Reconfigurable model pile and test system for multi-standard pile foundation bearing capacity comparison test

Abstract

The application discloses a reconfigurable model pile for multi-standard pile foundation bearing capacity comparison test and a test system, and relates to the technical field of geotechnical engineering model test. The model pile comprises a core pile, a plurality of groups of replaceable side friction resistance simulation sleeves and a replaceable pile end. The core pile is provided with an annular clamping groove outside and a quick-change interface at the bottom; the sleeve is movably connected by two half cylinders, the inner wall is provided with a clamping ring matched with the annular clamping groove, and the outer surfaces of different sleeves are different in features to simulate different standard side friction resistances; the pile end is connected through the quick-change interface and is various in geometric shapes to simulate different end bearing forms. Strain gauges are attached to the surface of the core pile, and a soil pressure cell is embedded in the pile end. The test system comprises a transparent soil box, a vertical loading frame, a displacement sensor and a data acquisition instrument. The application realizes direct comparison test of different standard pile foundation bearing capacities under the same physical model through modular design, and provides high-reliability physical test evidence for theoretical research and standard revision.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering model testing technology, specifically to a reconfigurable model pile and testing system for comparative testing of bearing capacity of multi-standard pile foundations. Background Technology

[0002] In the field of pile foundation engineering, different industry standards exhibit significant differences in the calculation methods and parameter selection logic for pile foundation bearing capacity. Their specifications for pile side skin friction, end resistance, and pile group effect coefficients also differ. Currently, comparative studies on the bearing capacity of pile foundations under multiple standards mainly rely on theoretical calculations or numerical simulations. While existing research has addressed the differences in pile foundation bearing capacity calculation results under different standard systems, most studies remain at the parameter level, lacking experimental methods capable of physically reproducing the parameter selection logic of different standards.

[0003] There are already some pile foundation model test devices in the prior art. For example, Chinese utility model patent CN222065597U (published on November 26, 2024) discloses a multi-functional multi-size pile foundation model test box, which can realize various loading conditions by adjusting the volume of the model box and setting horizontal and vertical pressure mechanisms.

[0004] For example, Chinese invention patent application CN122280218A (published on June 26, 2026) discloses a model test detection system and method for the pre-test stage of pile foundation testing using the fast load method, which realizes long pulse load input through load and buffer device.

[0005] However, these existing devices all use model piles with fixed shapes, making it impossible to simulate the different specifications of surface friction characteristics, end bearing forms, and size effects of different standards by changing local components. If the same model pile with a fixed surface roughness is used to verify different standards, the results cannot distinguish the influence of the parameter value logic of the standard itself and the variability of the strata, and it is also difficult to quantitatively reveal the contribution of the differences in the value logic of side friction and end resistance between different standards to the total bearing capacity.

[0006] Therefore, there is an urgent need for a model pile and test system that can simulate different standard design parameter genes through modular reconstruction, so as to provide a reliable technical means for physical comparison tests of the bearing capacity of multi-standard pile foundations. Summary of the Invention

[0007] To address the above technical problems, this invention provides a reconfigurable model pile for a multi-standard pile foundation bearing capacity comparison test, comprising: The core pile has an annular groove on the outside, is hollow inside and has a pre-tightening force adjusting screw, and is fixedly connected to a quick-change interface at the bottom. A sleeve, the sleeve having a hollow structure, with a retaining ring fixedly connected to the inner wall, the retaining ring and the annular groove being correspondingly arranged, the sleeve comprising two semi-cylinders, the semi-cylinders being detachably fixedly connected to each other; The pile end is movably connected to the quick-change interface.

[0008] The reconfigurable model pile scheme in this invention, through the modular design of the core pile, replaceable sleeve, and replaceable pile end, enables direct comparative testing of the bearing capacity of pile foundations meeting different industry standards under the same physical model conditions. The sleeve adopts a semi-open structure with two semi-cylindrical connections, allowing for rapid installation and replacement without disassembling the core pile, significantly shortening the model reconstruction time between different standard tests. The quick-change interface enables tool-free rapid assembly and disassembly of the pile end. Different sets of sleeves have different external surface features to simulate the side friction characteristics under different standards; different pile end shapes have different geometries to simulate the different standards' definitions of end bearing forms. Built-in strain gauges and micro earth pressure cells enable simultaneous and accurate measurement of the pile's axial force distribution and end resistance.

