CN114018970B - Multifunctional freezing low-temperature model test device for cold region - Google Patents
Multifunctional freezing low-temperature model test device for cold region Download PDFInfo
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- CN114018970B CN114018970B CN202111316273.3A CN202111316273A CN114018970B CN 114018970 B CN114018970 B CN 114018970B CN 202111316273 A CN202111316273 A CN 202111316273A CN 114018970 B CN114018970 B CN 114018970B
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- 238000012360 testing method Methods 0.000 title claims abstract description 95
- 238000007710 freezing Methods 0.000 title claims abstract description 32
- 230000008014 freezing Effects 0.000 title claims abstract description 32
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 110
- 239000002689 soil Substances 0.000 claims abstract description 87
- 239000007788 liquid Substances 0.000 claims abstract description 57
- 230000001502 supplementing effect Effects 0.000 claims abstract description 49
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 32
- 229910052802 copper Inorganic materials 0.000 claims abstract description 32
- 239000010949 copper Substances 0.000 claims abstract description 32
- 238000006073 displacement reaction Methods 0.000 claims abstract description 14
- 229920000742 Cotton Polymers 0.000 claims abstract description 12
- 238000006243 chemical reaction Methods 0.000 claims abstract description 11
- 239000004576 sand Substances 0.000 claims abstract description 8
- 239000010410 layer Substances 0.000 claims description 14
- 238000004321 preservation Methods 0.000 claims description 10
- 230000005540 biological transmission Effects 0.000 claims description 7
- 238000009413 insulation Methods 0.000 claims description 7
- 229910000831 Steel Inorganic materials 0.000 claims description 5
- 239000010959 steel Substances 0.000 claims description 5
- 239000011229 interlayer Substances 0.000 claims description 4
- 238000010257 thawing Methods 0.000 abstract description 18
- 230000003993 interaction Effects 0.000 abstract description 8
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 9
- 238000001816 cooling Methods 0.000 description 8
- 238000000034 method Methods 0.000 description 8
- 238000011160 research Methods 0.000 description 8
- 238000010438 heat treatment Methods 0.000 description 5
- 101150054854 POU1F1 gene Proteins 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000006378 damage Effects 0.000 description 3
- 230000007246 mechanism Effects 0.000 description 3
- 238000012544 monitoring process Methods 0.000 description 3
- 230000001932 seasonal effect Effects 0.000 description 3
- YKTSYUJCYHOUJP-UHFFFAOYSA-N [O--].[Al+3].[Al+3].[O-][Si]([O-])([O-])[O-] Chemical compound [O--].[Al+3].[Al+3].[O-][Si]([O-])([O-])[O-] YKTSYUJCYHOUJP-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000003673 groundwater Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000005012 migration Effects 0.000 description 2
- 238000013508 migration Methods 0.000 description 2
- 238000005057 refrigeration Methods 0.000 description 2
- 239000013589 supplement Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 238000007664 blowing Methods 0.000 description 1
- 238000009933 burial Methods 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000009746 freeze damage Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 230000005476 size effect Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
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- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- 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 multifunctional freezing low-temperature model test device for a cold region belongs to the technical field of frost heaving and thawing sinking characteristic model tests. The foundation pit is internally provided with a model box and a fan, and fine sand, copper discharge pipes, water supplementing pipes, soil bodies, model box heat-insulating cotton and a double-mode soil pressure box are arranged in the model box; the copper calandria is communicated with the cold bath unit and the liquid bath circulating device, the water replenishing pipe is communicated with the water replenishing pump and the liquid level water pipe, a liquid level meter connected with a liquid level counting display is arranged in the liquid level water pipe, and a test piece assembly and a sensor assembly are arranged in soil body; the dual-mode soil pressure box is arranged in the middle of the test piece assembly, the upper end of the dual-mode soil pressure box is connected with the jack, and the counter-force frame is connected with the jack and the model box; the test piece assembly is connected with the data acquisition terminal; the reaction frame is provided with a displacement meter matched with the test piece assembly or the soil body. The invention is beneficial to researching the interaction relation between the test piece and the soil, improves the freezing or thawing efficiency of the soil body, and realizes the centralized loading or the distributed loading of the test piece.
