Adjustable inclination pile foundation self-balancing detection load box device and method

Abstract

This invention discloses an adjustable tilt angle pile foundation self-balancing load box device and method. The core of the device adopts a rotating connection structure between ball bearings and vertical reinforcement sleeves, which can release the constraint stress at the connection during tilt angle adjustment. Redundant distributed tilt angle sensors are used, and high-precision attitude monitoring is achieved throughout the entire process through staged adaptive sampling, Kalman filtering, and weighted data fusion. Four independently controlled hydraulic rods, combined with a segmented PI closed-loop control algorithm, can correct the tilt angle of the load box in real time during hoisting, lowering, and concrete pouring stages. The load box tilt angle adjustment accuracy of this invention is high, ensuring that its stress surface is perpendicular to the pile axis, significantly improving the accuracy of the detection results. At the same time, it avoids problems such as weld cracking and rebar deformation, reducing rework rates under complex working conditions. The control system is simple, reliable, and easy to implement in engineering, possessing high promotional value.

Description

Technical Field

[0001] This invention relates to the field of pile foundation self-balancing test load box technology, specifically to an adjustable tilt angle pile foundation self-balancing test load box device and method. Background Technology

[0002] In pile foundation self-balancing testing technology, the load cell is traditionally rigidly connected to the vertical main reinforcement of the steel cage by welding. However, when the load cell tilts due to construction forces (such as hoisting deviation, uneven soil layers, and concrete pouring impact), this rigid welding creates fixed-end constraints, generating significant additional bending moments and shear stresses at the connection. Under long-term effects, this may lead to weld fatigue cracking and localized deformation of the reinforcement, thereby affecting the structural integrity and the reliability of the testing data.

[0003] Once a traditional welded connection is completed, the orientation of the load cell is fixed. If an inclination deviation is detected during construction, it cannot be effectively adjusted, and the load cell must be passively accepted as tilted. This not only reduces the accuracy of pile foundation bearing capacity testing, but in severe cases, uneven stress may also affect the validity of the test results, potentially leading to rework and economic losses.

[0004] While some existing technologies attempt to incorporate tilt monitoring, they generally suffer from the following drawbacks: First, tilt sensors are mostly arranged at single points, making them susceptible to local vibrations and sensor malfunctions, resulting in low measurement reliability. Second, they lack comprehensive data acquisition and processing logic, leading to high noise and low accuracy in the raw data, failing to accurately reflect the true attitude of the load cell. Third, the control strategies are simple, often employing open-loop control, which lacks sufficient adjustment accuracy and response speed, making it impossible to achieve precise closed-loop control throughout the entire process. Fourth, the control algorithms are complex, making engineering implementation difficult and costly, hindering large-scale application on construction sites. Summary of the Invention

[0005] To overcome the above limitations, this invention proposes an adjustable tilt angle pile foundation self-balancing detection load box device and method that integrates redundant tilt angle monitoring, intelligent data processing and segmented PI closed-loop control. It fundamentally solves the defects of traditional rigid welded structures that are prone to deformation and cannot be adjusted at the connection when the load box attitude changes. At the same time, it ensures that the control system is simple, reliable and easy to implement in engineering, and significantly improves the adaptability and reliability of self-balancing detection under complex working conditions.

[0006] To achieve the above objectives, the present invention provides an adjustable tilt angle pile foundation self-balancing detection load box device, including a hydraulic rod 1, a lower end plate 2, an upper end plate 3, a self-balancing hydraulic press 4, an upper oil supply device 5, a No. 1 hydraulic valve 6, a No. 2 hydraulic valve 7, a No. 3 hydraulic valve 8, a No. 4 hydraulic valve 9, a telescopic rod 10, a tilt angle sensor 11, ball bearings 12, a vertical reinforcement sleeve 13, and a ball bearing nesting hole 14; the tilt angle sensor 11 is arranged on the lower end plate 2 and is used to measure the entire process of the self-balancing detection device after the reinforcement cage is lifted off the ground after welding. The inclination angle during the surface, lowering, and concrete pouring stages; the ball bearings 12 are embedded in the ball bearing nesting holes 14 and can rotate freely within the holes; the ball bearing nesting holes 14 are evenly distributed on the upper end plate 3 and the lower end plate 2, and their number can be customized and adjusted according to the number of vertical bars in the steel cage; the hydraulic rod 1 is fixedly connected to the lower end plate 2 and is raised and lowered by the control of the upper oil supply device 5 and various oil pressure valves; the two ends of the telescopic rod 10 are respectively hinged to the upper end plate 3 and the lower end plate 2, which is used to enhance the local load-bearing capacity of the load box and cooperate with the hydraulic rod to achieve all-round posture adjustment.

