CN113702266A - Constant head permeability measurement system and method for measuring permeability coefficient by using same - Google Patents
Constant head permeability measurement system and method for measuring permeability coefficient by using same Download PDFInfo
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- CN113702266A CN113702266A CN202111160374.6A CN202111160374A CN113702266A CN 113702266 A CN113702266 A CN 113702266A CN 202111160374 A CN202111160374 A CN 202111160374A CN 113702266 A CN113702266 A CN 113702266A
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- 230000035699 permeability Effects 0.000 title claims abstract description 79
- 238000005259 measurement Methods 0.000 title claims abstract description 36
- 238000000034 method Methods 0.000 title claims abstract description 29
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 217
- 230000008595 infiltration Effects 0.000 claims abstract 2
- 238000001764 infiltration Methods 0.000 claims abstract 2
- 238000009434 installation Methods 0.000 claims description 13
- 230000035515 penetration Effects 0.000 claims description 9
- 229920006395 saturated elastomer Polymers 0.000 claims description 7
- 230000007246 mechanism Effects 0.000 claims description 4
- 239000002689 soil Substances 0.000 abstract description 43
- 238000000691 measurement method Methods 0.000 abstract description 2
- 238000004364 calculation method Methods 0.000 description 6
- 230000008859 change Effects 0.000 description 3
- 238000010998 test method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000003204 osmotic effect Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- 235000017166 Bambusa arundinacea Nutrition 0.000 description 1
- 235000017491 Bambusa tulda Nutrition 0.000 description 1
- 241001330002 Bambuseae Species 0.000 description 1
- 235000015334 Phyllostachys viridis Nutrition 0.000 description 1
- 239000011425 bamboo Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 238000000205 computational method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/0806—Details, e.g. sample holders, mounting samples for testing
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- 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
-
- 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
- G01N2015/0813—Measuring intrusion, e.g. of mercury
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- General Health & Medical Sciences (AREA)
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- Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
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Abstract
The invention belongs to the technical field of permeability coefficient measurement, and provides a constant head permeability measurement system and a method for measuring a permeability coefficient by using the same. The infiltration system comprises a pressurizing structure, a test structure, a water quantity collecting structure and an automatic shutdown timing structure, wherein the test structure is connected with the pressurizing structure, the water quantity collecting structure is connected with the test structure, and the automatic shutdown timing structure is connected with the water quantity collecting structure. According to the constant head permeability measurement system and the permeability coefficient measurement method using the constant head permeability measurement system, the water source is pressurized by the pressurizing structure and then flows into the test structure, the permeability coefficient K of sandy soil and cohesive soil can be obtained, compared with the water quantity which can be directly seeped out through the test structure and flows into the water quantity collecting structure by the variable head and the time reading obtained by the automatic shutdown timing structure, the permeability coefficient K is obtained through Darcy's law, the requirement on the measurement environment is lowered, and the data reading operation is simple and convenient.
Description
Technical Field
The invention relates to the technical field of permeability coefficient measurement, in particular to a constant head permeability measurement system and a method for measuring a permeability coefficient by using the same.
Background
The permeability test is a test for measuring the permeability coefficient of rock soil by using some test instruments and is divided into an indoor test and a field test. Indoor permeability test there are many kinds of instruments and test methods for measuring the permeability coefficient k in a laboratory, and the test principle can be roughly divided into a "normal head method" and a "variable head method".
The constant head test is suitable for measuring the permeability coefficient of sandy soil with high water permeability. The permeability coefficient of the clay is very small, so the amount of water permeating is very small, and the test is not easy to be accurately measured and needs to be changed into a variable water head test. Because the constant water head test needs to keep a stable constant water level, clear water needs to be continuously injected into the test cylinder, and redundant water is drained, so that water resource waste is caused. Although the variable water head can also measure the permeability coefficient of the cohesive soil, the variable water head test needs larger pressure difference and is usually realized by increasing the height of the water head, common test instruments need a height space of more than 3m to ensure the water head pressure, and some test instruments even need a height of more than 6m to install instrument equipment, so that high requirements are provided for the room space. Moreover, the initial height of the water head and the final height of the water head after the penetration test are inconvenient to operate because the problem of installation height space needs to climb up and down through stairs for reading. The variable head permeability test needs to measure and read the initial height value of the permeability test and the final height value of the water head when the test is finished, the permeability coefficient of the cohesive soil is small, the test needs longer time and lower test efficiency, and the time and the labor are wasted because the viscous soil needs to climb up and down to read; in addition, the variable water head calculation formula is more complex, and is not as simple and convenient as the constant water head test calculation.
