CN110763610A - Closed-loop full-curve geotechnical permeability test system - Google Patents
Closed-loop full-curve geotechnical permeability test system Download PDFInfo
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- 238000012360 testing method Methods 0.000 title claims abstract description 164
- 230000035699 permeability Effects 0.000 title claims abstract description 40
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 176
- 230000008595 infiltration Effects 0.000 claims description 42
- 238000001764 infiltration Methods 0.000 claims description 42
- 238000005303 weighing Methods 0.000 claims description 25
- 238000007789 sealing Methods 0.000 claims description 10
- 239000012780 transparent material Substances 0.000 claims description 3
- 230000035515 penetration Effects 0.000 description 31
- 238000000034 method Methods 0.000 description 24
- 230000008569 process Effects 0.000 description 19
- 239000002689 soil Substances 0.000 description 18
- 238000010998 test method Methods 0.000 description 11
- 239000004927 clay Substances 0.000 description 8
- 238000006073 displacement reaction Methods 0.000 description 8
- 229910001220 stainless steel Inorganic materials 0.000 description 8
- 239000010935 stainless steel Substances 0.000 description 8
- 230000008859 change Effects 0.000 description 7
- 239000007788 liquid Substances 0.000 description 6
- 239000012466 permeate Substances 0.000 description 5
- 239000004576 sand Substances 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000004064 recycling Methods 0.000 description 3
- 239000004575 stone Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005086 pumping Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000003204 osmotic effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 238000000967 suction filtration Methods 0.000 description 1
- 229940099259 vaseline Drugs 0.000 description 1
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- 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
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Abstract
The invention relates to the technical field of geotechnical permeability tests, in particular to a closed-loop full-curve geotechnical permeability test system which comprises a water supply system, a permeability system and a data processing system, wherein the water supply system is connected with the permeability system through a pipeline; the water supply system comprises a constant weight type pressure regulator, a first valve and a second valve; the constant-weight type pressure regulator comprises a vertically arranged cylinder, a bottom plate hermetically mounted at the bottom end of the cylinder, a piston which is arranged in the cylinder and can slide up and down, a piston shaft which is arranged at the top of the piston and extends upwards to the outside of the cylinder, a weight seat fixed at the top of the piston shaft, and a weight placed on the weight seat; the outlet of the first valve is communicated with the inner cavity of the cylinder body, and the inlet of the second valve is communicated with the inner cavity of the cylinder body. By arranging the constant-weight pressure regulator, not only can the test pressure conditions of two test states of a constant head and a variable head which are required by specifications be constructed simultaneously, but also the water supply state of the test hydraulic gradient which is adjustable in the range of the critical hydraulic gradient of the sample can be constructed.
Description
Technical Field
The invention relates to the technical field of geotechnical permeability tests, in particular to a closed-loop full-curve geotechnical permeability test system.
Background
The soil permeability test is a test for measuring the permeability coefficient K of soil using some test instruments. At present, the soil penetration test is based on Darcy's law and is divided into a normal water head method and a variable water head method according to the water head change characteristics of a penetration test system.
No matter it is the constant head or the variable head permeability test, carry out the prerequisite of effective test and be: initial hydraulic gradient < test hydraulic gradient < sample critical hydraulic gradient. This is because, if the test hydraulic gradient is < the initial hydraulic gradient, the seepage is hindered by the viscous force and water does not seep out of the sample; if the test hydraulic gradient is greater than the critical hydraulic gradient of the sample, the sample will flow soil or piping. On the other hand, a complete penetration test process comprises a laminar flow state and a turbulent flow state, and the seepage hydraulic gradient and the flow rate in the laminar flow state are in a linear relation and accord with Darcy's law; when in a turbulent flow state, the seepage hydraulic gradient and the flow velocity are in a nonlinear relation and do not accord with Darcy's law; therefore, to obtain an accurate permeation test result, it is necessary to clearly judge whether the state of the permeation test is laminar or turbulent.
Therefore, the controllable hydraulic gradient of the test in a certain range is realized, the complete penetration test process of a laminar flow state and a turbulent flow state is further realized, and the effects of accurately judging the test state and improving the accuracy of the test result are obvious and easy to see. The complete penetration test procedure for the test soil sample is referred to herein as the full curve penetration test.
The viscosity of the test water has influence on the penetration test result, the test condition which is the same as or similar to the actual water viscosity of the seepage environment is constructed for testing, and the test result has more guiding significance. In the penetration test device disclosed at the present stage, water is not recycled after seeping from the sample, the penetration test device is called an open penetration test device in the text, and penetration water with viscosity being the same as or similar to that in the actual seepage environment is uneconomical in indoor construction, so that the conformity degree and the guiding significance of indoor test results are reduced to a certain extent.
In the geotechnical test method standard with the standard number of GB/T50123-2019, a constant water head permeation test device and a variable water head permeation test device are recorded. In the process of carrying out the penetration test by using the test device described in the standard, the test hydraulic gradient in the normal head method is controlled by the height of the overflow hole, and the test hydraulic gradient in the variable head method is controlled by the height of the variable water pipe. In most cases, the test devices described in the above standards are installed inside a laboratory, and therefore, the height of the head pipe is limited by the height of the building story of the laboratory and cannot exceed 2 m; however, since the initial hydraulic gradient of most of the dense clays exceeds 2m, when the test device described in the above standard is used to perform the penetration test on most of the dense clays, the full-curve penetration test cannot be realized, and the test state cannot be accurately judged at this time. In addition, the manual measuring and recording errors of pressure, flow data and the like are large, the efficiency is low, and the accuracy and the reliability of the test result are low.
