JP6737608B2 - Ground evaluation system, ready-made pile with acceleration sensor - Google Patents

Description

The present disclosure relates to a ground evaluation system and a ready-made pile with an acceleration sensor.

If a good support layer is deep in the ground, a pile foundation may be used to support the structure by burying piles in the ground. In pile foundations, piles are generally buried in the ground to a depth where the tip of the pile reaches a good support layer. The structure is supported by transmitting the load of the structure to the favorable support layer via the pile.

In such a pile foundation, it is extremely important to accurately grasp whether the tip of the pile has reached the assumed supporting layer (supporting layer management). For this support layer management, in the case of the driving method, a so-called pile driving test is performed and the dynamic bearing capacity of the pile is calculated from the amount of penetration and rebound of the pile, and it is confirmed whether the bearing capacity above the design is obtained. It is done by that.

In addition to the method of calculating the dynamic bearing force described above, the bearing force of the pile is estimated by analyzing the behavior of the driven pile based on the wave theory. For example, in Patent Document 1, a strain gauge and an accelerometer are attached to a pile head, and a wave theoretical analysis of the pile is performed by measuring a deformation and a wave associated with the driving of the pile, and a driving force for estimating a bearing capacity of the pile and the like. An invention relating to a pile measurement management system is disclosed.

JP, 10-78333, A JP, 2014-157138, A

By the way, the present inventor attaches the acceleration sensor to the tip portion of the pile instead of the pile head, and based on the acceleration information detected from the acceleration sensor at the time of driving the pile, the property of the ground at the tip portion of the pile is determined. I noticed that there is a possibility that it can be evaluated accurately. By applying this idea, as will be described in detail later, by appropriately evaluating the properties of the ground at the tip of the pile by the acceleration sensor attached to the tip of the pile, the above-mentioned support layer management is performed with high accuracy. It becomes possible. In addition, it becomes possible to evaluate the properties of the ground at the tip of the ready-made piles not only during the construction of the piles but also after the construction of the piles.

Patent Document 2 discloses an invention relating to a foundation pile evaluation system in which a sensor such as an inclinometer or an accelerometer is attached inside the pile. However, the invention disclosed in Patent Document 2 is a system for nondestructive inspection of foundation piles such as reinforced concrete piles to evaluate soundness, and is a system applied to support layer management of driven piles. Absent. Also, there is no disclosure of attaching a sensor to the tip of the pile.

The present invention is an invention made under the background of the prior art as described above, and the purpose thereof is to provide a ground evaluation system capable of accurately evaluating the properties of the ground at the tip of the ready-made pile, and It is to provide ready-made piles with an acceleration sensor.

(1) The ground evaluation system according to the embodiment of the present invention is
A ready-made pile with an acceleration sensor attached to the tip,
An evaluation device that evaluates the property of the ground at the tip based on the acceleration information detected by the acceleration sensor.

According to the ground evaluation system of the embodiment described in (1) above, the acceleration sensor is attached to the tip of the ready-made pile. Therefore, for example, when driving a ready-made pile into the ground, acceleration information (vibration waveform) at the tip of the pile can be accurately detected by the acceleration sensor. Then, by analyzing the detected acceleration information (vibration waveform) with an evaluation device, the property of the ground at the tip can be evaluated.

(2) In some embodiments, in the ground evaluation system according to (1) above, when the outer diameter of the ready-made pile is D, the acceleration sensor is located within a range of 2D from the tip of the ready-made pile. It is attached to ready-made piles so that

In the case of a support pile in which the tip of the pile is embedded in a good support layer, it depends on the property of the ground, the type of structure, and the field such as construction or civil engineering, but at least the outer diameter of the pile is supported. It is generally embedded in a layer.

Therefore, according to the embodiment described in the above (2), the acceleration sensor is attached to the ready-made pile so as to be located in the portion that is embedded in the support layer. Therefore, it is possible to accurately grasp the property of the ground at the tip of the ready-made pile, particularly the property of the support layer.

(3) In some embodiments, in the ground evaluation system according to (1) or (2), the acceleration sensor is embedded in concrete that is placed inside the tip of the ready-made pile. ..