Therefore, it is urgently needed to provide a permeability coefficient measuring method which can measure the permeability coefficient of sandy soil and clayey soil and is simple and convenient to operate.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a constant head permeability measurement system and a method for measuring permeability coefficient by using the same, and aims to solve the problems that the existing constant head method can only measure sandy soil, the variable head test operation is complex, and the measurement environment is limited.
In a first aspect, the invention provides a constant head permeability measurement system, which comprises a pressurizing structure, a test structure, a water quantity collecting structure and an automatic shutdown timing structure, wherein the test structure is connected with the pressurizing structure, the water quantity collecting structure is connected with the test structure, and the automatic shutdown timing structure is connected with the water quantity collecting structure;
the pressurizing structure comprises a water pump and a pressure gauge and is used for increasing the water pressure flowing into the test structure;
the test structure comprises a test cylinder and a sample mounting device, wherein the sample mounting device is detachably fixed at the bottom of the test cylinder;
the automatic shutdown timing structure is used for acquiring the time required by sample permeation;
the water quantity collecting structure is used for collecting water seeped out by the test structure.
According to the technical scheme, when the permeability of the cohesive soil is measured by the permeation technology, the permeability coefficient is smaller and the amount of permeated water is smaller due to the characteristics of the cohesive soil, so that the permeability coefficient cannot be accurately measured by the normal water head method. This application pressurizes the back through pressurization structure to the water source and flows into experimental structure, when realizing general sandy soil permeability coefficient measurement, can carry out permeability coefficient K's acquisition to cohesive soil. Although the variable water head method can also realize the permeability coefficient measurement of the cohesive soil, the water level needs to be read for many times, the technical scheme of the application reduces the requirement on the measurement environment, and simultaneously simplifies the operation steps, directly obtains the permeability coefficient K through the water volume V collected by the water volume collecting structure and the time reading t obtained by the automatic shutdown timing structure, and improves the measurement efficiency. And the fixed mode of detachable between test sample installation device and the test section of thick bamboo in experimental structure can prepare a plurality of sample installation devices simultaneously in the experimentation, has improved measurement of efficiency.
Optionally, the test structure further comprises a water source access pipe and a water amount collecting pipe, the water source access pipe is connected with the test cylinder and the high-pressure water pipe, and the water source access pipe is used for introducing water source from the high-pressure water pipe into the test cylinder; the water collection pipe is connected with the sample mounting device and is used for collecting the water seeped out by the sample mounting device into the measuring cup.
According to the technical scheme, the water source subjected to pressurization treatment is connected into the test cylinder through the water source connecting pipe, and the water source flows into the measuring cup through the water collection pipe after penetrating through the sample in the sample mounting device.
Optionally, a first water valve is further arranged on the high-pressure water pipe, and the first water valve is arranged behind the pressure gauge; and a second water valve is arranged on the test cylinder, and an exhaust valve is arranged on the sample mounting device.
According to the technical scheme, the first water valve, the second water valve and the exhaust valve are respectively arranged at the high-pressure water pipe, the test cylinder and the sample installation device, so that the water quantity is controllable.
Optionally, the automatic shutdown timing structure comprises a timer, and the timer is further connected with a power supply and a switch.
Optionally, the water collection structure comprises a measuring cup and a water level floating member, a scale rod is fixed on the inner wall of the measuring cup along the vertical direction, and when water flows into the measuring cup, the water level floating member floats in the measuring cup.
Optionally, a thimble is arranged at the top of the water level floating member, the switch is fixed in the measuring cup, when the water level in the measuring cup reaches a preset water level height, the scale rod is used for limiting the water level of the water level floating member, and the thimble controls the switch to be switched off.
