A system and method for detecting the bearing capacity of a pile foundation

Abstract

The application discloses a kind of pile foundation bearing capacity detection system and method, belong to pile foundation detection technical field, including loading module, sensing module, data acquisition module, analysis control module and feedback regulation module, the sensing module is electrically connected with data acquisition module, the data acquisition module is electrically connected with analysis control module, the present application is distributed along the distributed arrangement of strain sensor in pile body, in combination with strain-axial force conversion model, the axial force distribution and stress variation law of different depth of pile body can be acquired in real time, break through the single criterion limitation that traditional static load detection only relies on pile top settlement;At the same time, through multidimensional data collaborative verification and error correction technology, load measured value, temperature correction parameter and the like are fused, automatically exclude abnormal data, correct measurement deviation, ensure the reliability of detection data, and then improve the accuracy of bearing capacity determination, can accurately identify potential defects such as local stress concentration of pile body, avoid misjudgment, missed judgment.

Description

Technical Field

[0001] This invention relates to the field of pile foundation testing technology, specifically to a pile foundation bearing capacity testing system and method. Background Technology

[0002] As a core load-bearing component in building construction, the bearing capacity of pile foundations directly determines the structural safety and stability of the entire building. Therefore, pile foundation bearing capacity testing is an indispensable and crucial step in the construction process. Currently, the industry generally uses static load testing to determine the bearing capacity of pile foundations. This method involves applying a load to the top of the pile, observing the settlement at the top of the pile, and combining the load-settlement curve to determine the ultimate bearing capacity of the pile foundation.

[0003] Traditional static load testing techniques have several shortcomings, failing to meet the demands of modern engineering for accuracy, efficiency, and safety. Firstly, traditional static load testing relies solely on the pile top load-settlement curve as a single criterion, failing to capture the stress distribution within the pile body or quantify the real-time development of pile side friction and end resistance. This results in insufficient accuracy in bearing capacity assessment and difficulty in identifying potential defects such as localized stress concentration within the pile, easily leading to misjudgments and missed diagnoses. Secondly, the traditional surcharge loading process relies entirely on manual experience, resulting in uneven loading rates, inaccurate staged load control, and a lag in determining the ultimate limit state of the pile foundation, which can easily lead to… First, excessive pressure on the pile body can cause damage, and manual operation is inefficient and unsuitable for batch testing of complex pile types. Second, strain measurement is a core component of pile foundation bearing capacity testing, but traditional testing methods are susceptible to environmental temperature drift, sensor installation deviations, and lack real-time data correction mechanisms, resulting in large measurement errors and low reliability of test results. Third, for complex pile types such as ultra-long piles and large-diameter piles, the synergistic mechanism of pile side friction and pile end resistance is complex, and traditional testing methods cannot accurately separate the contribution values ​​of each part of the bearing capacity, making it difficult to meet the precise requirements of engineering design and quality acceptance.

[0004] In view of the shortcomings of the above-mentioned traditional technologies, there is an urgent need for a pile foundation bearing capacity testing system and method that can achieve intelligent, accurate and efficient testing, so as to solve the problems of low accuracy, poor efficiency, insufficient safety and unreliable data in traditional testing, and provide reliable guarantee for the quality of pile foundation engineering. Summary of the Invention

[0005] The purpose of this invention is to provide a pile foundation bearing capacity testing system and method. Through integrated system design and intelligent control, it achieves accurate testing of pile foundation bearing capacity, improves testing efficiency, reduces labor intensity, and ensures the reliability and safety of testing results, thereby solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a pile foundation bearing capacity detection system, comprising a loading module, a sensing module, a data acquisition module, an analysis and control module, and a feedback adjustment module. These modules are electrically connected and work collaboratively, with the specific connection relationships as follows: the sensing module is electrically connected to the data acquisition module, used to transmit collected strain data, pile top settlement data, load data, and ambient temperature data at different pile foundation depths to the data acquisition module; the data acquisition module is electrically connected to the analysis and control module, used to transmit synchronously acquired and pre-processed data to the analysis and control module; the analysis and control module is electrically connected to the feedback adjustment module, used to analyze, calculate, and adjust the errors of the acquired data. The system corrects and outputs relevant parameters of the pile foundation bearing capacity and generates control commands, which are then sent to the feedback adjustment module. The feedback adjustment module is electrically connected to the loading module and receives control commands from the analysis and control module. It adjusts the loading rate and graded load magnitude of the loading module to achieve closed-loop control of the loading process. The loading module applies graded loads to the pile foundation and dynamically regulates the loading process. The sensing module collects relevant pile foundation detection data. The data acquisition module synchronously collects various data output from the sensing module and performs preliminary preprocessing. The analysis and control module processes data, corrects errors, and generates control commands. The feedback adjustment module executes control commands and adjusts the working state of the loading module.

