Experimental device and experimental method for simulating water flow in hyporheic zone

Abstract

The present invention discloses an experimental device and an experimental method for simulating the water flow movement process in a subsurface flow zone, which relate to the field of subsurface flow zone simulation experiments. The experimental device includes a transparent experimental box, a water baffle, a pore water sampler, a pressure measuring piece and a shooting device. The transparent experimental box includes a flow area and a accommodating area arranged and connected in sequence along the upper and lower directions. The accommodating area is provided with a sand trough, a first water inlet trough, a second water inlet trough and a drainage trough. The first water inlet trough is provided at the bottom of the sand trough and is connected to the sand trough. The second water inlet trough and the drainage trough are provided on both sides of the sand trough in the first direction. At least one tracer hole and multiple sampling holes are opened on one side wall of the sand trough in the second direction. The tracer hole is close to the second water inlet trough relative to the sampling hole. The water baffle is located between the tracer hole and the sampling hole, the upper end is located in the flow area, and abuts against the upper side wall of the transparent experimental box, and the lower end is located in the sand trough. In this way, the interactive mixing process, spatial distribution relationship and flow field characteristics of surface water and groundwater are qualitatively and quantitatively described.

Description

Technical Field

[0001] The invention relates to the technical field of hyporheic zone simulation experiments, and in particular to an experimental device and an experimental method for simulating the movement process of water flow in a hyporheic zone. Background Art

[0002] The hyporheic zone is a water-saturated sediment layer located at the top and bottom of the riverbed, extending to both sides of the riverbank. It serves as a link between surface water and groundwater. Water movement in the hyporheic zone is a key driver of the exchange of matter and energy, and the biogeochemical reactions, between surface and groundwater. Driven by pressure or head gradients between the river and sediments or between the river and aquifer, surface water enters the riverbed pore water for convective exchange. This region is called the surface water-groundwater interaction zone, where the surface water content is 90-100%. After entering the riverbed through hyporheic exchange, surface water gradually mixes with the surrounding groundwater, and the surface water content decreases to 10-90%, forming the surface water-groundwater mixing zone. Compared to the interaction zone, the mixing zone is narrower, making its location and extent challenging to determine. Current research often treats the interaction zone and mixing zone as a single entity, ignoring the differences between the two. Summary of the Invention

[0003] The main purpose of the present invention is to propose an experimental device and experimental method for simulating the water flow process in the hyporheic zone, which can simulate and visualize the interactive mixing process of surface water and groundwater, and can qualitatively and quantitatively describe the spatial distribution relationship and flow field characteristics of the interactive zone and mixing zone.

[0004] To achieve the above-mentioned object, the present invention proposes an experimental device for simulating the flow process of hyporheic zone water, comprising:

[0005] A transparent experimental box includes a flow area and a accommodating area arranged in sequence and connected in the upper and lower directions, wherein the accommodating area is provided with a sand trough, a first water inlet trough, a second water inlet trough and a drainage trough, the sand trough is used to accommodate sediment, the first water inlet trough is provided at the bottom of the sand trough, is used to accommodate groundwater simulation liquid, and is connected to the sand trough, the second water inlet trough and the drainage trough are provided on both sides of the sand trough in the first direction, the second water inlet trough is used to accommodate surface water simulation liquid containing inert ions, and the surface water simulation liquid in the second water inlet trough can flow into the sand trough through the flow area, the drainage trough is used to accommodate liquid flowing out of the sand trough into the flow area, and at least one tracer hole and multiple sampling holes are opened on one side wall of the sand trough in the second direction, the tracer hole is provided near the second water inlet trough relative to the sampling hole, and is used to inject a tracer into the sand trough;

[0006] a water baffle, provided in the transparent experimental box and located between the tracer hole and the sampling hole, the water baffle extending along the up-down direction, the upper end of the water baffle being located in the flow area and abutting against the upper side wall of the transparent experimental box, and the lower end of the water baffle being located in the sand trough;

[0007] a pore water sampler, for collecting pore water in the sediment through the sampling hole, so as to detect the concentration of inert ions in the pore water;

[0008] a pressure measuring member for measuring the water pressure at at least one preset position in the sand tank; and

[0009] A photographing device, used for photographing the migration trajectory of the tracer in the transparent experimental box;

[0010] The first direction, the second direction and the up-down direction are perpendicular to each other.

[0011] Furthermore, the experimental device for simulating the water flow movement process in the subsurface flow zone also includes a first overflow device connected to the second water inlet trough and a second overflow device connected to the drainage trough. The height of the first overflow device and the height of the second overflow device are both adjustable so that the head difference between the liquid water levels on both sides of the baffle in the first direction can be adjusted.

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

[0013] Furthermore, at least one pressure measuring hole is provided on one side wall of the sand trough in the second direction;

[0014] The pressure measuring piece is a pressure measuring tube, and the pressure measuring tube is connected to the pressure measuring hole through a hose.

