CN113914257B - Indoor model test platform device for water flow scouring ecological river bank and test method thereof - Google Patents
Indoor model test platform device for water flow scouring ecological river bank and test method thereof Download PDFInfo
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- CN113914257B CN113914257B CN202111213935.4A CN202111213935A CN113914257B CN 113914257 B CN113914257 B CN 113914257B CN 202111213935 A CN202111213935 A CN 202111213935A CN 113914257 B CN113914257 B CN 113914257B
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
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Abstract
The invention discloses a water flow scouring ecological river bank indoor model test platform device and a test method thereof, wherein the water flow scouring ecological river bank indoor model test platform device comprises a water tank with openings at two ends; both ends of the bottom of the water tank are provided with a liftable supporting base device; the supporting base is fixedly connected with the sliding plate; a baffle is arranged at an opening at the front end of the water tank, a high-pressure water tank is arranged at the upper part of the tail end of the water tank, and a water pipe connected with a water tap communicated with the high-pressure water tank extends downwards to the bottom of the water tank; two boxes are arranged in the water tank at intervals; the box and the water tank side plate are arranged in parallel, a movable lateral support frame is arranged on the back face of the box, a first directional pulley is connected to the lower portion of the lateral support frame, and the first directional pulley is connected with the directional sliding rail in a sliding mode. The invention can simulate the working conditions of different river bank slopes, different river bed lengths, different river bed slopes and the like, thereby realizing the simulation of multifunctional parameters by one platform, and being capable of analyzing the influence of the slope coefficient of the river bank, the river length, the river slope and the like on the river bank scouring effect of the ecological slope protection.
Description
Technical Field
The invention belongs to the technical field of ecological test methods, and particularly relates to a water flow scouring ecological river bank indoor model test platform device and a test method thereof.
Background
With the emphasis on ecological environment in China, the traditional cement hardening river channel treatment mode cannot meet the new requirement of urban river channel improvement, and the novel ecological river channel treatment engineering adopting the geonets and plants is more and more widely applied. However, the stability of ecological river regulation engineering is always the key point of attention. Under the action of water flow scouring for a long time, the ecological slope protection riverway has serious erosion to the side slope, and can cause instability damage of the ecological side slope. The slope protection by utilizing the combination of the reinforced three-dimensional geonet cushion and different vegetation is a new mode of ecological slope protection in recent years, but the research mechanism in the field is less at present, so that the development of the indoor scouring model test research and stability analysis of the three-dimensional geonet cushion ecological slope protection under the action of river water flow is necessary.
At present, partial research work is carried out on the study of the scouring model of the geotechnical net pad by scholars at home and abroad, some progress is made, most of the common scouring model grooves are single-function model test devices at present, only a certain gradient of a river bank can be analyzed singly, or a river channel with single length can be analyzed, the variable adjusting factors of the existing indoor test model are few, repeated tests are high in cost, the problems of resource waste and the like, but the factor angle of the ecological slope protection of the river channel and the stability of the ecological slope protection of the river channel is influenced, such as the gradient coefficient of the river bank, the gradient of the river channel, the length of the river channel, the speed of water flow and the like. If multi-factor analysis is to be realized, a plurality of different punching die-shaped grooves need to be manufactured, so that the test cost is increased, and the resource of test equipment is wasted.
The existing water channel of the indoor model test platform for the waterflow-scouring ecological river bank is mostly vertical side wall, can not be adjusted and can not simulate the slope coefficient of the river bank. In addition, the length of the current common water tank is fixed, and the common water tank cannot adapt to different river channel simulation tests with multiple lengths, so that multiple mold grooves need to be manufactured when different river bank slopes and different river channel lengths are researched, and the test cost is increased.
The slope ratio of river course is the important factor that influences river course velocity of water, considers different river course slope coefficients to be model test's important variable in model test, and traditional basin is mostly the fixed stay base, and the basin is placed for the level, and basin end-to-end connection high pressure water tank's tap switch directly erodees, can't freely change the slope of basin river course, leads to the artificial mode groove of raising of many times. The higher base support is selected, so that the use is inconvenient.
The slope ratio of river course is the important factor that influences river course velocity of water, considers different river course slope coefficients to be model test's important variable in model test, and traditional basin is mostly the fixed stay base, and the basin is placed for the level, and basin end-to-end connection high pressure water tank's tap switch directly erodees, can't freely change the slope of basin river course, leads to the artificial mode groove of raising of many times. The higher base support is selected, so that the use is inconvenient.
