Test method for simulating vibration pile sinking of precast pile

Abstract

The invention discloses a test method for simulating vibration pile sinking of a precast pile. The test method comprises the following steps that the position and the irradiation direction of a laser transmitter are adjusted; vibration pile sinking of the tubular pile is achieved through the vibration device, in the downward displacement process of the tubular pile, the tubular pile drives the CCD sensor on the tubular pile to synchronously move downwards, and a curve that the pile sinking penetration speed changes along with the soil penetration depth is formed; a camera is aligned with the observation window so as to shoot three observation areas on the observation window, and whether the soil plug effect occurs in the tubular pile or not is evaluated according to the upward displacement of the soil body in the soil body displacement change and the radial displacement change of the tubular pile on the two sides in the circumferential direction of the pile; and the change relation of the pile-soil shear stress and the vertical stress of the pile side of the pipe pile along with the vibration acceleration of the pipe pile is established. Under the consideration of the influence of ground stress, the rule of displacement of the pile soil at the positions of the pile side and the pile end along with the soil body can be obtained, so that the formation of the pile end soil plug is simulated.

Description

Technical Field

[0001] The invention relates to the technical field of pipe pile sinking simulation test, in particular to a test method for simulating prefabricated pile vibration sinking. Background Art

[0002] Precast piles have become one of the widely used foundation forms for land and water construction structures due to their high pile-making efficiency and good quality control. Common precast piles include steel pipe piles and PHC piles. Precast piles are generally driven by impact, vibration, static pressure and other methods. Impact and vibration are both dynamic pile driving methods. Dynamic pile driving has high construction efficiency and strong adaptability, and is one of the main methods for pile foundation.

[0003] Faced with complex and changeable geological environments, many pile driving projects often encounter problems due to lack of understanding of the laws of dynamic pile driving or insufficient analysis experience and technology, including pile slippage, hammer refusal, and difficulty in meeting bearing capacity requirements, resulting in economic losses and safety risks. In the face of this problem, on-site pile tests (i.e., test pile driving) can be used to measure and obtain relevant parameters in order to calculate whether the relevant indicators meet the bearing capacity requirements. However, the cost of on-site pile tests is too high, and it is difficult to fully cover all the geology on site, especially special rock and soil with variable soil properties and varying hardness. Therefore, indoor simulated pile driving has become an important way to solve this problem.

[0004] Most of the existing simulation pile driving test devices are small-scale model pile tests that do not consider the influence of ground stress. They are mainly based on the measurement of mechanical parameters of pile-soil interaction, and mainly evaluate the parameters affecting the pile foundation force based on the changes in the pile-soil stress field around the pile during the pile driving process. This type of existing simulation pile driving test device lacks the measurement of the penetration of the pile driving process, especially the inability to effectively measure the development law of the pile-soil interaction at the pile side and pile end during the pile driving process with the displacement of the soil body, and cannot simulate the formation of soil plugs at the pile end, so it is impossible to establish the relationship between the pile driving displacement and the mechanical parameters of the pile-soil interaction, and then it is impossible to optimize the pile driving process based on this. Summary of the invention

[0005] In view of the deficiencies in the prior art, an object of the present invention is to provide a test method for simulating vibration pile sinking of precast piles, which can solve the problems described in the background art.

[0006] The technical solution for achieving the purpose of the present invention is: a test method for simulating vibration pile sinking of precast piles, which is applied to a test device for simulating dynamic pile sinking of precast piles, and the test method comprises the following steps:

[0007] Step 21: Adjust the position and irradiation direction of the laser transmitter so that the laser emitted by the laser transmitter is vertically irradiated to the sensing surface of the CCD sensor on the pipe pile;

[0008] Step 22: Install the vibration device on the hammer cap, and apply exciting force to the pipe pile through the vibration device to achieve vibration sinking of the pipe pile.

[0009] During the downward displacement of the pile, the pile drives the CCD sensor on the pile to move downward synchronously, and the position of the laser point irradiated by the laser on the CCD sensor also moves accordingly, and the position of the laser point is collected by the CCD sensor and transmitted to the computer through the wireless communication module.

[0010] The pile is sunk under the action of vibration. During the sinking process, the pile body vibrates up and down. When the accumulated displacement of the pile is d t When the distance is greater than the vertical movement range of the laser emitter on the CCD sensor, move the laser emitter downward by a distance of d. t ,

[0011] Vibration pile driving is continued, and the final pile penetration depth is equal to the sum of the moving distances of the laser transmitter each time, and a curve of the variation of the pile penetration speed with the penetration depth is formed;

[0012] Step 23: Before the vibrating device vibrates and sinks the pipe pile, the three laser lamps on the grid column are turned on. The lasers emitted by the three laser lamps are irradiated on the pile soil through the transparent member, and form speckles on the surface of the pile soil where the first observation area, the second observation area and the third observation area are located.

[0013] Aim the camera at the observation window to capture the three observation areas on the observation window. The camera continuously captures the soil image of the pile in the pipe pile during the pile sinking process, and obtains the displacement change of the pile soil through the image processing method.

[0014] Based on the upward displacement of the soil in the soil displacement change and the radial displacement change of the pile on both sides of the pile circumference, it is evaluated whether the soil plugging effect occurs in the pile.

[0015] The soil plugging effect of the pile-soil is evaluated based on the upward displacement of the pile-soil and the radial displacement on both sides of the pile-soil circumference. When the displacement change of the soil of the pile-soil is ≤ the first threshold value, and the radial displacement change on both sides of the pile-soil circumference is ≥ the second threshold value, the soil plugging effect is considered to have occurred; otherwise, it is considered that the soil plugging effect has not occurred.

[0016] Step 24: According to the piezoresistive sensor installed on the pile, the radial stress σ at the lower end of the pile is measured respectively. r and the vertical stress σ at the top of the pile v , and based on the radial stress σ r The shear stress τ at the lower end of the pile is obtained. It represents the pile-soil interface friction angle obtained from the indoor pile-soil test, so as to establish the pile-soil shear stress τ and vertical stress σ on the pile side.v The relationship with the change of vibration acceleration of the pipe pile.

[0017] Furthermore, the test device for simulating dynamic pile driving of precast piles comprises a reaction frame, a model tube, a sliding base, a jack, a pile driving device, a hammer cap and an observation device. The model tube is installed on the sliding base, a cavity for accommodating pile soil is provided in the model tube, the jack is installed at one end of the model tube away from the sliding base, and the jack is in contact with the reaction frame.

[0018] The hammer cap is installed on the pipe pile as the prefabricated pile. The pipe pile passes through the model tube and is inserted into the pile soil in the model tube. One end of the pipe pile is exposed outside the model tube. The hammer cap is located on the end of the pipe pile exposed outside the model tube.

[0019] The pile driving device is used to drive the pipe pile into the soil by dynamic pile driving to simulate the dynamic pile driving process of prefabricated piles.

[0020] The observation device is located outside the model tube.

[0021] Furthermore, the reaction frame includes a frame body, and a main crossbeam, a square base and anchor bars installed on the frame body. The jack is in contact with the main crossbeam, the square base is fixedly installed at the lower end of the frame body, and the main crossbeam spans the frame body.

[0022] The anchor bar passes through the main beam and the frame to fix the main beam and the frame together. An anchor block is installed on one end of the anchor bar passing through the main beam and the frame. The anchor bar also passes through the frame and the square base and is exposed on the outside of the square base. The anchor bar is used to penetrate the ground and be fixedly connected to the ground to fix the reaction frame on the ground.

[0023] Furthermore, the model cylinder includes a cylinder body, an airbag and a pressure plate, the cylinder body includes a cavity, the airbag is installed in the cavity, and the airbag is inflated and fits against the inner wall of the cavity of the cylinder body, and the cavity forms a accommodating space, and the accommodating space is used to hold pile soil, the pressure plate is covered on the cylinder body or on the cylinder body and the airbag, and through holes are respectively provided at the center and eccentricity of the pressure plate.