[0015] Furthermore, there are a plurality of pressure measuring holes, and the distance between any two adjacent pressure measuring holes in the vertical direction is set to 8.0 cm; and / or,

[0016] There are multiple pressure measuring holes, and the distance between any two adjacent pressure measuring holes in the multiple pressure measuring holes in the first direction is set to 8.0 cm and / or,

[0017] There are multiple pressure measuring holes distributed in an array. The distance between the pressure measuring hole at the bottom end and the bottom wall of the sand trough is set to 22 cm, and the distance between the pressure measuring hole close to the second water inlet trough in the first direction and the second water inlet trough is set to 9.0 cm.

[0018] Furthermore, the plurality of sampling holes are distributed at intervals along the first direction.

[0019] Furthermore, 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 close to the second water inlet trough among the plurality of sampling holes and the second water inlet trough is set to 22.5 cm;

[0020] The distance between the interface between the sediment and the liquid in the sand trough and the sampling hole in the vertical direction is greater than or equal to 2.0 cm and less than or equal to 5.0 cm.

[0021] Furthermore, a plurality of the tracer holes are provided, and the plurality of the tracer holes are spaced apart along the first direction, the distance between any two adjacent tracer holes among the plurality of the tracer holes is set to 5.0 cm, and the distance between the tracer hole close to the second water inlet trough and the second water inlet trough among the plurality of the tracer holes is set to 5.0 cm; and / or,

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

[0023] The present invention also provides an experimental method for simulating the movement process of water flow in a hyporheic zone, and an experimental device suitable for simulating the movement process of water flow in a hyporheic zone. The experimental method for simulating the movement process of water flow in a hyporheic zone comprises the following steps:

[0024] Step S1: placing sediment into a sand trough in a transparent experimental box, and storing and delivering groundwater simulation liquid into the sand trough through a first water inlet trough to saturate the sediment;

[0025] Step S2: After the sediment is saturated with water, the injection of the groundwater simulation liquid is stopped, and the head difference between the liquid water levels on both sides of the water barrier in the transparent experimental box in the first direction is adjusted, so that the surface water simulation liquid containing inert ions in the second water inlet trough in the transparent experimental box flows through the flow area to the sand trough, and then flows to the drainage trough in the transparent experimental box after bypassing the lower end of the water barrier, forming a surface water seepage path that first goes down and then goes up;

[0026] Step S3, injecting groundwater simulation liquid into the sand tank through the first water inlet tank to form an ascending groundwater flow path, and mixing the groundwater simulation liquid with the surface water simulation liquid between the sediments;

[0027] Step S4: injecting a tracer into the transparent experimental box through the tracer hole, and using a camera to observe, photograph, and record the flow path of the tracer at different times;

[0028] Step S5, calculating the length of the surface water seepage path and the average flow velocity of the pore water in the sediment based on the pictures taken by the shooting device and the distance between two adjacent sampling holes among the multiple sampling holes opened on the side wall of the sand trough;

[0029] Step S6: sampling pore water through the sampling holes provided on the sidewall of the sand trough using a pore water sampler, and detecting the concentration of inert ions in the pore water and the concentration of inert ions in the surface water simulation solution;

[0030] Step S7, determining the position and range of the interaction zone and the mixing zone of the groundwater simulated fluid and the surface water simulated fluid according to the concentration of the inert ions in the pore water and the concentration of the inert ions in the surface water simulated fluid, and calculating the width of the mixing zone;

[0031] Step S8: Use a pressure measuring piece to measure the water pressure at a preset position in the sand trough, and calculate the sediment diffusion coefficient and the Peclet number based on the average pore water flow velocity, the length of the surface water seepage path, and the width of the mixing zone to obtain the relative importance of convection and diffusion in the sand trough flow field.

[0032] Furthermore, the step S5 specifically includes:

[0033] Step S51: cropping the sand slot portion in the image captured by the camera to obtain a cropped image, and marking the position of the tracer on the cropped image to form a marking point;

[0034] Step S52: establishing a rectangular coordinate system, superimposing the cropped images of the pictures taken at different times, and connecting the marked points to obtain the surface water seepage path;

[0035] Step S53: using the distance between two adjacent sampling holes among the plurality of sampling holes as an image scale, and using ImageJ software to count and determine the length of the surface water seepage path;

[0036] Step S54: Determine the movement time of the tracer in each flow path in the surface water seepage path according to the shooting interval time of the shooting 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.

[0037] In the technical solution of the present invention, sediments are placed in the sand trough, and the surface water simulation liquid in the second water inlet trough flows into the sand trough through the flow area, bypasses the lower end of the baffle, and flows upward to the flow area, forming a surface water seepage path from bottom to top. The groundwater simulation liquid in the first water inlet trough is injected into the sand trough to form an ascending groundwater flow path, and is mixed with the surface water simulation liquid between the sediments in the sand trough by convection, and then flows through the flow area to the drainage trough in the transparent experimental box. Tracers are injected into the sand trough, which can be photographed by the shooting device. By observing the flow path of the tracer, the flow path of the surface water simulation fluid is determined, enabling visualization of the interactive mixing process of surface water and groundwater in the hyporheic zone. Furthermore, based on the images captured and recorded by the camera, the spacing between two adjacent sampling holes, the concentration of inert ions in the surface water simulation fluid sampled by the pore water sampler, and the water pressure measured by the pressure measuring device, the spatial distribution relationship and flow field characteristics of the interactive zone and mixing zone can be qualitatively and quantitatively described on a laboratory scale, thereby determining the relative importance of convection and diffusion in the sand trough flow field. The experimental device provided by the present invention has a simple structure, ingenious design, and strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0039] Figure 1 A schematic structural diagram of an embodiment of an experimental device for simulating the flow process of hyporheic zone water provided by the present invention;

