A single-pile horizontal static load test device and method under composite load

Abstract

The present application relates to the technical field of building construction, especially to a single pile horizontal static load test device and method under composite load. The device comprises a test pile foundation and a test loading device, wherein the test pile foundation comprises a test pile and a pile foundation pile cap, and the pile foundation pile cap is pre-buried with anchor bolts according to the position of the opening steel plate; the test loading device comprises an H-shaped steel beam and an electric hydraulic jack, and the electric hydraulic jack is fixedly arranged on the test pile and the H-shaped steel beam respectively. Compared with the traditional pile foundation bearing capacity test method and device, the method solves the problem that the vertical bearing capacity and the horizontal bearing capacity of the pile foundation are measured respectively, and cannot actually reflect the actual stress state of the pile foundation. The method can effectively measure the actual stress state of the pile foundation under the action of the composite load, and is very important for short piles, especially for heliostat pile foundations with high stability and precision requirements.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to a test device and method for horizontal static load testing of a single pile under combined loads. Background Technology

[0002] Tower solar thermal power generation, as an effective facility for the rational utilization of solar energy, is seeing an increasing number of projects being implemented in western China, driven by the national strategy of developing western regions. One of the main components of a tower solar thermal power generation system is the heliostat. The distance between the heliostat and the collector is typically over a kilometer, making the stability and accuracy of the heliostat extremely important for the entire solar thermal power generation system.

[0003] Heliostat monopile foundations are simple in structure and easy to construct and install, and have been widely used in completed solar thermal power plants. Due to the large pile diameter and the small weight of the heliostat, the vertical bearing capacity of monopile foundations is easily met. However, the short pile length makes them prone to large horizontal displacement and rotation at the pile top under horizontal forces and bending moments, thus placing higher demands on the horizontal bearing capacity of the pile foundation. Currently, the testing methods and devices for pile foundation bearing capacity measure the vertical and horizontal bearing capacities of the pile foundation separately, which cannot accurately reflect the actual stress state of the pile. Therefore, providing a static load testing device and method for measuring the actual combined loads on pile foundations is of great significance to the safety, economy, and practicality of heliostat pile foundation design. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a test device and method for horizontal static load testing of a single pile under combined loads.

[0005] Firstly, the present invention provides a horizontal static load test device for a single pile under combined loads, which adopts the following technical solution:

[0006] A horizontal static load test device for a single pile under combined loads includes:

[0007] The test pile foundation and test loading device include a test pile and a pile foundation cap, wherein anchor bolts are pre-embedded on the pile foundation cap according to the positions of the perforated steel plates; the test loading device includes an H-beam and electro-hydraulic jacks, wherein the electro-hydraulic jacks are respectively fixedly installed on the test pile and the H-beam, and wherein the electro-hydraulic jacks include a first electro-hydraulic jack, a second electro-hydraulic jack and a third electro-hydraulic jack.

[0008] Furthermore, the test loading device also includes an LVDT displacement gauge, a counterweight, a data acquisition instrument, a data cable, a square steel pipe, a magnetic base, anchor bolts, a perforated steel plate, a precast concrete slab, and blocks. The perforated steel plate is placed on the top of the pile foundation, the H-beam is placed on the perforated steel plate and tightly connected by anchor bolts, the precast concrete slab is symmetrically placed on both sides of the pile foundation, the counterweight is placed on the precast concrete slab, the square steel pipe is placed horizontally on both sides of the pile foundation, a magnetic base is placed on the square steel pipe, and an LVDT displacement gauge is installed on the magnetic base.

[0009] Secondly, the present invention provides a method for a horizontal static load test of a single pile under combined loads, which adopts the following technical solution:

[0010] The location and number of test piles will be determined based on the site conditions.

[0011] Determine the experimental loading method;

[0012] Determine the layout scheme of the experimental setup;

[0013] Piling foundation construction shall be carried out;

[0014] Install the test equipment;

[0015] The experiment loads and records data.

[0016] Furthermore, determining the test loading method includes determining, based on the site conditions, the static load test method under the combined load of the pile foundation as a single pile horizontal static load test, and selecting the slow sustained load method as the loading method.

[0017] Furthermore, the method for determining the test loading also includes applying the test load in five equal stages, ensuring that the horizontal force and bending moment increase proportionally during the loading process, while the vertical load remains unchanged.

