A steel cylinder vibration sinking simulation test system considering interface dynamic characteristics and a test method thereof

Abstract

This invention discloses a steel cylinder vibration sinking simulation test system and its test method, comprising: a steel cylinder model, a vibration sinking test device, a static pressure sinking test device, and a data acquisition system; the vibration sinking test device is used to conduct vibration sinking simulation tests, strain and stress data at various test points on the outer wall of the steel cylinder model are obtained through strain gauges on the outer wall of the steel cylinder model during vibration sinking, earth pressure sensors are used to obtain earth pressure change data at various test points during vibration sinking, earth pressure sensors and pore water pressure sensors are used to monitor the distribution data of lateral earth pressure and pore water pressure during vibration sinking through earth pressure sensors and pore water pressure sensors installed on the outer side of the steel cylinder model, and vibration acceleration signal data at various test points during vibration sinking are collected through acceleration sensors installed on the steel cylinder model; static pressure tests are conducted using the static pressure sinking test device to obtain the maximum pressure that the steel cylinder model can withstand when placed at different depths in the soil layer.

Description

Technical Field

[0001] This invention belongs to the field of marine steel cylinder vibration sinking technology, specifically a steel cylinder vibration sinking simulation test system and test method that considers interface dynamic characteristics. Background Technology

[0002] In recent years, large-diameter steel cylindrical structures have been increasingly widely used in marine engineering projects both domestically and internationally. The West Artificial Island of the Hong Kong-Zhuhai-Macau Bridge and the artificial island of the Shenzhen-Zhongshan Bridge have used them as island wall structures for artificial islands at sea, creating the engineering miracle of completing the islands in the same year that construction began. The Hong Kong-Zhuhai-Macau Bridge has used large-diameter steel cylindrical structures as temporary cofferdams at sea for the construction of bridge piers, innovating the construction method of dry construction of bridge piers for cross-sea bridges and further expanding the application scope of large-diameter steel cylindrical structures.

[0003] With the development of vibratory hammer technology, vibratory hammers with higher sinking capacity and multi-unit linked vibratory hammer groups have been successfully applied on the Hong Kong-Zhuhai-Macau Bridge West Artificial Island, making vibratory sinking installation the mainstream installation method for large-diameter steel pipe piles or steel cylinders. Regarding the feasibility of vibratory sinking of steel cylinders, Xu Xinwei et al. used various methods, including Japanese empirical formulas, French PTC empirical formulas, American ICE empirical formulas, the pile driving coefficient method, and the wave equation, to analyze the feasibility. However, the results obtained by different methods differed significantly, and the required output power, sinking rate of the steel cylinder, and sinking time could not be accurately predicted.

[0004] There are two main reasons for the inaccuracies in current vibratory sinker analysis: First, the unique nature of the marine soil and rock environment. Compared to terrestrial foundations, marine soils have stronger structures due to the influence of microorganisms, saturated water environments, and wave currents. This structure may result in higher initial strength, but the structure is prone to collapse under load, leading to weakened performance and a sharp drop in strength. Therefore, the static and dynamic characteristics of marine soils differ significantly from those of terrestrial soils, and the design methods for onshore engineering foundations cannot be directly applied to marine engineering. Second, the unique characteristics of offshore vibratory sinker conditions. High-frequency vibratory sinkers have their own unique features: compared to hammer-driven piles, vibratory sinkers exhibit significant dynamic effects, meaning that the vertical up-and-down vibration of the sinker causes the surrounding soil to be in a state of forced vibration, thus reducing effective stress and frictional resistance. Based on the unique characteristics of marine soils and offshore vibratory sinker conditions, the frictional resistance of the sinker is not only related to the engineering characteristics of the marine soil and the static frictional resistance of the soil-structure, but also affected by factors such as pore pressure, vibration frequency, and vibration acceleration, all of which cannot be fully considered by existing vibratory sinker analysis methods.

