CN115165675B - Device and method for in-situ measurement of gas diffusion coefficient and permeability coefficient of unsaturated soil - Google Patents
Device and method for in-situ measurement of gas diffusion coefficient and permeability coefficient of unsaturated soil Download PDFInfo
- Publication number
- CN115165675B CN115165675B CN202210413988.9A CN202210413988A CN115165675B CN 115165675 B CN115165675 B CN 115165675B CN 202210413988 A CN202210413988 A CN 202210413988A CN 115165675 B CN115165675 B CN 115165675B
- Authority
- CN
- China
- Prior art keywords
- gas
- air
- threaded steel
- steel pipe
- soil
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 239000002689 soil Substances 0.000 title claims abstract description 72
- 238000009792 diffusion process Methods 0.000 title claims abstract description 48
- 230000035699 permeability Effects 0.000 title claims abstract description 39
- 238000000034 method Methods 0.000 title claims abstract description 19
- 238000012625 in-situ measurement Methods 0.000 title claims abstract description 9
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 83
- 239000010959 steel Substances 0.000 claims abstract description 83
- 238000002347 injection Methods 0.000 claims abstract description 38
- 239000007924 injection Substances 0.000 claims abstract description 38
- 230000000087 stabilizing effect Effects 0.000 claims abstract description 32
- 239000000344 soap Substances 0.000 claims abstract description 15
- 239000000700 radioactive tracer Substances 0.000 claims abstract description 13
- 238000007789 sealing Methods 0.000 claims abstract description 11
- 230000035515 penetration Effects 0.000 claims abstract description 8
- 239000007789 gas Substances 0.000 claims description 192
- 238000005259 measurement Methods 0.000 claims description 14
- 239000004575 stone Substances 0.000 claims description 12
- 238000004364 calculation method Methods 0.000 claims description 9
- 230000000149 penetrating effect Effects 0.000 claims description 9
- 239000000565 sealant Substances 0.000 claims description 7
- 238000005553 drilling Methods 0.000 claims description 6
- 238000012544 monitoring process Methods 0.000 claims description 5
- 230000006641 stabilisation Effects 0.000 claims description 5
- 238000011105 stabilization Methods 0.000 claims description 5
- 238000002955 isolation Methods 0.000 claims description 4
- 239000002680 soil gas Substances 0.000 claims description 4
- 230000001276 controlling effect Effects 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 230000008859 change Effects 0.000 claims description 2
- 238000010998 test method Methods 0.000 claims 1
- 238000005070 sampling Methods 0.000 abstract description 4
- 238000012360 testing method Methods 0.000 description 13
- 239000001307 helium Substances 0.000 description 8
- 229910052734 helium Inorganic materials 0.000 description 8
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 8
- 239000011261 inert gas Substances 0.000 description 8
- 230000005012 migration Effects 0.000 description 8
- 238000013508 migration Methods 0.000 description 8
- 238000011065 in-situ storage Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 229910052704 radon Inorganic materials 0.000 description 3
- SYUHGPGVQRZVTB-UHFFFAOYSA-N radon atom Chemical compound [Rn] SYUHGPGVQRZVTB-UHFFFAOYSA-N 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 239000003566 sealing material Substances 0.000 description 3
- 238000013461 design Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 229910001018 Cast iron Inorganic materials 0.000 description 1
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000001066 destructive effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 229920001903 high density polyethylene Polymers 0.000 description 1
- 239000004700 high-density polyethylene Substances 0.000 description 1
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000002957 persistent organic pollutant Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000005067 remediation Methods 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- 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
-
- G—PHYSICS
- G01—MEASURING; TESTING
- 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
-
- 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
-
- G—PHYSICS
- G01—MEASURING; TESTING
- 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
- G01N2013/003—Diffusion; diffusivity between liquids
Landscapes
- Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- General Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Fluid Mechanics (AREA)
- Dispersion Chemistry (AREA)
- Sampling And Sample Adjustment (AREA)
Abstract
The invention relates to a device and a method for in-situ measurement of gas diffusion coefficient and gas permeability coefficient of unsaturated soil. The air supply device consists of an air steel cylinder containing trace gas with the volume concentration of 5-10%, a pressure reducing valve, a pressure stabilizing valve, a flow stabilizing valve and an air injection pipeline; the measuring device consists of a U-shaped pressure gauge, a soap film flowmeter, a plurality of sections of hollow threaded steel pipes, a porous breathable threaded steel pipe and a penetration cone; the gas sampling device consists of a sealing cutting sleeve, an injector and a gas taking pipeline, and is used for measuring the stable air pressure value of a specific depth and the tracer gas concentration value of a specific interval by injecting gas with constant volume flow into the soil with the depth to be measured, substituting a formula deduced from a theoretical model and a basic assumption to calculate the gas diffusion coefficient and the permeability coefficient in the soil.
