CN113533096B - Circulating pressure shear soil body frost heaving test system and method - Google Patents
Circulating pressure shear soil body frost heaving test system and method Download PDFInfo
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- CN113533096B CN113533096B CN202110725196.0A CN202110725196A CN113533096B CN 113533096 B CN113533096 B CN 113533096B CN 202110725196 A CN202110725196 A CN 202110725196A CN 113533096 B CN113533096 B CN 113533096B
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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Abstract
The invention discloses a cyclic compression-shear soil body frost heaving test system and a test method. Aiming at the test soil unit, the temperature control test cabin adopts the temperature control metal plate to form the temperature control space around the test piece, so that the test is not influenced by the atmospheric environment, and the stacked rings with smaller thickness are convenient to adopt in the test, and the loading effect of the horizontal circulating shear stress of the soil unit is improved. The vertical direction and the horizontal direction of the soil body frost heaving test system can be set to be static or dynamic loading, a soil body frost heaving test, a soil body melting test or a soil body freezing and thawing cycle test under the coupling of temperature and complex stress paths can be developed, and dynamic parameters such as dynamic shear modulus, damping ratio and the like of frozen soil or a normal temperature soil body can also be tested.
Description
Technical Field
The invention belongs to the technical field of geotechnical tests and relates to a circulating pressure shear soil body frost heaving test system and a test method.
Background
In the geotechnical body engineering in cold regions, soil frost heaving brings about numerous engineering diseases, and more economic losses are caused. The existing research shows that frost heaving of soil is a complex physical process and is influenced by factors such as temperature, moisture, load, soil texture and the like. For a roadbed soil body, under the action of a mobile traffic load, the stress borne by the roadbed soil units comprises vertical dynamic pressure stress, horizontal dynamic pressure stress and horizontal cyclic shear stress. In fact, for a soil body at a normal temperature, the horizontal cyclic shear stress can bring about the shear expansion phenomenon of soil particles, and has great influence on the deformation of the soil body and the pore water pressure inside the soil body. In frozen earth, the influence of horizontal cyclic shear stress components on water migration and ice crystal segregation in the earth freezing process should be considered. In addition, the soil unit under the traffic load stress effect has a stress main shaft rotation phenomenon, and a soil body frost heaving test under the temperature-complex stress path coupling is developed, so that the method is one of the technical bottlenecks which need to be broken through urgently in the current frozen soil research.
At present, a plurality of soil body frost heaving test systems have been developed at home and abroad, and the foundation for testing and researching the soil body frost heaving characteristics, behaviors, rules and the like is laid. In the American Standard test method for soil body frost heaving and thaw collapse sensitivity (ASTM D5819-13), it is specified that the side surface of a soil test piece with diameter of 146mm and height of 150mm is wrapped by a heat insulation ring, water is added at the bottom, the upper static load of a weight bearing plate and a freezing mode from top to bottom at a specified top and bottom temperature are adopted; in the Japanese "soil body frost heaving sensitivity test method" (JGS 0172-2003), it is stipulated that a heat insulation ring is adopted for the side surface of a soil test piece with the diameter of 100mm and the height of 50mm, and top water supplement, overlying static load adopting a loading plate and freezing from bottom to top at a specified top and bottom temperature are applied; russian's C CsCRP-746033' stipulates a freezing method of laterally adding a rigid sleeve and a heat-insulating ring to a soil test piece with the diameter of 100mm and the height of 150 +/-5 mm, adding water at the bottom, covering static load by air pressure and 'from top to bottom' at a specified top temperature; in the regulations in geotechnical test method Standard (GBT 50123-1999) in China, a heat preservation ring is required to wrap the side surface of a soil test piece with the diameter of 100mm and the height of 50mm, and a freezing mode of adopting the overlaying static load of weights, top water supplement and bottom-up at a specified top and bottom temperature is applied. Journal literature (experimental study on frost heaving characteristics of fine soil under dynamic and static load) adopts a load boundary with complete lateral limitation and overlying circulating compressive stress to develop a soil body frost heaving test. CN110940598A discloses a multifunctional frozen soil circulating single shear test device and a test method, wherein a shearing box of the test device controls the side temperature of a test piece in a circulating refrigerant liquid manner, so that the thickness of a single shearing box is too large, which causes that the applied horizontal shearing stress is not uniform in a soil unit for a fine soil test piece, and the test device is not suitable for the circulating single shear loading of fine soil.
In summary, it can be seen that the following disadvantages exist in the current soil body frost heaving test system and test method: (1) Most test systems realize lateral heat insulation by adding heat insulation materials on the side surface of a test piece, however, the existence of gaps in the actual situation causes the heat insulation effect to be not ideal, the temperature in the test process is still influenced by the outside (2) no device for carrying out a circulation single shear frost heaving test on fine-grained soil exists, and the influence of a horizontal circulation shear stress component on soil frost heaving cannot be reflected; (3) The current soil body frost heaving test system can not apply overlying dynamic pressure stress, horizontal dynamic pressure stress and horizontal shear stress simultaneously, and the effect of rotation of a main stress shaft of a soil unit in the test process can not be realized. The simulation of the soil body frost heaving process under the complete traffic load stress effect and the development of the soil body frost heaving test under the temperature-complex stress path coupling are still one of the directions which need to be broken through urgently in the current frozen soil research.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a circulating pressure shear soil body frost heaving test system and a test method.
