A lever type horizontal bearing capacity detection device and method for water pile foundation

Abstract

A lever-type device and method for testing the horizontal bearing capacity of underwater pile foundations is disclosed. The device includes a loading unit and a monitoring unit. The loading unit includes a support, a lever, a crossbeam, a cable, and a test vessel. The lower end of the support is fixed in the seabed or riverbed near the test pile. A bearing is welded normally to the upper end of the support. A hole is opened in the middle of the lever, serving as the fulcrum of the lever. The bearing at the upper end of the support passes through the opening in the middle of the lever and is connected to the support via a cap. The upper end of the lever is rigidly connected to one end of the crossbeam, and the other end of the crossbeam is rigidly connected to the outer wall of the test pile. One end of the cable is connected to the lower end of the lever, and the other end is connected to the test vessel. The monitoring unit includes a force gauge and a gyroscope. The force gauge is fixed to the crossbeam, and the gyroscope is fixed to the lever. Using this device for testing the horizontal bearing capacity of underwater pile foundations eliminates the need for high-level horizontal bearing capacity anchor piles to provide reaction force. It allows for single deployment, multiple tests, and reusability, making it economical and efficient.

Description

Technical Field

[0001] This invention belongs to the field of bearing capacity testing of underwater pile foundations, specifically relating to a lever-type underwater pile foundation horizontal bearing capacity testing device and method, which is applicable to the testing of horizontal bearing capacity of underwater pile foundations and the assessment of ultimate bearing capacity of pile foundations. Background Technology

[0002] Currently, most marine engineering projects, port and wharf projects, and water structures use pile foundations. However, extreme horizontal loads in the water environment, such as wind, waves, currents, and ship collisions, place high demands on the horizontal bearing capacity of pile foundations. In order to better study the bearing capacity mechanism of large-diameter pile foundations in water and further optimize the design and application of large-diameter pile foundations under extreme water conditions, it is essential to conduct on-site horizontal bearing capacity testing of pile foundations in water.

[0003] However, traditional methods for testing the horizontal bearing capacity of underwater pile foundations typically require driving one or more reaction piles near the test pile and setting up a large reaction platform and device on site. Horizontal loads are applied to the test piles using large pressurizing equipment and reaction devices, and the displacement development of the pile foundation is monitored to complete the assessment of the horizontal bearing capacity of the pile foundation. Traditional testing methods yield relatively reliable results, but their drawbacks are also obvious: 1) High economic cost: requiring several reaction anchor piles and a test platform, the cost of which can reach tens of millions, which is detrimental to the economic benefits of the project; 2) Long test cycle: driving anchor piles and building the reaction device platform requires a long period of time, and for different test piles, the original reaction anchor piles and devices need to be removed, and then new anchor piles need to be driven and the platform built. This process is very tedious and complex, and it also prolongs the test cycle; 3) Large test site: requiring the reservation of space around the test pile for driving multiple reaction piles and building the test platform. For pile foundations such as offshore drilling platforms, there may be insufficient test site or disturbance to the surrounding pile foundations; 4) Small test reaction force: in order to facilitate the removal of reaction anchor piles after the test, the diameter of the reaction anchor piles is usually not too large, which means that the horizontal reaction force provided by the reaction anchor piles may not be able to meet the huge test reaction force required by large-diameter pile foundations. With the improvement of offshore wind power construction, the capacity of wind turbine units is getting larger and larger, and the corresponding pile foundation diameter is also getting larger and larger. For example, the diameter of the wind turbine pile foundation of CGN Rudong 150MW offshore wind farm is 6.6 m. The small-diameter anchor piles driven by the traditional horizontal static load test method obviously cannot meet the horizontal test reaction force required for such a large diameter.

