Model test system for studying critical conditions of instability of vegetated slopes under rainfall

Abstract

The present invention discloses a model test system for studying critical conditions for instability of a vegetated slope under rainfall, wherein a vegetated slope model is provided in a centrifugal environment double-layer seepage model box; a graded rainfall feedback simulation system simulates the requirements of specific rainfall intensity and duration, and induces changes in the internal moisture field conditions of the vegetated slope model; an artificial root strain analysis system simulates the physical soil consolidation effect of the root system on the slope surface and the regulating effect of matrix suction; a high-speed camera system for slope surface cracks records the entire rainwater infiltration and slope surface scouring of the test slope, and clearly captures the entire process of development, extension and penetration of slope surface cracks; a rock and soil moisture content monitoring system realizes the response of the slope moisture field in real time under different rainfall and artificial root working conditions. The present invention is used to carry out model tests for studying critical conditions for instability of a vegetated slope under rainfall conditions, and provides an effective testing means for evaluating the influence of vegetation on slope stability under rainfall conditions.

Description

Technical Field

[0001] The invention relates to the fields of geotechnical engineering and geotechnical test model technology, and in particular to a model test system for studying critical conditions for instability of a vegetation-covered slope under rainfall. Background Art

[0002] my country is a mountainous country, with mountainous areas accounting for 69% of the country's land area. Geological disasters such as landslides induced by rainfall have become an important issue restricting my country's infrastructure and economic development. The main causes of existing landslide disasters include earthquakes, construction excavation disturbances, and precipitation infiltration. Landslides induced by atmospheric precipitation infiltration account for a large proportion of landslide disasters. The changes in slope seepage and the moisture field in the slope under rainfall are of great significance for revealing the critical conditions for slope instability. Under rainfall, slopes with good vegetation coverage are less likely to fail than bare slopes. This is because the vegetation root system not only has the functions of shallow reinforcement and soil consolidation on the slope surface and resisting rain erosion, but also can improve the shear strength of the soil through vegetation transpiration, and has a good regulating effect on the surface moisture field of the slope. Rainfall can trigger slope instability, while vegetation roots can improve slope stability. Establishing the correlation between the evolution of the moisture field in the slope under rainfall and the slope deformation and instability process has become a hot interdisciplinary research topic in the hydrology, ecology and geotechnical engineering fields in recent years.

[0003] At present, there is no comprehensive understanding of the mechanism of the influence of vegetation on slope stability in slope engineering at home and abroad, and there is a lack of experimental research on the influence of root soil consolidation and water regulation on the critical condition criterion of instability of vegetated slopes under rainfall. Geotechnical centrifuge model test can simulate the real stress field conditions of slopes, but the existing indoor slope rainfall model test systems are mostly test devices under normal gravity environment, which cannot restore the stress field of the slope prototype and cannot meet the similar conditions of model test. The existing centrifuge model test system is only suitable for the study of plain slopes without considering the vegetation coverage of slopes, and cannot consider the soil consolidation and water mechanical regulation of vegetation roots, and cannot meet the research needs of the critical conditions of instability of vegetated slopes under rainfall conditions. Therefore, there is an urgent need for a centrifuge model test system that can be used for the study of the critical conditions of instability of vegetated slopes under rainfall, explore the coupling relationship between rainfall conditions, root reinforcement and soil consolidation, and vegetation water regulation, and study the disaster mechanism of vegetated slopes under the coupling of ecology and rock and soil under rainfall.

[0004] At present, the model test system for studying the critical conditions of slope instability under rainfall at home and abroad has the following shortcomings:

[0005] (1) Most rainfall model test systems do not pay attention to the impact of slope vegetation cover on slope stability, and there is no systematic understanding of the impact of vegetation cover on slope seepage mechanism under rainfall;

[0006] (2) The rainfall model test is simulated under constant gravity conditions and cannot reproduce the actual stress field of the prototype slope;

[0007] (3) There is a lack of research on the root soil fixation and water regulation mechanisms of different vegetation types. The coupling mechanism between rainfall infiltration and root slope fixation has not yet been clarified, and the instability conditions of the slope cannot be determined;

[0008] (4) The existing model test equipment cannot be used to simulate the soil-fixing function of vegetation roots and cannot monitor the bending strain changes of roots during the reinforcement and anchoring process;

[0009] (5) It is difficult to simulate rainfall conditions in a centrifuge, and other seepage boundary conditions are often used instead, which loses the authenticity of restoring the rainfall seepage effect on the slope;

[0010] (6) Most rainfall control systems are based on controlling the water flow rate. When the geotechnical centrifuge is running, the hypergravity environment affects the rainfall intensity, resulting in rainfall intensity deviation, and it is impossible to monitor and feedback the real-time rainfall intensity;

[0011] (7) The monitoring image recording of the centrifuge model test system is relatively rough, and there is a lack of a high-speed camera system that can quickly and stably capture the development and extension of slope cracks and the entire process of slope deformation and destruction. Summary of the invention

[0012] The purpose of this patent is to provide a model test system for studying the critical conditions for instability of slopes covered with vegetation under rainfall to solve the deficiencies in the above research. This centrifugal model test system has precise design, stable operation, firm components, reasonable structure, repeatable tests, and strong versatility. This system can carry out model tests for studying the critical conditions for instability of slopes covered with vegetation under rainfall conditions, and provides an effective testing method for evaluating the impact of vegetation on slope stability under rainfall conditions.

