JP6319763B2 - Method for evaluating the diameter of a hardened rod with a cement-based hardener on site and vibration measuring instrument - Google Patents

Description

  The present invention relates to a method for evaluating the diameter of a hardened rod-shaped body made of a cement-based hardener on site and a vibration measuring instrument.

  Conventionally, in order to reduce the influence of construction work on the effective use of resources and environmental problems, the piles of existing buildings have been reused during the replacement work of buildings. When reusing a pile, the pile concrete must first have a predetermined shape. To that end, the approximate diameter of piles buried in the ground must be evaluated.

As a method of evaluating the pile diameter,
Drilling a boring hole from the upper end of the pile body to the lower part;
Using the vibration measuring instrument inserted in the borehole, the inner surface of the borehole is vibrated at the first point at a predetermined depth from the surface of the earth, and the elasticity is applied from this inner surface toward the boundary between the pile body and the ground. Transmitting waves,
Receiving an elastic wave returned from the boundary point at a second point slightly away from the first point in a vertical direction;
There has been known a method including a step of calculating a time from transmitting an elastic wave to receiving it and calculating a diameter of the pile body from this time (Patent Document 1).
Also, as the vibration measuring instrument, an elastic wave transmitter and receiver are provided in the main body inserted into the boring hole, and the time when the transmitter transmits the elastic wave and the time when the elastic wave is received can be recorded. It has been proposed (Patent Document 1).

Japanese Patent No. 495729

"JSME Text Series Vibrating" Published by the Japan Society of Mechanical Engineers First edition date September 16, 2005

  In the apparatus of Patent Document 1, the surface vibration wave that reaches the receiver through the inner surface of the borehole from the transmitter of the borehole is also received. The time required for the surface vibration wave to reach the receiver from the transmitter is not much different from the time required for the elastic wave to reflect from the transmitter to the boundary between the pile body and the ground and reach the receiver. For this reason, the receiver receives an elastic wave in which two vibration waves are mixed, and it is difficult to specify the arrival time of the elastic wave reflected at the interface between the pile body and the ground. For this reason, there existed a possibility that measurement accuracy might worsen.

  Although the vibration of the object to be measured is used, as a method for measuring the thickness of concrete based on a principle completely different from Patent Document 1, a pillar or wall is struck from outside to vibrate, and the peak frequency of the vibration is proportional to the concrete thickness. There is something that focuses on the relationship (page 66 of Non-Patent Document 1). In this method, it is possible to obtain a peak frequency by Fourier-transforming a time history waveform of vibration due to impact, and to evaluate the thickness of the concrete from the peak frequency. However, it is practically difficult to drive piles buried in the ground from outside.

  The inventors of the present application have studied this problem earnestly, and even when a boring hole is drilled in a pile body or the like and a pile body is hit from the hole, a proportional relationship is established between the peak frequency and the pile diameter. This has been experimentally confirmed, and measures have been taken to solve the inherent problems associated with internal blows, leading to the practical application of the present invention.

The first object of the present invention is to provide a method for evaluating the rod diameter from the peak frequency of vibration obtained by vertically setting a hole at the upper end opening in a hardened rod-shaped body made of cement-based hardener and hitting the inside of the hole. That is.
The second object of the present invention is to measure the rod diameter of a hardened rod made of cement-based hardener, which enables reliable data to be observed even when the hole is displaced from the center of the hardened rod made of cement-based hardener due to excavation error. It is to propose a measurement method.
The third object of the present invention is to propose a vibration measuring instrument suitable for carrying out the method of measuring the diameter of a hardened rod-like body made of the cement-based hardener.

The first means is a method for evaluating the diameter of a hardened rod-shaped body made of a cement-based hardener cast in-situ in a pothole,
A first step of drilling a boring hole extending downward from the upper end of the cured rod-shaped body made of cement-based curing material in the longitudinal direction of the cured rod-shaped body made of the cement-based cured material;
A second step of inserting a striking device with an acceleration sensor into the boring hole;
A third step of hitting a predetermined portion of the inner surface of the borehole using the hitting device;
A fourth step of measuring a time history waveform of a hardened rod-shaped body made of a cement-based hardener at the hitting position by the hitting;
A fifth step of obtaining a peak frequency of vibration of the hardened rod-shaped body by the cement-based hardener by Fourier transforming the time history waveform;
Using the vibration peak frequency and vibration body size conversion means prepared in advance, from the peak frequency of vibration of the cured rod-shaped body by the cement-based cured material, the diameter of the hitting point of the cured rod-shaped body by the cement-based cured material A sixth step to evaluate
Consists of
The said conversion means is the following functional formula, The evaluation method of the rod diameter of the hardening rod-shaped body by the on-site-type cementitious hardening material characterized by the above-mentioned.
[Formula 1] D = a · f (D is a diameter, f is a peak frequency, and a is a coefficient)

  This means evaluates the rod diameter of the hardened rod-shaped body C made of a cement-based hardener cast in place in the hole B shown in FIG. 1, and its features extend in the longitudinal direction on the rod-shaped body. A hole is drilled, the ball is struck in a certain direction from the inside of the hole, and the peak frequency is obtained by Fourier transforming the time history waveform resulting from the struck, and the rod diameter of the rod-shaped body (in this case, the diameter is calculated from this peak frequency). Corresponding value). Compared with the conventional method of measuring the arrival time of the vibration wave from the hit point to the measurement point through the reflection point (outer surface of the rod-like body) as in Patent Document 1, the extra vibration that passes other than the desired route is achieved by this means. The outer diameter of the rod-like body C can be accurately evaluated without being confused by noise caused by waves.

