Electromagnetic foundation bearing capacity intelligent testing device and method

Abstract

The present application relates to a kind of electromagnetic foundation bearing capacity intelligent testing device and method, belong to foundation bearing capacity detection technical field.The device is by counterforce frame, connecting rod, electromagnet, pressure sensor, pressure plate, stress displacement acquisition instrument, laser range finder, computer, battery, resistor, dial gauge and other components are composed of.The present application can realize the stable control of load, the automatic compensation of pressure, improve detection precision;Can realize the automatic acquisition and analysis of data, improve the accuracy of data;Use electromagnet as detection device main body can effectively avoid the defect that traditional jack oil pressure is not stable, oil leakage, and not affected by environmental temperature, solve the problem of insufficient foundation bearing capacity detection precision.

Description

Technical Field

[0001] This invention belongs to the field of foundation bearing capacity testing technology, specifically relating to an electromagnetic intelligent testing device and method for foundation bearing capacity. Background Technology

[0002] The most commonly used method for testing the bearing capacity of foundations in engineering is the static load test. This method involves applying a heavy load or using anchor piles to provide reaction force, and then using hydraulic jacks for staged loading. Because foundation compression deformation occurs during loading, the load value decreases. To maintain the vertical load, the jacks need to be continuously reloaded. However, hydraulic jacks have drawbacks such as low accuracy, susceptibility to oil leakage, and significant influence of ambient temperature on oil pressure, resulting in large data dispersion.

[0003] To improve the accuracy of foundation bearing capacity measurement, electromagnetic testing equipment has emerged in recent years. Patent CN110528489B discloses a dynamic cone penetration test (CPPT) device for improving the stability of foundation bearing capacity in highway construction. This device works by energizing an electromagnetic coil, causing it to become magnetic. A pendulum is attracted upwards by the magnetic force and comes into contact with the coil. After contact, the power is turned off, the coil loses its magnetism, and the pendulum moves downwards under gravity. When the pendulum hits the ground, the power is turned on again, and the pendulum is attracted upwards again. This process repeats, and the foundation bearing capacity can be detected based on the contact between the pendulum and the foundation. Automated loading is possible. While this method is a dynamic testing method, most engineering projects require static load testing to determine foundation bearing capacity. Currently, no reports have been found regarding electromagnetic testing equipment. Patent CN202211469348.6Z discloses a device for testing the bearing capacity of backfilled soil foundations. This device addresses the challenge of simulating different impact forces on the foundation at a fixed displacement distance in dynamic penetration testing, making it difficult to meet various testing conditions. It proposes a control method using two sets of electromagnetic components. The first electromagnetic component adjusts the current to create a repulsive force between itself and a magnetic plate, thereby adjusting the impact force of the counterweight box on the foundation. The second electromagnetic component controls the opening and closing of the counterweight box to achieve impact and lifting of the foundation. This method is suitable for rapid testing of the bearing capacity of foundations in small and medium-sized projects. However, for major engineering structures, especially those subjected to long-term static loads, this testing method cannot replace the static plate load method. Summary of the Invention

[0004] To address the shortcomings of the aforementioned technical issues, this invention provides an intelligent electromagnetic foundation bearing capacity testing device and method. Compared with traditional technologies, this invention enables: automatic data acquisition by stress and displacement acquisition instruments; automatic acquisition and compensation of the distance between electromagnets by a laser rangefinder to maintain a constant load; data analysis based on the proposed algorithm; and automatic pressure compensation by controlling the sliding of the resistor through computer adjustment, thereby improving detection accuracy, ensuring data accuracy, and completing intelligent foundation bearing capacity testing.

[0005] The technical solution adopted in this invention is as follows:

[0006] This invention provides an intelligent electromagnetic foundation bearing capacity testing device, including a reaction frame, a first electromagnet, a second electromagnet, a pressure sensor, a pressure plate, a stress-displacement acquisition instrument, a rangefinder, a controller, a power supply, a first resistor, and a second resistor;

[0007] A connecting rod is suspended on the reaction frame, and a first electromagnet and a rangefinder are fixed at the bottom of the connecting rod. A second electromagnet is set opposite to the first electromagnet. The second electromagnet is supported by a pressure plate, and a pressure sensor and a displacement sensor are also set on the pressure plate. The first electromagnet is connected to a first resistor, and the second electromagnet is connected to a second resistor. The first resistor and the second resistor are powered by a power source.