[0005] From a microscopic perspective, dynamic friction is the dynamic strength of the soil-structure interface. During vibratory sinking, dynamic friction varies with factors such as pore pressure, vibration frequency, and vibration acceleration, essentially depending on the stress-strain relationship of the soil-structure interface under different dynamic states. Therefore, the vibratory sinking mechanism of large-diameter steel cylinders can be analyzed from the perspective of the interface. Many scholars both domestically and internationally have conducted research on the dynamic response of soil-structure interfaces, mainly focusing on the cyclic effects of dynamic loads, namely strain accumulation, physical state evolution, and dilatation under cyclic shear. However, existing soil-structure interface studies mostly focus on remolded dry soil, neglecting the softening characteristics of marine soils and the role of water in saturated soil-structure interfaces. Furthermore, due to the high frequency of dynamic loads during vibratory sinking, the rate effect caused by dynamic loads needs to be considered, such as the influence of viscosity under high strain rates on the dynamic strength of the interface. This is a crucial difference between vibratory sinking and ordinary cyclic loading conditions, but it is often overlooked in existing studies on the dynamic response of soil-structure interfaces. Under high-frequency cyclic vibration, the structure-saturated soil interface not only undergoes cyclic weakening but also experiences phenomena such as a sharp increase in pore pressure, local liquefaction, and rate viscosity effects. These factors all affect the dynamic frictional resistance of the interface, leading to changes in the dynamic side frictional resistance of the vibratory pile driver. Clarifying the dynamic response of the saturated soil-structure interface under high-frequency cyclic shear is crucial for understanding the mechanism of vibratory pile driving, elucidating the variation law of dynamic side frictional resistance, and predicting the vibratory pile driving process. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a steel cylinder vibration sinking simulation test system and test method that considers the interfacial dynamic characteristics. It can perform dynamic characteristic analysis of the saturated soil (clay, sand)-structure interface of the steel cylinder under high-frequency cyclic vibration, as well as vibration sinking and driving performance analysis of the steel cylinder.

[0007] This invention is achieved through the following technical solution:

[0008] A steel cylinder vibration sinking simulation test system and test method, comprising: a steel cylinder model, a vibration sinking test device, a static pressure sinking test device, and a data acquisition system;

[0009] The vibratory sinking cylinder test apparatus includes a support gantry, a weight, a fixed pulley, a steel strand, a tension gauge, a vibration motor, a resonance frame, and a model box. The model box holds the test soil and test water. The support gantry is erected above the model box to provide the support reaction force required for the experiment. The fixed pulley is installed on the support gantry, and the steel strand is installed on the fixed pulley. One end of the steel strand is connected to the weight, and the other end is connected to one end of the tension gauge. The other end of the tension gauge is connected to the resonance frame through an array of ropes. The resonance frame is used to fix the steel cylinder model to the top, and a vibration motor is set on the resonance frame. The vibration motor is used to simulate the excitation force required when the steel cylinder vibrates and sinks. The excitation force is transmitted to the steel cylinder model through the resonance frame.

[0010] The static pressure sinking cylinder test device includes a support gantry, a hydraulic cylinder, a pressure gauge, a loading rod, a connecting frame, and a model box. The support gantry is erected above the model box, which holds the test soil and test water. The hydraulic cylinder is installed vertically downwards in the middle of the support gantry. One end of the pressure gauge is connected to the vertical actuating rod end of the hydraulic cylinder, and the other end of the pressure gauge is connected to the connecting frame through the loading rod. The connecting frame is used to fix the steel cylinder model to the top. The hydraulic cylinder is used to simulate the pressure required for the static pressure sinking of the steel cylinder. The connecting frame transmits the pressure generated by the hydraulic cylinder to the steel cylinder model. The pressure gauge is used to detect the pressure output by the hydraulic cylinder in real time.

[0011] The data acquisition system includes an accelerometer, strain gauge, soil pressure sensor, laser displacement sensor, pore pressure sensor, and the aforementioned tension gauge and pressure gauge. Each sensor is connected to the test data management platform.