Description
Technical Field
The invention belongs to the field of environmental geotechnical engineering, and particularly relates to a device and a method for in-situ measurement of gas diffusion coefficient and permeability coefficient of unsaturated soil.
Technical Field
In unsaturated soil, gas is an important component, and evaluating migration of gas in unsaturated soil is of great engineering significance. For example, in environmental pollution remediation projects, the migration of polluting gases in unsaturated soils is of great concern. In urban domestic garbage landfills, organic matters in garbage are degraded to generate polluted gases containing methane, odor (such as hydrogen sulfide) and the like, and the migration and distribution of the gases in an earth covering layer directly influence the emission reduction effect of the polluted gases in the landfills; in chemical pollution sites, a steam extraction method is often adopted in engineering to collect and reduce the concentration of volatile organic pollutant gas (VOC) in unsaturated soil, and the migration of the VOC in the soil directly influences the pollution site treatment effect. The migration of gas in soil is mainly controlled by the gas diffusion coefficient and permeability coefficient, so that in order to reveal the migration mechanism of the polluted gas in the unsaturated soil on site, thereby guiding the engineering design of the emission reduction of the polluted gas on site, and the device and the method for in-situ measuring the permeability coefficient and the diffusion coefficient of the soil are necessary to be developed.
Currently Feng Shijin et al (patent publication No. CN 106053317A), bi et al (patent publication No. CN 110308070A), du Yanjun et al (patent publication No. CN 110220823A) measure the gas diffusion coefficient and gas permeability coefficient of unsaturated soil by a small-scale unit test device in a laboratory, i.e., the gas diffusion coefficient and permeability coefficient are measured by retrieving an undisturbed soil sample on site. The undisturbed soil sample obtained at the site is typically of small size, and variability in gas migration is not considered during testing because small-sized samples collected at these sites are difficult to reflect site pore characteristics such as the presence of cracks, wormholes, roots and the presence of large particles of organics. Second, sampling from cracked or stone-bearing soil is quite difficult, and even if samples are taken, sample bias may be caused, even where large stones are not sampled at all. In addition, because the field soil body has large difference, the gas permeability coefficient and the diffusion coefficient of the field soil body have large space difference, and huge economic and labor cost is required to be consumed for measuring relevant parameters by collecting a large number of undisturbed soil samples for indoor unit test, so the method has no feasibility. Moreover, in situ sampling is a destructive activity, and long repeated measurements at the same measurement point are not possible. Therefore, the gas diffusion coefficient and the permeability coefficient measured by using the undisturbed soil sample in a laboratory have great differences from the actual condition of the site, and the spatial differences of relevant parameters of the soil body of the site are difficult to be described by taking the undisturbed soil sample for unit test.
Currently, devices for measuring the gas diffusion coefficient and the permeability coefficient of on-site soil exist in China. Wang Hongtao et al (invention patent publication No. CN 102053054A) developed a method for measuring the gas permeability coefficient of a landfill body on site, which requires large-scale instrument construction on site, has a complex calculation method and is difficult to apply in engineering; she Yongjun et al (patent publication No. CN 108680467A) discloses a method for measuring radon diffusion coefficient and radon generation rate capable of being moved in situ in underground engineering, which is characterized in that two holes with different radiuses are drilled on the surface of a rock wall to be tested, two sections of sealing materials are filled in the holes of the two holes, so that the hole wall and the two sections of sealing materials are enclosed to form a cylindrical cavity as radon collecting chamber, however, the method is capable of measuring by drilling holes with certain size at measuring depth, and the economic cost of drilling is high, meanwhile, the sealing materials are required to be thoroughly hardened, the measuring time is long, and engineering application is not facilitated. Zhan Liangtong et al (invention patent publication number: CN 110455673A) developed an in-situ measurement of the gas permeability coefficient and the diffusion coefficient of unsaturated soil by penetrating, but the device needs to be filled with gas twice to measure the gas diffusion coefficient and the permeability coefficient of soil body respectively, and can not realize the simultaneous measurement of the gas diffusion coefficient and the permeability coefficient by filling gas once; in addition, when the device is used for measuring the diffusion coefficient of soil, the pressure of the gas injection point in the soil needs to be controlled to be ignored, so that the precondition of the measurement of the gas diffusion coefficient of the soil body, namely the gas in the soil is moved by virtue of diffusion, and under the condition of large gas flux, the pressure of the gas injection point is difficult to be ignored, so that certain inconvenience exists in operation, and the measurement time is prolonged.
