Method for verifying test result of internal force of foundation pile

Abstract

The invention belongs to the technical field of foundation pile internal force testing, and particularly relates to a method for verifying a foundation pile internal force testing result, which comprises the following steps of: S1, forming a pile hole on site, processing and preparing a reinforcement cage according to foundation pile design parameters, fixedly connecting a displacement rod and a protection pipe assembly on a main reinforcement of the reinforcement cage, strain gauges are uniformly arranged upwards along the main reinforcement of the reinforcement cage to measure the strain at each section; s2, concrete is poured to form a pile according to the construction requirement of the foundation pile, and the concrete reaches the age strength required by the design; s3, a datum line beam is arranged above the foundation pile or on the side of the foundation pile; and a plurality of displacement sensors are arranged on the datum line beam and are respectively used for measuring the displacement of the displacement rod and the displacement guiding measurement rod at the top. A dual test method is adopted, external overall deformation and internal strain integral results are compared, when a foundation pile reaches a test load, whether data of an internal force test component conforms to the actual pile body deformation condition or not is verified, and it is ensured that an internal force test result is true and effective.

Description

Technical Field

[0001] The present invention belongs to the technical field of pile foundation internal force testing, and in particular, relates to a method for verifying pile foundation internal force test results. Background Art

[0002] According to the Technical Specifications for Building Foundation Piles (JGJ 94-2008), when conducting a single vertical compressive static load test on a test pile, the standard values ​​of the ultimate lateral resistance and ultimate end resistance of the pile should be measured by burying axial force test components in the pile body. However, due to the instability of the test components and the complexity of the interaction between the pile concrete and the components, the current conventional internal force test method mainly relies on test components (strain gauges) buried inside the pile body to deduce the internal force distribution of the pile body by measuring the strain data of each cross-section of the pile body. The accuracy of the test results cannot be guaranteed, and the test results of the test components cannot be effectively verified. If the internal force test results are used for engineering design without verification, it will leave hidden dangers to the project quality and safety.

[0003] On the one hand, based on a single internal stress test data, there is a lack of an independent external verification mechanism, and it is impossible to effectively check whether the strain value measured by the strain gauge is consistent with the overall deformation of the pile.

[0004] On the other hand, some external verification mechanisms in certain applications are interfered with by external environmental factors such as concrete impact, pouring vibration or impurity intrusion due to the lack of good protective structure design and construction standards, resulting in distorted measurement data and affecting the reliability of test data. Summary of the Invention

[0005] In order to solve the technical problems that the existing internal stress test data lacks an independent external verification mechanism; and the external verification mechanism is difficult to provide good structural protection in actual applications, the present invention provides a method for verifying the internal force test results of pile foundations. By constructing an "external displacement-internal strain" dual testing system; at the same time, a displacement rod and protective tube assembly with protective and displacement transmission is adopted, which effectively isolates the influence of the external environment on the sensor and ensures that the data is true and valid.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for verifying pile foundation internal force test results comprises the following steps:

[0008] Instrument layout and installation:

[0009] S1. Form a pile hole on site and prepare a reinforcement cage according to the pile foundation design parameters. Fasten displacement rods and protective tube assemblies to the main reinforcement of the reinforcement cage. Evenly arrange strain gauges along the main reinforcement of the reinforcement cage to measure strain at each cross-section. Specific construction methods include:

[0010] S101. Use pile-driving equipment to form pile holes on site according to the pile foundation design requirements;

[0011] S102. Prepare the reinforcement cage in advance according to the designed length, diameter, and load requirements of the pile;

[0012] S103. The displacement rod and protective tube assembly are fixedly connected to the main reinforcement of the steel cage. The bottom of the pre-connected displacement rod and protective tube assembly will be arranged at the bottom of the foundation pile, with its top flush with the top of the steel cage;

[0013] S104. Starting from the bottom of the prepared steel cage, place a strain gauge on each of the main bars of the steel cage near the displacement rod and the protective tube assembly to measure the strain at the bottom of the foundation pile. At the same time, place additional strain gauges at regular intervals upward along the two main bars to measure the strain at each cross-section of the foundation pile.

