Experimental device for simulating motion process of undercurrent with water flow

Abstract

The utility model discloses an experimental device for simulating the motion process of water flow in an undercurrent zone, and relates to the field of undercurrent zone simulation experiments, the experimental device comprises a transparent experimental box, a water-stop sheet, a pore water sampler, a pressure measuring piece and a shooting device, the transparent experimental box comprises a flowing area and a containing area which are sequentially arranged and communicated in the vertical direction, the containing area is provided with a sand groove, a first water inlet groove, a second water inlet groove and a drainage groove, the first water inlet groove is formed in the bottom of the sand groove and communicated with the sand groove, the second water inlet groove and the drainage groove are formed in the two sides of the sand groove in the first direction, and a plurality of tracing holes and a plurality of sampling holes are formed in one side wall of the sand groove in the second direction; the tracing holes are close to the second water inlet groove relative to the sampling holes, and the multiple tracing holes and the multiple sampling holes are distributed at intervals in the first direction; the water-stop sheet is located between the tracing hole and the sampling hole, the upper end abuts against the upper side wall of the transparent experiment box, and the lower end is located in the sand tank; and qualitatively and quantitatively describing an interactive mixing process of surface water and underground water, a spatial distribution relation and flow field characteristics.

Description

Technical Field

[0001] The utility model relates to the technical field of subsurface flow zone simulation experiments, and particularly relates to an experimental device for simulating the water flow movement process in the subsurface flow zone. Background Art

[0002] The subsurface flow zone is a water-saturated sediment layer located at the top layer of the riverbed and the bottom of the river, extending to both sides of the riverbank, and is the connection link between surface water and groundwater. The water flow movement in the subsurface flow zone is the key driving force for the material and energy exchange between surface water and groundwater bodies and the occurrence of biogeochemical reactions. Under the driving of the pressure or hydraulic head gradient between the river-sediment or river-aquifer, the area where surface water enters the pore water of the riverbed for convective exchange is called the surface water-groundwater interaction zone, and the surface water content is 90-100%; after the surface water enters the riverbed through subsurface flow exchange and gradually mixes with the surrounding groundwater, the area where the surface water content decreases to 10-90% is called the surface water-groundwater mixing zone. Compared with the interaction zone, the range of the mixing zone is narrower, and determining the position and range of the mixing zone is a research difficulty. Current research mostly takes the interaction zone and the mixing zone as a whole for research, while ignoring the differences between the two. Content of the Utility Model

[0003] The main purpose of the utility model is to propose an experimental device for simulating the water flow movement process in the subsurface flow zone, which can simulate and visualize the interaction and mixing process of surface water and groundwater, and can qualitatively and quantitatively describe the spatial distribution relationship and flow field characteristics of the interaction zone and the mixing zone.

[0004] To achieve the above purpose, an experimental device for simulating the water flow movement process in the subsurface flow zone proposed by the utility model includes:

[0005] A transparent experimental box, including a flow area and a placement area arranged and communicated in sequence along the up-down direction. A sand tank, a first water inlet tank, a second water inlet tank and a drainage tank are arranged in the placement area. The sand tank is used for placing sediments. The first water inlet tank is arranged at the bottom of the sand tank and is used for placing a groundwater simulation liquid and is communicated with the sand tank. The second water inlet tank and the drainage tank are arranged on both sides of the sand tank in the first direction. The second water inlet tank is used for placing a surface water simulation liquid containing inert ions, and the surface water simulation liquid in the second water inlet tank can flow into the sand tank through the flow area. The drainage tank is used for placing the liquid flowing out from the sand tank to the flow area. A plurality of tracer holes and a plurality of sampling holes are opened on one side wall of the sand tank in the second direction. The tracer holes are arranged closer to the second water inlet tank than the sampling holes and are used for injecting a tracer into the sand tank. The plurality of tracer holes and the plurality of sampling holes are respectively arranged at intervals along the first direction;

[0006] A water barrier plate is disposed inside the transparent experimental chamber and is located between the tracer hole and the sampling hole. The water barrier plate extends in the vertical direction. The upper end of the water barrier plate is located in the flow region and abuts against the upper side wall of the transparent experimental chamber. The lower end of the water barrier plate is located in the sand tank.

[0007] A pore water sampler is used to collect pore water in the sediment through the sampling hole for detecting the concentration of inert ions in the pore water.

[0008] A piezometric component is used to measure the water pressure at at least one preset position in the sand tank; and,

[0009] A photographing device is used to photograph the migration trajectory of the tracer in the transparent experimental chamber.

[0010] Wherein, any two of the first direction, the second direction and the vertical direction are perpendicular to each other.

[0011] Further, the experimental device for simulating the water flow movement process in the phreatic zone further includes a first overflow device communicated with the second water inlet tank and a second overflow device communicated with the drainage tank. The heights of the first overflow device and the second overflow device are adjustable, so that the head difference between the liquid levels on both sides of the water barrier plate in the first direction is adjustable.

