Post-tensioned prestressed cast-in-place pile pull-out test device and method

Abstract

The present invention discloses a pull-out force test device and method for post-tensioned prestressed cast-in-place piles. The pull-out force test device of the present invention comprises a base, a jacking device, and a tensioning support (13); the tensioning support is installed on the base based on the jacking device; the tensioning support comprises a first steel bar tensioning beam (131) and a second steel bar tensioning beam (132). The pull-out force test method of the present invention comprises: fixing the non-prestressed steel bars (21) of the post-tensioned prestressed cast-in-place pile (2) to the first steel bar tensioning beam; prestressing the non-prestressed steel bars of the post-tensioned prestressed cast-in-place pile until the elongation of the non-prestressed steel bars of the post-tensioned prestressed cast-in-place pile is consistent with that of the prestressed steel bars (22); and fixing the prestressed steel bars of the post-tensioned prestressed cast-in-place pile on the second steel bar tensioning beam. The pull-out force test device and method of the present invention can ensure that the elongation of the non-prestressed steel bars and the prestressed steel bars of the post-tensioned prestressed cast-in-place pile remains consistent.

Description

Technical Field

[0001] The invention relates to a cast-in-place pile test technology, in particular to a post-tensioning prestressed cast-in-place pile pull-out resistance test device and method. Background Art

[0002] During construction, the buoyancy of underground water on underground structures is a key factor causing cracking and leakage, and must be addressed. With the continuous innovation of pile foundation technology, post-tensioned prestressed cast-in-place piles have emerged. These piles effectively address the problem of cracking and leakage in underground structures caused by buoyancy, and have therefore been widely used in construction.

[0003] The post-tensioned prestressed cast-in-place pile consists of a concrete pile body, non-prestressed steel bars, and prestressed steel bars. Specifically, a hole is drilled at the pile foundation location, a steel cage containing non-prestressed and prestressed steel bars is placed, and then concrete is poured to form the post-tensioned cast-in-place pile.

[0004] In engineering practice, whether the bearing capacity of post-tensioned prestressed bored piles meets the pull-out requirements needs to be determined through pull-out tests. However, since post-tensioned prestressed bored piles contain both non-prestressed and prestressed steel bars, the elongation of the two is inconsistent, and traditional pull-out test equipment cannot be used, making it impossible to conduct pull-out tests on post-tensioned prestressed bored piles. Summary of the Invention

[0005] The object of the present invention is to provide a pull-out resistance test device and method for post-tensioned prestressed cast-in-place piles, which can perform pull-out resistance tests under the condition that the elongation of non-prestressed steel bars and prestressed steel bars of post-tensioned prestressed cast-in-place piles is always consistent, thereby obtaining accurate test data.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] A post-tensioned prestressed bored pile pull-out resistance test device comprises a base, a jacking device and a tensioning support; the base is placed at the post-tensioned prestressed bored pile, the jacking device is installed on the base, and the tensioning support is installed on the base based on the jacking device, and the jacking device can lift the tensioning support upward relative to the base; the tensioning support has a first steel bar tensioning beam and a second steel bar tensioning beam, the first steel bar tensioning beam is used to fix the non-prestressed steel bars of the post-tensioned prestressed bored pile, and the second steel bar tensioning beam is used to fix the prestressed steel bars of the post-tensioned prestressed bored pile.

[0008] Furthermore, a steel bar through hole is provided on the second steel bar tensile beam.

[0009] Furthermore, the lifting device is a jack.

