A prefabricated pipe pile planting process stress detection method

Abstract

The present application belongs to prefabricated pipe pile technical field, disclose a kind of prefabricated pipe pile stress detection method in process of planting, to solve the problem of high cost of model test, sensor is easily damaged in in-situ test, and provide a kind of prefabricated pipe pile stress detection method in process of planting.The present application installs strain gauge and acceleration sensor by the way of drilling in the process of prefabricated pipe pile implantation, and the data collected by strain gauge and acceleration sensor are transmitted to base pile dynamic tester and computer to obtain stress distribution.The present application integrates hammer pile into soil depth control, signal collection, data processing, curve output and other functions, and takes into account reliability and practicability, ensures the continuity of experimental process, and can be combined with numerical simulation verification in later period.

Description

Technical Field

[0001] This invention belongs to the field of precast pipe pile technology, specifically relating to a stress detection method during the precast pipe pile installation process. Background Technology

[0002] In recent years, with the acceleration of urbanization in my country, the design theory and construction technology of foundations, especially pile foundations, have made significant progress. Pile foundations, as a common form of foundation treatment, are diverse in type. They can be classified according to pile-forming process into non-displacement piles, partially displacement piles, and displacement piles; according to bearing characteristics into friction piles and end-bearing piles; and according to pile diameter into small-diameter piles, medium-diameter piles, and large-diameter piles. Among these, precast pipe piles constructed by static pressure or driving belong to the category of partially displacement piles or displacement piles, and their bearing characteristics vary depending on the soil layers, including friction pipe piles and end-bearing pipe piles. Currently, the main construction technologies for pipe piles are:

[0003] 1) The precast piles are pressed into the soil by the reaction force of the self-weight of the static pile driver and the counterweight on the pile frame.

[0004] 2) The pipe pile is driven into the soil by a hydraulically driven pile hammer and a pile cap.

[0005] Static pressure piling avoids the vibration, noise, and pollution caused by hammer piling. However, due to its highly complex construction process, it is mostly used in areas with good geological conditions. Hydraulic hammer piling, while producing more vibration and noise, offers greater hammer force, controllable drop distance, strong penetration, and better adaptability to different geological formations. Therefore, those skilled in the art will choose different pipe pile implantation methods depending on the specific circumstances.

[0006] Current pile foundation testing technologies and related standards also provide detailed explanations of the quality inspection and acceptance of pipe pile construction. Conventional testing techniques include static load testing, low-strain testing, high-strain testing, acoustic wave transmission, and core sampling.

[0007] However, the above testing technologies are all aimed at analyzing and judging the integrity and bearing capacity of the pile body after the pile is formed (i.e., the pipe pile has been implanted into the soil).

[0008] For certain special strata, the distribution and changes in pile stress during the pile formation process are also very important, as they affect the selection of construction parameters and the control of pile quality.

[0009] Currently, stress monitoring methods mainly include model experiments, in-situ experiments (with pre-embedded sensors), and high strain monitoring.

[0010] Model experiment: This refers to a simulation experiment conducted in the laboratory based on the geological information of the pipe pile being implanted, the size of the pipe pile, etc.

[0011] In-situ testing (i.e., embedding sensors in the pipe pile during the pipe pile manufacturing process): For example, the method for detecting horizontal stress in prestressed concrete pipe piles disclosed in application number 201310326927.X describes "placing a precast concrete stress sensor block in a sealed box; pouring concrete into the reinforcing cage, pouring concrete into the top and bottom of the support, and placing the prestressed concrete pipe pile with the embedded concrete stress sensor in a high-temperature and high-pressure autoclave for curing." Another example is the stress testing method for closed-end prestressed concrete pipe piles disclosed in application number 2018105679040, which describes "setting a reinforcing bar stress gauge and stress sensing line on the longitudinal reinforcing bars of the reinforcing cage."

[0012] High-strain testing (e.g., the high-strain testing method disclosed in application number 2020105936180) is a testing method for determining the vertical compressive bearing capacity and pile integrity of a single pile. During the experiment, a heavy hammer (weighing 1%-1.5% of the estimated ultimate bearing capacity of the single pile) is used to impact the top of the pile, causing sufficient penetration into the prestressed pile. The resulting stress and acceleration response of the pile's mass points are measured, and the vertical bearing capacity and pile integrity are determined through wave theory analysis. Impacting the pile top with a heavy hammer causes sufficient relative displacement between the pile and the soil to fully stimulate the soil resistance around the pile and the end bearing force. Currently, the main high-strain testing methods for prestressed piles include the Case method, the CAPWAPC method, waveform fitting, and wave equation method. Therefore, high-strain testing can only be performed after the pile has been completed (i.e., the pipe pile has been driven into the soil to a predetermined depth).

