Test device for inhibiting rainfall from infiltrating side slope by using automatic supercharged capillary barrier layer

Abstract

The invention provides an automatic pressurization type test device for inhibiting rainfall from infiltrating into a side slope through a capillary barrier layer. The automatic pressurization type test device comprises a model tank, a protection side slope, the capillary barrier layer, a rainfall system, a soil matrix suction monitoring system and an automatic pressurization system. The model groove comprises a model cavity and a wedge body arranged at the bottom of the model cavity, the bottom of the model cavity is filled with cohesive soil to form a protective slope, the protective slope is filled with various kinds of soil to form a capillary barrier layer, and the capillary barrier layer sequentially comprises a coarse grain layer, a transition layer and a fine grain layer from bottom to top; the automatic pressurization system is used for injecting set air pressure into the coarse grain layer when the soil matrix suction value, monitored by the soil matrix suction monitoring system, in the fine grain layer is smaller than a critical value, so that certain air pressure is formed in the coarse grain layer, and it is restrained that rainfall breaks through a fine grain layer / transition layer interface; rainwater is moved and discharged from the fine particle layer above the fine particle layer / transition layer interface. According to the invention, the coarse grain layer can be automatically pressurized, so that the capillary barrier layer can completely block rainfall infiltration.

Description

Technical Field

[0001] The invention relates to the field of slope landslide disaster management, in particular to a test device for suppressing rainfall infiltration into a slope with an automatic pressurized capillary barrier layer. Background Art

[0002] Controlling rainfall infiltration into slopes is one of the fundamental methods to control slope landslide disasters. At present, surface treatment methods such as cement spraying and film covering are mainly used to inhibit rainfall infiltration, but under the influence of long-term thermal expansion and contraction, dry-wet cycles, human and animal activities, surface cracking and damage are prone to occur, causing rainfall to infiltrate the slope again, causing the slope to face the risk of landslide again.

[0003] A capillary barrier layer with a fine-grained upper layer and a coarse-grained lower layer can be used to inhibit rainfall infiltration into the slope (patent application numbers 201310339617.1, 201910104167.5, 202010337655.3, etc.). However, according to existing literature (Wu Qinghua et al. Physical model test of slope with unsaturated drainage structure to control rainfall infiltration. Chinese Journal of Geotechnical Engineering, 2017, 39(1): 154-160), it is found that when the rainfall is large and lasts for a long time, the water content of the fine-grained layer is close to saturation, and the suction of the soil matrix in the fine-grained layer drops to the critical value of the fine-grained layer / coarse-grained layer interface of the capillary barrier layer, a small amount of rainfall can still penetrate the fine-grained layer / coarse-grained layer interface and enter the coarse-grained layer, which significantly reduces the efficiency of the capillary barrier layer in inhibiting rainfall infiltration. Rainfall that enters the coarse-grained layer quickly moves to the slope along the large pores in the coarse-grained layer and infiltrates. The water content of the slope strata increases, and softening occurs, resulting in a decrease in its soil mechanics parameters and worsening slope stability. In severe cases, slope instability may occur, such as landslides and other geological disasters, so this method still has certain risks in actual application in dealing with landslide disasters. Summary of the invention

[0004] In view of the problem that the current capillary barrier layer has a poor effect in inhibiting rainfall infiltration, the present invention proposes a test device for an automatic pressurized capillary barrier layer to inhibit rainfall infiltration on a slope, which can automatically increase the pressure in the coarse-grained layer to ensure that the capillary barrier layer completely blocks rainfall infiltration.