The purpose of the invention is realized by the following technical scheme:
the utility model provides a circulation compression shear soil body frost heaving test system, includes that temperature control test cabin, level are to loading motor, vertical loading motor, level to displacement sensor, level to force transducer, vertical displacement sensor, vertical force transducer, pore pressure collection appearance, temperature controller, ma shi moisturizing bottle, power, wherein:
the temperature control test chamber comprises side plates, folding heat insulation cloth, a base, a bottom plate, a stack ring, an upper cooling disc, a top plate, a latex film, a soil test piece, a thermocouple, permeable stones, a pore pressure sensor and a limiting member;
the side plates, the bottom plate and the top plate jointly form a temperature control test environment space of the soil test piece;
the side plates, the top plate, the upper cooling disc and the bottom plate are all provided with liquid inlet and outlet ports, temperature sensors and semiconductor refrigerating sheets;
the top plate is connected with the top of the upper cold plate through a top plate dowel bar at the lower part of the top plate;
the bottom plate is positioned at the upper part of the base;
one end of the folding heat-preservation cloth is bonded with the side plate, and the other end of the folding heat-preservation cloth is bonded with the base;
the soil test piece is wrapped with a latex film, a thermocouple and a pore pressure sensor are embedded in the soil test piece, and permeable stones are clamped between the bottom of the upper cold plate and the top of the soil test piece and between the bottom of the soil test piece and the top of the bottom plate;
the base plate comprises 3 hole channels, the hole channel A and the hole channel C are respectively used for leading out a thermocouple and a pore pressure sensor wire in the soil test piece, and the hole channel B is used for externally connecting a Ma's water replenishing bottle to replenish water to the bottom of the soil test piece;
the bottom of the limiting component is fixed on the bottom plate and symmetrically arranged at the positions of the stacked rings in the vertical and horizontal shearing directions, and is used for limiting the movement of the stacked rings in the vertical direction;
the horizontal loading motor is used for controlling the horizontal movement of the base so as to drive the bottom plate and the stacking ring to move horizontally, and the application of the horizontal shear stress to the soil test piece is realized;
the vertical loading motor loads the top plate through the force transmission rod;
the horizontal displacement sensor and the horizontal force sensor are used for collecting horizontal displacement and horizontal load;
the vertical displacement sensor and the vertical force sensor are used for collecting vertical displacement and vertical load;
the horizontal displacement sensor, the horizontal force sensor, the vertical displacement sensor and the vertical force sensor are all connected with a pressure and displacement acquisition instrument;
the pore pressure sensor is connected with the pore pressure acquisition instrument;
the liquid inlet and outlet ports of the side plates, the top plate, the upper cooling plate and the bottom plate are connected with an external circulating cooling bath box;
the semiconductor refrigerating sheet, the temperature sensor and the thermocouple are all connected with the temperature controller;
the power supply is connected with the temperature controller.
A method for performing a frost heaving test on a circular compression shear soil body by using the test system comprises the following steps:
setting the temperatures of a side plate, a top plate, a bottom plate and an upper cooling disc as the required test environment temperature, and applying a vertical static load to a soil test piece to solidify the soil test piece;
step two, stabilizing the temperature of the soil test piece at the initial temperature required by the test, and basically tending to stabilize the vertical consolidation displacement;
and step three, changing the control temperature of the upper cooling plate into the negative temperature required by the test, and applying a cyclic compression shear load with cyclic load in the horizontal direction and the vertical direction or a cyclic single shear load with cyclic load in the horizontal direction and static load in the vertical direction according to the requirement, so as to further carry out the soil body frost heaving test under the temperature-complex stress path coupling.
Compared with the prior art, the invention has the following advantages:
1. the soil body frost heaving test device provided by the invention aims at the test soil unit, and the temperature control test cabin adopts the temperature control metal plate to form the temperature control space around the test piece, so that on one hand, the test is prevented from being influenced by the atmospheric environment, on the other hand, the stacked rings with smaller thickness are convenient to adopt in the frozen soil test, the loading effect of the horizontal circulating shear stress of the soil unit is improved, and the soil body frost heaving test device is suitable for the circulating single shear loading of fine-grained soil.
2. The soil body frost heaving test system can respectively or simultaneously apply horizontal cyclic shear stress and vertical dynamic pressure stress to the soil units in the soil body freezing test process, and can effectively test and research the soil body frost heaving characteristic under the traffic load stress effect. When the appointed vertical and horizontal cyclic loads are applied simultaneously, the load application effect of the rotation of the main stress shaft in the traffic load can be simulated.