[0009] As is common knowledge in the field, core piles are made of high-strength steel to ensure foundation rigidity. Their cross-sectional shape is typically cylindrical, but can also be other polyhedral shapes symmetrical about the vertical axis. Unless specifically specified, the cross-sectional shape of the core pile is not particularly limited in this invention. The wall thickness of the sleeve can be selected according to the required simulated pile diameter. Different sets of sleeves can have the same wall thickness to ensure consistent outer diameter, or they can have different wall thicknesses to simulate different pile diameter conditions. Unless specifically specified, the wall thickness specification of the sleeve is not particularly limited in this invention. The movable connection between the semi-cylinders can be any of the following: snap-fit ​​connection, bolt connection, or hinge connection. Those skilled in the art can choose the appropriate connection method according to actual needs, which will not be elaborated here.

[0010] Furthermore, the core pile has an axial through hole inside, through which a preload adjusting screw passes. Both ends of the screw are locked with nuts. By tightening or loosening the nuts, the preload applied to the core pile can be precisely adjusted, thereby changing the overall bending stiffness of the model pile to match the implicit assumptions about the modulus of the pile material in different standard designs.

[0011] In this design, the preload adjusting screw is inserted inside the core pile, and its two ends are locked to the two end faces of the core pile by nuts. Specifically, the nuts are positioned on the two end faces of the core pile (top and bottom faces). That is, after the preload adjusting screw is inserted into the axial through hole inside the core pile, its upper end extends out of the top end face of the core pile and is fixed with a locking nut, while its lower end extends out of the bottom end face of the core pile (near the quick-change interface) and is fixed with another locking nut. Rotating these two nuts compresses the end faces of the core pile, thereby applying axial preload to the pile body.

[0012] The preload adjusting screw is an independent preload system. The screw itself does not directly participate in bearing or transmitting force, but changes the stiffness characteristics of the pile body by applying axial preload to the core pile, so that the same core pile can simulate the different requirements of different industry standards for the modulus of the pile body material.

[0013] Furthermore, several sets of annular grooves are horizontally arranged along the vertical axis of the core pile. By setting multiple sets of annular grooves, on the one hand, the sleeve can be engaged at different height positions along the axial direction of the core pile, improving the connection stability between the sleeve and the core pile; on the other hand, the multiple groove structure gives the sleeve multiple constraint points in the axial direction, which can effectively prevent the sleeve from axially moving when subjected to vertical loads, ensuring the reliability of the side friction resistance transmission path.

[0014] Furthermore, the number of retaining rings and the number of annular grooves are the same, and their cross-sectional shapes interlock. This matching design of quantity and cross-section ensures that each set of retaining rings can be engaged in the corresponding set of annular grooves, forming a multi-layered axial locking structure. This makes the sleeve and the core pile form a reliable whole in the axial direction, avoiding relative slippage between the sleeve and the core pile during loading and ensuring the accuracy of the test data.

[0015] Furthermore, the retaining ring has a T-shaped cross-section, and the annular groove has a T-shaped cross-section, allowing the retaining ring to engage with the annular groove. The T-shaped retaining ring and the T-shaped annular groove cooperate with each other, forming a cross-sectional locking structure after the retaining ring engages with the annular groove—the flange portion of the T-shape is embedded in the groove, and the neck passes through the groove opening, forming a reliable constraint in the radial direction. This prevents the sleeve from detaching from the core pile under vertical loads and also achieves the dual functions of axial positioning and anti-rotation of the sleeve on the core pile. The structure is simple and the connection is reliable.

[0016] Furthermore, a positioning groove is formed on the outside of the core pile, and the positioning groove is arranged parallel to the vertical axis. A positioning pin is fixedly connected to the inner wall of the sleeve, and the positioning pin is positioned corresponding to the positioning groove. The positioning groove allows the sleeve to slide in along a predetermined direction during installation, avoiding deflection of the sleeve during installation and ensuring that the relative orientation of the sleeve and the core pile remains consistent after each installation. This eliminates systematic errors introduced by changes in installation orientation and improves the repeatability of multi-standard comparative tests.

[0017] Furthermore, the number of positioning slots is two, and they are arranged symmetrically around the vertical axis of the core pile.

[0018] Furthermore, strain gauges are attached to the outer surface of the core pile, with the annular grooves and strain gauges evenly spaced apart. By axially offsetting the annular grooves and strain gauges, the groove structure avoids occupying and interfering with the strain gauge bonding area, ensuring that the strain gauges can be firmly attached to the flat core pile surface and obtain accurate pile strain data. As is common knowledge in the art, the spacing and number of strain gauges need to be determined according to the required axial force distribution measurement accuracy for the test. The strain gauge layout scheme can be adjusted accordingly for different test purposes. Unless specifically limited, this invention does not impose a particular limitation on the specific number of strain gauges.

