Device for simulating influence of seepage of underground seepage interception wall on seawater invasion

Abstract

The utility model discloses a device for simulating the influence of the seepage of an underground seepage interception wall on seawater invasion, which comprises a tank body with an opening at the upper part, two first partition plates are arranged in the tank body, and the tank body is sequentially divided into a saline water area, a medium area and a fresh water area along the length direction; a narrow groove with an opening in the upper end is formed in the medium area, a drawable third partition plate used for water insulation is arranged in the narrow groove, and when the third partition plate is inserted into the narrow groove, a complete underground seepage interception wall is simulated; when the third partition plate is pulled out of the narrow groove, an underground seepage interception wall with cracks is simulated; an observation well, a pumping well and a water injection well are arranged at one end close to the fresh water area in the medium area; structures for adjusting water heads are arranged in the salt water area and the fresh water area. According to the utility model, the influence of the leakage of the underground cutoff wall on seawater invasion can be intuitively reflected.

Description

Technical Field

[0001] This utility model belongs to the field of coastal hydrogeological research and relates to a simulation test device, specifically a device for simulating the impact of underground cutoff wall leakage on seawater intrusion. Background Technology

[0002] Seawater intrusion refers to the phenomenon where the groundwater level in coastal areas drops, causing a hydrodynamic imbalance between seawater and freshwater, leading to the shift of the brackish water interface towards land. It is generally caused by excessive human-induced groundwater extraction. Seawater intrusion leads to a series of ecological and environmental problems, such as water quality deterioration and soil salinization, significantly hindering the socio-economic development of coastal areas. Commonly used methods to address seawater intrusion include controlling groundwater extraction, artificial groundwater recharge, and constructing underground cutoff walls and seepage prevention dams.

[0003] Underground cutoff walls have relatively low permeability. During construction, they are typically built up to the impermeable slab of the unconfined aquifer at the bottom and to a certain point in the middle of the aquifer or to the surface at the top. They prevent seawater intrusion by cutting off the intrusion channels, serving a dual purpose of intercepting underground currents flowing into the sea and blocking seawater intrusion. However, water conservancy projects involve numerous construction procedures and are affected by various factors such as construction personnel, external environment, and materials. Therefore, leakage may occur during or after the construction of underground cutoff walls, allowing seawater to still intrude into freshwater aquifers. Thus, it is necessary to study the extent of their impact on seawater intrusion. Utility Model Content

[0004] Purpose of the utility model: The purpose of this utility model is to provide an experimental simulation device for studying the impact of leakage from underground cutoff walls on seawater intrusion.

[0005] Technical Solution: The device for simulating the impact of seawater intrusion caused by leakage of an underground cutoff wall, as described in this utility model, includes a tank with an opening at the top. Two first baffles are installed in the tank, dividing it sequentially along its length into a saline water area, a medium area, and a fresh water area. A narrow channel with an opening at the top is provided in the medium area. The lower section of the channel is a water-retaining area in contact with the bottom of the tank, and the upper section is a water-passing area. The two sides of the underground dam's water-retaining area have identical fissures. A removable third baffle for water isolation is installed in the channel. When the third baffle is inserted into the channel, it simulates a complete underground cutoff wall; when the third baffle is pulled out of the channel, it simulates a cracked underground cutoff wall. An observation well, a pumping well, and an injection well are installed at the end of the medium area near the fresh water area. The observation well is used to measure the conductivity of the water at that location to determine the process of saline water intrusion. The pumping well is connected to a peristaltic pump to simulate the water extraction process. The injection well is used to inject water and control the water head height at that location. Structures for adjusting the water head are provided in both the saline water area and the fresh water area.

[0006] Furthermore, the structure for adjusting the water head in the saline and freshwater areas includes a second partition with adjustable height located on the side of the upper water chamber. The upper water chamber has an injection hole on its side wall, and the lower water tank has a pumping hole on its side wall. Water in the lower water tank is pumped into the upper water chamber through the injection hole and the pumping hole by a water pump. Excess water overflows from the top of the second partition and returns to the lower water tank, thus achieving water head control.

