Pile load test fixture and pile load test method

Abstract

This invention provides a load testing fixture for piles, comprising: a stress transfer member abutting from above a lifting device mounted on the upper end of a test pile inserted into the ground via a tubular reaction pile; and a plurality of rod-shaped members arranged circumferentially around the reaction pile, with their upper ends engaged with the stress transfer member and their lower ends engaged with the reaction pile. Furthermore, this invention provides a load testing fixture for piles, comprising: a stress transfer member abutting from above a lifting device mounted on the upper end of a tubular reaction pile inserted into the ground; and a plurality of rod-shaped members arranged circumferentially around the test pile, with their upper ends engaged with the stress transfer member and their lower ends engaged with the test pile inserted into the ground via a tubular reaction pile.

Description

[Technical Field]

[0001] This invention relates to a load testing fixture for piles and a load testing method for piles. [Previous Technology]

[0002] Patent Document 1 (Japanese Patent Application Publication No. 2017-166137) discloses a technique for conducting pile load tests using a general reaction pile without a special shape, eliminating the need to penetrate the reaction pile into the front support layer, and enabling tests to be conducted even in confined areas. Specifically, Patent Document 1 uses a cylindrical reaction pile with a larger diameter and shorter length than the test pile, designed for insertion into the test pile, and which does not reach the support layer. It provides a pile load test apparatus in which a lifting device for applying a reaction force to the reaction pile to press or pull out the test pile is attached to the pile head of the reaction pile. [Summary of the Invention]

[0003] [The problem the invention aims to solve]

[0004] However, in the embodiment described in Patent Document 1 above, since the lifting device is positioned inside the reaction pile during the pressing test, the diameter of the reaction pile is relatively large, requiring large-scale equipment for moving or installing the reaction pile. Furthermore, when the lifting device is positioned inside the reaction pile, wiring during installation and handling post-installation issues are not easy. On the other hand, since multiple lifting devices are arranged side-by-side on the reaction pile during the pull-out test, the load must be finely adjusted between each lifting device. Also, since the lifting device is positioned on the outer periphery of the test device, the installation accuracy must be improved to prevent the lifting device from falling off under load.

[0005] Therefore, the object of the present invention is to provide a pile load test fixture and a pile load test method that can improve the constructability of pile load test.

[0006] [1] A load test fixture for a pile, comprising: a stress transmission member abutting from above a lifting device placed on the upper end of a test pile inserted into the ground via a tubular reaction pile; and a plurality of rod-shaped members arranged circumferentially around the reaction pile, with their upper ends locked to the stress transmission member and their lower ends locked to the reaction pile.

[0007] [2] A load test fixture for a pile, comprising: a stress transmission member abutting from above a lifting device placed on the upper end of a tubular reaction pile penetrating into the ground; and a plurality of rod-shaped members arranged around the circumference of the test pile, the upper ends of which are engaged with the stress transmission member and the lower ends of which are engaged with the test pile penetrating into the ground inside the reaction pile.

[0008] [3] The load test fixture of [2] further comprises: a tubular member disposed outside the locking portion of a plurality of rod-shaped members and the test pile; a base plate abutting against the lower end of the tubular member and the upper end of the reaction pile respectively, and forming an opening for the upper end of the test pile to pass through; and a cover plate abutting against the upper end of the tubular member, forming an opening for the plurality of rod-shaped members to pass through, and for mounting a lifting device.

[0009] [4] The load test fixture for a pile as described in any of [1] to [3], wherein the upper ends of each of the plurality of rod-shaped members are inserted through an opening formed in the stress transmission member and a nut is screwed into the upper end.

[0010] [5] The load test fixture for a pile as described in any of [1] to [4], wherein the lower ends of each of the plurality of rod-shaped members are inserted into an opening formed on a flange plate fixed to the reaction pile or test pile, and a nut is screwed into the lower end.

[0011] [6] The load test fixture for a pile as described in any of [1] to [5], wherein at least one of a load sensor or a spacing adjustment member is inserted between the lifting device and the stress transmission member, or between the lifting device and the test pile or the reaction pile.

[0012] [7] The load test fixture for a pile as described in any of [1] to [6] further comprises: a plurality of intermediate reinforcing plates, which are inserted between the lifting device and the stress transmission member, or between the lifting device and the test pile or the reaction pile; and a plurality of guide rods, which are slidably inserted through openings formed on the plurality of intermediate reinforcing plates respectively.

