CN110988302B - Model device of vertical isolation engineering barrier based on dry-wet cycle and use method and application thereof - Google Patents
Model device of vertical isolation engineering barrier based on dry-wet cycle and use method and application thereof Download PDFInfo
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- CN110988302B CN110988302B CN201911292917.2A CN201911292917A CN110988302B CN 110988302 B CN110988302 B CN 110988302B CN 201911292917 A CN201911292917 A CN 201911292917A CN 110988302 B CN110988302 B CN 110988302B
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/24—Earth materials
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N13/00—Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects
- G01N13/04—Investigating osmotic effects
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/082—Investigating permeability by forcing a fluid through a sample
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/082—Investigating permeability by forcing a fluid through a sample
- G01N15/0826—Investigating permeability by forcing a fluid through a sample and measuring fluid flow rate, i.e. permeation rate or pressure change
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/24—Earth materials
- G01N33/246—Earth materials for water content
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
- G01N5/02—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by absorbing or adsorbing components of a material and determining change of weight of the adsorbent, e.g. determining moisture content
- G01N5/025—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by absorbing or adsorbing components of a material and determining change of weight of the adsorbent, e.g. determining moisture content for determining moisture content
Abstract
The invention discloses a model device of a vertical isolation engineering barrier based on dry-wet circulation and a use method and application thereof, and the model device comprises a model box, a large water tank, a small water tank, an air pressure control valve, an air compressor, a glass bottle, Whatman #42 filter paper and the like. The testing device can measure the actual total suction, the water content, the saturated permeability coefficient, the effective diffusion coefficient and the blocking factor performance of each type of vertical isolation engineering barrier after dry-wet circulation in the depth direction. Meanwhile, the invention also provides a test method of the model device of the vertical isolation engineering barrier for retarding the migration of pollutants by considering the dry-wet cycle, the test method is simple and easy to implement, the total suction change and the moisture content change of the engineering barrier after the dry-wet cycle can be measured, and the saturated permeability coefficient, the effective diffusion coefficient and the retardation factor performance of the engineering barrier can be measured, so that a scientific basis is provided for the design scheme of the vertical isolation engineering barrier.
Description
Technical Field
The invention relates to the field of environmental and geotechnical engineering, in particular to a model device of a vertical isolation engineering barrier based on dry-wet circulation, and a use method and application thereof.
Background
The vertical isolation engineering barrier is an in-situ isolation technology for controlling the migration of pollutants in polluted underground water and soil of a polluted site. During the service process of the vertical isolation engineering barrier, the barrier is in direct contact with underground water. The climate has day-night, seasonal and perennial change rules, and the groundwater affected by the climate also forms corresponding periodic changes, wherein the seasonal changes have the most obvious influence on the diving dynamic. The climate of China is influenced by the season wind, precipitation is concentrated in summer, and at the moment, precipitation supply is increased remarkably. The temperature rises, the relative humidity of the air also increases, the evaporation is not strong, and therefore the diving water level rises. At the moment, most of the vertical isolation engineering barrier is positioned below the water level and is in a saturated state. After the rainy season, the supply is reduced suddenly, the excretion is increased relatively, and the diving position is gradually reduced. Before the next rainy season, the rainfall is less, the relative humidity is low, the evaporation is strong, the runoff excretion is continued, and therefore the diving position is lowest. At this time, the vertical isolation engineering barrier which is in the saturated state before can be in the unsaturated state. A peak and a valley appear in the diving space all the year round. Therefore, in the long-term service process of the vertical isolation engineering barrier, the water level of underground water periodically rises due to climatic factors, and part of the vertical isolation engineering barrier is influenced by dry-wet circulation, so that the engineering performance of the vertical isolation engineering barrier is influenced.
