CN112268844B - Seepage erosion control system and test method under GDS triaxial apparatus drainage condition - Google Patents
Seepage erosion control system and test method under GDS triaxial apparatus drainage condition Download PDFInfo
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- 230000003628 erosive effect Effects 0.000 title claims abstract description 51
- 238000010998 test method Methods 0.000 title claims abstract description 7
- 230000006835 compression Effects 0.000 claims abstract description 93
- 238000007906 compression Methods 0.000 claims abstract description 93
- 239000011148 porous material Substances 0.000 claims abstract description 64
- 238000012360 testing method Methods 0.000 claims abstract description 64
- 239000002689 soil Substances 0.000 claims abstract description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 79
- 238000002347 injection Methods 0.000 claims description 19
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- 229920001971 elastomer Polymers 0.000 claims description 11
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- 238000000034 method Methods 0.000 claims description 7
- 230000008569 process Effects 0.000 claims description 6
- 230000008859 change Effects 0.000 claims description 4
- 238000007596 consolidation process Methods 0.000 claims description 4
- 230000035699 permeability Effects 0.000 claims description 4
- 238000002360 preparation method Methods 0.000 claims description 3
- 238000007789 sealing Methods 0.000 claims description 3
- 230000008595 infiltration Effects 0.000 abstract description 7
- 238000001764 infiltration Methods 0.000 abstract description 7
- 239000000523 sample Substances 0.000 description 103
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 12
- 238000000079 presaturation Methods 0.000 description 11
- 229910002092 carbon dioxide Inorganic materials 0.000 description 6
- 239000001569 carbon dioxide Substances 0.000 description 6
- 238000012545 processing Methods 0.000 description 4
- 239000004576 sand Substances 0.000 description 4
- 238000006073 displacement reaction Methods 0.000 description 3
- 239000004575 stone Substances 0.000 description 3
- 238000010276 construction Methods 0.000 description 2
- 239000013068 control sample Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
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- 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
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D7/00—Control of flow
- G05D7/06—Control of flow characterised by the use of electric means
- G05D7/0617—Control of flow characterised by the use of electric means specially adapted for fluid materials
- G05D7/0629—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means
- G05D7/0635—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means by action on throttling means
- G05D7/0641—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means by action on throttling means using a plurality of throttling means
- G05D7/0652—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means by action on throttling means using a plurality of throttling means the plurality of throttling means being arranged in parallel
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Abstract
The invention discloses a seepage erosion control system and a test method under the drainage condition of a GDS triaxial apparatus, wherein the system comprises a top pore pressure sensor, a bottom pore pressure sensor, two volume compression controllers, a converter valve, a top pore pressure valve and a bottom pore pressure valve; four interfaces are arranged on the outer ring of the converter valve at equal intervals and are used for being connected with a sample top pipeline, a sample bottom pipeline and two volume compression controllers respectively; the converter valve is internally provided with a rotatable disc, and two opposite C-shaped channels are arranged in the disc and can be communicated with any two adjacent interfaces on the outer ring of the converter valve; by freely switching the connection state of the volume compression controller and the sample inside the GDS triaxial apparatus, stable and continuous seepage can be formed inside the sample, the test requirement of a soil body constant shear drainage test is met, the problem that the total volume of the maximum seepage volume of a single volume compression controller is 200cc and is not enough to complete the whole infiltration erosion test is solved, and the efficiency and the scientificity of the soil body infiltration erosion test are improved.
Description
Technical Field
The invention relates to the related field of groundwater seepage erosion under a drainage working condition in the construction process of geotechnical engineering projects, and a GDS triaxial apparatus seepage erosion test can be developed more scientifically and efficiently by utilizing a seepage erosion control system and a test method under the drainage condition of the GDS triaxial apparatus.
Background
With the rapid development of economy and the continuous promotion of urban construction progress in China, the number of engineering projects such as deep foundation pits, tunnels, bridges and the like in coastal areas is continuously increased in recent years, so that a large number of foundation pit projects constructed in a water-rich stratum environment appear. In a water-rich stratum, hydrogeological conditions are very complex, and if the hydrogeological conditions are not properly treated, the problems of seepage erosion damage such as piping and soil flow and the like are easily caused, engineering accidents such as instability and collapse of a foundation pit and the like are easily caused, the problems of inclined settlement of surrounding buildings, cracking and collapse of a road surface and the like are also caused, and the serious threat to life and property safety is caused. Therefore, the research on the soil seepage erosion is extremely important.
