CN216525358U - Clamping device and system for measuring permeability coefficient of low-permeability soil - Google Patents
Clamping device and system for measuring permeability coefficient of low-permeability soil Download PDFInfo
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- CN216525358U CN216525358U CN202123116987.8U CN202123116987U CN216525358U CN 216525358 U CN216525358 U CN 216525358U CN 202123116987 U CN202123116987 U CN 202123116987U CN 216525358 U CN216525358 U CN 216525358U
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Abstract
The utility model provides a clamping device for measuring permeability coefficient of low-permeability soil, which comprises a base, a cutting ring seat, a plug capable of being matched with the inner surface of the cutting ring seat and a top plate, wherein a fluid inlet and a first channel are arranged in the base, the cutting ring seat, the plug capable of being matched with the inner surface of the cutting ring seat and the top plate, wherein the base, the cutting ring seat and the plug matched with the inner surface of the cutting ring seat jointly define a cavity. Also provided is a system for measuring the permeability coefficient of low permeability soil, the system comprising: a water tank; a vacuum pump fluidly connectable to the vacuum pump; the first detection assembly comprises the clamping device; and a flow measurement tube. The utility model avoids the problem that the soil sample is deformed and even punctured due to the adoption of a large hydraulic gradient, and simultaneously, the micro-tube flow measuring method for preventing the evaporation effect is adopted, so that the test precision and the test efficiency of the experiment are improved.
Description
Technical Field
The utility model relates to a clamping device for measuring the permeability coefficient of low-permeability soil and a system for measuring the permeability coefficient of soil.
Background
The permeability of loose pore media represented by the cohesive soil is accurately measured, and the method has very important significance on aspects of scientific research and production practice in fields of regional water resource balance analysis, groundwater water quality protection, ground settlement and the like of vast flush plain areas of China. Due to low permeability of the clay, e.g. the permeability coefficient of the clay is less than 10-5-10- 7cm/s, therefore, it takes a long time to perform a permeability test of a low permeable loose pore medium under normal pressure conditions.
In order to shorten the testing time, the current common laboratory testing method is a pressure infiltration method, and the hydraulic gradient value is usually hundreds or even thousands. Hydraulic gradient refers to head loss per unit of osmotic path in the direction of water flow. The ground water is required to overcome frictional resistance in the movement process, and mechanical energy is continuously consumed, so that head loss is generated. Hydraulic gradient is also understood to be the ratio of the difference in water level between any two points to the distance between the two points.
Although the method adopting the large hydraulic gradient greatly shortens the experimental time, the experimental method can cause undesirable results, such as that the experimental soil sample is easy to be subjected to mechanical deformation and even to be subjected to hydraulic breakdown under the action of the large hydraulic gradient. Under the condition that the experimental soil sample is deformed or is punctured by water flow, the experimental result has larger errors, so that the analysis accuracy is influenced. In addition, the experimental result of the large hydraulic gradient calculation cannot objectively represent the permeability of the soil body in the actual natural seepage state due to the influence of the Darcy flow.
In addition, the current automated technology is widely applied to outlet flow monitoring of clay permeability test, wherein the automated monitoring needs to use a sensor to monitor the permeation process, and although the measurement precision of an instrument in the test process is high, the flow rate of each permeation flow at the outlet may be only a few milliliters for the permeation flow of clay, so that even if the measurement error of the instrument is small, the measurement result is greatly influenced. In some experiments, the permeation flow rate is monitored by adopting a method of weighing the flow rate by using a high-precision balance, but because the permeation flow rate is small, the water flowing out by the method is easily affected by evaporation, and further fluctuation and instability of results are caused.
SUMMERY OF THE UTILITY MODEL
In order to solve the above problems, the present application provides a holding device for measuring permeability coefficient of low permeability soil, the holding device comprising: a base having a fluid inlet and a first channel disposed therein; a ring cutter supported by the base; a ring cutter seat supported by the base, and an inner surface of the ring cutter seat abuts against an outer surface of the ring cutter, while a bottom surface of the ring cutter seat is higher than a bottom surface of the ring cutter; a plug capable of mating with an inner surface of the ring cutter seat, and the fluid outlet and the second channel being disposed in the plug; and a top plate connected to the base by guide posts, wherein the base, the ring cutter seat and a plug engaged with an inner surface of the ring cutter seat collectively define a chamber.
In one embodiment, a pressing cap is arranged on the outer side of the plug.
In a certain embodiment, the top plate is further provided with a compression bolt.
In a certain embodiment, the clamping device further comprises a plurality of seals.