Description
Technical Field
The invention relates to a multifunctional freezing low-temperature model test device for a cold region, and belongs to the technical field of freezing-swelling thawing-sinking characteristic model tests.
Background
The operators in the extremely freeze thawing areas of China are wide, and traffic geotechnical engineering with multiple provinces such as inner Mongolia, jilin, heilongjiang and the like often needs to span a permafrost area and a seasonal permafrost area. As the construction steps of traffic infrastructures are quickened in large cities, a plurality of infrastructures located in cold areas often need to cross over a freezing and thawing area, frost heaving and thawing of soil are two major frost damages of cold area engineering, and the frost heaving damage or thawing collapse of a foundation is caused, so that the frost damage mechanism and prevention and control are widely focused.
The model test can replay and even replay the same engineering in multiple layers and multiple angles, and avoids the problems of high difficulty, high cost, low cycle repeatability and the like which are derived from the field test, thereby becoming an effective way of scientific research at present.
At present, cold region frozen soil engineering researches are mostly focused on related physical and mechanical property researches of soil bodies or frost heaving deformation researches of small-size test pieces, the test pieces or the soil bodies are small in size and obvious in size effect, and actual working conditions (such as natural factors of ambient temperature, underground water, geothermal heat and the like) are not truly reflected. Relatively little research is conducted on the interaction of the components and the soil, and frost heaving or thawing in actual engineering is mostly represented by the interaction of the components and the soil, and a more perfect freezing model test system for the components and the soil is not available.
Disclosure of Invention
In order to solve the problems in the background technology, the invention provides a multifunctional freezing low-temperature model test device for a cold region.
The invention adopts the following technical scheme: a multifunctional freezing low-temperature model test device for a cold region comprises a foundation pit, a box body unit, a loading unit, a temperature control unit, a data acquisition unit and a water supplementing unit;
the box body unit comprises a model box, fine sand, copper calandria and soil body;
the loading unit comprises a reaction frame, a jack, a test piece assembly, a double-mode soil pressure box and a plurality of displacement meters;
the temperature control unit comprises a fan, a cold bath unit and a liquid bath circulation device;
the data acquisition unit comprises a liquid level counting display, a liquid level meter, a data acquisition terminal and a sensor assembly;
the water supplementing unit comprises a water supplementing pipe, a water supplementing pump and a liquid level water pipe;
the foundation pit is internally provided with a model box and a fan, wherein fine sand, a warm end of a copper calandria, a water supplementing pipe, a soil body, a cold end of the copper calandria, model box heat-insulating cotton and a double-mode soil pressure box are sequentially paved in the model box from bottom to top; the heating end of the copper calandria is communicated with the cold bath unit, the cold end of the copper calandria is communicated with the liquid bath circulating device, the water inlet end of the water supplementing pipe is communicated with the water supplementing pump, the water supplementing pipe is communicated with one end of the liquid level water pipe, one end of the liquid level water pipe is arranged in the model box, the other end of the liquid level water pipe is arranged outside the model box, a liquid level meter is arranged in the liquid level water pipe, the liquid level meter is in data transmission connection with the liquid level counting display, and a test piece assembly and a sensor assembly are arranged in the soil body; the dual-mode soil pressure box is arranged in the middle of the test piece assembly, the upper end of the dual-mode soil pressure box is vertically in contact connection with the output end of the jack, the fixed end of the jack is connected with the reaction frame, and the reaction frame is connected with the model box; the test piece assembly is in data transmission connection with the data acquisition terminal; the reaction frame is provided with a plurality of displacement meters, and the displacement meters are matched with the test piece assembly or the soil body.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention can be used for performing frozen soil related test work, and also can be used for performing frost heaving and thawing and sinking characteristic model test research on large test pieces such as independent foundations, underground continuous walls, overwintering foundation pits, tunnel inlets and outlets, and the like, so that the stress deformation distribution rule of the test piece in actual engineering is reduced to the maximum extent, the test piece has large size and obvious interaction with soil, and the invention is beneficial to researching the interaction relation between the test piece and soil under the conditions of different freezing temperature fields, upper load, water supplement, compactness and the like;
