Experimental method for researching slope surface erosion of waste dump slope under rainfall condition

Abstract

The invention relates to an experimental method for researching slope surface erosion of a waste dump slope under rainfall conditions, which comprises the following steps: laying simulated soil in an experimental tank in layers and compacting the simulated soil, the inner core of the simulated soil is a slag mixture in an actual open pit coal mine waste dump, and the surface covering soil of the simulated soil is humus covering soil of the waste dump slope; performing manual slope cutting to obtain a side slope, so that the longitudinal section of the simulated soil body is in a right trapezoid shape; planting vegetation on the surface layer of the side slope, and culturing the vegetation to grow; an artificial rainfall device is arranged above the simulated soil body and comprises a plurality of sprayers, and the pitch diameter and the end point velocity of raindrops are calibrated before artificial rainfall; starting an artificial rainfall device, spraying water to the upper surface of the simulated soil body by a nozzle, simulating rainfall, and recording the total runoff volume; the soil on the surface of the side slope is subjected to water loss under the action of simulated rainfall and slides to the sample collecting device at the bottom of the side slope, the sediment yield in the sample collecting device is recorded, and the water and soil loss condition is judged.

Description

Technical Field

[0001] The invention belongs to the technical field of soil and water conservation on the slope of an open-pit coal mine dump, and in particular relates to an experimental method for studying the erosion of the slope surface of a dump under rainfall conditions. Background Art

[0002] Most of my country's large coal mines are located in arid and semi-arid areas, such as the Inner Mongolia Plateau, the Loess Plateau and desertified areas, where the ecological environment is extremely fragile. Since the founding of the People's Republic of China, my country has mainly adopted open-pit coal mining methods. Open-pit coal mining directly strips the topsoil and the overlying rock strata of the coal seam, and the stripped rock and soil are stacked in layers inside and outside the mining area to form a spoil dump. The spoil dump is stacked in layers, and a platform is set at the top and bottom of each layer of the slope, step by step upward, forming a tower-shaped mountain.

[0003] The stripped rock and soil in the spoil dump is mixed and loose, with a unique structure. It is the source of sand produced by open-pit mines and the area with the most serious soil and water loss in industrial and mining construction areas. In terms of soil and water loss, most scholars mainly study the slopes of the Loess Plateau. The rock and soil dispersion, transportation, and deposition laws of the spoil dump are different from those of the Loess Plateau, and the research results of the Loess Plateau cannot be used. Therefore, the study of the sand production process of slope runoff erosion in large open-pit coal mine spoil dumps has important practical significance for soil and water conservation and ecological restoration in mining areas.

[0004] It is known that rainfall characteristics have an important impact on the erosion of the spoil dump slope. However, the characteristics of natural rainfall are complex and difficult to control. In this field, artificial rainfall is mainly used for experimental research. However, artificial rainfall is quite different from natural rainfall. Those skilled in the art have not yet reached a consensus on which aspects of artificial rainfall have a greater impact on the erosion of the spoil dump slope, resulting in inconsistent standards for experimental research and the inability to conduct systematic research. Summary of the invention

[0005] In view of the above problems, the present invention provides an experimental method for studying the erosion of the slope surface of a dump under rainfall conditions, comprising the following steps:

[0006] S1: The simulated soil is laid in layers in the test trough and compacted. The core of the simulated soil is the slag mixture inside the actual open-pit coal mine dump, and the surface covering soil of the simulated soil is the humus covering soil of the dump slope;

[0007] S2: artificially cutting the slope to obtain a side slope, so that the longitudinal section of the simulated soil is a right-angle trapezoid; then planting vegetation on the surface of the side slope to cultivate vegetation growth;

[0008] S3: An artificial rainfall device is installed above the simulated soil, including several sprinklers. The median diameter and terminal velocity of raindrops are calibrated before artificial rainfall.

[0009] S4: Turn on the artificial rainfall device, and the nozzle sprays water to the upper surface of the simulated soil to simulate rainfall, and record the total runoff; the soil on the slope surface loses water under the action of simulated rainfall and slides to the sample collection device at the bottom of the slope. The sediment output in the sample collection device is recorded to determine the soil and water loss situation.

[0010] Optionally, step S1 specifically includes:

[0011] (1) First, measure the bulk density of the humus soil on the slope surface and the slag mixture inside the actual spoil dump. For the humus soil on the slope surface, measure the bulk density every 20 cm until there is no humus soil left.

