CN112362813B - Root system drawing test system and method based on PIV technology - Google Patents

Abstract

The invention discloses a root system pulling test system and method based on PIV technology. The system includes a pressure chamber, a confining pressure control device, a suction force control device, a root system pulling device and a PIV test device. The whole pressure chamber is in the shape of a semi-cylindrical body. Sealed structure, its side is transparent, and a semi-cylindrical sample is placed in the pressure chamber, and the vertical side of the sample contains a plant root system split from the center along the vertical direction; confining pressure control device and pressure chamber Two-way communication is used to adjust the confining pressure, the suction control device is connected to the pressure chamber to adjust the substrate suction, the root pulling device is set above the sample, and the PIV test device is located directly in front of the transparent side of the pressure chamber to measure soil particles and plants. Root trajectory and velocity. The method adopts the root pull-out test system based on PIV technology to realize the pull-out characteristic parameters of roots of different ages in root-containing soil under the action of different confining pressures and matrix suction.

Description

Root Pulling Test System and Method Based on PIV Technology

technical field

The invention belongs to the field of geotechnical test equipment in the civil engineering industry, and relates to a root system pulling test system and method based on PIV technology.

Background technique

In recent years, my country has made breakthroughs in the construction of transportation infrastructure such as roads and railways, and countless artificial slopes have been formed all over the country. Its effective protection is an important part of the current geological disaster prevention and control. As a measure that can significantly improve the strength of shallow soil, plant ecological protection is widely used in soil slope protection, and its mechanism is mainly due to the mechanical soil-fixing effect of plant roots. Plant roots are intertwined in the soil, and together with the soil, they form a root-soil composite material. When the soil is deformed under the action of external force, the tension of the root system will limit the deformation of the soil, thereby improving the shear strength of the soil. In practical engineering, when the shallow soil of the slope slides, some of the roots are broken due to reaching the tensile strength, and some are pulled out instead of being broken, causing the surrounding soil to loosen. Reduce soil strength and slope stability. Therefore, it is of great significance to study the anti-pulling properties of plant roots.

At present, although the single root pullout resistance of some plants has been reported in the literature, the pullout resistance of the root system when the root system interacts with the soil is rarely analyzed, and the damage to nearby roots when the root system is broken or pulled out is rarely analyzed. The degree and scope of soil disturbance is mainly due to the lack of instruments and equipment for carrying out research in this area. Existing test methods such as single root pull test and direct shear test have many difficulties and problems in determining the pull-out resistance of plant roots, mainly including:

1. Almost all root-containing soils are unsaturated, and plant growth will absorb water in the soil, thereby reducing soil pore water pressure and increasing matrix suction. The existence of matrix suction will significantly change the strength and deformation characteristics of soil, making it completely different from conventional saturated soil. Correspondingly, the properties of the root-soil interface also changed significantly. However, existing instruments cannot consider the influence of substrate suction when measuring the pullout resistance of roots.

2. Due to the different natural environment, the confining pressure of the soil body is different, resulting in different degree of tightness of the soil body, so the interaction force between the plant root system and the soil body is also different. Obviously, this will further affect the pull-out resistance of plant roots. However, the existing instruments cannot precisely control the confining pressure of the soil when conducting the pullout test, so the influence of the confining pressure on the pullout characteristics of the root system cannot be considered.

3. When the subgrade slope is protected by plants, in extreme cases, if the shallow soil of the slope slides under the action of external loads, many plant roots will be pulled out to the outside of the slope, which will inevitably affect the surrounding soil. Therefore, the stability of the deep soil mass of the slope is affected. However, the existing instruments cannot accurately measure the slip deformation of plant roots in the soil and the degree and scope of disturbance to the surrounding soil.

In summary, in order to accurately determine the pull-out characteristics (tensile strength, pull-out resistance and root-soil interface friction coefficient) of a single root at different ages in root-containing soil under different confining pressures and matrix suction, and root systems at different ages The pull-out characteristics (tensile strength of main root and root pull-out resistance) are analyzed, and the deformation and movement trajectory of soil, single root or root system of soil, single root or root system during the pulling process are analyzed, and the disturbance range of soil mass caused by single root or root system slip is discussed. , revealing the relevant mechanism, it is very necessary to develop a new type of plant root pulling test system.

SUMMARY OF THE INVENTION

The purpose of the embodiments of the present invention is to provide a root pulling test system and method based on PIV technology, so as to solve the problem that the existing instruments cannot consider the influence of matrix suction and confining pressure on the root pulling characteristics when measuring the anti-pulling characteristics of roots. However, existing instruments cannot accurately measure the slip deformation of plant roots in the soil and the degree and scope of disturbance to the surrounding soil.

The technical solution adopted in the embodiment of the present invention is: a root system pulling test system based on PIV technology, including a pressure chamber, a confining pressure control device, a suction control device, a root system pulling device, a PIV test device and a data acquisition system; the overall pressure chamber It is a semi-cylindrical sealing structure, the side of which is transparent, and a semi-cylindrical sample is placed in the pressure chamber. The vertical side of the sample contains a plant root system that is split from the center in the vertical direction. The top of the root system is exposed on the top of the sample; the confining pressure control device is in two-way communication with the pressure chamber to adjust the confining pressure of the sample in the pressure chamber; the suction control device is in two-way communication with the pressure chamber to perform matrix control on the sample in the pressure chamber. Suction adjustment; the root system pulling device is arranged above the sample to exert pulling force on the plant root system; the PIV testing device is arranged in front of the transparent side of the pressure chamber, and the movement trajectory of soil particles and plant roots is affected. and the rate are measured and recorded; the data acquisition system is electrically connected to the confining pressure control device, the suction control device, and the PIV test device in both directions, and is electrically connected to the signal output end of the root pulling device;

The pressure chamber includes a steel bottom plate, a plexiglass side wall, and a steel top cover. The steel top cover, the plexiglass side wall, and the steel bottom plate are sequentially connected from top to bottom to form a semi-cylindrical sealed space. Inside the semi-cylindrical sealed space, and the plexiglass sidewall is vertically arranged on the side periphery of the sample, the top of the plexiglass sidewall is sealed with the bottom surface of the steel top cover, and the bottom of the plexiglass sidewall is connected to the top surface of the steel bottom plate. sealed connection;

The middle area of the upper surface of the steel base plate is provided with a funnel-shaped drainage groove, a terracotta plate is fixed on the top of the drainage groove, and the sample is placed on the terracotta plate;

One side of the steel base plate is provided with a water inlet and outlet pipe interface with water inlet and outlet pipe valves, a confining pressure water pipe interface with a confining pressure water pipe valve and a back pressure water pipe interface with a back pressure water pipe valve, and one end of the water inlet and outlet pipe interface and the confining pressure water pipe interface It is communicated with the interior of the pressure chamber, and the other end of the inlet and outlet water pipe interface and the confining pressure water pipe interface is communicated with the confining pressure control device;

Further, the top of the pressure chamber, that is, the steel top cover, is provided with an exhaust hole communicating with the interior of the pressure chamber and the periphery of the sample, and the exhaust hole is provided with an exhaust screw threadedly connected with it; the curve of the sample is provided. The side is wrapped with a latex film that seals it;

The confining pressure control device includes a confining pressure water pipe, a confining pressure controller, an inlet and outlet water pipe, a water tank and a water pump. The pressure water pipe is communicated with the confining pressure water pipe interface of the pressure chamber;

The confining pressure controller is in bidirectional communication with the data acquisition system.

Further, the top of the pressure chamber, that is, the steel top cover, is provided with an air inlet pipe interface communicating with the interior of the pressure chamber, and the air inlet pipe interface is arranged above the sample;

The suction control device includes a back pressure controller, an air compressor, a filter, a dryer, an air pressure controller, a safety tank, a back pressure water pipe and an air intake pipe. The back pressure controller passes through the back pressure water pipe and the back pressure water pipe of the pressure chamber. The interface is connected, one end of the intake pipe is connected to the interface of the intake pipe at the top of the pressure chamber, and the other end is connected to the air compressor through the safety tank, the air pressure controller, the dryer and the filter in turn;

The back pressure controller and the air pressure controller are respectively in bidirectional communication with the data acquisition system.

Further, the steel top cover is provided with a convex cavity corresponding to the upper and lower sides of the sample, the top of the convex cavity is provided with a hole for the lower end of the root pulling device to protrude, and a second sealing ring is arranged around the hole; the sample A plurality of porous annular spacers nested in sequence are arranged on the upper part, and a metal gasket is arranged between the porous annular spacer and the steel top cover;

The root system pulling device includes a horizontal clamping device and a vertical pulling device. The lower end of the vertical pulling device extends into the pressure chamber through the hole at the top of the convex cavity of the steel top cover, and the horizontal clamping device is arranged on the steel top cover. The horizontal clamping device is fixed on the lower end of the vertical pulling device, and the vertical pulling device can drive the horizontal clamping device to move vertically downward in the pressure chamber.

