CN110082275B - Large-scale original grading coarse-grained soil vertical penetration deformation tester and test method - Google Patents
Large-scale original grading coarse-grained soil vertical penetration deformation tester and test method Download PDFInfo
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- CN110082275B CN110082275B CN201910430027.7A CN201910430027A CN110082275B CN 110082275 B CN110082275 B CN 110082275B CN 201910430027 A CN201910430027 A CN 201910430027A CN 110082275 B CN110082275 B CN 110082275B
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- 239000002689 soil Substances 0.000 title claims abstract description 43
- 230000035515 penetration Effects 0.000 title claims abstract description 25
- 238000010998 test method Methods 0.000 title claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 196
- 238000012360 testing method Methods 0.000 claims abstract description 107
- 238000000034 method Methods 0.000 claims abstract description 26
- 230000007704 transition Effects 0.000 claims abstract description 11
- 239000008187 granular material Substances 0.000 claims abstract description 3
- 230000035699 permeability Effects 0.000 claims description 19
- 239000010419 fine particle Substances 0.000 claims description 18
- 230000003204 osmotic effect Effects 0.000 claims description 18
- 239000002245 particle Substances 0.000 claims description 17
- 230000008859 change Effects 0.000 claims description 12
- 238000013461 design Methods 0.000 claims description 7
- 230000000630 rising effect Effects 0.000 claims description 6
- 239000011362 coarse particle Substances 0.000 claims description 5
- 230000008569 process Effects 0.000 claims description 5
- 230000001105 regulatory effect Effects 0.000 claims description 4
- 230000000087 stabilizing effect Effects 0.000 claims description 4
- 238000004140 cleaning Methods 0.000 claims description 3
- 238000005056 compaction Methods 0.000 claims description 3
- 230000001066 destructive effect Effects 0.000 claims description 3
- 230000005484 gravity Effects 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 239000011148 porous material Substances 0.000 claims description 3
- 238000002360 preparation method Methods 0.000 claims description 3
- 229920006395 saturated elastomer Polymers 0.000 claims description 3
- 238000007789 sealing Methods 0.000 claims description 3
- 238000000926 separation method Methods 0.000 claims description 3
- 230000000149 penetrating effect Effects 0.000 claims 2
- 238000005422 blasting Methods 0.000 abstract 1
- 235000017166 Bambusa arundinacea Nutrition 0.000 description 8
- 235000017491 Bambusa tulda Nutrition 0.000 description 8
- 241001330002 Bambuseae Species 0.000 description 8
- 235000015334 Phyllostachys viridis Nutrition 0.000 description 8
- 239000011425 bamboo Substances 0.000 description 8
- 239000000463 material Substances 0.000 description 6
- 238000006467 substitution reaction Methods 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 4
- 238000009434 installation Methods 0.000 description 4
- 239000012466 permeate Substances 0.000 description 4
- 230000009467 reduction Effects 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000009530 blood pressure measurement Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229920001971 elastomer Polymers 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000011435 rock Substances 0.000 description 2
- 239000003566 sealing material Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- -1 bubble emergence Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000004503 fine granule Substances 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 238000012812 general test Methods 0.000 description 1
- 239000008202 granule composition Substances 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 230000009191 jumping Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000011257 shell material Substances 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D21/00—Measuring or testing not otherwise provided for
- G01D21/02—Measuring two or more variables by means not covered by a single other subclass
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
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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
- 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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- Chemical & Material Sciences (AREA)
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- General Health & Medical Sciences (AREA)
- Immunology (AREA)
- Pathology (AREA)
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- Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
A large-scale original grading coarse granule soil vertical penetration deformation tester is provided with a base, a transition cylinder, a first water permeable plate, a test cylinder, a water collecting cylinder and a top plate are sequentially arranged on the base, pressure measuring units are arranged on the side wall of the test cylinder at intervals, the pressure measuring units are communicated with the test cylinder, a drain pipe provided with a drain valve is arranged on the side wall of the water collecting cylinder, the drain pipe is communicated with the measuring cylinder, the lower part of the base is communicated with one end of a water inlet pipe, a water inlet valve is arranged on the water inlet pipe, the other end of the water inlet pipe is communicated with a pressure tank, the pressure tank is communicated with a variable frequency adjusting pump set, a pipe network pressure sensor is arranged on a pipeline between the pressure tank and the variable frequency adjusting pump set, the variable frequency adjusting pump set is communicated with a water tank, and the pipe network pressure sensor, the variable frequency adjusting pump set are electrically connected with a PID regulator; the experimental device and the method are suitable for testing the vertical penetration deformation of coarse-grained soil, namely blasting stones and gravel stones with the grain size of more than 600 mm.