[0024] Furthermore, the model cylinder also includes an observation window, and a through hole is dug on the cylinder body and the airbag respectively. When the airbag is inflated and fits against the inner wall of the cavity of the cylinder body, the through hole on the cylinder body and the through hole on the airbag are just opposite to each other. The through hole on the cylinder body is provided with a grid column, and the grid column is embedded in the through hole. The through hole on the airbag is provided with a transparent part, and the grid column is located directly in front of the transparent part. When the pipe pile passes through the through hole and is inserted into the pile soil, the pipe pile is directly opposite to the observation window.

[0025] Furthermore, the grid column includes a plurality of vertical poles, each vertical pole is cross-connected to form an array, and the grid column is also equipped with a first laser light, a second laser light and a third laser light with different directions, and the first laser light, the second laser light and the third laser light are away from the observation device and can irradiate the pile soil surface in the model tube,

[0026] The grid column divides the observation window into a first observation area, a second observation area and a third observation area in a certain direction. The first laser light is located in the first observation area, the second laser light is located in the second observation area, and the third laser light is located in the third observation area.

[0027] The pipe pile is provided with a strain gauge and a CCD sensor on one end of the model tube, and the inner side wall and the outer side wall of the top end and the lower end of the pipe pile are respectively provided with a piezoresistive sensor.

[0028] Furthermore, the sliding base includes a sliding frame, and a first snap plate, a second snap plate, a support plate, a plurality of sliding shafts and a plurality of fixed blocks installed on the sliding frame, the sliding shafts are arranged in parallel and spaced apart, the two ends of the sliding shafts are respectively fixedly connected to the fixed blocks, the fixed blocks are fixedly installed at the two ends of the sliding frame, the support plate is installed on the sliding frame and is located above the sliding shaft, the first snap plate and the second snap plate are snap-connected to the sliding frame, the first snap plate and the second snap plate are respectively located on both sides of the support plate and fixedly connected to the support plate, the first snap plate and the second snap plate are both located above the sliding frame, the model cylinder is installed on the support plate,

[0029] The sliding shafts are arranged in sequence from low to high and then to low along the axial direction of the sliding frame.

[0030] Furthermore, the pile driving device includes a vibration device, which includes an upper box, a lower box, a first vibration device, a second vibration device, a connecting column, a vibration hammer cap column and a plurality of wedge blocks, the first vibration device is installed in the lower box, the second vibration device is installed in the upper box, the upper box is stacked and installed on the upper end of the lower box, the upper box and the lower box are fixedly or detachably connected, the lower box is connected to the upper end of the connecting column, the lower end of the connecting column is fixedly connected to the vibration hammer cap column, the wedge block is fixedly connected to the end of the vibration hammer cap column away from the connecting column, and the wedge blocks are arranged at intervals.

[0031] Further, the first vibration device includes a first motor, a first gear, a second gear, a first rotating shaft, a second rotating shaft, a first movable cam piece, a second movable cam piece, a first fixed cam piece and a first base, the first motor is installed on the first base, the output end of the first motor is connected to the first rotating shaft, the first gear is sleeved and fixed on the first rotating shaft, the first movable cam piece is fixedly installed on the end of the first rotating shaft away from the first motor, the first gear and the first movable cam piece are arranged at intervals, one end of the second rotating shaft is rotatably installed on the first base, and the other end extends away from the first base and is located on the outside of the first base, the second rotating shaft and the first rotating shaft are arranged in parallel and at intervals, the second gear is sleeved and fixed on the second rotating shaft, the second gear is meshed with the first gear, the second movable cam piece is fixedly installed on the end of the second rotating shaft away from the first base, the second movable cam piece and the first movable cam piece are arranged in parallel, and along the axial direction of the second rotating shaft, at least a part of the first movable cam piece and the second movable cam piece overlap together, the first fixed cam piece is sleeved and fixed on the second rotating shaft, and the second fixed cam piece is between the first base and the second gear,

[0032] The second vibration device includes a second motor, a third gear, a fourth gear, a third rotating shaft, a fourth rotating shaft, a third movable cam piece, a fourth movable cam piece, a third fixed cam piece, a fourth fixed cam piece and a second base, the second motor is mounted on the second base, the output end of the second motor is connected to the third rotating shaft, the third gear is sleeved and fixed on the third rotating shaft, the third movable cam piece is fixedly mounted on an end of the third rotating shaft away from the second motor, the third gear and the third movable cam piece are arranged at intervals, one end of the fourth rotating shaft is rotatably mounted on the second base, and the other end extends in a direction away from the second base and is located on the outside of the second base, the fourth The rotating shaft and the third rotating shaft are arranged in parallel and at intervals, the fourth gear is sleeved and fixed on the fourth rotating shaft, the fourth gear and the third gear are meshingly connected, the fourth movable cam piece is fixedly installed on an end of the fourth rotating shaft away from the second base, the fourth movable cam piece and the third movable cam piece are arranged in parallel, and along the axial direction of the fourth rotating shaft, the third movable cam piece and the fourth movable cam piece at least partially overlap together, the third fixed cam piece is sleeved and fixed on the third rotating shaft, the third fixed cam piece is between the second base and the third gear, the fourth fixed cam piece is sleeved and fixed on the fourth rotating shaft, and the fourth fixed cam piece is between the second base and the fourth gear.

[0033] Furthermore, the observation device includes a camera, a laser emitter, a tripod, a support rod, a computer and a wireless communication module. The camera is installed on the top of the tripod, the camera is connected to the computer for communication, the laser emitter is slidably installed on the support rod and can slide along the axis of the support rod, the laser emitter is electrically connected to the computer, and the laser emitter emits laser to the CCD sensor.

[0034] The camera shoots at an observation window on the model tube, and three laser lights in the observation window illuminate the pile soil surfaces at different positions in the model tube respectively.

[0035] The beneficial effects of the present invention are as follows: the present invention can well realize dynamic pile driving, including impact pile driving and vibration pile driving, and apply pressure to the pressure plate through the jack and then act on the pile soil to simulate the influence of ground stress, so as to realize the measurement of the penetration degree in the pile driving process under the consideration of the influence of ground stress, and in the measurement of the pile driving process, realize the law of the displacement of the pile soil at the pile side and the pile end with the soil body to simulate the formation of the pile end soil plug (effect), so as to establish the relationship between the pile driving displacement and the mechanical parameters of the pile-soil interaction.

[0036] In addition, the test device has a simple structure, is easy to maintain, has a long service life, and can set the pipe pile at the center or side position of the pile soil as needed. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is the structural schematic diagram of the test device;

[0038] Figure 2 It is a structural schematic diagram of the reaction frame of the test device;

[0039] Figure 3 The figure is a schematic diagram of the decomposed structure of the model tube;

[0040] Figure 4 It is a schematic diagram of the structure of the grid column;

[0041] Figure 5 This is a front view of the grid column;

[0042] Figure 6 It is a schematic diagram of the position between the pipe piles and the grid;

[0043] Figure 7 It is a schematic diagram of the structure of the model tube on the sliding base;

[0044] Figure 8 It is a schematic diagram of the structure of the impact device;

[0045] Fig. 9 A schematic diagram of the structure in which the impact motor of the impact device is installed in the inner box;

[0046] Fig.10 A schematic diagram of a structure in which an impact motor of an impact device is installed in an inner box and the inner box is installed in an outer box;

[0047] Fig.11 It is a schematic diagram of the structure in which the impact device is installed in the hammer cap;

[0048] Fig.12A schematic diagram of the structure of the impact device installed in the hammer cap from another viewing angle;

[0049] Fig.13 is a schematic diagram of the structure of the vibration device;

[0050] Fig.14 It is a structural schematic diagram showing that the vibration device is installed in the hammer cap;

[0051] Fig.15 This is a schematic diagram of the structure in which the vibration device is installed in the hammer cap from another perspective;