2. according to the invention, firstly, the fan is used for refrigerating to provide an environment temperature, so that the model box in the foundation pit is not influenced by the outside temperature when being cooled in one direction, the cooling rate of the cold end is improved, and the cold bridge effect formed by the steel plates inside and outside the model box is avoided, thereby causing quick temperature dissipation in the box; secondly, fully considering the geothermal influence, arranging a warm end temperature field at the bottom of the model box, inputting an alcohol circulating liquid into a copper pipe through a cold bath unit, performing constant temperature control, reducing the actual engineering to the maximum extent, and simultaneously accelerating the soil in the box to reach the same temperature at the fastest speed in the whole soil temperature control link before the test, and laying a cushion for the later unidirectional cooling; finally, the uppermost copper calandria in the model box is subjected to unidirectional cooling or heating under the control of the liquid bath circulation device, a process of unidirectional heat transfer from the surface temperature to the soil body is simulated, the surface temperature has less heat loss in the downward transfer process under the control of the stable environment temperature and the warm end temperature field in the earlier stage, the soil body absorbs more, and the freezing or melting efficiency of the soil body is improved;
3. the invention provides an open water supplementing environment and loading system, and the influence of water supplementing conditions on freezing and thawing and sinking characteristics can be fully considered in a model test stage so as to reflect the influence of the presence or absence of groundwater levels on the freezing effect of an upper soil body. Meanwhile, the movable loading unit can accurately control the size and loading mode of the upper load, is simple to operate, can randomly move the loading position, and can realize centralized loading or distributed loading of the test piece by assisting the loading frame.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIG. 2 is a schematic structural view of a mold box;
FIG. 3 is a rear view of FIG. 2;
FIG. 4 is a graph of data for a constant temperature freezing temperature field at-15℃for an independent basic frost heaving test based on the present invention;
FIG. 5 is a graph of tangential frost heave force data for an independent base frost heave test according to the invention;
FIG. 6 is a graph of horizontal frost heave force data for an independent base frost heave test according to the invention;
FIG. 7 is a graph of data on frost heaving capacity for an independent base frost heaving test according to the present invention.
Detailed Description
The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the invention, but not all embodiments, and all other embodiments obtained by those skilled in the art without making creative efforts based on the embodiments of the present invention are all within the protection scope of the present invention.
A multifunctional freezing low-temperature model test device for cold areas comprises a foundation pit 1, a box body unit, a loading unit, a temperature control unit, a data acquisition unit and a water supplementing unit,
the box body unit comprises a model box 2, fine sand 13, copper pipes 17 and soil 25;
the loading unit comprises a reaction frame 19, a jack 22, a test piece assembly 23, a dual-mode soil pressure box 24 and a plurality of displacement meters 21;
the temperature control unit comprises a fan 4, a cold bath unit 8 and a liquid bath circulation device 18;
the data acquisition unit comprises a liquid level counting display 7, a liquid level meter 9, a data acquisition terminal 20 and a sensor assembly;
the water supplementing unit comprises a water supplementing pipe 12, a water supplementing pump 16 and a liquid level water pipe;
a model box 2 and a fan 4 are arranged in the foundation pit 1,
the fan 4 is controlled by the integrated circuit, and is used for blowing air and cooling in the closed environment of the foundation pit 1; the fan 4 is used for providing foundation pit environment temperature regulation, the fan 4 utilizes the compressor to blow and control the temperature, the environment temperature is built, and the constant temperature is set to be 5 ℃;
the mold box 2 is internally and sequentially paved with fine sand 13, a warm end of a copper calandria 17, a water supplementing pipe 12, soil mass 25, a cold end of the copper calandria 17, mold box heat-insulating cotton and a double-mold soil pressure box 24 from bottom to top;