[0012] For the slag mixture inside the spoil dump, it is sufficient to measure the soil bulk density once;

[0013] (2) taking the slag mixture from the spoil dump, removing large rocks, and spraying water until the bulk density reaches the soil bulk density of the slag mixture measured in step (1); laying the slag mixture in layers, and after each layer is laid, compacting it before laying the next layer;

[0014] (3) Take humus soil from the spoil dump, first remove impurities (such as waste slurry, weeds, etc.) in the humus soil, then spread the humus soil evenly, and then spray water until the bulk density reaches the soil bulk density of the humus soil measured in step (1); mix the humus soil evenly, then spread it evenly, cover it with plastic film, and the simulated soil setting is completed.

[0015] Further optionally, in step (1), the soil bulk density is determined by a conventional method;

[0016] In step (2), the thickness of each layer of slag mixture is 15-25 cm; when compacting, a heavy object (such as a discus) is dropped from a height of 30 cm to evenly compact the soil layer and squeeze out the bubbles between the soil layers as much as possible, which is conducive to consolidation and reduces the influence of the inner wall of the experimental tank on runoff, sand production and infiltration; after each layer is compacted, a ring knife is used to take samples at several different positions to determine whether the bulk density of the layer reaches the bulk density of the slag mixture soil determined in step (1); if not, water is sprayed again;

[0017] After the ring knife sampling, the topsoil is roughened to eliminate the vertical layer force between the two layers of soil, increase the compactness between the soil bodies, make the adjacent soil layers well bonded, and prevent the soil layers from slipping when the slope is steep.

[0018] Since step S2 of the present invention requires slope cutting, a general square experimental trough cannot meet the slope cutting requirement, so the present invention provides an experimental trough, which is a rectangular parallelepiped, including a main body trough, a detachable triangular side wall and a movable side wall, the main body trough is a trapezoidal body, two opposite side walls of the main body trough are trapezoidal, and the top has a downwardly inclined top edge, and the other two opposite side walls are square, and the height of the square side wall at the front end of the main body trough is greater than the height of the square side wall at the rear end;

[0019] The movable side wall is square and is used to connect the top of the square side wall with a smaller height. The two vertical sides of the movable side wall are respectively provided with a docking groove for docking the triangular side walls on both sides.

[0020] The triangular side wall is used to connect the top edge of the trapezoidal side wall of the main body groove to form the square side wall of the experimental groove. The vertical side of the triangular side wall is provided with a slot piece protruding outward for inserting into the corresponding docking groove of the movable side wall.

[0021] Further optionally, the main body trough is a right-angled trapezoid, and the top of the front end of the main body trough is a horizontal section; the material of the experimental trough is a transparent acrylic material, which is convenient for observing the state of the internal soil layer.

[0022] Further optionally, in step S1, after the two triangular side walls and the movable side wall are plugged into the main groove to form a rectangular parallelepiped, a simulated soil body forming the rectangular parallelepiped is laid in the experimental groove; before cutting the slope in step S2, the triangular side walls and the movable side walls are removed to expose a triangular part of the simulated soil body, waiting for slope cutting; after the triangular part is removed, the remaining simulated soil body is a trapezoidal body with a horizontal slope top and a downward sloping slope surface, which can simulate the positional relationship between the platform and the slope of an actual spoil dump.

[0023] The conventional experimental idea is to directly lay a trapezoidal simulated soil body, but the layered laying process requires compaction. When the inclined slope is compacted, it is subjected to both the force perpendicular to the slope surface and the vertical downward force. The vertical downward force will cause the soil to slide downward, which is not conducive to forming a relatively solid slope as a whole, and will also form faults or landslides inside the slope. This impact cannot be quantified and explored, and will aggravate the soil erosion of the slope. Therefore, directly laying the simulated soil body will produce a large experimental error.

[0024] The present invention firstly manufactures a cuboid simulated soil body, horizontally lays each layer and compacts it horizontally, thereby eliminating the hidden dangers of internal faults or landslides of the simulated soil body, forming a square soil body balanced in all directions, and minimizing experimental errors.

[0025] Optionally, the artificial slope cutting in step S2 specifically includes:

[0026] (4) First, two slope cutting cutters are used to move from the left and right sides of the main groove, along the inclined top edge of the main groove, toward each other to perform a slope cutting operation. When the two slope cutting cutters stop, there is a gap between the blades.

[0027] (5) The two slope cutting cutters are then used to move from the front and rear sides of the main groove, along the inclined top edge of the main groove, toward each other, to perform secondary slope cutting, and completely cut out the inclined slope.

[0028] Further optionally, in step (4), when the two slope cutters stop cutting the slope, the distance between the two blades accounts for 20-23% of the width of the slope, and after one cutting, the portion between the two blades in the middle of the slope is not cut. If the portion not cut is too wide, the cutting burden in the front and rear directions of the secondary cutting is large, and the impact on the slope in this direction is also large, which ultimately affects the experimental results; if the portion not cut is too narrow, the blades of the two slope cutters are too close, and it is difficult to control the stop of the first cutting, resulting in damage to the slope cutters.

