Pile foundation characteristic parameter detection method based on optical fiber strain detection technology

Abstract

The invention provides a pile foundation characteristic parameter detection method based on an optical fiber strain detection technology. The pile foundation characteristic parameter detection method comprises the steps that first strain data and second strain data are obtained; calculating the negative frictional resistance and the negative bearing capacity of the upper-section pile and the positive frictional resistance and the positive bearing capacity of the lower-section pile based on the first strain data; based on the second strain data, the positive friction resistance and the positive bearing capacity of the upper pile section and the negative friction resistance and the negative bearing capacity of the lower pile section are calculated; and the pile foundation bearing capacity of the prefabricated steel pipe pile is calculated based on the negative bearing capacity and the positive bearing capacity of the upper pile section and the negative bearing capacity and the positive bearing capacity of the lower pile section. The measuring optical fiber is arranged in the prefabricated steel pipe pile, so that the side friction resistance of the pile foundation is additionally obtained on the basis of the first strain data / second strain data recorded in the back-to-back / face-to-face movement process of the upper pile body and the lower pile body of the prefabricated steel pipe pile, and more complete characteristic parameter calculation is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of pile foundation detection, and in particular to a pile foundation characteristic parameter detection method based on optical fiber strain detection technology. Background Art

[0002] The bearing capacity of pile foundations is crucial for pile foundation engineering design. Common methods for determining the bearing capacity include static load tests (direct loading, anchor pile-beam reaction method, and heaped load method), dynamic testing (high-strain and low-strain dynamic testing), in-situ testing (standard penetration test, static cone penetration test), theoretical calculation (load transfer method, empirical formula method), and code recommendations. Each of these methods has its own unique characteristics. Static load tests are accurate but costly, dynamic testing and in-situ testing are rapid and economical, theoretical calculations are suitable for theoretical research and design, and code recommendations are simple and easy to implement. In practical applications, the appropriate method should be selected based on a comprehensive consideration of factors such as project requirements, geological conditions, and economic benefits.

[0003] The self-balancing method is a method used to measure the bearing capacity of pile foundations. The principle of the self-balancing method is to set one or more load boxes inside the pile body, and by applying pressure inside the load box, the pile body is displaced upward, and at the same time the soil on the side of the pile generates a downward reaction force, thereby balancing the applied load. This method reduces the impact of the test on the site and construction progress, and is suitable for a variety of geological conditions and construction environments. Although the self-balancing method for measuring pile bearing capacity does not require an external reaction device and reduces the impact of the site, its disadvantages include theoretical assumption limitations, load box installation problems, complex test result interpretation, soil layer differences, pile body displacement limitations, high cost, and low accuracy due to the conversion of positive and negative friction resistance. These factors may lead to errors in the test results and affect the promotion of the test method.

[0004] To this end, the reverse self-balancing method was proposed. Its core principle is to add a vertical loading device to the pile top in the traditional self-balancing test. This method solves the technical challenge of converting the negative friction in the upper section of the pile into positive friction during the self-balancing pile test. It can also test the pile's tensile bearing capacity. The effectiveness of this method has been verified through theoretical analysis and numerical simulation, which will help promote its application in practical projects and further improve the evaluation method for the vertical bearing capacity of single piles.

[0005] In the existing pile foundation load test based on the reverse self-balancing method, due to the limitations of the test equipment, only the pile foundation bearing capacity can be calculated based on the measurement results, and it is difficult to obtain the characteristic parameters required for other pile foundation tests. Summary of the Invention

[0006] The present invention provides a pile foundation characteristic parameter detection method based on optical fiber strain detection technology, which is used to solve the defect in the existing technology that it is difficult to obtain the characteristic parameters required for other pile foundation tests in the pile foundation load force test based on the reverse self-balancing method, and realizes a pile foundation characteristic parameter detection method, which is particularly used to obtain the lateral friction resistance of the pile foundation.

[0007] The present invention provides a method for detecting characteristic parameters of a pile foundation based on optical fiber strain detection technology. The characteristic parameters include at least pile foundation bearing capacity and frictional resistance. The prefabricated steel pipe pile on which the method is based includes an upper pile body, a pile body loading section, and a lower pile body. The inner wall of the prefabricated steel pipe pile is also provided with at least one measuring optical fiber along its axial direction. The method comprises: Acquire first strain data and second strain data; Calculating the negative friction and negative bearing capacity of the upper pile segment, and the positive friction and positive bearing capacity of the lower pile segment based on the first strain data; Calculating the positive friction and positive bearing capacity of the upper pile segment, and the negative friction and negative bearing capacity of the lower pile segment based on the second strain data; Calculating the pile foundation bearing capacity of the prefabricated steel pipe pile based on the negative bearing capacity and positive bearing capacity of the upper pile segment and the negative bearing capacity and positive bearing capacity of the lower pile segment; wherein the pile body load box of the pile body loading section is loaded to drive the upper pile body and the lower pile body to deform in opposite directions, and the first strain data is determined based on the strain data of the optical fiber measured during the opposite deformation process; The pile top load box at the top of the prefabricated steel pipe pile is loaded to drive the upper pile body and the lower pile body to deform toward each other, and second strain data is determined based on the strain data of the optical fiber measured during the deformation process.

[0008] According to a pile foundation characteristic parameter detection method based on optical fiber strain detection technology provided by the present invention, a temperature compensation optical fiber is further provided on the prefabricated steel pipe pile. The step of determining first strain data based on the strain data of the optical fiber measured during the opposite deformation process includes: taking the difference between the strain data of the measuring optical fiber and the strain data of the temperature compensating optical fiber during the opposite deformation process as the first strain data; The step of determining the second strain data based on the strain data of the optical fiber measured during the opposite deformation process includes: The difference between the strain data of the measuring optical fiber and the strain data of the temperature compensating optical fiber during the opposite deformation process is used as the second strain data.

