Runoff collection device and method considering difference between soil thickness distribution and bedrock infiltration

Abstract

To provide an improved runoff collection device considering difference between soil thickness distribution and bedrock permeability.SOLUTION: A runoff collection device includes a soil tank, a soil tank partition plate, a runoff collection tank, a bottom plate and a soil tank base. The soil tank is divided into two small soil tanks, a permeable small soil tank and an impermeable small soil tank, by the soil tank partition plate. The runoff collection tank is used for collecting surface runoff, intermediate runoff and base runoff. The bottom plate is divided into a permeable support plate and an impermeable support plate, which are located in the two small soil tanks respectively, thereby realizing different bedrock permeability designs. A support bracket with adjustable orientation is provided below the support plate, which can realize different soil thickness distribution designs in the soil tank. The soil tank base is located below the soil tank, which can support and move the soil tank to adjust different gradients. The runoff generation process of continuous rainfall runoff under different underlying surface morphology conditions of typical mountain slopes can be well simulated and analyzed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to the technical field of slope runoff monitoring under artificial rainfall conditions, and in particular to a runoff collection device and method taking into account soil thickness distribution and bedrock infiltration differentials. [Background technology]

[0002] Mountain flood disasters, characterized by their suddenness, wide distribution and destructive power, cause serious damage to the national economy and the lives and property of the people. Heavy and continuous rainfall in mountainous areas causes flood concentration, and the movement of flood waters induces complex multiple disasters such as landslides and debris flows, which cause damage to areas of human activity. Research into the runoff generation mechanism and process of small mountain watersheds under heavy and continuous rainfall conditions is of great significance for improving mountain flood disaster prevention technology in mountainous areas.

[0003] In the study of runoff generation mechanism under heavy rainfall and continuous rainfall conditions, currently, the most widely adopted method is to artificially simulate rainfall tests indoors and use soil tanks to collect runoff generation under different rainfall conditions for related analytical research. However, the soil tanks currently used for rainfall tests are still limited in design to some extent and cannot well represent the typical characteristics of small mountainous watershed slopes. The topography of small mountainous watersheds is highly undulating, the soil thickness distribution is uneven, and the bedrock permeability varies greatly. Most of the existing soil tanks can only simulate the runoff generation process under the same soil thickness distribution and the same bedrock permeability. Moreover, one rainfall test can often only set a single rainfall intensity and a single underlying surface condition, and tests under different rainfall conditions often cause test errors due to adjustment of the rain gauge, re-filling, and changes in site conditions. Furthermore, most soil tanks are made of opaque materials, making it impossible to observe the movement of the wetting front in the soil in real time during rainfall. Summary of the Invention

[0004] In response to the shortcomings of the prior art, the present invention provides a runoff collection device and method that takes into account soil thickness distribution and bedrock permeability differences. The device can set different soil thickness distributions and different bedrock permeability conditions in the same soil tank, and collect continuous runoff generation processes under different rainfall conditions through continuous rainfall of different rainfall intensities, which can reduce test errors caused by external conditions such as rainfall intensity location, re-filling, and location changes, while at the same time observing the movement of the wetting front in the soil in real time, thereby realizing accurate recording and analysis of the slope runoff generation process under rainfall conditions.

[0005] In order to achieve the above objectives, the present invention adopts the following technical solutions.

[0006] A runoff collection device taking into consideration soil thickness distribution and bedrock permeability differences, comprising: a soil tank, a soil tank partition plate, a runoff collection tank, a bottom plate, and a soil tank base, the soil tank being divided by the soil tank partition plate into two left and right small permeable soil tanks and an impermeable soil tank, each having the same volume; the runoff collection tank being located at one end of the soil tank and used to collect surface flow and intermediate flow; the bottom plate being divided into a permeable support plate and an impermeable support plate, the permeable support plate and the impermeable support plate being located in the permeable small soil tank and the impermeable small soil tank, respectively, thereby realizing different bedrock permeability designs; support brackets are provided below the permeable support plate and the impermeable support plate, and by adjusting the direction in which the support brackets are placed, different soil thickness distribution designs in the soil tank can be realized; the soil tank base is located below the soil tank and can support and move the soil tank, and is further used to raise and lower the soil tank to adjust to different gradients.