  Specifically, this means includes at least a first step of drilling a boring hole D in a hardened rod-like body C made of a cement-based hardener [see FIG. 6 (A)], and a striking device 8 in the boring hole D. Second step of insertion [see FIG. 6 (B)], third step of striking the inner surface of the boring hole D with the striking device 8 [see FIG. 7 (D)], and time history waveform obtained by the striking A fourth step [see FIG. 7 (D)], a fifth step (see FIG. 8) to obtain a peak frequency by Fourier transform of the time history waveform, and an outer diameter of the rod-like body C from the peak frequency. Obtaining a sixth step.

  The “hardened rod-shaped body made of cement-based hardener” includes, in addition to a concrete pile body, a concrete pier erected in water as shown in FIG. 22, a cemented bar-shaped ground improvement body by injecting cement milk into the soil. “Blowing” of this means includes continuous hitting (continuous hitting) at the same place without changing the conditions. “Conversion means” includes a conversion table in which individual numerical values of peak frequencies correspond to predetermined rod diameters, in addition to a function expression. “Evaluation” refers to determining whether or not the outer diameter of the rod-shaped body meets the required standard, and is a broader concept than measurement. For example, it includes the case where the right or wrong of reuse is determined from the knowledge of the relative change in the outer diameter of the rod-like body in the longitudinal direction. The “boring hole” can be evaluated with good accuracy if the hole has a sufficiently small diameter with respect to the outer diameter of the rod-shaped body. In the performance test of the present invention, it is desirable that [the diameter of the boring hole] / [the outer diameter of the rod-shaped body] is 0.22 or less. The cross-sectional shape of the cured rod-like body may be not only a perfect circle (see FIG. 9) but also an oval (see FIG. 24) or a quadrangle. Further, the present invention can be applied by evaluating a regular polygon not less than a pentagon as a circle. One boring hole is preferably provided at the centroid (the center of the figure), but in the case of a shape that is long in the horizontal direction, such as the above-described oval shape, a plurality of boring holes may be provided in the longitudinal direction.

In this means, it is proposed to use a linear function formula established between the diameter D and the peak frequency f. According to the experiment by the inventors of the present application, as shown in FIG. 10, in the intermediate portion C3 excluding the upper end portion and the lower end portion of the hardened rod-shaped body made of cement-based hardener, the vibration mode (“both It was found that the "cantilever type vibration mode" is considered to hold. Thereby, as a specific aspect of Equation 1, Equation 3 described later is established.

The second means includes a first means, and is the striking device comprises a locking means for temporarily locking the percussion device itself in the hole, and in the second step, the striking apparatus in the borehole There is a sub-step of locking the striking device against the inner surface of the borehole between the sub-step of inserting the bore and the sub-step of striking the inner surface of the borehole with a hitting device at a constant height.

  This means is that after the batting device 8 is inserted into the boring hole D and before the boring device 8 strikes the boring hole D, the locking means 16 of the batting device 8 is moved as shown in FIGS. It is proposed to actuate and lock the striking device 8 against the inner surface of the borehole D. Thereby, the striking direction is not shaken and a constant striking force can be applied.

The third means has the first means or the second means, and the hitting device hits one place in the circumferential direction of the hole surface of the boring hole and can change the hitting position in the circumferential direction. Is composed of
In the third step, after hitting one place in the circumferential direction of the hole surface of the boring hole with the hitting device at a certain height, the direction of the hitting device is changed to hit another place in the circumferential direction. I did it.

  This means proposes to change the orientation of the striking device 8 at the same height of the boring hole D as shown in FIG. 7 (E) to FIG. 7 (F). Thus, as shown in FIG. 1, when a dent R is formed at a specific location in the circumferential direction of the rod-shaped body C, the value of the peak frequency in that direction as shown in FIG. Since it decreases compared to the value of the peak frequency in the other direction, the formation of a local recess can be detected. If the cause of the dent is generally a jumper or the like due to poor construction, the dent usually occurs locally, so the application of this means is effective.

The fourth means has third means, and the boring hole is drilled in the longitudinal direction of the rod-shaped body from the center point of the upper end surface of the cured rod-shaped body made of cement-based hardener,
Stroke to each location in the circumferential direction of the cured rod-shaped body C with the cement-based hardener is performed continuously under the same conditions, and the measurement accuracy is obtained from a series of peak frequencies obtained by this continuous strike. .

In this means, on the premise that the striking direction is changed at a constant depth, it is proposed to obtain measurement accuracy from a plurality of peak frequencies obtained by striking a plurality of times in each direction. By evaluating the measurement accuracy, it is possible to evaluate the deviation of the boring hole D from the center of the hardened rod C due to the cement-based hardener at a predetermined depth. That is, as shown in FIG. 19A, when there is a boring hole at the center of the hardened rod-shaped body made of cement-based hardener, the distance (thickness t) from the borehole D to the surface of the hardened rod-shaped body C made of cement-based hardener is While the constant value (19.5 cm in an arbitrary direction in the illustrated example), when the boring hole D is in an eccentric position as shown in FIG. 20A, the thickness varies depending on the direction ( In the case of the illustrated example, t ₁ = 9.5 cm in the direction in which the boring hole D is displaced from the center, t ₃ = 29.5 cm on the opposite side, and t ₂ = 17.4 cm in the direction orthogonal to the direction of displacement. ). When a batting test was performed in each direction (see FIG. 21), the measurement accuracy when striking in the direction perpendicular to the direction of deviation was particularly low compared to other cases. From this, it can be seen from the magnitude of the measurement accuracy whether the boring hole is deviated from the center of the rod-like body C.