[0009] According to a pile foundation characteristic parameter detection method based on optical fiber strain detection technology provided by the present invention, three measuring optical fibers are evenly distributed along the circumference of the prefabricated steel pipe pile, and the step of determining first strain data based on the strain data of the measuring optical fibers during the opposite deformation process includes: The average of the strain data of the three measuring optical fibers during the opposite deformation process is used as the first strain data; The step of determining the second strain data based on the strain data of the optical fiber measured during the opposite deformation process includes: The average value of the strain data of the three measuring optical fibers during the opposite deformation process is used as the second strain data.

[0010] According to a pile foundation characteristic parameter detection method based on optical fiber strain detection technology provided by the present invention, a stress sensor is also provided on the inner wall of the prefabricated steel pipe pile, and the strain data of the measuring optical fiber at the stress sensor is calibrated based on the stress data of the stress sensor.

[0011] According to a pile foundation characteristic parameter detection method based on optical fiber strain detection technology provided by the present invention, the prefabricated steel pipe pile also includes a force transmission rod for connecting the pile top load box and the lower pile body, and the force transmission rod is also provided with an axial force sensor for measuring its axial force. The axial force of the rod generated by the pile top load box and the pile body load box is calibrated according to the reading of the axial force sensor.

[0012] According to a pile foundation characteristic parameter detection method based on optical fiber strain detection technology provided by the present invention, the characteristic parameters also include pile end resistance, which is determined according to the sudden change in the negative bearing capacity of the lower pile.

[0013] The present invention also provides a pile foundation characteristic parameter detection system based on optical fiber strain detection technology, comprising: A strain data acquisition module, configured to acquire first strain data and second strain data; a characteristic parameter determination module, configured to calculate the negative friction and negative bearing capacity of the upper pile segment, and the positive friction and positive bearing capacity of the lower pile segment based on the first strain data; The characteristic parameter determination module is further configured to calculate the positive friction and positive bearing capacity of the upper pile segment, and the negative friction and negative bearing capacity of the lower pile segment based on the second strain data; The characteristic parameter determination module is further configured to calculate the pile foundation bearing capacity of the prefabricated steel pipe pile based on the negative bearing capacity and positive bearing capacity of the upper pile segment and the negative bearing capacity and positive bearing capacity of the lower pile segment; wherein the pile body load box of the pile body loading section is loaded to drive the upper pile body and the lower pile body to deform in opposite directions, and the first strain data is determined based on the strain data of the optical fiber measured during the opposite deformation process; The pile top load box at the top of the prefabricated steel pipe pile is loaded to drive the upper pile body and the lower pile body to deform toward each other, and second strain data is determined based on the strain data of the optical fiber measured during the deformation process.

[0014] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the method for detecting characteristic parameters of a pile foundation based on optical fiber strain detection technology as described above is implemented.

[0015] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the method for detecting characteristic parameters of a pile foundation based on optical fiber strain detection technology as described above is implemented.

[0016] The present invention also provides a computer program product, comprising a computer program, which, when executed by a processor, implements any of the above-mentioned methods for detecting characteristic parameters of pile foundations based on optical fiber strain detection technology.

[0017] The pile foundation characteristic parameter detection method based on optical fiber strain detection technology provided by the present invention realizes strain-based characteristic parameter measurement by arranging a measuring optical fiber in a prefabricated steel pipe pile based on the first strain data / second strain data recorded during the back-to-back / toward movement of the upper and lower pile bodies of the prefabricated steel pipe pile. On the basis of determining the bearing capacity of the pile foundation, the lateral friction resistance of the pile foundation can also be additionally obtained, thereby realizing a more complete characteristic parameter calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 Schematic diagram of the structure of the prefabricated steel pipe pile on which the pile foundation characteristic parameter detection method based on optical fiber strain detection technology provided by the present invention is based; Figure 2 Schematic diagram of the process of detecting pile foundation characteristic parameters based on optical fiber strain detection technology provided by the present invention; Figure 3 Schematic diagram of the structure of the pile foundation characteristic parameter detection system based on optical fiber strain detection technology provided by the present invention; Figure 4 It is a structural schematic diagram of the electronic device provided by the present invention.

[0020] Reference numerals: 1. Pile cap loading section; 2. Ordinary pile body section; 21. Upper pile body section; 22. Lower pile body section; 3. Loading pile body section; 4. Pile head section; 5. Measuring optical fiber. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0022] First, the prefabricated steel pipe piles based on the pile foundation characteristic parameter detection method based on optical fiber strain detection technology of the present invention are introduced. Figure 1 As shown, The prefabricated steel pipe pile includes a pile cap loading section 1, a common pile body section 2, a loading pile body section 3, and a pile head section 4. The common pile body section 2 includes an upper pile body 21 and a lower pile body 22. The pile cap loading section 1, the upper pile body 21, the loading pile body section 3, the lower pile body 22, and the pile head section 4 are sequentially connected along the axial direction to form a steel pipe pile body. The pile cap loading section 1 and the upper pile body 21 constitute the upper pile body, and the lower pile body 22 and the pile head section 4 constitute the lower pile body; like Figure 1 As shown, the ordinary pile body section 2 constitutes the pile section of the prefabricated steel pipe pile body, wherein the portion of the loading pile body section 3 close to the pile cap loading section 1 is the upper pile body 21, and the portion of the loading pile body section 3 close to the pile head section 4 is the lower pile body 22.