3. The vertical direction and the horizontal direction of the soil body frost heaving test system can be set to be static or dynamic loading, and the soil body frost heaving test, the soil body melting test or the soil body freezing and thawing cycle test under the coupling of temperature and complex stress paths can be developed by combining the matched test environment temperature control design and the test piece top and bottom temperature control design, and dynamic parameters such as dynamic shear modulus, damping ratio and the like of frozen soil or normal temperature soil body can also be tested.
Drawings
FIG. 1 is a schematic diagram of the lateral and forward structure of a temperature control test chamber;
fig. 2 is a schematic structural view of a side plate, (a) is a schematic structural view of the whole side plate, (b) is a schematic structural view of a side plate metal plate and a side plate temperature control plate, and (c) is a schematic structural view of the side plate temperature control plate;
FIG. 3 is a schematic structural diagram of a base plate, (a) is a schematic structural diagram of the base plate as a whole, and (b) is a schematic structural diagram of a temperature control plate and a metal plate of the base plate; (c) is a structural schematic diagram of the bottom of the temperature control plate of the bottom plate;
FIG. 4 is a schematic diagram of the structure of the top plate, (a) is a schematic diagram of the whole structure of the top plate, (b) is a schematic diagram of the temperature control plates at the middle part and the bottom part of the heat dissipation box of the top plate, and (c) is a schematic diagram of the structure of the temperature control plates of the top plate;
FIG. 5 is a schematic structural diagram of an upper cooling plate, (a) is a schematic structural diagram of the upper cooling plate, (b) is a schematic structural diagram of the middle part of a heat dissipation box of the upper cooling plate and a temperature control plate of the upper cooling plate, and (c) is a schematic structural diagram of the temperature control plate of the upper cooling plate;
FIG. 6 is a schematic view of the stop member;
FIG. 7 is a schematic diagram of a concrete embodiment of a cyclic compression-shear soil body frost heaving test system;
FIG. 8 is a diagram showing the application of horizontal and vertical cyclic loads (taking a loading period of 0.2s as an example) when the main stress axis of the simulated traffic load rotates;
in the figure, 1: side plate, 1-1: side plate heat dissipation box, 1-1-1: side plate heat dissipation box metal plate A, 1-1-2: side plate radiating box rubber sheet, 1-1-3: side plate heat dissipation box metal plate B, 1-2: side plate temperature control plate, 1-3: temperature sensor a, 1-4: semiconductor cooling sheets a, 2: folding heat-insulating cloth, 3: base, 4: bottom plate, 4-1: bottom plate metal plate A, 4-1-a: pore channel A, 4-1-b: pore channel B, 4-1-c: pore channel C, 4-2: bottom plate temperature control board, 4-3: bottom plate rubber sheet, 4-4: bottom plate metal plates B, 4-5: semiconductor refrigerating sheet B, 4-6: temperature sensors B, 5: ring folding, 6: upper cooling plate, 6-1: temperature sensors D, 6-2: upper cooling plate temperature control plate, 6-3: semiconductor refrigerating sheet D, 6-4: upper cooling plate heat dissipation box, 6-4-1: middle part of upper cooling plate heat dissipation box, 6-4-2: upper cold plate rubber sheet, 6-4-3: go up cold dish heat dissipation case top, 7: top plate, 7-1: roof heat dissipation case, 7-1-1: top plate metal plate, 7-1-2: top plate rubber sheet, 7-1-3: middle part of the top plate heat dissipation box, 7-2: top plate temperature control plate, 7-3: temperature sensors C, 7-4: semiconductor refrigerating sheet C, 7-5: top plate dowel bar, 8: latex film, 9: soil test piece, 10: thermocouple, 11: permeable stone, 12: pore pressure sensor, 13: stop member, 14: vertical displacement sensor, 15: temperature control test chamber, 16: metal frame, 17: horizontal displacement sensor, 18: horizontal force sensor, 19: horizontal loading motor, 20: dowel bar, 21: horizontal sliding guide, 22: temperature controller, 23: pore pressure acquisition instrument, 24: ma's water supplement bottle, 25: power supply, 26: vertical force sensor, 27: vertical loading motor, 28: pressure and displacement acquisition instrument.
Detailed Description
The technical solution of the present invention is further described below with reference to the accompanying drawings, but not limited thereto, and any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be covered by the protection scope of the present invention.
The invention provides a cyclic compression shear soil body frost heaving test system, wherein a main body part of the test system is a temperature control test cabin 15. As shown in fig. 1, the temperature control test chamber 15 mainly comprises a side plate 1, a folding heat preservation cloth 2, a base 3, a bottom plate 4, a folding ring 5, an upper cooling plate 6, a top plate 7, an emulsion film 8, a soil test piece 9, a thermocouple 10, a permeable stone 11, a pore pressure sensor 12 and a limiting component 13, wherein:
and (3) controlling the temperature of the test environment: the 4 side plates 1, the 1 bottom plate 4 and the 1 top plate 7 jointly form a temperature control test environment space of the soil test piece 9. Liquid inlet and outlet ports are arranged on the side plate 1, the bottom plate 4 and the top plate 4 and are used for exchanging energy generated by the semiconductor refrigerating sheets (1-4, 4-5 and 7-4). One end of the folding heat-insulating cloth 2 is bonded with the bottom of the side plate 1, the other end of the folding heat-insulating cloth is bonded with the top of the base 3, so that the packaging of a temperature control test environment space can be formed, the exchange with external heat is reduced, and the additional restraint of the closed test space on the stress of the soil test piece 9 can be avoided.