[0013] The invention is based on the similarity theory theorem, with a unique rainfall component design, the biomechanical effect of the root system, a reasonable double-layer structure, clear seepage path distinction, and perfect deformation and moisture monitoring functions. This test system can carry out centrifuge model tests to explore the stability of vegetated slopes under rainfall conditions, and can be used to determine the critical instability conditions of various types of vegetated slopes under different rainfall conditions, providing testing technology and ideas for studying the instability and destruction mechanism of vegetated slopes under rainfall.

[0014] To achieve the above object, the present invention provides the following solutions:

[0015] A model test system for studying the critical conditions for instability of vegetated slopes under rainfall, including a centrifugal environment double-layer seepage model box, a graded rainfall feedback simulation system, an artificial root strain analysis system, a high-speed camera system for slope surface cracks, and a rock and soil moisture content monitoring system;

[0016] The centrifugal environment double-layer seepage model box is provided with a vegetation-covered slope model;

[0017] The hierarchical rainfall feedback simulation system simulates the requirements of specific rainfall intensity and duration, and induces changes in the moisture field conditions inside the slope of the vegetation-covered slope model;

[0018] The artificial root strain analysis system simulates the physical soil consolidation effect of the root system on the slope and the regulation effect of the matrix suction;

[0019] The slope crack high-speed camera system records the entire rainwater infiltration and slope scouring of the test slope, and clearly captures the entire process of slope crack development, extension and penetration;

[0020] The rock and soil moisture content monitoring system can monitor the response of the slope moisture field in real time under different rainfall and artificial root conditions, obtain the time-course response distribution cloud map of the moisture content of the vegetation-covered slope, quantify the slope infiltration and slope runoff during rainfall, and study the seepage process and evolution path of rainfall moisture on the slope.

[0021] The graded rainfall feedback simulation system is used to induce the change of the internal moisture field conditions of the slope, and at the same time simulate the soil consolidation and moisture control function of the slope vegetation roots, triggering the slope instability during the rainfall water infiltration process, realizing the simulation of the stability of the vegetation-covered slope, clarifying the relationship between the rainfall infiltration conditions and the slope instability process, and providing a reference for determining the critical conditions for the instability of the vegetation-covered slope under rainfall conditions. The designed rainfall intensity, the graded rainfall feedback simulation system can adjust the pump power and water delivery time to meet the requirements of simulating specific rainfall intensity and duration, and monitor the feedback rainfall intensity data in real time through the micro-optical rainfall sensor to ensure the accuracy of the rainfall intensity.

[0022] The centrifugal environment double-layer seepage model box comprises a cast aluminum model box body, the side walls of the cast aluminum model box body are provided with visible glass side walls, the top is provided with an aluminum alloy box body upper cover, and the bottom is provided with an aluminum waterproof bottom plate; a vegetation-covered slope model is installed on the aluminum waterproof bottom plate; a reaction force bracket with seepage holes is provided at the foot of the vegetation-covered slope model; a filter sponge is filled inside the reaction force bracket, a support column is provided at the bottom of the aluminum waterproof bottom plate, and a water storage space is formed under the aluminum waterproof bottom plate; a plurality of drainage holes are provided on one side of the aluminum waterproof bottom plate close to the foot of the slope;

[0023] The hierarchical rainfall feedback simulation system comprises a water storage tank, a water level transmitter is arranged at the bottom of the water storage tank, and a high-pressure diaphragm pump with adjustable flow rate, a one-way solenoid valve, a micro-turbine flowmeter, and a high-pressure atomizing rainfall nozzle group are connected in sequence to the water outlet pipe of the water storage tank, and the high-pressure atomizing rainfall nozzle group is installed on the slope surface of the vegetation-covered slope model through a nozzle fixing support rod bracket; a micro-optical rainfall sensor is arranged on the slope surface; the high-pressure diaphragm pump with adjustable flow rate, the micro-optical rainfall sensor and the micro-turbine flowmeter are connected to a PWM water pump speed regulator and a static data acquisition instrument through a centrifuge arm channel;

[0024] According to the slope model and rainfall uniformity requirements, the high-pressure atomization rainfall nozzle group and its water supply pipeline are arranged at the set position on the slope, and the nozzle fixed support rod bracket is fixed between the two side walls of the model box. The pure water in the water tank is pressurized by a high-pressure diaphragm pump with adjustable flow rate and enters the nozzle pipeline through a micro-turbine flowmeter. By monitoring real-time flow data and adjusting the PWM water pump speed regulator, the rainfall intensity is controlled, and the micro-optical rainfall sensor is assisted to feedback the rainfall intensity in real time, and the water pump output power is further finely adjusted.

