Assembled recovery loading device and static load test method for providing reaction force for pile cap

Abstract

The present application relates to the technical field of static load test for single pile compressive strength, and provides an assembled and recovered loading device and static load test method in which a cap and pile are added to provide reaction force. The single pile static load test device comprises: a plurality of engineering piles set in the foundation soil, a cap connecting the tops of all engineering piles, at least one test pile set in the foundation soil, and a displacement measurement system for measuring the settlement of the test pile. The cap is provided with a channel corresponding to the center line of the test pile, the side wall of the channel is fixed with a fixed steel plate, a jack is provided on the test pile, a load-bearing steel plate is provided on the jack, a detachable steel plate is provided on the load-bearing steel plate, and the detachable steel plate is detachably connected to the fixed steel plate by a number of fasteners. If a problem is encountered during the test or after the test is completed, the fasteners and the detachable steel plate can be disassembled to check and recover the jack and the displacement measurement system, which not only realizes the controllability of the test process, but also effectively reduces the test cost and waste of resources.

Description

Technical Field

[0001] The present application belongs to the technical field of single pile compressive static load testing, and in particular relates to an assembled recovery loading device and a static load testing method for providing reaction force by adding piles to a cap. Background Art

[0002] Pile foundations are the most commonly used foundation form for important structures, such as railways and highway bridges, which are almost all based on pile foundations, especially in soft soil areas. However, soft soil is widely distributed in my country, primarily in coastal areas, plains, inland lake basins, depressions, and along riverbanks. These areas are economically developed, densely populated, and feature densely developed municipal, housing, and transportation infrastructure. Soft soils have the characteristics of low bearing capacity, large deformation, and easily unstable foundations. When the load value for a single pile vertical compressive static load test requires a large tonnage (up to 1,000 tons), the use of traditional static load tests (heap loading method, anchor pile method) is subject to high costs (transportation, installation, foundation reinforcement, etc.), large engineering workload, long construction cycles, and difficulty in ensuring safety. The self-balancing method also has disadvantages such as the inability to directly obtain the ultimate compressive bearing capacity of a single pile, provide design parameters, or obtain load transfer patterns.

[0003] In order to solve the above technical problems, the applicant applied for a patent with patent number CN202110793696.8, which discloses a single pile static load test device and method that uses a group of piles and a pedestal to provide a reaction force. The test device uses the deadweight of the pedestal and the engineering piles as reaction devices, abandoning the traditional loading method of setting up a large-area loading platform and huge loads. Therefore, it can eliminate safety hazards to the greatest extent, ensure the safety of the project and the test, and save working time. However, the device is pre-buried, and the parts such as the loading device jack and measuring device embedded in the pedestal cannot be recovered, which is costly; if a fault occurs during the test, it cannot be repaired, resulting in test failure. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the embodiment of the present application aims to provide an assembled and recyclable loading device for providing reaction force by adding piles to a cap.

[0005] To achieve the above-mentioned purpose, the technical solution adopted in this application is: to provide an assembled and recoverable loading device with a base and piles to provide a reaction force, comprising: a plurality of engineering piles arranged in the foundation soil, a base connecting the tops of all the engineering piles, at least one test pile arranged in the foundation soil, and a displacement measurement system for measuring the settlement of the test pile, the base is provided with a channel corresponding to the center line of the test pile, the side wall of the channel is fixed with a fixed steel plate, the test pile is provided with a jack, the jack is provided with a load-bearing steel plate, the load-bearing steel plate is provided with a detachable steel plate, and the detachable steel plate is detachably connected to the fixed steel plate by a number of fasteners.

[0006] In one embodiment, the fixed steel plate is provided with a plurality of studs with internal threaded holes, one end of the stud is flush with the surface of the fixed steel plate, and the other end of the stud extends into the base, and the removable steel plate is provided with a plurality of through holes coaxial with each of the studs, and the fasteners pass through the through holes and are screwed to the internal threaded holes.

[0007] In one embodiment, the fastener is a screw, or the fastener includes a threaded rod and a nut.

[0008] In one embodiment, a steel diagonal brace is provided on the back of the fixed steel plate, one end of the steel diagonal brace is welded to the back of the fixed steel plate, and the other end is fixed to the main reinforcement laid on the bottom of the base.