[0007] Preferably, the loading module includes a stacking platform, jacks, a hydraulic pump station, and an automatic loading controller; the jacks are fixedly installed below the stacking platform, and the output end of the jacks is aligned with the top of the pile foundation; the hydraulic pump station is connected to the jacks to provide power to them; the automatic loading controller is electrically connected to the hydraulic pump station and the analysis and control module, and is used to receive control commands from the analysis and control module, adjust the output pressure of the hydraulic pump station, and thus control the loading rate and load size of the jacks.

[0008] Preferably, the sensing module includes a distributed strain sensor, a load sensor, a displacement gauge, and a temperature sensor; the distributed strain sensor is distributed along the axial direction of the pile body to collect axial strain data at different depths of the pile body in real time; the load sensor is installed between the jack and the top of the pile body to measure the real-time load value during the loading process; the displacement gauge is installed on the reference beam at the top of the pile body to collect the settlement data of the pile top; the temperature sensor is arranged adjacent to the distributed strain sensor to collect the ambient temperature data around the pile body, providing parameters for temperature correction of the strain data.

[0009] Preferably, the data acquisition module adopts a multi-channel synchronous acquisition instrument, which is electrically connected to a distributed strain sensor, a load sensor, a displacement gauge and a temperature sensor respectively. The acquisition frequency is adjustable in the range of 1-10Hz and has a data caching function to avoid data loss. The preliminary preprocessing includes data noise reduction, preliminary screening of abnormal data and data format conversion.

[0010] Preferably, the analysis and control module incorporates a strain-axial force conversion model, a data verification model, and a bearing capacity determination model. The strain-axial force conversion model is used to calculate the axial force values ​​at different depths of the pile body and generate axial force distribution curves based on the strain data collected by distributed strain sensors. The data verification model is used to integrate the measured values ​​of load sensors, the calculated axial force values ​​at the pile top, strain drift compensation data, and temperature correction parameters to automatically eliminate abnormal data and correct measurement deviations. The bearing capacity determination model is used to integrate the load-settlement curve, the pile axial force distribution curve, and the pile stress change curve to achieve a coordinated determination of the pile foundation bearing capacity.

[0011] Preferably, the calculation formula for the strain-axial force conversion model is as follows:

[0012] N(x) = E·A·ε(x)

[0013] Where N(x) is the axial force at pile depth x, E is the elastic modulus of the pile foundation concrete, A is the cross-sectional area of ​​the pile, and ε(x) is the axial strain at pile depth x.

[0014] Preferably, the feedback adjustment module adopts closed-loop control logic, using the maximum allowable strain of the pile body and the settlement rate of the pile top as dual control thresholds; when the pile body strain reaches 90% of the maximum allowable strain or the settlement rate of the pile top exceeds the preset threshold, the feedback adjustment module controls the loading module to reduce the loading rate; when the pile body strain reaches the maximum allowable strain or the settlement rate of the pile top continues to exceed the preset threshold and shows no convergence trend, the feedback adjustment module controls the loading module to stop loading to avoid pile crushing.

[0015] Preferably, it also includes a wireless transmission module and a terminal display module; the wireless transmission module is electrically connected to the data acquisition module and the analysis and control module, and is used to wirelessly transmit the acquired data and analysis results to the terminal display module; the terminal display module is used to display various types of test data, curves and load-bearing capacity determination results in real time, and has data storage, export and printing functions.

[0016] Based on a pile foundation bearing capacity testing system, a pile foundation bearing capacity testing method is also included, comprising the following steps:

[0017] S1: Preparations before testing: Distributed strain sensors are distributed along the pile axis, load sensors, displacement gauges and temperature sensors are installed, and the loading module, data acquisition module, analysis and control module and feedback adjustment module are debugged to ensure that each module works normally.

[0018] S2: Graded loading, graded loads are applied to the pile foundation through the loading module. The initial load is 10%-15% of the estimated ultimate bearing capacity, and the subsequent load increment is 5%-10% of the estimated ultimate bearing capacity. After each load is applied, the load is kept stable for a preset time.

[0019] S3: Data synchronous acquisition. The data acquisition module synchronously acquires strain data, load data, pile top settlement data and temperature data at different depths of the pile body, and transmits them to the analysis and control module after preliminary preprocessing.

[0020] S4: Data processing and error correction. The analysis and control module calculates the axial force distribution of the pile body through the strain-axial force conversion model, and removes abnormal data and corrects measurement deviations caused by temperature drift and sensor installation deviations through the data verification model.