[0012] Further, the head difference between the liquid level on the side of the water barrier plate close to the second water inlet tank and the liquid level on the side close to the drainage tank in the first direction is greater than 0 and less than or equal to 5 cm.

[0013] Further, the head difference between the liquid level on the side of the water barrier plate close to the second water inlet tank and the liquid level on the side close to the drainage tank in the first direction is 1.8 cm.

[0014] Further, at least one piezometric hole is formed in a side wall of the sand tank in the second direction;

[0015] The piezometric component is a piezometric tube, and the piezometric tube is connected to the piezometric hole through a hose.

[0016] Further, there are a plurality of piezometric holes, and the distance between any two adjacent piezometric holes in the vertical direction is set to 8.0 cm.

[0017] Further, there are a plurality of piezometric holes, and the distance between any two adjacent piezometric holes in the first direction is set to 8.0 cm.

[0018] Furthermore, there are multiple pressure measuring holes, which are arranged in an array. The distance between the lowermost pressure measuring hole among the multiple pressure measuring holes and the bottom wall of the sand tank is set to 22 cm, and the distance between the pressure measuring hole among the multiple pressure measuring holes that is close to the second water inlet tank in the first direction and the second water inlet tank is set to 9.0 cm.

[0019] Furthermore, the distance between any two adjacent sampling holes among the multiple sampling holes is set to 3.0 cm, and the distance between the sampling hole among the multiple sampling holes that is close to the second water inlet tank and the second water inlet tank is set to 22.5 cm;

[0020] The interface between the sediment and the liquid in the sand tank and the sampling hole have a distance in the up and down direction that is greater than or equal to 2.0 cm and less than or equal to 5.0 cm.

[0021] Furthermore, the distance between any two adjacent tracer holes among the multiple tracer holes is set to 5.0 cm, and the distance between the tracer hole among the multiple tracer holes that is close to the second water inlet tank and the second water inlet tank is set to 5.0 cm; and / or,

[0022] The interface between the sediment and the liquid in the sand tank and the tracer hole have a distance in the up and down direction that is greater than or equal to 2.0 cm and less than or equal to 5.0 cm.

[0023] In the technical solution of the present utility model, sediment is placed in the sand tank, the surface water simulation liquid in the second water inlet tank flows into the sand tank through the flow area, bypasses the lower end of the water isolation plate, and flows upward to the flow area, forming a surface water seepage path that first goes down and then goes up. The groundwater simulation liquid in the first water inlet tank is injected into the sand tank, forming an upward groundwater flow path, and convectively mixes with the surface water simulation liquid between the sediments in the sand tank, and then flows through the flow area to the drainage tank in the transparent experimental box. Moreover, a tracer is injected into the sand tank, and the flow path of the surface water simulation liquid can be determined by observing the flow path of the tracer through the photographing device, realizing the visualization of the interaction and mixing process of surface water and groundwater in the hyporheic zone; furthermore, according to the pictures obtained by photographing and recording with the photographing device, the distance between two adjacent sampling holes, the concentration of inert ions in the surface water simulation liquid sampled by the pore water sampler, and the water pressure measured by the pressure measuring member, the spatial distribution relationship and flow field characteristics of the interaction zone and the mixing zone can be qualitatively and quantitatively described at the laboratory scale, and the relative importance of convection and diffusion in the sand tank flow field can be obtained. The experimental device provided by the present utility model has a simple structure, ingenious design and strong practicability. Description of the Drawings

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0025] Figure 1 It is a schematic structural diagram of an embodiment of an experimental device for simulating the water flow movement process in the subsurface flow zone provided by the present invention;

[0026] Figure 2 It is a flowchart of an experimental method for simulating the water flow movement process in the subsurface flow zone provided by the present invention;

[0027] Figure 3 For Figure 2 It is a flowchart of step S5 in

[0028] Figure 4 It is a tracer image of the surface water seepage path during the experiment;

[0029] Figure 5 It is an analysis diagram of the mixing zone width of the surface water simulation liquid and the groundwater simulation liquid during the experiment;

[0030] Figure 6 It is a spatial distribution diagram of the water head in the sand tank during the experiment;

[0031] Figure 7 It is a schematic diagram of the interactive mixing spatial distribution relationship between the surface water simulation liquid and the groundwater simulation liquid during the experiment.

[0032] Explanation of the reference numerals in the drawings:

[0033]

[0034] The realization, functional features, and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the drawings. Specific embodiments

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0036] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present utility model, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a certain specific posture (as shown in the attached drawings). If the specific posture changes, the directional indications will also change accordingly.

