A suspended particle water flow penetration experimental device and experimental method

Abstract

The present invention provides a suspended particle water flow infiltration experimental device and experimental method, including a fixed flow infiltration module, a seepage workbench, a rotary sampling module and a monitoring and data analysis processing module, wherein the fixed flow infiltration module includes a suspended particle stirring device and a lifting unit, the seepage workbench includes a cylinder with a funnel-shaped drainage unit at the bottom and a fluid density meter, the cylinder is provided with an axial force application unit and a movable sample table, the seepage workbench also includes a plurality of pressure ports, the rotary sampling module is arranged at the outlet end of the funnel-shaped drainage unit, the rotary sampling module includes a rotary sampling unit and an overflow unit that are interconnected, and the rotary sampling unit is controlled to rotate to collect eroded particles under different parameters. The present invention can realize the simulation and dynamic observation and analysis of the original soil sample under the suspended particle inflow infiltration erosion phenomenon, facilitates the experimenter to analyze the changes in the mechanical properties of the soil under the erosion, and can meet different experimental requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical engineering, and in particular relates to a suspended particle water flow penetration experimental device and an experimental method. Background Art

[0002] The safety of dams or levees is one of the risks faced by cities. Internal erosion is a complex phenomenon and one of the most common causes of failure of levees and earth dams. It includes concentrated seepage erosion, retreat erosion, contact erosion and piping erosion, all of which belong to internal soil erosion, especially the occurrence of erosion. Erosion refers to the erosion of fine soil particles under the action of dynamic water pressure, which washes away the fine particles, destroys the structure of the soil and forms caves. Erosion is difficult to observe because there are no obvious features, or there may be some subtle evidence, but the evidence may be covered by water, which makes it easy to ignore these evidences. If not discovered and treated in time, the cavity will expand rapidly in a short period of time, and its momentum will be unstoppable, leading to the failure and collapse of the dam. Therefore, it is important to consider and reduce the possibility of internal erosion during dam construction.

[0003] Existing soil seepage experiments all use clean water as the infiltration fluid for infiltration experiments, but it is impossible for clean water to infiltrate the soil in the natural environment. The existing technology lacks analysis and observation of suspended particle infiltration experiments, and previous infiltration experiments can only conduct triaxial infiltration experiments at a specific infiltration rate to measure various data of the original soil sample. The obtained data is quite different from the real data and has poor referenceability. In addition, most of the existing technologies cannot measure the spatial changes in density and pore pressure of the original soil sample along the original soil, which makes it difficult to meet various experimental needs. It is impossible to dynamically observe and analyze the seepage erosion phenomenon of the original soil sample, resulting in the inability to know the changes in the particle composition of the original soil sample under a specific pressure. Summary of the invention

[0004] The purpose of the present invention is to address the shortcomings of the prior art and provide a suspended particle flow infiltration experiment that can utilize suspended particle flow, and the infiltration rate can be adjusted, so as to realize the simulation and dynamic observation and analysis of the original soil sample under the suspended particle flow infiltration erosion phenomenon, the measured data has strong reference value, and is convenient for analyzing the changes in the mechanical properties of the soil under the action of erosion, and is suitable for a variety of experimental conditions and meets different experimental needs. The suspended particle water flow infiltration experimental device and experimental method.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A suspended particle water flow penetration experimental device comprises a constant flow penetration module, a seepage workbench, a rotating sampling module and a monitoring and data analysis processing module, wherein the constant flow penetration module, the seepage workbench and the rotating sampling module are connected in sequence, wherein the constant flow penetration module comprises a suspended particle stirring device and a lifting unit arranged at the bottom of the suspended particle stirring device, the seepage workbench comprises a cylinder with a funnel-shaped drainage unit at the bottom and a fluid density meter, the cylinder is provided with an axial force applying unit and a movable sample table, the seepage workbench also comprises a plurality of pressure ports arranged at different positions, the rotating sampling module is arranged at the outlet end of the funnel-shaped drainage unit, the rotating sampling module comprises a rotating sampling unit and an overflow unit which are connected to each other, the rotating sampling unit is controlled to rotate to collect erosion particles under different parameters, and the constant flow penetration module, the seepage workbench and the rotating sampling module are all connected to the monitoring and data analysis module for data transmission.

[0007] Furthermore, the rotating sampling unit includes a sampling water tank and a rotating tray arranged in the sampling water tank, the outlet end of the funnel-shaped drainage unit extends into the sampling water tank, the rotating tray is a cylindrical structure with an open top, and the internal space of the rotating tray is divided into N equal parts, each of which is equipped with a beaker, and the beaker is placed in a position corresponding to the outlet end of the funnel-shaped drainage unit. The rotating tray also includes a rotating handle that passes through the sampling water tank upward, the sampling water tank is connected to the overflow unit, and the overflow unit includes an overflow trough with a drainage outlet. The rotating handle is connected to the rotating shaft of the rotating tray, which extends upward from the sampling water tank, so that the experimenter can drive the rotating tray to rotate by controlling the rotation of the rotating handle. When the beaker in the previous unit is collected, the rotating handle is turned to rotate the rotating tray to the outlet end of the funnel-shaped drainage unit corresponding to the beaker in the next unit, and the relevant experimental parameters are changed to continue collecting, so as to meet different experimental needs and be suitable for a variety of experimental conditions. The overflow unit plays a drainage role to ensure that the cylinder and the rotating sampling unit are always in a saturated state before the experiment begins. At the same time, at the beginning of the experiment, negative pressure is applied to the overflow unit to discharge the water in the cylinder and the rotating sampling unit to ensure the smooth progress of the experiment, reduce the influence of air on the experimental data, and the measured data has strong reference value.