According to the technical scheme, the inner wall of the measuring cup is provided with the scale rod in the vertical direction, the switch position is arranged at the position where the water level buoy can contact when the water level reaches the preset water level, when the thimble of the water level buoy reaches the preset position, the thimble triggers the switch to be switched off, the timer stops timing, the reading obtains the test time, and the permeability coefficient k can be calculated by directly utilizing the Darcy law and using a normal water head method. Compared with the method that the time can be acquired by timing, the method can improve the accuracy of the permeability coefficient k. In addition, the timing is controlled without a water level sensor, and the control cost can be realized.
Optionally, the water level float is a water level float.
In a second aspect, the present invention provides a permeability coefficient measuring method using a constant head permeability measuring system including any one of the first aspect or possible implementations of the first aspect, including:
s1, preparing a permeation sample: detaching the sample mounting device from the bottom of the test cylinder, and placing the prepared sample into the sample mounting device;
s2, reading sample cross-sectional area a and sample height L: the sample installation device obtained in the step S1 is placed into water to be soaked until the sample installation device is saturated; reading the cross-sectional area A and the height L of the sample in the sample mounting device;
s3, measuring the height h1 from the center position of the pressure gauge to the surface of the sample: mounting the sample mounting device containing the saturated sample at the bottom of the test cylinder, and measuring the height h1 from the center of the pressure gauge to the surface of the sample;
s4, starting the automatic shutdown timing structure and the pressurization structure simultaneously;
s5, obtaining the equivalent water column height h 2: reading the pressure value of the pressure gauge to obtain the equivalent water column height h 2;
s6, obtaining an equivalent water head height delta h of the penetration test, wherein the delta h is h1+ h 2;
s7, obtaining the sample penetration time t: when the water level reaches a preset height, the water quantity collecting structure controls the automatic shutdown timing structure to stop timing, measures the water quantity V collected in the water quantity collecting structure, reads the automatic shutdown timing structure, and obtains the time t for sample permeation;
s8, calculating a permeability coefficient K: calculating a permeability coefficient K according to the cross-sectional area A of the sample, the height L of the sample, the equivalent head height delta h, the water volume V and the sample permeation time t which are obtained in the steps S1-S7,
according to the technical scheme, the permeability coefficient can be calculated based on the constant head calculation method by using the method for measuring the permeability coefficient of the constant head permeability measurement system, sandy soil and clayey soil can be calculated, and the selectivity of the calculable soil sample is expanded. Simultaneously, can prepare a plurality of samples simultaneously in the experimentation to place in different sample installation devices, directly change sample installation device after every soil sample is experimental, realize the high efficiency of experimentation.
By adopting the technical scheme, the application has the following beneficial effects:
1) adopt the technical scheme of this application, can be based on the flood peak of constant pressure value, can guarantee stable and sufficient flood peak pressure through the pressurization structure, under the cooperation of pressurization structure and test structure, make the problem that constant head test can only survey sandy soil permeability coefficient have been avoided to the permeability coefficient measurement method in this application, can all carry out the permeability coefficient survey to sandy soil and cohesive soil, all have fine adaptability to the soil of different soil properties.
2) By adopting the technical scheme, the permeability coefficient can be directly measured by adopting Darcy's law, calculation is carried out according to the formula of the constant head test method, and the calculation method is simpler and more convenient compared with the variable head test method. Meanwhile, the water head pressure is not required to be ensured through the installation height, and the requirement on the environment is reduced.
3) Adopt the technical scheme of this application, can guarantee stable and sufficient tap pressure through the pressurization structure, test time shortens, and test efficiency improves. Meanwhile, because the pressurizing structure is sealed, no redundant water flows away, and water resources are saved.
Drawings
In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings that are needed in the detailed description of the invention or the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.
Fig. 1 is a schematic structural diagram of a constant head permeability measurement system provided in an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of an automatic shutdown timing structure according to an embodiment of the present invention;
fig. 3 is a flowchart of a method for measuring permeability coefficient by using a constant head permeability measurement system according to an embodiment of the present invention.
Reference numerals:
10-a pressurized structure; 101-a water pump; 102-tee fitting; 103-pressure gauge; 104-high pressure water pipe; 105-a first water valve; 20-test structure; 201-test cartridge; 2011-second water valve; 202-water source access pipe; 203-sample mounting means; 2031-exhaust valve; 204-water collection pipe; 30-a water collection structure; 301-measuring cup; 302-water level float; 40-automatic shutdown timing structure; 401-a timer; 402-a power supply; 403-switch.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.