[0005] An experimental device for suppressing rainfall infiltration into a slope with an automatic pressurized capillary barrier layer, comprising a model trough, a protective slope, a capillary barrier layer, a rainfall system, a soil matrix suction monitoring system, an automatic pressurization system and a drainage collection system;

[0006] The model trough comprises a model cavity and a wedge placed at the bottom of the model cavity, the bottom of the model cavity is filled with clay to form the protective slope, various types of soil are filled on the protective slope to form the capillary barrier layer, and the capillary barrier layer is composed of a coarse-grained layer, a transition layer and a fine-grained layer from bottom to top;

[0007] The rainfall system is placed on the upper part of the model trough to simulate rainfall of different intensities;

[0008] The soil matrix suction monitoring system is used to monitor the soil matrix suction value in the fine particle layer;

[0009] The automatic pressurization system is used to inject a set air pressure into the coarse grain layer when the soil matrix suction value in the fine grain layer monitored by the soil matrix suction monitoring system is less than a critical value, so as to form a certain air pressure in the coarse grain layer, thereby forming a supporting effect on the water in the interface of the fine grain layer / transition layer, inhibiting rainfall from breaking through the interface of the fine grain layer / transition layer, and allowing rainfall to migrate and drain from the fine grain layer above the interface of the fine grain layer / transition layer, thereby completely preventing rainfall from infiltrating the coarse grain layer;

[0010] The drainage collection system is used to collect drainage from the fine-grained layer, the coarse-grained layer and the protective slope.

[0011] Furthermore, the upper part of the model cavity is hollowed out, and the left side within 10 cm from the top of the model cavity is a side porous plate, and the other surfaces are all impermeable plates.

[0012] Furthermore, the inclination angle of the wedge is 20°-30°, and the model cavity 1 is tilted and placed on the inclined surface of the wedge after the soil sample is filled.

[0013] Furthermore, the fine-grained layer is made of fine sand or sub-sand suitable for vegetation growth, and the saturated permeability coefficient is 5.0×10 -4 ~1×10 -3 cm / s; the coarse-grained layer is made of coarse sand, gravel sand, angular gravel and other materials with a permeability of 1 to 10 cm / s; a transition layer is added between the fine-grained layer and the coarse-grained layer to enhance the efficiency of the unsaturated structure with a fine-grained layer on the upper layer and a coarse-grained layer on the lower layer in suppressing rainfall infiltration into the slope. The average particle size of the transition layer is between the fine-grained layer and the coarse-grained layer, and the fine-grained layer and the coarse-grained layer are mixed in a mass ratio of 1:3 to 3:1.

[0014] Furthermore, the rainfall system includes a water inlet pipe, a rainfall simulation water tank, an overflow pipe, a needle and a rainfall bracket. The rainfall simulation water tank is a rectangular cavity and is placed on the rainfall bracket; the rainfall bracket is a hollow rectangular wedge with the same inclination angle as the wedge, which is placed on the model cavity to provide a horizontal rainfall support platform for the rainfall system; the needles are evenly distributed at the bottom of the rainfall simulation water tank, and the overflow pipe is connected to the rainfall simulation water tank; the needles are used to simulate raindrops, and different rainfall intensities are obtained by adjusting the water level in the rainfall simulation water tank.

[0015] Furthermore, the soil matrix suction monitoring system includes a soil matrix suction sensor, a data line and a soil matrix suction value collection and wireless transmission system. A plurality of soil matrix suction sensors are evenly buried in the fine particle layer near the contact interface between the fine particle layer and the transition layer. The soil matrix suction sensors are connected to the soil matrix suction value collection and wireless transmission system through the data line. The soil matrix suction value collection and wireless transmission system is used to send the soil matrix suction value collected by the soil matrix suction sensor to the automatic pressurization system.

[0016] Furthermore, the soil matrix suction sensor is a clay tensiometer.

[0017] Furthermore, the automatic pressurization system includes an air compressor, a micro-pressure controller, a coarse-grained layer air release system, a soil matrix suction value receiving and power start-stop control system, and an air injection pipe. The air compressor is used to provide a high-pressure air source, which is then injected into the micro-pressure controller to form a lower-pressure air source after pressure stabilization treatment, and then the coarse-grained layer air release system is injected and pressurized through the air injection pipe. The coarse-grained layer air release system is buried in the coarse-grained layer; the soil matrix suction value receiving and power start-stop control system is used to start and close the power of the air compressor and the micro-pressure controller according to the soil matrix suction value in the fine grain layer monitored by the soil matrix suction monitoring system.