[0021] S5: Loading closed-loop regulation, the analysis and control module determines whether the pile strain and pile top settlement rate have reached the control threshold based on the data processing results, and adjusts the loading rate of the loading module and the size of the next level load through the feedback adjustment module;

[0022] S6: Bearing capacity determination. When the settlement rate at the top of the pile continuously exceeds the preset threshold and shows no convergence trend, or when the maximum allowable strain of the pile body is reached, the loading is stopped. The analysis and control module integrates various curve data through the bearing capacity determination model and outputs the ultimate bearing capacity of the pile foundation and the resistance contribution value of each part.

[0023] S7: Inspection complete, unload the load, organize the inspection data and judgment results, and export or print the inspection report through the terminal display module.

[0024] Preferably, in S2, the stabilization time for each load level is 5-10 minutes. When the settlement rate at the pile top is less than 0.1 mm / min, the next load level can be applied. In S6, the maximum allowable strain of the pile body is determined according to the strength grade of the pile foundation concrete, and the value range is 1500-2500 με.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. This invention utilizes distributed strain sensors deployed along the pile shaft, combined with a strain-axial force conversion model, to acquire the axial force distribution and stress variation patterns at different depths of the pile shaft in real time. This overcomes the limitations of traditional static load testing, which relies solely on the single criterion of pile top settlement. Simultaneously, through multi-dimensional data collaborative verification and error correction technology, it integrates measured load values, temperature correction parameters, etc., to automatically eliminate abnormal data and correct measurement deviations, ensuring the reliability of the test data. This improves the accuracy of bearing capacity determination and enables precise identification of potential defects such as local stress concentration in the pile shaft, avoiding misjudgments and omissions.

[0027] 2. This invention employs a strain-settlement dual closed-loop loading control mechanism, using the maximum allowable strain of the pile body and the settlement rate at the pile top as dual thresholds. Through the collaborative work of the analysis control module and the feedback adjustment module, it achieves automated and intelligent adjustment of the loading process, replacing traditional manual experience-based operation. This not only avoids the risk of pile crushing caused by uneven loading rates and delayed judgment of limit states, but also significantly improves detection efficiency. Compared with traditional detection methods, the detection efficiency is improved, which can meet the batch detection needs of complex pile types.

[0028] 3. This invention integrates three core curve data through a joint bearing capacity determination system, which can accurately separate the bearing capacity contribution values ​​of pile side friction and pile end resistance. It solves the problem that traditional methods cannot quantify the soil resistance behavior of complex pile types such as ultra-long piles and large-diameter piles, and provides accurate data support for engineering design, construction optimization and quality acceptance.

[0029] 4. This invention constructs an integrated intelligent detection system that combines "loading-sensing-acquisition-analysis-feedback-control," realizing the automation and intelligence of the detection process. A single person can complete the entire detection operation, reducing labor intensity. At the same time, it is equipped with a wireless transmission module and a terminal display module, which can view the detection data and results in real time, facilitating data archiving, exporting, and printing, and adapting to the detection needs of various engineering scenarios. Attached Figure Description

[0030] Figure 1 This is a system block diagram of the present invention;

[0031] Figure 2 This is a flowchart of the method of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention provides a pile foundation bearing capacity testing system, including a loading module, a sensing module, a data acquisition module, an analysis and control module, and a feedback adjustment module. These modules are electrically connected and work collaboratively to form an integrated intelligent testing system encompassing loading, sensing, acquisition, analysis, feedback, and control. The specific structure and connection relationships are as follows:

[0034] 1. Loading Module: This module applies graded loads to the pile foundation and dynamically controls the loading process. It serves as the power output unit of the entire testing system. The loading module includes a surcharge platform, jacks, a hydraulic pump station, and an automatic loading controller. The surcharge platform provides the reaction force required for loading. It can rationally stack counterweights based on the estimated ultimate bearing capacity to ensure sufficient and stable reaction force. The jacks are fixedly installed below the surcharge platform, with their output ends aligned with the top of the pile foundation. This ensures the load is applied vertically and evenly to the pile foundation, preventing uneven stress on the pile due to load eccentricity. The hydraulic pump station is connected to the jacks, providing stable hydraulic power. Its output pressure can be adjusted according to loading requirements. The automatic loading controller is electrically connected to the hydraulic pump station and the analysis and control module. As the control core of the loading module, it receives control commands from the analysis and control module, precisely adjusts the output pressure of the hydraulic pump station, and thus controls the loading rate and load magnitude of the jacks. This achieves automated and intelligent control of the loading process, replacing traditional manual operation based on experience.