[0008] Furthermore, the cylinder is a rigid cylindrical container with an openable top cover, the funnel-shaped drainage unit includes a funnel-shaped container connected to the bottom of the rigid cylindrical container, an outlet pipe with a needle valve is arranged at the outlet end of the funnel-shaped container, the pressure port includes a plurality of first pressure ports and a third pressure port arranged on the outlet pipe, the plurality of first pressure ports are arranged axially from top to bottom at intervals and are arranged in pairs on the outer side wall of the rigid cylindrical container, the seepage workbench also includes a reaction force frame arranged outside the funnel-shaped container, and the rotary sampling unit is arranged in the reaction force frame. After the beaker rotates, it corresponds to the position of the water outlet pipe. The liquid is gathered to the water outlet pipe through the funnel-shaped container, and then flows into the beaker to be collected. Several first pressure ports are arranged in pairs along the outer wall of the rigid cylindrical container. Each group is arranged at intervals along the axial direction. The two first pressure ports in the same group are located at both ends of the same diameter. The pressure ports are connected to the pressure gauge. The data is imported into the monitoring and data analysis and processing module through the pressure gauge. The computer automatically records the changes in the hydraulic head, flow rate and original soil sample length of each pressure port. These data reflect the detailed situation of the internal erosion of the original soil sample, which is convenient for analyzing the changes in the mechanical properties of the soil under erosion.

[0009] Furthermore, the fluid density meter is arranged at the top of the reaction force frame toward the cylinder, and the fluid density meter is connected to the monitoring and data analysis module for data transmission. The fluid density meter is arranged on the reaction force frames on both sides of the funnel-shaped container, and is used to monitor the average density of the liquid in the funnel-shaped container to calculate the mass of the suspended particles in the liquid. The total mass of the eroded original soil sample can be obtained by adding the large-diameter particles in the rotating sampling module, and the erosion sensitivity of the soil sample can be deduced by combining other data. The design of the fluid density meter can improve the accuracy of the measurement data and enhance the reference value of the data.

[0010] Furthermore, the fluid density meter is arranged on the reaction force frame through a bracket, and the bracket includes a track for controlling the fluid density meter to move up and down. The bracket can be set to a certain speed to drive the fluid density meter to move up and down along the track on the outer wall of the rigid cylindrical container, specifically, a cruising speed and an approach speed are set respectively, which respectively control the travel duration and position difference, and receive the scintillation counter light source through the density calculator of the fluid density meter and calculate the average density of the sample part within a certain range within the focus axis of the scintillation counter, so as to perform subsequent data calculation and analysis.

[0011] Furthermore, the axial force applying unit includes a cylinder located at the top of the cylinder and a piston extending into the cylinder, the piston includes a top plate, a partition and a bottom plate connected in sequence from top to bottom, the top plate and the bottom plate are perforated plates, a large-aperture honeycomb material layer is provided in the partition, a rubber layer is filled between the piston and the inner wall of the cylinder, a linear variable differential transformer and a displacement sensor are provided between the cylinder and the piston, and the pressure port includes a second pressure port provided at the bottom of the piston. The piston is controlled by a cylinder, which consists of two 15 mm thick stainless steel perforated plates with a partition in the middle. The top plate and the bottom plate are filled with a rubber layer from the inner wall of the rigid cylindrical container to seal and prevent the liquid from leaking upwards, thus ensuring the reliability of the experimental data. The partition separates the two perforated plates. The large-aperture honeycomb material layer arranged in the partition is used to change the point-like water flow at the water inlet into a surface-like water flow that enters the original soil sample for seepage, making the simulation closer to reality and enhancing the referenceability of the data. A linear variable differential transformer and a displacement sensor are provided to facilitate the control of the cylinder's activities, so as to realize the position control of the piston, thereby changing the axial load applied to the original soil sample, which can meet different experimental requirements. The second pressure port is in contact with the top surface of the original soil sample, and the measured data is transmitted to the computer through a pressure gauge, which is convenient for analyzing the changes in the mechanical properties of the soil.

[0012] Furthermore, the movable sample platform includes a movable support and a stainless steel mesh screen arranged on the movable support, a telescopic support foot is arranged at the bottom of the movable support, a boss matching the telescopic support foot is arranged at the bottom of the cylinder, and geotextile is filled between the movable sample platform and the inner wall of the cylinder. The stainless steel mesh screen includes two upper and lower ones. The lower stainless steel mesh screen is connected to the movable support. The original soil sample is located between the upper and lower stainless steel mesh screens. The upper stainless steel mesh screen is placed on the top surface of the original soil sample to prevent fine particles from migrating into the piston. The mesh aperture size of the stainless steel mesh screen is selected according to the type of the original soil sample. By adjusting the telescopic legs of the movable support or selecting stainless steel mesh screens with different mesh apertures, the installation of original soil samples of different sizes and shapes can be completed, which can meet different experimental needs and is suitable for a variety of experimental conditions. Adding geotextile between the movable sample stage and the rigid cylindrical container can eliminate particle migration between the movable sample stage and the rigid cylindrical container. During the experiment, the position of the piston is adjusted until the bottom surface of the bottom plate just contacts the top surface of the original soil sample so as to apply an axial load. The original soil sample will be consolidated under the axial load and double drainage conditions to dissipate excess gap pressure in the upward and downward directions.

[0013] Furthermore, the constant flow infiltration module also includes a water tank and a connecting pipeline, the lifting unit includes a lifting platform, the water tank is placed above the lifting platform, the suspended particle stirring device is arranged at the bottom of the water tank, the water tank includes a water inlet, a particle injection port and a water outlet, the water inlet is arranged at the top of the cylinder, the two ends of the connecting pipeline are respectively connected to the water outlet and the water inlet, and the connecting pipeline body is provided with a flow meter and an upstream gate. Preferably, two water inlets are arranged, the lifting platform is used to control the lifting of the water tank, and the suspended particle stirring device is used to stir the water and suspended particles injected into the water tank, so that the suspended particle flow flows through the connecting pipeline to the water inlet and enters the rigid cylindrical container, and the suspended particle flow is used to perform the infiltration experiment, so that the measured data is closer to reality and has strong reference, which is convenient for analyzing the changes in the mechanical properties of the soil under the action of erosion and proposing corresponding countermeasures, and the experimental parameters can be changed by controlling the position of the lifting platform, so as to meet different experimental needs, and the design of the flow meter and the upstream gate is convenient for controlling the flow size of the constant flow infiltration module.