[0052] Fig.16 is a schematic diagram of the structure of the first vibration device and the second vibration device;

[0053] Fig.17 A schematic diagram of the principle of the first vibration device and the second vibration device generating the force;

[0054] Fig.18 It is a side schematic diagram of the test device;

[0055] Fig.19 It is the front schematic diagram of the test device;

[0056] Fig. 20 It is a top view schematic diagram of the test device;

[0057] Fig.21 It is a schematic diagram of the structure for moving the pipe pile to the center of the model tube;

[0058] Fig. 22 Schematic diagram of the relationship between the maximum displacement DMX, penetration s and pile body rebound c;

[0059] Fig.23 Schematic diagram of soil plugging effect and no soil plugging effect;

[0060] Fig.24 It is a schematic diagram of the flow chart of the test method of impact pile driving;

[0061] Fig.25 The figure is a flow chart of the test method of vibration pile driving;

[0062] In the figure, 1-main beam, 2-pile sinking device, 3-hammer cap, 4-jack, 5-reaction frame, 6-cylinder, 7-square base, 8-camera, 9-laser transmitter, 10-tripod, 11-support rod, 12-computer, 13-wireless communication module, 14-anchor bar, 15-anchor block, 16-pressure plate, 17-observation window, 18-air bag, 19-pile, 20-grid column, 21-vent valve, 22-column rod, 23 - first laser light, 24 - second laser light, 25 - second laser light, 26 - first observation area, 27 - second observation area, 28 - third observation area, 29 - strain gauge, 30 - CCD sensor, 31 - first snap plate, 32 - sliding shaft, 33 - fixed block, 34 - sliding frame, 35 - second snap plate, 36 - pad, 37 - impact motor, 38 - impact output shaft, 39 - hammer, 40 - plug rod, 41 - impact hammer Cap column, 42-hammer cap external thread, 43-traction rope, 44-inner box, 45-outer box, 46-upper box, 47-lower box, 48-wedge block, 49-vibration hammer cap column, 50-column rod, 51-first vibration device, 511-first motor, 512-first gear, 513-first rotating shaft, 514-first movable cam piece, 515-second rotating shaft, 516-second movable cam piece, 517-first fixed cam piece, 518-second gear, 519-first base, 52-second vibration device, 521-second base, 522-second motor, 523-third fixed cam piece, 524-third gear, 525-fourth fixed cam piece, 526-fourth gear, 527-third movable cam piece, 528-third rotating shaft, 529-fourth movable cam piece, 530-fourth rotating shaft, 53-load-bearing column, 54-support plate, 55-connecting column rod. DETAILED DESCRIPTION

[0063] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0064] like Figure 1-Figure 23As shown, this embodiment provides a test device for simulating dynamic pile driving of precast piles, including a reaction frame 5, a model tube, a sliding base, a jack 4, a pile driving device 2, a hammer cap 3 and an observation device. The model tube is installed on the sliding base, and a cavity for accommodating pile soil is provided in the model tube. The jack 4 is installed at one end of the model tube away from the sliding base, and the jack 4 is in contact with the reaction frame 5. The reaction frame 5 is used to provide a reaction force to the model tube through the jack 4 to press the pile soil in the model tube. The hammer cap 3 is installed on a pipe pile 19 as the precast pile, and the pipe pile 19 passes through the model tube and is inserted into the pile soil in the model tube. One end of the pipe pile 19 is exposed outside the model tube, and the hammer cap 3 is located on the end of the pipe pile 19 exposed outside the model tube. The pile driving device 2 is used to penetrate the pipe pile 19 into the pile soil through the hammer cap 3. The pile driving device 2 can penetrate the pipe pile 19 into the pile soil in a dynamic pile driving manner to simulate the dynamic pile driving process of the precast pile. The observation device is located outside the model tube. The observation device is used to observe pile soil displacement, pile soil resistance change and other pile soil related parameters in the model tube during the pile sinking process, as well as pile displacement, pile penetration rate and other parameters of the pipe pile 19 during the pile sinking process, so that the pile soil displacement, pile soil resistance change and the pile displacement and pile penetration rate of the pipe pile 19 can be associated with each other.

[0065] Exemplarily, the reaction frame 5 includes a frame body, a main beam 1, a square base 7 and anchor bars 14 installed on the frame body, the jack 4 is in contact with the main beam 1, the square base 7 is fixedly installed at the lower end of the frame body, and the main beam 1 spans the frame body. The anchor bars 14 pass through the main beam 1 and the frame body to fix the main beam 1 and the frame body through the anchor bars 14, and an anchor block 15 is also installed on one end of the anchor bars 14 passing through the main beam 1 and the frame body. The anchor bars 14 also pass through the frame body and the square base 7 and are exposed outside the square base 7. In actual use, the reaction frame 5 is fixedly installed on the ground by the anchor bars 14 penetrating into the ground and being fixedly connected to the ground, so that after the jack 4 acts on the reaction frame 5, the reaction frame 5 remains fixed and can provide a reaction force to the jack 4, and then acts on the pile soil in the machine model tube of the pressure plate 16.

[0066] The jack 4 abuts against the center of the main beam 1. The jack 4 abuts against the main beam 1 through a pad 36, and the pad 36 is between the jack 4 and the main beam 1. The pad 36 can be a square block.

[0067] Exemplarily, the model cylinder includes a cylinder body 6, an airbag 18 and a pressure plate 16, the cylinder body 6 includes a cavity, the airbag 18 is installed in the cavity, and the airbag 18 is attached to the inner wall of the cavity of the cylinder body 6 in an inflated state, and partially fills the cavity to form a receiving space in the cavity, and the receiving space is used to hold the pile soil. The pressure plate 16 covers the cylinder body 6, or covers the cylinder body 6 and the airbag 18.

[0068] The pressure plate 16 is provided with through holes at the center and eccentric positions, respectively, and the pipe pile 19 can pass through the through holes, so that the pipe pile 19 can be inserted into the center of the pile soil or the side of the pile soil.

[0069] Exemplarily, the model tube also includes an observation window 17, and a through hole is dug on the cylinder 6 and the air bag 18 respectively, and the through hole can be square or circular or other shapes. When the air bag 18 is inflated and fits the inner wall of the cavity of the cylinder 6, the through hole on the cylinder 6 and the through hole on the air bag 18 are just opposite. The through hole on the cylinder 6 is provided with a grid column 20, and the grid column 20 is embedded in the through hole. The through hole on the air bag 18 is provided with a transparent part, which plays a role of isolating the pile soil. The grid column 20 is located just in front of the transparent part, and the transparent part can be transparent glass or transparent acrylic board and other transparent materials. When the pipe pile 19 passes through the through hole and is inserted into the pile soil, the pipe pile 19 is opposite to the observation window 17, so that the pipe pile 19 can be observed through the observation window 17, so that the observation device can observe the pile soil and the pipe pile 19 in the accommodation space through the observation window 17.

[0070] Exemplarily, a vent valve 21 is also installed on the cylinder 6, and the vent valve 21 is connected to the airbag 18 so as to inflate the airbag 18 or discharge gas from the airbag 18 (i.e., evacuate air) through the vent valve 21.

[0071] The grid column 20 includes a plurality of vertical poles, each of which is cross-connected to form an array. The grid column 20 is also equipped with a first laser light 23, a second laser light 24 and a third laser light 25 with different directions. The first laser light 23, the second laser light 24 and the third laser light 25 are away from the observation device and can irradiate the pile soil surface in the model tube, that is, the first laser light 23, the second laser light 24 and the third laser light 25 are facing inward and can irradiate the pile soil surface.

[0072] Exemplarily, the grid column 20 divides the observation window 17 into a first observation area 26, a second observation area 27 and a third observation area 28 in a certain direction, the first laser light 23 is located in the first observation area 26, the second laser light 24 is located in the second observation area 27, and the third laser light 25 is located in the third observation area 28.

