CA3090105C - Multi-load-mode frost heave tester for unsaturated soil and method for_testing amount of frost heave - Google Patents
Multi-load-mode frost heave tester for unsaturated soil and method for_testing amount of frost heave Download PDFInfo
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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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Abstract
Ab str act The present invention discloses a multi-load-mode frost heave tester for unsaturated soil and a method for testing the amount of frost heave. The frost heave tester includes a sample storage system, a load control system, a humidity control system, a temperature control system and a thermotank, where the sample storage system includes a sample cylinder and a temperature-controlled plate, a gas inlet being formed at the bottom end of the sample cylinder, a liquid inlet and a liquid outlet being formed at the top of the cavity, the temperature-controlled plate being arranged in the top end of the sample cylinder, and the sample cylinder being placed in the thermotank; the load control system includes a counter-force frame and a load control mechanism, the load control mechanism being arranged in the counter-force frame and connected to the temperature-controlled plate, and the counter-force frame erecting in the thermotank. Date Recue/Date Received 2020-08-14
Description
MULTI-LOAD-MODE FROST HEAVE TESTER FOR UNSATURATED SOIL AND
METHOD FOR TESTING AMOUNT OF FROST HEAVE
TECHNICAL FIELD
The present invention belongs to the technical field of geotechnical engineering, and in particular relates to a multi-load-mode frost heave tester for unsaturated soil and a method for testing the amount of frost heave.
BACKGROUND
Frost heave of the roadbed is a main threat to cold region engineering, especially for expressways, high-speed railways and the like in the cold region. Test simulation is an important method to study the frost heave property of roadbed filler. When the environment temperature of the cold region falls below 0 C (32 F), pore water in soil reaches a freezing point and gets frozen. The frost heave of the roadbed requires water supply. The latest research result shows that vapour transfer in unsaturated soil has an important effect on the frost heave of the geomaterials such as the unsaturated coarse-grained soil and the like. For example, unsaturated coarse-grained soil filler is the main material of the high-speed railway roadbed, but there are few theories and tests about migration of vapour into ice in the reports on the frost heave phenomenon of the high-speed railway.
The frost heave of soil has always been an important research subject in the field of geotechnical engineering. The frost heave test of soil is an important method to study the frost heave mechanism and the frost heave sensitivity of the soil. The amount of frost heave and the frost heave force are two important basic physical quantities of frozen soil and are measured through the frost heave test of the soil. When studying the frost heave characteristic of the soil, it is necessary to measure the amount of free frost heave under the no-load condition, that is, the zero-load state of the soil is the precondition for measuring the amount of free frost heave of the soil. Vertical load is an important boundary condition of frost heave of the soil. The frost heave characteristics of the soil under different load conditions are important basis for the roadbed foundation design in cold region engineering. Vertical static load is used to simulate the influence on the frost heave of the roadbed by the static load, and vertical dynamic load is used to simulate the influence on the frost heave by dynamic load such as traffic load and the like.
Date Recue/Date Received 2020-08-14 There are a variety of frost heave testers available at home and abroad, but supply of vapour cannot be realized, and the overburden pressure (provided by the dead weight of the temperature-controlled plate and the refrigerating fluid as well as the friction force of the temperature-controlled plate and the sample cylinder) of the soil sample cannot be eliminated. The frost heave tester which cannot realize supply of the vapour cannot be used to study the frost heave characteristic of roadbed filler such as the unsaturated coarse-grained soil and the like. The vertical pressure on the soil sample cannot be eliminated and the error of the measured amount of frost heave is large; therefore, scientific research with higher requirements at this stage cannot be met.
SUMMARY
An objective of the present invention is to overcome the shortcomings of the prior art and provide a multi-load-mode frost heave tester for unsaturated soil capable of supplying vapour to induce frost heave of unsaturated coarse-grained soil as well as a method for testing the amount of frost heave.
The multi-load-mode frost heave tester for unsaturated soil according to the present invention includes a sample storage system, a load control system, a humidity control system, a temperature control system and a thermotank, where the sample storage system includes a sample cylinder and a temperature-controlled plate, a gas inlet being formed at the bottom end of the sample cylinder, a cavity being formed in the temperature-controlled plate, a waterproof and gas-insulating membrane being arranged outside the bottom of the cavity, a liquid inlet and a liquid outlet being formed at the top of the cavity, the temperature-controlled plate being arranged in the top end of the sample cylinder, and the sample cylinder being placed in the thermotank; the load control system includes a counter-force frame and a load control mechanism, the load control mechanism being arranged in the counter-force frame and connected to the temperature-controlled plate, and the counter-force frame erecting in the thermotank; the humidity control system is communicated with the gas inlet of the sample cylinder; and an output port of the temperature control system is communicated with the liquid inlet on the temperature-controlled plate, and an outlet of the temperature control system is communicated with the liquid outlet on the temperature-controlled plate.
Preferably, the sample cylinder has two open ends, temperature sensors and stress sensors are buried at different heights of a sample in the sample cylinder, and a perforated plate is arranged at the inner bottom of the sample cylinder.
METHOD FOR TESTING AMOUNT OF FROST HEAVE
TECHNICAL FIELD
The present invention belongs to the technical field of geotechnical engineering, and in particular relates to a multi-load-mode frost heave tester for unsaturated soil and a method for testing the amount of frost heave.
BACKGROUND
Frost heave of the roadbed is a main threat to cold region engineering, especially for expressways, high-speed railways and the like in the cold region. Test simulation is an important method to study the frost heave property of roadbed filler. When the environment temperature of the cold region falls below 0 C (32 F), pore water in soil reaches a freezing point and gets frozen. The frost heave of the roadbed requires water supply. The latest research result shows that vapour transfer in unsaturated soil has an important effect on the frost heave of the geomaterials such as the unsaturated coarse-grained soil and the like. For example, unsaturated coarse-grained soil filler is the main material of the high-speed railway roadbed, but there are few theories and tests about migration of vapour into ice in the reports on the frost heave phenomenon of the high-speed railway.
The frost heave of soil has always been an important research subject in the field of geotechnical engineering. The frost heave test of soil is an important method to study the frost heave mechanism and the frost heave sensitivity of the soil. The amount of frost heave and the frost heave force are two important basic physical quantities of frozen soil and are measured through the frost heave test of the soil. When studying the frost heave characteristic of the soil, it is necessary to measure the amount of free frost heave under the no-load condition, that is, the zero-load state of the soil is the precondition for measuring the amount of free frost heave of the soil. Vertical load is an important boundary condition of frost heave of the soil. The frost heave characteristics of the soil under different load conditions are important basis for the roadbed foundation design in cold region engineering. Vertical static load is used to simulate the influence on the frost heave of the roadbed by the static load, and vertical dynamic load is used to simulate the influence on the frost heave by dynamic load such as traffic load and the like.