According to the invention relating to the first means, the inside of the cured rod-shaped body C made of cement-based hardened material is hit, and the peak frequency of vibration is obtained from the time history waveform of the hitting location, so that The rod diameter can be accurately evaluated.
According to the invention relating to the first means, since the function formula is used, the numerical value of the rod diameter converted from the peak value can be objectively obtained, and the numerical value can be mechanically calculated using a computer or the like.
According to the invention relating to the second means, the striking device is inserted into the boring hole, and the striking device is locked after being fixed at a certain height, so that the striking force becomes uniform, and a more reliable result can be obtained. .
According to the third aspect of the invention, since several places in the circumferential direction of the boring hole are struck at a constant height, the dent R generated in a part in the circumferential direction due to a change in peak frequency due to the struck direction. Can be detected.
According to the invention relating to the fourth means, the measurement accuracy can be obtained from a series of peak frequencies obtained by repeatedly striking several places in the circumferential direction, and more reliable evaluation can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall view of an application example of a method for evaluating a rod diameter of a hardened rod-shaped body made of a cement-based hardener according to the first embodiment of the present invention and a vibration measuring machine. FIG. 2 is an almost entire view of the vibration measuring machine of FIG. 1. It is a side view of the principal part (striking device) of the vibration measuring device of FIG. It is explanatory drawing which looked at the operation | movement of the hit | damage apparatus of FIG. 3 in the boring hole from the side. It is explanatory drawing which looked at operation | movement of the striking device of FIG. 3 in a boring hole from the front direction. It is explanatory drawing of the step which comprises the evaluation method of the rod diameter of FIG. 1, The same figure (A) shows the step which drills a boring hole in a pile body, The same figure (B) shows an impact apparatus in a boring hole. FIG. 5C shows a step of locking the hitting device at a fixed height in the polling hole. It is a figure for demonstrating the continuation of the step which comprises the evaluation method of the rod diameter of FIG. 1, The figure (D) is a step which strikes the inside of a boring hole with a striking device, The figure (E) is the figure. The step of releasing the locked state inside the boring hole D and FIG. 5F show the step of changing the direction of the striking device. It is explanatory drawing of the step which derives | leads-out a peak frequency from the time calendar waveform obtained by the said impact. In order to explain the step of changing the direction of the striking device of FIG. 7 (F), FIG. 9 (A) is a cross-sectional view of the pile body in a healthy state, with the pile body cut at the striking location. FIG. 9 (B) is a cross-sectional view of a pile body having a dent in a part thereof. It is explanatory drawing of the vibration mode when hitting each part of a pile body, the same figure (A) shows a mode that hits the upper end part of a pile body, the same figure (B) shows a mode that hits the lower end part of a pile body, The figure (C) depicts a state in which the middle part of the pile body in the vertical direction is hit. It is a conceptual diagram of the concrete pile body of the existing building which is the object which applies the rod diameter measuring method of FIG. It is a figure which shows the preliminary procedure prior to the procedure shown in FIGS. 6-7 of the said rod diameter measuring method. It is explanatory drawing of the experiment conducted with the rectangular pillar as a reference example of this invention, The figure (A) is a longitudinal cross-sectional view of a pillar, The figure (B) is a cross-sectional view of a pillar. It is a graph showing the result of having performed the impact test about the pillar of FIG. 13, and measuring the relationship between the thickness of the concrete of an impact direction, and a peak frequency. It is explanatory drawing of the experiment conducted with the pile body with a hole which cut off the right-and-left side part as Experimental example 1 of this invention, The figure (A) is a cross-sectional view of a pile body, The figure (B) is the figure It is a longitudinal cross-sectional view of a pile body. It is a graph showing the result of having performed the impact test about the pile body of FIG. 15, and measuring the relationship between the outer diameter of concrete in a striking direction and the peak frequency. It is explanatory drawing of the experiment conducted with the pile body with a hole horizontally mounted on two support stand as Experimental example 2 of this invention, The figure (A) is a cross-sectional view of a pile body, FIG. (B) is a longitudinal sectional view of the pile body. It is a graph showing the result of having performed the impact test about the pile body of FIG. 17, and measuring the relationship between the distance between fulcrums, and a peak frequency. It is explanatory drawing of the 1st pile body which drilled the hole in the center part used for Experimental example 3 of this invention, The figure (A) is a cross-sectional view of a pile body, The figure (B) It is a longitudinal cross-sectional view of the pile body. It is explanatory drawing of the 2nd pile body which drilled the hole in the eccentric position used for Experimental example 3 of the present invention, The figure (A) is a cross-sectional view of a pile body, The figure (B) It is a longitudinal cross-sectional view of the pile body. It is a graph showing the result of having struck the inside of the hole of the said 1st pile body and a 2nd pile body, and measuring the relationship between the thickness of the concrete of a striking direction, and a peak frequency. It is the longitudinal cross-sectional view which represented the bridge pier made from concrete which is the application object of 2nd Embodiment of this invention, showing the structure of the bridge with the imaginary line. It is explanatory drawing showing the state which applied this invention with respect to the concrete pier of FIG. It is a cross-sectional view of the pier shown in FIG.

  FIG. 1 to FIG. 21 show a first embodiment of the present invention. This embodiment includes a measuring mechanism including a method for evaluating the diameter of a hardened rod-shaped body using a cement-based hardened material on site and a vibration measuring instrument. It is an example applied to a pile. For the convenience of explanation, the explanation of the mechanism is first given before the explanation of the method.

  FIG. 1 is an overall view in which the measurement mechanism 1 is applied to a pile structure. In the figure, A is the ground, B is a pit, C is a pile body, and D is a boring hole drilled in the pile body.

  The measuring mechanism for measuring the rod diameter includes the vibration measuring device 2 and the analyzer 40. The vibration measuring instrument 2 is a means for inserting into the boring hole D, and its specific structure is disclosed in FIGS. The analyzer 40 is installed on the ground surface.

  FIG. 2 shows the overall configuration of the vibration measuring instrument 2. The vibration measuring machine 2 includes a vertical shaft 4 and a striking device 8.