Further, the vertical pulling device includes a pulling machine, a beam, a bracket, a base and a pulling rod, the base and the beam are fixedly connected through the bracket, the pressure chamber is fixed on the base, and the telescopic rod of the pulling machine is arranged on the beam; The top of the pulling rod passes through the beam and is fixedly connected with the bottom end of the telescopic rod of the tensile machine. The bottom of the pulling rod extends into the pressure chamber through the hole at the top of the convex cavity of the steel top cover and is connected with the horizontal clamping device; the telescopic rod of the tensile machine is connected to the horizontal clamping device. A tension sensor is fixed between the pulling rods, and a displacement sensor is vertically fixed at the bottom of the beam; the pulling rod is composed of a clamping device fixing rod and a pulling telescopic rod, and the top of the pulling extension rod is detachably connected to the bottom of the clamping device fixing rod ;A displacement measuring rod is fixed on the pull-out telescopic rod, and the pointer head of the displacement sensor contacts the displacement measuring rod;

The horizontal clamping device includes a motor, a threaded rod, a connecting rod, a rubber pad, a clip, a clip fixing rod and a horizontal force sensor, the motor is a bidirectional synchronous motor, and two output shafts of the motor are respectively connected with a threaded rod, Each threaded rod is threadedly connected with a nut seat, and the bottom of each nut seat is fixedly connected to a horizontally placed clip fixing rod through a connecting rod. The ends close to each other are movably connected with clips, and the clip fixing rod can slide along the inside of the clip under the driving of the threaded rod, and the clip fixing rod will slide to the end inside the clip and will be under the action of the threaded rod. Drive the clips to move together toward or away from the root system of the plant; a horizontal force sensor is fixed inside the clip, and one end of the clip fixing rod inside the clip is in contact with the horizontal force sensor embedded in the clip; the clip is connected to the plant The root contact surface is close to the rubber pad;

The lower end of the pulling telescopic rod is detachably connected with the motor, and the horizontal clamping device is fixed on the lower end of the vertical pulling device;

The signal output ends of the horizontal force sensor, the tensile force sensor and the displacement sensor are all electrically connected with the data acquisition system.

Further, the PIV test device includes a rectangular test cavity, a synchronizer, a laser power supply, a laser, a laser head, a CCD camera, an LED lamp and a PIV connecting line, and the rectangular test cavity and the pressure chamber are fixed in the vertical direction of the root system pulling device. On the base of the drawing device, the rectangular test chamber is located directly in front of the pressure chamber, and the rectangular test chamber is formed by a rectangular steel top plate, a rectangular steel bottom plate, three rectangular steel side walls and the transparent sides of the pressure chamber. Space; the laser head is installed in the lower part of the transparent side of the pressure chamber, the laser head is electrically connected to the output end of the laser, and the laser power supply is electrically connected to the power supply end of the laser; the transparent side of the rectangular test cavity is connected to the pressure chamber A CCD camera is fixed at the inner center of the oppositely arranged steel side wall. The synchronizer is connected to the CCD camera and the laser power supply. The synchronizer is bidirectionally connected to the computer of the data acquisition system through the PIV cable; One LED light is set in each direction;

The data acquisition system includes a computer and a data acquisition box; the input end of the data acquisition box is respectively connected to the confining pressure controller of the confining pressure control device, the back pressure controller and the air pressure controller of the suction control device, and the level of the root pulling device. The signal output ends of the force sensor, tension sensor and displacement sensor are electrically connected, and the output end of the data acquisition box and the signal input ends of the confining pressure controller, the back pressure controller and the air pressure controller are all electrically connected to the computer; the PIV The CCD camera of the test device is bidirectionally connected to the computer.

Further, the plexiglass side wall is formed by sealing the curved plexiglass side wall and the flat plexiglass side wall, wherein the curved plexiglass side wall is arranged on the periphery of the curved side of the sample, and the flat plexiglass side wall is arranged Directly in front of the vertical side of the sample, the curved plexiglass side wall and the flat plexiglass side wall are respectively sealed with the top surface of the steel bottom plate and the bottom surface of the steel top cover;

The latex film is rectangular when it is flattened, its width is the same as the height of the sample, and its length is greater than the length of the bottom side of the curved side of the sample; the extra part on both sides of the latex film wrapping the sample is along the side of the flat plexiglass. The wall is unfolded away from the sample, and is fixed and compacted on the side wall of the flat plexiglass by the plexiglass fixing plate, so that the latex film seals the sample; the plexiglass fixing plate is located between the steel bottom plate and the steel top cover and is Removable connection with steel bottom plate and steel top cover;

A plurality of support pipes are arranged on the periphery of the side walls of the curved plexiglass, the steel top cover and the support pipes are provided with reserved holes vertically passing through them, and the top surface of the steel bottom plate is provided with a steel top cover. The reserved holes correspond to the threaded holes one by one. The steel top cover and the steel bottom plate are connected by screws. The screws pass through the steel top cover and the reserved holes on the support tube from top to bottom in turn and connect with the steel bottom plate. Threaded hole screw connection.

Another technical scheme adopted in the embodiment of the present invention is: the root system pulling test method based on PIV technology, adopts the described root system pulling test system based on PIV technology, and carries out according to the following steps:

Step S1, sample preparation: first lay 50~60mm thick test soil in the test box, put the plant seeds to be tested into the center of the test box, then fill the test box with the test soil, and then water regularly to cultivate; When the growth reaches the level required for the test, remove the flowers, stems, and leaves of the plants above the soil surface, and keep only the root system, and then use a cylindrical mold to take the root system as the center; after demoulding, cut the cylindrical sample vertically along the center of the root system into half. Cylinder, prepare the sample containing root system required for the test;

Step S2, sample installation: use degassed distilled water to completely saturate the clay plate on the steel bottom plate of the pressure chamber, and then put the root-containing sample into the pressure chamber so that the vertical side and the pressure chamber are transparent. Then, wrap the latex film on the side of the sample to seal the sample; then place an appropriate number of porous annular spacers on the upper part of the sample to control the raised area of the top of the sample during the root pulling process; A metal gasket is placed on the annular spacer, and the root system of the plant to be tested is pierced 2-3cm from the center of the porous annular spacer and the metal spacer;

Step S3, installation of root pulling device: insert the lower end of the pulling telescopic rod of the vertical pulling device of the root pulling device into the hole at the top of the convex cavity of the steel top cover, and then insert the horizontal clamping device of the root pulling device The motor is fixed on the lower end of the pulling and retracting rod; finally, the steel top cover is installed, and the screw is threaded through the steel top cover and the reserved holes on the support pipe and then connected with the threaded holes on the steel bottom plate, and the support pipe is located in the steel top cover. Between the top cover and the steel bottom plate, and the periphery of the plexiglass side wall;

Step S4, equipment startup: connect the computer of the data acquisition system, the data acquisition box, the confining pressure controller of the confining pressure control device, and the power supply of the back pressure controller and the air pressure controller of the suction control device and start up;

Step S5, root system clamping: turn on the pulling machine of the vertical pulling device, drive the pulling extension rod to move downward through the downward movement of the telescopic rod of the hydraulic control pulling machine, and the pulling extension rod drives the horizontal clamping device to move down to The clip is aligned with the part of the plant root system to be tested that protrudes from the metal gasket, and then the tension machine is turned off; the horizontal force sensor of the horizontal clamping device is reset to zero, and then the motor is turned on. The motor rotates and passes through the two threaded rods and the upper The nut seat drives the two clip fixing rods to approach the root system of the plant to be measured through the connecting rod. At the same time, the reading of the horizontal force sensor is observed in real time during this process, and the rubber pads on the two clips clamp the plant to be measured. When the root system is turned off, the motor is turned off, and the indication of the horizontal force sensor at this time is recorded, which is the horizontal clamping force;

Step S6, applying confining pressure: loosen the exhaust screw in the exhaust hole on the steel top cover, open the valve of the water inlet and outlet, and pump the distilled water in the water tank through the water inlet and outlet pipes into the pressure chamber through the water pump of the confining pressure control device. , when the distilled water inside the pressure chamber slowly flows out from the exhaust hole, tighten the exhaust screw and close the valve of the inlet and outlet water pipes; clear the reading of the confining pressure controller to zero, then open the valve of the confining pressure water pipe, and set the test requirements through the confining pressure controller. The applied confining pressure value, real-time observation of back pressure volume change data to judge whether the consolidation of the sample is completed;

Step S7, apply suction: after the confining pressure value reaches the set value and stabilizes, clear the readings of the back pressure controller and air pressure controller of the suction control device to zero, then open the back pressure water pipe valve and the intake pipe valve, and open the suction control device The required back pressure value and air pressure value are set by the back pressure controller and the air pressure controller respectively, and the back pressure volume change is collected in real time through the data acquisition box of the data acquisition system, and the back pressure volume change data is observed in real time to judge. Whether the suction is balanced;

Step S8, turn on the PIV: after the suction is balanced, the computer of the data acquisition system controls the synchronizer of the PIV test device to make the laser power supply work synchronously with the CCD camera, and the laser emits laser light in the transparent side of the pressure chamber through the laser head, and turns on LED light, start to record the movement direction and speed of the plant roots and soil particles to be tested;

Step S9, root system pulling: turn on the motor, and apply the set horizontal clamping force to the root system of the plant to be measured through the horizontal clamping device; then clear the tension sensor and the displacement sensor of the vertical pulling device, and then turn on the tension machine , so that the pulling machine drives the pulling and retracting rod to move at a uniform rate and exerts upward pulling force on the root system of the plant to be tested. be pulled off;

Step S10, system reset: turn on the motor and the tension machine in turn, reset the horizontal clamping device and the pulling and retractable rod, stop the PIV test device, adjust the air pressure and back pressure to zero through the air pressure controller and the back pressure controller, and pass the The confining pressure controller adjusts the confining pressure to zero; then close the back pressure water pipe valve, the intake pipe valve and the confining pressure water pipe valve, open the inlet and outlet water pipe valves and exhaust screws, discharge the water inside the pressure chamber through the inlet and outlet water pipes, and finally open it again The steel top cover of the pressure chamber is removed from the sample;

Step S11 , analyzing and processing the test data through a computer to obtain the characteristic parameters of the pull-out resistance of the roots of different ages in the root-containing soil under the action of different confining pressures and matrix suction.

