JP5765816B2 - Pile loading test method - Google Patents

Description

The present invention relates to a pile loading test method . Specifically, the present invention relates to a pile loading test method for performing a loading test of a test pile.

Conventionally, in order to predict the strength of piles in a building, a pile loading test is often performed before building the building.
In the loading test of this pile, the test pile is constructed and the peripheral friction resistance and tip resistance that constitute the bearing capacity of this test pile are obtained, but it is important to obtain these peripheral friction resistance and tip resistance with high accuracy. .
The reason is as follows. In other words, if the pile diameter of the test pile is about the same as the pile diameter of the actual pile, the load applied in the load test will increase and the load test equipment will become larger, so the pile that actually uses the pile diameter of the test pile Often smaller than the pile diameter. This is because it is necessary to accurately grasp the peripheral surface friction resistance and tip resistance of the pile in order to reflect the loading test result of the test pile smaller than the actual pile in the design of the pile.

  Here, as a pile loading test, an indentation test, a tip loading test, and a tip loading test using an auxiliary reaction force combined method have been proposed.

In the indentation test, as shown in FIG. 4, the test pile 110, the reaction force pile 130 built around the test pile 110, the loading girder 140 installed between the pile heads of the reaction force pile 130, The loading test apparatus 100 provided with the pile head side force application apparatus 160 provided between the loading girder 140 and the test pile 110 is used (refer nonpatent literature 1).
The part from the ground surface 2 to the predetermined depth of the test pile 110 is a part corresponding to the underground structure of the building or a part that does not need to be measured in the test. For example, the part is surrounded by a cylindrical double steel pipe 170 and is subjected to friction cutting. Is given.

  In this loading test apparatus 100, a reaction force is applied to the reaction force pile 130 via the loading girder 140 by the pile head side force application apparatus 160 and the test pile 110 is pushed downward. Then, the amount of strain at a plurality of locations in the pile body of the test pile 110 is measured, and the circumferential friction resistance and tip resistance are calculated by multiplying the measured strain amount by the Young's modulus and the cross-sectional area of the pile body. Thereby, an upward pulling force acts on the reaction force pile 130 as shown by an arrow in FIG.

According to this loading test apparatus 100, since the load condition of an actual building can be simulated, a test result close to the actual bearing capacity characteristic of a pile can be obtained.
However, the above loading test apparatus 100 has the following problems.
First, there is a problem that it takes considerable time to install and remove the loading test apparatus 100. That is, since the pull-out resistance of the pile is smaller than the indentation resistance of the pile, a plurality of reaction-force piles are required to secure the reaction force necessary for the loading test. Furthermore, when the stability of the loading test apparatus 100 is taken into consideration, the number of reaction force piles needs to be arranged in a well-balanced manner such as two, four, and eight. Moreover, when the pile length of a test pile becomes large, it is necessary to increase the number of reaction force piles. Since it is necessary to construct a plurality of reaction force piles in this way, it takes considerable time.

  Secondly, there is a problem that it is difficult to accurately obtain the peripheral frictional resistance and the tip resistance. That is, the strain distribution is not constant within one cross section, the Young's modulus of the concrete is not constant in the depth direction, and the Young's modulus of the concrete changes depending on the magnitude of the strain. This is because it is difficult to calculate the axial force.

In order to solve the problems in the above indentation test, a tip loading test is known (see Non-Patent Document 2).
In the tip loading test, as shown in FIG. 5, a loading test device 200 including a test pile 110 and a tip-side force applying device 210 provided on the tip side of the test pile 110 is used.
That is, the test pile 110 is divided into two at the front end side, and the test pile 110 is used as the front end portion 111 and the pile main body 112, and the front end side force device 210 is provided between the front end portion 111 and the pile main body 112.
According to this loading test apparatus 200, as indicated by an arrow in FIG. 5, a force is applied in the direction in which the distal end portion 111 and the pile body 112 are separated by the distal end side force applying device 210, By measuring the strain amount of the upper and lower surfaces, the tip resistance of the tip portion 111 and the circumferential frictional resistance of the pile body 112 can be calculated separately with high accuracy.
Moreover, since the reaction force pile is not provided, it is possible to reduce time and effort required for installing and removing the loading test apparatus 200.

  However, this tip loading test has a problem that only the smaller one of the peripheral frictional resistance and the tip resistance can be measured. This is because the reaction force of the loading test apparatus 200 cannot be taken when the smaller one of the circumferential frictional resistance and the tip resistance is exceeded.