[0007] Furthermore, the runoff collection tank includes a surface flow collection tank, a middle intermediate flow collection tank, and a lower intermediate flow collection tank, which are arranged in order from top to bottom on one side of the soil tank, and a surface flow drain outlet, a middle intermediate flow drain outlet, and a lower intermediate flow drain outlet are arranged in order from top to bottom on one side of the soil tank, and the surface flow collection tank, the middle intermediate flow collection tank, and the lower intermediate flow collection tank are connected to the surface flow drain outlet, the middle intermediate flow drain outlet, and the lower intermediate flow drain outlet, respectively.

[0008] Furthermore, the surface flow drain is located at the top of one side of the soil tank, the bottom of the surface flow drain is flush with the surface of the soil filled in the soil tank, and when the soil layer is designed so that the soil at the foot of the slope is thin and the soil at the toe of the slope is thick due to the arrangement direction of the support brackets, the bottom of the middle intermediate flow drain is flush with the bottom of the reverse filtration layer at the bottom of the soil layer, and when the soil layer is designed so that the soil at the foot of the slope is thick and the soil at the toe of the slope is thin due to the arrangement direction of the support brackets, the middle intermediate flow drain needs to be blocked and the lower intermediate flow drain is flush with the bottom of the soil tank. Furthermore, the side walls of the soil tank are visible side panels, which are made of transparent organic glass material, allowing the movement of the wetting front of the soil layer in the permeable small soil tank and the impermeable small soil tank to be observed in real time.

[0009] Furthermore, a water return is provided at a location close to the lower intermediate flow drain outlet at the bottom of the small permeable soil tank, a bottom base outflow drain outlet is provided on one side of the water return, and the distance between the other side of the water return and the lower intermediate flow drain outlet is 5 cm.The water return is used to block base outflow and prevent the base outflow from continuing to flow downward and out of the lower intermediate flow drain outlet.

[0010] Furthermore, the runoff collection tank further includes a bottom base runoff collection tank connected to a bottom base runoff drain outlet provided at the bottom of the soil tank.

[0011] Furthermore, a reverse filtration layer is laid flat on the permeable support plate and the impermeable support plate, and the reverse filtration layer is covered with two layers of lath mesh, with a nonwoven fabric filter provided between the two layers of lath mesh.

[0012] Furthermore, the support bracket has right-angled trapezoids on both sides and a rectangular bottom, with vertical and horizontal support rods provided inside the right-angled trapezoids on both sides, and no support rod in the center of the rectangular bottom of the support bracket.

[0013] Furthermore, the soil tank base includes a base support bracket, a universal wheel, and a hydraulic lifting machine, the base support bracket is a rectangular steel frame structure, the length and width of the bottom are equal to the length and width of the soil tank, and there are four universal wheels at the four corners of the bottom, the bottom of the soil tank is provided with a large hinge connecting the bottom of the soil tank to the top of one end of the base support bracket, the soil tank can rotate around the large hinge, the hydraulic lifting machine is fixed to the base support bracket, and the position of the hydraulic lifting machine's support column and the bottom of the soil tank are connected via the large hinge, and by adjusting the rise and fall of the hydraulic lifting column, the slope of the soil tank can be changed within the range of 0° to 30°.

[0014] A runoff collection method taking into account soil thickness distribution and bedrock infiltration differentials, which is carried out using the above device, includes steps 1 to 8: In step 1, adjust the orientation of the support brackets (405) in the permeable small soil tank (101) and the impermeable small soil tank (102) to match the soil thickness distribution of the two small soil tanks, place the permeable support plate (401) and the impermeable support plate (402) on the support brackets (405) in the permeable small soil tank (101) and the impermeable small soil tank (102) respectively, then lay the reverse filtration layer (403) and two layers of lath screen (404) in sequence, and finally fill the soil samples into the two small soil tanks to prepare for use; In step 2, the hydraulic lift (503) of the soil tank base (5) is adjusted so that the soil tank has a constant design slope; In step 3, four rainfall intensities are designed according to the specific study area, and the runoff generation time length for each rainfall intensity is designed to be 45 min. Runoff samples are taken every minute for the first 5 min, and every 5 minutes for the next 40 min. After each rainfall, a 30-minute break is required before the next rainfall. The above sampling process is repeated. In step 4, start rainfall at the design rainfall intensity, and when the water drips into the runoff collection tank (3), use a water receiving container to receive the surface runoff, intermediate runoff and base runoff respectively within a certain time period, and complete the rainfall and runoff sampling of the four design rainfall intensities in accordance with step 3 in sequence; In step 5, the weight of the muddy water sample in the water receiving container is weighed and designated as Ma, the water receiving container is set aside, the sediment in the muddy water sample is dried, and the weight of the dried sediment is weighed and designated as Mb, and the runoff rates of the surface flow, intermediate flow and base runoff are calculated using equation (1), respectively;

number

number

[0015] Compared with the conventional techniques, the present invention has the following significant beneficial effects:

[0016] 1. The present invention changes the single soil thickness design and single bedrock permeability design in the traditional soil tank, and changes it into an adjustable movable support bracket and permeable and impermeable support plate to realize the changed designs of different soil thickness distributions and different bedrock permeability, which can more realistically reflect the characteristics of the soil thickness distribution and bedrock permeability differences in the slopes of small watersheds in mountainous areas, and make the test more in line with the actual situation.

[0017] 2. The present invention changes the conventional rainfall-runoff collection test, which only allows a single rainfall intensity and a single ground surface design to be set in one rainfall test. It adopts dividing the large soil tank into two small soil tanks, which can realize the setting of different ground surface conditions within the same soil tank. At the same time, four designed rainfall intensities are used to continuously rain on the same soil tank, which reduces the test errors caused by adjusting the rainfall intensity, re-filling, and changes in site conditions, and makes the test results more accurate.

[0018] 3. In addition to setting up surface flow and intermediate flow collection tanks following the general soil tank, the present invention also sets up a base runoff collection tank, which can more completely collect all runoff components generated by the soil sample during rainfall.

[0019] 4. The present invention uses a visible side panel to observe the movement of the wetting front during rainfall in real time, and can grasp the moisture transport process in the soil more intuitively and accurately. [Brief description of the drawings]

[0020] [Figure 1] 1 is a structural schematic diagram of a runoff collection device taking into account soil thickness distribution and bedrock infiltration differentials according to an embodiment of the present invention; [Diagram 2] 1 is a plan view showing the structure of a soil tank according to an embodiment of the present invention; [Diagram 3] 1 is a schematic diagram of the front structure of a soil tank according to an embodiment of the present invention. [Figure 4] FIG. 13 is a structural schematic diagram of the embodiment of the present invention after changing the direction of the bottom plate. [Diagram 5] 1 is a schematic perspective view of a support bracket according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be described clearly and completely below with reference to the drawings in the embodiments of the present invention, and it is clear that the described embodiments are only some embodiments of the present invention, and are not all embodiments. All other embodiments obtained by those skilled in the art without creative labor based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0022] As shown in Fig. 1, an embodiment of the present invention provides a runoff collection device considering soil thickness distribution and bedrock infiltration difference, which includes a soil tank 1, a soil tank partition plate 2, a runoff collection tank 3, a bottom plate 4, and a soil tank base. The soil tank 1 is divided into two small soil tanks by the soil tank partition plate 2 (see Fig. 2), which are a permeable small soil tank 101 and an impermeable small soil tank 102, respectively, and each of the two small soil tanks has a runoff collection tank 3 at one end for collecting surface runoff, intermediate runoff, and base runoff.

[0023] A bottom plate 4 is provided in the soil tank 1, and the bottom plates 4 in the two small soil tanks are permeable and impermeable, respectively, that is, the bottom plate 4 in the permeable small soil tank 101 is permeable, and the bottom plate 4 in the impermeable small soil tank 102 is impermeable. A soil tank base 5 is provided below the soil tank 1, and the slope of the soil tank 1 can be adjusted, and the soil tank 1 can also be moved horizontally indoors. At the start of the test, soil is filled into each of the two small soil tanks according to a predetermined design standard, and the soil tank base 5 is adjusted so that the soil tank 1 maintains the design slope. After adjusting the design rainfall intensity and starting rainfall, when water drips into the runoff collection tank 3, the water receiving container receives the surface runoff, intermediate runoff, and base runoff, respectively.