Disclosure of Invention
The invention aims to provide a water flow scouring ecological river bank indoor model test platform device and a test method thereof aiming at the defects in the prior art, so that the simulation of working conditions such as different river bank slopes, different river bed lengths, different river bed slopes and the like can be realized, the simulation of multifunctional parameters of one platform is realized, and the problems are solved or improved.
In order to achieve the purpose, the invention adopts the technical scheme that:
on one hand, the indoor model test platform device for the waterflow-flushing ecological river levee comprises a water tank with openings at two ends; both ends of the bottom of the water tank are provided with a liftable supporting base device; the supporting base is fixedly connected with a sliding plate for adjusting the gradient of the water tank;
a water level baffle for adjusting the water level in the water tank is arranged at an opening at the front end of the water tank, a high-pressure water tank equipped with a flow rate meter is arranged at the upper part of the tail end of the water tank, and a water pipe connected with a water tap communicated with the high-pressure water tank extends downwards to the bottom of the water tank;
at least two boxes for filling soil and net pads are arranged in the water tank at intervals; the box and the side plate of the water channel are arranged in parallel, the movable lateral support frame is arranged on the back face of the box, a first directional pulley with a pinch plate brake is connected to the lower portion of the lateral support frame, and the first directional pulley is connected with the directional slide rail in a sliding mode and used for simulating different river bank slopes on two sides of the river channel.
Furthermore, a circular sliding rail is arranged at the lower part of the water tank, and the circular sliding rail is in sliding fit with a second directional pulley arranged on the expansion plate and used for realizing expansion of the expansion plate; both sides of the expansion plate are respectively movably connected with the outer side plate.
Furthermore, hinges are arranged at four corners of the edge of the telescopic plate.
Furthermore, concave clamping grooves for mounting the water level baffle are formed in the inner sides of the end parts of the outer side plates of the water tank side plate and the telescopic plate.
Furthermore, the basin is the rectangle box body of top and both ends open-ended, and the size of rectangle box body is length 2500mm, and width 600mm, height 300mm.
Further, the box is installed in the position 200mm away from the edge inside the water tank, and the size of the box is 900mm in length, 600mm in width and 300mm in height.
Further, the length of expansion plate is 1500mm, and the width is 600mm.
On one hand, the water flow scouring ecological river bank indoor model test platform device and the test method thereof comprise the following steps:
s1, paving filling soil in a side plate of a box according to construction requirements, covering a three-dimensional geotechnical reinforcement mesh pad, backfilling a soil sample above the three-dimensional geotechnical reinforcement mesh pad, planting tall fescue, periodically applying nutrient solution, and starting a water tank scouring test of the ecological slope protection river bank of the three-dimensional mesh pad after vegetation grows to a preset height;
s2, adjusting a telescopic plate at the bottom of the water tank, controlling the telescopic length to be 500mm, fixing the position of the telescopic plate and forming a whole with the bottom plate of the water tank;
s3, adjusting the heights of the two ends of the water tank by adjusting the two supporting base devices until the height difference of the two ends of the water tank reaches a preset value, and forming the water tank into a preset inclined slope;
s4, adjusting a movable lateral support frame at the back of the side plate of the box to enable the gradient coefficient of the side plate of the box to reach a preset ratio;
s5, unfolding and fixing the two outer side plates of the water tank expansion plate, fixedly installing a liftable water level baffle in the concave clamping grooves of the two side plates, and adjusting the lifting height to be a preset value;
s6, measuring the flow velocity of water flow in real time by a flow velocity monitor, firstly performing flushing with the water flow velocity of V1, and continuously flushing for 30min in each test;
s7, simultaneously, shooting the loss of the filling soil in the side plates of the box and the exposure condition of the three-dimensional geonet pad in real time by adopting a high-speed camera;
determining the sand content of the slope surface flow, taking a muddy water sample of about 500ml every 1min, accurately measuring the volume of the muddy water sample by using a measuring cylinder, weighing the mass of the muddy water sample by using an electronic balance, and finally converting the sand content of each sample by using a displacement method;
measuring the width of the water surface of the slope;
and S8, comparing and analyzing various monitoring data indexes in other groups of different test schemes.
