CN104631519B - Pile foundation bearer properties model test apparatus and test method under complicated loads - Google Patents

Abstract

The invention discloses a pile foundation bearing characteristic model test device under complex load, which comprises a model groove, a horizontal loading system, a vertical loading system and a measuring device. The model tank is made of plexiglass plate and reinforced by channel steel; the horizontal loading system is composed of pulleys and weights; the vertical loading system is composed of vertical channel steel, reaction beams, jacks, and linear sliding guide rails; the measuring device includes measuring pile head level The miniature laser displacement sensor system for displacement and pile top settlement can move horizontally with the movement of the pile head; the measuring device also includes a stay rope displacement sensor system for measuring the horizontal displacement of the pile body. The invention also discloses a test method of the device. The test device and test method are easy to load and the load direction is stable, and can accurately measure data such as model pile settlement, pile head horizontal displacement, and pile body horizontal displacement. Model test study of load bearing characteristics.

Description

Model test device and test method for pile foundation bearing characteristics under complex loads

technical field

The invention relates to a pile foundation model test device and a test method, in particular to a pile foundation bearing characteristic model test device and a test method under complex loads.

Background technique

As a foundation treatment technology, pile foundation has the advantages of wide application range, fast construction speed, and good reinforcement effect. It is widely used in foundation treatment engineering fields such as highways, railways, ports, airports, and housing construction. While the pile foundation is subjected to the vertical load generated by the superstructure, it will also be subjected to the horizontal load generated by wind, earthquake, water, vehicles, etc. Research on the bearing characteristics of pile foundation under vertical-horizontal coupled load is one of the important topics that researchers pay attention to. This model test device is required to carry out the influence of vertical load on the bearing characteristics of horizontally loaded piles, the influence of horizontal load on the bearing characteristics of vertically loaded piles, and the bearing characteristics of pile foundations under the action of vertical-horizontal coupled loads.

Prior to the present invention, the paper "Model Test of Lateral Bearing Characteristics of Large-diameter Reduced-diameter Pile" (Journal of China Highway Society, November 2013, Volume 26, Issue 6, 80-86) disclosed a pile under the action of lateral static load Base bearing characteristic test device, which is composed of a model box, a horizontal loading device, and a measuring device, and can only be used for horizontal one-way loading.

The traditional pile foundation model test device has a single loading direction, and there is no need to consider the interaction between loads in different directions during the loading process. In the existing pile foundation model test device, the vertical load will deflect as the horizontal load is applied during the test, and the measurement is inaccurate; there is no measuring instrument for the horizontal displacement of the pile body, and the horizontal displacement of the pile body is mostly obtained by linear interpolation. The results may not accurately reflect the actual situation. Therefore, we invented a pile foundation bearing characteristic under complex loads, which is simple to manufacture, easy to load, stable in load magnitude and direction, and capable of effectively measuring the settlement of the molded pile head, the horizontal displacement of the pile head, the horizontal displacement of the pile body, and the bending moment of the pile body. Model test equipment and test methods are very meaningful work.

Contents of the invention

Purpose of the invention: The purpose of the present invention is to overcome the above-mentioned defects and provide a model test device and test method for the bearing characteristics of pile foundations under complex loads.

Technical solution: In order to solve the above technical problems, a model test device for pile foundation bearing characteristics under complex loads of the present invention includes a model tank, a horizontal loading system, a vertical loading system and a measuring device, and a model is placed in the model tank Pile; the horizontal loading system includes a pulley, a weight and a steel wire rope, the steel wire rope connects the weight and the pile top of the model pile, the pulley is fixed on the outside of the model groove, and the steel wire rope is slidingly matched with the pulley;

The vertical loading system includes a vertical channel steel, a reaction beam, a jack and a linear sliding guide rail, the vertical channel steel is fixedly connected with the model groove, the reaction force beam is fixed on the top of the vertical channel steel, and the linear sliding guide rail Installed on the reaction beam, the jack is slidingly matched with the linear sliding guide rail;

The measuring device includes a miniature laser displacement sensor system and a stay rope displacement sensor system;

The miniature laser displacement sensor system includes a first miniature laser displacement sensor for measuring the horizontal displacement of the pile head, and a second miniature laser displacement sensor for measuring the settlement of the pile top; the second miniature laser displacement sensor and the reaction beam Connected by a linear sliding guide rail; it can move horizontally with the movement of the pile head to ensure that the measured data is the vertical settlement of the pile top;

The stay rope displacement sensor system is used to measure the horizontal displacement of the pile body, including a thin steel pipe arranged between the model pile and the inner wall of the model tank, a stay rope pierced in the thin steel pipe, and a drawstring fixed on the side wall of the tank body. Rope displacement sensor. The horizontal displacement of the pile body can be accurately measured without affecting the force of the pile and soil.