[0012] A vibration sinking test device was used to conduct a vibration sinking simulation test on a steel cylinder model. Strain gauges on the outer wall of the steel cylinder model were used to obtain strain and stress data at various test points on the cylinder wall during the vibration sinking process. Soil pressure sensors installed on the steel cylinder model were used to obtain soil pressure change data at various test points during the vibration sinking process. Soil pressure sensors and pore water pressure sensors installed on the outside of the steel cylinder model were used to monitor the distribution data of lateral soil pressure and pore water pressure during the vibration sinking process. Accelerometers installed on the steel cylinder model were used to collect vibration acceleration signal data at various test points during the vibration sinking process. The vibration frequency was obtained by spectrum analysis of the vibration acceleration signal.

[0013] A static pressure test was conducted on a steel cylinder model using a static pressure sinking test device. The maximum pressure that the steel cylinder model could withstand when it was placed at different depths in the soil was obtained using the pressure gauge on the static pressure sinking test device, which is the static friction resistance of the soil layer on the steel cylinder model.

[0014] In the above technical solution, the static friction resistance of the steel cylinder model measured above is enlarged according to the scale of the steel cylinder model to obtain the static friction resistance of the actual steel cylinder to be driven into the soil at different depths. When it is necessary to start the vibratory hammer to drive the steel cylinder at a certain depth, the starting force P0 of the vibratory hammer is made to be greater than the static friction resistance.

[0015] In the above technical solution, the weight is an iron block or a concrete block, and the weight of the weight is equal to the weight of the other end of the steel strand, ensuring that the entire vibration sinking test device is in a static state without the action of external force.

[0016] In the above technical solution, two vibration motors are required, and to ensure stable fixation on a steel plate, the steel plate is riveted to the resonance frame, and the size of the steel plate is slightly larger than the bottom area of ​​the vibration motor.

[0017] In the above technical solution, the resonance frame is made of stainless steel. To ensure uniform force transmission, it has a hollow internal structure. The resonance frame is arranged in a cross shape and has four points connected to the steel cylinder model. It is connected to the top of the steel cylinder model with bolts.

[0018] In the above technical solution, based on the strain data of each test point on the cylinder wall, the stress formula is as follows:

[0019] σ=E·με·10 -6 ………………………………(1)

[0020] σ — Stress at the measuring point (unit: MPa);

[0021] E – Elastic modulus of steel (2.1 × 10⁻⁶ for steel) 5 (Unit: MPa);

[0022] με — the measured strain;

[0023] Formula 1 yields the stresses at the measuring point within the sampling interval, including: maximum tensile stress, maximum compressive stress, average tensile stress value, average compressive stress value, as well as the time, measuring point number, location, and stress magnitude of the maximum tensile stress occurring within the sampling interval, and the time, measuring point number, location, and stress magnitude of the maximum compressive stress occurring within the sampling interval.

[0024] In the above technical solution, the maximum amplitude of the steel cylinder at a specified soil depth and under a set periodic load vibration condition is predicted using a vibratory cylinder test device; then, the obtained maximum amplitude is compared with the maximum displacement of the soil in the elastic stage under the same conditions to determine whether the steel cylinder can be driven into the soil layer.

[0025] The maximum displacement of the soil in the elastic stage is measured by a static pressure sinking test device: a steel cylinder model is placed into the static pressure sinking test device at the same depth as the steel cylinder model placed into the vibratory sinking test device, and the test soil and test water contained in the static pressure sinking test device are the same as those contained in the vibratory sinking test device. Then, the hydraulic cylinder of the static pressure sinking test device is activated, and its real-time pressure data and real-time sinking displacement data are collected. When the pressure suddenly decreases abruptly, it indicates that the soil around the steel cylinder model has just exceeded the elastic stage. The sinking displacement of the steel cylinder model at this time is considered to be the maximum displacement of the soil in the elastic stage.