[0019] Furthermore, the outer surface of the sleeve is a smooth surface. Sleeves with smooth surfaces are used to simulate standard operating conditions where side friction is neglected or extremely low, such as the conservative design scenario in some industry standards where side friction is not considered for specific soil layers. The smooth surface provides a lower bound reference point for the value of side friction, facilitating comparison of test results with sleeves of other roughness surfaces and quantitatively revealing the contribution of differences in side friction values ​​to the total bearing capacity.

[0020] Furthermore, the outer surface of the sleeve is provided with irregularities, which can be one or more of the following: transverse corrugations, dotted protrusions, and detachable elastic friction plates. Transverse corrugations are used to simulate standards with higher values ​​for the side friction resistance of cohesive soil; their shape and spacing can be designed according to the distribution characteristics of the side friction resistance of cohesive soil. Dotted protrusions are used to simulate the side friction resistance characteristics in dense sand; the spacing and height of the protrusions can be adjusted according to the particle size distribution of the sand. The surface roughness of the detachable elastic friction plate is determined by calculation using the effective stress method and is used to simulate the side resistance characteristics in the American standard AASHTO. The irregularities on the outer surface of the sleeve allow the same core pile to simulate different standards for the differentiated definition of side friction resistance by changing different sleeves. The specific dimensions, distribution density, and other parameters of the irregularities can be adapted and adjusted according to the soil type and standard specifications to be simulated. Those skilled in the art can determine suitable values ​​through a limited number of tests, and will not be elaborated upon here.

[0021] Furthermore, the number of core piles is one, and the number of sleeves is two to six. This scheme of configuring one core pile with multiple sets of sleeves allows for replacement of only the sleeves during testing, without needing to replace the core pile itself. This ensures that the stiffness conditions of the core pile remain consistent across different tests and covers the side friction simulation requirements of various industry standards. The number of sleeves is chosen to cover the main standard types while controlling manufacturing costs; typically, four sets of sleeves are sufficient to cover most mainstream industry standards. Of course, the number of sleeve sets can be increased or decreased according to the actual number of standards to be compared, and is not strictly limited to the above range.

[0022] Furthermore, the number of pile ends is two to four. The configuration of multiple pile ends allows a single model pile to simulate the bearing characteristics of pure friction piles, end-bearing piles, and piles under different end-resistance size effects. The number of ends covers the main end-bearing forms while also considering manufacturing costs. The specific specifications of the pile ends can be further subdivided according to actual needs. For example, the cone angle of the conical bottom can be set to different angles such as 60° and 90° according to different standards for end-resistance correction coefficients. The diameter of the enlarged base can be set in multiple increments according to the needs of size effect research. Those skilled in the art can design flexibly according to the experimental plan, which will not be elaborated here.

[0023] Furthermore, the quick-change interface has a slot at its bottom, and the pile end has a hook with a locking head at its top. The quick-change interface and the pile end are connected by a snap-fit ​​connection. This snap-fit ​​connection structure enables quick assembly and disassembly of the pile end—when the hook head engages with the slot, it forms an axial lock, ensuring that the pile end will not detach from the bottom of the core pile when subjected to pile end resistance. When the end needs to be replaced, the lock can be released by pressing or rotating the hook. The entire process does not require special tools, significantly improving the switching efficiency between tests of different end bearing forms. The specific structural form of the snap-fit ​​connection can be any of a rotary snap-fit, a press snap-fit, or an elastic snap-fit. Those skilled in the art can choose the appropriate implementation method as needed, which will not be elaborated here.

[0024] Furthermore, a miniature earth pressure cell is installed on the top of the hook. Installing the miniature earth pressure cell on the top of the hook, i.e., the uppermost end face of the pile tip, ensures that the pressure cell is positioned precisely on the force transmission path between the pile tip and the bottom of the core pile after installation. This allows for direct measurement of the earth pressure transmitted to the pile tip. The measured data is a direct physical quantity of the pile tip resistance, avoiding the accumulation of errors introduced when indirectly calculating the tip resistance through the axial force of the pile body, and significantly improving the accuracy of pile tip resistance measurement.

[0025] Furthermore, the pile end also includes a chassis, which is positioned below the hook.