At present, the law that the dry-wet circulation influences the performance of the vertical isolation engineering barrier through a means of simulating the periodic rising and falling of the groundwater level does not exist, and the suction influence range of the groundwater level rising and falling on the vertical isolation engineering barrier cannot be evaluated through an indoor test.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a model device of a vertical isolation engineering barrier based on dry-wet circulation, a using method and application thereof, and the device can simulate the influence range of the suction change of various vertical isolation engineering barriers (including a grouting curtain, a cement soil stirring wall, a soil-bentonite series vertical isolation wall and a soil-cement-bentonite series vertical isolation wall) after undergoing the dry-wet circulation caused by the water level rise and fall of underground water, measure the saturated permeability coefficient, the effective diffusion coefficient and the retardation factor, and provide scientific basis for evaluating the performance of the vertical isolation engineering barrier under the action of the dry-wet circulation in the operation process.
The utility model provides a model device of vertical isolation engineering barrier based on dry and wet circulation, includes mold box, big water tank, the little water tank in left side and the little water tank in right side, the aspect ratio of mold box is less than 1:10, the bottom of mold box is spread with plain concrete bed course, the space more than plain concrete bed course is cut into 3 regions by 2 vertical baffles, and 3 regions are left side layering soil body region respectively according to the order from a left side to the right, and vertical isolation engineering region and right side layering soil body region are regional, divide into N layers in left side layering soil body region and the right side layering soil body region according to from bottom to top direction, and be equipped with first hole and third hole on the stringcourse that is close to vertical isolation engineering region on the front bezel of each layer of corresponding mold box, the front bezel of the corresponding mold box in vertical isolation engineering region is equipped with the second hole, is equipped with the fourth hole on the rear bezel, and first hole, The height of the second hole, the height of the third hole and the height of the fourth hole are equal, a plastic cover is embedded in the second hole and connected with a glass bottle, Whatman #42 type filter paper is arranged in the glass bottle, a probe type TDR instrument is embedded in the fourth hole and connected with a data acquisition instrument; the left layered soil area and the inner side surface of the model box are provided with left porous vertical plates, the right layered soil area and the inner side surface of the model box are provided with right porous vertical plates, the top of the model box is provided with an upper porous base plate and a T-shaped sealing top cover from bottom to top, the upper porous base plate is divided into two blocks which are respectively positioned at the tops of the left layered soil body area and the right layered soil body area and have the same size; the height of the protruding part of the T-shaped sealing top cover is consistent with the thickness of the upper porous cushion plate, the protruding part is the same as the top of the vertical isolation engineering barrier area, each layer in the left layered soil area is gathered to the left lower two-way valve through a pipeline and then communicated with the left large water tank, the left side of the large water tank is provided with a drainage two-way valve, the model box is communicated with the left small water tank through the left upper two-way valve, each layer in the right layered soil area is gathered to the right upper two-way valve through a pipeline and then communicated with the right small water tank, and the other side of the right small water tank is connected with an air compressor through an air pressure control valve and controls and keeps the water pressure in the right small water tank through the air pressure control valve.
The improvement is that the left layered soil body area and the right layered soil body area are divided into three layers from bottom to top.
The improvement is that the plain concrete cushion layer is a prefabricated plain concrete plate.
The improvement is that a rubber sealing cushion layer is arranged between the upper porous base plate and the T-shaped sealing top cover, the size of the rubber sealing cushion layer is larger than the outer diameter of the top of the model box, and the protruding part corresponding to the T-shaped sealing top cover is provided with a rectangular opening, so that no gap is left between the T-shaped sealing top cover and the whole periphery of the model box.
As an improvement, the materials of the model box, the upper porous cushion plate, the left porous vertical plate and the right porous vertical plate are all polytetrafluoroethylene.
The vertical isolation engineering barrier is a grouting curtain, a cement soil mixing wall, a soil-bentonite series vertical isolation wall, a soil-cement-bentonite series vertical isolation wall or a steel sheet pile.
As an improvement, an O-shaped sealing gasket is arranged between the glass bottle and the plastic cover.
And an O-shaped sealing gasket is arranged between the second hole and the probe type TDR instrument.