[0026] The advantages and beneficial effects of this invention are as follows:

[0027] This invention proposes for the first time a large-diameter steel cylinder vibration-sinking test system and experimental method considering the interfacial dynamic characteristics. This test system can analyze the dynamic characteristics of the saturated soil (clay, sand)-structure interface under high-frequency vibration of the steel cylinder, as well as analyze the penetration performance of the steel cylinder during vibration-sinking. It can detect the strain stress, deformation, sinking acceleration, and real-time monitoring of the sinking amount of the steel cylinder model during vibration-sinking, as well as the soil pressure and pore water pressure data around the steel cylinder model. Furthermore, it can use the pressure gauges on the static pressure sinking cylinder test device to obtain the maximum pressure that the steel cylinder model can withstand at different depths in the soil layer, clarifying the ultimate static friction resistance of different soil layers. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the vibration sinking cylinder test device in this invention;

[0029] Figure 2 This is a schematic diagram of the static pressure sinker test device in this invention;

[0030] Figure 3 This is a strain data curve of a test point on a steel cylinder model.

[0031] For those skilled in the art, other related figures can be obtained from the above figures without any creative effort. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below with reference to specific embodiments.

[0033] Example 1

[0034] Please see Figure 1-2 As shown, a steel cylinder vibration sinking simulation test system includes: a steel cylinder model, a vibration sinking test device, a static pressure sinking test device, and a data acquisition system.

[0035] The steel cylinder model is made at a 1:50 scale, using 1mm thick aluminum plates in a double-layered configuration. Steel strips are used in the middle for vertical and horizontal reinforcement to enhance the force transmission of the steel cylinder and ensure the integrity of the steel cylinder model.

[0036] See appendix Figure 1 The vibration sinking cylinder test device includes a support gantry 1, a weight 2, a fixed pulley 3, a steel strand 4, a tension gauge 5, a vibration motor 6, a resonance frame 7, and a model box 8.

[0037] The model box 8, with dimensions of 1500mm*1500mm*1000mm, is used to hold the test soil 8.1 and the test water 8.2.

[0038] The support gantry 1 is erected above the model box to provide the support reaction force required for the experiment. It is made of steel and can withstand the weight of the experimental equipment and the steel cylindrical model. After calculation, it needs to withstand a force of 10kN without deformation.

[0039] The fixed pulley 3 is installed on the support gantry; specifically, there are two fixed pulleys, one of which is located at the center of the top of the support gantry, and the other is located at the top corner of the support gantry.

[0040] The steel strand 4 is installed on the two fixed pulleys. One end of the steel strand is connected to a weight, and the other end is connected to one end of a tension gauge. The other end of the tension gauge is connected to a resonance frame 7 through an array of pull ropes. The resonance frame is used to fix the steel cylinder model 0 on top, and a vibration motor 6 is set on the resonance frame. The vibration motor is used to simulate the excitation force required when the steel cylinder vibrates and sinks. The excitation force is transmitted to the steel cylinder model through the resonance frame.

[0041] Furthermore, the weight 2 can be an iron block or a concrete block. The weight of the weight is equal to the weight of the other end of the steel strand (i.e., equal to the sum of the weights of the tension gauge, the vibration motor, the resonance frame, and the steel cylinder model). Under no external force, the entire vibration sinking test device is kept in a static state.

[0042] Furthermore, two vibration motors are required, and to ensure stable mounting on a steel plate, the steel plate is riveted to the resonance frame. The steel plate is slightly larger than the bottom area of ​​the vibration motor. The motor models are (±300N, 15-50HZ) and (±1000N, 15-50HZ).

[0043] Furthermore, the resonant frame is made of stainless steel. To ensure uniform force transmission, it has a hollow internal structure. The stainless steel material is 2mm thick. The resonant frame is arranged in a cross shape and has four points connected to the steel cylindrical model. It is connected to the top of the steel cylindrical model with bolts.

[0044] See appendix Figure 2 The static pressure sinker test device includes a support gantry 11, a hydraulic cylinder 12, a pressure gauge 13, a loading rod 14, a connecting frame 15, and a model box 16.

[0045] The model box 16, with dimensions of 1500mm*1500mm*1000mm, is used to hold the experimental soil and experimental water.

[0046] The support gantry 11 is erected above the model box to provide the support reaction force required for the experiment. It is made of steel and can withstand the weight of the experimental equipment and the steel cylindrical model. After calculation, it needs to withstand a force of 10kN without deformation.