In general, the existing in-situ measurement device and method for measuring the permeability coefficient and the diffusion coefficient of unsaturated soil gas have the following disadvantages:
(1) The time for measuring the gas diffusion coefficient is longer.
(2) The gas diffusion coefficient and the permeability coefficient of the soil body cannot be obtained simultaneously based on one measurement.
(3) The calculation method is influenced by the empirical coefficient, is too complex (such as numerical calibration and nonlinear curve fitting are needed), and is difficult to manually, accurately and quickly calculate and determine the gas permeability coefficient and the diffusion coefficient.
(4) In measuring the gas diffusion coefficient, it is necessary to control or assume that the gas pressure at the gas injection point in the soil is sufficiently small that the influence of gas permeation, i.e. the gas in the soil is transported mainly by diffusion, can be neglected. This brings a certain inconvenience to the actual measurement.
(5) And huge cost is required to build test facilities on site.
Disclosure of Invention
In order to overcome the defects of the device and the method for measuring the gas diffusion coefficient and the permeability coefficient of the unsaturated soil in situ, the invention aims to simultaneously measure the gas diffusion coefficient and the permeability coefficient of the unsaturated soil by injecting the gas with constant volume flow into the soil with depth to be measured at one time.
The invention is realized by adopting the following technical scheme:
The device for in-situ measurement of the diffusion coefficient and permeability coefficient of unsaturated soil gas comprises an air steel cylinder containing trace gas (such as inert gas helium) with the volume concentration of 5-10%, a pressure reducing valve, a pressure stabilizing valve and a flow stabilizing valve. The opening valve of the air steel cylinder containing 5-10% of trace gas (such as inert gas helium) by volume concentration is tightly connected with the pressure reducing valve, the pressure stabilizing valve and the flow stabilizing valve in sequence through the gas injection pipeline. The gas injection pipeline and the gas taking pipeline are arranged in the multi-section hollow threaded steel pipe, and the multi-section hollow threaded steel pipe is screwed and sealed by the rod end internal thread matched with the sealing rubber gasket; the first porous air-permeable threaded steel pipe is internally filled with broken stone, the opening end of the air taking pipeline is fixed at the center of the first porous air-permeable threaded steel pipe, the second porous air-permeable threaded steel pipe is internally filled with broken stone, the opening of the air injection pipeline is fixed at the center of the second porous air-permeable threaded steel pipe, the air injection point is separated from the air taking point by r, and isolation between the air taking point and the air taking point is realized by filling sealant.
The measuring method specifically comprises the following steps:
Measuring a gas diffusion coefficient and a target depth of soil with a permeability coefficient according to requirements, calculating the number of sections of the hollow threaded steel pipes required, and penetrating a gas injection pipeline and a gas taking pipeline into the plurality of sections of hollow threaded steel pipes; installing and fixing a gas taking pipeline in the first porous air-permeable threaded steel pipe at the upper part; installing and fixing an air injection pipeline in the second porous air-permeable threaded steel pipe at the lower part; the first porous air-permeable threaded steel pipe and the second porous air-permeable threaded steel pipe are isolated by sealant, and broken stone is filled in the pipes; finally, the hollow threaded steel pipe, the first porous air-permeable threaded steel pipe, the second porous air-permeable threaded steel pipe and the penetration cone which are internally provided with the air injection pipeline and the air taking pipeline are screwed and connected through an internal thread matched sealing rubber pad in sequence;
secondly, pre-drilling a hole slightly smaller than the measuring device by an electric drill, and penetrating the measuring device into the soil target depth;
Thirdly, sequentially connecting an air steel cylinder containing trace gas (such as inert gas helium) with the volume concentration of 5-10%, a pressure reducing valve, a pressure stabilizing valve, a flow stabilizing valve, a U-shaped pressure gauge and a soap film flowmeter in series through a gas injection pipeline;