Application No. 201721074672.2, application date is 2017.08.25's patent application, discloses an indoor variable water head infiltration test device. The test hydraulic gradient of the test device is the same as that recorded in the geotechnical test method standard of GB/T50123-2019, and is also controlled by the height of the variable water head pipe. Therefore, the test device can not realize the full curve penetration test for the compact clay with higher initial hydraulic gradient.
Patent application No. 201721642550.9, application date is 2017.11.30, discloses a constant head soil column infiltration test device. The Mariotte bottle and the laser demarcation device are introduced into the test device, so that although the accuracy of measuring and recording the height of the water head is improved, the control range of the test hydraulic gradient is still limited by the height of the water head control chamber. Therefore, the test device can not realize the full curve penetration test for the compact clay with higher initial hydraulic gradient.
Application number 201821725030.9, application date 2018.10.24 discloses a novel geotechnical variable head infiltration test device. The test hydraulic gradient of the test device is the same as that recorded in the geotechnical test method standard of GB/T50123-2019, and is also controlled by the height of the variable water head pipe. Therefore, the test device can not realize the full curve penetration test for the compact clay with higher initial hydraulic gradient.
Patent application No. 201821335384.2, application date 2018.08.20 discloses a pump-push type clay constant head infiltration test device. The test hydraulic gradient of the test device is provided by the injection pump, although the space limitation is broken through, the full-curve penetration test can be realized aiming at the compact clay with higher initial hydraulic gradient, but the reliability of the penetration state in the test process is difficult to accurately judge due to the limitation of the volumes of the injection pump and the suction filtration bottle; and the injection pump has larger starting pressure and pressure deviation, so that the hydraulic gradient of an actual test can fluctuate in the test process, accurate control cannot be achieved, and the test result is inaccurate.
An permeation test system is disclosed in patent application No. 201910263337.4, filing date 2019.04.02. Although the height of the water head liquid supply device in the test system is adjustable, the space limitation of a test room is not broken through, and the test system still cannot realize full-curve penetration test aiming at the compact clay with higher initial hydraulic gradient, so that the accuracy and the application value of indoor penetration test results cannot be improved.
Disclosure of Invention
The invention aims to solve the technical problem of providing a closed-loop type full-curve geotechnical permeability test system with test hydraulic gradient adjustable in the range of sample critical hydraulic gradient.
The technical scheme adopted by the embodiment of the invention for solving the technical problem is as follows: the closed-loop full-curve geotechnical permeability test system comprises a water supply system, a permeability system and a data processing system; the water supply system comprises a constant weight type pressure regulator, a first valve and a second valve; the constant-weight type pressure regulator comprises a vertically arranged cylinder, a bottom plate hermetically mounted at the bottom end of the cylinder, a piston arranged in the cylinder and capable of sliding up and down, a piston shaft arranged at the top of the piston and extending upwards to the outside of the cylinder, a weight seat fixed at the top of the piston shaft, and a weight placed on the weight seat; the outlet of the first valve is communicated with the inner cavity of the cylinder, and the inlet of the second valve is communicated with the inner cavity of the cylinder;
the infiltration system comprises a tubular infiltration container, end covers which are hermetically arranged at two ends of the infiltration container, a weigher internally provided with a weighing sensor and a water collecting cup placed on the weigher; at least two pressure sensors for measuring the internal pressure of the infiltration container are arranged on the outer wall of the infiltration container at intervals along the axial direction of the infiltration container; one end cover is provided with a first inlet communicated with the inner cavity of the permeation container, and the first inlet is communicated with the outlet of the second valve through a pipeline; the other end cover is provided with a first outlet communicated with the inner cavity of the infiltration container, and the first outlet is communicated with the water collecting cup through a pipeline; the pressure sensor and the weighing sensor in the weighing device are both connected with the input end of the data processing system.
Furthermore, the water supply system also comprises a water storage tank and a self-suction constant pressure pump; the inlet of the self-suction constant pressure pump is communicated with the water storage tank, and the outlet of the self-suction constant pressure pump is communicated with the inlet of the first valve.
Further, the infiltration system also comprises a siphon-type drain pipe; a through hole is formed in the side wall of the water collecting cup, and the siphon drain pipe penetrates through the through hole, so that the inlet of the siphon drain pipe is positioned inside the water collecting cup, and the outlet of the siphon drain pipe is positioned outside the water collecting cup; the through hole is hermetically connected with the outer wall of the siphon-type drain pipe; the elevation of the highest point of the siphon-type drain pipe is lower than or equal to the elevation of the through hole.
Further, the osmosis system also comprises a return pipe; the inlet end of the return pipe is arranged higher than other positions of the return pipe; the inlet end of the return pipe is arranged right below the outlet of the siphon-type drain pipe, and the outlet of the return pipe is communicated with the water storage tank.
Further, the infiltration container includes the cylindrical body that forms by two half-tube body concatenations, sets up the seal structure in two half-tube body concatenation departments for fixed two half-tube body's fixed knot constructs.