At present, most of the experimental researches on soil body seepage erosion are to develop a constant shear drainage test; about invariable shear drainage test, its experimental principle is that the confining pressure and the axial pressure of keeping the sample are unchangeable, utilize top pore pressure and bottom pore pressure to form a pressure differential to form a steady continuous seepage in the sample inside, under the effect of lasting seepage erosion, can cause the soil body fine particle to take place the migration in the pore channel between the coarse grain, cause soil body density, porosity to change, exert an influence to soil body permeability, and soil body structure changes under the seepage erosion effect, and then influence soil body mechanical properties.
Currently, the development of the seepage erosion test is mostly carried out by adopting a seepage module of a GDS triaxial apparatus, but the GDS triaxial apparatus is used for carrying out a volume compression controller configured for the seepage test at present, the volume range of the volume compression controller is 200cc (namely 200 mL), the stored water is insufficient, the soil body is damaged by seepage erosion, in order to complete a constant shear drainage test, the test must be stopped halfway, and the volume compression controller absorbs water, so that the test cannot be efficiently developed. Therefore, a set of seepage erosion module of the GDS triaxial apparatus meeting the test requirements is needed to ensure the high efficiency and the scientificity of the seepage erosion test.
Disclosure of Invention
In order to solve the related problems in the current infiltration erosion test, the invention provides an infiltration erosion control system and a test method under the GDS triaxial apparatus drainage condition, which solve the problem of discontinuous infiltration process of the constant shear drainage test and ensure the high efficiency and scientificity of the infiltration erosion test.
The purpose of the invention is realized by the following technical scheme:
the invention provides a seepage erosion control system under the GDS triaxial apparatus drainage condition, which comprises a top pore pressure sensor, a bottom pore pressure sensor, a first volume compression controller, a second volume compression controller, a converter valve, a top pore pressure valve and a bottom pore pressure valve; through this seepage flow erosion control system under GDS triaxial apparatus drainage condition, the user can freely switch the connection state of first volume compression controller, second volume compression controller and the sample tip pipeline interface of sample top, sample bottom, and then realizes the free connection of first volume compression controller, second volume compression controller and sample top and bottom for sample inside obtains and lasts the seepage flow.
Furthermore, the converter valve is provided with an outer ring structure and an inner disc structure;
the outer ring of the converter valve is fixed, four interfaces are arranged around the outer ring at equal intervals and are used for being respectively connected with a sample top pipeline, a sample bottom pipeline, a first volume compression controller and a second volume compression controller, wherein two sample end pipeline interfaces connected with the top and the bottom of the sample are symmetrically distributed, the two volume compression controller interfaces are symmetrically distributed, and the sample end pipeline interfaces and the volume compression controller interfaces are adjacently distributed;
the inner disc structure of the converter valve can rotate around a center shaft at the circle center, and two opposite C-shaped channels are arranged in the disc and can be communicated with any two adjacent interfaces of the outer ring of the converter valve; one of the sample end pipe interfaces is communicated with the top of the sample through a pipeline, and a top pore pressure sensor and a top pore pressure valve are sequentially arranged on the pipeline to form a drainage branch; the other end part pipeline interface of the sample is communicated with the bottom of the sample through a pipeline, and a bottom pore pressure sensor and a bottom pore pressure valve are sequentially arranged on the pipeline to form a water injection branch; the first volume compression controller and the second volume compression controller can be freely communicated with the water injection branch and the water drainage branch through the converter valve, and the two volume compression controllers are communicated with the water injection branch, the sample and the water drainage branch to form a complete seepage passage;
the conversion valve is rotated to realize the arbitrary switching of the connection states of the two volume compression controllers, the water injection branch and the drainage branch, further realize the switching of the connection states of the two volume compression controllers, the top and the bottom of the sample, solve the problem that the maximum seepage volume total amount of a single volume compression controller is 200cc and is not enough to complete the whole seepage erosion test, ensure the stable and continuous seepage formed in the sample through the external circulation of seepage water flow and the switching of the two volume compression controllers, and meet the test requirement of the soil body constant shear drainage test.