Date Recue/Date Received 2020-08-14 There are a variety of frost heave testers available at home and abroad, but supply of vapour cannot be realized, and the overburden pressure (provided by the dead weight of the temperature-controlled plate and the refrigerating fluid as well as the friction force of the temperature-controlled plate and the sample cylinder) of the soil sample cannot be eliminated. The frost heave tester which cannot realize supply of the vapour cannot be used to study the frost heave characteristic of roadbed filler such as the unsaturated coarse-grained soil and the like. The vertical pressure on the soil sample cannot be eliminated and the error of the measured amount of frost heave is large; therefore, scientific research with higher requirements at this stage cannot be met.
SUMMARY
An objective of the present invention is to overcome the shortcomings of the prior art and provide a multi-load-mode frost heave tester for unsaturated soil capable of supplying vapour to induce frost heave of unsaturated coarse-grained soil as well as a method for testing the amount of frost heave.
The multi-load-mode frost heave tester for unsaturated soil according to the present invention includes a sample storage system, a load control system, a humidity control system, a temperature control system and a thermotank, where the sample storage system includes a sample cylinder and a temperature-controlled plate, a gas inlet being formed at the bottom end of the sample cylinder, a cavity being formed in the temperature-controlled plate, a waterproof and gas-insulating membrane being arranged outside the bottom of the cavity, a liquid inlet and a liquid outlet being formed at the top of the cavity, the temperature-controlled plate being arranged in the top end of the sample cylinder, and the sample cylinder being placed in the thermotank; the load control system includes a counter-force frame and a load control mechanism, the load control mechanism being arranged in the counter-force frame and connected to the temperature-controlled plate, and the counter-force frame erecting in the thermotank; the humidity control system is communicated with the gas inlet of the sample cylinder; and an output port of the temperature control system is communicated with the liquid inlet on the temperature-controlled plate, and an outlet of the temperature control system is communicated with the liquid outlet on the temperature-controlled plate.
Preferably, the sample cylinder has two open ends, temperature sensors and stress sensors are buried at different heights of a sample in the sample cylinder, and a perforated plate is arranged at the inner bottom of the sample cylinder.
2 Date Recue/Date Received 2020-08-14 Further, the sample storage system further includes a base, positioning cylinders and a heat-insulating cylinder; the base is an annular base, and a hygrothermograph and an electric heating rod are arranged on the inner wall of the base; a perforated plate is arranged on a top surface of each positioning cylinder, and the positioning cylinders are coaxially arranged on the base; the sample cylinder sleeves the positioning cylinder, and a sealing ring is arranged between the sample cylinder and the positioning cylinder; and the sample cylinder is coated with the heat-insulating cylinder.
In a specific implementation, the counter-force frame is door-shaped and includes a cross beam and a pair of columns, where the columns are each provided with threaded sections; through holes are formed at the two ends of the cross beam; and the cross beam is engaged with the two columns and is locked through a pair of nuts.
To perform dynamic and static load frost heave tests, the load control mechanism includes a hydraulic servo control device and an axial force sensor, where the hydraulic servo control device is mounted below the cross beam and a loading end of the hydraulic servo control device is connected to the temperature-controlled plate; and the axial force sensor is arranged on the temperature-controlled plate.
To perform a no-load frost heave test, the load control mechanism includes a winding drum, a slip rope and a pulley, where the winding drum is arranged in the counter-force frame, the pulley is connected below the cross beam, and one end of the slip rope is wound on the winding drum and the other end of the slip rope is connected to the temperature-controlled plate after going around the pulley; and the winding drum rotates to lift the temperature-controlled plate through the pulley, which can ensure that there is always no load on the soil sample during the test.
In a specific implementation, the humidity control system includes an environmental box, an air stirrer, a heater, a cooler, a blower fan, a humidifier and a dehumidifier, where an air outlet and a return air inlet are formed in the side wall of the environmental box, the blower fan is arranged at the air outlet, and an output end of the blower fan is communicated with the gas inlet of the sample cylinder through a steam tube, and the other end of the steam tube is communicated with the return air inlet; a pair of through holes are formed in a bottom surface of the environmental box and are respectively communicated with the humidifier and the dehumidifier; the air stirrer is hung on a top surface of the environmental box; and the heater and the cooler are arranged on a bottom surface of the environmental box.
In a specific implementation, the counter-force frame is door-shaped and includes a cross beam and a pair of columns, where the columns are each provided with threaded sections; through holes are formed at the two ends of the cross beam; and the cross beam is engaged with the two columns and is locked through a pair of nuts.
To perform dynamic and static load frost heave tests, the load control mechanism includes a hydraulic servo control device and an axial force sensor, where the hydraulic servo control device is mounted below the cross beam and a loading end of the hydraulic servo control device is connected to the temperature-controlled plate; and the axial force sensor is arranged on the temperature-controlled plate.
To perform a no-load frost heave test, the load control mechanism includes a winding drum, a slip rope and a pulley, where the winding drum is arranged in the counter-force frame, the pulley is connected below the cross beam, and one end of the slip rope is wound on the winding drum and the other end of the slip rope is connected to the temperature-controlled plate after going around the pulley; and the winding drum rotates to lift the temperature-controlled plate through the pulley, which can ensure that there is always no load on the soil sample during the test.
In a specific implementation, the humidity control system includes an environmental box, an air stirrer, a heater, a cooler, a blower fan, a humidifier and a dehumidifier, where an air outlet and a return air inlet are formed in the side wall of the environmental box, the blower fan is arranged at the air outlet, and an output end of the blower fan is communicated with the gas inlet of the sample cylinder through a steam tube, and the other end of the steam tube is communicated with the return air inlet; a pair of through holes are formed in a bottom surface of the environmental box and are respectively communicated with the humidifier and the dehumidifier; the air stirrer is hung on a top surface of the environmental box; and the heater and the cooler are arranged on a bottom surface of the environmental box.
3 Date Recue/Date Received 2020-08-14 For specific implementation, the temperature control system may set a constant temperature or a sinusoidal variation temperature; the output port of the temperature control system is communicated with the liquid inlet of the temperature-controlled plate; a reflux inlet of the temperature control system is communicated with the liquid outlet of the temperature-controlled plate; and the temperature control system controls a temperature through circulation of refrigerating fluid.