[0013] While model experiments offer fewer constraints and controllable variables, simulating hydraulic hammer piles is challenging, and the cost of model experiment equipment is high. In-situ experimental data is reliable and closest to reality, but embedding sensors in the pile body is difficult, and the survival rate of sensors during the pipe pile manufacturing process (high-temperature curing) directly affects the experimental results.

[0014] Therefore, there is an urgent need for a convenient and reliable testing method to detect stress during the pipe pile implantation process, so as to obtain the distribution and changes of stress in the pile body during the pile formation process, and thus adjust the construction parameters during the pipe pile implantation process. Summary of the Invention

[0015] To address the issues of high cost in model experiments and easy damage to sensors in in-situ experiments, this invention provides a stress detection method for the precast pipe pile driving process. This method balances reliability and practicality, analyzes the stress distribution and variation patterns in the pile body during the driving process, identifies potential pile quality problems during actual construction, and thus guides on-site work, ensuring construction safety and efficiency.

[0016] To solve the technical problem, the technical solution adopted by this invention is as follows:

[0017] A method for stress detection during the installation of precast pipe piles, characterized by comprising the following steps:

[0018] (1) Obtain a geological survey report to determine the stratigraphic distribution of the strata where the precast pipe piles are to be implanted, and determine the location of the precast pipe pile implantation point.

[0019] (2) Marking points are set on the pile body of the precast pipe pile, including sensor marking points and hammer stop marking points.

[0020] (3) Use drilling equipment to drill holes at the sensor marking points to form holes, wherein the sensor marking points include at least strain gauge marking points and accelerometer marking points;

[0021] (4) The precast pipe piles are hoisted to the implantation point and implanted and stabilized into the stratum;

[0022] (5) Install strain gauges and acceleration sensors at the strain gauge marking points and acceleration sensor marking points respectively, and connect the strain gauges, acceleration sensors and pile dynamic testing instruments to the external pile dynamic testing instruments through lines. The pile dynamic testing instruments are connected to the external computer through lines.

[0023] (6) Continue to drive the precast pipe pile into the stratum. When the precast pipe pile reaches the stop hammer mark, remove the strain gauge and acceleration sensor and install the strain gauge and acceleration sensor at the next sensor mark.

[0024] (7) Repeat steps (5) and (6) until all sensor markers have acquired data through strain gauges and accelerometers;

[0025] (8) The stress distribution of the precast pipe pile during the implantation process is obtained by using data collected by accelerometer and strain gauge.

[0026] In some embodiments, in step (2), when setting the marker points, multiple sensor marker points and multiple stop hammer marker points are set along the length direction of the precast pipe pile body, each sensor marker point corresponds to a stop hammer marker point; and the stop hammer marker point is located 0.5-0.6m below the corresponding sensor marker point.

[0027] In some embodiments, the distance between the uppermost sensor marker point of the precast pipe pile and the top surface of the precast pipe pile is 1.5-2m.

[0028] In some embodiments, in step (3), after the detection of the current sensor marker point is completed, the next sensor marker point is drilled.

[0029] In some embodiments, when the strain gauge and accelerometer at the sensor marker point are removed, the borehole at that location should be filled and repaired.

[0030] In some embodiments, the strain gauge, accelerometer, and pile dynamic testing instrument are calibrated before use.

[0031] In some embodiments, strain gauges and acceleration sensors are installed on both sides of the precast pipe pile body, with two strain gauges on the precast pipe pile body arranged symmetrically to each other, and two acceleration sensors on the precast pipe pile body arranged symmetrically to each other.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The stress detection method for precast pipe pile installation in this invention achieves both the reliability of in-situ testing and avoids potential sensor damage issues in in-situ experiments, thus balancing reliability and practicality. Compared to existing in-situ testing methods, it improves both data reliability and accuracy (as the sensors do not suffer from the damage issues associated with high-temperature curing). Furthermore, the wiring layout of the sensors (strain gauges, accelerometers) in this invention is relatively simple, making it easy to operate. In contrast, in-situ testing requires not only pre-embedding the sensors but also pre-embedding their wiring within the precast pipe pile, increasing the complexity of the precast pipe pile manufacturing process.