The present application also provides a system for measuring the permeability coefficient of low permeability soil, the system comprising: a water tank; a vacuum pump fluidly connectable to the water tank; the first detection assembly comprises the clamping device for measuring the permeability coefficient of the soil; and a flow rate measurement pipe having a small aperture, wherein a fluid inlet of the holding device of the first detection member is communicated with the water tank, and a fluid outlet of the holding device of the first detection member is communicated with the flow rate measurement pipe.
In a certain embodiment, the first detection assembly further comprises a first flow control valve, a second flow control valve, and a third flow control valve, the water tank is fluidly connected to the holding fixture through the fourth valve and the first flow control valve, and gas in the holding fixture is capable of flowing through the second flow control valve, the first flow control valve, and the third valve to the vacuum pump.
In a certain embodiment, the first detection assembly further comprises a displacement gauge disposed on the clamping device.
Further, the aperture of the flow measuring tube is smaller than 1mm, e.g. 0.8mm and 0.6 mm.
Further, the flow measuring tube is a hose.
In a certain embodiment, the system further comprises one or more second detection components, the second detection components having the same configuration as the first detection components.
The utility model avoids the problem that the soil sample is deformed and even punctured due to the adoption of a large hydraulic gradient, and simultaneously, the micro-tube flow measuring method for preventing the evaporation effect is adopted, so that the test precision and the test efficiency of the experiment are improved.
The utility model provides a multi-path parallel high-precision penetration experiment system for low-permeability loose pore media, which can finish batch clay penetration capability test in high precision in a short time under the condition of small hydraulic gradient (the numerical value is within 10).
Drawings
The utility model will be discussed in more detail on the basis of exemplary embodiments in the figures, in which:
fig. 1 shows a system for measuring soil permeability coefficient according to an embodiment.
Fig. 2 shows a clamping device according to an embodiment.
Fig. 3 shows a top view of the base of the clamping device.
Fig. 4 shows a cross-sectional view of the base of the clamping device along the line a-a in fig. 3.
Detailed Description
FIG. 1 illustrates an embodiment of a system for measuring soil permeability coefficient of the present invention. As shown in fig. 1, the system may include a water tank 31, the water tank 31 being fluidly connected to a water supply inlet 311 so that water for experimental testing may be introduced into the system. The water tank 31 is provided with a first valve 21, and the first valve 21 is configured to adjust the air pressure of the system and discharge the excessive water introduced into the water tank 31 via the water supply inlet 311 from the water tank 31.
The water tank 31 may be fluidly connected to the vacuum pump 11 via the second valve 22 and the third valve 23 connected in series, the vacuum pump 11 being used to evacuate the entire system to substantially degas the soil sample in the holding device. The water tank 31 may also be fluidly connected to the holding device 60 via the fourth valve 24 and the first flow control valve 41 connected in series. Optionally, a fifth valve 25 connected to the water tank 31 is connected in parallel with the fourth valve 24.
The water in the water tank 31 may flow through the fourth valve 24 and the first flow control valve 41 in order to the holding device 60, and the gas in the holding device 60 may also flow through the second flow control valve 51, the first flow control valve 41 and the fourth valve 24 in order to the vacuum pump 11.
The holding device 60 is a device for accommodating a soil sample, the details of which will be described later. The clamping device 60 may be provided with a displacement meter 71, and the displacement meter 71 is used for detecting whether the soil sample is deformed or punctured by water flow. The holding device 60 and the displacement gauge 71 are accommodated in the oven 100.
The clamping device 60 may be fluidly connected to the flow measurement pipe 9 via a fluid outlet (as shown in fig. 2), and a third flow control valve 81 is provided between the clamping device 60 and the flow measurement pipe 9.
The first detection assembly of the present system may include a first flow control valve 41, a second flow control valve 51, a clamping device 60, a displacement gauge 71, a third flow control valve 81, and an incubator 100. In order to further improve the measurement accuracy, one or more second detection assemblies with the configuration similar to or the same as that of the first detection assembly can be further arranged, and the combination of the first detection assembly and the one or more second detection assemblies can effectively reduce errors caused by damage of parts in the detection assemblies.
Referring to the system for measuring soil permeability coefficient of the present invention shown in fig. 1, the present invention also discloses a method for measuring soil permeability coefficient.
All valves were closed prior to testing.