And fourthly, opening a pressure reducing valve of an air steel cylinder containing trace gas (such as inert gas helium) with the volume concentration of 5-10%, regulating and controlling stable inlet air volume flow through a pressure stabilizing valve and a flow stabilizing valve, and carrying out real-time monitoring by matching with a soap film flowmeter. Collecting gas in a soil body with a target measurement depth through an injector, and detecting the concentration of trace gas by using a gas chromatograph; monitoring the pressure change in the soil body through a U-shaped pressure gauge, and measuring the gas volume flow value (q v) by utilizing a soap film flowmeter; when the concentration value (C 0) of the trace gas and the pressure value (P 0) of the gas tend to be stable, recording the concentration value (C 0) of the trace gas, the pressure value (P 0) of the gas and the volume flow value (q v) of the gas at the moment;
Fifthly, carrying the measured tracer gas concentration value (C 0), the gas pressure value (P 0) and the gas volume flow value (q v) into the following calculation formulas to obtain the gas diffusion coefficient and the permeability coefficient of the unsaturated soil:
The permeability coefficient K (m 2) of the gas in the soil can be calculated according to the following formula:
The gas diffusion coefficient D (m 2/s) in the soil can be calculated as follows:
Wherein, the concentration of the trace gas in the C 1 air steel cylinder (m 3 Tracer gas m-3 Mixed gas );qv is the inlet volume flow value (m 3/s), pi is the circumference ratio (dimensionless), r 0 is the distance (m) between the gas injection center and the gas pressure and the trace gas concentration measuring point, C 0 is the concentration of the trace gas measured at r 0 after stabilization (m 3 Tracer gas m-3 Mixed gas );P0 is the gas pressure value measured at r 0 after stabilization), and mu a is the dynamic viscosity (Pa s) of the gas in the soil.
Compared with the prior art, the invention has the following beneficial effects:
(1) The test device can realize that the gas diffusion coefficient and the permeability coefficient of the soil body can be measured simultaneously by only introducing the trace gas into the soil body once.
(2) The device can realize the rapid measurement of the gas diffusion coefficient and the permeability coefficient of the unsaturated soil at multiple points on site.
(3) The time for measuring the gas migration parameter is short, the calculation method is simple, and the measurement result is accurate.
(4) The experimental device only needs to measure the gas pressure value and the trace gas concentration value of one measuring point, avoids multipoint measurement, and can obtain the gas permeability coefficient and the gas diffusion coefficient of the soil based on the corresponding gas permeability coefficient and the calculation formula of the diffusion coefficient deduced by the invention, and the operation is simple and convenient.
(5) The device and the method provided by the invention avoid the complicated and time-consuming process of sampling and sending to a laboratory for testing, and do not need to expend huge resources to build test facilities on site, and have the characteristics of low cost, simple structure and portability.
The present invention will be further described in detail below with reference to specific embodiments and associated drawings in order to make the objects, technical solutions, calculation methods and advantages of the present invention more apparent.
Drawings
FIG. 1 is a schematic diagram of the structure of the device of the present invention;
FIG. 2 is a detailed cross-sectional view of the device of the present invention;
FIG. 3 is a schematic view of the flow of gas in the soil surrounding the gas injection chamber of the apparatus of the present invention;
the reference numerals in the figures illustrate: 1-an air steel cylinder containing trace gas (such as inert gas helium) with the volume concentration of 5-10%, a 2-pressure reducing valve, a 3-pressure stabilizing valve, a 4-pressure stabilizing valve, a 5-U-shaped pressure gauge, a 6-soap film flowmeter, a 7-gas injection pipeline, an 8-hollow threaded steel pipe, a 9-sealed rubber pad, a 10-first porous gas-permeable threaded steel pipe, a 11-second porous gas-permeable threaded steel pipe, a 12-penetration cone, a 13-gas taking pipeline, a 14-injector and a 15-sealed clamping sleeve.
Detailed Description
As shown in figure 1, the device mainly comprises an air supply device, a measuring device and an air collecting device.
The air supply device includes: an air steel cylinder 1 containing 5-10% of trace gas (such as inert gas helium), a pressure reducing valve 2, a pressure stabilizing valve 3 and a flow stabilizing valve 4. The opening valve of the air steel bottle 1 containing 5-10% of trace gas (such as inert gas helium) in volume concentration is sequentially and tightly connected with the pressure reducing valve 2, the pressure stabilizing valve 3 and the pressure stabilizing valve 4 through the gas injection pipeline 7.