[0029] In step (5), when the two slope cutters stop cutting the slope, the blades of the two slope cutters contact each other, and the soil above the slope cutters is completely cut off. Since most of the slope cutting area has been completed in step (4), only a strip of soil in the middle along the length of the slope needs to be cut off, which greatly reduces the cutting burden of step (5), and reduces the moving resistance of the slope cutters in step (5), making speed control easier, and achieving the effect that the blades of the two slope cutters contact but do not damage each other.

[0030] The slope cutting method proposed in the present invention is to first cut horizontally and leave a small part of the soil, and then cut vertically to completely cut off the simulated soil. Most of the soil is cut horizontally to complete most of the slope cutting tasks. The horizontal cutting generates a horizontal force on the soil, which has little effect on the overall downward soil and water loss. The remaining small part of the task is completed by the vertical cutting of step (5). The vertical downward cutting is in the same direction as the soil and water loss, which may cause some unknown geological forms or structures inside and outside the soil that promote soil and water loss. The vertical upward cutting is opposite to the direction of soil and water loss, which can offset the adverse effects of the vertical downward cutting to a certain extent, thereby minimizing the impact of slope cutting on subsequent soil and water loss experiments as a whole.

[0031] The cultivation of vegetation in step S2 controls the area and time of planting vegetation according to the experimental requirements for the slope vegetation coverage. The experimental method of the present invention can simulate the slope erosion of the spoil dump under different vegetation coverage, vegetation type and slope angle conditions.

[0032] Optionally, the artificial rainfall device includes a movable bracket, a water supply main, a plurality of water supply branches and a nozzle, the movable bracket is erected above the main trough, the plurality of water supply branches are parallel to each other, one end of the water supply branch is slidably connected to the movable bracket, and the other end is connected to the water supply main; a plurality of nozzles are evenly arranged on the lower surface of each water supply branch for evenly spraying water onto the slope below to simulate rainfall; the water supply main is connected to a water storage tank.

[0033] Further optionally, the mobile bracket includes a vertical stand and two horizontal track frames, and the stand is used to support the track frames;

[0034] The horizontal part of the water supply main is parallel to the track frame and is located between the two track frames; the vertical part of the water supply main is used to connect the water storage tank;

[0035] A number of evenly arranged water supply branches are arranged between the horizontal part of the water supply main and each track frame. A valve is arranged at one end of the water supply branch connected to the horizontal part of the water supply main to control whether the water supply branch supplies water; a slope corresponds to the bottom of each row of water supply branches.

[0036] The horizontal part of the water supply main and the water supply branches on both sides thereof can move along the track frame, that is, move along the length direction of the slope, and cooperate with the position of the main trough below to achieve uniform precipitation (rainfall).

[0037] Further optionally, a vertical rain curtain is provided below the horizontal portion of the water supply main to prevent the water supply branch from discharging precipitation to other slopes; and the nozzle is a solid conical nozzle.

[0038] The solid cone nozzle produces a cone spray with a circular spray area and a spray angle of 43-120 degrees. It can produce a uniformly distributed spray with medium to large droplet size under a wide range of flow and pressure. This nozzle has a certain initial velocity when spraying water, which helps the raindrops reach the terminal velocity to obtain sufficient rainfall erosion; and the raindrops it produces are composed of different diameters, which are similar to the raindrop particle size composition of natural rainfall, making it easy to obtain a rainfall process similar to natural rainfall.

[0039] Further optionally, the bottom outlet of the water storage tank is connected in sequence to a variable frequency self-priming pump, a main water valve, a flow meter, a filter, a water inlet valve and the inlet of a vertical part of a water supply main, and the rainfall intensity of the artificial rainfall device is controlled by adjusting the flow and pressure. Specifically, by opening the valves of different water supply branches, controlling the pressure and total flow of the variable frequency self-priming pump, and allowing different numbers of nozzles to work, a pre-set rainfall intensity value can be obtained.

[0040] Optionally, in step S3, the present invention selects a raindrop median diameter and terminal velocity calibration method to measure whether the performance of artificial rainfall is close to natural rainfall.

[0041] Optionally, in step S4, the sample collecting device includes a conical collector and a sample barrel, the collector is larger at the top and smaller at the bottom, the top of the collector docks with the bottom of the slope, and the bottom of the collector docks with the sample barrel. A weighing device is provided at the bottom of the sample barrel for recording sediment production.