The present invention further provides a method for testing frost heave of unsaturated soil under negative dynamic and static load conditions, where the method is implemented by the above frost heave tester and includes the following steps:
(1) preparing a soil sample and placing the soil sample in a sample cylinder;
(2) covering the top of the sample with a waterproof and gas-insulating membrane;
(3) placing a temperature-controlled plate on the waterproof and gas-insulating membrane;
The present invention further provides a method for testing frost heave of unsaturated soil under negative dynamic and static load conditions, where the method is implemented by the above frost heave tester and includes the following steps:
(1) preparing a soil sample and placing the soil sample in a sample cylinder;
(2) covering the top of the sample with a waterproof and gas-insulating membrane;
(3) placing a temperature-controlled plate on the waterproof and gas-insulating membrane;
(4) mounting a hydraulic servo control device on a counter-force frame to enable a force applying end to be in contact with the temperature-controlled plate, and recording an initial position;
(5) setting a target relative humidity and starting a humidity control system;
(6) setting a target temperature, starting a temperature control system, circulating refrigerating fluid into the temperature-controlled plate, controlling a temperature, setting a target temperature of a thermotank and starting the thermotank;
(7) setting a vertical pressure on a target and starting the hydraulic servo control device; and
(8) starting to measure, recording and storing related data, drawing a soil temperature distribution curve according to the measured soil temperature to obtain a frozen depth, and obtaining a frost heave rate through the amount of frost heave measured by a deformation gauge.
The present invention further provides a method for testing the amount of free frost heave of unsaturated soil, where the method is implemented by the above frost heave tester and includes the following steps:
(1) preparing a soil sample and placing the soil sample in a sample cylinder;
(2) covering the top of the sample with a waterproof and gas-insulating membrane;
(3) placing a temperature-controlled plate on the waterproof and gas-insulating membrane;
(4) mounting a pulley on a counter-force frame;
(5) connecting a slip rope to the temperature-controlled plate, rotating a winding drum and Date Recue/Date Received 2020-08-14 adjusting the slip rope to enable the temperature-controlled plate to be in contact with the top of the sample without pressure;
(6) starting a humidity control system to supply vapour;
(7) starting a temperature control device and enabling refrigerating fluid to enter the temperature-controlled plate to realize temperature control; and (8) controlling rotation of the winding drum and lifting the slip rope until the vertical pressure on the sample is zero, enabling the temperature-controlled plate to be in contact with the top of the sample and performing a zero-load frost heave test, where during the test, when the top is subjected to load due to upward frost heave of the soil, the slip rope is controlled to be continuously lifted by a signal transmitted by a pressure sensor between the temperature-controlled plate and the sample, thereby ensuring that there is always no vertical load on the sample in the whole test process.
During use, the soil sample is firstly placed in the sample cylinder, then the waterproof and gas-insulating membrane and the temperature-controlled plate are laid, and different load control mechanisms are mounted under the counter-force frame according to working conditions, thereby carrying out frost heave tests under different loads. The present invention can eliminate the vertical pressure on the soil sample by using a zero-load control device, reduce the error of the measured amount of free frost heave and meet scientific research with higher requirements at this stage.
Meanwhile, starting the humidity control system and the temperature control system can inject steam in the soil sample in the sample cylinder to supply vapour so as to induce frost heave of the coarse-grained soil; therefore, the present invention is suitable for researching the frost heave characteristic of roadbed filler such as the unsaturated coarse-grained soil and the like.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic diagram of a use state of a preferred example I of the present invention.
FIG. 2 is an enlarged schematic diagram of a sample storage system in a preferred example I.
FIG. 3 is an enlarged schematic diagram of assembly of a load control mechanism in a preferred example I.
FIG. 4 is an enlarged schematic diagram of a humidity control system in a preferred example I.
FIG. 5 is an enlarged schematic diagram of connection of a temperature control system and a temperature-controlled plate in a preferred example I.
FIG. 6 is an enlarged schematic diagram of assembly of a zero-load control mechanism in a Date Recue/Date Received 2020-08-14 preferred example I.
Reference numerals:
1-sample storage system, 11-sample cylinder, 12-temperature-controlled plate, 13-base, 14-positioning cylinder, 15-heat-insulating cylinder, 16-temperature sensor, 17-stress sensor, 18-waterproof and gas-insulating membrane, 19-perforated plate;
2-load control system, 21-counter-force frame, 211-cross beam, 212-column, 213-nut, 22-load control mechanism, 221-hydraulic cylinder, 222-axial force sensor, 223-displacement sensor;
3-humidity control system, 31-environmental box, 32-air stirrer, 33-heater, 34-cooler, 35-blower fan, 36-humidifier, 37-dehumidifier, 38-hygrothermograph;
4-temperature control system; 5-thermo tank; 6-steam tube; and 7-zero-load control mechanism, 71-winding drum, 72-slip rope, 73-pulley.
DETAILED DESCRIPTION
In a preferred example I, as shown in FIG. 1, the frost heave tester for unsaturated soil according to the example is suitable for performing negative dynamic and static load frost heave tests of unsaturated soil and includes a sample storage system 1, a load control system 2, a humidity control system 3, a temperature control system 4 and a thermotank 5.
As shown in FIG. 2, the sample storage system 1 includes a sample cylinder 11, a temperature-controlled plate 12, a base 13, positioning cylinders 14 and a heat-insulating cylinder 15. The sample cylinder 11 has two open ends and is made of an organic glass material, where a cylinder wall is perforated according to objective requirements, a temperature sensor 16 and a stress sensor 17 are buried in the soil sample in the cylinder, the temperature sensor 16 adopts a thermal resistor for measuring the temperature of the soil sample, and the stress sensor 17 adopts a membrane soil pressure box. the temperature-controlled plate 12 is a cylindrical plate with an outer diameter matched with an inner diameter of the sample cylinder, is made of stainless steel and is internally provided with a cavity, where a liquid inlet and a liquid outlet are formed at the top of the cavity, the temperature-controlled plate 12 is placed on the waterproof and gas-insulating membrane 18 after the waterproof and gas-insulating membrane 18 is laid, and the waterproof and gas-insulating membrane 18 is made of a polyethylene (PE) material and is used to prevent wet air Date Recue/Date Received 2020-08-14 from entering the soil sample from the top. The base 13 is an annular base and is provided with a hygrothermograph and an electric heating rod on its inner wall. The positioning cylinder 14 and the heat-insulating cylinder 15 are cylinders, where an outer diameter of each positioning cylinder 14 is matched with an inner diameter of the sample cylinder; a perforated plate 19 is arranged on a top surface of each positioning cylinder; an opening area of the perforated plate is not less than 50%;
and the heat-insulating cylinder is made of glass wool. When the sample storage system is assembled, the positioning cylinders are coaxially arranged on the base, the sample cylinder sleeves the positioning cylinder, and a sealing ring is arranged between the sample cylinder and the positioning cylinders. A gas inlet of the sample cylinder is arranged at the position of the perforated plate so as to ensure that steam can enter smoothly, the soil sample is placed in the sample cylinder, the waterproof and gas-insulating membrane is laid on a bottom surface of the soil sample, and the temperature-controlled plate is placed.
As shown in FIG. 3, the load control system 2 includes a counter-force frame 21 and a load control mechanisms 22. The counter-force frame 21 is door-shaped and includes a cross beam 211 and a pair of columns 212, where the columns are each provided with threaded sections; through holes are formed at the two ends of the cross beam; and the cross beam is engaged with the two columns and is locked through a pair of nuts 213, such that a height of the cross beam is adjustable.