[0014] Casting piles:

[0015] S2. Hoist the steel cage, complete with the test components, displacement rods, and protective tube assembly, into the pile hole. Pour concrete according to pile foundation construction requirements and wait for the concrete to reach the design age strength.

[0016] Loading and test data collection:

[0017] S3. Place a reference beam above or beside the foundation pile. Install several displacement sensors on the reference beam to measure the displacement of the displacement rod and the displacement guide rod at the top. Specific construction methods include:

[0018] S301. Arrange a reference beam on the ground or on the side of the foundation pile that is relatively stable and not affected by the load;

[0019] S302. Install several displacement sensors on the reference beam to measure the displacement of the displacement rod and the displacement measuring rod at the top, so as to obtain the displacement of the bottom of the foundation pile and the displacement of the top of the foundation pile.

[0020] Data Analysis:

[0021] S401. When the pile under test is loaded with the test load, the displacement measured by each displacement sensor and the strain of each cross-section measured by the strain gauge are recorded in real time. The internal force test results of the strain gauge, the displacement measured at the top of the pile, and the displacement at the bottom of the pile conform to the deformation relationship of yield stress:

[0022] Δ=Δ2-Δ1≈Σε i l i ;

[0023] Where Δ represents the overall deformation of the pile; Δ1 represents the displacement measured at the top of the pile; Δ2 represents the displacement measured at the bottom of the pile; ε iIndicates the strain at each measuring point of the pile cross section; l i Indicates the uniform spacing of the cross-section of each strain gauge measurement point;

[0024] S402. If the deformation relationship equation is established, it indicates that the internal force test result of the test component is accurate; if the above equation is not established, it indicates that the internal force test result is inaccurate and cannot be used for engineering design.

[0025] Preferably, the strain gauge is a resistance strain gauge or a vibrating wire strain gauge; the resistance strain gauge is specifically a steel bar gauge.

[0026] Preferably, the connection structure of the displacement rod and the protective tube assembly is:

[0027] A hollow protective tube is sleeved on the outside of the displacement rod; a steel plate is welded on the bottom of the displacement rod, and the steel plate and the bottom of the protective tube are sealed together; the protective tube is fixedly connected to the main reinforcement of the steel cage.

[0028] Preferably, the displacement rods are made of the same material as the main reinforcement of the reinforcement cage, that is, the mechanical properties of the materials are the same.

[0029] Preferably, step S103 further includes: reserving an electric measuring line on each strain gauge, and bundling the electric measuring lines together and leading them out of the top of the steel cage for connection with the pile measuring instrument.

[0030] Preferably, the test load is loaded in the following manner: a hydraulic device is configured, the hydraulic device includes a jack, a jack is arranged on the top of the foundation pile, a loading steel beam is arranged above the jack, and a counterweight block or a reaction frame is arranged on the loading steel beam to provide reaction force support.

[0031] Preferably, the hydraulic equipment further comprises an oil pump and an oil pipe, and the oil pump and the oil pipe are used to control the jack to apply the load, and the pressure is gradually increased to the test load.

[0032] Preferably, step S401 further includes: obtaining the required vertical bearing capacity and pile cross-sectional area A of the foundation pile according to the design data and geological data, and estimating the test load required to be applied to the tested foundation pile;

[0033] The test load is set according to the following criteria: depending on the test purpose, if the performance of the pile body is verified under a state close to the limit, a limit load lower than the yield stress of the main reinforcement of the steel cage is set; if the test purpose is to verify the working condition of the internal force test components, a lower load is set.

[0034] Preferably, in step S402, the normal deviation thresholds on both sides of the relationship are determined by referring to relevant engineering specifications or by comprehensive verification of multiple tests.