And (3) controlling the top and bottom temperature boundary of the test piece: the bottom plate 4 controls the temperature boundary at the bottom of the test chamber 15 and the bottom of the soil specimen 9. The upper cooling plate 6 controls the top temperature boundary of the soil test piece 9. The outside of the soil test piece 9 is wrapped with a latex film 8. The bottom plate 4 is positioned on the upper part of the base 3 and is fixed with the base 3 by screws. A thermocouple 10 is embedded in the soil test piece 9, and the temperature field change in the test process can be monitored. The bottom plate 4 can provide a bottom temperature boundary and bottom water supplement for the soil test piece 9 and can provide a channel of a lead for the thermocouple 10 and the pore pressure sensor 12 in the soil test piece 9. The top of soil test piece 9, bottom all are equipped with the permeable stone 11 of sintering metal material, and permeable stone 11 possesses the advantage that permeates water, increase frictional force, heat conductivity are strong, can compromise the heat conduction in the test process and permeate water, have great frictional force simultaneously. And 3 through-hole channels with the same size are also arranged at the positions, which are the same as the bottom plate 4, of the permeable stones 11 positioned between the bottom of the soil test piece 9 and the bottom plate 4. The thermocouple 10 and the pore pressure sensor 12 in the soil test piece 9 are respectively led out through a pore channel A4-1-a and a pore channel C4-1-C of the bottom plate 4, and the pore channel B4-1-B is used for being connected with a Ma's water replenishing bottle 24. In addition, the top plate 7 and the side plate 1 can be bonded by strong glue or fixed by screws.
And (3) controlling the load boundary of the test piece: the outer side of the latex film 8 is sleeved with a plurality of stacking rings 5, the base 3 drives the bottom plate 4 and the stacking rings 5 to move horizontally after receiving a horizontal load, and the horizontal load is transmitted to the soil test piece 9, so that the horizontal shear stress of the soil test piece 9 is applied. In addition, the top of the top plate 7 is provided with a circular groove with a certain depth, so that the top of the top plate 7 can bear the load from the upper vertical loading rod, and the vertical load is transmitted to the top load bearing part of the upper cooling disc 6 through the top plate dowel bar 7-5 at the lower part of the top plate dowel bar, so that the vertical stress of the soil test piece 9 is applied. The limiting component 13 is fixed on the bottom plate 4 through screws, and vertical displacement of the stack ring 5 caused by frost heaving of the test piece 9 is restrained.
As shown in figure 2, the side plate 1 mainly comprises a side plate heat dissipation box 1-1, a side plate temperature control plate 1-2, a temperature sensor A1-3 and a semiconductor refrigerating sheet A1-4. The side plate heat dissipation box 1-1 mainly comprises a side plate heat dissipation box metal plate A1-1-1, a side plate heat dissipation box rubber sheet 1-1-2 and a side plate heat dissipation box metal plate B1-1-3, wherein a liquid inlet and outlet 1-1-5 is formed in the side plate heat dissipation box metal plate A1-1-1, and a screw 1-1-4 clamps and seals the side plate heat dissipation box 1-1 and the side plate temperature control plate 1-2. A heat-conducting silica gel is clamped between the semiconductor refrigerating sheet A1-4 and the side plate heat dissipation box 1-1, the semiconductor refrigerating sheet A1-4 is positioned in the groove of the side plate temperature control plate 1-2, and a lead penetrates out of the side face. The temperature sensor A1-3 penetrates through the side surface of the side plate temperature control plate 1-2 by punching and penetrates out of the bottom surface of the side plate temperature control plate 1-2 for testing the air temperature in the test chamber 15.
As shown in FIG. 3, the soleplate 4 mainly comprises a soleplate metal plate A4-1, a soleplate temperature control plate 4-2, a soleplate rubber sheet 4-3, a soleplate metal plate B4-4, a semiconductor refrigerating sheet B4-5 and a temperature sensor B4-6. The bottom plate metal plate A4-1, the bottom plate temperature control plate 4-2, the bottom plate rubber sheet 4-3 and the bottom plate metal plate B4-4 are sequentially arranged from top to bottom and fixed by screws. The upper part of the bottom plate metal plate A4-1 is a round base, which is convenient for installing the soil test piece 9 and the permeable stone 11. The bottom plate metal plate A4-1 comprises 3 hole channels, the hole channel A4-1-a and the hole channel C4-1-C are respectively used for leading out a thermocouple 10 and a hole pressure sensor 12 lead in the soil test piece 9, and the hole channel B4-1-B is used for externally connecting a Ma's water replenishing bottle 24 to replenish water to the bottom of the soil test piece 9. The bottom of the bottom plate temperature control plate 4-2 is provided with a circuitous water tank for liquid circulation to dissipate heat, and the top is provided with a square cutting recess for mounting a semiconductor refrigerating sheet B4-5. The bottom plate rubber sheet 4-3 is stuck to the bottom of the bottom plate temperature control plate 4-2 by sealant and is used for sealing the water tank at the bottom of the bottom plate temperature control plate 4-2. The temperature sensor B4-6 is inserted by punching a hole on the side surface of the bottom plate temperature control plate 4-2 and is used for testing the air temperature in the test chamber 15.