The soil sample is placed in the holding device 60, and the respective components of the holding device 60 are tightly sealed by a plurality of sealing members, and then the holding device 60 is inserted into the pipeline. The water supply inlet 311 and the first valve 21 are opened, an appropriate amount of water is introduced into the water tank 31, and then the water supply inlet 311 and the first valve 21 are closed. After a suitable amount of water is in the water tank 31, the soil sample and the lines begin to be evacuated. Specifically, the second valve 22, the third valve 23, the first flow control valve 41 and the second flow control valve 51 are opened (at which point the other valves in the system are closed), and the vacuum pump 11 is activated, the vacuum pump 11 may be turned on for, for example, 2 hours in a single test to sufficiently degas the soil sample disposed in the holding device 60. After the evacuation step is completed, the second valve 22 and the third valve 23 are closed, thereby closing or blocking the line between the water tank 31 and the vacuum pump 11. Thereafter, a step of saturating the soil sample is required, in which the first valve 21 and the fourth valve 24 are opened (at this time, the first flow control valve 41 and the second flow control valve 51 are still open), so that the water in the water tank 31 flows into the soil sample in the piping and holding device 60. In order to fully saturate the rock sample, the duration of the step of saturating the soil sample should be at least 2 hours. After the step of saturating the soil sample is completed, the second flow control valve 51 is closed so that water in the water tank 31 can only pass through the fourth valve 24 and the first flow control valve 41 to the holding device 60.
And after the steps are completed in sequence, measuring the soil permeability coefficient. In this step, the third flow control valve 81 is opened so that water passing through the soil sample in the holding device 60 can flow into the flow measurement pipe 9 via the third flow control valve 81. The flow measuring tube 9 may be a flexible tube and have a relatively small bore diameter (preferably less than 1mm, e.g. 0.8mm, 0.6mm, 0.5mm, etc.) so that a predetermined permeation flow of water can flow/displace a relatively long distance within the flow measuring tube 9, e.g. a permeation flow of 1ml of water can flow/displace a distance of about 50cm within the flow measuring tube 9 having a bore diameter of 1mm, by which means the permeability coefficient of the soil sample can be monitored effectively.
Based on multiple experiments, the system of the present application can effectively test 10 in a hydraulic gradient range of 10 or less- 7cm/s-10-6Permeability coefficient in cm/s. The system for measuring the soil permeability coefficient uses the small-bore pipe to improve the visualization degree of flow change, thereby improving the experiment precision and shortening the experiment period.
The clamping device 60 of the present application will now be described in detail. Referring to fig. 2, the clamping device 60 includes a base 610 and a top plate 612, the base 610 and the top plate 612 are connected by a guide post 614, and a pressing bolt 616 is disposed on the top plate 612.
Fig. 3 shows a top view of the base 610 of the holding device 60. In fig. 3 it can be seen that the base 610 has two opposing holes 6110, the holes 6110 being used for mounting the guiding posts 614. Fig. 4 shows a cross-sectional view of the base along line a-a in fig. 3, and it can be seen that a fluid inlet 641 and corresponding fluid channel are provided in the base.
The base 610 supports the cutting ring 630 and the cutting ring seat 631, wherein after the assembly of the clamping device 60 is completed, the inner surface of the cutting ring seat 631 abuts against the outer surface of the cutting ring 630, while the bottom surface of the cutting ring seat 631 is higher than the bottom surface of the cutting ring 630. The clamping device 60 further includes a plug 620, and the plug 620 can be forced downward by a compression bolt 616 passing through the top plate 612. Plug 620 may engage the inner surface of seat 631. The inner surface of the ring seat 631 consists of two cylindrical surfaces of different diameters. A press cap 632 having a threaded portion is further installed on the outer side of the ring holder 631 (the threaded portion of the press cap 632 is used for threaded engagement with the base 610), and the press cap 632 is used for radially fixing the ring holder 631 and the ring cutter 630 after the clamping device 60 is assembled.
After the assembly of the holding device 60 is completed, the base 610, the cutting ring 630, the cutting ring seat 631 and the stopper 620 together define a chamber for receiving a soil sample (which is radially held by the cutting ring 630) and a buffer device, in the embodiment shown in fig. 2, two buffer devices 621 and a soil sample clamped between the two buffer devices are received in the chamber. The buffer device 621 may be a body such as stone, gravel, sand, etc. for storing moisture and making the water pressure uniform. The cutting ring 630 is sized to receive a predetermined volume of soil sample.
The base 610 is further provided with a fluid inlet 641 for water to flow into the holding device 60, water being flowable into the chamber via the fluid inlet 641 and one or more first channels (only one first channel is shown in fig. 2). In an embodiment, the water flowing into the chamber may sequentially pass through the first buffer, the soil sample, and the second buffer, wherein the first buffer and the first buffer may be separately provided as one of stone, gravel, sand, and a mixture thereof. The plug 620 is further provided with a fluid outlet 642 for water to flow out of the holding device 60, water being able to flow out of the holding device 6 via one or more second channels (only one second channel is shown in fig. 2) and the fluid outlet 642.