[0024] Specifically, referring to Figures 2 and 3, the soil tank 1 includes a permeable small soil tank 101, an impermeable small soil tank 102, a visible side plate 103, a surface flow outlet 104, a middle intermediate flow outlet 105, a lower intermediate flow outlet 106, a water return 107, and a bottom base outflow outlet 108. The surface flow outlet 104 is located at the top of one side of the soil tank 1, and the bottom of the surface flow outlet 104 is flush with the surface of the soil filled in the soil tank 1, the bottom of the middle intermediate flow outlet 105 is 25 cm away from the soil surface, and the lower intermediate flow outlet 106 is flush with the bottom of the soil tank 1. The visible side plate 103 is made of a transparent organic glass material and serves as the side wall of the soil tank 1, allowing the movement of the soil wetting front in the soil tank to be observed in real time. The water return 107 is made of an impermeable plastic material and is 50 cm wide, 2 cm high and 2 cm thick. It is located between the lower intermediate flow drain outlet 106 and the bottom base outflow drain outlet 108. One side of the water return 107 is the bottom base outflow drain outlet 108, and the other side is spaced 5 cm from the lower intermediate flow drain outlet 106. In the permeable small soil tank 101, base runoff from the soil flows to the bottom of the soil tank 1, and since the soil tank 1 has a certain gradient, the base runoff flows from top to bottom along the bottom of the soil tank 1, and finally gathers and flows out at the bottom base outflow drain outlet 108. The water return 107 can block base runoff and prevent base runoff in the soil of the permeable small soil tank 101 from flowing out from the lower intermediate flow drain outlet 106.

[0025] Specifically, referring to Figures 3 and 4, the runoff collection tank 3 includes a surface flow collection tank 301, a middle intermediate flow collection tank 302, a lower intermediate flow collection tank 303, and a bottom base runoff collection tank 304, which are arranged in order from top to bottom. Here, the lengths of the surface flow collection tank 301, the middle intermediate flow collection tank 302, and the lower intermediate flow collection tank 303 are 40 cm, 25 cm, and 10 cm, respectively, to ensure that different runoffs can be collected simultaneously. The surface flow collection tank 301 is connected to the surface flow outlet 104, the middle intermediate flow collection tank 302 is connected to the middle intermediate flow outlet 105, and the lower intermediate flow collection tank 303 is connected to the lower intermediate flow outlet 106. The base runoff collection tank 304 is 10 cm long and is connected to the bottom base runoff outlet 108.

[0026] Specifically, referring to FIG. 4, the bottom plate 4 includes a permeable support plate 401, an impermeable support plate 402, a reverse filtration layer 403, a lath net 404, and a support bracket 405. The permeable support plate 401 is located in the permeable small soil tank 101, and the impermeable support plate 402 is located in the impermeable small soil tank 102. The permeable support plate 401 and the impermeable support plate 402 are both rectangular steel plates with a thickness of 1.5 cm, a length of 200 cm, and a width of 50 cm. The permeable support plate 401 has circular holes with an inner diameter of 1 cm or less uniformly distributed, the interval between the circular holes is 2 cm or less, and the impermeable support plate 402 has no holes. The reverse filtration layer 403 is coarse sand with a grain size of 2 cm or more, which is laid evenly on the permeable support plate 401 and the impermeable support plate 402, and has a thickness of 3 cm. The lattice mesh 404 has a total of two layers, with a mesh width of 0.5 cm, and is layered and covered on the reverse filtration layer 403. Between the two layers of lattice mesh 404, there is one layer of nonwoven fabric filter with a pore size of 0.3 cm, and the total thickness of the two layers of lattice mesh 404 is 0.5 cm.

[0027] Specifically, referring to FIG. 5, the support bracket 405 is a threaded rebar steel structure, and the diameter of the rebar is 1 cm or more. Both sides of the support bracket 405 are right-angled trapezoids, which are connected and fixed by a bottom rectangle, and the bottom rectangle is 150 cm long and 50 cm wide. The right-angled trapezoid has an upper base of 20 cm and a lower base of 5 cm, and two vertical support rods and two horizontal support rods are uniformly distributed inside the right-angled trapezoids on both sides. In order to ensure that the base runoff in the permeable small soil tank 101 flows smoothly through the bottom of the soil tank and into the bottom base runoff outlet 108, there is no support rod in the middle of the bottom rectangle of the support bracket 405.