According to the embodiment described in (3) above, the acceleration sensor can be firmly attached to the tip of the ready-made pile. Therefore, it is possible to avoid a situation in which the acceleration sensor comes off when driving a ready-made pile, for example. Further, it is not necessary to attach the acceleration sensor during the manufacturing process of the prefabricated pile, and the acceleration sensor can be retrofitted to the prefabricated prefabricated pile which is in general circulation.

(4) In some embodiments, in the ground evaluation system according to (3), the concrete is cast integrally with an anchor member fixed to the inner peripheral wall of the ready-made pile.

According to the embodiment described in (4) above, the concrete and the ready-made pile are firmly integrated by the anchor member fixed to the inner peripheral wall of the ready-made pile. Therefore, for example, when driving a ready-made pile, it is possible to prevent the concrete in which the acceleration sensor is embedded from moving or being damaged. As a result, the tip of the ready-made pile and the acceleration sensor are firmly integrated, and the acceleration acting on the tip of the ready-made pile can be accurately detected.

(5) The ready-made pile with the acceleration sensor according to the embodiment of the present invention is
Ready-made piles,
An acceleration sensor attached to the inside of the ready-made pile,
The acceleration sensor is embedded in concrete cast inside the tip portion of the ready-made pile.

According to the embodiment described in (5) above, it is possible to provide a ready-made pile with an acceleration sensor in which the acceleration sensor is firmly attached to the tip of the ready-made pile. Therefore, for example, when driving a ready-made pile with an acceleration sensor, the situation where the acceleration sensor comes off can be avoided. Further, it is not necessary to attach the acceleration sensor during the manufacturing process of the prefabricated pile, and the acceleration sensor can be retrofitted to the commercially available prefabricated pile, which is excellent in manufacturability.

According to at least one embodiment of the present invention, it is possible to provide a ground evaluation system capable of accurately evaluating the properties of the ground at the tip of the prefabricated pile and a prefabricated pile with an acceleration sensor.

It is a schematic structure figure showing the ground evaluation system concerning one embodiment of the present invention. It is a block diagram for explaining the function of the evaluation device concerning one embodiment of the present invention. FIG. 3A is a diagram showing an example of the vibration waveform, and FIG. 3B is a diagram showing an example of the result of frequency analysis of the vibration waveform. It is an expanded sectional view in the tip part of the ready-made pile (ready-made pile with an acceleration sensor) concerning one embodiment of the present invention. It is an expanded sectional view in the tip part of the ready-made pile (ready-made pile with an acceleration sensor) concerning one embodiment of the present invention. It is an AA sectional view in the tip part of the ready-made pile (ready-made pile with an acceleration sensor) shown in FIG. It is an expanded sectional view in the tip part of the ready-made pile (ready-made pile with an acceleration sensor) concerning one embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative positions, and the like of the components described as the embodiments or shown in the drawings are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. Absent.
For example, the expression "relative or absolute" such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" is strict. In addition to representing such an arrangement, it also represents a state in which the components are relatively displaced by a tolerance or an angle or a distance at which the same function can be obtained.
For example, expressions such as "identical", "equal", and "homogeneous" that indicate that they are in the same state are not limited to a state in which they are exactly equal. It also represents the existing state.
For example, the representation of a shape such as a quadrangle or a cylindrical shape does not only represent a shape such as a quadrangle or a cylindrical shape in a geometrically strict sense, but also an uneven portion or a chamfer within a range in which the same effect can be obtained. The shape including parts and the like is also shown.
On the other hand, the expressions “comprising”, “comprising”, “comprising”, “including”, or “having” one element are not exclusive expressions excluding the existence of other elements.
Further, in the following description, the same components may be given the same reference numerals and detailed description thereof may be omitted.

FIG. 1 is a schematic configuration diagram showing a ground evaluation system according to an embodiment of the present invention. FIG. 2 is a block diagram for explaining the function of the evaluation device according to the embodiment of the present invention. FIG. 3A is a diagram showing an example of the vibration waveform, and FIG. 3B is a diagram showing an example of the result of frequency analysis of the vibration waveform. 4, 5, and 7 are enlarged cross-sectional views of a tip portion of a ready-made pile (prepared pile with an acceleration sensor) according to an embodiment of the present invention. FIG. 6 is a cross-sectional view taken along line AA at the tip of the ready-made pile (ready-made pile with an acceleration sensor) shown in FIG.