[0025] The artificial root strain analysis system comprises cellulose acetate artificial roots of different root types, the cellulose acetate artificial roots are located in the slope surface of the vegetation covered slope model; strain gauges are symmetrically arranged on the surface of the cellulose acetate artificial roots, and each cellulose acetate artificial root is connected to a water storage tank through a water suction pipeline and a one-way check valve; the water storage tank is connected to a water storage tank negative pressure transmitter and an oil-free vacuum pump, and the oil-free vacuum pump is provided with a vacuum pump negative pressure start-stop switch;

[0026] The rock and soil moisture monitoring system includes multiple groups of GS-1 moisture sensors buried inside the vegetation-covered slope model and high-precision water level sensors located in the water storage space; the multiple groups of GS-1 moisture sensors and high-precision water level sensors are all connected to a static data acquisition instrument, and the static data acquisition instrument is connected to a computer that monitors and records data in real time;

[0027] The slope surface crack high-speed camera system comprises a high-speed camera located inside a cast aluminum model box body and facing the slope model surface of a vegetation-covered slope body, and a camera bracket fixed to an upper cover of the aluminum alloy box body.

[0028] The nozzle fixing strut bracket includes a stainless steel screw, and the two ends of the stainless steel screw are respectively connected to rubber supports; the stainless steel screw is extended and retracted by locking the screw nut, and the rubber supports at both ends are tightly against the left and right side walls of the cast aluminum model box; the stainless steel screw is also provided with a slidable rain nozzle fixing seat for fixing the high-pressure atomizing rain nozzle group. The support rod bracket screw is provided with a slidable rain nozzle fixing seat, which can flexibly adjust the position of the nozzle. The rainfall coverage of each nozzle is superimposed on the slope to ensure the uniformity of rainfall on the slope. The fixing method of the nozzle fixing strut bracket is simple and firm, and can flexibly utilize the limited model box space.

[0029] Part of the rainfall water infiltrates the slope, while the non-infiltrated part forms the slope runoff of the model and converges at the foot of the slope. The runoff flows into the drainage hole of the aluminum waterproof bottom plate through the reaction support with holes at the foot of the slope and the filter sponge filled inside the support, and is stored in the water storage space under the aluminum waterproof bottom plate. The water storage space design effectively reduces the convergence of slope runoff water at the foot of the slope, eliminates the interference of the infiltration boundary at the foot of the slope on the seepage path of the vegetation-covered slope model, and makes the simulation of rainfall infiltration conditions more accurate. A high-precision water level sensor is installed at the bottom of the water storage space to monitor the amount of water converged by the slope runoff, quantify the amount of slope infiltration and slope runoff during rainfall, study the infiltration process and seepage evolution path of rainfall water on the slope, and reveal the mechanism of the influence of water infiltration conditions on slope stability.

[0030] The artificial root strain analysis system realizes the physical soil consolidation effect of the root system on the slope and the regulation effect of the matrix suction. The soil consolidation effect and the water regulation effect are superimposed to improve the stability of the slope. The cellulose acetate artificial root is made of cellulose acetate (CA) tube, which has an air intake value of 100kPa, allowing water to pass through but not gas. The tube shape of the cellulose acetate tube is designed to have specific tensile and bending strengths, which meets the mechanical similarity conditions of artificial roots simulating real roots to reinforce the soil.

[0031] The ends of cellulose acetate artificial roots of different root types were sealed, and the root tails were connected to the water suction pipeline, water storage tank and oil-free vacuum pump. The suction force was controlled by the negative pressure start and stop of the vacuum pump to simulate the regulation of slope moisture by vegetation. The negative pressure transmitter of the water storage tank monitors the negative pressure and the amount of water pumped in real time. Strain gauges were symmetrically attached to the surface of cellulose acetate artificial roots to test the strain and bending moment changes of the artificial roots in the reinforcement and anchoring process of the slope deformation, obtain the mechanical mechanism of the root reinforcement and anchoring effect, and evaluate the influence of the root soil consolidation effect on the slope stability.

[0032] The adjustable flow rate high-pressure diaphragm pump, micro optical rainfall sensor and micro turbine flowmeter are connected to the PWM pump speed regulator and static data acquisition instrument through the centrifuge arm channel, so as to monitor the water supply of the pump and the model rainfall intensity in real time during the test, and control the water supply of the pump through the speed regulator to adjust the rainfall intensity. The maximum output power of the adjustable flow rate high-pressure diaphragm pump is 100W, and the maximum working pressure is 1MPa.

[0033] The rock and soil materials of the vegetation-covered slope model follow the similarity criterion of the centrifuge test. The physical and mechanical parameters of the prototype soil are tested, and the model materials are prepared with similar materials to meet the similar physical and mechanical parameters of the slope materials. The filling process of the vegetation-covered slope is layered filling and compaction, which is convenient for the burial of sensors inside the slope and artificial roots on the slope surface. The model is formed by overall filling and then slope cutting.

[0034] Compared with the prior art, the present invention has achieved the following technical effects:

[0035] (1) The test system of the present invention is a model test system for studying the critical conditions for instability of a vegetated slope under rainfall. The artificial root strain analysis system of this test can not only simulate the regulating effect of vegetation on the moisture of shallow soil, but also simulate the reinforcement and soil consolidation effect of the root system, and test the stress and bending moment changes of the root system during the slope instability process, and quantify the influence of the mechanical action of the root system at each position on the stability of the vegetated slope.