[0040] Figure 2 A flow chart of the experimental method for simulating the water flow movement process in the hyporheic zone provided by the present invention;

[0041] Figure 3 for Figure 2 Flowchart of step S5;

[0042] Figure 4 This is the tracer image of the surface water seepage path during the experiment;

[0043] Figure 5 This is an analytical diagram of the mixing zone width of surface water simulated fluid and groundwater simulated fluid during the experiment;

[0044] Figure 6 is the spatial distribution diagram of the water head in the sand tank during the experiment;

[0045] Figure 7 Schematic diagram of the spatial distribution relationship of interactive mixing of surface water simulated fluid and groundwater simulated fluid during the experiment.

[0046] Description of Figure Numbers:

[0047]

[0048] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0049] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0050] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0051] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the meaning of "and / or" appearing throughout the text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0052] The hyporheic zone is a water-saturated sediment layer located at the top and bottom of the riverbed, extending to both sides of the riverbank. It serves as a link between surface water and groundwater. Water movement in the hyporheic zone is a key driver of the exchange of matter and energy, and the biogeochemical reactions, between surface and groundwater. Driven by pressure or head gradients between the river and sediments or between the river and aquifer, surface water enters the riverbed pore water for convective exchange. This region is called the surface water-groundwater interaction zone, where the surface water content is 90-100%. After entering the riverbed through hyporheic exchange, surface water gradually mixes with the surrounding groundwater, and the surface water content decreases to 10-90%, forming the surface water-groundwater mixing zone. Compared to the interaction zone, the mixing zone is narrower, making its location and extent challenging to determine. Current research often treats the interaction zone and mixing zone as a single entity, ignoring the differences between the two.

[0053] In view of this, the present invention provides an experimental device 100 for simulating the flow process of hyporheic zone water. Figure 1 This is an embodiment of an experimental device 100 for simulating the water flow process in the hyporheic zone provided by the present invention.

[0054] See also Figure 1The experimental device 100 for simulating the flow process of the subsurface flow zone includes a transparent experimental box 1, a baffle 2, a pore water sampler, a pressure measuring piece and a shooting device. The transparent experimental box 1 includes a flow area 12 and a receiving area 11 arranged and connected in sequence along the upper and lower directions. The receiving area 11 is provided with a sand trough 111, a first water inlet trough 112, a second water inlet trough 113 and a drainage trough 114. The sand trough 111 is used to accommodate sediments. The first water inlet trough 112 is provided at the bottom of the sand trough 111 for The sand trough 111 is connected to the second water inlet trough 113 and the drainage trough 114. The second water inlet trough 113 is used to accommodate the surface water simulation liquid containing inert ions, and the surface water simulation liquid in the second water inlet trough 113 can flow into the sand trough 111 through the flow area 12. The drainage trough 114 is used to accommodate the liquid flowing out of the sand trough to the flow area. The sand trough 111 is connected to the second water inlet trough 113 and the drainage trough 114. At least one tracer hole 1111 and a plurality of sampling holes 1112 are provided on one side wall, and the tracer hole 1111 is arranged near the second water inlet trough 113 relative to the sampling hole 1112, and is used to inject the tracer into the sand trough 111; the water baffle 2 is arranged in the transparent experimental box 1, and is located between the tracer hole 1111 and the sampling hole 1112, and the water baffle 2 is extended along the up and down direction, and the upper end of the water baffle 2 is located in the flow area 12 and abuts against the transparent experimental box. The upper side wall of the test box 1, the lower end of the water-blocking plate 2 is located in the sand trough 111; the pore water sampler is used to collect pore water in the sediment through the sampling hole 1112 for detecting the concentration of inert ions in the pore water; the pressure measuring piece is used to measure the water pressure at at least one preset position in the sand trough 111; the shooting device is used to shoot the migration trajectory of the tracer in the transparent test box 1; wherein, the first direction, the second direction and the up and down directions are perpendicular to each other.

[0055] In the technical solution of the present invention, sediment is placed in the sand trough 111, and the surface water simulation liquid in the second water inlet trough 113 flows into the sand trough 111 through the flow area 12, and bypasses the lower end of the baffle 2, and flows upward to the flow area 12, forming a surface water seepage path from bottom to top, and the groundwater simulation liquid in the first water inlet trough 112 is injected into the sand trough 111 to form an ascending groundwater flow path, and is mixed with the surface water simulation liquid between the sediments in the sand trough 111 by convection, and then flows through the flow area 12 to the drainage trough 114 in the transparent experimental box 1, and the sand trough 111 is injected with The tracer can be observed through the camera to determine the flow path of the surface water simulation fluid, thereby visualizing the interactive mixing process of surface water and groundwater in the hyporheic zone. Furthermore, based on the images captured by the camera, the spacing between two adjacent sampling holes 1112, the concentration of inert ions in the surface water simulation fluid obtained by sampling with the pore water sampler, and the water pressure measured by the pressure measuring device, the spatial distribution relationship and flow field characteristics of the interactive zone and mixing zone can be qualitatively and quantitatively described on a laboratory scale, and the relative importance of convection and diffusion in the flow field of the sand trough 111 can be determined. The experimental device provided by the present invention has a simple structure, ingenious design, and strong practicality.

