CN112630126A - Nondestructive in-situ permeability testing device and method suitable for cemented soil - Google Patents
Nondestructive in-situ permeability testing device and method suitable for cemented soil Download PDFInfo
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- CN112630126A CN112630126A CN202110042723.8A CN202110042723A CN112630126A CN 112630126 A CN112630126 A CN 112630126A CN 202110042723 A CN202110042723 A CN 202110042723A CN 112630126 A CN112630126 A CN 112630126A
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- 239000002689 soil Substances 0.000 title claims abstract description 75
- 230000035699 permeability Effects 0.000 title claims abstract description 67
- 238000012360 testing method Methods 0.000 title claims abstract description 32
- 238000011065 in-situ storage Methods 0.000 title claims abstract description 14
- 238000000034 method Methods 0.000 title abstract description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 120
- 230000002787 reinforcement Effects 0.000 claims abstract description 10
- 229920001296 polysiloxane Polymers 0.000 claims description 30
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims description 25
- 238000007789 sealing Methods 0.000 claims description 13
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 12
- 238000002347 injection Methods 0.000 claims description 11
- 239000007924 injection Substances 0.000 claims description 11
- 239000000741 silica gel Substances 0.000 claims description 11
- 229910002027 silica gel Inorganic materials 0.000 claims description 11
- 239000000243 solution Substances 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 8
- 230000003139 buffering effect Effects 0.000 claims description 6
- 238000011010 flushing procedure Methods 0.000 claims description 5
- 239000012466 permeate Substances 0.000 claims description 5
- 230000009471 action Effects 0.000 claims description 4
- 238000002474 experimental method Methods 0.000 claims description 3
- 239000008399 tap water Substances 0.000 claims description 3
- 235000020679 tap water Nutrition 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 238000005259 measurement Methods 0.000 abstract description 2
- 230000008569 process Effects 0.000 abstract description 2
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 10
- 239000011148 porous material Substances 0.000 description 7
- 229910000019 calcium carbonate Inorganic materials 0.000 description 5
- 101000965313 Legionella pneumophila subsp. pneumophila (strain Philadelphia 1 / ATCC 33152 / DSM 7513) Aconitate hydratase A Proteins 0.000 description 4
- -1 acryl Chemical group 0.000 description 3
- 239000003673 groundwater Substances 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 230000003204 osmotic effect Effects 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 2
- 239000008187 granular material Substances 0.000 description 2
- 244000005700 microbiome Species 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 229920000297 Rayon Polymers 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000033558 biomineral tissue development Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 239000003292 glue Substances 0.000 description 1
- 230000008595 infiltration Effects 0.000 description 1
- 238000001764 infiltration Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
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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
- G01N15/0806—Details, e.g. sample holders, mounting samples for testing
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Abstract
The invention provides a nondestructive in-situ permeability testing device and method suitable for cemented soil. The device mainly comprises a grouting reinforcement device and a permeability testing device. The grouting reinforcement device and the permeability testing device can be converted only through the top cover plate, and the whole process has no disturbance to the soil body basically. The permeability testing device mainly comprises a water head controller, a sample cylinder, a porous filter plate and an effluent controller. Particularly, the permeability and hydraulic slope drop measurement of soil bodies with different cementation degrees can be met by adjusting the water head controller. The device has the advantages of simple structure, clear principle, simple and convenient operation, low manufacturing cost and strong applicability. The device provided by the invention can be used for carrying out nondestructive in-situ permeability test on various cemented soils formed after grouting treatment, avoids the problems of poor applicability of the original permeability device and sample disturbance before the permeability test, and has important significance for saving the manufacturing cost of the permeability test device and improving the permeability test accuracy of the cemented soils.
Description
Technical Field
The invention belongs to the field of soil permeability test. Specifically, the invention relates to a nondestructive in-situ permeability testing device and method suitable for cemented soil.
Background
The soil body is used as a loose porous medium, and the pores of the soil body can be used as a flow passage of underground water. When groundwater flows in soil body pore space, can produce the osmotic force to the soil body, when the osmotic force was too big, will arouse the removal of soil granule, make the soil body produce the infiltration and warp, cause fine soil granule even to be taken out by the water and lead to the ground bearing capacity to descend, ground uplift scheduling problem seriously influences building safety. Therefore, in a region with a large permeability, improvement of the permeability of the soil body is required. In addition, when the groundwater is polluted, measures need to be taken rapidly to reduce the permeability of the soil body, block the flow channel of the groundwater and avoid the diffusion of pollutants. By pouring appropriate grouting materials into the soil body, the generated cementing materials can fill the pores of the soil body, and the permeability of the soil body is reduced.