As shown in FIG. 4, the top plate 7 is composed of a top plate heat dissipation box 7-1, a top plate temperature control plate 7-2, a temperature sensor C7-3, a semiconductor refrigerating sheet C7-4 and a top plate dowel bar 7-5. The middle part 7-1-3 of the top plate radiating box comprises a circuitous water tank, and a top plate rubber sheet 7-1-2 is arranged on the circuitous water tank and used for sealing the water tank. The upper part of the top plate rubber sheet 7-1-2 is provided with a top plate metal plate 7-1-1, and the center of the top plate metal plate 7-1-1 is provided with a cylindrical recess 7-1-4 for bearing the vertical load from the vertical loading motor 27 externally connected with a dowel bar. A semiconductor refrigerating sheet C7-4 is arranged between the top plate heat dissipation box 7-1 and the top plate temperature control plate 7-2, and the semiconductor refrigerating sheet C7-4 is positioned in a groove of the top plate temperature control plate 7-2. The temperature sensor C7-3 penetrates through the side surface of the top plate temperature control plate 7-2 and penetrates out of the bottom surface of the top plate temperature control plate 7-2 and is used for testing the air temperature in the test chamber 15. The bottom of the top plate temperature control plate 7-2 is provided with a top plate dowel bar 7-5 which is used for transmitting vertical load to the top load bearing part of the upper cooling plate 6.
As shown in FIG. 5, the upper cooling plate 6 mainly comprises an upper cooling plate heat dissipation box 6-4, an upper cooling plate temperature control plate 6-2, a semiconductor cooling sheet D6-3 and a temperature sensor D6-1. The center of the upper top surface of the top 6-4-3 of the upper cooling plate heat dissipation box is provided with a hemispherical indent for bearing the vertical load from the top plate dowel bar 7-5. The middle part 6-4-1 of the upper cooling plate radiating box is provided with a mosquito-repellent incense shape circuitous water return groove, and an upper cooling plate rubber sheet 6-4-2 used for sealing the mosquito-repellent incense shape circuitous water return groove is arranged on the upper cooling plate radiating box. A semiconductor refrigerating sheet D6-3 is arranged between the upper cooling plate radiating box 6-4 and the upper cooling plate temperature control plate 6-2, and the semiconductor refrigerating sheet D6-3 is positioned in a groove of the upper cooling plate temperature control plate 6-2. The temperature sensor D6-1 is punched and penetrated by the upper cooling plate temperature control plate 6-2, and the leads of the temperature sensor D6-1 and the semiconductor refrigerating sheet D6-3 are vertical to the upper cooling plate heat dissipation box 6-4 and penetrate upwards.
As shown in fig. 6, the position limiting members 13 are fixed to the bottom plate 4 by screws, and are symmetrically arranged at the positions in the vertical and horizontal shearing directions for limiting the movement of the position of the ring stack 5 in the vertical direction.
As shown in fig. 7, the temperature-controlled test chamber 15 was mounted on the metal frame 16. The horizontal loading motor 19 controls the horizontal movement of the base 3, so as to drive the bottom plate 4 and the stacking ring 5 to move horizontally, the application of horizontal shear stress on the soil test piece 9 is carried out, and meanwhile, the horizontal displacement and the horizontal load are respectively collected through the horizontal displacement sensor 17 and the horizontal force sensor 18; the vertical loading motor 27 loads the top plate 7 through the force transmission rod, and vertical displacement and vertical load are collected through the vertical displacement sensor 14 and the vertical force sensor 26. The horizontal displacement sensor 17, the horizontal force sensor 18, the vertical displacement sensor 14 and the vertical force sensor 26 are all connected to a pressure and displacement acquisition instrument 28. In addition, the side plate 1, the top plate 7, the upper cooling plate 6 and the bottom plate 4 are respectively provided with a temperature sensor A1-3, a temperature sensor C7-3, a temperature sensor D6-1 and a temperature sensor B4-6, and the temperature controller 22 adjusts the working power of the semiconductor chilling plate according to the feedback temperature signal to realize the active adjustment of the test environment temperature in the temperature control test chamber 15 and the top and bottom temperatures of the soil test piece 9. The lead of the thermocouple 10 inside the soil test piece 9 is led out from the hole channel A4-1-a of the bottom plate 4, and a temperature controller 22 is adopted to collect corresponding temperature signals. And the hole channel B4-1-B of the bottom plate 4 is connected with the Ma's water replenishing bottle 24 to realize the bottom water replenishing in the test process. If the pore pressure needs to be collected, the pore pressure sensor 12 can be embedded in the soil test piece 9 or at the bottom, and the pore pressure sensor lead is led out from the pore channel C4-1-C of the bottom plate 4 to the pore pressure collector 23. The pore water pressure, temperature distribution, vertical displacement and load condition data of the soil test piece 9 are respectively monitored by a pore pressure acquisition instrument 23, a temperature controller 22 and a pressure and displacement sensor 28. Curb plate 1 in the temperature control test chamber 15, roof 7, bottom plate 4, it all has the semiconductor refrigeration piece to go up cold dish 6 inside, with curb plate 1, roof 4, go up cold dish 6, the business turn over liquid mouth of bottom plate 4 links to each other with the heat that gives off the semiconductor refrigeration piece production with external circulation cold bath case, and with corresponding semiconductor refrigeration piece, temperature sensor's wire links to each other with temperature controller 22, connect the circuit between power 25 and the temperature controller 22, power 25 supplies power for the temperature controller 22, can develop the soil body frost heaving experiment of considering circulation single shear stress effect. And (3) applying overlying dynamic pressure stress and horizontal circulating shear stress respectively or independently, and carrying out a soil body frost heaving test under the traffic load stress effect.