Further, prepare the sample containing the single root to be tested according to the following method: measure the diameter of the single root to be tested, configure the cylinder sample with the required moisture content according to the requirements of the test plan, and place the sample to be tested in the center of the cylinder sample. Measure a single root, after demoulding, cut the cylindrical sample into a semi-cylinder along the center of the single root to be tested, and prepare the required sample containing the single root to be tested;

Then repeat steps S2 to S10 for the sample containing the single root to be tested, and repeat the test data obtained from steps S2 to S10 for the sample containing the single root to be tested through computer analysis to obtain the root-containing system under different confining pressures and matrix suction. The anti-pullout parameters of the single root in the soil of different ages are expected to be measured, and the root pull-out test of the single root to be tested in the root-containing soil of different ages under the action of different confining pressures and matrix suction is completed.

The beneficial effects of the embodiments of the present invention are:

1. The embodiment of the present invention adopts the axis translation technology to control the substrate suction, so as to consider the influence of different substrate suctions on the pull-out resistance of plant roots in unsaturated soils, thereby truly simulating the dry and wet conditions of natural soils and restoring plant roots as much as possible. It is in the natural environment, which solves the problem that the existing instruments cannot consider the influence of matrix suction on the root pulling characteristics when measuring the anti-pulling characteristics of roots;

2. In the embodiment of the present invention, distilled water is used as the medium, and different levels of confining pressure are applied on the outside of the sample wrapped by the latex film through the pressure controller to simulate the lateral pressure and stress history of the soil body, and then study the soil mass under different confining pressure conditions. The pull-out resistance of single root and root system solves the problem that the influence of confining pressure on root pull-out characteristics cannot be considered when measuring the pull-out resistance of root system by existing instruments;

3. In the embodiment of the present invention, particle image velocimetry (PIV) is used to measure the movement direction and speed of soil particles and plant roots in real time during the pull-out test, so as to explore the degree and scope of disturbance to nearby soil by single root and root pull-out , and reveal the relevant mechanism, which solves the problem that the existing instruments cannot accurately measure the slip deformation of the plant root system in the soil and the degree and scope of the disturbance to the surrounding soil.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

FIG. 1 is a structural diagram of a root pulling test system based on PIV technology according to an embodiment of the present invention (the PIV test device is not shown).

FIG. 2 is a partial structural diagram of a root pulling test system based on PIV technology according to an embodiment of the present invention.

3 is a structural diagram of a pressure chamber of a root pulling test system based on the PIV technology according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of a confining pressure control device of a root system pulling test system based on PIV technology according to an embodiment of the present invention.

5 is a schematic diagram of a suction control device of a root pulling test system based on PIV technology according to an embodiment of the present invention.

6 is a schematic diagram of a vertical pulling device of a root system pulling test system based on the PIV technology according to an embodiment of the present invention.

7 is a schematic diagram of a horizontal clamping device of a root system pulling test system based on the PIV technology according to an embodiment of the present invention.

8 is a structural diagram of a PIV test device of a root pulling test system based on PIV technology according to an embodiment of the present invention.

FIG. 9 is a schematic diagram of a data acquisition system of a root pulling test system based on PIV technology according to an embodiment of the present invention.

In the figure, 1. Pressure chamber, 2. Confining pressure control device, 3. Suction control device, 4. Root pulling device, 5. PIV test device, 6. Data acquisition system, 7. Steel base plate, 8. Plexiglass Side wall, 9. Steel top cover, 10. Support tube, 11. Screw, 12. Sample, 13. Latex film, 14. Plexiglass fixing plate, 15. Clay plate, 16. Porous annular spacer, 17. Metal gasket, 18. Inlet and outlet water pipe interface, 19. Confining pressure water pipe interface, 20. Back pressure water pipe interface, 21. Water pump, 22. Drainage groove, 23. Curved plexiglass side wall, 24. Flat plexiglass side wall, 25. Drawing rod, 26. Intake pipe interface, 27. Exhaust hole, 28. Second sealing ring, 29. Exhaust screw, 30. Plant root system, 31. Confining pressure water pipe, 32. Confining pressure controller, 33 .Inlet and outlet pipes, 34. Water tank, 35. Back pressure controller, 36. Air compressor, 37. Filter, 38. Dryer, 39. Air pressure controller, 40. Safety tank, 41. Back pressure water pipe, 42 .Intake pipe, 43. Horizontal clamping device, 44. Vertical pulling device, 45. Motor, 46. Threaded rod, 47. Connecting rod, 48. Rubber pad, 49. Clip, 50. Clip fixing rod , 51. Horizontal force sensor, 52. Tension machine, 53. Beam, 54. Bracket, 55. Base, 56. Tension sensor, 57. Displacement sensor, 58. Displacement measuring rod, 59. Clamping device fixing rod, 60. Pull out telescopic rod, 61. Rectangular test cavity, 62. Synchronizer, 63. Laser power supply, 64. Laser, 65. Laser head, 66. CCD camera, 67. LED light, 68. PIV cable, 69. Computer, 70. Data acquisition box, 71. In and out water pipe valve, 72. Confining pressure water pipe valve, 73. Back pressure water pipe valve, 74. Intake pipe valve.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

An embodiment of the present invention provides a root pulling test system based on PIV technology, as shown in Figures 1-2, including a pressure chamber 1, a confining pressure control device 2, a suction control device 3, a root pulling device 4, and a PIV test device 5 and the data acquisition system 6; the pressure chamber 1 is a semi-cylindrical sealed structure as a whole, and its side is transparent, and a semi-cylindrical sample 12 is placed in the pressure chamber 1, and the vertical side of the sample 12 contains A plant root system 30 split vertically from the center. And the top of the plant root system 30 is exposed on the top of the sample 12; the confining pressure control device 2 is in bidirectional communication with the pressure chamber 1 to adjust the confining pressure of the sample 12 in the pressure chamber 1; the suction control device 3 is connected to the pressure chamber 1 two-way communication, the substrate suction of the sample 12 in the pressure chamber 1 is adjusted; the root system pulling device 4 is arranged on the top of the sample 12, and a pulling force is applied to the plant root system 30; the PIV testing device 5 is provided In front of the transparent side of the pressure chamber 1, the movement trajectory and speed of soil particles and plant roots 30 are measured and recorded; the data acquisition system 6, the confining pressure control device 2, the suction control device 3, the PIV test device 5 is electrically connected in both directions, and is electrically connected with the signal output end of the root pulling device 4 .

The pressure chamber 1 is the main generating device for the root pull test, as shown in Figures 2 to 3, including a steel bottom plate 7, a plexiglass side wall 8, a steel top cover 9 and a sample 12, a steel top cover 9, organic glass The glass side wall 8 and the steel bottom plate 7 are sequentially fixed and connected from top to bottom to form a semi-cylindrical sealed space. On the side periphery, the top of the plexiglass side wall 8 is sealed with the bottom surface of the steel top cover 9 , and the bottom of the plexiglass side wall 8 is sealed with the top surface of the steel bottom plate 7 .

As shown in FIG. 2 , the plexiglass sidewall 8 is formed by sealingly connecting the curved plexiglass sidewall 23 and the flat plexiglass sidewall 24, wherein the curved plexiglass sidewall 23 is arranged on the periphery of the curved side of the sample 12, The flat plexiglass side wall 24 is arranged directly in front of the vertical side of the sample 12, and the curved plexiglass side wall 23 and the flat plexiglass side wall 24 are sealed with the top surface of the steel bottom plate 7 and the bottom surface of the steel top cover 9 respectively. connect.

Specifically, the top surface of the steel bottom plate 7 and the bottom surface of the steel top cover 9 are vertically correspondingly provided with grooves for fixing the plexiglass side wall 8, and the bottom of the plexiglass side wall 8 is embedded in the top surface of the steel bottom plate 7. in the groove for fixing the plexiglass side wall 8, and seal the connection with glass glue to prevent water leakage; the top of the plexiglass side wall 8 is embedded in the groove on the bottom surface of the steel top cover 9 for fixing the plexiglass side wall 8, and the two They are sealed and connected by a first sealing ring located in the groove on the bottom surface of the steel top cover 9 . The curved plexiglass side wall 23 and the flat plexiglass side wall 24 are sealed and connected by embedding and then adding glass glue. Font shape, the connecting part of the flat plexiglass side wall 24 and the curved plexiglass side wall 23 is correspondingly designed into a concave shape, the flat plexiglass side wall 24 and the curved plexiglass side wall 23 are embedded through the combination of concave and convex parts, and after embedding, inside and outside the seam All sealed with glass glue.

A plurality of support tubes 10 are arranged on the periphery of the curved plexiglass side wall 23, the steel top cover 9 and the support tubes 10 are provided with reserved holes vertically passing through them, and the top surface of the steel bottom plate 7 is provided with The reserved holes on the steel top cover 9 correspond to the threaded holes one by one. The steel top cover 9 and the steel bottom plate 7 are connected by a screw 11, and the screw 11 passes through the steel top cover 9 and the support tube 10 in sequence from top to bottom. The reserved holes on the steel base plate 7 are then threadedly connected to the threaded holes on the steel base plate 7 . Since a large water pressure needs to be applied to the pressure chamber 1 during the test, the pressure chamber 1 must bear a large pressure, and the support tube 10 plays a supporting role to protect the plexiglass side wall 8 . Secondly, compared with the side wall of the pressure chamber 1, the steel top cover 9 and the steel bottom plate 7 of the pressure chamber 1 also need to play the role of sealing the pressure chamber 1 up and down, so they are fixed by the screw 11.