The measuring device includes: the device comprises a U-shaped pressure gauge 5, a soap film flowmeter 6, an air injection pipeline 7, a hollow threaded steel pipe 8, a sealing rubber pad 9, a first porous air-permeable threaded steel pipe 10, a second porous air-permeable threaded steel pipe 11 and a penetration cone 12; the gas injection pipeline 7 and the gas taking pipeline 13 are arranged in the multi-section hollow threaded steel pipe 8 as shown in fig. 2, and the multi-section hollow threaded steel pipe is screwed and hermetically connected through the rod end internal thread matched sealing rubber gasket 9; the first porous air-permeable threaded steel pipe 10 is internally filled with crushed stone and is provided with an air taking pipeline 12, the second porous air-permeable threaded steel pipe 11 is internally filled with crushed stone and is provided with an air injection pipeline 7, the air injection point and the air taking point are separated by a distance r 0, and the isolation between the air injection point and the air taking point is realized by filling sealant.
The gas production device comprises: the ferrule 15 and the syringe 14 are sealed.
As shown in fig. 1, an air cylinder 1 containing a tracer gas (such as inert gas helium) at a concentration of 5% -10% by volume provides air to be delivered to a location to be measured; the pressure reducing valve 2 and the pressure stabilizing valve 3 control the pressure of the delivered gas; the flow stabilizing valve 4 controls the flow of the conveyed gas; the U-shaped pressure gauge 5 detects the pressure of the inlet air, so that the air pressure value in the device in the experimental process is ensured to be within a safe range; the soap film flowmeter 6 accurately measures the gas flow rate when diffusion and permeation reach stability; the gas injection pipeline 7 and the gas taking pipeline 12 play a role in conveying gas; pre-drilling holes slightly smaller than the diameter of the measuring device by using an electric hand drill, and continuously and stably penetrating the gas injection pipeline 7, the gas taking pipeline 12, the first porous gas-permeable threaded steel pipe 10, the second porous gas-permeable threaded steel pipe 11 and the penetrating cone 15 into the depth to be measured to avoid disturbance of soil at the position to be measured; the tracer gas enters the soil body through the first porous air-permeable threaded steel pipe 10, the second porous air-permeable threaded steel pipe 11 provides gas diffusion and permeation channels, broken stones are filled in the porous air-permeable threaded steel pipe, and the holes of the porous air-permeable threaded steel pipe are prevented from being blocked by soil, so that gas diffusion and permeation paths are influenced. The isolation between the gas injection point and the gas taking point in the porous air-permeable threaded steel pipe is realized by filling sealant; after the injector takes gas, the concentration of trace gas at the depth to be measured is measured by a gas chromatograph, and the air pressure at the depth to be measured is measured by a U-shaped pressure gauge.
In the embodiment, the gas injection pipeline 7 and the gas taking pipeline 13 are made of wear-resistant and pressure-resistant HDPE materials; the hollow threaded steel pipe 8, the first porous air-permeable threaded steel pipe 10, the second porous air-permeable threaded steel pipe 11 and the penetration cone 12 are made of cast iron materials with high rigidity; the inner diameter and the outer diameter of the hollow threaded steel pipe 8, the first porous air-permeable threaded steel pipe 10, the second porous air-permeable threaded steel pipe 11 and the penetration cone 12 are 3.4cm and 4cm, and the height of the internal thread and the external thread connected is 2cm. The apertures of the first porous air-permeable threaded steel pipe 10 and the second porous air-permeable threaded steel pipe 11 are 3mm, and the air steel cylinder 1, the pressure reducing valve 2, the pressure stabilizing valve 3 and the flow stabilizing valve 4 (the measuring range is 0-500mL/min, the precision is less than or equal to 1.5% mL/15 min), the U-shaped pressure gauge 5 (the measuring range is 0-10kPa, the precision is 0.01 kPa), the soap film flowmeter 6 (the measuring range of the low-range flowmeter is 0.02-5mL/min, the precision is 0.02mL/min, the measuring range of the high-range flowmeter is 1-1000mL/min, and the precision is 1 mL/min) which contain trace gases with the volume concentration of 5% -10% are all conventional parameter instruments.