  Therefore, for example, when calculating the tip resistance, the pile length of the pile body 112 is increased to increase the peripheral friction resistance, or the tip area is reduced by reducing the tip area of the tip side force device 210. It is necessary to let On the other hand, when it is desired to calculate the circumferential frictional resistance, it is necessary to increase the tip resistance by increasing the pile length of the tip portion 111 or by expanding the tip of the pile.

In order to solve the above-described problems in the tip loading test, a tip loading test of an auxiliary reaction force combined method in which an indentation test and a tip loading test are combined has been proposed (see Non-Patent Document 2 and Patent Document 1).
In the tip loading test using the auxiliary reaction force combined method, as shown in FIG. 6, the test pile 110, the tip side force device 210 provided on the tip side of the test pile 110, and the test pile 110 were constructed. A reaction force pile 130, a loading girder 140 installed between the pile heads of the reaction force pile 130, and a pile head side force device 160 provided between the loading girder 140 and the test pile 110. A loading test apparatus 300 is used.

According to this loading test apparatus 300, when the circumferential frictional resistance is made smaller than the tip resistance and the circumferential frictional resistance is measured, the tip side force device 210 applies a reaction force to the tip portion 111. And press the pile body upward.
On the other hand, when measuring the tip resistance, as shown by an arrow in FIG. 6, the tip side force device 210 applies a reaction force to the pile body 112 to press the tip portion 111 downward. At this time, since the reaction force of the pile main body 112 is insufficient and a pressing force sufficient to measure the tip resistance cannot be secured, the pile head side force device 160 reacts against the reaction force pile 130 via the loading girder 140. The pile main body 112 is pressed downward by taking a force, thereby supplementing the reaction force.

As described above, according to the tip loading test using the auxiliary reaction force combined method, both the circumferential frictional resistance and the tip resistance can be accurately measured.
In addition, since the reaction force is applied to the pile body 112 by the tip side force device 210, the number of reaction force piles can be reduced or the size of the reaction force pile (pile diameter, pile length, etc.) compared to the indentation test. ) Can be made smaller. Therefore, the effort concerning installation and removal of the loading test apparatus 300 can be reduced.

Geotechnical Society Standard (JGS 1811-2002) Pile Indentation Test Method Geotechnical Society Geotechnical Society Standard (JGS 1812-2002) Pile Tip Loading Test Method Geotechnical Society

Japanese Patent No. 3264740

  However, in recent years, it has been required to further reduce the number of reaction force piles or to further reduce the size of the reaction force piles in order to further reduce the labor required for installing and removing the loading test apparatus.

An object of the present invention is to provide a loading test method capable of accurately measuring both the peripheral friction resistance and the tip resistance while reducing the labor required for installation and removal.

In the pile loading test method according to claim 1 , the loading test apparatus (for example, a loading test apparatus 1 described later) includes a tip portion (for example, a tip section 11 described later) and a pile body (for example, a pile body 12 described below). ) And a test pile (e.g., test pile 10 described later), and a tip-side force device (e.g., tip-side jack 20 described later) provided between the tip and the pile body. A reaction force member (for example, a reaction force pile 30 described later) constructed around the test pile, and a pile head side force device (for example, described later) supported by the reaction force member and applied to the test pile. The pile head side jack 60), and the tip side force applying device takes a reaction force on the tip part and presses the pile body, or takes a reaction force on the pile body and the tip part. The pile head side force applying device takes a reaction force on the reaction force member. Characterized in that it is capable of pulling the test pile upwards.

The pile loading test method according to claim 1 , wherein the tip resistance of the tip is measured by pressing the tip with a reaction force applied to the pile body by the tip side force applying device. And

The pile loading test method according to claim 1 , wherein the pile body side pressure device is pressed against the pile body by applying a reaction force to the tip portion by the tip side force device, and applied to the reaction force member by the pile head side force device. The circumferential frictional resistance of the pile main body is measured by taking the reaction force and pulling the pile main body upward.

Here, examples of the reaction force member include a reaction force pile and a foot-like reinforced concrete frame.
According to this invention, when the peripheral frictional resistance of the pile body is made larger than the distal end resistance of the tip, and when measuring the peripheral frictional resistance, the reaction force is applied to the pile main body by the pile head side force device. The tip is pressed downward.
On the other hand, when measuring the circumferential frictional resistance, the pile body is pressed upward by applying a reaction force to the tip portion by the tip side pressurizing device. At this time, the reaction force at the tip is insufficient, and a pressing force sufficient to measure the peripheral frictional resistance cannot be secured. Pull up to compensate for the reaction force.