Furthermore, a positioning groove is formed in the inner surface of at least one half pipe body and located between two adjacent pressure sensors.
Furthermore, the inner surfaces of the two half pipe bodies are provided with positioning grooves, and the positioning grooves on the inner surfaces of the two half pipe bodies are arranged in pairs.
Furthermore, the positioning grooves which are arranged in pairs on the inner surfaces of the two half pipe bodies are spliced to form an annular positioning groove.
Furthermore, the infiltration container is made of transparent materials.
Further, the number of the permeation systems is at least two; and the outlets of the second valves are respectively communicated with all the first inlets through pipelines.
The invention has the beneficial effects that: according to the closed-loop full-curve geotechnical permeability test system provided by the embodiment of the invention, by arranging the constant-weight pressure regulator, not only can the test pressure conditions of two test states of a constant water head and a variable water head which are required by specifications be constructed simultaneously, but also the water supply state of the test hydraulic gradient which is adjustable in the range of the sample critical hydraulic gradient can be constructed; the problem of unstable test water pressure in the prior art is also solved, the limitation of space is broken through, and a full-curve penetration test can be realized for the compact clay with higher initial hydraulic gradient. The pressure parameter and the weight parameter can be acquired in real time through the data processing system in the test process, so that the test process can be determined to be in a laminar flow state or a turbulent flow state, reading errors are avoided, the accuracy of test data is improved, and the accuracy and the reliability of test results are further ensured.
Drawings
FIG. 1 is a schematic structural diagram of a closed-loop full-curve geotechnical permeability test system according to an embodiment of the invention;
fig. 2 is a schematic structural diagram of a constant weight voltage regulator according to an embodiment of the present invention;
FIG. 3 is a cross-sectional view of a fine soil sample installed into a infiltration vessel;
FIG. 4 is a cross-sectional view of a sand sample installed into a infiltration vessel;
fig. 5 is a schematic structural diagram of a closed-loop full-curve geotechnical permeation test system according to another embodiment of the invention.
The reference numbers in the figures are: 1-water supply system, 2-osmotic system, 3-data processing system, 5-stainless steel cutting ring, 6-water stop gasket, 7-fixed snap ring, 8-permeable stone, 9-sample cylinder, 10-stainless steel net, 11-water storage tank, 12-self-suction constant pressure pump, 13-first valve, 14-constant weight type pressure regulator, 15-second valve, 16-water pumping pipe, 21-osmotic container, 22-end cover, 23-weighing device, 24-water collecting cup, 25-pressure sensor, 26-siphon type water discharging pipe, 27-return pipe, 31-multichannel data collector, 32-computer, 51-ear edge, 141-cylinder, 142-bottom plate, 143-piston, 144-piston shaft, 145-weight seat, 146-weight, 147-leg, 148-weight guide bar, 149-top cover, 211-half tube, 212-positioning groove, 221-first inlet, 222-first outlet.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
As shown in fig. 1 to 5, the closed-loop full-curve geotechnical permeability test system of the embodiment of the present invention includes a water supply system 1, a permeability system 2 and a data processing system 3; the water supply system 1 comprises a constant weight type pressure regulator 14, a first valve 13 and a second valve 15; the constant-weight pressure regulator 14 comprises a vertically arranged cylinder 141, a bottom plate 142 hermetically mounted at the bottom end of the cylinder 141, a piston 143 arranged inside the cylinder 141 and capable of sliding up and down, a piston shaft 144 arranged at the top of the piston 143 and extending upwards to the outside of the cylinder 141, a weight seat 145 fixed at the top of the piston shaft 144, and a weight 146 placed on the weight seat 145; the outlet of the first valve 13 is communicated with the inner cavity of the cylinder body 141, and the inlet of the second valve 15 is communicated with the inner cavity of the cylinder body 141;
the infiltration system 2 comprises a tubular infiltration container 21, end covers 22 which are hermetically arranged at two ends of the infiltration container 21, a weigher 23 with a built-in weighing sensor, and a water collecting cup 24 which is arranged on the weigher 23; at least two pressure sensors 25 for measuring the internal pressure of the infiltration container 21 are arranged on the outer wall of the infiltration container 21 at intervals along the axial direction; one end cover 22 is provided with a first inlet 221 communicated with the inner cavity of the permeation container 21, and the first inlet 221 is communicated with the outlet of the second valve 15 through a pipeline; the other end cover 22 is provided with a first outlet 222 communicated with the inner cavity of the permeation container 21, and the first outlet 222 is communicated with the water collecting cup 24 through a pipeline; the pressure sensor 25 and the weighing sensor in the weighing device 23 are both connected with the input end of the data processing system 3.
As shown in fig. 2, the constant-weight voltage regulator 14 includes a cylinder 141, a bottom plate 142, a piston 143, a piston shaft 144, a weight seat 145, and a weight 146. The bottom plate 142 is horizontally disposed, and the bottom of the bottom plate 142 is provided with legs 147, through which the bottom plate 142 is supported. The cylinder 141 is a vertically arranged cylinder structure, the axis of the cylinder 141 is perpendicular to the upper surface of the bottom plate 142, the bottom end of the cylinder 141 is connected with the upper surface of the bottom plate 142 in a sealing manner, the bottom opening of the cylinder 141 is sealed through the bottom plate 142, and water in the cylinder 141 is prevented from leaking from the connecting position between the cylinder 141 and the bottom plate 142.