Preferably, in order to facilitate the observation of the test state, ensure the strength of the model tank, and simplify the manufacturing process, the model tank is made of a plexiglass plate, and a channel steel reinforcing hoop is provided outside the model tank.

Preferably, in order to maintain the stability of the vertical loading direction and make the entire vertical loading system detachable, the vertical channel steel, the reaction beam, the jack and the linear sliding guide rail are detachably connected by screws, and the jack and the linear A steel plate is arranged between the sliding guide rails, and the steel plate is slidingly matched with the linear sliding guide rail. The jack and the second miniature laser displacement sensor are installed on the steel plate through screws; there are two second miniature laser displacement sensors, It is symmetrically fixed on both sides of the model pile along the horizontal stress direction of the model pile and kept vertical.

As a preference, in order to accurately measure the displacement of the pile body, the vertical steel plate is fixedly installed under the reaction beam, the pile top is equipped with a ranging panel for echo ranging, and the first miniature laser displacement sensor is installed on the vertical There are two first miniature laser displacement sensors, one of which is at the same level as the top of the pile, and the other is slightly higher than the top of the pile and kept horizontal.

As a preference, in order to test the displacement of different positions of the pile body, four of the stay rope displacement sensors are installed downward from the pile top on the side wall of the model groove, wherein the distance between two adjacent stay rope displacement sensors is 1/8 of the pile length.

As preferably, the top of the pile is equipped with a pile head protection ring, a pressure sensor and a rubber pad in sequence, the pile head protection ring is used to protect the pile head of the model pile and is used as a horizontal stress point of the model pile, and the rubber pad is used Used to adjust the contact between the jack and the pressure sensor.

The present invention proposes the test method of above-mentioned test device simultaneously, comprises the following steps:

(1) Prepare materials for the test device. Before making, prepare plexiglass plate, channel steel, steel plate, angle steel, thin steel pipe, and prepare linear sliding guide rail, screw, pulley, jack, steel wire rope, weight plate and weight.

(2) Make a model slot. According to the size of the drawing, cut out the plexiglass plate and assemble it into a model tank, cut out the channel steel, reinforce 3 rings of channel steel around the model tank from bottom to top, and weld and reinforce the same ring of channel steel with angle steel; and mark the position according to the drawing , Drill holes at the installation positions of the four stay rope displacement sensors on the plexiglass plate of the model groove.

(3) Make parts. According to the size of the drawing, make the reaction beam, vertical channel steel, place steel plate, distance measuring panel, pile head protection ring, cut out the calibrated size thin steel pipe, install the reaction beam on the vertical channel steel, the position where the wire rope passes, and model Open holes at the connection position of the channel steel, and open holes at the installation position of the vertical channel steel on the reaction beam, the installation position of the linear sliding guide rail, and the installation position of the vertical steel plate.

(4) Install the pulley. According to the position marked on the drawing, the pulley is installed on the channel steel of the model with screws, and the horizontal loading system is installed.

(5) Assemble the vertical loading system. According to the position calibrated on the drawing, first use screws to install the linear sliding guide rail on the reaction beam, and then use screws to fix the linear sliding guide rail, place the steel plate, and the jack as a whole, and then pass the vertical steel plate of the miniature laser displacement sensor for measuring the horizontal displacement of the pile head through Screws and angle steel are installed on the reaction beam. The vertical loading system is assembled. The parts required for the model test device are ready.

(6) Preparation of test materials and test instruments. Before the test, prepare the test soil, model piles, rope displacement sensors and data collectors, micro laser displacement sensors and data collectors, pressure sensors and data collectors, and the resistance strain gauges and data collectors configured according to the test needs, Earth pressure cell and frequency meter; standard sand or clay can be used for the test soil, wood, aluminum tube and other materials can be selected for the model pile, and the cross-section of the model pile can be selected in different shapes such as circle, square, and ring.