  Therefore, compared to the indentation test described above, the volume of the reaction force pile can be reduced by reducing the number of reaction force piles or by reducing the pile diameter of the reaction force pile. Time and effort can be reduced. In addition, both the peripheral friction resistance and the tip resistance can be measured with high accuracy.

  When a force in the pushing direction is applied to the pile, a greater resistance can be obtained by the resistance of the tip end face of the pile than when a force in the pulling direction is applied. Therefore, in the present invention, since the reaction force is taken so that the pushing force is applied to the reaction force member, when the pulling force acts on the reaction force member as in the tip loading test of the above-mentioned auxiliary reaction force combined method, Compared with, the pile diameter and depth of the reaction pile can be reduced. Therefore, the effort concerning installation and removal of the loading test apparatus can be reduced.

The pile loading test method according to claim 1 , wherein the test pile is constructed to be deeper than a predetermined depth (for example, depth P), extends downward from the ground surface, and is connected to the upper end portion of the pile body. It is preferable that a rod-shaped connecting member (for example, a steel rod 54 described later) is provided, and the pile head side force applying device pulls the connecting member upward.

In the tip loading test using the above-mentioned auxiliary reaction force combined method, indentation force is applied to the test pile, so it is necessary to build a rigid reinforced concrete structure pile near the ground surface to prevent buckling failure of the test pile . Further, when an underground building is provided in an actual building, the peripheral surface frictional resistance of the portion corresponding to the underground frame does not occur, and therefore it is necessary to remove the peripheral surface frictional resistance of this portion.
Therefore, while constructing the pile body of the test pile to the vicinity of the ground surface, friction cutting was performed to reduce the peripheral frictional resistance of the portion corresponding to the underground frame, and it took time and effort to construct and dismantle the test pile.

In the present invention, since the pulling force is applied to the test pile instead of the pushing force, it is not necessary to construct a pile body having high rigidity of the test pile to the vicinity of the ground surface as in the tip loading test of the above-described auxiliary reaction force combined use method. .
Therefore, in accordance with the actual pile construction depth, a test pile is constructed to a depth not less than a predetermined depth (for example, depth P) and further extends downward from the ground surface and is connected to the upper end of the pile body. A member was provided, and the connecting member was pulled upward by a pile head side force device.
Therefore, since the volume of the test pile can be reduced and the friction cut is not required, the labor required for construction and dismantling of the test pile can be reduced.

The pile loading test method according to claim 2 , wherein the test pile is constructed deeper than a predetermined depth, extends downward from the ground surface, penetrates the pile body, and is connected to a lower end portion of the pile body. It is preferable that a rod-shaped connecting member (for example, a steel rod 54A described later) is provided, and the pile head side force applying device pulls the connecting member upward.

  Here, the peripheral surface of a connection member is made into the structure (unbond) which reduces the adhesion resistance with a pile main body.

According to this invention, in accordance with the actual depth of construction of the pile, the test pile is constructed to be deeper than a predetermined depth, further extends downward from the ground surface, penetrates the pile body, and is connected to the lower end of the pile body. A rod-shaped connecting member is provided, and the connecting member is pulled upward by a pile head side force device.
Therefore, since the volume of the test pile can be reduced and the friction cut is not required, the labor required for construction and dismantling of the test pile can be reduced.

  Also, when measuring the peripheral frictional resistance, the pile head side force device exerts a reaction force on the reaction force member and pulls the lower end of the pile body upward, so no tensile force acts on the pile body. The occurrence of tensile cracks in the pile body of the main body can be prevented, and the distribution of the peripheral surface frictional resistance of the pile body can be accurately measured.

  According to the present invention, since the number of reaction force piles can be reduced or the pile diameter of the reaction force piles can be reduced compared to the indentation test described above, the volume of the reaction force piles can be reduced. Can reduce the time and labor required for installing In addition, both the peripheral friction resistance and the tip resistance can be measured with high accuracy. In addition, since the reaction force was taken so that the pushing force was applied to the reaction force pile, compared to the case where the pulling force acts on the reaction force pile as in the tip loading test of the above-mentioned auxiliary reaction force combined method, The pile diameter and depth of the reaction pile can be reduced. Therefore, the effort concerning installation and removal of the loading test apparatus can be reduced.