[0056] It should be noted that, in the present invention, the sediment includes quartz sand; further, the sediment also includes gravel. Specifically, during the experiment, quartz sand was first laid in the sand trough 111, and then gravel was laid on the quartz sand to prevent the groundwater simulation fluid from rushing into the sand trough 111 through the first water inlet trough 112 and disturbing the surface of the sand trough 111. Furthermore, in the present invention, the particle size and lithology of the sediment are not restricted, and complex riverbed sediment characteristics can be simulated by varying the particle size and lithology of the sediment.

[0057] It should also be noted that, in the present invention, the photographing device includes a camera.

[0058] Further, see Figure 1The experimental device 100 for simulating the water flow movement process in the subsurface flow zone also includes a first overflow device 3 connected to the second water inlet trough 113 and a second overflow device 4 connected to the drainage trough 114. The height of the first overflow device 3 and the height of the second overflow device 4 are both adjustable so that the head difference between the liquid water levels on both sides of the baffle 2 in the first direction can be adjusted; in this way, the head of the surface water simulation liquid in the second water inlet trough 113 can be adjusted by adjusting the height of the first overflow device 3, and the head of the liquid in the drainage trough 114 can be adjusted by adjusting the height of the second overflow device 4, thereby adjusting the head difference between the liquid water levels on both sides of the baffle 2 in the first direction, thereby simulating different hydrodynamic conditions.

[0059] It should be noted that, in the present invention, both the first overflow device 3 and the second overflow device 4 include a water tank and a siphon tube.

[0060] Furthermore, the head difference between the liquid level on the baffle plate 2 close to the second water inlet groove 113 in the first direction and the liquid level on the side close to the drainage groove 114 is greater than 0 and less than or equal to 5 cm.

[0061] Furthermore, in one embodiment of the present invention, the head difference between the liquid level on the baffle plate 2 close to the second water inlet groove 113 in the first direction and the liquid level on the side close to the drainage groove 114 is 1.8 cm.

[0062] Specifically, in one embodiment of the present invention, a plurality of water inlet holes are provided on the bottom wall of the sand trough 111 and are connected to the first water inlet trough 112. The first water inlet trough 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. In this way, the groundwater simulation liquid in the water supply tank is pumped into the first water inlet trough 112 by the peristaltic pump, and then flows into the sand trough 111 through the water inlet hole. At the same time, the flow rate of the groundwater simulation liquid can be controlled by the peristaltic pump to simulate different hydrodynamic conditions.

[0063] More specifically, a mesh is provided on a side of the bottom wall of the sand trough 111 away from the first water inlet trough 112 to prevent sediment in the sand trough 111 from flowing into the first water inlet trough 112 .

[0064] For details, please refer to Figure 1 At least one pressure measuring hole 1113 is formed on one side wall of the sand trough 111 in the second direction. The pressure measuring element is a pressure measuring tube connected to the pressure measuring hole 1113 via a flexible pipe. Thus, the pressure head distribution in the sand trough 111 can be measured simply and quickly via the pressure measuring tube.

[0065] Furthermore, there are multiple pressure measuring holes 1113, and the distance between any two adjacent pressure measuring holes 1113 in the upper and lower directions is set to 8.0 cm.

[0066] Specifically, there are multiple pressure measuring holes 1113, and the distance between any two adjacent pressure measuring holes 1113 in the first direction is set to 8.0 cm.

[0067] Specifically, there are multiple pressure measuring holes 1113 distributed in an array. The distance between the pressure measuring hole 1113 at the bottom among the multiple pressure measuring holes 1113 and the bottom wall of the sand trough 111 is set to 22 cm, and the distance between the pressure measuring hole 1113 close to the second water inlet trough 113 in the first direction and the second water inlet trough 113 is set to 9.0 cm.

[0068] It should be noted that, in the present invention, the above three technical features can be set selectively or simultaneously. Specifically, in one embodiment of the present invention, the above three technical features are set simultaneously, that is, a plurality of pressure measuring holes 1113 are provided and distributed in an array, the spacing between any two adjacent pressure measuring holes 1113 in the vertical direction and in the first direction is set to 8.0 cm, and the spacing between the pressure measuring holes 1113 at the bottom of the plurality of pressure measuring holes 1113 and the bottom wall of the sand trough 111 is set to 22 cm, and the spacing between the pressure measuring holes 1113 located near the second water inlet trough 113 in the first direction and the second water inlet trough 113 is set to 9.0 cm.

[0069] For more details, see Figure 1 , 25 pressure measuring holes 1113 are distributed in an array on the side wall of the sand tank 111.

