Portable small-tonnage base pile uplift detection counterforce device

Abstract

This invention discloses a portable, small-tonnage pile pull-out reaction force testing device. It comprises a frustum-shaped reaction force steel cage consisting of two sets of four supporting steel pipes each, a bottom annular steel plate, a bottom circular steel hoop, a top annular steel plate, and several pins. All supporting steel pipes have circular holes at both ends. The top annular steel plate has a through hole in the center and is surrounded by annular lifting lugs. One supporting steel pipe from each set is connected and fixed to an adjacent annular lifting lug. The bottom annular steel plate has annular lifting lugs distributed around its inner and outer rings and around the bottom circular steel hoop. The innermost supporting steel pipe is connected and fixed to an adjacent annular lifting lug in the inner ring, while the outermost supporting steel pipe is connected and fixed to adjacent annular lifting lugs in the outer ring and the bottom circular steel hoop. Using this reaction force device, for pile pull-out testing with a bearing capacity below 800kN, it is easy to install and retract on-site, eliminating the need for large machinery such as cranes, significantly reducing costs, and broadening its applicability.

Description

Technical Field

[0001] This invention relates to an external auxiliary system for static load testing of single pile foundations in infrastructure construction, and more particularly to a portable, small-tonnage device for detecting the pull-out reaction force of foundation piles. Background Technology

[0002] With the rapid development of the national economy, the volume of infrastructure construction projects is enormous, including industrial plants, civil buildings, roads, bridges, and rail transit projects. Before the construction of the superstructure, static load testing of the foundation piles is required. According to the stress mode of the foundation piles, this can be divided into single-pile vertical compressive static load testing, single-pile vertical tensile static load testing, and single-pile horizontal static load testing. As is well known in the industry, the specifications for single-pile vertical tensile static load testing require that the distance between the center of the test pile and the edge of the support be greater than 2 meters and not less than 4 times the pile diameter, and the compressive stress under the support not exceed 1.5 times the characteristic value of the foundation bearing capacity. Traditional tensile static load testing typically uses a main beam, jacks, a hanging basket connected to the reinforcing steel, and a concrete support for placing the main beam.

[0003] However, conventional steel beams and concrete supports are relatively heavy objects, and their transport from the site to the site usually requires cranes, resulting in high operating costs. Some static load tests need to be conducted inside the excavated foundation pit, which is inconvenient for crane operations. Moreover, static load tests using foundation reaction devices require the foundation to provide the reaction force needed for the maximum load, and since the foundation bearing capacity is a constant, the required support area is often large, leading to high volume and weight. Summary of the Invention

[0004] The purpose of this invention is to provide a portable, small-tonnage pile pull-out reaction force testing device that can complete static load operations without the need for a crane and can adapt to various application scenarios.

[0005] The technical solution of this invention to achieve the above-mentioned objective is a portable small-tonnage pile pull-out reaction force detection device, characterized in that: a frustum-shaped reaction steel cage is composed of two sets of four supporting steel pipes each, a bottom annular steel plate, a bottom circular steel hoop, a top annular steel plate, and several pins, wherein the bottom annular steel plate serves as a reaction support, with a projected area relative to the foundation pit ground greater than 6㎡, and the top annular steel plate is provided with annular lifting lugs distributed at four equal divisions of the circumference; both ends of all supporting steel pipes are formed with circular holes, and one pipe in each set... The supporting steel pipe is connected and fixed to an adjacent annular lifting lug through a pin with a through hole. The top annular steel plate is provided with through holes suitable for the reinforcement of the pull-out pile. The bottom annular steel plate is provided with annular lifting lugs distributed at four equal parts of the circumference of the inner and outer rings and the bottom circular steel hoop. The supporting steel pipe on the inner side of the two groups is connected and fixed to an adjacent annular lifting lug in the inner ring through a pin with a through hole. The supporting steel pipe on the outer side of the two groups is connected and fixed to an adjacent annular lifting lug in the outer ring and the bottom circular steel hoop through a pin with a through hole.

[0006] Furthermore, the bottom annular steel plate is provided with four sets of V-shaped steel beams for force maintenance, which are connected at the top between two supporting steel pipes of the same annular lifting lug. One end of the V-shaped steel beam is welded to the outer supporting steel pipe, and the other end is welded to the inner supporting steel pipe. The bottom tip of the V-shaped steel beam is welded to the middle diameter track of the bottom annular steel plate.

[0007] Furthermore, a through-hole jack is installed in the center of the top side annular steel plate, which is driven to push the anchor plate and pull upward the reinforcing steel of the foundation pile used for pull-out testing.

[0008] Furthermore, the device is suitable for pull-out testing of foundation piles with a bearing capacity of less than 800kN.

[0009] Furthermore, the bottom annular steel plate is evenly provided with foldable and fixed pulleys. During the erection of the device, the pulleys fold downwards and contact the ground of the foundation pit or the passageway. During the pull-out test of the device, the pulleys fold upwards and detach from the ground of the foundation pit, and the bottom annular steel plate independently serves as a reaction support.

[0010] Furthermore, the outer diameter of the bottom annular steel plate is 5m, the inner diameter is 4m, and the overall bearing area of ​​the reaction support exceeds 7㎡.

[0011] The application of the reaction device of this invention in the construction of a pile pull-out testing device has the following significant advantages: For the pull-out testing of piles with a bearing capacity of less than 800kN, the reaction device has simple components, small overall weight and volume, making it easy to install and assemble on site, eliminating the need for large machinery such as cranes, greatly reducing costs, and adapting to a wider range of scenarios; it transforms the traditional static pull-out load reaction force from relying on the bending stiffness of the main steel beam to relying on the axial force of the members, making the reaction system more stable; it transforms the contact area between the reaction support and the ground from the two sides of the pile to the circumference of the pile, resulting in higher utilization and better meeting the testing requirements for the foundation bearing capacity.

[0012] Furthermore, the introduction of V-shaped steel beams and adjustable pulleys for force support further enhances the stability of the reaction support system and the ease of device relocation and positioning. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the overall assembly structure of the portable small-tonnage pile pull-out reaction force detection device of the present invention.

[0014] Figure 2 yes Figure 1 A partially enlarged schematic diagram of A in the reaction device shown.

[0015] Figure 3 yes Figure 1A partially enlarged schematic diagram of B in the reaction device shown. Implementation

[0016] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, so as to make the technical solution of the present invention easier to understand and master, and thus to make a clearer definition of the scope of protection of the present invention.

[0017] The inventors of this invention address the current inconveniences in the erection of reaction supports for vertical pull-out static load testing of monopile piles. These devices require heavy steel beams and concrete supports, necessitating crane assistance for lifting, transport, and erection, which leads to significant costs. Through technical analysis and modeling experiments, they have innovatively proposed a portable, low-tonnage pile pull-out reaction force testing device. This device uses relatively compact rigid components to construct a frustum-shaped reaction force steel cage, enabling rapid setup around the pile and facilitating adaptability to various application scenarios and efficient deployment in testing operations.

[0018] like Figures 1 to 3 The diagram shows a partially enlarged view of the overall assembly structure and its A and B parts of the portable small-tonnage pile pull-out reaction device of the present invention. As can be seen from the diagram, the structural features of the reaction device can be described as follows: it consists of a frustum-shaped reaction steel cage composed of a set of four slightly longer supporting steel pipes 11, a set of four slightly shorter supporting steel pipes 12, a bottom annular steel plate 2, a bottom circular steel hoop 3, a top annular steel plate 4, and several pins 5. The bottom annular steel plate 2 serves as a reaction support, with a projected area relative to the foundation pit floor greater than 6 square meters, exceeding the ground contact area of ​​traditional concrete supports, thus fully utilizing the bearing capacity of the foundation pit floor. The top annular steel plate 4 is generally circular, with a through hole 42 at its center suitable for the reinforcement of the pull-out pile, and annular lifting lugs 41 distributed at four equal divisions of the circumference. All supporting steel pipes have circular holes 13 at both ends, and one supporting steel pipe in each set is connected and fixed to an adjacent annular lifting lug through a pin that passes through the circular hole. by Figure 2 The enlarged view shows that a slightly longer outer support steel pipe 11 and a slightly shorter inner support steel pipe 12 are aligned with each other through a circular hole 13. The ends of the two support steel pipes are then inserted through annular lugs 41, and bolt-type pins are inserted through the two circular holes, thus securing the support steel pipes to the top annular steel plate in one direction. The other three directions are fixed in the same way. The bottom annular steel plate 2 has annular lugs distributed at four equal divisions of the circumference of the inner and outer rings and the bottom circular steel hoop. The innermost support steel pipe in each group is fixed to an adjacent annular lug in the inner ring through a pin inserted through a circular hole, while the outermost support steel pipe in each group is fixed to an adjacent annular lug in the outer ring and the bottom circular steel hoop through a pin inserted through a circular hole. Figure 1As shown near the bottom, the outer ring of the bottom annular steel plate has four annular lifting lugs 21, and the inner ring also has four annular lifting lugs 22 at corresponding positions. The bottom circular steel hoop 3 is designed to enhance the limiting ability of the assembled bottom annular steel plate 2 and the bottom end of the outer supporting steel pipe 11, preventing the frustum-shaped reaction steel cage from collapsing due to deformation under stress. The annular lifting lugs 31 can also be adjusted during the installation of the steel hoop to align with the positions of the outer annular lifting lugs. Here, the bottom end of the supporting steel pipe 12 is individually fixed to the inner annular lifting lugs 22 via through-hole pins; the assembly structure is described below. Figure 3 As shown, the assembly in all four directions is similar; however, the bottom end of the supporting steel pipe 11 is fixed to the outer annular lifting lug 22 and the annular lifting lug 31 in the bottom circular steel hoop by means of a through-pin. The assembly structure here can also be referenced. Figure 2 and Figure 3 As shown in the combined diagram, except for the lack of a supporting steel pipe, what needs to be connected are one annular lifting lug from each of the two components.

[0019] It should be noted that the state of all the annular lifting lugs shown in the illustration is only for easy identification (some are perpendicular to the plate surface, and some are formed horizontally). In the actual finished components, these annular lifting lugs are welded to a preset outward angle relative to each plate and hoop to facilitate the assembly of the supporting steel pipes. The thickness and strength of the aforementioned bottom annular steel plate are sufficient to ensure that no deformation occurs within the planar range under the pressure of each supporting steel pipe during the assembly and pull-out test.

[0020] In the preferred embodiment described above, the bottom annular steel plate can be set with an outer diameter of 5m and an inner diameter of 4m. Thus, by calculating "π×(52-42) / 4≈7.1㎡", the overall bearing area of ​​the reaction support exceeds 7㎡, which reliably ensures the bearing capacity of the reaction force.

[0021] As a key technical improvement in the preferred embodiment illustrated, the surface of the bottom annular steel plate 2 is further provided with four sets of V-shaped steel beams 6 for force distribution maintenance. These beams are matched and connected to the paired inner and outer supporting steel pipes that are mounted on the same annular lifting lug at the top. One end of each V-shaped steel beam is welded to the outer supporting steel pipe 11, and the other end is welded to the inner supporting steel pipe 12. The bottom tip of the V-shaped steel beam is welded to the mid-diameter trajectory of the bottom annular steel plate. Here, the mid-diameter trajectory refers to the midpoint value corresponding to the inner and outer diameters of the steel plate, i.e., the annular area with a radius of 2.25m in the embodiment. Through these V-shaped steel beams, the axial downward force on the two supporting steel pipes can be maintained by force distribution, changing from the original two-point contact with the bottom annular steel plate to three-point contact, which can better homogenize the pressure of the steel plate on the pit floor.

[0022] When this reaction device is applied to the pull-out test of the foundation pile, the bottom annular steel plate 2 is fitted around the foundation pile 7 and adjusted to be basically concentric. Then, the supporting steel pipes are installed one by one from the bottom side. Then, a small lifting tool (not a large crane) is used to suspend the top annular steel plate 4 to a suitable height, and then... Figure 2 The assembly structure shown completes the assembly and fixation of the annular lifting lugs on the top of the supporting steel pipe and the top annular steel plate one by one until the entire frustum-shaped reaction steel cage is formed. Afterwards, a through-hole jack 8 can be used to lift the steel bar 71 connected to the foundation pile 7 through its hollow inner cavity. Then, the main body of the jack is attached to the center of the surface of the top annular steel plate, and the top of the steel bar 71 is fixed to the anchor plate 81. Under the output driving force of the jack, the anchor plate is pushed and the steel bar of the foundation pile used for pull-out testing is pulled upwards.

[0023] Compared with traditional single-pile pull-out testing facilities, the reaction device of this invention has a simpler structure and is easier to assemble. Within a limited testing range, it can optimize testing operations and reduce cost investment. It is especially suitable for pull-out testing of foundation piles with a bearing capacity of less than 800kN.

[0024] like Figure 1 In the preferred embodiment shown, the bottom annular steel plate 2 is also evenly provided with foldable and fixed pulleys 9. These pulleys can be connected and fixed to the bottom annular steel plate using hardware connectors such as hinges, or an automatic flipping component can be integrated into the bottom annular steel plate for assembly. However, the implementation method of this flipping setting is not the focus of this application, so detailed description of the embodiment is omitted. During the erection of the device, the pulleys fold downwards to contact the foundation pit floor or passageway, and can be quickly positioned by simple pushing, saving manpower. When constructing the frustum-shaped reaction steel cage, during the process of connecting the bottom annular steel plate to the foundation piles, these pulleys can fold upwards and detach from the foundation pit floor during the pull-out test, allowing the bottom annular steel plate to independently serve as a reaction support.

[0025] Besides the assembly structure of the preferred embodiment shown in the figure, the connection structure between the above-mentioned supporting steel pipe and the bottom annular steel plate and the top annular steel plate can have a variety of optional implementation methods while ensuring the assembly strength. For example, provided that the thickness and strength of the bottom annular steel plate meet the requirements, several shallow concave slots can be opened on the surface, and the round holes at both ends of the supporting steel pipe will be omitted. In actual assembly, it is only necessary to insert the supporting steel pipe into the slots and make a slight adjustment to the vertical angle. Alternatively, a coarser thread groove can be further machined in the slot, and a matching external thread can be machined at the end of the supporting lever, and the two can be screwed together for fixation. Or, the supporting steel pipe can be directly contacted with the surface of the bottom annular steel plate at a preset inclination angle and spot welded at the root to form an integral shape.

[0026] The application of the reaction device of this invention in the construction of facilities for pile pull-out testing has the following significant advantages: For pull-out testing of piles with a bearing capacity of less than 800kN, the reaction device has simple components, small overall weight and volume, making it easy to install and assemble on site, eliminating the need for large machinery such as cranes, significantly reducing costs, and adapting to a wider range of scenarios; it transforms the traditional static load reaction force, which relies on the bending stiffness of the main steel beam, into one maintained by the axial force of the members, making the reaction system more stable; and it transforms the contact area between the reaction support and the ground from the two sides of the pile to the circumference of the pile, resulting in higher utilization and better meeting the testing requirements for the foundation bearing capacity.

[0027] Furthermore, the introduction of V-shaped steel beams and adjustable pulleys for force support further enhances the stability of the reaction support system and the ease of device relocation and positioning.

[0028] In addition to the above embodiments, the present invention may have other implementation methods. All technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection claimed by the present invention.

Claims

1. A portable, small-tonnage pile pull-out reaction force testing device, characterized in that: The device is suitable for testing the pull-out resistance of foundation piles with a bearing capacity of less than 800kN. It consists of a frustum-shaped reaction steel cage formed by two sets of four supporting steel pipes each, a bottom annular steel plate, bottom circular steel hoops, a top annular steel plate, and several pins. The bottom annular steel plate serves as a reaction support, with a projected area relative to the foundation pit floor greater than 6㎡. A through-hole jack is installed in the center of the top annular steel plate, driving the jack to push the anchor plate and pull upwards the reinforcing steel of the foundation pile used for pull-out testing. The top annular steel plate has annular lifting lugs distributed at four equal divisions of its circumference. All supporting steel pipes have circular holes at both ends, and one supporting steel pipe in each set is connected and fixed to an adjacent annular lifting lug via pins passing through the circular holes. The top annular steel plate is equipped with features suitable for pull-out testing of the pile. The bottom annular steel plate has through holes for rebar splicing; the bottom annular steel plate is provided with annular lifting lugs distributed at the four equal divisions of the circumference of the inner and outer rings and the bottom circular steel hoop. The innermost supporting steel pipe of the two groups is connected and fixed to an adjacent annular lifting lug in the inner ring through a pin with a through hole. The outermost supporting steel pipe of the two groups is connected and fixed to an adjacent annular lifting lug in the outer ring and the bottom circular steel hoop through a pin with a through hole. The surface of the bottom annular steel plate is provided with four groups of V-shaped steel beams for force distribution maintenance. The top is installed between two supporting steel pipes of the same annular lifting lug. One end of the V-shaped steel beam is welded to the outermost supporting steel pipe, and the other end is welded to the innermost supporting steel pipe. The bottom tip of the V-shaped steel beam is welded to the middle diameter track of the bottom annular steel plate.

2. The portable small-tonnage pile pull-out reaction force detection device according to claim 1, characterized in that: The bottom annular steel plate is evenly provided with foldable and fixed pulleys. During the erection of the device, the pulleys fold downwards and contact the ground of the foundation pit or the passageway. During the pull-out test of the device, the pulleys fold upwards and detach from the ground of the foundation pit, and the bottom annular steel plate independently serves as a reaction support.

3. The portable small-tonnage pile pull-out reaction force detection device according to claim 1 or 2, characterized in that: The outer diameter of the bottom annular steel plate is 5m, the inner diameter is 4m, and the overall bearing area of ​​the reaction support exceeds 7㎡.

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