[0013] [8] A method for testing the load of a pile, comprising: placing a lifting device on the upper end of a test pile that penetrates into the ground inside a tubular reaction pile; arranging a plurality of rod-shaped members around the reaction pile and securing the lower ends of each of the plurality of rod-shaped members to the reaction pile; abutting a stress-transferring member against the lifting device from above; securing the upper ends of each of the plurality of rod-shaped members to the stress-transferring member; and extending the lifting device to apply a pull-out reaction force to the reaction pile and a pressing force to the test pile.

[0014] [9] A method for testing the load of a pile, comprising: a step of placing a lifting device on the upper end of a tubular reaction pile penetrating into the ground; arranging a plurality of rod-shaped members circumferentially on a test pile penetrating into the ground inside the reaction pile, and securing the lower ends of each of the plurality of rod-shaped members to the test pile; a step of abutting a stress-transferring member against the lifting device from above; securing the upper ends of each of the plurality of rod-shaped members to the stress-transferring member; and a step of extending the lifting device to apply a reaction force in the pressing direction to the reaction pile and a force in the pulling direction to the test pile.

[0015] According to the above configuration, by separately locking the plurality of rod-shaped members to the stress transmission members and the reaction pile or test pile, tensile force can be transmitted without the need for welding. Furthermore, since the lifting device and other components are housed within the plurality of rod-shaped members arranged in a cage-like configuration, even if the lifting device and other components detach from their designated positions for some reason, they can be prevented from scattering to the outside. Therefore, the constructability of the pile load test can be improved.

Implementation Method

[0017] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Furthermore, in this specification and drawings, redundant descriptions of constituent elements having substantially the same functional configuration are omitted by using the same reference numerals.

[0018] (First Embodiment: Fixture for Load Testing) Figure 1 is a side view of the load testing fixture for a pile according to the first embodiment of the present invention, and Figure 2 is a sectional view along line II-II of Figure 1. In the illustrated example, the load testing fixture 10 includes: a stress transmission member 11, which abuts from above against a lifting device 3 placed on the upper end of a test pile 2 inserted into the ground via a tubular reaction pile 1; and steel bars 12A-12D (also collectively referred to as steel bars 12), the upper end of which is engaged with the stress transmission member 11, and the lower end of which is engaged with the reaction pile 1. The steel bars 12A-12D are arranged circumferentially around the reaction pile 1. In the illustrated example, the stress transmission member 11 abuts from above against the lifting device 3 through the load sensor 4, the spacing adjustment member 13, and intermediate reinforcing plates 14A, 14B, 14C inserted between them. Furthermore, the lifting device 3 is placed on the upper end of the test pile 2 through the intermediate reinforcing plate 14D.

[0019] In this specification, the rod-shaped member is a slender member such as steel bars 12A to 12D, meaning a member that can transmit force from one to another. The rod-shaped member is not limited to a solid member like a steel bar, but can also be a hollow member like a steel pipe. The cross-sectional shape of the rod-shaped member is not limited to a circle, but can also be a shape such as a corner bar or corner tube, or a flat bar. Although the surface of the steel bars 12A to 12D is shown as smooth, it can also be formed with unevenness on the surface of the rod-shaped member, for example, like a shaped steel bar. Furthermore, the end of the rod-shaped member is locked to other members, meaning that the rod-shaped member can be connected to other members to transmit tensile force. Specifically, the upper end of the steel bar 12 has a threaded portion, and the steel bar 12 is locked to the stress transmission member 11 by inserting the steel bar 12 through the opening formed in the stress transmission member 11 and then screwing the nut 121 into the threaded portion from above. On the other hand, a threaded portion is also formed at the lower end of the steel rod 12. By inserting the steel rod 12 through the opening formed on the flange plate 122 fixed to the upper end of the reaction pile 1, the nut 123 is screwed into the threaded portion from below, thereby securing the steel rod 12 to the reaction pile 1. By securing the steel rod 12 to each component in this way, when the lifting device 3 extends, the upward force acting on the stress transmission member 11 is transmitted to the reaction pile 1 as a tensile force acting on the steel rod 12. Therefore, in this embodiment, a pile indentation load test is performed, in which a reaction force in the pull-out direction is applied to the reaction pile 1 and a force in the indentation direction is applied to the test pile 2.

[0020] Furthermore, in the illustrated example, guide rods 15A-15D (also collectively referred to as guide rods 15) are mounted on the flange plate 122 and extend upward. The guide rods 15 are slidably inserted into openings formed in the intermediate reinforcing plates 14A-14D. Although the intermediate reinforcing plates 14A-14D move along the guide rods 15, their vertical displacement is unrestricted. By arranging the guide rods 15, horizontal displacement of the intermediate reinforcing plates 14A-14D can be prevented, thereby enabling stable force transmission between the components including the stress transmission member 11 and the lifting device 3 as described above.