[0014] Furthermore, the monitoring and data analysis processing module includes a computer and a data acquisition device, the constant flow infiltration module, the seepage workbench and the rotary sampling module are all connected to the data acquisition device for data transmission, and the data acquisition device is connected to the computer through a line. The data acquisition device connects the flow meter, the linear variable differential transformer LVDT, the displacement sensor, the fluid density meter, the pressure port and the pressure gauge to the data acquisition device, the data acquisition device receives the measured data and transmits it to the computer through the line, and automatically calculates through the VBA program to obtain the permeability coefficient, which is convenient for analyzing the changes in the mechanical properties of the soil under erosion.

[0015] The present invention also provides an experimental method for a suspended particle water flow penetration experimental device, comprising the following steps:

[0016] S1. First, make the device saturated, plug the pressure port to prevent the sample from entering, and inject water into the cylinder with the self-determined flow rate permeation module until the water covers all the pressure ports, and all the pressure ports are connected to the monitoring and data analysis and processing module. At this time, the cylinder and the rotating sampling module are both in a saturated state;

[0017] S2. Prepare the original soil sample on site. After the original soil sample is prepared, divide the original soil sample into three layers and measure the particle size distribution of each layer to obtain the original soil sample. After the cylinder and the rotating sampling module are saturated, drain the water in the device through the overflow unit. Determine the size of the movable sample stage according to the measured particle size, and place the original soil sample on the movable sample stage and then put it into the device. Before the test, inject carbon dioxide into the cylinder from the overflow unit for 20 minutes to remove the air between the soil particles of the original soil sample. Then slowly inject water from the overflow unit into the cylinder to fill the original soil sample with water. Complete the installation of the movable sample stage, and adjust the position of the axial force application unit to just contact the original soil sample to apply the axial load;

[0018] S3. Add water and suspended particles to the constant flow infiltration module, start the suspended particle stirring device to fully stir and adjust the lifting unit to a suitable height so that the suspended particles flow into the cylinder. Adjust the hydraulic gradient by adjusting the lifting unit. The test is divided into two groups at the beginning. The effective stress of the test is the same constant value. The hydraulic load applied by the first group is discrete. The hydraulic gradient is increased every 30 minutes. After reaching the next level, the rotating sampling unit is controlled to rotate one unit to collect eroded particles; the hydraulic head of the second group is continuously increased, and the hydraulic gradient is changed every 6 minutes. After changing the hydraulic gradient twice, the rotating sampling unit is controlled to rotate one unit, that is, one unit is used to collect eroded particles on two hydraulic gradients. When adjusting the heights of different lifting units, the constant flow infiltration module needs to be kept closed and water and suspended particles need to be refilled;

[0019] S4. After the original soil sample is subjected to axial load and seepage downward, data collection begins. All pressure ports are connected to the monitoring and data analysis processing module. The monitoring and data analysis processing module automatically records and calculates the hydraulic head of each pressure port and the change in the length of the original soil sample. The formula V (volume) = Q × t = v × A × t is used. According to Darcy's law, v = k × i and Derived Calculate the permeability coefficient, where v is the Darcy seepage velocity, i is the hydraulic gradient, k is the permeability coefficient of the soil sample, Q is the flow rate, ΔH is the head difference, and L and A are the length and cross-sectional area of ​​the original soil sample, respectively;

[0020] S5. Calculate the average density of the original soil sample by a fluid densitometer;

[0021] S6. After the experiment is completed, the rotating sampling unit is taken out for drying and weighing. The total erosion mass is calculated by weighing the eroded particles in the rotating sampling unit, and then the energy loss measured by the pressure port is compared and analyzed. After the experiment is completed, the particle size distribution of the original soil sample is tested, and the particle size distribution of each layer of the original soil sample after the experiment is measured. Compared with the particle size distribution measured in S2, it is determined whether each layer of soil has been eroded and the degree of erosion.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention utilizes suspended particle flow to conduct infiltration experiments, and the infiltration rate is adjustable, so as to realize the simulation and dynamic observation and analysis of the original soil sample under the infiltration erosion phenomenon of suspended particle flow. The measured data has strong reference value, which is convenient for experimenters to analyze the changes in the mechanical properties of the soil under the action of erosion. The invention is applicable to a variety of experimental conditions and meets different experimental needs. By setting up a constant flow infiltration module, a seepage workbench, a rotary sampling module, and a monitoring and data analysis and processing module, the simulation and dynamic observation of the internal erosion of soil samples under the action of specific seepage force and specific seepage water flow are realized, providing accurate and efficient basic experimental data for some geological disasters such as dam breach, soil erosion, and environmental pollution induced by erosion phenomena, and the measured data has strong reference value; based on the unidirectional compression effect, the seepage force and axial load are applied under saturated conditions and the seepage erosion phenomenon is measured and observed, which is suitable for a variety of experimental conditions and can meet different experimental needs; the axial load is controlled by the axial force application unit to simulate the field stress, and the constant flow infiltration module is set up to provide the soil sample with a stable downward seepage force. Before the experiment, the original soil sample and the rigid cylindrical container need to be saturated and a certain pressure is maintained throughout the experiment to avoid the influence of air and other factors on the experimental results and ensure the reference value of the data; a movable sample table and a funnel-shaped drainage unit are set up and a rotating sampling module, so that the eroded fine particles can flow into the rotating sampling module through the funnel-shaped drainage unit to be collected, processed and analyzed, providing basic data for the analysis of particle size changes of the original soil sample after erosion; a number of pressure ports are set, and all are connected to the pressure gauge, and the data are imported into the computer system in the monitoring and data analysis processing module through the pressure gauge. The computer system automatically records the changes in the hydraulic head, flow rate and length of the original soil sample of each pressure port, so as to reflect the detailed situation of the internal erosion of the original soil sample through the data changes and analyze it conveniently; a fluid density meter is installed to monitor the average density of the liquid in the cylinder to calculate the mass of the suspended particles in the liquid, and then the large-diameter particles in the rotating sampling module are added to obtain the total mass of the original soil sample eroded, and then the erosion sensitivity of the soil sample can be deduced in combination with other data, so as to realize the simulation and dynamic observation and analysis of the original soil sample under the phenomenon of suspended particle inflow and infiltration erosion, so as to facilitate the analysis of the changes in the mechanical properties of the soil under the action of erosion and propose countermeasures. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0025] Figure 2 It is a cross-sectional view of the water storage tank of the present invention.