[0023] Taking the loading pile body section 3 as the boundary, the pile cap loading section 1 and the upper pile body 21 above the loading pile body section 3 are determined as the upper pile body, and the pile head section 4 and the lower pile body 22 below the loading pile body section 3 are determined as the lower pile body, so as to detect the characteristic parameters of the pile foundation.

[0024] The loading pile body section 3 includes a pile body load module, which is used to drive the upper pile body and the lower pile body to move away from each other to generate a negative bearing capacity of the upper pile body and a positive bearing capacity of the lower pile body; The pile body load module is arranged in the loading pile body section 3 .

[0025] Optionally, the pile body load module can be any form of linear drive component, such as an oil cylinder, an air cylinder or a jack. In this embodiment, a load box is selected, that is, a pile body load box, and the loading and unloading of the load box can be achieved by remotely controlling the servo motor of the load box.

[0026] The pile cap loading section 1 is equipped with a pile top load module, which is also connected to the lower pile body through a connector. The pile top load module is used to drive the upper pile body and the lower pile body to move toward each other.

[0027] The pile top load module is arranged in the pile cap loading section 1 .

[0028] Optionally, the pile top load module may be the same as or different from the pile body load module. In this embodiment, a load box that is the same as the pile body load module is selected as the pile top load module, namely, the pile top load box.

[0029] The connecting piece can be connected to any position inside the lower pile body, such as the lower pile body 22 or the pile head section 4 .

[0030] The pile body further comprises at least one measuring optical fiber 5 , which is attached to the inner wall of the steel pipe pile body along the axial direction of the steel pipe pile body.

[0031] like Figure 2 As shown, the characteristic parameter detection method includes: Step 201, obtaining first strain data and second strain data; wherein the pile body load box of the pile body loading section is loaded to drive the upper pile body and the lower pile body to deform in opposite directions, and the first strain data is determined based on the strain data of the optical fiber measured during the opposite deformation process; The pile top load box at the top of the prefabricated steel pipe pile is loaded to drive the upper pile body and the lower pile body to deform toward each other, and second strain data is determined based on the strain data of the optical fiber measured during the deformation process.

[0032] In this embodiment, the load modules of the pile body loading section and the pile cap loading section are both load boxes, namely the pile body load box and the pile top load box.

[0033] The pile body load box / pile top load box is used to drive the upper pile body and the lower pile body to move in opposite directions / towards each other, and various data during the movement are recorded.

[0034] Optionally, the pile body load box can be loaded first to drive the upper pile body and the lower pile body to displace away from each other, and then the pile top load box can be loaded to drive the upper pile body and the lower pile body to displace toward each other; or, the pile top load box can be loaded first to drive the upper pile body and the lower pile body to displace toward each other, and then the pile body load box can be loaded to drive the upper pile body and the lower pile body to displace away from each other.

[0035] During the process of the upper pile body and the lower pile body moving away from each other or towards each other, the strain data of the measuring optical fiber are recorded respectively.

[0036] It is understandable that, when there is only one measuring optical fiber, the strain data of the measuring optical fiber recorded in the corresponding process can be directly used as the first strain data and the second strain data.

[0037] Optionally, if there are multiple measuring optical fibers, the strain data recorded by the multiple measuring optical fibers during the corresponding process can be used for comparison. For example, when there are three measuring optical fibers, after excluding abnormal points with large differences in strain data from the other two measuring optical fibers, the average is taken as the first strain data and the second strain data.

[0038] Step 202: Calculate the negative friction and negative bearing capacity of the upper pile segment, and the positive friction and positive bearing capacity of the lower pile segment based on the first strain data. Step 203: Calculate the positive friction and positive bearing capacity of the upper pile segment, and the negative friction and negative bearing capacity of the lower pile segment based on the second strain data; A measuring optical fiber is attached axially along the inner wall of the prefabricated steel pipe pile. The measured strain can be converted into the axial force of the pile body's axial cross-section. This is combined with the axial force provided by the pile top load box and the pile body load box, the friction provided by the soil around the prefabricated steel pipe pile, and the axial force generated by the pile body's own weight. The pile body friction and pile foundation bearing capacity can be calculated using the principle of elastic deformation.

[0039] Specifically, the force balance equation of precast steel pipe piles is as follows: ; Where, and Any segment of prefabricated steel pipe piles The upper and lower axial forces, D Indicates the diameter of prefabricated steel pipe piles. t Indicates the wall thickness of the prefabricated steel pipe column, Indicates the weight of prefabricated steel pipe piles. Indicates the side friction resistance of the pile in this segment.

[0040] On this basis, the pile body stress equation of prefabricated steel pipe pile can be obtained: ; (1) ; Where z represents the coordinate along the axis of the prefabricated steel pipe pile. That is, the lateral friction resistance of the pile body at position z.

[0041] The axial force of the prefabricated steel pipe pile at position z can be calculated by the strain at that position: ; (2) Where, is the strain measured at the z position, is the elastic modulus of the steel used for prefabricated steel pipe piles, It represents the area of ​​the circular cross section of the steel pipe of the prefabricated steel pipe pile.

[0042] Combining formula (1) and formula (2), the friction resistance of the prefabricated steel pipe pile at any position of the pile axis can be derived: ; ; (3) Where, Represents the variation of axial strain of prefabricated steel pipe pile with depth z.

[0043] In other words, based on the strain at any axial position of the prefabricated steel pipe pile, the frictional resistance at that position can be calculated.