In addition, in FIG. 1, the prefabricated pile 10 (prefabricated pile 10A with an acceleration sensor) is driven into the ground from the construction ground GL, so that the tip portion 11 thereof sequentially penetrates the stratum G1, the stratum G2, and the stratum G3, It shows conceptually the process until reaching a good support layer GS.

As shown in FIGS. 1 and 3 and 4, the ground evaluation system 1 according to the embodiment of the present invention includes a ready-made pile 10 having an acceleration sensor 22 attached to a tip 11 (a ready-made pile 10A with an acceleration sensor). An evaluation device 30 for evaluating the properties of the ground at the tip 11 (the properties of the formation Gn in which the tip 11 is located) based on acceleration information such as a vibration waveform detected by the acceleration sensor 22. There is.

The ready-made pile 10 is a ready-made pile that is manufactured in a factory or the like and then transported to a construction site and buried in the ground. In this respect, it is distinguished from cast-in-place piles, which are manufactured by placing reinforced concrete in holes drilled in the ground at the construction site. The ready-made pile 10 has a cylindrical shape. Further, as shown in FIGS. 4 and 5, a conical tip bit 14 is attached to the tip of the ready-made pile 10.

In the present invention, the type of the ready-made pile 10 is not particularly limited, and generally used reinforced concrete piles (RC piles), prestressed concrete piles (PC piles), high-strength prestressed concrete piles (PHC piles), steel pipe piles, and outer shells. Includes concrete piles with steel pipes (SC piles). In the illustrated embodiment, the prefabricated pile 10 comprises a PHC pile.

The acceleration sensor 22 is a sensor for measuring the acceleration of an object. In the illustrated embodiment, the acceleration sensor 22 is attached to the tip portion 11 of the prefabricated pile 10 while being arranged in the case 24 of the detection device 20. Then, it is configured to behave integrally with the ready-made pile 10 and detect the acceleration acting on the tip portion 11 of the ready-made pile 10.

The evaluation device 30 is a device for evaluating the properties of the ground at the tip 11 based on the acceleration information (vibration waveform) detected by the acceleration sensor 22. As shown in FIG. 2, the evaluation device 30 of the present embodiment has an amplifier 31, an A/D converter 32, a storage unit 33, an evaluation unit 34, and an output unit 35.

The amplifier 31 is a device for amplifying the vibration waveform output by the acceleration sensor 22 with a predetermined gain.

The A/D converter 32 is a device for converting the signal (analog signal) amplified by the amplifier 31 into a digital signal.

The storage unit 33 is for storing the digitized vibration waveform. The storage unit 33 may also be configured to store an analysis result performed by the evaluation unit 34 described later.

The evaluation unit 34 is for evaluating the properties of the ground at the tip 11 (the properties of the stratum in the vicinity where the tip 11 is buried) based on the data regarding the vibration waveform stored in the storage unit 33. ..

In some embodiments, the evaluation unit 34 determines that the stratum in which the tip 11 is located in the vibration waveform data V (see FIG. 3A) in which the horizontal axis represents time and the vertical axis represents acceleration. Frequency analysis is performed on the vibration waveform data VS in Gn (for example, GS that is a good support layer). FIG. 3B shows an example of the result of the frequency analysis. Then, the evaluation unit 34 evaluates the properties of the stratum GS based on the result of the frequency analysis (for example, the value of the peak frequency or the magnitude of the power spectral density at the peak frequency). At this time, the storage unit 33 may store data (actual data) regarding the relationship between the frequency analysis result and the property of the ground, which is created from past construction results and the like. Then, the evaluation unit 34 may be configured to evaluate the property of the formation Gn in which the tip 11 is located by collating the frequency analysis result with the actual data.

Further, in some embodiments, the evaluation unit 34 is configured to evaluate the property of the formation Gn in which the tip portion 11 is located, based on the magnitude of acceleration detected and the integrated value (velocity) thereof. May be.