[0008] The pressure sensor and displacement sensor are connected to the stress and displacement acquisition instrument, which is in turn connected to the controller.

[0009] As a further technical solution, the connecting rod is a telescopic connecting rod.

[0010] As a further technical solution, the rangefinder is connected to the controller, and the controller controls the telescopic connecting rod according to the measurement data of the rangefinder.

[0011] As a further technical solution, the displacement sensor is a dial gauge.

[0012] Secondly, embodiments of the present invention provide an electromagnetic intelligent testing method for foundation bearing capacity, comprising the following steps:

[0013] First, the foundation needs to be treated: surveying and setting out lines, leveling and compacting, taking care to maintain the soil structure and natural moisture content.

[0014] Place the pressure plate, pressure sensor, and electromagnet below onto the foundation to be tested in sequence, and then fix the displacement sensor on both sides of the pressure plate.

[0015] Fix the reaction frame to the foundation to be tested, place the upper electromagnet, and use an automatically adjustable connecting rod to fix it to the reaction frame, ensuring that the upper electromagnet is aligned with the lower electromagnet.

[0016] A laser rangefinder is mounted on the electromagnet above, and the distance is calculated and determined according to the electromagnetic force formula.

[0017] Connect the two sets of resistors to the battery and connect them to the upper and lower electromagnets respectively.

[0018] Connect the displacement sensor and pressure sensor to the stress displacement acquisition instrument.

[0019] Furthermore, the computer is connected to a stress displacement acquisition instrument, a laser rangefinder, and a resistor, which are used to control the load level, measure the displacement of the bearing plate, measure the distance between magnets, and control the resistor value, respectively.

[0020] Furthermore, according to the electromagnetic principle of a closed circuit, the resistor connected to the battery will generate a magnetic field, which will cause the upper and lower electromagnets to generate a repulsive force (electromagnetic force).

[0021] Furthermore, the computer control program is opened, the number of turns of the resistor coil is adjusted to control the current, the distance between the magnets is adjusted synchronously to control the load, and the loading accuracy is confirmed by comparing with the pressure sensor before applying the first level of load.

[0022] Furthermore, the load on the lower bearing plate will compress the foundation, which will cause the bearing plate to move downward and increase the distance between the electromagnets. The load on the bearing plate is automatically collected and compensated by the pressure sensor, and the distance between the electromagnets is automatically collected and compensated by the laser rangefinder to maintain a constant load.

[0023] Furthermore, when the deformation at this level meets the settlement control standard, the resistor connection position is adjusted to increase the current and apply the next load level.

[0024] Further, repeat the above steps until any one of the termination test conditions specified in the foundation bearing capacity test is met, at which point the loading can be terminated. This indicates that the foundation deformation has reached its limit value. From this, a load-displacement (PS) curve is plotted. Based on the obvious inflection point method of the PS curve or the Slogt method (settlement rate method), the foundation bearing capacity can be determined according to the following formula.

[0025]

[0026] In the formula, [P] represents the characteristic value of the ultimate bearing capacity of the foundation.

[0027] P j —The load preceding the foundation failure load;

[0028] K – Safety factor, typically 2.

[0029] As a further technical solution, the pressure compensation method during the experiment is as follows:

[0030] Real-time acquisition and analysis of stress sensor values ​​σ on the bearing plate, and comparison with the initial set stress σ for each load level. i0 In comparison, if (σ i0 -σ) / σ i0 If the value is less than 0.1%, the loading value will remain unchanged.

[0031] If (σ i0 -σ) / σ i0 When the value is ≥0.1%, the electromagnetic control system is activated, and the current density is increased by reducing the coil length, thereby increasing the electromagnetic repulsion force.