[0018] Furthermore, the coarse-grained layer air release system is an air injection network composed of hollow copper tubes, on which a plurality of air injection holes are evenly arranged for evenly injecting air into the coarse-grained layer, so that a uniform air pressure is formed at the interface between the entire coarse-grained layer and the transition layer.

[0019] Furthermore, the soil matrix suction value receiving and power start-stop control system includes a wireless signal receiving element, a power start-stop control element, and a soil matrix suction value and power switch associated component. The wireless signal receiving element is used to receive the soil matrix suction value sent by the soil matrix suction value collection and wireless transmission system, and to judge through the soil matrix suction value and power switch associated component. When the soil matrix suction value is less than a critical value, the power of the air compressor and the micro-pressure controller is started through the power start-stop control element to inject gas into the coarse-grained layer. When the soil matrix suction value is greater than the critical value, the power of the air compressor and the micro-pressure controller is shut down through the power start-stop control element to stop injecting gas into the coarse-grained layer. The critical value is the soil matrix suction value of the fine-grained layer when rainfall begins to enter the transition layer.

[0020] The present invention injects air of a certain pressure into the coarse-grained layer of the capillary barrier layer, forms a certain air pressure in the coarse-grained layer below the interface of the fine-grained layer / transition layer, forms a supporting effect on the moisture in the interface of the fine-grained layer / transition layer, inhibits rainfall from breaking through the interface of the fine-grained layer / transition layer, causes rainfall to migrate from the fine-grained layer above the interface of the fine-grained layer / transition layer and be discharged therefrom, completely prevents rainfall from infiltrating the coarse-grained layer, and significantly improves the efficiency of the capillary barrier layer in inhibiting rainfall infiltration; in the traditional capillary barrier layer with a fine-grained layer on the upper layer and a coarse-grained layer on the lower layer, the capillary barrier layer can effectively prevent rainfall from infiltrating the coarse-grained layer. Adding a transition layer to the interface of the fine-grained layer / coarse-grained layer in the barrier layer can significantly improve the barrier effect of the traditional capillary barrier layer on rainfall infiltration; at the same time, the device can automatically increase the pressure in the coarse-grained layer to meet the complete blocking of rainfall infiltration by the capillary barrier layer, that is, when the soil matrix suction of the soil negative pressure sensor buried in the fine-grained layer is less than the critical value (such as 20hPa), the coarse-grained layer pressurization system is automatically started to pressurize the coarse-grained layer, and when the soil matrix suction is greater than the critical value (such as 20hPa), the coarse-grained layer pressurization is stopped. This method automatically starts the coarse-grained layer pressurization system only when there is continuous rainfall or heavy rainfall (the water content of the fine-grained layer is high, that is, the soil matrix suction is low), and stops pressurizing when the rainfall stops and the soil matrix suction of the fine-grained layer is high. The capillary barrier layer device can automatically block the infiltration of rainfall into the slope, providing an important means for the research and development of the capillary barrier layer to control the slope rainfall infiltration technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of a test device for suppressing rainfall infiltration into a slope using an automatic pressurized capillary barrier layer according to an embodiment of the present invention;

[0022] Figure 2 is a schematic structural diagram of a coarse-grained layer air release system according to an embodiment of the present invention;

[0023] Figure 3 The comparison of the effect of suppressing rainfall infiltration when a transition layer is added between the fine-grained layer and the coarse-grained layer in this aspect is implemented;

[0024] Figure 4 The present invention compares the effects of suppressing rainfall infiltration by a pressurized coarse-grained layer and a non-pressurized capillary barrier layer.