[0047] The hydraulic cylinder 12 is vertically mounted downwards in the middle of the support frame. One end of the pressure gauge 13 is connected to the vertical actuating rod end of the hydraulic cylinder, and the other end of the pressure gauge is connected to the connecting frame 15 via the loading rod 14. The connecting frame is used to fix the steel cylinder model to the top. The hydraulic cylinder is used to simulate the pressure required for the static sinking of the steel cylinder. The connecting frame transmits the pressure generated by the hydraulic cylinder to the steel cylinder model, and the pressure gauge is used to detect the pressure output by the hydraulic cylinder in real time.

[0048] The data acquisition system includes accelerometers, strain gauges, soil pressure sensors, laser displacement sensors, pore pressure sensors, and the aforementioned tension gauges and pressure gauges. Each sensor is connected to the test data management platform. These sensors detect the strain stress, deformation, sinking acceleration, and real-time monitoring of the sinking amount of the steel cylinder model during its sinking process, as well as the soil pressure and pore water pressure data surrounding the steel cylinder model. Specifically:

[0049] An accelerometer is used to measure the acceleration during the sinking of the steel cylinder model, denoted as a. The accelerometer is arranged on the outer wall of the steel cylinder model and on the resonance frame. Preferably, a total of 20 accelerometers are arranged, of which 16 are arranged on the outer wall of the steel cylinder model, including 4 rows, which are evenly distributed along the circumference, with 4 accelerometers arranged at equal intervals along the height direction in each row; the remaining 4 are arranged on the resonance frame.

[0050] Strain gauges are used to measure the deformation and stress of the steel cylindrical model during the sinking process. They are arranged on the outer wall of the steel cylindrical model in 5 columns, with 10 gauges evenly spaced along the height direction in each column, with an 8cm interval, for a total of 50 gauges.

[0051] Five soil pressure sensors are installed on the inner and outer walls of the steel cylindrical model, with one sensor every 10 cm from the bottom of the cylinder upwards. These sensors are used to measure the soil pressure during the sinking process and can measure the soil pressure inside and outside the cylinder respectively, which is used for calculating the side friction resistance.

[0052] Laser displacement sensors were deployed on the outer wall of the steel cylindrical model, with a set of sensors spaced 15 cm apart, for a total of 4 sets. These sensors were used to measure the real-time sinking amount of the steel cylindrical model during its descent.

[0053] Pore ​​pressure sensors (i.e., pore water pressure sensors) are installed in the soil around the steel cylinder model to measure the changes in pore pressure in the soil during the sinking of the steel cylinder model. The pore pressure sensors are miniature sensors, including three groups arranged horizontally at intervals (5cm / 10cm / 15cm away from the outer wall of the cylinder, respectively), and each group includes 4-6 pore pressure sensors arranged vertically at intervals.

[0054] Example 2

[0055] The vibratory sinking test apparatus in Example 1 was used to conduct a vibratory sinking test on the steel cylinder model. Data was collected during the vibratory sinking test using a data acquisition system, and the collected data was analyzed as follows:

[0056] 1. Stress-Strain Analysis

[0057] Strain data at various test points on the outer wall of the steel cylindrical model can be obtained through strain gauges on the outer wall during the vibratory sinking process. Figure 3 For example, consider the strain data curve at a specific test point. Based on this strain data curve, the following analysis can be performed:

[0058] Maximum strain value – The maximum strain value measured at this measuring point in a certain data segment. This value has only one definite value and is used to analyze the instantaneous maximum strain that occurs during the vibration and sinking of the steel cylinder.

[0059] Strain maximum value - The maximum peak value of strain measured at this measuring point in a certain data segment. There will be several strain maxima in this data segment. By obtaining the average value of the maxima, the stress state of the measuring point during a certain time period of vibration and sinking of the steel cylinder can be analyzed.

[0060] The average value of the maximum strain is used to analyze the stress state at the measuring point during a certain period of vibration and sinking of the steel cylinder, and is also used to calculate the excitation force of the vibratory hammer.

[0061] Minimum strain value – The minimum strain value measured at this measuring point in a certain data segment. This value has only one definite value and is used to analyze the instantaneous minimum strain that occurs during the vibration and sinking of the steel cylinder.