The load control mechanism 22 is connected below the cross beam and includes a hydraulic servo control device and an axial force sensor 222, where a hydraulic cylinder 221 of the hydraulic servo control device is mounted below the cross beam; the axial force sensor 222 is arranged outside an end part of a loading head; and a displacement sensor 223 is arranged on the temperature-controlled plate. During assembling, the sample storage system is firstly placed in the thermotank 5, then counter-force frame of the load control system spans across the sample cylinder, and a loading end of the load control system is connected to the temperature-controlled plate.
The hydraulic servo control device has a model number of TTCSUD-1, the axial force sensor adopts an SPX-2 type axial force sensor, and the displacement sensor adopts an LWX002 type linear displacement sensor.
As shown in FIG. 4, the humidity control system 3 inputs steam to the soil sample in the sample cylinder 11 through the steam tube 6. The humidity control system 3 includes an environmental box 31, an air stirrer 32, a heater 33, a cooler 34, a blower fan 35, a humidifier 36 and a dehumidifier 37, where a hygrothermograph 38 is arranged in the environmental box 31 and is used to monitor a temperature and a humidity in the environmental box and feed back the Date Recue/Date Received 2020-08-14 measurement result to the control system timely. The air stirrer 32 is hung on a top surface of the environmental box 31 and is used to uniformly balance a relative humidity of the environmental box. The heater 33 and the cooler 34 are arranged on a bottom surface of the environmental box 31.
The heater with the model number of KEW-M47DR and the cooler with the model number of OR-60 are respectively used to heat and cool the environmental box to maintain the temperature of the environmental box to be in a dynamic balance state. An air outlet is formed at one side of the environmental box 31 and a return air inlet is formed at the other side of the environmental box 31.
The blower fan 35 is arranged at the air outlet and is used to blow steam into the sample cylinder through a steam tube 6. The steam tube 6 is a three-way tube, where the first end of the steam tube is communicated with an output port of the blower fan, the second end of the steam tube is communicated with the gas inlet of the sample cylinder, and the third end of the steam tube is communicated with the return air inlet, such that the steam can start from the environmental box and pass through a bottom opening of the sample, and one part of steam enters the sample and the other part of steam circulates back to the environmental box. A pair of through holes are formed in the bottom surface of the environmental box and are respectively communicated with the humidifier 36 and the dehumidifier 37. The humidifier 36 is an ultrasonic humidifier of WM-SCA1000 and the dehumidifier 37 is of EFA5-100-A. The humidifier and the dehumidifier are respectively used to increase and reduce the relative humidity of the environmental box to enable the humidity of the environmental box to be in a dynamic balance state.
As shown in FIG. 5, the temperature control system 4 adopts a TMS8035-R40 type temperature control system, may set a constant temperature or sinusoidal variation temperature, where an output port of the temperature control system is communicated with the liquid inlet on the temperature-controlled plate; an inlet of the temperature control system is communicated with the liquid outlet on the temperature-controlled plate; and refrigerating fluid enters the temperature-controlled plate from the liquid inlet and passes through the liquid outlet of the temperature-controlled plate to return a temperature groove, such that the temperature is controlled through circulation of the refrigerating fluid.
In the example, a test on the frost heave tester for unsaturated soil with vertical load and supplied by vapour is implemented according to the following specific steps:
(1) connect related data line and power line in good condition;
(2) sieve and dry soil to prepare soil with different water contents, place the prepared soil in a Date Recue/Date Received 2020-08-14 sample cylinder, perform layered compaction to a target height, prepare a target sample, and bury a temperature sensor and a stress sensor at the target height of the sample;
(3) cover the top of the sample with a waterproof and gas-insulating membrane;
(4) place a temperature-controlled plate on the waterproof and gas-insulating membrane;
(5) mount a hydraulic servo control device on a counter-force frame, adjust a force transferring shaft to be in contact with the temperature-controlled plate, adjust a deformation gauge and record an initial position;
(6) set a target relative humidity and start a humidity control system;
(7) set a target temperature, start a temperature control system, circulate refrigerating fluid into the temperature-controlled plate, control a temperature, set a target temperature of a thermotank and start the thermotank;
(8) set a vertical pressure on a target and start a loading device;
The present invention further provides a method for testing the amount of free frost heave of unsaturated soil, where the method is implemented by the above frost heave tester and includes the following steps:
(1) preparing a soil sample and placing the soil sample in a sample cylinder;
(2) covering the top of the sample with a waterproof and gas-insulating membrane;
(3) placing a temperature-controlled plate on the waterproof and gas-insulating membrane;
(4) mounting a pulley on a counter-force frame;
(5) connecting a slip rope to the temperature-controlled plate, rotating a winding drum and Date Recue/Date Received 2020-08-14 adjusting the slip rope to enable the temperature-controlled plate to be in contact with the top of the sample without pressure;
(6) starting a humidity control system to supply vapour;
(7) starting a temperature control device and enabling refrigerating fluid to enter the temperature-controlled plate to realize temperature control; and (8) controlling rotation of the winding drum and lifting the slip rope until the vertical pressure on the sample is zero, enabling the temperature-controlled plate to be in contact with the top of the sample and performing a zero-load frost heave test, where during the test, when the top is subjected to load due to upward frost heave of the soil, the slip rope is controlled to be continuously lifted by a signal transmitted by a pressure sensor between the temperature-controlled plate and the sample, thereby ensuring that there is always no vertical load on the sample in the whole test process.
During use, the soil sample is firstly placed in the sample cylinder, then the waterproof and gas-insulating membrane and the temperature-controlled plate are laid, and different load control mechanisms are mounted under the counter-force frame according to working conditions, thereby carrying out frost heave tests under different loads. The present invention can eliminate the vertical pressure on the soil sample by using a zero-load control device, reduce the error of the measured amount of free frost heave and meet scientific research with higher requirements at this stage.
Meanwhile, starting the humidity control system and the temperature control system can inject steam in the soil sample in the sample cylinder to supply vapour so as to induce frost heave of the coarse-grained soil; therefore, the present invention is suitable for researching the frost heave characteristic of roadbed filler such as the unsaturated coarse-grained soil and the like.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic diagram of a use state of a preferred example I of the present invention.
FIG. 2 is an enlarged schematic diagram of a sample storage system in a preferred example I.
FIG. 3 is an enlarged schematic diagram of assembly of a load control mechanism in a preferred example I.
FIG. 4 is an enlarged schematic diagram of a humidity control system in a preferred example I.
FIG. 5 is an enlarged schematic diagram of connection of a temperature control system and a temperature-controlled plate in a preferred example I.