  The vertical shaft 4 is a vertically long bar-like member in which the hitting device 8 is connected to the lower end portion, and has an operation portion 6 for operating the hitting device 8 at the upper end portion. In a preferred illustrated example, the vertical shaft 4 is composed of an outer tube portion 4a and a shaft rod portion 4b. The shaft 4 may be formed as a hollow tube and the vertical shaft 4 may be formed in a double tubular shape. The operation portion 6 is attached to the upper end of the shaft rod portion 4b. The outer tube portion 4a is connected to the device main body 10 of the impact device 8 described later, and the orientation of the impact device 8 can be changed by rotating the outer tube portion 4a. The shaft rod portion 4b is connected to a gear box 14 which will be described later, and is formed such that a lock means 16 which will be described later moves in conjunction with the rotation of the shaft rod portion 4b via the gear box. These functions will be described later.

  In a preferred example of illustration, the vertical shaft 4 is divided into a plurality of parts in the longitudinal direction, and the joints 5 formed at the ends of these parts are connected to each other so as to have a predetermined length. It can be added. In the drawing, only the joint of the outer tube portion 4a appears, but the joint also exists in the shaft rod portion 4b. Further, the striking device 8 may be detachable from the lower end portion of the vertical shaft 4. Thereby, at the time of a movement, the striking device 8 and the vertical shaft 4 can be separated, and the vertical shaft 4 can be further divided into several parts, so that it is easy to carry to the construction site.

  As shown in FIGS. 3 and 4 which are side views, the hitting device 8 includes a main body 10, a lock means 16, a hitting means 22, and an acceleration sensor 32.

  The apparatus main body 10 is provided with a first auxiliary plate portion 12a extending upward from a front end portion of a horizontal base 12, a gear box 14 is disposed at a middle portion in the front-rear direction of the base, and a rear portion of the base 12 An acceleration sensor 32 described later is attached to the upper surface. Further, as shown in FIG. 5 which is a side view, the lower end of the vertical connecting plate 13 that is wide in the front-rear direction is connected to one side of the base 12 in the left-right direction, and the left-right direction from the upper end of the connecting plate 13 is connected. A second auxiliary plate portion 13a that covers the upper side of the gear box 14 protrudes to the other side of the gear box 14. The first auxiliary plate portion 12a has a first through hole 12b, and the second auxiliary plate portion 13a has a second through hole 13b.

  The lower part of the shaft portion 4b of the vertical shaft 4 enters the gear box 14 through the second through hole 13b. The gear box 14 incorporates a gear mechanism that converts the rotational force of the shaft rod portion 4b into the advancing / retreating force of the pressing rod 18 described later.

  The locking means 16 includes a pressing rod 18 that protrudes forward from the gear box 14 via the first through hole 12 b, and a pressing portion 20 that is attached to the front end of the pressing rod 18.

  The striking means 22 may have any structure as long as it can strike the weight portion 28 having a certain weight against the inner surface of the boring hole D. The striking means 22 of the present embodiment projects a rotating arm 26 from a lower end of a hanging plate portion 23 that is suspended from the lower surface of the base 12 via a pivoting portion 24, and a weight is placed on the distal end side of the rotating arm 26. The part 28 is attached. The illustrated rotating arm 26 is formed of a strip-like elongated plate material, but the shape thereof can be changed as appropriate. In a more preferred example, the rotating arm 26 is formed by connecting a base portion 26a projecting from the pivot attachment portion 24 and a tip portion 26b with a bolt 27, and the weight portion 28 is attached to the tip portion 26b. ing.

  The end portion 26b of the rotating arm 26 is connected to an end portion of a drawstring 30 suspended from above. At all times (except when the batting operation is performed), the rotating arm is pulled away from the inner surface of the boring hole D by being pulled by the string 30, and when the string 30 is released, the rotating arm 26 is restored to the original position. The weight portion 28 attached to the rotating arm is driven to the inner surface of the boring hole D.

  The acceleration sensor 32 is provided so that acceleration can be measured by bringing the rear surface (the surface opposite to the installation position of the locking means 16) into contact with the inner surface of the boring hole D. In the illustrated example, the lower surface of the front portion of the box-shaped acceleration sensor 32 is attached to the upper surface of the base 12 so that the rear portion of the acceleration sensor 32 protrudes rearward of the apparatus main body 10. The acceleration sensor 32 and the ground analyzer 40 are connected by a signal line 34.

  In the illustrated example, as shown in FIG. 2, a holding tool 36 that holds a string 30 and a signal line 34 extending from the striking device 8 to the ground along the vertical shaft 4 in the vicinity of the vertical shaft 4 at appropriate positions in the vertical direction. It is attached to the vertical shaft 4.

  In the above configuration, the striking device 8 attached to the vertical shaft 4 is inserted into a portion of the boring hole D at a certain depth. When the operation unit 6 is rotated, the shaft 4b of the vertical shaft 4 is rotated, and the rotational force is converted into a forward force of the pressing unit 20 by the gear box 14, and the front surface of the pressing unit 20 and the rear surface of the acceleration sensor 32 are moved. It abuts on the boring hole D. When the string 30 is released in this state, the rotating arm 26 rotates and the weight portion 28 of the tip portion 26b of the rotating arm 26 strikes the inner surface of the boring hole D. The vibration due to the impact is measured by the acceleration sensor 32, and the measurement result is transmitted as a signal to the analyzer 40 via the signal line. Next, when the operation unit 6 is rotated in the reverse direction, the pressing unit 20 moves backward, and the pressing unit 20 and the acceleration sensor 32 are separated from the inner surface of the boring hole D. Next, when the outer tube portion 4a is rotated, the entire striking device 8 is rotated and its direction can be changed. A more detailed operation will be described in the method of the present invention.