[0010] A method for testing the pull-out resistance of post-tensioned prestressed cast-in-place piles, comprising:

[0011] Set up a pull-out test device at the post-tensioned prestressed cast-in-place pile;

[0012] The pull-out test device includes a base, a jacking device, and a tensile support; the base is placed at a post-tensioned prestressed cast-in-place pile, the jacking device is installed on the base, and the tensile support is installed on the base based on the jacking device, and the jacking device can lift the tensile support upward relative to the base; the tensile support has a first steel tensile beam and a second steel tensile beam;

[0013] The non-prestressed steel bars of the post-tensioned prestressed cast-in-place pile are fixedly connected to the first reinforced tensile beam;

[0014] Controlling the jacking device to start jacking, prestressing the non-prestressed steel bars of the post-tensioned prestressed cast-in-place pile until the elongation of the non-prestressed steel bars of the post-tensioned prestressed cast-in-place pile is consistent with the elongation of the prestressed steel bars, and fixing the prestressed steel bars of the post-tensioned prestressed cast-in-place pile on the second steel bar tension beam;

[0015] The lifting force of the jacking device is adjusted step by step, and the deformation of the post-tensioned prestressed bored pile is detected after each adjustment of the jacking force.

[0016] Furthermore, the second steel bar tensile beam is provided with a steel bar through hole;

[0017] Before the non-prestressed steel bars of the post-tensioned prestressed pile are fixedly connected to the first reinforced tensile beam, the prestressed steel bars of the post-tensioned prestressed pile are passed through the steel bar through holes of the second reinforced tensile beam.

[0018] Furthermore, the lifting device is a jack.

[0019] In the pull-out test device of the present invention, the tensile support has a first steel bar tensile beam and a second steel bar tensile beam. When the pull-out test method of the present invention is used to perform a pull-out test on the post-tensioned prestressed cast-in-place pile, the non-prestressed steel bars of the post-tensioned prestressed cast-in-place pile are first connected to the first steel bar tensile beam, and then the jacking device is controlled to jack up, and the non-prestressed steel bars of the post-tensioned prestressed cast-in-place pile are prestressed until the elongation of the non-prestressed steel bars of the post-tensioned prestressed cast-in-place pile is consistent with the elongation of the prestressed steel bars. Then, the prestressed steel bars of the post-tensioned prestressed cast-in-place pile are fixed on the second steel bar tensile beam, and then the pull-out test is continued. The elongation of the non-prestressed steel bars and the prestressed steel bars of the post-tensioned prestressed cast-in-place pile is always consistent.

[0020] Compared with the prior art, the pull-out test device and method of the present invention have the following beneficial effects: during the pull-out test conducted using the pull-out test device and method of the present invention, the elongation of the non-prestressed steel bars and the prestressed steel bars of the post-tensioned prestressed cast-in-place piles always remains consistent, so that the test data finally obtained can accurately reflect the pull-out resistance of the post-tensioned prestressed cast-in-place piles. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a schematic diagram of a post-tensioned prestressed cast-in-place pile pull-out test apparatus for performing a pull-out test on a post-tensioned prestressed cast-in-place pile.

[0022] In the figure: 1-pullout test device, 11-lower foundation beam, 12-jack, 13-tension support, 131-first steel bar tension beam, 132-second steel bar tension beam, 2-post-tensioned prestressed piles, 21-non-prestressed steel bars, 22-prestressed steel bars. DETAILED DESCRIPTION

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0024] This embodiment provides a pull-out resistance test device for post-tensioned prestressed bored piles. The pull-out resistance test device 1 is used to perform a “pull-out resistance test” on post-tensioned prestressed bored piles 2 .

[0025] Those skilled in the art will appreciate that the post-tensioned prestressed cast-in-place pile 2 is a type of cast-in-place pile in the prior art, in which two types of steel bars are pre-buried, one being non-prestressed steel bars and the other being prestressed steel bars.

[0026] See also Figure 1 The pull-out test device 1 of this embodiment includes a lower foundation beam 11 , two jacks 12 and a tensile support 13 .

[0027] The lower foundation beam 11 is placed on the soil where the post-tensioned prestressed cast-in-place piles 2 are located. Specifically, the foundation soil is first leveled, and then concrete blocks are pre-laid to support the lower foundation beam 11. The lower foundation beam 11 is then placed on the concrete blocks. The position of the lower foundation beam 11 must remain fixed relative to the post-tensioned prestressed cast-in-place piles 2. The lower foundation beam 11 spans above the post-tensioned prestressed cast-in-place piles 2.