[0062] Strain minimum value - The minimum peak value of strain measured at this measuring point in a certain data segment. There will be several strain minimum values ​​in this data segment. By calculating the average value of the minimum values, the stress state of the measuring point during a certain time period of vibration and sinking of the steel cylinder can be analyzed.

[0063] The average value of the minimum strain value is used to analyze the stress state at the measuring point during a certain period of vibration and sinking of the steel cylinder, and is also used to calculate the excitation force of the vibratory hammer.

[0064] Based on the strain data at various test points on the cylinder wall, the stress can be calculated using the following formula:

[0065] σ=E·με·10 -6 ………………………………(1)

[0066] σ — Stress at the measuring point (unit: MPa);

[0067] E – Elastic modulus of steel (2.1 × 10⁻⁶ for steel) 5 (Unit: MPa);

[0068] με — the measured strain;

[0069] Formula 1 can be used to obtain the stresses at the measuring point within the sampling interval, including: maximum tensile stress, maximum compressive stress, average tensile stress value, average compressive stress value, as well as the time, measuring point number, location, and stress magnitude of the maximum tensile stress occurring within the sampling interval, and the time, measuring point number, location, and stress magnitude of the maximum compressive stress occurring within the sampling interval.

[0070] 2. Earth pressure analysis on the steel cylinder

[0071] Earth pressure sensors installed on the steel cylindrical model can be used to obtain data on the changes in earth pressure at each measuring point during the vibration and sinking process. This allows us to obtain the maximum, minimum, and average earth pressure values ​​at each measuring point during the vibration and sinking process.

[0072] 3. Pore water pressure analysis of the soil layer surrounding the steel cylinder

[0073] During the vibratory sinking of the steel cylinder, the surrounding soil is subjected to impact force, which destroys the original soil structure, increases pore water pressure, and reduces effective stress, allowing the steel cylinder to sink smoothly to the design position. Then, the excess static water pressure gradually dissipates, and the effective stress gradually recovers slowly. Subsequently, during the construction processes such as surcharge preloading and dewatering, the pore water pressure further decreases, and the effective stress increases significantly, ultimately achieving the design goal of foundation reinforcement.

[0074] By using earth pressure sensors and pore water pressure sensors installed on the outside of the steel cylinder to monitor the distribution of lateral earth pressure and pore water pressure during the vibratory settling process of the cylinder structure, the changes in effective stress of the soil around the cylinder after vibratory settling and during subsequent construction can be analyzed.

[0075] 4. Vibration Spectrum Analysis of Steel Cylinder

[0076] By collecting vibration acceleration signal data at various measuring points during the vibration sinking process of the steel cylinder using acceleration sensors installed on the cylinder, the vibration frequency can be obtained through spectral analysis of the vibration acceleration signal.

[0077] Example 3

[0078] A static pressure test was conducted on the steel cylinder model using the static pressure sinking cylinder test apparatus described in Example 1. The maximum pressure that the steel cylinder model could withstand when placed at different depths in the soil was obtained using the pressure gauge on the apparatus; this pressure is the static friction resistance of the soil layer on the steel cylinder model. Specifically, during the test, the steel cylinder model was placed at a specified depth in the soil. After a period of time, the hydraulic cylinder of the static pressure sinking cylinder test apparatus was activated, and the pressure gauge readings were collected simultaneously. The hydraulic cylinder was stopped when the steel cylinder model experienced a downward displacement. The maximum pressure value detected by the pressure gauge during this process is the static friction resistance of the soil layer on the steel cylinder model.

[0079] By scaling up the static friction of the steel cylinder model as measured above, we can obtain the static friction of the actual steel cylinder at different depths in the soil. When the vibratory hammer needs to be started to drive the steel cylinder at a certain depth, the starting force P0 of the vibratory hammer needs to be greater than the static friction to make the steel cylinder start to move downward into the soil.