Biomineralization is an emerging technology for improving foundations. By pouring the microorganism liquid and the cementing liquid into the soil body, calcium carbonate can be generated in the soil body under the action of microorganisms. The calcium carbonate can obviously reduce the permeability of the soil body by generating cementation among the soil particles or filling the pores of the soil body. The degree of improvement of soil permeability is directly determined by the calcium carbonate yield in the soil, and the larger the calcium carbonate yield is, the larger the reduction of soil permeability is, the smaller the calcium carbonate yield is, and the less obvious the reduction of soil permeability is. In addition, the permeability of different soil layers can vary widely. For example, the permeability of cohesive soils is typically 10-10-10-7cm/s, and the permeability of coarse sand can reach 10-2-10-1cm/s. The difference in permeability of the soil may be greater after MICP modification. In practical engineering, the soil body permeability needing to be improved is often different significantly, so that the development of a permeability testing device with the largest application range has great practical value.
In addition, the disturbance to the soil sample can significantly affect the permeability of the soil. After the soil body is disturbed, the pore structure, the pore size, the pore distribution and the like of the soil body are changed to different degrees, and the indexes are closely related to the permeability characteristic of the soil body. Therefore, in order to ensure the permeability evaluation accuracy of the MICP modified soil, the disturbance to the sample should be minimized. If an integrated device capable of directly measuring soil permeability in situ after grouting reinforcement treatment is developed, the problem of soil disturbance caused by sampling before the permeability of grouting reinforced soil is measured can be solved, the error of permeability measurement is reduced, and the accuracy of cemented soil permeability evaluation is improved.
Disclosure of Invention
In order to realize the functions, the invention provides a nondestructive in-situ permeability testing device and method suitable for cemented soil, and mainly aims to improve the applicability of the permeability testing device and avoid disturbance to a soil body after grouting reinforcement and before permeability testing.
The technical scheme of the invention is as follows:
a nondestructive in-situ permeability testing device suitable for cemented soil comprises a sample device, a water head controller, a water injection system, an outflow device and a rack;
the sample device mainly comprises a first acrylic cylinder 1, a first flange plate 2, a bottom cover plate 3, a top cover plate 4 and a silica gel sealing washer 5; the top and the bottom of the first acrylic cylinder 1 are respectively fixed with a first flange 2, the first flange 2 is a hollow disc, and the inner diameter of the first flange is consistent with that of a sample device; 4 threaded holes are uniformly formed in the outer edge of the first flange 2 at a certain distance and are used for connecting the first flange 2 with a bottom cover plate 3, a top cover plate 4 or other sample devices; a circular groove 9 is arranged on one circular surface of the first flange plate 2, the circular surface is an outer end surface, and the other circular surface is an inner end surface; the circular groove 9 on the outer end face is used for placing the silica gel sealing washer 5;
the outer diameters of the top cover plate 4 and the bottom cover plate 3 are the same as the outer diameter of the first flange plate 2, a through hole is formed in the middle of the top cover plate and the bottom cover plate, and a pagoda joint 8 is screwed into the through hole; a circular groove 9 is formed in one circular surface of the top cover plate 4 and the bottom cover plate 3, the circular surface is an inner end surface, and the other circular surface is an outer end surface; the positions of the circular grooves 9 on the top cover plate 4 and the bottom cover plate 3 correspond to the positions of the circular grooves 9 on the first flange plate 2;
the inner end face of the bottom cover plate 3 is connected with a first porous filter plate 11 made of PVC material; four identical filter plate supports 12 are arranged between the first porous filter plate 11 and the bottom cover plate 3, and a water containing layer 13 is formed between the first porous filter plate 11 and the bottom cover plate 3; the filter plate support 12 is made of an acrylic plate in a rectangular parallelepiped shape; the outer diameter of the first porous filter plate 11 is the same as the inner diameter of the sample device, and a plurality of through holes 14 are uniformly distributed on the first porous filter plate 11 and used as a passage for solution to flow;
the water head controller mainly comprises a second acrylic cylinder 15, a second flange 19, a pagoda joint 8, a control valve and a silicone tube 18; the second acrylic cylinder 15 is connected with the top of the sample device through a second flange 19, and the inner diameter and the thickness of the second acrylic cylinder 15 are the same as those of the first acrylic cylinder 1; along the height direction of the water head controller, 6 through holes are arranged on the side wall of the second acrylic cylinder 15 at equal intervals, and pagoda joints 8 are screwed into the through holes to be used as overflow holes 16 of the water head controller; the pagoda joint 8 is connected with a silicone tube 18 provided with a second water stop valve 22; controlling the head height of the head controller by opening and closing the second water stop valve 22 on each overflow hole 16; the first flange plate 2 and the second flange plate 19 have the same structure;