It is to be noted that, unless otherwise specified, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art to which the invention pertains.
In the description of the present application, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.
Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In this application, unless expressly stated or limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can include, for example, fixed connections, removable connections, or integral parts; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through intervening media. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
Example 1
Referring to fig. 1, the constant head permeability measurement system provided by the invention comprises a pressurizing structure 10, a test structure 20, a water quantity collecting structure 30 and an automatic shutdown timing structure 40, wherein the test structure 20 is connected with the pressurizing structure 10, the water quantity collecting structure 30 is connected with the test structure 20, and the automatic shutdown timing structure 40 is connected with the water quantity collecting structure 30;
the pressurizing structure 10 comprises a pressure gauge 103 and a water pump 101 for increasing the water pressure flowing into the test structure 20;
the test structure 20 comprises a test cylinder 201 and a sample mounting device 203, wherein the sample mounting device 203 is detachably fixed at the bottom of the test cylinder 201;
an automatic shut-down timing mechanism 40 for obtaining the time required for sample penetration;
the water collection structure 30 is used to collect water seeping from the test structure 20.
Specifically, according to the constant head permeability measurement system provided by the invention, a water source is pressurized by the pressurizing structure 10 and then flows into the test structure 20, the permeability coefficient K of cohesive soil can be obtained, and the constant head permeability measurement system is suitable for sandy soil permeability coefficient measurement and is also suitable for cohesive soil permeability coefficient measurement compared with a constant head method.
In one possible embodiment, the sample mounting device 203 of the measurement system provided by the present application may be mounted on the bottom of the test cartridge 201 by a screw, and the sample mounting device 203 may be detached from the bottom of the test cartridge 201 for specific operations when preparing the sample. Or, a plurality of samples can be prepared simultaneously in the experimental process, so that the measurement efficiency is improved.
Referring to fig. 1, the pressurizing structure 10 further includes a tee pipe 102, a high-pressure water pipe 104, and the water pump 101, the tee pipe 102 and the pressure gauge 103 are sequentially connected to the high-pressure water pipe 104.
Optionally, the water pump 101 is connected to an automatic shut down timing mechanism 40.
Specifically, because the osmotic pressure that the cohesive soil often needs is higher than sandy soil, cause in normal water head method can't carry out the penetration test to the cohesive soil, change water head method and be applicable to the cohesive soil, but because the computational method and the specific operating process are complicated, cause the measured efficiency not high. Through the pump 101 lift in the pressurization structure 10, increased the pressure of water, make this application not only be applicable to sandy soil but also be applicable to cohesive soil, have fine adaptability to the measurement of the osmotic coefficient of different soil properties.
Optionally, the test structure 20 further comprises a water source access pipe 202 and a water amount collecting pipe 204, the water source access pipe 202 connects the test cylinder 201 and the high-pressure water pipe 104, and the water source access pipe 202 is used for introducing water source from the high-pressure water pipe 104 into the test cylinder 201; the water collection header 204 is connected to the sample mounting device 203, and collects water seeped out from the sample mounting device 203 into the measuring cup 301.
Specifically, a pressurized water source is introduced into the test cartridge 201 through the water source introduction tube 202, and the water source permeates through the sample in the sample mounting device 203 and flows into the measuring cup 301 through the water collection tube 204.
Optionally, the high-pressure water pipe 104 is further provided with a first water valve 105, and the first water valve 105 is arranged behind the pressure gauge 103; a second water valve 2011 is arranged on the test cartridge 201, and an exhaust valve 2031 is arranged on the sample mounting device 203.
Specifically, the first water valve 105, the second water valve 2011, and the exhaust valve 2031 are disposed at the high-pressure water pipe 104, the test cartridge 201, and the sample mounting device 203, respectively. In order to prevent water leakage when replacing the sample mounting device 203, a first water valve 105 is provided at the high-pressure water pipe 104, and a second water valve 2011 is provided at the test cartridge 201. When the number of samples to be measured is large, the sample mounting device 203 needs to be frequently replaced, so that the opening and closing frequency of the second water valve 2011 is high, and in order to avoid the loss of water between a water source and the test tube 201 after the second water valve 2011 is damaged, the water source can be disconnected through the first water valve 105, and the waste of water resources is avoided.