The piston 143 is disposed in the cylinder 141, and the piston 143 can slide up and down in the cylinder 141, and the side wall of the piston 143 is in close contact with the inner wall of the cylinder 141, so as to prevent the water in the cylinder 141 from leaking between the side wall of the piston 143 and the inner wall of the cylinder 141 when the piston 143 slides up and down. The weight seat 145 is arranged outside the cylinder 141 and located right above the cylinder 141, the weight seat 145 is fixedly connected with the piston 143 through the piston shaft 144, the axis of the piston shaft 144 is coaxially arranged with the axis of the cylinder 141, the upper surface of the weight seat 145 is a plane perpendicular to the axis of the cylinder 141, and the weight 146 is placed on the weight seat 145.
In order to improve the stability and reliability of the weight 146 placed on the weight seat 145, it is preferable that an upwardly extending weight guide rod 148 is fixed to the upper surface of the weight seat 145, the weight guide rod 148 is coaxially disposed with the axis of the cylinder 141, and a center hole through which the weight 146 guide rod 148 passes is disposed at the center of the weight 146. As shown in fig. 2, the weight 146 is placed on the weight seat 145, and the weight guide rod 148 passes through the center hole of the weight 146; when the number of the weights 146 is plural, the plural weights 146 are stacked on the weight seat 145 in order.
A top cover 149 is installed on the top of the cylinder 141, and a hole through which the piston shaft 144 passes is formed at the center of the top cover 149, and the piston shaft 144 can move up and down in the hole. Preferably, the upper surface of the bottom plate 142 is provided with a level outside the cylinder 141, and the bottom plate 142 can be conveniently leveled by the level, so that the axis of the cylinder 141 is in a vertical state. As shown in fig. 2, the bottom of the side wall of the cylinder 141 is provided with a water inlet and a water outlet, the outlet of the first valve 13 is communicated with the water inlet on the cylinder 141, so that the first valve 13 is communicated with the inner cavity of the cylinder 141, and the inlet of the second valve 15 is communicated with the water outlet on the cylinder 141, so that the second valve 15 is communicated with the inner cavity of the cylinder 141.
In the prior art, no matter pump pushing type water supply or self-absorption constant pressure pump water supply, large starting pressure and constant pressure deviation are required, the constant pressure deviation is about 20%, if water is directly supplied to the infiltration system 2 through a pump, actual test water pressure cannot be accurately controlled in the test process, and then the accuracy of the test result is influenced.
In the invention, by arranging the constant-weight type pressure regulator 14, the test pressure in the test process is controlled by the weight of the weight 146, so that the test water supply state with stable test pressure and controllable precision can be constructed, and the problem of unstable test water pressure in the prior art is solved.
In the constant-weight pressure regulator 14 of the embodiment of the present invention, in the test process, the test pressure is the output water pressure of the constant-weight pressure regulator 14, the output water pressure is mainly controlled by the weight of the weight 146, and the pressure calculation formula is as follows:
in the formula, P is the output water pressure of the constant weight type pressure regulator 14, and the unit is Pa; f1Is the weight of weight 146, in units of N; f2Is the running resistance of the piston 143 in units of N; a is the area of the piston 143 in m2；P1The water head difference between the upper limit of the stroke of the piston 143 and the sample is in Pa.
As can be seen from the above equation (1), when the size of the constant weight regulator 14 is determined, the gravity of the weight 146, the size of the piston 143, and the running resistance of the piston 143 can be measured with high precision. During the actual test, when F1、F2After A is determined, and P1Since the output water pressure P of the constant-weight pressure regulator 14 decreases as the piston 143 moves downward, the test mode of the variable head system can be realized.
The constant weight regulator 14 is further described below with reference to specific embodiments: the relationship between the weight of the weight 146 and the equivalent water head in the variable water head penetration test device in geotechnical test method standard is shown in the following table 1:
table 1:
in the constant-weight voltage regulator 14 of the embodiment, the height from the upper surface of the weight seat 145 to the bottom of the supporting leg 147 is 26cm, and when the number of the weights 146 is 40, the total height of the constant-weight voltage regulator 14 is 66 cm. From table 1, it can be seen that the variable water head test condition which can be realized only under the condition of the pressure measuring pipe with the height of 1490.4cm in the geotechnical test method standard and similar variable water head permeation test devices can be realized by the constant weight type pressure regulator 14 with the total height of 66 cm. When the variable water head penetration test device in the geotechnical test method standard is adopted for penetration test, the height of the pressure measuring pipe is generally not more than 200cm due to the limitation of the height of a laboratory.