[0044] Corresponding to the strain data acquisition process in this embodiment, the first strain data obtained in the process of driving the upper pile and the lower pile to move in opposite directions is substituted into formula (3) to calculate the negative friction resistance of the upper pile: and the positive friction resistance of the lower pile .

[0045] Substituting the second strain data obtained during the process of driving the upper pile and the lower pile toward each other into formula (3), the positive friction resistance of the upper pile can be calculated: and the negative friction of the lower pile .

[0046] The above four frictional resistances obtained by calculation are the frictional resistances among the characteristic parameters of prefabricated steel pipe piles.

[0047] Furthermore, based on the ability to determine the pile axial force, the pile foundation bearing capacity can also be calculated based on the pile axial force: (4) Where, Indicates the axial force at the reference starting point, Indicates depth Axial force at position, Indicates the calculation i The height of each segment.

[0048] On this basis, the first strain data obtained in the process of driving the upper and lower piles to move in opposite directions is substituted into formula (4) to calculate the negative bearing capacity of the upper pile: and the positive bearing capacity of the lower pile .

[0049] Substituting the second strain data obtained during the process of driving the upper pile and the lower pile toward each other into formula (3), the positive friction resistance of the upper pile can be calculated: and the negative friction of the lower pile .

[0050] Step 204 : Calculate the pile foundation bearing capacity of the prefabricated steel pipe pile based on the negative bearing capacity and positive bearing capacity of the upper pile segment and the negative bearing capacity and positive bearing capacity of the lower pile segment.

[0051] On this basis, calculate 、 The deadweight of prefabricated steel pipe piles W The sum of the vertical compressive bearing capacity of the test pile is , .calculate of and the deadweight of prefabricated steel pipe piles W The difference between the two is taken as the total vertical pull-out bearing capacity of the test pile , , thereby realizing the pile foundation bearing capacity detection based on the reverse self-balancing principle, and the calculated total compressive bearing capacity and total pull-out bearing capacity are the pile foundation bearing capacity in the characteristic parameters of the prefabricated steel pipe pile.

[0052] The principle is to add a pile top load module to the traditional self-balancing test device. During the test, the pile body load module located in the middle pile is used to make the upper pile (i.e., the upper pile body) and the lower pile (i.e., the lower pile body) move in opposite directions, and the negative bearing capacity of the upper pile is measured. and the positive bearing capacity of the lower pile Then the pile body load box in the pile body load module returns oil, and the pile top load module is loaded, so that the upper and lower piles are displaced toward each other, and the positive bearing capacity of the upper pile is measured. and the negative bearing capacity of the lower pile Finally, the total ultimate vertical compressive bearing capacity of the test pile is the sum of the positive bearing capacity of the upper pile segment and the negative bearing capacity of the lower pile segment plus the pile weight; the total ultimate vertical pullout bearing capacity of the test pile is the sum of the negative bearing capacity of the upper pile segment and the positive bearing capacity of the lower pile segment minus the pile weight.

[0053] The present invention arranges a measuring optical fiber within a prefabricated steel pipe pile to implement strain-based characteristic parameter measurement based on the first strain data / second strain data recorded during the movement of the upper and lower pile bodies of the prefabricated steel pipe pile toward / away from each other. In addition to determining the bearing capacity of the pile foundation, the lateral friction resistance of the pile foundation can also be additionally obtained, thereby achieving a more complete characteristic parameter calculation.

[0054] At the same time, the layout of measuring optical fibers based on prefabricated steel pipe piles can be completed during the steel pipe column splicing stage. The operation is simple and there is no need to specially set up a protective channel for the measuring optical fibers.

[0055] In the pile foundation characteristic parameter detection method based on optical fiber strain detection technology of the present invention, a temperature compensation optical fiber is further provided on the prefabricated steel pipe pile. The step of determining the first strain data based on the strain data of the optical fiber measured during the opposite deformation process includes: taking the difference between the strain data of the measuring optical fiber and the strain data of the temperature compensating optical fiber during the opposite deformation process as the first strain data; The step of determining the second strain data based on the strain data of the optical fiber measured during the opposite deformation process includes: The difference between the strain data of the measuring optical fiber and the strain data of the temperature compensating optical fiber during the opposite deformation process is used as the second strain data.

[0056] Since the strain data of the measuring optical fiber is affected by temperature, in addition to the measuring optical fiber used to obtain the first strain data / second strain data, a temperature compensation optical fiber can also be additionally provided to perform temperature compensation on the strain data of the measuring optical fiber before calculating the characteristic parameters.

[0057] like Figure 1 As shown, in this embodiment, two measuring optical fibers and one temperature compensation optical fiber are arranged in the prefabricated steel pipe pile. The length direction of the three optical fibers is the pile axis direction, and the three optical fibers are evenly arranged along the circumference of the pile body.

[0058] In other feasible implementations, the temperature compensation optical fiber may also be attached to other positions along the pile axis, so as to obtain the temperature compensation strain at any position along the pile axis without interfering with other structures.

[0059] Temperature compensation can be achieved based on the following formula: ; Where, It is the strain data used to calculate the characteristic parameters at the z position, namely the first strain data / second strain data, To measure the strain data of the z position obtained by the optical fiber, The strain data of the temperature-compensated optical fiber at the z position Alternatively, if there is only one fiber to be measured, It can directly record the strain data of the measuring fiber when the upper pile body and the lower pile body move in opposite / toward directions. It can be the average value of strain data of multiple measurement optical fibers after excluding abnormal data.