[0021] Figures 3A and 3B are illustrations showing an example of the assembly method of the pile load test fixture according to the first embodiment of the present invention. As shown in Figure 3A, firstly, steel rods 12A to 12D are inserted through an opening formed in the flange plate 122 of the reaction pile 1 that is fixed to the ground by pre-welding or bolting. At this point, since the steel rods 12 are not fixed for downward movement, they can be prevented from falling, for example, by wrapping adhesive tape around the steel rods 12. Then, while the steel rods 12A to 12D are inserted into the opening, an intermediate reinforcing plate 14D is arranged, and a lifting device 3 is mounted on the intermediate reinforcing plate 14D.

[0022] Next, as shown in Figure 3B, with steel bars 12A-12D inserted through the opening, an intermediate reinforcing plate 14C is placed on the lifting device 3, and a load sensor 4 is placed on it. Similarly, the intermediate reinforcing plate 14B, the spacing adjustment member 13, the intermediate reinforcing plate 14A, and the stress transfer member 11 are placed sequentially, and the nut 121 is screwed into the threaded portion of the upper end of the steel bars 12A-12D inserted into the opening of the stress transfer member 11, thus completing the load test fixture 10 as shown in Figure 1. In addition, regarding the guide bars 15A-15D, as shown in the example, they can be configured at the time of configuring any intermediate reinforcing plate, or they can be pre-installed on the flange plate 122, or they can be configured after the above steps.

[0023] In this embodiment, since the lifting device 3 can be positioned above the reaction pile 1 by transmitting stress through the steel rod 12, the diameter of the reaction pile 1 can be minimized as necessary. Furthermore, since the lifting device 3 protrudes from between the steel rods 12, wiring during installation and handling of post-installation issues become easier. Also, by securing the steel rod 12 to the stress transmission member 11 and the reaction pile 1 respectively, tensile force can be transmitted without welding. Furthermore, since the lifting device 3 and other components are housed within the cage-like steel rods 12 (and guide rods 15), even if the lifting device 3 and other components detach from their designated positions for some reason, they can be prevented from scattering to the outside. Therefore, this embodiment improves the constructability of pile load tests.

[0024] (Second Embodiment: Fixture for Tensile Load Test) Figure 4 is a side view of the pile load test fixture according to the second embodiment of the present invention, and Figure 5 is a cross-sectional view along line VV of Figure 4. In the illustrated example, the load test fixture 20 includes: a stress transmission member 11, which abuts from above against a lifting device 3 mounted on the upper end of a reaction pile 1 inserted into the ground; and steel bars 12A-12D, the upper ends of which are engaged with the stress transmission member 11, and the lower ends of which are engaged with the test pile 2 inserted into the ground. The steel bars 12A-12D are arranged circumferentially on the test pile 2. In the illustrated example, the stress transmission member 11 abuts from above against the lifting device 3, intervening in the load sensor 4, the spacing adjustment member 23, and intermediate reinforcing plates 14A, 14B, 14C inserted between them.

[0025] Furthermore, in the illustrated example, the lifting device 3 is mounted on the upper end of the reaction pile 1, separated by the base plate 26, the steel pipe 27, and the cover plate 28. The base plate 26 is mounted on the flange plate 122 fixed to the upper end of the reaction pile 1, the steel pipe 27 is mounted on the base plate 26, and the cover plate 28 is mounted on the steel pipe 27. An opening is formed in the center of the base plate 26 for the upper end of the test pile 2 to pass through. The upper and lower ends of the steel pipe 27 are open, and the inner side has a diameter for the locking portion for arranging the test pile 2 and the steel bars 12A-12D. Furthermore, the cover plate 28 has an opening for the steel bars 12A-12D to pass through. Thus, according to this embodiment, the lifting device 3 can be mounted on the upper end of the reaction pile 1 without interfering with the test pile 2 and the steel bars 12A-12D.

[0026] In this embodiment, after the steel rod 12 is inserted through the opening formed in the stress transmission member 11, the steel rod 12 is secured to the stress transmission member 11 by engaging the nut 121 through the threaded portion formed at the upper end of the steel rod 12. Similarly, after the steel rod 12 is inserted through the opening formed in the flange plate 124 fixed to the upper end of the test pile 2, the steel rod 12 is secured to the test pile 2 by engaging the nut 123 through the threaded portion formed at the lower end of the steel rod 12. By securing the steel rod 12 to each member in this way, when the lifting device 3 extends, the upward force acting on the stress transmission member 11 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 is performed on the pile to which a reaction force in the pressing direction acts on the reaction force pile 1 and a force in the pull-out direction acts on the test pile 2.