[0032] The beneficial effects of this invention are as follows:

[0033] This invention uses two symmetrically arranged electromagnets (first and second) as the main body of the detection device, along with pressure sensors, displacement sensors, stress-displacement acquisition instruments, rangefinders, resistors, and a first and second resistor. This effectively avoids the defects of unstable hydraulic pressure and oil leakage in traditional jacks, and is unaffected by ambient temperature, solving the problem of insufficient accuracy in foundation bearing capacity detection. Specifically, this invention sets pressure sensor values, collects and analyzes the pressure sensor values ​​of the bearing plate in real time, and compares them with the initial set stress of each load level to achieve automatic pressure compensation. By setting a rangefinder to monitor the spacing between the magnets, the distance between the upper first electromagnet and the lower second electromagnet can be accurately set according to the set distance, thereby ensuring the accuracy of bearing capacity detection. The displacement sensor (dial gauge) can test the vertical displacement of the bearing plate during the graded loading process to plot the load-displacement curve. Finally, through the cooperation of various sensors, electromagnets, and resistors, accurate detection of foundation bearing capacity, stable load control, and automatic pressure compensation are achieved, improving detection accuracy. Attached Figure Description

[0034] Figure 1 A schematic diagram of the overall electromagnetic foundation bearing capacity intelligent testing device provided in this invention example;

[0035] Among them, 1-reaction frame, 2-connecting rod, 3-first electromagnet, 4-second electromagnet, 5-pressure sensor, 6-pressure plate, 7-stress and displacement acquisition instrument, 8-computer, 9-first battery, 10-second battery, 11-first resistor, 12-second resistor, 13-dial gauge, 14-laser rangefinder. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments 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.

[0037] Terminology Explanation: The terms "connected" and "connected" in this invention should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction relationship between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0038] The present invention will be further described below with reference to embodiments.

[0039] This embodiment provides an intelligent testing device and method for electromagnetic foundation bearing capacity. The intelligent testing device mainly includes four parts: a first electromagnet 3, a second electromagnet 4, a pressure plate 6, a stress displacement acquisition instrument 7, a computer 8, a first resistor 11, a second resistor 12, a laser rangefinder 14, a counterweight device, a reaction device, a loading device, and a measuring device.

[0040] The reaction device consists of a reaction frame 1, on which a connecting rod 2 is suspended. A first electromagnet 3 and a laser rangefinder 14 are fixed at the bottom of the connecting rod 2. A second electromagnet 4 is positioned opposite the first electromagnet 3 and is supported by a pressure plate 6. A pressure sensor 5 is also positioned below the second electromagnet 4. A dial indicator 13 is also fixed on the pressure plate 6. The first electromagnet 3 is connected to a first resistor 11, and the second electromagnet 4 is connected to a second resistor 12. The first resistor 11 is connected to a first battery 9, and the second resistor 12 is connected to a second battery 10.

[0041] The pressure sensor 5 and dial gauge 13 are connected to the stress and displacement acquisition instrument 7. The pressure sensor 5 is used to detect the compressive stress value; the dial gauge 13 is installed on both sides of the pressure plate 6 to detect the displacement value.

[0042] Furthermore, the electromagnetic intelligent testing device and method for foundation bearing capacity provided in this embodiment includes the following steps when testing soft soil foundations and pile foundations:

[0043] First, the foundation needs to be treated, measured and laid out, leveled and compacted to ensure its stability. At the same time, care should be taken to maintain the original structure and natural moisture of the experimental soil layer.

[0044] Furthermore, the bearing plate 6, pressure sensor 5, and the second electromagnet 4 below are sequentially placed on the foundation to be tested. The pressure sensor 5 is used to detect the compressive stress value, which is related to the initial set stress σ for each load level. i0 In comparison, if (σ i0 -σ) / σ i0 <0.1%, keep the loading value unchanged; if (σ i0 -σ) / σ i0 When the pressure is ≥0.1%, the electromagnetic control system is activated. By reducing the coil length and increasing the current density, the electromagnetic repulsion force is enhanced, thereby achieving automatic real-time pressure compensation.

[0045] The left and right dial gauges 13 are then placed on both sides of the bearing plate 6 to detect the vertical displacement value of the bearing plate after each load is applied, and to plot the foundation load-displacement curve.

[0046] Furthermore, the reaction frame 1 is placed on the foundation to be tested, and then the first electromagnet 3 above it is installed. The connecting rod 2 is used to fix it to the reaction frame 1, ensuring that the two electromagnets above and below are aligned. The connecting rod 2 can automatically adjust its length.

[0047] Furthermore, the laser rangefinder 14 is installed on the upper first electromagnet 3 to measure the distance between the magnets. By monitoring the distance between the magnets through the laser rangefinder 14, it can be ensured that the distance between the upper first electromagnet 3 and the lower second electromagnet 4 is accurately set according to the set distance, thereby ensuring the accuracy of the load-bearing capacity detection. The distance value between the upper first electromagnet 3 and the lower second electromagnet 4 can be calculated and determined according to the electromagnetic force formula.