[0026] Furthermore, the chassis shape includes: a flat bottom, a conical bottom, and an enlarged chassis bottom with adjustable diameter. The flat bottom is used to simulate the end-bearing conditions of a pure friction pile, providing a benchmark reference point for end resistance values; the conical bottom is used to simulate an end-bearing pile, and its cone angle can be selected according to different standards for the size effect correction coefficient of pile end resistance; the enlarged chassis bottom has an adjustable diameter structure, and by replacing enlarged chassis of different diameters, the influence of the end resistance size effect coefficient on bearing capacity can be quantitatively studied. The above three chassis shapes basically cover the definition methods of end-bearing forms in mainstream industry standards. The bottom surface of the chassis can be roughened or equipped with an anti-slip structure to improve the stability and repeatability of end resistance testing. Those skilled in the art can make corresponding settings according to specific test requirements, which will not be elaborated here.

[0027] This invention also provides a test system for a reconfigurable model pile for comparative testing of bearing capacity of multi-standard pile foundations, comprising: A transparent soil box, the inner cavity of which is filled with test soil; The reconfigurable model pile is vertically embedded inside the test soil. A vertical loading frame is fixedly mounted on top of a transparent soil box. The loading end of the vertical loading frame is coaxially abutted against the top surface of the reconfigurable model pile. It should be noted that the loading end acts directly on the top surface of the core pile, not on the screw. There is no direct force transmission relationship between the screw and the loading end. A displacement sensor, wherein the detection end of the displacement sensor is fixedly connected to the top surface of the reconfigurable model pile. The data acquisition device is installed on the side wall of the transparent soil box, and its signal input terminal is electrically connected to the signal output terminals of the strain gauge, the micro earth pressure cell, and the displacement sensor of the reconfigurable model pile, respectively.

[0028] Furthermore, the transparent soil box is a box structure made of highly transparent acrylic material. The horizontal dimension of the inner cavity of the transparent soil box is larger than the range of influence of soil sliding on the pile body of the reconfigurable model pile. The loading axis of the vertical loading frame coincides with the central axis of the reconfigurable model pile. The measurement axis of the displacement sensor is parallel to the central axis of the reconfigurable model pile. The measurement range of the displacement sensor covers the entire range of pile top settlement of the reconfigurable model pile.

[0029] Furthermore, the data acquisition instrument has a built-in multi-channel synchronous sampling unit. The sampling channels of the multi-channel synchronous sampling unit correspond one-to-one with the strain gauges, miniature earth pressure cells, and displacement sensors. The data acquisition instrument synchronously acquires, stores, and outputs the sampling data from all channels in real time. The sampling frequency of the data acquisition instrument is matched with the loading step size of the vertical loading frame.

[0030] This invention also provides a method for using a reconfigurable model pile test system for comparative testing of bearing capacity of multi-standard pile foundations, comprising the following steps: Step S1, Model Pile Reconstruction: According to the industry standard to be simulated, select a set of replaceable side friction simulation sleeves with different external surface characteristics that corresponds to the industry standard. By cooperating with the annular groove on the core pile, the selected sleeve is quickly installed on the core pile. At the same time, according to the definition of the end bearing type in the industry standard, select the corresponding pile end head from a variety of replaceable pile end heads and connect it to the bottom of the core pile through the quick-change interface to complete the reconstruction of the model pile. Step S2: Conduct a static load test: Place the reconstructed reconfigurable model pile in the predetermined position of the transparent soil box, and start the vertical loading frame to apply a load to the top of the pile; Step S3: Data Acquisition: During the loading process, the axial force distribution of each section of the pile body is measured in real time by strain gauges attached to the surface of the core pile, the pile end resistance is directly measured by a miniature earth pressure cell embedded in the pile end, and the pile top settlement is recorded by a displacement sensor. All data are transmitted to the data acquisition instrument in real time. Step S4, Data Processing: By processing the axial force data, the distribution and utilization value of the pile side friction are calculated, and the load-settlement Qs curve is generated; Step S5: Data Comparison. Under the same soil box and soil layer conditions, repeat steps S1 to S4 to obtain multiple load-settlement Qs curves corresponding to different standards, quantitatively revealing the impact of the differences in the logic of side friction and end resistance values ​​between different standards on the total bearing capacity.