after the grouting reinforcement test is finished, unscrewing M8 bolts 7 on the periphery of the top cover plate 4 of the sample tester, and after the top cover plate 4 is taken down, keeping the silica gel sealing washer 5 in place; fixing the first flange 2 and the second flange 19 together by using M8 bolts 7; the second porous filter plate 20 made of PVC material is arranged at the top of the sample and used for buffering water flow during water injection, so that the top of the sample is prevented from being damaged by water flushing; the outer diameter of the second porous filter plate 20 is the same as the inner diameter of the sample device, and a plurality of through holes 14 are uniformly arranged on the second porous filter plate 20 and used as a passage for the circulation of solution;
the water injection system comprises a water reservoir 21, a silicone tube 18 and a first water stop valve 17; one end of the silicone tube 18 is arranged at the bottom of the water reservoir 21, and the other end is arranged in the water head controller; a first water stop valve 17 is arranged on the silicone tube 18 and used for controlling water supply;
the outflow device mainly comprises a support cross rod 23 and a stand, the stand comprises a base 24 and an upright rod 25, and the upright rod 25 is welded on the base 24; the supporting cross rod 23 is connected to the upright rod 25 through an elastic bolt 26, and the height of the supporting cross rod 23 is adjusted by adjusting the elastic bolt 26; one end of a silicone tube 18 serving as an outflow channel is connected to the pagoda joint 8 on the bottom cover plate 3, the other end of the silicone tube is fixed on the supporting cross rod 23, and the water head difference of the whole permeation device is adjusted by adjusting the height of the supporting cross rod 23; a measuring cylinder 27 is arranged on the base 24, and the measuring cylinder 27 is positioned right below the port of the silicone tube 18 and is used for measuring the amount of the permeated water.
The application method of the nondestructive in-situ permeability testing device suitable for the cemented soil comprises the following steps:
after the grouting reinforcement experiment is completed, unscrewing M8 bolts 7 on the periphery of the top cover plate 4 of the sample tester, taking down the top cover plate 4, and keeping the silica gel sealing washer 5 in the original position; fixing a first flange 2 at the upper end of the sample instrument and a second flange 19 of the water head controller together by using M8 bolts 7 and nuts; a first porous filter plate 11 is arranged at the upper end of the sample and used for buffering water impact pressure and preventing soil from being damaged by water impact; the water injected into the water head controller flows out along the overflow hole at the position of the set water head height; adjusting the fixing bolts to fix the supporting cross bar 23 to a position lower than the lower surface of the sample; closing the second water stop valve 22 of the lowest overflow hole 16 on the side wall of the water head controller, and opening the second water stop valves 22 of other overflow holes 16; connecting a water injection system, starting a constant pressure water pump, and injecting tap water into the water head controller; collecting the solution discharged from the sample outlet system by using a measuring cylinder 27; judging the reasonability of an overflow hole opened on the water head controller according to the amount of the outflow liquid; in a certain time, when the outflow liquid is too little, the overflow hole 16 at the higher part is selected to be opened, and the overflow hole 16 at the lower end is closed; the permeability coefficient and the hydraulic slope drop of the soil bodies with different permeability are measured by controlling the opening and closing of different overflow holes 16, so that the applicability of the permeability device is expanded;
adjusting the loose and tight bolts 26, fixing the supporting cross rod 23 at a position higher than the upper top surface of the sample, and continuing to inject water for a certain time to completely saturate the soil body;
adjusting the loose bolts 26 to fix the support cross rods 23 at positions higher than the bottom surface of the sample; placing the measuring cylinder 27 in the positive direction of the port of the silicone tube 18 of the outflow channel; under the action of the water head pressure, the injected water can permeate in the soil body and flow into the measuring cylinder 27 through the outflow channel; by recording the amount of water seeping from the soil body within a certain time, the permeability coefficient can be calculated according to the following formula:
wherein: k is a permeability coefficient and the unit is cm/s;
v is the volume of the measured permeation flow in the measuring cylinder and is in cm3；
L is the height of the sample, and the unit is cm;
a is the cross-sectional area of the soil filled in the cylindrical barrel, and the unit is cm2；
Delta h is a water head difference which is equal to the height difference between the upper overflow hole and the lower end outflow port, and the unit is cm;
t is the time to measure the permeate flow in units of s.