[0037] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present utility model, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and / or" appearing throughout the text includes three parallel scenarios. Taking "A and / or B" as an example, it includes scenario A, or scenario B, or the scenario where both A and B are satisfied simultaneously. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0038] The hyporheic zone is a water-saturated sediment layer located at the top layer of the riverbed and the bottom of the river, extending to both sides of the riverbank, and is the link between surface water and groundwater. The flow movement in the hyporheic zone is the key driving force for the material and energy exchange and biogeochemical reactions between surface water and groundwater bodies. The area where surface water enters the pore water of the riverbed for convective exchange under the drive of the pressure or hydraulic head gradient between the river-sediment or river-aquifer is called the surface water-groundwater interaction zone, where the surface water content is 90 - 100%; after the surface water enters the riverbed through hyporheic exchange and gradually mixes with the surrounding groundwater, the area where the surface water content decreases to 10 - 90% is called the surface water-groundwater mixing zone. Compared with the interaction zone, the range of the mixing zone is narrower, and determining the position and range of the mixing zone is a research difficulty. Current research mostly treats the interaction zone and the mixing zone as a whole, ignoring the differences between the two.

[0039] In view of this, the present utility model provides an experimental device 100 for simulating the flow movement process in the hyporheic zone. Figure 1 This is an embodiment of the experimental device 100 for simulating the flow movement process in the hyporheic zone provided by the present utility model.

[0040] Please refer to Figure 1, the experimental device 100 for simulating the water flow movement process in the subsurface flow zone includes a transparent experimental box 1, a water isolation plate 2, a pore water sampler, a piezometric component, and a photographing device. The transparent experimental box 1 includes a flow zone 12 and a placement zone 11 that are sequentially arranged and communicated in the vertical direction. The placement zone 11 is provided with a sand tank 111, a first water inlet tank 112, a second water inlet tank 113, and a drainage tank 114. The sand tank 111 is used to hold sediments. The first water inlet tank 112 is arranged at the bottom of the sand tank 111 for holding a groundwater simulation liquid and is communicated with the sand tank 111. The second water inlet tank 113 and the drainage tank 114 are arranged on both sides of the sand tank 111 in the first direction. The second water inlet tank 113 is used to hold a surface water simulation liquid containing inert ions, and the surface water simulation liquid in the second water inlet tank 113 can flow into the sand tank 111 through the flow zone 12. The drainage tank 114 is used to hold the liquid flowing out of the sand tank into the flow zone. A plurality of tracer holes 1111 and a plurality of sampling holes 1112 are formed in one side wall of the sand tank 111 in the second direction. The tracer holes 1111 are arranged closer to the second water inlet tank 113 than the sampling holes 1112 and are used to inject a tracer into the sand tank 111. The plurality of tracer holes 1111 and the plurality of sampling holes 1112 are respectively spaced apart along the first direction; the water isolation plate 2 is arranged in the transparent experimental box 1 and is located between the tracer holes 1111 and the sampling holes 1112. The water isolation plate 2 extends in the vertical direction. The upper end of the water isolation plate 2 is located in the flow zone 12 and abuts against the upper side wall of the transparent experimental box 1. The lower end of the water isolation plate 2 is located in the sand tank 111; the pore water sampler is used to collect the pore water in the sediments through the sampling holes 1112 for detecting the concentration of inert ions in the pore water; the piezometric component is used to measure the water pressure at at least one preset position in the sand tank 111; the photographing device is used to photograph the migration trajectory of the tracer in the transparent experimental box 1; wherein, any two of the first direction, the second direction, and the vertical direction are perpendicular to each other.

[0041] In the technical solution of the present utility model, sediments are placed in the sand tank 111. The surface water simulation liquid in the second water inlet tank 113 flows into the sand tank 111 through the flow area 12, bypasses the lower end of the water isolation plate 2, and flows upward to the flow area 12, forming a surface water seepage path that first goes down and then up. The groundwater simulation liquid in the first water inlet tank 112 is injected into the sand tank 111, forming an upward groundwater flow path, and convectively mixes with the surface water simulation liquid between the sediments in the sand tank 111, and then flows through the flow area 12 to the drainage tank 114 in the transparent experimental box 1. Moreover, a tracer is injected into the sand tank 111, and the flow path of the surface water simulation liquid can be determined by observing the flow path of the tracer through the photographing device, realizing the visualization of the interaction and mixing process of surface water and groundwater in the hyporheic zone. Further, according to the pictures obtained by photographing and recording with the photographing device, the distance between two adjacent sampling holes 1112, the concentration of inert ions in the surface water simulation liquid sampled by the pore water sampler, and the water pressure measured by the piezometric component, the spatial distribution relationship and flow field characteristics of the interaction zone and the mixing zone can be qualitatively and quantitatively described at the laboratory scale, and the relative importance of convection and diffusion in the flow field of the sand tank 111 can be obtained. The experimental device provided by the present utility model has a simple structure, ingenious design and strong practicability.

[0042] It should be noted that in the present utility model, the sediments include quartz sand; further, the sediments also include gravel. Specifically, during the experiment, quartz sand is first laid in the sand tank 111, and then gravel is laid on the quartz sand to prevent the water flow from flushing and disturbing the surface of the sand tank 111 when the groundwater simulation liquid is injected into the sand tank 111 through the first water inlet tank 112. At the same time, in the present utility model, the particle size and lithology of the sediments are not limited, and the characteristics of complex riverbed sediments can be simulated by changing the particle size and lithology of the sediments.