[0080] Example 4

[0081] In order for the steel cylinder to sink smoothly under vibration, the soil near the steel cylinder must be liquefied to convert the ultimate static friction resistance of the steel cylinder into dynamic friction resistance. Therefore, the maximum amplitude generated by the steel cylinder under vibration load must overcome the maximum displacement of the soil in its elastic stage. Otherwise, the amplitude will be too small, the steel cylinder will not be able to break free from the soil, and no dynamic friction resistance will be generated. Therefore, it is necessary to calculate the maximum amplitude generated by the steel cylinder.

[0082] When a steel cylinder undergoes simple harmonic motion under a cyclic load, the maximum amplitude that can be generated during the vibration is calculated using the following formula:

[0083]

[0084] A n —The maximum amplitude produced by the steel cylinder;

[0085] a nmax —The maximum vibration acceleration generated by the steel cylinder can be obtained by conducting a vibration sinking test on the steel cylinder model using a vibration sinking test device;

[0086] f—the vibration frequency of the steel cylinder, which can be obtained by conducting a vibration sinking test on the steel cylinder model using a vibration sinking test device.

[0087] Therefore, when predicting whether a steel cylinder can be successfully driven into the soil under vibration, the maximum amplitude of the steel cylinder at a specified soil depth and under a set periodic load vibration condition is first predicted using a vibratory cylinder test device. Then, the obtained maximum amplitude is compared with the maximum displacement of the soil in the elastic stage under the same conditions to determine whether the steel cylinder can be driven into the soil. That is, when the maximum amplitude is greater than the maximum displacement of the soil in the elastic stage, it indicates that the steel cylinder can be driven into the soil at that depth and under the current vibration conditions.

[0088] The maximum displacement of the soil in the elastic stage is measured by a static pressure sinking test device: a steel cylinder model is placed into the static pressure sinking test device to the same depth as the steel cylinder model placed into the vibratory sinking test device, and the test soil and test water contained in the static pressure sinking test device are the same as those contained in the vibratory sinking test device. Then, the hydraulic cylinder of the static pressure sinking test device is activated to collect its real-time pressure data and real-time sinking displacement data. When the pressure suddenly decreases abruptly, it indicates that the soil around the steel cylinder model has just exceeded the elastic stage. The sinking displacement of the steel cylinder model at this time is considered to be the maximum displacement of the soil in the elastic stage.

[0089] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A test method for a steel cylinder vibration-sinking simulation test system, characterized in that, include: Steel cylinder model, vibration sinking cylinder test apparatus, static pressure sinking cylinder test apparatus, and data acquisition system; The vibratory sinking test apparatus includes a support gantry, a weight, a fixed pulley, steel strands, a tension gauge, a vibration motor, a resonance frame, and a model box. The model box holds the test soil and test water. The support gantry is erected above the model box to provide the support reaction force required for the experiment. A fixed pulley is installed on the support frame, and a steel strand is installed on the fixed pulley. One end of the steel strand is connected to a weight, and the other end is connected to one end of a tension gauge. The other end of the tension gauge is connected to a resonance frame through an array of pull ropes. The resonance frame is used to fix the steel cylinder model on top, and a vibration motor is set on the resonance frame. The vibration motor is used to simulate the excitation force required when the steel cylinder vibrates and sinks. The excitation force is transmitted to the steel cylinder model through the resonance frame. The static pressure sinking cylinder test device includes a support gantry, a hydraulic cylinder, a pressure gauge, a loading rod, a connecting frame, and a model box. The support gantry is erected above the model box, which holds the test soil and test water. The hydraulic cylinder is installed vertically downwards in the middle of the support gantry. One end of the pressure gauge is connected to the vertical actuating rod end of the hydraulic cylinder, and the other end of the pressure gauge is connected to the connecting frame through the loading rod. The connecting frame is used to fix the steel cylinder model to the top. The hydraulic cylinder is used to simulate the pressure required for the static pressure sinking of the steel cylinder. The connecting frame transmits the pressure generated by the hydraulic cylinder to the steel cylinder model. The pressure gauge is used to detect the pressure output by the hydraulic cylinder in real time. The data acquisition system includes an accelerometer, strain gauge, soil pressure sensor, laser displacement sensor, pore pressure sensor, and the aforementioned tension gauge and pressure gauge. Each sensor is connected to the test data management platform. A vibration sinking test device was used to conduct a vibration sinking simulation test on a steel cylinder model. Strain gauges on the outer wall of the steel cylinder model were used to obtain strain and stress data at various test points on the cylinder wall during the vibration sinking process. Soil pressure sensors installed on the steel cylinder model were used to obtain soil pressure change data at various test points during the vibration sinking process. Soil pressure sensors and pore water pressure sensors installed on the outside of the steel cylinder model were used to monitor the distribution data of lateral soil pressure and pore water pressure during the vibration sinking process. Accelerometers installed on the steel cylinder model were used to collect vibration acceleration signal data at various test points during the vibration sinking process. The vibration frequency was obtained by spectrum analysis of the vibration acceleration signal. A static pressure test was conducted on a steel cylinder model using a static pressure sinking test device. The maximum pressure that the steel cylinder model could withstand when it was placed at different depths in the soil was obtained using the pressure gauge on the static pressure sinking test device, which is the static friction resistance of the soil layer on the steel cylinder model.