[0026] Figure 3 It is a top view of the top cover of the present invention.

[0027] Figure 4 This is a cross-sectional view of the sampling water tank of the present invention.

[0028] Among them, 1-constant flow infiltration module, 11-water storage tank, 12-lifting unit, 13-suspended particle stirring device, 14-water inlet, 15-particle injection port, 16-water outlet, 17-connecting pipeline, 18-flow meter, 19-upstream gate, 2-seepage workbench, 21-top cover, 22-cylinder, 23-linear variable differential transformer, 24-displacement sensor, 25-water inlet, 26-large aperture honeycomb material layer, 27-interlayer, 28-piston, 29-stainless steel mesh Sieve, 210-movable support, 211-fluid density meter, 212-funnel-type container, 213-needle valve, 214-water outlet pipe, 215-reaction force frame, 216-first pressure port, 217-second pressure port, 218-third pressure port, 3-rotating sampling module, 31-sampling water tank, 32-rotating tray, 33-beaker, 34-rotating handle, 35-overflow unit, 36-drain port, 4-monitoring and data analysis and processing module, 41-computer. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be described clearly and completely below in combination with the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0030] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0031] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0032] The suspended particle water flow infiltration experimental device shown in the figure includes a constant flow infiltration module 1, a seepage workbench 2, a rotary sampling module 3 and a monitoring and data analysis processing module 4. The constant flow infiltration module 1, the seepage workbench 2 and the rotary sampling module 3 are connected in sequence, wherein the constant flow infiltration module 1 includes a suspended particle stirring device 13 and a lifting unit 12 arranged at the bottom of the suspended particle stirring device 13, the seepage workbench 2 includes a cylinder with a funnel-shaped drainage unit at the bottom and a fluid density meter 211, the cylinder is provided with an axial force applying unit and a movable sample table, the seepage workbench 2 also includes a plurality of pressure ports arranged at different positions, the rotary sampling module 3 is arranged at the outlet end of the funnel-shaped drainage unit, the rotary sampling module 3 includes a rotary sampling unit and an overflow unit 35 connected to each other, the rotary sampling unit is controlled to rotate to collect erosion particles under different parameters, and the constant flow infiltration module 1, the seepage workbench 2 and the rotary sampling module 3 are all connected to the monitoring and data analysis module 4 for data transmission. By setting up a constant flow infiltration module, a seepage workbench, a rotary sampling module, and a monitoring and data analysis and processing module, the simulation and dynamic observation of the internal erosion of soil samples under the action of specific seepage force and specific seepage water flow are realized, providing accurate and efficient basic experimental data for some geological disasters such as dam breach, soil erosion, and environmental pollution induced by erosion phenomena, and the measured data has strong reference value; based on the unidirectional compression effect, the seepage force and axial load are applied under saturated conditions and the seepage erosion phenomenon is measured and observed, which is suitable for a variety of experimental conditions and can meet different experimental needs; the axial load is controlled by the axial force application unit to simulate the field stress, and the constant flow infiltration module is set up to provide the soil sample with a stable downward seepage force. Before the experiment, the original soil sample and the rigid cylindrical container need to be saturated and a certain pressure is maintained throughout the experiment to avoid the influence of air and other factors on the experimental results and ensure the reference value of the data; a movable sample table and a funnel-shaped drainage unit are set up and a rotating sampling module, so that the eroded fine particles can flow into the rotating sampling module through the funnel-shaped drainage unit to be collected, processed and analyzed, providing basic data for the analysis of particle size changes of the original soil sample after erosion; a number of pressure ports are set, and all are connected to the pressure gauge, and the data are imported into the computer system in the monitoring and data analysis processing module through the pressure gauge. The computer system automatically records the changes in the hydraulic head, flow rate and length of the original soil sample of each pressure port, so as to reflect the detailed situation of the internal erosion of the original soil sample through the data changes and analyze it conveniently; a fluid density meter is installed to monitor the average density of the liquid in the cylinder to calculate the mass of the suspended particles in the liquid, and then the large-diameter particles in the rotating sampling module are added to obtain the total mass of the original soil sample eroded, and then the erosion sensitivity of the soil sample can be deduced in combination with other data, so as to realize the simulation and dynamic observation and analysis of the original soil sample under the phenomenon of suspended particle inflow and infiltration erosion, so as to facilitate the analysis of the changes in the mechanical properties of the soil under the action of erosion and propose countermeasures.The present invention utilizes suspended particle flow to conduct infiltration experiments, and the infiltration rate is adjustable, so as to realize the simulation and dynamic observation and analysis of the original soil sample under the infiltration erosion phenomenon of suspended particle flow. The measured data has strong reference value, which is convenient for experimenters to analyze the changes in the mechanical properties of the soil under the action of erosion. The invention is applicable to a variety of experimental conditions and meets different experimental needs.