The implementation working process of the invention comprises the following steps:
Firstly, calculating the number of sections of the hollow threaded steel pipes according to the soil gas diffusion coefficient and the target depth of the permeability coefficient to be measured, and penetrating an air injection pipeline and an air taking pipeline into the plurality of sections of hollow threaded steel pipes; installing and fixing a gas taking pipeline in the porous air-permeable threaded steel pipe at the upper part; installing and fixing the gas injection pipeline in the lower porous air-permeable threaded steel pipe; the porous air-permeable threaded steel pipe is isolated by sealant, and broken stone is filled in the pipe; finally, the hollow threaded steel pipe, the porous breathable threaded steel pipe and the penetration cone which are internally provided with the gas injection pipeline and the gas taking pipeline are screwed and connected sequentially through the internal thread matched sealing rubber gasket;
secondly, pre-drilling a hole slightly smaller than the measuring device by a hand-held electric drill, and penetrating the measuring device into the soil to a target depth of 0.4m;
thirdly, sequentially connecting an air steel cylinder containing 8% CO 2 by volume concentration, a pressure reducing valve, a pressure stabilizing valve, a flow stabilizing valve, a U-shaped pressure gauge and a soap film flowmeter in series through an air injection pipeline;
And fourthly, opening a pressure reducing valve of an air steel cylinder containing 8% CO 2 by volume concentration, regulating and controlling stable low inlet air volume flow (200 mL/min) through a pressure stabilizing valve and a flow stabilizing valve, and carrying out real-time monitoring by matching with a soap film flowmeter. Every 20-30 minutes, collecting trace gas in 3mL soil body by using a syringe with a measuring range of 5mL, detecting the concentration of the trace gas by using a gas chromatograph, and recording the concentration value of the trace gas (C 0 is 0.042m 3 Tracer gas m-3 Mixed gas ), the pressure value of the gas in the soil body (P 0 is 19.6 Pa) and the volume flow value of the gas (q v1 is 195.78 mL/min) measured by a soap film flowmeter when the concentration value of the trace gas (C 0 in 50min is less than 0.2%) and a U-shaped pressure gauge are stable;
Fifthly, carrying the measured tracer gas concentration value (C 0), the gas pressure value (P 0) and the gas volume flow value (q v) into the following calculation formulas to obtain the gas diffusion coefficient and the permeability coefficient of the unsaturated soil:
The permeability coefficient K (m 2) of the gas in the soil can be calculated according to the following formula:
The gas diffusion coefficient D (m 2/s) in the soil can be calculated as follows:
Wherein, the concentration of the trace gas in the C 1 air steel cylinder (m 3 Tracer gas m-3 Mixed gas );qv is the inlet volume flow value (m 3/s); pi is the circumference ratio (dimensionless), r 0 is the distance between the gas injection center and the gas pressure and the trace gas concentration measuring point, 0.07m is taken here, C 0 is the trace gas concentration measured at r 0 after stabilization (m 3 Tracer gas m-3 Mixed gas );P0 is the gas pressure value measured at r 0 after stabilization, mu a is the dynamic viscosity of the gas in the soil, and mu a is taken here to be 1.83 multiplied by 10 -5 Pa s.
Sixth, in order to verify the effectiveness of the device, after the field test is finished, taking an undisturbed soil sample of a measuring point, measuring the gas permeability coefficient and the diffusion coefficient of the undisturbed soil sample by the indoor small-scale unit test, and comparing and verifying the field measurement result and the unit test measurement result of the device, wherein the verification result is shown in the following table:
In summary, the method only needs to introduce one-time gas to measure the gas pressure/gas concentration and the corresponding gas flow of the point at the designed depth, and can obtain the gas permeability coefficient and the diffusion coefficient of the unsaturated soil of the measuring point through simple calculation. Compared with the prior art, the invention has the characteristics of low manufacturing cost, simple testing process, reliable testing result and the like, and has important significance for the design and long-term safety evaluation of the site pollution gas emission reduction engineering.
Claims (2)
1. An in-situ measurement unsaturated soil gas diffusion coefficient and permeability coefficient's device, its characterized in that: the device consists of an air supply device, a measuring device and an air collecting device;
The air supply device comprises: the air cylinder (1) containing the trace gas with the volume concentration of 5-10%, the pressure reducing valve (2), the pressure stabilizing valve (3) and the flow stabilizing valve (4), wherein the bottleneck valve of the air cylinder (1) containing the trace gas with the volume concentration of 5-10% is used for tightly connecting the pressure reducing valve (2), the pressure stabilizing valve (3) and the flow stabilizing valve (4) in sequence through the gas injection pipeline (7);
The measuring device includes: the device comprises a U-shaped pressure gauge (5), a soap film flowmeter (6), an air injection pipeline (7), a hollow threaded steel pipe (8), a sealing rubber pad (9), a first porous air-permeable threaded steel pipe (10), a second porous air-permeable threaded steel pipe (11) and a penetration cone (12); the hollow threaded steel pipe (8) is internally provided with an air injection pipeline (7) and an air taking pipeline (13), and a plurality of sections of hollow threaded steel pipes are screwed and connected in a sealing manner through a rod end internal thread matching sealing rubber gasket (9); the inside of the first porous air-permeable threaded steel pipe (10) is filled with crushed stone, the opening end of the air taking pipeline (13) is fixed at the center of the first porous air-permeable threaded steel pipe (10), the inside of the second porous air-permeable threaded steel pipe (11) is filled with crushed stone, the opening of the air injection pipeline (7) is fixed at the center of the second porous air-permeable threaded steel pipe (11), the air injection point and the air taking point are separated by r 0, and the isolation between the two air injection points is realized by filling sealant;
the gas production device comprises: a sealing ferrule (15) and a syringe (14).