[0034] This invention, by rationally arranging the construction process and interspersing stress monitoring during the conventional construction of precast pipe piles, minimizes the impact on the construction period and, at the same time, avoids the problem of reduced accuracy of sensors due to long-term vibration, thereby further improving the accuracy of the data.

[0035] This invention integrates functions such as hammer pile penetration depth control, signal collection, data processing, and curve output, ensuring the continuity of the experimental process. It can also be verified by numerical simulation in the later stage.

[0036] This invention analyzes the stress distribution and variation patterns of the pile body during the pile driving process, identifies potential pile quality problems that may be encountered during actual construction, and thus guides on-site work to ensure construction safety and efficiency. Attached Figure Description

[0037] Figure 1 This is a schematic diagram showing the division of marking points on the precast pipe piles of the present invention;

[0038] Figure 2 This is a schematic diagram showing the connection between the sensor (including strain gauge and acceleration sensor) of the present invention, the pile dynamic testing instrument, and the computer.

[0039] Figure 3 This is a schematic diagram of the marking points on the pile body of the precast pipe pile of the present invention;

[0040] Figure 4 This is a flowchart of the present invention;

[0041] The markings in the diagram are: 1. Sensor marker point; 2. Stop hammer marker point; 3. Ground line; 4. Accelerometer; 5. Strain gauge; 6. Expansion bolt; 7. Hole; 8. Pile dynamic testing instrument; 9. Computer; 10. Precast pipe pile; 11. Wiring. Implementation

[0042] The present invention will be further described below with reference to embodiments. These embodiments are merely some, not all, of the embodiments of the present invention. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the protection scope of the present invention.

[0043] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0044] Combined with appendix Figure 1 To be continued Figure 4 The stress detection method for the precast pipe pile installation process of the present invention includes the following steps:

[0045] (1) Obtain a geological survey report to determine the stratum distribution of the strata where the precast pipe piles are implanted, and determine the implantation point of the precast pipe pile 10, that is, determine the position of the precast pipe pile on the ground line 3.

[0046] (2) Marking points are set on the pile body of the precast pipe pile 10, including sensor marking point 1 and hammer stop marking point 2; in the actual real-time process, a measuring tape can be used in conjunction with a paint gun, paintbrush, etc. to set the marking points on the pile body. The purpose of setting hammer stop marking point 2 is to reserve the penetration depth for the hammer test and to prevent the sensor from being buried in the soil.

[0047] (3) Drill holes 7 at sensor marker point 1 using drilling equipment, wherein sensor marker point 1 includes at least strain gauge marker point and accelerometer marker point;

[0048] (4) The precast pipe pile 10 is hoisted to the implantation point and implanted and stabilized into the stratum;

[0049] (5) Strain gauge 5 and acceleration sensor 4 are installed at the strain gauge marking points and acceleration sensor marking points respectively, that is, strain gauge 5 and acceleration sensor 4 are installed in the corresponding holes 7, and strain gauge 5 and acceleration sensor 4 are connected to the external pile dynamic testing instrument 8 through line 11. The pile dynamic testing instrument 8 is connected to the external computer 9 through line 11. That is to say, the pile dynamic testing instrument 8 and computer 9 are not located on the pile body of the precast pipe pile 10. In the actual real-time process, the sensors (acceleration sensor and strain gauge) are installed in the holes 7 with screws, which facilitates the disassembly of the sensors.

[0050] (6) Continue to drive the precast pipe pile 10 into the stratum. When the precast pipe pile 10 reaches the stop hammer mark 2, remove the strain gauge 5 and the acceleration sensor 4, and install the strain gauge 5 and the acceleration sensor 4 at the next sensor mark.

[0051] (7) Repeat steps (5) and (6) until all sensor markers have acquired data through strain gauges and accelerometers;

[0052] (8) The stress distribution of the precast pipe pile during the implantation process is obtained by using data collected by accelerometer and strain gauge.

[0053] In some embodiments, in step (2), when setting the marker points, multiple sensor marker points and multiple stop hammer marker points are set along the length direction of the precast pipe pile body, with each sensor marker point corresponding to a stop hammer marker point; and the stop hammer marker point is located 0.5-0.6m below the corresponding sensor marker point. In the actual real-time process, the spacing between adjacent sensor marker points is determined according to the stratum distribution and the length of a single pile section. Generally, the spacing between adjacent sensor marker points is set at 2-3m.

