CN113092283B - Apparatus and method for analyzing mechanical properties of soil under the action of plant roots - Google Patents

Abstract

The invention discloses a device and a method for analyzing mechanical characteristics of soil under the action of a plant root system, wherein the device comprises a cultivation container and a cultivation control system; a porous plate is arranged in the cultivation container, and a cultivation sleeve is arranged on the porous plate; the cultivation control system comprises a first water level sensor, a temperature sensor, a timer, a controller, a first electromagnetic valve, a second electromagnetic valve, a third electromagnetic valve, a water pumping device, a nutrient solution pumping device, a water tank, a nutrient solution tank and a heating sheet; the cultivating container is provided with a transfusion hose. The invention also provides a method for testing by adopting the analysis device, which comprises the steps of cultivating the root-soil complex sample, taking out the root-soil complex sample, carrying out a triaxial compression test, carrying out a direct shear test and carrying out a root system extraction test in the cultivating sleeve. The device has the advantages of convenient demoulding and effective obtaining of an original sample, and the mechanical property research of the soil under the action of the plant root system can be carried out by adopting the device and the method.

Description

Apparatus and method for analyzing mechanical properties of soil under the action of plant roots

technical field

The invention belongs to the technical field of civil test equipment, and in particular relates to a device and method for analyzing mechanical properties of soil under the action of plant roots.

Background technique

With the development of urban construction and transportation infrastructure, the slope surface soil sliding, soil erosion and other disasters caused by engineering activities are increasing year by year, causing potential harm to cities, railways and highways to a certain extent, and also bringing about social and economic construction and development. There is a certain influence. Therefore, speeding up the restoration of slope vegetation, improving the stability of the slope, and reducing soil erosion are urgent problems to be solved at this stage. At present, the role of plant roots in effectively preventing and controlling natural disasters such as shallow slope landslides has been widely recognized and accepted. An important indicator to measure the effect of plant roots in soil consolidation and slope protection is the effect of plants on the shear strength of soil, which is the key to understanding the strengthening effect of plant roots on soil strength. It is an important way to stabilize slopes excavated in engineering facilities and avoid soil erosion.

At present, the common laboratory tests of soil shear strength include direct shear test, triaxial compression test, and unconfined compressive strength test. It is difficult to test indoors, and it is difficult to take samples outdoors, so remolded soil is often used in the laboratory for testing. However, since the reshaped root-soil complex soil is artificially formed, compared with the root-soil complex under natural conditions, the The structure cannot be kept consistent. How to effectively obtain the undisturbed samples and use the obtained undisturbed samples to analyze the mechanical properties of soil under the action of plant roots is an important way to reduce the experimental error and improve the experimental accuracy.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a device and method for analyzing the mechanical properties of soil under the action of plant roots, aiming at the above-mentioned deficiencies of the prior art. The device for analyzing the mechanical properties of soil under the action of the plant root system of the invention has the advantages of convenient demoulding, can effectively obtain the original sample, and can conduct research on the influence of the plant root system on the strength properties of loess.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is: a device for analyzing the mechanical properties of soil under the action of plant roots, which is characterized in that it includes: a cultivation container and a cultivation control system for cultivating a root-soil composite sample; The cultivation container is provided with a permeable plate, and the permeable plate is provided with a cultivation sleeve for plant seeds to be sprinkled into, and the number of the cultivation sleeve is multiple;

The cultivation control system includes a first water level sensor, a temperature sensor, a timer, a controller, a first solenoid valve, a second solenoid valve, a third solenoid valve, a water pumping device, a nutrient solution pumping device, a water tank, and a nutrient solution tank. and heating plate;

The first water level sensor is arranged in the incubation container; the heating sheet and the temperature sensor are both arranged on the incubation container;

the first water level sensor, temperature sensor, timer, first solenoid valve, second solenoid valve and third solenoid valve are all electrically connected with the controller;

The water tank is provided with a first water inlet pipe, and the end of the first water inlet pipe that is far away from the water tank is connected to the cultivation container, the water pumping device is arranged in the water tank and communicated with the first water inlet pipe, the first electromagnetic a valve is arranged on the first water inlet pipe;

The first water inlet pipe is connected with a second water inlet pipe, and the second solenoid valve is arranged on the second water inlet pipe;

The nutrient solution tank is provided with a third water inlet pipe, and the cultivation container is provided with an infusion hose; the end of the second water inlet pipe away from the first water inlet pipe and the end of the third water inlet pipe away from the nutrient solution tank are both connected On the infusion hose, a liquid outlet hole is opened on the wall of the infusion hose; the nutrient solution pumping device is arranged in the nutrient solution tank and communicated with the third water inlet pipe, and the third solenoid valve is arranged on the third water inlet pipe. Three inlet pipes.

The above-mentioned device for analyzing the mechanical properties of soil under the action of a plant root system, is characterized in that the cultivating sleeve comprises a plurality of pipe sections arranged in sequence, and a connecting sleeve for connecting adjacent pipe sections is sleeved on the pipe section, Each of the pipe sections is provided with a pipe tie; the pipe section includes a left half pipe section and a right half pipe section, and the left half pipe section and the right half pipe section have the same shape and structure.

The above-mentioned device for analyzing the mechanical properties of soil under the action of a plant root system is characterized in that the connecting sleeve includes a left half connecting sleeve and a right half connecting sleeve, and the left half connecting sleeve and the right half connecting sleeve The shape and structure are the same, and the cultivation sleeve further includes a sleeve tie that can be bound and arranged on the connection sleeve.

The above-mentioned device for analyzing the mechanical properties of soil under the action of plant roots is characterized in that the cultivation container is a cultivation container with an interlayer, and the heating sheet is arranged in the interlayer.

The above-mentioned device for analyzing the mechanical properties of soil under the action of plant roots is characterized in that, the device for analyzing mechanical properties further comprises a camera, an LED lamp, a bottom plate, a universal wheel, a solar panel, and a battery capable of storing the electrical energy generated by the solar panel. ;

The bottom plate is arranged under the cultivation container, and a mounting bracket for installing the solar panel, the camera and the LED light is arranged on the bottom plate;

The mounting bracket is a height-adjustable mounting bracket;

The universal wheel is installed on the lower part of the bottom plate.

In addition, the present invention also provides a method for making a device for analyzing mechanical properties of soil under the action of plant roots as described above, characterized in that it includes a method for making a casing for cultivation, and the method for making a casing for cultivation includes:

Step 1: Cut the pipe into N segments to obtain N segmented pipes; the N≥2;

Step 2, cutting each of the segmented pipes in the axial direction, and correspondingly obtaining N groups of left half pipe sections and right half pipe sections with the same shape and structure;

Step 3: aligning the left half-pipe section with the corresponding right half-pipe section to obtain N pipe sections, and respectively tying the pipe sections along the circumferential direction of the pipe sections with cable ties;

Step 4. Place the N pipe sections bound with the pipe section ties in turn to form (N-1) adjacent parts of the pipe sections, and set (N-1) the connecting sleeves to the adjacent parts of the pipe sections, respectively, to obtain: The incubation cannula.