[0009] In one embodiment, the length of the fixing steel plate is greater than the height of the cap, and the raised portion of the fixing steel plate surrounds the test pile.

[0010] In one embodiment, the displacement measurement system includes a displacement guide rod and a dial indicator. A first protective tube and a second protective tube are vertically provided in the channel. The displacement guide rod is slidably inserted into the first protective tube and fixedly connected to the test pile. A foundation pit is provided in the foundation soil, and the pedestal is provided in the foundation pit. A reference beam spanning the foundation pit is provided on the surface of the foundation soil. Both ends of the reference beam are supported by reference piles provided on the surface of the foundation soil. The dial indicator is fixed on the reference beam for measuring the movement of the displacement guide rod. The oil pipe of the jack passes through the second protective tube and is connected to the oil pump on the pedestal.

[0011] In one embodiment, a test pile cap is provided on the test pile, a positioning steel plate is provided on the test pile cap, and the jack is arranged on the positioning steel plate.

[0012] In one embodiment, a plurality of jacks are provided on the jacks and are arranged at equal arc distances around the center line of the channel.

[0013] Another object of the present application is to provide a static load test method for an assembled recovery loading device for providing reaction force by adding piles to a cap, comprising the following steps:

[0014] S1. Construct engineering piles and test piles as required, and the center distance between engineering piles and test piles shall meet the minimum spacing requirements of the specification;

[0015] S2. Excavate the foundation pit, make a test pile cap on the test pile, and install a positioning steel plate on the top of the test pile cap;

[0016] S3. Drill holes at predetermined locations on the fixed steel plates, install one end of a stud with an internal threaded hole on the fixed steel plates through the holes, and insert four fixed steel plates into the foundation soil along the sides of the test pile cap. The four fixed steel plates serve as support templates to enclose a working space, with the end faces of the studs flush with the working space surfaces of the fixed steel plates.

[0017] S4. Construct a cap in the foundation pit outside the fixed steel plate, pour concrete and embed studs in the cap. After the concrete of the cap reaches the design strength, install jacks on the positioning steel plate.

[0018] S5. Install one end of the displacement guide rod on the positioning steel plate, install the load-bearing steel plate on the jack, and extend the displacement guide rod and the oil pipe connected to the jack through the load-bearing steel plate to the surface of the foundation soil;

[0019] S6. Install the removable steel plate on the stressed steel plate, with the lower end of the removable steel plate abutting against the stressed steel plate, and the side surface of the removable steel plate abutting against the fixed steel plate and connected to the studs via fasteners;

[0020] S7. After the concrete of the foundation reaches the design strength, install the displacement measurement system, connect the oil pipe of the jack to the oil pump, and start the static load test;

[0021] S8. After the static load test is completed, the displacement measurement system, fasteners, removable steel plates, load-bearing steel plates, jacks, and positioning steel plates are removed in sequence for recycling;

[0022] S9. Lay two layers of steel mesh in the working space and fill it with concrete to fill the working space.

[0023] In one embodiment, one end of the fixing steel plate is 40 cm lower than the bottom surface of the platform, and the other end of the fixing steel plate is 10 cm higher than the top surface of the platform;

[0024] When pouring the concrete of the cap, steel diagonal braces are provided on the outside of the four fixed steel plates;

[0025] A first protection tube for protecting the displacement guide rod is provided on the positioning steel plate, and a second protection tube for protecting the oil pipe is provided on the stress-bearing steel plate.

[0026] The beneficial effects of the assembled and recovered loading device and static load test method provided by the present application for providing reaction force by adding piles to the cap are:

[0027] Economical and safe: Since both the detachable steel plate and the load-bearing steel plate can be detached, the jack and displacement measurement system can be recovered after the test, making it convenient to use them in multiple subsequent tests, thereby saving resources and reducing test costs.

[0028] Controllable test process: In existing embedded systems, if a problem occurs with a jack or other parts, the entire test will fail, resulting in significant economic losses. However, in this application, if damage or abnormality occurs to the jack or displacement measurement system during the test, the detachable steel plates and fasteners can be removed for inspection and replacement, achieving controllability of the entire test process and improving the reliability and accuracy of the test data.

[0029] The bearing mechanism is clear: the working mechanism of the test pile under loading is consistent with that of the compressive engineering pile, and the bearing capacity and deformation properties of the pile can be objectively, truly and directly revealed through the test.