FIG. 6 is an enlarged schematic diagram of assembly of a zero-load control mechanism in a Date Recue/Date Received 2020-08-14 preferred example I.
Reference numerals:
1-sample storage system, 11-sample cylinder, 12-temperature-controlled plate, 13-base, 14-positioning cylinder, 15-heat-insulating cylinder, 16-temperature sensor, 17-stress sensor, 18-waterproof and gas-insulating membrane, 19-perforated plate;
2-load control system, 21-counter-force frame, 211-cross beam, 212-column, 213-nut, 22-load control mechanism, 221-hydraulic cylinder, 222-axial force sensor, 223-displacement sensor;
3-humidity control system, 31-environmental box, 32-air stirrer, 33-heater, 34-cooler, 35-blower fan, 36-humidifier, 37-dehumidifier, 38-hygrothermograph;
4-temperature control system; 5-thermo tank; 6-steam tube; and 7-zero-load control mechanism, 71-winding drum, 72-slip rope, 73-pulley.
DETAILED DESCRIPTION
In a preferred example I, as shown in FIG. 1, the frost heave tester for unsaturated soil according to the example is suitable for performing negative dynamic and static load frost heave tests of unsaturated soil and includes a sample storage system 1, a load control system 2, a humidity control system 3, a temperature control system 4 and a thermotank 5.
As shown in FIG. 2, the sample storage system 1 includes a sample cylinder 11, a temperature-controlled plate 12, a base 13, positioning cylinders 14 and a heat-insulating cylinder 15. The sample cylinder 11 has two open ends and is made of an organic glass material, where a cylinder wall is perforated according to objective requirements, a temperature sensor 16 and a stress sensor 17 are buried in the soil sample in the cylinder, the temperature sensor 16 adopts a thermal resistor for measuring the temperature of the soil sample, and the stress sensor 17 adopts a membrane soil pressure box. the temperature-controlled plate 12 is a cylindrical plate with an outer diameter matched with an inner diameter of the sample cylinder, is made of stainless steel and is internally provided with a cavity, where a liquid inlet and a liquid outlet are formed at the top of the cavity, the temperature-controlled plate 12 is placed on the waterproof and gas-insulating membrane 18 after the waterproof and gas-insulating membrane 18 is laid, and the waterproof and gas-insulating membrane 18 is made of a polyethylene (PE) material and is used to prevent wet air Date Recue/Date Received 2020-08-14 from entering the soil sample from the top. The base 13 is an annular base and is provided with a hygrothermograph and an electric heating rod on its inner wall. The positioning cylinder 14 and the heat-insulating cylinder 15 are cylinders, where an outer diameter of each positioning cylinder 14 is matched with an inner diameter of the sample cylinder; a perforated plate 19 is arranged on a top surface of each positioning cylinder; an opening area of the perforated plate is not less than 50%;
and the heat-insulating cylinder is made of glass wool. When the sample storage system is assembled, the positioning cylinders are coaxially arranged on the base, the sample cylinder sleeves the positioning cylinder, and a sealing ring is arranged between the sample cylinder and the positioning cylinders. A gas inlet of the sample cylinder is arranged at the position of the perforated plate so as to ensure that steam can enter smoothly, the soil sample is placed in the sample cylinder, the waterproof and gas-insulating membrane is laid on a bottom surface of the soil sample, and the temperature-controlled plate is placed.
As shown in FIG. 3, the load control system 2 includes a counter-force frame 21 and a load control mechanisms 22. The counter-force frame 21 is door-shaped and includes a cross beam 211 and a pair of columns 212, where the columns are each provided with threaded sections; through holes are formed at the two ends of the cross beam; and the cross beam is engaged with the two columns and is locked through a pair of nuts 213, such that a height of the cross beam is adjustable.
The load control mechanism 22 is connected below the cross beam and includes a hydraulic servo control device and an axial force sensor 222, where a hydraulic cylinder 221 of the hydraulic servo control device is mounted below the cross beam; the axial force sensor 222 is arranged outside an end part of a loading head; and a displacement sensor 223 is arranged on the temperature-controlled plate. During assembling, the sample storage system is firstly placed in the thermotank 5, then counter-force frame of the load control system spans across the sample cylinder, and a loading end of the load control system is connected to the temperature-controlled plate.
The hydraulic servo control device has a model number of TTCSUD-1, the axial force sensor adopts an SPX-2 type axial force sensor, and the displacement sensor adopts an LWX002 type linear displacement sensor.
As shown in FIG. 4, the humidity control system 3 inputs steam to the soil sample in the sample cylinder 11 through the steam tube 6. The humidity control system 3 includes an environmental box 31, an air stirrer 32, a heater 33, a cooler 34, a blower fan 35, a humidifier 36 and a dehumidifier 37, where a hygrothermograph 38 is arranged in the environmental box 31 and is used to monitor a temperature and a humidity in the environmental box and feed back the Date Recue/Date Received 2020-08-14 measurement result to the control system timely. The air stirrer 32 is hung on a top surface of the environmental box 31 and is used to uniformly balance a relative humidity of the environmental box. The heater 33 and the cooler 34 are arranged on a bottom surface of the environmental box 31.
The heater with the model number of KEW-M47DR and the cooler with the model number of OR-60 are respectively used to heat and cool the environmental box to maintain the temperature of the environmental box to be in a dynamic balance state. An air outlet is formed at one side of the environmental box 31 and a return air inlet is formed at the other side of the environmental box 31.
The blower fan 35 is arranged at the air outlet and is used to blow steam into the sample cylinder through a steam tube 6. The steam tube 6 is a three-way tube, where the first end of the steam tube is communicated with an output port of the blower fan, the second end of the steam tube is communicated with the gas inlet of the sample cylinder, and the third end of the steam tube is communicated with the return air inlet, such that the steam can start from the environmental box and pass through a bottom opening of the sample, and one part of steam enters the sample and the other part of steam circulates back to the environmental box. A pair of through holes are formed in the bottom surface of the environmental box and are respectively communicated with the humidifier 36 and the dehumidifier 37. The humidifier 36 is an ultrasonic humidifier of WM-SCA1000 and the dehumidifier 37 is of EFA5-100-A. The humidifier and the dehumidifier are respectively used to increase and reduce the relative humidity of the environmental box to enable the humidity of the environmental box to be in a dynamic balance state.
As shown in FIG. 5, the temperature control system 4 adopts a TMS8035-R40 type temperature control system, may set a constant temperature or sinusoidal variation temperature, where an output port of the temperature control system is communicated with the liquid inlet on the temperature-controlled plate; an inlet of the temperature control system is communicated with the liquid outlet on the temperature-controlled plate; and refrigerating fluid enters the temperature-controlled plate from the liquid inlet and passes through the liquid outlet of the temperature-controlled plate to return a temperature groove, such that the temperature is controlled through circulation of the refrigerating fluid.
