JPH0634463A - Strain gauge for measuring supporting force of pile - Google Patents

Abstract

PURPOSE:To obtain a strain gauge which can be easily and safely fitted to a pile even by an unskilled person, can be repeatedly used for another pile by easily removing the gauge from the pile after measurement is completed, and can simultaneously measure a strain and acceleration with high responsiveness and sensitivity. CONSTITUTION:In a strain starting body 1, a constricted part 4 is formed by axisymmetrically forming two elliptical openings 5 and 5' with respect to a reference line 1a and slits 6 and 6' are respectively formed from the openings 5 and 5' to both sides of the body 1. Both-end-supported beam type strain starting sections 10 and 10' are formed by forming a lateral rectangular opening 9 below the openings 5 and 5' and section 4 and four strain gauges 12a and 12b are stuck to the lower surface 9a of the opening 9. At the time of fitting the body 1 to a steel pile, two bolts 18 are inserted into holes 2 and 3 while a protective plate 17 is fitted with small bolts 19 and the bolts 18 are tightened in female screw sections formed in the pile.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain gauge for pile supporting force measurement for detecting the supporting force of a pile driven into the ground by a dynamic measuring method.

[0002]

2. Description of the Related Art When constructing a building, a foundation of the building is constructed by driving steel piles or concrete piles into the ground until reaching a hard bedrock. in this case,
At the time when the pile is driven to the planned depth, it is determined whether or not the driven pile has reached a state where it can exhibit a predetermined supporting force, but the static supporting force of the pile at this time (hereinafter, simply A static measuring method and a dynamic measuring method are used for measuring the "pile supporting force".

The static measurement method of the pile is, for example, a predetermined weight (for example, 100
In this method, the weight of t) is placed to detect the amount of pile sinking in a unit time, and the pile supporting force is measured based on this.

On the other hand, the dynamic pile measuring method means, for example, that the head of the pile (exposed end on the ground) is hit, and at this time, the head moves from the head of the pile toward the tip of the pile. Waves and receding waves returning from the pile tip are detected by a sensor, and both detected values are processed by wave theory to detect the dynamic pile penetration resistance, and in consideration of ground conditions etc. It is a method of estimating the pile bearing capacity presumably.

[0005]

However, when constructing a heavy building, it is necessary to drive piles into several tens of places per at least one building. Therefore, in the former method, several tens of heavy weights are used. A major drawback is that the work of measuring the piles of books while reloading them is extremely labor-intensive and time-consuming.

On the other hand, in the latter method, first, the outer peripheral surface of each pile is pre-processed, and at least a pair of compression type strain gauges (hereinafter, referred to as
Write the position where the "C-type strain gauge") and the tension-type strain gauge (hereinafter, "T-type strain gauge") are attached, and attach at least a pair of strain gauges precisely according to this writing line. In addition, since wiring work must be performed, it is a major drawback that it requires skill and time for the sticking work and the wiring work. Moreover, the strain gauges that have been so hard attached are discarded as they are as they are. It was also a disadvantage of uneconomical that it had to be done.

A conventional strain gauge may be used for the dynamic pile measuring method. The strain gauge is originally designed as an apparatus for static measurement. Therefore, if this is used in a dynamic measurement method, it will result in problems in response and impact resistance, and it will not be possible to detect dynamic strain during pile driving. .

The present invention has been made in view of such circumstances, and even an unskilled person can easily and safely perform the mounting work, and simultaneously measure strain and acceleration with high responsiveness and sensitivity. It is an object of the present invention to provide a strain gauge for pile supporting force measurement that can be used and can repeatedly use a strain gauge.

[0009]

In order to achieve the above-mentioned object, the present invention has a joint having high rigidity in at least an upper part and a lower part, and an impact applied perpendicularly to the head of a pile to be measured. And a strain element detachably attached to the outer peripheral surface of the pile via the coupling portion so that a traveling wave generated from the head of the pile and traveling toward the tip portion of the pile is transmitted to itself. Provided in the middle of this region in order to detect the strain generated in the predetermined length portion of the pile due to the traveling wave in the region between the upper and lower joints in the strain element. And a plurality of strain gauges attached to the strain-flexing portion, and an accelerometer provided on the strain-flexing body in a region of high rigidity near one of the two coupling portions. And, attached to the strain-flexing part A strain gauge may detect a strain generated in a portion of the pile having a predetermined length due to the traveling wave, and the accelerometer may detect an acceleration generated in the pile due to the traveling wave. It is characterized by being configured in.

