Method for detecting single-pile compression bearing capacity of steel pipe inclined pile

Abstract

This invention discloses a method for testing the compressive bearing capacity of a single steel pipe inclined pile, comprising: S1, arranging two steel pipe inclined piles with the same inclination angle and opposite directions; S2, constructing a loading platform above the two steel pipe inclined piles, with a force-sharing device at the bottom of the loading platform, the force-sharing device having two thrust planes, the two thrust planes being perpendicular to the axes of the two steel pipe inclined piles; S3, setting a loading device between the two thrust planes and the pile heads of the two steel pipe inclined piles; S4, controlling the two loading devices to load synchronously, so that the two steel pipe inclined piles bear axial pressure; the horizontal component force generated by synchronous loading cancels each other out at the force-sharing device, and the resulting vertical resultant force is balanced by the reaction force provided by the loading platform; S5, collecting test data through a monitoring system to determine the compressive bearing capacity of the single steel pipe inclined pile. This invention cleverly transforms the complex stress problem that is difficult to handle in inclined pile testing into a vertical stress problem that can be solved using a mature loading platform.

Description

Technical Field

[0001] This invention relates to the field of testing technology for the bearing capacity of inclined steel pipe piles, and in particular to a method for testing the compressive bearing capacity of a single inclined steel pipe pile. Background Technology

[0002] In the field of pile foundation engineering, determining the vertical compressive bearing capacity of a single pile is a crucial design step, and the accuracy of its value directly affects the safety of the superstructure and the economy of the project. Static load testing, as the most intuitive and reliable method for testing this bearing capacity, has a well-developed technical system, including reaction devices, loading methods, and data acquisition. Standards such as the "Technical Specification for Testing Building Foundation Piles" (JGJ106-2014) provide comprehensive regulations for vertical piles. With increasing demands for adaptability to complex geological conditions in the construction engineering field, steel pipe inclined piles are widely used in foundation pit support, bridge foundations, and other engineering scenarios due to their advantages in resisting lateral displacement and optimizing foundation stress.

[0003] However, inclined steel pipe piles face significant bottlenecks in bearing capacity testing. Existing mature and reliable static load testing methods and equipment are "tailor-made" for vertical piles. Their core reaction force provision methods (such as the surcharge method and the anchor pile method) are all based on the assumption of vertical force transmission. The inclined characteristics of inclined piles fundamentally differ their stress mechanism from that of vertical piles, leading to structural incompatibility and stress mode mismatch issues when traditional static load testing equipment is used for inclined piles.

[0004] Therefore, in current engineering practice, the testing of the compressive bearing capacity of inclined piles still generally relies on empirical estimations from geological reports or indirect methods such as high-strain dynamic testing. These methods have a high degree of presumption and limited accuracy. Increasing the value too high may lead to safety hazards, while decreasing the value too low may result in unnecessary economic waste. Summary of the Invention

[0005] In view of this, the present invention proposes a method for testing the compressive bearing capacity of a single steel pipe inclined pile, which can fundamentally solve the compatibility problem between traditional static load tests and steel pipe inclined piles, and provide a direct and reliable testing method for evaluating the bearing capacity of inclined piles.

[0006] The solutions provided by this invention include:

[0007] A method for testing the compressive bearing capacity of a single steel pipe inclined pile includes the following steps:

[0008] S1. Arrange two inclined steel pipe piles with the same inclination angle and opposite directions;

[0009] S2. Construct a loading platform above the two steel pipe inclined piles. The bottom of the loading platform is equipped with a force-sharing device. The force-sharing device has two thrust planes, which are perpendicular to the axes of the two steel pipe inclined piles.

[0010] S3. A loading device is installed between the two thrust planes and the pile heads of the two steel pipe inclined piles respectively;

[0011] S4. Control the two loading devices to load synchronously so that the two steel pipe inclined piles bear axial pressure; the horizontal component force generated by the synchronous loading cancels each other out at the component force device, and the resulting vertical resultant force is balanced by the reaction force provided by the surcharge platform.