the warm end of the copper calandria 17 is communicated with the cold bath unit 8, the cold bath unit 8 uses alcohol as circulating liquid to heat and refrigerate, the alcohol circulating liquid enters from the water inlet of the copper calandria 17, the copper calandria 17 returns to the box body of the cold bath unit 8 from the water outlet after circulating, and the alcohol circulating liquid circulates periodically; the cold bath unit 8 is used for providing the warm end temperature (geothermal) of the copper calandria 17, the water inlet and the water outlet of the cold bath unit 8 are sequentially connected with the cold bath water inlet 28 and the cold bath water outlet 29 of the copper calandria 17 at the bottom of the box body through rubber tubes, and the constant temperature of the bottom is kept to be 5 ℃ through alcohol circulation refrigeration; the pipe of the cold bath water inlet 28 of the cold bath unit 8 is a corrosion-resistant and low-temperature-resistant rubber pipe;
the cold end water inlet 30 and the cold end water outlet 31 of the cold end of the copper calandria 17 are communicated with the high-low temperature constant-temperature liquid bath circulation device 18, the high-low temperature constant-temperature liquid bath circulation device 18 also adopts alcohol for circulation refrigeration, the alcohol is communicated with the cold end of the copper calandria 17, after entering the copper calandria 17 for circulation through the water outlet of the circulation device, the alcohol returns to the box body of the liquid bath circulation device 18 from the water return port, and the liquid bath circulation device 18 carries out unidirectional cooling circulation by sending the calandria into the copper calandria 17 after cooling or heating the alcohol through circulation in a compressor; the liquid bath circulation device 18 is used for providing cold end temperature (temperature control end) adjustment;
the water supplementing pipe water inlet 27 at the water inlet end of the water supplementing pipe 12 is communicated with the water supplementing pump 16 through a hose, water is connected into the water supplementing pipe 12 through a guide pipe to form a water supplementing system, the water supplementing pipe water outlet 26 of the water supplementing pipe 12 extends to the outer side of the model box 2 and is used for draining water, and too much water supplementing is avoided in the process of cleaning a lower soil body after a subsequent test is finished; the water supplementing pipe 12 is communicated with one end of a semi-closed liquid level water pipe, one end of the liquid level water pipe is arranged in the model box 2, the other end of the liquid level water pipe is arranged outside the model box 2, a liquid level meter 9 is arranged in the liquid level water pipe, the liquid level meter 9 is in data transmission connection with a liquid level counting display 7, and the liquid level counting display 7 is used for displaying the water supplementing amount; a semi-closed pipeline is arranged at a position 10cm away from the bottom of the model box 2, a liquid level meter 9 is arranged in the semi-closed pipeline, after a water supplementing pump 16 is started, a stable underground water layer exists at the bottom of the box, the liquid level meter 9 in the pipeline displays the water level height of the water supplementing amount through a liquid level counting display 7, and as the test is carried out, water migrates upwards and the water level drops, the water supplementing pump 16 is started to pressurize and supplement water, so that the water level is maintained in a stable water level state;
a test piece assembly 23 and a sensor assembly are arranged in the soil body 25; the dual-mode soil pressure box 24 is placed in the middle of the test piece assembly 23, the middle of the upper end of the dual-mode soil pressure box is vertically in contact connection with the output end of the jack 22 so as to apply concentrated load, the load size can be controlled according to a pressure gauge on the jack 22, and meanwhile, the jack 22 can be connected with a load unit for distributing load so as to apply distributed load to the test piece assembly 23; the dual-mode soil pressure box 24 monitors the upper load change condition in the frost heaving or thawing process, and simultaneously can also connect the jack 22 with a distributed load applying unit to apply distributed load; the fixed end of the movable jack 22 with the pressure gauge is fixedly connected with the middle part of the reaction frame 19 which is horizontally arranged, and the height of the reaction frame 19 can be adjusted according to the requirement of the test piece assembly 23;
the test piece assembly 23 is in data transmission connection with the data acquisition terminal 20; the data acquisition terminal 20 is arranged outside the foundation pit 1, and the data acquisition terminal 20 is provided with a remote automatic acquisition module and a manual serial acquisition module, and a static strain gauge is used for data acquisition.