It is a side view of the loading test apparatus which concerns on 1st Embodiment of this invention. It is a side view for demonstrating operation | movement of the loading test apparatus which concerns on the said embodiment. It is a side view of the loading test apparatus which concerns on 2nd Embodiment of this invention. It is a side view of the loading test apparatus which concerns on the 1st prior art example of this invention. It is a side view of the loading test apparatus which concerns on the 2nd prior art example of this invention. It is a side view of the loading test apparatus which concerns on the 3rd prior art example of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the embodiments, the same constituent elements are denoted by the same reference numerals, and the description thereof is omitted or simplified.
[First Embodiment]
FIG. 1 is a cross-sectional view of a loading test apparatus 1 according to the first embodiment of the present invention.
The loading test apparatus 1 includes a test pile 10 provided at a predetermined depth or more from the ground surface 2, a tip-side jack 20 as a tip-side force applying device provided on the tip side of the test pile 10, and the test pile 10. A reaction force pile 30 as a plurality of reaction force members constructed around, a loading girder 40 installed between the pile heads of these reaction force piles 30 on the ground surface 2, and a loading girder 40. A pile head side jack 60 as a pile head side force applying device that applies force to the underground test pile 10 via the transmission mechanism 50.

The portion from the ground surface 2 to the depth P is a portion corresponding to the underground skeleton of the building or a portion that does not need to be measured in the test, and the test pile 10 is constructed to a depth greater than this depth P.
The test pile 10 has a cylindrical shape and reaches the support layer 3. This test pile 10 is divided into a tip portion 11 and a pile body 12 on the tip side, and the peripheral frictional resistance by the pile body 12 is larger than the tip resistance by the tip portion 11.

The front end side jack 20 is provided between the front end part 11 and the pile main body 12 so that the bearing surface is positioned vertically. Therefore, the upper bearing surface of the tip jack 20 is in contact with the lower end surface of the pile main body 12, and the lower bearing surface is in contact with the upper end surface of the tip portion 11.
This front end side jack 20 applies a force in a direction in which the upper end surface of the front end portion 11 and the lower end surface of the pile main body 12 are separated from each other, thereby taking a reaction force on the front end portion 11 and pressing the pile main body 12 upward. Alternatively, a reaction force can be applied to the pile body 12 to press the tip 11 downward.

The loading girder 40 is constructed between the reaction force piles 30 so as to straddle the test pile 10.
The pile head side jack 60 is disposed on the loading girder 40 and immediately above the test pile 10 so that the bearing surface is positioned vertically. Accordingly, the lower bearing surface of the pile head side jack 60 abuts on the upper surface of the loading girder 40, and the pile head side jack 60 is supported by the reaction force pile 30 via the loading girder 40.

  The transmission mechanism 50 includes a first horizontal member 51 provided substantially horizontally on the bearing surface on the upper side of the pile head side jack 60, and a second horizontal member provided substantially horizontally between the loading girder 40 and the ground surface 2. 52, a rod-shaped steel rod 53 extending downward from the first horizontal member 51 and connected to the second horizontal member 52, and a rod-shaped steel rod extending downward from the second horizontal member 52 and connected to the upper end of the pile body 12 Steel rod 54 as a connecting member.

  The pile head side jack 60 applies a force in a direction in which the loading girder 40 and the first horizontal member 51 are separated from each other, thereby taking a reaction force on the reaction force pile via the loading girder 40 and moving the pile main body 12 upward. It is possible to pull on.

The method for measuring the tip resistance and the circumferential frictional resistance by the loading test apparatus 1 is as follows.
When measuring the tip resistance by the tip portion 11, as shown by an arrow in FIG. 1, the tip side jack 20 presses the tip portion 11 downward by applying a reaction force to the pile body 12.
On the other hand, when measuring the peripheral frictional resistance, as shown by the arrow in FIG. Here, since the pressing force applied to the pile main body 12 is insufficient, the pile head jack 60 pulls the pile main body 12 upward by applying a reaction force to the reaction force pile 30. Thereby, indentation force acts on the reaction force pile 30, and tensile force acts on the steel rod 53 and the steel rod 54.

The above loading test apparatus 1 is constructed in the following procedure.
First, the test pile 10 and the reaction force pile 30 are constructed. When constructing the test pile 10, the front end jack 20 is attached to the front end side of the test pile 10, and a steel bar 54 is attached to the pile head of the test pile 10, and the upper end side of the steel bar 54 extends from the ground surface 2. Leave it exposed.
After passing the curing period of the concrete of the test pile 10 and the reaction force pile 30, the loading girder 40 and the pile head side jack 60 are installed.
Next, the first horizontal member 51, the steel bar 53, and the second horizontal member 52 are attached, and the steel bar 54 exposed from the ground surface 2 is connected to the second horizontal member 52.