Further, S1 lays the banket according to the construction demand in the box curb plate to cover three-dimensional geotechnological reinforced net pad and at its top backfill sample, plant the tall fescue, regularly apply the nutrient solution, treat that the vegetation is grown to preset height, begin the basin and erode the ecological bank protection river levee of three-dimensional net pad and erode the test, include:
before the three-dimensional geonet pad is laid, filling soil with the thickness of about 8cm at the bottom of the water tank, and ensuring the same soil thickness and the level of the slope surface through a level gauge and a leveling rod; filling soil is tamped by manual layered filling and layering, and a super filling slope cutting mode is adopted; the filling soil in the water tank side slope is controlled by filling soil with the same weight in the same surface area, and the filling soil weight is calculated according to the volume, the density under the corresponding water content and the compaction degree.
Further, four water flow speeds V1, V2, V3 and V4 are adopted; two kinds of turf and 1:1 and 1:2 two river bank slopes, 32 groups of tests are carried out in total;
in the test, a water quality analysis system is respectively adopted to analyze the water and soil loss condition of a surface soil body, and a high-speed camera and a measuring tool are adopted to determine the change rule of an erosion ditch, the pore water pressure of the soil body at the net pad, the shear strength of the plant net pad soil layer and the like; carrying out comparative analysis on the erosion characteristics of the aged natural turf and the turf protected by the net mat under different water flow scours; under different lengths of water tanks, the influence of different lengths of simulated natural river channels on the erosion of river channel side slopes is explored, and the telescopic range is 2500-4000mm.
The indoor model test platform device for the waterflow-flushing ecological river levee and the test method thereof provided by the invention have the following beneficial effects:
1. the invention can simulate the working conditions of different river bank slopes, different river bed lengths, different river bed slopes and the like, thereby realizing the simulation of multifunctional parameters of one platform, and being used for analyzing the influence of the slope coefficient of the river bank, the river length, the river bank slope and the like on the river bank scouring effect of the ecological slope protection.
2. The invention changes the fixed support at the bottom of the water tank into the lifting support base device with adjustable height, not only can realize the random adjustment of the height of the river bank and the water tank test platform, but also can realize the simulation of different natural slopes of the river channel and the simulation of different river channel slopes in the natural world, thereby realizing the purpose that one device simulates different river channel slopes, and simultaneously can also disclose the internal relation between the river channel slope and the erosion of the ecological slope protection river banks for analyzing the anti-erosion effect of the river channel slope on the river banks at two sides, thereby providing reference data for the subsequent engineering design of the ecological slope protection of the river channel, overcoming the problem that the traditional water tank can not automatically adjust the slope, and leading the research of the experiment to be more in line with the actual situation.
3. The length change of the scouring water channel can be realized by the aid of the telescopic plate structure designed on the scouring water channel, different channel lengths can be simulated, the influence of the channel lengths on water flow speed and the scouring effect of ecological slope protection structures on two sides of a river bank can be analyzed, the device can be repeatedly used for indoor model test research of different lengths, waste caused by disposable use of the traditional fixed-length scouring water channel is avoided, and test cost can be effectively reduced. In addition, the length adjustment of the expansion plate can be used for simulating the influence of water flow scouring of the ecological river bank for slope protection on erosion, flow velocity and stability of the ecological slope protection in river channels with different lengths, thereby providing reference for the engineering design and construction of the ecological river bank for slope protection.
4. The back of the box is provided with a directional pulley, and the directional pulley and a directional slide rail are matched to simulate different river bank slopes of river bank slopes on two sides of a river channel, so that multi-angle adjustment of river bank side plates is realized, and various common river bank slopes of natural river channels are simulated; and the intrinsic relation between the gradient coefficient of the river levee and the scouring strength of the river levee can be analyzed, so that the device can be repeatedly used for model test research of different river levee gradients, the traditional fixed side plate is prevented from simulating the fixed river levee gradient, the defect that a model test platform cannot be used for multiple times is overcome, and the test cost can be effectively reduced.
5. The water level baffle at the front outlet of the chute has a lifting function, the height of the water storage level in the river channel is changed by adjusting the height of the baffle, so that the function of adjusting the water depth of the river channel is realized, and the function of adjusting the water level height cannot be realized by the traditional fixed height mode.
Drawings
FIG. 1 is a schematic structural diagram of a test platform device.
FIG. 2 is a bottom schematic view of a test platform mounting structure.