Further, the present invention also provides a method for conducting research by using the above-mentioned device for analyzing the mechanical properties of soil under the action of plant roots, which is characterized in that it includes the cultivation of the root-soil composite sample, the extraction of the root-soil composite sample, Triaxial compression test, direct shear test and root pull-out test in the cultivation casing; the cultivation of the root-soil composite sample includes:

Step 1, filling the sand grains in the cultivation container to form a sand layer with a height of 5cm to 10cm, placing the permeable plate on the sand layer, and vertically setting the cultivation sleeve on the permeable plate;

Step 2, filling the soil into the cultivating casing, ramming and filling in layers, and sprinkling plant seeds;

Step 3: Transport water into the cultivation container, the water entering the cultivation container passes through the sand layer and the permeable plate and then enters the cultivation sleeve, the first water level sensor detects the water level in the cultivation container and transmits the detected water level signal to the controller , the controller controls the first solenoid valve to open, until the water level in the cultivation container reaches the preset height, the first solenoid valve is closed, and the water delivery is completed;

Step 4. The nutrient solution in the nutrient solution tank is transported to the infusion hose through the third water inlet pipe, and the water in the water tank flows into the infusion hose through the second water inlet pipe, and the nutrient solution and water in the infusion hose are passed through the infusion hose. The liquid outlet hole is sprayed into the cultivation casing, sprayed to the preset time, the controller controls the second solenoid valve and the third solenoid valve to close, and the nutrient solution spraying is completed;

Step 5: The temperature sensor detects the temperature, and transmits the detected temperature signal to the controller. The controller compares the obtained temperature signal with the preset temperature value, and when the obtained temperature signal value is lower than the preset temperature value, controls The controller controls the heating sheet to heat until the preset temperature value is reached;

Step 6: Cultivate to the preset cultivation time according to the above steps, and complete the cultivation.

The above-mentioned method is characterized in that, the method for taking out the root-soil composite sample comprises:

After the cultivation is completed, the cultivation sleeve containing the root-soil composite sample is taken out from the cultivation container, the connecting sleeve is removed, and the adjacent part of the pipe section is cut, and the upper section is taken to obtain the root-soil composite sample. In the upper section of the casing, the root-soil composite sample is separated from the inner wall surface of the upper section of the casing, and the tie for the pipe section is removed to obtain the root-soil composite sample.

The above-mentioned method, is characterized in that, the root system pull-out test method in the described cultivation casing comprises:

After the cultivation is completed, the cultivation casing containing the root-soil complex sample is taken out, cut along the junction of the root system of the plant and the plant stem, and the stem-containing part is removed;

Cut along the upper surface of the root-soil composite sample, remove the soil portion 1 cm to 2 cm from the edge of the upper surface, and clamp the root exposed on the upper surface of the root-soil composite sample with a clamp; install the tension gauge on the clamp, The tension meter pulls the clamp, and the clamp drives the root system to the root system to pull out. When the root system breaks during the root system pulling out, record the reading of the pull-down force meter in the fractured state, the diameter of the fracture and the breaking length. When the root system is not broken during the root system pulling out, record the slip. Pull-down force gauge readings, diameter at the end of the taproot, and slip length.

The above method is characterized in that the method further includes a method for determining the shear strength of the root-soil composite, and the determination method includes:

Step 1: Determine the pull-out force T _b according to the root system pull-out test in the cultivation casing, and the unit of T _b is KN;

Step 2: Determine the measured value of the shear strength of the root-soil composite and the measured value of the shear strength of the plain soil according to the triaxial compression test and the direct shear test;

Step 3: Bring the pull-out force T _b described in Step 1 into the formula S _r =1.2·T _b /A to obtain the theoretical value S _r of the root-soil composite cohesion, the unit of S _r is KPa, and A is the shear force. The cross-sectional area, in m ² ;

Step 4, using the measured value of the shear strength of the root-soil composite described in step 2 to subtract the measured value of the shear strength of the plain soil to obtain the measured value of the root-soil composite cohesion;

进行拟合，得到拟合后的根土复合体黏聚力理论值与时间的函数关系S_r(t)；其中a、c、d、k为拟合参数；t为培育时间，以年计；Step 5. Use the theoretical value of root-soil complex cohesion under different incubation times

Fitting is performed to obtain the functional relationship between the theoretical value of root-soil complex cohesion and time S _r (t); where a, c, d, and k are fitting parameters; t is the cultivation time, in years ;

进行拟合，得到根土复合体黏聚力与时间的函数关系c_r(t)；其中a′、c′、d′、k′为拟合参数；t为培育时间，以年计；Step 6. Utilize the cohesion of the root-soil complex under different incubation times

Fitting is performed to obtain the functional relationship between root-soil complex cohesion and time cr ( _t ); where a', c', d', k' are fitting parameters; t is the cultivation time, in years;

，得到修正系数k″(t)；其中，c_素土为素土黏聚力，单位为KPa；Step 7. Bring S _r (t) of Step 5 and _cr (t) of Step 6 into

, the correction coefficient k″(t) is obtained; among them, c _{plain soil} is the cohesion force of plain soil, and the unit is KPa;

Step 8. Bring the correction coefficient k″(t) described in Step 7 into the formula S(t)=k″(t)·S _r +c _{plain soil} to obtain the shear strength S _(t) of the root-soil complex, The unit of S _(t) is KPa.

Compared with the prior art, the present invention has the following advantages:

1. The device of the present invention including the cultivation container, the cultivation sleeve and the cultivation control system has the advantages of convenient demoulding, and can effectively obtain the original sample, and can conduct research on the influence of plant roots on the strength characteristics of loess.

2. Preferably, the cultivation casing of the present invention includes a plurality of pipe sections connected in sequence, and the pipe sections include a left half pipe section and a right half pipe section that can be enclosed, which is more convenient to peel off the internal soil sample.

3. The method of the present invention includes a method for determining the shear strength of the root-soil complex obtained after correcting the Wu-Waldron model according to the root pull-out strength test, and the determination method incorporates the influence of the cultivation time on the root pull-out strength into theoretical calculation. Among them, and using the fitting method to determine the correlation between the correction coefficient and time, the expression of k″ and the S _r calculation formula S _r =k″·1.2·T _b /A are obtained. It can effectively improve the accuracy of the Wu-Waldron model, and is more conducive to the effective evaluation of the soil stabilization stability of the root system based on the test results. Soil and water conservation provides scientific basis.

The technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

Instruction drawings

FIG. 1 is a schematic structural diagram of the present invention.

Fig. 2 is a flow chart of the production of the culture sleeve.

Figure 3 is a block diagram of the control principle of the cultivation control system.

Figure 4 shows the stress-strain relationship diagram of the root-soil composite under unconsolidated and undrained conditions in the triaxial compression test.

Figure 5 shows the stress path diagram of the root-soil composite under the unconsolidated and undrained condition in the triaxial compression test.