A funnel-shaped drainage groove 22 is arranged in the middle area of the upper surface of the steel bottom plate 7 , the top of the drainage groove 22 is fixed with a clay plate 15 , and the sample 12 is placed on the clay plate 15 . One side of the steel base plate 7 is provided with a water inlet and outlet pipe interface 18 with a water inlet and outlet pipe valve 71, a confining pressure water pipe interface 19 with a confining pressure water pipe valve 72 and a back pressure water pipe interface 20 with a back pressure water pipe valve 73; One end of the confining pressure water pipe interface 19 is communicated with the inside of the pressure chamber 1, the other end of the inlet and outlet water pipe interface 18 and the confining pressure water pipe interface 19 is communicated with the confining pressure control device 2; The other end communicates with the suction control device 3 .

The curved side of the sample 12 is wrapped with a latex film 13, and the latex film 13 is rectangular when it is flattened, its width is the same as the height of the sample 12, and its length is greater than the length of the bottom side of the curved side of the sample 12; The extra parts on both sides of the film 13 are spread out along the flat side wall of the plexiglass side wall 8 (the flat plexiglass side wall 24 ) in the direction away from the sample 12 , and are fixed and compacted on the plexiglass side wall by the plexiglass fixing plate 14 . 8 on the side wall of the flat plate (the flat plexiglass side wall 24 ), so that the latex film 13 seals the sample 12 . The specific method is to embed the bottom of the plexiglass fixing plate 14 into the top surface of the steel bottom plate 7 after the excess parts on both sides of the latex film 13 are extended along the flat side wall of the plexiglass side wall 8 in a direction away from the sample 12. The fixing plate 14 is a rigid material, and the latex film 13 is compressible, so after one end of the plexiglass fixing plate 14 is fixed, a certain pressing force will be generated on the latex film 13 , so that the latex film 13 is closely attached to the flat plexiglass side wall 24 . As shown in FIG. 2 , the plexiglass fixing plate 14 is located between the steel bottom plate 7 and the steel top cover 9 and is detachably connected to the steel bottom plate 7 and the steel top cover 9 . Specifically, the top surface of the steel bottom plate 7 The bottom surface of the steel top cover 9 is provided with a corresponding groove for connecting the plexiglass fixing plate 14, and the top of the plexiglass fixing plate 14 is embedded in the bottom surface of the steel top cover 9. The groove for connecting the plexiglass fixing plate 14 Inside, the bottom of the plexiglass fixing plate 14 is embedded in the groove on the top surface of the steel base plate 7 for connecting the plexiglass fixing plate 14 .

The steel top cover 9 is provided with a convex cavity corresponding to the upper and lower sides of the sample 12, the top of the convex cavity is provided with a hole for the pulling rod 25 of the root pulling device 4 to extend, and a second sealing ring 28 is arranged around the hole. In order to ensure the air tightness of the pressure chamber 1. The convex cavity of the steel top cover 9 is also provided with an intake pipe interface 26 with an intake pipe valve 74 communicating with the interior of the convex cavity, and the pressure chamber 1 is connected to the suction control device 3 through the intake pipe interface 26 . In addition, the steel top cover 9 is also provided with an exhaust hole 27 that communicates with the semi-cylindrical sealed space where the sample 12 is located. The opening and closing of the valve is controlled by the exhaust screw 29 with the third sealing ring, and the exhaust rate can be adjusted by the tightness of the connection between the exhaust screw 29 and the exhaust hole 27. The exhaust hole 27 is used in the pressure chamber 1 Maintain the air pressure balance inside and outside the pressure chamber 1 during water injection or when the pressure chamber 1 is drained.

The upper surface of the sample 12 is provided with a plurality of porous annular spacers 16 which are nested in sequence. The porous annular spacer 16 is provided with a metal gasket 17, and the metal gasket 17 is located on the porous annular spacer 16 and the steel top cover 9. In the meantime, in the case of using multiple porous annular spacers 16, the innermost porous annular spacer 16 is not pressed by the steel top cover 9, and may become loose during the test, failing to control the bulge of the top of the sample. The porous annular spacer 16 can be restrained by the metal spacer 17, so as to control the raised area of the top of the sample during the root pulling process. Nesting of different numbers of porous annular spacers 16 can control the allowable raised area of the top of the sample 12 when the plant root system 30 is pulled out. Fewer porous annular spacers 16 are nested; for the root system with thin rhizomes, it is only necessary to reserve a small area, and more porous annular spacers 16 can be used.

The porous annular spacer 16 has a porous structure, and its top and side surfaces have through holes for gas circulation. The porous annular spacer 16 is set to a porous structure because the suction control device 3 will pass through the inlet pipe interface 26 during the test to the sample. The air pressure is applied inside 12, and the porous annular spacer 16 is arranged in a porous structure to allow the air pressure to be applied to the sample 12 from the top more uniformly.

The confining pressure control device 2 is used to adjust the hoop pressure on the sample 12 in the pressure chamber 1 to simulate different stress states on the soil. As shown in FIG. 4 , the confining pressure control device 2 includes a confining pressure water pipe 31 , a confining pressure controller 32 , a water inlet and outlet pipe 33 , a water cylinder 34 and a water pump 21 . The water pump 21 is located in the water cylinder 34, and the water pump 21 is communicated with the water inlet and outlet pipe interface 18 of the pressure chamber 1 through the water inlet and outlet pipes 33. The confining pressure control device 2 can extract the distilled water in the water cylinder 34 through the water pump 21 to inject water into the pressure chamber 1 or inject water into the pressure chamber 1. The water inside the pressure chamber 1 is discharged to the water cylinder 34; the confining pressure controller 32 is communicated with the confining pressure water pipe interface 19 of the pressure chamber 1 through the confining pressure water pipe 31, and the confining pressure controller 32 is used for real-time control and measurement of the pressure chamber 1 internal test. The confining pressure of sample 12 and the volume of water entering and leaving the confining pressure water pipe 31. The confining pressure controller 32 is a controller that can store a certain amount of water inside. It is mainly composed of a water pump, a water storage chamber, a controller and a sensor. ADVDPC type advanced pressure/volume controller produced. The signal output terminal of the confining pressure controller 32 is electrically connected to the input terminal of the data acquisition box 70 of the data acquisition system 6, and the signal input terminal of the confining pressure controller 32 is electrically connected to the computer 69 of the data acquisition system 6, and the computer 69 controls the The confining pressure controller 32 works, and the confining pressure controller 32 transmits the measured confining pressure of the sample 12 in the pressure chamber 1 and the change value of the water volume in and out of the confining water pipe 31 to the data acquisition box 70 in real time.

The suction control device 3 is mainly used to control the substrate suction of the sample 12 in the pressure chamber 1. As shown in FIG. 5, the suction control device 3 includes a back pressure controller 35, an air compressor 36, a filter 37, a dryer 38, an air pressure The controller 39, the safety tank 40, the back pressure water pipe 41 and the air inlet pipe 42; the back pressure controller 35 is connected to the back pressure water pipe interface 20 of the pressure chamber 1 through the back pressure water pipe 41; one end of the air inlet pipe 42 is connected to the air inlet pipe of the pressure chamber 1 The interface 26 is connected, and the other end is connected to the air compressor 36 through the safety tank 40, the air pressure controller 39, the dryer 38, and the filter 37 in sequence. The air compressor 36 is used to provide air pressure, the filter 37 is used to filter the solid particles and impurities in the compressed air, and the dryer 38 can dry the compressed air. The back pressure controller 35 is used for real-time control and measurement of the pore water pressure of the sample 12 in the pressure chamber 1 and the volume of water in and out of the back pressure water pipe 41 . The air pressure controller 39 is used to control and measure the pore air pressure applied to the sample 12 . The signal output ends of the back pressure controller 35 and the air pressure controller 39 are electrically connected to the input end of the data acquisition box 70 of the data acquisition system 6 , and the signal input ends of the back pressure controller 35 and the air pressure controller 39 are connected to the data acquisition system 6 . The computer 69 is electrically connected, the computer 69 controls the back pressure controller 35 and the air pressure controller 39 to work, and the back pressure controller 35 transmits the measured pore water pressure of the sample 12 and the back pressure water pipe 41 to the data acquisition box 70 in real time. According to the change value of the water volume, the air pressure controller 39 transmits the measured pore air pressure of the sample 12 to the data collection box 70 in real time. The safety tank 40 is used to collect moisture when the water in the sample 12 is discharged from the air inlet pipe 42 to prevent damage to the air pressure controller 39 .