In the constant-weight regulator 14 of the present embodiment, the inner diameter of the cylinder 141 is 10cm, and the inner diameter of the pressure measuring tube in the geotechnical test method standard is 0.82cm, so that the cross-sectional area of the cylinder 141 is 148.72 times that of the pressure measuring tube in the geotechnical test method standard. When the piston 143 descends, the stroke amount of 1cm is equivalent to the water head depth reduction of 148.72cm of the variable water head pressure measuring pipe in the geotechnical test method standard. The relationship between the displacement of the piston 143 and the equivalent head drop of the penetration test apparatus in the geotechnical test method standard is shown in the following table 2:
table 2:
with reference to tables 1 and 2, when the displacement of the piston 143 is 1cm, the relationship between the output water pressure and the proportion of the water pressure change due to the displacement of the piston to the output water pressure is shown in table 3:
table 3:
as can be seen from table 3, the proportion of the change in water pressure due to the displacement of the piston to the output water pressure gradually decreases as the output water pressure increases. When the output water pressure is 146059.2Pa, the proportion of the water pressure change to the output water pressure is 0.000067, and the influence of the water pressure change caused by the displacement of the piston 143 on the test result can be ignored, so that the constant weight type pressure regulator 14 can realize a constant head mode test mode under the condition of higher output water pressure. Further, as can be seen from tables 1, 2, and 3, when the output water pressure is not changed, the smaller the displacement of the piston, the smaller the proportion of the change in the water pressure due to the displacement of the piston to the output water pressure. Therefore, the constant-weight pressure regulator 14 according to the embodiment of the present invention can be constructed in a high pressure test mode, and a constant head mode can be realized under the control condition of a small stroke amount of the piston.
In the invention, a test water supply state with stable pressure and controllable precision can be constructed by the water supply system 1 mainly composed of the constant weight type pressure regulator 14; under the conditions of high output water pressure and small piston stroke amount control, a constant head test mode can be realized, so that the test pressure conditions of two test states of a constant head and a variable head which are required by specifications are simultaneously established by one system; the output water pressure of the constant-weight pressure regulator 14 can be adjusted by adjusting the number of the weights 146, so that a water supply state that the test hydraulic gradient is adjustable within the range of the critical hydraulic gradient of the sample is established; the range of the output water pressure of the constant-weight pressure regulator 14 in this embodiment is 0-146 KPa, and the test requirements of the initial hydraulic gradient of the low-permeability soil and the critical hydraulic gradient of the sample can be met, so that the full-curve penetration test is realized.
As shown in fig. 1, the permeation system 2 of the embodiment of the present invention mainly includes a permeation vessel 21, an end cap 22, a scale 23, a water collection cup 24, and a pressure sensor 25. The infiltration container 21 is a tubular structure, and during the test, the infiltration container 21 is horizontally arranged, and the sample is installed inside the infiltration container 21, so as to facilitate observing the infiltration condition of the sample, preferably, the infiltration container 21 is made of a transparent material, for example, a glass material or an acrylic material, but not limited to the above materials.
The number of the end caps 22 is two, and the two end caps are respectively hermetically installed at two ends of the infiltration container 21, so that water leakage from the position where the end cap 22 is connected with the infiltration container 21 is avoided. The end of the permeate vessel 21 may be connected to an end cap 22 by a flange structure, for example: the end of the infiltration container 21 is provided with a flange ring, a sealing gasket is arranged between the flange ring and the end cover 22, and the flange ring and the end cover 22 are fixed through a bolt structure. The end of the permeation vessel 21 may be connected to the end cap 22 by a screw structure, for example, the inner surface of the end of the permeation vessel 21 is provided with an internal screw thread, the end cap 22 is provided with an external screw thread matching with the internal screw thread, and the permeation vessel 21 and the end cap 22 are in screw sealing fit.
The pressure sensor 25 is a device or apparatus that can sense the pressure signal and convert the pressure signal into a usable output electrical signal according to a certain rule. In this embodiment, at least two pressure sensors 25 are mounted on the outer wall of the permeation vessel 21 in the axial direction thereof for the purpose of measuring the pressure at different locations inside the permeation vessel 21 and transmitting the measured pressures to the data processing system 3 for processing. Preferably, the pressure sensor 25 may be a temperature and pressure sensor that measures both the pressure inside the permeation vessel 21 and the temperature inside the permeation vessel 21.
The water collection cup 24 is for collecting permeate water flowing out from the inside of the permeate container 21. The volume of the water collection cup 24 may be large enough to hold the permeate water throughout the test. The weighing sensor is a device which converts a mass signal into a measurable electric signal to be output. In the embodiment of the present invention, the weighing device 23 with a built-in weighing sensor may be an electronic balance, an electronic scale, etc. for weighing the weight of the water collecting cup 24 and the permeated water therein, and transmitting the weight signal to the data processing system 3 for processing through the weighing sensor. Compared with the prior art, in the embodiment, the weigher 23 with the built-in weighing sensor is used for weighing the water in the water collecting cup 24, so that the defects of low artificial reading effect and poor accuracy in the prior art are overcome, and conditions are provided for acquiring data in real time. During the test, the amount of water in the water collection cup 24 was linear with time when the permeation process was laminar and non-linear with time when the permeation process was turbulent. After the test is finished, whether the permeation process is in a laminar flow state or a turbulent flow state can be accurately judged according to the relation between the weight and the time recorded in the data processing system 3.