[0028] Specifically, as shown in Fig. 4, the soil tank base 5 includes a base support bracket 501, a universal wheel 502, and a hydraulic lift 503. The base support bracket 501 is a rectangular steel frame structure, the length and width of the bottom are equal to the length and width of the soil tank 1, and there are four universal wheels 502 at the four corners of the bottom. At the top of one end of the base support bracket 501, there is a large hinge connected to the bottom of the soil tank 1, the distance from the large hinge to the lower intermediate flow outlet 106 is 40 cm, and the soil tank 1 can rotate around the large hinge. The hydraulic lift 503 is fixed to the base support bracket 501, and the support column of the hydraulic lift 503 is connected to the bottom of the soil tank 1 via a large hinge. The distance from the large hinge to the lower intermediate flow drain outlet 106 is 160 cm. By adjusting the raising and lowering of the support column of the hydraulic lift 503, the slope of the soil tank can be changed within the range of 0° to 30°.

[0029] The soil tank 1 of the present invention is divided into two small soil tanks by the soil tank partition plate 2, and a permeable support plate 401 and an impermeable support plate 402 are placed in the two small soil tanks, respectively, to realize two different bedrock permeability designs, permeable and impermeable. In addition, by adjusting the direction of the bottom plate support bracket 405 in the soil tank 1, the permeable support plate 401 and the impermeable support plate 402 are placed in the two small soil tanks with a certain inclination, respectively, so that the test soil sample is filled into the soil tank 1 according to a certain design index, thereby realizing the design of different soil thickness distributions at the upper and lower parts of the soil tank in the same soil tank. The slope of the soil tank 1 is adjusted to the design value by adjusting the hydraulic lift 503 of the soil tank base 5. The amount of runoff generation within a certain time interval under different rainfall intensity conditions is collected by the runoff collection tank 3, and the runoff generation law under different rainfall conditions is calculated and analyzed to analyze the runoff generation process and law under different soil thickness distributions and different bedrock permeability conditions.

[0030] An embodiment of the present invention further provides a runoff collection method taking into account soil thickness distribution and bedrock infiltration difference, which is carried out by using the above-mentioned device, and the specific steps are as follows:

[0031] Step 1: Adjust the placement direction of the support brackets 405 in the permeable small soil tank 101 and the impermeable small soil tank 102, make the soil thickness distribution of the two small soil tanks consistent (for example, both are thick at the top of the slope and thin at the bottom of the slope), place the permeable support plate 401 and the impermeable support plate 402 on the support brackets 405 in the permeable small soil tank 101 and the impermeable small soil tank 102 respectively, then lay the reverse filtration layer 403 and two layers of lath mesh 404 in sequence, and finally fill the soil samples into the two small soil tanks in preparation for use. Step 2: Adjust the hydraulic lift 503 of the soil tank base 5 so that the soil tank has a certain design slope, for example 15°. Step 3: Design four rainfall intensities according to the specific study area, and design the runoff generation time length for each designed rainfall intensity as 45 min. Take runoff samples every minute for the first 5 min, and every 5 minutes for the next 40 min. After each rainfall, pause for 30 minutes before the next rainfall, and repeat the above sampling process. Step 4: Start rainfall at the design rainfall intensity, and when the water drips into the runoff collection tank 3, use the water receiving container to receive the surface flow, intermediate flow and base runoff respectively within a certain time period, and follow step 3 to complete the sampling of rainfall and runoff at the four design rainfall intensities sequentially. Step 5: Weigh the weight of the muddy water sample in the water receiving container and call it Ma. Leave the water receiving container to rest and dry the sediment in the muddy water sample. Weigh the weight of the dried sediment and call it Mb. Using equation (1), calculate the runoff rates of surface flow, intermediate flow, and base runoff, respectively.

[0032]

number

[0033]

number

[0034] Step 7: After receiving the final rainfall and runoff sampling under the fourth design rainfall intensity condition, end the experiment, take out soil samples in the two small soil tanks, wash the soil tanks, adjust the slope of the soil tank, and repeat steps 1 to 7 to conduct rainfall and runoff observation tests under other design slope conditions until all rainfall and runoff observation tests under all design slope conditions are completed.

[0035] Step 8: After completing all the rainfall tests with different design rainfall intensities and different design slopes under the same soil thickness distribution condition, adjust the arrangement direction of the support bracket 405, and repeat steps 1 to 7 to perform tests under design conditions with different soil thickness distribution. If the soil thickness distribution is designed to be thin at the top of the slope and thick at the bottom of the slope and the lower intermediate flow outlet 106 needs to be used to collect the intermediate flow, before performing the soil filling operation described in step 1, the middle intermediate flow outlet 105 of the two small soil tanks is sealed with an organic glass plate and a sealant to prevent the intermediate flow in the soil layer from flowing out of the middle intermediate flow outlet 105. After completing all the rainfall tests with different design rainfall intensities and different design slopes under the same soil thickness distribution condition, by repeating steps 1 to 7 by adjusting only the design rainfall intensity and the slope of the soil tank, the arrangement direction of the support bracket 405 may be adjusted to perform rainfall tests under other conditions.