Fig. 3 and 4 are grass planting diagrams of ecological revetments of riverways and river banks.
FIG. 5 is a schematic view of a structure for adjusting the height and the inclination angle of the test water tank.
Fig. 6 is a schematic view of the river bank side plate back lateral support device.
Fig. 7 is a schematic view of a channel bottom plate length expansion adjusting plate.
FIG. 8 is a schematic view of a channel model formed by fixing a channel bottom plate after the channel bottom plate is extended in length.
Wherein, 1, a water tank; 2. supporting the base unit; 3. a slide plate; 4. a water level baffle; 5. a high pressure water tank; 6. connecting a water pipe; 7. a box; 8. a lateral support frame; 9. a first directional pulley; 10. a directional slide rail; 11. a circular slide rail; 12. a second directional pulley; 13. a retractable plate; 14. a hinge; 15. an outer panel; 16. concave draw-in groove.
Detailed Description
The following description of the embodiments of the present invention is provided to facilitate the understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and it will be apparent to those skilled in the art that various changes may be made without departing from the spirit and scope of the invention as defined and defined in the appended claims, and all matters produced by the invention using the inventive concept are protected.
According to the first embodiment of the application, referring to fig. 1-8, the indoor model test platform device for water flow scouring ecological river bank in the scheme comprises a water tank 1, wherein the top and two ends of the water tank 1 are both provided with openings, and the water tank 1 is in a cuboid shape and has the size of 2500mm in length, 600mm in width and 300mm in height, and is used for simulating a river channel.
The liftable supporting base device 2 is arranged at two ends of the bottom of the water tank 1, the supporting base device 2 is a telescopic supporting rod, the supporting base device 2 can adjust the height of two ends of the water tank 1, and a certain height difference between two ends of the water tank 1 can be achieved.
The supporting base device 2 can adjust the height of the test platform of the river bank water tank 1 at will, and can simulate different situations of natural slopes of a river channel, so that the purpose of simulating different river channel slopes in the nature is achieved.
A water level baffle 4 for adjusting the water level in the water tank 1 is installed at an opening at the front end of the water tank 1, and the water level in the water tank 1 is controlled by adjusting the water level baffle 4, so that the river depth of a river channel is simulated.
Through the height of adjusting water level baffle 4 for the water storage level height in the river course changes, thereby realizes the function of adjusting the river course depth of water, and water level baffle 4 can realize simulating the influence of different river course depths of water to the washing away of ecological river course bank protection engineering, thereby can simulate the anti scour protection effect analysis of ecological bank protection river bank under the different depth of water condition, provides the participation data for on-the-spot ecological bank protection engineering design, construction.
The upper part of the tail end of the water tank 1 is provided with a high-pressure water tank 5 provided with a flow rate meter, a water tap connecting pipe 6 communicated with the high-pressure water tank 5 extends downwards to the bottom of the water tank 1, and when a valve of the water tank is opened in specific application, the speed of water flow can be directly read through the flow rate meter on the valve.
At least two boxes 7 for filling soil and net mats are arranged in the water tank 1 at intervals, and the boxes 7 are arranged in the position 200mm away from the edge inside the water tank 1 and are vertically arranged.
The size of box 7 is length 900mm, width 600mm, and height 300mm, and box 7 is used for adorning earth and the rete is used for simulating the river bank of river course both sides.
The box 7 is arranged in parallel with a side plate of the water tank 1, a movable lateral support frame 8 is arranged on the back of the box 7, a first directional pulley 9 with a pinch plate brake is connected to the lower portion of the lateral support frame 8, and the first directional pulley 9 is connected with a directional slide rail 10 in a sliding mode and used for simulating different river bank slopes on two sides of a river channel.
The first directional pulley 9 moves on the directional slide rail 10 to change the angle of the side plate of the box 7 at will, so that different river bank slopes of river bank slopes on two sides of a river channel are simulated, and simulation of any working condition of different river bank slopes is realized.
According to the invention, the first directional pulley 9 is arranged at the back of the box 7, and the first directional pulley 9 is matched with the directional slide rail 10, so that different river bank slopes of river bank slopes at two sides of a river channel can be simulated, the multi-angle adjustment of the side plates of the river banks can be realized, and various common river bank slopes of natural river channels can be simulated.