[0035] Preferably, the method further comprises step S5: performing a load-unload cycle test, wherein after the load is unloaded, the strain gauge reading returns to the initial value or is within a smaller residual strain range;

[0036] If severe drift or inconsistency occurs after multiple cyclic tests, it means there is a problem with the strain gauge or its bonding condition. The internal force test results are inaccurate and cannot be used for engineering design.

[0037] Beneficial effects of the present invention:

[0038] 1. Using a double test method, by comparing the external overall deformation and the internal strain integral results, when the foundation pile reaches the test load, verify whether the data of the internal force test component (rebar meter) is consistent with the actual pile deformation, ensuring that the internal force test results are true and valid.

[0039] 2. The structural design of the "displacement rod and protective tube assembly" effectively isolates the direct impact of concrete and the external environment on the displacement rod through the hollow protective tube and steel plate sealing structure. The displacement rod, protective tube and welded steel plate form a complete protection and transmission unit, enhancing the scientific nature and reliability of engineering design and safety assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 The present invention is a flowchart of the steps of a method for verifying the internal force test results of pile foundations.

[0042] Figure 2 This is a structural diagram of the arrangement of test components in a method for verifying pile foundation internal force test results of the present invention.

[0043] Figure 3 This is a diagram of the connection structure of the displacement rod and the protective tube assembly in a method for verifying the internal force test results of a pile foundation according to the present invention.

[0044] Figure 4 This is a structural diagram of the arrangement of the displacement rod and protective tube assembly in a method for verifying the internal force test results of a pile foundation according to the present invention.

[0045] Figure numerals: 1-reference beam; 2-oil pump; 3-pile measuring instrument; 4-displacement sensor; 5-side wall of pile foundation; 6-rebar cage; 7-pile foundation; 8-loading jack; 9-bearing layer; 10-protective pipe; 11-rebar meter; 12-displacement rod; 13-displacement guide rod; 14-oil pipe; 15-counterweight block; 16-loading steel beam. DETAILED DESCRIPTION

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0047] See also Figures 1-4 As shown, a method for verifying the internal force test results of pile foundations includes the following steps:

[0048] Instrument layout and installation:

[0049] S1. Form a pile hole on site and prepare a steel cage 6 according to the pile foundation design parameters. Attach displacement rods and protective tube assemblies to the main reinforcement of the steel cage 6. Evenly arrange strain gauges 11 along the main reinforcement of the steel cage 6 to measure strain at each cross-section. Specific construction methods include:

[0050] S101. On-site pile design requirements are followed by the use of pile-forming equipment to form pile holes; the pile holes provide space for subsequent pouring of piles, ultimately forming pile foundations 7;

[0051] S102 according to the design length, diameter and force requirements of the pile, advance processing preparation steel cage 6;

[0052] S103. The displacement rod and protective tube assembly are fixedly connected to the main reinforcement of the steel cage 6. The bottom of the pre-connected displacement rod and protective tube assembly will be arranged at the bottom of the foundation pile, ie, close to the bearing layer 9, and its top is flush with the top of the steel cage 6;

[0053] S104. Starting from the bottom of the prepared steel cage 6, a strain gauge 11 is placed on each of the main bars of the steel cage 6 near the displacement rod and the protective tube assembly to measure the strain at the bottom of the pile, which can be denoted as G1 and H1. At the same time, additional strain gauges are placed evenly spaced upward along the two main bars to measure the strain at various cross-sections of the pile, which can be denoted as G2, G3, ... Gi, and H2, H3, ... Hi.

[0054] During implementation, pile hole construction must ensure the verticality of the pile hole walls. Specifically, the pile sidewalls 5 must remain vertical, and the diameter and depth must meet design requirements. During instrument placement and installation, the strain gauges are welded to the main reinforcement surface to ensure rapid and accurate transmission of strain signals. Furthermore, the welding process requires strict control of temperature and time to prevent local overheating that could affect the reinforcement material and the strain gauges themselves.