[0036] The above is merely a specific embodiment of the present invention, and the scope of protection of the present invention is not limited thereto, and any modifications or replacements that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined based on the claims.

Claims

1. The soil tank includes a soil tank partition plate, a runoff collection tank, a bottom plate, and a soil tank base; The soil tank is divided into two left and right small permeable soil tanks and a small impermeable soil tank, each having the same volume, by the soil tank partition plate. The runoff collection tank is located at one end of the soil tank and is used to collect surface runoff and intermediate runoff; The bottom plate is divided into a permeable support plate and an impermeable support plate, and the permeable support plate and the impermeable support plate are respectively positioned in the permeable small soil tank and the impermeable small soil tank, thereby realizing different bedrock permeability designs; A support bracket is provided under the permeable support plate and the impermeable support plate, and the direction of the support bracket can be adjusted to realize different soil thickness distribution designs in the soil tank; The soil tank base is located below the soil tank, can support and move the soil tank, and can be used to raise and lower the soil tank to adjust to different gradients. A runoff collection device that takes into account soil thickness distribution and bedrock infiltration differences.

2. The runoff collection tank includes a surface flow collection tank, a middle intermediate flow collection tank, and a lower intermediate flow collection tank, which are provided in order from top to bottom on one side of the soil tank. On one side of the soil tank, a surface flow drain outlet, a middle intermediate flow drain outlet, and a lower intermediate flow drain outlet are provided in order from top to bottom. The surface flow collection tank, the middle intermediate flow collection tank, and the lower intermediate flow collection tank are connected to the surface flow drain outlet, the middle intermediate flow drain outlet, and the lower intermediate flow drain outlet, respectively.

2. The runoff collection device according to claim 1, taking into account soil thickness distribution and bedrock infiltration differences.

3. The surface flow drain outlet is located at the top of one side of the soil tank, and the bottom of the surface flow drain outlet is flush with the surface of the soil filled in the soil tank; When the soil layer is designed such that the soil at the foot of the slope is thin and the soil at the toe of the slope is thick due to the arrangement direction of the support bracket, the bottom of the central intermediate flow outlet is flush with the bottom of the reverse filtration layer at the bottom of the soil layer, and when the soil layer is designed such that the soil at the foot of the slope is thick and the soil at the toe of the slope is thin due to the arrangement direction of the support bracket, the central intermediate flow outlet needs to be blocked; The lower intermediate flow outlet is flush with the bottom of the soil tank.

3. A runoff collection device taking into account soil thickness distribution and bedrock infiltration differences as claimed in claim 2.

4. The side walls of the soil tank are visible side panels, which are made of transparent organic glass material, and the movement of the wetting front of the soil layers in the permeable small soil tank and the impermeable small soil tank can be observed in real time.

3. A runoff collection device taking into account soil thickness distribution and bedrock infiltration differences as claimed in claim 2.

5. A water return is provided at a location adjacent to the lower intermediate flow outlet at the bottom of the permeable soil tank, A bottom base outflow drain is provided on one side of the water return, and the distance between the other side of the water return and the lower intermediate flow drain is 5 cm. The water return is used to block the base outflow and prevent the base outflow from continuing to flow downward and out of the lower intermediate flow drain.

3. A runoff collection device taking into account soil thickness distribution and bedrock infiltration differences as claimed in claim 2.

6. The runoff collection tank further includes a bottom base runoff collection tank connected to the bottom base runoff drain outlet provided at the bottom of the soil tank.

6. A runoff collection device taking into account soil thickness distribution and bedrock infiltration differences as claimed in claim 5.

7. A reverse filtration layer is laid evenly on the permeable support plate and the impermeable support plate, and two layers of lath netting are overlapped and covered on the reverse filtration layer, and a nonwoven fabric filter is provided between the two layers of lath netting.

3. A runoff collection device taking into account soil thickness distribution and bedrock infiltration differences as claimed in claim 2.