[0010]

With the strain gauge for pile supporting force measurement configured as described above, the strain-measuring body is fixed to the outer peripheral surface of the pile by using, for example, two bolt connecting means at the upper and lower portions, so that the strain-measuring object can be measured. A traveling wave generated due to an impact applied vertically to a pile head and traveling from the pile head to the tip is transmitted to the strain generating element of the pile supporting force measuring strain gauge.

Then, when an impact force is applied to the pile head in order to measure the pile supporting force, the dynamic strain generated in the pile portion between the upper and lower two connecting means is -Measure with a strain gauge attached to the strain-flexing body portion between the lower two connecting means.

At the same time, the acceleration generated in the pile is measured as the acceleration generated in the flexure element using an accelerometer.

The upper and lower two connecting means serve to remove the pile supporting force measuring strain gauge from the outer peripheral surface of the pile and attach it to the next pile when the measurement in the arbitrary pile is completed.

In this case, a protective member for protecting a precision portion such as a strain gauge from an external force is previously provided on the non-pile mounting surface side of the strain gauge for measuring pile supporting force, and the strain gauge for measuring pile supporting force is attached to the pile. Keep the protective member in the protective state until it is fixed, and after fixing the strain gauge for pile supporting force measurement to the pile, release the protective member's protective state to enable dynamic strain measurement. Move.

After the dynamic strain measurement is completed, the protection member is returned to the protection state again, and the pile supporting force measuring strain gauge is removed from the outer peripheral surface of the pile.

[0016]

EXAMPLES The construction of the strain gauge for pile supporting force measurement according to the present invention will be described below based on examples.

FIG. 1 is a perspective view showing the construction of an embodiment of a strain gauge for pile supporting force measurement of the present invention with a protective plate disassembled.

FIG. 2 is a side view of the strain gauge for pile supporting force measurement shown in FIG. 1, FIG. 3 is a front view of the strain gauge for pile supporting force measurement shown in FIG. 1, and FIG. 4 is a pile shown in FIG. It is the rear view seen from the pile mounting surface side of the strain gauge for supporting force measurement.

In each drawing, reference numeral 1 is a strainer of a strain gauge for piles, which is made of an appropriate metal material as a whole into a rectangle of, for example, 105 mm long × 50 mm wide, and its width direction (horizontal direction) is almost the same. It is configured to have a temporary reference line (sensing axis) 1a set in the vertical direction from the upper end of the flexure element 1 in the center.

Since the reference line 1a is temporarily used for setting the positions of the bolt mounting holes 2 and 3 and the constricted portion 4 as two connecting means which will be described later at the time of designing and manufacturing, it is completed. It is not necessary for the strain gauge for piles later.

Reference numeral 2 is an upper bolt mounting hole for detachably mounting the flexure element 1 on the outer peripheral surface of the upper portion of the steel pile P (see FIG. 8) to be measured. Hexagon socket head bolt or stud bolt 18) with an oval (7mm x 9mm) mounting hole that allows vertical adjustment with some adjustment margin.
It is formed on the reference line 1a.

Reference numeral 3 denotes a lower bolt mounting hole for removably mounting the flexure element 1 on the outer peripheral surface of the upper portion of the steel pile P in cooperation with the upper bolt mounting hole 2. The coupling bolt 18 is precisely fitted. Circular (7mm
(Diameter) mounting hole is formed on the reference line 1a located below the upper bolt mounting hole 2.

These two bolt mounting holes 2 and 3 are
For transmitting a traveling wave generated due to an impact applied perpendicularly to the head of the steel pile P and traveling from the head of the pile P toward the tip end to the flexure element 1 via the two coupling bolts 18. Therefore, the installation interval on the reference line 1a is the installation interval (50 mm) between the _two female screw parts P ₁ and P ₂ (see FIG. 8) pre-screwed on the outer peripheral surface of the head of the steel pile P.
Will be set to the interval corresponding to.

Reference numeral 4 is a constricted portion provided on the reference line 1a located between the upper bolt mounting hole 2 and the lower bolt mounting hole 3.

In the constricted portion 4, a traveling wave traveling from the pile head to the tip portion due to an impact applied vertically to the head of the pile P has two coupling bolts 18 and two bolt mounting holes 2 , 3 to form a traveling wave transmitting portion for adjusting the traveling wave and transmitting the traveling wave downward along the reference line 1a.

