A model test detection system and method for a pre-stage of rapid loading method pile foundation detection

Abstract

This invention discloses a model test system and method for the preliminary stage of pile foundation testing using the rapid load method. The system includes a model box and a model pile. Soil acceleration sensors, pore pressure gauges, and earth pressure gauges are installed at different heights within the model box. Strain gauges are installed inside the model pile. A force sensor, a pile acceleration sensor, and a displacement detection system are fixed to the top of the model pile. A buffer device is installed above the force sensor, and a load is installed above the buffer device to apply force to it. The load causes the model pile to sink vertically in the soil. The load is mounted on a guide rod and moves vertically. A lifting system is connected to the load to control its release or retraction. This invention simplifies the preliminary test steps of the rapid load method, saves the pile foundation rest time after the preliminary test, and greatly improves the efficiency of pile foundation testing.

Description

Technical Field

[0001] This invention relates to a model test device and method for detecting the vertical bearing capacity of pile foundations, and more particularly to a model test system and method for the pre-test stage of pile foundation testing using the fast load method. Background Technology

[0002] The vertical bearing capacity of pile foundations is a crucial indicator for assessing pile foundation quality. Common testing methods include static load testing and high-strain dynamic testing, which are fundamentally different methods for determining pile foundation bearing capacity. In static load testing, the load is applied to the pile top in a slowly increasing manner. During static load testing, the pile body only experiences static displacement, with settlement gradually increasing until the test requirements are met. The advantage of static load testing is its accurate and reliable results; however, it suffers from drawbacks such as requiring extensive equipment, having a long testing cycle, high testing costs, and low sampling rates. High-strain pile foundation bearing capacity testing, on the other hand, utilizes an instantaneous test load applied to the pile top, causing the pile body to exhibit strong dynamic phenomena to assess its bearing capacity. While it offers a shorter testing cycle and lower cost, it still has some insurmountable limitations compared to static load testing. For example: (1) Tension waves caused by stress waves may cause damage or breakage of the pile body; (2) Bending stress caused by eccentric loading may damage the pile body; (3) Due to the large difference between the mechanical and physical properties of the soil exhibited by rapid loading and static load, the bearing capacity tested by dynamic testing in many cases needs to be verified by static load test. Self-balancing pile testing is a newly developed pile foundation bearing capacity testing method. This method is an indirect static load test method based on seeking the loading reaction force inside the pile foundation. This method uses the pile's own resistance as the reaction force, and the device is simple, time-saving and economical. However, this method also has some shortcomings: when using engineering piles for testing, if the load box position forms a broken pile after loading, it is not easy to deal with; the load box balance point position needs to be estimated, and the friction force of the upper pile body and the friction force and end resistance of the lower pile body are not easy to balance; in addition, during the test, the upper part of the load box reads the negative friction force, which is different from the actual situation and needs to be adjusted according to experience.

[0003] The rapid load method for pile foundation testing is a novel method for testing the ultimate bearing capacity of pile foundations. This method significantly increases the width of the force pulse by extending the duration of the hammer impact on the pile top, resulting in similar settlement behavior across different parts of the pile. The stress distribution and relative displacements of various points on the pile obtained from the test closely resemble those of a static load test. Before conducting pile testing using the rapid load method, a trial pile drive is required to determine the necessary testing mass and the characteristics of the buffer device. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a model test system for the pre-testing stage of pile foundation testing using the fast load method, which can effectively reduce testing time and improve testing quality; another purpose of this invention is to provide a method using the above-mentioned system.

[0005] Technical Solution: The fast-load pile foundation testing model system of the present invention includes a model box for loading soil and a model pile with its bottom extending into the soil; soil acceleration sensors, pore pressure gauges, and earth pressure gauges are installed at different heights inside the model box; strain gauges are installed inside the model pile; a force sensor, a pile acceleration sensor, and a displacement detection system are fixed at the top of the model pile; a buffer device for converting dynamic load into long-pulse load is fixed above the force sensor and the pile acceleration sensor; a load for applying force to the buffer device is installed above the buffer device; the load acts on the buffer device, causing the model pile to sink vertically in the soil; the load is sleeved on a guide rod for vertical movement along the guide rod; the load is connected to a lifting system for controlling the release or retraction of the load.