[0027] Furthermore, in the illustrated example, guide rods 15A-15D are installed on the cover plate 28 and extend upwards. The guide rods 15 are inserted into openings formed in the intermediate reinforcing plates 14A-14C. Although the intermediate reinforcing plates 14A-14C move along the guide rods 15, their vertical displacement is not restricted. By arranging the guide rods 15, horizontal displacement of the intermediate reinforcing plates 14A-14C can be prevented, thereby enabling stable force transmission between the components including the stress transmission member 11 and the lifting device 3 as described above.

[0028] Figures 6A and 6B are illustrations showing an example of the assembly method of the pile load test fixture according to the second embodiment of the present invention. As shown in Figure 6A, firstly, steel rods 12A to 12D are inserted through an opening formed in the flange plate 124 of the test pile 2, which is fixed to the ground by pre-welding or bolting. At this point, since the steel rods 12 are not fixed in a downward movement state, they can be prevented from falling, for example, by wrapping adhesive tape around the steel rods 12. Furthermore, a base plate 26 is placed on the flange plate 122 of the reaction pile 1, which is fixed to the reaction pile 1 by pre-welding or bolting.

[0029] Next, as shown in Figure 6B, a steel pipe 27 and a cover plate 28 are placed on the base plate 26, and a lifting device 3 and an intermediate reinforcing plate 14C are placed on the cover plate 28. The cover plate 28 and the intermediate reinforcing plate 14C are configured such that steel bars 12A~12D are inserted through the opening on one side. Similarly, the load sensor 4, the intermediate reinforcing plate 14B, the interval adjustment member 23, the intermediate reinforcing plate 14A, and the stress transmission member 11 are sequentially placed, and nuts 123 are screwed into the threaded portions of the steel bars 12A~12D inserted through the opening of the stress transmission member 11, thus completing the load test fixture 20 shown in Figure 4. In addition, regarding the guide bars 15A~15D, as shown in the example, they can be configured at the time of configuring any intermediate reinforcing plate, or they can be pre-installed on the cover plate 28, or they can be configured after the above steps.

[0030] In this embodiment, since the lifting device 3 can be positioned on the axis of the reaction pile 1 and the test pile 2 by transmitting stress via the steel rod 12, it is not necessary to configure multiple lifting devices, and there is no need for steps such as fine adjustment of the load. Furthermore, since the lifting device 3 positioned on the axis of the reaction pile 1 and the test pile 2 is not easily dislodged under load, compared to the case where the lifting device is configured on the outer periphery of the test device, installation accuracy is not required. Also, by locking the steel rod 12 to the stress transmission member 11 and the test pile 2 respectively, tensile force can be transmitted without welding. Furthermore, in this embodiment, since the lifting device 3 and other components are configured within the cage-like steel rod 12 (and guide rod 15), even if the lifting device 3 detaches from a specific position for some reason, it can be prevented from scattering to the outside. Therefore, this embodiment improves the constructability of pile load tests.

[0031] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to these examples. Those skilled in the art to which this invention pertains should understand that various modifications or alterations can be conceived within the scope of the technical concept described in the claims, and should understand that such modifications and alterations naturally also fall within the technical scope of this invention. [Simplified Explanation of the Diagram]

[0016] Figure 1 is a side view of the pile load testing fixture according to the first embodiment of the present invention. Figure 2 is a sectional view along line II-II of Figure 1. Figure 3A is a diagram showing an example of the assembly method of the pile load testing fixture according to the first embodiment of the present invention. Figure 3B is a diagram showing an example of the assembly method of the pile load testing fixture according to the first embodiment of the present invention. Figure 4 is a side view of the pile load testing fixture according to the second embodiment of the present invention. Figure 5 is a sectional view along line VV of Figure 4. Figure 6A is a diagram showing an example of the assembly method of the pile load testing fixture according to the second embodiment of the present invention. Figure 6B is a diagram showing an example of the assembly method of the pile load testing fixture according to the second embodiment of the present invention.