[0004] Given the drawbacks of traditional methods for testing the horizontal bearing capacity of underwater pile foundations and the stringent requirements for the horizontal bearing capacity of pile foundations in complex underwater structures, proposing a new method for testing the horizontal bearing capacity of underwater pile foundations is of obvious engineering urgency. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a lever-type horizontal bearing capacity testing device and method for underwater pile foundations, which addresses the above-mentioned shortcomings of existing testing methods for horizontal bearing capacity of underwater pile foundations. The device and method use a lever adaptive method to test the horizontal bearing capacity of underwater pile foundations, eliminating the need to drive multiple reaction piles around the test pile, thus saving a lot of costs associated with the prefabrication, transportation, hoisting, and labor of reaction anchor piles. It also greatly reduces the testing period and allows the testing equipment to be reused, further saving on project costs.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: A lever-type underwater pile foundation horizontal bearing capacity testing device includes at least a loading unit and a testing unit. The loading unit includes a support, a lever, a crossbeam, a cable, and a test vessel. The lower end of the support is fixed in the seabed or riverbed near the test pile. A bearing is welded to the upper end of the support in the normal direction. A hole is opened in the middle of the lever, which serves as the movable fulcrum of the lever. The bearing at the upper end of the support passes through the hole in the middle of the lever and is connected to the support through a cap. The bearing and the cap restrict the lever to rotate (oscillate) only in a vertical plane around the movable fulcrum. The upper end of the lever is rigidly connected to one end of the crossbeam, and the other end of the crossbeam is rigidly connected to the outer wall of the test pile (pile foundation). One end of the cable is connected to the lower end of the lever, and the other end of the cable is connected to the test vessel. The testing unit includes a force gauge and a gyroscope. The force gauge is fixed on the crossbeam, and the gyroscope is fixed on the lever.

[0007] According to the above scheme, the crossbeam is made of high-strength alloy I-beam, and the dimensions of the crossbeam are designed according to the design bearing capacity of the test pile to ensure that the crossbeam has sufficient compressive stiffness and to avoid deformation of the crossbeam during the test loading process.

[0008] According to the above scheme, one end of the crossbeam that is rigidly connected to the test pile is cut into an inward concave shape, and the concave arc is consistent with the arc of the outer wall of the test pile. The crossbeam is temporarily welded to the outer wall of the test pile to prevent slippage at the connection between the crossbeam and the test pile during the test loading process.

[0009] According to the above scheme, the end of the crossbeam that is rigidly connected to the test pile is welded with a hoop, and the crossbeam is fixedly connected to the test pile through the hoop.

[0010] According to the above scheme, the force gauge is fixed in the I-beam groove of the crossbeam and is used to measure the axial force of the crossbeam. Under quasi-static conditions, the axial force of the crossbeam is the same as the horizontal thrust applied to the test pile, so that the horizontal force acting on the test pile can be monitored in real time.

[0011] According to the above scheme, the lever is made of high-strength alloy steel plate, and the length of the steel plate is as long as possible, in the shape of a long strip; the thickness of the steel plate is the same as the web thickness of the I-beam used for the crossbeam, the side of the lever and the web of the I-beam of the crossbeam are aligned and rigidly fixed, and the crossbeam and the lever are arranged at a 90° angle.

[0012] According to the above scheme, the gyroscope is installed on the upper part of the lever near the top end to measure the rotation angle of the lever and to calculate the horizontal displacement of the connection point between the lever and the crossbeam using the rotation angle of the lever.

[0013] According to the above scheme, the support is made of high-strength steel rod or hollow steel pipe.

[0014] According to the above scheme, the cable is made of high-strength and high-toughness steel strand.

[0015] The present invention also provides a method for testing the horizontal bearing capacity of underwater pile foundations using the above-mentioned lever-type underwater pile foundation horizontal bearing capacity testing device, comprising the following steps: (1) Preliminary preparation: According to the project requirements, survey and select the test site, design the test plan, prefabricate the test piles, crossbeams, levers, supports and cables of the corresponding specifications, and prepare the force gauge, gyroscope and test boat; (2) On-site setup: Transport each component of the lever-type water pile foundation horizontal bearing capacity testing device to the vicinity of the designed pile location water area. First, test piles are driven. During the pile driving process, the pile body is kept vertical and the inclination is within the allowable range of the project. Then, the support is buried at a distance of 2 to 4 times the pile diameter from the test pile. The lever, the crossbeam, and the cable are connected, and the force gauge and the gyroscope are set up. (3) Start the test: By starting the test ship to tension the cable to provide the reaction force, the load is gradually applied in stages. At the same time, the axial force of the beam measured by the force gauge and the tilt angle of the lever measured by the gyroscope are recorded under each load level. (4) Follow-up work: After the test, retrieve the lever-type underwater pile foundation horizontal bearing capacity testing device, process the test data, draw the load-displacement curve, analyze the pile foundation load-displacement curve, evaluate the ultimate bearing capacity of the pile foundation, and complete the underwater pile foundation horizontal bearing capacity test.