[0030] Strong adaptability: For deep and soft foundations, there is no need to reinforce the soft foundations in advance to meet the bearing capacity requirements of the traditional loading method piers, and it has strong adaptability to the foundations of the test site.

[0031] Improved test accuracy: There is no large-scale pile loading and concentrated pressure from piers in the test site, which reduces the impact of concentrated pressure from piers on the additional stress and displacement of the test pile foundation under soft foundation conditions, reduces interference from external factors during the test, and can further improve the accuracy of the test displacement.

[0032] Friendly working environment: During the test, loading and data testing are carried out on the solid and flat top surface of the pedestal, and the working environment is practical and friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0034] Figure 1 A front plan view of an assembled and recyclable loading device that provides a reaction force for pile capping provided in an embodiment of the present application;

[0035] Figure 2 A schematic top plan view of an assembled and recyclable loading device that provides a reaction force for pile capping provided in an embodiment of the present application;

[0036] Figure 3 A schematic diagram of the engineering piles and test piles after construction in the assembled recovery loading device for providing reaction force for pile caps provided in an embodiment of the present application;

[0037] Figure 4 A schematic diagram of the excavation of the foundation pit and the reinforcement and widening of the test pile head in the assembled recovery loading device for providing reaction force for the pile cap provided in an embodiment of the present application;

[0038] Figure 5 A schematic diagram of the installation of fixed steel plates and studs in the assembled recovery loading device that provides reaction force for pile caps provided in an embodiment of the present application;

[0039] Figure 6 A schematic diagram of the cap after construction is completed, showing the concrete being poured outside the fixed steel plate in the assembled recovery loading device for providing reaction force for the cap pile provided in an embodiment of the present application;

[0040] Figure 7 A schematic diagram of the assembly recovery loading device for providing reaction force for pile capping provided in an embodiment of the present application after the first protection tube, the second protection tube, the oil pipe, the displacement guide rod and the load-bearing steel plate are installed and welded;

[0041] Figure 8 A schematic diagram of the assembled and retractable steel plates and fasteners after installation in the assembly and recovery loading device for providing reaction force for pile caps provided in an embodiment of the present application;

[0042] Figure 9 A schematic diagram of the displacement measurement system after installation in the assembled recovery loading device that provides reaction force for the pile cap provided in an embodiment of the present application;

[0043] Figure 10 A schematic front view of the structure of the assembly recovery loading device for providing reaction force for pile capping provided in an embodiment of the present application, in which a steel mesh is installed after the loading system is removed;

[0044] Figure 11 A schematic diagram of the top view of the structure of the assembled recovery loading device for providing reaction force for the pile cap provided in an embodiment of the present application, after the loading system is removed and the steel mesh is installed.

[0045] Among them, the reference numerals in the figures are:

[0046] 1. Engineering piles; 2. Capping platform; 3. Test piles; 4. Fixed steel plate; 5. Jack; 6. Load-bearing steel plate; 7. Removable steel plate; 8. Fasteners; 9. Studs; 10. Steel diagonal brace; 11. Displacement guide rod; 12. Dial indicator; 13. First protective tube; 14. Second protective tube; 15. Foundation pit; 16. Reference beam; 17. Reference piles; 18. Oil pipe; 19. Oil pump; 20. Test pile cap; 21. Positioning steel plate; 22. Steel mesh. DETAILED DESCRIPTION

[0047] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0048] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0049] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0050] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0051] like Figures 1-11 As shown, an assembly and recovery type loading device for providing reaction force by adding a pile to a cap provided in an embodiment of the present application will now be described. The assembly and recovery type loading device for providing reaction force by adding a pile to a cap is used to perform a static load test on a single pile. The device comprises: a plurality of engineering piles 1 set in the foundation soil, a cap 2 connecting the tops of all the engineering piles 1, at least one test pile 3 set in the foundation soil, and a loading system for measuring the settlement of the test pile 3, wherein the loading system includes detachable components such as a displacement measurement system, a jack, a load-bearing steel plate, a positioning steel plate, a detachable steel plate, fasteners, and a displacement guide rod.