The root system pulling device 4 includes a horizontal clamping device 43 and a vertical pulling device 44. As shown in Figures 6-7, the horizontal clamping device 43 is used to provide a horizontal clamping force to the plant root system 30 in the sample 12, The vertical pulling device 44 is used to provide vertical pulling force to the plant root system 30 in the soil. The lower end of the vertical pulling device 44 extends into the convex cavity through the hole at the top of the convex cavity of the steel top cover 9, and the horizontal clamping device 43 is arranged in the convex cavity of the steel top cover 9, and the horizontal clamping device 43 It is fixed on the lower end of the vertical pulling device 44 , and the vertical pulling device 44 can drive the horizontal clamping device 43 to move vertically downward in the pressure chamber 1 . As shown in FIG. 6 , the vertical pulling device 44 includes a pulling machine 52 , a beam 53 , a bracket 54 , a base 55 , a pulling rod 25 , a tension sensor 56 , a displacement sensor 57 and a displacement measuring rod 58 , and the base 55 and the beam 53 pass through The bracket 54 is fixedly connected, the pressure chamber 1 is fixed on the base 55, and the telescopic rod of the tension machine 52 is arranged on the beam 53; The hole on the top of the convex cavity extends into the pressure chamber 1 and is connected to the horizontal clamping device 43; the drawing rod 25 and the outer shell of the horizontal clamping device 43 are made of the same material, and can be connected by welding. A tension sensor 56 is fixed between the telescopic rod of the tension machine 52 and the pulling rod 25, and a displacement sensor 57 is vertically fixed at the bottom of the beam 53; The top of the pulling telescopic rod 60 is detachably connected to the bottom of the clamping device fixing rod 59. Specifically, the top of the pulling telescopic rod 60 is provided with external threads, the bottom of the clamping device fixing rod 59 is provided with internal threads, and the bottom of the clamping device fixing rod 59 is provided with internal threads. Threaded connection with the top of the pull-out telescopic rod 60. The pointer head of the displacement sensor 57 contacts the displacement measuring rod 58 to record the vertical displacement of the plant root system 30 in real time.

The drawing rod 25 is of hollow design, that is, the drawing and telescopic rod 60 and the fixing rod 59 of the clamping device are of hollow design. And the clamping device fixing rod 59 can be composed of an inner layer and an outer layer, the inner layer and the outer layer can move relatively, the bottom of the inner layer is provided with an inner thread, the inner bottom of the clamping device fixing rod 59 and the top of the pulling telescopic rod 60 Threaded connection; the top of the inner layer of the fixing rod 59 of the clamping device is connected to the bottom of the tension sensor 56, and the top of the tension sensor 56 is fixedly connected to the bottom of the telescopic rod of the tension machine 52. The connection can be made by bolts, riveting, welding, etc. The pulling machine 52 can use a hollow hydraulic jack.

As shown in FIG. 7 , the horizontal clamping device 43 includes a motor 45, a threaded rod 46, a connecting rod 47, a rubber pad 48, a clip 49, a clip fixing rod 50 and a horizontal force sensor 51. The motor 45 is a bidirectional synchronous motor. The two output shafts of the motor 45 are respectively connected with a threaded rod 46, each threaded rod 46 is threadedly connected with a nut seat, and the bottom of each nut seat is fixedly connected to a horizontally placed clip fixing rod 50 through a connecting rod 47, and two The ends of the clip fixing rods 50 to which the nut seat on the threaded rod 46 is fixedly connected via the connecting rod 47 are arranged opposite to each other, and the two clip fixing rods 50 are movably connected to each other at the ends of the clip fixing rods 50 , respectively. The threaded rod 46 can slide along the inside of the clip 49. The clip 49 is fixed with a horizontal force sensor 51. The clip fixing rod 50 is located at one end of the clip 49 and the horizontal force sensor embedded in the clip 49. 51 contacts. In order to ensure the stability of the threaded rod 46, it can be arranged in the casing of the horizontal clamping device, one end of which is fixedly connected to the output shaft of the motor 45, and the other end is movably connected to the casing of the horizontal clamping device through bearings, etc. The bottom of the holding device housing is provided with an opening that facilitates the left and right movement of the connecting rod 47 .

Specifically, one end of the two clip fixing rods 50 that are close to each other extends into the interior of the clip 49 from the back of the clip 49. The clip 49 is provided with a chute along the length direction of the clip fixing rod 50, and the clips are fixed One end edge of the rod 50 extending into the interior of the clip 49 is provided with a protrusion, the protrusion on the clip fixing rod 50 is matched and connected with the chute in the clip 49, and the protrusion on the clip fixing rod 50 can be along the clip. The chute in 49 moves; there is a gap between the inside of the clip 49 and the clip fixing rod 50, and lubricating oil is applied in the upper and lower gaps to reduce the resistance of the clip fixing rod 50 moving in the clip 49; the clip 49 The contact surface with the plant root system 30 is in close contact with the rubber pad 48 . The clip 49 can clamp the plant root system 30 and exert a horizontal clamping force through the expansion and contraction of the clip fixing rod 50. The clip fixing rod 50 can slide along the inside of the clip 49 under the driving of the threaded rod 46, and the clip is fixed. After the rod 50 slides to the end inside the clip 49 , under the action of the threaded rod 46 , the clip 49 is driven to move toward or away from the plant root system 30 together. The output end of the horizontal force sensor 51 is connected to the data acquisition box 70 of the data acquisition system 6 outside the pressure chamber 1 through a connecting line passing through the inner space of the drawing rod 25 .

The vertical pulling device 44 is placed on the test bench, and the horizontal clamping device 43 and the vertical pulling device 44 are threadedly connected by pulling the thread at the lower end of the telescopic rod 60 and the threaded hole at the top of the motor 45 . The wires of the horizontal clamping device 43 are drawn out from the hollow drawing and telescopic rod 60 and connected to the data acquisition box 70 of the data acquisition system 6 . Before the test, the horizontal clamping device 43 was unscrewed from the pulling telescopic rod 60 of the vertical pulling device 44, the wires were disconnected, and the horizontal clamping device 43 was removed, so that the steel top cover of the pressure chamber 1 could be opened. 9. After installing the sample, first connect the wires of the horizontal clamping device 3, then connect the horizontal clamping device 43 and the vertical pulling device 44 to the thread on the top of the motor 45 by pulling the telescopic rod 60, and finally install the pressure chamber. The steel top cover 9 of the 1, so as to realize the integral assembly of the root pulling device 4.

The PIV test device 5 can measure the movement trajectory and speed of soil particles and plant roots 30. As shown in FIG. 8, the PIV test device 5 includes a rectangular test cavity 61, a synchronizer 62, a laser power source 63, a laser 64, a laser head 65, a CCD Camera 66 , LED light 67 and PIV connection line 68 . The rectangular test chamber 61 and the pressure chamber 1 are both fixed on the base 55 of the vertical drawing device 44. The rectangular test chamber 61 is located directly in front of the pressure chamber 1, and the rectangular test chamber 61 is composed of a rectangular steel top plate, a rectangular steel bottom plate, The closed space formed by the three rectangular steel side walls and the transparent side surface of the pressure chamber 1 (the flat plexiglass side wall 24 ). The laser head 65 is installed at the lower part in front of the flat organic glass side wall 24 of the pressure chamber 1 . A CCD camera 66 is fixed at the inner center of the steel side wall of the rectangular test chamber 61 and the flat plexiglass side wall 24 opposite to the side wall 24 . The computer 69 of the system 6 is connected in two directions, with the CCD camera 66 as the center, and an LED light 67 is set around it to ensure that the field of view of the CCD camera 66 is bright and clear. The synchronizer 62 is used to synchronize the laser power supply 63 and the CCD camera 66. frequency, valid data is recorded by the CCD camera 66 while the laser 64 is lasing.

The data acquisition system 6 is used to record various data changes during the test. As shown in FIG. 9 , the data acquisition system 6 includes a data acquisition box 70 and a computer 69. The input ends of the data acquisition box 70 are respectively connected with the confining pressure control device 2. The confining pressure controller 32, the back pressure controller 35 of the suction control device 3, the air pressure controller 39 of the suction control device 3, and the signal output terminals of the horizontal force sensor 51, the tension sensor 56, and the displacement sensor 57 of the root pulling device 4 Electrically connected, the output end of the data acquisition box 70 and the signal input ends of the confining pressure controller 32, the back pressure controller 35, and the air pressure controller 39 are all electrically connected to the computer 69, and the CCD camera 66 of the PIV test device 5 It is directly connected to the computer 69 in both directions, and the test data is directly collected by the computer 69 .

The internal dimensions of the pressure chamber 1 in the embodiment of the present invention are: 300 mm in diameter and 150 mm in height; the dimensions of the sample 12 are: 200 mm in diameter and 100 mm in height, and the dimensions of the pressure chamber 1 and the sample 12 can be adjusted according to actual needs; the horizontal force sensor 51 And tension sensor 56 has a range of 10kN and an accuracy of 0.001kN; displacement sensor 57 has a range of 0±200mm and an accuracy of 0.001mm; the maximum adjustment displacement of the threaded rod: 20mm; the maximum clamping force of the clip: 2kN; the maximum tension of the tension machine: 10kN; the pressure control range of the confining pressure controller 32 is 0~2MPa, the volume control range is 0~100000mm ³ , the pressure accuracy is 0.1kPa, and the volume accuracy is 0.1mm ³ ; the pressure control range of the back pressure controller 35 is 0~2MPa, The volume control range is 0~100000mm ³ , the pressure precision is 0.1kPa, and the volume precision is 0.1mm ³ ; the pressure control range of the air pressure controller 39 is 0~2MPa, and the pressure precision is 0.1kPa; the maximum sampling frequency of the CCD camera 66 is 15Hz; The plate 15 intake value is 1500 kPa.