[0054] In some embodiments, the distance between the uppermost sensor marker point of the precast pipe pile and the top surface of the precast pipe pile is 1.5-2m.

[0055] In some embodiments, in step (3), after the detection of the current sensor marker point is completed, the next sensor marker point is drilled. That is to say, during the process of implanting the precast pipe pile 10 into the stratum, after completing one detection, the next sensor marker point is drilled, thereby minimizing the impact of drilling on the stress distribution of the precast pipe pile body.

[0056] In some embodiments, when the strain gauge 5 and accelerometer 4 at the sensor marker points are removed, the borehole at that location should be filled and repaired. For example, the borehole location can be filled and repaired by applying a durable high-strength repair material. Filling and repairing holes in concrete is prior art, which is understood by those skilled in the art and will not be described in detail here.

[0057] In some embodiments, the strain gauge 5, accelerometer 4, and pile dynamic testing instrument 8 are calibrated before use. During calibration, the calibration personnel must obtain a calibration certificate and strictly follow relevant regulations.

[0058] In some embodiments, strain gauges 5 and acceleration sensors 4 are installed on both sides of the precast pipe pile 10. The two strain gauges 5 on the precast pipe pile 10 are arranged symmetrically to each other, and the two acceleration sensors 4 on the precast pipe pile 10 are arranged symmetrically to each other.

[0059] The stress detection method for precast pipe pile installation in this invention achieves both the reliability of in-situ testing and avoids potential sensor damage issues in in-situ experiments, thus balancing reliability and practicality. Compared to existing in-situ experimental methods, it improves both data reliability and accuracy (as the sensors do not suffer from the damage issues associated with high-temperature curing). Furthermore, the wiring layout of the sensors (strain gauges, accelerometers) in this invention is relatively simple, making it easy to operate. In contrast, in-situ testing requires not only pre-embedding the sensors but also pre-embedding their wiring within the precast pipe pile, increasing the complexity of the precast pipe pile manufacturing process. Compared to existing model experiments, this method offers lower cost and greater practicality.

[0060] This invention, by rationally arranging the construction process and interspersing stress monitoring during the conventional construction of precast pipe piles, minimizes the impact on the construction period and, at the same time, avoids the problem of reduced accuracy of sensors due to long-term vibration, thereby further improving the accuracy of the data.

[0061] This invention integrates functions such as hammer pile penetration depth control, signal collection, data processing, and curve output, ensuring the continuity of the experimental process. It can also be verified by numerical simulation in the later stage.

[0062] This invention analyzes the stress distribution and variation patterns of the pile body during the pile driving process, identifies potential pile quality problems that may be encountered during actual construction, and thus guides on-site work to ensure construction safety and efficiency.

[0063] As an embodiment of the invention, taking the site investigation report of a foundation treatment project in Chengdu as an example, the site, from top to bottom, consists of 11m thick miscellaneous fill, 10.1m thick fine sand, 3.5m thick medium-coarse sand, and 8.3m thick fine sand. This indicates that the site contains a sand layer with a thickness greater than 20m. Due to the special site conditions, it is preliminarily predicted that the skin friction between the soil layer and the pile body will be relatively large during construction. Therefore, stress monitoring is required during the driving process of precast pipe piles. The method of this invention specifically includes the following:

[0064] 1. Calibrate the strain gauge 5, accelerometer 4, and pile dynamic testing instrument 8 according to the specifications and obtain a qualified calibration certificate; install the computer software 9 and prepare for monitoring.

[0065] 2. Obtain the geological survey report, determine the stratum distribution at the test point, and determine the monitoring depth as the pile length minus the remaining length of 25-1.5=23.5m; 10 precast pipe piles were precast and transported to the site. The precast pipe pile model is PHC 600 AB 110 14 / 13 / 12 / 11, and the hydraulic hammer pile machine model is RH06 with a hammer weight of 16t.

[0066] 3. Use a measuring tape and paint spray to generate sensor marker point 1 and hammer stop marker point 2. First, sensor marker point 1 is determined according to the stratum distribution and the length of a single section of the precast pipe pile, with the spacing controlled at 3m; then spray hammer stop marker point 2 (i.e., the actual measured depth into the soil) 0.5m below the installation position of accelerometer 4 and strain gauge 5.

[0067] 4. Use a miniature drill to drill a hole 7 at sensor marker point 11, and check whether the hole position is symmetrical.