[0052] Specifically, a channel corresponding to the centerline of the test pile 3 is provided on the foundation 2. Fixed steel plates 4 are fixed to the side walls of the channel. Four fixed steel plates 4 form a working space within the channel. A jack 5 is provided on the test pile 3. A load-bearing steel plate 6 is provided on the jack 5. A removable steel plate 7 is provided on the load-bearing steel plate 6. The removable steel plate 7 is removably connected to the fixed steel plate 4 via a number of fasteners 8. The removable steel plate 7 and the fixed steel plate 4 are connected together by fasteners 8 to achieve force transmission between the foundation 2, the load-bearing steel plate 6, and the jack 5. The removable steel plate 7 and the load-bearing steel plate 6 are removable, thereby facilitating the disassembly and assembly of the jack 5 and the displacement measurement system. They can be recycled and repaired, saving costs and ensuring test accuracy.

[0053] Specifically, in this embodiment, the channel is a rectangular channel, and four fixed steel plates 4 are provided and arranged in a rectangular shape by welding. The fixed steel plates 4 are installed in the channel and used as support templates. Similarly, the removable steel plates 7 are arranged in a rectangular shape. In this embodiment, each fixed steel plate 4 is provided with a number of studs 9 with internal threaded holes. The studs 9 on each fixed steel plate 4 are arranged in a rectangular array, and the specific number is determined according to the test requirements. Among them, one end of the stud 9 is flush with the inner surface of the fixed steel plate 4 (the side surface close to the channel), which makes it convenient for the removable steel plate 7 to fit in and abut against the load-bearing steel plate 6; the other end of the stud 9 extends into the base 2, so that the base 2 and the fixed steel plate 4 become an integrated structure. The removable steel plate 7 is provided with several through holes coaxial with the studs 9. After the removable steel plate 7 is inserted into the channel and fits with the fixed steel plate 4, the through holes are coaxially aligned with the internal threaded holes, and the fasteners 8 pass through the through holes and are screwed into the internal threaded holes, thereby firmly connecting the removable steel plate 7 and the fixed steel plate 4 together.

[0054] In this embodiment, the fastener 8 is a screw, or the fastener 8 includes a screw and a nut. The screw or screw is threadedly connected to the internal threaded hole of the stud 9 and is tightened against the removable steel plate 7 through the nut of the screw. When the nut is manually screwed, the nut is a butterfly nut to facilitate force.

[0055] In this embodiment, the pedestal is formed by pouring concrete and main reinforcement (rebar) is laid inside. A steel diagonal brace 10 is provided on the back of the fixed steel plate 4. One end of the steel diagonal brace 10 is welded to the back of the fixed steel plate 4 (the side close to the pedestal 2), and the other end is fixed to the main reinforcement laid at the bottom of the pedestal. The function of the steel diagonal brace 10 is to ensure that the fixed steel plate 4 is in a vertical state when pouring concrete to form the pedestal 2, so as to facilitate the subsequent insertion of the removable steel plate 7.

[0056] In this embodiment, the length of the fixed steel plate 4 is greater than the height of the pedestal 2 and the raised portion of the fixed steel plate 4 is surrounded by a test pile 3. The purpose of this is to ensure that the fixed steel plate 4 will not deviate. The raised portion of the fixed steel plate 4 is inserted into the foundation soil and the depth is 0.3-0.5m, preferably 0.4m; the top of the fixed steel plate 4 is 0.1m higher than the top of the pedestal, which makes it convenient to pour concrete to form the pedestal without causing concrete to enter the channel.

[0057] In this embodiment, the displacement measurement system includes a displacement guide rod 11 and a dial indicator 12. A first protective tube 13 and a second protective tube 14 are vertically arranged within the channel. The displacement guide rod 11 slides through the first protective tube 13 and is fixedly connected to the test pile 3. The second protective tube 14 is used to protect the oiled rod. A foundation pit 15 is provided within the foundation soil, and the cap 2 is disposed within the foundation pit 15. A reference beam 16 is provided on the surface of the foundation soil, spanning the foundation pit 15. Both ends of the reference beam 16 are supported by reference piles 17 disposed on the surface of the foundation soil. The dial indicator 12 is fixedly mounted on the reference beam 16 to measure the movement of the displacement guide rod 11. The oil pipe 18 of the jack 5 extends from the second protective tube 14 and is connected to an oil pump 19 on the cap 2. The first and second protective tubes 13 and 14 serve as protective devices. The reference piles 17 and the reference beam 16 ensure that the position of the dial indicator 12 remains fixed, allowing the absolute settlement of the test pile 3 to be measured. In this embodiment, two displacement guide rods 11 and two dial indicators 12 are provided at intervals, which can reduce test errors.