[0031] Compared with existing technologies, the advantages and effects of this application are as follows: 1. This application, through the modular design of core piles, replaceable side friction sleeves, and replaceable pile ends, enables direct comparative tests of the bearing capacity of pile foundations of different industry standards under the same physical model conditions. This reduces the interference caused by factors such as stratum variability and soil heterogeneity in traditional methods, ensuring that the measured bearing capacity differences are purely due to the parameter value logic of different standards, and providing highly reliable physical test evidence for theoretical research and standard revision.

[0032] 2. This application makes the pile stiffness adjustable by setting the preload adjusting screw, which can match the implicit assumptions about the pile material modulus in different standard designs, and further expands the applicability of the model pile.

[0033] 3. The cooperation between the positioning groove and the positioning pin in this application ensures the precise circumferential positioning of the sleeve and the core pile, prevents relative rotation after the sleeve is installed, and ensures the accuracy of the strain gauge measurement orientation.

[0034] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the preferred embodiments of this application are described in detail below with reference to the accompanying drawings.

[0035] The above and other objects, advantages and features of this application will become more apparent to those skilled in the art from the following detailed description of specific embodiments in conjunction with the accompanying drawings. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0037] in: Figure 1 This is a structural breakdown diagram of the reconfigurable model pile; Figure 2 A schematic diagram of the core pile of a reconfigurable model pile; Figure 3 A schematic diagram of node A of the sleeve for a reconfigurable model pile; Figure 4 A schematic diagram of the structure of various sleeves for reconfigurable model piles; Figure 5 This is a schematic diagram of the reconfigurable model pile test system.

[0038] Explanation of reference numerals in the attached drawings: 1. Core pile; 2. Annular groove; 3. Quick-change interface; 4. Sleeve; 5. Snap ring; 6. Pile end; 7. Strain gauge; 8. Miniature earth pressure cell; 9. Preload adjusting screw; 10. Transparent soil box; 11. Vertical loading frame; 12. Displacement sensor; 13. Data acquisition instrument; 14. Positioning groove; 15. Positioning pin; 16. Hook; 17. Chassis; 18. Loading end. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. In the following description, specific details such as specific configurations and components are provided merely to help fully understand the embodiments of this application. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. In addition, for clarity and brevity, descriptions of known functions and structures are omitted in the embodiments.

[0040] It should be understood that the phrase "an embodiment" or "this embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "an embodiment" or "this embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0041] Furthermore, reference numerals and / or letters may be repeated in different examples within this application. Such repetition is for the purpose of simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or settings discussed.

[0042] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" describes another type of relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the related objects before and after it have an "or" relationship.

[0043] In this article, the term "at least one" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, "at least one of A and B" can mean: A exists alone, A and B exist simultaneously, or B exists alone.

[0044] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion.

[0045] Example 1 This embodiment introduces a reconfigurable model pile for a comparative test of the bearing capacity of multiple standard pile foundations. Please refer to... Figure 1-3 As shown, Figure 1 This is a structural breakdown diagram of a reconfigurable model pile. Figure 2 This is a schematic diagram of the core pile of a reconfigurable model pile. Figure 3 This is a schematic diagram of node A of the sleeve of a reconfigurable model pile.

[0046] A reconfigurable model pile for a multi-standard pile foundation bearing capacity comparison test includes: Core pile 1, the core pile 1 has an annular groove 2 on the outside, is hollow inside and has a pre-tightening force adjusting screw 9, and is fixedly connected to a quick-change interface 3 at the bottom; Sleeve 4, which is a hollow structure, with a retaining ring 5 fixedly connected to its inner wall. The retaining ring 5 and the annular groove 2 are correspondingly arranged. The sleeve 4 includes two semi-cylinders, which are bolted together. The pile end 6 is snap-fitted to the quick-change interface 3.

[0047] The annular groove 2 is arranged in several groups horizontally along the vertical axis of the core pile 1.

[0048] The number of retaining rings 5 ​​and the number of annular grooves 2 are the same, and their cross-sectional shapes interlock.

[0049] The retaining ring 5 has a T-shaped cross-section, and the annular groove 2 has a T-shaped cross-section. The retaining ring 5 can be inserted into the annular groove 2.

[0050] The core pile 1 has a positioning groove 14 on its outside, and the positioning groove 14 is set parallel to the vertical axis.

[0051] The inner wall of the sleeve 4 is fixedly connected with a positioning pin 15, and the positioning pin 15 is positioned corresponding to the positioning groove 14.

[0052] The number of positioning grooves 14 is two, and they are arranged symmetrically around the vertical axis of the core pile 1.