[0043] It should also be noted that in the present utility model, the photographing device includes a camera.

[0044] Further, please refer to Figure 1, the experimental device 100 for simulating the water flow movement process in the subsurface flow zone further includes a first overflow device 3 communicating with the second water inlet tank 113 and a second overflow device 4 communicating with the drainage tank 114. The heights of the first overflow device 3 and the second overflow device 4 are adjustable, so as to make the water head difference between the liquid levels on both sides of the water isolation plate 2 in the first direction adjustable. Thus, the water head of the surface water simulation liquid in the second water inlet tank 113 can be adjusted by adjusting the height of the first overflow device 3, and the water head of the liquid in the drainage tank 114 can be adjusted by adjusting the height of the second overflow device 4, thereby adjusting the water head difference between the liquid levels on both sides of the water isolation plate 2 in the first direction, so as to simulate different hydrodynamic conditions.

[0045] It should be noted that in the present utility model, both the first overflow device 3 and the second overflow device 4 include a water tank and a siphon tube.

[0046] Furthermore, the water head difference between the liquid level on the side of the water isolation plate 2 close to the second water inlet tank 113 and the liquid level on the side close to the drainage tank 114 in the first direction is greater than 0 and less than or equal to 5 cm.

[0047] Furthermore, in an embodiment of the present utility model, the water head difference between the liquid level on the side of the water isolation plate 2 close to the second water inlet tank 113 and the liquid level on the side close to the drainage tank 114 in the first direction is 1.8 cm.

[0048] Specifically, in an embodiment of the present utility model, a plurality of water inlet holes are formed in the bottom wall of the sand tank 111 and communicate with the first water inlet tank 112. The first water inlet tank 112 is connected to a water supply tank containing groundwater simulation liquid through a water inlet pipe, and a peristaltic pump is provided on the water inlet pipe. Thus, the groundwater simulation liquid in the water supply tank is pumped into the first water inlet tank 112 through the peristaltic pump, and then flows into the sand tank 111 through the water inlet holes. At the same time, the flow rate of the groundwater simulation liquid can be controlled by the peristaltic pump, so as to simulate different hydrodynamic conditions.

[0049] More specifically, a wire mesh is provided on the side of the bottom wall of the sand tank 111 away from the first water inlet tank 112 to prevent the sediment in the sand tank 111 from flowing into the first water inlet tank 112.

[0050] Specifically, please refer to Figure 1 , at least one piezometric hole 1113 is formed in a side wall of the sand tank 111 in the second direction; the piezometric component is a piezometric tube, and the piezometric tube is connected to the piezometric hole 1113 through a flexible hose. Thus, the pressure head distribution in the sand tank 111 can be measured simply and quickly through the piezometric tube.

[0051] Further, a plurality of pressure measurement holes 1113 are provided, and the distance between any two adjacent pressure measurement holes 1113 in the vertical direction is set to 8.0 cm.

[0052] Specifically, a plurality of pressure measurement holes 1113 are provided, and the distance between any two adjacent pressure measurement holes 1113 in the first direction is set to 8.0 cm.

[0053] Specifically, a plurality of pressure measurement holes 1113 are provided and are arranged in an array. The distance between the lowermost pressure measurement hole 1113 and the bottom wall of the sand tank 111 is set to 22 cm, and the distance between the pressure measurement hole close to the second water inlet tank 113 in the first direction among the plurality of pressure measurement holes 1113 and the second water inlet tank 113 is set to 9.0 cm.

[0054] It should be noted that in the present utility model, the above three technical features can be set alternatively or simultaneously. Specifically, in an embodiment of the present utility model, the above three technical features are set simultaneously, that is, a plurality of pressure measurement holes 1113 are provided and are arranged in an array. The distance between any two adjacent pressure measurement holes 1113 in the vertical direction and the distance in the first direction are both set to 8.0 cm. The distance between the lowermost pressure measurement hole 1113 and the bottom wall of the sand tank 111 is set to 22 cm, and the distance between the pressure measurement hole close to the second water inlet tank 113 in the first direction among the plurality of pressure measurement holes 1113 and the second water inlet tank 113 is set to 9.0 cm.

[0055] More specifically, please refer to Figure 1 , in an embodiment of the present utility model, 25 pressure measurement holes 1113 are arranged in an array on the side wall of the sand tank 111.

[0056] Specifically, the diameter of the pressure measurement hole 1113 is greater than or equal to 1 cm and less than or equal to 2 cm; to prevent the side wall of the sand tank 111 from cracking during hole opening due to too large a diameter of the pressure measurement hole. More specifically, in an embodiment of the present utility model, the diameter of the pressure measurement hole 1113 is 1 cm.