Both the confining pressure controller 32 and the back pressure controller 35 in this embodiment can be selected from the ADVDPC type advanced pressure/volume controller produced by British GDS (Geotechnical Digital Systems Instruments Ltd); the air compressor 36 can be selected from Zhejiang Lawston welding equipment LAHW-1030 silent oil-free air compressor produced by Co., Ltd.; filter 37 can choose VFL-66 vacuum special straight-through filter produced by Xiamen Qijin Industry and Trade Co., Ltd.; dryer 38 can choose Wenling Jinyu general equipment The 02/0.8MPa oil-water filter produced by Co., Ltd.; the air pressure controller 39 can choose the GDSPPC air pressure controller produced by the British GDS company; the motor 45 can choose the ZWBPD032032-4 motor produced by Shenzhen Zhaowei Electromechanical Co., Ltd.; The horizontal force sensor 51 and the tensile force sensor 56 can be selected from the ZZ210-010 tension and pressure bidirectional mechanical sensor produced by Shanghai Qizhan Measurement and Control System Co., Ltd.; the tensile force machine 52 can be selected from the electronic tensile force testing machine produced by Jinan Meites Testing Technology Co., Ltd.; displacement The sensor 57 can be selected from the MTR magnetic drag type waterproof linear displacement sensor produced by Shenzhen Milang Technology Co., Ltd.; the CCD camera 66, the laser 64, and the PIV cable 68 can be selected from the 2D2C PIV system produced by Beijing CubeTiandi Technology Development Co., Ltd.; The LED lamp 67 can be selected from the JU-LE-41489 bulb produced by OPPLE Company; the data acquisition box 70 can be selected from the ADVDCS V2 high-speed digital control and acquisition system produced by the British GDS Company.

Example 2

With reference to Fig. 1～9, the embodiment of the present invention proposes a kind of root system pull-out test method based on PIV technology, carries out the pull-out test of root system in root-containing soil under the action of different confining pressure and matrix suction, adopts the method described in Example 1 The root pulling test system based on PIV technology, the operation steps are as follows:

Step S1, sample preparation: first lay 50~60mm thick test soil in the test box, put the plant seeds to be tested into the center of the test box, then fill the test box with the test soil, and then water regularly to cultivate; When the growth reaches the level required for the test, remove the flowers, stems, and leaves of the plants above the soil surface, and keep only the root system, and then use a cylindrical mold to take the root system as the center; after demoulding, cut the cylindrical sample vertically along the center of the root system into half. Cylinder, to prepare the sample 12 containing the root system required for the test;

Step S2, sample installation: use degassed distilled water to completely saturate the terracotta plate 15 on the steel bottom plate 7 of the pressure chamber 1, and then put the root-containing sample 12 into the pressure chamber 1, so that the vertical side and the The transparent sides of the pressure chamber 1 (the flat plexiglass side wall 24 ) are in contact with each other, and then the latex film 13 is wrapped. Then install the plexiglass fixing plate 14 to press the latex film 13, so that the latex film 13 seals the sample 12, and then place an appropriate number of porous annular spacers 16 on the upper part of the sample 12 to control the root system during the pulling process of the sample. Top bulge area; place metal gasket 17 on the porous annular spacer 16 again, and make the plant root system 30 to be tested penetrate 2~3cm from the center of the porous annular spacer 16 and the metal gasket 17;

Step S3, installation of the root system pulling device: insert the lower end of the pulling telescopic rod 60 of the vertical pulling device 44 into the top hole of the convex cavity of the steel top cover 9, and then clamp the thread at the lower end of the pulling telescopic rod 60 with the horizontal clamping. The thread on the top of the motor 45 of the device 43 connects the horizontal clamping device 43 to the lower end of the drawing and telescopic rod 60; The reserved hole is threadedly connected with the threaded hole on the steel base plate 7;

Step S4, equipment startup: turn on the power of the computer 69, the data acquisition box 70, the confining pressure controller 32, the back pressure controller 35 and the air pressure controller 39 and turn it on;

Step S5, root system clamping: open the tension machine 52, and drive the pulling and retractable rod 60 to move downward through the downward movement of the retractable rod of the hydraulic control tension machine 52, and the pulling and retractable rod 60 drives the horizontal clamping device 43 to move down to the clamping position. The sheet 49 is aligned with the part of the plant root system 30 to be tested protruding from the metal washer 17, and then the tension machine is turned off; the horizontal force sensor 51 is cleared and then the motor 45 is turned on. The motor 45 rotates and passes through the two threaded rods 46 and connecting rods 47 Drive the two clip fixing rods 50 to approach the direction of the plant root system 30 to be tested, and observe the reading of the horizontal force sensor 51 in real time during this process, and clamp the rubber pads 48 on the two clips 49 to be tested. Turn off the motor 45 when the plant root system is 30, and record the indication of the horizontal force sensor 51 at this time, which is the horizontal clamping force;

Step S6, applying confining pressure: loosen the exhaust screw 29 on the steel top cover 9, open the inlet and outlet water pipe valves 71, and pump the distilled water in the water cylinder 34 through the water inlet and outlet pipes 33 into the pressure chamber 1 through the water pump 21. When the distilled water in the chamber 1 slowly flows out from the exhaust hole 27, tighten the exhaust screw 29 and close the inlet and outlet water pipe valves 71; Determine the confining pressure value required for the test, and observe the volume change data of back pressure in real time to judge whether the consolidation of the sample is completed;

The real-time monitoring of the back pressure volume change is due to the determination of whether the consolidation of the sample is completed or not based on whether the change of the back pressure volume in a period of time exceeds a certain limit. That is, the back pressure volume change does not exceed 0.01cm ³ , and the total duration is not less than 48 hours, and it can be judged whether the set value is reached by reading the data of the confining pressure controller 32 or the computer 69 .

Step S7, applying suction: after the confining pressure value reaches the set value and stabilizes, clear the readings of the back pressure controller 35 and the air pressure controller 39 to zero, then open the back pressure water pipe valve 73 and the intake pipe valve 74, and turn on the air compressor. After 36, the required back pressure value and the air pressure value are respectively set by the back pressure controller 35 and the air pressure controller 39, the back pressure volume change is collected in real time through the data acquisition box 70, and the back pressure volume change data is observed in real time to judge whether the suction is balanced;

Step S8, turn on PIV: after the suction is balanced, the computer 69 controls the synchronizer 62 to make the laser power supply 63 work synchronously with the CCD camera 66, and the laser 64 passes through the laser head 65 on the transparent side of the pressure chamber 1, that is, the flat plexiglass side wall 24. The laser is emitted in the middle, and the LED light 67 is turned on, and the movement direction and speed of the plant root system 30 and soil particles are started to be recorded;

Step S9, root system pulling: turn on the motor 45, and apply the set horizontal clamping force to the plant root system 30 to be measured through the horizontal clamping device 43; then clear the tension sensor 56 and the displacement sensor 57, and then open the tension machine 52 , so that the pulling force machine 52 drives the pulling and retracting rod 60 to move at a constant rate to the plant root system 30 to be tested and applies upward pulling force, the displacement sensor 57 and the tension sensor 56 record the displacement and the pulling force in the test in real time, until the plant to be tested. The root system 30 is pulled out or pulled off;

The tensile force sensor 56 and the displacement sensor 57 are both the longitudinal tensile force and the longitudinal displacement measured after the test starts. After the horizontal clamping force is applied, the tensile force sensor 56 and the displacement sensor 57 are cleared to reduce the horizontal clamping force. The influence of a sensor, the experimental error is minimized.

Step S10, system reset: turn on the motor 45 and the tension machine 52 in turn, reset the horizontal clamping device 43 and the pulling and retractable rod 60, stop the PIV test device 5, and use the air pressure controller 39 and the back pressure controller 35 to adjust the air pressure and the counter pressure. The pressure is adjusted to zero, and the confining pressure is adjusted to zero through the confining pressure controller 32; then the back pressure water pipe valve 73, the intake pipe valve 74 and the confining pressure water pipe valve 72 are closed, and the inlet and outlet water pipe valve 71 and the exhaust of the pressure chamber 1 are opened. Screw 29, drain the water inside the pressure chamber 1 through the water inlet and outlet pipes 33, and finally open the steel top cover 9 of the pressure chamber 1 to remove the sample 12;

In step S11, the test data is analyzed and processed by the computer 69, and the pull-out characteristic parameters (main root tensile strength and root pull-out resistance) of roots of different ages in the root-containing soil under the action of different confining pressures and matrix suction can be obtained, and The deformation and movement trajectories of soil and plant roots during the pulling process were analyzed, the disturbance range of the soil during the root pulling process was discussed, and the relevant mechanisms were revealed.

Example 3

With reference to Fig. 1～9, the embodiment of the present invention proposes another kind of using method of the root system pulling test system based on PIV technology, for testing the pulling resistance test of single root plant root system, the operation steps are as follows:

Step 1. Use a vernier caliper to measure the diameter of the single root to be tested, configure a cylindrical sample with the required moisture content according to the requirements of the test plan, and place the single root to be tested in the center of the cylindrical sample (single root refers to a root in the root system. ), after demoulding, cut the cylindrical sample into a semi-cylindrical body along the center of the single root to be tested, and prepare the sample 12 containing the single root to be tested required for the test;

The purpose of measuring the diameter of the single root to be tested is to calculate the tensile strength of the single root to be tested. The tensile strength is equal to the pullout force divided by the cross-sectional area of the single root to be tested. When calculating, the cross-section of the single root to be tested is approximated as a circle. .