That is, the constricted portion 4 adjusts the unequal distribution of the uneven load and the inclined load transmitted to the strain generating body 1 into a straight vertical load, and the strain gauge 1 in the strain generating portion 10 which will be described later.
The structure is such that it can be transmitted to the attachment surface 9a of 1a, 11b and 12a, 12b.

In this case, the constricted portion 4 is formed by using, for example, the following machining method.

That is, on both sides of the area which is planned as the constricted portion 4, there are two space portions having a widthwise length sufficient for strain detection to be carried out in cooperation with a strain detection opening 9 which will be described later. The oval openings 5 and 5'are formed by, for example, milling, and further, a part of the outer arc portion of the two oval openings 5 and 5'is cut off toward the side surface of the flexure element 1 by milling or milling. Thus, the slits 6 and 6'are formed.

Denoted at 7 and 8 are the upper half and lower half of the strain-generating body, which are set in the upper and lower regions of the narrowed portion 4 with the narrowed portion 4 interposed therebetween. A predetermined range 7a of the non-pile mounting surface (hereinafter, simply referred to as "predetermined range 7a of the flexure element upper half 7") and a strain detection opening 9 described later.
In a rectangular region that extends over a predetermined range 8a of the non-pile attachment surface of the lower strain body 8 including the (hereinafter, simply referred to as “predetermined range 8a of the lower strain body 8”), Protection plate 1
A protective plate mounting area for mounting 7 is formed.

In this case, the predetermined range 7a of the upper half portion 7 of the flexure element
Near the side edges of the small bolt holes 17a above the protection plate 17.
1 is provided for each of the female threaded portions 20, and two female threaded portions 21 corresponding to the small bolt holes 17b below the protection plate 17 are provided in the predetermined range 8a of the lower half portion 8 of the flexure element. Will be provided.

The protective plate mounting areas 7a and 8a
In the illustrated embodiment, is set as a rectangular region that is recessed from the surface of the flexure element 1 from one side edge of the flexure element 1 to the other side edge. You may set it as it is above. When set in this way, the boundaries between the protective plate attachment areas 7a and 8a on the surface of the flexure element 1 and other areas become unclear.

Numeral 9 is a strain detecting opening formed in the region of the lower half portion 8 of the strain-generating body at a predetermined distance in the downward direction with respect to the two oval openings 5 and 5 '. It is formed as a rectangular opening that is long in the lateral direction (horizontal direction).

In this case, between the lower inner peripheral surfaces (straight portions) 5a, 5a 'of the two oval openings 5, 5'and the inner peripheral surface 9a of the strain detecting opening 9 on the constricted portion 4 side. 2 formed
The two beam-shaped portions constitute strain-flexing portions 10 and 10 'of the strain gauge for pile supporting force measurement, and the shape and the plate thickness thereof are determined by the calculation of the responsiveness by so-called FEM analysis, and the constricted portion 4 is formed. It is configured to be set to such a value as to detect the distortion caused by the traveling wave transmitted through.

The lateral dimension of the strain detecting opening 9 is such that the vertical inner peripheral surfaces on both sides of the opening 9 are located outside the lower linear portions of the oval openings 5 and 5'described above. In addition, it is configured to have a value that gives sufficient rigidity to the portions of the flexure element 1 located on both sides thereof.
The vertical opening size of the strain detection opening 9 is set appropriately.

The strain detecting opening 9 having such a shape and structure is formed, for example, by press working to form an approximate opening shape, and then the necessary inner peripheral surface is shaped by milling, or a wire cutting method or the like. Is formed by. In this case, the inner peripheral surface 9a on the side of the constricted portion 4 serves as a strain detecting surface for attaching strain gauges 11a, 11b and 12a, 12b, which will be described later, and thus is shaped as a particularly uniform plane.

Numerals 11a and 11b are a pair of strain gauges attached at a predetermined interval near the outer end and the inner end of the strain detection surface 9a region on the left side (on the drawing) of the reference line 1a, and near the outer end. Strain gauge 11a attached to the position
In this case, since the striking force in the compression direction is applied to the strain gauge, the compression type strain gauge and the strain gauge 11b attached to the position near the inner end function as a tension type strain gauge.

Reference numerals 12a and 12b denote another pair of strain gauges attached to the strain detection surface 9a region on the right side of the reference line 1a (on the drawing) near the outer end and the inner end thereof at predetermined intervals. Strain gauge 1 attached near the edge
2a functions as a compression type strain gauge, and the strain gauge 12b attached to a position near the inner end functions as a tension type strain gauge.