[0025] In the figure: 1-model cavity, 2-fine-grained layer; 3-transition layer, 4-coarse-grained layer, 5-coarse-grained layer air release system, 6-protective slope, 7-wedge, 8-slope porous plate, 9-slope drainage collection cavity; 10-gravel layer, 11-water flow direction, 12-water inlet pipe, 13-rainfall simulation trough, 14-overflow pipe, 15-needle, 16-rainfall bracket, 17-side porous plate, 18-soil matrix suction sensor, 19-fine-grained layer drainage collection device, 20-coarse-grained layer drainage collection device, 21-slope soil drainage collection device, 22-data line, 23-soil matrix suction value acquisition and wireless transmission system, 24-soil matrix suction value reception and power start-stop control system, 25-air flow direction, 26-air injection pipe, 27-air compressor, 28-micro-pressure controller, 29-air injection hole. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Figure 1 The figure shows an experimental device for suppressing rainfall infiltration into a slope with an automatic pressurizing capillary barrier layer according to an embodiment of the present invention, comprising a model trough, a protective slope 6, a capillary barrier layer, a rainfall system, a soil matrix suction monitoring system, an automatic pressurizing system and a drainage collection system.

[0028] The model tank includes a model cavity 1 and a wedge 7 placed at the bottom of the model cavity 1. The model cavity 1 is a cuboid of 20 cm in length, 16 cm in width and 20 cm in height, and is used to fill various types of soil, etc. The material is 1 cm thick organic glass. The upper part of the model cavity 1 is hollowed out for easy filling. The left side is a side porous plate 17 within a range of 10 cm from the top of the model cavity 1, and the other surfaces are all impermeable plates. The inclination angle of the wedge 7 is 20°-30°. After the soil sample is filled in the model cavity 1, it will be placed on the inclined surface of the wedge 7 to form a protective slope 6 with an inclination angle of 20°-30°.

[0029] The protective slope 6 is a clay slope with an inclination of 20° to 30° and a thickness of 3 cm. It is filled according to the designed dry density and is a capillary barrier layer to suppress rainfall infiltration. The bottom of the protective slope 6 is a slope porous plate 8 for water drainage.

[0030] The capillary barrier layer is the key part of the slope to inhibit rainfall infiltration, including the fine-grained layer 2, transition layer 3 and coarse-grained layer 4 arranged from top to bottom. The thickness of the fine-grained layer 2, transition layer 3 and coarse-grained layer 4 are 9 cm, 2 cm and 5 cm respectively. The fine-grained layer 2 is mainly made of fine sand or sub-sand suitable for vegetation growth. It has strong permeability and can meet the requirement of not forming surface runoff during heavy rain. Its saturated permeability coefficient is generally 5.0×10 -4 ~1×10 -3 cm / s. Compared with the fine-grained layer 2, the average particle size of the coarse-grained layer 4 is significantly larger, and it is mainly made of coarse sand, gravel sand, angular gravel and other materials, and its permeability coefficient is generally 1 to 10 cm / s. In order to enhance the effect of the traditional capillary barrier composed of the fine-grained layer and the coarse-grained layer in inhibiting rainfall infiltration, a transition layer 3 is added between the fine-grained layer 2 and the coarse-grained layer 4. The average particle size of the transition layer 3 is between that of the fine-grained layer 2 and the coarse-grained layer 4, and is generally formed by mixing the fine-grained layer 2 and the coarse-grained layer 4 in a mass ratio of 1:3 to 3:1.