The lower part of the water tank 1 is provided with a circular slide rail 11, a second directional pulley 12 is adopted to connect an expansion plate 13, the expansion plate 13 is 1500mm long and 600mm wide, four corners of the edge of the expansion slide plate 3 are provided with hinges 14, and the hinges are used for turning outer side plates 15 on two sides of the expansion plate 13 outwards to be vertical to the expansion plate 13 after the expansion plate 13 extends to the maximum length, so that the extended expansion plate 13 and the vertical side plates form a chute platform
According to the second embodiment of the application, the test method of the indoor model test platform device for the waterflow scouring ecological river bank comprises the following specific steps:
because the factors influencing the anti-scouring effect of the ecological slope protection are more, in order to analyze the influence of the gradient coefficient, the length of the river channel, the gradient of the river channel and the like on the scouring effect of the river levee of the ecological slope protection, a plurality of variables are set, and the influence of the variable factor change on the anti-scouring performance of the river levee of the ecological slope protection is specifically analyzed.
The multiple contents to be observed in the scouring test comprise:
the change trend of the slope surface flow in the scouring process of the slope surface comprises the flow velocity of the slope surface flow; the sand content and the erosion amount of the slope surface flow change along with time; the experiment mainly develops research work on the anti-scouring performance of the three-dimensional geotechnical mesh pad according to four aspects of different flow rates, different river channel lengths, different river channel gradients and different river bank gradients. According to field observation, an hour is selected as a test period in the test, a group of numerical values are measured every 15 minutes, the residual soil amount in the self-made river bank side plate, the length, the width and the number of erosion ditches, the condition that plants are washed away and the condition that silt is collected at the outlet of the water tank 1 are observed, and the water and soil loss condition of the silt is analyzed, so that the anti-washing performance of the ecological river bank protection slope is determined.
The test is divided into 32 groups, the anti-scouring capacity of the ecological river bank and the geotechnical net cushion under different flow rates, different river channel lengths, different river channel slopes and different river bank slopes is explored, and specific test variables are shown in table 1.
This time, a certain group of model tests are taken as an example for detailed description, that is, the water flow speed is V1, the water tank has a 1-degree slope of 15 °, and the slope coefficient of the side plate of the river bank is 1: the vegetation type tall fescue is provided with a reinforced three-dimensional geonet pad, the length of a telescopic plate 13 of a water tank 1 is 500mm, the height of a liftable water level baffle 4 is 200mm, the model test method is as follows, and the detailed scheme and equipment operation of other test working conditions are shown in the following table 2.
The specific steps of this set of experiments included:
s1, paving filling soil in a side plate of a river bank according to construction requirements, covering a three-dimensional geotechnical reinforcement mesh pad, backfilling a soil sample above the three-dimensional geotechnical reinforcement mesh pad, planting tall fescue, periodically applying nutrient solution, and starting an ecological slope protection river bank scouring test when vegetation grows to a proper height;
s2, adjusting a telescopic plate 13 at the bottom of the water tank 1 to be 500mm in telescopic length, and then fixing the telescopic plate with a fixing device to form a whole with the bottom plate of the raw water tank 1;
s3, adjusting a supporting base device 2 arranged at the bottom of the water tank 1 to generate a height difference in front and at the back of the water tank 1, wherein the water tank 1 forms an inclination of 15 degrees;
s4, adjusting a movable support rod behind a side plate of the river bank to enable the gradient coefficient of the side plate to be 1:1;
s5, unfolding and fixing two side plates of the telescopic plate 13 of the water tank 1, fixedly installing the water level baffle 4 in concave clamping grooves 16 of the two side plates, and adjusting the rising height to be 200mm;
s6, measuring the flow velocity of water flow by using a flow velocity monitor, firstly performing flushing with the flow velocity of V1, and continuously flushing for 30min in each test;
s7, shooting the loss condition of filling soil in a side plate of the river levee and the exposure condition of the three-dimensional geotechnical net pad by using a high-speed camera in the test process, taking a muddy water sample of about 500ml every 1min for determining the sand content of the slope surface flow, accurately measuring the volume of the muddy water sample by using a measuring cylinder, weighing the muddy water sample by using an electronic balance, and finally converting the sand content of each sample by using a displacement method; the width of the water surface of the slope surface is measured in the scouring process;
and S8, various monitoring data indexes in other different test schemes are contrasted and analyzed, so that the anti-scouring capacity and the water and soil retention capacity of the river bank side plate under different vegetation types, different water tank 1 gradients, different gradient ratios, different water tank 1 lengths, different water flow speeds and different water flow depths are disclosed, and reference is provided for engineering prevention and control.