The use method of the model device of the vertical isolation engineering barrier based on the dry-wet cycle comprises the following steps:
step 1, closing an upper left two-way valve, a lower left two-way valve, a drainage two-way valve and a right two-way valve, putting a plain concrete cushion layer into the bottom of a model box, and putting a left porous base plate and a right porous base plate into two sides of the model box;
step 2, plugging the first hole, the second hole, the third hole and the fourth hole of the model box by using plugs;
step 3, respectively arranging vertical baffles at two sides of the designed part of the vertical isolation engineering barrier in the model box, and filling vertical isolation engineering barrier materials between the vertical baffles;
step 4, filling various types of soil bodies on two sides of the vertical isolation engineering barrier layer in a layered mode to the top of the model box, wherein sandy soil is filled by a rain and sand method, and cohesive soil is filled by controlling dry density and water content;
step 5, drawing out the left vertical baffle arranged in the step 3;
step 7, opening a drainage two-way valve to drain distilled water in a large water tank so as to control a left layered soil body water head to enable the water level in a left layered soil body area to drop until no water is drained, and closing the drainage two-way valve;
17, placing upper porous base plates on the tops of the left layered soil body and the right layered soil body, and sealing the top of the model box through a T-shaped sealing top cover;
in the formula (1), rho is the density of the penetrating fluid; g is the acceleration of gravity, 9.8m/s2(ii) a L is the width of the vertical isolation engineering barrier; q is the volume of permeate; p is water pressure; a is the lateral sectional area of the vertical isolation engineering barrier; Δ t is the interval duration;
D＝D*+DmdFormula (3)
Dmd＝αLv type (5)
In formula (2), c is the left-side contaminant concentration; c. C0Right pollutant concentration; v is the seepage velocity; t is time; rdIs the retardation coefficient; d is hydrodynamic dispersion coefficient; x is the calculated distance; dmdIs the mechanical dispersion coefficient; d*Effective diffusion coefficient; tau is a bending factor of soil pore space; alpha is alphaLIs the longitudinal dispersion.
The application of the model device of the vertical isolation engineering barrier based on the dry-wet cycle in retarding the migration of pollutants is provided.
The improvement is that the pollutant is heavy metal polluted liquid or organic polluted liquid.
Has the advantages that:
compared with the prior art, the model device of the vertical isolation engineering barrier based on the dry-wet cycle and the using method and application thereof have the following advantages:
1) the suction and the moisture content of the vertical isolation engineering barrier after the dry-wet circulation are monitored. By simulating the lifting and circulating times of the water level of the underground water, the different depths and widths of the vertical isolation engineering barrier, the soil layer distribution on two sides, the flow condition of the underground water and the pollution source types, the suction influence range of the lifting and circulating times of the water level of the underground water on the vertical isolation engineering barrier and the permeability characteristic of the barrier after dry and wet circulation are determined, and a scientific basis is provided for evaluating the performance of the vertical isolation engineering barrier in the operation process under the action of the dry and wet circulation;
2) the test cost is low, and the operation is simple and convenient. The characteristics of the vertical isolation engineering barrier under various working conditions can be simulated by changing factors such as dry-wet cycle times, pollutant types and water heads.
Drawings
Fig. 1 is a schematic structural diagram of a model device of a vertical isolation engineering barrier based on a dry-wet cycle according to an embodiment of the present invention;
figure 2 is a side view of a model arrangement of a vertical isolation engineering barrier based on a wet and dry cycle according to an embodiment of the present invention,
wherein, 1-model box, 2-big water tank, 3-left small water tank, 4-right small water tank, 5-plain concrete cushion layer, 6-vertical baffle, 7-left layered soil body area, 8-right layered soil body area, 9-first hole, 10-third hole, 11-second hole, 12-fourth hole, 13-plastic cover, 14-glass bottle, 15-Whatman #42 type filter paper, 16-probe type TDR instrument, 17-data acquisition instrument, 18-left porous vertical plate, 19-right porous vertical plate, 20-upper porous backing plate, 21-T type sealing top cover, 22-vertical isolation engineering barrier area, 23-lower left two-way valve, 24-left two-way valve, 25-upper right two-way valve, 26-air pressure control valve, 27-air compressor, 28-rubber sealing cushion layer, 29-drainage two-way valve and 30-O type sealing washer.
Detailed Description
The invention is further described with reference to specific examples.