[0006] The displacement detection system includes a displacement sensor installed above the model pile.

[0007] The displacement detection system further includes platforms extending from the outer wall of the model pile to both sides; a displacement sensor is installed above one platform and below the other; marker points are respectively provided on the surface of the platforms and at corresponding positions of the laser spots of the displacement sensors on both sides, for detecting whether the laser spots of the displacement sensors are accurately positioned. The marker points are convex points.

[0008] The model box is provided with a support frame on the outside, and the guide rod is fixed to the bottom of the support frame.

[0009] The support frame is fixed with a pulley, and the lifting system is connected to the load through a rope wound around the pulley, which is used to move the load up and down along the guide rod.

[0010] The buffer device is made of metal, non-metal, or a mixture of metal and non-metal.

[0011] It also includes a computer and a data acquisition device connected to the computer; the data acquisition device is connected to strain gauges, soil acceleration sensors, pore pressure gauges, earth pressure gauges, force sensors, pile acceleration sensors and displacement detection systems respectively.

[0012] The fast-load pile foundation testing method using the above-described system includes the following steps:

[0013] (1) Monitoring of test pile driving: In the specified soil, a corresponding long pulse load is formed by using load and buffer device, so as to carry out a series of long pulse load inputs, wherein the load mass and lifting stroke are adjusted to each other;

[0014] The corresponding time history curves are plotted using information from force sensors, pile acceleration sensors, displacement detection systems, and strain gauges. The corresponding time history curves are plotted using information from soil acceleration sensors, pore pressure gauges, and earth pressure gauges. The criteria for judging vertical bearing capacity test driving and the criteria for selecting counterweights and buffer devices for pile foundation testing using the fast load method are given.

[0015] (2) For pile foundation testing using the rapid loading method:

[0016] Based on the buffer device for pile driving monitoring using test piles, force sensors, displacement detection systems, pile acceleration sensors, and strain gauges are used to detect the actual dynamic characteristics of the model pile foundation and plot the corresponding time history curves, including force time history, acceleration time history, displacement time history, and stress / strain time history curves. Soil acceleration sensors, pore pressure gauges, and earth pressure gauges are used to detect the dynamic characteristics of the soil and plot the corresponding time history curves, including soil stress change time history and pore water pressure time history curves. The basis for determining the test driving energy of vertical bearing capacity is given, as well as the basis for selecting the counterweight mass and buffer device material for pile foundation testing using the fast load method.

[0017] The bearing capacity of the engineering pile foundation is calculated by back-calculating the similarity principle and then verified in the project. If the verification is qualified, the pile foundation test by the fast load method is completed; if it is not qualified, the above steps are repeated until the test is completed.

[0018] The method for implementing pile driving monitoring using the above system includes the following steps:

[0019] (1) Monitoring of test pile driving: In the specified soil, a corresponding long pulse load is formed by using load and buffer device, so as to carry out a series of long pulse load inputs, wherein the load mass and lifting stroke are adjusted to each other;

[0020] Using information from force sensors, displacement detection systems, pile acceleration sensors, and strain gauges, corresponding time history curves are plotted. Using information from soil acceleration sensors, pore pressure gauges, and earth pressure gauges, corresponding time history curves are plotted. The criteria for judging vertical bearing capacity by test driving are given, as well as the criteria for selecting counterweights and buffer devices for pile foundation testing using the fast load method.

[0021] (2) Based on the vertical bearing capacity test judgment criteria, and the selection of counterweight and buffer device for pile foundation testing by the fast load method, combined with the existing on-site test pile design conditions and geological survey data, appropriate model piles are configured, corresponding soil is mixed, and the load mass and corresponding lifting stroke are configured according to the similarity principle. The pile force, displacement, and acceleration time history curves and the soil acceleration, pore pressure time history curves and earth pressure time history curves under different counterweights / different lifting heights are recorded. Based on the above data, pre-pile driving parameters are given, and these parameters are applied in engineering test piles.

[0022] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects:

[0023] (1) For the fast load method, the existing technology is only for the characteristics of the pile foundation and can only give the vertical bearing capacity of the pile foundation for the actual pile foundation test in the field test. The present invention is the pre-test stage of the fast load method. It uses model test to give the selection of counterweight and buffer device for the field test of the fast load method. The present invention simplifies the pre-test steps of the fast load method, saves the pile foundation rest time after the pre-test (7d-25d), and greatly improves the pile foundation test efficiency.