Firstly paving a layer of fine sand 13 with the thickness of 1cm on the bottom of the inner part of the model box 2, leveling, sequentially paving a warm end temperature control and water supplementing system for installing the copper calandria 17, after the installation is finished, starting to fill soil bodies 25 in a layered mode, simultaneously placing a test piece assembly 23 (test pieces such as an independent foundation, an underground diaphragm wall, a tunnel lining, an entrance and exit hole and the like) in the center of the soil bodies 25, burying a sensor assembly (including a temperature sensor, a humidity sensor, a soil pressure box sensor and the like) at the periphery of the test piece assembly 23, then covering the cold end of the copper calandria 17, finally covering model box heat preservation cotton (preferably aluminum silicate material) on the copper calandria 17, leaking 2-3 cm outside the model box heat preservation cotton at the top of the test piece assembly 23, and placing a double-mode soil pressure box 24 at the top of the test piece assembly 23 for connection with a jack 22;
the jack 22 is connected with the dual-mode soil pressure box 24 and is used for applying concentrated load to the test piece assembly 23 in the vertical direction or applying distributed load by utilizing a loading frame, and the upper part of the test piece assembly 23 is monitored to apply load and frozen pulling force through the dual-mode soil pressure box 24;
the sensor assembly is used for monitoring indexes such as a temperature field, a water content, a frost heaving capacity, a displacement, a frost pulling capacity and the like of a test piece, burying the test piece assembly 23 according to test requirements when the soil body 25 is filled in layers, and arranging a dual-mode soil pressure box 24 and a displacement meter 21 in the vertical direction of the top center of the test piece assembly 23 after the test piece assembly 23 is put into the soil body 25;
the reaction frame 19 is provided with a plurality of displacement meters 21, and the displacement meters 21 are matched with the test piece assembly 23 or the soil body 25. The lifting or sinking amount of the test piece assembly 23 is monitored to prevent uneven settlement or monitor the frost heaving amount of the soil body 25.
The inner wall of foundation ditch 1 is equipped with foundation ditch heated board 3, carries out heat preservation and insulation to foundation ditch 1 through heated board 3. The top of foundation ditch 1 is equipped with heat preservation apron 5. The top of the heat preservation cover plate 5 is provided with a heat preservation cotton layer 6 made of aluminum silicate.
The outer wall of the model box 2 is externally hung with a model box heat insulation board 10, and the inner wall is stuck with a heat insulation layer 11. The box body of the model box 2 comprises a heat-insulating cotton interlayer 14 and two layers of combined steel plates 15, and the heat-insulating cotton interlayer 14 is arranged between the two layers of combined steel plates 15.
A gasket is arranged between the output end of the jack 22 and the middle part of the double-mode soil pressure box 24.
The outside of the water supplementing pipe 12 is wrapped with gauze to ensure that the water supplementing holes are not blocked.