[0031] The rainfall system includes a water inlet pipe 12, a rainfall simulation water tank 13, an overflow pipe 14, a needle 15 and a rainfall bracket 16. The rainfall simulation water tank 13 is a rectangular cavity with a length of 20 cm, a width of 16 cm and a height of 20 cm, a thickness of 1 cm, and is made of organic glass material and is placed on the rainfall bracket 16. The rainfall bracket 16 is a hollow rectangular wedge with an inclination angle of 20°-30°, made of organic glass, and has the same inclination angle as the wedge 7. It is placed on the model cavity 1 to provide a horizontal rainfall support platform for the rainfall system. The needles 15 are evenly distributed at the bottom of the rainfall simulation water tank 13, and the overflow pipe 14 is connected to the rainfall simulation water tank 13. The needles 15 are used to simulate raindrops, and different rainfall intensities can be obtained by adjusting the water level in the rainfall simulation water tank 13. The needles 15 can be medical needles with an inner diameter of 5 mm and a spacing of 2.5 cm. To prevent the needle 15 from being blocked, filtered tap water or purified water can be injected into the water inlet pipe 12, and its flow rate should be slightly greater than the rainfall intensity of the rainfall system, and the excess rainfall will flow out through the overflow pipe 14. To prevent the gas in the water from blocking the needle 15, the indoor temperature should be kept constant throughout the test process.

[0032] The soil matrix suction monitoring system includes a soil matrix suction sensor 18, a data line 22, and a soil matrix suction value acquisition and wireless transmission system 23. The soil matrix suction sensor 18 is a clay tensiometer, which mainly measures the matrix suction of the soil in the fine particle layer 2, and its measurement range is +85KPa to -85KPa, and the measurement accuracy is 0.1hPa. Three soil matrix suction sensors 18 are evenly buried in the fine particle layer 2cm away from the contact interface between the fine particle layer 2 and the transition layer 3. The soil matrix suction sensor 18 is connected to the soil matrix suction value acquisition and wireless transmission system 23 through the data line 22. The soil matrix suction value acquisition and wireless transmission system 23 consists of an acquisition system and a wireless signal transmission module. The acquisition frequency of the acquisition system is 1 time / 2min to 1 time / 24h, which can be freely set according to needs; the soil matrix suction value is wirelessly transmitted through the wireless signal transmission module.

[0033] The automatic pressurization system includes an air compressor 27, a micro-pressure controller 28, a coarse-grained layer air release system 5, a soil matrix suction value receiving and power start-stop control system 24, and an air injection pipe 26. The air compressor 27 provides a high-pressure air source, which is then injected into the micro-pressure controller 28. After pressure stabilization, a lower-pressure air source is formed, and then air is injected and pressurized into the coarse-grained layer air release system 5 through the air injection pipe 26. The air pressure range output by the micro-pressure controller 28 is the atmospheric pressure value + 0 to 50 hPa, forming a pressure difference of 0 to 50 hPa, and the injection pressure into the coarse-grained layer 4 cannot be too large, otherwise the fine-grained layer 2 will be lifted. The coarse-grained layer air release system 5 is an air injection network composed of hollow copper tubes with a diameter of 10 mm, such as Figure 2 As shown. An air injection hole 29 with a diameter of 6 mm is set every 3 cm on the hollow copper tube, which is used to uniformly inject air into the coarse-grained layer 4, so that a relatively uniform air pressure is formed at the interface between the entire coarse-grained layer 4 and the transition layer 3. The soil matrix suction value receiving and power start-stop control system 24 is a key element for the device of the present invention to realize the automatic start-stop boosting system, including a wireless signal receiving element, a power start-stop control element, and a soil matrix suction value and power switch associated component, wherein the wireless signal receiving element receives the soil matrix suction value sent by the soil matrix suction value collection and wireless transmission system 23, and the soil matrix suction value and power switch associated component are judged. When the soil matrix suction value is less than the critical value of 20hPa, the power of the air compressor 27 and the micro-pressure controller 28 is started through the power start-stop control element, and air is injected into the coarse-grained layer 4. When the soil matrix suction value is greater than the critical value of 20hPa, the power of the air compressor 27 and the micro-pressure controller 28 is shut down through the power start-stop control element, and the injection of air into the coarse-grained layer 4 is stopped.