[0012] S5. Collect test data through the monitoring system, and determine the single pile compressive bearing capacity of the steel pipe inclined pile based on the test data.

[0013] As a further optional solution, the stacking platform includes a steel base and multiple counterweights stacked on the steel base, which are removed after the test is completed.

[0014] As a further alternative, the force-distributing device is a horizontally placed triangular prism steel structure filled with cement slurry.

[0015] As a further alternative, the force-sharing device is welded from steel plates and has internal stiffening ribs.

[0016] As a further optional option, the two loading devices are hydraulic jacks of the same specification.

[0017] As a further optional solution, a fixed support is welded to the pile head of the steel pipe inclined pile. The fixed support is used to fix the loading device to ensure that the resultant force center of the loading device coincides with the pile axis.

[0018] As a further optional solution, the fixed support includes a pile head plate, an arc-shaped support plate for supporting the loading device, and multiple vertical stiffening ribs; the pile head plate is welded to the end of the inclined steel pipe pile; the arc-shaped support plate is welded to the pile head plate; and the vertical stiffening ribs are vertically welded between the pile head plate and the inclined steel pipe pile.

[0019] As a further optional solution, at least four vertical stiffening ribs are provided.

[0020] As a further optional feature, the monitoring system includes a displacement sensor for monitoring pile top settlement and a strain sensor for monitoring pile body strain.

[0021] Compared with existing technologies, the method for testing the compressive bearing capacity of single steel pipe inclined piles in this application has at least the following advantages:

[0022] 1. A groundbreaking method for direct static load testing of inclined piles: This method successfully solves the fundamental problem of incompatibility between traditional vertical pile static load testing systems and inclined piles in terms of structure and stress patterns. Through an innovative design combining "symmetrical arrangement of inclined piles" with "force distribution devices," the complex stress problems that are difficult to handle in inclined pile testing are cleverly transformed into vertical stress problems that can be solved using mature surcharge platforms. This provides, for the first time, a dedicated method for direct and reliable static load testing of inclined piles.

[0023] 2. The test results are direct, accurate and reliable: This method directly measures the compressive ultimate bearing capacity of the steel pipe inclined pile through static load test. The data obtained truly reflects the actual working conditions under the interaction between the pile and the soil. The results are far more accurate and reliable than indirect methods such as geological report experience estimation and high strain dynamic testing. It provides an authoritative basis for engineering design, greatly ensures engineering safety and avoids economic risks caused by improper bearing capacity values.

[0024] 3. Efficient force balance and safe, stable testing process: Symmetrical synchronous loading is achieved using two inclined piles with the same inclination angle but opposite directions, ensuring that the harmful horizontal components generated by the two jacks cancel each other out within the force-reacting device. This design eliminates the need for additional horizontal reaction devices, removing the risk of the testing device becoming unstable due to the enormous horizontal force, and ensuring the safety of the entire testing process and the stability of the data.

[0025] 4. Simple device, convenient operation, and high cost-effectiveness: The advantage of this method lies in its ingenuity rather than its complexity. It maximizes the reuse of the technically mature and clearly defined vertical pile surcharge reaction system, adding only a simple force-sharing device to achieve the function. The device is easy to set up, and the surcharge platform can be dismantled and reused after the test. The overall cost is low, making it highly valuable for promotion.

[0026] 5. Compatible with standards and highly scalable: The loading, data acquisition and judgment criteria of this method can all follow the principles of existing standards (such as JGJ106-2014), which is convenient for engineering technicians to understand and implement, and has broad application prospects. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the implementation structure of a method for detecting the compressive bearing capacity of a single steel pipe inclined pile according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram (perspective) of the force-sharing device according to an embodiment of the present invention.