Figure 6 shows the stress-strain relationship diagram of the root-soil composite under the consolidated undrained condition in the triaxial compression test.

Figure 7 shows the relationship between the strain of the root-soil composite and the pore water pressure under the consolidated undrained condition in the triaxial compression test.

Figure 8 shows the stress path diagram of the root-soil composite under the consolidated undrained condition in the triaxial compression test.

Figure 9 shows the effective stress path diagram of the root-soil composite under the consolidated undrained condition in the triaxial compression test.

Figure 10 shows the stress-strain relationship diagram of the root-soil composite in the direct shear test of plain soil.

Figure 11 is a graph showing the stress-strain relationship of the root-soil composite sample in the direct shear test after cultivating for 60 days.

Figure 12 is a graph showing the stress-strain relationship of the root-soil composite sample in the direct shear test after culturing for 90 days.

Fig. 13 is a graph showing the stress-strain relationship of the root-soil composite samples cultivated for 120 days in the direct shear test.

Figure 14 is a graph showing the stress-strain relationship of the root-soil composite sample in the direct shear test after cultivating for 150 days.

Figure 15 is a schematic diagram of the principle of the Wu-Waldron model.

reference number

1—bottom plate; 2—cultivation container; 3—sand layer;

411—left half pipe segment; 412—right half pipe segment;

431—left half connecting sleeve; 432—right half connecting sleeve;

44—the cable tie for the pipe section; 45—the cable tie for the casing; 5—the permeable plate;

6—controller; 7—water tank; 71—first water inlet pipe;

72—the second water inlet pipe; 8—water pumping device;

9—the second water level sensor; 10—the nutrient solution tank; 101—the third water inlet pipe;

11—nutrient solution pumping device; 12—infusion hose; 121—liquid outlet;

13—the first water level sensor; 14—the temperature sensor; 15—the first installation rod;

16—solar panel; 17—second installation rod; 18—battery;

19—rod for reinforcement; 20—camera; 21—LED light;

22—Universal wheel; 23—Interlayer; 25—Timer;

26—the first solenoid valve; 27—the second solenoid valve; 28—the third solenoid valve.

Detailed ways

Example 1

This embodiment provides a device for analyzing the mechanical properties of soil under the action of plant roots, including: a cultivation container 2 for cultivating a root-soil composite sample and a cultivation control system; The plate 5 is provided with a cultivating sleeve for plant seeds to be sprinkled into, and the number of the cultivating sleeve is multiple;

The cultivation control system includes a first water level sensor 13, a temperature sensor 14, a timer 25, a controller 6, a first solenoid valve 26, a second solenoid valve 27, a third solenoid valve 28, a water pumping device 8, and a nutrient solution pump. Sending device 11, water tank 7, nutrient solution tank 10 and heating sheet;

The first water level sensor 13 is arranged in the incubation container 2; the heating sheet and the temperature sensor 14 are both arranged on the incubation container 2;

The first water level sensor 13, the temperature sensor 14, the timer 25, the first solenoid valve 26, the second solenoid valve 27 and the third solenoid valve 28 are all electrically connected to the controller 6;

The water tank 7 is provided with a first water inlet pipe 71. The end of the first water inlet pipe 71 away from the water tank 7 is connected to the cultivation container 2. The water pumping device 8 is arranged in the water tank 7 and is connected to the first water inlet pipe. 71 is connected, and the first solenoid valve 26 is arranged on the first water inlet pipe 71;

The first water inlet pipe 71 is connected with a second water inlet pipe 72, and the second solenoid valve 27 is arranged on the second water inlet pipe 72;

The nutrient solution tank 10 is provided with a third water inlet pipe 101, and the cultivation container 2 is provided with an infusion hose 12; the end of the second water inlet pipe 72 is far away from the first water inlet pipe 71 and the third water inlet pipe 101 is far away. One end of the nutrient solution tank 10 is connected to the infusion hose 12, and a liquid outlet hole 121 is opened on the wall of the infusion hose 12; the nutrient solution pumping device 11 is arranged in the nutrient solution tank 10 and is connected to the third The water inlet pipe 101 is connected, and the third solenoid valve 28 is arranged on the third water inlet pipe 101 .

In this embodiment, the plant seeds may be grass seeds, and the grass seeds may be grass seeds for common plants;

In this embodiment, a second water level sensor 9 disposed in the water tank 7 can also be included. The second water level sensor 9 can monitor the water level in the water tank 7. When the water level is lower than the predetermined water level, it is convenient for water replenishment to prevent the water pumping device 8 from idling. .

In this embodiment, the water pumping device 8 and the nutrient solution pumping device 11 are both liquid pumping devices commonly used in the field, such as a liquid delivery pump; the first solenoid valve 26 , the second solenoid valve 27 and the third solenoid valve The valve 28 is a solenoid valve for liquid commonly used in the art.

As a feasible implementation manner, the infusion hose 12 in this embodiment is surrounded in a ring shape and is arranged along the top edge of the incubation container 2 , and the liquid outlet hole 121 is opened in a part of the infusion hose 12 facing the inner cavity of the incubation container 2 . On the other hand, the liquid in the infusion hose 12 is flushed out from the liquid outlet hole 121 and then falls into the cultivation sleeve to simulate rainfall.

In the device for analyzing the mechanical properties of soil under the action of the plant root system of the present embodiment, the cultivation casing includes a plurality of pipe sections arranged in sequence, and the pipe sections are sleeved with connecting casings for connecting adjacent pipe sections. Each of the pipe sections is provided with a pipe section tie 44; a plurality of the pipe sections include a left half pipe section 411 and a right half pipe section 412, and the left half pipe section 411 and the right half pipe section 412 have the same shape and structure. In this embodiment, the cultivation sleeve can be formed by connecting a plurality of pipe sections in sequence, as long as the total length after connection is between 40cm and 45cm. The lengths are respectively 14cm, which can effectively improve the flexibility of installation and combination; the pipe section can be a pipe section with a through cut that can be closed under the action of stress, or a combination of multiple pipe sections, such as the The right half-pipe section 411 and the right half-pipe section 412 enclose the pipe section, which is more convenient to peel off the internal soil sample. As a feasible implementation manner, in this embodiment, the inner diameter of the pipe section is 67.8 mm, the outer diameter is 75 mm, and the inner diameter of the connecting sleeve is 75 mm. In the present embodiment, the cultivation container 2 is a barrel-shaped cultivation container, the upper diameter of the barrel-shaped cultivation container is 32.5cm, the inner diameter is 30cm, the lower diameter outer diameter is 28.1cm, the inner diameter is 26.1cm, and the height of the barrel-shaped cultivation container is 38.5 cm. cm.