Description
Technical Field
The invention belongs to the technical field of hydraulic and hydroelectric engineering construction devices and methods, and particularly relates to a large-scale original grading coarse-grained soil vertical penetration deformation tester and a testing method.
Background
In the design of the earth-rock dam, the actual requirements of the engineering are combined at first, and dam seepage analysis is carried out, so that the leakage damage phenomenon of the earth-rock dam can be greatly reduced. In order to study the seepage law and characteristics of water in the soil structure of the dam filling material, a seepage deformation test of coarse-grained soil is needed, parameters required by dam seepage stability analysis and calculation are provided for design, and reasonable seepage prevention arrangement types are selected. The dam filling materials are usually blasted Dan Zhaliao, gravel stones and the like, and the materials have the characteristics of large particle size, wide particle size range, large density, large void ratio, irregular and the like, and the permeability characteristic rule of the materials is different from that of common homogeneous soil particle materials. The permeability coefficient comprehensively reflects the permeability characteristic of the soil body, the permeability gradient reflects the impermeability of the integral structure of the soil body, the two technical indexes are required to be measured through an indoor test, the diameter of a sample cylinder of a permeation device used for the current indoor test for measuring coarse-grained soil permeability is determined according to the maximum grain diameter of the sample, the inner diameter of an instrument is regulated to be 5 times larger than the grain diameter d 85 of the sample according to the test rule, when the inner diameter of the instrument of the conventional test cannot meet the requirement, a large-diameter permeation deformation instrument is designed, or the sample can be subjected to scale reduction treatment by adopting an equivalent removal method, an equivalent substitution method, a similar grading method or a mixing method on the grains above the maximum allowable grain diameter according to the condition of the sample, the size specification of the instrument used for the current indoor test is mainly designed for coarse-grained soil (grains smaller than 60 mm), the permeation test method discussion of main rockfill (generally Dmax is smaller than or equal to 800 mm), the applicability of the ultra-diameter size grains is still required to be tested and verified by adopting a scale reduction method on the osmotic deformation test, the fine grains are greatly changed in the permeation test scale by adopting a division method and the fine grain mixing method, and the content is just influenced by the method on the critical factors for measuring the osmotic coefficient, so the two methods are not suitable for obvious permeation test; the similar grading method maintains the non-uniform coefficient of grading unchanged, but the graded granule composition after the method is scaled has larger difference with the original grading curve, the granule is obviously thinned, the content of fine granule is far greater than the original grading content, the permeability coefficient measured by the method is obviously reduced by an order of magnitude, and the difference is an order of magnitude, so the method is also unreasonable; the equivalent substitution method ensures that the content of the sample fine particles is unchanged by adopting equivalent substitution fine particle part content measures, but equivalent substitution of different particle sizes of the fine particle part influences the content change of the rest part, so that the result of the osmotic coefficient measurement is also influenced, and therefore, the method has the technical problems of determining reasonable substitution particle size and maximum allowable substitution amount. In summary, the reduction effect has adverse effects on accurate measurement of coarse-grained soil and even coarse-grained soil penetration test results, so that the coarse-grained soil penetration test should be measured by adopting an original grading sample, but no specific method for the coarse-grained soil penetration test and an amorphous coarse-grained soil vertical penetration deformer are proposed in the current test procedure.
Disclosure of Invention
The invention aims to solve the technical problems of overcoming the defects of the prior art, and provides the large-scale original graded coarse-grained soil vertical penetration deformation tester and the testing method which are reasonable in design, simple in structure, capable of realizing functions of automatic pressure supply, constant pressure, pressurization and the like, and greatly improving the testing accuracy.
The technical scheme adopted for solving the technical problems is as follows: be provided with the base on the support, be provided with the transition section of thick bamboo on the base, transition section of thick bamboo top is provided with first water permeable plate, be provided with test section of thick bamboo on the first water permeable plate, be provided with pressure measurement unit and blast pipe on the test section of thick bamboo lateral wall, be provided with discharge valve on the blast pipe, pressure measurement unit is linked together with test section of thick bamboo, test section of thick bamboo top is provided with the catchment section of thick bamboo top, be provided with the drain pipe of installation drain valve on the catchment section of thick bamboo lateral wall, the drain pipe is linked together with the graduated flask, the base lower part is linked together with inlet tube one end, install the water intaking valve on the inlet tube, the inlet tube other end is linked together with the overhead tank, the overhead tank is linked together with the frequency conversion and adjusts the pump package, be provided with pipe network pressure sensor on the pipeline between overhead tank and the frequency conversion and adjust the pump package, the pipe network pressure sensor, frequency conversion is adjusted the pump package and PID regulator electricity is connected.