[0024] (2) The present invention provides a test system for a test pile model. Compared with on-site test pile driving, the system can effectively solve the problem of selecting the corresponding parameters for test pile driving and reduce the number of test piles required for test pile driving.

[0025] (3) The sensor setting scheme for pile foundation and soil in the system of the present invention provides a dynamic monitoring scheme for pile foundation, surrounding soil and pile soil. The time history curves of force, displacement, stress / strain, soil stress and pore water pressure can truly reflect the pile-soil mechanical characteristics of dynamic testing. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the system structure of the present invention;

[0027] Figure 2 This is a front view of the buffer device of the present invention and its components between it and the model pile;

[0028] Figure 3 This is a top view of the buffer device of the present invention and its components between it and the model pile. Detailed Implementation

[0029] The present invention will now be described in further detail.

[0030] like Figures 1-3As shown, this invention discloses a rapid load method pile foundation testing model system, including a model box 11 for loading soil. Soil acceleration sensors 8, pore pressure gauges 9, and earth pressure gauges 10 are installed at different heights within the model box 11. A model pile 5 extends into the soil within the model box 11, and strain gauges are installed inside the model pile 5. A force sensor 3, a pile acceleration sensor (not shown in the figure), and a displacement detection system are fixed to the top of the model pile 5. A buffer device 12 for converting dynamic load into long pulse load is fixed above the force sensor 3. A load 2 for applying force to the buffer device 12 is installed above the buffer device 12, causing the model pile 5 to sink vertically in the soil after the load 2 acts on the buffer device 12. Initially, the load 2 is not in contact with the buffer device 12. The load 2 is sleeved on a guide rod 1 for vertical movement along the guide rod 1. A support frame 6 is provided outside the model box 11, and the guide rod 1 is fixed below the support frame 6. A lifting system 7 is connected to the load 2 for controlling its release or retraction. A fixed pulley is fixed on the support frame 6. The lifting system 7 is connected to the load 2 via a rope wound around the fixed pulley, which is used to move the load 2 up and down along the guide rod 1. The support frame 6 mainly provides support for lifting and releasing the load 2, and provides a fixing device for the guide rod 1.

[0031] The displacement detection system includes a displacement sensor 4 positioned above the model pile 5. It also includes platforms 13 extending from the outer wall of the model pile 5 to both sides; displacement sensors are positioned above one platform 13 and below the other; marker points 14 are marked on the surface of the platform 13 corresponding to the laser spots of the displacement sensors 4 on both sides, used to detect whether the laser spots of the displacement sensors 4 are accurately positioned. These marker points are convex points. When performing the rapid load method test, to ensure accuracy and repeatability, the displacement detection system should have at least one sensor on each side of the model pile, and the emitted laser spots should be positioned at the convex points of the platforms. During the test, the spot position should be fixed at the convex point. If the laser spots on both sides are accurately positioned, the displacement time history curve is obtained by averaging both values. If the laser spots deviate from the convex point during the test, the test is invalid.

[0032] The pile acceleration sensor can be fixed on the same layer as the force sensor 3, or it can be fixed on the platform 13.

[0033] The material of the buffer device 12 is selected according to the different loads 2 to ensure that the pulse load generated by the load 2 is held for a time greater than 100ms; the force sensor 3 and the pile acceleration sensor are selected according to the load 2 and the design value of the vertical bearing capacity of the pile foundation. The material and strain gauge settings of the model pile 5 should be set in conjunction with the simulated test pile. The lifting system 7 can be equipped with a suitable winch, etc., according to the mass of the load 2.

[0034] The detection system of the present invention also includes a computer (not shown in the figure) and a data acquisition instrument (not shown in the figure) connected to the computer; the data acquisition instrument is connected to a strain gauge, a soil acceleration sensor 8, a pore pressure gauge 9, an earth pressure gauge 10, a force sensor 3, a pile acceleration sensor and a displacement detection system.