[0057] Specifically, the distance between any two adjacent sampling holes 1112 is set to 3.0 cm, and the distance between the sampling hole close to the second water inlet tank 113 among the plurality of sampling holes 1112 and the second water inlet tank 113 is set to 22.5 cm. To prevent the distance between two adjacent sampling holes 1112 from being too large to monitor the position of the mixing zone, and also to prevent the distance from being too small to affect the flow field during sampling.

[0058] Specifically, the distance between the interface 200 of the sediment and the liquid in the sand tank 111 and the sampling hole 1112 in the vertical direction is greater than or equal to 2.0 cm and less than or equal to 5.0 cm.

[0059] It should be noted that in the present utility model, the above two technical features can be set alternatively or simultaneously. Specifically, in an embodiment of the present utility model, the above two technical features are set simultaneously, that is, the distance between any two adjacent sampling holes 1112 among the multiple sampling holes 1112 is set to 3.0 cm, and the distance between the sampling hole 1112 close to the second water inlet tank 113 among the multiple sampling holes 1112 and the second water inlet tank 113 is set to 22.5 cm, and the distance between the interface 200 of the sediment and the liquid in the sand tank 111 and the sampling hole 1112 is set to 5.0 cm.

[0060] More specifically, in an embodiment of the present utility model, the distance between the interface 200 of the sediment and the liquid in the sand tank 111 and the sampling hole 1112 in the vertical direction is set to 5.0 cm.

[0061] Specifically, the distance between any two adjacent tracer holes 1111 among the multiple tracer holes 1111 is greater than or equal to 3.0 cm and less than or equal to 5.0 cm, and the distance between the tracer hole 1111 close to the second water inlet tank 113 among the multiple tracer holes 1111 and the second water inlet tank 113 is set to 5.0 cm.

[0062] Specifically, the distance between the interface 200 of the sediment and the liquid in the sand tank 111 and the tracer hole 1111 in the vertical direction is greater than or equal to 2.0 cm and less than or equal to 5.0 cm.

[0063] It should be noted that in the present utility model, the above two technical features can be set alternatively or simultaneously. Specifically, in an embodiment of the present utility model, the above two technical features are set simultaneously, that is, there are multiple tracer holes 1111, and the multiple tracer holes 1111 are distributed at intervals along the first direction. The distance between any two adjacent tracer holes 1111 among the multiple tracer holes 1111 is set to 5.0 cm, and the distance between the tracer hole 1111 close to the second water inlet tank 113 among the multiple tracer holes 1111 and the second water inlet tank 113 is greater than or equal to 3.0 cm and less than or equal to 5.0 cm, and the distance between the interface 200 of the sediment and the liquid in the sand tank 111 and the tracer hole 1111 is set to 5.0 cm.

[0064] More specifically, in an embodiment of the present utility model, the distance between any two adjacent tracer holes 1111 among the multiple tracer holes 1111 is set to 5.0 cm. The distance between the tracer hole 1111 closest to the second water inlet tank 113 among the multiple tracer holes 1111 and the second water inlet tank 113 is 5.0 cm. The distance between the interface 200 between the sediment and the liquid in the sand tank 111 and the tracer hole 1111 in the vertical direction is set to 5.0 cm.

[0065] Specifically, in the present utility model, the surface water simulation liquid containing inert ions may be a surface water simulation liquid containing bromide ions or chloride ions, etc., such as a surface water simulation liquid containing sodium bromide, potassium bromide, potassium chloride or sodium chloride.

[0066] The present utility model also provides an experimental method for simulating the water flow movement process in the hyporheic zone, which is applicable to the experimental device for simulating the water flow movement process in the hyporheic zone described above.

[0067] Please refer to Figure 2 , the experimental method for simulating the water flow movement process in the hyporheic zone includes the following steps:

[0068] Step S1: Put sediment into the sand tank in the transparent experimental box, and store and transport the groundwater simulation liquid through the first water inlet tank into the sand tank to saturate the sediment.

[0069] In this step, the sediment includes quartz sand and gravel. Specifically, first fill the sand tank with quartz sand in layers, and saturate each layer after it is laid until multiple layers of quartz sand are filled, and then lay a layer of gravel on the quartz sand.

[0070] It should be noted that when laying each layer of quartz sand, it is necessary to tamp it to make its density uniform and compact the boundary to avoid generating gaps during the filling process and prevent the occurrence of preferential flow when the groundwater simulation liquid is injected, thus affecting the test.

[0071] It should also be noted that in an embodiment of the present utility model, each layer of quartz sand is 5.0 cm high, and multiple layers are filled to 60.0 cm.

[0072] Step S2: After the sediment is saturated, stop injecting the groundwater simulation liquid, and adjust the head difference between the liquid levels on both sides of the water isolation plate in the first direction in the transparent experimental box, so that the surface water simulation liquid containing inert ions in the second water inlet tank in the transparent experimental box flows through the flow area in the transparent experimental box to the sand tank, bypasses the lower end of the water isolation plate, and flows to the drainage tank in the transparent experimental box, forming a surface water seepage path from bottom to top (as shown in Figure 7 a in).