[0042] Optionally, in order to eliminate the influence of slope cutting on the slope soil erosion experiment, the present invention proposes a correction factor F, which is determined by the following formula:

[0043]

[0044] Wherein, F is the correction factor, dimensionless; h is the length of the slope, mm; θ is the slope angle of the slope; a is the distance between the two cutting edges when the two slope cutters stop cutting the slope in step (4), mm; c is a constant parameter, with a value of 25; the correction factor F is applicable to the experimental scenario with a slope angle of 15-40°, which is the most commonly used slope angle range in the spoil dump; the correction factor F is applicable to the experimental scenario with a slope length-to-width ratio of approximately 4;

[0045] The final sediment yield A of the experiment is:

[0046] A=B / F

[0047] Among them, A is the final sediment production of the experiment, g / min; B is the sediment production collected in the sample bucket, g / min. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic diagram of the experimental device structure of Example 1;

[0049] Figure 2 This is a schematic diagram of the experimental tank of Example 1;

[0050] Figure 3 Schematic diagram of the artificial rainfall device of Example 1.

[0051] In the attached drawings, 1-experimental tank, 2-main tank, 3-triangular side wall, 4-movable side wall, 5-water supply main pipe, 6-water supply branch pipe, 7-sprinkler, 8-track rack, 9-water storage tank, 10-rain curtain, 11-collector, 12-sample barrel. DETAILED DESCRIPTION

[0052] Example 1

[0053] The experimental method of studying the erosion of the slope surface of the dump under rainfall conditions in this embodiment includes the following steps:

[0054] S1: simulated soil is laid in layers in the experimental tank 1 and compacted. The core of the simulated soil is the slag mixture inside the actual open-pit coal mine dump, and the surface covering soil of the simulated soil is the humus covering soil of the dump slope;

[0055] S2: artificially cutting the slope to obtain a side slope, so that the longitudinal section of the simulated soil is a right-angle trapezoid; then planting vegetation on the surface of the side slope to cultivate vegetation growth;

[0056] S3: an artificial rainfall device is arranged above the simulated soil, including a plurality of nozzles 7. Before artificial rainfall, the median diameter and terminal velocity of raindrops are calibrated;

[0057] S4: Turn on the artificial rainfall device, and the nozzle 7 sprays water to the upper surface of the simulated soil to simulate rainfall, and records the total runoff; the soil on the slope surface loses water under the action of the simulated rainfall and slides to the sample collection device at the bottom of the slope, and the sediment production in the sample collection device is recorded to determine the soil and water loss situation.

[0058] Step S1 specifically includes:

[0059] (1) First, measure the bulk density of the humus soil on the slope surface and the slag mixture inside the actual spoil dump. For the humus soil on the slope surface, measure the bulk density every 20 cm until there is no humus soil left.

[0060] For the slag mixture inside the spoil dump, it is sufficient to measure the soil bulk density once;

[0061] (2) taking the slag mixture from the spoil dump, removing large rocks, and spraying water until the bulk density reaches the soil bulk density of the slag mixture measured in step (1); laying the slag mixture in layers, and after each layer is laid, compacting it before laying the next layer;

[0062] (3) Take humus soil from the spoil dump, first remove impurities (such as waste slurry, weeds, etc.) in the humus soil, then spread the humus soil evenly, and then spray water until the bulk density reaches the soil bulk density of the humus soil measured in step (1); mix the humus soil evenly, then spread it evenly, cover it with plastic film, and the simulated soil setting is completed.

[0063] In step (1), the actual dump is the dump outside the Dongming Mining Industry in Hailar District, Hulunbuir City, Inner Mongolia Autonomous Region, the soil sampling depth is 0-2m, and the soil bulk density is determined by a conventional method;

[0064] In step (2), the thickness of each layer of slag mixture is 20 cm, and there are 10 layers in total; when compacting, a discus is dropped from a height of 30 cm to evenly compact the soil layer; then, a ring knife is used to take samples at three different positions to determine whether the bulk density of the layer reaches the bulk density of the slag mixture soil determined in step (1); if not, water is sprayed again; after the ring knife sampling, the topsoil of the soil layer is roughened.

[0065] like Figure 1-Figure 2As shown, the experimental tank 1 is a rectangular parallelepiped, including a main tank 2, a detachable triangular side wall 3 and a movable side wall 4. The main tank 2 is a trapezoidal body, and the two opposite side walls of the main tank 2 are trapezoidal, and the top has a downwardly inclined top edge, and the other two opposite side walls are square, and the height of the square side wall at the front end of the main tank 2 is greater than the height of the square side wall at the rear end;

[0066] The movable side wall 4 is square and is used to connect the top of the square side wall with a smaller height. The two vertical sides of the movable side wall 4 are respectively provided with a docking groove for docking the triangular side walls 3 on both sides.