[0029] Figure 3 yes Figure 2 Schematic diagram of the cross section of AA;

[0030] Figure 4 yes Figure 2 Cross-sectional view of BB;

[0031] Figure 5 This is a schematic diagram of the structure of the fixed support set on the inclined steel pipe pile according to an embodiment of the present invention;

[0032] In the diagram: 1. Steel pipe inclined pile;

[0033] 2. Stacking platform; 21. Steel base; 22. Counterweight;

[0034] 3. Force distribution device; 31. Stiffening rib; 311. Grouting hole;

[0035] 4. Loading device;

[0036] 5. Fixed support; 51. Pile head plate; 52. Vertical stiffening rib; 53. Arc-shaped support plate. Detailed Implementation

[0037] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0038] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "vertical", "horizontal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0039] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0040] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that they are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0041] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0042] An embodiment of the present invention illustrates a method for testing the compressive bearing capacity of a single steel pipe inclined pile. The relevant structural details in the implementation process can be found in the following reference. Figure 1-5 The method includes the following steps:

[0043] Step S1: Arrange two inclined steel pipe piles 1 with the same inclination angle and opposite directions;

[0044] In this context, "same inclination angle" means that the angles between the two inclined steel pipe piles 1 and the vertical direction are identical; in this embodiment, this angle is set to 30°-60°. "Opposite directions" means that the inclination directions of the two piles are opposite. The purpose is to construct a foundation structure that cancels out the horizontal force components. By arranging the piles with the same inclination angle and opposite directions, the horizontal force components generated by the two piles during subsequent loading are equal in magnitude and opposite in direction, fundamentally solving the problem of unbalanced horizontal force components in inclined piles during traditional static load tests, and providing structural conditions for the stable conduct of inclined pile static load tests.

[0045] Step S2: Construct a loading platform 2 above the two steel pipe inclined piles 1. The bottom of the loading platform 2 is provided with a force distribution device 3. The force distribution device 3 has two thrust planes, which are perpendicular to the axes of the two steel pipe inclined piles 1 respectively.

[0046] The surcharge platform 2 is constructed to provide the reaction force required for the test. The vertical resultant force generated by the load is balanced by the surcharge weight of the bearing platform to meet the reaction force requirements of the static load test. The purpose of setting the force distribution device 3 is to establish a precise interface for load transfer. Its two thrust planes are designed to be perpendicular to the pile axis to ensure that the load is transferred along the pile axis and avoid load deviation that would cause test data distortion.

[0047] Step S3: A loading device 4 is installed between the two thrust planes and the pile heads of the two steel pipe inclined piles 1 respectively;

[0048] Among them, the loading device 4, as the force output component, needs to be located between the force distribution device 3 and the pile head to ensure that the reaction force of the force distribution device 3 can be converted into axial pressure on the pile body, thus ensuring the controllability of load application.

[0049] Step S4: Control the two loading devices 4 to load synchronously so that the two steel pipe inclined piles 1 bear axial pressure; the horizontal component force generated by the synchronous loading cancels each other out at the force component device 3, and the resulting vertical resultant force is balanced by the reaction force provided by the surcharge platform;

[0050] Among them, synchronous loading can ensure that the loads of the two piles grow synchronously, so that the horizontal components always cancel each other out and eliminate the interference of forces in the horizontal direction; at the same time, the vertical resultant force is transmitted to the surcharge platform 2 through the main beam, and forms a balance with the platform reaction force, ensuring the overall stability of the test system and avoiding instability during the loading process.

[0051] Step S5: Collect test data through the monitoring system, and determine the single pile compressive bearing capacity of the steel pipe inclined pile 1 based on the test data.

[0052] In summary, the method of this embodiment can successfully solve the fundamental problem of "incompatibility" between traditional vertical pile static load test systems and inclined piles in terms of structure and stress mode. Through the innovative design of combining "symmetrical arrangement of inclined piles" with "force component device 3", the complex stress problem that is difficult to handle in inclined pile testing is cleverly transformed into a vertical stress problem that can be solved using the mature surcharge platform 2.