Furthermore, a water-stopping rubber ring is arranged at a gap between the outer ring of the converter valve and the inner disc, so that the outer ring of the converter valve and the inner disc are ensured to rotate relatively, and the better sealing performance is realized.
The invention also provides a seepage erosion drainage test method based on the seepage erosion control system, which comprises the following steps:
(1) A GDS triaxial apparatus is utilized to carry out a constant shear drainage test, the preparation, saturation and consolidation processes of a sample are completed according to test specifications and test schemes, the stress state of the sample required by the test scheme is achieved and maintained, and a seepage erosion drainage test is prepared.
(2) Closing the top pore pressure valve and the bottom pore pressure valve, emptying the first volume compression controller, fully sucking the second volume compression controller without water, rotating the converter valve to enable the first volume compression controller to be connected with the water drainage branch to be communicated with the top of the sample, and enabling the second volume compression controller to be connected with the water injection branch to be communicated with the bottom of the sample; the method comprises the following steps that seepage parameters such as the size of a top pressure value and a bottom pressure value, pressure difference and seepage velocity are preset on a computer test operation interface, so that seepage from bottom to top can occur in a sample, a second volume compression controller can inject water into the sample under the action of the pressure difference, and a first volume compression controller absorbs water into the sample; the top and bottom pore pressure valves were opened and the test was started by clicking. Under the action of pressure difference, the seepage erosion control system of the GDS triaxial apparatus discharges water from the second volume compression controller, water is injected to the bottom of the sample through the converter valve, flows through the interior of the sample, discharges water from the top of the sample, and then is sucked into the first volume compression controller through the converter valve, so that a seepage erosion test is started; and then, a data acquisition system of the GDS triaxial apparatus automatically records and stores the axial deformation, volume deformation, axial pressure, confining pressure, pore water pressure and permeability coefficient change data of the sample.
(3) When no water in the second volume compression controller is about to be drained, seepage parameters such as the size of a top bottom pressure value, pressure difference, seepage speed and the like are reversely set on a computer operation interface in advance, the second volume compression controller can suck water inwards under the action of the pressure difference, and the first volume compression controller can inject water outwards. Then pausing the operation of the previous test stage on the computer operation interface; then rapidly rotating the converter valve to enable the second volume compression controller to be connected with the drainage branch to be communicated with the top of the sample, and the first volume compression controller to be connected with the water injection branch to be communicated with the bottom of the sample; and immediately continuing the seepage erosion test according to preset seepage parameters, and continuously generating seepage from bottom to top in the sample.
(4) And (4) repeating the operation of the step (3) to enable the interior of the sample to generate continuous seepage until the sample generates seepage erosion damage, and ending the test.
(5) After the test is finished, according to the test operation specification, the pressure is unloaded from inside to outside, and then the sample is disassembled and the instrument is cleaned.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention utilizes the converter valve to realize the free switching of the connection states of the two volume compression controllers and the top and the bottom of the sample, and the problem of repeatedly disassembling the instrument connection interface is solved.
2. The invention realizes the recycling of the seepage water flow in the seepage erosion process, ensures that the stable and continuous seepage is formed in the sample by switching the connection state of the two volume compression controllers with the top and the bottom of the sample, and solves the problem that the maximum seepage volume total amount of a single volume compression controller is 200cc and is not enough to complete the whole seepage erosion test.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a GDS triaxial apparatus;
FIG. 2 is a schematic view of a converter valve state I connection;
FIG. 3 is a schematic view of the flow direction of the seepage flow in the case of the converter valve at state I;
FIG. 4 is a schematic view of a converter valve state II connection;
FIG. 5 is a schematic view of the flow direction of the seepage flow in the case of state II of the converter valve;
in the figure, 1, a top pore pressure sensor; 2. a bottom hole pressure sensor; 3. a first volume compression controller; 4. a second volumetric compression controller; 5. a converter valve; 6-1, a top pore pressure valve; 6-2, a bottom pore pressure valve; 6-3, a shaft pressure valve; 6-4, a confining pressure valve; 6-5, a pressure chamber water inlet/drain valve; 7. a shaft pressure controller; 8. a shaft pressure sensor; 9. a sample top cap; 10. a sample; 11. a sample base; 12. a pressure protection cover; 13. a displacement sensor; 14. a base; 15. a water inlet pump; 16. a confining pressure sensor; 17. a confining pressure controller; 18. a data acquisition system; 19. and (4) a computer.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced otherwise than as specifically described herein, and it will be appreciated by those skilled in the art that the present invention may be practiced without departing from the spirit and scope of the present invention and that the present invention is not limited by the specific embodiments disclosed below.