[0034] The drainage collection system includes a fine-grained layer drainage device 19, a coarse-grained layer drainage device 20, and a slope drainage device 21. The fine-grained layer drainage device 19 and the slope drainage device 21 are open water containers, and the coarse-grained layer drainage device 20 is a closed water container, whose air pressure is consistent with the coarse-grained layer 4, ensuring that the coarse-grained layer 4 is drained without exhaust, so that the air pressure in the coarse-grained layer 4 is maintained unchanged when the coarse-grained layer 4 is drained. The water containers of the fine-grained layer drainage device 19, the coarse-grained layer drainage device 20, and the slope drainage device 21 are all placed on an electronic balance to dynamically monitor the drainage rate of the fine-grained layer, the coarse-grained layer, and the slope.

[0035] Working principle: Place the model cavity 1 horizontally, and then fill the configured protective slope 6 (clay), coarse-grained layer 4, transition layer 3 and fine-grained layer 2 from bottom to top in order according to the designed density and initial water content, and finally lay a crushed stone layer 10 on the surface of the fine-grained layer 2 to prevent rainfall erosion. When filling the coarse-grained layer 4, bury the coarse-grained layer air release system 5 in the coarse-grained layer 4 as required; when filling the fine-grained layer 2, bury and connect the soil matrix suction sensor 18 as required. Place the filled model cavity 1 on the wedge 7, and then place the rainfall bracket 16 on the model cavity 1 to form a horizontal platform, and then place the rainfall simulation trough 13 on the rainfall bracket 16, and set the height of the overflow pipe 14 (corresponding to the designed rainfall intensity). Before the rainfall test begins, set the fine-grained layer drainage device 19, the coarse-grained layer drainage device 20 and the protective slope drainage device 21, and use a large-range (0.1g accuracy) electronic balance to dynamically monitor the drainage volume.

[0036] Water is supplied to the rainfall simulation tank 13 through the water inlet pipe 12, and rainfall begins. If the rainfall intensity is large, so that the soil matrix suction value in the fine-grained layer 2 is less than the critical value of 20hPa, a start signal is sent to the soil matrix suction value receiving and power supply start-stop control system 24 through the soil matrix suction value acquisition and wireless transmission system 23, and the air compressor 28 and the micro-pressure controller 29 are started to start injecting the set air pressure into the coarse-grained layer 4. If the soil matrix suction value in the fine-grained layer 2 is greater than the critical value of 20hPa, a shutdown signal is sent to the soil matrix suction value receiving and power supply start-stop control system 24 through the soil matrix suction value acquisition and wireless transmission system 23, and the air compressor 28 and the micro-pressure controller 29 are shut down, and the injection of air into the coarse-grained layer 4 is stopped.

[0037] The present invention fundamentally makes up for the shortcoming that the current capillary barrier layer composed of a fine-grained layer and a coarse-grained layer has a poor effect in inhibiting rainfall infiltration, and achieves the purpose of completely blocking rainfall infiltration with a capillary barrier layer. The present invention adds a transition layer to the interface of the fine-grained layer / coarse-grained layer in a traditional capillary barrier layer with a fine-grained layer on the upper layer and a coarse-grained layer on the lower layer, which can significantly improve the blocking effect of the traditional capillary barrier layer on rainfall infiltration. The comparison of the rainfall infiltration inhibition effect when the present invention is implemented by adding a transition layer between the fine-grained layer and the coarse-grained layer is shown in FIG. Figure 3; In addition, the present invention dynamically monitors the matrix suction value of the fine-grained layer 2 cm above the interface of the fine-grained layer / transition layer and compares and distinguishes it with its critical value, and dynamically associates the soil matrix suction value in the fine-grained layer above the interface of the fine-grained layer / transition layer with the start of the automatic pressurization system through a wireless transmission signal module, so as to realize the automatic pressurization-stop function, that is, when the matrix suction value of the fine-grained layer is lower than the critical value (when the matrix suction of the fine-grained layer is less than the critical value, the water content of the fine-grained layer is relatively large, and part of the rainfall breaks through the boundary of the fine-grained layer / transition layer and enters the coarse-grained layer; when the matrix suction of the fine-grained layer is greater ... When the water content of the fine-grained layer is low, the rainfall is not easy to break through the boundary of the fine-grained layer / transition layer, then all rainfall is discharged from the fine-grained layer and does not enter the coarse-grained layer) the automatic pressurization system is started to inhibit rainfall from breaking through the interface of the fine-grained layer / transition layer; when the matrix suction value of the fine-grained layer is higher than the critical value (when the water content is low), the automatic pressurization system is stopped, and automatic control of opening and closing the automatic pressurization system is realized, so that the unsaturated capillary barrier layer can completely and automatically inhibit different rainfall from infiltrating the slope, significantly improving the efficiency and application range of the unsaturated capillary barrier layer. The effect of suppressing rainfall infiltration by the coarse-grained layer pressurized and unpressurized capillary barrier layer in the present invention is shown in FIG. Figure 4 .