[0068] 5. Connect the acceleration sensor 4 and strain gauge 5 on the pile body, the pile dynamic tester 8 and the computer 9 using line 11, and turn on the equipment to check if it is working properly.

[0069] 6. Continue driving the precast pipe pile 10 downwards, controlling the drop distance to 30cm; when the hammer reaches the stop mark 2, instruct the team to stop the hammering and install the accelerometer 4 and strain gauge 5; after ensuring that the accelerometer 4 and strain gauge 5 are securely installed, open the computer 9 testing software, control the drop distance, and instruct the team to hammer the pile; after collecting and storing the data, the accelerometer 4 and strain gauge 5 can be removed; instruct the team to hammer the pile to the next stop mark 2 and repeat the above test.

[0070] In the specific real-time process, when the final monitoring depth is reached, about 2m above the precast pipe pile 10, the monitoring ends after data collection. Then, the instruments and equipment are cleaned up and organized (4, 5, 8, 9, and 11). The data is processed indoors, and the curve is fitted. The data processing is an existing technology, which can be understood by those skilled in the art, so it will not be described in detail here.

[0071] As the preferred implementation method in this case, the monitoring target should preferably be a large-diameter precast pipe pile 10, because small-diameter pipe piles are prone to problems such as eccentricity during hammering. At the same time, the precast pipe piles should be hammered with heavy blows at low speeds to prevent eccentric hammering.

[0072] As a preferred implementation method in this case, the pile markings are measured with a tape measure and generated by paint spraying; the measuring tape range should be greater than the length of a single pile section, and the paint color should preferably be a bright color such as red.

[0073] As the preferred implementation method in this case, 3-5 sets of monitoring signals with good performance should be selected, that is, the sensor signals on the left and right sides of the precast pipe pile are basically synchronized, the peak values ​​are basically overlapping, the force curve is positive and always above the velocity curve.

Claims

1. A method for stress detection during the installation of precast pipe piles, characterized in that, Includes the following steps: (1) Obtain a geological survey report to determine the stratigraphic distribution of the strata where the precast pipe piles are to be implanted, and determine the location of the precast pipe pile implantation points; (2) Marking points are set on the pile body of the precast pipe pile, including sensor marking points and hammer stop marking points. When setting the marking points, multiple sensor marking points and multiple hammer stop marking points are set along the length direction of the precast pipe pile body. Each sensor marking point corresponds to a hammer stop marking point. The hammer stop marking point is located 0.5-0.6m below the corresponding sensor marking point. (3) Use drilling equipment to drill holes at the sensor marking points to form holes, wherein the sensor marking points include at least strain gauge marking points and accelerometer marking points; after the current sensor marking point is detected, drill holes at the next sensor marking point; (4) The precast pipe piles are hoisted to the implantation point and implanted and stabilized into the stratum; (5) Install strain gauges and acceleration sensors at the strain gauge marking points and acceleration sensor marking points respectively, and connect the strain gauges and acceleration sensors to an external pile dynamic testing instrument via a line. The pile dynamic testing instrument is connected to an external computer via a line. (6) Continue to drive the precast pipe pile into the stratum. When the precast pipe pile reaches the stop hammer mark, remove the strain gauge and acceleration sensor and install the strain gauge and acceleration sensor at the next sensor mark. (7) Repeat steps (5) and (6) until all sensor markers have acquired data through strain gauges and accelerometers; (8) The stress distribution of the precast pipe pile during the implantation process is obtained by using data collected by accelerometer and strain gauge.

2. The stress detection method for the precast pipe pile installation process according to claim 1, characterized in that, The distance between the uppermost sensor marker point of the precast pipe pile and the top surface of the precast pipe pile is 1.5-2m.

3. The stress detection method for the precast pipe pile installation process according to claim 1, characterized in that, When removing strain gauges and accelerometers from sensor marker points, the boreholes at those locations should be filled and repaired.

4. The stress detection method for the precast pipe pile installation process according to claim 1, characterized in that, The strain gauges, accelerometers, and pile dynamic testing instruments are calibrated before use.

5. The method for stress detection during the installation process of precast pipe piles according to any one of claims 1-4, characterized in that, Strain gauges and acceleration sensors are installed on both sides of the precast pipe pile. The two strain gauges on the precast pipe pile are arranged symmetrically to each other, and the two acceleration sensors on the precast pipe pile are arranged symmetrically to each other.

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