A method for performing a frost heaving test on a circular compression shear soil body by using the test system comprises the following steps:
the method comprises the following steps: a soil specimen 9 was prepared. And (3) drying the soil taken on site after passing through a 2mm round hole sieve, preparing corresponding wet soil according to the required water content, and finally forming a cylindrical soil test piece with the diameter of 100mm and the height of 50mm by adopting a static pressure method. The samples were saturated according to the vacuum saturation method of the road soil test protocol (TTG 3430-2020-T01022007) and subsequently removed.
Step two: a sensor lead. The permeable stone 11 is placed on the bottom plate 4 with the circular holes aligned with the circular holes on the top surface of the bottom plate 4. And leading wires of the thermocouple 10 and the pore pressure sensor 12 into the permeable stone 11 and the top hole of the bottom plate 4 in sequence and leading out from the hole channel A4-1-a and the hole channel C4-1-C. Then the latex film 8 is sleeved on the top cylindrical bulge of the bottom plate 4, and a rubber ring is added to fix the bottom of the latex film on the top cylindrical bulge of the bottom plate 4.
Step three: and (5) installing a soil test piece. And (2) reserving 3 holes with the depth of 50mm and the distance of 12.5mm in the height direction from the side surface of the soil test piece 9 along the radial direction by adopting a slender steel needle with the diameter of 1mm, then inserting 3 thermocouples 10 into the holes, and embedding 2 thermocouples 10 at the top and the bottom of the soil test piece 9 respectively. The probe of the pore pressure sensor 12 is buried in the bottom or inside of the soil test piece 9. The latex film 8 is stroked upward, and the soil test piece in which the thermocouple 10 and the hole pressure sensor 12 are embedded is wrapped and fixed by the latex film 8.
Step four: and installing the cooling disc. The permeable stone 11 and the upper cold plate 6 are sequentially placed at the top of the soil test piece 9 and wrapped in the latex film 8, and the latex film 8 and the upper cold plate 6 are fixed by a rubber ring. So far, the soil test piece 9 with the permeable stone 11 at the top and the bottom is sealed in the space of the latex film 8. And then the stack ring 5 is sleeved on the upper portion of the upper cooling plate 6. The limiting member 13 is fixed on the base 3 by screws, and the top of the limiting member 13 presses the stack ring 5 which is flush with the upper cold plate 6, so as to limit the vertical movement of the stack ring 5.
Step five: and installing the top plate and the side plates. 4 side plates 1 and 1 top plate 7 are bonded into a whole by strong glue in advance, the whole is installed as shown in figure 1, and a top plate dowel bar 7-5 is pressed into a top round ball groove of an upper cold plate 6. And the vertical loading rod of the vertical loading motor 27 passing through the vertical force sensor 26 is pressed into the groove 7-1-4 on the upper top surface of the top plate 7.
Step six: connecting the pipelines. The water inlets and outlets of the side plate 1, the top plate 7, the bottom plate 4 and the upper cooling plate 6 are connected with a circulating cooling bath box. The temperature sensors of the side plates 1, the top plate 7, the bottom plate 4 and the upper cooling plate 6 and the lead wires of the semiconductor cooling sheet are connected to a temperature controller 22. And (3) connecting the hole channel B4-1-B of the bottom plate 4 with the Ma water replenishing bottle 24, and enabling the water level of the Ma water replenishing bottle to be flush with the bottom of the soil test piece 9. The power supply 25 is connected to the temperature controller 22. The pore pressure sensor 12 is led out from the pore channel C4-1-C and then connected to the pore pressure acquisition instrument 23, and the thermocouple 10 is led out from the pore channel A4-1-a and then connected to the temperature controller 22 for monitoring and acquisition. The horizontal displacement sensor 17, the horizontal force sensor 18, the vertical displacement sensor 14 and the vertical force sensor 26 are all connected to a pressure and displacement acquisition instrument 28 for data acquisition.