[0028] It should be noted that the lower foundation beam 11 actually serves as a "base". In other embodiments, other forms of components may be used to replace the lower foundation beam 11 as the base.

[0029] The two jacks 12 are hydraulic jacks. The bases of the two jacks 12 are installed on the lower foundation beam 11. The lifting ends of the two jacks 12 are both facing upward. The two jacks 12 are respectively located on both sides of the post-tensioned prestressed pile 2.

[0030] The lower portion of the tensile support 13 has two jacking parts, and the two jacking parts of the tensile support 13 are respectively installed and connected to the jacking ends of the two jacks 12. In this way, the two jacks 12 can lift the tensile support 13 upward relative to the lower foundation beam 11.

[0031] If the two jacks 12 are regarded as a complete jacking device, the following summary can be made: in summary, the jacking device is installed on the lower foundation beam 11, and the tensile support 13 is installed on the lower foundation beam 11 based on the jacking device. The jacking device can lift the tensile support 13 upward relative to the lower foundation beam 11.

[0032] It should be noted that, in other embodiments, other lifting devices in the prior art may be used to replace the two jacks 12, as long as the effect of "lifting the tensile support 13 upward relative to the lower foundation beam 11" can be achieved.

[0033] The tensile support 13 has two beams, one high and one low, wherein the low beam is called a first steel tensile beam 131 , and the high beam is called a second steel tensile beam 132 .

[0034] The first steel bar tensile beam 131 is used to fix the non-prestressed steel bars 21 of the post-tensioned prestressed pile 2 when performing a pull-out test.

[0035] The second steel bar tension beam 132 is used to secure the prestressed steel bars 22 of the post-tensioned prestressed cast-in-place pile 2 during a pull-out test. More specifically, the second steel bar tension beam 132 is provided with a number of through holes, referred to as steel bar through holes. These through holes are transparent from top to bottom and are used to pass through and secure the prestressed steel bars 22 of the post-tensioned prestressed cast-in-place pile 2 during a pull-out test.

[0036] The method and steps for performing a pull-out test on a post-tensioned prestressed cast-in-place pile 2 using the pull-out test device 1 of this embodiment are as follows:

[0037] S1, the pull-out resistance test device 1 is set at the post-tensioned prestressed cast-in-place pile 2.

[0038] S2: Insert the prestressed steel bars 22 of the post-tensioned cast-in-place pile 2 through the steel bar holes of the second steel bar tension beam 132. This prevents the prestressed steel bars 22 of the post-tensioned cast-in-place pile 2 from separating from the second steel bar tension beam 132 during the subsequent prestressing of the non-prestressed steel bars 21 of the post-tensioned cast-in-place pile 2. This facilitates subsequent fixed connection of the prestressed steel bars 22 to the second steel bar tension beam 132.

[0039] S3, the non-prestressed steel bars 21 of the post-tensioned prestressed pile 2 are fixedly connected to the first steel bar tension beam 131 by welding.

[0040] S4, control the two jacks 12 serving as the jacking device to start jacking, so as to prestress the non-prestressed steel bars 21 of the post-tensioned prestressed pile 2 until the elongation of the non-prestressed steel bars 21 of the post-tensioned prestressed pile 2 is consistent with the elongation of the prestressed steel bars 22, and then use anchors to anchor the prestressed steel bars 22 of the post-tensioned prestressed pile 2 on the second steel bar tension beam 132.

[0041] Those skilled in the art will understand that the elongation of a steel bar refers to the amount of elastic deformation (the ratio of the elongation value to the original length of the steel bar) produced when tensile stress is applied to the steel bar.

[0042] S5, control the two jacks 12, adjust the lifting force of the jacks 12 step by step, and use the equipment of the prior art to detect the deformation of the post-tensioned prestressed bored pile 2 after each adjustment of the lifting force, thereby realizing the pull-out resistance test of the post-tensioned prestressed bored pile 2.