[0038] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A test device for automatically pressurizing a capillary barrier layer to inhibit rainfall infiltration into a slope, characterized in that: It includes model trough, protective slope, capillary barrier, rainfall system, soil matrix suction monitoring system, automatic pressurization system and drainage collection system; The model trough comprises a model cavity and a wedge placed at the bottom of the model cavity, the bottom of the model cavity is filled with clay to form the protective slope, various types of soil are filled on the protective slope to form the capillary barrier layer, and the capillary barrier layer is composed of a coarse-grained layer, a transition layer and a fine-grained layer from bottom to top; The rainfall system is placed on the upper part of the model trough to simulate rainfall of different intensities; The soil matrix suction monitoring system is used to monitor the soil matrix suction value in the fine particle layer; The automatic pressurization system is used to inject a set air pressure into the coarse grain layer when the soil matrix suction value in the fine grain layer monitored by the soil matrix suction monitoring system is less than a critical value, so as to form a certain air pressure in the coarse grain layer, thereby forming a supporting effect on the water in the interface of the fine grain layer / transition layer, inhibiting rainfall from breaking through the interface of the fine grain layer / transition layer, and allowing rainfall to migrate and drain from the fine grain layer above the interface of the fine grain layer / transition layer, thereby completely preventing rainfall from infiltrating the coarse grain layer; The drainage collection system is used to collect drainage from the fine-grained layer, the coarse-grained layer and the protective slope.

2. The test device for suppressing rainfall infiltration into slopes with an automatic pressurized capillary barrier layer as claimed in claim 1, characterized in that: The upper part of the model cavity is hollowed out, the left side is a porous plate within a range of 10 cm from the top of the model cavity downward, and the other surfaces are all impermeable plates.

3. The test device for suppressing rainfall infiltration into slopes with an automatic pressurized capillary barrier layer as claimed in claim 1, characterized in that: The inclination angle of the wedge is 20°-30°, and the model cavity 1 is tilted and placed on the inclined surface of the wedge after the soil sample is filled.

4. The test device for suppressing rainfall infiltration into slopes with an automatic pressurized capillary barrier layer as claimed in claim 1, characterized in that: The fine-grained layer is made of fine sand or sub-sand suitable for vegetation growth, and the saturated permeability coefficient is 5.0×10 -4 ~1×10 -3 cm / s; the coarse-grained layer is made of coarse sand, gravel sand and angular gravel, and the permeability coefficient is 1 to 10 cm / s; a transition layer is added between the fine-grained layer and the coarse-grained layer to enhance the efficiency of the unsaturated structure with a fine-grained layer on the upper layer and a coarse-grained layer on the lower layer to inhibit rainfall infiltration into the slope. The average particle size of the transition layer is between the fine-grained layer and the coarse-grained layer, and the fine-grained layer and the coarse-grained layer are mixed in a mass ratio of 1:3 to 3:

1.