Step 2. Repeat steps S2 to S10 for the sample 12 containing the single root to be tested;

Step 3. Analyze and process the test data by the computer 69, and obtain the pull-out characteristic parameters (tensile strength, pull-out resistance and root-soil interface) of the single root in the root-containing soil of different ages under the action of different confining pressures and matrix suction. Friction coefficient), and analyze the deformation and motion trajectories of the soil and single plant roots during the pulling process, discuss the disturbance range of the single root pulling process to the soil, and reveal the relevant mechanism.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims (9)

1. A root system pulling test system based on PIV technology, characterized in that it includes a pressure chamber (1), a confining pressure control device (2), a suction control device (3), a root system pulling device (4), a PIV test device ( 5) and a data acquisition system (6); the pressure chamber (1) is a semi-cylindrical sealed structure as a whole, the side of which is transparent, and a semi-cylindrical sample (12) is placed in the pressure chamber (1), The vertical side surface of the sample (12) includes a plant root system (30) split from the center in the vertical direction, and the top of the plant root system (30) is exposed on the top of the sample (12); the confining pressure control device ( 2) Two-way communication with the pressure chamber (1) to adjust the confining pressure of the sample (12) in the pressure chamber (1); The sample (12) in 1) is subjected to matrix suction adjustment; the root system pulling device (4) is arranged above the sample (12) to apply a pulling force to the plant root system (30); the PIV testing device ( 5) Set in front of the transparent side of the pressure chamber (1), measure and record the movement trajectory and speed of soil particles and plant roots (30); the data acquisition system (6) and the confining pressure control device ( 2) The suction control device (3) and the PIV test device (5) are electrically connected in both directions, and are electrically connected with the signal output end of the root pulling device (4); The pressure chamber (1) comprises a steel bottom plate (7), a plexiglass side wall (8) and a steel top cover (9), a steel top cover (9), a plexiglass side wall (8) and a steel bottom plate (7) The semi-cylindrical sealed space is formed by fixed connection from top to bottom, the sample (12) is located in the semi-cylindrical sealed space, and the plexiglass side wall (8) is vertically arranged on the side of the sample (12). On the side periphery, the top of the plexiglass side wall (8) is sealedly connected with the bottom surface of the steel top cover (9), and the bottom of the plexiglass side wall (8) is sealed with the top surface of the steel bottom plate (7); A funnel-shaped drainage groove (22) is arranged in the middle area of the upper surface of the steel bottom plate (7), a clay plate (15) is fixed on the top of the drainage channel (22), and the sample (12) is placed on the clay plate (15) superior; One side of the steel bottom plate (7) is provided with a water inlet and outlet pipe interface (18) with a water inlet and outlet pipe valve (71), a confining pressure water pipe interface (19) with a confining pressure water pipe valve (72), and a back pressure water pipe valve ( 73) of the back pressure water pipe interface (20), one end of the inlet and outlet water pipe interface (18) and the confining pressure water pipe interface (19) are connected to the inside of the pressure chamber (1), the inlet and outlet water pipe interface (18) and the confining pressure water pipe interface (19) The other end is communicated with the confining pressure control device (2); one end of the back pressure water pipe interface (20) is communicated with the bottom of the drainage groove (22), and the other end of the back pressure water pipe interface (20) is communicated with the suction control device (3). 2. The root system pulling test system based on PIV technology according to claim 1, characterized in that, the top of the pressure chamber (1), that is, the steel top cover (9), is provided with inside of the pressure chamber (1), The exhaust hole (27) communicated with the periphery of the sample (12) is provided with an exhaust screw (29) threadedly connected with the exhaust hole (27); the curved side of the sample (12) is wrapped with a Sealed latex film (13); The confining pressure control device (2) includes a confining pressure water pipe (31), a confining pressure controller (32), a water inlet and outlet pipe (33), a water cylinder (34) and a water pump (21), and the water pump (21) is located in the water cylinder ( 34), and the water pump (21) communicates with the water inlet and outlet pipes (18) of the pressure chamber (1) through the water inlet and outlet pipes (33), and the confining pressure controller (32) communicates with the pressure chamber (1) through the confining pressure water pipes (31) The confining pressure water pipe interface (19) is connected; The confining pressure controller (32) is in bidirectional communication with the data acquisition system (6). 3. The root system pulling test system based on PIV technology according to claim 1, characterized in that, the top of the pressure chamber (1), that is, the steel top cover (9), is provided with a connection with the interior of the pressure chamber (1). The air inlet pipe interface (26) is provided, and the air inlet pipe interface (26) is arranged above the sample (12); The suction control device (3) includes a back pressure controller (35), an air compressor (36), a filter (37), a dryer (38), an air pressure controller (39), a safety tank (40), a The pressure water pipe (41) and the air inlet pipe (42), the back pressure controller (35) is connected to the back pressure water pipe interface (20) of the pressure chamber (1) through the back pressure water pipe (41), and one end of the air inlet pipe (42) is connected to the pressure The inlet pipe interface (26) at the top of the chamber (1) is connected, the other end of which is connected to the air compressor (36) through the safety tank (40), the air pressure controller (39), the dryer (38), the filter (37) and the air compressor (36) in turn. connect; The back pressure controller (35) and the air pressure controller (39) are respectively in bidirectional communication with the data acquisition system (6). 4. The root system pulling test system based on PIV technology according to claim 1, wherein the steel top cover (9) is provided with convex cavities corresponding to the upper and lower sides of the sample (12), and the top of the convex cavity is A hole is left for the lower end of the root pulling device (4) to protrude, and a second sealing ring (28) is arranged around the hole; the sample (12) is provided with a plurality of porous annular spacers (16) which are nested in sequence. ), a metal gasket (17) is arranged between the porous annular spacer block (16) and the steel top cover (9); The root system pulling device (4) includes a horizontal clamping device (43) and a vertical pulling device (44). The lower end of the vertical pulling device (44) passes through the hole at the top of the convex cavity of the steel top cover (9). Extending into the pressure chamber (1), the horizontal clamping device (43) is arranged in the convex cavity of the steel top cover (9), and the horizontal clamping device (43) is fixed on the lower end of the vertical pulling device (44), The vertical pulling device (44) can drive the horizontal clamping device (43) to move vertically downward in the pressure chamber (1). 5. The root system pulling test system based on PIV technology according to claim 4, wherein the vertical pulling device (44) comprises a pulling machine (52), a beam (53), a bracket (54), The base (55) and the pulling rod (25), the base (55) and the beam (53) are fixedly connected through the bracket (54), the pressure chamber (1) is fixed on the base (55), and the telescopic rod of the pulling machine (52) is arranged on the beam (53); the top of the drawing rod (25) passes through the beam (53) and is fixedly connected with the bottom end of the telescopic rod of the tension machine (52), and the bottom of the drawing rod (25) passes through the steel top cover (9). ) at the top of the convex cavity extends into the pressure chamber (1) and is connected to the horizontal clamping device (43); a tension sensor (56) is fixed between the telescopic rod and the pulling rod (25) of the tension machine (52), A displacement sensor (57) is vertically fixed at the bottom of the beam (53); the pulling rod (25) is composed of a clamping device fixing rod (59) and a pulling telescopic rod (60). The bottom of the holding device fixing rod (59) is detachably connected; a displacement measuring rod (58) is sleeved and fixed on the pull-out telescopic rod (60), and the pointer head of the displacement sensor (57) contacts the displacement measuring rod (58); The horizontal clamping device (43) includes a motor (45), a threaded rod (46), a connecting rod (47), a rubber pad (48), a clip (49), a clip fixing rod (50) and a horizontal force The sensor (51), the motor (45) is a bidirectional synchronous motor, the two output shafts of the motor (45) are respectively connected with a threaded rod (46), each threaded rod (46) is threadedly connected with a nut seat, each The bottom of the nut seat is fixedly connected to a horizontally placed clip fixing rod (50) via a connecting rod (47), one end of the two clip fixing rods (50) is arranged opposite to each other, and the two clip fixing rods (50) are close to each other A clip (49) is movably connected to one end of the clip, the clip fixing rod (50) can slide along the inside of the clip (49) under the driving of the threaded rod (46), and the clip fixing rod (50) is in the clip (49) After sliding to the end, the clip (49) will be driven to move towards or away from the plant root system (30) together under the action of the threaded rod (46); the clip (49) is fixed with a horizontal force sensor inside (51), one end of the clip fixing rod (50) located inside the clip (49) is in contact with the horizontal force sensor (51) embedded in the clip (49); the clip (49) is in contact with the plant root system (30) The contact surface is close to the rubber pad (48); The lower end of the pulling telescopic rod (60) is detachably connected to the motor (45), and the horizontal clamping device (43) is fixed on the lower end of the vertical pulling device (44); The signal output ends of the horizontal force sensor (51), the tensile force sensor (56) and the displacement sensor (57) are all electrically connected to the data acquisition system (6). 6. The root system pulling test system based on PIV technology according to claim 1, wherein the PIV test device (5) comprises a rectangular test cavity (61), a synchronizer (62), a laser power source (63) , laser (64), laser head (65), CCD camera (66), LED light (67) and PIV connecting line (68), rectangular test cavity (61) and pressure chamber (1) are all fixed on the root pulling device On the base (55) of the vertical pulling device (44) of (4), the rectangular test chamber (61) is located directly in front of the pressure chamber (1), and the rectangular test chamber (61) is made of a rectangular steel top plate, a rectangular steel The closed space formed by the bottom plate, the three-sided rectangular steel side walls and the transparent side of the pressure chamber (1); the laser head (65) is installed in the lower part in front of the transparent side of the pressure chamber (1). ) is electrically connected to the output end of the laser (64), and the laser power supply (63) is electrically connected to the power supply end of the laser (64); the rectangular test cavity (61) is arranged opposite to the transparent side of the pressure chamber (1). A CCD camera (66) is fixed at the inner center of the steel side wall, a synchronizer (62) is connected to the CCD camera (66) and the laser power supply (63), and the synchronizer (62) is connected to the data acquisition system through a PIV connection line (68). The computer (69) of (6) is bidirectionally connected; with the CCD camera (66) as the center, an LED light (67) is arranged in each of the four directions around it; The data acquisition system (6) comprises a computer (69) and a data acquisition box (70); the input end of the data acquisition box (70) is respectively connected with the confining pressure controller (32) of the confining pressure control device (2), and the suction control The back pressure controller (35), the air pressure controller (39) of the device (3), and the signal output of the horizontal force sensor (51), tension sensor (56), and displacement sensor (57) of the root pulling device (4) The terminals are electrically connected, and the output terminal of the data acquisition box (70) and the signal input terminals of the confining pressure controller (32), the back pressure controller (35), and the air pressure controller (39) are all electrically connected to the computer (69). ; The CCD camera (66) of the PIV testing device (5) is bidirectionally connected with the computer (69). 