[0060] In the pile foundation characteristic parameter detection method based on optical fiber strain detection technology of the present invention, three measuring optical fibers are evenly distributed along the circumference of the prefabricated steel pipe pile. The step of determining the first strain data based on the strain data of the measuring optical fibers during the opposite deformation process includes: The average of the strain data of the three measuring optical fibers during the opposite deformation process is used as the first strain data; The step of determining the second strain data based on the strain data of the optical fiber measured during the opposite deformation process includes: The average value of the strain data of the three measuring optical fibers during the opposite deformation process is used as the second strain data.

[0061] Although the strain data of one measuring optical fiber can be used to calculate the characteristic parameters of the pile foundation, in order to improve the accuracy of the calculation results, in this embodiment, three measuring optical fibers are attached to the inner wall of the prefabricated steel pipe pile.

[0062] In this embodiment, the three measuring optical fibers are evenly arranged around the circumference of the prefabricated steel pipe pile. In other feasible embodiments, the positions of the measuring optical fibers can also be determined according to the installation positions of other equipment in the prefabricated steel pipe pile, such as the load box, to avoid interference.

[0063] On this basis, the average strain data of the three measuring optical fibers recorded during the opposite deformation process is used as the first strain data, and the average strain data of the three measuring optical fibers recorded during the opposite deformation process is used as the second strain data, thereby obtaining first strain data and second strain data that are more accurate than directly recording the data, and ultimately obtaining more accurate characteristic parameter calculation results.

[0064] In the pile foundation characteristic parameter detection method based on optical fiber strain detection technology of the present invention, a stress sensor is further provided on the inner wall of the prefabricated steel pipe pile, and the strain data of the measuring optical fiber at the stress sensor is calibrated based on the stress data of the stress sensor.

[0065] In order to obtain more accurate first strain data and second strain data and to avoid characteristic parameter errors caused by errors in measuring optical fibers as much as possible, in this embodiment, a stress sensor is further provided on the inner wall of the prefabricated steel pipe pile.

[0066] Among them, several stress sensors are arranged at positions where the measuring optical fiber error is large and / or the measuring optical fiber often has errors. For example, if the strain data error of the measuring optical fiber at the depth z of the pile axis is large, then multiple stress sensors are evenly installed around the circumference of the inner wall of the prefabricated steel pipe pile at the depth z position. The number of stress sensors can correspond to the number of measuring optical fibers.

[0067] Alternatively, the strain at that location can be calculated using the ratio of the stress data from the stress sensor to the elastic modulus of the prefabricated steel pipe pile, and used as the first / second strain data for calculating the characteristic parameter. Alternatively, the ratio of the stress data from the stress sensor to the elastic modulus of the prefabricated steel pipe pile can be first calculated as a first result, and the sum of the first result and the temperature-compensated strain at that location can be calculated as the first / second strain data for calculating the characteristic parameter.

[0068] In the pile foundation characteristic parameter detection method based on optical fiber strain detection technology of the present invention, the prefabricated steel pipe pile also includes a force transmission rod for connecting the pile top load box and the lower pile body, and the force transmission rod is also provided with an axial force sensor for measuring its axial force. The axial force of the rod generated by the pile top load box and the pile body load box is calibrated through the reading of the axial force sensor.

[0069] like Figure 1 As shown, the pile cap loading section is connected to the lower pile body through a force transmission rod. One end of the force transmission rod arranged inside the steel pipe pile body is anchored to the lower pile body, and the other end is connected to the output end of the pile top load box. In this embodiment, an axial force sensor for measuring its axial force is also provided on the force transmission rod.

[0070] It can be understood that the reading of the axial force sensor represents the actual axial force exerted on the force transmission rod, and the output of the pile top load box / pile body load box represents the target axial force of the force transmission rod, that is, the target axial force needs to be output for pile foundation load testing.

[0071] On this basis, the reading of the axial force sensor is compared with the output display data of the pile top load box / pile body load box in the corresponding process, and the output of the pile top load box / pile body load box is calibrated based on the reading of the axial force sensor until the error between the actual reading and the target axial force is within the preset range, thereby reducing the test error, obtaining more accurate first strain data and second strain data, and then calculating more accurate characteristic parameters.

[0072] In the pile foundation characteristic parameter detection method based on optical fiber strain detection technology of the present invention, the characteristic parameters also include pile end resistance, which is determined according to the sudden change of the negative bearing capacity of the lower pile.

[0073] Under ideal conditions, when conducting a pile foundation load test, the loading section of the pile body needs to be located at the neutral point of the prefabricated steel pipe pile. However, in reality, it is difficult to select the loading section of the pile body exactly at the theoretical equilibrium point, that is, the position where the bearing capacity of the upper and lower piles is equal. Therefore, the unbalanced force needs to be borne by the force transmission rod.

[0074] On this basis, when the upper and lower pile bodies are driven to move in opposite directions, if the pile end of the lower pile body moves out of the free space and contacts the solid foundation, the bearing capacity curve of the lower pile body will suddenly increase. The increase can be considered as the bearing capacity provided by the pile end part.

[0075] Therefore, the bearing capacity curve when the upper and lower pile bodies move in opposite directions is drawn based on the calculation results of the bearing capacity, and the pile end resistance can be determined based on the position of the curve mutation and the value corresponding to the position.

[0076] The following describes the pile foundation characteristic parameter detection system based on optical fiber strain detection technology provided by the present invention. The pile foundation characteristic parameter detection system based on optical fiber strain detection technology described below and the pile foundation characteristic parameter detection method based on optical fiber strain detection technology described above can be referenced to each other.