The invention is particularly suitable for carrying out the research of frost heaving and thawing sinking characteristic model tests on the basis of permafrost or seasonal frost in cold areas, underground continuous walls, tunnel openings, overwintering foundation pits and the like, and can also be used for carrying out conventional rock-soil material freezing tests and researching the frost heaving mechanism of soil bodies. The invention can complete the water-heat-force three-field coupling large-scale indoor model test and simulate the interaction between a test piece and soil under the working conditions of stable atmospheric environment, geothermal, underground water layer and the like. The three-field temperature control system, the open water supplementing system and the loading system are utilized to realize three-field coupling of a water division field, a temperature field and a stress field, and the method is particularly suitable for carrying out a multifunctional freezing low-temperature chamber model test of large-scale components and soil interaction, has a wide application range, and is convenient for revealing a cold region traffic geotechnical engineering freeze injury mechanism. The frost heaving deformation and thawing and sinking conditions of the components in the open water supplementing environment in the soil body under different freezing temperature conditions can be simulated. The influence of factors such as upper load, water supplementing amount, underground water level burial depth, surface temperature, initial water content, compactness and the like on the unidirectional freezing and thawing property of the test piece can be considered. The change of physical mechanical quality changes such as soil temperature field, moisture migration, frost heaving force, unfrozen water content, freezing depth, frost heaving quantity, frost heaving force, displacement and the like in the freezing and thawing process is monitored through a remote automatic acquisition or manual serial port automatic acquisition device.
Before the test, the soil body 25 in the model box 2 is subjected to integral temperature control, the ambient temperature, the cold end temperature and the warm end temperature are all set to be 5 ℃, and after the temperature of the whole soil body 25 reaches 5 ℃, the temperature reduction or heating test is started.
The temperature control unit firstly utilizes the fan 4 to provide a constant temperature and humidity environment, simulates a stable atmospheric environment, is convenient for the accurate temperature control of the model box 2, and then carries out the unidirectional cooling or heating freezing and thawing test of the upper soil body 25 under the action of the liquid bath circulation device 18 and the cooling bath unit 8 through the copper calandria 17 buried in the soil body 25.
The data acquisition unit is respectively connected with the soil body 25, the loading unit, the water supplementing unit and the temperature control unit and is used for monitoring the temperature, the water content, the soil pressure and the frost heaving amount of the soil body 25 and the frost heaving force, the frost heaving force and the displacement of the test piece assembly 23.
The water replenishing unit is used for pressurizing and replenishing water to the lower soil body 25 through the water replenishing pump 16 and the water replenishing pipe 12, simulating a stable underground water layer structure under an open system, and simultaneously controlling the water level through the liquid level meter 9 and the liquid level counting display 7.
The box body unit is used for filling soil body, and the test component and the sensor are sequentially buried in the soil body; the loading unit is used for applying a fixed concentrated load or a distributed load; the temperature control unit is used for controlling the ambient temperature of the foundation pit, the cold end temperature and the warm end temperature of the copper plate pipe; the data acquisition unit is used for acquiring data of each monitoring index of the soil body and the test piece assembly; the water supplementing unit is used for simulating the pressurized water supplementing of the open system.
The invention provides a scientific research platform for researching the physical and mechanical properties of the artificial frozen soil and optimizing the artificial freezing method. The method can be widely applied to freezing method construction model tests in the fields of traffic geotechnical engineering, underground engineering, tunnel engineering and the like, and simulate frost heaving, thawing, sinking and stress deformation conditions of buildings or structures such as large concrete foundations, underground continuous walls, tunnel entrance and exit holes, deep foundation pits, natural frozen soil and the like under different temperature environments or over-load working conditions under the conditions of open groundwater environment, environmental temperature and geothermal environment of seasonal frozen soil areas or perennial frozen soil areas.
Inventive test principle:
in the invention, a transmission tower shallow foundation frost heave test is taken as an example, firstly, after a heat preservation and insulation layer is arranged outside the box body, a constant temperature field is applied to the bottom surface of a test piece (according to the local ground temperature), the ground temperature is simulated, and the cold end of a top copper plate pipe is cooled according to the annual average air temperature, so that a stable temperature field is formed inside a structure formed by the test piece and the soil body. And the facility water supplementing unit ensures water supplementing in the frost heaving process under an open system, so that water migrates under the actions of capillary force, dynamic load, negative pore pressure and the like, and the water is frozen above a freezing frontal surface to cause the volume expansion of a sample, thereby causing frost heaving deformation and interaction of a test piece and a soil body. When a thawing and sinking test is carried out, a designated normal temperature is applied to the top surface of the test piece reaching the maximum frost heaving capacity, so that the test piece is slowly melted under a designated stable normal temperature gradient to generate sedimentation, and further deformation and stress conditions of the test piece and frost heaving capacity, moisture migration and temperature field alternation of the soil body in the thawing process after the soil body is frozen are researched.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.