[0067] The triangular side wall 3 is used to connect the top edge of the trapezoidal side wall of the main groove 2 to form the square side wall of the experimental groove 1. The vertical side of the triangular side wall 3 is provided with a slot piece protruding outward for inserting into the corresponding docking groove of the movable side wall 4.

[0068] The bottom of the movable side wall 4 is connected to the top of the shorter square side wall of the main groove 2, and can be plugged in. The triangular side wall 3 is a right triangle, and the hypotenuse at the bottom is plugged into the top edge of the trapezoidal side wall of the main groove 2. The slot piece is perpendicular to the triangular side wall 3 and parallel to the movable side wall 4, so that the two triangular side walls 3 and the movable side wall 4 can also be plugged in. The width direction is between the two trapezoidal side walls of the main groove 2, and the length direction is between the two square side walls.

[0069] The main body tank 2 is a right-angled trapezoid, and the top of the front end of the main body tank 2 is a horizontal section; the material of the experimental tank 1 is a transparent acrylic material, which is convenient for observing the internal soil layer state.

[0070] In step S1, after the two triangular side walls 3 and the movable side wall 4 are plugged into the main groove 2 to form a rectangular parallelepiped, a simulated soil body forming a rectangular parallelepiped is laid in the experimental groove 1; before cutting the slope in step S2, the triangular side walls 3 and the movable side walls 4 are removed to expose a triangular part of the simulated soil body, waiting for slope cutting; after the triangular part is removed, the remaining simulated soil body is a trapezoidal body with a horizontal slope top and a downward sloping slope surface, which can simulate the positional relationship between the platform and the slope of an actual spoil dump.

[0071] The artificial slope cutting in step S2 specifically includes:

[0072] (4) First, two slope cutting cutters are used to move from the left and right sides of the main groove 2 along the inclined top edge of the main groove 2 toward each other to perform a slope cutting operation. When the two slope cutting cutters stop, there is a gap between the blades.

[0073] (5) The two slope cutting cutters are then used to move toward each other from the front and rear sides of the main groove 2 along the inclined top edge of the main groove 2 to perform secondary slope cutting to completely cut out the inclined slope.

[0074] In step (4), when the two slope cutting cutters stop cutting the slope, the distance between the two blades accounts for 20% of the slope width, and the slope width is 150 mm.

[0075] In step (5), when the two slope cutters stop cutting the slope, the blades of the two slope cutters contact each other, completely cutting off the soil above the slope cutters to obtain a slope with a slope of 20°.

[0076] In step S2, the leguminous plant alfalfa is planted and cultivated, protected from light, and left to stand for two weeks to solidify under its own gravity so that the plant roots can be more fully rooted in the slope soil, thereby obtaining a slope vegetation coverage rate of 30%.

[0077] like Figure 3 As shown, the artificial rainfall device includes a movable bracket, a water supply main pipe 5, a plurality of water supply branches 6 and a nozzle 7. The movable bracket is erected above the main tank 2. The plurality of water supply branches 6 are parallel to each other. One end of the water supply branch 6 is slidably connected to the movable bracket, and the other end is connected to the water supply main pipe 5. Two nozzles 7 are evenly arranged on the lower surface of each water supply branch 6 for evenly spraying water to the slope below to simulate rainfall. The water supply main pipe 5 is connected to a water storage tank 9.

[0078] The mobile bracket includes a vertical stand and two horizontal track frames 8, the stand is used to support the track frames 8; the horizontal part of the water supply main 5 is parallel to the track frames 8 and is located between the two track frames 8; the vertical part of the water supply main 5 is used to connect to the water storage tank 9; eleven evenly arranged water supply branches 6 are provided between the horizontal part of the water supply main 5 and each track frame 8, and a valve is provided at one end of the water supply branch 6 connected to the horizontal part of the water supply main 5 to control whether the water supply branch 6 supplies water; each row of water supply branches 6 corresponds to a slope below, and experiments on two slopes can be carried out simultaneously.

[0079] The horizontal part of the water supply main pipe 5 and the water supply branches 6 on both sides thereof can move along the track frame 8, that is, move along the length direction of the slope, and cooperate with the position of the main trough 2 below to achieve uniform precipitation (rainfall).

[0080] A vertical rain curtain 10 is arranged below the horizontal part of the water supply main pipe 5 to prevent the water supply branch 6 from raining to other slopes; the nozzle 7 is a solid cone nozzle 7.

[0081] The bottom outlet of the water storage tank 9 is connected to the inlet of the vertical part of the variable frequency self-priming pump, the main water valve, the flow meter, the filter, the water inlet valve and the water supply main pipe 5 in sequence, and the rainfall intensity of the artificial rainfall device is controlled by adjusting the flow and pressure. Specifically, by opening the valves of different water supply branches 6, controlling the pressure and total flow of the variable frequency self-priming pump, and allowing different numbers of nozzles 7 to work, a pre-set rainfall intensity value can be obtained.