Step seven: the test was started. The temperatures of the side plate 1, the top plate 7, the bottom plate 4 and the upper cooling plate 6 are all required test environment temperatures, and vertical static load is applied to the soil test piece to solidify the soil test piece. And (3) stabilizing the temperature of the soil test piece 9 to the temperature required by the test, and basically tending to stabilize the vertical consolidation displacement. And then changing the control temperature of the upper cooling plate 6 into the negative temperature required by the test, and applying a cyclic compressive shear load with cyclic load in the horizontal direction and the vertical direction or a cyclic single shear load with cyclic load in the horizontal direction and static load in the vertical direction according to the requirement, so as to further carry out the soil body frost heaving test under the temperature-complex stress path coupling.
It should be noted that when the waveforms of the vertical cyclic stress and the horizontal cyclic stress are shown in fig. 8, the effect of the rotation of the main stress axis under the traffic load can be simulated. The vertical stress consists of vertical circulating compressive stress and vertical static compressive stress, and the vertical stress and the horizontal stress are calculated according to the following formulas (1) and (2):
σ v ＝σ s +σ vample ·ξ σv (1)
τ vh ＝τ vhample ·ξ τvh (2)
in the formula: sigma v The stress is vertical stress and comprises a vertical static stress part and a vertical cyclic stress part; sigma s Is a static stress part in the vertical stress; sigma vample Amplitude of vertical cyclic stress; xi shape σv Is the vertical cyclic load coefficient; tau is vh Horizontal shear stress; tau is vhample Amplitude of horizontal shear stress; xi τvh Is circulated horizontallyAnd (4) load factor.
Meanwhile, the test system can also perform the melting and freezing-thawing cycle test of the soil body on the boundary of the cycle single shear load and the cycle compression shear load; in addition, for frozen soil or normal temperature soil, after the test environment temperature is adjusted to the required negative temperature or normal temperature, the dynamic shear modulus and the damping ratio of the soil body can be tested by applying a cyclic single shear load.
Claims (5)
1. The utility model provides a circulation compression shear soil body frost heaving test system which characterized in that test system includes temperature control test cabin, level to loading motor, vertical loading motor, level to displacement sensor, level to force transducer, vertical displacement sensor, vertical force transducer, pore pressure collection appearance, temperature controller, ma shi water-replenishing bottle, power, wherein:
the temperature control test cabin comprises side plates, folding heat insulation cloth, a base, a bottom plate, a folding ring, an upper cooling disc, a top plate, a latex film, a soil test piece, a thermocouple, permeable stones, a pore pressure sensor and a limiting component;
the side plates, the bottom plate and the top plate jointly form a temperature control test environment space of the soil test piece;
the side plates, the top plate, the upper cooling disc and the bottom plate are provided with liquid inlet and outlet ports, temperature sensors and semiconductor refrigerating pieces;
the top plate is connected with the top of the upper cold plate through a top plate dowel bar at the lower part of the top plate;
the bottom plate is positioned at the upper part of the base;
one end of the folding heat-preservation cloth is bonded with the side plate, and the other end of the folding heat-preservation cloth is bonded with the base;
the soil test piece is wrapped with a latex film, a thermocouple and a pore pressure sensor are embedded in the soil test piece, permeable stones are clamped between the bottom of the upper cold plate and the top of the soil test piece and between the bottom of the soil test piece and the top of the bottom plate, and the permeable stones are made of sintered metal;
the base plate comprises 3 hole channels, the hole channel A and the hole channel C are respectively used for leading out a thermocouple and a pore pressure sensor wire in the soil test piece, and the hole channel B is used for externally connecting a Ma's water replenishing bottle to replenish water to the bottom of the soil test piece;
the bottom of the limiting component is fixed on the bottom plate and symmetrically arranged at the positions of the stacked rings in the vertical and horizontal shearing directions, and is used for limiting the movement of the stacked rings in the vertical direction;
the horizontal loading motor is used for controlling the horizontal movement of the base so as to drive the bottom plate and the stacking ring to move horizontally, and the application of the horizontal shear load to the soil test piece is realized;
the vertical loading motor loads the top plate through the force transmission rod;
the horizontal displacement sensor and the horizontal force sensor are used for collecting horizontal displacement and horizontal load;
the vertical displacement sensor and the vertical force sensor are used for collecting vertical displacement and vertical load;
the horizontal displacement sensor, the horizontal force sensor, the vertical displacement sensor and the vertical force sensor are all connected with a pressure and displacement acquisition instrument;
the pore pressure sensor is connected with the pore pressure acquisition instrument;
the liquid inlet and outlet ports of the side plates, the top plate, the upper cooling plate and the bottom plate are connected with an external circulating cold bath box;
the semiconductor refrigerating sheet, the temperature sensor and the thermocouple are all connected with the temperature controller;
the power supply is connected with the temperature controller;
the side plate consists of a side plate heat dissipation box, a side plate temperature control plate, a temperature sensor A and a semiconductor refrigerating sheet A, wherein heat-conducting silica gel is clamped between the semiconductor refrigerating sheet A and the side plate heat dissipation box;