(7) Selection of test loading scheme. Select the loading method, data collection standard and loading termination standard according to the "Technical Specifications for Building Foundation Pile Inspection" (JGJ106-2014), and estimate the horizontal bearing capacity and vertical bearing capacity of the model pile; select the corresponding loading scheme according to the different simulated working conditions , to simulate the force of the bridge pier, first apply the horizontal load to a certain level, and then apply the vertical load to failure; simulate the bearing characteristics of the pile foundation under the wind load of a tall building, first apply the vertical load to a certain level, then apply the horizontal load and vertical load Alternate grading is applied to pile foundation failure.

(8) Fill soil and embed model piles. According to the needs of the test, fill the soil in layers. When filling to the pile bottom elevation, fix the position of the model pile first, then continue to fill the soil, and paste the resistance strain gauge and embed the earth pressure cell according to the test needs.

(9) Install the rope displacement sensor. When filling the soil to the installation position of the stay rope displacement sensor at the bottom layer, first fix the stay rope displacement sensor on the plexiglass plate, then pass the stay rope through the thin steel pipe and connect it to the thin wire wound on the model pile. The winding position of the thin wire should be the same as that of the stay rope The outlets of the displacement sensors are at the same horizontal line. During the filling process, pay attention to keep the thin steel pipe level; continue to fill the soil and install the other 3 pull rope displacement sensors. Fill the soil to the calibrated mud surface and complete the filling.

(10) Install the vertical loading system. According to the position marked on the drawing, the angle steel is used as the connecting part, and the vertical channel steel is installed on the model channel steel through screws, and then the assembled vertical loading system is connected to the vertical channel steel through screws and angle steel.

(11) Install the miniature laser displacement sensor. Fix the first and second miniature laser displacement sensors to the vertical steel plate and the placement steel plate respectively; the two second miniature laser displacement sensors for measuring pile top settlement should be symmetrically fixed on both sides of the model pile along the horizontal stress direction of the model pile, And note to keep vertical; Two first miniature laser displacement sensors of pile head horizontal displacement, one is on the same horizontal line with pile top, and one is slightly higher than pile top, and note keeps level.

(12) Measuring instrument connection. Connect the miniature laser displacement sensor to the data collector, connect the rope displacement sensor to the data collector, connect the resistance strain gauge leads set according to the test requirements to the data collector, and connect the earth pressure box to the frequency meter.

(13) Place pile head protection ring, ranging panel and pressure sensor. Put the prepared pile head protection ring on the model pile, and the leading part faces the side of the pulley; place the distance measuring panel on the pile head protection ring, pay attention to the position corresponding to the micro laser displacement sensor; place the pressure sensor on the distance measurement panel connected to the data collector.

(14) Install and adjust the loading device. Place a rubber pad on the pressure sensor, adjust the jack to make it just in contact with the rubber pad; connect one end of the wire rope to the weight plate, then pass the wire rope through the pulley through the vertical channel steel hole, and connect it to the leader of the pile head protection ring , and adjust the pile head protection ring to make the wire rope level.

(15) Load application and data collection. Load according to the selected loading scheme, and collect data according to the selected data collection standard; when applying vertical load, collect the data of two miniature laser displacement sensors that measure the settlement of the pile top; when applying horizontal load, collect the data of the pile head The data of two micro-laser displacement sensors for horizontal displacement, the data of four pull-rope displacement sensors are collected, and the data of pile resistance strain gauges and earth pressure cells set according to the test requirements are collected.

(16) Data processing. The settlement of the pile top is obtained by averaging the data of the two micro-laser displacement sensors on the top of the pile; the rotation angle of the pile top is calculated from the data of the two micro-laser displacement sensors measuring the horizontal displacement of the pile head and the vertical distance of the installation position. The data of the miniature laser displacement sensor is the horizontal displacement of the pile head; the deformation curve of the upper part of the pile body is obtained by fitting the data of the four pull rope displacement sensors; The soil pressure on the side of the pile is obtained from the measured data of the earth pressure cell set according to the test requirements.

The beneficial effects of the present invention are:

(1) The present invention adopts the plexiglass panel to make the model groove, and adopts the channel steel to reinforce, which is easy to process, firm in structure and good in durability.