[0070] Specifically, the diameter of the pressure measuring hole 1113 is greater than or equal to 1 cm and less than or equal to 2 cm. This is to prevent the pressure measuring hole from being too large in diameter, which may cause the sidewall of the sand tank 111 to break when the hole is opened. More specifically, in one embodiment of the present invention, the diameter of the pressure measuring hole 1113 is 1 cm.

[0071] For details, please refer to Figure 1 , the plurality of sampling holes 1112 are distributed at intervals along the first direction.

[0072] Furthermore, the spacing between any two adjacent sampling holes 1112 among the plurality of sampling holes 1112 is set to 3.0 cm, and the spacing between the sampling hole closest to the second water inlet trough 113 and the second water inlet trough 113 is set to 22.5 cm. This avoids the spacing between two adjacent sampling holes 1112 being too large, which would prevent the location of the mixing zone from being detected, and the spacing being too small, which would affect the flow field during sampling.

[0073] Specifically, the distance between the interface 200 between the sediment and the liquid in the sand trough 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.

[0074] It should be noted that, in the present invention, the above two technical features can be set selectively or simultaneously. Specifically, in one embodiment of the present invention, the above two technical features are set simultaneously, that is, the spacing between any two adjacent sampling holes 1112 among the plurality of sampling holes 1112 is set to 3.0 cm, and the spacing between the sampling holes 1112 near the second water inlet trough 113 and the second water inlet trough 113 among the plurality of sampling holes 1112 is set to 22.5 cm, and the spacing between the interface 200 between the sediment and liquid in the sand trough 111 and the sampling holes 1112 is set to 5.0 cm.

[0075] More specifically, in one embodiment of the present invention, the distance between the interface 200 between 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.

[0076] For details, please refer to Figure 1 There are multiple tracer holes 1111, and the multiple tracer holes 1111 are spaced apart along the first direction. 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. Moreover, the distance between the tracer hole 1111 close to the second water inlet trough 113 and the second water inlet trough 113 among the multiple tracer holes 1111 is set to 5.0 cm.

[0077] Specifically, 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 greater than or equal to 2.0 cm and less than or equal to 5.0 cm.

[0078] It should be noted that, in the present invention, the above two technical features can be set selectively or simultaneously. Specifically, in one embodiment of the present invention, the above two technical features are set simultaneously, that is, a plurality of tracer holes 1111 are provided, and the plurality of tracer holes 1111 are spaced apart along the first direction, the spacing between any two adjacent tracer holes 1111 among the plurality of tracer holes 1111 is set to 5.0 cm, and the spacing between the tracer hole 1111 near the second water inlet trough 113 and the second water inlet trough 113 among the plurality of tracer holes 1111 is greater than or equal to 3.0 cm and less than or equal to 5.0 cm, and the spacing between the interface 200 between the sediment and the liquid in the sand trough 111 and the tracer hole 1111 is set to 5.0 cm.

[0079] More specifically, in one embodiment of the present invention, 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 close to the second water inlet trough 113 among the multiple tracer holes 1111 and the second water inlet trough 113 is 5.0 cm, and the distance between the interface 200 of the sediment and the liquid in the sand trough 111 and the tracer hole 1111 in the up and down directions is set to 5.0 cm.

[0080] Specifically, in the present invention, the surface water simulation liquid containing inert ions can be a surface water simulation liquid containing bromide ions or chloride ions, for example, a surface water simulation liquid containing sodium bromide, potassium bromide, potassium chloride or sodium chloride.

[0081] The present invention also provides an experimental method for simulating the movement process of water flow in a hyporheic zone, which is applicable to the experimental device for simulating the movement process of water flow in a hyporheic zone described above.

[0082] See also Figure 2 The experimental method for simulating the water flow movement process in the hyporheic zone includes the following steps:

[0083] Step S1: Put sediment into the sand trough in the transparent experimental box, and store and transport groundwater simulation liquid into the sand trough through the first water inlet trough to saturate the sediment.

[0084] In this step, the sediment includes quartz sand and gravel. Specifically, the quartz sand is first filled in layers in the sand trough, and after each layer is laid, it is saturated with water until multiple layers of quartz sand are filled, and then a layer of gravel is laid on the quartz sand.

[0085] It should be noted that each layer of quartz sand needs to be compacted when it is laid to make its density uniform and to compact the boundaries to avoid gaps during the filling process and to prevent preferential flow when the groundwater simulation fluid is injected, thereby affecting the test.

[0086] It should also be noted that, in one embodiment of the present invention, each layer of quartz sand is 5.0 cm high, and multiple layers are filled to 60.0 cm.

[0087] Step S2: After the sediment is saturated with water, stop injecting the groundwater simulation liquid, and adjust the head difference between the liquid water levels on both sides of the water barrier in the transparent experimental box in the first direction, so that the surface water simulation liquid containing inert ions in the second water inlet trough in the transparent experimental box flows through the flow area in the transparent experimental box to the sand trough, bypasses the lower end of the water barrier, and flows to the drainage trough in the transparent experimental box, forming a surface water seepage path from bottom to top (such as Figure 7 (as shown in a).