The base of the invention is as follows: the conical convergence of base body lower extreme, the convergence end is provided with the inlet connection pipe that is linked together with the inlet tube, and base body top is provided with the second and permeates water the board, and processing has at least 30 rings of holes that permeate water on the second permeate water the board, and adjacent two rings of holes that permeate water are staggered arrangement.
The test cylinder is formed by connecting at least 3 sections of cylinders.
The pressure measuring unit of the invention is as follows: one end of the pressure measuring connecting pipe is communicated with the test cylinder, one path of the other end of the pressure measuring connecting pipe is communicated with the pressure measuring pipe through the first valve and the third valve, and the other path of the pressure measuring connecting pipe is connected with the pressure sensor of the test cylinder through the third valve and the second valve.
At least 30 circles of water permeable holes are processed on the first water permeable plate, and every two adjacent circles of water permeable holes are arranged in a staggered mode.
The bracket of the invention is as follows: the cross section is rectangular support body lower part and is provided with 6 piece at least and erects and prop, and support body lower part and erects and prop the junction and correspond and be provided with the bracing, and support body middle part is provided with annular support, and annular support's diameter suits with the diameter of base.
The invention relates to a test method of a large-scale original grading coarse-grained soil vertical penetration deformation tester, which is characterized by comprising the following steps:
S1, debugging equipment: assembling the permeation tester, opening a water inlet valve and a water outlet valve, filling water into the test cylinder from the water inlet valve until water overflows from the water outlet pipe and the gas outlet hole, closing the water outlet valve and the gas outlet valve, and then simulating high-pressure water required by the test to check whether the sealing system is good under the test pressure;
S2, sample preparation and sample loading: calculating the dry density rho d and the porosity n of a sample according to the requirements, calculating the number of the required samples according to the volume of the prepared sample, grading, layering, batching, loading the samples, manually layering, tamping, compacting, hermetically connecting the vibrating rammer in layers by using a penetration test device, cleaning the surface of the sample after reaching the required height, mounting a top plate, introducing water for test, and applying pressurized water from bottom to top by using a penetration water flow in the test method; in order to ensure the uniformity of the sample and reduce the separation of coarse and fine particles, the particle size distribution of each layer of filling sample is kept consistent, water accounting for about 3% of the mass of the sample can be added, the mixture is uniformly mixed and then filled into a test container, and a large-size surface vibrator is adopted for carrying out layer-by-layer compaction, so that the filling dry density of the sample meets the design dry density requirement;
The sample dry density ρ d and porosity n are calculated as follows:
Wherein: ρ d -dry density, g/cm3; m d -dry mass g of sample, area of A-sample, cm2; h-the actual height of the sample, cm; n-porosity,%; ρ ω -density of water, g/cm3; gs-soil particle specific gravity;
S3, sample saturation: after the sample is assembled, measuring the actual thickness of the sample, then adopting an exhaust water head saturation method to saturate the sample, leading the water pressure water level to be slightly higher than the bottom surface position of the sample, slowly lifting the water pressure, leading the water to infiltrate upwards from the bottom of the instrument along with the rising of the water supply pressure, leading the sample to be slowly saturated so as to completely remove the air in the sample, and simultaneously, along with the rising of the water level, switching on a corresponding pressure measuring unit so as to reduce the problem that the air bubbles separated from the test water in the test process block the sample pores, thereby influencing the test accuracy and leading the temperature of the test water to be not lower than the room temperature;
s4, measuring by a penetration test:
a. according to the fine particle content in the sample, primarily judging the destructive form of the osmotic deformation of the sample, selecting initial osmotic gradient and osmotic gradient increment value, wherein the osmotic initial gradient is 0.3-0.5, and the increment value is controlled within the range of 0.5-0.8 according to the soil sample property;
b. Step a is regulated to step up the water head step by step, after each water head is lifted, the seepage time t is recorded, the pressure stabilizing time is not less than 30min, the pressure tube reading and the measuring cylinder reading are started to be measured and recorded to determine the seepage water quantity Q, each water head level is measured and read 3 times, each time interval is not less than 30min, the water temperature and the air temperature are measured and read simultaneously, and the seepage slope drop i and the seepage flow velocity v under each water head level are calculated