[0073] Exemplarily, a strain gauge 29 and a CCD sensor 30 are provided on one end of the pipe pile 19 located at the model tube, and the strain gauge 29 is used to measure the hammer force generated by the pile driving device 2 when impacting the pipe pile 19 or the exciting force generated by vibration pile driving.

[0074] Piezoresistive sensors (not shown in the figure) are installed on the inner and outer walls of the top and bottom ends of the pipe pile 19 . The piezoresistive sensors are used to measure the stress on the pipe pile 19 .

[0075] Exemplarily, the sliding base includes a sliding frame 34, and a first snap plate 31, a second snap plate 35, a support plate 54, a plurality of sliding shafts 32 and a plurality of fixed blocks 33 mounted on the sliding frame 34, each sliding shaft 32 is arranged in parallel and spaced apart, and both ends of the sliding shaft 32 are fixedly connected to the fixed blocks 33, respectively, and the fixed blocks 33 are fixedly mounted on both ends of the sliding frame 34. The support plate 54 is mounted on the sliding frame 34 and is located above the sliding shaft 32, the first snap plate 31 and the second snap plate 35 are snap-connected to the sliding frame 34, the first snap plate 31 and the second snap plate 35 are respectively located on both sides of the support plate 54 and are fixedly connected to the support plate 54, and the first snap plate 31 and the second snap plate 35 are both located above the sliding frame 34. The model cylinder is mounted on the support plate 54.

[0076] The sliding shaft 32 is arranged in sequence from low to high and then to low along the axial direction of the sliding frame 34. Such a height change is conducive to moving the model tube on the support plate 54 into and out of the sliding frame 34.

[0077] The entire sliding base supports the model tube and constrains the movement of the model tube, provides support force for the cylindrical model tube and limits the displacement of the model tube, offsets the stress caused by the deformation of the side wall of the model tube caused by the ground stress provided by the reaction force on the model tube, thereby ensuring the overall stability of the model tube.

[0078] Exemplarily, the pile driving device 2 includes an impact device and a vibration device, which are two independent discrete components. When impact pile driving is required, the pile driving device 2 uses the impact device, and when vibration pile driving is required, the pile driving device 2 uses the vibration device.

[0079] The impact device includes an impact motor 37, an impact output shaft 38, a traction rope 43, a hammer 39, a plug rod 40 and an impact hammer cap column 41. The output shaft (i.e., the rotor) of the impact motor 37 is connected to the impact output shaft 38. One end of the traction rope 43 is wound around the impact output shaft 38, and the other end of the traction rope 43 is fixedly connected to the hammer 39. The impact motor 37 rotates forward or reverses to reel in or release the traction rope 43, thereby extracting the hammer 39 or lowering the hammer 39.

[0080] The hammer body 39 is fixedly connected to one end of the plug rod 40, and the other end of the plug rod 40 is fixedly connected to the impact hammer cap column 41, and the outer wall of the impact hammer cap column 41 is provided with a hammer cap external thread 42. The impact hammer cap column 41 matches the internal thread of the inner wall of the hammer cap 3 through the hammer cap external thread 42, so that the impact hammer cap column 41 is threadedly connected to the hammer cap 3, so that the impact device is connected to the hammer cap 3, and the impact device is installed on the hammer cap 3.

[0081] Exemplarily, the impact device further includes an inner box 44 , the impact motor 37 is installed in the inner box 44 , and one end of the impact output shaft 38 away from the impact motor 37 passes through the inner box 44 and is exposed outside the inner box 44 .

[0082] Exemplarily, the impact device also includes an outer box body 45, the inner box body 44 is located in the outer box body 45, one end of the impact shaft exposed from the inner box body 44 is located in the outer box body 45, and the end of the traction rope 43 away from the impact shaft passes through the outer box body 45 and is connected to the hammer body 39.

[0083] Exemplarily, the vibration device includes an upper box 46, a lower box 47, a first vibration device 51, a second vibration device 52, a connecting column 55, a vibration hammer cap column 49 and a plurality of wedge blocks 48, wherein the first vibration device 51 is installed in the lower box 47, and the second vibration device 52 is installed in the upper box 46. The upper box 46 is stacked and installed on the upper end of the lower box 47, and the upper box 46 and the lower box 47 are fixedly or detachably connected. The lower box 47 is connected to the upper end of the connecting column 55, and the lower end of the connecting column 55 is fixedly connected to the vibration hammer cap column 49. The wedge block 48 is fixedly connected to one end of the vibration hammer cap column 49 away from the connecting column 55, and each wedge block 48 is arranged at intervals.

[0084] The first vibration device 51 includes a first motor 511, a first gear 512, a second gear 518, a first rotating shaft 513, a second rotating shaft 515, a first movable cam piece 514, a second movable cam piece 516, a first fixed cam piece 517 and a first base 519. The first motor 511 is mounted on the first base 519. The output end (i.e., the rotor) of the first motor 511 is connected to the first rotating shaft 513, and the first motor 511 can drive the first rotating shaft 513 to rotate. The first gear 512 is sleeved and fixed on the first rotating shaft 513, and the first gear 512 can rotate with the first rotating shaft 513. The first movable cam piece 514 is fixedly mounted on one end of the first rotating shaft 513 away from the first motor 511, and the first gear 512 and the first movable cam piece 514 are arranged at intervals.

[0085] One end of the second rotating shaft 515 is rotatably mounted on the first base 519, for example, the second rotating shaft 515 is mounted on the first base 519 by a bearing or other components, and the other end extends away from the first base 519 and is located outside the first base 519. The second rotating shaft 515 is arranged parallel to and spaced from the first rotating shaft 513. The second gear 518 is sleeved and fixed on the second rotating shaft 515, and the second gear 518 is meshedly connected with the first gear 512. Through the meshing transmission of the first gear 512 and the second gear 518, the first motor 511 can synchronously drive the first rotating shaft 513 and the second rotating shaft 515 to rotate. The second movable cam piece 516 is fixedly mounted on one end of the second rotating shaft 515 away from the first base 519, and the second movable cam piece 516 is arranged in parallel with the first movable cam piece 514, and along the axial direction of the second rotating shaft 515, the first movable cam piece 514 and the second movable cam piece 516 at least partially overlap together, that is, the first movable cam piece 514 and the second movable cam piece 516 are projected along the axial direction of the second rotating shaft 515, and the two movable cam pieces at least partially overlap together.

[0086] The first fixed cam piece 517 is sleeved and fixed on the second rotating shaft 515 . The second fixed cam piece is located between the first base 519 and the second gear 518 . The first fixed cam piece 517 plays a protective role.

[0087] When the first motor 511 is started, the first motor 511 drives the first rotating shaft 513 to rotate, and then drives the first movable cam piece 514 to rotate. The first movable cam piece 514 rotates together with the first rotating shaft 513 to achieve 360° rotation. Synchronously, the first motor 511 drives the second rotating shaft 515 to rotate synchronously with the first rotating shaft 513. The second rotating shaft 515 drives the second movable cam piece 516 to rotate. The second movable cam piece 516 rotates together with the second rotating shaft 515 to achieve 360° rotation.

[0088] Since the first gear 512 drives the second gear 518 to rotate, the rotation directions of the first gear 512 and the second gear 518 are exactly opposite, one rotates clockwise and the other rotates counterclockwise, so that the rotation directions of the first movable cam piece 514 and the second movable cam piece 516 are also exactly opposite.

[0089] The second vibration device 52 includes a second motor 522, a third gear 524, a fourth gear 526, a third rotating shaft 528, a fourth rotating shaft 530, a third movable cam piece 527, a fourth movable cam piece 529, a third fixed cam piece 523, a fourth fixed cam piece 525 and a second base 521. The second motor 522 is mounted on the second base 521. The output end (i.e., the rotor) of the second motor 522 is connected to the third rotating shaft 528, and the second motor 522 can drive the third rotating shaft 528 to rotate. The third gear 524 is sleeved and fixed on the third rotating shaft 528, and the third gear 524 can rotate with the third rotating shaft 528. The third movable cam piece 527 is fixedly mounted on one end of the third rotating shaft 528 away from the second motor 522, and the third gear 524 and the third movable cam piece 527 are arranged at intervals.