[0016] Compared with traditional horizontal bearing capacity testing methods, the advantages of this invention are: 1. The proposed lever adaptive method does not require the installation of high-bearing-capacity anchor piles to provide reaction force. Theoretically, the horizontal force on the beam and cable is equivalent, and the horizontal force at the movable fulcrum of the lever is relatively limited. Therefore, the horizontal resistance requirement of the support is low. The support only needs to bear the weight of the lever and part of the beam, which can greatly save economic costs. 2. The overall device has a simple and compact structure, is easy and efficient to construct, and has a significant time cost advantage compared to traditional testing methods. It can also adapt well to the complex and ever-changing testing environment on water. 3. By setting up a support frame and selecting crossbeams of different specifications, pile foundations within a certain spatial distribution range can be tested, achieving the effect of "single arrangement, multiple tests", which has great prospects for engineering promotion and social and economic benefits. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the lever-type underwater pile foundation horizontal bearing capacity testing device of the present invention; Figure 2 This is a partial side view of the connection between the lever and the bracket in this invention; Figure 3 This is a partial top view of the connection between the crossbeam and the test pile of the present invention; In the diagram: 1-Test pile, 2-Crossbeam, 3-Lever, 4-Support, 5-Force gauge, 6-Gyroscope, 7-Orifice cap, 8-Cable, 9-Test vessel. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0019] Reference Figure 1 As shown, the lever-type underwater pile foundation horizontal bearing capacity testing device of the present invention is arranged near the test pile 1 and includes a support 4, a lever 3, a crossbeam 2, a force gauge 5, a gyroscope 6, a cable 8, and a test vessel 9. The lower end of the support 4 is embedded in the seabed or riverbed near the test pile 1 for fixation. Figure 2 As shown, a bearing is welded to the upper end of the bracket 4 in the normal direction to connect the lever 3. A hole is opened in the middle of the lever 3, which serves as the movable fulcrum of the lever 3. The bearing at the upper end of the bracket 4 passes through the hole in the middle of the lever 3. The lever 3 is connected to the upper end of the bracket 4 through the bearing at the upper end of the bracket 4 and a cap 7. The bearing and the cap 7 restrict the lever 3 to rotate (oscillate) only in the vertical plane with the movable fulcrum as the center. The upper end of the lever 3 is welded to one end of the crossbeam 2, and the other end of the crossbeam 2 is rigidly connected to the outer wall of the test pile 1 (pile foundation). One end of the cable 8 is connected to the lower end of the lever 3, and the other end of the cable 8 is connected to the test ship 9. The force gauge 5 is fixed on the crossbeam 2 to measure the axial force of the crossbeam. The gyroscope 6 is fixed on the lever 3 to determine the rotation angle of the lever 3.

[0020] The crossbeam 2 is made of high-strength alloy I-beam. The force gauge 5 is fixed in the I-beam groove of the crossbeam 2. Under quasi-static conditions, the axial force of the crossbeam is the same as the horizontal thrust applied to the test pile, thus allowing real-time monitoring of the horizontal force acting on the test pile. The dimensions of the crossbeam 2 are designed based on the design bearing capacity of the test pile 1 to ensure that the crossbeam 2 has sufficient compressive stiffness and to prevent deformation of the crossbeam 2 during the test loading process.

[0021] Reference Figure 3 As shown, one end of the crossbeam 2 that is rigidly connected to the test pile 1 is cut into an inward concave shape. The concave arc is consistent with the arc of the outer wall of the test pile 1. The crossbeam 2 is temporarily welded to the outer wall of the test pile 1 to prevent slippage at the connection between the crossbeam 2 and the test pile 1 during the test loading process.