[0053] The outer surface of the core pile 1 is also fitted with strain gauges 7, and the annular groove 2 is spaced apart from the strain gauges 7.

[0054] The outer surface of the sleeve 4 is a smooth surface.

[0055] The core pile 1 is made of high-strength steel.

[0056] A miniature earth pressure box 8 is installed on the top of the pile end 6.

[0057] The technical advantages of this embodiment are as follows: The T-shaped interlocking mechanism between the outer annular groove of the core pile and the inner wall retaining ring of the sleeve achieves reliable axial positioning and anti-rotation locking of the sleeve on the core pile, ensuring that the sleeve will not slip or rotate during vertical loading, thus guaranteeing the stability of the side friction resistance transmission path. The sleeve adopts a semi-open structure composed of two movable semi-cylinders, allowing for rapid installation and replacement without disassembling the core pile, significantly shortening the model reconstruction time between different standard tests. The symmetrical arrangement of the positioning groove and positioning pin ensures precise circumferential positioning of the sleeve and the core pile, ensuring that the strain gauges attached to the core pile surface always maintain the preset measurement orientation. The preload adjustment screw makes the overall bending stiffness of the pile adjustable, matching the implicit assumptions of different standards regarding the pile material modulus. The miniature earth pressure cell is embedded in the top of the pile end, enabling direct measurement of the pile end resistance and avoiding errors caused by indirect calculations. This embodiment provides a structurally stable, easily reconstructable, and accurately measured basic platform for multi-standard bearing capacity comparison tests.

[0058] Example 2 Based on Example 1, this example discloses a further design of a reconfigurable model pile for a multi-standard pile foundation bearing capacity comparison test. Please refer to... Figure 4 As shown, Figure 4 This is a schematic diagram of the structure of various sleeves for reconfigurable model piles.

[0059] Furthermore, the outer surface of the sleeve 4 is provided with concave and convex shapes, which are one or more of the following: transverse corrugations, dotted protrusions, and detachable elastic friction pads.

[0060] Furthermore, the number of core piles 1 is one, and the number of sleeves 4 is two to six.

[0061] Furthermore, the number of pile ends 6 is two to four.

[0062] Furthermore, the quick-change interface 3 is provided with a slot at the bottom, and the pile end 6 is provided with a hook 16 with a hook head at the top, and the quick-change interface 3 and the pile end 6 are snapped together.

[0063] Furthermore, a miniature earth pressure box 8 is installed on the top of the hook 16.

[0064] Furthermore, the pile end 6 also includes a chassis 17, which is disposed below the hook 16.

[0065] Furthermore, the shape of the chassis 17 includes: a flat bottom, a conical bottom, and an enlarged chassis bottom with adjustable diameter.

[0066] The technical advantages of this embodiment are as follows: The transverse corrugations, dotted protrusions, and detachable elastic friction pads on the outer surface of the sleeve can simulate the side friction resistance values ​​under different industry standards. The transverse corrugations simulate the Chinese railway standard, which has a higher side friction resistance value for cohesive soil; the dotted protrusions simulate the side resistance characteristics under compacted sand; and the detachable elastic friction pads simulate the side resistance characteristics in the American standard AASHTO based on the effective stress method. This achieves the physical reproduction of side resistance parameters from multiple standards on the same model pile. The snap-fit ​​connection structure of the quick-change interface enables tool-free quick assembly and disassembly of the pile end. The chassis is designed with a flat bottom, a conical bottom, and an enlarged bottom with an adjustable diameter, corresponding to the experimental requirements of pure friction piles, end-bearing piles, and end resistance size effect studies, respectively. The combination configuration of multiple sets of sleeves and multiple pile ends (two to six sleeves and two to four pile ends) allows one model pile to cover the parameter combinations of most mainstream industry standards, significantly reducing the equipment and time costs of multi-standard comparison tests.

[0067] Example 3 Based on Example 1, this example discloses a test system for a reconfigurable model pile used in a comparative test of the bearing capacity of multiple standard pile foundations. Please refer to [link / reference]. Figure 5 As shown, Figure 5 This is a schematic diagram of the reconfigurable model pile test system.