[0090] One end of the fourth rotating shaft 530 is rotatably mounted on the second base 521, for example, the fourth rotating shaft 530 is mounted on the second base 521 by a bearing or other components, and the other end extends away from the second base 521 and is located outside the second base 521. The fourth rotating shaft 530 and the third rotating shaft 528 are arranged in parallel and spaced apart. The fourth gear 526 is sleeved and fixed on the fourth rotating shaft 530, and the fourth gear 526 is meshedly connected with the third gear 524. Through the meshing transmission of the third gear 524 and the fourth gear 526, the second motor 522 can synchronously drive the third rotating shaft 528 and the fourth rotating shaft 530 to rotate. The fourth movable cam piece 529 is fixedly mounted on one end of the fourth rotating shaft 530 away from the second base 521, and the fourth movable cam piece 529 and the third movable cam piece 527 are arranged in parallel, and along the axial direction of the fourth rotating shaft 530, the third movable cam piece 527 and the fourth movable cam piece 529 at least partially overlap together, that is, the third movable cam piece 527 and the fourth movable cam piece 529 are projected along the axial direction of the fourth rotating shaft 530, and the two movable cam pieces at least partially overlap together.

[0091] The third fixed cam piece 523 is sleeved and fixed on the third rotating shaft 528, and the third fixed cam piece 523 is between the second base 521 and the third gear 524, and the third fixed cam piece 523 plays a protective role. The fourth fixed cam piece 525 is sleeved and fixed on the fourth rotating shaft 530, and the fourth fixed cam piece 525 is between the second base 521 and the fourth gear 526, and the fourth fixed cam piece 525 plays a protective role.

[0092] When the second motor 522 is started, the second motor 522 drives the third rotating shaft 528 to rotate, and then drives the third movable cam piece 527 to rotate. The third movable cam piece 527 rotates together with the third rotating shaft 528 to achieve 360° rotation. Synchronously, the third motor drives the fourth rotating shaft 530 to rotate synchronously with the third rotating shaft 528. The fourth rotating shaft 530 drives the fourth movable cam piece 529 to rotate. The fourth movable cam piece 529 rotates together with the fourth rotating shaft 530 to achieve 360° rotation.

[0093] Since the third gear 524 drives the fourth gear 526 to rotate, the rotation directions of the third gear 524 and the fourth gear 526 are exactly opposite, one rotates clockwise and the other rotates counterclockwise, so that the rotation directions of the third movable cam piece 527 and the fourth movable cam piece 529 are also exactly opposite.

[0094] refer to Fig.17 , the first movable cam piece 514 to the fourth movable cam piece 529 are all semi-arc plates, which can be semi-circular arc or semi-elliptical arc structures. The four movable cam pieces can act on the corresponding upper box body 46 or lower box body 47, thereby generating a force on the vibration hammer cap column 49. When the first movable cam piece 514 and the second movable cam piece 516 rotate to the first position, the first movable cam piece 514 and the second movable cam piece 516 both act downward and vertically on the lower box body 47, and the first vibration device 51 generates a downward force with a force magnitude of F. At this time, the third movable cam piece 527 and the fourth movable cam piece 529 rotate to the third position, the third movable cam piece 527 and the fourth movable cam piece 529 both act downward and vertically on the upper box body 46, and the second vibration device 52 generates a downward force with a force magnitude of F. The magnitude of the resultant force generated by the first vibration device 51 and the second vibration device 52 is 2F, and the direction of the resultant force is vertically downward. No force is exerted on the upper box body 46 and the lower box body 47 in the horizontal direction, that is, no force is exerted on the vibration hammer cap column 49, and the magnitude of the force is 2F.

[0095] Similarly, when the first movable cam piece 514 and the second movable cam piece 516 are still in the first position, at this time, the third movable cam piece 527 and the fourth movable cam piece 529 rotate to the second position, the third movable cam piece 527 and the fourth movable cam piece 529 both face upward and act vertically on the upper box body 46, and the second vibration device 52 generates an upward force with a magnitude of F. Since the first vibration device 51 and the second vibration device 52 generate forces of equal magnitude and opposite directions, the combined force of the first vibration device 51 and the second vibration device 52 is 0, and no force is generated on the vibration hammer cap column 49. When the first movable cam piece 514 and the second movable cam piece 516 continue to rotate and rotate to the second position, the first movable cam piece 514 and the second movable cam piece 516 both face upward and act vertically on the lower box body 47, and the first vibration device 51 generates an upward force with a magnitude of F. At this time, the third movable cam piece 527 and the fourth movable cam piece 529 rotate to the fourth position, and the third movable cam piece 527 and the fourth movable cam piece 529 both face upward and vertically act on the upper box body 46, and the second vibration device 52 generates an upward force with a magnitude of F. The magnitude of the combined force generated by the first vibration device 51 and the second vibration device 52 is 2F, and the direction of the combined force is vertically upward. The horizontal direction does not generate a force on the upper box body 46 and the lower box body 47, that is, it generates a force on the vibration hammer cap column 49, and the magnitude of the force is 2F.

[0096] Therefore, by controlling the first vibration device 51 and the second vibration device 52, the force acting on the vibration hammer cap column 49 can be changed periodically along the vertical direction: ↓2F→0→↑2F→0→↓2F→0→↑2F→…. Among them, ↑ indicates that the direction of the resultant force is upward, ↓ indicates that the direction of the resultant force is downward, and → indicates the direction of change of the resultant force. Thus, periodic vibration is achieved, vibration with controllable force size is achieved, and no force is generated in the horizontal direction.

[0097] Exemplarily, the observation device includes a camera 8, a laser emitter 9, a tripod 10, a support rod 11, a computer 12 and a wireless communication module 13. The camera 8 is mounted on the top of the tripod 10, and the camera 8 is connected to the computer 12 for communication. The laser emitter 9 is slidably mounted on the support rod 11 and can slide along the axial direction of the support rod 11. The laser emitter 9 is electrically connected to the computer 12. The laser emitter 9 cooperates with the CCD sensor 30 to achieve the observation and measurement of the penetration of the pipe pile 19. The laser emitter 9 emits laser light to the CCD sensor 30, and the displacement of the pile 19 is determined by the position change of the laser light on the CCD sensor 30, and the laser emitter 9 is controlled to move on the support rod 11 according to the displacement of the pile, and moves to the corresponding position. The CCD sensor 30 uploads the measured laser point position to the computer 12, and the computer 12 controls the position of the laser emitter 9 on the support according to the position of the laser light.

[0098] The camera 8 shoots at the observation window 17 on the model tube. The three laser lights in the observation window 17 respectively illuminate the pile-soil surface at different positions in the model tube, thereby forming three observation areas. The camera 8 collects the pile-soil image with laser speckle formed on the surface through shooting, and then obtains the pile-soil displacement data through image algorithm processing.

[0099] refer to Figure 1 and Fig.21 , Figure 1 The middle pipe pile 19 is inserted into the eccentric position of the model tube and is located at a side position. Fig.21 The middle pipe pile 19 is inserted into the center (i.e., the center of the circle) of the model tube and is located in the middle position. When the pipe pile 19 is inserted into the middle position of the model tube, it also includes a load-bearing column 53, the two ends of which are respectively abutted on the pad 36 and the pressure plate 16, and the jack 4 is installed on the pad 36, and the jack 4 is abutted against the main beam 1.