[0018] Furthermore, the determination of the test device layout scheme includes setting a first electro-hydraulic jack to provide a horizontal force F1, a second electro-hydraulic jack to provide a vertical force N1, and a third electro-hydraulic jack to provide a vertical force N2, wherein the vertical forces N1 and N2 are in opposite directions.

[0019] Furthermore, the pile foundation construction includes pouring the pile foundation and pre-embedding the finished anchor bolts on the pile foundation abutment according to the positions of the perforated steel plates.

[0020] Furthermore, the installation of the test device includes placing a perforated steel plate on top of the pile and passing anchor bolts through the perforated steel plate; placing an H-shaped steel beam with a hole on one side of the web on the perforated steel plate and connecting it tightly with anchor bolts; and, according to the test device layout plan, placing precast concrete slabs symmetrically on both sides of the pile foundation and then placing counterweights on the precast concrete slabs.

[0021] Furthermore, the installation of the test device also includes arranging three electric hydraulic jacks according to the test device layout plan, wherein the first electric hydraulic jack is suspended and supported by masonry blocks, the second electric hydraulic jack is placed on a precast concrete slab, and the third electric hydraulic jack is placed on an H-beam.

[0022] Furthermore, the installation of the test device also includes placing the square steel pipe horizontally on both sides of the pile foundation according to the test device layout plan to avoid disturbance by the pile foundation; placing a magnetic base on the square steel pipe, installing an LVDT displacement meter on the magnetic base, the magnetic base being attracted to the square steel pipe by attraction, and connecting the LVDT displacement meter to a data acquisition instrument via a data cable for data acquisition.

[0023] In summary, the present invention has the following beneficial technical effects:

[0024] Compared with traditional methods and devices for testing the bearing capacity of pile foundations, this invention solves the problem that measuring the vertical and horizontal bearing capacity of pile foundations separately cannot actually reflect the actual stress state of the pile foundation. It can effectively measure the actual stress state of the pile foundation under combined loads, which is very important for short piles, especially heliostat pile foundations with extremely high requirements for stability and accuracy.

[0025] The method of this invention is novel and has a clear concept. It can quickly and conveniently carry out loading tests under composite loads on pile foundations, and the loading device used can be reused, reducing material waste.

[0026] In summary, this method effectively measures the actual stress state of pile foundations under combined loads and provides a convenient and quick on-site test method for combined loads on pile foundations. It has good economic and social benefits and is worth promoting in similar systems. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a single pile horizontal static load test device under composite load according to Embodiment 1 of the present invention.

[0028] Figure 2 This is another structural schematic diagram of a single pile horizontal static load test device under composite load according to Embodiment 1 of the present invention.

[0029] Figure 3 This is a schematic diagram of the test device applying load in Embodiment 2 of the present invention.

[0030] Among them, 1-pile foundation, 2-H-shaped steel beam, 3-LVDT displacement gauge, 4-first electric hydraulic jack, 4-second electric hydraulic jack, 4-third electric hydraulic jack, 5-counterweight, 6-data acquisition instrument, 7-data cable, 8-soil, 9-square steel pipe, 10-magnetic gauge base, 11-anchor bolt, 12-perforated steel plate, 13-precast concrete slab, 14-block, 15-pile foundation cap. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings.

[0032] Example 1

[0033] Reference Figure 1 and Figure 2 This embodiment provides a single-pile horizontal static load test device under combined loads, comprising:

[0034] The test pile foundation and the test loading device include a test pile and a pile foundation cap, wherein anchor bolts are pre-embedded on the pile foundation cap according to the positions of the perforated steel plates; the test loading device includes an H-beam and an electric hydraulic jack, wherein the electric hydraulic jack is fixedly mounted on the test pile and the H-beam respectively.

[0035] The electro-hydraulic jacks include a first electro-hydraulic jack, a second electro-hydraulic jack, and a third electro-hydraulic jack.

[0036] The test loading device also includes an LVDT displacement gauge, a counterweight, a data acquisition instrument, a data cable, a square steel pipe, a magnetic base, anchor bolts, a perforated steel plate, a precast concrete slab, and blocks. The perforated steel plate is placed on the top of the pile foundation, the H-beam is placed on the perforated steel plate and tightly connected by anchor bolts, the precast concrete slab is symmetrically placed on both sides of the pile foundation, the counterweight is placed on the precast concrete slab, the square steel pipe is placed horizontally on both sides of the pile foundation, a magnetic base is placed on the square steel pipe, and an LVDT displacement gauge is installed on the magnetic base.

[0037] Working principle of the device:

[0038] The method includes: 1. Determining the location and number of test piles based on the site conditions. 2. Determining the loading method: Based on the site conditions, the static load test method under the combined load of the pile foundation is determined to be a single-pile horizontal static load test. The slow-maintained load method is selected. Since the test load value is relatively small and it is not testing the ultimate bearing capacity of the pile foundation, the test load is applied in five levels on average. During the loading process, the horizontal force F1 and bending moment M are increased proportionally, while the vertical load Q remains unchanged. 3. Determining the test device layout: Three electric hydraulic jacks provide horizontal force F1, vertical force N1, and vertical force N2 respectively. The vertical forces N1 and N2 are in opposite directions. According to the formula, the vertical load is always kept at Q. The distance from N1 to the pile center is L, which is a known distance. The distance from N2 to the pile center is D, which can be calculated according to the formula. M i Given the known bending moments at various levels, i = 2, 3, 4, 5, where the distance unit is meters (m), the load unit is kN, and the bending moment unit is kN·m. Calculation formula: N1 × L + N2 × D = M i N2 = N1 + Q. Based on the above calculations, the placement of the electric hydraulic jacks can be determined, and then the layout plan of the test apparatus can be drawn. 4. Prepare the test loading device: The test loading device includes an H-beam, LVDT displacement gauge, electric hydraulic jacks, counterweight, data acquisition instrument, data cable, square steel pipe, magnetic base, anchor bolts, perforated steel plate, precast concrete slab, and blocks. 5. Pile foundation construction: When pouring the pile foundation, the pre-embedded anchor bolts are placed on the pile foundation cap according to the position of the perforated steel plate. 6. Installation of the test apparatus: (a) Place the perforated steel plate on top of the pile, and pass the anchor bolts through the perforated steel plate; (b) Place the H-beam with a perforation on one side of the web on the perforated steel plate and connect it tightly with anchor bolts; (c) According to the test apparatus layout plan, place the precast concrete slabs symmetrically on both sides of the pile foundation, and then place the counterweight on the precast concrete slabs; (d) According to the test apparatus layout plan, arrange three electric hydraulic jacks, one of which is suspended and supported by masonry blocks, and the other two are placed on the precast concrete slab and the other on the H-beam; (e) According to the test apparatus layout plan, place the square steel pipes horizontally on both sides of the pile foundation to avoid disturbance from the pile foundation; place a magnetic base on the square steel pipe, install an LVDT displacement meter on the magnetic base, and the magnetic base is attracted to the square steel pipe by attraction. Connect the LVDT displacement meter to the data acquisition instrument through a data cable for data acquisition. 7. Test loading: According to the test plan, conduct a loading test using the slow sustained load method and record the data.

[0039] Example 2

[0040] The difference between this embodiment and Embodiment 1 is that this embodiment provides a method for testing the horizontal static load of a single pile under combined loads, such as... Figure 3As shown, the following technical solution is adopted:

[0041] The location and number of test piles will be determined based on the site conditions.

[0042] Determine the experimental loading method;

[0043] Determine the layout scheme of the experimental setup;

[0044] Piling foundation construction shall be carried out;

[0045] Install the test equipment;

[0046] The experiment loads and records data.

[0047] The determination of the test loading method includes, based on site conditions, selecting a single-pile horizontal static load test as the static load test method under the combined load of the pile foundation, and choosing the slow-maintained load method as the loading method. The determination of the test loading method also includes applying the test load in five equal stages, ensuring that the horizontal force and bending moment increase proportionally during the loading process, while the vertical load remains constant. The determination of the test device layout includes setting up a first electro-hydraulic jack to provide the horizontal force F.

[0048] 1. A second electro-hydraulic jack provides a vertical force N1, and a third electro-hydraulic jack provides a vertical force N2, wherein the vertical forces N1 and N2 are in opposite directions. The pile foundation construction includes pouring the pile foundation and simultaneously pre-embedding the fabricated anchor bolts on the pile foundation platform according to the positions of the perforated steel plate. The installation of the testing device includes placing the perforated steel plate on top of the pile, with the anchor bolts passing through the perforated steel plate; placing an H-beam with a perforation on one side of the web on the perforated steel plate and connecting it tightly with anchor bolts; according to the testing device layout plan, symmetrically placing precast concrete slabs on both sides of the pile foundation, and then placing counterweights on the precast concrete slabs. The installation of the testing device also includes arranging three electro-hydraulic jacks according to the testing device layout plan, wherein the first electro-hydraulic jack is suspended and supported by masonry blocks, the second electro-hydraulic jack is placed on the precast concrete slab, and the third electro-hydraulic jack is placed on the H-beam. The installation of the test device also includes placing the square steel pipe horizontally on both sides of the pile foundation according to the test device layout plan to avoid disturbance from the pile foundation; placing a magnetic base on the square steel pipe, installing an LVDT displacement meter on the magnetic base, the magnetic base being attracted to the square steel pipe by attraction, and connecting the LVDT displacement meter to a data acquisition instrument through a data cable for data acquisition.

[0049] Specifically,

[0050] The following combination Figure 3 The present invention will be further described in detail below. A method for horizontal static load testing of a single pile in a short pile foundation under combined loads includes:

[0051] 1. Determine the location and number of test piles based on the site conditions.

[0052] 2. Determining the Loading Method: Based on the site conditions, the static load test method under the combined load of the pile foundation was determined to be a single-pile horizontal static load test. The slow-maintained load method was selected. Since the test load values ​​were relatively small and not testing the ultimate bearing capacity of the pile foundation, the test load was applied in five stages. During the loading process, the horizontal force F1 and bending moment M were increased proportionally, while the vertical load Q remained constant. Because the first stage load was too small, loading started directly from the second stage. The estimated loads are shown in Table 1, and the staged loads are shown in Table 2. After each stage of loading, settlement and horizontal displacement were measured at intervals of 5 min, 10 min, 15 min, 15 min, and 15 min. Each observation was recorded in the test record sheet, and any exposed cracks in the pile body during the test were recorded in detail. If the deformation value within 15 minutes did not exceed 0.1 mm and occurred twice consecutively, the deformation was considered to have reached a relatively stable standard, and the next stage of load was applied.

[0053] Table 1 Estimated Loads

[0054]

[0055] Table 2 Loads at all levels

[0056]

[0057] 3. Determine the layout of the test device: Three electric hydraulic jacks (4) provide horizontal force F1, vertical force N1, and vertical force N2 respectively. The vertical forces N1 and N2 are in opposite directions. According to the formula, the vertical load can always be kept at Q. The distance of N1 from the center of the pile is L, which is a known distance. The distance of N2 from the center of the pile is D. According to the formula, the distance of D from the center of the pile can be calculated. M i Given the known bending moments at various levels, i = 2, 3, 4, 5, where the distance unit is meters (m), the load unit is kN, and the bending moment unit is kN·m. Calculation formula: N1 × L + N2 × D = M i N2 = N1 + Q. Based on the above calculations, the location of the electric hydraulic jack (4) can be determined, and then the layout scheme of the test device can be drawn.

[0058] 4. Prepare the test loading device: The test loading device includes H-beam (2), LVDT displacement meter (3), electric hydraulic jack (4), counterweight (5), data acquisition instrument (6), data cable (7), square steel pipe (9), magnetic base (10), anchor bolt (11), perforated steel plate (12), precast concrete slab (13), and block (14).

[0059] 5. Construction of pile foundation (1): When pouring the pile foundation (1), the finished anchor bolts (11) are pre-embedded on the pile foundation cap (15) according to the position of the perforated steel plate (12).

[0060] 6. Install the test apparatus: (a) Place the perforated steel plate (12) on the top of the pile, and pass the anchor bolts (11) through the perforated steel plate (12); (b) Place the H-beam (2) with a hole in one side of the web on the perforated steel plate (12) and connect it tightly with the anchor bolts (11); (c) According to the test apparatus layout plan, place the precast concrete slab (13) symmetrically on both sides of the pile foundation (1), and then place the counterweight (5) on the precast concrete slab (13); (d) According to the test apparatus layout plan, arrange three electric hydraulic jacks (4), one of which is suspended below the electric hydraulic jack (4). Place blocks (14) for support, and place one of the two electric hydraulic jacks (4) on the precast concrete slab (13) and the other on the H-beam (2); (e) According to the test device layout plan, place the square steel pipe (9) horizontally on both sides of the pile foundation (1) to avoid being disturbed by the pile foundation (1); place the magnetic base (10) on the square steel pipe (9), install the LVDT displacement meter (3) on the magnetic base (10), the magnetic base is attracted to the square steel pipe (9) by attraction, and connect the LVDT displacement meter (3) to the data acquisition instrument (6) through the data cable (7) for data acquisition.

[0061] 7. Test loading: Conduct loading tests according to the test plan using the slow sustained load method and record the data.

[0062] Compared with traditional methods and devices for testing the bearing capacity of pile foundations, this invention solves the problem that measuring the vertical and horizontal bearing capacity of pile foundations separately cannot actually reflect the actual stress state of the pile foundation. It can effectively measure the actual stress state of the pile foundation under combined loads, which is very important for short piles, especially heliostat pile foundations with extremely high requirements for stability and accuracy.

[0063] This method is novel and has a clear approach. It can quickly and conveniently conduct loading tests on pile foundations under combined loads, and the loading device used can be reused, reducing material waste.

[0064] In summary, this method effectively measures the actual stress state of pile foundations under combined loads and provides a convenient and quick on-site test method for combined loads on pile foundations. It has good economic and social benefits and is worth promoting in similar systems.

[0065] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for horizontal static load testing of a single pile under combined loads, characterized in that, A horizontal static load test device for a single pile under combined loads is provided. The device includes a test pile foundation and a test loading device. The test pile foundation includes a test pile and a pile foundation cap, with anchor bolts pre-embedded on the pile foundation cap according to the positions of the perforated steel plates. The test loading device includes an H-beam and electro-hydraulic jacks, which are respectively fixedly mounted on the test pile and the H-beam. The electro-hydraulic jacks include a first electro-hydraulic jack, a second electro-hydraulic jack, and a third electro-hydraulic jack. The method includes: The location and number of test piles will be determined based on the site conditions. Determine the experimental loading method; Determine the layout scheme of the experimental setup; Piling foundation construction shall be carried out; Install the test equipment; The experiment loads and records data; The method for determining the test loading also includes applying the test load in five equal stages, ensuring that the horizontal force and bending moment increase proportionally during the loading process, while keeping the vertical load constant. The determination of the test device layout scheme includes setting a first electro-hydraulic jack to provide a horizontal force F1, a second electro-hydraulic jack to provide a vertical force N1, and a third electro-hydraulic jack to provide a vertical force N2, wherein the vertical forces N1 and N2 are in opposite directions.

2. The method for horizontal static load test of a single pile under combined load as described in claim 1, characterized in that, The device also includes an LVDT displacement meter, a counterweight, a data acquisition instrument, a data cable, a square steel pipe, a magnetic base, anchor bolts, a perforated steel plate, a precast concrete slab, and blocks. The perforated steel plate is placed on the top of the pile foundation, the H-beam is placed on the perforated steel plate and tightly connected by anchor bolts, the precast concrete slab is symmetrically placed on both sides of the pile foundation, the counterweight is placed on the precast concrete slab, the square steel pipe is placed horizontally on both sides of the pile foundation, a magnetic base is placed on the square steel pipe, and an LVDT displacement meter is installed on the magnetic base.

3. The method for a horizontal static load test of a single pile under combined load as described in claim 2, characterized in that, The construction of the pile foundation includes pouring the pile foundation and pre-embedding the finished anchor bolts on the pile foundation abutment according to the position of the perforated steel plate.

4. The method for horizontal static load test of a single pile under combined load as described in claim 3, characterized in that, The installation of the test device includes placing a perforated steel plate on top of the pile and passing anchor bolts through the perforated steel plate; placing an H-shaped steel beam with a hole on one side of the web on the perforated steel plate and connecting it tightly with anchor bolts; and, according to the test device layout plan, placing precast concrete slabs symmetrically on both sides of the pile foundation and then placing counterweights on the precast concrete slabs.

5. The method for a horizontal static load test of a single pile under combined load as described in claim 4, characterized in that, The installation of the test device also includes arranging three electric hydraulic jacks according to the test device layout plan. The first electric hydraulic jack is suspended and supported by masonry blocks, the second electric hydraulic jack is placed on a precast concrete slab, and the third electric hydraulic jack is placed on an H-shaped steel beam.

6. The method for testing the horizontal static load of a single pile under combined loads according to claim 5, characterized in that, The installation of the test device also includes placing the square steel pipe horizontally on both sides of the pile foundation according to the test device layout plan to avoid disturbance from the pile foundation; placing a magnetic base on the square steel pipe, installing an LVDT displacement meter on the magnetic base, the magnetic base being attracted to the square steel pipe by attraction, and connecting the LVDT displacement meter to a data acquisition instrument through a data cable for data acquisition.

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