The invention has the beneficial effects that: compared with other permeability testing devices and methods, the device provided by the invention can be used for carrying out in-situ permeability testing on the soil body reinforced by the MICP, the whole process has no disturbance on the soil body, and the permeability testing accuracy of the MICP cemented soil is improved. Meanwhile, the device adjusts the height of the overflow hole in real time through the water head controller, and can realize permeability determination of soil bodies with various cementation degrees under reasonable seepage rate. The device simple structure, low in manufacturing cost, the principle is clear and definite, easy operation, portable has the significance to the manufacturing cost of saving permeability testing arrangement, improvement cemented soil's permeability test efficiency and accuracy.
Drawings
Fig. 1 is a front view of the sample holder.
FIG. 2 is a front view of a permeability testing apparatus.
Fig. 3 is a top view of the flange.
Fig. 4 is a top and bottom cover plate plan view.
Fig. 5 is a top view of the porous filter plate.
In the figure: 1 acrylic cylinder; 2, a flange plate; 3, a bottom cover plate; 4, a top cover plate; 5, sealing a silica gel gasket; 6, a first flange plate threaded hole; 7M8 bolt; 8, a pagoda joint; 9, a circular groove; 10M8 threaded holes; 11 a first porous filter plate; 12, supporting a filter plate; 13 water holding layer; 14 through holes; 15 a second acrylic cylinder; 16 overflow holes; 17 a first water stop valve; 18 silicone tube; 19 a second flange; 20 a second porous filter plate; 21 a water reservoir; 22 a second water stop valve; 23 supporting a cross bar; 24 a base; 25, erecting a rod; 26 loosening and tightening bolts; 27 measuring cylinder.
Detailed Description
In order to make the technical solutions of the present invention better understood, those skilled in the art will be further described in detail with reference to the accompanying drawings.
The invention provides a nondestructive in-situ permeability testing device and method suitable for cemented soil. The device mainly comprises a sample main body device and a permeability testing device.
As shown in fig. 1-5, the sample device is mainly composed of a first acrylic cylinder 1, a first flange 2, a bottom cover plate 3, a top cover plate 4, and a silica gel sealing gasket 5. The first acrylic cylinder 1 has an inner diameter of 70mm, a wall thickness of 10mm, and a length of 150 mm. The top and the bottom of the first acrylic cylinder 1 are respectively bonded on the first flange 2 by acrylic viscose glue. The first flange 2 is a hollow disc having a thickness of 10mm, an inner diameter corresponding to the inner diameter of the sample holder, and an outer diameter of 150 mm. Evenly set up 4 symmetric distribution's screw hole 6 on first ring flange 2, the distance of screw hole 6 center to first ring flange 2 outward flange is 15 mm. The threaded hole 6 has a diameter of 6.8mm, corresponding to the M8 bolt 7. One of the circular surfaces of the first flange plate 2 is provided with a circular groove 9 with the outer diameter of 106mm, the width of 3mm and the depth of 1.5mm, and the circular groove is used for placing a silica gel sealing gasket 5. The face with the annular groove 9 is called the outer end face, and the face without the annular groove 9 is the inner end face.
The top cover plate 4 and the bottom cover plate 3 are circular and made of acrylic plates with a thickness of 10 mm. The outer diameters of the top cover plate 4 and the bottom cover plate 3 are the same as the outer diameter of the first flange plate 2, and a through hole of 10mm is arranged in the middle. The large-diameter end of the pagoda joint 8 is screwed into the through hole, and the inner diameter of the pagoda joint 8 is 5 mm. One of the circular surfaces of the cover plate is provided with a circular groove 9, the circular surface is an inner end surface, and the surface which is not provided with the circular groove 9 is an outer end surface. The position of the circular groove 9 on the cover plate corresponds to the position of the circular groove 9 on the first flange plate 2. Evenly set up 4 symmetrical distribution's M8 screw hole 10 on the apron, the distance of M8 screw hole 10 center to first ring flange 2 outward flange is 15 mm. The diameter of the bottom hole of the M8 threaded hole 10 is 6.8mm, which corresponds to the M8 bolt 7.