The data processing system is a system formed by processing information by using a computer, processes, arranges and calculates the data information through the data processing system to obtain various analysis indexes, converts the analysis indexes into an information form which is easily accepted by people, and can store the processed information. As shown in fig. 1, the data processing system 3 in this embodiment is used to collect data measured by the pressure sensor 25 and the load cell in the weighing device 23 in real time, and process, arrange and calculate the data to obtain the permeability coefficient of the sample. The data processing system 3 comprises a multi-channel data acquisition unit 31 and a computer 32, wherein the pressure sensor 25 and a weighing sensor in the weighing device 23 are both connected with the input end of the multi-channel data acquisition unit 31, and the output end of the multi-channel data acquisition unit 31 is connected with the input end of the computer 32; when the device works, the pressure sensor 25 and the weighing sensors in the weighing device 23 transmit the collected data to the multichannel data collector 31, the multichannel data collector 31 transmits the collected data to the computer 32, and the computer 32 processes, arranges and calculates the data to obtain the permeability coefficient of the sample. The data processing system 3 may also adopt a structure as in the background art, and may also adopt other structures in the prior art, which is not specifically limited herein.
The working principle of the closed-loop full-curve geotechnical permeability test system provided by the embodiment of the invention is as follows: as shown in fig. 1, before the test is started, the required weight of the weight 146 is calculated according to the test pressure requirement, and then the weight 146 is placed on the weight seat 145 along the weight guide rod 148. And (3) placing the standard sample in the infiltration container 21 according to the test requirement, communicating the outlet of the pump with the inlet of the first valve 13, and setting the pressure of the pump to be higher than the test pressure. The second valve 15 is closed, the first valve 13 is opened, water is delivered into the cylinder 141 by the pump, and the water in the cylinder 141 pushes the piston 143 to move upward to the upper limit of the stroke, and then the first valve 13 is closed. Then, the second valve 15 is opened, and the water in the cylinder 141 permeates through the sample under the action of the weight 146, and then flows into the water collecting cup 24 through the pipeline to be collected, so that the water level in the water collecting cup 24 rises, and the weight is increased. In the permeation process, the water in the permeation container 21 generates pressure loss due to the fact that the water overcomes the permeation resistance of the sample, pressure information is transmitted to the data processing system 3 through the pressure sensor 25, weight information is transmitted to the data processing system 3 through the weighing sensor in the weighing device 23, and the data processing system 3 calculates pressure parameters, weight parameters and temperature parameters which are simultaneously acquired in real time to obtain the permeation coefficient of the sample.
The temperature parameter is the temperature of water in the test process, and the temperature parameter can be measured by a thermometer and then manually input into the data processing system 3 because the temperature of the water does not change in the whole test process; the temperature parameter can also be measured by a temperature pressure sensor and transmitted to the data processing system 3 in real time.
Preferably, the water supply system 1 further comprises a water storage tank 11 and a self-priming constant pressure pump 12; the inlet of the self-suction constant pressure pump 12 is communicated with the water storage tank 11, and the outlet of the self-suction constant pressure pump 12 is communicated with the inlet of the first valve 13. The water storage tank 11 is used for storing water for the test, and after the test is finished, the water in the water collecting cup 24 can be poured into the water storage tank 11 for recycling.
As shown in fig. 1, the water storage tank 11 is of an open-top structure, an inlet of the self-priming constant pressure pump 12 is communicated with the water storage tank 11 through a water pumping pipe 16, and water flowing back into the water storage tank 11 can be conveyed into the constant weight type pressure regulator 14 through the self-priming constant pressure pump 12 for recycling, so that a closed loop type circulation state of test water is realized. According to the invention, through the recycling of the test water, the characteristics of the test water can be effectively controlled, the penetration test under different viscosity water conditions can be simulated, and the simulation requirement of the penetration test under a special water environment can be met.
Preferably, the osmosis system 2 further comprises a siphon drain 26; a through hole is formed in the side wall of the water collecting cup 24, and the siphon drain pipe 26 penetrates through the through hole, so that the inlet of the siphon drain pipe 26 is positioned inside the water collecting cup 24, and the outlet of the siphon drain pipe 26 is positioned outside the water collecting cup 24; the through hole is hermetically connected with the outer wall of the siphon drain pipe 26; the elevation of the highest point of the siphon-type drain pipe 26 is lower than or equal to the elevation of the through hole.
As shown in fig. 1, a through hole for the siphon drain pipe 26 to pass through is formed in the side wall of the water collection cup 24, and the water in the water collection cup 24 is prevented from flowing into the outside of the water collection cup 24 through the through hole and the outer wall of the siphon drain pipe 26 by sealing connection. By making the elevation of the highest point of siphon drain pipe 26 lower than or equal to the elevation of the through hole, the highest position of the liquid level in water collection cup 24 can be made equal to or lower than the height of the through hole to avoid the water in water collection cup 24 from overflowing from the top of water collection cup 24. During the test, water enters the water collecting cup 24 after passing through the test sample, the liquid level in the water collecting cup 24 rises, when the liquid level in the water collecting cup 24 is higher than the highest point of the siphon drain pipe 26, the siphon drain pipe 26 automatically drains the water in the water collecting cup 24 to the container or the water storage tank 11 outside the water collecting cup 24 for collection, when the liquid level in the water collecting cup 24 is lower than the inlet of the siphon drain pipe 26, the siphon drain pipe 26 stops draining, then the liquid level in the water collecting cup 24 begins to rise again, and the next cycle is carried out until the test is completed.