[0033] Preferably, the rotary sampling unit includes a sampling water tank 31 and a rotating tray 32 disposed in the sampling water tank 31, the outlet end of the funnel-shaped drainage unit extends into the sampling water tank 31, the rotating tray 32 is a cylindrical structure with an open top, and the internal space of the rotating tray 32 is divided into N equal parts, each of which is provided with a beaker 33, and the beaker 33 is placed at a position corresponding to the outlet end of the funnel-shaped drainage unit, and the rotating tray 33 also includes a rotating handle 34 that passes through the sampling water tank 31 upward, and the sampling water tank 31 is connected to the overflow unit 35, and the overflow unit 35 includes an overflow trough with a drainage port 36. Preferably, the internal space of the rotating tray is divided into eight parts, and a beaker is provided in each part. The rotating handle is connected to the rotating shaft of the rotating tray, which extends upward from the sampling water tank, so that the experimenter can drive the rotating tray to rotate by controlling the rotation of the rotating handle. When the beaker in the previous unit is collected, the rotating handle is turned to rotate the rotating tray to the outlet end of the funnel-shaped drainage unit corresponding to the beaker in the next unit, and the relevant experimental parameters are changed to continue collecting, so as to meet different experimental needs and be suitable for a variety of experimental conditions. The overflow unit plays a drainage role to ensure that the cylinder and the rotating sampling unit are always in a saturated state before the experiment begins. At the same time, at the beginning of the experiment, negative pressure is applied to the overflow unit to discharge the water in the cylinder and the rotating sampling unit to ensure the smooth progress of the experiment, reduce the influence of air on the experimental data, and the measured data has strong reference value.

[0034] Preferably, the cylinder is a rigid cylindrical container with an openable top cover 21, the funnel-shaped drainage unit includes a funnel-shaped container 212 connected to the bottom of the rigid cylindrical container, an outlet pipe 214 with a needle valve 213 is arranged at the outlet end of the funnel-shaped container 212, the pressure port includes a plurality of first pressure ports 216 and a third pressure port 218 arranged on the outlet pipe 214, the plurality of first pressure ports 216 are arranged axially from top to bottom at intervals and are arranged opposite to each other on the outer wall of the rigid cylindrical container, the seepage workbench 2 also includes a reaction force frame 215 arranged outside the funnel-shaped container 212, and the rotary sampling unit is arranged in the reaction force frame 215. After the beaker is rotated, it corresponds to the position of the water outlet pipe. The liquid is gathered to the water outlet pipe through the funnel-shaped container, and then flows into the beaker to be collected. Several first pressure ports are arranged in pairs along the outer wall of the rigid cylindrical container. Each group is arranged at intervals along the axial direction. The two first pressure ports in the same group are located at both ends of the same diameter. The first pressure port can not only reflect the vertical seepage situation, but also the horizontal seepage situation. The pressure ports are all connected to the pressure gauge. The data is imported into the monitoring and data analysis and processing module through the pressure gauge. The computer automatically records the changes in the hydraulic head, flow rate and original soil sample length of each pressure port. These data reflect the detailed situation of the internal erosion of the original soil sample, which is convenient for analyzing the changes in the mechanical properties of the soil under erosion.

[0035] Preferably, the fluid density meter 211 is arranged at the top of the reaction force frame 215 toward the cylinder, and the fluid density meter 211 is connected to the monitoring and data analysis module 4 for data transmission. The fluid density meter is arranged on the reaction force frames on both sides of the funnel-shaped container, and is used to monitor the average density of the liquid in the funnel-shaped container to calculate the mass of the suspended particles in the liquid. The total mass of the eroded original soil sample can be obtained by adding the large-diameter particles in the rotating sampling module, and the erosion sensitivity of the soil sample can be deduced by combining other data. The design of the fluid density meter can improve the accuracy of the measurement data and enhance the reference value of the data.

[0036] Preferably, the fluid density meter 211 is arranged on the reaction force frame 215 through a bracket, and the bracket includes a track for controlling the up and down movement of the fluid density meter 211. The bracket can be set to a certain speed to drive the fluid density meter to move up and down along the track on the outer wall of the rigid cylindrical container, specifically, a cruising speed and an approach speed are set respectively, which respectively control the travel duration and position difference, and receive the scintillation counter light source through the density calculator of the fluid density meter and calculate the average density of the sample part within a certain range within the focus axis of the scintillation counter, so as to perform subsequent data calculation and analysis.

[0037] Preferably, the axial force applying unit includes a cylinder 22 located at the top of the cylinder and a piston 28 extending into the cylinder. The piston 28 includes a top plate, a partition 27 and a bottom plate connected in sequence from top to bottom. The top plate and the bottom plate are perforated plates. A large-pore honeycomb material layer 26 is provided in the partition 27. A rubber layer is filled between the piston 28 and the inner wall of the cylinder. A linear variable differential transformer 23 and a displacement sensor 24 are provided between the cylinder 22 and the piston 28. The pressure port includes a second pressure port 217 provided at the bottom of the piston 28. The piston is controlled by a cylinder, which consists of two 15 mm thick stainless steel perforated plates with a partition in the middle. The top plate, partition and bottom plate are connected as a whole through the movable end of the cylinder. The top plate and the bottom plate are filled with a rubber layer from the inner wall of the rigid cylindrical container to seal and prevent the liquid from leaking upwards, ensuring the reliability of the experimental data. The partition separates the two perforated plates. The large-aperture honeycomb material layer arranged in the partition is used to change the point-like water flow at the water inlet into a surface-like water flow that enters the original soil sample for seepage, making the simulation closer to reality and enhancing the referenceability of the data. A linear variable differential transformer and a displacement sensor are set to facilitate the detection and control of the activity of the cylinder to achieve the control of the movement position of the piston and the detection of the length change of the original soil sample, thereby changing the axial load applied to the original soil sample to meet different experimental needs. The second pressure port is in contact with the top surface of the original soil sample, and the measured data is transmitted to the computer through the pressure gauge, which is convenient for analyzing the changes in the mechanical properties of the soil.