[0007] Furthermore, the first partition consists of two parts, including an orifice plate and a water-blocking plate located outside the orifice plate that can be pulled up and down.

[0008] Furthermore, the tank body is made of transparent acrylic sheet to allow for observation of fluid movement; the observation well, pumping well, and injection well are all covered with water-permeable holes, all made of transparent acrylic material.

[0009] Furthermore, the perforated plate, as well as the observation well, pumping well, and injection well, are all covered with filter sheets.

[0010] Furthermore, the filter sheet is made of geotextile.

[0011] Furthermore, the saline chamber in the upper part of the saline area has a larger capacity than the freshwater chamber in the upper part of the freshwater area, which is used to maintain a constant saline concentration during the experiment.

[0012] Beneficial effects: Compared with the prior art, this utility model has the following advantages:

[0013] This invention can intuitively reflect the distribution and flow direction of saline water at the moment of intrusion, facilitating monitoring. Furthermore, it allows for free control of saline and freshwater levels according to experimental needs, enabling analysis of the seawater intrusion process and facilitating research on the impact of underground cutoff wall leakage on seawater intrusion. Simultaneously, it allows for the effective integration of underground cutoff walls with multiple measures such as pumping and injection in the laboratory. This invention fills a gap in related simulation experimental devices. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the device for simulating the impact of underground seepage intercepting wall leakage on seawater intrusion provided in this embodiment of the utility model;

[0015] Figure 2 This is a side view of the saline water area in an embodiment of this utility model;

[0016] Figure 3 This is a schematic diagram of the perforated plate that makes up the first partition in an embodiment of the present invention;

[0017] Figure 4 This is a schematic diagram of the slot structure in an embodiment of this utility model. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings.

[0019] Appendix Figures 1 to 4 The accompanying figure labels are as follows:

[0020] 1. Tank; 2. Saline water zone; 3. Medium zone; 4. Fresh water zone; 5. First partition; 6. Pumping hole; 7. Injection hole; 8. Observation well; 9. Pumping well; 10. Second partition; 11. Slot; 12. Pump; 13. Injection well.

[0021] like Figure 1 As shown, this utility model embodiment provides a device for simulating the impact of seawater intrusion caused by leakage from an underground cutoff wall. It includes a tank 1 with an opening at the top. The tank 1 is made of a transparent acrylic plate with a certain strength, allowing observation of the fluid movement within the tank 1 from the outside. Two first partitions 5 are installed in the tank 1, dividing it sequentially along its length into a saline water region 2, a medium region 3, and a fresh water region 4. Each first partition 5 consists of two parts: the part closest to the medium region 3 is a perforated plate wrapped with geotextile, such as… Figure 3 As shown, the partition plate furthest from the medium area 3 is a pull-down baffle plate, the height of which matches the height of the tank 1. In this embodiment, a double-layered first partition plate 5 is used, which can ensure the normal passage of saline water during the experiment while preventing the passage of medium particles, and can also ensure the accurate preparation of saline water in the saline water area 2 before the start of the experiment.

[0022] A narrow groove 11 with an open top is provided in the medium region 3, dividing the medium region 3 into two sides. The lower section of the groove 11 is a water-retaining area that contacts the bottom of the groove, and the upper section is a water-passing area. The two sides of the water-retaining area have the same cracks, such as... Figure 4 As shown, a removable third baffle for water isolation is provided in the slot 11. When the third baffle is inserted into the slot 11, it simulates a complete underground cutoff wall; when the third baffle is pulled out from the slot 11, it simulates an underground cutoff wall with cracks.

