A device and method for rapidly determining the permeability coefficient of low permeability soils

Abstract

The application discloses a device and method for rapidly determining the permeability coefficient of low-permeability soil bodies, and relates to a device and method for determining the permeability of low-permeability soil bodies in a laboratory in the fields of ocean engineering, geological engineering and geotechnical engineering. The device comprises a fluid supply part, a sleeve determination part, a fluid collection part and a test test part. Compared with existing equipment for determining the permeability coefficient of low-permeability soil bodies, the device has the characteristics of simple structure and portability. The hydrophilic porous polyester material and other components used in the device make the method have the characteristics of rapidity, time saving, high sensitivity and accurate determination. Furthermore, the application provides a matching determination method.

Description

Technical Field

[0001] This invention relates to an apparatus and method for determining the permeability of low-permeability soils in the laboratory fields of marine engineering, geological engineering, and geotechnical engineering. The samples to be measured include types such as soft clay, dense sandstone, mudstone, and shale. Background Technology

[0002] The permeability coefficient, also known as the hydraulic conductivity coefficient, is defined as the flow rate of a fluid passing through a soil mass with a unit hydraulic gradient per unit cross-sectional area. It reflects the ease with which a fluid passes through the pores of the soil skeleton. Conveniently, quickly, and accurately determining the soil permeability coefficient and describing its permeability performance is of great significance and importance for practical applications in fields such as natural gas and oil development, geological exploration, and engineering design. Currently, conventional permeability coefficient measuring devices are mostly designed for coarse-grained soils with good permeability, making them difficult to apply directly to low-permeability soils, including soft clay, dense sandstone, mudstone, and shale. In low-permeability soils, the seepage volume is very small when the pressure difference is small. To increase the seepage volume, it is often necessary to increase the volume of the soil sample or increase the pressure difference between the inlet and outlet surfaces of the sample, such as using a large cylinder or a high-powered air pump. This results in existing permeability coefficient measuring devices for low-permeability soils having numerous components, being inconvenient to carry, time-consuming, and complex to operate.

[0003] To overcome the shortcomings of existing devices, a small and lightweight material or component capable of rapid water extraction can be sought for use in the collection of seepage fluids from soil. In fields such as chemical, pharmaceutical, food, and wastewater treatment, hydrophilic membranes can filter water under very low pressure, achieving the separation, purification, and concentration of liquids. Hydrophilic membranes using materials such as polyhexenol, povidone, and polyethersulfone are widely used commercially, but their application in geotechnical testing has not yet been reported. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention, in conjunction with the aforementioned characteristics of hydrophilic membranes, provides a specific device for rapidly determining the permeability coefficient of low-permeability soil by varying water head. Furthermore, based on this device, a matching measurement method is also provided.

[0005] To achieve the above objectives, the present invention can adopt the following technical solutions:

[0006] (1) A fluid supply section, comprising a tray and fluid, wherein the fluid is the same as the fluid in the sample being tested;

[0007] (2) The sleeve measuring part includes a lower sleeve and an upper cover, which are threaded together; the lower sleeve is a hollow tubular structure with external threads on the outer side of its upper end and a sealing strip on the inner side of its upper end; the upper part of the upper cover is a clamping sealing connector, and both the upper cover and the clamping sealing connector have holes, and the inner surface of the upper cover is an internal thread.

[0008] (3) Fluid collection part, including water collection composite pipe and water collection hose, the lower end of the water collection hose is connected to the water collection composite pipe; water collection device, the lower part of which is connected to the water collection hose, the surface of which is marked with scale values, and the inside of which has a negative pressure handle with a piston end; a limiting rod is placed between the negative pressure handle and the water collection device; the fluid flows into the water collection device through the water collection composite pipe and the water collection hose.

[0009] (4) The test section includes the test sample and the soil cutting ring, with a permeable stone at each end.

[0010] A second aspect of the present invention provides an osmotic pressure testing method using the apparatus described in the first aspect, comprising the following steps:

[0011] (1) Connect the two ends of the water-drawing hose to the water-drawing composite pipe and the water-drawing device respectively to form a fluid collection section;

[0012] (2) Fill the tray with the same fluid as the sample being tested, and add fluid continuously during the measurement to keep the liquid level stable, thus forming the aforementioned fluid supply section;

[0013] (3) Samples were prepared in accordance with the "Standard for Geotechnical Testing Methods" GB / T-50123-2019 to form the aforementioned test section;

[0014] (4) Assemble each part and test it, and calculate the permeability coefficient according to the formula described below.

[0015] Compared with the prior art, the beneficial effects of this invention are as follows: it is the first time that hydrophilic porous polyester material has been applied to the same type of application, which makes the method fast, time-saving, highly sensitive and accurate; compared with existing similar inventions that are large in size and have many parts, this invention has a simple structure and is easy to carry; the structure and method of this device can be easily integrated into related equipment, and has room for further expansion. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the measuring device according to an embodiment of the present invention;

[0018] Figure 2 yes Figure 1 Schematic diagram of the lower middle sleeve;

[0019] Figure 3 yes Figure 1 Cross-sectional view;

[0020] Figure 4 yes Figure 1 A schematic diagram of the test section inside the lower middle sleeve.