[0035] Soil acceleration sensor 8 is used to detect soil acceleration during the rapid loading stage; pore pressure gauge 9 is used to detect pore water pressure in the soil during the rapid loading stage; earth pressure gauge 10 is used to detect soil stress at the pile bottom throughout the rapid loading process.

[0036] The fast-load pile foundation testing method using the above-described system includes the following steps:

[0037] (1) Monitoring of test pile driving: In the designated soil, a corresponding long pulse load is formed using load 2 and buffer device 12, thereby inputting a series of long pulse loads. Specifically, the lifting system 7 releases the load 2 with a specific weight through pulleys. The load 2 moves down rapidly and acts on the buffer device 12 of a specific material. Under the buffering effect of the buffer device 12, the dynamic load is converted into a quasi-static load, realizing the input of long pulse loads. Among them, the mass of load 2 and the lifting stroke are mutually adjusted;

[0038] Using information from force sensor 3, pile acceleration sensor, displacement detection system, and strain gauge, corresponding time history curves are plotted. Using information from soil acceleration sensor 8, pore pressure gauge 9, and earth pressure gauge 10, corresponding time history curves are plotted. The criteria for vertical bearing capacity test driving and the criteria for selecting counterweight and buffer device 12 for pile foundation testing using the fast load method are given.

[0039] (2) For pile foundation testing using the rapid loading method:

[0040] Based on the pile driving monitoring buffer device 12, force sensors, pile acceleration sensors, displacement detection systems, and strain gauges are used to detect the actual dynamic characteristics of the model pile foundation and plot the corresponding time history curves, including force time history, acceleration time history, displacement time history, and stress / strain time history curves. Soil acceleration sensors 8, pore pressure gauges 9, and earth pressure gauges 10 are used to detect the dynamic characteristics of the soil and plot the corresponding time history curves, including soil stress change time history and pore water pressure time history curves. The basis for determining the vertical bearing capacity test driving energy, as well as the basis for selecting the counterweight mass and the material selection of the buffer device 12 for the pile foundation testing using the fast load method, are given.

[0041] The bearing capacity of the engineering pile foundation is calculated by back-calculating the similarity principle and then verified in the project. If the verification is qualified, the pile foundation test by the fast load method is completed; if it is not qualified, the above steps are repeated until the test is completed.

[0042] The method for implementing pile driving monitoring using the above system includes the following steps:

[0043] (1) Monitoring of test pile driving: In the specified soil, the load 2 and the buffer device 12 are used to form a corresponding long pulse load, thereby inputting a series of long pulse loads, wherein the mass of the load 2 and the lifting stroke are mutually adjusted.

[0044] Using information from force sensor 3, pile acceleration sensor, displacement detection system, and strain gauge, corresponding time history curves are plotted. Using information from soil acceleration sensor 8, pore pressure gauge 9, and earth pressure gauge 10, corresponding time history curves are plotted. The criteria for vertical bearing capacity test driving are given, as well as the criteria for selecting counterweight and buffer device 12 materials for pile foundation testing using the fast load method.

[0045] (2) Based on the vertical bearing capacity test judgment criteria, and the fast load method pile foundation test counterweight selection and buffer device criteria, combined with the existing field test pile design conditions and geological survey data, configure appropriate model piles, mix the corresponding soil, configure the load mass and corresponding lifting stroke according to the similarity principle, record the pile foundation force, displacement, acceleration time history curves and soil acceleration, pore pressure time history curves and earth pressure time history curves under different counterweights / different lifting heights, and give the pre-driving pile design application in engineering test piles based on the above data.

[0046] For clay, the system of this invention can be used for pile driving monitoring and rapid load method pile foundation testing.

[0047] The main steps for monitoring test pile driving are as follows:

[0048] (1) Based on the existing on-site test pile design conditions and geological survey data, appropriate model piles are configured. The main control parameters for the configuration of these model piles are the geometric shape and material properties of the model piles.

[0049] Model pile geometry: For example, pipe piles should typically be configured as tubular structures to simulate the hollow cross-sectional characteristics of actual piles; for closed pipe piles, the sealing of the pile bottom needs to be determined based on the effect of soil plugging, which involves the interaction mechanism between the soil and the pile and the assessment of bearing capacity; cast-in-place piles should be configured as solid rod-like structures to accurately reflect their solid and uniform geometric characteristics. Furthermore, other types such as precast piles or micropiles also need to be modeled according to their actual design shapes.