When the reservoir 11 is positioned directly below the outlet of the siphon drain 26, water within the water collection cup 24 may flow into the reservoir 11 through the siphon drain 26. In order to allow the water in the water collecting cup 24 to flow into the water storage tank 11 when the water storage tank 11 is not disposed right under the siphon drain pipe 26, it is preferable that the infiltration system 2 further includes a return pipe 27; the inlet end of the return pipe 27 is arranged higher than other positions of the return pipe 27; the inlet end of the return pipe 27 is arranged right below the outlet of the siphon-type drain pipe 26, and the outlet of the return pipe 27 is communicated with the water storage tank 11. As shown in fig. 1, in the test, the water in the water collecting cup 24 flows into the return pipe 27 through the siphon-type drain pipe 26, and then flows back to the water storage tank 11 through the return pipe 27, so as to recycle the permeating water.
The infiltration container 21 can be monolithic structure, also can be split type structure, provides a split type structure's infiltration container 21 in figure 1, infiltration container 21 includes the cylindrical body that forms by two half body 211 concatenations, sets up the seal structure in two half body 211 concatenation departments for fixed two half body 211's fixed knot constructs.
As shown in fig. 1, the two half pipe bodies 211 are spliced to form a cylindrical pipe body, a sealing structure is provided at the splicing position of the two half pipe bodies 211, the sealing structure includes a sealing surface provided at the splicing position of the two half pipe bodies 211 to be matched, and a sealing gasket provided between the two sealing surfaces, the two half pipe bodies 211 are connected by a fixing structure, and the fixing structure may be a flange connection structure or a clamping structure. When installing the sample, open fixed knot earlier and construct, move away the half body 211 of top, then install standard sample in the half body 211 of below, then place sealed the pad in the concatenation position department of two half bodies 211, splice the half body 211 of top and the half body 211 of below again, and through fixed knot construct with two half body 211 fixed connection, through seal structure and fixed knot structure, avoid permeating the water in the container 21 and leak from the concatenation position of two half bodies 211.
Further, a positioning groove 212 is provided on the inner surface of at least one of the half pipe bodies 211 between the adjacent two pressure sensors 25. Preferably, the inner surfaces of both half pipe bodies 211 are provided with positioning grooves 212, and the positioning grooves 212 on the inner surfaces of both half pipe bodies 211 are provided in pairs. The positioning grooves 212 arranged in pairs on the inner surfaces of the two half tube bodies 211 are combined to form an annular positioning groove. Through setting up positioning groove 212, carry on spacingly to the standard sample of installing in infiltration container 21, prevent that axial displacement from taking place at the experimental in-process sample.
The closed-loop all-curve geotechnical permeability test system provided by the embodiment of the invention can not only perform permeability test on sandy soil or coarse-grained soil with high water permeability, but also perform permeability test on clay or fine-grained soil with low water permeability. Different mounting modes are adopted according to different samples, and fig. 3 is a cross-sectional view of a fine soil sample mounted in a permeation container 21; fig. 4 shows a cross-sectional view of a sand sample installed into the infiltration vessel 21.
As shown in fig. 3, there are two samples, and three pressure sensors 25 are arranged on the permeation container 21, the two samples divide the inner cavity of the permeation container 21 into three isolated chambers, and each pressure sensor 25 is communicated with one of the chambers. When the sample is fine soil, firstly preparing the sample with the stainless steel cutting ring 5 outside and the fine soil inside according to the current standard specification, then coating vaseline on the outer surface of the stainless steel cutting ring 5, arranging a water-stopping gasket 6 sleeved on the stainless steel cutting ring 5 at the ear edge 51 of the stainless steel cutting ring 5, then opening the half pipe body 211 positioned above, installing the sample in the half pipe body 211 below through a fixed snap ring 7, enabling a positioning lug on the fixed snap ring 7 to be positioned in a positioning groove 212 of the half pipe body 211, then placing a permeable stone 8 at the left end and the right end of the sample, and fixing the permeable stone by using a spring support rod, wherein the water-stopping gasket 6 is in contact with the inner wall of a permeation container 21; then, the upper half pipe body 211 is covered on the lower half pipe body 211 and is fixed through a fixing structure, so that the fine soil sample is installed, and then a penetration test can be performed.
As shown in fig. 4, the number of the samples is one, three pressure sensors 25 are provided on the permeation vessel 21, and the three pressure sensors 25 are arranged uniformly along the axial direction of the permeation vessel 21. When the sample is sandy soil, according to the requirements of the current standard specification, the infiltration container 21 can be directly filled with sandy soil in a layered manner, and the two ends of the sandy soil are provided with the stainless steel nets 10 to form the sample for the test; sand can be filled in the sample cylinder 9 in a layered manner to form a sample with the sand inside and the sample cylinder 9 outside, and then stainless steel nets 10 are arranged at two ends of the sample cylinder 9 for standby; wherein, the outer diameter of the sample cylinder 9 is matched with the inner diameter of the infiltration container 21; the outer surface of the sample cylinder 9 is provided with a positioning boss matched with the positioning groove 212, and a through hole is formed in the sample cylinder 9 at a position corresponding to the pressure sensor 25 so as to measure the pressure of the sample at different positions through the pressure sensor 25; then, the half pipe body 211 positioned above is opened, the sample is installed in the half pipe body 211 positioned below, the positioning boss is positioned in the positioning groove 212 of the half pipe body 211, then the half pipe body 211 positioned above is covered on the half pipe body 211 positioned below and is fixed through the fixing structure, so that the installation of the sand sample is completed, and then the penetration test can be carried out.