[0088] Specifically, in one embodiment of the present invention, the water head h1 of the baffle plate close to the second water inlet trough in the first direction is 85.5 cm, and the water head h2 of the baffle plate close to the drainage trough in the first direction is 83.7 cm. Thus, the water head difference is 1.8 cm.

[0089] Step S3: injecting groundwater simulation liquid into the sand tank through the first water inlet trough to form an ascending groundwater flow path (such as Figure 7 d in the middle), and mixed with the simulated surface water between the sediments (as shown in Figure 7 As shown in b and c, b is the surface water simulated liquid-groundwater simulated liquid interaction area, and c is the surface water simulated liquid-groundwater simulated liquid mixing area).

[0090] Specifically, in one embodiment of the present invention, the bottom wall of the sand trough is provided with multiple water inlet holes that communicate with the first water inlet trough. The first water inlet trough is connected to a water supply tank containing groundwater simulating liquid via an inlet pipe. The inlet pipe is provided with a peristaltic pump. Thus, the flow state of the groundwater simulating liquid can be controlled by the peristaltic pump. Furthermore, in one embodiment of the present invention, the peristaltic pump controls the injection rate q of the groundwater simulating liquid to 9.45 mL / min, allowing the groundwater simulating liquid to flow steadily into the sand trough.

[0091] Step S4: injecting a tracer into the transparent experimental box through the tracer hole, and using a camera to observe, photograph, and record the flow path of the tracer at different times.

[0092] In this step, the time when the tracer is injected through the tracer hole is recorded as time 0, and a camera is used to take pictures and record them at different times, so that multiple pictures can be obtained.

[0093] It should be noted that, in one embodiment of the present invention, there are three tracer holes, each of which is injected with 1 g / L of brilliant blue tracer, and the injection time is recorded as time 0, and the shooting device is used to take pictures at multiple times such as time 0.5, time 1, time 1.5, time 2, time 2.5, and time 3.

[0094] It should also be noted that, in this step, an opaque object is used to cover the sand trough and the camera, and under a given single light source, the flow path of the tracer is observed, photographed, and recorded by the photographing device.

[0095] Step S5: Calculate the length of the surface water seepage path and the average flow rate of the pore water in the sediment according to the recording results of the shooting device and the distance between two adjacent sampling holes among the multiple sampling holes opened on the side wall of the sand trough.

[0096] Further, see Figure 3 , the step S5 specifically includes:

[0097] Step S51: cropping the sand trough portion of the image captured by the camera to obtain a cropped image, and marking the position of the tracer on the cropped image to form a marking point (e.g., Figure 4 shown).

[0098] Step S52: Establish a rectangular coordinate system, superimpose the cropped images of the pictures taken at different times, and connect the marked points to obtain the surface water seepage path.

[0099] In this step, the rectangular coordinate system is established with the lower corner of the sand trough close to the second water inlet trough as the origin, the direction in the first direction toward the drainage trough as the x-axis, and the upward direction as the y-axis.

[0100] Furthermore, in one embodiment of the present invention, y=10 cm and x=49 cm are used as the horizontal and vertical fixed edges of the cropped image, the cropped images of the pictures taken at different times are superimposed, and the marking points at different times are connected to obtain a continuous tracer streamline formed by multiple flow paths, that is, the surface water seepage path.

[0101] Step S53: using the distance between two adjacent sampling holes among the plurality of sampling holes as an image scale, and using ImageJ software to count and determine the length of the surface water seepage path.

[0102] In this step, the sum of the lengths of the surface water seepage paths is the total length of the tracer streamlines.

[0103] Furthermore, the calculation formula for the surface water seepage path length is:

[0104] L=∑L i (1)

[0105] In formula (1), L i is the length of each flow path in the tracer streamline, that is, the length between two adjacent marking points, in cm;

[0106] L is the length of the surface water seepage path, in cm.

[0107] Step S54: Determine the movement time of the tracer in each flow path in the surface water seepage path according to the shooting interval time of the shooting 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.

[0108] Furthermore, the calculation formula for the flow rate of the pore water in each flow path is:

[0109]

[0110] In formula (2), v p i is the pore water velocity in each flow path, in cm / h;

[0111] t i is the movement time of the tracer in each flow path, in h.

[0112] The calculation formula for the average flow velocity of the pore water on the surface water seepage path is:

[0113]

[0114] In formula (3), v p is the average flow velocity of the pore water in the surface water seepage path, in cm / h.

[0115] Further based on the embodiment described above that "there are three tracer holes, each of which is injected with 1g / L brilliant blue tracer, and the injection time is recorded as time 0, and the camera is used to take pictures at multiple times such as time 0.5, time 1, time 1.5, time 2, time 2.5, time 3, etc.", as Figure 4 As 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 respectively, and the average flow rates 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.

[0116] Step S6: sampling the pore water through the sampling holes provided on the side wall of the sand trough using a pore water sampler, and detecting the concentration of inert ions in the pore water and the concentration of inert ions in the surface water simulation fluid.

[0117] In this step, a Luer lock is connected to the pore water collector, and sediment pore water is extracted using a syringe. The concentration of inert ions in the pore water and the surface water simulation fluid is measured using ion chromatography.