Wherein: i-permeation gradient, v-permeation flow rate, cm/s, delta H-water head difference of two pressure measuring pipes to be measured, cm, L-permeation path length corresponding to the two pressure measuring pipes to be measured, cm, Q-permeation water quantity within t time, cm 3, t-permeation time and s;
Calculating the permeability coefficient k T
Wherein: k T -permeability coefficient at T ℃, cm/s, k 20 -permeability coefficient at 20 ℃, cm/s;
c. Drawing a relation curve of the permeation gradient i and the seepage velocity v, drawing a double-logarithmic coordinate by taking the permeation gradient i as an ordinate and the seepage velocity v as an abscissa, drawing a relation curve of the seepage velocity v and the time t, starting to change according to the slope of the relation curve of the permeation gradient i and the seepage velocity v, and considering that the sample reaches critical gradient when fine particles start to jump or are carried out by water flow, and calculating the critical gradient according to the following conditions:
Wherein: i k -critical ramp down; i 2 -a dip in the onset of piping; i 1 -the slope of the stage before piping begins to appear;
According to the relation curve of the permeation gradient i and the seepage velocity v, as the water head is gradually increased, fine particles are continuously washed away, the permeation flow Q is increased, when the water head is increased to a sample and the seepage resistance strength is lost, the gradient is called as the damage gradient of the sample, and the damage gradient is calculated according to the following formula:
Wherein: i F -destroy ramp down; i' 2 -decrease in permeation upon failure; i' 1 -destroy the osmotic ramp down of the previous stage;
when the flowing soil is damaged and the permeation gradient is not easy to measure when the slope is damaged, taking the permeation gradient of the stage before the damage as the permeation damage gradient of coarse-grained soil;
S5, closing a water inlet valve after the test is finished, extracting residual water in the sample, observing the change of the sample, measuring the height of the sample after the test according to the requirement, unloading the loaded sample in time and observing rebound condition, unloading a top cover, sucking residual water on the sample, unloading a first water permeable plate, draining residual water of an instrument, removing the sample, taking out the sample after the test is finished, and carrying out particle analysis and density test on the sample.
According to the test method, the permeability coefficient of a sample and the permeability gradient (piping) of fine particles gradually lost along with seepage when coarse particle soil passes through the seepage and the damage gradient (flowing soil) of soil body when the fine particles float wholly are measured according to the Darcy law permeability test principle, the particle size of the sample is controlled according to the maximum particle size Dmax less than or equal to 600mm required by the dam shell material of an engineering project, the test cylinder is designed in a sectional manner and is adjustable in height, the water permeable plate is arranged in the cylinder, water flow enters the transition cylinder and is buffered in the transition cylinder, the first water permeable plate enters the test cylinder, the water flow applies pressure from bottom to top, the vertical permeability working condition in actual engineering can be well simulated, a plurality of groups of pressure measuring units are arranged according to the size of the test cylinder, the pressure at different water heads is measured, the permeability gradient i, the permeability flow velocity v, the permeability coefficient k T at all levels are obtained, the functions of automatic pressure supply, the constant pressure and the pressurizing are realized through an automatic water supply system, the functions of the automatic pressure supply, the constant pressure, the pressurizing and the like are greatly improved, the large-scale test operation becomes simple and easy to operate, and the test is suitable for measuring the vertical permeability deformation of coarse particle (the particle size > 600 mm) and gravel.
Drawings
Fig. 1 is a schematic diagram of the structure of an embodiment of the present invention.
Fig. 2 is a schematic sectional view of the test cartridge 7 of fig. 1.
Fig. 3 is a schematic diagram of the installation of the load cell 8 of fig. 1.
Fig. 4 is a schematic view of the structure of the bracket 16 in fig. 1.
Fig. 5 is a top view of fig. 4.
Fig. 6 is a cross-sectional view A-A of fig. 1.
Fig. 7 is a schematic view of the structure of the base 15 in fig. 1.
In the figure: 1. a water tank; 2. frequency conversion adjusting pump group; 3. a pressure tank; 4. a pipe network pressure sensor; 5. a water inlet valve; 6. a water inlet pipe; 7. a test cartridge; 8. a pressure measuring unit; 9. a water collecting cylinder; 10. a top plate; 11. a drain valve; 12. a drain pipe; 13. a measuring cylinder; 14. a first water permeable plate; 15. a base; 16. a bracket; 17. a transition barrel; 18. a PID regulator; 8-1, a piezometer tube; 8-2, a first valve; 8-3, a second valve; 8-4, testing a cylinder pressure sensor; 8-5, a third valve; 8-6, pressure measuring connecting pipes; 15-1, a base body; 15-2, a second water permeable plate; 16-1, diagonal bracing; 16-2, a bracket body; 16-3, vertical support; 16-4, annular supports.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, but the present invention is not limited to these examples.