[0050] The material properties of the model pile should be set according to the specific purpose of monitoring the test pile driving to ensure that the model pile can realistically simulate the actual stopping of the hammer during the test and provide accuracy and reliability for the monitoring data. For example, if the monitoring purpose is to evaluate the hammer stress of the pile, the material should have high strength and durability; if the purpose is to study the deformation characteristics of the pile, attention should be paid to the elastic modulus and creep properties of the material. In addition, the material selection should also consider the construction method of the test pile driving, environmental conditions, and cost factors to optimize the overall testing plan.

[0051] The above model pile indicators should be considered comprehensively. The judgment criteria are based on the consistency between the time history curves of soil stress and pore water pressure from the soil sensor and the actual situation, and the two should be mutually verified.

[0052] (2) According to the purpose of test pile driving monitoring, namely to evaluate the effect of foundation treatment, ensure the quality of pile foundation construction, and optimize design parameters, the original foundation soil needs to be fully mixed according to the predetermined mix ratio to form a uniform and stable composite soil. This process must be carried out using professional mixing machinery, such as twin-shaft or single-shaft mixers, in layers, with the thickness of each layer controlled within a reasonable range to ensure uniform mixing. At the same time, the moisture content of the soil must be strictly controlled, usually adjusted through field tests or laboratory measurements, and the mixing time must be precisely managed to avoid over- or under-mixing affecting the soil properties. These measures aim to ensure that the composite soil reaches the compaction required by the design, such as through compaction tests, and strength indicators, such as unconfined compressive strength or bearing capacity.

[0053] The above soil parameters should be considered comprehensively, and the judgment criteria are mainly based on the force-time history curve in the pile, which reflects the force changes during pile driving. The maximum force value is considered a critical value because it indicates that the soil has sufficient energy absorption and transmission capacity, meeting the requirements for pile driving.

[0054] (3) Based on the principle of similarity, the load mass and corresponding lifting stroke are configured. The main purpose is to convert the maximum stroke and maximum energy value (or force value) of the equipment used on site into free fall. For example, if the pile driving equipment on site is controlled by energy, the corresponding potential energy conversion can be performed. Since the conversion of potential energy and kinetic energy in free fall is simple and reliable, this invention can only use free fall to simulate energy conversion in order to ensure the reliability and repeatability of the simulation reality.

[0055] (4) Conduct pile driving tests, measure the corresponding pile driving curves, record the relationship between pile driving resistance and penetration under different lifting heights, determine the bearing capacity recovery coefficient of the pile, and give the pre-pile design based on the above data for application in engineering test piles.

[0056] The main steps in pile foundation testing using the fast-load method are as follows:

[0057] Based on existing on-site test pile design conditions and detailed geological survey data, model piles matching the actual engineering pile materials and geometric properties were selected, and soil samples conforming to the actual soil layer physical and mechanical parameters were prepared to ensure that the model test and on-site conditions met the similarity principle in terms of geometry, materials, and boundary conditions. The load capacity and corresponding lifting stroke were reasonably calculated and determined based on the similarity relationship, and then rapid load testing was conducted.

[0058] In a pre-prepared soil model that meets design requirements, a pile driving load is applied through the coordinated action of a load-bearing system and a buffer device to simulate the dynamic loading process in actual engineering. During the experiment, the matching relationship between the counterweight mass and the lifting height is dynamically adjusted according to the real-time response of the pile-soil system to ensure the effectiveness of load transfer and the rationality of the waveform. Using force sensors 3, pile acceleration sensors, displacement detection systems, and strain gauges installed on the model pile, the response data of the pile under dynamic load is collected in real time, and curves of force, displacement, acceleration, and strain changing over time are plotted. At the same time, using acceleration sensors, pore pressure gauges, and earth pressure gauges embedded in the soil, the dynamic response inside the soil is monitored, and data on soil stress changes and pore water pressure are obtained, and corresponding time history curves are plotted.