[0073] Specifically, in an embodiment of the present utility model, the water head h1 of the water separation plate close to the second water inlet tank in the first direction is 85.5 cm, and the water head h2 of the water separation plate close to the drainage tank in the first direction is 83.7 cm. Thus, the water head difference is 1.8 cm.

[0074] Step S3: Inject the groundwater simulation liquid into the sand tank through the first water inlet tank to form an upward groundwater flow path (as shown in d), and convectively mix with the surface water simulation liquid between the sediments (as shown in b and c, b is the surface water simulation liquid - groundwater simulation liquid interaction area, and c is the surface water simulation liquid - groundwater simulation liquid mixing area). Figure 7 as shown in Figure 7 b and c, where b is the surface water simulation liquid - groundwater simulation liquid interaction area and c is the surface water simulation liquid - groundwater simulation liquid mixing area).

[0075] Specifically, in an embodiment of the present utility model, a plurality of water inlet holes are opened on the bottom wall of the sand tank and communicated with the first water inlet tank. The first water inlet tank is connected to a water supply tank containing the groundwater simulation liquid through a water inlet pipe, and a peristaltic pump is provided on the water inlet pipe. Thus, the flow state of the groundwater simulation liquid can be controlled through the peristaltic pump. Further, in an embodiment of the present utility model, the injection speed q of the groundwater simulation liquid is controlled to be 9.45 mL / min through the peristaltic pump, so that the groundwater simulation liquid can stably flow into the sand tank.

[0076] Step S4: Inject the tracer into the transparent experimental box through the tracer hole, and observe and record the flow path of the tracer by using a photographing device at different times.

[0077] In this step, the moment when the tracer is injected into the tracer hole is recorded as the 0 moment, and subsequent photographs are taken by using the photographing device at different times, and multiple pictures can be obtained.

[0078] It should be noted that, in an embodiment of the present utility model, there are three tracer holes, and 1 g / L brilliant blue tracer is injected into each tracer hole. The injection time is recorded as the 0 moment, and the photographing device is used to take pictures at multiple times such as the 0.5 moment, the 1 moment, the 1.5 moment, the 2 moment, the 2.5 moment, and the 3 moment.

[0079] It should also be noted that, in this step, an opaque object is used to cover the sand tank and the camera, and a single light source is given, and the flow path of the tracer is observed and recorded by using the photographing device.

[0080] Step S5: Calculate the length of the surface water seepage path and the average flow velocity of the pore water in the sediment according to the recording result of the photographing device and the distance between two adjacent sampling holes among the multiple sampling holes opened on the side wall of the sand tank.

[0081] Further, please refer to Figure 3 , and step S5 specifically includes:

[0082] Step S51: Crop the part of the sand tank in the picture obtained by using the photographing device to obtain a cropped image, and mark the position of the tracer on the cropped image to form marked points (as Figure 4 shown).

[0083] Step S52: Establish a rectangular coordinate system, superimpose the cropped images of the pictures obtained at different times, and connect the marked points to obtain the surface water seepage path.

[0084] In this step, take the lower corner of the sand tank close to the second water inlet tank as the origin, the direction towards the drainage tank in the first direction as the x-axis, and the upward direction as the y-axis to establish the rectangular coordinate system.

[0085] Further, in an embodiment of the present utility model, take y = 10 cm and x = 49 cm as the horizontal and vertical fixed sides of the cropped image, superimpose the cropped images of the pictures obtained at different times, and connect the marked points at different times to obtain a continuous tracer streamline formed by multiple flow paths, that is, the surface water seepage path.

[0086] Step S53: Take the distance between two adjacent sampling holes among the multiple sampling holes as the image scale, and use ImageJ software to statistically determine the length of the surface water seepage path.

[0087] In this step, the sum of the lengths of the surface water seepage paths is the total length of the tracer streamline.

[0088] Further, the calculation formula for the length of the surface water seepage path is:

[0089] L = ∑L i (1)

[0090] In formula (1), L i is the length of each flow path in the tracer streamline, that is, the length between two adjacent marked points, with the unit of cm;

[0091] L is the length of the surface water seepage path, with the unit of cm.

[0092] Step S54: Determine the movement time of the tracer in each flow path of the surface water seepage path according to the shooting interval time of the photographing device, and calculate the flow velocity of the pore water in each flow path and the average flow velocity of the pore water in the surface water seepage path.

[0093] Further, the calculation formula for the flow velocity of the pore water in each flow path is as follows:

[0094]

[0095] In Equation (2), v p i is the flow velocity of the pore water in each flow path, with the unit of cm / h;

[0096] t i is the movement time of the tracer in each flow path, with the unit of h.

[0097] The calculation formula for the average flow velocity of the pore water in the surface water seepage path is as follows:

[0098]

[0099] In Equation (3), v p is the average flow velocity of the pore water in the surface water seepage path, with the unit of cm / h.