[0053] This method directly measures the compressive ultimate bearing capacity of the steel pipe inclined pile 1 through static load test. The obtained data truly reflects the actual working conditions under the interaction between the pile and the soil. The results are far more accurate and reliable than indirect methods such as geological report experience estimation and high strain dynamic testing. It provides an authoritative basis for engineering design, greatly ensures engineering safety, and avoids economic risks caused by improper bearing capacity values.

[0054] By using two inclined piles with the same inclination angle but opposite directions for symmetrical synchronous loading, the harmful horizontal components generated by the two jacks cancel each other out within the force-reacting device 3. This design eliminates the need for additional horizontal reaction devices, thus removing the risk of the test device becoming unstable due to the enormous horizontal force, and ensuring the safety of the entire test process and the stability of the data.

[0055] The advantage of this method lies in its ingenuity rather than its complexity. It makes maximum use of the technically mature and well-defined vertical pile surcharge reaction system, requiring only the addition of a simple force-sharing device 3 to achieve the desired function. The device is easy to assemble, and the surcharge platform 2 can be disassembled and reused after the test, resulting in low overall cost and significant potential for widespread adoption.

[0056] The loading, data acquisition, and judgment criteria of this method can all follow the principles of existing specifications (such as JGJ106-2014), which makes it easy for engineering technicians to understand and implement, and has broad application prospects.

[0057] In some embodiments, such as Figure 1 As shown, the stacking platform 2 includes a steel base 21 and multiple counterweights 22 stacked on the steel base 21, which are removed after the test is completed.

[0058] The steel base 21 provides a solid, flat, and uniformly distributed rigid foundation for the entire surcharge platform 2. This steel base 21 is typically a lattice platform constructed by welding or splicing main and secondary beams of structural steel (such as I-beams and H-beams). Its dimensions and structure can be calculated according to actual needs to ensure it can withstand the weight of all the counterweights 22 above and the vertical reaction forces generated during the test without excessive deformation. Its function is to prevent the counterweights 22 from directly pressing on the ground or pile foundation, ensuring the stability and reliability of reaction force transmission.

[0059] The counterweight 22 can be made of stone or reinforced concrete. By stacking multiple counterweights 22 onto the steel base 21, the sufficiently large reverse balancing force required for the test can be flexibly adjusted.

[0060] In some embodiments, such as Figure 2-4 As shown, the force-distributing device 3 is a horizontally placed triangular prism steel structure, which is filled with cement slurry.

[0061] Among them, such as Figure 2 As shown, the cross-section of the force-distributing device 3 is an inverted triangle, forming two thrust planes at its lower angle. This results in high structural stability and strong resistance to deformation. The interior of the force-distributing device 3 is filled with cement to enhance its overall rigidity and local pressure-bearing capacity.

[0062] Preferably, the force-distributing device 3 is welded from steel plates, and stiffening ribs 31 are provided inside. Wherein, for example... Figure 3 and Figure 4 As shown, the stiffening rib plate 31 is provided with grouting holes 311, which makes it easy to fill the interior of the force distribution device 3 when cement grout is injected, so as to ensure that the cement grout and the steel structure are completely bonded and share the load.

[0063] In some embodiments, the two loading devices 4 are hydraulic jacks of the same specification. These hydraulic jacks are the loading devices 4 used in conventional static load tests. The two hydraulic jacks can be supplied with oil by the same oil pump system, ensuring that their output and lifting speed remain synchronized at all times. This guarantees that the loads applied to the two inclined piles are always equal, achieving complete cancellation of horizontal components and correct superposition of vertical resultant forces.

[0064] In some embodiments, such as Figure 1 and Figure 5 As shown, a fixed support 5 is welded to the pile head of the inclined steel pipe pile 1. The fixed support 5 is used to fix the loading device 4 to ensure that the resultant force center of the loading device 4 coincides with the pile axis. In this way, it can avoid the loading device 4 and the inclined steel pipe pile 1 being out of axis, which would lead to eccentric load. Eccentric load will generate additional bending moment in the pile body, which will seriously affect the accuracy of the test data and may even cause the test pile to fail due to bending moment before reaching the true compressive bearing capacity.