[0100] When it is actually needed, the anchor bar 14 is penetrated into the ground to a sufficient depth to meet the reaction force required by the reaction frame 5. The airbag 18 is inflated through the vent valve 21, and then the inflation is stopped. The airbag 18 is attached to the inner wall of the cylinder 6, and then the simulated soil used as the pile soil is filled into the accommodating space to a preset height, for example, 0.1m (meter) from the top of the cylinder 6. Then, the pressure plate 16 is added, and the pipe pile 19 equipped with the hammer cap 3 is inserted into the pile soil, and the bottom end of the pipe pile 19 is just aligned with the position of the observation window 17 of the model cylinder, for example, the bottom end of the pipe pile 19 is just aligned with the middle position of the observation window 17, so that the bottom end of the pipe pile 19 can be observed through the observation window 17.

[0101] The model cylinder with pile soil is dragged to the middle position of the sliding base by hoisting, and then the first snap plate 31 and the second snap plate 35 are fastened and locked on the sliding frame 34. The jack 4 is hoisted to the pressure plate 16 of the model cylinder. After the output end (i.e., the plunger) of the jack 4 is extended, the pad 36 is tightly fitted to the bottom of the main beam 1, thereby applying a vertical pressure P. The airbag 18 is inflated through the vent valve 21, so that the air pressure in the airbag 18 reaches K times the pressure P, that is, the air pressure in the airbag 18 reaches K*P, where K is calculated based on the Poisson's ratio of the pile soil, K=v / (1-v), and v represents the Poisson's ratio of the soil.

[0102] refer to Fig.24 Based on the test device for simulating dynamic pile driving of precast piles, this embodiment further provides a test method for simulating impact pile driving of precast piles, and the test method comprises the following steps:

[0103] Step 11: Adjust the position and irradiation direction of the laser emitter 9 so that the laser emitted by the laser emitter 9 is perpendicularly irradiated to the sensing surface of the CCD sensor 30 on the pipe pile 19 .

[0104] Step 12: Install the impact device on the hammer cap 3, and control the impact motor 37 of the impact device to control the impact sinking of the pipe pile 19. During the downward displacement of the pipe pile 19, the pipe pile 19 drives the CCD sensor 30 on the pipe pile 19 to move downward synchronously, and the position of the laser point irradiated by the laser on the CCD sensor 30 also moves accordingly, and the laser point position is collected by the CCD sensor 30, and the collected laser point position is transmitted to the computer 12 through the wireless communication module 13.

[0105] Step 13: During the hammering of the pipe pile 19 by the impact device, the pipe pile 19 will rebound. Therefore, it is necessary to analyze the displacement change information of the laser point on the CCD sensor 30 over time during the pile sinking process to accurately measure the penetration s of the pipe pile 19. Taking the initial position of the laser point as the reference, the maximum displacement DMX in the entire pile sinking process is calculated according to the displacement peak value of the laser point, and the last position of the laser point is used as the penetration s of the pipe pile 19. The pile body rebound c of the pipe pile 19 has the following relationship: c=DMX-s. At the same time, according to the information of the displacement change of the laser point over time, the velocity time history curve of the laser point can be obtained, and then the energy transmitted to the pipe pile 19 by the hammering action of the impact device can be obtained according to the kinetic energy equation, and then the conversion efficiency η of potential energy to kinetic energy can be determined.

[0106] Step 14: According to the penetration degree s of the pipe pile 19 , the laser emitter 9 moves downward by an amount s to adjust the position of the laser emitter 9 .

[0107] Step 15: Repeat steps 13 and 14 to realize continuous sinking of the pipe pile 19. The depth of the pipe pile 19 into the soil is equal to the final moving distance of the laser transmitter 9, thereby obtaining the final variation curves of the maximum displacement DMX of the pile, the penetration s, and the pile body rebound c. Fig. 22 It is a schematic diagram of the change curves among the maximum displacement DMX, penetration s, and pile body rebound c.

[0108] Step 16: Before the impact device starts to sink the pipe pile 19, the three laser lights (the first laser light 23, the second laser light 24 and the third laser light 25) on the grid column 20 are turned on. The lasers emitted by the three laser lights are irradiated on the pile soil through the transparent part, and form speckles on the pile soil surface where the first observation area 26, the second observation area 27 and the third observation area 28 are located.

[0109] Step 17: The camera 8 is aimed at the observation window 17 to capture three observation areas, and further capture the pile soil where the three observation areas are located.

[0110] When the impact device hammers the pipe pile 19 to achieve impact pile driving, the pipe pile 19 moves downward, squeezes the pile soil and causes the pile soil to deform. The camera 8 continuously captures images of the pile soil during the pile driving process, and the displacement of the pile soil is obtained through image processing technology.

[0111] Among them, the upward displacement of the pile soil in the observation window 17 and the radial displacement change on both sides of the pile soil are used to evaluate the soil plugging effect of the pile soil. When the soil displacement of the pile soil is basically unchanged (the change can be regarded as basically unchanged within the threshold value), and the radial displacement on both sides of the pile soil increases sharply (the rate of change exceeds the preset threshold value and can be regarded as a sharp increase), it means that the soil plugging effect has occurred. And by correlating the pile sinking control parameters such as the pile sinking depth and pile sinking penetration of the pipe pile 19 when the soil plugging effect occurs, the critical point of the soil plugging effect in the pile sinking process can be determined.

[0112] According to the piezoresistive sensor installed on the pipe pile 19, the radial stress σ at the lower end of the pipe pile 19 is measured. r and the vertical stress σ at the top of pile 19 v . And based on the radial stress σ r The shear stress τ at the lower end of the pipe pile 19 is obtained. It represents the pile-soil interface friction angle obtained by indoor pile-soil test. Thus, the curve relationship between the pile-soil shear stress and the vertical displacement on the pile side of the pipe pile 19 and the curve relationship between the pile-soil vertical stress and the vertical displacement at the pile end of the pipe pile 19 can be established.

[0113] refer to Fig.23 , Step 18: Calculate the total resistance R of the pile 19 according to formula ① d , calculate the static soil resistance R of pile 19 according to formula ② static :

[0114]

[0115] In the formula, A s A represents the pile side surface area of ​​the pipe pile 19. p represents the pile end surface area of ​​the pipe pile 19. When the soil plugging effect does not occur, the pile end surface area of ​​the pipe pile 19 is the net area of ​​the circular ring at the bottom of the pipe pile 19. When the soil plugging effect occurs, the calculation is more complicated. outer represents the outer friction resistance of the pile 19, τ innerrepresents the inner friction resistance of the pipe pile 19, d is the diameter of the pipe pile 19, t is the wall thickness of the pipe pile 19, that is, the side wall thickness of the pipe pile 19, mg represents the weight of the impact hammer cap column 41, and h represents the falling height of the impact hammer cap column 41, that is, the falling hammer height.

[0116] For the test method of impact pile driving, the impact hammer cap column 41 will be affected by air resistance when it falls, and energy loss will occur in the form of heat energy generated by collision, so the conversion efficiency η needs to be considered, which represents the energy reduction efficiency. Each time the impact motor 37 rotates one circle, the distance d traveled by the traction rope 43 is driven. Therefore, the impact motor 37 can be a servo motor, and the number of rotations of the impact motor 37 can be controlled, so that the impact hammer cap column 41 can be lifted to different levels of lifting heights such as d, 2d, and 3d by the traction rope 43, so as to control the downward impact force of the impact hammer cap column 41 by the lifting height, and realize impact pile driving. The hammer force at the top of the pipe pile 19 can collect the strain coefficient ε through the strain gauge 29, and then calculate the stress σ through Hooke's law, and obtain the hammer force F calculation formula shown in the following formula based on the stress and Hooke's law: F = σA, A represents the pile top surface area of ​​the pipe pile 19.

[0117] refer to Fig.25 Based on the test device for simulating dynamic pile sinking of precast piles, this embodiment further provides a test method for simulating vibration pile sinking of precast piles, the test method comprising the following steps:

[0118] Step 21 : Adjust the position and irradiation direction of the laser emitter 9 so that the laser emitted by the laser emitter 9 irradiates the sensing surface of the CCD sensor 30 on the pipe pile 19 vertically.