Example 1
In the large-scale original grading coarse-grained soil vertical penetration deformation tester, a base 15 is fixedly connected and installed on a support 16 through a screw fastening connecting piece, further, the support 16 of the embodiment is formed by connecting an inclined support 16-1, a support body 16-2, a vertical support 16-3 and an annular support 16-4, the support body 16-2 is welded into a structure with a rectangular cross section through square steel or channel steel, at least 6 vertical supports 16-3 are welded and fixed at the lower part of the support body 16-2, the inclined support 16-1 is welded and fixed at the joint of the lower part of the support body 16-2 and the vertical support 16-3 correspondingly, the annular support 16-4 is welded and fixed at the middle part of the support body 16-2, the diameter of the annular support 16-4 is matched with that of the base 15, the base 15 is formed by connecting a base body 15-1 and a second water permeable plate 15-2, the base body 15-1 is of a hollow structure with a conical convergence at the lower end, a water inlet connecting pipe communicated with the water inlet pipe 6 is integrally designed at the convergence end, the second water permeable plate 15-2 is fixedly connected and installed at the top of the base body 15-1 through a threaded fastening connecting piece, at least 30 circles of water permeable holes with the diameter of 5mm are processed on the second water permeable plate 15-2, two adjacent circles of water permeable holes are arranged in a staggered way and are 10mm apart, a transition cylinder 17 is fixedly connected and installed on the base 15 through a threaded fastening connecting piece, test water enters the base 15 through the water inlet connecting pipe, is collected in a cavity of the base 15 until reaching the second water permeable plate 15-2, enters the transition cylinder 17 through the second water permeable plate 15-2 and gradually fills the transition cylinder 17, the test water pressure was allowed to rise steadily and maintained at a constant pressure.
The top of the transition cylinder 17 is fixedly connected with a first water permeable plate 14 by a screw fastening connecting piece, at least 30 circles of water permeable holes are processed on the first water permeable plate 14, two adjacent circles of water permeable holes are arranged in a staggered way and are 10mm apart, the first water permeable plate 14 is fixedly connected with a test cylinder 7 by the screw fastening connecting piece, at least 6 groups of pressure measuring units 8 are symmetrically and equally spaced on two opposite sides of the side wall of the test cylinder 7, the installation number and the installation spacing of the pressure measuring units 8 are determined according to test requirements, the pressure measuring units 8 are communicated with the test cylinder 7, an exhaust pipe is arranged on the side wall of the test cylinder 7, an exhaust valve is arranged on the exhaust pipe, the pressure measuring units 8 of the embodiment are formed by connecting a pressure measuring pipe 8-1, a first valve 8-2, a second valve 8-3, a test cylinder pressure sensor 8-4, a third valve 8-5 and a pressure measuring connecting pipe 8-6, one end of each pressure measuring connecting pipe 8-6 is communicated with the test cylinder 7 by the first valve 8-2 and the third valve 8-5, the other path is communicated with the test cylinder 8-1 by the third valve 8-3, when the pressure measuring values of the corresponding liquid level difference or the water seepage difference value of the two side walls 8-4 is measured according to the measured values of the test cylinder 8-4, or the water seepage value is measured at any position, or the position of the corresponding position of the first valve 8-4, the water level value is measured, and the water level value is measured, the vertical distance between the two sections is the corresponding seepage diameter under the water head difference. The test cylinder 7 is formed by fixedly connecting at least three sections of cylinders through screw fastening connectors according to the height of a sample in the test, rubber sealing materials are arranged at the joint of the cylinders to stop water, the top of the test cylinder 7 is fixedly connected with a water collecting cylinder 9 through screw fastening connectors, the top of the water collecting cylinder 9 is fixedly connected with a top plate 10 through screw fastening connectors, a drain pipe 12 is arranged on the side wall of the water collecting cylinder 9, a drain valve 11 is arranged on the drain pipe 12 and is communicated with the measuring cylinder 13, when the test is carried out, the water quantity in a certain seepage time period is the seepage quantity Q of the certain seepage time period after the seepage is stabilized, and the rubber sealing materials are arranged at the joint of the cylinders to stop water.
The lower part of the base 15 is fixedly connected with a water inlet pipe 6 through a connecting flange, a water inlet valve 5 is arranged on the water inlet pipe 6, the other end of the water inlet pipe 6 is communicated with a pressure tank 3, the pressure tank 3 is communicated with a variable frequency adjusting pump set 2, the pressure tank 3 plays a role in stabilizing pressure of test water flow, a pipe network pressure sensor 4 is arranged on a pipeline between the pressure tank 3 and the variable frequency adjusting pump set 2, the variable frequency adjusting pump set 2 is communicated with a water tank 4, the water tank 1 provides a water source for the test, the pressure sensor 4 is electrically connected with a PID regulator 18 through a pressure transmitter, the variable frequency adjusting pump set 2 is connected with the PID regulator 18, the pipe network pressure sensor 4 senses pressure change of the pipe network, signals are fed back to the PID regulator 18 through the pressure transmitter, the PID regulator 18 compares the test control pressure with a system, then corresponding variable frequency instructions are given, and the running speed of the centrifugal pump is changed, so that the water pressure and the control pressure of the pipe network are kept consistent.
