each section. Install, hit the area with a hammer,
The elastic wave detected by the accelerometer is subjected to frequency analysis, and whether or not a peak appears at a specific frequency, based on determining the presence or absence of the foundation pile immediately below the impact point, to investigate the position of the foundation pile. Non-destructive survey method for foundation piles. 2. A non-destructive inspection method for investigating a diameter of a foundation pile immediately below a column from a foundation slab body interposed between the column and the foundation pile, the method being more appropriate than a center point position of a bottom surface of the column. Take measurement points on a straight line at an appropriate interval, install an accelerometer at each measurement point, hit the vicinity with a hammer, analyze the elastic wave detected by the accelerometer, and find a peak at a specific frequency. By judging the presence or absence of the foundation pile immediately below the impact point, by measuring the distance between the measurement point determined to have the foundation pile at the position farthest from the column position and the center point of the column bottom, A nondestructive method for investigating a foundation pile, comprising measuring a diameter of the foundation pile.