(2) The reaction beam and the model groove of the present invention are connected by a detachable vertical channel steel, and the vertical channel steel and the reaction beam can be detached before the soil filling test, which is convenient for soil filling and embedding of model piles.

(3) The present invention uses a linear sliding guide rail to connect the jack and the reaction beam, which is easy to install and operate. During the test process, the jack moves horizontally along the linear sliding guide rail with the pile head, which can maintain the stability of the vertical load direction during the test process.

(4) The present invention uses a miniature laser displacement sensor to measure the horizontal displacement of the pile head and the settlement of the pile head. Compared with the dial indicator, the accuracy is high, and the artificial estimation error can be avoided.

(5) The miniature laser displacement sensor used to measure the settlement of the present invention is placed between the steel plate and the reaction beam to connect with a linear sliding guide rail. Vertical subsidence of the top.

(6) The present invention uses a pull rope displacement sensor to measure the horizontal displacement of the pile body, which has high precision and can directly reflect the horizontal displacement law of the entire pile body along the depth without affecting the stress on the pile body. This is the first time.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is the frame schematic diagram of pile foundation bearing characteristic model test device under the complex load action of the embodiment of the present invention;

Fig. 2 is the structural diagram of Fig. 1;

FIG. 3 is a side view of FIG. 1 .

Fig. 4 is a partial enlarged view of position A in Fig. 3;

In the figure 1. plexiglass plate, 2. channel steel, 3. vertical channel steel, 4. reaction beam, 5. linear sliding guide rail, 6. weight plate and weight, 7. steel wire rope, 8. pulley, 9. Drawstring displacement sensor, 10. Miniature laser displacement sensor data collector, 11. Pressure sensor data collector, 12. Pull rope displacement sensor data collector, 13. Vertical steel plate, 14. Place steel plate, 15. Range measuring panel, 16. Pile head protection ring, 17. Rubber pad, 18. Pressure sensor, 19. Jack, 20. Miniature laser displacement sensor, 21. Model pile, 22. Screw, 23. Angle steel, 24. Thin steel pipe.

detailed description

The model test device for pile foundation bearing characteristics under complex loads in this embodiment is shown in Figures 1 and 2, including a model tank, a horizontal loading system, a vertical loading system, and a loading device.

Wherein the model groove is made by organic glass plate 1, and adopts channel steel 2 to reinforce. The horizontal loading system is composed of pulley 8, weight plate and weight 6, and steel wire rope 7.

As shown in Figure 3 and Figure 4, the vertical loading system is composed of vertical channel steel 3, reaction beam 4, jack 19, and linear sliding guide rail 5, and the linear sliding guide rail 5 is fixed to the reaction beam by screws 22, It is fixed together with the steel plate 14 and the jack 19. The jack 19 applies a vertical load and can move horizontally along the linear sliding guide rail 5 to maintain the stability of the vertical loading direction, and the entire vertical loading system is detachable.

The measuring device includes a miniature laser displacement sensor 20 system for measuring the horizontal displacement of the pile head and pile top settlement, which has high precision, and the miniature laser displacement sensor 20 for measuring the settlement is connected to the reaction beam 4 through a linear sliding guide rail 5, which can be moved along with the pile The head moves horizontally to ensure that the measured data is the vertical settlement of the pile top; the measuring device also includes a cable displacement sensor 9 system for measuring the horizontal displacement of the pile body, which can accurately measure the pile without affecting the force of the pile soil. It is the first time in the existing similar inventions; the measuring device also includes resistance strain gauges and data acquisition instruments, earth pressure cells and frequency meters arranged according to the test needs; the test device also includes pile head protection rings 16, Small parts such as ranging panel 15, rubber pad 17.

The vertical steel plate 13 and the steel plate 14 are used to fix the miniature laser displacement sensor 20, wherein the miniature laser displacement sensor 20 for measuring the horizontal displacement of the pile head is installed under the reaction beam 4 through the vertical steel plate 13, and the miniature laser displacement sensor for measuring the settlement of the pile top. Laser displacement sensor 20 is fixed as a whole by screw 22 with placing steel plate 14 and linear sliding guide rail 5, jack 19.

The rope displacement sensor 9 system is composed of the rope displacement sensor 9, the data collector 12, the thin steel pipe 24, etc.; two rope displacement sensors are installed on the plexiglass plate 1 every 1/8 of the pile length from the top of the pile downwards 9, four in total, and then connect the stay rope to the model pile 21 after passing through the thin steel pipe 24, wherein the thin steel pipe 24 protects the stay rope from being affected by the soil.