In the device for analyzing the mechanical properties of soil under the action of plant roots in this embodiment, the connecting sleeve includes a left half connecting sleeve 431 and a right half connecting sleeve 432, the left half connecting sleeve 431 and the right half connecting sleeve 432 has the same shape and structure, and the cultivation sleeve also includes a sleeve tie 45 that can be tied to the connecting sleeve. In this embodiment, the connecting sleeve is a connecting sleeve that can be sleeved and fixed on the pipe section, for example, it can be a connecting sleeve with a through-cut that can be enclosed under the action of stress, or can be a combination of multiple connecting sleeve parts For example, the connecting sleeve formed by the left half connecting sleeve 431 and the right half connecting sleeve 432 in this embodiment is tied with the sleeve with a cable tie 45 to form a connecting sleeve with a fixed inner diameter, which is easy to disassemble and easy to use.

In this embodiment, the permeable plate 5 is provided with a groove for placing the cultivation sleeve.

In the apparatus for analyzing the mechanical properties of soil under the action of plant roots in this embodiment, the cultivation container 2 is a cultivation container with an interlayer 23 , and the heating sheet is arranged in the interlayer 23 .

In this embodiment, a heating controller is connected to the heating chip; the first water level sensor 13, the second water level sensor 9 and the temperature sensor 14 are all connected to the input end of the controller 6, the first solenoid valve 26, the second The solenoid valve 27, the third solenoid valve 28 and the heating controller are all connected to the output end of the controller 6, and the timer 25 is connected to the controller 6; as a feasible implementation, the water pumping device 8 and the nutrient solution The pumping devices 11 are all connected to the output end of the controller 6;

The water pumping device 8 can be connected to the output end of the controller 6 through the switch circuit of the water pumping device connected to the power supply circuit of the water pumping device 8, and the nutrient solution pumping device 11 can be connected to the power supply circuit of the nutrient solution pumping device 11. The switch circuit of the nutrient solution pumping device is connected to the output end of the controller 6; the switch circuit of the water pumping device and the switch circuit of the nutrient solution pumping device can both be relays;

The process of the controller 6 controlling the water pumping device 8 can be as follows: the controller 6 compares the water level signal transmitted by the first water level sensor 13 with the preset height, and when the water level in the cultivation container 2 is lower than the preset height, the controller 6 opens or maintains The water pumping device 8 and the first solenoid valve 26 are opened, and when the water level in the incubation container 2 reaches the preset height, the controller 6 simultaneously controls the water pumping device 8 and the first solenoid valve 26 to close;

The process for the controller 6 to control the nutrient solution pumping device 11 may be: spraying to a preset time, the controller 6 controls the nutrient solution pumping device 11 , the second solenoid valve 27 and the third solenoid valve 28 to close.

In the device for analyzing the mechanical properties of soil under the action of plant roots in this embodiment, the device for analyzing mechanical properties further includes a camera 20 , an LED light 21 , a bottom plate 1 , a universal wheel 22 , a solar panel 16 , and a storage device generated by the solar panel 16 . battery 18 for electrical energy;

The bottom plate 1 is arranged under the cultivation container 2, and a mounting bracket for installing the solar panel 16, the camera 20 and the LED light 21 is arranged on the bottom plate 1;

The mounting bracket is a height-adjustable mounting bracket;

The universal wheel 22 is installed on the lower part of the base plate 1 .

As a feasible implementation manner, the height-adjustable mounting bracket in this embodiment is composed of a first mounting rod 15 vertically disposed on the base plate 1 and a second mounting rod 17 one end of which is vertically connected to the first mounting rod 15 , the end of the second installation rod 17 away from the first installation rod 15 extends toward the cultivation container 2, the second installation rod 17 is installed on the first installation rod 15 through a bolt and nut assembly, the first installation rod 15 is provided with suitable threaded holes, the number of the threaded holes is multiple, and the plurality of threaded holes are evenly distributed along the axial direction of the first installation rod 15. The height is adjustable; in addition, preferably, the height-adjustable mounting bracket also includes a reinforcing rod 19 connected with the first installation rod 15 and the second installation rod 17, and the reinforcing rod 19 can be used for the first installation rod 15. It is reinforced with the second installation rod 17 to improve the stability of the installation bracket; in this embodiment, as a feasible installation method, the solar panel 16 is installed on the end of the first installation rod 15, and the battery 18 and the camera 20 are installed on the first installation rod 15. On the second installation rod 17, the LED light 21 is installed on the end of the second installation rod 17 facing the cultivation container 2; the movement of the entire analysis device is realized through the movable bottom plate, which is convenient and quick.

The controller 6 is installed on the side of the incubation container 2 ; the timer 25 is arranged on the upper side of the incubation container 2 ; the controller 6 and the timer 25 are located on opposite sides of the incubation container 2 .

Example 2

The present embodiment provides a method for making the device for analyzing the mechanical properties of soil under the action of the plant root system of Example 1, and the method for making the sleeve for cultivation includes:

Step 1: Cut the pipe into N segments to obtain N segmented pipes; the N≥2;

The pipe material is a PVC pipe; the length of the segmented pipe material can be 8cm to 15cm; in this embodiment, the pipe material is cut into three pipe sections with a length of 14cm, which are connected to obtain a cultivation sleeve that meets the standard GB/T50123-2019 Pipe, those skilled in the art will know that, based on the easier stripping of the pipe section or other purposes, connecting two or more than three pipe sections in length to obtain a casing for cultivation, also within the concept of the present invention;

Step 2: Cut each of the segmented pipes in the axial direction, and correspondingly obtain N groups of left half pipe sections 411 and right half pipe sections 412 with the same shape and structure;

Step 3: Align the left half-pipe section 411 with the corresponding right half-pipe section 412 to obtain N pipe sections, and tie the pipe sections with cable ties 44 along the circumference of the pipe section respectively; 412 is encircled to form a tubular body with a fixed diameter; the inner diameter of the tubular body = the inner diameter of the pipe in step 1;

Step 4. Place the N pipe sections bound with the pipe section ties 44 in turn to form (N-1) pipe section adjoining places, and (N-1) the connecting sleeves are respectively sleeved to the pipe section adjoining places, The incubation sleeve is obtained. The length of the cannula for cultivation was 42 cm.

Alternatively, take (N-1) pieces of connecting sleeve pipe fittings and cut them in the axial direction to obtain (N-1) sets of left half connecting sleeves 431 and right half connecting sleeves 432 with the same shape and structure, respectively. The half-connecting sleeve 431 and the corresponding right half-connecting sleeve 432 face each other and are sleeved on the adjoining part of the pipe section. After the connecting sleeve is sleeved on the pipe section, the sleeve tie 45 is used along the circumference of the connecting sleeve. Binding to obtain the cultivation casing; the inner diameter of the pipe for connecting the casing is equal to the outer diameter of the pipe in step 1.