[0038] Preferably, the movable sample platform includes a movable support 210 and a stainless steel mesh screen 29 arranged on the movable support 210, a telescopic support foot is arranged at the bottom of the movable support 210, a boss matching the telescopic support foot is arranged at the bottom of the cylinder, and geotextile is filled between the movable sample platform and the inner wall of the cylinder. The stainless steel mesh screen includes two upper and lower ones. The lower stainless steel mesh screen is connected to the movable support. The original soil sample is located between the upper and lower stainless steel mesh screens. The upper stainless steel mesh screen is placed on the top surface of the original soil sample to prevent fine particles from migrating into the piston. The mesh aperture size of the stainless steel mesh screen is selected according to the type of the original soil sample. When the movable sample stage is placed into the cylinder, its telescopic legs cooperate with the boss to achieve fixation. By adjusting the length of the telescopic legs or selecting stainless steel mesh screens with different mesh apertures, the installation of original soil samples of different sizes and shapes can be completed, which can meet different experimental needs and is suitable for a variety of experimental conditions. Adding geotextile between the movable sample stage and the rigid cylindrical container can eliminate particle migration between the movable sample stage and the rigid cylindrical container. During the experiment, the position of the piston is adjusted until the bottom surface of the bottom plate just contacts the top surface of the original soil sample so as to apply an axial load. The original soil sample will be consolidated under the axial load and double drainage conditions to dissipate excessive gap pressure in the upward and downward directions.

[0039] Preferably, the constant flow infiltration module 1 also includes a water tank 11 and a connecting pipe 17, the lifting unit 12 includes a lifting platform, the water tank 11 is placed above the lifting platform, the suspended particle stirring device 13 is arranged at the bottom of the water tank 11, the water tank 11 includes a water inlet 14, a particle injection port 15 and a water outlet 16, a water inlet 25 is arranged on the top of the cylinder, and the two ends of the connecting pipe 17 are respectively connected to the water outlet 16 and the water inlet 25, and the pipe body of the connecting pipe 17 is provided with a flow meter 18 and an upstream gate 19. Preferably, two water inlets are provided, and the lifting platform is used to control the lifting of the water tank. The suspended particle stirring device is used to stir the water and suspended particles injected into the water tank so that the suspended particle flow flows through the connecting pipeline to the water inlet and enters the rigid cylindrical container. Preferably, the suspended particle stirring device is an electrically controlled stirring blade. The suspended particle flow is used for the infiltration experiment. Suspended particles of different sizes can be selected according to the simulation situation, so that the measured data is closer to reality, has strong reference, and can meet different experimental needs. It is convenient to analyze the changes in the mechanical properties of the soil under erosion and propose corresponding countermeasures. The experimental parameters can be changed by controlling the position of the lifting platform to meet different experimental needs. The flow meter and the upstream gate are designed to facilitate the control of the flow size of the fixed flow infiltration module.

[0040] Preferably, the monitoring and data analysis processing module 4 includes a computer 41 and a data acquisition device, and the constant flow infiltration module 1, the seepage workbench 2 and the rotary sampling module 3 are all connected to the data acquisition device for data transmission, and the data acquisition device is connected to the computer 41 through a line. The flow meter, the linear variable differential transformer LVDT, the displacement sensor, the fluid density meter, the pressure port and the pressure gauge are all connected to the data acquisition device, and the data acquisition device receives the measured data and transmits it to the computer through the line, and automatically calculates through the VBA program to obtain the permeability coefficient, which is convenient for analyzing the changes in the mechanical properties of the soil under erosion.

[0041] As a preferred embodiment, the present invention also writes a VBA program to perform automatic calculations. Taking flow as an example, there is a table recording data. First, the first column is converted into the duration of the experiment, the second column is the time for the water to pass through the pressure port, and the third column is the flow rate through the pressure port. For this example, assuming that the test duration is 2 minutes, there are 36 values ​​in total, and the VBA program code is as follows:

[0042] Sub flow()

[0043] Dim i,k,m As Integer

[0044] Dim sum As Double

[0045] Sum=0

[0046] I=0

[0047] M=0

[0048] For k=0To 2

[0049] Do

[0050] sum=sum+Sheets(1).Cells(i+2,3)

[0051] i=i+1

[0052] m=m+1

[0053] Loop While Sheets(1).Cells(i+2,2)=k

[0054] Sheets(1).Cells(k+2,4)=sum / m

[0055] Sum = 0

[0056] M=0

[0057] Next k

[0058] End Sub

[0059] The average value of the flow rate per minute is automatically calculated and displayed in the fourth column. The hydraulic head and the change in undisturbed sample length are handled by the input code.

[0060] The present invention also designs an experimental method for a suspended particle water flow penetration experimental device, comprising the following steps:

[0061] S1, first start to inject water to make the device in a saturated state, fill the pressure port through the filter to prevent the sample from entering, and inject water into the cylinder with the self-determined flow rate permeation module until the water covers all the pressure ports (except the second pressure port 217), and all the pressure ports are connected to the monitoring and data analysis and processing module 4 through the pressure gauge, at this time the cylinder and the rotating sampling module 3 are in a saturated state;

[0062] S2. Prepare the original soil sample on site. After the original soil sample is prepared, divide the original soil sample into three layers and measure the particle size distribution of each layer. Use a sieve to measure the particles with a particle size greater than 2 mm, and use a laser particle size analyzer to measure the particles with a particle size less than 2 mm to obtain the original soil sample. After the cylinder and the rotating sampling module 3 are saturated, drain the water in the device through the overflow unit 35. Determine the size of the movable sample stage according to the measured particle size. First, connect the stainless steel mesh screen 29 below to the movable support 210 to allow only the migration of fine particles. Place the original soil sample on the stainless steel mesh screen 29 below, put the movable sample stage into the cylinder, and adjust the telescopic support 210 to adjust the size of the movable sample stage. The bottom of the telescopic support foot is stuck on the boss. Before the test, carbon dioxide is injected into the cylinder from the overflow unit 35 for 20 minutes to remove the air between the soil particles of the original soil sample. Then water is slowly injected into the cylinder from the overflow unit 35 to fill the original soil sample with water. The upper stainless steel mesh screen 29 is placed on the top of the original soil sample to complete the installation of the movable sample table to prevent fine particles from migrating into the piston 28. The position of the axial force applying unit is adjusted to just contact with the original soil sample, that is, the bottom surface of the bottom plate of the piston 28 contacts the top surface of the original soil sample to apply the axial load. The original soil sample will be consolidated under the axial load and double drainage conditions to dissipate the excessive gap pressure in the upward and downward directions;