In this case, the two compression type strain gauges 11a and 12a have oval openings 5 and 5'as much as possible so that the bending strain of the compression portion can be detected efficiently.
Of the tension type strain gauges 11b and 12b attached to the positions of the strain generating portions 10 and 10 'on the outer side of the
Are attached to positions inside the oval openings 5 and 5 '(close to the reference line 1a) as much as possible so that the bending strain of the tensile portion can be detected efficiently.

Then, these two pairs of strain gauges 11
a, 11b and 12a, 12b are strain detection surfaces 9a
In order to accurately detect the amount of bending strain that occurs in
They are electrically connected to form a strain detection circuit (Wheatstone bridge circuit, not shown) known per se.

Reference numeral 13 is a strain gauge cable for outputting the electric detection output of the strain detection circuit to an external strain measuring device (not shown). For example, as shown in the bottom view of FIG. The lower half portion 8 is configured to be extracted downward through a hollow cable extraction hole 14 formed along the reference line 1a and connected to an external strain measuring device (not shown).

15a, 15b and 16a, 16b are
In the mounting seat group when mounting the flexure element 1 on the outer peripheral surface of the upper portion of the pile P, the upper mounting seats 15a and 15b are located on both sides of the upper bolt mounting hole 2 on the pile mounting surface of the upper half portion 7 of the flexure element. , The lower mounting seat 16a,
16b are set on both sides of the lower bolt mounting hole 3 on the pile mounting surface of the lower half portion 8 of the flexure element.

In this case, two sets of mounting seats 15a, 15
The bile contact surfaces of b and 16a, 16b are formed into curved surfaces that match the curvature of the outer peripheral surface of the pile having a standard diameter so that the flexure element 1 and the outer peripheral surface of the pile are in good contact. Is preferred.

Reference numeral 17 denotes a protective plate mounting area 7 on the flexure element 1.
a, a protective plate formed in a shape capable of covering 8a, and three small bolt holes 17a on each side, at a portion close to both side edges of the protective plate.
17b is provided.

In this case, the two upper left and right small bolt holes 1
7a is provided at a position corresponding to the female threaded portion 20 provided in the predetermined range 7a of the upper half portion 7 of the flexure element, and the lower 4
The small bolt holes 17b are provided in a predetermined range 8 of the lower half portion 8 of the flexure element.
It is provided at a position corresponding to the female screw portion 21 provided on a.

The protective plate 17 has two plate-like parts (straining parts) 10 and 10 'and a constricted part 4 which are formed when the pile strain gauge is attached to or removed from the pile P.
Of these strain gauges 11a, 11b and 12a, 12b to protect these parts from twisting and / or before the pile strain gauge is attached to the steel pile P. It is provided to protect the strain gauge.

Therefore, at the time of strain detection, the pile strain gauge must be set in a state in which the two strain generating sections 10 and 10 'can perform the strain detecting action.

For this reason, the protective plate 17 has a length of 6 mm until the pile strain gauge is attached to the steel pile P.
Small bolts (for example, a diameter of 3 mm) 19 are inserted into all of the small bolt holes 17a and 17b, and the small bolts 19 are inserted into the female thread portions 20 of the strain-flexing member upper half 7 and the strain-flexing member lower half 8. 21
The upper half portion 7 of the flexure element and the lower half portion 8 of the flexure body are firmly connected to each other by screwing into the strain element 10, 10 ', two pairs of strain gauges 11a, 11b and 12a, 12b, and a constriction. It is used to keep the portion 4 in a state in which it can be protected. Further, at the time of strain detection, by removing the two small bolts 19 from at least the two small bolt holes 17a on the upper side, the upper half portion 7 of the strain-generating body is removed. It is used to release the rigid connection with the lower half portion 8 of the strain-flexing body so that the two strain-flexing portions 10 and 10 'can be set to a state capable of performing strain detection.

Reference numeral 30 denotes an accelerometer provided in the region on the reference line 1a of the lower half portion 8 of the strain-generating body in order to detect the acceleration at the time of driving the pile on the strain-generating body 1, for example, as shown in FIG. It is configured as an air damping type accelerometer having a different structure.

In FIG. 6, reference numerals 31 and 32 denote a weight portion and a fixed portion, which are connected to the outer peripheral side and the central portion via a thin-walled strain generating portion 33, which will be described later, and the weight portion 31 located on the outer peripheral side. Is configured as a portion having a thick annular shape, and the fixing portion 32 located in the center is configured as a portion having a thick cylindrical shape. Further, at least one surface of each of the weight portion 31 and the fixing portion 32 is formed. (In the illustrated embodiment, the lower surface) is configured to be located in the same plane.