[0119] Step 22: Install the vibration device on the hammer cap 3, and control the vibration sinking of the pipe pile 19 by controlling the impact motor 37 of the vibration device. During the downward displacement of the pipe pile 19, the pipe pile 19 drives the CCD sensor 30 on the pipe pile 19 to move downward synchronously, and the position of the laser point irradiated by the laser on the CCD sensor 30 also moves accordingly, and the laser point position is collected by the CCD sensor 30, and the collected laser point position is transmitted to the computer 12 through the wireless communication module 13.

[0120] The pipe pile 19 is sunk under the action of vibration. During the sinking process, the body of the pipe pile 19 vibrates up and down. When the accumulated displacement d of the pipe pile 19 is t When the distance is greater than the vertical movement range of the laser emitter 9 on the CCD sensor 30, the laser emitter 9 is moved downward by a distance d. t .

[0121] According to the displacement information of the laser position point irradiated on the CCD sensor 30 over time, the vibration acceleration characterizing the vibration of the pipe pile 19 can be further obtained, and the accumulated movement distance of the laser transmitter 9 is recorded as the sinking depth of the pipe pile 19 into the ground.

[0122] The vibration pile driving is continued, and the final pile driving depth into the soil is equal to the sum of the moving distances of the laser emitter 9 each time, thereby forming a curve of the variation of the pile driving penetration speed with the soil driving depth.

[0123] Step 23: Before the vibration device vibrates and sinks the pipe pile 19, the three laser lights (the first laser light 23, the second laser light 24 and the third laser light 25) on the grid column 20 are turned on. The lasers emitted by the three laser lights are irradiated on the pile soil through the transparent part, and form speckles on the pile soil surface where the first observation area 26, the second observation area 27 and the third observation area 28 are located.

[0124] The camera 8 is aimed at the observation window 17 so as to be able to capture three observation areas (the first observation area 26, the second observation area 27 and the third observation area 28) on the observation window 17. The camera 8 continuously captures the soil image of the pile soil in the pipe pile 19 during the pile sinking process, and the soil displacement change of the pile soil is obtained by an image processing method.

[0125] Whether the soil plugging effect occurs in the pipe pile 19 is evaluated based on the upward displacement of the soil in the soil displacement change and the radial displacement change of the pipe pile 19 on both sides along the pile circumference direction. When the upward displacement of the soil in the pipe pile 19 is basically unchanged (the upward displacement of the soil is less than the threshold value and can be regarded as basically unchanged), and the radial displacement on both sides of the circumference of the pipe pile 19 increases sharply (the radial displacement exceeds the threshold value and can be regarded as a sharp increase), it means that the soil plugging effect occurs, otherwise, it means that the soil plugging effect does not occur.

[0126] Step 24: Using the piezoresistive sensor installed on the pipe pile 19, the radial stress σ at the lower end of the pipe pile 19 is measured. r and the vertical stress σ at the top of pile 19 v . , and based on the radial stress σ r The shear stress τ at the lower end of the pipe pile 19 is obtained, and the shear stress τ = σ r *tanφ, It represents the pile-soil interface friction angle obtained from the indoor pile-soil test. Thus, the pile-soil shear stress τ and vertical stress σ on the pile side of pipe pile 19 can be established. v The relationship between the vibration acceleration of the pipe pile 19 is studied to study the weakening law of the pile soil under the vibration load based on the change relationship.

[0127] After the test, the jack 4 is depressurized, the sliding base is removed, and the gas in the airbag 18 is extracted through the vent valve 21, that is, the air is pumped out, the compacted pile soil is separated from the inner wall of the airbag 18, the pile soil is broken up and the clay is taken out of the airbag 18.

[0128] The present invention can well realize dynamic pile driving, including impact pile driving and vibration pile driving, and applies pressure to the pressure plate 16 through the jack 4 and then acts on the pile soil to simulate the influence of ground stress, so as to realize the measurement of the penetration degree in the pile driving process under the consideration of the influence of ground stress, and to obtain the law of the displacement of the pile soil at the pile side and the pile end with the soil body during the pile driving process, so as to simulate the formation of the soil plug (effect) at the pile end, so as to establish the relationship between the pile driving displacement and the mechanical parameters of the pile-soil interaction.

[0129] In addition, the test device has a simple structure, is easy to maintain, has a long service life, and can set the pipe pile 19 at the center or side position of the pile soil as needed.

[0130] The impact pile driving test method can well evaluate whether the soil plugging effect occurs during the impact pile driving process, and calculate the total resistance and static soil resistance of the pipe pile 19. And the vibration pile driving with regular impact force can be achieved by controlling the number of rotations of the impact motor 37.

[0131] The vibration pile driving test method can also be used to evaluate whether the soil plugging effect occurs during the impact pile driving process, and to establish the pile-soil shear stress τ and vertical stress σ on the pile side. v The relationship between the vibration acceleration of the pipe pile 19 is studied to study the weakening law of the pile soil under the vibration load based on the change relationship.

[0132] The embodiment disclosed in this specification is only an example of a unilateral feature of the present invention, and the protection scope of the present invention is not limited to this embodiment, and any other functionally equivalent embodiments fall within the protection scope of the present invention. For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A test method for simulating vibration pile sinking of precast piles, characterized in that: A test device for simulating dynamic pile sinking of precast piles, the test method comprising the following steps: Step 21: Adjust the position and irradiation direction of the laser transmitter so that the laser emitted by the laser transmitter is vertically irradiated to the sensing surface of the CCD sensor on the pipe pile; Step 22: Install the vibration device on the hammer cap, and apply exciting force to the pipe pile through the vibration device to achieve vibration sinking of the pipe pile. During the downward displacement of the pile, the pile drives the CCD sensor on the pile to move downward synchronously, and the position of the laser point irradiated by the laser on the CCD sensor also moves accordingly, and the position of the laser point is collected by the CCD sensor and transmitted to the computer through the wireless communication module. The pile is sunk under the action of vibration. During the sinking process, the pile body vibrates up and down. When the accumulated displacement of the pile is d t When the distance is greater than the vertical movement range of the laser emitter on the CCD sensor, move the laser emitter downward by a distance of d. t , Vibration pile driving is continued, and the final pile penetration depth is equal to the sum of the moving distances of the laser transmitter each time, and a curve of the variation of the pile penetration speed with the penetration depth is formed; Step 23: Before the vibrating device vibrates and sinks the pipe pile, the three laser lamps on the grid column are turned on. The lasers emitted by the three laser lamps are irradiated on the pile soil through the transparent member, and form speckles on the surface of the pile soil where the first observation area, the second observation area and the third observation area are located. Aim the camera at the observation window to capture the three observation areas on the observation window. The camera continuously captures the soil image of the pile in the pipe pile during the pile sinking process, and obtains the displacement change of the pile soil through the image processing method. Based on the upward displacement of the soil in the soil displacement change and the radial displacement change of the pile on both sides of the pile circumference, it is evaluated whether the soil plugging effect occurs in the pile. The soil plugging effect of the pile-soil is evaluated based on the upward displacement of the pile-soil and the radial displacement on both sides of the pile-soil circumference. When the displacement change of the soil of the pile-soil is ≤ the first threshold value, and the radial displacement change on both sides of the pile-soil circumference is ≥ the second threshold value, the soil plugging effect is considered to have occurred; otherwise, it is considered that the soil plugging effect has not occurred. Step 24: According to the piezoresistive sensor installed on the pile, the radial stress σ at the lower end of the pile is measured respectively. r and the vertical stress σ at the top of the pile v , and based on the radial stress σ r The shear stress τ at the lower end of the pile is obtained. It represents the pile-soil interface friction angle obtained from the indoor pile-soil test, so as to establish the pile-soil shear stress τ and vertical stress σ on the pile side. v The relationship with the change of vibration acceleration of the pipe pile.