It also includes pile head protection ring 16, ranging panel 15, rubber pad 17 and other small parts. The pile head protection ring 16 protects the pile head of the model pile 21 and serves as the horizontal stress point of the model pile 21. The distance measuring panel 15 is used for micro-laser displacement. The sensor 20 is echo ranging, and the rubber pad 17 is used to adjust the contact between the jack 19 and the pressure sensor 18 .

The test method using the above test device includes the following steps:

(1) Prepare materials for the test device. Prepare materials such as plexiglass plate, channel steel, steel plate, angle steel, and thin steel pipe before making, and prepare parts such as linear sliding guide rail 5, screw 22, pulley 8, jack 19, steel wire rope 7, weight plate and weight 6.

(2) Make a model slot. According to the size of the drawing, cut out the plexiglass plate 1, assemble the plexiglass plate 1 into a model groove; cut out the channel steel 2 according to the size of the drawing, and reinforce 3 rings of channel steel 2 around the model groove from bottom to top, and the same ring of channel steel 2 are welded and reinforced with angle steel 23; and according to the position marked on the drawings, holes are opened at the installation positions of four stay rope displacement sensors 9 on the model groove plexiglass plate 1.

(3) Make vertical channel steel 3 and reaction beam 4. According to the size of the drawing, cut out the channel steel of the calibrated size to make the vertical channel steel 3 and the reaction beam 4, and open the installation position of the reaction beam 4 on the vertical channel steel 3, the passing position of the steel wire rope 7, and the connection position of the model channel steel 2. Hole, vertical channel steel 4 installation positions, linear sliding guide rail 5 installation positions, vertical steel plate 13 installation positions are perforated on the reaction force beam 4.

(4) Make test device accessories. According to drawing size, cut out the thin steel pipe 24 of demarcated size, make ranging panel 15, pile head protection ring 16, vertical steel plate 13, place steel plate 14.

(5) Install pulley 8. According to the position marked on the drawing, the pulley 8 is installed on the channel steel 2 with the screw 22. The horizontal loading system is installed.

(6) Install the linear slide guide 5. According to the position marked on the drawing, the linear sliding guide rail 5 is installed on the reaction beam 4 with screws 22 .

(7) Install the jack 19 and place the steel plate 14. According to the position marked on the drawings, the linear sliding guide rail 5, the placing steel plate 14, and the jack 19 are fixed as a whole with screws 22. The vertical loading system is assembled.

(8) Install the vertical steel plate 13 of the miniature laser displacement sensor. According to the position marked on the drawing, the angle steel 23 is used as the connection part, and the vertical steel plate 13 is installed under the reaction beam 4 by using the screw 22 . The test equipment and accessories are ready.

(9) Preparation of test materials and test instruments. Before the test, prepare the test soil, model pile 21, pull rope displacement sensor 9 and data collector 12, micro laser displacement sensor 20 and data collector 10, pressure sensor 18 and data collector 11, and the resistance configured according to the test needs Strain gauge and data acquisition instrument, earth pressure cell and frequency meter; standard sand or clay can be selected for the test soil, wood, aluminum tube and other materials can be selected for the model pile 21, and the cross-section of the model pile 21 can be selected to be circular, square, circular, etc. different shapes.

(10) Selection of test loading scheme. Select the loading method, data collection standard and loading termination standard according to the "Technical Specifications for Building Foundation Pile Inspection" (JGJ106-2014), and estimate the horizontal bearing capacity and vertical bearing capacity of the model pile; select the corresponding loading scheme according to the different simulated working conditions , to simulate the force of the bridge pier, first apply the horizontal load to a certain level, and then apply the vertical load to failure; simulate the bearing characteristics of the pile foundation under the wind load of a tall building, first apply the vertical load to a certain level, then apply the horizontal load and vertical load Alternate grading is applied to pile foundation failure.

(11) Filling soil and embedding model piles 21. According to the needs of the test, fill the soil layer by layer. When filling to the pile bottom elevation, first fix the position of the model pile 21, then continue to fill the soil, and paste the resistance strain gauge and embed the earth pressure cell according to the test needs.