6 and 7 show the main steps of the method for evaluating the diameter of a hardened rod-shaped body with a cement-based hardener according to the present invention. The evaluation method will be described based on these drawings.
(1) First step of boring hole D [FIG. 6 (A)]
First of all, the existing pile body left after the existing building is removed (hardened rod-like body C made of cement-based hardener according to claim 1) is drilled so as not to be displaced from the vertical axis of the pile body as much as possible. Hole D is drilled. When there are a plurality of pile bodies to be reused, it is desirable to drill boring holes D in all pile bodies. For example, a method of evaluating after selecting a pile body to be drilled by a random sampling method is also suitable. Can be implemented. At this time, in order to measure the vibration characteristics of the pile body (coefficient a in Equation 1) and the like, it is desirable to remove at least one soil on the top of the pile body. explain.

(2) Second step of inserting the striking device 8 into the boring hole D [FIG. 6B]
The hitting device 8 is attached to the lower end of the vertical shaft 4, and the hitting device 8 is inserted into the boring hole D. At this time, depending on the depth of the boring hole D, the parts of the vertical shaft 4 may be added as necessary to ensure a sufficient length.

(3) A third step of hitting the inside of the boring hole with the hitting device [FIG. 6 (C) to FIG. 7 (D)].
When the striking device 8 inserted into the boring hole D reaches a certain depth, the shaft bar portion 4b is rotated. Then, the pressing portion 20 of the locking means 16 is pushed outward and the pressing portion 20 and the acceleration sensor 32 are pressed into the bore hole D. Thereby, the striking device 8 is locked. When the string 30 is released in the locked state, the rotating arm 26 with the weight portion 28 rotates around the pivoting portion 24, and the weight portion 28 strikes a predetermined location in the boring hole D. As described above, the reason for locking the hitting device 8 is that the hitting device 8 can be hit without being displaced by the reaction when the rotating arm 26 swings, and the hitting device 8 is fixed. It is to be able to obtain a striking force.
In addition, when hitting the predetermined location in the boring hole D, it is desirable to hit continuously several times for every predetermined location (continuous hit). This is because the peak frequency of vibration can be obtained more precisely when there are a plurality of measured values. The continuous hitting is performed with a certain time interval so that the vibrations of the hits do not overlap. Moreover, it is a case where the boring hole D is drilled at the center of the pile body, and the vibration peak frequency obtained when striking a certain direction and the vibration obtained by striking the opposite direction are obtained. The peak frequency is theoretically the same measured value. This is not limited to a circular pile body in a plan view, and the same applies to a rectangle or an ellipse.

(4) Fourth step of measuring a time calendar waveform of vibration caused by the hitting [FIG. 7D]
The hard rod C made of cement hardener vibrates due to the impact of the impact device 8, and the acceleration sensor 32 senses this vibration. This measured value is sent to the analyzer 40 via the signal line 34.

(5) Fifth step of obtaining a vibration peak frequency from the time calendar waveform [FIG. 8]
When the above time calendar waveform is displayed as it is on the display of the analyzer 40 with the vertical axis as the waveform size and the horizontal axis as the time axis, the result is as shown in FIG. Next, when the time calendar waveform is Fourier-transformed using the calculation function of the analyzer 40, a peak appears on the left side in the illustrated example of FIG. Incidentally, the vibration peak of the apparatus main body 10 itself (the peak on the right side in the illustrated example) appears in the figure after the Fourier transform. Since the peaks of the apparatus main body 10 appear in the same size and position, they can be easily distinguished.

(6) Sixth step of obtaining the rod diameter of the rod-shaped body from the peak frequency of the vibration Using the following function formula prepared in advance and stored in the analyzer 40, the cured rod-shaped body made of the cement-based hardener is From the peak frequency of vibration, the diameter of the hitting portion of the hardened rod-shaped body with the cement-based hardener is evaluated.
[Formula 1] D = a · f (D is a diameter, f is a peak frequency, and a is a coefficient)
The meaning of this mathematical expression and how to obtain the coefficient a will be described later.

(7) Seventh step of changing the direction of the impact device [FIGS. 7E to 7F]
As shown in FIG. 7E, when the operation unit 6 is rotated in the direction opposite to that shown in FIG. 6C, the pressing unit 20 is pulled inward (on the apparatus main body side) with the rotation of the shaft bar 4b. The locked state is released.
Next, as shown in FIG. 7F, when the outer tube portion 4a is rotated, the orientation of the entire apparatus changes. By doing so, the hit | damage location of a hit | damage apparatus is changed and the operation | work of said (2) to (6) is repeated. As a preferred embodiment, in FIG. 9, the measurement is performed for the observation points 1 to 8 on the inner peripheral surface of the boring hole D at intervals of 45 °. FIG During P ₁ is the centroid. The reason for placing a plurality of locations in the circumferential direction is that, first, when a dent R is formed on a part of the outer peripheral surface of the pile body, it appears as a shift in peak frequency for each direction. Second, when the boring hole D is deviated from the true center due to an error in excavation work, it appears in the form of an increase in the deviation of the peak frequency multiple times. These will be further described later.

  After performing the steps (3) to (7) with respect to the predetermined depth of the boring hole D, the striking device 8 is moved down or raised to move to a position with a different depth. The same work should be done. Thereby, when the dent is produced in a part of the pile body in the vertical direction, the presence of the dent can be accurately sensed. The vertical length that can vibrate the pile body by a series of striking operations vibrates only about 91 to 95 cm in the vicinity of the striking point as will be described later. If the hit position is changed by changing the depth position of hitting at a distance of 45 to 50 cm, high quality evaluation can be performed without missing the dent generated in the pile body.

In the present embodiment, the peak frequency of the vibration is measured by moving the striking device 8 in the bore hole D as described above, but the evaluation of the rod diameter, hitting the upper portions C ₁ and a lower end portion C ₂ of the rod-shaped body Then, as shown in FIGS. 10 (A) and 10 (B), a vibration mode in which one end is a fixed end and the other end is free (referred to as a “cantilever type vibration mode”) is a rod-like shape excluding the upper end and the lower end. when struck the middle part C ₃ of the body, the vibration mode of the doubly supported beam type as shown in FIG. 10 (C). Formula 1 of the present embodiment corresponds to the above-mentioned doubly supported beam vibration mode. The length Le of each end is about 1 m. The theoretical support for what is described in this paragraph will be explained in a later reference example. The upper end and the lower end can be relatively evaluated by the method described in paragraph 0052.