[0055] Casting piles:

[0056] S2. Hoist the steel cage 6 with the installed test components, displacement rods, and protective tube assembly into the pile hole, pour concrete into the pile according to the construction requirements of the foundation pile 7, and wait for the concrete to reach the design age strength; at the same time, protect all arranged test components, displacement rods, and protective tube assemblies from damage or deformation.

[0057] During the concrete pouring process, to prevent impact or damage to sensitive instruments, a special film protective cover can be applied to the instrument surface to protect electronic components from moisture in the concrete. Continuous pouring is also employed to prevent concrete fractures and other phenomena. After the concrete reaches the specified age strength, the overall quality of the pile is tested, including concrete strength, pile integrity, and instrument operating status, to ensure that all pre-installed test components are functioning properly and that the data acquisition system is functioning properly.

[0058] Loading and test data collection:

[0059] S3. Place a reference beam above or beside the foundation pile. Install several displacement sensors on the reference beam to measure the displacement of the displacement rod and the displacement guide rod at the top. Specific construction methods include:

[0060] S301. Arrange a reference beam 1 on the ground or pile side that is relatively stable and not affected by the load;

[0061] S302. A plurality of displacement sensors 4 are installed on the reference beam 1, respectively, for measuring the displacement of the displacement rod 12 and the displacement of the top displacement guide rod 13, thereby obtaining the displacement Δ2 of the bottom of the pile and the displacement Δ1 of the top of the pile; the displacement sensor 4 is connected to the pile measuring instrument 3, and the collected displacement data is recorded in real time;

[0062] During the specific implementation process, based on the design data and geological data, the design bearing capacity of the foundation pile is first calculated, including the bearing capacity at the pile bottom and the friction resistance on the pile side. Then, the overall bearing capacity of the pile is determined by combining the cross-sectional area A of the pile body and the pile body length. At the same time, it should be ensured that the applied test load does not exceed the yield limit of the component reinforcement cage 6. Then, based on the set test load, loading equipment with corresponding rated loads, such as jacks and load boxes, is selected to ensure stable pressure control. In addition, the layout of the reference beam 1 should ensure that it remains absolutely stationary during the loading process and does not produce its own displacement. A level instrument, total station, etc. can be used for calibration to ensure that the foundation pile side wall 5 remains vertical and is on the same horizontal reference as the pile body. It serves as a reference reference for the displacement sensor 4. Several high-precision displacement sensors 4 are arranged on the reference beam 1 according to the design requirements. These high-precision displacement sensors 4 need to be respectively aligned with the displacement guide rod 13 at the top of the pile to measure the pile top displacement Δ1 and transmit the pile bottom displacement Δ2 to the ground through the displacement rod 12, thereby measuring its small displacement on the ground. During the installation process, pay attention to the fixed position and direction of the sensor so that it can accurately capture small displacement changes and try to avoid interference caused by loading vibration.

[0063] Data Analysis:

[0064] S401. When the pile under test is loaded with the test load, the displacement measured by each displacement sensor 4 and the strain at each cross section measured by the strain gauge are recorded in real time; wherein, the internal force test results of the strain gauge 11 and the displacement measured at the top and bottom of the pile conform to the deformation relationship of the yield stress:

[0065] Δ=Δ2-Δ1≈Σε i l i ;

[0066] Where Δ represents the overall deformation of the pile; Δ1 represents the displacement measured at the top of the pile; Δ2 represents the displacement measured at the bottom of the pile; ε i Indicates the strain at each measuring point of the pile cross section; l i Indicates the uniform spacing of the cross-section of each strain gauge measurement point;

[0067] S402. If the deformation relationship equation is established, it indicates that the internal force test result of the test component is accurate; if the above equation is not established, it indicates that the internal force test result is inaccurate and cannot be used for engineering design.