Reference numeral 33 denotes a strain-flexing portion 33 which constitutes a diaphragm.
Then, a necessary number of strain gauges 34 are attached to the one surface so that the bending strain of the strain-flexing portion 33 can be detected.

In this case, the required number of strain gauges 34 is
Assembled in a Wheatstone bridge circuit, its input end and output end will be electrically connected to a bridge power supply circuit and an accelerometer (not shown) known per se.

On the other hand, the above-mentioned fixing portion 32 is placed on the casing 36 of the accelerometer via the spacer 35 made of a thin plate, and the flat plate-like pressing member 37 is placed on the upper surface side of the casing 32 by the bolt 38. It is firmly fixed to 36.

This casing 36 is made up of the strain-flexing portion 33 described above.
In such a posture that the line orthogonal to the plane of FIG. 6 becomes vertical (the posture shown in FIG. 6), it is firmly fixed to the region on the reference line 1a of the lower half portion 8 of the strain body by appropriate four small bolts 39. (Fig. 3).

In this case, a predetermined air gap g is formed between the upper surface of the casing 36 and the lower surface of the weight portion 31, and this air gap g causes the weight portion 31 to be displaced in the vertical direction. This is for preventing the weight portion 31 from resonating with respect to the acceleration motion in the vicinity of the resonance frequency when the (oscillating operation) is performed.

Reference numeral 40 denotes an accelerometer cable for taking out the detection output of the accelerometer to the outside (and for supplying a bridge power source from the bridge power source circuit). As shown in FIG. It is configured so as to be taken out downward from the lower end portion of the casing 36 in a state of being in parallel with and to be connected to an external acceleration measuring device (not shown).

In the accelerometer 30 having the above-described structure, when the casing 36 receives the acceleration from the flexure element 1 and performs an acceleration motion, the weight part 31 connected to the flexure part 33 is provided.
Is displaced relative to the casing 36 in the vertical direction to generate strain in the strain-flexing portion 33, and the strain amount at this time is converted into an electric signal by the strain gauge 34, so that the strain-generating body 1 (even in the pile to be measured) It is configured to be able to detect acceleration).

Reference numeral 41 denotes an elastic member made of, for example, a rubber material, and as shown in FIG. 2, a pile attachment surface region of the strain-flexing body 1 corresponding to a region of the strain-flexing body lower half portion 8 in which the accelerometer 30 is provided. Lower part 8 of the strain-inducing body which is attached to the outer surface of the pile P and is attached to the outer surface of the pile P.
The space between the pile attachment surface and the outer peripheral surface of the pile can be filled.

That is, since the accelerometer 30 is not directly attached to the outer peripheral surface of the steel pile P, the weight of the mounting portion of the accelerometer 30 (lower half portion 8 of the strain generating body) acts as an inertial force during strain detection. Will end up.

Therefore, in the illustrated embodiment, in order to remove this inertial force, the elastic member 41 is interposed between the pile mounting surface of the lower half portion 8 of the strain-flexing body and the outer peripheral surface of the pile P to lower the strain-generating body. The half portion 8 is configured so that it can be displaced integrally with the pile P.

Next, the usage or operation of the strain gauge for pile supporting force measurement having such a configuration will be described with reference to the flow chart of FIG.

First, in preparation for the dynamic strain measurement, the upper bolt mounting hole 2 and the lower bolt mounting hole of the flexure element 1 are previously formed on the outer peripheral surfaces of the upper portions of the plurality of steel piles P to be measured. Female screw parts P ₁ and P ₂ corresponding to 3 are respectively screwed and placed.

Then, the steel pile P in such a state is driven deep into the ground by using an appropriate pile driving machine so that the head (upper) portion of the steel pile P is exposed at the final stage of the driving operation. To

In this state, the strain gauge for pile supporting force measurement, in which the six small bolts 19 of the protective plate 17 are attached, is attached to the outer peripheral surface of the head portion of the target first steel pile P. Positioning the two connecting bolts 18 through the upper bolt mounting hole 2 and the lower bolt mounting hole 3 as shown in FIG.
Screw to ₁ and P ₂ .