(12) Install the rope displacement sensor 9. When filling soil to the position of the stay cord displacement sensor 9 on the lowest floor, first fix the stay cord displacement sensor 9 on the notch of the plexiglass plate 1, and then pass the stay cord through the thin steel pipe 24 to be connected to the thin wire wound on the model pile 21, the thin wire The winding position should be on the same horizontal line as the wire outlet of the stay rope displacement sensor 9, and attention should be paid to keeping the thin steel pipe 24 level in the soil filling process; continue to fill the soil and install another 3 stay rope displacement sensors 9. Fill the soil to the calibrated mud surface and complete the filling.

(13) Install the vertical loading system. According to the position marked on the drawings, using the angle steel 23 as the connecting part, install the vertical channel steel 3 on the model channel steel 2 through the screw 22, and then install the assembled vertical loading system on the vertical channel steel through the screw 22 and the angle steel 23 3.

(14) Install the miniature laser displacement sensor 20 . Fix the miniature laser displacement sensor 20 on the vertical steel plate 13 and place the steel plate 14; among them, the two miniature laser displacement sensors 20 for measuring the settlement of the pile top should be symmetrically fixed on both sides of the model pile 21 along the horizontal force direction of the model pile 21, and pay attention to Keep vertical; 2 miniature laser displacement sensors 20 of measuring pile head horizontal displacement, two are on the same horizontal line with pile top, two are slightly higher than pile top, and note keeping level.

(15) Measuring instrument connection. Connect the miniature laser displacement sensor 20 to the data collector 10, connect the rope displacement sensor 9 to the data collector 12, connect the resistance strain gauge leads set according to the test needs to the data collector, and connect the earth pressure box to the frequency meter .

(16) Place the pile head protection ring 16 and the distance measuring panel 15. Put the prepared pile head protection ring 16 on the pile head of the model pile 21, with the leading part facing the pulley side; place the distance measuring panel 15 on the pile head protection ring 16, and pay attention to the corresponding position of the micro laser displacement sensor 20.

(17) Place the pressure sensor 18. The pressure sensor 18 is placed on the ranging panel 15 and connected to the data collector 11 .

(18) Adjust the vertical loading system. Place a rubber pad 17 on the pressure sensor 18 so that the pressure sensor 18 is evenly pressed, and adjust the jack 19 to make it just in contact with the rubber pad 17.

(19) Adjust the horizontal loading system. First steel wire rope 7 one end is connected weight plate 6, then steel wire rope 7 passes pulley 8 and passes vertical channel steel 3 apertures behind, is connected to pile head protection ring 16 leader, and adjustment pile head protection ring 16 makes wire rope 7 level.

(20) Load application and data collection. Carry out loading according to the selected loading scheme, and carry out data collection according to the selected data collection standard; when applying vertical load, collect the data of 2 miniature laser displacement sensors 20 for measuring pile top settlement; when applying horizontal load, collect the data of measuring pile The data of two miniature laser displacement sensors 20 for the horizontal displacement of the head are collected, the data of four stay rope displacement sensors 9 are collected, and the data of pile body resistance strain gauges and earth pressure cells set according to the needs of the test are collected.

(21) Data processing. The settlement of the pile top is obtained by averaging the data of the 2 miniature laser displacement sensors 20 on the pile top; the pile top rotation angle is calculated from the data of the 2 miniature laser displacement sensors 20 measuring the horizontal displacement of the pile head and the vertical distance of the installation position. Among them, the data of the miniature laser displacement sensor 20 of the lower floor is the horizontal displacement of the pile head; the deformation curve of the upper part of the pile body is obtained by fitting the data of the four stay rope displacement sensors 9; body bending moment; the soil pressure on the side of the pile is obtained from the measured data of the earth pressure cell set according to the test needs.