[0082] The rainfall intensity of this experiment is 30 mm / h, the water supply main and the water supply branch 6 are PPR pipes, the inner diameter of the water supply main is 25 mm, and the inner diameter of the water supply branch 6 is 20 mm. The mesh number of the filter is 80 meshes.

[0083] The variable frequency self-priming pump is the SD-1100BP variable frequency constant pressure single-phase self-priming booster pump produced by Zhongwei Pump Industry (Jiangsu) Co., Ltd. The specific parameters are: working voltage 220V, rated power 1100W, maximum head 50m, maximum flow 8m 3 / h, rated head 38m, rated flow 4m 3 / h, maximum suction range 8m, adjustable pressure 0-5bar.

[0084] The solid cone nozzle 7 is a BB1 / 8SS1 solid cone nozzle 7 produced by Changyuan Electromechanical Business Department in Hanyang District, Wuhan City. The nominal nozzle hole diameter is 0.79 mm and the maximum free flow channel diameter is 0.64 mm.

[0085] In step S3, (1) the raindrop median diameter and terminal velocity are determined as follows:

[0086] The diameter of raindrops is one of the important parameters for measuring the kinetic energy of rainfall. It is of great significance in the study of soil erosion caused by rainfall. Different raindrop sizes have different splashing effects on the soil surface. The most commonly used method for calibrating raindrop diameter is the filter paper color spot method. This method is based on the assumption that the size of the water droplet itself and the size of the color spot formed by the water droplet on the same material are in a certain proportion. The relationship between the color spot size and the water droplet size on a certain material is calibrated in advance, and then the raindrop size is calculated by observing the color spot size.

[0087] A medium-speed qualitative filter paper with a diameter of 150 mm produced by Xinhua Paper Mill was used, and a mixed powder of eosin and talcum powder was used as the coating. The above two coatings were finely ground and mixed evenly in a mass ratio of 1:10. Before the test, the coating was evenly applied to the surface of the filter paper with a brush. After drying, the filter paper did not show color. When raindrops landed on the filter paper, each raindrop produced a nearly circular color spot. At each rainfall intensity, 3 pieces of filter paper were used to collect raindrops to obtain a sufficient number of raindrop color spots. After sampling, the color spot diameter D of the raindrops was measured, and the diameters of the color spots of different sizes were classified and counted. The color spot diameter was converted into the raindrop diameter using the formula:

[0088] d=0.356×D 0.712 (R 2 =9988)

[0089] Where: d is the raindrop diameter, mm; D is the color spot diameter, mm.

[0090] Substituting the diameter of the spots in the three filter papers under each rainfall intensity into the formula, the raindrop diameter is obtained. After classification and statistics, the volume sum of different diameters is calculated to obtain the cumulative curve of raindrop diameter under each rainfall intensity, and the median diameter of raindrops is calculated based on this. The median diameter of raindrops refers to the raindrop diameter corresponding to the cumulative volume percentage of raindrops being 50%.

[0091] The formula for the mean diameter of raindrops was obtained by regression analysis, and then the mean diameter of raindrops under various rainfall intensities was calculated. The calculation results are shown in Table 1. The range of the mean diameter of raindrops corresponding to the rainfall intensity of this test is between 1.4 and 1.8 mm. The distribution of the diameter of raindrops in natural rainfall generally fluctuates between 0.1 and 6.0 mm. Therefore, the mean diameter of raindrops designed for this rainfall system conforms to the law of natural rainfall.

[0092] Table 1 Parameter ratings of artificial rainfall simulation system

[0093]

[0094] According to Newtonian mechanics and the law of universal gravitation, natural rainfall raindrops will reach a terminal velocity during the process of falling in the air. This requires determining an appropriate indicator for the falling height of raindrops for simulated rainfall. Research on natural rainfall raindrops by American scholar Ross et al. shows that the distribution of the size of natural rainfall raindrops fluctuates between 0 and 6 mm, and the corresponding terminal velocity is 2 to 2.9 mm / s, and the corresponding falling height required for more than 90% of raindrops is 7 to 9 m. According to the research on the falling velocity of raindrops by some scholars in the United States, Australia and other countries, the downward spray nozzle 7 with an initial velocity can satisfy the terminal velocity of raindrops of different diameters at a rainfall height of 2 m. The nozzle 7 of the artificial simulated rainfall device designed in this experiment is fixed more than 2 m above the research area of ​​the slope model so that the falling velocity of raindrops of different diameters is similar to that of natural rainfall.