Example 3

This embodiment provides a method for research using the device for analyzing the mechanical properties of soil under the action of the plant root system of Example 1, including the cultivation of the root-soil composite sample, the extraction of the root-soil composite sample, the triaxial compression test, Direct shear test and root pull-out test in cultivating casing;

In the method of this embodiment, the cultivation of the root-soil composite sample includes:

Step 1, filling the sand grains in the cultivation container 2, forming a sand layer 3 with a height of 5cm～10cm, placing the permeable plate 5 on the sand layer 3, and vertically setting the cultivation sleeve on the permeable plate 5;

Step 2, filling the soil into the cultivating casing, ramming and filling in layers, until the cultivating casing is filled, stop filling the soil, and sprinkle plant seeds; the soil is loess;

Step 3: Transport water to the cultivation container 2, and the water entering the cultivation container 2 enters the cultivation casing after passing through the sand layer 3 and the permeable plate 5. The first water level sensor 13 detects the water level in the cultivation container 2 and detects the obtained water level. The water level signal is transmitted to the controller 6, and the controller 6 controls the first solenoid valve 26 to open, until the water level in the cultivation container 2 reaches a preset height, the first solenoid valve 26 is closed, and the water delivery is completed; the preset height can be 5cm～ 15cm;

Step 4: The nutrient solution in the nutrient solution tank 10 is transported to the infusion hose 12 through the third water inlet pipe 101, while the water in the water tank 7 flows into the infusion hose 12 through the second water inlet pipe 72, and merges into the nutrient solution in the infusion hose 12. And water is sprayed into the cultivation sleeve through the liquid outlet hole 121 on the infusion hose 12, the time signal of the timer 15 is transmitted to the controller 6, and the controller 6 receives the time signal and compares it with the preset time. To the preset time, the controller 6 controls the timer 15 to stop and the controller 6 controls the second solenoid valve 27 and the third solenoid valve 28 to close to complete the nutrient solution spraying; with the spray flow rate of 4mL/min, the preset time Can be 3min;

The sequence of the process of inputting water in the step 3 and the process of spraying the nutrient solution in the step 4 can be exchanged or carried out simultaneously;

Step 5. In the above process, the temperature sensor 14 detects the temperature and transmits the detected temperature signal to the controller 6. The controller 6 compares the obtained temperature signal with the preset temperature value. When the obtained temperature signal value is low At the preset temperature value, the controller 6 controls the heating plate to heat until the preset temperature value is reached; the preset temperature may be 15°C to 30°C;

The camera 20 monitors the plant growth condition in real time and transmits the growth condition picture to the user's mobile phone, and the user adjusts the illumination intensity of the LED light 21 according to the plant growth condition;

The solar panel 16 absorbs the solar energy and converts it into electrical energy and transmits the electrical energy to the battery 18, and the battery 18 can supply power to the device;

The position of the device can be moved by pushing the bottom plate 1 under the action of the universal wheel 22; in step 6, the cultivation is carried out according to the above steps until the preset cultivation time is reached, and the cultivation is completed. The preset incubation time is 60 days, 90 days, 120 days or 150 days.

Appropriate steps can be selected for strength testing according to needs.

In the method of this embodiment, the method for taking out the root-soil composite sample includes:

After the cultivation is completed, the cultivation sleeve containing the root-soil complex sample is taken out from the cultivation container 2, and the removed part of the cultivation sleeve containing the root-soil complex sample and close to the exposed part of the plant is removed. The connecting sleeve is removed to expose the adjoining part of the upper pipe section and the middle pipe section, and cut along the adjoining part, so that the soil sample and root system inside are cut off at the same time, and the upper pipe section with the exposed part of the plant is taken to obtain The upper section of the casing with the root-soil composite sample; the length of the upper section of the casing in the upper section of the casing of the root-soil composite sample is 14 cm; wherein, the method of removing the connecting casing can be: directly by adding Remove the connecting sleeve with the through incision, or cut the cable tie 45 for the sleeve, and separate the enclosed multiple connecting sleeve parts, such as the left half connecting sleeve 431 and the right half connecting sleeve 432; use a cutter Circumferentially cut along the inner wall surface of the pipe section near the above-ground part of the plant, separate the root-soil composite sample from the inner wall surface of the upper section of the casing, remove the cable tie 44 for the pipe section, and place the opposite left half pipe section 411 with the corresponding right section. The half-pipe section 412 is divided to obtain a root soil composite sample.

In the method of this embodiment, the triaxial compression test includes preparing a sample for triaxial compression, and the preparation method for the sample for triaxial compression includes:

The obtained root-soil composite sample is trimmed and placed between the two nail plates of the soil cutting plate, and the cutting can be placed in the soil cutting plate; The outside of the root-soil composite sample between the nail plates, and then flatten the two ends to obtain the soil sample after cutting, and cut off the exposed root system to obtain the sample for triaxial compression; the height of the soil sample after cutting is 7.82cm～9.78cm cm, the diameter is 3.91cm;

Triaxial compression experiments were performed on the obtained samples for triaxial compression according to GB/T 50123-2019, and the experimental results are shown in Figures 4-9.

Figures 4 and 5 show the test results of the root-soil composite samples incubated for 150 days under unconsolidated and undrained conditions. It can be seen from Figures 4 and 5 that with the increase of confining pressure , the stress-strain relationship curve of the root-soil composite sample showed an overall upward trend, and no peak strength appeared during the shearing process, which changed with the soil (ie plain soil, not shown) loaded into the cultivation casing The law is consistent; the stress path of the root-soil composite sample approaches a straight line, and the slope of the straight line of the stress path is not much different under different confining pressures, and the two tend to be parallel. In addition, it can be seen that the dense points of the stress path are always Appears at the upper right of the straight line, which indicates that under the same axial strain condition, the deviatoric stress increases with the increase of confining pressure, that is, increasing the confining pressure can restrain soil deformation and increase soil strength.

Figures 6 to 7 show the test results of the root-soil composite samples incubated for 150 days under the consolidated undrained condition. It can be seen from Figures 6 to 7 that during the shearing process, when the strain is less than At 4%, the stress increases rapidly; with the increase of shear strain, the increasing trend of stress decreases suddenly. The variation trend of pore water pressure during the shearing process is basically the same. When the shear strain is less than 4%, the pore water pressure increases rapidly with the increase of the shear strain, and when the shear strain is greater than 4%, the pore water pressure is relatively stable. This shows that the plant root system has the effect of enhancing soil strength and resisting deformation.

It can be seen from the comparison of Figures 8 to 9 with Figures 4 to 5 that the stress path characteristics of the unconsolidated undrained test and the consolidated undrained test are basically the same. Drainage test; the overall shape of the effective stress path curve is semi-circular. Compared with the dense points of the stress path, the dense points of the effective stress path move to the left as a whole on the basis of basically the same height, and the distance to the left is equal to the stable value of pore water pressure.

In the method of this embodiment, the method for the direct shear test includes a method for preparing a sample for the direct shear test, and the method for preparing a sample for the direct shear test includes:

The root-soil composite sample is cut, and then the edge of the ring knife coated with Vaseline is aligned with the upper surface of the root-soil composite sample after cutting, so that the center of the upper surface coincides with the center of the ring knife, and the ring knife is used to carry out Circumcising and leveling to obtain the sample for direct shear test; the diameter of the sample for direct shear test is 6.18cm and the height is 2cm;

The obtained samples for the direct shear test are subjected to the direct shear test according to GB/T 50123-2019, and the test results are shown in Figure 10 to Figure 14.