[0063] S3, add water and suspended particles to the constant flow infiltration module 1, start the suspended particle stirring device 13 to stir fully and adjust the lifting unit 12 to a suitable height, open the upstream gate 19 and the needle valve 213, so that the suspended particles flow into the cylinder, and control the piston 28 to apply an axial load to the original soil sample. It should be noted that whether there is a blockage in the interlayer; the hydraulic gradient is adjusted by controlling the height of the lifting unit 12 to increase by increments. The test is divided into two groups at the beginning, and the effective stress of the test is the same constant value. The hydraulic load applied by the first group is discrete, that is, the hydraulic head is 0.1, 0. 2, 0.3, 0.6, 1, 2, 5, the hydraulic gradient is increased every 30 minutes, and when it reaches the next level, the rotary sampling unit is controlled to rotate the beaker 33 in one unit to collect eroded particles; the second group of hydraulic head increases continuously from about 0.02 to 2.5, and the hydraulic gradient is changed every 6 minutes. After changing the hydraulic gradient twice, the rotary sampling unit is controlled to rotate one unit to replace the next beaker 33, that is, one beaker 33 is used to collect eroded particles on two hydraulic gradients. When adjusting the height of different lifting units 12, the upstream gate 19 and the needle valve 213 must be kept closed and the water and suspended particles must be refilled;

[0064] S4. After the original soil sample is subjected to axial load and seepage downward, data collection begins. All pressure ports are connected to the monitoring and data analysis processing module 4 through pressure gauges. The data of the pressure gauges are imported into the computer 41. The computer 41 can automatically record and calculate the hydraulic head, flow rate and change of the original soil sample length of each pressure port. Because the experiment takes a long time and each variable has many measured values ​​within one minute, the VBA program is used for automatic calculation. According to the formula V (volume) = Q × t = v × A × t, according to Darcy's law, v = k × i and Derived Calculate the permeability coefficient, where v is the Darcy seepage velocity, i is the hydraulic gradient, k is the permeability coefficient of the soil sample, Q is the flow rate, ΔH is the head difference, L and A are the length and cross-sectional area of ​​the original soil sample respectively, and the permeability coefficient is calculated by this formula;

[0065] S5, calculating the average density of the original soil sample by the fluid densitometer 211, setting a cruising speed and an approach speed for the bracket to drive the fluid densitometer 211 to move up and down, thereby controlling the travel duration and position difference of the fluid densitometer 211, receiving the scintillation counter light source through the density calculator of the fluid densitometer 211 and calculating the average density of the sample portion located within a certain range within the focusing axis of the scintillation counter;

[0066] S6. After the experiment is completed, stop adding water to the water storage tank 11, close the upstream gate 19 and the needle valve 213, drain the water from the sampling water tank 31, take out the beaker 33 of the rotary sampling unit, dry and weigh it, and calculate the total eroded mass by weighing the eroded particles in the beaker 33. Then, compare and analyze the energy loss measured by the pressure port, which can indicate the sensitivity of the soil to erosion. If the erosion amount is small and the energy consumed is large, it means that the soil is relatively stable and not easily eroded. Since seepage involves selective erosion of fine particles, the particle size distribution before and after the test is particularly important. After the experiment is completed, the particle size distribution of the original soil sample is tested, and the measurement is performed in the same way as before the test. The particle size distribution of each layer of the original soil sample after the experiment is measured and compared with the particle size distribution measured in S2, it can be determined whether each layer of soil has been eroded and the degree of erosion.

[0067] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A suspended particle water flow penetration experimental device, characterized in that: The invention comprises a fixed flow infiltration module (1), a seepage workbench (2), a rotating sampling module (3) and a monitoring and data analysis module (4), wherein the fixed flow infiltration module (1), the seepage workbench (2) and the rotating sampling module (3) are connected in sequence, wherein the fixed flow infiltration module (1) comprises a suspended particle stirring device (13) and a lifting unit (12) arranged at the bottom of the suspended particle stirring device (13), the seepage workbench (2) comprises a cylinder with a funnel-shaped drainage unit at the bottom and a fluid density meter (211), the cylinder is provided with an axial force applying unit and a movable sample table, the seepage workbench (2) further comprises a plurality of pressure ports arranged at different positions, the rotating sampling module (3) is arranged at the outlet end of the funnel-shaped drainage unit, the rotating sampling module (3) comprises a rotating sampling unit and an overflow unit (35) which are connected to each other, and the rotating sampling unit is controlled to rotate so as to collect erosion particles under different parameters, and the fixed flow infiltration module (1), the seepage workbench (2) and the rotating sampling module (3) are all connected to the monitoring and data analysis module (4) for data transmission; The rotary sampling unit comprises a sampling water tank (31) and a rotating tray (32) arranged in the sampling water tank (31); the outlet end of the funnel-shaped drainage unit extends into the sampling water tank (31); the rotating tray (32) is a cylindrical structure with an open top; the internal space of the rotating tray (32) is divided into N equal parts, each of which is provided with a beaker (33); the beaker (33) is placed at a position corresponding to the outlet end of the funnel-shaped drainage unit; the rotating tray (32) further comprises a rotating handle (34) that passes through the sampling water tank (31) upward; the sampling water tank (31) is connected to an overflow unit (35); the overflow unit (35) comprises an overflow trough with a drainage port (36); The cylinder is a rigid cylindrical container with an openable top cover (21); the funnel-shaped drainage unit comprises a funnel-shaped container (212) connected to the bottom of the rigid cylindrical container; a water outlet pipe (214) with a needle valve (213) is provided at the outlet end of the funnel-shaped container (212); the pressure port comprises a plurality of first pressure ports (216) and a third pressure port (218) provided on the water outlet pipe (214); the plurality of first pressure ports (216) are arranged axially from top to bottom at intervals and are provided in pairs on the outer side wall of the rigid cylindrical container; the seepage workbench (2) further comprises a reaction force frame (215) provided outside the funnel-shaped container (212); and the rotary sampling unit is provided in the reaction force frame (215); The axial force applying unit comprises a cylinder (22) located at the top of the cylinder and a piston (28) extending into the cylinder, the piston (28) comprising a top plate, a partition (27) and a bottom plate connected in sequence from top to bottom, the top plate and the bottom plate are both perforated plates, a large-aperture honeycomb material layer (26) is provided in the partition (27), a rubber layer is filled between the piston (28) and the inner wall of the cylinder, a linear variable differential transformer (23) and a displacement sensor (24) are provided between the cylinder (22) and the piston (28), and the pressure port comprises a second pressure port (217) provided at the bottom of the piston (28); The movable sample platform comprises a movable support (210) and a stainless steel mesh screen (29) arranged on the movable support (210); a telescopic support foot is arranged at the bottom of the movable support (210); a boss matching the telescopic support foot is arranged at the bottom of the cylinder; and a geotextile is filled between the movable sample platform and the inner wall of the cylinder; The constant flow infiltration module (1) further comprises a water tank (11) and a connecting pipeline (17); the lifting unit (12) comprises a lifting platform; the water tank (11) is placed above the lifting platform; the suspended particle stirring device (13) is arranged at the bottom of the water tank (11); the water tank (11) comprises a water inlet (14), a particle injection port (15) and a water outlet (16); a water inlet (25) is arranged at the top of the cylinder; two ends of the connecting pipeline (17) are respectively connected to the water outlet (16) and the water inlet (25); and a flow meter (18) and an upstream gate (19) are arranged on the pipe body of the connecting pipeline (17).