2. The test method for simulating vibration pile sinking of precast piles according to claim 1, characterized in that: The test device for simulating dynamic pile driving of prefabricated piles comprises a reaction frame, a model tube, a sliding base, a jack, a pile driving device, a hammer cap and an observation device. The model tube is installed on the sliding base, a cavity for accommodating pile soil is provided in the model tube, the jack is installed at one end of the model tube away from the sliding base, and the jack is in contact with the reaction frame. The hammer cap is installed on the pipe pile as the prefabricated pile. The pipe pile passes through the model tube and is inserted into the pile soil in the model tube. One end of the pipe pile is exposed outside the model tube. The hammer cap is located on the end of the pipe pile exposed outside the model tube. The pile driving device is used to drive the pipe pile into the soil by dynamic pile driving to simulate the dynamic pile driving process of prefabricated piles. The observation device is located outside the model tube.

3. The test method for simulating vibration pile sinking of precast piles according to claim 2, characterized in that: The reaction frame includes a frame body, a main crossbeam, a square base and anchor bars installed on the frame body, the jack is in contact with the main crossbeam, the square base is fixedly installed at the lower end of the frame body, and the main crossbeam spans the frame body. The anchor bar passes through the main beam and the frame to fix the main beam and the frame together. An anchor block is installed on one end of the anchor bar passing through the main beam and the frame. The anchor bar also passes through the frame and the square base and is exposed on the outside of the square base. The anchor bar is used to penetrate the ground and be fixedly connected to the ground to fix the reaction frame on the ground.

4. The test method for simulating vibration pile sinking of precast piles according to claim 2, characterized in that: The model cylinder includes a cylinder body, an airbag and a pressure plate. The cylinder body includes a cavity. The airbag is installed in the cavity. The airbag is inflated and fits against the inner wall of the cavity of the cylinder body, and the cavity forms a accommodating space. The accommodating space is used to hold pile soil. The pressure plate covers the cylinder body or covers the cylinder body and the airbag. Through holes are respectively provided at the center and eccentricity of the pressure plate.

5. The test method for simulating vibration pile sinking of precast piles according to claim 4 is characterized in that: The model cylinder also includes an observation window. A through hole is dug on the cylinder body and the airbag respectively. When the airbag is inflated and fits against the inner wall of the cavity of the cylinder body, the through hole on the cylinder body and the through hole on the airbag are just opposite to each other. The through hole on the cylinder body is provided with a grid column, and the grid column is embedded in the through hole. The through hole on the airbag is provided with a transparent part, and the grid column is located directly in front of the transparent part. When the pipe pile passes through the through hole and is inserted into the pile soil, the pipe pile is directly opposite to the observation window.

6. The test method for simulating vibration pile sinking of precast piles according to claim 5, characterized in that: The grid column includes a plurality of vertical poles, each vertical pole is cross-connected to form an array, and the grid column is also equipped with a first laser light, a second laser light and a third laser light facing in different directions, the first laser light, the second laser light and the third laser light are away from the observation device and can irradiate the pile soil surface in the model tube, The grid column divides the observation window into a first observation area, a second observation area and a third observation area in a certain direction. The first laser light is located in the first observation area, the second laser light is located in the second observation area, and the third laser light is located in the third observation area. The pipe pile is provided with a strain gauge and a CCD sensor on one end of the model tube, and the inner side wall and the outer side wall of the top end and the lower end of the pipe pile are respectively provided with a piezoresistive sensor.

7. The test method for simulating vibration pile sinking of precast piles according to claim 2, characterized in that: The sliding base includes a sliding frame, and a first snap plate, a second snap plate, a support plate, a plurality of sliding shafts and a plurality of fixed blocks installed on the sliding frame. The sliding shafts are arranged in parallel and spaced apart. Both ends of the sliding shafts are fixedly connected to the fixed blocks respectively. The fixed blocks are fixedly installed at both ends of the sliding frame. The support plate is installed on the sliding frame and is located above the sliding shaft. The first snap plate and the second snap plate are snap-connected to the sliding frame. The first snap plate and the second snap plate are respectively located on both sides of the support plate and are fixedly connected to the support plate. The first snap plate and the second snap plate are both located above the sliding frame. The model cylinder is installed on the support plate. The sliding shafts are arranged in sequence from low to high and then to low along the axial direction of the sliding frame.

8. The test method for simulating vibration pile sinking of precast piles according to claim 2, characterized in that: The pile driving device includes a vibration device, which includes an upper box, a lower box, a first vibration device, a second vibration device, a connecting column, a vibration hammer cap column and a plurality of wedge blocks. The first vibration device is installed in the lower box, and the second vibration device is installed in the upper box. The upper box is stacked and installed on the upper end of the lower box. The upper box and the lower box are fixedly or detachably connected. The lower box is connected to the upper end of the connecting column, and the lower end of the connecting column is fixedly connected to the vibration hammer cap column. The wedge block is fixedly connected to the end of the vibration hammer cap column away from the connecting column, and the wedge blocks are arranged at intervals.

9. The test method for simulating vibration pile sinking of precast piles according to claim 8, characterized in that: The first vibration device includes a first motor, a first gear, a second gear, a first rotating shaft, a second rotating shaft, a first movable cam piece, a second movable cam piece, a first fixed cam piece and a first base, the first motor is installed on the first base, the output end of the first motor is connected to the first rotating shaft, the first gear is sleeved and fixed on the first rotating shaft, the first movable cam piece is fixedly installed on the end of the first rotating shaft away from the first motor, the first gear and the first movable cam piece are arranged at intervals, one end of the second rotating shaft is rotatably installed on the first base, and the other end extends away from the first base and is located on the outside of the first base, the second rotating shaft and the first rotating shaft are arranged in parallel and at intervals, the second gear is sleeved and fixed on the second rotating shaft, the second gear is meshed and connected with the first gear, the second movable cam piece is fixedly installed on the end of the second rotating shaft away from the first base, the second movable cam piece and the first movable cam piece are arranged in parallel, and along the axial direction of the second rotating shaft, at least a part of the first movable cam piece and the second movable cam piece overlap together, the first fixed cam piece is sleeved and fixed on the second rotating shaft, and the second fixed cam piece is between the first base and the second gear, The second vibration device includes a second motor, a third gear, a fourth gear, a third rotating shaft, a fourth rotating shaft, a third movable cam piece, a fourth movable cam piece, a third fixed cam piece, a fourth fixed cam piece and a second base, the second motor is mounted on the second base, the output end of the second motor is connected to the third rotating shaft, the third gear is sleeved and fixed on the third rotating shaft, the third movable cam piece is fixedly mounted on an end of the third rotating shaft away from the second motor, the third gear and the third movable cam piece are arranged at intervals, one end of the fourth rotating shaft is rotatably mounted on the second base, and the other end extends in a direction away from the second base and is located on the outside of the second base, the fourth The rotating shaft and the third rotating shaft are arranged in parallel and at intervals, the fourth gear is sleeved and fixed on the fourth rotating shaft, the fourth gear and the third gear are meshingly connected, the fourth movable cam piece is fixedly installed on an end of the fourth rotating shaft away from the second base, the fourth movable cam piece and the third movable cam piece are arranged in parallel, and along the axial direction of the fourth rotating shaft, the third movable cam piece and the fourth movable cam piece at least partially overlap together, the third fixed cam piece is sleeved and fixed on the third rotating shaft, the third fixed cam piece is between the second base and the third gear, the fourth fixed cam piece is sleeved and fixed on the fourth rotating shaft, and the fourth fixed cam piece is between the second base and the fourth gear.

10. The test method for simulating vibration pile sinking of precast piles according to claim 2, characterized in that: The observation device includes a camera, a laser transmitter, a tripod, a support rod, a computer and a wireless communication module. The camera is installed at the top of the tripod, the camera is connected to the computer for communication, the laser transmitter is slidably installed on the support rod and can slide along the axis of the support rod, the laser transmitter is electrically connected to the computer, and the laser transmitter emits laser to the CCD sensor. The camera takes pictures through an observation window on the model tube, and three laser lights in the observation window illuminate the pile soil surfaces at different positions in the model tube respectively.

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