[0118] Step S7: Determine the position and range of the interaction zone and mixing zone of the groundwater simulation fluid and the surface water simulation fluid according to the concentration of the inert ions in the pore water and the concentration of the inert ions in the surface water simulation fluid, and calculate the width of the mixing zone.

[0119] In this step, the concentration of inert ions in the pore water is divided by the concentration of inert ions in the surface water simulation solution, and then the polynomial linear interpolation method is used to calculate the interface between surface water and groundwater and the mixing zone, that is, the position of the mixing zone. The calculation formula for the mixing zone position is:

[0120] d mix =x(c / c0=0.9)(4)

[0121] In formula (4), d mix is the position of the hybrid zone, in cm;

[0122] c is the concentration of inert ions in the pore water, in mg / L;

[0123] c0 is the concentration of inert ions in the surface water simulation solution, in mg / L;

[0124] x is the horizontal coordinate of the location of the relative concentration of inert ions.

[0125] Furthermore, the calculation formula for the width of the hybrid belt is:

[0126] d thickness =x(c / c0=0.1)-x(c / c0=0.9)(5)

[0127] In formula (5), d thickness is the width of the hybrid tape, in cm.

[0128] Specifically, in one 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:

[0129] Table 1 Statistics of relative concentrations of inert ions (bromide ions)

[0130] 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

[0131] More specifically, if Figure 5 As shown, in one embodiment of the present invention, the position d of the mixing zone mix Located 42.0 cm from the second water inlet trough, the width d of the mixing zone thickness is 7.62cm.

[0132] Step S8: Use a pressure measuring piece to measure the water pressure at a preset position in the sand trough, and calculate the sediment diffusion coefficient and the Peclet number based on the average pore water flow velocity, the length of the surface water seepage path, and the width of the mixing zone to obtain the relative importance of convection and diffusion in the sand trough flow field.

[0133] In this step, the calculation formula of the diffusion coefficient is:

[0134] D t =d thickness 2 v p / L(6)

[0135] In formula (6), D t is the diffusion coefficient, in cm 2 / h.

[0136] The calculation formula of the Peclet number is:

[0137] Pe=v p L / D t (7)

[0138] In formula (7), P e is the Peclet number of the sediment.

[0139] More specifically, in one embodiment of the present invention, 25 pressure measuring holes are set at equal intervals of 8 cm × 8 cm on the side wall of the sand tank, and the pressure measuring tube is connected by a hose to measure the pressure head distribution in the sand tank. The spatial distribution diagram of the water head in the sand tank is shown in FIG. Figure 6 .

[0140] 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 respectively, and the average flow rates 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", according to the longest of the three surface water seepage paths, the surface water seepage path L is 66.49 cm, and the average flow rate of the pore water v is p is 4.45 cm / h, the diffusion coefficient D t3.88cm 2 / h, so the Peclet number P e The calculation is 76.14, that is, in the process of interaction and mixing of surface water and groundwater, convection is dominant (such as Figure 7 shown).

[0141] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention description and drawings under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. An experimental device for simulating the flow process of hyporheic zone water, characterized in that: The experimental device for simulating the water flow movement process in the hyporheic zone includes: A transparent experimental box includes a flow area and a accommodating area arranged in sequence and connected in the upper and lower directions, wherein the accommodating area is provided with a sand trough, a first water inlet trough, a second water inlet trough and a drainage trough, the sand trough is used to accommodate sediment, the first water inlet trough is provided at the bottom of the sand trough, is used to accommodate groundwater simulation liquid, and is connected to the sand trough, the second water inlet trough and the drainage trough are provided on both sides of the sand trough in the first direction, the second water inlet trough is used to accommodate surface water simulation liquid containing inert ions, and the surface water simulation liquid in the second water inlet trough can flow into the sand trough through the flow area, the drainage trough is used to accommodate liquid flowing out of the sand trough into the flow area, and at least one tracer hole and multiple sampling holes are opened on one side wall of the sand trough in the second direction, the tracer hole is provided near the second water inlet trough relative to the sampling hole, and is used to inject a tracer into the sand trough; a water baffle, provided in the transparent experimental box and located between the tracer hole and the sampling hole, the water baffle extending along the up-down direction, the upper end of the water baffle being located in the flow area and abutting against the upper side wall of the transparent experimental box, and the lower end of the water baffle being located in the sand trough; a pore water sampler, for collecting pore water in the sediment through the sampling hole, so as to detect the concentration of inert ions in the pore water; a pressure measuring member for measuring the water pressure at at least one preset position in the sand tank; and A photographing device, used for photographing the migration trajectory of the tracer in the transparent experimental box; The first direction, the second direction and the up-down direction are perpendicular to each other.

2. The experimental device for simulating the movement of water flow in the hyporheic zone according to claim 1, characterized in that: The experimental device for simulating the water flow movement process in the subsurface flow zone also includes a first overflow device connected to the second water inlet trough and a second overflow device connected to the drainage trough. The height of the first overflow device and the height of the second overflow device are both adjustable so that the head difference between the liquid water levels on both sides of the baffle in the first direction can be adjusted.