Specifically, after the sample mounting device 203 and the test cartridge 201 are connected, the space between the sample mounting device 203 and the test cartridge 201 is closed, and excess gas in the sample mounting device 203 is discharged through the exhaust valve 2031, so that it is ensured that excess gas does not exist in the sample mounting device 203, and the pressure maintained in the sample mounting device 203 is maintained within a stable range.
Optionally, referring to fig. 2, the auto-off timing structure 40 includes a timer 401, and a power source 402 and a switch 403 are also connected to the timer 401.
Alternatively, the water collecting structure 30 includes a measuring cup 301 and a water level float 302, a scale rod is fixed on the inner wall of the measuring cup 301 along the vertical direction, water flows into the measuring cup 301, and the water level float 302 floats in the measuring cup.
Optionally, a thimble is arranged at the top of the water level floating member 302, the switch 403 is fixed in the measuring cup 301, when the water level in the measuring cup 301 reaches a preset water level height, the scale rod is used for limiting the water level of the water level floating member 302, and the thimble controls the switch 403 to be turned off.
Specifically, a scale rod in the vertical direction is arranged on the inner wall of the measuring cup 301, the switch 403 is arranged at a position where the water level floating member 302 can contact when the water level reaches a preset water level, when the thimble on the water level floating member 302 reaches the preset position, the thimble touches the switch 403 to be switched off, the timer 401 stops timing, the reading obtains the test time t, and the permeability coefficient K can be calculated by directly utilizing the darcy law and using a normal water head method. Compared with the method that the accuracy of obtaining time can be achieved through self timing, the accuracy of the permeability coefficient K is improved, timing is not required to be controlled by a water level sensor, and cost control can be achieved.
In one possible embodiment, the water level float 302 is a water level float. The water level float 302 is provided in the measuring cup 301, and the water oozed from the sample mounting device 203 is collected in the measuring cup 301 through the water collection pipe 204 and floats the water level float, which is connected to the automatic shut-off timer mechanism 40.
Example 2
The present application further provides a method of measuring permeability coefficient using any of the constant head permeability measurement systems of any of the possible implementations provided in example 1, see fig. 3, comprising:
s1, preparing a permeation sample: detaching the sample mounting device 203 from the bottom of the test cylinder 201, and placing the prepared sample into the sample mounting device 203;
s2, reading sample cross-sectional area a and sample height L: the sample mounting device 203 obtained in step S1 is placed in water and soaked until saturated; reading a cross-sectional area a and a height L of the sample in the sample mounting device 203;
s3, measuring the height h1 from the center position of the pressure gauge 103 to the surface of the sample: mounting a sample mounting device 203 containing a saturated sample on the bottom of a test cylinder 201, and measuring the height h1 from the center position of a pressure gauge 103 to the surface of the sample;
s4, starting the automatic stop timing structure 40 and the pressurizing structure 10 at the same time;
s5, obtaining the equivalent water column height h 2: reading the pressure value of the pressure gauge 103 to obtain the equivalent water column height h 2;
s6, obtaining an equivalent water head height delta h of the penetration test, wherein the delta h is h1+ h 2;
s7, obtaining the sample penetration time t: when reaching the preset water level height, the water quantity collecting structure 30 controls the automatic shutdown timing structure 40 to stop timing, measures the water quantity V collected in the water quantity collecting structure 30, reads the automatic shutdown timing structure 40, and obtains the sample permeation time t;
s8, calculating a permeability coefficient K: calculating a permeability coefficient K according to the cross-sectional area A of the sample, the height L of the sample, the equivalent head height delta h, the water volume V and the sample permeation time t which are obtained in the steps S1-S7,
it should be noted that the pressure value of the pressure gauge 103 read in the method of the present application can be converted according to the water column of 1 meter, which is 0.0098MPa and 0.01MPa, so that in step S3 of the method, the equivalent water column height h2 can be obtained.
Specifically, the permeability coefficient can be calculated based on the constant head calculation method by using the method for measuring the permeability coefficient of the constant head permeability measurement system of the first aspect, and sandy soil and clayey soil can be calculated, thereby widening the selectivity of the calculable soil sample. Simultaneously, can prepare a plurality of samples simultaneously in the experimentation to place in different sample installation devices, directly change sample installation device after every soil sample is experimental, realize the high efficiency of experimentation.