  FIG. 11 schematically shows a state in which the superstructure of an existing building is removed and only the pile bodies II embedded in the ground are left. Based on this figure, one Example in the case of reusing the existing cast-in-place pile of this invention is described. In this case, it is assumed that there is a design book showing the position and shape of the pile. As shown in FIG. 11, when there are nine pile bodies having the same diameter and length, the bore holes are drilled in each pile body, and at the same interval in the depth direction by the method of the present invention. Perform a placement test. In the vibration measuring machine, the vertical shaft can be added, and measurement is possible even at a deep depth. It is desirable to perform a plurality of hitting directions. It is assumed that the peak frequency obtained in each pile is obtained as shown in Table 1 below. Compared to the peak frequency of the same depth obtained in each pile body, the pile body that obtained a small peak frequency value, unlike other pile bodies at this depth, may not satisfy the design diameter Judge that there is sex. For example, it is determined that the predetermined diameter is not satisfied at the depth 4 m of the pile body (c) and the depth 7 m of the pile body (f) in Table 1. The determination may be carried out with reference to a value of about 13% or more. The reason will be described later. This method utilizes the fact that each pile body shows the same peak frequency if it has the same shape and the same depth. It is considered that the present invention can be applied even when all the pile bodies are widened piles and the shapes of the shaft portion and the pile tip portion are different.

  In actual measurement, as shown in FIG. 12, at least one of the plurality of piles is excavated from the ground surface to a certain depth L and investigated. However, L is sufficiently larger (preferably several m) than the length Le of the upper end portion of the rod-shaped body. Then, by measuring the pile diameter of the part that vibrates under the condition of the cantilever at the upper end and the part that vibrates under both-end fixing conditions several meters below the ground surface, the proportional constant a between the peak frequency value and the pile diameter It is desirable to determine the proportionality constant a using the accumulated data of pile bodies measured in the past such as the Young's modulus and density of concrete. Thereby, as above-mentioned, if another pile body also shows the same peak frequency as this pile body, it can be judged that it is the same pile diameter. In addition, the measurement accuracy of the result obtained by the present applicant from Experimental Example 3 described later was 12.8%.

  Next, experiments conducted as support for the present invention will be described as reference examples and experimental examples. In the reference example, a column having a rectangular cross section is used as an experiment object, and does not belong to the technical scope of the present invention. However, it is necessary for understanding the technical contents of the present invention.

  13 and 14 show a reference example. In this reference example, as shown in FIG. 13, a striking experiment was performed on a column with a rectangular cross section in which the lower end portion was fixed to the floor and the upper end portion was fixed to the ceiling. The length L of the column is 270 cm to 400 cm, the striking point is at a position 100 cm from the floor, and the relationship between the thickness t and the peak frequency is measured using the column thickness t as a parameter. The analysis value was compared with the formula. Both these values are shown in FIG. In the figure, diamond marks represent experimental values, and circle marks represent analysis values. An experiment was performed on each rectangular column having a thickness t of 22 cm, 60 cm, 80 cm, 100 cm, and 133 cm. The hitting device shown in FIG. 2 was used. A stainless steel ball having a diameter of 1 inch was used as the weight portion. Its weight is 68g.

It is known that the theoretical solution of the peak frequency when a concrete column is hit from the outside is expressed by the following equation (Non-patent Document 1). This shows that the peak frequency is proportional to the concrete thickness.
[Formula 2] f = (π / 2L ² ) × √ (EgI / ρA) = (πt / 2L ² ) × √ (EgI / 12ρ)
Where L is the concrete length, t is the concrete thickness, E is the Young's modulus of the concrete, g is the gravitational acceleration, and ρ is the concrete density.

  When the experimental values are arranged, a relational expression y = 15.793x is obtained in FIG. 14, and it is understood that this is approximately matched with the analysis value. This result is used for comparison with a first experimental example described later. In the relational expression y = 15.793x, D in Expression 1 corresponds to x and f corresponds to y. Therefore, when rewritten as x = (1 / 15.793) y, it becomes D = a · f in Equation 1, and the coefficient a can be determined as (1 / 15.793) from the experimental results.

  The following table shows the result of back-calculating the length L of the column using a theoretical formula from the peak frequency value obtained in the rectangular section of the column. The length of the concrete pillar actually struck was L = 270 to 400 cm, whereas the above value is as small as about 90 cm. This is probably because the striking energy of the weight portion is small, and only about 90 cm of vibration near the striking point vibrates. This knowledge will be confirmed in Experimental Example 2 described later.

  15 and FIG. 16 are experimental example 1 of the present invention, and a hole obtained by drilling a round hole 30 in the center of a specimen C-Sample of a hardened rod-shaped body made of a cement-based hardener having a circular cross section is used. This is an example of hitting from the inside.

  FIG. 15 shows the structure of the specimen. The specimen is a reinforcing bar, the diameter of the specimen is 50 cm, and the diameter of the bore hole D is 11 cm. The covering depth of the reinforcing bar is 5 cm. As shown in FIG. 15 (A), place concrete on the left 5 cm portion of the test piece in the left-right direction (the portion surrounded by the arc that is part of the outer periphery of the test piece and the string that connects both ends of the arc). The junker J is formed on the right side of 5 cm. Thereby, the thickness of the concrete in the front-rear direction of the test body is designed to be 50 cm, and the thickness in the left-right direction is 43 cm.