[0095] In step S4, the sample collection device includes a conical collector 11 and a sample barrel 12. The collector 11 is large at the top and small at the bottom, and plays a diversion role. The top of the collector 11 is connected to the bottom of the slope, and the bottom of the collector 11 is connected to the sample barrel 12. A weighing device is provided at the bottom of the sample barrel 12 to record the sediment yield.

[0096] In order to eliminate the influence of slope cutting on the slope soil erosion experiment, a correction factor F is proposed, which is determined by the following formula:

[0097]

[0098] Wherein, F is the correction factor, dimensionless; h is the length of the slope, 585 mm; θ is the slope angle of the slope, 20°; a is the distance between the two cutting edges when the two cutting cutters stop cutting the slope in step (4), 30 mm; c is a constant parameter, with a value of 26; F = 0.98;

[0099] The final sediment yield A of the experiment is:

[0100] A=B×F=10.81×0.98=10.59

[0101] Among them, A is the final sediment production of the experiment, g / min; B is the sediment production collected in the sample bucket, 10.81 g / min.

[0102] Example 2

[0103] The present embodiment studies the experimental method for the slope erosion of the spoil dump under rainfall conditions, which is the same as that of the embodiment 1, except that in step (4), when the two slope cutters stop cutting the slope, the distance between the two blades accounts for 23% of the slope width, F is 0.85, the sediment yield collected in the sample bucket is 12.96 g / min, and the final sediment yield of the experiment is 11.02 g / min.

[0104] Example 3

[0105] The present embodiment studies the experimental method for slope erosion of a spoil dump under rainfall conditions, which is the same as that of Embodiment 1, except that in step (4), when the two slope cutters stop cutting the slope, the distance between the two blades accounts for 24% of the slope width, F is 0.81, the sediment yield collected in the sample bucket is 13.82 g / min, and the final sediment yield of the experiment is 11.19 g / min.

[0106] Example 4

[0107] This embodiment studies the experimental method of slope erosion of the spoil dump under rainfall conditions, which is the same as that of Embodiment 1, except that, when manually cutting the slope in step S2, a slope cutter is used to cut directly downward from the predetermined top of the slope to complete the slope cutting. The final sediment production of the experiment is the sediment production collected in the sample bucket, which is specifically 15.21 g / min.

[0108] A whole piece of soil is dug out from the slope of the actual spoil dump. The other sides of the soil can be cut to make the soil adapt to the main trough, but the integrity of the upper surface slope of the soil is retained for experiments. The collected sediment yield is used as the actual sediment yield of the actual slope under artificial rainfall.

[0109] Table 2 Comparison of the final sediment yield of Examples 1-4 and the sediment yield of the actual slope

[0110] project Sediment output (g / min) project Sediment output (g / min) Example 1 10.59 Example 4 15.21 Example 2 11.02 Real Example 9.85 Example 3 11.19

[0111] As can be seen from the above table, Examples 1-3 use the slope cutting method proposed by the present invention to conduct experiments, and then use the correction factor to correct the actual sediment yield to obtain a sediment yield that is closer to the actual (real example), and the difference with the real example data is not large. However, Example 4 uses the traditional slope cutting method, and the actual sediment yield obtained is quite different from the real example.

Claims

1. An experimental method for studying the erosion of the slope of a dump site under rainfall conditions, characterized in that: The following steps are involved: S1: The simulated soil is laid in layers in the test trough and compacted. The core of the simulated soil is the slag mixture inside the actual open-pit coal mine dump, and the surface covering soil of the simulated soil is the humus covering soil of the dump slope; S2: artificially cutting the slope to obtain a side slope, so that the longitudinal section of the simulated soil is a right-angle trapezoid; then planting vegetation on the surface of the side slope to cultivate vegetation growth; S3: An artificial rainfall device is installed above the simulated soil, including several sprinklers. The median diameter and terminal velocity of raindrops are calibrated before artificial rainfall. S4: Turn on the artificial rainfall device, and the nozzle sprays water to the upper surface of the simulated soil to simulate rainfall, and record the total runoff; the soil on the slope surface loses water under the action of simulated rainfall and slides to the sample collection device at the bottom of the slope. The sediment output in the sample collection device is recorded to determine the soil and water loss situation.

2. The experimental method according to claim 1, characterized in that Step S1 specifically includes: (1) First, measure the bulk density of the humus soil on the slope surface and the slag mixture inside the actual spoil dump. For the humus soil on the slope surface, measure the bulk density every 20 cm until there is no humus soil left. For the slag mixture inside the spoil dump, it is sufficient to measure the soil bulk density once; (2) taking the slag mixture from the spoil dump, removing large rocks, and spraying water until the bulk density reaches the soil bulk density of the slag mixture measured in step (1); laying the slag mixture in layers, and after each layer is laid, compacting it before laying the next layer; (3) Take humus soil from the spoil dump, remove impurities from the humus soil, then spread the humus soil evenly, and then spray water until the bulk density reaches the soil bulk density of the humus soil measured in step (1); mix the humus soil evenly, then spread it evenly, cover it with plastic film, and the simulated soil setting is completed.