2. The suspended particle water flow penetration experimental device according to claim 1, characterized in that: The fluid density meter (211) is arranged at the top of the reaction force frame (215) toward the cylinder, and the fluid density meter (211) is connected to the monitoring and data analysis module (4) for data transmission.

3. The suspended particle water flow penetration experimental device according to claim 2, characterized in that: The fluid density meter (211) is arranged on a reaction force frame (215) via a bracket, and the bracket comprises a track for controlling the upward and downward movement of the fluid density meter (211).

4. The suspended particle water flow penetration experimental device according to any one of claims 1 to 3, characterized in that: The monitoring and data analysis module (4) comprises a computer (41) and a data acquisition device, the constant flow infiltration module (1), the seepage workbench (2) and the rotary sampling module (3) are all connected to the data acquisition device for data transmission, and the data acquisition device is connected to the computer (41) via a line.

5. An experimental method using the suspended particle water flow penetration experimental device according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. First, the device is in a saturated state. The pressure ports are plugged to prevent the sample from entering. The self-determined flow rate permeation module injects water into the cylinder until the water covers all the pressure ports. All the pressure ports are connected to the monitoring and data analysis module (4). At this time, the cylinder and the rotary sampling module (3) are both in a saturated state. S2. Prepare the original soil sample on site. After the original soil sample is prepared, divide the original soil sample into three layers and measure the particle size distribution of each layer to obtain the original soil sample. After the cylinder and the rotating sampling module (3) are saturated, drain the water in the device through the overflow unit (35). Determine the size of the movable sample stage according to the measured particle size. Place the original soil sample on the movable sample stage and then put it into the device. Before testing, inject carbon dioxide into the cylinder from the overflow unit (35) for 20 minutes to remove the air between the soil particles of the original soil sample. Then slowly inject water from the overflow unit (35) into the cylinder to fill the original soil sample with water. Complete the installation of the movable sample stage and adjust the position of the axial force application unit to just contact the original soil sample to apply the axial load. S3, adding water and suspended particles to the constant flow infiltration module (1), starting the suspended particle stirring device (13) to stir fully and adjusting the lifting unit (12) to a suitable height so that the suspended particles flow into the cylinder, adjusting the hydraulic gradient by adjusting the lifting unit (12), the test is divided into two groups at the beginning, the effective stress of the test is the same constant value, wherein the hydraulic load applied to the first group is discrete, the hydraulic gradient is increased every 30 minutes, and after reaching the next level, the rotating sampling unit is controlled to rotate one unit to collect eroded particles; the hydraulic head of the second group is continuously increased, the hydraulic gradient is changed every 6 minutes, and the rotating sampling unit is controlled to rotate one unit after changing the hydraulic gradient twice, that is, one unit is used to collect eroded particles on two hydraulic gradients, and when adjusting the heights of different lifting units (12), the constant flow infiltration module (1) needs to be kept closed and refilled with water and suspended particles; S4. After the original soil sample is subjected to axial load and seepage, data collection begins. All pressure ports are connected to the monitoring and data analysis module (4). The monitoring and data analysis module (4) automatically records and calculates the hydraulic head of each pressure port and the change in the length of the original soil sample. The formula V = Q × t = v × ×t, according to Darcy's law, v= × and , derive , calculate the permeability coefficient, where v is the Darcy seepage velocity, is the hydraulic gradient, is the permeability coefficient of the soil sample, Q is the flow rate, is the head difference, L and are the length and cross-sectional area of ​​the undisturbed soil sample, respectively; S5. Calculating the average density of the original soil sample by a fluid density meter (211); S6. After the experiment is completed, the rotating sampling unit is taken out for drying and weighing. The total erosion mass is calculated by weighing the eroded particles in the rotating sampling unit, and then the energy loss measured by the pressure port is compared and analyzed. After the experiment is completed, the particle size distribution of the original soil sample is tested, and the particle size distribution of each layer of the original soil sample after the experiment is measured. Compared with the particle size distribution measured in S2, it is determined whether each layer of soil has been eroded and the degree of erosion.

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