[0021] In the diagram: 1. Tray; 2. Fluid; 3. Lower sleeve; 4. Upper cover; 41. External thread; 5. Sealing strip; 6. Clamping sealing connector; 7. Internal thread; 8. Water-drawing composite pipe; 9. Water-drawing hose; 10. Water-drawing device; 11. Scale value; 12. Negative pressure handle; 13. Limiting rod; 14. Test sample; 15. Soil-cutting ring; 16. Permeable stone. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0023] Example:

[0024] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, in the embodiments of this invention are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0025] It should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0026] In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0028] like Figure 1 As shown, the device for rapid determination of the permeability coefficient of low-permeability soil by variable head according to the present invention includes: a fluid supply section, a sleeve measuring section, a fluid collection section, and a test section. The fluid supply section mainly consists of a tray 1, and the fluid 2 is the same fluid as that in the sample being tested. The sleeve measuring section includes a lower sleeve 3 and an upper cover 4, which are threadedly connected. Exemplarily, the lower sleeve 3 is a hollow tubular structure. Figure 2 As shown, the outer side of the upper end of the lower sleeve 3 has an external thread 41, while the inner side of the upper end of the lower sleeve 3 has a sealing strip 5. Figure 3As shown, the upper part of the top cover 4 has a clamping and sealing connector 6. Both the top cover 4 and the clamping and sealing connector 6 have openings, and the inner surface of the top cover 4 has a vertical internal thread 7. The fluid collection part includes a water-collecting composite pipe 8 and a water-collecting hose 9, wherein the lower end of the water-collecting hose 9 is connected to the water-collecting composite pipe 8; the lower part of the water-collecting device 10 is connected to the water-collecting hose 9, and the surface of the water-collecting device 10 is marked with scale values ​​11, and it has a negative pressure handle 12 with a piston end inside. Further, in some embodiments, a limiting rod 13 is also provided, which is placed between the negative pressure handle 12 and the water-collecting device 10. The fluid flows into the water-collecting device 10 through the water-collecting composite pipe 8 and the water-collecting hose 9.

[0029] The test section includes test sample 14 and soil cutting ring cutter 15, such as Figure 4 As shown, there is a permeable stone 16 at the top and bottom of the test sample 14 and the soil cutting ring 15.

[0030] As an optional implementation, in some embodiments, the lower sleeve 3 and the upper top cover 4 are made of stainless steel;

[0031] As an optional implementation, in some embodiments, the clamping sealing connector 6 is made of rubber.

[0032] As an optional implementation, in some embodiments, the lower end of the water-drawing composite pipe 8 is a hydrophilic membrane made of a hydrophilic porous polyester material.

[0033] Compared with existing permeability coefficient measuring equipment for low-permeability soils, this device is simple in structure and lightweight. The hydrophilic porous polyester material and other components used in this device make this method fast, time-saving, highly sensitive and accurate.

[0034] The method for determining the permeability coefficient of the present invention, using the apparatus described above, taking marine soil as an example, includes the following steps:

[0035] (1) Connect the two ends of the water-drawing hose 9 to the water-drawing composite pipe 8 and the lower part of the water-drawing device 10 respectively to form a fluid collection section;

[0036] (2) Fill tray 1 with seawater and add seawater continuously during the measurement to keep the liquid level stable, thus forming the aforementioned fluid supply section;

[0037] (3) Sample preparation according to GB / T-50123-2019 Standard for Geotechnical Testing Methods: Apply a thin layer of Vaseline to the inner wall of the cutting ring 15, place it on the soil sample with the cutting edge facing down; use the cutting knife to cut the soil sample into a soil column slightly larger than the diameter of the cutting ring 15, then press the cutting ring 15 vertically downwards while cutting, until the soil sample extends out of the cutting ring 15; remove the excess soil at both ends and smooth it, and wipe the outer wall of the cutting ring 15 clean;

[0038] (4) Place one permeable stone 16, the soil cutting ring 15 containing the test sample 14, and another permeable stone 16 in sequence, according to... Figure 4 The schematic diagram is placed in tray 1 to form the aforementioned test section;

[0039] (5) Insert the lower sleeve 3 vertically into the test section, carefully pour seawater slowly onto the permeable stone 16 above until no more bubbles emerge, and screw in the upper top cover 4 to form the aforementioned sleeve test section.

[0040] (6) Carefully insert the water collection composite pipe 8 of the fluid collection part into the clamping sealing connector 6, pull up the negative pressure handle 12 to form negative pressure in the water collection device 10, and place the limiting rod 13 between the negative pressure handle 12 and the water collection device 10 to maintain negative pressure.