Example 1
The model device comprises a model box 1, a large water tank 2, a left small water tank 3, a right small water tank 4, a plain concrete cushion 5, a vertical baffle 6, a left layered soil body area 7, a right layered soil body area 8, a first hole 9, a third hole 10, a second hole 11, a fourth hole 12, a plastic cover 13, a glass bottle 14, Whatman #42 type filter paper 15, a probe type TDR instrument 16, a data acquisition instrument 17, a left porous vertical plate 18, a right porous vertical plate 19, an upper porous base plate 20, a T-shaped sealing top cover 21, a vertical isolation engineering barrier area 22, a left lower two-way valve 23, a left two-way valve 24, a right upper two-way valve 25, an air pressure control valve 26, an air compressor 27, a rubber sealing cushion 28, a drainage two-way valve 29 and an O-shaped sealing gasket 30.
The model box 1 is made of Polytetrafluoroethylene (PTFE) material, the top is open when the test for simulating the underground water level lifting measurement suction and the water content is carried out, and the model box is in a sealed state when the permeability coefficient is tested. The T-shaped seal top cover 21, the rubber seal cushion 28 and the upper porous backing plate 20 are sequentially placed on the mold box 1 from top to bottom. The front wall and the rear wall of the model box 1 are provided with a first hole 9, a second hole 11, a third hole 10 and a fourth hole 12, the diameter of an opening is 20mm, the width of the inner side of the model box 1 is 0.4m, the height of the inner side of the model box 1 is 1.3m, the length of the inner side of the model box is 1m, and the depth of each layer of soil is 0.4 m.
The vertical baffle 6, the side perforated vertical plate 18, the right side perforated vertical plate 19, the T-shaped seal top cover 21, the upper perforated base plate 20 and the plastic cover 13 are made of polyvinyl chloride (PTFE) materials, and the width of the vertical baffle is equal to that of the inner side of the model box 1.
The top of the mold box 1 is closed by a T-shaped seal top cover 21 and a rubber seal cushion 28, and the two are fixed by bolts. The height of the protruding portion of the T-shaped seal top cover 21 corresponds to the thickness of the upper porous backing plate 20.
Further, the size of the rubber seal pad 28 is larger than the outer diameter of the mold box 1 in a vertical top view, a rectangular opening is arranged in the rubber seal pad 28, the size and the shape of the rectangular opening are consistent with those of the protruding part of the T-shaped seal top cover 21, and the position of the rectangular opening corresponds to that of the protruding part of the T-shaped seal top cover 21.
The upper porous backing plate 20 is divided into a left porous backing plate and a right porous backing plate, which are respectively arranged on the tops of the left layered soil body 7 and the right layered soil body 8 on two sides of the vertical isolation engineering barrier 22, and the shapes and the sizes of the left porous backing plate and the right porous backing plate are consistent with the shapes and the sizes of the vertical overlooking sectional areas of the left layered soil body 7 and the right layered soil body 8. Each vertical pore passage of the upper porous backing plate 20 is horizontally communicated with the left small water tank 3, and the switch is controlled by the upper left two-way valve 24.
The plain concrete cushion layer 5 is a prefabricated plain concrete plate and is arranged at the bottom of the model box 1, the size of the plain concrete cushion layer is consistent with the shape and the size of the inner side section of the model box 1, and the thickness of the plain concrete cushion layer is 50mm, so that the integral stability of the model box is ensured.
The embedded positions of the probe type TDR instrument 16 and the plastic cover 13 correspond to the second hole 11 and the fourth hole 12 of the model box one by one, the horizontal positions are located at the horizontal central lines of the layered soils of the left layered soil 7 and the right layered soil 8, and the vertical positions are located at the vertical central lines of the vertical isolation engineering barrier 22.
Further, no gap is ensured between the second hole 11 of the mold box and the probe-type TDR instrument 16 by the O-ring seal 30. The glass bottle 14 is connected with the plastic cover 13, and no gap is ensured between the glass bottle 14 and the plastic cover 13 through an O-shaped sealing gasket 30.