According to this embodiment, there are the following effects.
(1) Compared with the indentation test, the number of reaction force piles can be reduced, or the pile diameter of the reaction force piles can be reduced. Since the pushing force acts on the reaction force pile 30, the volume of the reaction force pile 30 can be reduced, so that the labor required for installing the loading test apparatus 1 can be reduced. In addition, both the peripheral friction resistance and the tip resistance can be measured with high accuracy.

  When a force in the pushing direction is applied to the pile, a greater resistance can be obtained by the resistance of the tip end face of the pile than when a force in the pulling direction is applied. Therefore, according to the loading test apparatus 1, since the reaction force is applied so that the pushing force is applied to the reaction force pile 30, the pulling force acts on the reaction force pile as in the tip loading test of the auxiliary reaction force combined type. Compared with the structure, the pile diameter and depth of the reaction force pile 30 can be reduced. Therefore, the effort concerning installation and removal of the loading test apparatus 1 can be reduced.

(2) In accordance with the actual pile construction depth, the test pile 10 is constructed to a depth equal to or greater than the predetermined depth P, and further extends downward from the ground surface 2 and is connected to the upper end of the pile main body 12. The steel rod 54 was pulled upward by the pile head side jack 60.
Therefore, since the frame volume of the test pile 10 can be reduced and the friction cut is not required, the labor required for construction and disassembly of the test pile 10 can be reduced.

[Second Embodiment]
FIG. 3 is a side view of a loading test apparatus 1A according to the second embodiment of the present invention.
This embodiment is different from the first embodiment in that a steel rod 54 </ b> A as a connecting member extends downward from the ground surface 2, penetrates the pile main body 12, and is connected to the lower end portion of the pile main body 12.
The peripheral surface of this steel rod 54A has a structure (unbond) that reduces adhesion resistance to the pile body 12.

According to the present embodiment, in addition to the above (1) and (2), there are the following effects.
(3) When measuring the circumferential frictional resistance, the pile head side jack 60 takes the reaction force on the reaction force pile 30 and pulls the lower end of the pile body 12 upward, so that no tensile force acts on the pile body 12. Therefore, the occurrence of tensile cracks in the pile body 12 can be prevented, and the distribution of the peripheral frictional resistance of the pile body 12 can be accurately measured.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.

DESCRIPTION OF SYMBOLS 1, 1A ... Loading test apparatus 2 ... Ground surface 3 ... Support layer 10 ... Test pile 11 ... Tip part 12 ... Pile main body 20 ... Tip side jack (tip side force device)
30 ... Reaction force pile (Reaction force member)
DESCRIPTION OF SYMBOLS 40 ... Loading girder 50 ... Transmission mechanism 51 ... 1st horizontal member 52 ... 2nd horizontal member 53 ... Steel bar 54, 54A ... Steel bar (connection member)
60 ... Pile head side jack (Pile head side force device)
DESCRIPTION OF SYMBOLS 100, 200, 300 ... Conventional loading test apparatus 110 ... Test pile 111 ... Tip part 112 ... Pile main body 130 ... Reaction force pile 140 ... Loading girder 160 ... Pile head side force device 170 ... Steel pipe 210 ... Tip side force device P: Predetermined depth

Claims (2)

A test pile that reaches the support layer and is divided into a tip portion and a pile body, a tip-side force device provided between the tip portion and the pile body, and a structure around the test pile. A reaction force member, a pile head side force device supported by the reaction force member and applying force to the test pile, and a rod-shaped member extending downward from the pile head side force device and connected to the pile body. a connecting member, a loading test method using a loading tester Ru provided with,
When the peripheral friction resistance by the pile body of the test pile is larger than the tip resistance by the tip,
A loading test that measures the tip resistance of the tip by pressing the tip by taking a reaction force on the pile body by the tip side force device;
The pile body side is pressed against the pile body by applying a reaction force to the tip portion by the tip side force applying device, and the connecting member is pulled upward by taking a reaction force on the reaction force member by the pile head side force device. A load test method for piles, comprising: a load test for measuring a peripheral frictional resistance of the pile body. 2. The pile loading test method according to claim 1, wherein the connecting member extends downward from the pile head side force applying device, penetrates the pile main body, and is connected to a lower end portion of the pile main body.

Images