The output unit 35 outputs the vibration waveform stored in the storage unit 33 and the evaluation result of the evaluation unit 34 to a display unit such as a display or a printer.

The vibration waveform detected by the acceleration sensor 22 is transmitted to the evaluation device 30 by wireless or wired communication means. In the illustrated embodiment, the wireless communication unit 23 (see FIGS. 4 and 5) of the detection device 20 to the first relay 26 is wirelessly transmitted. Transmission from the first repeater 26 to the second repeater 28 is performed via the communication line 27. The second relay 28 to the evaluation device 30 are wirelessly transmitted.

According to the ground evaluation system 1 according to the embodiment of the present invention configured as described above, the acceleration sensor 22 is attached to the tip portion 11 of the ready-made pile 10. Therefore, for example, when driving the prefabricated pile 10 into the ground, the acceleration sensor 22 can accurately detect the acceleration information (vibration waveform) at the tip portion 11 thereof. Then, by analyzing the detected acceleration information (vibration waveform) by the evaluation device 30, the property of the ground at the tip portion 11 can be evaluated.

Therefore, for example, it is also possible to determine whether or not the tip portion 11 of the ready-made pile 10 has reached the favorable support layer. Therefore, it is possible to perform the support layer management with high accuracy, as compared with the conventional case where the support layer management is performed by the so-called pile driving test.

In addition to the above, when the acceleration sensor 22 is attached to the pile head 12, the vibration waveform detected by the acceleration sensor 22 is not limited to the vibration waveform reflected and returned from the tip portion 11 of the pile. It is considered that various vibration waveforms (noise) are superimposed. Therefore, the method of attaching the acceleration sensor 22 to the pile head 12 is insufficient in accuracy to accurately grasp the property of the ground at the tip portion 11 of the pile. In this respect, according to the ground evaluation system 1 according to the above-described embodiment, the acceleration sensor 22 is attached to the tip portion 11 of the ready-made pile 10 as described above. Therefore, the property of the ground at the tip portion 11 can be evaluated with high accuracy.

Further, according to the ground evaluation system 1 according to the above-described embodiment, not only the driving method, but also the ready-made pile 10 buried in the ground by the embedding method is used to evaluate the property of the ground at the tip portion 11 thereof. You can The embedding method is a method of excavating the ground to a predetermined depth with an excavating device such as an auger or a rod, and then constructing and inserting the ready-made pile 10 in the excavation hole. With respect to the ready-made piles 10 buried in the ground by such an embedding method, for example, vibration is applied to the ground by an exciter or the like installed on the ground, and the vibration is detected by the acceleration sensor 22, whereby the tip end portion is detected. The properties of the ground in No. 11 can be evaluated.

Further, according to the ground evaluation system 1 according to the above-described embodiment, the property of the ground at the tip 11 of the ready-made pile 10 can be evaluated not only when the pile is constructed but also after the pile is constructed. In this case, for example, by applying vibration to the ground by an exciter installed on the ground and detecting this vibration with the acceleration sensor 22, the property of the ground at the tip 11 of the ready-made pile 10 can be evaluated. Therefore, it can be confirmed after the construction whether or not the tip portion 11 of the ready-made pile 10 has reached the favorable support layer GS.

Further, according to the ground evaluation system 1 according to the above-described embodiment, it is possible to evaluate the soundness of the ready-made pile 10 after the construction of the pile. In this case, for example, by applying vibration to the pile head 12 of the ready-made pile 10 by a vibrator installed on the ground, and detecting this vibration with the acceleration sensor 22 attached to the tip portion 11 of the ready-made pile 10, The soundness of the ready-made pile 10 such as the presence or absence of cracks can be evaluated.

Further, according to the ground evaluation system 1 according to the above-described embodiment, when an earthquake occurs, the seismic force acting on the tip portion 11 of the ready-made pile 10 can be directly detected by the acceleration sensor 22. On the other hand, when such an acceleration sensor 22 is not attached to the tip portion 11 of the ready-made pile 10, the seismic force acting on the ready-made pile 10 buried in the ground is estimated from the magnitude of the shaking on the ground surface. Therefore, it is difficult to accurately grasp the seismic force acting on the tip 11. Therefore, according to such an embodiment, based on the detection value of the acceleration sensor 22 attached to the tip portion 11 of the ready-made pile 10, the presence or absence of damage to the ready-made pile 10 due to an earthquake and its degree are accurately analyzed. It becomes possible.