[0007] Furthermore, hydraulic valves 6 (No. 1), 7 (No. 2), 8 (No. 3), and 9 (No. 4) are connected to four self-balancing hydraulic presses 4, respectively, and can independently control the oil intake of each self-balancing hydraulic press 4, thereby precisely regulating the lifting height of the four hydraulic rods 1 to adjust the tilt angle of the load box.

[0008] Furthermore, the vertical rib sleeve 13 is fixedly connected to the outer spherical surface of the ball bearing 12, and the vertical reinforcing bar is inserted into the vertical rib sleeve 13 and then welded and fixed; the vertical rib sleeve 13 can rotate freely synchronously with the ball bearing 12 to eliminate the additional deformation and stress generated at the connection due to the change of the load box tilt angle.

[0009] Furthermore, the tilt sensor 11 collects the attitude data of the load box in real time during the entire process of hoisting, lowering and finally positioning. When an angle deviation is detected, the tilt angle of the load box is corrected in real time by adjusting the oil volume of the four self-balancing hydraulic presses 4 to control the lifting and lowering of the corresponding hydraulic rods 1.

[0010] Furthermore, when adjusting the tilt angle of the load box, the telescopic rod 10 extends and retracts synchronously with the hydraulic rod 1, ensuring smooth relative movement between the upper end plate 3 and the lower end plate 2, and realizing the load box's all-round, jam-free lifting and lowering.

[0011] Furthermore, the tilt sensor 11 adopts a redundant distributed arrangement: one tilt sensor is set at each of the four symmetrical positions in the lower end plate 2; all tilt sensors are embedded and sealed, with the mounting surface completely in contact with and parallel to the upper surface of the lower end plate 2, and the sensor coordinate system coincides with the load box reference coordinate system.

[0012] Furthermore, it also includes a data acquisition and processing unit, which is electrically connected to all tilt sensors 11, and its data acquisition and processing logic is as follows: D1. The sampling frequency is set in stages: 10-20Hz for hoisting, 5-10Hz for lowering, and 1-5Hz for concrete pouring. D2 uses the Kalman filter algorithm to filter the original tilt angle data to eliminate construction vibration, electromagnetic interference and sensor noise; D3 uses the 3σ criterion to identify anomalies in the data of each sensor in real time and removes abnormal data; if the number of valid sensors after removal is less than 2, a sensor fault alarm is triggered and construction is suspended; for the remaining valid data, weights are dynamically allocated according to the number of sensors, and a weighted average is performed to obtain the actual roll angle and pitch angle of the load cell. D4. Compare the actual tilt angle with the preset initial tilt angle to calculate the roll angle deviation Δθ and pitch angle deviation Δφ.

[0013] Furthermore, it also includes a closed-loop control unit, which is electrically connected to the data acquisition and processing unit and hydraulic valves 1-4, and its control strategy algorithm is as follows: T1 adopts a piecewise proportional-integral control algorithm, which divides the tilt angle deviation into different adjustment ranges and uses corresponding control parameters in each range. T2, establish a linear mapping relationship between the lifting height of the hydraulic rod and the tilt angle deviation: the roll angle deviation Δθ corresponds to the differential lifting of the left and right hydraulic rods, and the pitch angle deviation Δφ corresponds to the differential lifting of the front and rear hydraulic rods. T3, set the tilt angle deviation threshold: when |Δθ|≤0.1° and |Δφ|≤0.1°, stop adjustment; when 0.1°<|Δθ|≤3° or 0.1°<|Δφ|≤3°, start normal adjustment mode; when |Δθ|>3° or |Δφ|>3°, trigger audible and visual alarm and suspend construction until manual inspection and resumption.