8. The support bracket has right-angled trapezoids on both sides and a rectangular bottom, and vertical and horizontal support rods are provided inside the right-angled trapezoids on both sides, and there is no support rod in the center of the rectangular bottom of the support bracket.

8. A runoff collection device taking into account soil thickness distribution and bedrock infiltration differences as claimed in claim 7.

9. The soil tank base includes a base support bracket, a universal wheel, and a hydraulic lift; The base support bracket is a rectangular steel structure, the length and width of the bottom are equal to the length and width of the soil tank, and there are four universal wheels at the four corners of the bottom; A large hinge is provided at the bottom of the soil tank to connect the bottom of the soil tank to the top of one end of the base support bracket, and the soil tank is rotatable around the large hinge; The hydraulic lift is fixed to the base support bracket, and the support position of the hydraulic lift is connected to the bottom of the soil tank via a large hinge. By adjusting the elevation of the support of the hydraulic lift, the slope of the soil tank can be changed within a range of 0° to 30°.

2. The runoff collection device according to claim 1, taking into account soil thickness distribution and bedrock infiltration differences.

10. A runoff collection method that takes into account soil thickness distribution and bedrock infiltration differences, comprising: The runoff collection method is carried out using an apparatus according to any one of claims 1 to 9 and comprises steps 1 to 8, In step 1, adjust the orientation of the support brackets in the permeable soil tank and the impermeable soil tank to match the soil thickness distribution in the two small soil tanks, place the permeable support plate and the impermeable support plate on the support brackets in the permeable soil tank and the impermeable soil tank, respectively, then lay a reverse filtration layer and two layers of lath screen in sequence, and finally fill the two small soil tanks with soil samples to prepare for use; In step 2, the hydraulic lifting device of the soil tank base is adjusted so that the soil tank has a constant design slope; In step 3, four rainfall intensities are designed according to the specific research area, and the runoff generation time length for each designed rainfall intensity is designed to be 45 min. Runoff samples are taken every minute for the first 5 min, and every 5 minutes for the next 40 min. After each rainfall, a 30-minute break is required before the next rainfall. The above sampling process is repeated. In step 4, start rainfall at a design rainfall intensity, and when water drips into the runoff collection tank, use a water receiving container to receive the surface runoff, intermediate runoff and base runoff respectively within a certain time period, and complete the rainfall and runoff sampling of the four design rainfall intensities in accordance with step 3 in sequence; In step 5, the weight of the muddy water sample in the water receiving container is weighed and designated as Ma, the water receiving container is allowed to stand, the sediment in the muddy water sample is dried, and the weight of the dried sediment is weighed and designated as Mb, and the runoff rates of the surface flow, intermediate flow and base runoff are calculated using equation (1), respectively; [0010] where Q is the runoff rate (L / min), Ma is the weight of the muddy water sample (g), Mb is the weight of the dried soil (g), ρ is the water density (1.0 g / cm3), and t is the runoff sampling time (s). In step 6, the transport mass of sediment within a certain area per unit time, i.e., the erosion rate D, is calculated using equation (2); [0025] where D is the erosion rate (g / (m s)), M is the weight of the soil after drying (g), b is the width of the soil tank (m), L is the length of the soil tank (m), and t is the runoff sampling time (s). In step 7, after the last rainfall and runoff sampling under the fourth design rainfall intensity condition is completed, the experiment is terminated, the soil samples in the two small soil tanks are taken out, the soil tanks are washed, the slope of the soil tank is adjusted, and steps 1 to 7 are repeated to conduct rainfall and runoff observation tests under other design slope conditions until all rainfall and runoff observation tests under all design slope conditions are completed; In step 8, after all the rainfall tests with different designed rainfall intensities and different designed gradients under the same soil thickness distribution conditions are completed, adjust the arrangement direction of the support bracket, and repeat steps 1 to 7 to perform tests under different designed soil thickness distribution conditions. When the soil thickness distribution is designed to be thin at the top of the slope and thick at the bottom of the slope and the lower intermediate flow outlet needs to be used to collect the intermediate flow, seal the middle intermediate flow outlets of the two small soil tanks with organic glass plates and sealant to prevent the intermediate flow in the soil layer from flowing out from the middle intermediate flow outlet before carrying out the soil filling operation described in step 1. This runoff collection method takes into account soil thickness distribution and bedrock infiltration differences.

Images