[0059] Through systematic analysis of data measured by force sensors, pile acceleration sensors, displacement detection systems, and strain gauges, the true dynamic characteristics of the model pile under dynamic loads are accurately identified, and a comprehensive response spectrum including force time history, acceleration time history, displacement time history, and stress / strain time history is plotted. Simultaneously, based on the monitoring results of soil acceleration, pore water pressure, and earth pressure, the deformation and strength response laws of the soil under dynamic loads are analyzed, and soil stress time history and pore water pressure time history curves are plotted. Based on the obtained dynamic response information, an energy-based judgment criterion is proposed for vertical bearing capacity testing, clarifying the principles for determining the counterweight mass and the selection criteria for key parameters of buffer device materials (such as dynamic Young's modulus) in the rapid load method pile foundation testing. Finally, based on the similarity principle, the test results of the model pile are inverted and extrapolated to the actual engineering pile foundation to predict its bearing capacity, and on-site engineering verification is conducted. If the verification results meet the design requirements, the rapid load method pile foundation testing process ends; if not, the model parameters, counterweight, or buffer conditions need to be readjusted, and the test repeated until verification is successful.

[0060] The following is a detailed debugging process that provides a basis for selecting load-bearing and buffer materials for pile foundation testing using the rapid load method:

[0061] In this experiment, the selection of load and buffer material for the rapid load test is generally divided into two cases: one is the test pile test, and the other is the test pile test. Regardless of the case, the rapid load test must meet two principle conditions: (1) the test force should be greater than the bearing capacity of the pile foundation itself; (2) the holding time should make the pile foundation undergo a similar mechanical process to the static load test. Generally speaking, the test load pulse time is greater than 100ms.

[0062] In pile testing, the selection of load-bearing and buffer materials is generally based on preliminary geological survey data. Appropriate load-bearing counterweights and buffer materials are selected according to the geological survey data. Generally, the load-bearing counterweight is the test load / 20g, and the buffer device should be designed for a pulse time greater than 100ms. After the test begins, if the requirements are not met, the lifting stroke should be adjusted accordingly. If the requirements are met after adjustment, the pile bearing capacity can be obtained. If the adjustment does not meet the requirements, the counterweight should be adjusted according to the measured force-time history curve, increasing the counterweight mass. If the requirements are met after adjustment, the pile bearing capacity can be obtained. If the adjustment does not meet the requirements, the buffer device should be adjusted using the force-time history curve. Once the requirements are met, the pile bearing capacity can be obtained.

[0063] In the testing of engineering piles, the selection of load-bearing and buffer materials is generally based on the static load data of the previous pile test. Generally speaking, the load counterweight is the vertical bearing capacity of the static load of the pile test / 20g, and the buffer device should be based on a pulse time greater than 100ms. After the test starts, if the force, displacement, acceleration and strain time history curves obtained from the pile foundation test meet the requirements, the pile foundation is qualified; otherwise, the pile foundation is unqualified.

Claims

1. A model test detection system for the pre-testing stage of pile foundation testing using the rapid load method, characterized in that, The system includes a model box (11) for loading soil and a model pile (5) extending into the soil at the bottom; a soil acceleration sensor (8), a pore pressure gauge (9), and an earth pressure gauge (10) are installed at different heights inside the model box (11); a strain gauge is installed inside the model pile (5), and a force sensor (3), a pile acceleration sensor, and a displacement detection system are fixed at the top of the model pile (5); a buffer device (12) for converting dynamic load into long pulse load is fixed above the force sensor (3), and a load (2) for applying force to the buffer device (12) is installed above the buffer device (12), and the load (2) causes the model pile (5) to sink vertically in the soil after acting on the buffer device (12); the load (2) is sleeved on the guide rod (1) for moving the load (2) vertically along the guide rod (1); the load (2) is connected to a lifting system (7) for controlling the release or retraction of the load (2).

2. The model test detection system for the pre-test stage of pile foundation testing using the rapid load method according to claim 1, characterized in that, The displacement detection system includes a displacement sensor (4) installed above the model pile.

3. The model test detection system for the pre-test stage of pile foundation testing using the rapid loading method according to claim 2, characterized in that, The displacement detection system also includes platforms (13) extending from the outer wall of the model pile (5) to both sides; displacement sensors are provided above one platform (13) and below the other platform (13); marking points (14) are provided on the surface of the platform (13) and at the corresponding positions of the laser spots of the displacement sensors (4) on both sides, for detecting whether the laser spots of the displacement sensors (4) are accurately positioned.