3. The experimental method according to claim 2, characterized in that: In step (2), the thickness of each layer of slag mixture is 15-25 cm; when compacting, a weight is dropped from a high place to evenly compact the soil layer; then, a ring knife is used to take samples at several different positions to determine whether the bulk density of the layer reaches the bulk density of the slag mixture soil determined in step (1); if not, water is sprayed again; after the ring knife sampling, the topsoil of the soil layer is roughened.

4. The experimental method according to claim 1, characterized in that The experimental tank is a rectangular parallelepiped, including a main tank, a detachable triangular side wall and a movable side wall. The main tank is a trapezoidal body, and the two opposite side walls of the main tank are trapezoidal, and the top has a top edge inclined downward, and the other two opposite side walls are square, and the height of the square side wall at the front end of the main tank is greater than the height of the square side wall at the rear end; The movable side wall is square and is used to connect the top of the square side wall with a smaller height. The two vertical sides of the movable side wall are respectively provided with a docking groove for docking the triangular side walls on both sides. The triangular side wall is used to connect the top edge of the trapezoidal side wall of the main body groove to form the square side wall of the experimental groove. The vertical side of the triangular side wall is provided with a slot piece protruding outward for inserting into the corresponding docking groove of the movable side wall.

5. The experimental method according to claim 4, characterized in that: The main body tank is a right-angled trapezoid, and the top of the front end of the main body tank is a horizontal section; the material of the experimental tank is a transparent acrylic material, which is convenient for observing the internal soil layer state; In step S1, after the two triangular side walls and the movable side wall are plugged into the main groove to form a rectangular parallelepiped, a simulated soil body forming a rectangular parallelepiped is laid in the experimental groove; before cutting the slope in step S2, the triangular side walls and the movable side walls are removed to expose a triangular part of the simulated soil body, waiting for slope cutting; after the triangular part is cut off, the remaining simulated soil body is a trapezoidal body with a horizontal slope top and a downward sloping slope surface, which can simulate the positional relationship between the platform and the slope of an actual spoil dump.

6. The experimental method according to claim 1, characterized in that: The artificial slope cutting in step S2 specifically includes: (4) First, two slope cutting cutters are used to move from the left and right sides of the main groove, along the inclined top edge of the main groove, toward each other to perform a slope cutting operation. When the two slope cutting cutters stop, there is a gap between the blades. (5) The two slope cutting cutters are then used to move toward each other from the front and rear sides of the main groove, along the inclined top edge of the main groove, to perform secondary slope cutting, and completely cut out the inclined slope.

7. The experimental method according to claim 6, characterized in that: In step (4), when the two slope cutting cutters stop cutting the slope, the distance between the two cutting edges accounts for 20-23% of the slope width; In step (5), when the two slope cutting cutters stop cutting the slope, the blades of the two slope cutting cutters contact each other, completely cutting off the soil above the slope cutting cutters.

8. The experimental method according to claim 1, characterized in that: The artificial rainfall device comprises a movable bracket, a water supply main pipe, a plurality of water supply branches and a nozzle. The movable bracket is erected above the main trough. The plurality of water supply branches are parallel to each other. One end of the water supply branch is slidably connected to the movable bracket, and the other end is connected to the water supply main pipe. A plurality of nozzles are evenly arranged on the lower surface of each water supply branch for evenly spraying water to the slope below to simulate rainfall. The water supply main pipe is connected to a water storage tank.

9. The experimental method according to claim 6, characterized in that: In step S4, the sample collection device includes a conical collector and a sample barrel. The collector is larger at the top and smaller at the bottom. The top of the collector docks with the bottom of the slope, and the bottom of the collector docks with the sample barrel. A weighing device is provided at the bottom of the sample barrel to record the sediment yield.

10. The experimental method according to claim 9, characterized in that: In order to eliminate the influence of slope cutting on the slope soil erosion experiment, a correction factor F is proposed, which is determined by the following formula: Wherein, F is the correction factor, dimensionless; h is the length of the slope, mm; θ is the slope angle of the slope; a is the distance between the two cutting edges when the two cutting cutters stop cutting the slope in step (4), mm; c is a constant parameter, with a value of 25; The final sediment yield A of the experiment is A=B / F Among them, A is the final sediment production of the experiment, g / min; B is the sediment production collected in the sample bucket, g / min.

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