[0022] The end of the crossbeam 2 that is rigidly connected to the test pile 1 is also welded with a hoop, and the crossbeam 2 is fixedly connected to the test pile 1 through the hoop.

[0023] Lever 3 is made of high-strength alloy steel plate, which is as long as possible and in the shape of a long strip. The thickness of the steel plate is the same as the web thickness of the I-beam used for crossbeam 2. The side of lever 3 and the web of the I-beam of crossbeam 2 are aligned and welded together. Crossbeam 2 and lever 3 are at a 90° angle to each other.

[0024] A gyroscope 6 is installed on the upper part of lever 3 near the top. The rotation angle of lever 3 is used to calculate the horizontal displacement of the connection point between lever 3 and crossbeam 2. When lever 3 is long, it can be approximated that the crossbeam 2 connected to it only undergoes horizontal translation during the entire loading process. Therefore, the horizontal displacement of the connection point between lever 3 and crossbeam 2 is equal to the horizontal displacement of the connection point between crossbeam 2 and test pile 1, thus obtaining the actual horizontal displacement of test pile 1. At this point, the horizontal force and displacement values ​​acting on test pile 1 are obtained, leading to the force-displacement (FDI) ratio. p - y The curve is used to evaluate its horizontal load-bearing characteristics.

[0025] The support 4 is made of hollow steel pipe.

[0026] The cable 8 is made of high-strength and high-toughness steel strand. During the test, the test vessel 9 can provide tension to the cable 8. Under the action of the force, the lever 3 rotates around the movable fulcrum. When the lever 3 is long enough and the horizontal displacement of the test pile 1 is very limited, it can be considered that the crossbeam 2 always applies a horizontal thrust to the test pile 1.

[0027] This invention discloses a method for testing the horizontal bearing capacity of underwater pile foundations using a lever-type underwater pile foundation horizontal bearing capacity testing device, comprising the following steps: (1) Preliminary preparation: According to the project requirements, survey and select the test site, design the test plan, prefabricate the test pile 1, crossbeam 2, lever 3, bracket 4, cable 8 and other devices of the corresponding specifications, and prepare the force gauge 5, gyroscope 6, test boat 9 and other equipment. (2) On-site setup: Transport each component of the lever-type water pile foundation horizontal bearing capacity testing device to the vicinity of the designed pile location water area. First, drive the test pile 1. During the pile driving process, keep the pile body vertical and the inclination within the allowable range of the project. Then, embed the support 4 at a distance of 2 to 4 times the pile diameter from the test pile, connect the lever 3, crossbeam 2, and cable 8, and set up the force gauge 5 and gyroscope 6. (3) Start the test: By starting the test ship 9 to provide the reaction force through the tension cable 8, the load is gradually applied in stages. At the same time, the axial force of the beam 2 measured by the force gauge 5 and the tilt angle of the lever 3 measured by the gyroscope 6 are recorded under each load level. (4) Follow-up work: After the test, retrieve the lever-type underwater pile foundation horizontal bearing capacity testing device, process the test data, draw the load-displacement curve, analyze the pile foundation load-displacement curve, evaluate the ultimate bearing capacity of the pile foundation, and complete the underwater pile foundation horizontal bearing capacity test.

[0028] This invention is not limited to the applications listed in the specification and embodiments. For those skilled in the art, various corresponding modifications and variations can be made according to this invention, and all such modifications and variations fall within the protection scope of the claims of this invention.

Claims

1. A lever-type underwater pile foundation horizontal bearing capacity testing device, characterized in that, The system includes at least a loading unit and a monitoring unit. The loading unit comprises a support, a lever, a crossbeam, a cable, and a test vessel. The lower end of the support is fixed in the seabed or riverbed near the test pile. A bearing is welded to the upper end of the support in the normal direction. A hole is opened in the middle of the lever, which serves as the movable fulcrum of the lever. The bearing at the upper end of the support passes through the opening in the middle of the lever and is connected to the support through a cap. The bearing and the cap restrict the lever to rotate only in a vertical plane around the movable fulcrum. The upper end of the lever is rigidly connected to one end of the crossbeam, and the other end of the crossbeam is rigidly connected to the outer wall of the test pile. One end of the cable is connected to the lower end of the lever, and the other end of the cable is connected to the test vessel. The monitoring unit includes a force gauge and a gyroscope. The force gauge is fixed to the crossbeam, and the gyroscope is fixed to the lever.