[0077] like Figure 3 As shown, the pile foundation characteristic parameter detection system based on optical fiber strain detection technology of the present invention includes a strain data acquisition module 301 and a characteristic parameter determination module 302; The strain data acquisition module 301 is used to acquire first strain data and second strain data; wherein the pile body load box of the pile body loading section is loaded to drive the upper pile body and the lower pile body to deform in opposite directions, and the first strain data is determined based on the strain data of the optical fiber measured during the opposite deformation process; The pile top load box at the top of the prefabricated steel pipe pile is loaded to drive the upper pile body and the lower pile body to deform toward each other, and second strain data is determined based on the strain data of the optical fiber measured during the deformation process.

[0078] In this embodiment, the load modules of the pile body loading section and the pile cap loading section are both load boxes, namely the pile body load box and the pile top load box.

[0079] The pile body load box / pile top load box is used to drive the upper pile body and the lower pile body to move in opposite directions / towards each other, and various data during the movement are recorded.

[0080] Optionally, the pile body load box can be loaded first to drive the upper pile body and the lower pile body to displace away from each other, and then the pile top load box can be loaded to drive the upper pile body and the lower pile body to displace toward each other; or, the pile top load box can be loaded first to drive the upper pile body and the lower pile body to displace toward each other, and then the pile body load box can be loaded to drive the upper pile body and the lower pile body to displace away from each other.

[0081] During the process of the upper pile body and the lower pile body moving away from each other or towards each other, the strain data of the measuring optical fiber are recorded respectively.

[0082] It is understandable that, when there is only one measuring optical fiber, the strain data of the measuring optical fiber recorded in the corresponding process can be directly used as the first strain data and the second strain data.

[0083] Optionally, if there are multiple measuring optical fibers, the strain data recorded by the multiple measuring optical fibers during the corresponding process can be used for comparison. For example, when there are three measuring optical fibers, after excluding abnormal points with large differences in strain data from the other two measuring optical fibers, the average is taken as the first strain data and the second strain data.

[0084] a characteristic parameter determination module 302 for calculating the negative friction and negative bearing capacity of the upper pile segment, and the positive friction and positive bearing capacity of the lower pile segment based on the first strain data; The characteristic parameter determination module 302 is further configured to calculate the positive friction and positive bearing capacity of the upper pile segment, and the negative friction and negative bearing capacity of the lower pile segment based on the second strain data; The surface axial force is combined with the axial force provided by the pile top load box and the pile body load box, the friction force provided by the soil along the outside of the prefabricated steel pipe pile, and then the axial force generated by the pile body's own weight is subtracted. The pile body friction force and pile foundation bearing capacity can be calculated using the principle of elastic deformation.

[0085] Specifically, the force balance equation of precast steel pipe piles is as follows: ; Where, and Any segment of prefabricated steel pipe piles The upper and lower axial forces, D Indicates the diameter of prefabricated steel pipe piles. t Indicates the wall thickness of the prefabricated steel pipe column, Indicates the weight of prefabricated steel pipe piles. Indicates the side friction resistance of the pile in this segment.

[0086] On this basis, the pile body stress equation of prefabricated steel pipe pile can be obtained: ; (1) ; Where z represents the coordinate along the axis of the prefabricated steel pipe pile. That is, the lateral friction resistance of the pile body at position z.

[0087] The axial force of the prefabricated steel pipe pile at position z can be calculated by the strain at that position: ; (2) Where, is the strain measured at the z position, is the elastic modulus of the steel used for prefabricated steel pipe piles, It represents the area of ​​the circular cross section of the steel pipe of the prefabricated steel pipe pile.

[0088] Combining formula (1) and formula (2), the friction resistance of the prefabricated steel pipe pile at any position of the pile axis can be derived: ; ; (3) Where, Represents the variation of axial strain of prefabricated steel pipe pile with depth z.

[0089] In other words, based on the strain at any axial position of the prefabricated steel pipe pile, the frictional resistance at that position can be calculated.

[0090] Corresponding to the strain data acquisition process in this embodiment, the first strain data obtained in the process of driving the upper pile and the lower pile to move in opposite directions is substituted into formula (3) to calculate the negative friction resistance of the upper pile: and the positive friction resistance of the lower pile .

[0091] Substituting the second strain data obtained during the process of driving the upper pile and the lower pile toward each other into formula (3), the positive friction resistance of the upper pile can be calculated: and the negative friction of the lower pile .

[0092] The above four frictional resistances obtained by calculation are the frictional resistances among the characteristic parameters of prefabricated steel pipe piles.

[0093] Furthermore, based on the ability to determine the pile axial force, the pile foundation bearing capacity can also be calculated based on the pile axial force: (4) Where, Indicates the axial force at the reference starting point, Indicates depth Axial force at position, Indicates the calculation i The height of each segment.

[0094] On this basis, the first strain data obtained in the process of driving the upper and lower piles to move in opposite directions is substituted into formula (4) to calculate the negative bearing capacity of the upper pile: and the positive bearing capacity of the lower pile .

[0095] Substituting the second strain data obtained during the process of driving the upper pile and the lower pile toward each other into formula (3), the positive friction resistance of the upper pile can be calculated: and the negative friction of the lower pile .