[0058] In this embodiment, a test pile cap 20 is provided on the test pile 3, a positioning steel plate 21 is provided on the test pile cap 20, and the jack 5 is provided on the positioning steel plate 21. Optionally, a plurality of jacks 5 are provided and are arranged at equal arc distances around the center line of the channel, such as Figure 2 As shown, there are four jacks 5 , which are arranged at equal arc distances to ensure uniform force application by the jacks 5 .

[0059] In this embodiment, the test pile 3 is set at the center of the engineering pile group 1. The pile length of each test pile 3 is different. There are four engineering piles 1, which are respectively set at the four corners of the base 2.

[0060] The assembled recovery loading device provided in this embodiment provides reaction force for the pedestal and piles. The engineering piles 1 and the test piles located in the pile group are constructed as required, the test pile caps are processed, the jacks 5 are installed on the top of the test pile caps and embedded in the pile group pedestal 2, and the deadweight of the pedestal 2 and the engineering piles 1 are fully utilized as anchor piles to provide reaction force to realize vertical compressive static load test loading.

[0061] like Figure 3-Figure 11 As shown, this embodiment also provides a static load test method of an assembled recovery loading device using a pile cap to provide a reaction force, comprising the following steps:

[0062] S1. Construct engineering pile 1 and test pile 3 as required. The center distance between engineering pile 1 and test pile 3 meets the minimum spacing requirements of the specification.

[0063] S2, excavating the foundation pit 15, making a test pile cap 20 on the test pile 3, and installing a positioning steel plate 21 on the top of the test pile cap 20;

[0064] S3. Drill holes at predetermined locations on the fixed steel plates 4, install one end of a stud with an internal threaded hole on the fixed steel plates through the holes, insert four fixed steel plates 4 into the foundation soil along the sides of the test pile cap, and use the four fixed steel plates 4 as support templates to enclose a working space. The end faces of the studs are flush with the surfaces of the fixed steel plates near the working space; multiple holes are provided and distributed in an array, and the number of studs is the same as the number of holes. The studs can be installed in the holes by threading or welding; the studs are made of steel;

[0065] S4. Construct the cap 2 in the foundation pit 15 outside the fixed steel plate 4, pour concrete and embed the studs in the cap 2. After the concrete of the cap 2 reaches the design strength, install the jack 5 on the positioning steel plate 21;

[0066] S5. Install one end of the displacement guide rod 11 on the positioning steel plate 21, install the load-bearing steel plate 6 on the jack 5, and extend the displacement guide rod 11 and the oil pipe 18 connected to the jack 5 through the load-bearing steel plate 6 to the surface of the foundation soil;

[0067] S6. Install the removable steel plate 7 on the stressed steel plate 6, with the lower end of the removable steel plate 7 abutting against the stressed steel plate 6, and the side surface of the removable steel plate 7 abutting against the fixed steel plate 4 and connected to the studs through the fasteners 8;

[0068] S7. After the concrete of the foundation reaches the design strength, install the displacement measurement system, connect the oil pipe 18 of the jack 5 to the oil pump 19, and start the static load test;

[0069] S8. After the static load test is completed, the displacement measurement system, fasteners, removable steel plates, load-bearing steel plates, jacks, and positioning steel plates are removed in sequence for recycling;

[0070] S9. Lay two layers of steel mesh 22 in the working space and fill the working space with concrete to fill it.

[0071] During the specific implementation process, firstly, the total reaction force provided by the pedestal 2 and the engineering pile 1 (anchor pile) to the reaction device is estimated based on the size and deadweight of the bridge pile foundation pedestal 2 and the number, size, geological data, etc. of the single pile design, and the safety factor is ensured to be equal to or greater than the total reaction force / maximum vertical load value ≥ 1.2. Then, the number and diameter of the studs and the thickness of the fixed steel plate 4 are determined based on the total reaction force provided by the jack 5, ensuring that the total shear force and extrusion force provided by the fastener 8 are greater than the total reaction force, and the hole positions are marked in advance on the removable steel plate 7 based on the number of fasteners 8, such as screws. When the number of test piles 3 is one, the center of the test pile 3 is at the center of the plane of the pedestal 2 to ensure that the loading reaction force does not generate an eccentric load on the pedestal 2. The center distance between the test pile 3 and the nearest engineering pile 1 is not less than 3 times the pile diameter.