Further, the probe type TDR instrument 16 and the plastic cover 13 are inserted into the model box 1 after the simulated groundwater level rise and fall are finished until the infiltration test is started. The rest of the time the mold box second orifice 11 and fourth orifice 12 are both in a closed state.
Example 2
The use method of the model device of the vertical isolation engineering barrier based on the dry-wet cycle comprises the following steps:
step 1: closing the upper left two-way valve 24, the lower left two-way valve 23, the drain two-way valve 29 and the right two-way valve 25, putting the plain concrete cushion 5 into the bottom of the model box 1, and putting the left porous base plate (18) and the right porous base plate (19) into the two sides of the model box;
step 2: plugging the first hole 9, the second hole 11, the third hole 10 and the fourth hole 12 of the mold box 1 with plugs;
and 3, step 3: arranging vertical baffles 6 on two sides of the designed part of the vertical isolation engineering barrier 22 in the model box 1 respectively, and filling materials of the vertical isolation engineering barrier 22 between the vertical baffles 6;
and 4, step 4: filling various types of soil bodies on two sides of the vertical isolation engineering barrier 22 in a layered mode, and filling the soil bodies to the top of the model box 1, wherein sandy soil is filled by a rain and sand method, and cohesive soil is filled by controlling dry density and water content;
and 5, step 5: the left vertical baffle 6 arranged in the step 3 is drawn out;
and 6, step 6: distilled water is injected into the large water tank 2, the lower left two-way valve 23 is opened, the water head of the left layered soil body area 7 is controlled through the height of the water level in the large water tank 2, and the left layered soil body area 7 is saturated with water;
and 7, step 7: and opening the drainage two-way valve 29 to drain distilled water in the large water tank 2 so as to control the water head of the left layered soil body 7, so that the water level of the left layered soil body 7 is lowered until no water is drained, and closing the drainage two-way valve 29.
And 8, step 8: repeating the step 6 and the step 7 according to the number of times of simulating the water level of the underground water;
step 9: closing the lower left two-way valve 23 and removing the plugs of the first 9, second 11, third 10 and fourth 12 orifices;
step 10: calibrating and adjusting the probe type TDR instrument 16 and the data acquisition instrument 17, embedding the probe type TDR instrument 16 into the second hole 11, and fixing and sealing the probe type TDR instrument by an O-shaped sealing washer 30;
and 11, step 11: placing a dry Whatman #42 filter paper 15 in the glass bottle 14, and attaching the glass bottle 14 to the plastic cap 13, inserting the fourth well 12, and fixing and closing the same by means of an O-ring seal 30;
step 12: observing whether the probe type TDR instrument 16 and the second hole 11 as well as the plastic cover 24 and the fourth hole 12 have water seepage, if so, repeating the sealing work of the step 9 and the step 10, and if not, performing the step 13;
step 13: weighing the mass of each Whatman #42 type filter paper 15 at intervals, recording the suction change of each depth of the vertical isolation engineering barrier 22 according to the suction-water content table of the Whatman #42 type filter paper 15, and monitoring the water content change of each depth of the vertical isolation engineering barrier 22 in real time through the probe type TDR instrument 16;
step 14: obtaining a soil-water characteristic curve according to the result of the step 12 to evaluate the influence range of the suction change of the vertical isolation engineering barrier 22 caused by the dry-wet cycle caused by the change of the underground water and the migration condition of the water content;
step 15: removing the probe-type TDR instrument 16 and the plastic cover 13, and closing the second hole 11 and the fourth hole 12 by using plugs;
step 16: drawing out the right vertical baffle 6 arranged in the step 3;
step 17: placing an upper porous base plate 20 on the tops of the left layered soil body 7 and the right layered soil body 8, and filling a rubber sealing cushion layer 28 on the porous base plate, wherein the top of the model box 1 is sealed by a T-shaped sealing top cover 21;
step 18: distilled water is injected into the large water tank 2, the lower left two-way valve 23 is opened, and the water head of the left layered soil body 7 is controlled through the height of the water level in the large water tank 2, so that the left layered soil body 7 is saturated;
step 19: closing the lower left two-way valve 23, opening the right two-way valve 25 and the upper left two-way valve 24, and setting the water pressure in the small right water tank 4 filled with the polluted liquid by adjusting the air pressure control valve 26 to saturate the right layered soil body 8;
step 20: observing whether water seepage occurs on the upper part of the model box 1 and the T-shaped sealing top cover 21, if the water seepage occurs, repeating the sealing operation in the step 17, and if the water seepage does not occur, performing the step 21;
step 21: recording the water volume of the left small water tank at intervals), and calculating the permeability coefficient of the vertical isolation engineering barrier 22 according to the formula (1) when the water volume increases for the same time;
in the formula (1), rho is the density of the penetrating fluid; g is the acceleration of gravity, 9.8m/s2(ii) a L is the width of the vertical isolation engineering barrier (20); q is the volume of permeate; p is water pressure; a is the lateral sectional area of the vertical isolation engineering barrier (20); Δ t is the interval duration.
Step 22: removing the plugs of the first hole 9 and the third hole 10, sucking liquid through the needle tubes, respectively measuring the concentration of the pollutants in the collected solutions, and fitting the data according to the formula (2) to obtain the hydrodynamic dispersion coefficient D and the retardation factor RdThe effective diffusion coefficient D is obtained from the formulae (3), (4) and (5)*，
D＝D*+DmdFormula (3)
Dmd＝αLv type (5)
In formula (2), c is the left-side contaminant concentration; c. C0Is the right side sewageConcentration of the dye; v is the seepage velocity; t is time; rdIs the retardation coefficient; d is hydrodynamic dispersion coefficient; x is the calculated distance; dmdIs the mechanical dispersion coefficient; d*Effective diffusion coefficient; tau is a bending factor of soil pore space; alpha is alphaLIs the longitudinal dispersion.
Claims (10)
1. A model device of a vertical isolation engineering barrier based on dry-wet circulation is characterized by comprising a model box (1), a large water tank (2), a left small water tank (3) and a right small water tank (4), wherein the width-height ratio of the model box is less than 1:10, a plain concrete cushion (5) is paved at the bottom of the model box (1), the space above the plain concrete cushion (5) is divided into 3 regions by 2 vertical baffles (6), the 3 regions are respectively a left layered soil body region (7), a vertical isolation engineering barrier region (22) and a right layered soil body region (8) according to the sequence from left to right, soil layers in the left layered soil body region (7) and the right layered soil body region (8) are divided into N layers from bottom to top, and a first hole (9) and a third hole (10) are arranged on a waist line, close to the vertical isolation engineering barrier region, on a front plate of the corresponding box of each layer, a second hole (11) is formed in a front plate of the corresponding model box in the vertical isolation engineering barrier area, a fourth hole (12) is formed in a rear plate, the heights of the first hole (9), the second hole (11), the third hole (10) and the fourth hole (12) are equal, a plastic cover (13) is embedded in the second hole (11), the plastic cover (13) is connected with a glass bottle (14), Whatman #42 type filter paper (15) is arranged in the glass bottle (14), a probe type TDR instrument (16) is embedded in the fourth hole (12), and the probe type TDR instrument (16) is connected with a data acquisition instrument (17); the left layered soil body area (7) and the inner side face of the model box are provided with left porous vertical plates (18), the right layered soil body area (8) and the inner side face of the model box are provided with right porous vertical plates (19), an upper porous base plate (20) and a T-shaped sealing top cover (21) are arranged at the top of the model box (1) from bottom to top, the upper porous base plate (20) is divided into two blocks, the two blocks are respectively positioned at the tops of the left layered soil body area (7) and the right layered soil body area (8), and the two blocks are equal in size; the height of the protruding part of the T-shaped seal top cover (21) is consistent with the thickness of the upper porous backing plate (20), and the size of the protruding part is the same as that of the top of the vertical isolation engineering barrier area (22), each layer of the left layered soil body area (7) is gathered to a left lower two-way valve (23) through a pipeline, then is communicated with a left big water tank (2), a drain two-way valve (29) is arranged at the left side of the big water tank (2), the model box (1) is communicated with the left small water tank (3) through a left upper two-way valve (24), each layer in the right layered soil body area (8) is gathered to an upper right two-way valve (25) through a pipeline and then is communicated with a right small water tank (4), the other side of the right small water tank (4) is connected with an air compressor (27) through an air pressure control valve (26), and the water pressure in the small water tank (4) on the right side is controlled and maintained by the air pressure control valve (26).