[0014] The present invention also provides a method for detecting the self-balancing load box of an adjustable tilt angle pile foundation, which is implemented using the device described in any one of claims 1-8, and includes the following steps: S1, Pre-assembly and initial calibration: The lower end plate (2) of the self-balancing load box is horizontally assembled and welded to the lower end of the steel cage through the ball bearing (12) and the vertical bar sleeve (13). The upper end plate (3) is assembled and welded to the upper end of the steel cage in the same way. The data acquisition and processing unit is started to record the initial values ​​of all tilt sensors (11) and their average values ​​are set as the reference tilt angles θ0 and φ0. S2, hoisting and lowering stage control: The steel cage is hoisted as a whole and lowered into the hole. The data acquisition and processing unit collects tilt angle data at a preset frequency and performs filtering and fusion processing to calculate the real-time tilt angle deviation. The closed-loop control unit outputs control signals according to the tilt angle deviation, independently adjusts the oil inlet of the four self-balancing hydraulic presses 4, controls the lifting and lowering of the corresponding hydraulic rods 1, and corrects the tilt angle of the load box to the reference tilt angle range in real time. S3, Concrete pouring stage control: After the steel cage is lowered into place, concrete is poured. During the concrete flow and solidification process, the change of the load cell tilt angle is continuously monitored, and the same control logic is used to adjust the tilt angle to the initial reference value. S4, Test Preparation: After the concrete strength reaches the design requirements, shut down the tilt angle monitoring and control system and conduct the pile foundation self-balancing bearing capacity test.

[0015] The beneficial effects of this invention are: This invention, through real-time monitoring by tilt sensors and the coordinated work of hydraulic rods independently controlled by multiple hydraulic presses, enables closed-loop adjustment of the load cell's attitude throughout the entire process of hoisting, lowering, and concrete pouring, completely changing the situation in traditional methods where the load cell's tilt angle is passively fixed and cannot be corrected.

[0016] This invention utilizes a rotating connection design between the ball bearing and the sleeve, enabling the load cell to release the bending moment and shear constraint at the weld joint through the rotation of the sleeve when adjusting the tilt angle. This avoids problems such as stress concentration, fatigue damage, or steel bar deformation caused by angular deviations in traditional rigid welding.

[0017] This invention maintains the load cell at its designed tilt angle, ensuring its upper and lower stress surfaces are perpendicular to the pile axis. This results in uniform and symmetrical force transmission, fundamentally reducing test data deviations caused by load cell tilt and improving the accuracy and reliability of self-balancing method test results. Under complex construction conditions such as inclined piles and uneven soil layers, the system can respond in real-time to angular disturbances caused by geological changes, reinforcement cage deflection, or concrete flow, reducing rework, adjustments, and even test failures due to attitude control issues, thus improving construction efficiency and economy.

[0018] This invention achieves adjustable functionality while ensuring a secure connection between the sleeve and the reinforcing steel through welding, without sacrificing the reliability of the force transmission path. The entire system is compatible with existing self-balancing processes, requiring no significant changes to the construction procedure, and possesses high engineering application value. The use of redundant distributed tilt sensors avoids monitoring failures caused by single-point sensor malfunctions, improving the reliability of the measurement system. The embedded sealed installation design adapts to harsh environments such as underwater and concrete pouring, extending the sensor's lifespan.

[0019] This invention employs staged adaptive sampling combined with Kalman filtering and weighted data fusion to effectively eliminate construction noise and interference, improve tilt angle measurement accuracy, and provide a reliable data foundation for precise control. Simultaneously, it utilizes a piecewise PI control algorithm, which is simple in structure, convenient in parameter tuning, and has strong anti-interference capabilities. It is easy to implement in engineering and has low cost, while ensuring adjustment accuracy and response speed, fully meeting the engineering requirements for pile foundation self-balancing detection. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the adjustable tilt angle pile foundation self-balancing detection load box device proposed in this invention; Figure 2 These are the front and side views of the upper end plate; Figure 3 These are the front and side views of the lower end plate; Figure 4 This is a schematic diagram of the upper oil conveying device controlling the oil press to drive the hydraulic rod to rise and fall; Figure 5 This is a schematic diagram showing the arrangement of the tilt sensor on the lower end plate; In the diagram: 1-Hydraulic rod, 2-Lower end plate, 3-Upper end plate, 4-Self-balancing hydraulic press, 5-Upper oil delivery device, 6-No. 1 hydraulic valve, 7-No. 2 hydraulic valve, 8-No. 3 hydraulic valve, 9-No. 4 hydraulic valve, 10-Telescopic rod, 11-Tilt sensor, 12-Ball bearing, 13-Vertical rib sleeve, 14-Ball bearing nesting hole. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0022] Reference Figures 1-5 This invention discloses a specific embodiment of an adjustable tilt angle pile foundation self-balancing detection load box device and method. The device includes a hydraulic rod 1, a lower end plate 2, an upper end plate 3, a self-balancing hydraulic press 4, an upper oil delivery device 5, a No. 1 hydraulic valve 6, a No. 2 hydraulic valve 7, a No. 3 hydraulic valve 8, a No. 4 hydraulic valve 9, a telescopic rod 10, a tilt angle sensor 11, a ball bearing 12, a vertical reinforcement sleeve 13, a ball bearing nesting hole 14, a data acquisition and processing unit, and a closed-loop control unit.