2. The test method for in-situ measurement of the gas diffusion coefficient and the permeability coefficient of unsaturated soil according to claim 1, which is characterized in that: the method comprises the following steps:
Firstly, measuring a gas diffusion coefficient and a target depth of soil with a permeability coefficient according to requirements, calculating the number of required hollow threaded steel pipes (8), and penetrating a gas injection pipeline (7) and a gas taking pipeline (13) into the plurality of sections of hollow threaded steel pipes (8); installing and fixing a gas taking pipeline (13) in the first porous air-permeable threaded steel pipe (10) at the upper part; installing and fixing the gas injection pipeline (7) in the second porous and breathable threaded steel pipe (11) at the lower part; the first porous air-permeable threaded steel pipe (10) and the second porous air-permeable threaded steel pipe (11) are isolated by sealant, and broken stone is filled in the pipes; finally, the hollow threaded steel pipe (8) internally provided with the gas injection pipeline (7) and the gas taking pipeline (13), the first porous air-permeable threaded steel pipe (10), the second porous air-permeable threaded steel pipe (11) and the penetration cone (12) are screwed and connected through an internal thread matched sealing rubber pad in sequence;
secondly, pre-drilling a hole slightly smaller than the measuring device by an electric drill, and penetrating the measuring device into the soil target depth;
thirdly, an air steel cylinder (1), a pressure reducing valve (2), a pressure stabilizing valve (3), a flow stabilizing valve (4), a U-shaped pressure gauge (5) and a soap film flowmeter (6) which contain trace gas with the volume concentration of 5-10% are sequentially connected in series through an air injection pipeline (7);
Step four, opening a pressure reducing valve (2) of an air steel cylinder (1) containing trace gas with the volume concentration of 5-10%, regulating and controlling stable inlet air volume flow through a pressure stabilizing valve (3) and a flow stabilizing valve (4), and carrying out real-time monitoring by matching with a soap film flowmeter (6); collecting gas in a soil body with a target measurement depth through an injector (14), and detecting the concentration of trace gas by using a gas chromatograph; monitoring the pressure change in the soil body through a U-shaped pressure gauge, and measuring the gas volume flow value q v by utilizing a soap film flowmeter (6); when the concentration value C 0 of the tracer gas and the pressure value P 0 of the gas tend to be stable, recording the concentration value C 0 of the tracer gas, the pressure value P 0 of the gas and the volume flow value q v of the gas at the moment;
Fifthly, carrying the measured tracer gas concentration value C 0, the gas pressure value P 0 and the gas volume flow value q v into the following calculation formulas to obtain the gas diffusion coefficient and the permeability coefficient of unsaturated soil:
the gas permeability coefficient K in the soil is calculated according to the following formula:
The gas diffusion coefficient D in the soil is calculated according to the following formula:
Wherein q v is an intake air volume flow value; mu a is the dynamic viscosity of the gas in the soil; pi is the circumference ratio;
r 0 is the distance between the gas injection center and the gas pressure and trace gas concentration measuring point; the concentration of trace gas in a C 1 air steel cylinder; c 0 is the trace gas concentration measured at r 0 after stabilization.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210413988.9A CN115165675B (en) | 2022-04-14 | 2022-04-14 | Device and method for in-situ measurement of gas diffusion coefficient and permeability coefficient of unsaturated soil |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210413988.9A CN115165675B (en) | 2022-04-14 | 2022-04-14 | Device and method for in-situ measurement of gas diffusion coefficient and permeability coefficient of unsaturated soil |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN115165675A CN115165675A (en) | 2022-10-11 |
| CN115165675B true CN115165675B (en) | 2024-07-02 |
Family
ID=83482623
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210413988.9A Active CN115165675B (en) | 2022-04-14 | 2022-04-14 | Device and method for in-situ measurement of gas diffusion coefficient and permeability coefficient of unsaturated soil |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115165675B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115508256A (en) * | 2022-10-20 | 2022-12-23 | 福州大学 | Gas injection ball for measuring gas permeability coefficient and diffusion coefficient of soil in pre-embedded mode |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105300849A (en) * | 2015-11-27 | 2016-02-03 | 西南石油大学 | Device and method for testing gas diffusion coefficient in porous medium |