[0036] (2) The graded rainfall simulation feedback system of the present invention is mainly composed of a water storage tank, an adjustable flow rate high-pressure diaphragm pump, a single-way solenoid valve, a micro-turbine flowmeter, a high-pressure atomizing rainfall nozzle group, a nozzle fixed support rod bracket and a nozzle water supply pipeline. This system realizes the remote and precise control of rainfall intensity and duration during centrifugal loading, and at the same time, a micro-optical rainfall sensor is set to feedback and correct the actual rainfall intensity. This rainfall simulation feedback system can maintain uniform, continuous and reliable rainfall, and improve the accuracy of rainfall intensity simulation in a centrifugal environment.

[0037] (3) The nozzle fixing strut bracket is composed of a stainless steel screw, a rubber support and a nozzle fixing bracket. The screw nut is locked to extend and retract. After the strut is extended, it is tightly pressed against the side walls of the model box, and the friction is used to fix it. This nozzle fixing strut bracket is firm and reliable, and can flexibly utilize the limited model box space. A slidable nozzle fixing seat is provided on the bracket screw, which can move and adjust the position of the nozzle. The rainfall coverage area of ​​the nozzle spraying on the slope surface partially overlaps, so that the rainfall on the slope surface is uniform.

[0038] (4) The rock and soil moisture content monitoring system of the present invention includes multiple groups of moisture content sensors buried inside the vegetation-covered slope model, high-precision water level sensors at the bottom of the box, static data acquisition instruments, connecting data lines, and computers for monitoring and recording data. The rock and soil moisture content monitoring system realizes the full-time real-time monitoring of the response of the slope moisture field under different rainfall and artificial root conditions, and obtains the time-course response distribution cloud map of the moisture content of the vegetation-covered slope. At the same time, a high-precision water level sensor is arranged at the bottom of the box, which can quantify the slope infiltration and slope runoff during rainfall, and study the seepage process and evolution path of rainfall water on the slope.

[0039] (5) The lower part of the aluminum waterproof bottom plate of the present invention has a 5 cm high water storage space, and a plurality of drainage holes are provided on the side of the bottom plate close to the slope foot. A reaction support with holes is provided at the slope foot, and a filter sponge is filled inside to absorb and filter the water gathered at the slope foot. These components work together to store excess water from the slope runoff and reduce the amount of water collected at the slope foot. The provision of the water storage space eliminates the influence of infiltration at the slope foot on the seepage boundary, thereby achieving the purpose of more realistic simulation of slope rainfall infiltration conditions.

[0040] (6) The slope crack high-speed camera system of the present invention comprises a high-speed camera located inside the model box and a fixed bracket. The high-speed camera can efficiently record the rainwater infiltration and slope scouring of the entire slope, capture the development, extension and penetration of the slope cracks, monitor the deformation evolution process of the vegetation-covered slope, and provide a basis for determining the instability mode of the slope under rainfall infiltration conditions.

[0041] (7) The present invention has a unique concept, strong innovation, reasonable structure and complete functions. The system has a high degree of automation integrity and low dependence on the information level of the supporting centrifuge equipment. It can rely on existing geotechnical centrifuges to carry out tests. The system has strong versatility and a complete process flow for reference in the production of vegetation cover models. It can be used to study the stability of various types of vegetation covered slopes under rainfall conditions. The system creatively incorporates the monitoring of the bending strain of vegetation roots and quantitatively analyzes the mechanical anchoring mechanism of the root mechanical soil fixation. The present invention has improved the standards and technical levels for the technical development of rainfall model test systems to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to clearly illustrate the technical solutions and implementation methods of the present invention in the prior art, the drawings used in the embodiments are introduced.

[0043] Figure 1 It is a structural schematic diagram of the present invention;

[0044] Figure 2 It is a front view of the present invention;

[0045] Figure 3 This is the structural layout diagram of the aluminum waterproof bottom plate;

[0046] Figure 4 The structure diagram of the fixed support rod bracket and the sprinkler head for the rainfall system sprinkler head;

[0047] Figure 5 Schematic diagram of the spray range of slope rainfall sprinkler. DETAILED DESCRIPTION

[0048] Combined with the accompanying drawings of the implementation cases of the present invention, the technical solutions in the implementation cases of the present invention are systematically described. The implementation cases are only partial implementation cases of the present invention, not all implementation cases. Based on the embodiments of the present invention, all other implementation cases obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0049] like Figure 1 and Figure 2 As shown, the model test system for studying the critical conditions of instability of vegetated slopes under rainfall includes a centrifugal environment double-layer seepage model box, a graded rainfall feedback simulation system, an artificial root strain analysis system, a high-speed camera system for slope surface cracks, and a rock and soil moisture content monitoring system;

[0050] The centrifugal environment double-layer seepage model box is provided with a vegetation covered slope model 31;

[0051] The hierarchical rainfall feedback simulation system simulates the requirements of specific rainfall intensity and duration, and induces changes in the moisture field conditions inside the slope of the vegetation cover slope model 31;

[0052] The artificial root strain analysis system simulates the physical soil consolidation effect of the root system on the slope and the regulation effect of the matrix suction;

[0053] The slope crack high-speed camera system records the entire rainwater infiltration and slope scouring of the test slope, and clearly captures the entire process of slope crack development, extension and penetration;

[0054] The rock and soil moisture content monitoring system can monitor the response of the slope moisture field in real time under different rainfall and artificial root conditions, obtain the time-course response distribution cloud map of the moisture content of the vegetation-covered slope, quantify the slope infiltration and slope runoff during rainfall, and study the seepage process and evolution path of rainfall moisture on the slope.

[0055] Specifically, Figure 1 and Figure 2 As shown, the centrifugal environment double-layer seepage model box includes a cast aluminum model box body 9, the side wall of the cast aluminum model box body 9 is provided with a visible glass side wall 10, the top is provided with an aluminum alloy box body upper cover 11, and the bottom is provided with an aluminum waterproof bottom plate 12; a vegetation-covered slope model 31 is installed on the aluminum waterproof bottom plate 12; a reaction force bracket 13 with seepage holes is provided at the slope foot of the vegetation-covered slope model 31; a filter sponge 14 is filled inside the reaction force bracket 13, a support column is provided at the lower part of the aluminum waterproof bottom plate 12, and a water storage space 21 is formed under the aluminum waterproof bottom plate 12; a plurality of drainage holes 20 are provided on the side of the aluminum waterproof bottom plate 12 close to the slope foot;

[0056] The hierarchical rainfall feedback simulation system comprises a water storage tank 1, a water level transmitter 8 is provided at the bottom of the water storage tank 1, and an adjustable flow rate high-pressure diaphragm pump 2, a one-way solenoid valve 3, a micro-turbine flowmeter 4, and a high-pressure atomizing rainfall nozzle group 5 are sequentially connected to the water outlet pipe of the water storage tank 1, and the high-pressure atomizing rainfall nozzle group 5 is installed on the slope surface of the vegetation covered slope model 31 through a nozzle fixing support rod bracket 6; a micro-optical rainfall sensor 24 is provided on the slope surface; the adjustable flow rate high-pressure diaphragm pump 2, the micro-optical rainfall sensor 24 and the micro-turbine flowmeter 4 are connected to a PWM water pump speed regulator 7 and a static data acquisition instrument 27 through a centrifuge arm channel;

[0057] The artificial root strain analysis system comprises cellulose acetate artificial roots 15 of different root types, the cellulose acetate artificial roots 15 are located in the slope surface of the vegetation cover slope model 31; strain gauges 16 are symmetrically arranged on the surface of the cellulose acetate artificial roots 15, and each cellulose acetate artificial root 15 is connected to a water storage tank 19 through a water suction pipeline 23 and a one-way check valve 17; the water storage tank 19 is connected to a water storage tank negative pressure transmitter 18 and an oil-free vacuum pump 22, and the oil-free vacuum pump 22 is provided with a vacuum pump negative pressure start-stop switch 25;

[0058] The rock and soil moisture monitoring system includes multiple groups of GS-1 moisture sensors 26 buried in the vegetation covered slope model 31 and high-precision water level sensors 32 located in the water storage space 21; the multiple groups of GS-1 moisture sensors 26 and high-precision water level sensors 32 are connected to a static data acquisition instrument 27, and the static data acquisition instrument 27 is connected to a computer 28 for real-time monitoring and recording data;

[0059] The slope surface crack high-speed camera system comprises a high-speed camera 30 located inside the cast aluminum model box 9 facing the slope surface of the vegetation-covered slope model 31 and a camera bracket 29 fixed to the upper cover 11 of the aluminum alloy box.

[0060] like Figure 4 As shown, the nozzle fixing strut bracket 6 includes a stainless steel screw, and the two ends of the stainless steel screw are respectively connected to rubber supports; the stainless steel screw is extended and retracted by locking the screw nut, and the rubber supports at both ends are tightly against the left and right side walls of the cast aluminum model box 9; a slidable rainfall nozzle fixing seat is also provided on the stainless steel screw, which is used to fix the high-pressure atomizing rainfall nozzle group 5.

[0061] The specific parameters are:

[0062] like Figure 3 As shown, the aluminum waterproof bottom plate 12 is made of a 20mm thick whole aluminum plate, and is supported by 5 5cm high aluminum support legs at the bottom. Holes are opened between the support legs and the bottom plate and connected by fixing bolts. The overall dimensions of the bottom plate are 80cm long × 60cm wide × 7cm high. The lower water storage space 21 has a net height of 5cm, which stores excess water from the slope runoff and reduces the water collection at the slope foot. The aluminum waterproof bottom plate 12 is provided with 8 drainage holes 20 on one side close to the slope foot.

[0063] The reaction support 13 is made of stainless steel and welded, with a length × width × height of 60 cm × 10 cm × 5 cm. Holes are opened on the steel plate surface to facilitate the entry and exit of water. To prevent the soil from blocking the small holes, the steel plate surface is covered with a 50-mesh gauze. The rear of the reaction support 13 is filled with a filter sponge 14 to filter the water gathered at the foot of the slope to prevent the drainage hole 20 from being blocked.

[0064] The maximum power of the adjustable flow rate high pressure diaphragm pump 2 is 100W, and the maximum working pressure is 1MPa. The adjustable flow rate high pressure diaphragm pump 2 has a length×width×height size of 20cm×10cm×8cm and is installed on the aluminum alloy upper cover 11 of the model box by bolts.

[0065] The micro turbine flowmeter 4 uses the turbine principle to measure tiny flow. Its maximum working pressure is 2MPa, the diameter is 1.15mm, the measuring range is 0.035-1.6L / min, and the accuracy level is ±1%.

[0066] The main body and ejector pin of the high-pressure atomizing rainfall nozzle group 5 are made of stainless steel, the nozzle is a ceramic laser hole with a hole diameter of 0.3mm, and the spring pressure is moderate and suitable for a larger pressure range. The nozzle water supply pipe joint is brass nickel-plated, which is firm and durable. The water supply pipe uses a hard PU pipe with a diameter of 9.5mm.

[0067] The nozzle fixing support rod bracket 6 is extended and retracted by locking the screw nut, and the length adjustment range is 55-65cm. After the support rod is opened, it is tightly pressed against the side walls of the model box, and the friction force is used to fix it. This nozzle fixing support rod bracket fixing method is firm and reliable, and can flexibly utilize the limited internal space of the model box. The support screw is provided with a slidable nozzle fixing seat to facilitate the adjustment of the nozzle position. Figure 5 As shown, the spray ranges of the rainfall nozzles partially overlap to ensure rainfall uniformity.

[0068] In order to monitor and feedback real-time rainfall intensity data, a micro optical rain sensor 24 is placed in the middle of the slope and fixed by a wooden support. The rain sensor uses telemetry algorithm and 485 communication protocol. The rainfall accuracy in rain sensing mode reaches 0.01mm, ensuring the accuracy of rainfall monitoring. With the help of the data from the micro optical rain sensor 24, the flow data of the high-pressure diaphragm pump is fine-tuned to ensure the accuracy of rainfall intensity.

[0069] The adjustable flow rate high pressure diaphragm pump 2 draws pure water from the 30-liter water storage tank 1. After the water flows through the diaphragm pump, it enters the micro turbine flow meter 4, and then enters the nozzle water supply pipeline, and is sprayed out by the high pressure atomization rainfall nozzle group 5. The control line of the adjustable flow rate high pressure diaphragm pump 2 is connected to the static data acquisition instrument 27 in the control room through the centrifuge arm. According to the flow data collected by the micro turbine flow meter 4 and the real-time rainfall intensity data fed back by the micro optical rainfall sensor 24, the PWM water pump speed regulator 7 can be used to adjust the water supply rate to meet the set rainfall working condition requirements.

[0070] The cellulose acetate artificial root 15 is made of cellulose acetate (CA) tube and has an air intake value of 100kPa. By selecting different tube types and diameters, it has specific tensile and bending strengths to meet the mechanical similarity conditions of artificial roots simulating real root soil fixation. Strain gauges 16 are symmetrically attached to the surface of the artificial root to test the root strain and bending moment changes in real time during slope deformation, obtain the mechanical action process of root reinforcement and anchoring, and evaluate the influence of root soil fixation on the stability of the vegetation covered slope. The artificial root is made according to the required root shape, its end is closed and the root end is connected to the water absorption pipeline 23.

[0071] The water suction pipeline 23 is connected to a 3-liter water tank 19, and water is sucked out by the cellulose acetate artificial root 15 and enters the water tank 19. A water tank negative pressure transmitter 18 is provided at the bottom of the water tank to output the negative pressure value in the water tank in real time, and the real-time pumping volume data can be obtained for observation and recording in the control room. The water tank is provided with negative pressure by a vacuum pump 22, and the maximum vacuum degree is -97kPa. The suction force is controlled by the vacuum pump negative pressure switch 25 to simulate the regulating effect of vegetation on soil moisture.

[0072] According to the characteristics of the rainwater seepage path on the slope, the GS-1 moisture content sensor 26 is distributedly installed inside the slope, with a dense arrangement near the slope surface and a sparse arrangement deep in the slope. The moisture content sensor is pre-buried when the slope is filled, and the data line is close to the two side walls of the model box to reduce interference with the model boundary effect.

[0073] The water storage space 21 is located at the bottom of the model box, and a high-precision water level sensor 32 is installed to monitor the amount of water gathered by slope runoff. It works together with multiple groups of GS-1 moisture content sensors 26 to quantify the slope infiltration and slope runoff during rainfall, study the rainfall infiltration process and seepage evolution path on the slope, and reveal the impact mechanism of water infiltration on slope stability.

[0074] The static data acquisition and processing instrument 27 is placed in the control room of the geotechnical centrifuge and is connected to various sensors in the model box through the reserved channels of the centrifuge.

[0075] The high-speed camera system for slope cracks includes a high-speed camera 30 located inside the model box and a camera bracket 29 fixed to the upper cover 11 of the box. The high-speed camera 30 has a large-capacity storage capacity and can transmit the captured content to other mobile devices such as mobile phones in real time through a wireless LAN. The camera's built-in anti-shake stabilization function also ensures that unfavorable conditions such as shaking inside the box during the test are effectively overcome, and the entire rainwater infiltration and slope scouring of the test slope are efficiently recorded, the development, extension, and penetration of slope cracks are monitored, and complete image data of the instability process of the vegetation-covered slope is collected.