[0068] A test system for a reconfigurable model pile used in a comparative test of the bearing capacity of multi-standard pile foundations includes: A transparent soil box 10, the inner cavity of which is filled with test soil; The reconfigurable model pile is vertically embedded inside the test soil. A vertical loading frame 11 is fixedly installed on the top of the transparent soil box 10, and the loading end 18 of the vertical loading frame 11 is coaxially abutted against the top surface of the reconfigurable model pile. Displacement sensor 12, the detection end of which is fixedly connected to the top surface of the reconfigurable model pile. The data acquisition instrument 13 is installed on the side wall of the transparent soil box 10, and its signal input terminal is electrically connected to the signal output terminals of the strain gauge 7, the micro earth pressure cell 8, and the displacement sensor 12 of the reconfigurable model pile, respectively.

[0069] Furthermore, the transparent soil box 10 is a box structure made of highly transparent acrylic material. The horizontal dimension of the inner cavity of the transparent soil box 10 is larger than the influence range of the soil sliding of the reconfigurable model pile. The loading axis of the vertical loading frame 11 coincides with the central axis of the reconfigurable model pile. The measurement axis of the displacement sensor 12 is parallel to the central axis of the reconfigurable model pile. The measurement range of the displacement sensor 12 covers the entire range of the pile top settlement of the reconfigurable model pile.

[0070] Furthermore, the data acquisition instrument 13 has a built-in multi-channel synchronous sampling unit. The sampling channels of the multi-channel synchronous sampling unit correspond one-to-one with the strain gauge 7, the miniature earth pressure cell 8, and the displacement sensor 12. The data acquisition instrument 13 synchronously acquires, stores, and outputs the sampling data from all channels in real time. The sampling frequency of the data acquisition instrument 13 is matched with the loading step size of the vertical loading frame 11.

[0071] The technical effects of this embodiment are as follows: Through the modular core pile, replaceable side friction sleeve, and replaceable pile end design, direct comparative tests on the bearing capacity of pile foundations of different industry standards are realized under the same physical model conditions. This reduces the interference caused by factors such as stratum variability and soil heterogeneity in traditional methods, and ensures that the measured bearing capacity differences are purely due to the parameter value logic of different standards. This provides highly reliable physical test evidence for theoretical research and standard revision.

[0072] Example 4 Based on Example 3, this example discloses a method for using a test system for a reconfigurable model pile used in a comparative test of the bearing capacity of multiple standard pile foundations.

[0073] During the comparative test, the operator first selects a set of replaceable side friction simulation sleeves 4 with corresponding external surface characteristics according to the industry standard to be simulated, such as highway, railway, waterway, and American standard. The sleeves are then quickly installed on the core pile 1 by the cooperation of the retaining ring 5 and the annular groove 2. At the same time, according to the definition of the end bearing type in the standard, the operator selects the corresponding replaceable pile end head 6, such as flat bottom, conical or enlarged disc, and connects it to the bottom of the core pile 1 through the quick-change interface 3.

[0074] After the reconstruction of the model pile is completed, it is placed in the predetermined position of the transparent soil box 10. The vertical loading frame 11 is activated to apply a load to the top of the pile. At the same time, the strain gauge 7 attached to the surface of the core pile 1 measures the axial force distribution of each section of the pile body in real time. The miniature earth pressure cell 8 embedded in the pile end 6 directly measures the pile end resistance. The displacement sensor 12 records the settlement of the pile top. All data is transmitted to the data acquisition instrument 13 in real time. By processing the axial force data, the distribution and performance value of the pile side friction can be calculated.

[0075] By alternating the sleeve 4 and pile end 6, representing different standard design parameters, under the same soil box and soil layer conditions, and repeatedly conducting static load tests, multiple load-settlement Qs curves corresponding to different standards can be obtained. By directly comparing these curves, the influence of the differences in the logic of side friction and end resistance values ​​between different standards on the total bearing capacity can be quantitatively revealed.

[0076] The above description is merely a preferred embodiment of the present invention and does not limit the scope of protection of the present invention. Various modifications and variations are possible with respect to the present invention. Any changes, modifications, substitutions, integrations, and parameter alterations to these embodiments within the spirit and principles of the present invention fall within the scope of protection of the claims of the present invention.

Claims

1. A reconfigurable model pile for comparative tests of bearing capacity of multi-standard pile foundations, characterized in that, include: The core pile (1) has an annular groove (2) on its outside, and a preload adjusting screw (9) passes through its hollow interior. A quick-change interface (3) is fixedly connected to its bottom, and a groove is provided at the bottom of the quick-change interface (3). Sleeve (4), the sleeve (4) is a hollow structure, and a retaining ring (5) is fixedly connected to the inner wall. The retaining ring (5) and the annular groove (2) are correspondingly arranged. The sleeve (4) includes two semi-cylinders, which are detachably fixedly connected to each other. The pile end (6) is provided with a hook (16) with a hook head at the top, and the hook (16) is connected to the slot by a snap fastener.