[0035] 2. Sensing Module: Used to comprehensively collect various key data during the pile foundation testing process, providing a foundation for subsequent data processing and bearing capacity determination. It is the data acquisition unit of the testing system. The sensing module includes distributed strain sensors, load sensors, displacement gauges, and temperature sensors. The distributed strain sensors are arranged axially along the pile shaft, with the spacing adjustable according to pile length and accuracy requirements, typically 1-3 meters. Their core function is to collect axial strain data at different depths of the pile in real time, accurately capturing the stress variation within the pile. The load sensors are installed between the jack and the top of the pile, closely fitting both, to measure real-time load values ​​during loading, providing a measurement benchmark for data verification and error correction. The displacement gauges are installed on a reference beam at the top of the pile, which must be fixed to a stable foundation far from the loading influence zone to ensure the accuracy of the measurement data. The displacement gauges are used to collect real-time pile top settlement data, capturing the deformation pattern of the pile top during loading. The temperature sensors are arranged adjacent to the distributed strain sensors, with a spacing of no more than 5 cm, to collect ambient temperature data around the pile, providing key parameters for temperature drift correction of strain data and avoiding strain measurement deviations caused by temperature changes.

[0036] 3. Data Acquisition Module: This module is used to synchronously acquire various types of data output from the sensor module and perform preliminary preprocessing to ensure the integrity and validity of the data. It is the data transmission and preprocessing unit of the detection system. The data acquisition module employs a multi-channel synchronous acquisition instrument, which is electrically connected to distributed strain sensors, load sensors, displacement gauges, and temperature sensors. This enables simultaneous acquisition of multiple types and channels of data. The acquisition frequency is adjustable from 1 to 10 Hz, allowing for flexible settings based on required detection accuracy. For example, for complex pile types, the acquisition frequency can be adjusted to 8-10 Hz to ensure the capture of subtle stress and deformation changes in the pile body. Simultaneously, the multi-channel synchronous acquisition instrument features a data caching function with a capacity of at least 100 GB to prevent data loss due to sudden power outages or data transmission interruptions. Preliminary preprocessing includes data denoising, preliminary screening of abnormal data, and data format conversion. Data denoising utilizes wavelet analysis algorithms to eliminate noise data caused by environmental interference and equipment vibration. Preliminary screening of abnormal data uses a threshold method to mark data exceeding a reasonable range as abnormal and temporarily remove it. Data format conversion unifies the different formats of data output from various sensors into digital signals recognizable by the analysis and control module, facilitating subsequent data processing.

[0037] 4. Analysis and Control Module: As the core control and data processing unit of the entire detection system, it is used to perform in-depth analysis, calculation, and error correction on the collected data, output relevant parameters of pile foundation bearing capacity, generate control commands, and coordinate the collaborative work of various modules. The analysis and control module incorporates a strain-axial force conversion model, a data verification model, and a bearing capacity determination model. The strain-axial force conversion model is used to calculate the axial force values ​​at different depths of the pile body and generate an axial force distribution curve based on the strain data collected by distributed strain sensors and the pile foundation's own parameters. Its calculation formula is as follows:

[0038] N(x) = E·A·ε(x),

[0039] In the formula, N(x) is the axial force value at pile depth x (unit: kN), E is the elastic modulus of pile foundation concrete (unit: MPa), which can be determined according to the strength grade of pile foundation concrete, A is the cross-sectional area of ​​pile body (unit: m²), which is calculated based on pile diameter, and ε(x) is the axial strain value at pile depth x (unit: με).

[0040] Data is collected by distributed strain sensors. The data verification model integrates measured values ​​from load sensors, calculated values ​​of axial force at the pile top, strain drift compensation data, and temperature correction parameters to construct a multi-dimensional data verification system. This system automatically eliminates abnormal data and corrects measurement deviations. Specifically, by comparing the measured values ​​from load sensors with the calculated values ​​of axial force at the pile top, if the deviation exceeds 5%, an abnormal data elimination mechanism is triggered. Simultaneously, temperature data collected by temperature sensors is used to correct temperature drift in the strain data, and sensor installation deviation parameters are used to compensate for deviations in the measurement data, ensuring the reliability of the detection data. The bearing capacity determination model integrates three core data points: load-settlement curves, pile axial force distribution curves, and pile stress change curves. It establishes a bearing capacity determination method that combines macroscopic deformation and microscopic stress, accurately identifying the point where side friction is fully utilized, the starting point of pile end resistance, and the critical point of ultimate bearing capacity, avoiding misjudgments caused by a single criterion.

[0041] 5. Feedback Adjustment Module: Used to receive control commands from the analysis and control module, adjust the loading rate and graded load size of the loading module, realize closed-loop control of the loading process, and ensure the safety and accuracy of the loading process. The feedback adjustment module employs closed-loop control logic, using the maximum allowable strain of the pile body and the pile top settlement rate as dual control thresholds. The maximum allowable strain is determined based on the concrete strength grade of the pile foundation, ranging from 1500 to 2500 με. For example, the maximum allowable strain for a C30 concrete pile foundation is 2000 με, and for a C40 concrete pile foundation, it is 2300 με. The preset threshold for the pile top settlement rate is 0.2 mm / min (which can be flexibly adjusted according to project requirements). Specifically, when the pile strain reaches 90% of the maximum allowable strain or the pile top settlement rate exceeds the preset threshold, the feedback adjustment module immediately sends a deceleration command to the loading module, controlling the loading module to reduce the loading rate by 50%. When the pile strain reaches the maximum allowable strain or the pile top settlement rate continuously exceeds the preset threshold without convergence (lasting more than 3 minutes), the feedback adjustment module sends a stop loading command, controlling the loading module to immediately stop loading, preventing the pile from crushing due to excessive pressure and ensuring the safety of the testing process.