| CN109883892A (en) * | 2019-03-26 | 2019-06-14 | 福州大学 | Gas diffusivity measuring device and method in a kind of unsaturated soil |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4011731A1 (en) * | 1990-04-11 | 1991-10-17 | Interatom | DEVICE FOR MEASURING THE GAS PERMEATION THROUGH RUBBER ELASTIC MEMBRANES |
| CN110455673B (en) * | 2019-09-03 | 2020-08-07 | 浙江大学 | Device and method for in-situ measurement of gas migration parameters in unsaturated soil layer through penetration |
| CN111458274B (en) * | 2020-04-20 | 2022-03-11 | 福州大学 | Soil column device and method for measuring gas permeability and diffusion coefficient of unsaturated soil body |
| CN212060097U (en) * | 2020-04-30 | 2020-12-01 | 重庆朕尔医学研究院有限公司 | Gas chromatograph with high detection efficiency |
-
2022
- 2022-04-14 CN CN202210413988.9A patent/CN115165675B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105300849A (en) * | 2015-11-27 | 2016-02-03 | 西南石油大学 | Device and method for testing gas diffusion coefficient in porous medium |
| CN109883892A (en) * | 2019-03-26 | 2019-06-14 | 福州大学 | Gas diffusivity measuring device and method in a kind of unsaturated soil |
Also Published As
| Publication number | Publication date |
|---|---|
| CN115165675A (en) | 2022-10-11 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| AU2017282788B2 (en) | Method for determining diffusion radius of in-situ injection and remediation of contamined soil and groundwater | |
| CN103424341A (en) | Simulator for transport of soil pollutant | |
| CN105717275A (en) | One-dimensional testing device for simulating transport of volatile organic pollutants in soil | |
| CN115165675B (en) | Device and method for in-situ measurement of gas diffusion coefficient and permeability coefficient of unsaturated soil | |
| US12007318B2 (en) | Device and method for in situ penetration measurement of gas transport parameters in unsaturated soil layer | |
| CN111872095B (en) | Flexible bushing and pollution site monitoring method combined with flexible bushing | |
| CN105021660A (en) | Gas-permeable probe capable of quantificationally detecting concentration of volatile organic compounds in polluted soil | |
| CN110082423B (en) | Quick sampling analysis device for soil gas in gas-coated zone | |
| CN111487297B (en) | Method and device for measuring suction force of polluted soil body and concentration of pore solution | |
| CN208399316U (en) | It is a kind of for testing the experimental provision of unsaturation dielectric gas diffusion coefficient and infiltration coefficient | |
| CN111610309A (en) | Device for testing gas adsorption capacity and oxidation efficiency of soil body with controllable soil body external load | |
| CN209206027U (en) | A kind of device for VOCs in meet an urgent need detection and injection rehabilitating soil | |
| CN104713741A (en) | Device and method for evaluating collection efficiency of gas collecting system for volatile organic compounds | |
| CN109839494B (en) | Test device capable of measuring size of capillary gas-phase seepage influence area | |
| CN113686750A (en) | Coal measure stratum composite phase state CO2Seepage characteristic test device and application | |
| CN114813981A (en) | Technology for detecting volatile flux of VOCs (volatile organic compounds) in field | |
| CN206725386U (en) | For determining the experimental rig of oxygen diffusion coefficient in cement-based material | |
| Magnusson | A method for equilibration chamber sampling and gas Chromatographie analysis of the soil atmosphere | |
| CN112903858B (en) | Quick detection device of soil organic pollutant | |
| Feng et al. | A new method and instrument for measuring in situ gas diffusion coefficient and gas coefficient of permeability of unsaturated soil | |
| CN115078635A (en) | Volume-swelling leakage plugging liquid testing device and testing method | |
| Kerfoot | Shallow-probe soil-gas sampling for indication of ground-water contamination by chloroform | |
| CN107192786B (en) | The enrichment preparation facilities and its method of gas in a kind of water body | |
| CN110653250A (en) | In-situ high-pressure rotary spraying injection repairing device for organic pollution site | |
| CN109108060A (en) | A kind of device and method for VOCs in meet an urgent need detection and injection rehabilitating soil |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant |