Pile load test jig and pile load test method

Abstract

To improve workability of a pile loading test.SOLUTION: A pile loading test jig includes: a stress transmission member which is brought into contact with a jack mounted on the upper end of a tubular reaction pile penetrated into the ground, above the jack; and a plurality of rod-like members which are engaged with a test pile whose upper ends are engaged with the stress transmission member and lower ends are inside the reaction pile and are penetrated into the ground, and are arranged in a circumferential direction of the test pile.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a pile load test jig and a pile load test method. [Background technology]

[0002] Patent Document 1 describes a technique for conducting pile load tests in small areas using ordinary reaction piles that do not have a special shape, without the need to penetrate the reaction pile all the way to the supporting layer at the tip. Specifically, Patent Document 1 uses a reaction pile that is larger in diameter than the test pile, shorter in length than the test pile, and is cylindrical in shape and does not reach the supporting layer. A pile load test device is provided in which a jack is disposed at the head of the reaction pile, which applies a reaction force to the reaction pile to push in or pull out the test pile. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-166137 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the embodiment described in Patent Document 1, the jacks are placed inside the reaction piles in the push-in test, which increases the diameter of the reaction piles and requires large-scale equipment for transporting and installing the reaction piles. Furthermore, if the jacks are placed inside the reaction piles, it is not easy to wire them during installation or to troubleshoot problems after installation. On the other hand, in the pull-out test, multiple jacks are lined up on top of the reaction piles, so the load amount must be finely adjusted between each jack. Furthermore, because the jacks are placed on the outer periphery of the testing equipment, high installation precision is required to prevent the jacks from falling off during loading.

[0005] Therefore, an object of the present invention is to provide a pile load test jig and a pile load test method that can improve the ease of performing pile load tests. [Means for solving the problem]

[0006] [1] A pile loading test jig comprising: a stress transmission member that is placed on the upper end of a tubular reaction pile that has penetrated the ground and is abutted against the jack from above; and a plurality of rod-shaped members whose upper ends are engaged with the stress transmission member and whose lower ends are engaged with a test pile that has penetrated the ground inside the reaction pile, and which are arranged circumferentially around the test pile. [2] The pile load test jig described in [1] further comprises a tubular member positioned outside the engagement portion between the multiple rod-shaped members and the test pile, a bottom plate that abuts against the lower end of the tubular member and the upper end of the reaction pile, respectively, and has an opening through which the upper end of the test pile passes, and a cover plate that abuts against the upper end of the tubular member, has an opening through which the multiple rod-shaped members pass, and on which a jack is placed. [3] A pile load test jig as described in [1] or [2], in which the upper end of each of the multiple rod-shaped members is inserted into an opening formed in the stress transfer member, and a nut is screwed onto the upper end. [4] A pile load test jig as described in any one of [1] to [3], in which the lower end of each of the multiple rod-shaped members is inserted into an opening formed in a flange plate fixed to the reaction pile or test pile, and a nut is screwed onto the lower end. [5] A pile load test jig described in any one of [1] to [4], in which at least one of a load cell or a spacing adjustment member is interposed between the jack and the stress transmission member, or between the jack and the test pile or the reaction pile. [6] A pile loading test jig described in any one of [1] to [5], further comprising a plurality of intermediate reinforcing plates interposed between the jack and the stress transmission member, or between the jack and the test pile or reaction pile, and a plurality of guide rods arranged in a cage-like shape around the circumferential direction of the reaction pile or test pile together with a plurality of rod-shaped members, and slidably inserted into openings formed in each of the plurality of intermediate reinforcing plates. [7] A method for loading tests on piles, comprising the steps of: placing a jack on the upper end of a tubular reaction pile that has penetrated the ground; arranging a plurality of rod-shaped members in the circumferential direction of the test pile that has penetrated the ground inside the reaction pile and engaging the lower ends of each of the plurality of rod-shaped members to the test pile; abutting a stress transmission member against the jack from above the jack; engaging the upper ends of each of the plurality of rod-shaped members to the stress transmission member; and extending the jack to apply a reaction force in the pushing direction to the reaction pile while applying a force in the pulling direction to the test pile. [Effects of the Invention]

[0007] According to the above configuration, by engaging the multiple rod-shaped members with the stress transmission members and the reaction piles or test piles, respectively, it is possible to transmit tensile force without the need for welding. Furthermore, because the jack and other components are placed inside the multiple rod-shaped members arranged in a cage-like configuration, even if the jack or other components deviate from their designated positions for some reason, they are prevented from scattering to the outside. This improves the ease of pile load testing. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a side view of a pile load test jig according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3A] 1A to 1C are diagrams illustrating an example of a method for assembling a pile load test jig according to a first embodiment of the present invention. [Figure 3B] 1A to 1C are diagrams illustrating an example of a method for assembling a pile load test jig according to a first embodiment of the present invention. [Figure 4] FIG. 10 is a side view of a pile load test jig according to a second embodiment of the present invention. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6A] FIG. 10 is a diagram showing an example of a method for assembling a pile load test jig according to a second embodiment of the present invention. [Figure 6B] FIG. 10 is a diagram showing an example of a method for assembling a pile load test jig according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0010] (First embodiment: Jig for indentation load test) FIG. 1 is a side view of a pile load test jig according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. In the illustrated example, the load test jig 10 includes a stress transmission member 11 that abuts from above against a jack 3 placed on the upper end of a test pile 2 that has penetrated the ground inside a tubular reaction pile 1 that has penetrated the ground, and steel rods 12A-12D (collectively referred to as steel rods 12) whose upper ends are engaged with the stress transmission member 11 and whose lower ends are engaged with the reaction pile 1. The steel rods 12A-12D are arranged circumferentially around the reaction pile 1. In the illustrated example, the stress transmission member 11 abuts against the jack 3 from above via a load cell 4, a spacing adjustment member 13, and intermediate reinforcing plates 14A, 14B, and 14C that are interposed between the load cell 4 and the spacing adjustment member 13. The jack 3 is placed on the upper end of the test pile 2 via an intermediate reinforcing plate 14D.

[0011] In this specification, a rod-shaped member refers to a long, thin member, such as steel rods 12A-12D, capable of transmitting force from one side to another. The rod-shaped member is not limited to a solid member such as a steel rod, but may also be a hollow member such as a steel pipe. The cross-sectional shape of the rod-shaped member is not limited to a circular shape, but may be, for example, a square bar, a square pipe, or a flat bar. While the surfaces of the steel rods 12A-12D are illustrated as being smooth, the surface of the rod-shaped member may have an uneven surface, such as a deformed steel bar. Furthermore, the term "engaging the end of a rod-shaped member with another member" means that the rod-shaped member is connected to another member so as to be able to transmit a tensile force. Specifically, a threaded portion is formed at the upper end of the steel rod 12, and the steel rod 12 is inserted into an opening formed in the stress transmission member 11, and then a nut 121 is screwed onto the threaded portion from above to engage the steel rod 12 with the stress transmission member 11. Meanwhile, a threaded portion is also formed at the lower end of the steel rod 12, and the steel rod 12 is inserted into an opening formed in a flange plate 122 fixed to the upper end of the reaction pile 1, and then a nut 123 is screwed onto the threaded portion from below, thereby locking the steel rod 12 to the reaction pile 1. By locking the steel rod 12 to each member in this way, the upward force acting on the stress transmission member 11 when the jack 3 is extended is transmitted to the reaction pile 1 as a tensile force acting on the steel rod 12. Therefore, in this embodiment, a pile compressive load test is carried out in which a reaction force in the pull-out direction is applied to the reaction pile 1, and a force in the push-in direction is applied to the test pile 2.

[0012] Additionally, in the illustrated example, guide rods 15A to 15D (collectively referred to as guide rods 15) are attached to the flange plate 122 and extend upward. The guide rods 15 are slidably inserted into openings formed in the intermediate reinforcing plates 14A to 14D. The intermediate reinforcing plates 14A to 14D move along the guide rods 15, but are not restricted in their vertical displacement. The provision of the guide rods 15 prevents horizontal displacement of the intermediate reinforcing plates 14A to 14D, enabling stable transmission of force between members including the stress transmission members 11 and the jacks 3 as described above.

[0013] 3A and 3B are diagrams illustrating an example of a method for assembling a pile load test jig according to the first embodiment of the present invention. As shown in FIG. 3A, first, steel rods 12A-12D are inserted through openings formed in a flange plate 122 that has been previously fixed by welding, bolting, or the like to a reaction pile 1 that has penetrated the ground. At this point, the steel rods 12 are not secured against downward movement, so they may be prevented from falling by, for example, wrapping adhesive tape around the steel rods 12. Next, an intermediate reinforcing plate 14D is placed while the steel rods 12A-12D are inserted through the openings, and a jack 3 is placed on the intermediate reinforcing plate 14D.

[0014] Next, as shown in Fig. 3B, the intermediate reinforcing plate 14C is placed on the jack 3 while the steel rods 12A to 12D are inserted into the openings, and the load cell 4 is placed on top of the intermediate reinforcing plate 14C. Similarly, the intermediate reinforcing plate 14B, the spacing adjustment member 13, the intermediate reinforcing plate 14A, and the stress transmission member 11 are placed in this order, and nuts 121 are screwed onto the threaded portions on the upper ends of the steel rods 12A to 12D inserted into the openings of the stress transmission member 11, thereby completing the load test jig 10 as shown in Fig. 1. Note that the guide rods 15A to 15D may be placed when several intermediate reinforcing plates have been placed, as in the illustrated example, or may be attached to the flange plate 122 in advance, or may be placed after the above-mentioned process.

[0015] In this embodiment, the jack 3 can be placed above the reaction pile 1 by transmitting stress via the steel rods 12, allowing the diameter of the reaction pile 1 to be minimized. Furthermore, because the jack 3 is exposed between the steel rods 12, wiring during installation and troubleshooting after installation are simplified. Furthermore, by locking the steel rods 12 with the stress transmission members 11 and the reaction pile 1, respectively, welding is not required while still allowing tensile force to be transmitted. Furthermore, because components such as the jack 3 are placed inside the steel rods 12 (and guide rods 15) arranged in a cage-like configuration, they are prevented from scattering outside even if they deviate from their designated positions for some reason. Therefore, this embodiment improves the ease of pile load testing.

[0016] (Second embodiment: Jig for tensile load test) Fig. 4 is a side view of a pile load test jig according to a second embodiment of the present invention, and Fig. 5 is a cross-sectional view taken along line VV in Fig. 4. In the illustrated example, the load test jig 20 includes a stress transmission member 11 that abuts from above against a jack 3 placed on the upper end of a reaction pile 1 that has penetrated the ground, and steel rods 12A-12D whose upper ends are engaged with the stress transmission member 11 and whose lower ends are engaged with the test pile 2 that has penetrated the ground. The steel rods 12A-12D are arranged in the circumferential direction of the test pile 2. In the illustrated example, the stress transmission member 11 abuts from above against the jack 3 via a load cell 4, a spacing adjustment member 23, and intermediate reinforcing plates 14A, 14B, and 14C that are interposed between them.

[0017] In the illustrated example, the jack 3 is placed on the upper end of the reaction pile 1 via a bottom plate 26, a steel pipe 27, and a cover plate 28. The bottom plate 26 is placed on a flange plate 122 fixed to the upper end of the reaction pile 1, the steel pipe 27 is placed on the bottom plate 26, and the cover plate 28 is placed on the steel pipe 27. An opening is formed in the center of the bottom plate 26 through which the upper end of the test pile 2 passes. The steel pipe 27 is open at both the upper and lower ends and has a diameter large enough to accommodate the engagement portions between the test pile 2 and the steel rods 12A-12D. The cover plate 28 also has openings through which the steel rods 12A-12D pass. As a result, in this embodiment, the jack 3 can be placed on the upper end of the reaction pile 1 without interfering with the test pile 2 and the steel rods 12A-12D.

[0018] In this embodiment, the steel rod 12 is inserted into an opening formed in the stress transmission member 11, and then a nut 121 is screwed onto a threaded portion formed on the upper end of the steel rod 12, thereby locking the steel rod 12 to the stress transmission member 11. Also, the steel rod 12 is inserted into an opening formed in a flange plate 124 fixed to the upper end of the test pile 2, and then a nut 123 is screwed onto a threaded portion formed on the lower end of the steel rod 12, thereby locking the steel rod 12 to the test pile 2. By locking the steel rod 12 to each member in this manner, the upward force acting on the stress transmission member 11 when the jack 3 is extended is transmitted to the test pile 2 as a tensile force acting on the steel rod 12. Therefore, in this embodiment, a pull-out load test of a pile is carried out in which a reaction force in the pushing direction acts on the reaction pile 1, and a force in the pulling direction acts on the test pile 2.

[0019] Additionally, in the illustrated example, guide rods 15A to 15D are attached to the cover plate 28 and extend upward. The guide rods 15 are inserted into openings formed in the intermediate reinforcing plates 14A to 14C. The intermediate reinforcing plates 14A to 14C move along the guide rods 15, but are not restricted in their vertical displacement. By providing the guide rods 15, horizontal displacement of the intermediate reinforcing plates 14A to 14C can be prevented, and force can be stably transmitted between the members including the stress transmission member 11 and the jack 3 as described above.

[0020] 6A and 6B are diagrams showing an example of a method for assembling a pile load test jig according to a second embodiment of the present invention. As shown in FIG. 6A, first, steel rods 12A to 12D are inserted into openings formed in a flange plate 124 that has been previously fixed by welding, bolting, or the like to a test pile 2 that has penetrated the ground. At this point, the steel rod 12 is not fixed against downward movement, so it may be prevented from falling by, for example, wrapping adhesive tape around the steel rod 12. Next, a bottom plate 26 is placed on a flange plate 122 that has been previously fixed to the reaction pile 1 by welding, bolting, or the like.

[0021] Next, as shown in FIG. 6B, steel pipe 27 and cover plate 28 are placed on bottom plate 26, and jack 3 and intermediate reinforcing plate 14C are placed on cover plate 28. Cover plate 28 and intermediate reinforcing plate 14C are placed with steel rods 12A-12D inserted through their openings. Similarly, load cell 4, intermediate reinforcing plate 14B, spacing adjustment member 23, intermediate reinforcing plate 14A, and stress transmission member 11 are placed in this order, and nuts 123 are screwed onto the threaded portions on the upper ends of steel rods 12A-12D inserted through the openings of stress transmission member 11, completing load test jig 20 as shown in FIG. 4. Note that guide rods 15A-15D may be placed when several intermediate reinforcing plates have been placed, as in the illustrated example, or may be attached to cover plate 28 in advance, or may be placed after the above-mentioned process.

[0022] In this embodiment, stress is transmitted via the steel rod 12, allowing the jack 3 to be positioned on the axis of the reaction pile 1 and the test pile 2. This eliminates the need for multiple jacks and the need for processes such as fine-tuning the load amount. Furthermore, the jack 3 positioned on the axis of the reaction pile 1 and the test pile 2 is less likely to fall off during loading, so installation precision is not required compared to when the jack is positioned on the outer periphery of the test equipment. Furthermore, by locking the steel rod 12 with the stress transmission member 11 and the test pile 2, respectively, welding is not required while still allowing the transmission of tensile force. Furthermore, in this embodiment, components such as the jack 3 are positioned within the steel rods 12 (and guide rod 15) arranged in a cage-like configuration, preventing the jack 3 from scattering outside even if it deviates from its designated position for some reason. Therefore, this embodiment improves the ease of pile load testing.

[0023] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications or alterations within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0024] 1...reaction pile, 2...test pile, 3...jack, 4...load cell, 10, 20...load test jig, 11...stress transfer member, 12A to 12D...steel rod, 121, 123...nut, 122, 124...flange plate, 13, 23...spacing adjustment member, 14A to 14D...intermediate reinforcing plate, 15A to 15D...guide rod, 26...bottom plate, 27...steel pipe, 28...cover plate.

Claims

1. A stress transmission member that is placed on the upper end of a tubular reaction pile that penetrates the ground and abuts against the jack from above the jack; A plurality of rod-shaped members whose upper ends are engaged with the stress transmission member and whose lower ends are engaged with test piles that penetrate into the ground inside the reaction pile, and which are arranged in the circumferential direction of the test pile; a tubular member disposed outside the engagement portion between the plurality of rod-shaped members and the test pile; a bottom plate that abuts against the lower end of the tubular member and the upper end of the reaction pile, respectively, and has an opening through which the upper end of the test pile passes; a cover plate that is in contact with the upper end of the tubular member, has openings through which the plurality of rod-shaped members pass, and on which the jack is placed; A pile load test jig comprising:

2. 2. The pile load test jig according to claim 1, wherein an upper end of each of the plurality of rod-shaped members is inserted into an opening formed in the stress transmission member, and a nut is screwed onto the upper end.

3. 3. A pile load test jig as described in claim 1 or claim 2, wherein the lower end of each of the plurality of rod-shaped members is inserted into an opening formed in a flange plate fixed to the reaction pile or the test pile, and a nut is screwed onto the lower end.

4. A pile loading test jig as described in any one of claims 1 to 3, wherein at least one of a load cell or a spacing adjustment member is interposed between the jack and the stress transmission member, or between the jack and the test pile or the reaction pile.

5. A plurality of intermediate reinforcing plates interposed between the jack and the stress transmission member, or between the jack and the test pile or the reaction pile; a plurality of guide rods arranged in a cage shape in the circumferential direction of the reaction pile or the test pile together with the plurality of rod-shaped members and slidably inserted into openings formed in the plurality of intermediate reinforcing plates, respectively; The pile load test jig according to any one of claims 1 to 4, further comprising:

6. A step of arranging a plurality of rod-shaped members in a circumferential direction of the test pile penetrated into the ground and engaging the lower end portions of the plurality of rod-shaped members with the test pile; A step of placing a bottom plate having an opening on the upper end of a tubular reaction pile that has penetrated into the ground outside the test pile, while passing the test pile through the opening; a step of placing a tubular member having an open upper end and a open lower end outside the engagement portions between the plurality of rod-shaped members and the test pile, and placing the tubular member so that the lower end of the tubular member abuts against the bottom plate; a step of placing a cover plate, which has openings formed therein through which the plurality of rod-shaped members pass, on the tubular member such that upper ends of the tubular member abut against the cover plate while inserting the plurality of rod-shaped members into the openings; placing a jack on the cover plate; a step of bringing a stress transmission member into contact with the jack from above the jack; a step of engaging an upper end portion of each of the plurality of rod-shaped members with the stress transmission member; a step of extending the jack to apply a force in a pulling direction to the test pile while applying a reaction force in a pushing direction to the reaction pile; A method for load testing piles, including:

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