[0068] Specifically, the present invention combines two measurement methods of the overall axial internal force deformation of the foundation pile, namely the displacement difference between the pile top and the pile bottom by the external measurement method and the strain integral along the pile body by the internal measurement method, and verifies the internal force test results of the foundation pile by the external measurement method. Through this internal and external comparison method, the accuracy of the pile body internal force test can be effectively verified, thereby improving the reliability of the foundation pile bearing capacity assessment and engineering design.

[0069] Furthermore, the strain gauge is a resistance strain gauge or a vibrating wire strain gauge; the resistance strain gauge is specifically a steel bar gauge.

[0070] Specifically, a rebar gauge is a sensor used to measure the strain of rebar or the steel reinforcement framework within concrete. It typically incorporates strain gauges pre-welded to the rebar and equipped with appropriate protection and signal transmission devices, enabling accurate measurement of minute deformations of the rebar under stress even after construction or concrete pouring. When the rebar experiences strain, tension, or compression due to external forces, the resistance of the strain gauge welded to the rebar surface changes with the deformation. By measuring this change in resistance, the strain value of the rebar can be calculated.

[0071] Furthermore, the connection structure of the displacement rod and the protective tube assembly is:

[0072] A hollow protective tube 10 is sheathed around the displacement rod 12. A steel plate is welded to the bottom of the displacement rod 12, sealing the bottom of the protective tube 10. The protective tube 10 is securely connected to the main reinforcement of the reinforcement cage 6. The protective tube 10 protects the displacement rod 12 from damage or jamming during concrete pouring and subsequent use. The steel plate at the bottom ensures the stability of the bottom of the displacement rod 12, maintaining its position during concrete pouring.

[0073] Furthermore, the displacement rod 12 is made of the same material as the main bars of the rebar cage 6, i.e., they have the same mechanical properties. When the elastic modulus, yield strength, and other mechanical properties of the two materials are identical, the strain and deformation they produce under the same load are consistent. This ensures that the displacement changes measured by the displacement rod 12 truly reflect the actual deformation of the main bars of the rebar cage 6 under load, thereby ensuring comparability and accuracy in the subsequent calculation of the overall displacement using strain integration.

[0074] Furthermore, step S103 includes reserving electrical measuring wires on each strain gauge, bundling the wires together, and leading them out of the top of the steel cage 6 for connection to the pile tester 3. The pile tester is a "data collection and processing terminal" responsible for collecting, processing, and visualizing signals from the steel gauges and other sensors, thereby helping engineers make accurate judgments on the mechanical behavior and bearing capacity of the foundation piles.

[0075] Furthermore, the test load is applied using hydraulic equipment, including a jack 8, positioned atop the pile. A loading steel beam 16 is positioned above the jack, and a counterweight 15 or reaction frame is positioned atop the loading steel beam 16 to provide reaction support. Using the selected jack and hydraulic equipment, the load is gradually applied to the pile via oil pipes. This allows for a step-by-step, controllable vertical test load to be applied to the pile top, simulating the vertical compressive stress of the pile.

[0076] Furthermore, the hydraulic equipment further includes an oil pump 2 and an oil pipe 14 , through which a load is applied to the jack 8 , and pressurized step by step to a test load.

[0077] Furthermore, step S401 further includes: obtaining the required vertical bearing capacity and pile cross-sectional area A of the foundation pile 7 based on the design data and geological data, and estimating the test load required to be applied to the tested foundation pile 7;

[0078] The test load setting standard is: according to the test purpose, if the performance of the foundation pile is verified under the limit state, the limit load is set to be lower than the yield stress of the steel cage 6; if the test purpose is to verify the working state of the internal force test components, a lower load is set.

[0079] Furthermore, in step S402, the normal deviation thresholds on both sides of the relationship are determined by reference to relevant engineering specifications or through comprehensive multiple test verification. In specific implementations, the normal deviation thresholds on both sides of the relationship are primarily based on the coupling relationship between the rebar gauge and concrete, and can be determined by reference to relevant engineering specifications or through comprehensive multiple test verification.