TABLE 1 water flow scouring ecological river bank model indoor model test variation factor scheme
TABLE 2 indoor model test scheme for waterflow scouring ecological river levee model
Further, the test also includes the following steps:
(1) The experiment simulates the hydraulic characteristics and the erosion characteristics of the soil slope under the action of the three-dimensional geonet pad protection slope, and in order to restore the outdoor engineering practice to the maximum extent, before the three-dimensional geonet pad is laid, soil with the thickness of about 8cm is filled at the bottom of the water tank 1, and the same soil thickness and slope level are ensured through a level gauge and a leveling rod. Filling soil is carried out in a mode of manual layered filling, layered tamping and slope superfilling; the filling soil in the side slope of the water tank 1 is controlled by filling soil with the same weight in the same surface area, and the filling soil weight can be calculated by the volume and the density and the compactness under the corresponding water content.
(2) Before the test, after the river bank side plates are filled with planting soil, two earthwork net pads are paved on four river bank side plates respectively, tall fescue is planted on the four river bank side plates, tall fescue grass is planted on the two soilless earthwork net pads, then the movable lateral support behind the river bank side plates is adjusted, the river bank gradient is 1:1, and the length of the test water tank 1 is 2500mm.
(3) And (3) regularly applying nutrient solution to the turf, and starting a water tank 1 to scour the three-dimensional net cushion ecological slope protection river bank after the grass seeds grow to a certain length. The flow rate of the water flow is measured by using a flow rate monitor, the flushing with the water flow rate of V1 is firstly carried out, and the flushing lasts for 30min in each test. In order to determine the sand content of the slope surface flow, about 500ml of muddy water sample is taken every 1min, the volume of the muddy water sample is accurately measured by using a measuring cylinder, the mass of the muddy water sample is weighed by using an electronic balance, and finally, the sand content of each sample is converted by using a displacement method. The width of the water surface of the slope and the exposure condition of the three-dimensional geonet pad are measured in the scouring process, and after scouring is finished, the following data are measured:
determination of sand content and erosion
In the test rainfall process, collecting runoff samples every 2min, weighing the runoff samples and analyzing the change of soil erosion amount; meanwhile, 500ml of muddy water samples are taken every minute, and the content of the silt is measured by a pycnometer method after the test is finished, so that the change of the sand content in the runoff is analyzed.
Depth of slope surface water
The slope flowing water is not negligible in the research of the slope flowing water as the basic hydraulic characteristic. Because the depth of the water of the slope surface flow is large and is greatly influenced by the sugar rate of the contact surface, at present, in various tests about the thin layer water flow, the depth of the water of the slope surface flow cannot be directly measured under other test conditions except a fixed bed resistance test. In the fixed bed hydraulics test, a calculation formula of the thin layer leveling average water depth in the test can be obtained according to an empirical formula:
h＝q m j n Δ 1/6 /A (1)
in the formula, Δ: bed surface roughness, mm;
q: single wide flow, m 3 /(m·s)；
A: cross-sectional area of flow, m 2 ；
J: the slope drop is the value sin theta, and theta is the slope gradient of the side slope;
m, n: parameters, obtained by regression statistics.
Reynolds number
The flow regime of the slope flow is divided into laminar flow, turbulent flow and transitional flow according to the Reynolds number. When the flow state is laminar flow, the fluid flows in layers without mixing, and the mass points of the fluid move smoothly and linearly along the solid surface which is contacted with the bottom surface of the fluid and approximately along the parallel direction. The motion trail of the fluid micro-element has no large-range irregular pulsation, and only the energy generated by the thermal motion of the fluid molecules is exchanged between adjacent layers. When the flow state is turbulent flow, the flow velocity of the fluid is generally high, a plurality of process accidents exist in the flow field, and the flow line is hardly recognizable. In the elementary flow, the fluid microelements move disorderly and are mixed with each other. The loss of fluid energy is mainly caused by the additional shear stress created by the turbulence. According to the judgment standard of general open channel flow, the slope surface flow can be regarded as a two-dimensional open channel, and the two-dimensional Reynolds number discrimination method is adopted in the research of the test: when Re is less than 500, the flow state of the slope flow is laminar flow; when Re is more than 500, the flow state of the slope flow is turbulent flow; when Re =500 or so, the flow regime is transition flow.