the bottom plate comprises a bottom plate metal plate A, a bottom plate temperature control plate, a bottom plate rubber sheet, a bottom plate metal plate B, a semiconductor refrigerating sheet B and a temperature sensor B, wherein the bottom plate metal plate A, the bottom plate temperature control plate, the bottom plate rubber sheet and the bottom plate metal plate B are sequentially arranged from top to bottom; the bottom plate metal plate A contains 3 pore channels; the bottom of the bottom plate temperature control plate is provided with a circuitous water tank for liquid circulation and heat dissipation, and the top of the bottom plate temperature control plate is provided with a square cutting recess for mounting a semiconductor refrigerating sheet B; the bottom plate rubber sheet is adhered to the bottom of the bottom plate temperature control plate and used for sealing the water tank at the bottom of the bottom plate temperature control plate; the temperature sensor B is inserted from the side surface of the bottom plate temperature control plate by punching;
the top plate consists of a top plate heat dissipation box, a top plate temperature control plate, a temperature sensor C, a semiconductor refrigerating sheet C and a top plate dowel bar, wherein the middle part of the top plate heat dissipation box comprises a circuitous water tank, and a top plate rubber sheet is arranged on the circuitous water tank and used for sealing the water tank; a top plate metal plate is arranged at the upper part of the top plate rubber sheet, and a cylindrical recess is formed in the center of the top plate metal plate and used for bearing a vertical load from a vertical loading motor and an external dowel bar; a semiconductor refrigerating sheet C is arranged between the top plate heat dissipation box and the top plate temperature control plate and is positioned in the groove of the top plate temperature control plate; the temperature sensor C penetrates through the side surface of the top plate temperature control plate in a punching way and penetrates out of the bottom surface of the top plate temperature control plate to be used for testing the air temperature in the test cabin; the bottom of the top plate temperature control plate is provided with a top plate dowel bar for transmitting vertical load to a top load bearing part of the upper cooling plate;
the upper cooling plate consists of an upper cooling plate heat dissipation box, an upper cooling plate temperature control plate, a semiconductor refrigerating sheet D and a temperature sensor D, wherein the center of the upper top surface of the upper cooling plate heat dissipation box is provided with a hemispherical indent for bearing the vertical load of a dowel bar from a top plate; the middle part of the upper cooling disc radiating box is provided with a mosquito-repellent incense shape circuitous water return groove, and an upper cooling disc rubber sheet is arranged on the upper cooling disc rubber sheet and used for sealing the mosquito-repellent incense shape circuitous water return groove; a semiconductor refrigerating sheet D is arranged between the upper cooling plate radiating box and the upper cooling plate temperature control plate, and is positioned in the groove of the upper cooling plate temperature control plate; the temperature sensor D is punched by the upper cooling plate temperature control plate and penetrates in the upper cooling plate heat dissipation box vertically and upwards.
2. The system according to claim 1, wherein 3 through-hole channels of the same size are provided at the same positions of the permeable stones between the bottom of the soil specimen and the bottom plate.
3. A method of conducting a cyclic compression shear soil frost heave test using the test system of any of claims 1-2, the method comprising the steps of:
setting the temperatures of a side plate, a top plate, a bottom plate and an upper cooling disc as the required test environment temperature, and applying vertical static load to a soil test piece to solidify the soil test piece;
step two, stabilizing the temperature of the soil test piece at the initial temperature required by the test, and basically tending to stabilize the vertical consolidation displacement;
and step three, changing the control temperature of the upper cooling plate into the negative temperature required by the test, and applying a cyclic compression shear load with cyclic load in the horizontal direction and the vertical direction or a cyclic single shear load with cyclic load in the horizontal direction and static load in the vertical direction according to the requirement, so as to carry out the soil body frost heaving test under the coupling of the temperature and the complex stress path.
4. The cyclic annular compression shear soil body frost heaving test method according to claim 3, wherein in the third step, when a cyclic compression shear load with cyclic loads both in the horizontal direction and in the vertical direction is applied, the application effect of rotation of the main stress shaft under the effect of traffic load can be simulated, wherein the vertical stress consists of vertical cyclic compression stress and vertical static pressure stress, and the vertical and horizontal stresses are calculated according to the formulas (1) and (2):
σ v ＝σ s +σ vample ·ξ σv (1)
τ vh ＝τ vhample ·ξ τvh (2)
in the formula: sigma s Is a static stress part in the vertical stress; sigma vample Amplitude of vertical cyclic stress; xi σv Is the vertical cyclic load coefficient; tau is vh Horizontal shear stress; tau is vhample Amplitude of horizontal shear stress; xi τvh The horizontal cyclic load coefficient.
5. The method for frost heaving test of soil mass by cyclic compression shear of claim 3, wherein in the third step, the soil mass melting and freezing-thawing cycle test can be performed under the boundary of cyclic single shear load and cyclic compression shear load; aiming at frozen soil or positive temperature soil, after the test environment temperature is respectively adjusted to the required negative temperature or positive temperature, the dynamic shear modulus and the damping ratio of the soil body can be tested by applying a cyclic single shear load mode.
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