The invention relates to a test method of a large-scale original grading coarse-grained soil vertical penetration deformation tester, which comprises the following steps:
S1, debugging equipment: and after the requirements are met, the test is carried out according to the test scheme and steps, and the continuous water supply process ensures the water pressure required by the test so as to ensure the accuracy of the test results.
S2, sample preparation and sample loading: providing dry density and the number of samples required by the prepared sample volume calculation trial experiment according to the design, grading and layering, carrying out batching and sample loading, manually tamping and compacting by a vibrating rammer, carrying out layered sealing connection on a penetration test device, cleaning the surface of the sample after reaching the required height, installing a top plate, introducing water for the trial, and applying pressurized water from bottom to top by using penetration water flow in the test method; in order to ensure the uniformity of the sample and reduce the separation of coarse and fine particles, the particle size distribution of each layer of filling sample is kept consistent, water accounting for about 3% of the mass of the sample can be added, the mixture is uniformly mixed and then filled into a test container, and a large-size surface vibrator is adopted for carrying out layer-by-layer compaction, so that the filling dry density of the sample meets the design dry density requirement;
The sample dry density ρ d and porosity n are calculated as follows:
Wherein: ρ d -dry density, g/cm3; m d -dry mass g of sample, area of A-sample, cm2; h-the actual height of the sample, cm; n-porosity,%; ρ ω -density of water, g/cm3; gs-soil particle specific gravity;
the calculation formula of the dry mass m d of the sample is as follows:
md＝ρd*Ah
Wherein: ρ d -dry density, g/cm 3;md -sample dry mass g, A-sample area, cm 2; h-the actual height of the sample, cm;
S3, sample saturation: after the sample is assembled, measuring the actual thickness of the sample, then adopting an exhaust water head saturation method to saturate the sample, leading the water pressure water level to be slightly higher than the bottom surface position of the sample, slowly lifting the water pressure, leading the water to infiltrate upwards from the bottom of the instrument along with the rising of the water supply pressure, leading the sample to be slowly saturated so as to completely remove the air in the sample, and simultaneously, along with the rising of the water level, switching on a corresponding pressure measuring unit so as to reduce the problem that the air bubbles separated from the test water in the test process block the sample pores, thereby influencing the test accuracy and leading the temperature of the test water to be not lower than the room temperature;
s4, measuring by a penetration test:
a. according to the fine particle content in the sample, primarily judging the destructive form of the osmotic deformation of the sample, selecting initial osmotic gradient and osmotic gradient increment value, wherein the osmotic initial gradient is 0.3-0.5, and the increment value is controlled within the range of 0.5-0.8 according to the soil sample property; the permeation gradient increment should be reduced by an appropriate amount when approaching the critical gradient, and the value may be increased appropriately when in the form of a soil flux failure.