[0042] To enhance the convenience and practicality of the testing system, the system also includes a wireless transmission module and a terminal display module. The wireless transmission module is electrically connected to the data acquisition module and the analysis and control module, and uses 5G or WiFi wireless transmission protocols to wirelessly transmit various types of raw data, preprocessed data, and analysis results and bearing capacity determination results output by the analysis and control module to the terminal display module in real time. The terminal display module can be a mobile terminal such as a computer or tablet to display various types of testing data, curves (load-settlement curves, pile axial force distribution curves, pile stress change curves, etc.) and bearing capacity determination results in real time. It also has data storage, export, and printing functions, and can export testing data and reports to Excel, PDF, and other formats for easy archiving and quality acceptance in subsequent projects.

[0043] This includes a pile foundation bearing capacity testing system and a pile foundation bearing capacity testing method.

[0044] In practical use, the following steps are included:

[0045] S1: Pre-test preparation to ensure smooth testing. First, pre-treat the pile foundation by cleaning debris and laitance from the pile top surface to ensure a flat and clean surface, avoiding any impact on the uniformity of load application. Second, distribute the strain sensors along the pile axis. Before installation, calibrate the sensors to ensure measurement accuracy. Use specialized fasteners to tightly attach the sensors to the pile body during installation to prevent measurement deviations caused by sensor loosening. The spacing is determined based on the pile length and required testing accuracy, generally 1-3 meters. Finally, install the load cells between the jack and the top of the pile, ensuring a tight fit and no obstruction. During the interval, the displacement gauge is installed on the reference beam at the top of the pile foundation, and the sensitivity of the displacement gauge is adjusted to ensure accurate detection of pile top settlement. At the same time, the temperature sensor and the distributed strain sensor are placed close together, with a spacing of no more than 5 cm. Finally, the loading module, data acquisition module, analysis and control module, and feedback adjustment module are debugged, the connection of each module is checked, and a no-load test run is performed to ensure that each module works normally and data transmission is smooth. At the same time, relevant parameters of the pile foundation (elastic modulus of concrete, cross-sectional area of ​​pile body, concrete strength grade, etc.) are input to complete the parameter settings before testing.

[0046] S2: Graded loading ensures precise and stable load application. The loading module applies graded loads to the pile foundation using a continuous, graded loading method. The initial load is 10%-15% of the estimated ultimate bearing capacity, with each subsequent load increment being 5%-10% of the estimated ultimate bearing capacity. For example, if the estimated ultimate bearing capacity is 1000kN, the initial load is 100-150kN, and each subsequent load increment is 50-100kN. After each load is applied, a preset stabilization time of 5-10 minutes is maintained. When the pile top settlement rate is less than 0.1mm / min, the pile deformation is considered stable, and the next load level can be applied. If the pile top settlement rate remains greater than 0.1mm / min, the stabilization time is extended until the settlement rate stabilizes, preventing abnormal pile deformation due to excessively rapid load application.

[0047] S3: Synchronous data acquisition to obtain complete test data. During the graded loading process, the data acquisition module synchronously acquires strain data at different depths of the pile, load data measured by the load sensor, pile top settlement data acquired by the displacement gauge, and ambient temperature data acquired by the temperature sensor. The acquisition frequency is set to 1-10Hz according to the detection accuracy requirements. The data acquisition module performs preliminary preprocessing on the acquired data (data noise reduction, preliminary screening of abnormal data, and data format conversion) to ensure the integrity and validity of the data. The preprocessed data is then transmitted to the analysis and control module in real time.

[0048] S4: Data processing and error correction to improve data reliability. After receiving preprocessed data from the data acquisition module, the analysis and control module uses a built-in strain-axial force conversion model, combined with the input pile foundation parameters, to calculate the axial force values ​​at different depths of the pile and generate an axial force distribution curve. Simultaneously, through a data verification model, it integrates measured values ​​from load sensors, calculated axial force values ​​at the pile top, strain drift compensation data, and temperature correction parameters to perform in-depth data verification, automatically eliminating abnormal data and correcting measurement deviations caused by temperature drift and sensor installation errors, ensuring the accuracy and reliability of the detection data. Furthermore, the analysis and control module also generates a pile stress variation curve based on the processed data, providing support for subsequent bearing capacity determination.