[0072] Specifically, one end of the fixed steel plate 4 is 40 cm lower than the bottom surface of the base, and the other end of the fixed steel plate is 10 cm higher than the top surface of the base 2.

[0073] According to the designed position, the engineering pile 1 and the test pile 3 are constructed. Figure 3 shown.

[0074] Excavate the foundation pit 15, break the pile head to the ground elevation of the foundation 2. When large-tonnage test loading is performed, the pile head of the test pile 3 should be widened and processed (i.e., the pile head is made into a test pile cap 20) according to the number and diameter of the jacks 5. Under this condition, the pile head of the test pile 3 is broken to the bottom of the test pile cap 20. The pile head (cap) is reinforced according to the specification requirements. Figure 4 shown.

[0075] The following points should be noted: The concrete grade of the pile head (cap) should be higher than that of the pile body. The broken layer and weak or loose concrete at the top of the pile should be removed. The top surface of the pile head should be flat, and the center axis of the pile head (cap) should coincide with the center axis of the upper part of the pile body. Within 1 times the pile diameter from the top of the pile head (cap), a steel plate with a thickness of 3mm-5mm should be used to wrap it, or stirrups should be installed within 1.5 times the pile diameter from the top of the pile head (cap), with a spacing of no more than 100mm. Two layers of steel mesh should be installed at the top of the pile head (cap), with a spacing of 60-100mm.

[0076] First, install the positioning steel plate 21 (specification Q345b, thickness 10mm) on the top surface of the test pile cap. Then make holes in the fixed steel plate 4 with a thickness of 15mm in advance, weld studs 9 with internal threaded holes at the holes, and insert four fixed steel plates 4 of the same size along the test pile cap 20 0.3m below the ground of the pedestal 2. The height of the fixed steel plate 4 is flush with the design elevation of the pedestal 2 or 0.1m higher, and weld the four fixed steel plates 4 into one. The square area among the fixed steel plates 4 is the working space. In order to ensure that the fixed steel plates 4 do not fall over during the subsequent pouring of concrete to form the pedestal 2, steel diagonal braces 10 are set outside the four fixed steel plates 4, and multiple steel diagonal braces are set. One end of the steel diagonal brace 10 is welded to the fixed steel plate 4, and the other end is welded to the main reinforcement laid on the bottom surface of the foundation pit 15 to maintain the stability of the steel diagonal brace 10. As shown Figure 5 shown.

[0077] The foundation 2 is constructed until the concrete of the foundation 2 reaches the design strength, and the foundation pit 15 is not backfilled for the time being. Figure 6 shown.

[0078] According to the number and size of the jacks 5, design their positions on the positioning steel plate 21 and weld the positioning pins to accurately install the jacks 5 on the positioning steel plate 21. After the jacks 5 are installed, set the position of the displacement guide rod 11 on the positioning steel plate 21, and reserve installation channels for the first protective tube 13 to protect the displacement guide rod 11 and the second protective tube 14 to protect the oil pipe 18 on the load-bearing steel plate 6 with the same size as the positioning steel plate 21, and then install the load-bearing steel plate 6 on the jacks 5. Finally, install the first protective tube 13 (outer diameter 50mm, wall thickness 1mm) and the second protective tube 14 (outer diameter 50mm, wall thickness 1mm) at the channel position. And lead the oil pipe 18 of the jack 5, the first protective tube 13, the displacement guide rod 11 (28mm diameter steel bars can be used), and the second protective tube 14 to the appropriate height of the designed top surface of the base 2. As shown Figure 7 shown.

[0079] Measure the distance from the stress-bearing steel plate 6 to the opening of the fixed steel plate 4 and the spacing between the holes on the fixed steel plate 4, and reserve holes in a 30mm thick removable steel plate 7 for fasteners 8 such as screws to pass through. Install the removable steel plate 7 so that the lower end of the removable steel plate 7 contacts the stress-bearing steel plate 6 and the holes on the fixed steel plate 4 and the removable steel plate 7 are aligned, then insert the screw (with a diameter of 42mm) into the aligned hole and screw it into the stud 9 with an internal threaded hole. After screwing the screw to the bottom, screw the nut on the part of the screw left outside the removable steel plate 7 and tighten the nut. Install the four removable steel plates in sequence, as shown in the following figure. Figure 8 shown.