B. Step a is regulated to step up the water head step by step, after each water head is lifted, the seepage time t is recorded, the pressure stabilizing time is not less than 30min, the pressure tube reading and the measuring cylinder reading are started to be measured and recorded to determine the seepage water quantity Q, each water head level is measured and read 3 times, each time interval is not less than 30min, the water temperature and the air temperature are measured and read simultaneously, and the seepage slope drop i and the seepage flow velocity v under each water head level are calculated
Wherein: i-permeation gradient, v-permeation flow rate, cm/s, delta H-water head difference of two pressure measuring pipes to be measured, cm, L-permeation path length corresponding to the two pressure measuring pipes to be measured, cm, Q-permeation water quantity within t time, cm 3, t-permeation time and s;
Calculating the permeability coefficient k T
Wherein: k T -permeability coefficient at T ℃, cm/s, k 20 -permeability coefficient at 20 ℃, cm/s;
when the seepage amount measured and read for 3 times is stable, the pressure can be increased to the next level of water head to continue to measure, the steps are repeated until the test is finished, and an average value of 3 seepage coefficients with the reading close to each other is taken as a test value;
c. Drawing a relation curve of the permeation gradient i and the seepage velocity v, drawing a double logarithmic coordinate by taking the permeation gradient i as an ordinate and the seepage velocity v as an abscissa, drawing a relation curve of the seepage velocity v and the time t, and timely adjusting the duration time of each stage of water head and the stage difference of the water head according to curve change. When the slope of the relation between the permeation gradient i and the seepage velocity v starts to change and fine particles are observed to start to jump or be carried out by water flow, the sample is considered to reach the critical gradient, and the critical gradient is calculated according to the following formula:
Wherein: i k -critical ramp down; i 2 -a dip in the onset of piping; i 1 -the slope of the stage before piping begins to appear;
According to the relation curve of the permeation gradient i and the seepage velocity v, as the water head is gradually increased, fine particles are continuously washed away, the permeation flow Q is increased, when the water head is increased to a sample and the seepage resistance strength is lost, the gradient is called as the damage gradient of the sample, and the damage gradient is calculated according to the following formula:
Wherein: i F -destroy ramp down; i' 2 -decrease in permeation upon failure; i' 1 -destroy the osmotic ramp down of the previous stage;
when the flowing soil is damaged and the permeation gradient is not easy to measure when the slope is damaged, taking the permeation gradient of the stage before the damage as the permeation damage gradient of coarse-grained soil;
S5, closing a water inlet valve after the test is finished, extracting residual water in the sample, observing the change of the sample, measuring the height of the sample after the test according to the requirement, unloading the loaded sample in time and observing rebound condition, unloading a top cover, sucking residual water on the sample, unloading a first water permeable plate, draining residual water of an instrument, removing the sample, taking out the sample after the test is finished, and carrying out particle analysis and density test on the sample.
In the experimental process, various phenomena such as turbidity degree of the discharged water, bubble emergence, fine particle jumping, movement or water flow carrying, soil body suspension, seepage and change of the water level of the pressure measuring pipe are observed, and detailed description is carried out, and when critical gradient and precursor of the gradient damage occur, gradient increment value is adjusted in time. And when the sample is damaged or the water head cannot be increased any more, ending the test.
When the permeability coefficient is measured, the change value of the water level is lifted every time, the change value is different according to the size of the permeability coefficient predicted value of the test material, and the test can be completed after the general test water head is changed for 5 times.
Claims (5)
1. A large-scale original grading coarse granule soil vertical penetration deformation tester is characterized in that: the device comprises a bracket, a support, a transition cylinder, a first water permeable plate, a test cylinder, a pressure measuring unit, an exhaust pipe, a pressure measuring unit, a water collecting cylinder, a top plate, a drain pipe, a pressure tank, a variable frequency regulation pump set, a pipeline network pressure sensor, a variable frequency regulation pump set and a PID regulator, wherein the bracket is provided with the base;
The base is: the lower end of the base body is in conical convergence, a water inlet connecting pipe communicated with the water inlet pipe is arranged at the convergence end, a second water permeable plate is arranged at the top of the base body, at least 30 circles of water permeable holes are processed on the second water permeable plate, and two adjacent circles of water permeable holes are arranged in a staggered mode;
The pressure measuring unit is as follows: one end of the pressure measuring connecting pipe is communicated with the test cylinder, one path of the other end of the pressure measuring connecting pipe is communicated with the pressure measuring pipe through the first valve and the third valve, and the other path of the pressure measuring connecting pipe is communicated with the pressure sensor of the test cylinder through the third valve and the second valve.
2. The large-scale original graded coarse soil vertical penetration deformation tester according to claim 1, wherein: the test cylinder is formed by connecting at least 3 sections of cylinders.
3. The large-scale original graded coarse soil vertical penetration deformation tester according to claim 1, wherein: at least 30 circles of water permeable holes are processed on the first water permeable plate, and every two adjacent circles of water permeable holes are arranged in a staggered mode.
4. The large-scale original graded coarse-grained soil vertical penetration deformation tester according to claim 1, wherein the bracket is: the cross section is rectangular support body lower part and is provided with 6 piece at least and erects and prop, and support body lower part and erects and prop the junction and correspond and be provided with the bracing, and support body middle part is provided with annular support, and annular support's diameter suits with the diameter of base.