[0049] S5: Closed-loop loading regulation ensures the safety and accuracy of the loading process. Based on data processing results, the analysis and control module determines in real time whether the pile strain and pile top settlement rate have reached the preset control thresholds. If the pile strain reaches 90% of the maximum allowable strain or the pile top settlement rate exceeds the preset threshold (0.2 mm / min), the analysis and control module immediately generates a deceleration command and sends it to the feedback regulation module. Upon receiving the command, the feedback regulation module controls the loading module to reduce the loading rate (deceleration ratio is 50%). If the pile strain reaches the maximum allowable strain or the pile top settlement rate continues to exceed the preset threshold without convergence (duration exceeding 3 minutes), the analysis and control module generates a stop loading command, and the feedback regulation module controls the loading module to immediately stop loading to prevent pile crushing.

[0050] S6: Bearing capacity determination, outputting accurate test results. When the pile top settlement rate continuously exceeds the preset threshold and shows no convergence trend, or reaches the maximum allowable strain of the pile body, loading is stopped, at which point the pile body has reached its ultimate bearing capacity state. The analysis and control module integrates three core data points—load-settlement curve, pile axial force distribution curve, and pile stress change curve—through the built-in bearing capacity determination model. It accurately identifies the point where the side friction resistance is fully utilized and the starting point of the pile end resistance, separates the bearing capacity contribution values ​​of the pile side friction resistance and the pile end resistance, and finally outputs the ultimate bearing capacity of the pile foundation and the contribution values ​​of each resistance component, thus completing the bearing capacity determination.

[0051] S7: Inspection complete, data processing and report output finished. After loading stops, the load is slowly unloaded through the loading module at twice the loading rate to avoid sudden changes in pile stress due to excessive unloading. After unloading, all raw data, processed data, and bearing capacity determination results from the inspection process are processed. The inspection data, curves, and determination results are exported to Excel, PDF, and other formats through the terminal display module, and the inspection report is printed, completing the entire inspection process.

[0052] Example 1

[0053] Taking C30 concrete large-diameter pile foundation (pile diameter 1.2m, pile length 20m) as an example

[0054] A pile foundation bearing capacity testing system, the specific structure of which is as follows:

[0055] Loading Module: The shovel platform adopts a steel structure platform with a total counterweight weight of 1200kN to ensure sufficient reaction force; the jacks are hydraulic jacks with a rated load of 1500kN, fixedly installed below the shovel platform with the output end aligned with the top of the pile; the hydraulic pump station is a high-pressure hydraulic pump station with an output pressure adjustment range of 0-30MPa; the automatic loading controller adopts a PLC controller, which is electrically connected to the hydraulic pump station and analysis control module, and can accurately adjust the loading rate and load size.

[0056] Sensing Module: The distributed strain sensors are fiber optic strain sensors, arranged along the pile axis at 2m intervals, for a total of 10 sensors, used to collect axial strain data at different depths of the pile; the load sensors are pressure load sensors with a range of 0-1500kN, installed between the jack and the top of the pile; the displacement gauges are dial gauges with an accuracy of 0.01mm, installed on the reference beam; the temperature sensors are platinum resistance temperature sensors, arranged adjacent to each distributed strain sensor at a spacing of 3cm, used to collect ambient temperature data.

[0057] Data acquisition module: A multi-channel synchronous acquisition instrument with 32 channels is used, which is electrically connected to various sensors. The acquisition frequency is set to 5Hz and the buffer capacity is 120GB. The initial preprocessing uses wavelet analysis algorithm for data noise reduction and threshold method to filter out abnormal data.

[0058] Analysis and control module: adopts an industrial control computer, with built-in strain-axial force conversion model, data verification model and bearing capacity determination model; in the strain-axial force conversion model, the elastic modulus of C30 concrete is E=30000MPa, and the cross-sectional area of ​​the pile body is A=π×(1.2 / 2)²=1.131m²; the deviation threshold of the data verification model is set to 5%, and the temperature drift correction adopts a linear correction algorithm; the bearing capacity determination model integrates the data of the three curves to accurately identify the critical point of ultimate bearing capacity.

[0059] Feedback adjustment module: A closed-loop controller is adopted, which is electrically connected to the analysis control module and the loading module. The maximum allowable strain of the pile body is set to 2000με, and the preset threshold of the pile top settlement rate is 0.2mm / min, so as to realize closed-loop control of the loading process.

[0060] In addition, it is equipped with a 5G wireless transmission module and a laptop terminal, which can transmit and display test data and results in real time, and has data storage, export and printing functions.