  The acceleration sensor 32 was installed inside the hole of the test body, and the above-described hitting device was inserted, and hitting was applied a plurality of times in the left-right direction and the front-rear direction with respect to the inner surface of the hole. The measurement results are shown in FIG. The peak frequency when the outer diameter in the striking direction is 43 cm is 1056 Hz, and the peak frequency when the outer diameter is 50 cm is 1222 Hz. Accordingly, a proportional relationship is established between the outer diameter of the concrete pile in the striking direction and the peak frequency.

From this experimental result, it can be seen that Formula 1 or Formula 3 also holds for a hardened rod-shaped body made of a cement-based hardener having a vertical hole inside. However, d in the formula is not simply the thickness of the concrete in the striking direction but the outer diameter of the rod-shaped body in the striking direction.
[Formula 3] f = (πd / 2L ² ) × √ (EgI / 16ρ)
Where L is the concrete length, d is the concrete thickness, E is the Young's modulus of the concrete, g is the gravitational acceleration, and ρ is the concrete density.

In this experiment, the numerical value of [diameter of boring hole] / [outer diameter of rod-shaped body] is 11 cm / 50 cm (= 0.22). Although a small-diameter pile model was used due to experimental restrictions, in practice it is preferable to use 11 cm / 150 cm (= 0.07) or 11 cm / 100 cm (= 0.11). However, it is considered that sufficiently reliable evaluation can be obtained even under the conditions of this experiment. The error of this experimental condition is determined by the ratio of the square root of the secondary moment of the inner diameter and the square root of the second moment of the outer diameter.
The square root of the second moment of the outer diameter of ^{50cm = √ (πD 4 /64)=√(3.14×50 4} /64) = 554
The square root of the second moment of the inner diameter ^{11cm = √ (πD 4 /64)=√(3.14×11 4} /64) = 27
Therefore, the error is about 27/554 = 5%. This is an acceptable error.

  When the boring hole is at the center of the pile body, the variation in data is very small as shown in FIG. The 95 percent confidence interval is about 3-4%, and the difference of 3-4% in diameter can be evaluated.

Next, let us consider a case where the boring hole is displaced from the center of the rod-like body due to an excavation error of the boring hole. The difference between the average value of the peak frequency when multiple hit in the longitudinal direction, and the average value of the peak frequency when multiple hit in the lateral direction, (1222-1056) / [(1222 + 1056) / 2] = 14 .6%. As described in Experimental Example 2 below, the measurement accuracy due to excavation error of the borehole is about 13%, and the value of 14.6% is larger than that, so when the cross-sectional defect is relatively large as shown in the drawing It is considered that the possibility of cross-sectional defect can be estimated.

  17 and 18 show a second experimental example of the present invention. In this experimental example, a pile test body having a length of 85 cm and having a hole drilled along the central axis is set sideways as shown in FIG. 17, and both ends in the longitudinal direction of the sideways test body are 2 as shown in the figure. One support base S is used. The distance Ls between fulcrums is 76 cm. In this way, the center portion of the vibrating body was hit under the condition of fixing both ends of the test body. The result is depicted in FIG. The experimental values when hitting with a pile test specimen with a fulcrum distance Ls of 76 cm are in good agreement with the theoretical values. As described in Table 2 above, the length of the column obtained from the theoretical solution is shorter than the actual length of the column, suggesting that vibration may occur only in a part of the entire length of the column. Yes. Furthermore, taking into account the knowledge of this experiment, it is assumed that the actual vibration range is about 76 cm. Therefore, if the range of vibration due to the impact is set to 1 m with some allowance, the vibration condition with both ends fixed is established for the intermediate part excluding the 1 m part from the upper and lower ends of the pile body. It can be considered.

  19 to 21 show a third experimental example of the present invention. In this experimental example, a test body of a pile body provided with a boring hole having a diameter of 11 cm at the center of the pile shown in FIG. 19 and a test body of a pile body provided with a boring hole eccentric by 10 cm from the center as shown in FIG. The experiment was conducted using the body. The reason for conducting the test with the eccentric model is that when a boring hole is actually drilled in the pile body, there is a high possibility of causing a misalignment of about 10 cm due to the influence of construction accuracy. In all cases, the pile had a diameter of 50 cm and a length of 85 cm, and the experiment was conducted at the intermediate height (42.5 cm) of the pile. FIG. 21 shows the results obtained by performing 20 strikes in each of the four directions shown, and Fourier transforming the obtained time history waveform to obtain the peak frequency. Although the values varied in each striking direction, the average values were almost the same. Table 3 below summarizes the average value, standard deviation, and the value of the 95% confidence interval determined from these values.

In this test, the pile model vibrates at the peak frequency f when hitting in a cantilever mode where the lower end of the pile is fixed and the upper end is free. The theoretical value of the primary natural frequency of the cantilever is expressed by the following equation in vibration theory.
[Formula 4] f = (1.875 ² / 2πL ² ) / √ (EgI / ρA)

In the equation, L is the length of the specimen (42.5 cm in this experiment), E is the elastic modulus (E = 210,000 kg / cm ² this time), I is the secondary moment of section, and ρ is the density (this time ρ = 0.0023 kg / cm ³ ) and A is the cross-sectional area. According to this equation, the peak frequency of 50 cm in diameter is 1158 Hz, which is in good agreement with the experimental result (1222 Hz in the case of 50 cm in diameter) in FIG.

  In this test, it was struck in 4 directions, but it is considered that the pile diameter could be measured in all cases. Further, when the variation is large and the standard deviation is large, it can be estimated that the shape is eccentric from the pile core and the left and right shapes are different with respect to the striking direction.

  Hereinafter, other embodiments of the present invention will be described. In the description, the description of the same configuration as the first embodiment is omitted.