[0065] Specifically, the fixed support 5 includes a pile head plate 51, an arc-shaped support plate 53 for supporting the loading device 4, and multiple vertical stiffening ribs 52; the pile head plate 51 is welded to the end of the steel pipe inclined pile 1; the arc-shaped support plate 53 is welded to the pile head plate 51; and the vertical stiffening ribs 52 are vertically welded between the pile head plate 51 and the steel pipe inclined pile 1. Preferably, at least four vertical stiffening ribs 52 are provided.

[0066] Among them, the pile head plate 51 provides the foundation plane, the arc-shaped support plate 53 defines the position of the jack, and the vertical stiffening rib 52 ensures the connection strength. The three work together to ensure the accurate implementation of axial loading.

[0067] In some embodiments, the monitoring system (not shown) includes a displacement sensor for monitoring pile top settlement and a strain sensor for monitoring pile body strain.

[0068] The specific implementation details of the monitoring system, including but not limited to the selection criteria for strain sensors and displacement sensors (such as accuracy level and range requirements), the placement and fixing methods of sensors on the pile body, the frequency of data acquisition and recording requirements, and the criteria for judging the validity of data, can be found in the technical provisions of the "Technical Specification for Testing of Building Foundation Piles" (JGJ 106-2014), and therefore will not be elaborated upon here.

[0069] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A method for testing the compressive bearing capacity of a single steel pipe inclined pile, characterized in that, Includes the following steps: S1. Arrange two inclined steel pipe piles with the same inclination angle and opposite directions; S2. Construct a loading platform above the two steel pipe inclined piles. The bottom of the loading platform is equipped with a force-sharing device. The force-sharing device has two thrust planes, which are perpendicular to the axes of the two steel pipe inclined piles. S3. A loading device is installed between the two thrust planes and the pile heads of the two steel pipe inclined piles respectively; S4. Control the two loading devices to load synchronously so that the two steel pipe inclined piles bear axial pressure; the horizontal component force generated by the synchronous loading cancels each other out at the component force device, and the resulting vertical resultant force is balanced by the reaction force provided by the surcharge platform. S5. Collect test data through the monitoring system, and determine the single pile compressive bearing capacity of the steel pipe inclined pile based on the test data; The two loading devices are hydraulic jacks of the same specification; A fixed support is welded to the pile head of the steel pipe inclined pile. The fixed support is used to fix the loading device to ensure that the resultant force center of the loading device coincides with the pile axis. The fixed support includes a pile head plate, an arc-shaped support plate for supporting the loading device, and multiple vertical stiffening ribs; the pile head plate is welded to the end of the inclined steel pipe pile; the arc-shaped support plate is welded to the pile head plate; the vertical stiffening ribs are vertically welded between the pile head plate and the inclined steel pipe pile; The vertical stiffening ribs are provided in at least 4 pieces.

2. The method for testing the compressive bearing capacity of a single steel pipe inclined pile according to claim 1, characterized in that: The loading platform includes a steel base and multiple counterweights stacked on the steel base, which are removed after the test is completed.

3. The method for testing the compressive bearing capacity of a single steel pipe inclined pile according to claim 1, characterized in that: The force-shaping device is a horizontally placed triangular prism steel structure, which is filled with cement slurry.

4. The method for testing the compressive bearing capacity of a single steel pipe inclined pile according to claim 3, characterized in that: The force-sharing device is welded from steel plates and has internal stiffening ribs.

5. The method for testing the compressive bearing capacity of a single steel pipe inclined pile according to claim 1, characterized in that: The monitoring system includes a displacement sensor for monitoring pile top settlement and a strain sensor for monitoring pile body strain.

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