[0048] Furthermore, the first resistor 1 and the first resistor 2 are connected to the first storage battery 9 and the second storage battery 10, and respectively connected to the first electromagnet 3 and the second electromagnet 4.

[0049] Furthermore, the left and right dial gauges 13, pressure sensor 5, and pressure plate 6 are connected to a stress and displacement acquisition instrument 7 for automatic data acquisition.

[0050] Furthermore, stress and displacement acquisition instrument 7, laser rangefinder 14, and first resistor 1 and first resistor 2 are connected to both sides of the computer 8 for data analysis and program execution.

[0051] Furthermore, according to the electromagnetic principle of a closed circuit, when the first battery 9 and the second battery 10 are connected, the first resistor 1 and the first resistor 2 will generate a magnetic field, thereby generating a repulsive force (electromagnetic force) between the first electromagnet 3 and the second electromagnet 4, which in turn disrupts the original force balance.

[0052] Furthermore, the computer 8 control program is opened, the number of coil turns of the first resistor 11 and the second resistor 12 are adjusted to control the current, the distance between the first electromagnet 3 and the second electromagnet 4 is adjusted synchronously to control the load, and the loading accuracy is confirmed by comparing with the pressure sensor 5, and the first level of load is applied.

[0053] Furthermore, as the bearing plate 6 is subjected to load and moves downward, the foundation undergoes compression deformation, causing an increase in the distance between the first electromagnet 3 and the second electromagnet 4 above and below. The pressure sensor 5 automatically collects the load of the bearing plate and automatically compensates for it, while the laser rangefinder 14 automatically collects the distance between the magnets and automatically compensates for it, thus maintaining a constant load.

[0054] Furthermore, when the deformation of this level meets the settlement control standard, the number of turns of the first resistor 11 and the second resistor 12 coils are adjusted, the current is increased, and the next load level is applied.

[0055] Further, repeat the above steps until any one of the termination test conditions specified in the foundation bearing capacity test is met, at which point the loading can be terminated. This indicates that the foundation deformation has reached its limit value. From this, a load-displacement (PS) curve is plotted. The foundation bearing capacity is determined according to the formula based on the obvious inflection point method of the PS curve or the S-logt method (settlement rate method).

[0056]

[0057] In the formula, [P] represents the characteristic value of the ultimate bearing capacity of the foundation.

[0058] P j —The load preceding the foundation failure load;

[0059] K – Safety factor, typically 2.

[0060] Further, following the above operating steps, the soil is unloaded in stages to zero, completing the entire process of foundation bearing capacity testing.

[0061] This embodiment also proposes a complete automatic pressure compensation algorithm, the specific steps of which are as follows:

[0062] First, the stress sensor values ​​σ of the bearing plate are collected and analyzed in real time, and compared with the initial set stress σ for each load level. i0 In comparison, if (σ i0 -σ) / σ i0 If the value is less than 0.1%, the loading value will remain unchanged.

[0063] If (σ i0 -σ) / σ i0When the current density is ≥0.1%, the electromagnetic control system is activated. By reducing the coil length, the current density is increased, thereby enhancing the electromagnetic repulsion force. The specific principle is as follows:

[0064] According to the Ampere force formula: F = BIL,

[0065] In the formula, B is the magnetic field strength, I is the current, and L is the length of the conductor;

[0066] Based on the voltage, current, and resistance relationship: U = I × R,

[0067] In the formula, U is the voltage and R is the resistance.

[0068] With a fixed voltage, the shorter L is and the smaller R is, the larger I is.

[0069] Meanwhile, according to the formula for calculating magnetic field strength: magnetic field strength = number of turns of excitation coil × excitation current / effective magnetic circuit length, it can be seen that the strength of the magnetic field is directly proportional to the current intensity in the conductor. Therefore, the greater the current, the greater the magnetic induction intensity.

[0070] Therefore, by reducing the length of the energized coil to lower the resistance, the current can be increased, the magnetic field strength can be improved, and the repulsive force of the electromagnets can be increased. Based on the above principle, and combined with the analysis of real-time monitoring data from the pressure sensor, when (σ i0 -σ) / σ i0 If the load is less than 0.1%, the load will remain unchanged, and automatic load adjustment will be completed.