[0076] The specific operation steps of the model test for studying the critical conditions for instability of vegetated slopes under rainfall are as follows:

[0077] 1. According to the geological survey data of the on-site work site, the physical and mechanical parameters of the on-site rock and soil materials are tested indoors. The vegetation cover slope model 31 material follows the similarity theory of model test. The selected similar materials can simulate the physical and mechanical parameters of different slope strata structures on site. Before the test, the required model specimens are configured in advance and sealed and left to stand for 48 hours.

[0078] 2. Install the aluminum waterproof bottom plate 12 and the high-precision water level sensor 32 at the bottom of the box. Install the visual glass side wall 10 and seal the gap with glass glue to prevent water leakage. Install the reaction force bracket 13 and fill the filter sponge 14.

[0079] 3. Fill the vegetation covered slope model 31 in layers and blocks and compact it. During filling, bury multiple groups of GS-1 moisture sensors 26 and bury the required cellulose acetate artificial roots 15 at the slope surface. Weigh the required soil samples according to the model design density, fill them in one by one and compact them.

[0080] 4. After the overall filling of the vegetation-covered slope model 31 is completed, the slope cutting method is used to cut off the excess soil according to the side wall slope line, and multiple groups of GS-1 moisture content sensors 26 and cellulose acetate artificial roots 15 surface strain signal lines are led out. The root ends of the cellulose acetate artificial roots 15 on the slope are found and connected to the water absorption pipeline 23 to complete the production of the vegetation-covered slope model 31.

[0081] 5. Fix a wooden base near the side wall in the middle of the slope, and install a micro optical rainfall sensor 24 on the base. According to the principle of the same distance from the slope, determine the position and layout spacing of the high-pressure atomizing rainfall nozzle group 5, and fix the position of the nozzle fixing support rod bracket 6. Extend the support rod to support the two side walls of the model box, and use a wrench to lock the support rod adjustment nut to fix it. Fix the nozzle angle and spacing. Make the rainfall coverage of each nozzle partially overlap on the slope to ensure the uniformity of the slope rainfall. After that, install and arrange the rainfall water supply pipeline.

[0082] 6. Install the aluminum alloy upper cover 11, use an iron hoist to lift the aluminum alloy upper cover 11, and install the high-speed camera 30 at the bottom of the upper cover. Slowly lift the aluminum alloy upper cover 11 into place, and lead the data line and water and gas pipeline in the model box out from the opening of the upper cover. Use bolts to fix the water storage tank 1, adjustable flow rate high-pressure diaphragm pump 2, single-way solenoid valve 3, micro-turbine flowmeter 4, water storage tank 19 and oil-free vacuum pump 22 to the reserved position of the upper cover, connect the pipeline and test the connection status. Tighten the aluminum alloy upper cover 11 with bolts, and use a sealing film to seal the opening of the upper cover.

[0083] 7. Lift the cast aluminum model box 9 as a whole into the centrifuge arm hanging basket and fix it, connect the data lines and ports, connect the static data acquisition instrument 27 from the control room port, and check the collection status. Debug whether each system equipment is operating normally, whether the oil-free vacuum pump 22 and the adjustable flow rate high-pressure diaphragm pump 2 can be controlled to start and stop. Check the monitoring range of the high-speed camera and the shooting status of the imaging system. Close the centrifuge room and let the model stand for 48 hours before the formal test.

[0084] 8. After the centrifuge is turned on and reaches the predetermined speed, it enters the formal test phase. Keep the predetermined speed of the centrifuge stable, allow the model to initially consolidate for 1 hour, and then turn on the rainfall system to simulate different rainfall intensities and durations. According to the real-time flow data obtained by the micro-turbine flowmeter 4, supplemented by the actual rainfall intensity measured by the micro-optical rainfall sensor 24, the rainfall intensity is corrected and adjusted. Different intensities of rainfall are simulated in stages, which can be intermittent or continuous, to accurately simulate different rainfall conditions.

[0085] 9. While the rainfall system is working, start the artificial root strain analysis system to simulate the regulating effect of plant roots on the soil moisture field. Control the negative pressure through the vacuum pump negative pressure start-stop switch 25 to simulate the regulating effect of roots of different root types on moisture and shallow soil shear strength. Record the strain values ​​measured by the strain gauges 16 symmetrically attached to the surface of the artificial roots, the changes in the slope moisture field measured by multiple groups of GS-1 moisture content sensors 26, and the slope runoff water volume measured by the high-precision water level sensor 32. With the help of root strain data, study the soil-fixing mechanical effect of roots at different positions on the slope, and quantify the slope infiltration and slope runoff during rainfall.

[0086] 10. The control room manually monitors and records the process of crack development, extension and penetration as well as the time nodes of occurrence monitored by high-speed cameras.

[0087] 11. After the test rainfall loading process is completed, stop the machine. Save the test data and high-speed camera images. Lift the model box out of the box as a whole, take samples and take photos for record. Dismantle the model and clean the model box.

[0088] The model test for the critical conditions of slope instability under rainfall under the action of vegetation covered slopes completed according to the above steps can be used to test slope models of various slopes and vegetation covered root types under different rainfall conditions, and analyze the influence mechanism of rainfall conditions, soil conditions and different root types on the stability of vegetation covered slopes. The test data include the cracking and penetration process of slope surface cracks, the response data of slope water field and the deformation data of root strain. The critical conditions of slope instability can be determined by comprehensive analysis based on the data of slope infiltration and slope runoff during rainfall.