As shown in fig. 1, the GDS triaxial apparatus in this embodiment includes a GDS triaxial apparatus main body, a confining pressure control system, an axial pressure control system, a seepage erosion control system, and a data acquisition and processing system; wherein confined pressure control system links to each other with GDS triaxial apparatus pressure chamber, realize confined pressure control through water injection and drainage process, axial pressure control system links to each other with GDS triaxial apparatus base and top, realize sample axial pressure control through the lift of control sample base, GDS triaxial seepage flow erosion control system links to each other with the top and the bottom of the inside sample of GDS triaxial apparatus, through control sample top and bottom head pressure difference and the switching of module internal component, realize the inside stable seepage flow erosion that lasts of sample, above GDS triaxial seepage flow erosion control system, confined pressure control system, axial pressure control system all links to each other with data acquisition and processing system, receive its control and pass data back data acquisition and processing system.
The GDS triaxial apparatus main body includes: a sample top cap 9, a sample base 11, a pressure protection cover 12, a basic base 14, a water inlet pump 15 and a pressure chamber water inlet/drain valve 6-5. The sample 10 is placed between the sample base 11 and the sample top cap 9, within the pressure protection cap 12, above the base 14.
The axle pressure control system includes: the device comprises an axial pressure controller 7, an axial pressure sensor 8, an axial pressure valve 6-3 and a displacement sensor 13.
The confining pressure control system comprises: a confining pressure sensor 16, a confining pressure controller 17 and a confining pressure valve 6-4.
The data acquisition and processing system comprises: a data acquisition control system 18 and a computer 19.
The seepage erosion control system of the GDS triaxial apparatus comprises: a top pore pressure sensor 1, a bottom pore pressure sensor 2, a first volume compression controller 3, a second volume compression controller 4, a converter valve 5, a top pore pressure valve 6-1 and a bottom pore pressure valve 6-2;
four interfaces are arranged on the outer ring of the converter valve 5 at equal intervals and are used for being respectively connected with a sample 10 top pipeline, a sample 10 bottom pipeline, a first volume compression controller 3 and a second volume compression controller 4, wherein two sample end pipeline interfaces connected with the top and the bottom of the sample 10 are symmetrically distributed, the two volume compression controller interfaces are symmetrically distributed, and the sample end pipeline interfaces and the volume compression controller interfaces are adjacently distributed;
the converter valve 5 is internally provided with a rotatable disc which can rotate around a center shaft at the center of a circle, and two opposite C-shaped channels are arranged in the disc and can be communicated with any two adjacent interfaces on the outer ring of the converter valve 5; one of the sample end pipe ports is communicated with the top of the sample 10 through a pipeline, and a top pore pressure sensor 1 and a top pore pressure valve 6-1 are sequentially arranged on the pipeline to form a drainage branch; the other end part pipeline interface of the sample is communicated with the bottom of the sample 10 through a pipeline, and a bottom pore pressure sensor 2 and a bottom pore pressure valve 6-2 are sequentially arranged on the pipeline to form a water injection branch; the first volume compression controller 3 and the second volume compression controller 4 can be communicated with a water injection branch and a water drainage branch at will through a converter valve 5, and the two volume compression controllers are communicated with the water injection branch, the sample 10 and the water drainage branch to form a complete seepage passage; a water-stopping rubber ring is arranged at a gap between the outer ring of the converter valve 5 and the inner disc, so that the outer ring of the converter valve 5 and the inner disc are guaranteed to rotate relatively and have good sealing performance.
The rotation of the converter valve 5 can realize the arbitrary switching of the connection states of the two volume compression controllers and the water injection branch and the drainage branch, thereby realizing the switching of the connection states of the two volume compression controllers and the top and the bottom of the sample 10, solving the problem that the maximum seepage volume total amount of a single volume compression controller is 200cc and is not enough to complete the whole infiltration erosion test, and through the external circulation of seepage water flow and the switching of the two volume compression controllers, the stable and continuous seepage can be ensured to be formed inside the sample 10, and the test requirement of the soil constant shear drainage test is met.