2. The model arrangement of a vertical isolation engineering barrier based on a dry-wet cycle according to claim 1, characterized in that the left-side layered soil mass area (7) and the right-side layered soil mass area (8) are divided into three layers in the direction from bottom to top.
3. The model arrangement of a vertical insulation engineering barrier based on a wet and dry cycle according to claim 1, characterized in that the plain concrete bed (5) is a prefabricated plain concrete slab.
4. The model arrangement of the vertical insulation engineering barrier based on the dry-wet cycle according to claim 1, characterized in that a rubber gasket layer (28) is arranged between the upper porous backing plate (20) and the T-shaped seal cover (21), the size of the rubber gasket layer (28) is larger than the outer diameter of the top of the model box (1), and the protruding part corresponding to the T-shaped seal cover (21) is a rectangular opening, so as to ensure that the T-shaped seal cover (21) and the model box (1) have no gap on the whole periphery.
5. The model arrangement of vertical insulation engineering barrier based on dry-wet cycle according to claim 1, characterized in that the materials of the model box (1), the upper perforated liner (20), the left perforated riser (18) and the right perforated riser (19) are all polytetrafluoroethylene.
6. The dry-wet cycle based vertical isolation engineering barrier model arrangement according to claim 1, wherein the vertical isolation engineering barrier area (22) is a grouting curtain, a cement mixing wall, a soil-bentonite series vertical isolation wall, a soil-cement-bentonite series vertical isolation wall or a steel sheet pile.
7. The model arrangement of a vertical insulation engineering barrier based on a wet and dry cycle according to claim 1, characterized in that an O-ring seal (30) is provided between the glass bottle (14) and the plastic cover (13); an O-shaped sealing gasket (30) is arranged between the second hole (11) and the probe type TDR instrument (16).
8. The use method of the model device of the vertical isolation engineering barrier based on the dry-wet cycle according to claim 1, is characterized by comprising the following steps:
step 1, closing an upper left two-way valve (24), a lower left two-way valve (23), a drainage two-way valve (29) and an upper right two-way valve (25), putting a plain concrete cushion layer (5) into the bottom of a model box (1), and arranging a left porous vertical plate (18) and a right porous vertical plate (19) on two sides;
step 2, plugging a first hole (9), a second hole (11), a third hole (10) and a fourth hole (12) of the mold box (1) by using plugs;
step 3, arranging vertical baffles (6) on two sides of a designed part of a vertical isolation engineering barrier area (22) in the model box (1) respectively, and filling materials of the vertical isolation engineering barrier area (22) between the vertical baffles (6);
step 4, filling various types of soil bodies on two sides of a vertical isolation engineering barrier area (22) in a layered mode to the top of a model box (1), wherein sandy soil is filled by a rain and sand method, and cohesive soil is filled by controlling dry density and water content;
step 5, drawing out the left vertical baffle (6) arranged in the step 3;
step 6, distilled water is injected into the large water tank (2), the lower left two-way valve (23) is opened, the water head of the left layered soil body area (7) is controlled through the height of the water level in the large water tank (2), and water in the left layered soil body area (7) is saturated;
step 7, opening a drainage two-way valve (29) to drain distilled water in the large water tank (2) so as to control a water head of the left layered soil body area (7), enabling the water level of the left layered soil body area (7) to drop until no water is drained, and closing the drainage two-way valve (29);
step 8, repeating the step 6 and the step 7 according to the number of times of simulating the water level of the underground water;
step 9, closing the lower left two-way valve (23), removing the plugs of the first hole (9), the second hole (11), the third hole (10) and the fourth hole (12);
step 10, calibrating and adjusting the probe type TDR instrument (16) and the data acquisition instrument (17), and embedding the probe type TDR instrument (16) into the second hole (11) for fixing and sealing;