[0043] In the pull-out test device of this embodiment, the tensile support 13 has a first steel bar tensile beam 131 and a second steel bar tensile beam 132. When the pull-out test device of this embodiment is used to perform a pull-out test on the post-tensioned prestressed bored pile 2, the non-prestressed steel bars 21 of the post-tensioned prestressed bored pile 2 are first connected to the first steel bar tensile beam 131, and then the jack 12 is controlled to lift to prestress the non-prestressed steel bars 21 of the post-tensioned prestressed bored pile 2 until the elongation of the non-prestressed steel bars 21 of the post-tensioned prestressed bored pile 2 is consistent with the elongation of the prestressed steel bars 22. Then, the prestressed steel bars 22 of the post-tensioned prestressed bored pile 2 are tensioned by the through-type jack and anchored on the second steel bar tensile beam 132, and then the pull-out test is continued. Since the elongation of the non-prestressed steel bars 21 and the prestressed steel bars 22 of the post-tensioned prestressed pile 2 remains consistent during the pull-out test, the test data finally obtained can accurately reflect the pull-out resistance of the post-tensioned prestressed pile 2.

[0044] The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A post-tensioned prestressed cast-in-place pile pull-out test device, characterized by: including a base, a lifting device and a tensile support (13); The base is placed at the post-tensioned prestressed cast-in-place pile (2), the jacking device is installed on the base, and the tensile support (13) is installed on the base based on the jacking device, and the jacking device can jack the tensile support (13) upward relative to the base; The tensile support (13) comprises a first tensile steel bar beam (131) and a second tensile steel bar beam (132), wherein the first tensile steel bar beam (131) is used to fix the non-prestressed steel bars (21) of the post-tensioned prestressed cast-in-place pile (2), and the second tensile steel bar beam (132) is used to fix the prestressed steel bars (22) of the post-tensioned prestressed cast-in-place pile (2).

2. The post-tensioned prestressed cast-in-place pile pull-out test device according to claim 1, characterized in that: The second steel bar tensile beam (132) is provided with a steel bar through hole.

3. The pull-out resistance testing device for post-tensioned prestressed cast-in-place piles according to claim 1, characterized in that: The lifting device is a jack (12).

4. A method for testing the pull-out strength of post-tensioned prestressed cast-in-place piles, characterized by: include: A pull-out test device (1) is provided at the post-tensioned prestressed cast-in-place pile (2); The pull-out test device (1) comprises a base, a jacking device and a tensile support (13); the base is placed at a post-tensioned prestressed cast-in-place pile (2); the jacking device is installed on the base; the tensile support (13) is installed on the base based on the jacking device; the jacking device can jack the tensile support (13) upward relative to the base; the tensile support (13) has a first steel tensile beam (131) and a second steel tensile beam (132); The non-prestressed steel bars (21) of the post-tensioned prestressed cast-in-place pile (2) are fixedly connected to the first steel bar tensile beam (131); Controlling the jacking device to start jacking, prestressing the non-prestressed steel bars (21) of the post-tensioned prestressed cast-in-place pile (2) until the elongation of the non-prestressed steel bars (21) of the post-tensioned prestressed cast-in-place pile (2) is consistent with the elongation of the prestressed steel bars (22), and fixing the prestressed steel bars (22) of the post-tensioned prestressed cast-in-place pile (2) on the second steel bar tension beam (132); The lifting force of the lifting device is adjusted step by step, and the deformation of the post-tensioned prestressed bored pile (2) is detected after each adjustment of the lifting force.

5. The method for testing the pull-out strength of post-tensioned prestressed cast-in-place piles according to claim 4, characterized in that: The second steel bar tensile beam (132) is provided with a steel bar through hole; Before the non-prestressed steel bars (21) of the post-tensioned prestressed cast-in-place pile (2) are fixedly connected to the first steel bar tension beam (131), the prestressed steel bars (22) of the post-tensioned prestressed cast-in-place pile (2) are passed through the steel bar through-holes of the second steel bar tension beam (132).

6. The method for testing the pull-out resistance of post-tensioned prestressed cast-in-place piles according to claim 4, characterized in that: The lifting device is a jack (12).

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