Figures 10 to 14 show the test results of the direct shear test of the root-soil composite samples obtained from plain soil (without seeds), cultivated for 60 days, 90 days, 120 days and 150 days, respectively. From Figures 10 to 14 It can be seen that with the increase of vertical pressure, the stress-strain relationship curve shows an overall upward trend. By comparing Figures 10-14, it can be seen that in the samples of different root growth stages, when the vertical pressure is low (30kPa, 10kPa), with the increase of root growth time, the shear stress decreases and decreases after reaching the peak value The amplitude decreased continuously. When the growth time was 150 days, the shear stress remained stable after reaching the peak value, which indicated that the plant root system could significantly improve the residual strength of loess.

In the method of the present embodiment, the root system pull-out test method in the cultivating casing includes:

After the cultivation is completed, the cultivation casing containing the root-soil complex sample is taken out, cut along the junction of the root system of the plant and the plant stem, and the stem-containing part is removed;

Cut along the upper surface of the root-soil composite sample, remove the part of the soil 1 cm to 2 cm from the edge of the upper surface, and clamp the root exposed on the upper surface of the root-soil composite sample with a clamp; A small brush is used to brush off the excess soil on the surface of the soil body, and the length of the root system exposed on the surface is 1cm to 2cm; the clamp can be a woodworking clamp;

The dynamometer is installed on the fixture, the dynamometer pulls the fixture, the fixture drives the root system to pull out the root system, and the fixture drives the root system to pull out the root system. When the root system breaks during the process of pulling out the root system, record the reading of the pull-down dynamometer in the fractured state and the location of the break. When the root system was not broken during the root extraction process, the pull-down force meter readings in the slip state, the diameter at the end of the main root, and the slip length were recorded.

Exclude the test results corresponding to the 0-0.5cm distance from the fixture at the root fracture, and record other test results; collect the test results data that the fixture has no effect on the fracture, in order to avoid the effect of root fracture caused by clamping by the fixture. The measurement methods of the exposed surface root diameter and the diameter of the root system fracture are all measured by vernier calipers. The vernier calipers are Arrizo electronic vernier calipers. The vernier caliper has an accuracy of 0.01mm and a range of 0 to 150mm; The meter has a range of 500N and an accuracy of 1%.

The method of this embodiment further includes a method for determining the shear strength of the root-soil complex in the root system pull-out test in the cultivation casing, and the determination method includes calculating the shear strength of the root-soil complex according to the following formula: The formula is:

S(t)=k″(t)·S _r +c _{plain soil}

in,

S _r =k″·1.2·T _b /A;

In the above formula, S _(t) is the shear strength of the root-soil composite, in KPa;

S _r is the theoretical value of root-soil composite cohesion, in KPa;

c _{Plain soil} is the cohesive force of plain soil, the unit is KPa;

T _b is the pull-out force, in kN;

A is the shearing section area, the unit is m ² ;

t is the cultivation time, in years.

The above formula is based on an improvement of the Wu-Waldron model, a commonly used model for theoretical calculation of the shear strength of soil with roots.

的长度将增加至

In the Wu-Waldron model, the role of plant roots in the soil is called root-soil complex cohesion, and the model is based on the following assumptions: (1) all roots are perpendicular to the failure surface; (2) there is no sliding pullout (3) All root systems on the damaged surface were pulled off. The principle of Wu-Waldron model is shown in Fig. 15. When the upper soil mass in Fig. 15 produces displacement x, the root segment

will increase in length to

The average tensile stress T _a of the root system depends on the elastic modulus (E) and the length change Δl/l ₀ of the root system under stress, and the relationship is formula (a):

T _a =(Δl/l ₀ )E (a)

where Δl=Z(secβ-1),

The length of the root system after deformation under tensile force depends on the tensile stress in the root system. Formula (b) is calculated from the sum of the tensile stress and the tangential force on the cylindrical root system element:

dT/dl=4τ/D (b)

M is the point where the tensile stress of the root is zero, and M is at the lower end of the root system, τ' is the value of τ, and the tensile stress T _N at point N is obtained by integrating:

in

时根系在拉应力作用下的长度l为：when

The length l of the root system under the action of tensile stress is:

l=T _N D/2τ′ (d)

Taking the average tensile stress T _a as half of the tensile stress at N and l～l ₀ , the following formula (e) is obtained

and (f):

T _α =T _N /2=(Δl/l)E=2τ′EZ(secβ-1)/T _N D (e)

and

T _N =(4τ′ZE/D) ^1/2 (secβ-1) ^1/2 (f)

The first term on the right-hand side of equation (f) is a constant, that is

T _N = k(secβ-1) ^1/2 (g)

where k=(4τ′ZE/D) ^1/2

The root force acting on soil above N and below N can be decomposed into tangential force (F _t ) and normal force (F _n ) on the horizontal plane at N:

F _t =A _r Tsinβ=A _r k(secβ-1) ^1/2 sinβ (h)

F _n =A _r Tcosβ=A _r k(secβ-1) ^1/2 cosβ (i)

where _Ar is the total root cross-sectional area;

The Wu-Waldron model corrects the soil strength according to the force exerted by the root system on the soil. The formula for calculating the shear strength of the root-soil composite is formula (j):

St=C+ark(secβ-1) ^1/2 (sinβ+cosβtanφ)+σ _N tanφ (j)

According to (j), the shear strength of the root-soil composite is the sum of the strength of the plain soil and the cohesion S _r of the root-soil composite, and S _r is:

的取值范围为1.1～1.3，通常取1.2；in

The value range of is 1.1 to 1.3, usually 1.2;

That is, S _r is:

S _r =1.2·Tr ·(A _r /A ₎ (l)

Among them, _Ar is the total root cross-sectional area, in m ² ;

T _r is the tensile strength of the root system, in kPa;

A is the sheared cross-sectional area, in m ² .

The Wu-Waldron model is simple in principle and simple in calculation, and is currently the most widely used model in the study of shear strength prediction of soils with roots. The oversimplification of the root-soil interaction by the Wu-Waldron model makes the calculated results of the model differ greatly from the measured values, sometimes even an order of magnitude. Fracture or sliding process in soil, this test result is less affected by instrumental factors and environmental factors.