The following gives an example of a seepage erosion test performed on a sandy soil sample, and specifically comprises the following steps:
step 1: sand sample preparation and sample loading
(1) Weighing the dried sand sample and no water according to the test requirements, and uniformly stirring.
(2) And opening the bottom pore pressure valve 6-2 to fill the sample base 11 with water and exhaust air in the sample base 11. And (3) sliding the boiled permeable stone onto the sample base 11, wrapping the permeable stone on the sample base 11 by using an rubber belt, and putting filter paper to prevent sand from leaking into the sample base 11. Closing the bottom hole pressure valve 6-2, sleeving one end of the rubber film on the sample base 11 and fastening, sleeving the split mold on the sample base 11, turning the upper end of the rubber film outwards and sleeving the split mold, and then exhausting air to enable the rubber film to be tightly attached to the inner wall of the split mold;
(3) The samples are compacted in 5 layers according to the 10-degree height of the sample, and the soil quality of each layer is equal. After each layer is compacted to the required height, the surface is planed to be rough, and then the layer 2 soil is added; continuing the process until the last layer is compacted to fill the weighed sand sample with the specified volume; then putting filter paper, permeable stone and a sample top cap 9, turning up a rubber membrane, and fastening the rubber membrane on the sample top cap 9 by using a rubber belt;
(4) Connecting the negative pressure pre-saturation fitting with a port at the 6-1 position of the top pore pressure valve, and opening the negative pressure pre-saturation fitting to perform air suction, so that a certain negative pressure (20 kPa) is generated in the sample 10, and the sample 10 can stand; the split mold is removed, the height and diameter of the specimen 10 are measured, and the specimen dimensions are recorded.
Step 2: carbon dioxide saturation and head saturation
(1) After the sandy soil sample is installed, continuously exhausting air by using a negative pressure pre-saturation accessory, keeping the negative pressure of 20kPa in the sample 10, and checking whether a rubber film is damaged or not and leaking air; installing a pressure protection cover 12, opening a water inlet/discharge valve 6-5 of the pressure chamber, and injecting airless water into the pressure chamber until the sample 10 is submerged;
(2) Connecting the carbon dioxide gas tank with an interface at the bottom pore pressure valve 6-2, opening the bottom pore pressure valve 6-2, and adjusting the valve of the carbon dioxide gas tank to make bubbles in the negative pressure pre-saturation fitting uniformly and slowly emerge; continuously and slowly introducing carbon dioxide gas into the sample 10 for 30min, and then closing the bottom pore pressure valve 6-2 and the valve of the carbon dioxide gas tank; disconnecting the carbon dioxide gas tank from the interface at the bottom pore pressure valve 6-2;
(3) Connecting the non-aqueous presaturation fitting with an interface at the 6-2 position of the bottom pore pressure valve; after sufficient airless water is injected into the airless water pre-saturation fitting, slowly opening a bottom pore pressure valve 6-2, and under the action of stable negative pressure (20 kPa), the airless water in the airless water pre-saturation fitting is continuously and slowly injected into the sample 10, and meanwhile, bubbles are uniformly and slowly emitted from the negative pressure pre-saturation fitting; and after the air bubbles in the negative pressure pre-saturation fitting completely disappear, continuously injecting the air-free water for 60min, simultaneously closing the bottom pore pressure valve 6-2 and the top pore pressure valve 6-1, and disconnecting the connection between the negative pressure pre-saturation fitting and the interface at the top pore pressure valve 6-1 to complete the pre-saturation step of the sample 10.
And 3, step 3: counter pressure saturation
(1) During back pressure saturation, the pressure should be applied in stages, and the confining pressure applied in stages, to minimize disturbance to the sample 10. During the application of the counter-pressure, the confining pressure is always kept 10kPa greater than the counter-pressure. The increase of each stage of back pressure and confining pressure can reach 50kPa for sandy soil.
(2) During operation, the confining pressure is adjusted to 50kPa, the back pressure is adjusted to 40kPa, meanwhile, the confining pressure valve 6-4, the top pore pressure valve 5-1 and the bottom pore pressure valve 5-2 are synchronously opened, and after the pore pressure is stable, the B value is detected.