Then, the two connecting bolts 18 are firmly tightened to fix the pile supporting force measuring strain gauge to the outer peripheral surface of the upper portion of the steel pile P as shown in FIG. At this time, the elastic member 41 comes into close contact with the outer peripheral surface of the steel pile P to realize a state in which the lower half of the strain-flexing body 8 can be displaced integrally with the pile P [step: S1].

After that, of the six small bolts 19 fixing the protective plate 17, the two small bolts 19 located at the uppermost stage screwed into the female screw portion 20 of the upper half portion 7 of the flexure element, Figure 10
As shown in, the flexure element 1 and the protective plate 17 are removed.
That is, the rigid connection state between the upper half portion 7 of the strain generating body and the lower half portion 8 of the strain generating body is released, and the two strain generating portions 10, 1 of the strain generating body 1 are released.
0'is set to a state in which strain detection can be performed [step: S2].

Now, in such a state, when an impact is applied to the head of the steel pile P with a predetermined impact force, a traveling wave resulting from this impact causes the two coupling bolts 18 to move.
And the flexure element 1 through the two bolt mounting holes 2 and 3.
Be transmitted to.

At this time, the traveling wave transmitted from the upper coupling bolt 18 and the upper bolt attachment hole 2 to the upper half portion 7 of the strain-generating body of the strain-generating body 1 is adjusted by the constricted portion 4, and the strain generating portion 10, It reaches the strain detection surface 9a of 10 ', and a bending strain of an amount corresponding to the impact force is generated on the strain detection surface 9a.

Therefore, two pairs of strain gauges 11a, 11b and 12a attached to the strain detecting surface 9a,
12b is a region outside the strain detection surface 9a and the reference line 1
An amount of a minute bending strain at this time in a region near a is detected, and the amount of strain of the strain detecting surface 9a at that time is electrically converted through a strain detecting circuit to externally measure a strain (not shown). Output to the measuring instrument).

As a result, in the strain measuring instrument, the dynamic strain generated in the steel pile P portion between the _two female screw portions P ₁ and P ₂ is caused by the upper bolt mounting hole 2 and the lower bolt mounting hole 3. It is to be measured as a dynamic strain generated in the portion of the strain generating body 1 (that is, the strain detecting surface 9a).

On the other hand, the traveling wave is transmitted to the accelerometer 30 fixed to the lower half portion 8 of the strain generating element 1 through the lower coupling bolt 18 and the lower bolt mounting hole 3. From the above, the strain gauge 34 of the accelerometer 30 detects the strain amount of the strain-flexing portion 33 according to the acceleration at that time, and electrically detects the strain amount of the strain-generating portion 33 at that time via an accelerometer (not shown). It is converted and output to an external accelerometer.

In this case, the lower half portion 8 of the flexure element is elastic member 41.
Since it is in a state where it can be displaced integrally with the pile P via the, the acceleration measuring device can measure the acceleration generated in the steel pile P with higher accuracy as the acceleration generated in the strain body 1. [Step: S3].

When the work of strain measurement and acceleration measurement of the first steel pile P is completed in this way, the two small bolts 19 removed in step S2 are attached to the protective plate 17 at the top. The protective plate 17 is inserted into the two bolt holes 17a located in the upper stage and screwed into the female screw portion 20 of the upper half portion 7 of the strain body to firmly fix the protective plate 17 to the upper half portion 7 of the strain body to protect the protective plate 17. The state is returned to the current state [step: S4].

After that, the two connecting bolts 18 are turned in the opposite direction to that at the time of mounting to unscrew the female threads P ₁ and P ₂ of the steel pile P, and the upper bolt mounting hole 2 and the lower side. Remove from the bolt mounting hole 3 [step: S5].

Subsequently, the strain gauge for pile supporting force measurement is removed from the outer peripheral surface of the steel pile P [step: S6].

This completes the work of attaching the strain gauge for measuring pile supporting force to the first steel pile P, the work of measuring strain and acceleration, and the work of removing the strain gauge for measuring pile supporting force.

Therefore, a required number of strain gauges for pile supporting force measurement having such a configuration are prepared, and these strain gauges are attached to the outer peripheral surfaces of the second and subsequent steel piles P in advance, and the strain gauges are attached to these piles P. The same work as for the first steel pile P is carried out one after the other.

When the measurement of the pile supporting force for each steel pile P is completed, the pile supporting force measuring strain gauges are sequentially removed from the piles P for which the measurement has been completed and reused for the next measurement. To

When the pile supporting force of a large number of piles P is measured by using a limited number of strain gauges for measuring pile supporting force, when the pile supporting force of the first pile P is measured. Alternatively, the strain gauge for measuring pile supporting force may be removed and used for the second and subsequent steel piles P.