The present invention corrects the Wu-Waldron model according to the root pull-out strength test, that is, replaces the tensile force _Tr · _Ar corresponding to the root tensile strength in the formula (1) with the pull-out force T _b required for the root pull-out failure ,get:

S _r =1.2·T _b /A (m)

At the same time, the influence of cultivation time on root pull-out strength was included in the theoretical calculation, and the correlation between the correction coefficient and time was determined by using the Richard growth curve, and the method for determining the shear strength of the root-soil complex was obtained, including:

Step 1, determine the pull-out force T _b according to the root system pull-out test in the above-mentioned cultivation casing, and the unit of T _b is KN; the calculation results are shown in Table 1;

Step 2: According to the above-mentioned triaxial compression test and direct shear test, the measured value of the shear strength of the root-soil composite body and the measured value of the shear strength of the plain soil are obtained; see Table 3, wherein the cultivation time is 0 corresponding to the measured value of the plain soil shear strength. ;

Step 3: Bring the pull-out force T _b described in step 1 into the formula S _r =1.2·T _b /A, to obtain the theoretical value S _r of the cohesion of the root-soil complex, the unit of S _r is KPa, and A is the shear force. The cross-sectional area, in m ² ; the theoretical value S _r of the calculated root-soil composite cohesion is shown in Table 2;

Step 4, using the measured value of the shear strength of the root-soil composite described in step 2 to subtract the measured value of the shear strength of the plain soil to obtain the measured value of the root-soil composite cohesion;

进行拟合，得到拟合后的根土复合体黏聚力理论值与时间的函数关系S_r(t)；其中，a、c、d、k为拟合参数；t为培育时间，以年计；函数关系S_r(t)中各参数见表4；Step 5. Use the theoretical value of root-soil complex cohesion under different incubation times

After fitting, the functional relationship between the theoretical value of root-soil complex cohesion and time S _r (t) is obtained; among them, a, c, d, k are fitting parameters; t is the cultivation time, in years The parameters in the functional relationship S _r (t) are shown in Table 4;

In specific implementation, Origin2017 software is used for fitting;

进行拟合，得到根土复合体黏聚力实测值与时间的函数关系c_r(t)；其中，a′、c′、d′、k′为拟合参数；t为培育时间，以年计；函数关系c_r(t)中各参数见表5；Step 6. Utilize the measured value of root-soil complex cohesion under different incubation times

Fitting is performed to obtain the functional relationship between the measured value of root-soil complex cohesion and time cr ( _t ); among them, a', c', d', k' are fitting parameters; t is the cultivation time, in years The parameters in the functional relationship cr ( _t ) are shown in Table 5;

得到修正系数k″(t)；其中，c_素土为素土黏聚力，单位为KPa，通过室内试验测得；Step 7. Bring S _r (t) of Step 5 and _cr (t) of Step 6 into

The correction coefficient k″(t) is obtained; among them, c _{plain soil} is the cohesive force of plain soil, and the unit is KPa, which is measured by laboratory test;

Step 8. Bring the correction coefficient k″(t) described in Step 7 into the formula S(t)=k″(t)·S _r +c _{plain soil} to obtain the shear strength S _(t ) of the root-soil composite sample ₎ ,

Among them, S _(t) is the shear strength of the root-soil composite sample, the unit is KPa;

S _r is the theoretical value of root-soil composite cohesion, in KPa;

c _{Plain soil} is the cohesive force of plain soil, the unit is KPa;

T _b is the pull-out force, in kN;

A is the shearing section area, the unit is m ² ;

t is the cultivation time, in years.

Table 1 Calculation process and results of S _r (23.61kPa for c _{plain soil} )

Among them, the C _{-containing root soil} was tested by the indoor direct shear test.

Table 2 S _r data of different growth stages

Table 3 C _{root soil} data in different growth stages

Table 4 S _r fitting results by S Richards2 equation

Table 5 c _{Root-bearing soil} fitting results by the SRichards2 equation

In the present invention, the cultivation time is entered into the database including the measured value of the shear strength of the root-soil complex, the measured value of the shear strength of the plain soil and the pull-out force, and the formula is matched with the revised formula. Different test types are calculated and queried.

The invention corrects the Wu-Waldron model according to the root pull-out strength test, incorporates the influence of the cultivation time on the root pull-out strength into the theoretical calculation, and uses the Richard growth curve to determine the correlation between the correction coefficient and time, and obtains The expression of k″ and the calculation formula of S _r S _r =k″·1.2·T _b /A. It can effectively improve the accuracy of the Wu-Waldron model, and is more conducive to the effective evaluation of the soil stabilization stability of the root system based on the test results. Soil and water conservation provides scientific basis.

The above are only preferred embodiments of the present invention, and do not limit the present invention. Any simple modifications, changes and equivalent structural changes made to the above embodiments according to the technical essence of the invention still belong to the technical solutions of the present invention. within the scope of protection.

Claims (7)

1. A method for researching by using a mechanical property analysis device of soil under the action of a plant root system is characterized in that the mechanical property analysis device of soil under the action of the plant root system comprises: a culture vessel (2) and a culture control system for culturing a root-soil complex sample; a water permeable plate (5) is arranged in the cultivation container (2), cultivation sleeves capable of scattering plant seeds are arranged on the water permeable plate (5), and the number of the cultivation sleeves is multiple;

the cultivation control system comprises a first water level sensor (13), a temperature sensor (14), a timer (25), a controller (6), a first electromagnetic valve (26), a second electromagnetic valve (27), a third electromagnetic valve (28), a water pumping device (8), a nutrient solution pumping device (11), a water tank (7), a nutrient solution tank (10) and a heating sheet;

the first water level sensor (13) is arranged in the cultivation container (2); the heating sheet and the temperature sensor (14) are both arranged on the cultivation container (2);

the first water level sensor (13), the temperature sensor (14), the timer (25), the first electromagnetic valve (26), the second electromagnetic valve (27) and the third electromagnetic valve (28) are electrically connected with the controller (6);

a first water inlet pipe (71) is arranged on the water tank (7), one end, far away from the water tank (7), of the first water inlet pipe (71) is connected to the cultivation container (2), the water pumping device (8) is arranged in the water tank (7) and communicated with the first water inlet pipe (71), and the first electromagnetic valve (26) is arranged on the first water inlet pipe (71);

the first water inlet pipe (71) is communicated with a second water inlet pipe (72), and the second electromagnetic valve (27) is arranged on the second water inlet pipe (72);

a third water inlet pipe (101) is arranged on the nutrient solution box (10), and a transfusion hose (12) is arranged on the cultivation container (2); one end of the second water inlet pipe (72) far away from the first water inlet pipe (71) and one end of the third water inlet pipe (101) far away from the nutrient solution tank (10) are both connected to the infusion hose (12), and a liquid outlet hole (121) is formed in the pipe wall of the infusion hose (12); the nutrient solution pumping device (11) is arranged in the nutrient solution box (10) and is communicated with a third water inlet pipe (101), and the third electromagnetic valve (28) is arranged on the third water inlet pipe (101);

the cultivation sleeve comprises a plurality of pipe sections which are arranged in sequence, a connecting sleeve for connecting adjacent pipe sections is sleeved on each pipe section, and a tie (44) for the pipe sections is arranged on each pipe section; the pipe sections comprise a left half pipe section (411) and a right half pipe section (412), and the left half pipe section (411) and the right half pipe section (412) are identical in shape and structure;

the method comprises the steps of cultivating a root-soil complex sample, taking out the root-soil complex sample, performing a triaxial compression test, performing a direct shear test and performing a root system extraction test in a cultivating sleeve; the cultivation of the root soil complex test sample comprises the following steps:

step one, filling sand grains into a cultivation container (2) to form a sand layer (3) with the height of 5-10 cm, placing a water permeable plate (5) on the sand layer (3), and vertically arranging the cultivation sleeve on the water permeable plate (5);

filling soil into the cultivation sleeve, tamping the soil in layers, and scattering plant seeds;

step three, conveying water into the cultivation container (2), enabling the water entering the cultivation container (2) to enter a cultivation casing pipe after passing through a sand layer (3) and a permeable plate (5), detecting the water level in the cultivation container (2) by a first water level sensor (13) and transmitting a detected water level signal to a controller (6), controlling a first electromagnetic valve (26) to be opened by the controller (6) until the water level in the cultivation container (2) reaches a preset height, and closing the first electromagnetic valve (26) to finish water conveying;

conveying nutrient solution in the nutrient solution box (10) to a transfusion hose (12) through a third water inlet pipe (101), simultaneously enabling water in the water tank (7) to flow into the transfusion hose (12) through a second water inlet pipe (72), spraying the nutrient solution and the water which are converged into the transfusion hose (12) into a sleeve for cultivation through a liquid outlet hole (121) in the transfusion hose (12) until preset time is reached, and controlling a second electromagnetic valve (27) and a third electromagnetic valve (28) to be closed by a controller (6) to finish nutrient solution spraying;

step five, the temperature sensor (14) detects the temperature, and transmits a detected temperature signal to the controller (6), the controller (6) compares the obtained temperature signal with a preset temperature value, and when the obtained temperature signal value is lower than the preset temperature value, the controller (6) controls the heating sheet to heat until the temperature reaches the preset temperature value;

culturing according to the steps to preset culturing time, and finishing culturing;

the method comprises a determination method of the shear strength of the root-soil complex, and the determination method comprises the following steps:

step one, determining the extraction force T according to a root extraction test in a cultivation sleeve _b ，T _b The unit is KN;

determining a shear strength measured value of the root-soil complex and a shear strength measured value of the plain soil according to a triaxial compression test and a direct shear test;

step three, the pull-out force T in the step one is used _b Substituting into formula S _r ＝1.2·T _b A, obtaining a theoretical value S of the cohesive force of the root-soil complex _r ，S _r Has a unit of KPa, A is the shear cross-sectional area, and m is the unit ² ；

Step four, subtracting the shear strength measured value of the native soil from the shear strength measured value of the root soil complex in the step two to obtain a measured value of the cohesion of the root soil complex;

step five, utilizing the theoretical value of the cohesion of the root-soil complex under different cultivation time

Fitting to obtain the functional relation S between the theoretical value of cohesive force of the fitted root-soil complex and time _r (t); wherein a, c, d and k are fitting parameters; t is the cultivation time in years;

step six, utilizing the cohesion of the root-soil complex under different cultivation time

Fitting to obtain the functional relation c between the cohesive force of the root-soil complex and the time _r (t); wherein a ', c', d 'and k' are fitting parameters; t is the cultivation time in years;

step seven, the S of the step five _r (t) and c of step six _r (t) bringing in

Obtaining a correction coefficient k' (t); wherein, c _{Plain soil} The unit is the cohesive force of the plain soil and KPa;

step eight, mixingIn step seven, the correction coefficient k ″ (t) is substituted into the formula S (t) ═ k ″ (t) · S _r +c _{Plain soil} The shear strength S (t) of the root-soil composite is obtained, and the unit of S (t) is KPa.

2. The method according to claim 1, wherein said coupling sleeves comprise a left coupling sleeve half (431) and a right coupling sleeve half (432), said left coupling sleeve half (431) and said right coupling sleeve half (432) being identical in shape and structure, said cultivating sleeve further comprising a sleeve tie (45) attachable to said coupling sleeves.

3. The method according to claim 1, wherein the incubation container (2) is an incubation container with a sandwich (23), and the heating sheet is disposed in the sandwich (23).

4. The method according to claim 1, wherein the mechanical property analysis device further comprises a camera (20), an LED lamp (21), a bottom plate (1), a universal wheel (22), a solar light panel (16) and a storage battery (18) capable of storing electric energy generated by the solar light panel (16);

the bottom plate (1) is arranged below the cultivation container (2), and a mounting bracket for mounting the solar light panel (16), the camera (20) and the LED lamp (21) is arranged on the bottom plate (1);

the mounting bracket is a height-adjustable mounting bracket;

the universal wheels (22) are arranged at the lower part of the bottom plate (1).

5. The method of claim 1, wherein the method of removing the root-soil composite sample comprises:

after completion of the culture, the culture sleeve containing the sample of the root-soil complex is taken out of the culture container (2), the connecting sleeve is removed, the sleeve is cut along the adjacent position of the pipe section, the upper section of the sleeve containing the sample of the root-soil complex is taken out, the upper section of the sleeve containing the sample of the root-soil complex is obtained, the sample of the root-soil complex is separated from the inner wall surface of the upper section of the sleeve, and the tie (44) for the pipe section is removed, so that the sample of the root-soil complex is obtained.

6. The method of claim 1, wherein the root pull-out test method in the cultivation sleeve comprises:

after the cultivation is finished, taking out the cultivation sleeve filled with the root soil complex sample, cutting the cultivation sleeve along the joint of the root system and the plant stem of the plant, and removing the stem-containing part;

cutting along the upper surface of the root-soil complex sample, removing a soil body part 1-2 cm away from the edge of the upper surface, and clamping the root part of the upper surface of the exposed root-soil complex sample by using a clamp; install the tensiometer in on the anchor clamps, tensiometer pulling anchor clamps, anchor clamps drive the root system and extract to the root system, when the root system extracted the process root system fracture, under the record rupture state the tensiometer reading, the diameter and the rupture length of fracture department, when the root system extracted the process root system not fracture, under the record slippage state the tensiometer reading, main root terminal department diameter and the length of sliding.

7. A method for manufacturing a device for analyzing mechanical properties of soil under plant root system action, the device for analyzing mechanical properties of soil under plant root system action being the device for analyzing mechanical properties of soil under plant root system action as set forth in claim 1, the method for manufacturing the device for analyzing mechanical properties of soil under plant root system action comprising a method for manufacturing a cultivation sleeve, the method for manufacturing the cultivation sleeve comprising:

cutting a pipe into N sections to obtain N sectional pipes; n is more than or equal to 2;

step two, cutting each section of pipe material along the axial direction, and correspondingly obtaining N groups of left half pipe sections (411) and right half pipe sections (412) with the same shape and structure;

step three, the left half pipe section (411) is opposite to the corresponding right half pipe section (412) to obtain N pipe sections, and the pipe sections are bound by binding tapes (44) along the circumferential direction of the pipe sections respectively;

and step four, sequentially placing N pipe sections bound with the pipe section binding tapes (44) to form (N-1) pipe section adjacent positions, and respectively sleeving the (N-1) connecting sleeves to the pipe section adjacent positions to obtain the cultivation sleeves.

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