CN112268844A - 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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- CN112268844A CN112268844A CN202011099100.6A CN202011099100A CN112268844A CN 112268844 A CN112268844 A CN 112268844A CN 202011099100 A CN202011099100 A CN 202011099100A CN 112268844 A CN112268844 A CN 112268844A
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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
- 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
- G01N13/00—Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects
- G01N13/04—Investigating osmotic effects
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/56—Investigating resistance to wear or abrasion
- G01N3/567—Investigating resistance to wear or abrasion by submitting the specimen to the action of a fluid or of a fluidised material, e.g. cavitation, jet abrasion
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- 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
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 respectively connecting a sample top pipeline, a sample bottom pipeline and two volume compression controllers; 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 internal sample of the GDS triaxial apparatus, the stable and continuous seepage can be formed inside the sample, the test requirement of the soil body constant shear drainage test is met, the problem that the total 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 are easily caused, engineering accidents such as instability and collapse of a foundation pit 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 is caused to the life and property safety. 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; regarding the constant shear drainage test, the test principle is to keep the confining pressure and the axial pressure of the sample unchanged, and form a pressure difference by utilizing the pore pressure at the top and the pore pressure at the bottom, so that a stable and continuous seepage is formed inside the sample, and under the action of continuous seepage erosion, soil fine particles can migrate in pore channels among coarse particles, so that the density and the porosity of a soil body are changed, the permeability of the soil body is influenced, and the structure of the soil body is changed under the action of seepage erosion, so that the mechanical property of the soil body is influenced.
Currently, develop above-mentioned seepage erosion test and mostly adopt GDS triaxial apparatus from the seepage module of taking to go on, but present GDS triaxial apparatus is used for carrying out the volume compression controller that the seepage test disposed, and its volume range is 200cc (200 mL promptly), and the water yield that is deposited is not enough to let the soil body take place the infiltration erosion and destroys, in order to accomplish invariable shearing drainage test, must stop the experiment midway and let the volume compression controller absorb water for experimental can not high-efficiently develop. 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 osmotic erosion test, the invention provides an osmotic erosion control system and a test method under the GDS triaxial apparatus drainage condition, which solve the problem of discontinuous permeation process of the constant shear drainage test and ensure the high efficiency and scientificity of the osmotic 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 communicated with the water injection branch and the water drainage branch at will 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 random switching of the connection states of the two volume compression controllers, the water injection branch and the drainage branch, so that the switching of the connection states of the two volume compression controllers, the top and the bottom of a sample is realized, 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 is solved, the stable and continuous seepage can be formed in the sample through the external circulation of seepage water flow and the switching of the two volume compression controllers, and the test requirement of a soil body constant shear drainage test is met.
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 with no 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, the operation of the previous test stage is suspended 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 interior of the sample forms stable and continuous seepage 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, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to 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-tight cap 12, on 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 a 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 the anhydrous 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) compaction is carried out according to the height of 10 samples in 5 layers, and the soil quality of each layer is equal. After each layer is compacted to the required height, the surface is planed 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 6-1 interface of the top pore pressure valve, and opening the negative pressure pre-saturation fitting to perform air suction, so that a certain negative pressure (20kPa) is generated in the sample 10, and the sample 10 can stand; the split mold is removed, the height and diameter of the sample 10 are measured, and the sample dimensions are recorded.
Step 2: carbon dioxide saturation and head saturation
(1) After the sandy soil sample is installed, continuously pumping air by using a negative pressure pre-saturation accessory, keeping the negative pressure of 20kPa in the sample 10, and checking whether the rubber film is damaged or not; 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 waterless pre-saturated fitting with a port 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 (20kPa), 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 bubbles in the negative pressure pre-saturation fitting completely disappear, continuously injecting the non-aerated water for 60min, then closing the bottom pore pressure valve 6-2 and the top pore pressure valve 6-1 at the same time, 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 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 pore pressure increment delta u caused by the confining pressure, wherein B is delta u/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/400kPa), 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 the interior of the sample 10 to generate continuous seepage until the sample generates seepage erosion damage, 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 above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. 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 (3)
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);
four interfaces are arranged on the outer ring of the converter valve (5) at equal intervals and are 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 the two interfaces of the pipeline at the end part of the sample, which are connected with the top and the bottom of the sample (10), are symmetrically distributed, the two interfaces of the volume compression controller are symmetrically distributed, and the interfaces of the pipeline at the end part of the sample and the interfaces of the volume compression controller are adjacently distributed;
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 of the sample end pipe interfaces is communicated with the top of a 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;
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, so that the connection states of the two volume compression controllers and the top and the bottom of the sample (10) can be switched, and the stable and continuous seepage formed inside the sample (10) is ensured through the external circulation of seepage water flow and the switching of the two volume compression controllers, so that the test requirement of a soil body constant shear drainage test is met.
2. The seepage erosion control system under the GDS triaxial apparatus drainage condition as claimed in claim 1, wherein a water-stop 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.
3. A seepage erosion drainage test method based on the seepage erosion control system of claim 1 or 2, characterized by comprising:
(1) a constant shear drainage test is carried out by using a GDS triaxial apparatus, the preparation, saturation and consolidation processes of the sample (10) are completed according to test specifications and test schemes, the stress state of the sample (10) required by the test scheme is achieved and maintained, and a seepage erosion drainage test is prepared.
(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 drainage 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); seepage parameters such as the magnitude of a top and bottom pressure value, pressure difference and seepage velocity are preset in a test operation interface of a computer (19), so that seepage from bottom to top can occur in a sample (10), a second volume compression controller (4) can inject water into the sample (10) under the action of the pressure difference, and a first volume compression controller (3) can absorb water into the sample (10); the top pore pressure valve (6-1) and the bottom pore pressure valve (6-2) are opened, and the test is started by clicking. Under the action of pressure difference, a 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), drains water from the top of the sample (10), and is sucked into the first volume compression controller (3) through the converter valve (5), so that a seepage erosion test is started; and then, a data acquisition system (18) 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 (10).
(3) 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 absorb 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 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); and 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) And (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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