[0041] (7) Seawater is drawn into the water-drawing device 10, and the scale and time are recorded at a certain point. After a period of time, the amount of seawater drawn in is observed again, and the time difference is recorded. Based on the basic principle of the variable head permeability test, the permeability coefficient of the test sample 14 is calculated using the following formula:

[0042]

[0043] Where: k - permeability coefficient of sample 14; a - internal cross-sectional area of ​​water-drawing device 10; l - height of cutting ring 15; Δt - time interval between two adjacent readings; h i - The reading of the scale value at the i-th reading; h i+1 - The reading of the scale at the (i+1)th reading; A - The cross-sectional area of ​​the sample to be tested;

[0044] (8) In a set of test results, multiple readings and calculations are performed, and the average value is taken as the permeability coefficient of test sample 14.

[0045] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0046] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made based on the essence of the content of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A device for rapidly determining the hydraulic conductivity of a low permeability soil mass, characterised in that, The utility model relates to a variable head permeameter, comprising: a fluid supply unit comprising a tray containing a fluid with the same physicochemical properties as the sample to be measured; a sleeve measurement unit comprising a lower sleeve and an upper cover connected to the lower sleeve, the upper cover being provided with a clamping sealing connector on the upper part, and both the upper cover and the clamping sealing connector are perforated, and the inside of the lower sleeve has a containing cavity; a fluid collection unit comprising a water absorption composite tube, a water absorption soft water device and a limiting rod connected in sequence from bottom to top, the lower end of the water absorption composite tube being a hydrophilic membrane made of hydrophilic porous polyester material, the surface of the water absorption device being marked with scale values, and the inside of the water absorption device being provided with a negative pressure handle with a piston at the end, and the limiting rod is placed between the negative pressure handle and the water absorption device during measurement; a test sample and a cutting ring cutter for cutting the test sample, wherein the water absorption composite tube of the fluid collection part is inserted into the clamping sealing connector, the negative pressure handle is pulled upwards to form negative pressure in the water absorption device, and the limiting rod is placed between the negative pressure handle and the water absorption device to maintain the negative pressure; After the water absorption device absorbs the same fluid as the sample to be measured, the scale and time are recorded at a certain scale, the amount of absorbed fluid is observed again after a period of time, and the interval time difference is recorded, and according to the basic principle of variable head permeameter, the permeability coefficient of the test sample is calculated by the following formula: Δt In the formula: k - The permeability coefficient of the sample to be tested; a -Internal cross-sectional area of ​​the water-drawing device; l - Height of the soil cutting ring cutter; In a group of measurement tests, multiple readings and calculations are taken, and the average value is the permeability coefficient of the test sample. - The time interval between two consecutive readings; h i -No. i The reading of the degree value at the next reading time; h i+1 -No. i The reading of the degree value at the +1st reading; A - Cross-sectional area of ​​the sample to be tested; The outer side of the upper end of the lower sleeve is externally threaded, and the inner side of the upper end is provided with a sealing band; the inner surface of the upper cover is vertically internally threaded, and the internal thread cooperates with the external thread of the lower sleeve.

2. The device for rapidly determining the hydraulic conductivity of a low permeability earth mass according to claim 1, characterized in that, The clamping sealing connector is made of rubber material.

3. The device for rapidly determining the hydraulic conductivity of a low permeability earth formation according to claim 1, wherein, The lower sleeve and the upper cover are made of stainless steel material.

4. The device for rapidly determining the hydraulic conductivity of a low permeability earth formation according to claim 1, wherein, Before the negative pressure is formed, it further comprises:

5. The device for rapidly determining the hydraulic conductivity of a low permeability earth formation according to claim 1, wherein, connecting the two ends of the water absorption soft tube to the water absorption composite tube and the lower part of the water absorption device respectively to form a fluid collection unit; filling the tray with the same fluid as the sample to be measured, and adding fluid during the measurement period to keep the liquid level stable to form the fluid supply unit; According to the standard for soil test methods GB / T-50123-2019, a thin layer of vaseline is applied to the inner wall of the cutting ring cutter, the cutting edge is downward, and the cutting ring cutter is placed on the soil sample; the soil sample is cut into a soil column slightly larger than the diameter of the cutting ring cutter with the cutting ring cutter, then the cutting ring cutter is pressed vertically downward, and the soil sample is cut while being pressed until the soil sample extends out of the cutting ring cutter; the excess soil at both ends is removed and smoothed, and the outer wall of the cutting ring cutter is cleaned; a piece of permeable stone, a cutting ring cutter containing a test sample, and another piece of permeable stone are sequentially combined to form the test sample unit; the lower sleeve is vertically buckled into the test sample unit, the fluid is slowly poured onto the upper permeable stone, and the upper cover is screwed in to form the sleeve measurement unit. ​

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