step 11, placing dry Whatman #42 type filter paper (15) in a glass bottle (14), connecting the glass bottle (14) with a plastic cover (13), embedding the glass bottle into a fourth hole (12), and fixing and closing the glass bottle through an O-shaped sealing gasket (30);
12, observing whether the probe type TDR instrument (16) and the second hole (11) as well as the plastic cover (13) and the fourth hole (12) have water seepage, repeating the sealing work of the step 9 and the step 10 if the water seepage occurs, and performing the step 13 if the water seepage does not occur;
step 13, weighing the mass of each Whatman #42 type filter paper (15) at intervals, recording the suction change of each depth of the vertical isolation engineering barrier area (22) according to the suction-water content table of the Whatman #42 type filter paper (15), and monitoring the water content change of each depth of the vertical isolation engineering barrier area (22) in real time through a probe type TDR instrument (16);
step 14, obtaining a soil-water characteristic curve according to the result of the step 13 so as to evaluate the influence range of suction change of a vertical isolation engineering barrier area (22) caused by dry-wet circulation caused by groundwater change and the migration condition of water content;
step 15, removing the probe type TDR instrument (16) and the plastic cover (13), and sealing the second hole (11) and the fourth hole (12) by using plugs;
step 16, drawing out the right vertical baffle (6) arranged in the step 3;
17, placing upper porous base plates (20) at the tops of the left layered soil body area (7) and the right layered soil body area (8), and sealing the top of the model box (1) through a T-shaped sealing top cover (21);
step 18, distilled water is injected into the large water tank (2), a left lower two-way valve (23) is opened, and a water head of the left layered soil body area (7) is controlled through the height of the water level in the large water tank (2), so that the left layered soil body area (7) is saturated;
step 19, closing the lower left two-way valve (23), opening the upper right two-way valve (25) and the upper left two-way valve (24), and setting the water pressure in the small right water tank (4) filled with the polluted liquid by adjusting the air pressure control valve (26) to saturate the layered soil body area (8) on the right side;
step 20, observing whether water seepage occurs on the upper part of the model box (1) and the T-shaped sealing top cover (21), if so, repeating the sealing work in the step 17, and if not, performing the step 21;
step 21, recording the water volume of the left small water tank (3) at intervals, and calculating the permeability coefficient of the vertical isolation engineering barrier area (22) according to the formula (1) when the water volume is increased for the same time period
and step 22, removing the plugs of the first hole (9) and the third hole (10), sucking liquid through a needle tube, respectively measuring the concentration of pollutants in the collected solutions, and fitting data according to the formula (2) to obtain the hydrodynamic dispersion coefficientDAnd retardation factorR dThe effective diffusion coefficient is obtained from the formulas (3), (4) and (5)D *
In the formula (2), the reaction mixture is,cleft side contaminant concentration;c 0right pollutant concentration;vis the seepage velocity;tis time;R dis the retardation coefficient;Dis the hydrodynamic dispersion coefficient;xto calculate the distance;D mdis the mechanical dispersion coefficient;D *effective diffusion coefficient;
the bending factor of the soil pore space;
is the longitudinal dispersion.
9. Use of a model device based on a vertical isolation engineering barrier based on a wet and dry cycle according to claim 1 for retarding the migration of contaminants.
10. Use according to claim 9, wherein the contaminant is a heavy metal contaminated liquid or an organic contaminated liquid.
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| CN111595747B (en) * | 2020-05-13 | 2021-03-02 | 东南大学 | Model device for testing leakage of geomembrane composite vertical barrier and using method and application thereof |
| CN113804599A (en) * | 2020-06-17 | 2021-12-17 | 必照岩土科技(南京)有限公司 | Device for testing influence of construction defects on seepage flow of geomembrane composite barrier |
| CN112964610B (en) * | 2021-01-30 | 2022-04-26 | 浙江大学 | Hypergravity model test method for simulating migration of pollutants in vertical separation wall |
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