The inner end face of the bottom cover plate 3 is connected to a first perforated filter plate 11 of PVC material. Four identical filter support 12 are arranged between the first porous filter plate 11 and the bottom cover plate 3, and a water-containing layer 13 is formed between the first porous filter plate 11 and the bottom cover plate 3. The filter plate support 12 is made of an acrylic plate in a rectangular parallelepiped shape. The outer diameter of the first porous filter plate 11 is the same as the inner diameter of the sample device, and a plurality of through holes 14 with the diameter of 3mm are uniformly distributed on the first porous filter plate 11 and are used as a passage for solution to flow through. The first flange 2 at the top of the sample cell is attached to the top cover plate 4 by M8 bolts 7 and the flange at the bottom of the sample cell is attached to the bottom cover plate 4 by M8 bolts 7.
The water head controller consists of a second acrylic cylinder 15, an overflow hole 16, a first water stop valve 17, a silicone tube 18 and a second flange 19. The inner diameter and thickness of the second acryl cylinder 15 are the same as those of the first acryl cylinder 1. The height of the second acryl cylinder 15 is 200 mm. Along the direction of height of water head controller, equidistant 6 through-holes that the internal diameter is 6.9mm that set up on the lateral wall of second ya keli drum 15, the major diameter end of revolving into pagoda joint 8 in the through-hole, the minor diameter end is outside, as the overflow hole 16 of water head controller. The small diameter end of the pagoda joint 8 is connected with a silicone tube 18 with the inner diameter of 4.5mm, and the silicone tube 18 is provided with a first water stop valve 17. The head height of the head controller is controlled by opening and closing the first water stop valve 17 on each overflow hole 16. The first flange 2 on the sample device and the second flange 19 on the water head controller are identical in structure.
After the grouting reinforcement test is completed, the M8 bolts around the top cover plate 4 of the sample tester are unscrewed, and the top cover plate 4 is removed. The silicone sealing gasket 5 remains in place. The first flange 2 on the sample holder and the second flange 19 on the water head controller are fixed together by using M8 bolt nuts. The second porous filter plate 20 made of PVC material is arranged at the top of the sample and used for buffering the water flow pressure during water injection, so that the top of the sample is prevented from being damaged by water flushing. The porous filter plate is the same as the porous filter plate at the bottom of the sample holder.
The water injection system consists of a water reservoir 21, a second water stop valve 22 and a silicone tube 18. One end of the silicone tube 18 is placed at the bottom of the water reservoir 21 and the other end is placed in the head controller. The silicone tube 18 is provided with a second water stop valve 22.
The supporting device is composed of a supporting cross rod 23, a base 24 and a vertical rod 25. The upright 25 is welded to the base 24. The support cross bar is connected to the upright 25 by means of turnbuckles 26. The height of the support rail 23 can be adjusted by adjusting the draw bolts 26. One end of a silicone tube 18 as an outflow channel is connected to the pagoda joint 8 on the bottom cover plate 3, and the other end is fixed on the support cross rod 23. By adjusting the height of the support rail 23, the head difference of the entire osmotic device can be adjusted. A measuring cylinder 27 with the minimum scale of 0.2ml is arranged on the base 24 and is positioned right below the port of the silicone tube 18 and used for measuring the amount of the permeated water.
The use method of the nondestructive in-situ permeability testing device suitable for the cemented soil comprises the following steps:
after the grouting reinforcement experiment is completed, the M8 bolts 7 around the top cover plate 4 of the sample device are unscrewed, and the top cover plate is removed. The silicone sealing gasket 5 remains in place. The first flange 2 at the upper end of the sample device is fixed with the second flange 19 of the water head controller by using M8 bolt nuts. The second porous filter plate 20 is arranged at the upper end of the sample and used for buffering water flushing pressure and avoiding water flushing damage to soil. The water injected into the head controller will flow out along the overflow aperture 16 at the set head height. The jack bolts 26 are adjusted to fix the support bar 23 to a height slightly lower than the lower surface of the sample. The first water stop valve 17 of the lowest overflow hole 16 on the side wall of the water head controller is closed, and the first water stop valves 17 of other overflow holes are opened. And connecting a water injection system, closing the second water stop valve 22 and injecting tap water into the water head controller. The solution drained from the sample outlet system is collected with a graduated cylinder 27. And judging the reasonability of an overflow hole opened on the water flow controller according to the amount of the outflow liquid. And in a certain period of time, when the outflow liquid is too little, the overflow hole 16 at the higher part is selected to be opened, and the overflow hole 16 at the lower end is closed. By controlling the opening and closing of the different overflow holes 16, the permeability coefficient and the hydraulic slope drop of the soil bodies with different permeability can be measured, and the applicability of the permeability device is expanded.