2. The reconfigurable model pile for a multi-standard pile foundation bearing capacity comparison test according to claim 1, characterized in that, The annular groove (2) is horizontally arranged along the vertical axis of the core pile (1). The number of the retaining ring (5) and the annular groove (2) are the same, and their cross-sectional shapes interlock.

3. A reconfigurable model pile for a multi-standard pile foundation bearing capacity comparison test according to claim 1 or 2, characterized in that, The cross-sectional shape of the retaining ring (5) is T-shaped, the cross-sectional shape of the annular groove (2) is T-shaped, and the retaining ring (5) can be inserted into the annular groove (2).

4. The reconfigurable model pile for a multi-standard pile foundation bearing capacity comparison test according to claim 1, characterized in that, The core pile (1) has a positioning groove (14) on its outside, and the positioning groove (14) is set parallel to the vertical axis.

5. A reconfigurable model pile for a comparative test of bearing capacity of multiple standard pile foundations according to claim 4, characterized in that, The inner wall of the sleeve (4) is fixedly connected with a positioning pin (15), and the positioning pin (15) is positioned in correspondence with the positioning groove (14).

6. The reconfigurable model pile for a multi-standard pile foundation bearing capacity comparison test according to claim 3, characterized in that, The outer surface of the core pile (1) is also covered with strain gauges (7), and the annular groove (2) is spaced apart from the strain gauges (7).

7. The reconfigurable model pile for a multi-standard pile foundation bearing capacity comparison test according to claim 1, characterized in that, A miniature earth pressure box (8) is installed on the top of the hook (16).

8. A reconfigurable model pile for a multi-standard pile foundation bearing capacity comparison test according to claim 7, characterized in that, The pile end (6) also includes a chassis (17), which is located below the hook (16).

9. A reconfigurable model pile test system for comparative testing of bearing capacity of multi-standard pile foundations, characterized in that, include: A transparent soil box (10) is filled with test soil in its inner cavity; A reconfigurable model pile, as described in any one of claims 1-8, is vertically embedded inside the test soil. A vertical loading frame (11) is fixedly installed on the top of a transparent soil box (10), and the loading end (18) of the vertical loading frame (11) is coaxially abutted against the top surface of the reconfigurable model pile. Displacement sensor (12), the detection end of the displacement sensor (12) is fixedly connected to the top surface of the reconfigurable model pile; The data acquisition instrument (13) is set on the side wall of the transparent soil box (10), and its signal input terminal is electrically connected to the signal output terminals of the strain gauge (7), the micro earth pressure cell (8) and the displacement sensor (12) of the reconfigurable model pile, respectively.

10. The method of using the reconfigurable model pile test system for comparative testing of bearing capacity of multi-standard pile foundations according to claim 9, characterized in that, Includes the following steps: Step S1, Model Pile Reconstruction: According to the industry standard to be simulated, select a set corresponding to the industry standard from multiple sets of replaceable side friction simulation sleeves (4) with different external surface characteristics. By cooperating with the annular groove (2) on the core pile (1) through the snap ring (5), the selected sleeve (4) is quickly installed on the core pile (1). At the same time, according to the definition of the end bearing form in the industry standard, select the corresponding pile end head from multiple replaceable pile end heads (6) and connect it to the bottom of the core pile (1) through the quick-change interface (3) to complete the reconstruction of the model pile. Step S2: Conduct a static load test: Place the reconstructed reconfigurable model pile in the predetermined position of the transparent soil box (10), and start the vertical loading frame (11) to apply a load to the top of the pile; Step S3: Data collection: During the loading process, the axial force distribution of each section of the pile body is measured in real time by the strain gauge (7) attached to the surface of the core pile (1), the pile end resistance is directly measured by the micro earth pressure cell (8) embedded in the pile end (6), and the pile top settlement is recorded by the displacement sensor (12). All data are transmitted to the data acquisition instrument (13) in real time. Step S4, Data Processing: By processing the axial force data, the distribution and utilization value of the pile side friction are calculated, and the load-settlement Qs curve is generated; Step S5: Data Comparison. Under the same soil box and soil layer conditions, repeat steps S1 to S4 to obtain multiple load-settlement Qs curves corresponding to different standards, quantitatively revealing the impact of the differences in the logic of side friction and end resistance values ​​between different standards on the total bearing capacity.

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