In the example, a test on the frost heave tester for unsaturated soil with vertical load and supplied by vapour is implemented according to the following specific steps:
(1) connect related data line and power line in good condition;
(2) sieve and dry soil to prepare soil with different water contents, place the prepared soil in a Date Recue/Date Received 2020-08-14 sample cylinder, perform layered compaction to a target height, prepare a target sample, and bury a temperature sensor and a stress sensor at the target height of the sample;
(3) cover the top of the sample with a waterproof and gas-insulating membrane;
(4) place a temperature-controlled plate on the waterproof and gas-insulating membrane;
(5) mount a hydraulic servo control device on a counter-force frame, adjust a force transferring shaft to be in contact with the temperature-controlled plate, adjust a deformation gauge and record an initial position;
(6) set a target relative humidity and start a humidity control system;
(7) set a target temperature, start a temperature control system, circulate refrigerating fluid into the temperature-controlled plate, control a temperature, set a target temperature of a thermotank and start the thermotank;
(8) set a vertical pressure on a target and start a loading device;
(9) start a data acquisition system and begin to measure, record and store related data; and
(10) draw a soil temperature distribution curve according to the measured soil temperature, obtain a frozen depth A H, and measure the amount of frost heave A h by a deformation gauge to obtain a frost heave rate /I, where A h in the formula, /I represents the frost heave rate and A H represents the frozen depth.
The above is the implementation method of the frost heave tester with vertical pressure, which can be applied to engineering practice. The amount of free frost heave under the no-load condition is an import basis for researching the frost heave characteristic of the soil and classifying the frost heave sensitivity of the geomaterial.
In a preferred example II, as shown in FIG. 6, the difference between the example and the preferred example I is: the load control mechanism in the example adopts a zero-load control mechanism 7. The zero-load control mechanism 7 includes a winding drum 71, a slip rope 72 and a pulley 73, where during assembling, the winding drum is arranged in a counter-force frame 21, the pulley is connected below a cross beam 211, and one end of the slip rope is wound on the winding drum and the other end of the slip rope is connected to a temperature-controlled plate 12 after going around the pulley; at the beginning of the test, the winding drum rotates to lift the temperature-controlled plate through the pulley to enable the load on the soil sample is zero; and during the test, when the top is subjected to load due to upward frost heave of the soil, the slip rope Date Recue/Date Received 2020-08-14 is controlled to be lifted by a signal transmitted by a pressure sensor between the temperature-controlled plate and the sample, thereby ensuring that there is always no vertical load on the sample in the whole test process.
The preferred example is suitable for measuring the amount of free frost heave under the no-load condition, which is implemented according to the following steps:
(1) connect related data line and power line in good condition;
(2) sieve and dry soil to prepare soil with different water contents, place the prepared soil in a sample cylinder, perform layered compaction to a target height, prepare a target sample, and bury a temperature sensor and a stress sensor at the target height of the sample;
(3) cover the top of the sample with a waterproof and gas-insulating membrane;
(4) place a temperature-controlled plate on the waterproof and gas-insulating membrane;
(5) mount a pulley on a counter-force frame, connect a slip rope to the temperature-controlled plate, adjust the slip rope to enable the temperature-controlled plate to be in contact with the top of the sample without pressure, adjust a deformation gauge and record an initial position;
(6) set a target relative humidity and start a humidity control system;
(7) set a target temperature, start a temperature control system, circulate refrigerating fluid into the temperature-controlled plate, control a temperature, set a target temperature of a thermotank and start the thermotank;
(8) control a winding drum to work, wind the slip rope, lift the temperature-controlled plate by the slip rope to eliminate the vertical pressure on the sample, and stop lifting by the slip rope when the pressure is zero to maintain that the temperature-controlled plate is in contact with the top of the sample without pressure; and (9) start the test and begin to measure, record and store related data, where during the test, when the top is subjected to load due to upward frost heave of the soil, the slip rope is controlled to be lifted by a signal transmitted by a pressure sensor between the temperature-controlled plate and the sample, thereby ensuring that there is always no vertical load on the sample in the whole test process.
To sum up, the present invention can supply vapour to induce frost heave of coarse-grained soil and provides a test device for researching vapour supply to induce frost heave of the soil suitable for researching the frost heave characteristic of roadbed filler such as the unsaturated coarse-grained soil; the zero-load control system provides a solution of measuring the amount of free frost heave of Date Recue/Date Received 2020-08-14 the soil under the no-load condition; and the hydraulic servo control loading system enhances the measurement accuracy of an existing mechanical loading type frost heave tester. The present invention provides a method for implementing a dynamic and static loading type frost heave tester for unsaturated soil capable of supplying vapour, which has the advantages of high precision, simplicity in operation, high practicability and the like.
The above is the implementation method of the frost heave tester with vertical pressure, which can be applied to engineering practice. The amount of free frost heave under the no-load condition is an import basis for researching the frost heave characteristic of the soil and classifying the frost heave sensitivity of the geomaterial.
In a preferred example II, as shown in FIG. 6, the difference between the example and the preferred example I is: the load control mechanism in the example adopts a zero-load control mechanism 7. The zero-load control mechanism 7 includes a winding drum 71, a slip rope 72 and a pulley 73, where during assembling, the winding drum is arranged in a counter-force frame 21, the pulley is connected below a cross beam 211, and one end of the slip rope is wound on the winding drum and the other end of the slip rope is connected to a temperature-controlled plate 12 after going around the pulley; at the beginning of the test, the winding drum rotates to lift the temperature-controlled plate through the pulley to enable the load on the soil sample is zero; and during the test, when the top is subjected to load due to upward frost heave of the soil, the slip rope Date Recue/Date Received 2020-08-14 is controlled to be lifted by a signal transmitted by a pressure sensor between the temperature-controlled plate and the sample, thereby ensuring that there is always no vertical load on the sample in the whole test process.
The preferred example is suitable for measuring the amount of free frost heave under the no-load condition, which is implemented according to the following steps:
(1) connect related data line and power line in good condition;
(2) sieve and dry soil to prepare soil with different water contents, place the prepared soil in a sample cylinder, perform layered compaction to a target height, prepare a target sample, and bury a temperature sensor and a stress sensor at the target height of the sample;
(3) cover the top of the sample with a waterproof and gas-insulating membrane;
(4) place a temperature-controlled plate on the waterproof and gas-insulating membrane;
(5) mount a pulley on a counter-force frame, connect a slip rope to the temperature-controlled plate, adjust the slip rope to enable the temperature-controlled plate to be in contact with the top of the sample without pressure, adjust a deformation gauge and record an initial position;
(6) set a target relative humidity and start a humidity control system;
(7) set a target temperature, start a temperature control system, circulate refrigerating fluid into the temperature-controlled plate, control a temperature, set a target temperature of a thermotank and start the thermotank;
(8) control a winding drum to work, wind the slip rope, lift the temperature-controlled plate by the slip rope to eliminate the vertical pressure on the sample, and stop lifting by the slip rope when the pressure is zero to maintain that the temperature-controlled plate is in contact with the top of the sample without pressure; and (9) start the test and begin to measure, record and store related data, where during the test, when the top is subjected to load due to upward frost heave of the soil, the slip rope is controlled to be lifted by a signal transmitted by a pressure sensor between the temperature-controlled plate and the sample, thereby ensuring that there is always no vertical load on the sample in the whole test process.