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

For example, in the illustrated embodiment, since the steel pile P is described as an example, female screw portions P ₁ and P ₂ are screwed at two positions of the steel pile P, and the connecting bolts 18 are screwed therein. However, in the case of the concrete pile P ', the connecting bolt 18 is previously attached to the pile P'side.
A stud bolt (not shown) corresponding to the above is embedded and placed, and after a strain gauge for pile supporting force measurement is attached to the outer peripheral surface of the concrete pile P ′, an appropriate nut (not shown) is used for pile supporting force. The strain gauge for measurement may be detachably fixed.

Further, in the illustrated embodiment, the protective plate 17 is attached, but if there is no particular need for protective measures for the strain-flexing portions 10, 10 ', etc., the protective plate 17 is installed. Since it is not necessary to attach 17,
The protective plate 17 may be omitted from the structure.

The accelerometer 30 may be of a type other than the illustrated type, but when the illustrated type is used, it is hardly affected by temperature changes, has a good damping effect, and has a structure. Has the advantage of being simple and inexpensive. Further, the position where the accelerometer 30 is arranged may be on the upper half portion 7 side of the flexure element.

The vertical inner peripheral surfaces on both sides of the strain detecting opening 9 may be located at substantially the same positions as the lower linear portions of the elliptical openings 5 and 5 ′ located above them, but preferably the elliptical shape. The vertical inner peripheral surface of the opening 9 is formed to be larger than the lower straight portions of the openings 5 and 5 '. When formed in this way, the strain gauges 11a and 12a can be attached to the position where the bending strain (compressive strain in this case) is maximum, and furthermore, both ends of the strain detection opening 9 are formed large, The advantage is that the strain gauge can be easily attached.

[0084]

As described above, when the present invention is used, it is possible to provide a strain gauge for pile supporting force measurement which can exert the following various effects.

First, it is a simple work of fixing the strain gauge for measuring pile supporting force to the outer peripheral surface of the steel pile or the concrete pile by using the bolt connecting means through the upper and lower connecting portions. Since it has become possible to detect the dynamic strain at the time of driving with high sensitivity and high sensitivity, even an unskilled person can easily work.

Secondly, since the repeated measurement is possible, the work efficiency is improved and the strain gauge can be repeatedly used, so that the equipment cost and the work cost can be reduced.

Thirdly, since the accelerometer is integrated, the strain measurement and the acceleration measurement can be performed simultaneously.

Fourthly, since the structure is simple and the processing is easy, it is possible to reduce the manufacturing cost of the strain gauge for pile supporting force measurement.

Further, particularly when the present invention is carried out in the mode described in claim 4, in addition to these effects, the accuracy of the strain gauge for pile supporting force measurement can be kept high for a long period of time. It becomes possible to provide a strain gauge for pile supporting force measurement that can significantly extend the service life.

[Brief description of drawings]

FIG. 1 is a partially exploded perspective view showing the configuration of an embodiment of a strain gauge for pile supporting force measurement according to the present invention.

FIG. 2 is a side view of the pile supporting force measuring strain gauge of FIG.

3 is a front view of the strain gauge for pile supporting force measurement of FIG. 1. FIG.

4 is a rear view of the strain gauge for pile supporting force measurement of FIG. 1. FIG.

5 is a bottom view of the pile supporting force measuring strain gauge of FIG. 1. FIG.

6 is a vertical cross-sectional configuration diagram showing no example of an accelerometer attached to the strain gauge for pile supporting force measurement of FIG. 1. FIG.

FIG. 7 is a flow chart for explaining the usage or operation of the strain gauge for pile supporting force measurement of FIG.

FIG. 8 is a state explanatory view showing a state in which a strain gauge for pile supporting force measurement in a state where six small bolts of a protection plate are attached is positioned at an upper portion of a target steel pile.

9 is a state explanatory view showing a state in which the strain gauge for pile supporting force measurement in the state of FIG. 8 is fixed to an upper portion of the steel pile by using two connecting bolts.

FIG. 10 is a state explanatory view showing a state in which two small bolts of the protection plate are removed from the pile supporting force measuring strain gauge in the state of FIG.