For pressureless flow, the Reynolds number can be calculated as follows.
Re＝uR/v (2)
R＝A/χ (3)
In the formula, u: average flow velocity of slope surface flow, m/s
V: coefficient of kinematic viscosity, cm 2 /s
R: hydraulic radius, m
A: cross-sectional area of flow, m 2
χ: wet perimeter, perimeter of the portion of the solid boundary in contact with the fluid, m.
In the analysis process of the slope flow, the water depth of the slope flow is usually used to replace the hydraulic radius, which is convenient for developing make internal disorder or usurp due to the fact that the water depth is deep and shallow. When the flow state of the fluid is different, factors influencing the resistance and reasons for generating the resistance are greatly different, so the flow state needs to be judged before the flow resistance characteristic of the slope is analyzed.
The Darcy-Weisbach formula is a theoretical formula, and although the relational expression of the resistance coefficient lambda and the absolute roughness delta is obtained through a correlation test, the Reynolds number Re, the absolute roughness delta and other parameters influencing the resistance coefficient are considered in the Colebrook-White formula (namely the relational expression of the resistance coefficient lambda and the absolute roughness delta) in the comprehensive value of the resistance coefficient lambda. Most of the researchers make internal disorder or usurp thought the results of the computational analysis of the Darcy-Weisbach equation to be near practical, so the Darcy-Weisbach equation was used herein for the calculation of the drag coefficient.
λ＝8gRJ/u 2 (5)
In the formula, g: acceleration of gravity, N/kg;
r is hydraulic radius m;
j: sin θ, θ is slope
u: flow velocity of slope surface flow, m/s.
Abrahams research shows that the Darcy-Weisbach resistance coefficient is more suitable for representing the resistance characteristics of the slope surface, and in addition, the expression form of the resistance coefficient has definite physical concept and harmonious dimension, so the Darcy-Weisbach formula is adopted for the analysis and calculation of the resistance coefficient in the paper.
The invention adopts four water flow speeds V1, V2, V3 and V4; two turf and 1:1, 1:2 two bank slopes, for a total of 32 trials. And respectively analyzing the water and soil loss condition of the surface soil body by using a water quality analysis system, and measuring the change rule of the erosion ditch, the pore water pressure of the soil body at the net pad, the shear strength of the soil layer of the plant net pad and the like by using a high-speed camera and a measuring tool. And (4) carrying out comparative analysis on the erosion characteristics of the aged natural turf and the turf protected by the net mat under different water scouring. Meanwhile, the test device can also be provided with different lengths of the water tanks 1 so as to simulate different lengths of natural river channels to explore the influence on the erosion of the river channel side slopes, and the telescopic range is 2500-4000mm.
While the embodiments of the invention have been described in detail in connection with the accompanying drawings, it is not intended to limit the scope of the invention. Various modifications and changes may be made by those skilled in the art without inventive work within the scope of the appended claims.
Claims (6)
1. The utility model provides a rivers erode ecological river bank indoor model test platform device which characterized in that: comprises a water tank with two open ends; both ends of the bottom of the water tank are provided with a liftable supporting base device; the supporting base is fixedly connected with a sliding plate for adjusting the gradient of the water tank;
a water level baffle plate for adjusting the water level in the water tank is installed at an opening at the front end of the water tank, a high-pressure water tank equipped with a flow rate meter is arranged at the upper part of the tail end of the water tank, and a water tap connecting water pipe communicated with the high-pressure water tank extends downwards to the bottom of the water tank;
at least two boxes for filling soil and net mats are arranged in the water tank at intervals; the box is arranged in parallel with the side plate of the water tank, a movable lateral support frame is arranged on the back of the box, a first directional pulley with a pinch plate brake is connected below the lateral support frame, and the first directional pulley is connected with a directional slide rail in a sliding manner and used for simulating different river bank slopes on two sides of a river channel;
a circular sliding rail is arranged at the lower part of the water tank, and the circular sliding rail is in sliding fit with a second directional pulley arranged on the telescopic plate and used for realizing the telescopic of the telescopic plate; both sides of the expansion plate are respectively movably connected with the outer side plate;
hinges are arranged at four corners of the edge of the telescopic plate;
and concave clamping grooves for mounting the water level baffle are formed in the inner sides of the end parts of the outer side plates of the water tank side plate and the telescopic plate.