Claims (8)

1. pile foundation bearing characteristic model test device under a kind of complex load, comprise model groove, horizontal loading system, vertical loading system and measuring device, model pile is laid in the described model groove, it is characterized in that: The horizontal loading system includes a pulley, a weight and a steel wire rope, the steel wire rope connects the weight and the pile top of the model pile, the pulley is fixed on the outside of the model groove, and the steel wire rope is slidingly matched with the pulley; The vertical loading system includes a vertical channel steel, a reaction beam, a jack and a linear sliding guide rail, the vertical channel steel is fixedly connected with the model groove, the reaction force beam is fixed on the top of the vertical channel steel, and the linear sliding guide rail Installed on the reaction beam, the jack is slidingly matched with the linear sliding guide rail; The measuring device includes a miniature laser displacement sensor system and a stay rope displacement sensor system; The miniature laser displacement sensor system includes a first miniature laser displacement sensor for measuring the horizontal displacement of the pile head, and a second miniature laser displacement sensor for measuring the settlement of the pile top; the second miniature laser displacement sensor and the reaction beam Connected by linear sliding guide rail; The stay rope displacement sensor system is used to measure the horizontal displacement of the pile body, including a thin steel pipe arranged between the model pile and the inner wall of the model tank, a stay rope pierced in the thin steel pipe, and a drawstring fixed on the side wall of the tank body. Rope displacement sensor. 2. The model test device for pile foundation bearing characteristics under complex loads according to claim 1, characterized in that: the model groove is made of plexiglass plate, and a channel steel reinforcing hoop is provided outside the model groove. 3. pile foundation bearing characteristic model test device under complex load according to claim 1, it is characterized in that: described vertical channel steel, reaction beam, jack and linear sliding guide rail are detachably connected by screw, and described jack There is a placing steel plate between the linear sliding guide rail, the placing steel plate is slidingly matched with the linear sliding guide rail, the jack and the second miniature laser displacement sensor are installed on the placing steel plate through screws; the second miniature laser displacement sensor is two One, symmetrically fixed on both sides of the model pile along the horizontal stress direction of the model pile, and kept vertical. 4. The pile foundation bearing characteristic model test device under complex load according to claim 1, is characterized in that: the vertical steel plate is fixedly installed under the reaction beam, and the pile top is equipped with a rangefinder for echo rangefinder panel, the first miniature laser displacement sensor is installed on the vertical steel plate and points to the distance measuring panel; there are two first miniature laser displacement sensors, one of which is at the same level as the top of the pile, and the other is slightly higher than Pile top and keep it level. 5. The pile foundation bearing characteristic model test device under complex load according to claim 1, is characterized in that: described stay rope displacement transducer is installed with four from the top of the pile downwards on the side wall of the model groove, wherein adjacent The distance between the two stay-rope displacement sensors is 1/8 of the pile length. 6. pile foundation bearing characteristic model test device under complex load according to claim 1, it is characterized in that: described pile top is installed with pile head protective ring, pressure sensor and rubber pad successively, and described pile head protective ring is used for In order to protect the pile head of the model pile and serve as the horizontal stress point of the model pile, the rubber pad is used to adjust the contact between the jack and the pressure sensor. 7. adopt the test method of pile foundation bearing characteristic model test device under the complicated load action of claim 1, it is characterized in that comprising the following steps: (1) Preparation materials for the test device: plexiglass plate, channel steel, steel plate, angle steel, thin steel pipe, linear sliding guide rail, screw, pulley, jack, wire rope, weight plate and weight; (2) Make the model tank, assemble the plexiglass plate into the model tank, reinforce three rings of channel steel from bottom to top around the model tank, and weld and reinforce the same ring of channel steel with angle steel; Open holes for the installation positions of the four pull-cord displacement sensors on the plexiglass plate; (3) Make components, make reaction beams, vertical channel steel, vertical steel plates, place steel plates, distance measuring panels, pile head protection rings and thin steel pipes of calibrated sizes, install the reaction beams on the vertical channel steel, and wire ropes Holes are opened at the pass position and the connection position of the channel steel of the model, and holes are opened at the installation position of the vertical channel steel on the reaction beam, the installation position of the linear sliding guide rail, and the installation position of the vertical steel plate; (4) Install the pulley, use screws to install the pulley on the channel steel on the edge of the model tank, and the horizontal loading system is installed; (5) Assemble the vertical loading system, first install the linear sliding guide rail on the reaction beam with screws, then use screws to fix the linear sliding guide rail, place the steel plate, and the jack as a whole, and finally install the miniature laser displacement sensor for measuring the horizontal displacement of the pile head The vertical steel plate is installed under the reaction beam through screws and angle steel; the