(3) Keeping the volume of the back pressure unchanged, increasing the confining pressure by 20kPa to obtain the increment of pore pressure caused by the confining pressure, namely delta u, B =deltau/delta sigma 3 (delta sigma 3 is the confining pressure increment), if B is less than 0.98, the sample is not saturated, and then continuing to add the next stage of confining pressure and back pressure according to the steps. The confining pressure and the back pressure are increased step by step until the sample is saturated.
And 4, step 4: consolidation of drainage
And applying confining pressure (increasing the confining pressure on the basis of saturation, loading the confining pressure according to the test scheme of 100kPa/200kPa/300kPa/400 kPa), keeping the pressure value of the pore pressure of the back pressure unchanged, and keeping the pressure value for 24h, wherein the consolidation is considered to be finished.
And 5: seepage erosion constant shear drainage test
(1) Closing the top pore pressure valve 6-1 and the bottom pore pressure valve 6-2, emptying the first volume compression controller 3, filling the second volume compression controller 4 with no water, rotating the converter valve 5 to connect the first volume compression controller 3 with the water discharge branch to communicate with the top of the sample 10, and connecting the second volume compression controller 4 with the water injection branch to communicate with the bottom of the sample 10, as shown in fig. 2; seepage parameters such as the size of a top and bottom pressure value, pressure difference and seepage velocity are preset in a test operation interface of the computer 19, so that seepage from bottom to top can occur in the sample 10, the second volume compression controller 4 can inject water into the sample 10 under the action of the pressure difference, and the first volume compression controller 3 absorbs water into the sample 10; the top port pressure valve 6-1 and the bottom port pressure valve 6-2 were opened and the test was started by clicking. Under the action of pressure difference, the seepage erosion control system of the GDS triaxial apparatus discharges water from the second volume compression controller 4, water is injected to the bottom of the sample 10 through the converter valve 5, flows through the inside of the sample 10, discharges water from the top of the sample 10, and then is sucked into the first volume compression controller 3 through the converter valve 5, so as to start a seepage erosion test, as shown in FIG. 3; and then, a data acquisition system 18 of the GDS triaxial apparatus acquires data of the top pore pressure sensor 1, the bottom pore pressure sensor 2, the axial pressure sensor 8, the displacement sensor 13 and the confining pressure sensor 16, and automatically records and stores data of axial deformation, volume deformation, axial pressure, confining pressure, pore water pressure and permeability coefficient change of the sample 10.
(2) When no water in the second volume compression controller 4 is about to be drained, seepage parameters such as the size of a top and bottom pressure value, pressure difference, seepage speed and the like are reversely set on an operation interface of the computer 19 in advance, the second volume compression controller 4 can suck water inwards under the action of the pressure difference, and the first volume compression controller 3 injects water outwards. Then the operation of the previous test stage is suspended on the operation interface of the computer 19; then rapidly rotating the converter valve 5 to connect the second volume compression controller 4 with the drainage branch to communicate with the top of the sample 10, and connecting the first volume compression controller 3 with the water injection branch to communicate with the bottom of the sample 10, as shown in fig. 4; then, the seepage erosion test is immediately continued according to preset seepage parameters, and the seepage from bottom to top continues to occur in the sample 10, as shown in fig. 5.
(3) And (3) repeating the operation of the step (2) to enable continuous seepage to occur inside the sample 10 until the sample is damaged by seepage corrosion, and ending the test.
(4) After the test is finished, according to the test operation specification, the pressure is unloaded from inside to outside, and then the sample is disassembled and the instrument is cleaned.