3. The experimental device for simulating the movement of water flow in the hyporheic zone according to claim 2, characterized in that: The head difference between the liquid level on the side of the baffle close to the second water inlet groove in the first direction and the liquid level on the side close to the drainage groove is greater than 0 and less than or equal to 5 cm.

4. The experimental device for simulating the movement of water flow in the hyporheic zone according to claim 1, characterized in that: At least one pressure measuring hole is provided on one side wall of the sand trough in the second direction; The pressure measuring piece is a pressure measuring tube, and the pressure measuring tube is connected to the pressure measuring hole through a hose.

5. The experimental device for simulating the movement of water flow in the hyporheic zone according to claim 4, characterized in that: There are multiple pressure measuring holes, and the distance between any two adjacent pressure measuring holes in the vertical direction is set to 8.0 cm; and / or, There are multiple pressure measuring holes, and the distance between any two adjacent pressure measuring holes in the multiple pressure measuring holes in the first direction is set to 8.0 cm; and / or, There are multiple pressure measuring holes distributed in an array. The distance between the pressure measuring hole at the bottom end and the bottom wall of the sand trough is set to 22 cm, and the distance between the pressure measuring hole close to the second water inlet trough in the first direction and the second water inlet trough is set to 9.0 cm.

6. The experimental device for simulating the movement of water flow in the hyporheic zone according to claim 1, characterized in that: The plurality of sampling holes are distributed at intervals along the first direction.

7. The experimental device for simulating the movement of water flow in the hyporheic zone according to claim 6, 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 close to the second water inlet trough and the second water inlet trough among the plurality of sampling holes is set to 22.5 cm; The distance between the interface between the sediment and the liquid in the sand trough and the sampling hole in the vertical direction is greater than or equal to 2.0 cm and less than or equal to 5.0 cm.

8. The experimental device for simulating the movement of water flow in the hyporheic zone according to claim 1, characterized in that: There are multiple tracer holes, and the multiple tracer holes are spaced apart along the first direction. The distance between any two adjacent tracer holes among the multiple 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 close to the second water inlet trough and the second water inlet trough among the multiple tracer holes is set to 5.0 cm; and / or, The distance between the interface between the sediment and the liquid in the sand tank and the tracer hole in the vertical direction is greater than or equal to 2.0 cm and less than or equal to 5.0 cm.

9. An experimental method for simulating the flow process of hyporheic zone water, applicable to the experimental device for simulating the flow process of hyporheic zone water as claimed in any one of claims 1 to 7, characterized in that: The experimental method for simulating the water flow movement process of the hyporheic zone comprises the following steps: Step S1: placing sediment into a sand trough in a transparent experimental box, and storing and delivering groundwater simulation liquid into the sand trough through a first water inlet trough to saturate the sediment; Step S2: After the sediment is saturated with water, the injection of the groundwater simulation liquid is stopped, and the head difference between the liquid water levels on both sides of the water barrier in the transparent experimental box in the first direction is adjusted, so that the surface water simulation liquid containing inert ions in the second water inlet trough in the transparent experimental box flows through the flow area in the transparent experimental box to the sand trough, bypasses the lower end of the water barrier, and flows into the drainage trough in the transparent experimental box, forming a surface water seepage path that first goes down and then goes up; Step S3, injecting groundwater simulation liquid into the sand tank through the first water inlet tank to form an ascending groundwater flow path, and mixing the groundwater simulation liquid with the surface water simulation liquid between the sediments; Step S4: injecting a tracer into the transparent experimental box through the tracer hole, and using a camera to observe, photograph, and record the flow path of the tracer at different times; Step S5, calculating the length of the surface water seepage path and the average flow velocity of the pore water in the sediment based on the pictures taken by the shooting device and the distance between two adjacent sampling holes among the multiple sampling holes opened on the side wall of the sand trough; Step S6: sampling pore water through the sampling holes provided on the sidewall of the sand trough using a pore water sampler, and detecting the concentration of inert ions in the pore water and the concentration of inert ions in the surface water simulation solution; Step S7, determining the position and range of the interaction zone and the mixing zone of the groundwater simulated fluid and the surface water simulated fluid according to the concentration of the inert ions in the pore water and the concentration of the inert ions in the surface water simulated fluid, and calculating the width of the mixing zone; Step S8: Use a pressure measuring piece to measure the water pressure at a preset position in the sand trough, and calculate the sediment diffusion coefficient and the Peclet number based on the average pore water flow velocity, the length of the surface water seepage path, and the width of the mixing zone to obtain the relative importance of convection and diffusion in the sand trough flow field.

10. The experimental method for simulating the movement of water flow in the hyporheic zone according to claim 9, characterized in that: The step S5 specifically includes: Step S51: cropping the sand slot portion in the image captured by the camera to obtain a cropped image, and marking the position of the tracer on the cropped image to form a marking point; Step S52: establishing a rectangular coordinate system, superimposing the cropped images of the pictures taken at different times, and connecting the marked points to obtain the surface water seepage path; Step S53: using the distance between two adjacent sampling holes among the plurality of sampling holes as an image scale, and using ImageJ software to count and determine the length of the surface water seepage path; Step S54: Determine the movement time of the tracer in each flow path in the surface water seepage path according to the shooting interval time of the shooting 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.

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