  22 to 24 illustrate a second embodiment of the present invention. In this embodiment, a hardened rod-like body C made of a cement-based hardener is applied to a pier instead of a pile body. In FIG. 22, this pier is constructed by placing a cylindrical formwork F shown by imaginary lines in FIG. 22 on a base, and placing concrete in the inside of the tubular formwork with a cylindrical hole as a hole B. Consists of. In the figure, the superstructure at the end of the bridge girder etc. is also represented by imaginary lines.

  When the present invention is applied, the upper structure of the bridge is removed to expose the upper surface of the bridge pier, and a boring hole D is drilled therefrom. And what is necessary is just to insert the vibration measuring device 2 of this application in the boring hole D. FIG. The bridge piers standing underwater have the advantage of applying the present invention because there is a difficulty in actually measuring the outer diameter to some extent compared to the pile bodies buried in the ground.

  The cross section of the pier is often an oval shape as shown in FIG. In this specification, “oval” means a shape obtained by connecting two semicircular arcs with two line segments. When the major axis of the circle is not so long, it is considered that the vibration caused by striking the weight portion reflects the entire cross section, so it is sufficient to arrange one boring hole D at the centroid of the cross section. However, when the major axis is large as shown in the figure, it is preferable to provide a plurality of boring holes along the central axis indicated by the alternate long and short dash line in FIG. In the illustrated example, one boring hole D1 is formed in the centroid P1, and a boring hole D2 is formed in each center of curvature of each semicircular arc Cs on both sides of the pier. Then, at a predetermined depth, for example, as shown in FIG. 24, for each boring hole, the peripheral surface of each boring hole is struck by changing the striking direction equiangularly as in the first embodiment, and the vibration is measured. .

  Although not shown, the present invention can also be applied to a hardened rod-shaped body hardened with cement milk as a third embodiment. As is known in the art, this hardened bar is hardened into a bar by jetting cement milk at a high pressure by moving the jet hole in the vertical direction while rotating the jet hole attached to the pipe wall in the ground. It is something to be made. The procedure for evaluating the outer diameter of the rod-shaped body is the same as in the first embodiment.

  The embodiment described in the present specification is a form suitable for implementation, and the technical scope of the present invention should not be interpreted in a limited manner based on the description.

DESCRIPTION OF SYMBOLS 1 ... Rod diameter measuring system 2 ... Vibration measuring machine 4 ... Vertical shaft 4a ... Outer tube part 4b ... Shaft bar part 5 ... Joint 6 ... Operation part 8 ... Blowing device 10 ... Apparatus main body 12 ... Base 12a ... 1st auxiliary plate Part 12b ... 1st through-hole 13 ... Connection plate 13a ... 2nd auxiliary plate part 13b ... 2nd through-hole 14 ... Gear box 16 ... Locking means 18 ... Pressing rod 20 ... Pressing part
DESCRIPTION OF SYMBOLS 22 ... Impacting means 23 ... Drooping plate part 24 ... Pivoting part 26 ... Turning arm 26a ... Base part 26b ... Tip part 27 ... Bolt 28 ... Weight part 30 ... Pull string 32 ... Accelerometer 34 ... Signal line 36 ... Holder 40 ... Analyzer A ... Ground B ... Hole C C ... Rod-shaped body (stake body) C1 ... Upper end C2 ... Lower end C3 ... Intermediate part D ... Boring hole E ... Cylindrical formwork F ... Base Ls ... Distance between fulcrums R ... Depression S ... Support stand

Claims (4)

A method for evaluating the diameter of a hardened rod-shaped body made of a cement-based hardener placed in-situ in a pothole,
A first step of drilling a boring hole extending downward from the upper end of the cured rod-shaped body made of cement-based curing material in the longitudinal direction of the cured rod-shaped body made of the cement-based cured material;
A second step of inserting a striking device with an acceleration sensor into the boring hole;
A third step of hitting a predetermined portion of the inner surface of the borehole using the hitting device;
A fourth step of measuring a time history waveform of a hardened rod-shaped body made of a cement-based hardener at the hitting position by the hitting;
A fifth step of obtaining a peak frequency of vibration of the hardened rod-shaped body by the cement-based hardener by Fourier transforming the time history waveform;
Using the vibration peak frequency and vibration body size conversion means prepared in advance, from the peak frequency of vibration of the cured rod-shaped body by the cement-based cured material, the diameter of the hitting point of the cured rod-shaped body by the cement-based cured material And a sixth step to evaluate
The said conversion means is the following functional formula, The evaluation method of the rod diameter of the hardening rod-shaped body by the on-site-type cementitious hardening material characterized by the above-mentioned.
[Formula 1] D = a · f (D is a diameter, f is a peak frequency, and a is a coefficient)   The striking device has a locking means for temporarily locking the striking device itself in the hole, and in the second step, a sub-step of inserting the striking device into the boring hole and a constant height by the striking device. The hardening with a cementitious hardener according to claim 1, wherein there is a substep for locking the striking device against the inner surface of the borehole between the substep for hitting the inner surface of the borehole. Evaluation method of rod diameter of rod-shaped body. The hitting device is configured to hit one place in the circumferential direction of the hole surface of the boring hole and to change the hitting position in the circumferential direction.
In the third step, after hitting one place in the circumferential direction of the hole surface of the boring hole with the hitting device at a certain height, the direction of the hitting device is changed to hit another place in the circumferential direction. 3. The method for evaluating the diameter of a hardened rod-shaped body by using a cement-based hardened material in place according to claim 1 or 2, characterized in that it is configured as described above. The boring hole is drilled in the longitudinal direction of the rod-shaped body from the center point of the upper end surface of the cured rod-shaped body made of cement-based hardener,
The impact of each hardened rod-shaped body C on the circumferential direction with the cement-based hardener is performed continuously under the same conditions, and the measurement accuracy is obtained from a series of peak frequencies obtained by this continuous striking. The evaluation method of the rod diameter of the hardening rod-shaped object by the in-situ cement-type hardening material of Claim 3.