In some embodiments, as shown in FIGS. 4, 5, and 7, when the outer diameter of the prefabricated pile 10 is D, the acceleration sensor 22 is within 2D from the tip 11a of the prefabricated pile 10. It is attached to the ready-made pile 10 so as to be located in the range.

In the case of a support pile in which the tip 11 of the pile is embedded in a good support layer, it varies depending on the property of the ground, the type of structure, the type of construction method, and the field such as construction or civil engineering, but at least About 2 to 4 times the outer diameter D is generally embedded in the support layer.

Therefore, according to such an embodiment, the acceleration sensor 22 is attached to the ready-made pile 10 such that the acceleration sensor 22 is located at a portion embedded in the support layer. Therefore, it is possible to accurately grasp the property of the ground of the tip portion 11 of the ready-made pile 10, particularly the property of the support layer Gs.

In some embodiments, as shown in FIGS. 4 and 5, the acceleration sensor 22 is embedded in concrete 40 that is cast inside the tip 11 of the prefabricated pile 10.

That is, the ready-made pile 10 of the present embodiment is configured as the ready-made pile 10A with an acceleration sensor including the acceleration sensor 22 mounted inside the ready-made pile.

In the illustrated embodiment, the space inside the tip portion 11 and surrounded by the inner peripheral wall 10a is filled with concrete 40. The case 24 of the detection device 20 is embedded in the concrete 40. The acceleration sensor 22 is housed inside the case 24. The acceleration sensor 22 is firmly fixed to the case 24 and behaves integrally with the prefabricated pile 10.

Further, in the illustrated embodiment, the wireless communication unit 23 and the battery 21 are housed inside the case 24. The wireless communication unit 23 is for transmitting the vibration waveform detected by the acceleration sensor 22 to the above-described first repeater 26 (see FIG. 1). The battery 21 is a device for supplying electric power for driving the acceleration sensor 22 and the wireless communication unit 23. The battery 21 needs to supply power to the acceleration sensor 22 and the wireless communication unit 23 over the entire period in which the acceleration sensor 22 detects the vibration waveform. Therefore, for example, when the acceleration sensor 22 is used only for managing the support layer, a battery 21 having a capacity that can supply power to the acceleration sensor 22 and the wireless communication unit 23 only during the construction period should be prepared. Good. On the other hand, when power is to be continuously supplied to the acceleration sensor 22 and the wireless communication unit 23 even after construction, a power line (not shown) is extended from the ground to connect to the battery 21 so that the battery 21 can be charged. Just configure it.

In addition, above the case 24, a communication pipe portion 25 is formed that protrudes above the upper surface 40a of the concrete 40 and connects the internal space 10s of the ready-made pile 10 and the case 24. The signal transmitted from the wireless communication unit 23 passes through the communication space 25 a formed by the communication pipe unit 25 and the internal space 10 s, and is transmitted to the first repeater 26. Further, a communication line (not shown) for performing wired communication, a power line (not shown) for supplying electric power to the battery 21, and the like are also installed so as to pass through the communication space 25a and the internal space 10s. To be done.

According to such an embodiment, the acceleration sensor 22 can be firmly attached to the tip portion 11 of the prefabricated pile 10. Therefore, for example, it is possible to avoid the situation where the acceleration sensor 22 comes off when the ready-made pile 10 is driven. Further, since it is not necessary to attach the acceleration sensor 22 during the manufacturing process of the ready-made pile 10, the acceleration sensor 22 can be attached to the ready-made pile 10 which is generally in circulation, so that the manufacturability is excellent.

In some embodiments, as shown in FIGS. 5 and 6, the concrete 40 is cast integrally with the anchor member 42 fixed to the inner peripheral wall 10 a of the prefabricated pile 10.