[0023] Both the lower end plate 2 and the upper end plate 3 are circular steel plates with a diameter matching the pile diameter and a thickness of 30mm. The ball bearing nesting holes 14 are hemispherical grooves evenly distributed along the edges of the upper and lower end plates. In this embodiment, eight ball bearing nesting holes 14 are provided, corresponding to the eight vertical main bars of the reinforcing cage. The balls 12 are 20mm diameter stainless steel balls, embedded in the ball bearing nesting holes 14, and can rotate freely 360° within the holes. The vertical bar sleeve 13 is a steel pipe with an inner diameter identical to that of the vertical reinforcing bar. One end is welded to the outer spherical surface of the ball bearing 12, and the other end is used to insert the vertical reinforcing bar and weld it in place.

[0024] Four hydraulic rods 1 are arranged in a square on the upper surface of the lower end plate 2 and are connected to four self-balancing hydraulic presses 4 respectively. The upper oil supply device 5 includes a hydraulic pump, an oil tank, and oil supply pipelines, which supply oil to the four self-balancing hydraulic presses 4 through oil pressure valves 1 to 4 respectively. Four telescopic rods 10 are evenly arranged between the hydraulic rods 1, and their two ends are hinged to the upper end plate 3 and the lower end plate 2 respectively.

[0025] like Figure 5 As shown, the tilt sensors 11 are arranged redundantly, with four sensors installed at the connection between the lower end plate 2 and the hydraulic rod 1, and at four quadrant positions located halfway from the edge of the lower end plate. All tilt sensors are high-precision MEMS tilt sensors with a measurement accuracy of no less than ±0.01° and a range of ±15°, meeting the tilt measurement requirements throughout the entire pile foundation construction process. The sensors are embedded and sealed, with an external stainless steel waterproof protective cover providing IP68 protection, making them suitable for harsh environments such as underwater and concrete pouring.

[0026] The data acquisition and processing unit uses an STM32F407 microcontroller and communicates with four tilt sensors (11) via an RS485 bus. The sampling frequency can be automatically switched according to the construction stage. The closed-loop control unit uses a PLC controller and communicates with the data acquisition and processing unit via Ethernet, outputting control signals to the electromagnetic actuators of hydraulic valves 1-4. Its data acquisition and processing logic is as follows: 1. Phased adaptive sampling: Different sampling frequencies are set according to the dynamic characteristics of the construction phase: During the hoisting phase, the steel cage vibrates greatly and changes its posture rapidly, so the sampling frequency is set to 10-20Hz; during the lowering phase, the posture changes are relatively gentle, so the sampling frequency is set to 5-10Hz; during the concrete pouring phase, the posture changes slowly, so the sampling frequency is set to 1-5Hz, which reduces system power consumption while ensuring data accuracy.

[0027] 2. Kalman Filter Noise Reduction: To address mechanical vibration, electromagnetic interference, and sensor noise present during construction, a Kalman filter algorithm is used to process the raw tilt angle data. The tilt angle state equation and observation equation are established, and through an iterative prediction-update process, high-frequency noise is filtered out to obtain smooth tilt angle data.

[0028] 3. Outlier Removal and Data Fusion: The 3σ criterion is used to remove outliers from the filtered data. Data exceeding the mean ± 3 standard deviations are identified as outliers and deleted. When a sensor is identified as outlier, its data is automatically excluded from subsequent fusion, effectively avoiding the impact of single-point failures on the overall measurement results. If the number of valid sensors after removal is less than two, the monitoring system is considered to have failed, triggering an audible and visual alarm and suspending construction. For the remaining valid data, weights are dynamically allocated based on the number of valid sensors. For optimal performance, equal weights are assigned, i.e., the weight of each valid sensor = 1 / number of valid sensors. A weighted average fusion is then performed to obtain the actual roll angle θ and pitch angle φ of the load cell. In this embodiment, if there are no outlier sensors, the weight of each of the four sensors is 0.25; if one sensor is outlier, the weight of the remaining three sensors is 0.333, ensuring that the fusion result is not affected by faulty sensors.

[0029] 4. Tilt angle deviation calculation: Compare the actual tilt angle after fusion with the pre-calibrated reference tilt angles θ0 and φ0 to calculate the roll angle deviation Δθ=θ-θ0 and pitch angle deviation Δφ=φ-φ0, which are used as inputs for closed-loop control.

[0030] Closed-loop attitude control strategy and algorithm The closed-loop control unit is electrically connected to the data acquisition and processing unit and hydraulic valves 1-4. A piecewise proportional-integral (PI) control algorithm is used to achieve precise adjustment of the load cell tilt angle. This algorithm has a simple structure, convenient parameter tuning, and strong anti-interference ability, making it particularly suitable for the complex environment of the construction site. The specific control strategy is as follows: 1. Segmented PI controller design: The adjustment process is divided into three intervals based on the magnitude of the tilt angle deviation, and different PI control parameters are used in different intervals: 1. Large deviation range (1° < |Δθ| < 3° or |1° < Δφ| < 3°): Use a larger proportional coefficient and a smaller integral coefficient to ensure a fast system response and quickly reduce tilt angle deviation; 2. Medium deviation range (0.3° < |Δθ| ≤ 1° or 0.3° < |Δφ| ≤ 1°): Uses moderate proportional and integral coefficients to balance adjustment speed and stability; 3. Small deviation interval (0.1°<|Δθ|≤0.3° or 0.1°<|Δφ|≤0.3°): Use a smaller proportional coefficient and a larger integral coefficient to ensure stable convergence of the system and eliminate steady-state error.

[0031] 2. Hydraulic rod linkage control logic: Four hydraulic rods are arranged in a square at the four corners of the lower end plate (2), corresponding to the front, back, left, and right directions respectively. A linear mapping relationship between the lifting height of the hydraulic rods and the tilt angle deviation is established: the roll angle deviation Δθ corresponds to the differential lifting of the left and right hydraulic rods. When Δθ>0, the left hydraulic rod rises and the right hydraulic rod falls, and when Δθ<0, the opposite is true. The pitch angle deviation Δφ corresponds to the differential lifting of the front and rear hydraulic rods. When Δφ>0, the front hydraulic rod rises and the rear hydraulic rod falls, and when Δφ<0, the opposite is true. The telescopic rod 10 extends and retracts synchronously with the hydraulic rods to ensure that the upper and lower end plates move in parallel.

[0032] 3. Three-level safety protection mechanism: Setting three levels of tilt angle deviation thresholds: 1. Normal adjustment threshold: |Δθ|≤0.1° and |Δφ|≤0.1°, at which point adjustment stops and the system enters standby monitoring state; 2. Warning threshold: 0.1° < |Δθ| ≤ 3° or 0.1° < |Δφ| ≤ 3°. At this time, the normal adjustment mode is activated and a warning signal is issued. 3. Emergency stop threshold: |Δθ|>3° or |Δφ|>3°. At this time, an audible and visual alarm will be triggered immediately, and the lowering of the steel cage or the pouring of concrete will be suspended. Construction can only be resumed after the fault is manually checked and corrected.

[0033] The specific working process of this embodiment is as follows: 1. Pre-assembly and initial calibration: On a level platform at the construction site, place the lower end plate 2 of the self-balancing load cell horizontally. Insert the vertical reinforcing bars at the bottom of the steel cage one by one into the vertical bar sleeves 13 on the lower end plate 2, and weld them securely. Then, insert the vertical bar sleeves 13 of the upper end plate 3 into the vertical reinforcing bars at the top of the steel cage, and weld them securely. Start the data acquisition and processing unit and the closed-loop control unit. After standing for 5 minutes, record the output values ​​of the four tilt sensors 11, and calculate their average value as the reference tilt angle θ0 = 0.02° and φ0 = 0.01°.

[0034] 2. Lifting and Lowering Stage Control: A crane is used to lift the entire rebar cage and slowly move it above the pile hole. At this time, the data acquisition and processing unit collects tilt angle data at a frequency of 15Hz. After Kalman filtering and data fusion, the real-time tilt angle deviation is calculated. When the roll angle deviation Δθ = 0.5° and the pitch angle deviation Δφ = 0.3° are detected, the closed-loop control unit initiates segmented PI control, outputting control signals to hydraulic valves 1-4 to control the left hydraulic rod to rise by 2mm, the right hydraulic rod to fall by 2mm, the front hydraulic rod to rise by 1.2mm, and the rear hydraulic rod to fall by 1.2mm. Tilt angle changes are continuously monitored during adjustment. When |Δθ| ≤ 0.1° and |Δφ| ≤ 0.1°, adjustment is stopped. The rebar cage is lowered again, and the above adjustment process is repeated until the rebar cage is completely lowered into place.

[0035] 3. Concrete Pouring Stage Control: After the reinforcing cage is lowered into place, concrete pouring begins. During the concrete pouring process, the data acquisition and processing unit collects tilt angle data at a frequency of 2Hz. When a deviation of Δθ=0.2° in the load cell tilt angle is detected due to concrete flow, the closed-loop control unit automatically adjusts the height of the hydraulic rods on both sides to correct the tilt angle to the reference range. Before the concrete initially sets, the tilt angle of the load cell is continuously monitored and kept stable.

[0036] Test preparation: After the concrete strength reaches 100% of the design strength, turn off the tilt monitoring and control system, remove the external connection wires of the sensor, and conduct pile foundation bearing capacity test according to the conventional self-balancing test procedure.

[0037] The embodiments described in this specification are merely examples of implementations of the inventive concept and are for illustrative purposes only. The scope of protection of this invention should not be considered limited to the specific forms described in these embodiments; rather, it extends to equivalent technical means conceived by those skilled in the art based on the inventive concept.

Claims

1. An adjustable tilt angle pile foundation self-balancing load box device, characterized in that, The system includes a hydraulic rod (1), a lower end plate (2), an upper end plate (3), a self-balancing hydraulic press (4), an upper oil delivery device (5), a No. 1 hydraulic valve (6), a No. 2 hydraulic valve (7), a No. 3 hydraulic valve (8), a No. 4 hydraulic valve (9), a telescopic rod (10), an inclination sensor (11), ball bearings (12), a vertical reinforcement sleeve (13), and a ball bearing nesting hole (14). The inclination sensor (11) is located on the lower end plate (2) and is used to measure the self-balancing detection device throughout the entire process, including the lifting of the steel cage off the ground, lowering it, and the concrete pouring stage after welding. Inclination angle; the ball (12) is embedded in the ball nesting hole (14) and can rotate freely in the hole; the ball nesting hole (14) is evenly distributed on the upper end plate (3) and the lower end plate (2), and its number can be customized and adjusted according to the number of vertical bars of the steel cage; the hydraulic rod (1) is fixedly connected to the lower end plate (2) and is raised and lowered by the control of the upper oil supply device (5) and each oil pressure valve; the two ends of the telescopic rod (10) are respectively hinged to the upper end plate (3) and the lower end plate (2) to enhance the local load resistance of the load box and cooperate with the hydraulic rod to achieve all-round attitude adjustment.

2. The adjustable tilt angle pile foundation self-balancing detection load box device according to claim 1, characterized in that, Hydraulic valves No. 1 (6), No. 2 (7), No. 3 (8), and No. 4 (9) are connected to four self-balancing hydraulic presses (4) respectively, and can independently control the oil intake of each self-balancing hydraulic press (4), thereby precisely controlling the lifting height of the four hydraulic rods (1) to achieve the adjustment of the load box tilt angle.

3. The adjustable tilt angle pile foundation self-balancing detection load box device according to claim 1, characterized in that, The vertical reinforcement sleeve (13) is fixedly connected to the outer spherical surface of the ball (12). The vertical reinforcement is inserted into the vertical reinforcement sleeve (13) and then welded and fixed. The vertical reinforcement sleeve (13) can rotate freely synchronously with the ball (12) to eliminate the additional deformation and stress generated at the connection due to the change of the load box tilt angle.

4. The adjustable tilt angle pile foundation self-balancing detection load box device according to claim 1, characterized in that, The tilt sensor (11) collects the attitude data of the load box in real time during the entire process of hoisting, lowering and finally positioning. When an angle deviation is detected, the corresponding hydraulic rod (1) is raised and lowered by adjusting the oil volume of the four self-balancing hydraulic presses (4), and the tilt angle of the load box is corrected in real time.

5. The adjustable tilt angle pile foundation self-balancing detection load box device according to claim 1, characterized in that, When adjusting the tilt angle of the load box, the telescopic rod (10) moves up and down synchronously with the hydraulic rod (1) to ensure smooth relative movement between the upper end plate (3) and the lower end plate (2) and realize the load box's all-round unimpeded lifting and lowering.

6. The adjustable tilt angle pile foundation self-balancing detection load box device according to claim 1, characterized in that, The tilt sensor (11) adopts a redundant distributed arrangement: one tilt sensor is set at each of the four quadrants of the lower end plate (2); all tilt sensors are embedded and sealed, with the mounting surface completely attached to and parallel to the upper surface of the lower end plate (2), and the sensor coordinate system coincides with the load box reference coordinate system.

7. The adjustable tilt angle pile foundation self-balancing detection load box device according to claim 6, characterized in that, It also includes a data acquisition and processing unit, which is electrically connected to all tilt sensors (11), and its data acquisition and processing logic is as follows: D1. The sampling frequency is set in stages: 10-20Hz for hoisting, 5-10Hz for lowering, and 1-5Hz for concrete pouring. D2 uses the Kalman filter algorithm to filter the original tilt angle data to eliminate construction vibration, electromagnetic interference and sensor noise; D3 uses the 3σ criterion to identify anomalies in the data of each sensor in real time and removes abnormal data; if the number of valid sensors after removal is less than 2, a sensor fault alarm is triggered and construction is suspended; for the remaining valid data, weights are dynamically allocated according to the number of sensors, and a weighted average is performed to obtain the actual roll angle and pitch angle of the load cell. D4. Compare the actual tilt angle with the preset initial tilt angle to calculate the roll angle deviation Δθ and pitch angle deviation Δφ.

8. The adjustable tilt angle pile foundation self-balancing detection load box device according to claim 7, characterized in that, It also includes a closed-loop control unit, which is electrically connected to the data acquisition and processing unit and hydraulic valves 1-4, and its control strategy algorithm is as follows: T1 adopts a piecewise proportional-integral control algorithm, which divides the tilt angle deviation into different adjustment ranges and uses corresponding control parameters in each range. T2, establish a linear mapping relationship between the lifting height of the hydraulic rod and the tilt angle deviation: the roll angle deviation Δθ corresponds to the differential lifting of the left and right hydraulic rods, and the pitch angle deviation Δφ corresponds to the differential lifting of the front and rear hydraulic rods. T3, set the tilt angle deviation threshold: when |Δθ|≤0.1° and |Δφ|≤0.1°, stop adjustment; when 0.1°<|Δθ|≤3° or 0.1°<|Δφ|≤3°, start normal adjustment mode; when |Δθ|>3° or |Δφ|>3°, trigger audible and visual alarm and suspend construction until manual inspection and resumption.

9. A method for detecting the self-balancing load cell of an adjustable tilt angle pile foundation, characterized in that, Implemented using the apparatus according to any one of claims 1-8, comprising the following steps: S1, Pre-assembly and initial calibration: The lower end plate (2) of the self-balancing load box is horizontally assembled and welded to the lower end of the steel cage through the ball bearing (12) and the vertical bar sleeve (13). The upper end plate (3) is assembled and welded to the upper end of the steel cage in the same way. The data acquisition and processing unit is started to record the initial values ​​of all tilt sensors (11) and their average values ​​are set as the reference tilt angles θ0 and φ0. S2, hoisting and lowering stage control: the steel cage is hoisted as a whole and lowered into the hole. The data acquisition and processing unit collects the tilt angle data at a preset frequency and performs filtering and fusion processing to calculate the real-time tilt angle deviation. The closed-loop control unit outputs control signals according to the tilt angle deviation, independently adjusts the oil intake of the four self-balancing hydraulic presses (4), controls the lifting and lowering of the corresponding hydraulic rods (1), and corrects the tilt angle of the load box to the reference tilt angle range in real time. S3, Concrete pouring stage control: After the steel cage is lowered into place, concrete is poured. During the concrete flow and solidification process, the change of the load cell tilt angle is continuously monitored, and the same control logic is used to adjust the tilt angle to the initial reference value. S4, Test Preparation: After the concrete strength reaches the design requirements, shut down the tilt angle monitoring and control system and conduct the pile foundation self-balancing bearing capacity test.

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