[0023] In the medium zone 3, near the freshwater zone 4, there are observation wells 8, pumping wells 9, and injection wells 13. Observation well 8 is used to measure the electrical conductivity of the water at that location to determine the process of saline water intrusion; pumping well 9 is connected to a peristaltic pump to simulate the water extraction process; and injection well 13 is used to inject water and control the water head at that location. In this embodiment, observation well 8, pumping well 9, and injection well 13 are all transparent acrylic pipes with evenly distributed permeable holes and are wrapped with geotextile to block medium particles.

[0024] Combination Figure 2Both the saline water zone 2 and the fresh water zone 4 have an upper water chamber and a lower water tank, with the bottom of the upper water chamber basically flush with the bottom of the medium zone 3. Both saline water zone 2 and fresh water zone 4 are equipped with a head-regulating structure, including a height-adjustable second partition 10 located on the side of the upper water chamber. The upper water chamber has an injection hole 7 on its side wall, and the lower water tank has a suction hole 6 on its side wall. The injection hole 7 and suction hole 6 are connected to a water pump 12 via plastic tubing. Water from the lower water tank is pumped into the upper water chamber through the injection hole 7 and suction hole 6 by the water pump 12. Excess water overflows from the top of the second partition 10 and returns to the lower water tank, thus controlling the head. Simultaneously, water in the tank 1 can also be discharged through the suction hole 6.

[0025] During the experiment, fresh water in medium zone 3 will inevitably enter salt water zone 2. In order to maintain a constant salt concentration during the experiment and reduce the dilution effect of fresh water on the salt water in the salt water chamber, the capacity of the salt water chamber in the upper part of salt water zone 2 should be greater than the capacity of the fresh water chamber in the upper part of fresh water zone 4.

[0026] In this embodiment, the tank 1 is 6000mm long and 500mm wide; the saline water zone 2 is 500mm long and 3000mm high; the fresh water zone 4 is 500mm long and 3000mm high; the medium zone 3 is 5000mm long and 2000mm high; and the slit 11 is 1400mm high. Small holes with a diameter of 20mm and a center-to-center distance of 30mm are evenly distributed on the perforated plate of the first partition 5 and on the observation well 8, pumping well 9, and injection well 13.

[0027] This utility model embodiment also provides a method for simulating the impact of underground seepage cutoff wall leakage on seawater intrusion. The method, employing the apparatus described in this utility model embodiment for simulating the impact of underground seepage cutoff wall leakage on seawater intrusion, includes the following steps:

[0028] S1. Wash standard sand with a particle size of 0.5-1.0 mm and fill it into medium area 3 to simulate the coastal aquifer with a height of 1700 mm. Mix salt and brilliant blue in a ratio of 7:2500 to obtain mixed blue particles. Use these blue particles to prepare a brine solution with a concentration of 35 g / L.

[0029] S2. Add fresh water to fresh water zone 4 and let the fresh water flow into saline water zone 2 through medium zone 3. After ensuring that the sand layer is saturated, insert water-blocking plates on both sides to separate medium zone 3 from saline water zone 2 and fresh water zone 4. Drain the fresh water from saline water zone 2 and then add the prepared brine to saline water zone 2.

[0030] S3. Adjust the height of the second partition 10 on both sides to control the head of the saline water section to 1650mm and the head of the fresh water section to 1605mm. The underground cutoff wall in the medium zone 3 is located 1500mm away from the saline water zone. Insert a peristaltic pump into the pumping well 9.

[0031] S4. Remove the baffle plate at point 2 in the saline water area. The process of colored brine invading into the sand tank can be observed. After a certain period of time, it tends to stabilize. The saline water wedge is blocked by the narrow groove 11. It is generally believed that the saline water wedge moves no more than 1 mm in 30 minutes, and the test reaches a steady state.

[0032] S5. Remove the third partition in the slot 11. It can be observed that the colored brine continues to invade the fresh water along the cracks in the slot 11. After a period of time, it tends to stabilize. If the brine wedge moves no more than 1 mm in 30 minutes, the test reaches a steady state.

[0033] S6. Turn on the peristaltic pump and pump water at 300 mm / min. After a period of time, when the brine wedge reaches stability or when brine is pumped out, record the result.