[Explanation of symbols]

P Steel pile P ₁ , P ₂ Female threaded portion 1 Strain element 1a Reference line 2 Upper bolt mounting hole 3 Lower bolt mounting hole 4 Constricted portion 5, 5'Oval opening 5a, 5a 'Lower inner peripheral surface 6, 6 ′ Slit 7 Upper half of strain element 7a Predetermined range of upper half portion of strain element 8 Lower half portion of strain element 8a Predetermined range of lower half portion of strain element 7a, 8a Protective plate mounting area 9 Strain detection opening 9a Strain detection surface 10, 10 'Two beam-like parts (straining parts) 11a, 12a, 11b, 12b Strain gauge 13 Strain gauge cable 14 Cable extraction hole 15a, 15b Upper mounting seat 16a, 16b Lower mounting seat 17 Protective plate 17a , 17b Small bolt hole 18 Coupling bolt 19 Small bolt 20, 21 Female screw portion 30 Accelerometer 31 Weight portion 32 Fixed portion 33 Strain portion 34 Strain gauge 35 Spacer 36 Casing 37 Holding member 38 Bolt 39 Small bolt 40 Accelerometer cable 41 Elastic member g Air gap

Claims (4)

[Claims] 1. At least an upper portion and a lower portion having a joint having high rigidity, which is caused by an impact applied perpendicularly to the head of the pile to be measured, and from the head to the tip of the pile. So that the traveling wave traveling to you is transmitted to yourself,
A strain element detachably attached to the outer peripheral surface of the pile via the coupling portion, and a strain generated in a portion of the predetermined length of the pile due to the traveling wave to the upper portion of the strain element and In order to detect in the region between the lower joints, a strain-flexing part provided in the middle of this region, a plurality of strain gauges attached to this strain-flexing part, and one of the two joints An accelerometer provided on the strain-flexing body in a region of high rigidity near, and a predetermined length of the pile due to the traveling wave by a strain gauge attached to the strain-flexing part. A strain gauge for pile supporting force measurement, which is configured to detect a strain generated in a ridge portion and to detect an acceleration generated in the pile due to the traveling wave by the accelerometer. . 2. The pile is attached to an outer peripheral surface of a pile to be measured by an upper joint portion and a lower joint portion provided at predetermined intervals on a reference line in the sensitive axis direction set on itself, and the pile is attached to the outer peripheral surface of the pile. A traveling wave traveling from the head of the pile toward the tip due to an impact applied vertically to the head,
A flexure element configured to be received via the upper coupling part and the lower coupling part, and a traveling wave of the pile transmitted to the flexure element via the upper coupling part along the reference line. And a constriction portion provided in the strain-flexing body region in the middle between the upper coupling portion and the lower coupling portion, and the upper region of the strain-generating body using the constriction portion as a connecting portion. And a strain-flexible body upper half set as a region including the upper coupling portion, and a region including the lower coupling portion that is set in the lower region of the strain-generating body with the constriction portion as a connecting portion. A set lower half portion of the strain body, and two space portions formed on both sides of the constricted portion and between the upper half portion of the strain body and the lower half portion of the strain body, respectively. A riser located below the constriction and the two spaces. Between the strain detecting opening formed to have a predetermined length in the horizontal direction across the reference line in the region of the lower half of the body, between the two space portions and the strain detecting opening A thin beam-shaped strain generating portion, a plurality of strain gauges attached to the strain generating portion, the upper half of the strain generating body, or on the reference line of the lower half of the strain generating body. And an accelerometer provided in the region of, so that the strain gauge attached to the strain-flexing portion can detect the strain generated in the predetermined length portion of the pile due to the traveling wave. A strain gauge for pile supporting force measurement, characterized in that it is configured so that the acceleration generated in the pile due to the traveling wave can be detected by the accelerometer. 3. The interposition between the pile attachment surface region of the strain-generating body corresponding to the region of the lower half portion of the strain-generating body where the accelerometer is provided and the outer peripheral surface of the pile, The strain gauge for pile supporting force measurement according to claim 2, wherein an elastic member is attached to the pile attachment surface region of the lower half of the strain-flexing body. 4. A predetermined range of the non-pile mounting surface of the upper half of the strain generating body having high rigidity, and a predetermined range of the non-pile mounting surface of the lower half of the strain generating body having high rigidity. Is formed in a shape capable of covering the region spanning
Until the pile strain gauge is attached to the pile, each is coupled to the strain-flexing body upper half and the strain-flexing body lower half using bolt means, and at the time of strain detection, at least on the strain-flexing body. The strain gauge for pile supporting force measurement according to claim 2 or 3, further comprising a protective plate configured to be capable of releasing the connection with the half portion.