[0080] Construction reference pile 17, installation reference beam 16, installation of the reference beam 16 and the displacement guide rod 11 on the top surface of the vertical displacement test dial indicator 12, such as Figure 9 shown.

[0081] Connect the oil pipe 18 and the oil pump 19 of the jack 5, and carry out the vertical compressive static load test according to the test plan.

[0082] After the static load test is completed, the detachable components such as the displacement measurement system, fasteners, detachable steel plates, load-bearing steel plates, jacks and positioning steel plates are removed in turn, and these detachable components are recycled and reused to reduce costs.

[0083] After the disassembly is completed, two layers of steel mesh 22 are laid in the channel. Figure 10 and Figure 11 shown.

[0084] After laying the steel mesh, backfill the channel with concrete to compact it.

[0085] The beneficial effects of the assembled recovery loading device and static load test method provided in this embodiment for providing reaction force by adding piles to the cap are:

[0086] Economical and safe: Since the detachable steel plate 7 and the load-bearing steel plate 6 can be detached, the jack 5 and the displacement measurement system can be recovered after the test, which is convenient for use in multiple subsequent tests, thereby achieving the purpose of saving resources and reducing test costs.

[0087] Controllable test process: In the existing embedded test method, if there is a problem with the jack 5 or other parts, the entire test will fail, resulting in significant economic losses. However, in this application, if there is damage or abnormality in the jack 5 or the displacement measurement system during the test, the detachable steel plate 7 and fastener 8 can be disassembled for inspection and replacement, achieving controllability of the entire test process and improving the reliability and accuracy of the test data.

[0088] The bearing mechanism is clear: the working mechanism of the test pile 3 under loading is consistent with that of the compressive engineering pile 1. The test can objectively, truly and directly reveal the bearing capacity and deformation properties of the pile.

[0089] Strong adaptability: For deep and soft foundations, there is no need to reinforce the soft foundations in advance to meet the bearing capacity requirements of the traditional loading method piers, and it has strong adaptability to the foundations of the test site.

[0090] Improved test accuracy: There is no large-scale pile load and concentrated pressure from the piers at the test site, which reduces the impact of the concentrated pressure from the piers on the additional stress and displacement of the test pile 3 foundation under soft foundation conditions, reduces the interference of external factors during the test, and can further improve the accuracy of the test displacement.

[0091] Friendly working environment: During the test, loading and data testing are carried out on the solid and flat top surface of the base 2, and the working environment is practical and friendly.

[0092] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. The assembled recovery loading device for providing reaction force for the pile cap includes: A plurality of engineering piles (1) arranged in foundation soil, a cap (2) connecting the tops of all the engineering piles (1), at least one test pile (3) arranged in the foundation soil, and a displacement measurement system for measuring the settlement of the test pile (3), characterized in that the cap (2) is provided with a channel corresponding to the center line of the test pile (3), the side wall of the channel is fixedly provided with a fixed steel plate (4), the test pile (3) is provided with a jack (5), the jack (5) is provided with a load-bearing steel plate (6), and the load-bearing steel plate (6) is provided with a detachable steel plate ( 7), the lower end of the detachable steel plate (7) abuts against the load-bearing steel plate (6), and the detachable steel plate (7) is detachably connected to the fixed steel plate (4) through a plurality of fasteners (8); the fixed steel plate (4) is provided with a plurality of studs (9) with internal threaded holes, one end of the studs (9) is flush with the surface of the fixed steel plate (4), and the other end of the studs (9) extends into the base (2), and the detachable steel plate (7) is provided with a plurality of through holes coaxial with each of the studs (9), and the fasteners (8) pass through the through holes and are screwed to the internal threaded holes.

2. The assembly and recovery loading device for providing reaction force by adding piles to the platform as claimed in claim 1, characterized in that: The fastener (8) is a screw, or the fastener (8) includes a screw rod and a nut.

3. The assembly and recovery loading device for providing reaction force by adding piles to the cap according to claim 1, characterized in that: A steel diagonal brace (10) is provided on the back of the fixed steel plate (4), one end of the steel diagonal brace (10) is welded to the back of the fixed steel plate (4), and the other end is fixed to the main reinforcement laid on the bottom of the base.