In the illustrated embodiment, the anchor member 42 is, for example, a rod-shaped member such as a deformed bar and is fixed to the inner peripheral wall 10a by driving the base end portion thereof into the inner peripheral wall 10a of the ready-made pile 10. There is. As shown in FIG. 6, a plurality of anchor members 42 are fixed at intervals in the circumferential direction. Moreover, the anchor member 42 may be fixed to the inner peripheral wall 10a by, for example, welding when the ready-made pile 10 is a steel pipe pile.

According to such an embodiment, the concrete member 40 and the ready-made pile 10 are firmly integrated by the anchor member 42 fixed to the inner peripheral wall 10a of the ready-made pile 10. Therefore, for example, when driving the prefabricated pile 10, it is possible to prevent the concrete 40 in which the acceleration sensor 22 is embedded from moving or being damaged. As a result, the tip portion 11 of the ready-made pile 10 and the acceleration sensor 22 are firmly integrated, and the acceleration acting on the tip portion 11 of the ready-made pile 10 can be accurately detected.

In some embodiments, as shown in FIG. 6, the plurality of circumferentially spaced anchor members 42 include circumferentially extending hoop muscles 44, such as deformed rebar. It is connected. Then, the concrete 40 is cast integrally with the plurality of anchor members 42 and the hoop reinforcements 44. Thereby, the concrete 40 and the ready-made pile 10 can be more firmly integrated.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention.

For example, in the above-described embodiment, the case where the prefabricated pile 10 is buried in the ground by the driving method has been described as an example, but the present invention is not limited to this, and when the prefabricated pile 10 is buried in the ground by the burying method. Can also be applied to.
When the ready-made pile 10 is buried in the ground by the embedding method, the structure of the tip 11 as shown in FIG. 7 is adopted instead of the structure of the tip 11 as shown in FIGS. 4 and 5. be able to. In the tip portion 11 shown in FIG. 7, a case 24 accommodating the battery 21, the acceleration sensor 22, and the wireless communication unit 23 is fixed to the inner peripheral wall 10a of the ready-made pile 10. Thereby, the acceleration sensor 22 is attached to the tip portion 11 of the ready-made pile 10.

According to such an embodiment, the tip portion 11 is not closed, and the internal space 10S is continuously formed from the pile head 12 to the tip 11a. Therefore, when the ready-made pile 11 is buried, it becomes possible to insert an auger or the like into the internal space 10S.

Further, for example, in the above-described embodiment, the case where the tip portion 11 of the ready-made pile 10 is a support pile in which the favorable support layer GS is embedded has been described as an example, but the present invention is not limited to this. The tip portion 11 of the ready-made pile 10 is not embedded in the favorable support layer GS, and can also be applied to a friction pile that supports a structure by the peripheral frictional force of the ready-made pile 10.

1 Ground Evaluation System 10 Ready-made Pile 10A Ready-made Pile with Acceleration Sensor 10s Internal Space 10a Inner Wall 11 Tip 11a Tip 12 Pile Head 14 Tip Bit 20 Detecting Device 21 Battery 22 Accelerometer 23 Wireless Communication 24 Case 25 Communication Pipe 25a Communication Space 26 1st repeater 27 Communication line 28 2nd repeater 30 Evaluation device 31 Amplifier 32 Converter 33 Storage part 34 Evaluation part 35 Output part 40 Concrete 40a Upper surface 42 Anchor member 44 Hoop muscle

Claims (3)

And the already-made pile,
An acceleration sensor housed in a case fixed to the inner peripheral wall of the tip of the ready-made pile,
Based on the acceleration information detected by the acceleration sensor, an evaluation device for evaluating the properties of the ground at the tip portion ,
The ground evaluation system , wherein the prefabricated pile has a closed tip, and an internal space is continuously formed from the pile head to the tip . When the outer diameter of the ready-made pile is D,
The ground evaluation system according to claim 1, wherein the acceleration sensor is attached to the ready-made pile so as to be located within a range of 2D or less from the tip of the ready-made pile. Ready-made piles,
An acceleration sensor housed in a case fixed to the inner peripheral wall of the tip of the ready-made pile ;
The ready-made pile with an acceleration sensor , wherein the end of the ready-made pile is not closed and the internal space is continuously formed from the pile head to the end .

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