Claims

1. A load testing fixture for a pile, comprising: a stress transmission member abutting from above against a lifting device mounted on the upper end of a test pile inserted into the ground via a tubular reaction pile inside the ground; and a plurality of rod-shaped members arranged circumferentially around the reaction pile, with their upper ends engaged with the stress transmission member and their lower ends engaged with the reaction pile. A plurality of intermediate reinforcing plates are inserted between the lifting device and the stress transmission member, or between the lifting device and the test pile or the reaction pile; and a plurality of guide rods are arranged in a cage-like manner with the plurality of rod-shaped members in the circumferential direction of the reaction pile or the test pile, and are slidably inserted through openings formed on the plurality of intermediate reinforcing plates; and the distance between one of the plurality of rod-shaped members and one of the adjacent plurality of guide rods is less than the outer diameter of the lifting device, and the lifting device is disposed inside the cage-like arrangement of the plurality of rod-shaped members and the plurality of guide rods.

2. As requested in item 1, the load test fixture for the pile, wherein, The upper ends of each of the plurality of rod-shaped members are inserted into the opening formed in the stress transmission member, and a nut is screwed into the upper end.

3. As requested in item 1, the load test fixture for the pile, wherein, The lower ends of each of the aforementioned plurality of rod-shaped members are inserted into openings formed on flange plates fixed to the aforementioned reaction piles or the aforementioned test piles, and nuts are screwed into the aforementioned lower ends.

4. As requested in item 1, the load test fixture for the pile, wherein, At least one of a load sensor or an interval adjustment component is inserted between the aforementioned lifting device and the aforementioned stress transmission component, or between the aforementioned lifting device and the aforementioned test pile or the aforementioned reaction force pile.

5. A load testing fixture for a pile, comprising: a stress transmission member abutting from above a lifting device mounted on the upper end of a tubular reaction pile inserted into a ground; a plurality of rod-shaped members arranged circumferentially around the test pile, with their upper ends engaged with the stress transmission member and their lower ends engaged with the test pile inserted into the ground inside the reaction pile; a tubular member disposed outside the engaging portions of the plurality of rod-shaped members and the test pile; a base plate abutting the lower end of the tubular member and the upper end of the reaction pile, and having an opening for the upper end of the test pile to pass through; and a cover plate abutting the upper end of the tubular member, having an opening for the plurality of rod-shaped members to pass through, and for mounting the lifting device.

6. The load test fixture for the pile as claimed in claim 5 further comprises: a plurality of intermediate reinforcing plates, which are inserted between the lifting device and the stress transmission member, or between the lifting device and the test pile or the reaction pile; and a plurality of guide rods, which are slidably inserted through openings formed in the plurality of intermediate reinforcing plates respectively.

7. A method for testing the load of a pile, comprising: placing a lifting device on the upper end of a test pile that penetrates the ground inside a tubular reaction pile; arranging a plurality of rod-shaped members circumferentially on the reaction pile and securing the lower ends of each of the plurality of rod-shaped members to the reaction pile; abutting a stress-transferring member against the lifting device from above; securing the upper ends of each of the plurality of rod-shaped members to the stress-transferring member; inserting the rod-shaped members through an opening while simultaneously inserting a plurality of intermediate reinforcing plates between the lifting device and the stress-transferring member, or between the lifting device and the test pile or the reaction pile; and slidably inserting a plurality of guide rods, arranged in a cage-like manner along the circumferential direction of the reaction pile or the test pile, through openings formed in the plurality of intermediate reinforcing plates, wherein... The distance between one of the aforementioned plurality of rod-shaped members and one of the adjacent plurality of guide rods is less than the outer diameter of the aforementioned lifting device, and the aforementioned lifting device is disposed inside the plurality of rod-shaped members and the plurality of guide rods arranged in a cage-like manner; and the steps of extending the aforementioned lifting device, applying a pull-out reaction force to the aforementioned reaction force pile on one side, and applying a pressing force to the aforementioned test pile on the other side.

8. A method for testing the load of a pile, comprising: arranging a plurality of rod-shaped members circumferentially around a test pile penetrating into the ground, and securing the lower ends of each of the plurality of rod-shaped members to the test pile; passing the test pile through an opening in a base plate having an opening, and placing the base plate on the upper end of a tubular reaction pile penetrating into the ground outside the test pile; placing a tubular member, open at both its upper and lower ends, outside the securing portion between the plurality of rod-shaped members and the test pile, with the lower end of the tubular member abutting against the base plate; inserting the plurality of rod-shaped members through an opening in a cover plate having an opening for the plurality of rod-shaped members to pass through, and placing the cover plate on the tubular members with the upper ends of the tubular members abutting against the cover plate; and placing a lifting device on the cover plate. The steps are as follows: first, to place the stress transfer member against the lifting device from above; second, to lock the upper ends of each of the plurality of rod-shaped members against the stress transfer member; and third, to extend the lifting device to exert a reaction force in the pressing direction on the reaction pile and a force in the pulling direction on the test pile.

Images