[0061] A method for testing the bearing capacity of pile foundations, the specific steps of which are as follows:

[0062] S1: Preparations before testing: Clean the laitance and debris from the top of the pile, and calibrate various sensors; Arrange 10 distributed strain sensors along the axial direction of the pile at 2m intervals and fix them with special fasteners; Install the load sensor between the jack and the top of the pile, install the displacement gauge on the reference beam, and arrange the temperature sensor and strain sensor adjacent to each other; Debug each module, conduct a no-load test run, and input the pile foundation parameters (E=30000MPa, A=1.131m², concrete strength grade C30).

[0063] S2: Graded loading, with an estimated ultimate bearing capacity of 1000kN, an initial load of 120kN (12%), and subsequent load increments of 80kN (8%). After each load is applied, maintain stability for 8 minutes. When the settlement rate at the pile top is less than 0.1mm / min, apply the next load.

[0064] S3: Data synchronous acquisition, with the acquisition frequency set to 5Hz, synchronously acquires strain data, load data, pile top settlement data, and temperature data at different depths of the pile. After preliminary preprocessing by the data acquisition module, the data is transmitted to the analysis and control module.

[0065] S4: Data processing and error correction. The analysis and control module calculates the axial force distribution of the pile body through the strain-axial force conversion model and generates the axial force distribution curve. Through the data verification model, it integrates the measured load values ​​and temperature correction parameters, eliminates abnormal data, corrects measurement deviations, and generates the pile body stress change curve.

[0066] S5: Loading closed-loop regulation. When the load reaches level 8 (680kN), the pile strain reaches 1800με (90% of the maximum allowable strain), and the feedback regulation module controls the loading module to reduce the loading rate. When the load reaches level 10 (880kN), the pile top settlement rate continues to exceed 0.2mm / min and shows no convergence trend, and the feedback regulation module controls the loading module to stop loading.

[0067] S6: Bearing capacity determination. The analysis and control module integrates the load-settlement curve, pile axial force distribution curve, and pile stress change curve to identify the point where the side friction is fully utilized and the starting point of the pile end resistance. The contribution value of the pile side friction is 528kN, the contribution value of the pile end resistance is 352kN, and the output pile foundation ultimate bearing capacity is 880kN.

[0068] S7: The test is over. The load is slowly unloaded at twice the loading rate. The test data is organized, and the test report is exported and printed through the terminal to complete the test.

[0069] It should be noted that the detection system and method in this invention can flexibly adjust the sensor layout spacing, loading parameters, control thresholds, etc., according to different pile foundation types (ultra-long piles, large-diameter piles, precast piles, cast-in-place piles, etc.) and different concrete strength grades to adapt to the detection needs of various engineering scenarios. At the same time, the specific models and parameters of each module can be selected according to actual detection needs. As long as the technical solution of this invention can be realized, it falls within the protection scope of this invention.

[0070] Furthermore, the strain-axial force conversion model, data verification model, and bearing capacity determination model in this invention can be optimized and adjusted according to actual engineering data to further improve the accuracy of data processing and bearing capacity determination; the wireless transmission module can select different transmission protocols such as 5G and WiFi according to the network environment at the testing site to ensure the stability of data transmission.

[0071] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A pile foundation bearing capacity testing system, characterized in that, The system includes a loading module, a sensing module, a data acquisition module, an analysis and control module, and a feedback adjustment module. The sensing module is electrically connected to the data acquisition module, the data acquisition module is electrically connected to the analysis and control module, the analysis and control module is electrically connected to the feedback adjustment module, and the feedback adjustment module is electrically connected to the loading module. The loading module is used to apply graded loads to the pile foundation and achieve dynamic control of the loading process. The sensing module is used to collect relevant detection data of the pile foundation. The data acquisition module is used to synchronously collect various types of data output by the sensing module and perform preliminary preprocessing. The analysis and control module is used for data processing, error correction, and generation of control commands. The feedback adjustment module is used to execute control commands and adjust the working state of the loading module.

2. The pile foundation bearing capacity testing system according to claim 1, characterized in that: The loading module includes a stacking platform, jacks, a hydraulic pump station, and an automatic loading controller. The jacks are fixedly installed below the stacking platform, with their output ends aligned with the top of the pile foundation. The hydraulic pump station is connected to the jacks to provide power. The automatic loading controller is electrically connected to the hydraulic pump station and the analysis and control module, and is used to receive control commands from the analysis and control module, adjust the output pressure of the hydraulic pump station, and thus control the loading rate and load of the jacks.

3. The pile foundation bearing capacity testing system according to claim 1, characterized in that: The sensing module includes distributed strain sensors, load sensors, displacement gauges, and temperature sensors. The distributed strain sensors are distributed along the axial direction of the pile body to collect axial strain data at different depths of the pile body in real time. The load sensors are installed between the jack and the top of the pile body to measure the real-time load value during the loading process. The displacement gauges are installed on the reference beam at the top of the pile body to collect pile top settlement data. The temperature sensors are arranged adjacent to the distributed strain sensors to collect ambient temperature data around the pile body, providing parameters for temperature correction of the strain data.