[0096] The characteristic parameter determination module 302 is further configured to calculate the pile foundation bearing capacity of the prefabricated steel pipe pile based on the negative bearing capacity and positive bearing capacity of the upper pile segment and the negative bearing capacity and positive bearing capacity of the lower pile segment; On this basis, calculate 、 The deadweight of prefabricated steel pipe piles W The sum of the vertical compressive bearing capacity of the test pile is , .calculate of and the deadweight of prefabricated steel pipe piles W The difference between the two is taken as the total vertical pull-out bearing capacity of the test pile , , thereby realizing the pile foundation bearing capacity detection based on the reverse self-balancing principle, and the calculated total compressive bearing capacity and total pull-out bearing capacity are the pile foundation bearing capacity in the characteristic parameters of the prefabricated steel pipe pile.

[0097] The principle is to add a pile top load module to the traditional self-balancing test device. During the test, the pile body load module located in the middle pile is used to make the upper pile (i.e., the upper pile body) and the lower pile (i.e., the lower pile body) move in opposite directions, and the negative bearing capacity of the upper pile is measured. and the positive bearing capacity of the lower pile Then the pile body load box in the pile body load module returns oil, and the pile top load module is loaded, so that the upper and lower piles are displaced toward each other, and the positive bearing capacity of the upper pile is measured. and the negative bearing capacity of the lower pile Finally, the total ultimate vertical compressive bearing capacity of the test pile is the sum of the positive bearing capacity of the upper pile segment and the negative bearing capacity of the lower pile segment plus the pile weight; the total ultimate vertical pullout bearing capacity of the test pile is the sum of the negative bearing capacity of the upper pile segment and the positive bearing capacity of the lower pile segment minus the pile weight.

[0098] The present invention arranges a measuring optical fiber within a prefabricated steel pipe pile to implement strain-based characteristic parameter measurement based on the first strain data / second strain data recorded during the movement of the upper and lower pile bodies of the prefabricated steel pipe pile toward / away from each other. In addition to determining the bearing capacity of the pile foundation, the lateral friction resistance of the pile foundation can also be additionally obtained, thereby achieving a more complete characteristic parameter calculation.

[0099] Figure 4 An example of a physical structure diagram of an electronic device is shown below. Figure 4As shown, the electronic device may include: a processor (processor) 410, a communication interface (Communications Interface) 420, a memory (memory) 430 and a communication bus 440, wherein the processor 410, the communication interface 420, and the memory 430 communicate with each other through the communication bus 440. The processor 410 can call the logic instructions in the memory 430 to execute the pile foundation characteristic parameter detection method based on the optical fiber strain detection technology, which includes: obtaining first strain data and second strain data; calculating the negative friction resistance and negative bearing capacity of the upper pile, and the positive friction resistance and positive bearing capacity of the lower pile based on the first strain data; calculating the positive friction resistance and positive bearing capacity of the upper pile, and the negative friction resistance and negative bearing capacity of the lower pile based on the second strain data; calculating the pile foundation bearing capacity of the prefabricated steel pipe pile based on the negative bearing capacity and positive bearing capacity of the upper pile, and the negative bearing capacity and positive bearing capacity of the lower pile; wherein, the pile body load box of the pile body loading section is loaded to drive the upper pile body and the lower pile body to deform in opposite directions, and the first strain data is determined based on the strain data of the optical fiber measured during the opposite deformation process; the pile top load box at the top of the prefabricated steel pipe pile is loaded to drive the upper pile body and the lower pile body to deform in opposite directions, and the second strain data is determined based on the strain data of the optical fiber measured during the opposite deformation process.

[0100] Furthermore, the logic instructions in the aforementioned memory 430 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product, stored in a storage medium, includes instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0101] On the other hand, the present invention also provides a computer program product, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the pile foundation characteristic parameter detection method based on optical fiber strain detection technology provided by the above methods, the method comprising: obtaining first strain data and second strain data; calculating the negative friction resistance and negative bearing capacity of the upper pile and the positive friction resistance and positive bearing capacity of the lower pile based on the first strain data; calculating the positive friction resistance and positive bearing capacity of the upper pile based on the second strain data. The method comprises the following steps: calculating the pile foundation bearing capacity of the prefabricated steel pipe pile based on the negative bearing capacity and positive bearing capacity of the upper pile and the negative bearing capacity and positive bearing capacity of the lower pile; calculating the pile foundation bearing capacity of the prefabricated steel pipe pile based on the negative bearing capacity and positive bearing capacity of the upper pile and the negative bearing capacity and positive bearing capacity of the lower pile; wherein, the pile body load box of the pile body loading section is loaded to drive the upper pile body and the lower pile body to deform in opposite directions, and determining the first strain data based on the strain data of the optical fiber measured during the opposite deformation process; and loading the pile top load box at the top of the prefabricated steel pipe pile to drive the upper pile body and the lower pile body to deform in opposite directions, and determining the second strain data based on the strain data of the optical fiber measured during the opposite deformation process.

[0102] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to execute the pile foundation characteristic parameter detection method based on optical fiber strain detection technology provided by the above methods, the method comprising: obtaining first strain data and second strain data; calculating the negative friction resistance and negative bearing capacity of the upper pile section, and the positive friction resistance and positive bearing capacity of the lower pile section based on the first strain data; calculating the positive friction resistance and positive bearing capacity of the upper pile section, and the negative friction resistance of the lower pile section based on the second strain data and negative bearing capacity; the pile foundation bearing capacity of the prefabricated steel pipe pile is calculated based on the negative bearing capacity and positive bearing capacity of the upper pile section, and the negative bearing capacity and positive bearing capacity of the lower pile section; wherein, the pile body load box of the pile body loading section is loaded to drive the upper pile body and the lower pile body to deform in opposite directions, and the first strain data is determined based on the strain data of the optical fiber measured during the opposite deformation process; the pile top load box at the top of the prefabricated steel pipe pile is loaded to drive the upper pile body and the lower pile body to deform in opposite directions, and the second strain data is determined based on the strain data of the optical fiber measured during the opposite deformation process.