[0089] The protection scope of the present invention is not limited to the above specific embodiments.

[0090] The present invention uses specific engineering cases to systematically illustrate the principles and implementation methods of the present invention. The above specific implementation method description is only used to introduce the method and implementation method of the present invention. According to the specific implementation method and test scope of the present invention, a variety of combined working condition studies can be carried out. Those skilled in the art can derive other implementation methods based on the technical solution of the present invention, which also belongs to the technical innovation scope of the present invention.

Claims

1. A model test system for studying critical conditions of slope instability under rainfall, characterized by: It includes a centrifugal environment double-layer seepage model box, a graded rainfall feedback simulation system, an artificial root strain analysis system, a slope surface crack high-speed camera system, and a rock and soil moisture content monitoring system; The centrifugal environment double-layer seepage model box is provided with a vegetation-covered slope model (31); The hierarchical rainfall feedback simulation system simulates the requirements of specific rainfall intensity and duration, and induces changes in the moisture field conditions inside the slope of the vegetation cover slope model (31); The artificial root strain analysis system simulates the physical soil consolidation effect of the root system on the slope and the regulation effect of the matrix suction; The slope crack high-speed camera system records the entire rainwater infiltration and slope scouring of the test slope, and clearly captures the entire process of slope crack development, extension and penetration; The rock and soil moisture content monitoring system can monitor the response of the slope moisture field in real time under different rainfall and artificial root conditions, obtain the time-course response distribution cloud map of the moisture content of the vegetation-covered slope, quantify the slope infiltration and slope runoff during rainfall, and study the seepage process and evolution path of rainfall moisture on the slope. Specific: The centrifugal environment double-layer seepage model box comprises a cast aluminum model box body (9), the side walls of the cast aluminum model box body (9) are provided with visual glass side walls (10), the top is provided with an aluminum alloy box body upper cover (11), and the bottom is provided with an aluminum waterproof bottom plate (12); a vegetation-covered slope model (31) is installed on the aluminum waterproof bottom plate (12); a reaction force support (13) with seepage holes is provided at the foot of the slope of the vegetation-covered slope model (31); the reaction force support (13) is covered with a gauze; a filter sponge (14) is filled inside the reaction force support (13); a support column is provided at the bottom of the aluminum waterproof bottom plate (12), and a water storage space (21) is formed below the aluminum waterproof bottom plate (12); a plurality of drainage holes (20) are provided on the side of the aluminum waterproof bottom plate (12) close to the foot of the slope; The hierarchical rainfall feedback simulation system comprises a water storage tank (1), a water level transmitter (8) is provided at the bottom of the water storage tank (1), and a high-pressure diaphragm pump (2) with adjustable flow rate, a one-way solenoid valve (3), a micro-turbine flowmeter (4), and a high-pressure atomizing rainfall nozzle group (5) are connected in sequence to the outlet pipe of the water storage tank (1), and the high-pressure atomizing rainfall nozzle group (5) is installed on the slope surface of the vegetation covered slope model (31) through a nozzle fixing support rod bracket (6); a micro-optical rainfall sensor (24) is provided on the slope surface; the high-pressure diaphragm pump (2) with adjustable flow rate, the micro-optical rainfall sensor (24) and the micro-turbine flowmeter (4) are connected to a PWM water pump speed regulator (7) and a static data acquisition instrument (27) through a centrifuge arm channel; The artificial root strain analysis system comprises cellulose acetate artificial roots (15) of different root types, wherein the cellulose acetate artificial roots (15) are located within the slope surface of a vegetation covered slope model (31); strain gauges (16) are symmetrically arranged on the surface of the cellulose acetate artificial roots (15); each cellulose acetate artificial root (15) is connected to a water storage tank (19) via a water suction pipeline (23) and a one-way check valve (17); the water storage tank (19) is connected to a water storage tank negative pressure transmitter (18) and an oil-free vacuum pump (22); the oil-free vacuum pump (22) is provided with a vacuum pump negative pressure start-stop switch (25); The rock and soil moisture content monitoring system comprises a plurality of groups of GS-1 moisture content sensors (26) buried in a vegetation-covered slope model (31) and a high-precision water level sensor (32) located in a water storage space (21); the plurality of groups of GS-1 moisture content sensors (26) and the high-precision water level sensor (32) are all connected to a static data acquisition device (27), and the static data acquisition device (27) is connected to a computer (28) for real-time monitoring and recording data; The slope surface crack high-speed camera system comprises a high-speed camera (30) located inside a cast aluminum model box (9) facing the slope surface of a vegetation-covered slope model (31), and a camera bracket (29) fixed to an upper cover (11) of the aluminum alloy box.

2. The model test system for studying critical conditions of instability of vegetation-covered slopes under rainfall according to claim 1 is characterized by: The nozzle fixing support rod bracket (6) comprises a stainless steel screw, and the two ends of the stainless steel screw are respectively connected to rubber bearings; the stainless steel screw is extended and retracted by locking the screw nut, and the rubber bearings at the two ends are tightly against the left and right side walls of the cast aluminum model box (9); the stainless steel screw is also provided with a slidable rainfall nozzle fixing seat for fixing the high-pressure atomizing rainfall nozzle group (5).

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