The clamping device 60 may also include a plurality of seals. A first seal 6810 is disposed at the interface of the base 610, the ring cutter 630, and the first buffer to seal against fluid, a second seal 6820 is disposed at the interface of the base 610, the ring cutter 630, and the ring cutter seat 631 to seal against fluid, a third seal 6830 is disposed at the interface of the ring cutter 630, the ring cutter seat 631, and the second buffer to seal against fluid, and a fourth seal 6840 is disposed in the groove of the bulkhead 620. All sealing members are annular and are used for preventing water flow from permeating, so that the soil sample can be prevented from deforming or even breaking down under the action of osmotic pressure.
The method of use of the clamping device 60 is as follows, with reference to figures 2-4 of the drawings:
s1: placing a first cushioning device (e.g., a stone) in the base;
s2: fitting a first seal 6810 outside the upper end of the first buffer in the base;
s3: arranging the cutting ring filled with the soil sample on a first buffer device;
s4: fitting a second seal 6820 on the outside of the ring knife;
s5: a second buffer device is arranged on the upper end surface of the cutting ring;
s6: a third seal 6830 is fitted to the outside of the second buffer;
s7: the ring cutter seat is sleeved outside the ring cutter and the second buffer device;
s8: sleeving a pressing cap on the outer side of the cutting ring seat, and screwing the pressing cap;
s9: the fourth seal 6840 is sleeved in the plug groove;
s10: the end of the plug provided with the fourth sealing element 6840 extends into the ring cutter holder and is pressed against the second buffer device;
s11: sleeving the top plate on two guide columns fixed relative to the base, and fixing the top plate;
s12: the compression bolt 616 is made to compress the upper end of the plug through the middle screw hole of the top plate.
Claims (10)
1. A holding device for measuring the permeability coefficient of low permeability soil, the holding device comprising:
a base having a fluid inlet and a first channel disposed therein;
a ring cutter supported by the base;
a ring cutter seat supported by the base, and an inner surface of the ring cutter seat abuts against an outer surface of the ring cutter, while a bottom surface of the ring cutter seat is higher than a bottom surface of the ring cutter;
a plug capable of mating with an inner surface of the ring cutter seat, and the fluid outlet and the second channel being disposed in the plug; and
a top plate connected to the base through guide posts,
wherein the base, the cutting ring, the ring cutter holder and the plug matched with the inner surface of the ring cutter holder jointly define a cavity.
2. Clamping device according to claim 1, characterized in that the outer side of the stopper is provided with a press cap.
3. Clamping device according to claim 1, characterized in that the top plate is further provided with a compression bolt.
4. The clamping device of claim 1, further comprising a plurality of seals.
5. A system for measuring the permeability coefficient of low permeability soil, the system comprising:
a water tank;
a vacuum pump fluidly connectable to the water tank;
a first detection component comprising the clamping device for measuring low permeability soil permeability according to claim 1; and
a flow measuring tube having a small bore diameter,
wherein a fluid inlet of the clamping device of the first detection assembly is in communication with the water tank and a fluid outlet of the clamping device of the first detection assembly is in communication with the flow measurement tube.
6. The system of claim 5, wherein the first detection assembly further comprises a first flow control valve, a second flow control valve, and a third flow control valve, the water tank is fluidly connected to the holding fixture through the fourth valve and the first flow control valve, and gas in the holding fixture is able to flow through the second flow control valve, the first flow control valve, and the third valve to the vacuum pump.
7. The system of claim 5, wherein the first detection assembly further comprises a displacement gauge disposed on the clamping device.
8. The system of claim 5, wherein the flow measurement tube has an aperture diameter of less than 1 mm.
9. The system of claim 5, wherein the flow measurement tube is a hose.
10. The system of claim 5, further comprising one or more second detection components, the second detection components having the same configuration as the first detection components.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202123116987.8U CN216525358U (en) | 2021-12-13 | 2021-12-13 | Clamping device and system for measuring permeability coefficient of low-permeability soil |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202123116987.8U CN216525358U (en) | 2021-12-13 | 2021-12-13 | Clamping device and system for measuring permeability coefficient of low-permeability soil |
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| CN216525358U true CN216525358U (en) | 2022-05-13 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114018786A (en) * | 2021-12-13 | 2022-02-08 | 吉林大学 | Clamping device and system for measuring permeability coefficient of low-permeability soil |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114018786A (en) * | 2021-12-13 | 2022-02-08 | 吉林大学 | Clamping device and system for measuring permeability coefficient of low-permeability soil |
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