[0071] Preferably, this testing device is applicable to testing the bearing capacity of various soil layers and pile foundations.

[0072] Finally, it should be noted that relational terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electromagnetic intelligent testing device for foundation bearing capacity, characterized in that, It includes a reaction frame, a first electromagnet, a second electromagnet, a pressure sensor, a displacement sensor, a pressure plate, a stress-displacement acquisition instrument, a rangefinder, a controller, a power supply, a first resistor, and a second resistor; A connecting rod is suspended on the reaction frame, and a first electromagnet and a rangefinder are fixed at the bottom of the connecting rod. A second electromagnet is set opposite to the first electromagnet, and the second electromagnet is supported by a pressure plate. A pressure sensor and a displacement sensor are also set on the pressure plate. The first electromagnet is connected to a first resistor, and the second electromagnet is connected to a second resistor. The first resistor and the second resistor are powered by a power source, and the current is controlled by adjusting the number of turns of the resistor coil. The pressure sensor and displacement sensor are connected to the stress and displacement acquisition instrument, which is connected to the controller. The connecting rod is a telescopic connecting rod; The rangefinder is connected to the controller, and the controller controls the telescopic connecting rod according to the measurement data of the rangefinder. The pressure sensor automatically collects the load on the pressure plate and automatically compensates for it, while the rangefinder automatically collects the distance between the magnets and automatically compensates for it, maintaining a constant load.

2. The electromagnetic intelligent testing device for foundation bearing capacity as described in claim 1, characterized in that, The displacement sensor is a dial gauge.

3. The electromagnetic intelligent testing device for foundation bearing capacity as described in claim 1, characterized in that, The rangefinder mentioned is a laser rangefinder.

4. A testing method based on the electromagnetic intelligent foundation bearing capacity testing device according to any one of claims 1-3, characterized in that, as follows: The foundation is treated, and the bearing plate, pressure sensor and second electromagnet are placed on the foundation to be tested in sequence. Then the displacement sensor is fixed on the bearing plate. Fix the reaction frame to the foundation to be tested, install the first electromagnet, and ensure that the first electromagnet and the second electromagnet are aligned vertically. The rangefinder is mounted on the first electromagnet, and the distance is determined by calculation according to the electromagnetic force formula; Connect the displacement sensor and pressure sensor to the stress and displacement acquisition instrument, respectively, and connect the stress and displacement acquisition instrument to the controller. Connect the first resistor to the first electromagnet and the second resistor to the second electromagnet; and supply power to the first resistor and the second resistor; The drive control program adjusts the number of turns of the resistor coil to control the current, synchronously adjusts the distance between the magnets to control the load, and compares the load with the pressure sensor to confirm the loading accuracy before applying the first level of load. The lower bearing plate is subjected to load and compresses the foundation, which causes the bearing plate to move downward and increases the distance between the electromagnets. The distance between the electromagnets is automatically collected by the rangefinder and automatically compensated to maintain a constant load. When the deformation of this level meets the settlement control standard, the number of turns of the first resistor and the second resistor coil are adjusted to increase the current and apply the next load level. Repeat the above steps until any one of the termination test conditions specified in the foundation bearing capacity test is met, at which point the loading can be terminated. This indicates that the foundation deformation has reached the limit value. Plot the load-displacement curve and determine the foundation bearing capacity according to the obvious inflection point method or settlement rate method of the load-displacement curve. The pressure compensation method used during the experiment is as follows: Real-time acquisition and analysis of stress sensor values ​​for bearing plates σ and the initial stress set for each load level. σ i0 In comparison, if ( σ i0 - σ ) / σ i0 If the value is less than 0.1%, the loading value will remain unchanged. like( σ i0 - σ ) / σ i0 When the value is ≥0.1%, the electromagnetic control system is activated, and the current density is increased by reducing the coil length, thereby increasing the electromagnetic repulsion force.

5. The testing method of the electromagnetic foundation bearing capacity intelligent testing device as described in claim 4, characterized in that, The formula for determining the bearing capacity of the foundation is as follows: In the formula, [ P —Characteristic value of ultimate bearing capacity of foundation; P j —The load preceding the foundation failure load; k —The safety factor is generally 2.

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