[0103] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0104] Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented using software plus a necessary general-purpose hardware platform, or of course, hardware. Based on this understanding, the essence of the above technical solution, or the portion that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, or an optical disk, and includes a number of instructions for causing a computer device (such as a personal computer, server, or network device) to execute the methods described in each embodiment or certain portions of the embodiments.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A pile foundation characteristic parameter detection method based on optical fiber strain detection technology, characterized in that: The characteristic parameters include at least pile foundation bearing capacity and friction resistance. The prefabricated steel pipe pile on which the method is based includes an upper pile body, a pile body loading section, and a lower pile body. The inner wall of the prefabricated steel pipe pile is further provided with at least one measuring optical fiber along its axial direction. The method comprises: Acquire first strain data and second strain data; Calculating the negative friction and negative bearing capacity of the upper pile segment, and the positive friction and positive bearing capacity of the lower pile segment based on the first strain data; Calculating the positive friction and positive bearing capacity of the upper pile segment, and the negative friction and negative bearing capacity of the lower pile segment based on the second strain data; Calculating the pile foundation bearing capacity of the prefabricated steel pipe pile based on the negative bearing capacity and positive bearing capacity of the upper pile segment and the negative bearing capacity and positive bearing capacity of the lower pile segment; wherein the pile body load box of the pile body loading section is loaded to drive the upper pile body and the lower pile body to deform in opposite directions, and the first strain data is determined based on the strain data of the optical fiber measured during the opposite deformation process; The pile top load box at the top of the prefabricated steel pipe pile is loaded to drive the upper pile body and the lower pile body to deform toward each other, and second strain data is determined based on the strain data of the optical fiber measured during the deformation process.

2. The pile foundation characteristic parameter detection method based on optical fiber strain detection technology according to claim 1 is characterized in that: The prefabricated steel pipe pile is also provided with a temperature compensation optical fiber. The step of determining the first strain data based on the strain data of the optical fiber measured during the opposite deformation process includes: taking the difference between the strain data of the measuring optical fiber and the strain data of the temperature compensating optical fiber during the opposite deformation process as the first strain data; The step of determining the second strain data based on the strain data of the optical fiber measured during the opposite deformation process includes: The difference between the strain data of the measuring optical fiber and the strain data of the temperature compensating optical fiber during the opposite deformation process is used as the second strain data.

3. The pile foundation characteristic parameter detection method based on optical fiber strain detection technology according to claim 1 is characterized in that: The measuring optical fibers are uniformly arranged along the circumference of the prefabricated steel pipe pile. The step of determining the first strain data based on the strain data of the measuring optical fibers during the opposite deformation process includes: The average of the strain data of the three measuring optical fibers during the opposite deformation process is used as the first strain data; The step of determining the second strain data based on the strain data of the optical fiber measured during the opposite deformation process includes: The average value of the strain data of the three measuring optical fibers during the opposite deformation process is used as the second strain data.

4. The pile foundation characteristic parameter detection method based on optical fiber strain detection technology according to any one of claims 1 to 3, characterized in that: A stress sensor is further provided on the inner wall of the prefabricated steel pipe pile, and strain data of the measuring optical fiber at the stress sensor is calibrated based on stress data of the stress sensor.

5. The pile foundation characteristic parameter detection method based on optical fiber strain detection technology according to any one of claims 1 to 3, characterized in that: The prefabricated steel pipe pile also includes a force transmission rod for connecting the pile top load box and the lower pile body. The force transmission rod is also provided with an axial force sensor for measuring its axial force. The axial force of the rod generated by the pile top load box and the pile body load box is calibrated through the reading of the axial force sensor.

6. The pile foundation characteristic parameter detection method based on optical fiber strain detection technology according to any one of claims 1 to 3, characterized in that: The characteristic parameters also include pile end resistance, which is determined according to the sudden change in the negative bearing capacity of the lower pile.

7. The pile foundation characteristic parameter detection system based on optical fiber strain detection technology is characterized by: include: A strain data acquisition module, configured to acquire first strain data and second strain data; a characteristic parameter determination module, configured to calculate the negative friction and negative bearing capacity of the upper pile segment, and the positive friction and positive bearing capacity of the lower pile segment based on the first strain data; The characteristic parameter determination module is further configured to calculate the positive friction and positive bearing capacity of the upper pile segment, and the negative friction and negative bearing capacity of the lower pile segment based on the second strain data; The characteristic parameter determination module is further configured to calculate the pile foundation bearing capacity of the prefabricated steel pipe pile based on the negative bearing capacity and positive bearing capacity of the upper pile segment and the negative bearing capacity and positive bearing capacity of the lower pile segment; wherein the pile body load box of the pile body loading section is loaded to drive the upper pile body and the lower pile body to deform in opposite directions, and the first strain data is determined based on the strain data of the optical fiber measured during the opposite deformation process; The pile top load box at the top of the prefabricated steel pipe pile is loaded to drive the upper pile body and the lower pile body to deform toward each other, and second strain data is determined based on the strain data of the optical fiber measured during the deformation process.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the pile foundation characteristic parameter detection method based on optical fiber strain detection technology as described in any one of claims 1 to 6 is implemented.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for detecting characteristic parameters of a pile foundation based on optical fiber strain detection technology as claimed in any one of claims 1 to 6 is implemented.

10. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the method for detecting characteristic parameters of a pile foundation based on optical fiber strain detection technology as claimed in any one of claims 1 to 6 is implemented.

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