2. The waterflow-flushing ecological river bank indoor model test platform device as claimed in claim 1, wherein: the basin is top and both ends open-ended rectangle box body, and the size of rectangle box body is length 2500mm, and wide 600mm, height 300mm.
3. The waterflow-flushing ecological river bank indoor model test platform device as claimed in claim 1, wherein: the length of the expansion plate is 1500mm, and the width of the expansion plate is 600mm.
4. A method for testing the waterflow flushing ecological river bank indoor model test platform device according to any one of claims 1 to 3, which comprises the following steps:
s1, laying filling soil in a side plate of a box according to construction requirements, covering a three-dimensional geotechnical reinforcement mesh pad, backfilling a soil sample above the three-dimensional geotechnical reinforcement mesh pad, planting tall fescue, periodically applying nutrient solution, and starting a water flow scouring test for the ecological slope protection river bank of the three-dimensional mesh pad after vegetation grows to a preset height;
s2, adjusting a telescopic plate at the bottom of the water tank, controlling the telescopic length to be 500mm, fixing the position of the telescopic plate and forming a whole with the bottom plate of the water tank;
s3, adjusting the heights of the two ends of the water tank by adjusting the two supporting base devices until the height difference of the two ends of the water tank reaches a preset value, and forming a preset inclined slope on the water tank;
s4, adjusting a movable lateral support frame at the back of the side plate of the box to enable the gradient coefficient of the side plate of the box to reach a preset ratio;
s5, unfolding and fixing the two outer side plates of the water tank expansion plate, fixedly installing a liftable water level baffle in the concave clamping grooves of the two side plates, and adjusting the lifting height to be a preset value;
s6, the flow rate of water flow is measured in real time by a flow rate monitor, washing with the water flow rate V1 is carried out, and washing lasts for 30min in each test;
s7, simultaneously, shooting the loss of the filling soil in the side plates of the box and the exposure condition of the three-dimensional geonet pad in real time by adopting a high-speed camera;
determining the sand content of the slope surface flow, taking a muddy water sample of about 500ml every 1min, accurately measuring the volume of the muddy water sample by using a measuring cylinder, weighing the mass of the muddy water sample by using an electronic balance, and finally converting the sand content of each sample by using a displacement method;
measuring the width of the water surface of the slope;
and S8, comparing and analyzing various monitoring data indexes in other groups of different test schemes.
5. The test method of the indoor model test platform device for the waterflow-flushing ecological river levee is characterized in that S1, filling soil is laid in the side plates of the box according to construction requirements, the three-dimensional geotechnical reinforcement mesh pad is covered, soil samples are backfilled above the three-dimensional geotechnical reinforcement mesh pad, tall fescue is planted, nutrient solution is periodically applied, and when vegetation grows to a preset height, a waterflow-flushing test of the ecological slope protection river levee with the three-dimensional mesh pad is started, and the test method comprises the following steps:
before the three-dimensional geonet pad is laid, filling soil with the thickness of 8cm at the bottom of the water tank, and ensuring the same soil thickness and the level of a slope surface through a level gauge and a leveling rod; filling soil is tamped by manual layered filling and layering, and a mode of superfilling and cutting slope is adopted; the filling soil in the water tank side slope is controlled by filling soil with the same weight in the same surface area, and the filling soil weight is calculated according to the volume, the density under the corresponding water content and the compaction degree.
6. The test method of the waterflow-flushing ecological river bank indoor model test platform device as claimed in claim 5, wherein four water flow velocities V1, V2, V3 and V4 are adopted; two kinds of turf and 1:1, 1:2 two river bank slopes, 32 groups of tests are carried out;
in the test, water quality analysis is respectively adopted to analyze the water and soil loss condition of the surface soil body, and a high-speed camera and a measuring tool are adopted to measure the change rule of the erosion ditch, the pore water pressure of the soil body at the net pad and the shear strength of the plant net pad soil layer; the erosion characteristics of the aged natural turf and the turf protected by the net mat under different water flow scouring are compared and analyzed; and the influence on the side slope scouring of the river channel is explored by simulating different lengths of the natural river channel in different lengths of the water channels, and the telescopic range is 2500-4000mm.
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