The present invention has been described in terms of the preferred embodiment, and it is not intended to be limited to the embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (2)
1. A seepage erosion control system under a GDS triaxial apparatus drainage condition is characterized by comprising a top pore pressure sensor (1), a bottom pore pressure sensor (2), a first volume compression controller (3), a second volume compression controller (4), a converter valve (5), a top pore pressure valve (6-1) and a bottom pore pressure valve (6-2);
the outer ring of the converter valve (5) is provided with four interfaces at equal intervals and is used for being connected with a pipeline at the top of the sample (10), a pipeline at the bottom of the sample (10), a first volume compression controller (3) and a second volume compression controller (4) respectively, wherein two pipeline interfaces at the end part of the sample, which are connected with the top and the bottom of the sample (10), are symmetrically distributed, two interfaces of the volume compression controller are symmetrically distributed, and the pipeline interfaces at the end part of the sample and the interfaces of the volume compression controller are distributed adjacently;
the converter valve (5) is internally provided with a rotatable disc which can rotate around a center shaft at the circle center, and two opposite C-shaped channels are arranged in the disc and can be communicated with any two adjacent interfaces on the outer ring of the converter valve (5); one end part pipeline interface of the sample is communicated with the top of the sample (10) through a pipeline, and a top pore pressure sensor (1) and a top pore pressure valve (6-1) are sequentially arranged on the pipeline to form a drainage branch; the other end part pipeline interface of the sample is communicated with the bottom of the sample (10) through a pipeline, and a bottom pore pressure sensor (2) and a bottom pore pressure valve (6-2) are sequentially arranged on the pipeline to form a water injection branch; the first volume compression controller (3) and the second volume compression controller (4) can be communicated with the water injection branch and the water drainage branch at will through the converter valve (5), and the two volume compression controllers are communicated with the water injection branch, the sample (10) and the water drainage branch to form a complete seepage passage; a water-stopping rubber ring is arranged at a gap between the outer ring of the converter valve (5) and the inner disc, so that the outer ring of the converter valve (5) and the inner disc are ensured to rotate relatively and have good sealing performance;
the rotation of the converter valve (5) can realize the random switching of the connection states of the two volume compression controllers and the water injection branch and the drainage branch, so that the connection states of the two volume compression controllers and the top and the bottom of the sample (10) can be switched, the external circulation of seepage water flow and the switching of the two volume compression controllers ensure that the sample (10) forms stable and continuous seepage, and the test requirement of a soil body constant shear drainage test is met.
2. A seepage erosion drainage test method based on the seepage erosion control system of claim 1, comprising:
(1) Carrying out a constant shear drainage test by using a GDS triaxial apparatus, firstly completing the processes of preparation, saturation and consolidation of the sample (10) according to test specifications and test schemes, achieving and maintaining the stress state of the sample (10) required by the test schemes, and preparing for a seepage erosion drainage test;
(2) Closing the top pore pressure valve (6-1) and the bottom pore pressure valve (6-2), emptying the first volume compression controller (3), filling the second volume compression controller (4) with no water, rotating the converter valve (5) to enable the first volume compression controller (3) to be connected with a water discharge branch to be communicated with the top of the sample (10), and enabling the second volume compression controller (4) to be connected with a water injection branch to be communicated with the bottom of the sample (10); the sizes of top and bottom pressure values, pressure difference and seepage velocity are preset on a test operation interface of a computer (19), seepage from bottom to top occurs in a sample (10), a second volume compression controller (4) is enabled to inject water into the sample (10) under the action of the pressure difference, and a first volume compression controller (3) absorbs water into the sample (10); opening a top pore pressure valve (6-1) and a bottom pore pressure valve (6-2), and clicking to start the test; under the action of pressure difference, the seepage erosion control system of the GDS triaxial apparatus discharges water from the second volume compression controller (4), water is injected to the bottom of the sample (10) through the converter valve (5), flows through the inside of the sample (10), discharges water from the top of the sample (10), and then is sucked into the first volume compression controller (3) through the converter valve (5), so that a seepage erosion test is started; then, a data acquisition system (18) of the GDS triaxial apparatus automatically records and stores the data of axial deformation, volume deformation, axial pressure, confining pressure, pore water pressure and permeability coefficient change of the sample (10);
(3) When no water in the second volume compression controller (4) is about to be drained, reversely setting the size of a top and bottom pressure value, a pressure difference and a seepage speed on an operation interface of a computer (19), enabling the second volume compression controller (4) to suck water inwards under the action of the pressure difference, and injecting water outwards by the first volume compression controller (3); then the operation of the previous test stage is suspended on the operation interface of the computer (19); then rapidly rotating the converter valve (5) to enable the second volume compression controller (4) to be connected with the drainage branch to be communicated with the top of the sample (10), and enable the first volume compression controller (3) to be connected with the water injection branch to be communicated with the bottom of the sample (10); then, immediately continuing the seepage erosion test according to preset seepage parameters, and continuously generating seepage from bottom to top in the sample (10);
(4) Repeating the operation of the step (3) to enable the interior of the sample (10) to generate continuous seepage until the sample generates seepage erosion damage, and ending the test;
(5) After the test is finished, according to the test operation specification, the pressure is unloaded from inside to outside, and then the sample is disassembled and the instrument is cleaned.
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