2. The lever-type underwater pile foundation horizontal bearing capacity testing device according to claim 1, characterized in that, The crossbeam is made of high-strength alloy I-beam, and its dimensions are designed according to the design bearing capacity of the test pile to ensure that the crossbeam has sufficient compressive stiffness and to prevent deformation of the crossbeam during the test loading process.

3. The lever-type underwater pile foundation horizontal bearing capacity testing device according to claim 1, characterized in that, One end of the crossbeam that is rigidly connected to the test pile is cut into an inward concave shape, with the concave arc consistent with the arc of the outer wall of the test pile. The crossbeam is temporarily welded to the outer wall of the test pile to prevent slippage at the connection between the crossbeam and the test pile during the test loading process.

4. The lever-type underwater pile foundation horizontal bearing capacity testing device according to claim 1, characterized in that, The end of the crossbeam that is rigidly connected to the test pile is welded with a hoop, and the crossbeam is fixed to the test pile through the hoop.

5. The lever-type underwater pile foundation horizontal bearing capacity testing device according to claim 1, characterized in that, The force gauge is fixed in the I-beam groove of the crossbeam and is used to measure the axial force of the crossbeam. Under quasi-static conditions, the axial force of the crossbeam is the same as the horizontal thrust applied to the test pile, so the horizontal force acting on the test pile can be monitored in real time.

6. The lever-type underwater pile foundation horizontal bearing capacity testing device according to claim 1, characterized in that, The lever is made of high-strength alloy steel plate, and the length of the steel plate is as long as possible, forming a long strip shape; the thickness of the steel plate is the same as the web thickness of the I-beam used for the crossbeam, the side of the lever is aligned with the web of the I-beam of the crossbeam and rigidly fixed, and the crossbeam and the lever are arranged at a 90° angle.

7. The lever-type underwater pile foundation horizontal bearing capacity testing device according to claim 1, characterized in that, The gyroscope is installed on the upper part of the lever near the top and is used to measure the rotation angle of the lever. The horizontal displacement of the connection point between the lever and the crossbeam is calculated using the rotation angle of the lever.

8. The lever-type underwater pile foundation horizontal bearing capacity testing device according to claim 1, characterized in that, The support structure is made of high-strength steel rods or hollow steel pipes.

9. The lever-type underwater pile foundation horizontal bearing capacity testing device according to claim 1, characterized in that, The cable is made of high-strength, high-toughness steel strand.

10. A method for testing the horizontal bearing capacity of underwater pile foundations using the lever-type underwater pile foundation horizontal bearing capacity testing device according to any one of claims 1 to 9, characterized in that, Includes the following steps: (1) Preliminary preparation: According to the project requirements, survey and select the test site, design the test plan, prefabricate the test piles, crossbeams, levers, supports and cables of the corresponding specifications, and prepare the force gauge, gyroscope and test boat; (2) On-site setup: Transport each component of the lever-type water pile foundation horizontal bearing capacity testing device to the vicinity of the designed pile location water area. First, test piles are driven. During the pile driving process, the pile body is kept vertical and the inclination is within the allowable range of the project. Then, the support is buried at a distance of 2 to 4 times the pile diameter from the test pile. The lever, the crossbeam, and the cable are connected, and the force gauge and the gyroscope are set up. (3) Start the test: By starting the test ship to tension the cable to provide the reaction force, the load is gradually applied in stages. At the same time, the axial force of the beam measured by the force gauge and the tilt angle of the lever measured by the gyroscope are recorded under each load level. (4) Follow-up work: After the test, retrieve the lever-type underwater pile foundation horizontal bearing capacity testing device, process the test data, draw the load-displacement curve, analyze the pile foundation load-displacement curve, evaluate the ultimate bearing capacity of the pile foundation, and complete the underwater pile foundation horizontal bearing capacity test.

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