[0100] Further, based on the above-mentioned embodiment of "there are three tracer holes, each tracer hole is injected with 1 g / L brilliant blue tracer, and the injection time is recorded as the 0 moment, and the photographing device is used to take pictures at multiple moments such as the 0.5 moment, the 1 moment, the 1.5 moment, the 2 moment, the 2.5 moment, and the 3 moment", as Figure 4 shown, there are three surface water seepage paths, and according to the calculation formula, the lengths of the three surface water seepage paths are 32.59 cm, 47.71 cm, and 66.49 cm in sequence, and the average flow velocities of the pore water in the three surface water seepage paths are 6.29 cm / h, 5.58 cm / h, and 4.45 cm / h respectively.

[0101] Step S6: Use a pore water sampler to sample the pore water through the sampling holes opened on the side wall of the sand tank, and detect the concentration of inert ions in the pore water and the concentration of inert ions in the surface water simulation liquid.

[0102] In this step, connect a Luer lock to the pore water collector, use a syringe to extract the sediment pore water, and use ion chromatography to measure the concentration of inert ions in the pore water and the surface water simulation liquid.

[0103] Step S7: Determine the positions and ranges of the interaction zone and the mixing zone between the groundwater simulation liquid and the surface water simulation liquid according to the concentration of inert ions in the pore water and the concentration of inert ions in the surface water simulation liquid, and calculate the width of the mixing zone.

[0104] In this step, divide the concentration of inert ions in the pore water by the concentration of inert ions in the surface water simulation liquid, and then use the polynomial linear interpolation method to calculate the interface between the surface water and the groundwater interaction and mixing zone, that is, the position of the mixing zone. The calculation formula for the position of the mixing zone is:

[0105] d mix = x(c / c0 = 0.9)(4)

[0106] In formula (4), d mix is the position of the mixing zone, with the unit of cm;

[0107] c is the concentration of inert ions in the pore water, with the unit of mg / L;

[0108] c0 is the concentration of inert ions in the surface water simulation liquid, with the unit of mg / L;

[0109] x is the abscissa of the position where the relative concentration of inert ions is located.

[0110] Furthermore, the calculation formula for the width of the mixing zone is:

[0111] d thickness = x(c / c0 = 0.1) - x(c / c0 = 0.9)(5)

[0112] In formula (5), d thickness is the width of the mixing zone, with the unit of cm.

[0113] Specifically, in an embodiment of the present invention, 9 pore water samplers are provided, and the relative concentrations of inert ions detected by the 9 pore water samplers are shown in Table 1 below:

[0114] Table 1 Statistical table of relative concentrations of inert ions (bromide ions)

[0115] Serial number Relative concentration Serial number Relative concentration 1 0.93 6 0.93 3 0.95 7 0.90 4 0.89 8 0.80 5 0.86 9 0.47

[0116] More specifically, as Figure 5 shown, in an embodiment of the present invention, the position d mix of the mixing zone is 42.0 cm away from the second water inlet tank, and the width d thickness of the mixing zone is 7.62 cm.

[0117] Step S8: Use a piezometric component to measure the water pressure at a preset position in the sand tank, and calculate the sediment diffusion coefficient and the Peclet number according to the average pore water velocity, the surface water seepage path length, and the width of the mixing zone, so as to obtain the relative importance of convection and diffusion in the sand tank flow field.

[0118] In this step, the calculation formula for the diffusion coefficient is:

[0119] D t = d thickness 2 v p / L(6)

[0120] In Equation (6), D t is the diffusion coefficient, with the unit of cm 2 / h.

[0121] The calculation formula for the Peclet number is as follows:

[0122] Pe = v p L / D t (7)

[0123] In Equation (7), P e is the sediment Peclet number.

[0124] More specifically, in an embodiment of the present invention, 25 of the piezometric holes are equidistantly arranged on the side wall of the sand tank at 8 cm × 8 cm, and the piezometric tubes are connected through hoses to measure the distribution of the pressure head in the sand tank. The head space distribution diagram in the sand tank is shown in Figure 6 .

[0125] Based on the above-mentioned embodiment of "There are three surface water seepage paths, and according to the calculation formula, the lengths of the three surface water seepage paths are 32.59 cm, 47.71 cm, and 66.49 cm in sequence, and the average flow velocities of the pore water on the three surface water seepage paths are 6.29 cm / h, 5.58 cm / h, and 4.45 cm / h respectively", calculate according to the longest one of the three surface water seepage paths. The surface water seepage path L is 66.49 cm, the average flow velocity v p is 4.45 cm / h, the diffusion coefficient D t is 3.88 cm 2 / h. Thus, the Peclet number P e is calculated to be 76.14. That is to say, during the interaction and mixing of surface water and groundwater, convection dominates (as shown in Figure 7 ).