[0080] Furthermore, the method further includes step S5: performing a load-unload cycle test, wherein after the load is unloaded, the strain gauge reading returns to the initial value or is within a smaller residual strain range;

[0081] If severe drift or inconsistency occurs after multiple cyclic tests, it means there is a problem with the strain gauge or its bonding condition. The internal force test results are inaccurate and cannot be used for engineering design.

[0082] During the specific implementation process, the load must be slowly increased to the designed preset load or the predetermined maximum load value according to the pre-set loading scheme. During the loading process, the strain gauge readings are recorded in real time, and the data acquisition system is ensured to record the data completely and continuously. At the same time, the strain response is observed using the pile tester to confirm that the strain gauge readings show the expected linear or near-linear response with increasing load, ensuring that the instrument is operating properly. This stage verifies the initial sensitivity and linearity of the sensor and establishes a reference basis for subsequent unloading.

[0083] After reaching the test load, gradually reduce the applied load to ensure a steady unloading rate and prevent sudden changes in instrument readings due to sudden unloading. Record the strain values ​​at each moment during the unloading process, paying particular attention to the readings after the load is completely removed. At the same time, when unloading to near zero load, observe whether the readings of each strain gauge return to the initial value or only show minimal residual strain. If residual values ​​exist, their magnitude should be very low (for example, residual strain is generally required to be less than 5%-10% of the maximum applied strain).

[0084] In summary, the present invention proposes a method for verifying the internal force test results of pile foundations, which adopts a double testing method. By comparing the external overall displacement and the internal strain integral results, when the pile foundation reaches the test load, it verifies whether the data of the internal force test component (rebar meter) is consistent with the actual pile deformation, thereby ensuring that the internal force test results are true and valid. Through the specific construction steps (pile hole construction, instrument fixing, concrete pouring and loading process), clear operating procedures are provided to facilitate on-site construction personnel to strictly follow the standard procedures. The structural design of the "displacement rod and protective tube assembly" effectively isolates the direct influence of concrete and the external environment on the displacement rod 12 through the hollow protective tube 10 and the steel plate sealing structure; the displacement rod 12, the protective tube 10 and the welded steel plate constitute a complete protection and transmission unit, which is convenient for overall transportation and installation during prefabrication, hoisting and pouring, reduces construction difficulty, and reduces installation errors caused by improper operation; and enhances the scientificity and reliability of engineering design and safety assessment.

[0085] The present invention judges the accuracy of the test results of internal force test data by setting up a matching displacement rod and protective tube assembly and a displacement measuring rod at the pile top (which can measure the displacement changes at the pile top and pile bottom), making the internal force test results verifiable and filling the gap in application in this area.

[0086] In the description of the specification, the descriptions with reference to the terms "in the specific implementation process", "specifically", "further" and the like mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. The above content is merely an example and explanation of the structure of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they shall all fall within the scope of protection of the present invention.

Claims

1. A method for verifying pile foundation internal force test results, characterized in that: The following steps are involved: S1. Form a pile hole on site and prepare a reinforcement cage according to the pile foundation design parameters. Fasten displacement rods and protective tube assemblies to the main reinforcement of the reinforcement cage. Evenly arrange strain gauges upward along the main reinforcement of the reinforcement cage to measure strain at each cross-section. S2. Hoist the steel cage, complete with the test components, displacement rods, and protective tube assembly, into the pile hole. Pour concrete according to pile foundation construction requirements and wait for the concrete to reach the design age strength. S3. Arrange a reference beam above or beside the pile; install several displacement sensors on the reference beam, respectively, for measuring the displacement of the displacement rod and the displacement of the top displacement guide rod; S401. When the pile under test is loaded with the test load, the displacement measured by each displacement sensor and the strain at each cross-section measured by the strain gauge are recorded in real time. The internal force test results of the strain gauge, the displacement measured at the top of the pile, and the displacement at the bottom of the pile conform to the deformation relationship of yield stress: S402. If the deformation relationship equation is established, it indicates that the internal force test result of the test component is accurate; if the above equation is not established, it indicates that the internal force test result is inaccurate and cannot be used for engineering design.