Claims (8)
1. A cold region multifunctional freezing low-temperature model test device is characterized in that: the device comprises a foundation pit (1), a box body unit, a loading unit, a temperature control unit, a data acquisition unit and a water supplementing unit;
the box body unit comprises a model box (2), fine sand (13), copper pipes (17) and soil bodies (25);
the loading unit comprises a reaction frame (19), a jack (22), a test piece assembly (23), a dual-mode soil pressure box (24) and a plurality of displacement meters (21);
the temperature control unit comprises a fan (4), a cold bath unit (8) and a liquid bath circulation device (18);
the data acquisition unit comprises a liquid level counting display (7), a liquid level meter (9), a data acquisition terminal (20) and a sensor assembly;
the water supplementing unit comprises a water supplementing pipe (12), a water supplementing pump (16) and a liquid level water pipe;
a model box (2) and a fan (4) are arranged in the foundation pit (1), and fine sand (13), a warm end of a copper calandria (17), a water supplementing pipe (12), a soil body (25), a cold end of the copper calandria (17), model box heat-insulating cotton and a double-mode soil pressure box (24) are sequentially paved in the model box (2) from bottom to top; the warm end of the copper calandria (17) is communicated with the cold bath unit (8), the cold end of the copper calandria (17) is communicated with the liquid bath circulation device (18), the water inlet end of the water supplementing pipe (12) is communicated with the water supplementing pump (16), the water supplementing pipe (12) is communicated with one end of the liquid level water pipe, one end of the liquid level water pipe is arranged in the model box (2), the other end of the liquid level water pipe is arranged outside the model box (2), a liquid level meter (9) is arranged in the liquid level water pipe, the liquid level meter (9) is connected with the liquid level counting display (7) in a data transmission manner, and a test piece assembly (23) and a sensor assembly are arranged in the soil body (25); the dual-mode soil pressure box (24) is arranged in the middle of the test piece assembly (23), the upper end of the dual-mode soil pressure box is vertically in contact connection with the output end of the jack (22), the fixed end of the jack (22) is connected with the counterforce frame (19), and the counterforce frame (19) is connected with the model box (2); the test piece assembly (23) is in data transmission connection with the data acquisition terminal (20); the reaction frame (19) is provided with a plurality of displacement meters (21), and the displacement meters (21) are matched with the test piece assembly (23) or the soil body (25).
2. The cold region multifunctional freezing low-temperature model test device according to claim 1, wherein: the inner wall of the foundation pit (1) is provided with a foundation pit insulation board (3).
3. The cold region multifunctional freezing low-temperature model test device according to claim 2, wherein: the top of foundation ditch (1) is equipped with heat preservation apron (5).
4. A cold zone multi-functional frozen low temperature model test device according to claim 3, characterized in that: the top of the heat preservation cover plate (5) is provided with a heat preservation cotton layer (6).
5. The cold region multifunctional freezing low-temperature model test device according to claim 1 or 4, wherein: the outer wall of the model box (2) is provided with a model box heat insulation plate (10), and the inner wall is provided with a heat insulation layer (11).
6. The cold region multifunctional freezing low-temperature model test device according to claim 5, wherein: the box body of the model box (2) comprises a heat-insulating cotton interlayer (14) and two layers of combined steel plates (15), and the heat-insulating cotton interlayer (14) is arranged between the two layers of combined steel plates (15).
7. The cold region multifunctional freezing low-temperature model test device according to claim 1, 4 or 6, wherein: a gasket is arranged between the output end of the jack (22) and the double-mode soil pressure box (24).
8. The cold region multifunctional freezing low-temperature model test device according to claim 1, 4 or 6, wherein: gauze is wrapped on the outer side of the water supplementing pipe (12).
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