4. The model test detection system for the pre-test stage of pile foundation testing using the rapid loading method according to claim 1, characterized in that, The model box (11) is provided with a support frame (6) on the outside, and the guide rod (1) is fixed below the support frame (6).

5. The model test detection system for the pre-test stage of pile foundation testing using the rapid loading method according to claim 4, characterized in that, The support frame (6) is fixed with a pulley, and the lifting system (7) is connected to the load (2) by a rope wound around the pulley, so as to move the load (2) up and down along the guide rod (1).

6. The model test detection system for the pre-test stage of pile foundation testing using the rapid loading method according to claim 1, characterized in that, The buffer device (12) is made of metal, non-metal, or a mixture of metal and non-metal.

7. The model test detection system for the pre-test stage of pile foundation testing using the rapid loading method according to claim 1, characterized in that, It also includes a computer and a data acquisition device connected to the computer; the data acquisition device is connected to a strain gauge, a soil acceleration sensor (8), a pore pressure gauge (9), an earth pressure gauge (10), a force sensor (3), a pile acceleration sensor, and a displacement detection system.

8. A method for rapid load method pile foundation testing using the system described in claim 1, characterized in that, Includes the following steps: (A1) Monitoring of test pile driving: In the specified soil, a corresponding long pulse load is formed by using the load (2) and the buffer device (12) to carry out a series of long pulse load inputs, wherein the mass of the load (2) and the lifting stroke are mutually adjusted; Using the information from the force sensor (3), pile acceleration sensor, displacement detection system, and strain gauge, the corresponding time history curves are plotted. Using the information from the soil acceleration sensor (8), pore pressure gauge (9), and soil pressure gauge (10), the corresponding time history curves are plotted. The basis for judging the vertical bearing capacity test and the basis for selecting the counterweight and buffer device (12) for the pile foundation test of the fast load method are given. (B1) For pile foundation testing using the rapid load method: Based on the buffer device (12) for pile driving monitoring based on test pile driving, the dynamic characteristics of the model pile (5) are detected by force sensor (3), pile acceleration sensor, displacement detection system and strain gauge and the corresponding time history curves are plotted, including force time history, acceleration time history, displacement time history and stress / strain time history curves; the dynamic characteristics of the soil are detected by soil acceleration sensor (8), pore pressure gauge (9) and earth pressure gauge (10) and the corresponding time history curves are plotted, including soil stress change time history and pore water pressure time history curves; the basis for judging the vertical bearing capacity test driving energy, and the basis for selecting the counterweight mass and the material selection of the buffer device (12) for pile foundation testing by the fast load method are given; The bearing capacity of the engineering pile foundation is calculated by back-calculating the similarity principle and then verified in the project. If the verification is qualified, the pile foundation test by the fast load method is completed; if it is not qualified, the above steps are repeated until the test is completed.

9. A method for monitoring pile driving using the system described in claim 1, characterized in that, Includes the following steps: (A2) Monitoring of test pile driving: In the specified soil, a corresponding long pulse load is formed by using the load (2) and the buffer device (12) to carry out a series of long pulse load inputs, wherein the mass of the load (2) and the lifting stroke are mutually adjusted; Using the information from the force sensor, pile acceleration sensor (3), displacement detection system, and strain gauge, the corresponding time history curves are plotted. Using the information from the soil acceleration sensor (8), pore pressure gauge (9), and earth pressure gauge (10), the corresponding time history curves are plotted. The basis for judging the vertical bearing capacity test is given, as well as the basis for selecting the counterweight and buffer device (12) for the pile foundation test using the fast load method. (B2) Based on the vertical bearing capacity test judgment criteria, and the selection of counterweight and buffer device for pile foundation testing using the fast load method, combined with the existing on-site test pile design conditions and geological survey data, appropriate model piles are configured, and corresponding soil is mixed. Based on the similarity principle, the load mass and corresponding lifting stroke are configured. The pile force, displacement, and acceleration time history curves, as well as the soil acceleration, pore pressure time history curves, and earth pressure time history curves under different counterweights / lifting heights are recorded. Based on the above data, pre-pile driving parameters are given, and these parameters are applied in engineering test piles.

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