7. The root system pulling test system based on PIV technology according to any one of claims 1 to 6, wherein the plexiglass side wall (8) is composed of a curved plexiglass side wall (23) and a flat organic glass side wall (23). The glass side wall (24) is sealed and connected, wherein the curved plexiglass side wall (23) is arranged on the periphery of the curved side surface of the sample (12), and the flat plexiglass side wall (24) is arranged on the outer periphery of the sample (12). Directly in front of the vertical side, the curved plexiglass side wall (23) and the flat plexiglass side wall (24) are respectively sealed and connected with the top surface of the steel bottom plate (7) and the bottom surface of the steel top cover (9); The curved side of the sample (12) is wrapped with a latex film (13) that seals it, the latex film (13) is rectangular when flattened, its width is the same as the height of the sample (12), and its length is greater than The length of the bottom side of the curved side of the sample (12); the extra part on both sides of the latex film (13) wrapping the sample (12) is extended along the side wall of the flat plexiglass (24) in the direction away from the sample (12) , and is fixed and compacted on the flat plexiglass side wall (24) by the plexiglass fixing plate (14), so that the latex film (13) seals the sample (12); the plexiglass fixing plate (14) is located on the steel bottom plate ( 7) Removably connected with the steel top cover (9) and with the steel bottom plate (7) and the steel top cover (9); A plurality of support tubes (10) are arranged on the periphery of the curved plexiglass side wall (23), and the steel top cover (9) and the support tube (10) are provided with reserved holes vertically penetrating them. The top surface of the bottom plate (7) is provided with threaded holes corresponding to the reserved holes on the top cover (9), and the top cover (9) and bottom plate (7) are connected by screws (11). The threaded rod (11) passes through the steel top cover (9) and the reserved holes on the support pipe (10) in sequence from top to bottom, and is then threadedly connected to the threaded holes on the steel bottom plate (7). 8. the root system pulling test method based on PIV technology is characterized in that, adopt the root system pulling test system based on PIV technology described in any one of claim 1～6, carry out according to the following steps: Step S1, sample preparation: first lay 50~60mm thick test soil in the test box, put the plant seeds to be tested into the center of the test box, then fill the test box with the test soil, and then water regularly to cultivate; When the growth reaches the level required for the test, remove the flowers, stems, and leaves of the plants above the soil surface, and keep only the root system, and then use a cylindrical mold to take the root system as the center; after demoulding, cut the cylindrical sample vertically along the center of the root system into half. Cylinder, to prepare the root-containing sample (12) required for the test; Step S2, sample installation: completely saturate the clay plate (15) on the steel bottom plate (7) of the pressure chamber (1) with degassed distilled water, and then put the root-containing sample (12) into the pressure chamber ( 1), make its vertical side contact with the transparent side of the pressure chamber (1); then wrap the latex film (13) on the side of the sample (12), so that the latex film (13) seals the sample (12). ); then place an appropriate number of porous annular spacers (16) on the upper part of the sample (12) to control the raised area of the top of the sample during the root system pulling process; and then place a metal spacer (17) on the porous annular spacer (16). ), and make the plant root system (30) to be tested protrude 2-3 cm from the center of the porous annular spacer (16) and the metal spacer (17); Step S3, installation of the root system pulling device: insert the lower end of the pulling telescopic rod (60) of the vertical pulling device (44) of the root system pulling device (4) into the hole at the top of the convex cavity of the steel top cover (9) , and then fix the motor (45) of the horizontal clamping device (43) of the root pulling device (4) to the lower end of the pulling telescopic rod (60); finally install the steel top cover (9), and screw the screw (11) After passing through the steel top cover (9) and the reserved holes on the support pipe (10), it is threaded with the threaded holes on the steel bottom plate (7). The support pipe (10) is located between the steel top cover (9) and the steel Between the bottom plate (7) and the periphery of the plexiglass side wall (8); Step S4, equipment startup: turn on the computer (69) of the data acquisition system (6), the data acquisition box (70), the confining pressure controller (32) of the confining pressure control device (2), and the suction control device (3) The power supply of the back pressure controller (35) and the air pressure controller (39) are turned on; Step S5, root system clamping: open the pulling machine (52) of the vertical pulling device (44), and drive the pulling telescopic rod (60) to move downward by hydraulically controlling the downward movement of the telescopic rod of the pulling machine (52), and pull Pull out the telescopic rod (60) to drive the horizontal clamping device (43) to move downward until its clip (49) is aligned with the part of the plant root system (30) to be tested that protrudes from the metal washer (17), and then close the tension machine ( 52); reset the horizontal force sensor (51) of the horizontal clamping device (43) to zero and then turn on the motor (45), the motor (45) rotates and is connected through the two threaded rods (46) and the nut seat thereon The rod (47) drives the two clip fixing rods (50) to approach the root system (30) of the plant to be tested, and at the same time observes the reading of the horizontal force sensor (51) in real time during this process, and the two clips (49) When the rubber pad (48) on the ) clamps the plant root system (30) to be tested, the motor (45) is turned off, and the indication of the horizontal force sensor (51) at this time is recorded, which is the horizontal clamping force; Step S6, applying confining pressure: Loosen the vent screw (29) in the vent hole (27) on the steel top cover (9), open the inlet and outlet water pipe valve (71), and pass the confining pressure control device (2) The water pump (21) extracts the distilled water in the water cylinder (34) and injects it into the pressure chamber (1) through the water inlet and outlet pipes (33). When the distilled water in the pressure chamber (1) slowly flows out from the exhaust hole (27), tighten the exhaust Screw (29), close the inlet and outlet water pipe valves (71); clear the reading of the confining pressure controller (32) to zero, then open the confining pressure water pipe valve (72), and set the required applied pressure through the confining pressure controller (32). Confining pressure value, real-time observation of back pressure volume change data to judge whether the consolidation of the sample is completed; Step S7, applying suction: after the confining pressure value reaches the set value and stabilizes, clear the readings of the back pressure controller (35) and air pressure controller (39) of the suction control device (3) to zero, and then open the back pressure water pipe valve (73) and the intake pipe valve (74), open the air compressor (36) of the suction control device (3) and set the required back pressure value and For the air pressure value, the back pressure volume change is collected in real time through the data collection box (70) of the data collection system (6), and the back pressure volume change data is observed in real time to judge whether the suction is balanced; Step S8, turn on the PIV: after the suction is balanced, the computer (69) of the data acquisition system (6) controls the synchronizer (62) of the PIV test device (5) to make the laser power supply (63) and the CCD camera (66) work synchronously, The laser (64) emits laser light in the transparent side of the pressure chamber (1) through the laser head (65), and turns on the LED light (67), and starts to record the movement direction and direction of the plant root system (30) and soil particles to be tested. rate; Step S9, root system pulling: turn on the motor (45), and apply a set horizontal clamping force to the plant root system (30) to be tested through the horizontal clamping device (43); The tension sensor (56) and the displacement sensor (57) are reset to zero, and then the tension machine (52) is turned on, so that the tension machine (52) drives the pulling and retractable rod (60) to move at a constant rate to the plant root system (30) to be tested and applies upward pressure. Pulling force, the displacement sensor (57) and the pulling force sensor (56) record the displacement and the pulling force in real time in the test, until the root system (30) of the plant to be tested is pulled out or broken; Step S10, system reset: turn on the motor (45) and the tension machine (52) in turn, reset the horizontal clamping device (43) and the pulling and retractable rod (60), stop the PIV test device (5), and pass the air pressure controller ( 39) and the back pressure controller (35) to adjust the air pressure and back pressure to zero, and through the confining pressure controller (32) to adjust the confining pressure to zero; then close the back pressure water pipe valve (73), the intake pipe valve (74) ) and the confining pressure water pipe valve (72), open the inlet and outlet water pipe valve (71) and the exhaust screw (29), discharge the water inside the pressure chamber (1) through the inlet and outlet water pipe (33), and finally open the pressure chamber (1) The steel top cover (9) removes the sample (12); In step S11, the test data is analyzed and processed by the computer (69), and the pull-out characteristic parameters of the roots of different ages in the root-containing soil under the action of different confining pressures and matrix suction are obtained. 9. The root system pulling test method based on PIV technology according to claim 8, wherein the sample (12) containing the single root to be tested is prepared according to the following method: measure the diameter of the single root to be tested, press The test plan requires the configuration of a cylinder sample with the required moisture content, and a single piece to be tested is placed in the center of the cylinder sample. The required sample (12) containing the single root to be tested; Then, repeat steps S2 to S10 for the sample (12) containing the single root to be tested, and repeat the test data obtained from steps S2 to S10 for the sample (12) containing the single root to be tested by analyzing and processing the computer (69) to obtain different Under the action of confining pressure and matrix suction, the anti-pullout parameters of the single root of different ages in the root-containing soil are expected to be tested, and the root pull-out test of the single root to be tested in the root-containing soil of different ages under the action of different confining pressure and matrix suction is completed. .

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