And adjusting the elastic bolts 26 to fix the supporting cross rod 23 at a position higher than the upper top surface of the sample, and continuing to inject water for a certain time to completely saturate the soil body.
The support rail 23 is fixed at a position slightly higher than the bottom surface of the sample by adjusting the tension bolts 26. The measuring cylinder 27 is placed just below the end of the silicone tube 18 of the outflow channel. Under the action of the head pressure, the injected water will penetrate into the soil and flow through the outflow channel into the measuring cylinder 27. By recording the amount of water seeping from the soil body within a certain time, the permeability coefficient can be calculated according to the following formula:
wherein: k is a permeability coefficient and the unit is cm/s;
v is the volume of the measured permeation flow in the measuring cylinder and is in cm3；
L is the height of the sample, and the unit is cm;
a is the cross-sectional area of the soil filled in the cylindrical barrel, and the unit is cm2；
Delta h is a water head difference which is equal to the height difference between the upper overflow hole and the lower end outflow port, and the unit is cm;
t is the time to measure the permeate flow in units of s.
Claims (2)
1. The nondestructive in-situ permeability testing device suitable for cemented soil is characterized by comprising a sample device, a water head controller, a water injection system, an outflow device and a rack;
the sample device mainly comprises a first acrylic cylinder (1), a first flange plate (2), a bottom cover plate (3), a top cover plate (4) and a silica gel sealing gasket (5); the top and the bottom of the first acrylic cylinder (1) are respectively fixed with a first flange (2), the first flange (2) is a hollow disc, and the inner diameter of the first flange is consistent with that of the sample device; 4 threaded holes are uniformly formed in the outer edge of the first flange plate (2) at a certain distance and used for connecting the first flange plate (2) with a bottom cover plate (3), a top cover plate (4) or other sample devices; a circular groove (9) is arranged on one circular surface of the first flange plate (2), the circular surface is an outer end surface, and the other circular surface is an inner end surface; the circular groove (9) on the outer end face is used for placing the silica gel sealing washer (5);
the outer diameters of the top cover plate (4) and the bottom cover plate (3) are the same as the outer diameter of the first flange plate (2), a through hole is arranged in the middle, and a pagoda joint (8) is screwed into the through hole; a circular groove (9) is formed in one circular surface of the top cover plate (4) and the bottom cover plate (3), the circular surface is an inner end surface, and the other circular surface is an outer end surface; the positions of the circular grooves (9) on the top cover plate (4) and the bottom cover plate (3) correspond to the positions of the circular grooves (9) on the first flange plate (2);
the inner end surface of the bottom cover plate (3) is connected with a first porous filter plate (11) made of PVC material; four identical filter plate supports (12) are arranged between the first porous filter plate (11) and the bottom cover plate (3), and a water containing layer (13) is formed between the first porous filter plate (11) and the bottom cover plate (3); the filter plate support (12) is made of an acrylic plate in a rectangular parallelepiped shape; the outer diameter of the first porous filter plate (11) is the same as the inner diameter of the sample device, and a plurality of through holes (14) are uniformly distributed on the first porous filter plate (11) and are used as a passage for solution to flow;
the water head controller mainly comprises a second acrylic cylinder (15), a second flange plate (19), a pagoda joint (8), a control valve and a silicone tube (18); the second acrylic cylinder (15) is connected with the top of the sample device through a second flange plate (19), and the inner diameter and the thickness of the second acrylic cylinder (15) are the same as those of the first acrylic cylinder (1); along the height direction of the water head controller, 6 through holes (14) are arranged on the side wall of the second acrylic cylinder (15) at equal intervals, and pagoda joints (8) are screwed into the through holes to be used as overflow holes (16) of the water head controller; the pagoda joint (8) is connected with a silicone tube (18) which is provided with a second water stop valve (22); the water head height of the water head controller is controlled by opening and closing the second water stop valves (22) on the overflow holes (16); the first flange plate (2) and the second flange plate (19) have the same structure;