2. A method for verifying pile foundation internal force test results according to claim 1, characterized in that: The specific construction method of step S1 includes: S101. Use pile-driving equipment to form pile holes on site according to the pile foundation design requirements; S102. Prepare the reinforcement cage in advance according to the designed length, diameter, and load requirements of the pile; S103. The displacement rod and protective tube assembly are fixedly connected to the main reinforcement of the steel cage. The bottom of the pre-connected displacement rod and protective tube assembly will be arranged at the bottom of the foundation pile, with its top flush with the top of the steel cage; S104. Starting from the bottom of the prepared steel cage, place a strain gauge on each of the main bars of the steel cage near the displacement rod and the protective tube assembly to measure the strain at the bottom of the foundation pile. At the same time, place additional strain gauges at regular intervals upward along the two main bars to measure the strain at each cross-section of the foundation pile.

3. The method for verifying pile foundation internal force test results according to claim 1, characterized in that: The connection structure of the displacement rod and the protective tube assembly is as follows: A hollow protective tube is sleeved on the outside of the displacement rod; a steel plate is welded to the bottom of the displacement rod, and the steel plate and the bottom of the protective tube are sealed together; the protective tube is fixedly connected to the main reinforcement of the steel cage; the fixed connection method is welding.

4. The method for verifying pile foundation internal force test results according to claim 1, characterized in that: In step S401, the deformation relationship of the yield stress is: Δ = Δ2 - Δ1 ≈ ∑ε i l i ; Where Δ represents the overall deformation of the pile; Δ1 represents the displacement measured at the top of the pile; Δ2 represents the displacement measured at the bottom of the pile; ε i Indicates the strain at each measuring point of the pile cross section; l i Indicates the uniform spacing of the cross-section of each strain gauge measuring point.

5. The method for verifying pile foundation internal force test results according to claim 1, characterized in that: The specific construction method of step S3 includes: S301. Arrange a reference beam on the ground or on the side of the foundation pile that is relatively stable and not affected by the load; S302. Install several displacement sensors on the reference beam to measure the displacement of the displacement rod and the displacement measuring rod at the top, so as to obtain the displacement of the bottom of the foundation pile and the displacement of the top of the foundation pile.

6. The method for verifying pile foundation internal force test results according to claim 1, characterized in that: The test load is loaded in the following manner: a hydraulic device is configured, the hydraulic device includes a jack, a jack is arranged on the top of the foundation pile, a loading steel beam is arranged above the jack, and a counterweight block or a reaction frame is arranged on the loading steel beam to provide reaction support.

7. A method for verifying pile foundation internal force test results according to claim 6, characterized in that: The hydraulic equipment also includes an oil pump and an oil pipe, which control the jack to apply load through the oil pump and the oil pipe, and gradually increase the pressure to the test load.

8. The method for verifying pile foundation internal force test results according to claim 1, characterized in that: Step S401 also includes: obtaining the required vertical bearing capacity and pile cross-sectional area A of the foundation pile based on the design data and geological data, and estimating the test load required to be applied to the foundation pile under inspection; The test load setting standard is as follows: according to the test purpose, if the performance of the pile body is verified under the state close to the limit, the limit load is set to be lower than the yield stress of the main reinforcement of the steel cage; If the purpose of the test is to verify the working condition of the internal force test component, set a lower load.

9. The method for verifying pile foundation internal force test results according to claim 1, characterized in that: The method further includes step S5: performing a load-unload cycle test, wherein after the load is unloaded, the strain gauge reading returns to the initial value or to a smaller residual strain range; If severe drift or inconsistency occurs after multiple cyclic tests, it indicates that there is a problem with the strain gauge or its bonding condition, and the internal force test results are inaccurate and cannot be used for engineering design.

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