5. The test device for suppressing rainfall infiltration into slopes with an automatic pressurized capillary barrier layer as claimed in claim 1, characterized in that: The rainfall system includes a water inlet pipe, a rainfall simulation water tank, an overflow pipe, a needle and a rainfall bracket. The rainfall simulation water tank is a rectangular cavity and is placed on the rainfall bracket; the rainfall bracket is a hollow rectangular wedge with the same inclination angle as the wedge, which is placed on the model cavity to provide a horizontal rainfall support platform for the rainfall system; the needles are evenly distributed at the bottom of the rainfall simulation water tank, and the overflow pipe is connected to the rainfall simulation water tank; the needles are used to simulate raindrops, and different rainfall intensities are obtained by adjusting the water level in the rainfall simulation water tank.

6. The test device for suppressing rainfall infiltration into slopes with an automatic pressurized capillary barrier layer as claimed in claim 1, characterized in that: The soil matrix suction monitoring system includes a soil matrix suction sensor, a data line and a soil matrix suction value collection and wireless transmission system. A plurality of soil matrix suction sensors are evenly buried in the fine particle layer and near the contact interface between the fine particle layer and the transition layer. The soil matrix suction sensors are connected to the soil matrix suction value collection and wireless transmission system through the data line. The soil matrix suction value collection and wireless transmission system is used to send the soil matrix suction value collected by the soil matrix suction sensor to the automatic boosting system.

7. The test device for suppressing rainfall infiltration into slopes with an automatic pressurized capillary barrier layer as claimed in claim 6, characterized in that: The soil matrix suction sensor is a clay tensiometer.

8. The test device for suppressing rainfall infiltration into slopes with an automatic pressurized capillary barrier layer as claimed in claim 1 or 6, characterized in that: The automatic pressurization system includes an air compressor, a micro-pressure controller, a coarse-grained layer air release system, a soil matrix suction value receiving and power start-stop control system, and an air injection pipe. The air compressor is used to provide a high-pressure air source, which is then injected into the micro-pressure controller to form a lower-pressure air source after pressure stabilization treatment, and then the coarse-grained layer air release system is injected and pressurized through the air injection pipe. The coarse-grained layer air release system is buried in the coarse-grained layer; the soil matrix suction value receiving and power start-stop control system is used to start and close the power of the air compressor and the micro-pressure controller according to the soil matrix suction value in the fine-grained layer monitored by the soil matrix suction monitoring system.

9. The test device for suppressing rainfall infiltration into slopes with an automatic pressurized capillary barrier layer as claimed in claim 8, characterized in that: The coarse-grained layer air release system is an air injection network composed of hollow copper tubes, on which a plurality of air injection holes are evenly arranged for evenly injecting air into the coarse-grained layer, so that a uniform air pressure is formed at the interface between the entire coarse-grained layer and the transition layer.

10. The test device for suppressing rainfall infiltration into slopes with an automatic pressurized capillary barrier layer as claimed in claim 8, characterized in that: The soil matrix suction value receiving and power supply start-stop control system comprises a wireless signal receiving element, a power supply start-stop control element and a soil matrix suction value and power switch associated component. The wireless signal receiving element is used to receive the soil matrix suction value sent by the soil matrix suction value collection and wireless transmission system. The soil matrix suction value and power switch associated component are used to determine that when the soil matrix suction value is less than a critical value, the power supply of the air compressor and the micro-pressure controller is started through the power supply start-stop control element to inject gas into the coarse-grained layer. When the soil matrix suction value is greater than a critical value, the power supply of the air compressor and the micro-pressure controller is shut down through the power supply start-stop control element to stop injecting gas into the coarse-grained layer. The critical value is the soil matrix suction value of the fine-grained layer when rainfall begins to enter the transition layer.

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