In order to be able to test a plurality of samples simultaneously, it is preferable that the number of the permeation systems 2 is at least two; the outlet of the second valve 15 is communicated with all the first inlets 221 through pipes, respectively. In this embodiment, multiple osmotic systems 2 may be supplied simultaneously by a single constant weight regulator 14.
As shown in fig. 5, the number of the permeation systems 2 is two, the outlet of the second valve 15 is respectively communicated with the two first inlets 221 through a tee joint, and all the pressure sensors 25 and the weighing sensors in the weigher 23 are connected with the input end of the data processing system 3. During testing, the two osmosis systems can be tested simultaneously or alternatively, and the tests are determined according to the test requirements.
Claims (10)
1. The closed-loop full-curve geotechnical permeability test system comprises a water supply system (1), a permeability system (2) and a data processing system (3); the water supply system (1) is characterized by comprising a constant weight type pressure regulator (14), a first valve (13) and a second valve (15); the constant-weight pressure regulator (14) comprises a vertically arranged cylinder body (141), a bottom plate (142) hermetically mounted at the bottom end of the cylinder body (141), a piston (143) which is arranged in the cylinder body (141) and can slide up and down, a piston shaft (144) which is arranged at the top of the piston (143) and extends upwards to the outside of the cylinder body (141), a weight seat (145) fixed at the top of the piston shaft (144), and a weight (146) placed on the weight seat (145); the outlet of the first valve (13) is communicated with the inner cavity of the cylinder body (141), and the inlet of the second valve (15) is communicated with the inner cavity of the cylinder body (141);
the infiltration system (2) comprises a tubular infiltration container (21), end covers (22) which are hermetically arranged at two ends of the infiltration container (21), a weigher (23) internally provided with a weighing sensor, and a water collecting cup (24) placed on the weigher (23); at least two pressure sensors (25) for measuring the internal pressure of the permeation container (21) are arranged on the outer wall of the permeation container (21) at intervals along the axial direction of the permeation container; one end cover (22) is provided with a first inlet (221) communicated with the inner cavity of the permeation container (21), and the first inlet (221) is communicated with the outlet of the second valve (15) through a pipeline; the other end cover (22) is provided with a first outlet (222) communicated with the inner cavity of the permeation container (21), and the first outlet (222) is communicated with the water collecting cup (24) through a pipeline; the pressure sensor (25) and the weighing sensor in the weighing device (23) are connected with the input end of the data processing system (3).
2. The closed-loop full-curve geotechnical permeability test system according to claim 1, wherein said water supply system (1) further comprises a water storage tank (11) and a self-priming constant pressure pump (12); the inlet of the self-suction constant pressure pump (12) is communicated with the water storage tank (11), and the outlet of the self-suction constant pressure pump (12) is communicated with the inlet of the first valve (13).
3. The closed-loop, full-curve geotechnical permeability test system according to claim 1, wherein said permeability system (2) further includes a siphon drain (26); a through hole is formed in the side wall of the water collecting cup (24), the siphon-type drain pipe (26) penetrates through the through hole, so that the inlet of the siphon-type drain pipe (26) is positioned inside the water collecting cup (24), and the outlet of the siphon-type drain pipe (26) is positioned outside the water collecting cup (24); the through hole is hermetically connected with the outer wall of the siphon-type drain pipe (26); the elevation of the highest point of the siphon-type drain pipe (26) is lower than or equal to the elevation of the through hole.
4. The closed-loop full-curve geotechnical permeation test system according to claim 3, wherein said permeation system (2) further comprises a return pipe (27); the inlet end of the return pipe (27) is arranged higher than other positions of the return pipe (27); the inlet end of the return pipe (27) is arranged right below the outlet of the siphon-type drain pipe (26), and the outlet of the return pipe (27) is communicated with the water storage tank (11).
5. The closed-loop full-curve geotechnical permeability test system according to claim 1, wherein said permeability container (21) comprises a cylindrical pipe body formed by splicing two half pipe bodies (211), a sealing structure arranged at the splicing position of the two half pipe bodies (211), and a fixing structure for fixing the two half pipe bodies (211).
6. The closed-loop full-curve geotechnical permeability test system according to claim 5, wherein a positioning groove (212) is formed on the inner surface of at least one of the half pipe bodies (211) between two adjacent pressure sensors (25).
7. The closed-loop full-curve geotechnical permeability test system according to claim 6, wherein the inner surfaces of both half pipe bodies (211) are provided with positioning grooves (212), and the positioning grooves (212) on the inner surfaces of both half pipe bodies (211) are arranged in pairs.
8. The closed-loop full-curve geotechnical permeability test system according to claim 7, wherein said positioning grooves (212) are paired on the inner surfaces of said two half-pipe bodies (211) to form an annular positioning groove.
9. The closed-loop full-curve geotechnical permeability test system according to any one of claims 1-8, wherein said permeability container (21) is made of transparent material.
10. The closed-loop full-curve geotechnical permeability test system according to any one of claims 1-8, wherein said number of said permeability systems (2) is at least two; the outlets of the second valves (15) are respectively communicated with all the first inlets (221) through pipelines.
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| CN113109230A (en) * | 2021-03-30 | 2021-07-13 | 中国电建集团西北勘测设计研究院有限公司 | Novel earth and rockfill dam construction material seepage deformation test system and method |
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