To sum up, the present invention can supply vapour to induce frost heave of coarse-grained soil and provides a test device for researching vapour supply to induce frost heave of the soil suitable for researching the frost heave characteristic of roadbed filler such as the unsaturated coarse-grained soil; the zero-load control system provides a solution of measuring the amount of free frost heave of Date Recue/Date Received 2020-08-14 the soil under the no-load condition; and the hydraulic servo control loading system enhances the measurement accuracy of an existing mechanical loading type frost heave tester. The present invention provides a method for implementing a dynamic and static loading type frost heave tester for unsaturated soil capable of supplying vapour, which has the advantages of high precision, simplicity in operation, high practicability and the like.
11 Date Recue/Date Received 2020-08-14
Claims (10)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A multi-load-mode frost heave tester for unsaturated soil, comprising a sample storage system, a load control system, a humidity control system, a temperature control system and a thermotank, wherein the sample storage system comprises a sample cylinder and a temperature-controlled plate, a gas inlet being formed at the bottom end of the sample cylinder, a cavity being formed in the temperature-controlled plate, a waterproof and gas-insulating membrane being arranged outside the bottom of the cavity, a liquid inlet and a liquid outlet being formed at the top of the cavity, the temperature-controlled plate being arranged in the top end of the sample cylinder, and the sample cylinder being placed in the thermotank;
the load control system comprises a counter-force frame and a load control mechanism, the load control mechanism being arranged in the counter-force frame and connected to the temperature¨controlled plate, and the counter-force frame erecting in the thermotank;
the temperature control system is communicated with the gas inlet of the sample cylinder; and an output port of the temperature control system is communicated with the liquid inlet on the temperature-controlled plate and an inlet of the temperature control system is communicated with the liquid outlet on the temperature-controlled plate.
the load control system comprises a counter-force frame and a load control mechanism, the load control mechanism being arranged in the counter-force frame and connected to the temperature¨controlled plate, and the counter-force frame erecting in the thermotank;
the temperature control system is communicated with the gas inlet of the sample cylinder; and an output port of the temperature control system is communicated with the liquid inlet on the temperature-controlled plate and an inlet of the temperature control system is communicated with the liquid outlet on the temperature-controlled plate.
2. The multi-load-mode frost heave tester for unsaturated soil according to claim 1, wherein the sample cylinder has two open ends, temperature sensors and stress sensors are buried at different heights of a sample in the sample cylinder, and a perforated plate is arranged at the inner bottom of the sample cylinder.
3. The multi-load-mode frost heave tester for unsaturated soil according to claim 2, wherein the sample storage system further comprises a base, positioning cylinders and a heat-insulating cylinder;
the base is an annular base, and a hygrothermograph and an electric heating rod are arranged on the inner wall of the base; a perforated plate is arranged on a top surface of each positioning cylinder, and the positioning cylinders are coaxially arranged on the base; the sample cylinder sleeves the positioning cylinders, and a sealing ring is arranged between the sample cylinder and the positioning cylinders; and the sample cylinder is coated with the heat-insulating cylinder.
the base is an annular base, and a hygrothermograph and an electric heating rod are arranged on the inner wall of the base; a perforated plate is arranged on a top surface of each positioning cylinder, and the positioning cylinders are coaxially arranged on the base; the sample cylinder sleeves the positioning cylinders, and a sealing ring is arranged between the sample cylinder and the positioning cylinders; and the sample cylinder is coated with the heat-insulating cylinder.
4. The multi-load-mode frost heave tester for unsaturated soil according to claim 1, wherein the counter-force frame is door-shaped and comprises a cross beam and a pair of columns; the columns each are provided with threaded sections; through holes are formed at the two ends of the cross beam; and the cross beam is engaged with the two columns and is locked through a pair of nuts.
5. The multi-load-mode frost heave tester for unsaturated soil according to claim 4, wherein the load control mechanism comprises a hydraulic servo control device and an axial force sensor; the hydraulic servo control device is mounted below the cross beam and a loading end of the hydraulic servo control device is connected to the temperature-controlled plate; and the axial force sensor is arranged on the temperature-controlled plate.
6. The multi-load-mode frost heave tester for unsaturated soil according to claim 4, wherein the load control mechanism comprises a winding drum, a slip rope and a pulley; the winding drum is arranged in the counter-force frame, the pulley is connected below the cross beam, and one end of the slip rope is wound on the winding drum and the other end of the slip rope is connected to the temperature-controlled plate after going around the pulley; and the winding drum rotates to lift the temperature-controlled plate through the pulley, which can ensure that there is always no load on the soil sample during the test.
7. The multi-load-mode frost heave tester for unsaturated soil according to claim 1, wherein the humidity control system comprises an environmental box, an air stirrer, a heater, a cooler, a blower fan, a humidifier and a dehumidifier; an air outlet and a return air inlet are formed in a side wall of the environmental box, the blower fan is arranged at the air outlet, and an output end of the blower fan is communicated with the gas inlet of the sample cylinder through a steam tube, and the other end of the steam tube is communicated with the return air inlet; a pair of through holes are formed in a bottom surface of the environmental box and are respectively communicated with the humidifier and the dehumidifier; the air stirrer is hung on a top surface of the environmental box;
and the heater and the cooler are arranged on a bottom surface of the environmental box.
and the heater and the cooler are arranged on a bottom surface of the environmental box.
8. The multi-load-mode frost heave tester for unsaturated soil according to claim 1, wherein the temperature control system may set a constant temperature or a sinusoidal variation temperature;
the output port of the temperature control system is communicated with the liquid inlet of the temperature-controlled plate; a reflux inlet of the temperature control system is communicated with the liquid outlet of the temperature-controlled plate; and the temperature control system controls a temperature through circulation of refrigerating fluid.
the output port of the temperature control system is communicated with the liquid inlet of the temperature-controlled plate; a reflux inlet of the temperature control system is communicated with the liquid outlet of the temperature-controlled plate; and the temperature control system controls a temperature through circulation of refrigerating fluid.