after the grouting reinforcement test is finished, unscrewing M8 bolts (7) on the periphery of a top cover plate (4) of the sample tester, and after the top cover plate (4) is taken down, keeping the silica gel sealing washer (5) in the original position; fixing the first flange (2) and the second flange (19) together by using M8 bolts (7); a second porous filter plate (20) made of PVC material is arranged at the top of the sample and used for buffering water flow during water injection, so that the top of the sample is prevented from being damaged by water flushing; the outer diameter of the second porous filter plate (20) is the same as the inner diameter of the sample device, and a plurality of through holes (14) are uniformly distributed on the second porous filter plate (20) and are used as a passage for solution to flow;
the water injection system comprises a water reservoir (21), a silicone tube (18) and a first water stop valve (17); one end of the silicone tube (18) is arranged at the bottom of the water reservoir (21), and the other end is arranged in the water head controller; a first water stop valve (17) is arranged on the silicone tube (18) and used for controlling water supply;
the outflow device mainly comprises a support cross rod (23) and a stand, the stand comprises a base (24) and an upright rod (25), and the upright rod (25) is welded on the base (24); the supporting cross rod (23) is connected to the upright rod (25) through a loose bolt (26), and the height of the supporting cross rod (23) is adjusted by adjusting the loose bolt (26); one end of a silicone tube (18) used as an outflow channel is connected with a pagoda joint (8) on the bottom cover plate (3), the other end of the silicone tube is fixed on a supporting cross rod (23), and the water head difference of the whole permeation device is adjusted by adjusting the height of the supporting cross rod (23); a measuring cylinder (27) is arranged on the base (24), and the measuring cylinder (27) is positioned right below the port of the silicone tube (18) and used for measuring the amount of the permeated water.
2. A nondestructive in-situ permeability testing method applicable to cemented soil is characterized by comprising the following steps:
after the grouting reinforcement experiment is completed, unscrewing M8 bolts (7) on the periphery of a top cover plate (4) of the sample tester, taking down the top cover plate (4), and keeping the silica gel sealing washer (5) in the original position; fixing a first flange (2) at the upper end of the sample device and a second flange (19) of the water head controller together by using M8 bolts (7) and nuts; a first porous filter plate (11) is arranged at the upper end of the sample and used for buffering water impact pressure and preventing soil from being damaged by water impact; the water injected into the water head controller flows out along the overflow hole at the position of the set water head height; adjusting the fixing bolt to fix the supporting cross rod (23) at a height lower than the lower surface of the sample; closing a second water stop valve (22) of the overflow hole (16) at the lowest end on the side wall of the water head controller, and opening second water stop valves (22) of other overflow holes (16); connecting a water injection system, starting a constant pressure water pump, and injecting tap water into the water head controller; collecting the solution discharged from the sample outlet system by a measuring cylinder (27); judging the reasonability of an overflow hole opened on the water head controller according to the amount of the outflow liquid; in a certain time, when the outflow liquid is too little, the overflow hole (16) at the higher part is selected to be opened, and the overflow hole (16) at the lower end is closed; the permeability coefficient and the hydraulic slope drop of soil bodies with different permeability are measured by controlling the opening and closing of different overflow holes (16), so that the applicability of the permeability device is expanded;
adjusting an elastic bolt (26), fixing the supporting cross rod (23) at a position higher than the upper top surface of the sample, and continuing to inject water for a certain time to completely saturate the soil body;
adjusting an elastic bolt (26) to fix the support cross rod (23) at a position higher than the bottom surface of the sample; placing the measuring cylinder (27) in the positive direction of the port of the silicone tube (18) of the outflow channel; under the action of the water head pressure, the injected water can permeate in the soil body and flow into the measuring cylinder (27) through the outflow channel; by recording the amount of water seeping from the soil body within a certain time, the permeability coefficient can be calculated according to the following formula:
wherein: k is a permeability coefficient and the unit is cm/s;
v is the volume of the measured permeation flow in the measuring cylinder and is in cm3；
L is the height of the sample, and the unit is cm;
a is the cross-sectional area of the soil filled in the cylindrical barrel, and the unit is cm2；
Delta h is a water head difference which is equal to the height difference between the upper overflow hole and the lower end outflow port, and the unit is cm;
t is the time to measure the permeate flow in units of s.
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