[0034] S7. Turn off the peristaltic pump and inject fresh water into injection well 13. Control the water head height in injection well 13 to 1700mm. After a period of time, the saline wedge will stabilize again. Record the result.

[0035] According to the experimental plan, the slit 11 has multiple cracks at different heights. The height of the water-blocking zone of the slit is adjusted by controlling the pull-out height of the third baffle, thereby simulating the impact of different underground cutoff wall heights and crack locations on seawater intrusion. By adjusting the flow rate and direction of the peristaltic pump, the impact of pumping and injection of water at different flow rates on seawater intrusion is simulated. The experimental results under different scenarios are compared to study the influence of underground cutoff wall cracks on the seawater intrusion pattern.

Claims

1. A device for simulating the impact of seepage from underground cutoff walls on seawater intrusion, characterized in that, The system includes a tank (1) with an opening at the top. Two first partitions (5) are installed in the tank (1) to divide the tank (1) into a saline water area (2), a medium area (3), and a fresh water area (4) along the length direction. A narrow channel (11) with an opening at the top is provided in the medium area (3). The lower section of the narrow channel (11) is a water-blocking area that contacts the bottom of the tank, and the upper section is a water-passing area. The two sides of the water-blocking area have the same cracks. A removable third partition for water isolation is provided in the narrow channel (11). When the third partition is inserted into the narrow channel (11), a complete underground cutoff wall is simulated. When the third partition is pulled out from the narrow channel (11), an underground cutoff wall with cracks is simulated. (11) has multiple fissures at different heights. The height of the narrow channel water-blocking area is adjusted by controlling the pull-out height of the third partition, thereby simulating the effect of different underground cut-off wall heights and fissure locations on seawater intrusion. In the medium area (3), near the freshwater area (4), there are observation wells (8), pumping wells (9) and injection wells (13). The observation well (8) is used to measure the electrical conductivity of the water at that location to determine the process of saline water intrusion. The pumping well (9) is connected to a peristaltic pump to simulate the water pumping process. The injection well (13) is used to inject water and control the water head height at that location. Both the saline water area (2) and the freshwater area (4) are equipped with structures for adjusting the water head.

2. The device for simulating the impact of underground cutoff wall leakage on seawater intrusion according to claim 1, characterized in that, The structure for adjusting the water head in the saline water area (2) and the fresh water area (4) includes a second partition (10) with adjustable height located on the side of the upper water chamber. The upper water chamber has a water injection hole (7) on its side wall and a water extraction hole (6) on its side wall. Water in the lower water tank is injected into the upper water chamber through the water injection hole (7) and the water extraction hole (6) by a water pump (12). Excess water overflows from the top of the second partition (10) and returns to the lower water tank, thus achieving water head control.

3. The device for simulating the impact of underground cutoff wall leakage on seawater intrusion according to claim 1, characterized in that, The first partition (5) consists of two parts, including a perforated plate and a water-blocking plate located outside the perforated plate that can be pulled up and down.

4. The device for simulating the impact of underground cutoff wall leakage on seawater intrusion according to claim 3, characterized in that, The tank (1) is made of transparent acrylic sheet so as to observe the fluid movement state; the observation well (8), the pumping well (9) and the injection well (13) are all made of transparent acrylic material with water-permeable holes.

5. The device for simulating the impact of underground cutoff wall leakage on seawater intrusion according to claim 4, characterized in that, The perforated plate, as well as the observation well (8), pumping well (9) and injection well (13), are all covered with filter sheets.

6. The device for simulating the impact of underground cutoff wall leakage on seawater intrusion according to claim 5, characterized in that, The filter sheet is made of geotextile.

7. The device for simulating the impact of underground cutoff wall leakage on seawater intrusion according to claim 1, characterized in that, The capacity of the salt water chamber at the top of the saline water region (2) is greater than that of the fresh water chamber at the top of the fresh water region (4), which is used to maintain a constant salt water concentration during the experiment.

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