Note that, the saturation in step S2 means that the water content of the soil sample is greater than 85%, and sandy soil is easily saturated and directly soaked. The cohesive soil itself absorbs water slowly, and a sample device containing a soil sample is generally placed into a closed container to be pumped out to form vacuum negative pressure, and then water is discharged to enable the water content of the cohesive soil to be larger than 85%. Meanwhile, in step S2, the sample height L is obtained by reading the scale on the sample mounting device, and the sample cross-sectional area a is the cross-sectional area of the sample mounting device obtained in advance.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.
Claims (8)
1. A constant head permeability measurement system is characterized by comprising a pressurizing structure, a test structure, a water quantity collecting structure and an automatic shutdown timing structure, wherein the test structure is connected with the pressurizing structure, the water quantity collecting structure is connected with the test structure, and the automatic shutdown timing structure is connected with the water quantity collecting structure;
the pressurizing structure comprises a pressure meter and a water pump and is used for increasing the water pressure flowing into the test structure;
the test structure comprises a test cylinder and a sample mounting device, wherein the sample mounting device is detachably fixed at the bottom of the test cylinder;
the automatic shutdown timing structure is used for acquiring the time required by sample permeation;
the water quantity collecting structure is used for collecting water seeped out by the test structure.
2. The constant head permeability measurement system of claim 1, wherein the test structure further comprises a water source access tube and a water collection tube, the water source access tube connecting the test cartridge and the high pressure water tube, the water source access tube for introducing water source from the high pressure water tube into the test cartridge; the water collection pipe is connected with the sample mounting device and is used for collecting the water seeped out by the sample mounting device into the measuring cup.
3. The constant head permeability measurement system of claim 3, wherein a first water valve is further disposed on the high pressure water pipe, the first water valve being disposed behind the pressure gauge; and a second water valve is arranged on the test cylinder, and an exhaust valve is arranged on the sample mounting device.
4. The constant head permeability measurement system of claim 1, wherein the automatic shut down timer mechanism comprises a timer, the timer further connected to a power source and a switch.
5. The constant head permeability measuring system of claim 4, wherein the water collection structure comprises a measuring cup and a water level floating member, a scale rod is fixed on an inner wall of the measuring cup along a vertical direction, and the water level floating member floats in the measuring cup when water flows into the measuring cup.
6. The constant head infiltration measuring system of claim 5, wherein a thimble is arranged on the top of the water level floating member, the switch is fixed in the measuring cup, when the water level in the measuring cup reaches a preset water level height, the scale rod is used for limiting the water level of the water level floating member, and the thimble controls the switch to be switched off.
7. The constant head permeability measurement system of claim 5, wherein the water level float is a water level float.
8. A method of measuring permeability coefficients using the constant head permeability measurement system of any one of claims 1-7, comprising:
s1, preparing a permeation sample: detaching the sample mounting device from the bottom of the test cylinder, and placing the prepared sample into the sample mounting device;
s2, reading sample cross-sectional area a and sample height L: the sample installation device obtained in the step S1 is placed into water to be soaked until the sample installation device is saturated; reading the cross-sectional area A and the height L of the sample in the sample mounting device;
s3, measuring the height h1 from the center position of the pressure gauge to the surface of the sample: mounting the sample mounting device containing the saturated sample at the bottom of the test cylinder, and measuring the height h1 from the center of the pressure gauge to the surface of the sample;
s4, starting the automatic shutdown timing structure and the pressurization structure simultaneously;
s5, obtaining the equivalent water column height h 2: reading the pressure value of the pressure gauge to obtain the equivalent water column height h 2;
s6, obtaining the equivalent water head height delta h of the penetration test h1+ h 2;
s7, obtaining the sample penetration time t: when the water level reaches a preset height, the water quantity collecting structure controls the automatic shutdown timing structure to stop timing, measures the water quantity V collected in the water quantity collecting structure, reads the automatic shutdown timing structure, and obtains the time t for sample permeation;
s8, calculating a permeability coefficient K: calculating a permeability coefficient K according to the cross-sectional area A of the sample, the height L of the sample, the equivalent head height delta h, the water volume V and the sample permeation time t which are obtained in the steps S1-S7,
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