4. The assembly and recovery loading device for providing reaction force by adding piles to a cap as claimed in claim 3, characterized in that: The length of the fixed steel plate (4) is greater than the height of the bearing platform (2), and the raised portion of the fixed steel plate (4) surrounds the test pile (3).

5. The assembly and recovery loading device for providing reaction force by adding piles to the cap according to any one of claims 1 to 4, characterized in that: The displacement measurement system includes a displacement guide rod (11) and a dial indicator (12). A first protective tube (13) and a second protective tube (14) are vertically provided in the channel. The displacement guide rod (11) is slidably inserted into the first protective tube (13) and is fixedly connected to the test pile (3). A foundation pit (15) is provided in the foundation soil. The pedestal (2) is arranged in the foundation pit (15). A reference beam (16) spanning the foundation pit (15) is provided on the surface of the foundation soil. Both ends of the reference beam (16) are supported by reference piles (17) arranged on the surface of the foundation soil. The dial indicator (12) is fixedly arranged on the reference beam (16) for measuring the movement of the displacement guide rod (11). The oil pipe (18) of the jack (5) passes through the second protective tube (14) and is connected to the oil pump (19) on the pedestal (2).

6. The assembly and recovery loading device for providing reaction force by adding piles to the cap according to claim 5, characterized in that: The test pile (3) is provided with a test pile cap (20), the test pile cap (20) is provided with a positioning steel plate (21), and the jack (5) is arranged on the positioning steel plate (21).

7. The assembly and recovery loading device for providing reaction force by adding piles to a cap according to claim 6, characterized in that: The jacks (5) are arranged in multiple numbers and are arranged at equal arc distances around the center line of the channel.

8. A static load test method for an assembled recovery loading device with a pile cap providing reaction force, characterized in that: The following steps are involved: S1. Construct the engineering pile (1) and the test pile (3) as required, and the center distance between the engineering pile (1) and the test pile (3) meets the minimum spacing requirement of the specification; S2, excavating the foundation pit (15), making a test pile cap (20) on the test pile (3), and installing a positioning steel plate (21) on the top of the test pile cap (20); S3. A hole is opened at a predetermined position on the fixed steel plate (4), and one end of a stud with an internal threaded hole is installed on the fixed steel plate through the hole. Four fixed steel plates (4) are inserted into the foundation soil along the side of the test pile cap (20). The four fixed steel plates (4) serve as support templates to enclose an operating space, and the end face of the stud is flush with the surface of the operating space of the fixed steel plate; S4. Construct a cap (2) in the foundation pit (15) outside the fixed steel plate (4), pour concrete and embed studs in the cap (2). After the concrete of the cap (2) reaches the designed strength, install the jack (5) on the positioning steel plate (21); S5, one end of the displacement guide rod (11) is mounted on the positioning steel plate (21), and the load-bearing steel plate (6) is mounted on the jack (5), and the oil pipe (18) connecting the displacement guide rod (11) and the jack (5) passes through the load-bearing steel plate (6) and extends to the surface of the foundation soil; S6. Install the removable steel plate (7) on the stressed steel plate (6), with the lower end of the removable steel plate (7) abutting against the stressed steel plate (6), and the side surface of the removable steel plate (7) abutting against the fixed steel plate (4) and connected to the studs via fasteners (8); S7. After the concrete of the foundation reaches the designed strength, the displacement measurement system is installed, and the oil pipe (18) of the jack (5) is connected to the oil pump (19), and the static load test is started; S8. After the static load test is completed, the displacement measurement system, fasteners, removable steel plates, load-bearing steel plates, jacks, and positioning steel plates are dismantled and recovered in sequence; S9. Lay two layers of steel mesh in the working space and fill it with concrete to fill the working space.

9. The static load test method of the assembled and recovered loading device for providing reaction force by pile caps according to claim 8, characterized in that: One end of the fixed steel plate (4) is 40 cm lower than the bottom surface of the support platform, and the other end of the fixed steel plate is 10 cm higher than the top surface of the support platform (2); When pouring concrete for the foundation (2), steel diagonal braces (10) are provided on the outer sides of the four fixed steel plates (4); A first protection tube (13) for protecting the displacement guide rod (11) is provided on the positioning steel plate (21), and a second protection tube (14) for protecting the oil pipe (18) is provided on the stress-bearing steel plate.

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