5. The test method of the large-scale original graded coarse-grained soil vertical penetration deformation tester according to any one of the claims 1 to 4, which is characterized by comprising the following steps:
S1, debugging equipment: assembling the permeation tester, opening a water inlet valve and a water outlet valve, filling water into the test cylinder from the water inlet valve until water overflows from the water outlet pipe and the gas outlet hole, closing the water outlet valve and the gas outlet valve, and then simulating high-pressure water required by the test to check whether the sealing system is good under the test pressure;
S2, sample preparation and sample loading: calculating the dry density rho d and the porosity n of a sample according to the requirements, calculating the number of the required samples according to the volume of the prepared sample, grading, layering, batching, loading the samples, manually layering, tamping, compacting, hermetically connecting the vibrating rammer in layers by the penetrating test equipment, cleaning the surface of the sample after reaching the required height, installing a top plate, introducing water for test, and applying pressurized water from bottom to top by using penetrating water flow in the test method; in order to ensure the uniformity of the sample and reduce the separation of coarse and fine particles, the particle size distribution of each layer of filling sample should be kept consistent, water accounting for 3% of the mass of the sample is added, the mixture is uniformly mixed and then filled into a test container, and a large-size surface vibrator is adopted for carrying out layer-by-layer compaction, so that the filling dry density of the sample meets the design dry density requirement;
The sample dry density ρ d and porosity n are calculated as follows:
Wherein: ρ d -dry density, g/cm 3;md -sample dry mass g, A-sample area, cm 2; h-the actual height of the sample, cm; n-porosity,%; ρ ω —density of water, g/cm 3; gs-soil particle specific gravity;
S3, sample saturation: after the sample is assembled, measuring the actual thickness of the sample, then adopting an exhaust water head saturation method to saturate the sample, leading the water pressure water level to be slightly higher than the bottom surface position of the sample, slowly lifting the water pressure, leading the water to infiltrate upwards from the bottom of the instrument along with the rising of the water supply pressure, leading the sample to be slowly saturated so as to completely remove the air in the sample, and simultaneously, along with the rising of the water level, switching on a corresponding pressure measuring unit so as to reduce the problem that the air bubbles separated from the test water in the test process block the sample pores, thereby influencing the test accuracy and leading the temperature of the test water to be not lower than the room temperature;
s4, measuring by a penetration test:
a. according to the fine particle content in the sample, primarily judging the destructive form of the osmotic deformation of the sample, selecting initial osmotic gradient and osmotic gradient increment value, wherein the osmotic initial gradient is 0.3-0.5, and the increment value is controlled within the range of 0.5-0.8 according to the soil sample property;
b. Step a is regulated to step up the water head step by step, after each water head is lifted, the seepage time t is recorded, the pressure stabilizing time is not less than 30min, the pressure tube reading and the measuring cylinder reading are started to be measured and recorded to determine the seepage water quantity Q, each water head level is measured and read 3 times, each time interval is not less than 30min, the water temperature and the air temperature are measured and read simultaneously, and the seepage slope drop i and the seepage flow velocity v under each water head level are calculated
Wherein: i-permeation gradient, v-permeation flow rate, cm/s, delta H-water head difference of two pressure measuring pipes to be measured, cm, L-permeation path length corresponding to the two pressure measuring pipes to be measured, cm, Q-permeation water quantity within t time, cm 3, t-permeation time and s;
Calculating the permeability coefficient k T
Wherein: k T -permeability coefficient at T ℃, cm/s, k 20 -permeability coefficient at 20 ℃, cm/s;
c. Drawing a relation curve of the permeation gradient i and the permeation flow velocity v, drawing a relation curve of the permeation gradient i and the permeation flow velocity v on a double logarithmic coordinate by taking the permeation gradient i as an ordinate and the permeation flow velocity v as an abscissa, simultaneously drawing a relation curve of the permeation flow velocity v and the time, starting to change according to the slope of the relation curve of the permeation gradient i and the permeation flow velocity v, and considering that the sample reaches critical gradient when fine particles start to jump or are brought out by water flow, and calculating the critical gradient according to the following formula:
Wherein: i k -critical ramp down; i 2 -a dip in the onset of piping; i 1 -the slope of the stage before piping begins to appear;
According to the relation curve of the permeation gradient i and the permeation flow velocity v, as the water head is gradually increased, fine particles are continuously washed away, the permeation flow Q is increased, when the water head is increased to a sample and the impervious strength is lost, the gradient is called as the damage gradient of the sample, and the damage gradient is calculated according to the following formula:
Wherein: i F -destroy ramp down; i' 2 -decrease in permeation upon failure; i' 1 -destroy the osmotic ramp down of the previous stage;
when the flowing soil is damaged and the permeation gradient is not easy to measure when the slope is damaged, taking the permeation gradient of the stage before the damage as the permeation damage gradient of coarse-grained soil;
S5, closing a water inlet valve after the test is finished, extracting residual water in the sample, observing the change of the sample, measuring the height of the sample after the test according to the requirement, unloading the loaded sample in time and observing rebound condition, unloading a top cover, sucking residual water on the sample, unloading a first water permeable plate, draining residual water of an instrument, removing the sample, taking out the sample after the test is finished, and carrying out particle analysis and density test on the sample.
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