assembly of the model test device is completed; (6) Preparation of test materials and test instruments, preparation of test soil, model piles, rope displacement sensors and their data collectors, micro laser displacement sensors and their data collectors, pressure sensors and their data collectors, and Equipped with resistance strain gauge and data acquisition instrument, earth pressure cell and frequency instrument; (7) Select the test loading scheme, select the loading method, data collection standard and loading termination standard according to the "Technical Specifications for Building Foundation Pile Inspection" (JGJ106-2014), and estimate the horizontal bearing capacity and vertical bearing capacity of the model pile; according to the simulation Select the corresponding loading scheme for different working conditions, simulate the force of the bridge pier, first apply the horizontal load to a certain level, and then apply the vertical load to failure; simulate the bearing characteristics of the pile foundation under the wind load of a high-rise building, first apply the vertical load to a certain level , then the horizontal load and vertical load are alternately applied in grades until the pile foundation is destroyed; (8) Fill soil and embed model piles. Fill soil in layers according to the test requirements. When filling to the pile bottom elevation, first fix the position of the model piles, then continue to fill soil, and paste resistance strain gauges and embed earth pressure cells according to the test requirements. ; (9) Install the stay rope displacement sensor. When filling the soil to the installation position of the stay rope displacement sensor at the bottom layer, first fix the stay rope displacement sensor on the plexiglass plate, and then connect the stay rope through the thin steel pipe to the thin wire wound on the model pile , the winding position of the thin wire should be at the same level as the wire outlet of the pull rope displacement sensor. During the filling process, pay attention to keep the thin steel pipe level; continue to fill the soil and install the other three pull rope displacement sensors, fill the soil to the calibrated mud surface, complete; (10) Install the vertical loading system, using angle steel as the connecting part, install the vertical channel steel on the model channel steel through screws, and then install the assembled vertical loading system on the top of the vertical channel steel through screws and angle steel ; (11) Install the miniature laser displacement sensor, fix the first and second miniature laser displacement sensors on the vertical steel plate and the placement steel plate respectively; there are two second miniature laser displacement sensors, which are symmetrically fixed along the horizontal force direction of the model pile On both sides of the model pile, and kept vertical; the first miniature laser displacement sensor is two, one of which is at the same level as the top of the pile, and the other is slightly higher than the top of the pile, and kept horizontal; (12) Measuring instrument connection, connect the miniature laser displacement sensor to the data collector, connect the pull rope displacement sensor to the data collector, connect the resistance strain gauge leads set according to the test needs to the data collector, and connect the earth pressure box to the data collector. frequency meter; (13) Place the pile head protection ring, distance measuring panel and pressure sensor, put the prepared pile head protection ring on the pile head of the model pile, and the leader part faces the pulley side; place the distance measuring panel on the pile head protection ring , pay attention to the position of the corresponding miniature laser displacement sensor; place the pressure sensor on the ranging panel and connect it to the data collector; (14) Install and adjust the loading device, place a rubber pad on the pressure sensor, adjust the jack to make it just in contact with the rubber pad; connect one end of the wire rope to the weight plate, and then pass the wire rope through the pulley through the vertical channel steel hole, Connect to the leader of the pile head protection ring, and adjust the pile head protection ring to make the wire rope level; (15) Load application and data collection are carried out according to the selected loading scheme, and data collection is carried out according to the selected data collection standard; when vertical load is applied, the data of two miniature laser displacement sensors used to measure the settlement of the pile top are collected; When applying a horizontal load, collect the data of two micro-laser displacement sensors for measuring the horizontal displacement of the pile head, collect the data of four pull-cord displacement sensors, and collect the data of the pile body resistance strain gauge and earth pressure cell set according to the test requirements; (16) Data processing, the pile top settlement is obtained by averaging the data of the two second micro laser displacement sensors; the pile top rotation angle is calculated from the horizontal displacement data of the two first micro laser displacement sensors and the vertical distance of the installation position , in which the data of the miniature laser displacement sensor in the lower layer is the horizontal displacement of the pile head; the deformation curve of the upper part of the pile body is obtained by fitting the data of the four pull-cord displacement sensors; the bending moment of the pile body is obtained from the data measured by the resistance strain gauge of the pile body. The soil pressure on the side of the pile is obtained from the data measured by the earth pressure box. 8. The test method of the pile foundation bearing characteristic model test device under complex load according to claim 7, characterized in that: the test soil prepared in the step (6) is standard sand or clay, and the model pile It is a wooden pile or an aluminum pipe pile, and the section of the model pile is circular, square or circular.