4. The pile foundation bearing capacity testing system according to claim 1, characterized in that: The data acquisition module uses a multi-channel synchronous acquisition instrument, which is electrically connected to a distributed strain sensor, a load sensor, a displacement gauge, and a temperature sensor. The acquisition frequency is adjustable from 1 to 10 Hz and has a data caching function to avoid data loss. The preliminary preprocessing includes data noise reduction, preliminary screening of abnormal data, and data format conversion.

5. The pile foundation bearing capacity testing system according to claim 1, characterized in that: The analysis and control module incorporates a strain-axial force conversion model, a data verification model, and a bearing capacity determination model. The strain-axial force conversion model calculates the axial force values ​​at different depths of the pile and generates axial force distribution curves based on strain data collected by distributed strain sensors. The data verification model integrates measured values ​​from load sensors, calculated axial force values ​​at the pile top, strain drift compensation data, and temperature correction parameters to automatically eliminate abnormal data and correct measurement deviations. The bearing capacity determination model integrates load-settlement curves, pile axial force distribution curves, and pile stress change curves to achieve coordinated determination of pile foundation bearing capacity.

6. The pile foundation bearing capacity testing system according to claim 5, characterized in that: The calculation formula for the strain-axial force conversion model is as follows: N(x) = E·A·ε(x) Where N(x) is the axial force at pile depth x, E is the elastic modulus of the pile foundation concrete, A is the cross-sectional area of ​​the pile, and ε(x) is the axial strain at pile depth x.

7. The pile foundation bearing capacity testing system according to claim 1, characterized in that: The feedback adjustment module adopts closed-loop control logic, using the maximum allowable strain of the pile body and the settlement rate of the pile top as dual control thresholds. When the pile body strain reaches 90% of the maximum allowable strain or the settlement rate of the pile top exceeds the preset threshold, the feedback adjustment module controls the loading module to reduce the loading rate. When the pile body strain reaches the maximum allowable strain or the settlement rate of the pile top continues to exceed the preset threshold and shows no convergence trend, the feedback adjustment module controls the loading module to stop loading to avoid pile crushing.

8. The pile foundation bearing capacity testing system according to claim 1, characterized in that: It also includes a wireless transmission module and a terminal display module; the wireless transmission module is electrically connected to the data acquisition module and the analysis and control module, and is used to wirelessly transmit the acquired data and analysis results to the terminal display module; the terminal display module is used to display various types of test data, curves and load-bearing capacity determination results in real time, and has data storage, export and printing functions.

9. A method for testing the bearing capacity of a pile foundation, comprising the pile foundation bearing capacity testing system according to any one of claims 1-8, characterized in that: Includes the following steps: S1: Preparations before testing: Distributed strain sensors are distributed along the pile axis, load sensors, displacement gauges and temperature sensors are installed, and the loading module, data acquisition module, analysis and control module and feedback adjustment module are debugged to ensure that each module works normally. S2: Graded loading, graded loads are applied to the pile foundation through the loading module. The initial load is 10%-15% of the estimated ultimate bearing capacity, and the subsequent load increment is 5%-10% of the estimated ultimate bearing capacity. After each load is applied, the load is kept stable for a preset time. S3: Data synchronous acquisition. The data acquisition module synchronously acquires strain data, load data, pile top settlement data and temperature data at different depths of the pile body, and transmits them to the analysis and control module after preliminary preprocessing. S4: Data processing and error correction. The analysis and control module calculates the axial force distribution of the pile body through the strain-axial force conversion model, and removes abnormal data and corrects measurement deviations caused by temperature drift and sensor installation deviations through the data verification model. S5: Loading closed-loop regulation, the analysis and control module determines whether the pile strain and pile top settlement rate have reached the control threshold based on the data processing results, and adjusts the loading rate of the loading module and the size of the next level load through the feedback adjustment module; S6: Bearing capacity determination. When the settlement rate at the top of the pile continuously exceeds the preset threshold and shows no convergence trend, or when the maximum allowable strain of the pile body is reached, the loading is stopped. The analysis and control module integrates various curve data through the bearing capacity determination model and outputs the ultimate bearing capacity of the pile foundation and the resistance contribution value of each part. S7: Inspection complete, unload the load, organize the inspection data and judgment results, and export or print the inspection report through the terminal display module.

10. A method for testing the bearing capacity of a pile foundation according to claim 9, characterized in that: In S2, the stabilization time for each load level is 5-10 minutes. When the settlement rate at the top of the pile is less than 0.1 mm / min, the next load level can be applied. In S6, the maximum allowable strain of the pile body is determined according to the strength grade of the pile foundation concrete, and the value range is 1500-2500 με.

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