9. A method for testing frost heave of unsaturated soil under negative dynamic and static load conditions, wherein the method is implemented by the frost heave tester as defined in claim 5 and comprises the following steps:
(1) preparing a soil sample and placing the soil sample in a sample cylinder;
(2) covering the top of the sample with a waterproof and gas-insulating membrane;
(3) placing a temperature-controlled plate on the waterproof and gas-insulating membrane;
(4) mounting a hydraulic servo control device on a counter-force frame to enable a force applying end to be in contact with the temperature-controlled plate, and recording an initial position;
(5) setting a target relative humidity and starting a humidity control system;
(6) setting a target temperature, starting a temperature control system, circulating refrigerating fluid into the temperature-controlled plate, controlling a temperature, setting a target temperature of a thermotank and starting the thermotank;
(7) setting a vertical pressure on a target and starting the hydraulic servo control device; and (8) starting to measure, recording and storing related data, drawing a soil temperature distribution curve according to the measured soil temperature to obtain a frozen depth, and obtaining a frost heave rate through the amount of frost heave measured by a deformation gauge.
(1) preparing a soil sample and placing the soil sample in a sample cylinder;
(2) covering the top of the sample with a waterproof and gas-insulating membrane;
(3) placing a temperature-controlled plate on the waterproof and gas-insulating membrane;
(4) mounting a hydraulic servo control device on a counter-force frame to enable a force applying end to be in contact with the temperature-controlled plate, and recording an initial position;
(5) setting a target relative humidity and starting a humidity control system;
(6) setting a target temperature, starting a temperature control system, circulating refrigerating fluid into the temperature-controlled plate, controlling a temperature, setting a target temperature of a thermotank and starting the thermotank;
(7) setting a vertical pressure on a target and starting the hydraulic servo control device; and (8) starting to measure, recording and storing related data, drawing a soil temperature distribution curve according to the measured soil temperature to obtain a frozen depth, and obtaining a frost heave rate through the amount of frost heave measured by a deformation gauge.
10. A method for testing the amount of free frost heave of unsaturated soil, wherein the method is implemented by the frost heave tester as defined in claim 6 and comprises the following steps:
(1) preparing a soil sample and placing the soil sample in a sample cylinder;
(2) covering the top of the sample with a waterproof and gas-insulating membrane;
(3) placing a temperature-controlled plate on the waterproof and gas-insulating membrane;
(4) mounting a pulley on a counter-force frame;
(5) connecting a slip rope to the temperature-controlled plate, rotating a winding drum and adjusting the slip rope to enable the temperature-controlled plate to be in contact with the top of the sample without pressure;
(6) starting a humidity control system to supply vapour;
(7) starting a temperature control device and enabling refrigerating fluid to enter the temperature-controlled plate to realize temperature control; and (8) controlling rotation of the winding drum and lifting the slip rope until the vertical pressure on the sample is zero, enabling the temperature-controlled plate to be in contact with the top of the sample and performing a zero-load frost heave test, where during the test, when the top is subjected to load due to upward frost heave of the soil, the slip rope is controlled to be continuously lifted by a signal transmitted by a pressure sensor between the temperature-controlled plate and the sample, thereby ensuring that there is always no vertical load on the sample in the whole test process.
(1) preparing a soil sample and placing the soil sample in a sample cylinder;
(2) covering the top of the sample with a waterproof and gas-insulating membrane;
(3) placing a temperature-controlled plate on the waterproof and gas-insulating membrane;
(4) mounting a pulley on a counter-force frame;
(5) connecting a slip rope to the temperature-controlled plate, rotating a winding drum and adjusting the slip rope to enable the temperature-controlled plate to be in contact with the top of the sample without pressure;
(6) starting a humidity control system to supply vapour;
(7) starting a temperature control device and enabling refrigerating fluid to enter the temperature-controlled plate to realize temperature control; and (8) controlling rotation of the winding drum and lifting the slip rope until the vertical pressure on the sample is zero, enabling the temperature-controlled plate to be in contact with the top of the sample and performing a zero-load frost heave test, where during the test, when the top is subjected to load due to upward frost heave of the soil, the slip rope is controlled to be continuously lifted by a signal transmitted by a pressure sensor between the temperature-controlled plate and the sample, thereby ensuring that there is always no vertical load on the sample in the whole test process.
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| CN201911293622.7 | 2019-12-16 | ||
| CN201911293622.7A CN110954573B (en) | 2019-12-16 | 2019-12-16 | Unsaturated soil frost heaving instrument with multiple loading modes and frost heaving amount testing method |
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| CN112649262A (en) * | 2020-12-07 | 2021-04-13 | 江苏科技大学 | Sample preparation and demolding device and sample preparation method for multiple groups of rock and soil samples |
| CN112858138A (en) * | 2021-03-04 | 2021-05-28 | 吉林大学 | Seepage test device and method for porous medium freeze thawing process |
| CN113565529B (en) * | 2021-07-24 | 2023-10-27 | 郑州大学 | Rear buried type testing device for frost heaving pressure of segment lining and mounting method |
| CN114018970B (en) * | 2021-11-08 | 2024-02-09 | 哈尔滨工业大学 | Multifunctional freezing low-temperature model test device for cold region |
| CN114923947B (en) * | 2022-05-18 | 2024-07-12 | 中南大学 | Frost heave test device and method for unsaturated coarse-grained soil |
| CN116539519A (en) * | 2023-07-07 | 2023-08-04 | 哈尔滨工业大学 | Dynamic measuring device and system for internal consumption of structural sample |
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| CN101699284A (en) * | 2009-03-30 | 2010-04-28 | 刘建坤 | Frozen-soil experiment system capable of applying dynamic load |
| CN101806686B (en) * | 2010-03-26 | 2012-06-20 | 中国科学院地质与地球物理研究所 | Testing method used for measuring repeated expansion , shrinkage and deformation of soil sample |
| CN102004053B (en) * | 2010-09-20 | 2012-06-27 | 中国科学院寒区旱区环境与工程研究所 | Temperature-controllable portable multifunctional pressure chamber |
| CN202216953U (en) * | 2011-09-21 | 2012-05-09 | 南京林业大学 | Soil frost heaving thaw settlement test instrument based on thermoelectric refrigeration control |
| CN104316671B (en) * | 2014-10-10 | 2016-05-18 | 同济大学 | A kind of experimental rig that measures artificial freeze thawing soil frost-heave force and frost heaving amount |
| CN104655823B (en) * | 2015-02-12 | 2016-03-30 | 中南大学 | A kind of frost heaving meter |
| CN104990947B (en) * | 2015-07-22 | 2018-04-20 | 哈尔滨工业大学 | A kind of bilateral frost heave test device and test method for porous material |
| CN205157556U (en) * | 2015-12-02 | 2016-04-13 | 长安大学 | Soil body frozen -heave factor and melting sinks coefficient and jointly surveys test instrument |
| CN105372284A (en) * | 2015-12-04 | 2016-03-02 | 长安大学 | Device and method for testing frost heaving parameter of soil under standard compaction work |
| CN106644750B (en) * | 2016-12-07 | 2019-07-05 | 凌贤长 | Open system Thawing soil sound triaxial tester |
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