2. The test method of the steel cylinder vibration and sinking simulation test system according to claim 1, characterized in that: The static friction resistance of the steel cylinder model measured above is enlarged according to the scale of the steel cylinder model to obtain the static friction resistance of the actual steel cylinder to be driven into the soil at different depths. When the vibratory hammer needs to be started to drive the steel cylinder at a certain depth, the starting force P0 of the vibratory hammer is made to be greater than the static friction resistance.

3. The test method of the steel cylinder vibration and sinking simulation test system according to claim 1, characterized in that: The weight is made of iron or concrete and is equal to the weight of the other end of the steel strand. This ensures that the entire vibratory sinker test device remains stationary without any external force.

4. The test method of the steel cylinder vibration and sinking simulation test system according to claim 1, characterized in that: Two vibration motors are required, and to ensure stability, they are fixed to a steel plate, which is riveted to the resonance frame. The steel plate is slightly larger than the bottom area of ​​the vibration motor.

5. The test method of the steel cylinder vibration and sinking simulation test system according to claim 1, characterized in that: The resonance frame is made of stainless steel. To ensure uniform force transmission, it has a hollow internal structure. The resonance frame is arranged in a cross shape and has four points connected to the steel cylindrical model. It is connected to the top of the steel cylindrical model with bolts.

6. The test method of the steel cylinder vibration and sinking simulation test system according to claim 1, characterized in that: Based on the strain data at various test points on the cylinder wall, the stress formula is as follows: σ=E·with·10 -6 ; σ — Stress at the measuring point (unit: MPa); E – Elastic modulus of steel (2.1 × 10⁻⁶ for steel) 5 (Unit: MPa); με — the measured strain; The formulas are used to obtain the stresses at the measuring points within the sampling interval, including: maximum tensile stress, maximum compressive stress, average tensile stress value, average compressive stress value, as well as the time, measuring point number, location, and stress magnitude of the maximum tensile stress occurring within the sampling interval, and the time, measuring point number, location, and stress magnitude of the maximum compressive stress occurring within the sampling interval.

7. The test method of the steel cylinder vibration and sinking simulation test system according to claim 1, characterized in that: The maximum amplitude of the steel cylinder at a specified soil depth and under a set periodic load vibration condition is predicted using a vibratory cylinder test device. Then, the obtained maximum amplitude is compared with the maximum displacement of the soil in the elastic stage under the same conditions to determine whether the steel cylinder can be driven into the soil layer. The maximum displacement of the soil in the elastic stage is measured by a static pressure sinking test device: a steel cylinder model is placed into the static pressure sinking test device at the same depth as the steel cylinder model placed into the vibratory sinking test device, and the test soil and test water contained in the static pressure sinking test device are the same as those contained in the vibratory sinking test device. Then, the hydraulic cylinder of the static pressure sinking test device is activated, and its real-time pressure data and real-time sinking displacement data are collected. When the pressure suddenly decreases abruptly, it indicates that the soil around the steel cylinder model has just exceeded the elastic stage. The sinking displacement of the steel cylinder model at this time is considered to be the maximum displacement of the soil in the elastic stage.

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