[0126] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. An experimental device for simulating the water flow movement process in the hyporheic zone, characterized in that, The experimental device for simulating the water flow movement process in the hyporheic zone includes: A transparent experimental box, including a flow zone and a placement zone that are sequentially arranged and connected in the up-down direction. A sand tank, a first water inlet tank, a second water inlet tank, and a drainage tank are arranged in the placement zone. The sand tank is used to hold sediments. The first water inlet tank is arranged at the bottom of the sand tank and is used to hold the groundwater simulation liquid and is connected to the sand tank. The second water inlet tank and the drainage tank are arranged on both sides of the sand tank in the first direction. The second water inlet tank is used to hold the surface water simulation liquid containing inert ions, and the surface water simulation liquid in the second water inlet tank can flow into the sand tank through the flow zone. The drainage tank is used to hold the liquid flowing out of the sand tank into the flow zone. A plurality of tracer holes and a plurality of sampling holes are opened on one side wall of the sand tank in the second direction. The tracer holes are arranged closer to the second water inlet tank than the sampling holes and are used to inject tracers into the sand tank. The plurality of tracer holes and the plurality of sampling holes are respectively spaced along the first direction; A water isolation plate is arranged in the transparent experimental box and is located between the tracer holes and the sampling holes. The water isolation plate extends along the up-down direction. The upper end of the water isolation plate is located in the flow zone and abuts against the upper side wall of the transparent experimental box. The lower end of the water isolation plate is located in the sand tank; A pore water sampler is used to collect the pore water in the sediments through the sampling holes for detecting the concentration of inert ions in the pore water; A pressure measuring member is used to measure the water pressure at at least one preset position in the sand tank; and, A photographing device is used to photograph the migration trajectory of the tracer in the transparent experimental box; Wherein, any two of the first direction, the second direction, and the up-down direction are perpendicular to each other.

2. The experimental device for simulating the water flow movement process in the subsurface flow zone according to claim 1, characterized in that, The experimental device for simulating the water flow movement process in the hyporheic zone further includes a first overflow device connected to the second water inlet tank and a second overflow device connected to the drainage tank. The heights of the first overflow device and the second overflow device are both adjustable so that the head difference between the liquid levels on both sides of the water isolation plate in the first direction is adjustable.

3. The experimental device for simulating the water flow movement process in the subsurface flow zone according to claim 2, characterized in that, The head difference between the liquid level on the side of the water isolation plate closer to the second water inlet tank and the liquid level on the side closer to the drainage tank in the first direction is greater than 0 and less than or equal to 5 cm.

4. The experimental device for simulating the water flow movement process in the subsurface flow zone according to claim 3, characterized in that, The head difference between the liquid level on the side of the water isolation plate closer to the second water inlet tank and the liquid level on the side closer to the drainage tank in the first direction is 1.8 cm.

5. The experimental device for simulating the water flow movement process in the subsurface flow zone according to claim 1, wherein, At least one pressure measuring hole is opened on one side wall of the sand tank in the second direction; The pressure measuring member is a piezometer tube, and the piezometer tube is connected to the pressure measuring hole through a hose.

6. The experimental device for simulating the water flow movement process in the subsurface flow zone according to claim 5, characterized in that, A plurality of pressure measuring holes are provided, and the distance between any two adjacent pressure measuring holes in the up-down direction is set to 8.0 cm.

7. The experimental device for simulating the water flow movement process in the subsurface flow zone according to claim 5, characterized in that, A plurality of pressure measuring holes are provided, and the distance between any two adjacent pressure measuring holes in the first direction is set to 8.0 cm.

8. The experimental device for simulating the water flow movement process in the subsurface flow zone according to claim 5, wherein A plurality of the pressure measurement holes are provided and are arranged in an array. The distance between the lowermost pressure measurement hole among the plurality of pressure measurement holes and the bottom wall of the sand tank is set to 22 cm, and the distance between the pressure measurement hole among the plurality of pressure measurement holes that is close to the second water inlet tank in the first direction and the second water inlet tank is set to 9.0 cm.

9. The experimental device for simulating the water flow movement process in the subsurface flow zone according to claim 1, characterized in that, The distance between any two adjacent sampling holes among the plurality of sampling holes is set to 3.0 cm, and the distance between the sampling hole among the plurality of sampling holes that is close to the second water inlet tank and the second water inlet tank is set to 22.5 cm; The interface between the sediment and the liquid in the sand tank and the sampling hole have a distance in the up-and-down direction that is greater than or equal to 2.0 cm and less than or equal to 5.0 cm.

10. The experimental device for simulating the water flow movement process in the subsurface flow zone according to claim 1, characterized in that, The distance between any two adjacent tracer holes among the plurality of tracer holes is greater than or equal to 3.0 cm and less than or equal to 5.0 cm. The distance between the tracer hole among the plurality of tracer holes that is close to the second water inlet tank and the second water inlet tank is set to 5.0 cm; and / or, The interface between the sediment and the liquid in the sand tank and the tracer hole have a distance in the up-and-down direction that is greater than or equal to 2.0 cm and less than or equal to 5.0 cm.

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