Freeze-thaw creep measuring device for salinized soil

Abstract

The invention discloses a saline soil freeze-thaw creep measurement device, and particularly relates to the technical field of saline soil creep measurement, the saline soil freeze-thaw creep measurement device comprises a temperature control water bath device, a triaxial pressure chamber, a data acquisition assembly and a pressure volume controller, and a saline soil sample coated by a rubber membrane is placed in the triaxial pressure chamber; the axial loading device is used for applying a load to the salinized soil sample, and the confining pressure device can pressurize the salinized soil sample to enable the salinized soil sample to reach a confining pressure condition; the temperature control water bath device is used for conveying water bath circulating liquid with specific temperature into the triaxial pressure chamber; the data acquisition assembly is used for monitoring the temperature, displacement, pore water pressure and axial force of the salinized soil sample; the pressure volume controller can control the temperature, the confining pressure, the axial force and the applied axial load of the salinized soil sample according to the data acquired by the data acquisition assembly. According to the invention, the physical and mechanical property changes of the salinized soil under the freezing and thawing cycle effect can be researched, and the freezing and thawing creep measurement efficiency and accuracy of the salinized soil can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of saline soil creep measurement, in particular to a saline soil freeze-thaw creep measurement device. Background Art

[0002] Saline soil refers to various salinized lands. In seasonally frozen areas, the salt in the saline soil crystallizes when the temperature drops, resulting in salt swelling. At the same time, when the water in the soil freezes, frost heave occurs. The combined effect of salt swelling and frost heave can cause road pavement defects such as bulging and cracking. When the temperature rises in spring, the salt crystals in the saline soil dissolve, the soil strength decreases, and under the action of vehicle loads, the road surface is prone to muddying. Muddying can soften the road surface and even form mud, causing problems such as vehicles getting stuck.

[0003] At present, the influence of low temperature on the creep characteristics of saline soil is often ignored in conventional saline soil creep tests, resulting in unstable and non-uniform settlement of soil in foundation treatment, water conservancy projects and road and bridge projects, which has a series of impacts on engineering construction and protection. Summary of the invention

[0004] The purpose of the present invention is to provide a saline soil freeze-thaw creep measurement device to solve the problems existing in the above-mentioned prior art, to study the changes in the physical and mechanical properties of saline soil under the action of freeze-thaw cycles, and to improve the efficiency and accuracy of saline soil freeze-thaw creep measurement.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The invention provides a saline soil freeze-thaw creep measurement device, comprising a temperature-controlled water bath device, a triaxial pressure chamber, a data acquisition component and a pressure volume controller, wherein the triaxial pressure chamber comprises a shell and an axial loading device and a confining pressure device located in the shell, a saline soil sample wrapped by a rubber film is placed at the center of the shell, and an annular gap is provided between the rubber film and the inner side wall of the shell, the axial loading device is located at the top of the saline soil sample and is used to apply a load to the saline soil sample, and the confining pressure device can pressurize the saline soil sample to achieve a confining pressure condition; the temperature-controlled water bath device is connected to the shell and is used to transport a water bath circulating fluid of a specific temperature to the annular gap; the data acquisition component is placed in the shell and is used to monitor the temperature, displacement, pore water pressure and axial force of the saline soil sample; the data acquisition component, the temperature-controlled liquid bath device, the axial loading device and the confining pressure device are all connected to the pressure volume controller by signal, and the pressure volume controller can control the temperature, confining pressure, axial force and applied axial load of the saline soil sample according to the data collected by the data acquisition component.

[0007] Preferably, the data acquisition component includes a temperature sensor, an underwater load sensor, a displacement sensor and a pore water pressure sensor.

[0008] Preferably, the temperature sensor, the underwater load sensor and the pore water pressure sensor are all arranged in the saline soil sample to monitor the temperature, axial force and pore water pressure of the saline soil sample.

[0009] Preferably, the displacement sensor is arranged on the axial loading device, and the displacement sensor is used to monitor the displacement value generated when the axial loading device applies a load to the saline soil sample.

[0010] Preferably, the temperature-controlled water bath device comprises a water bath circulating fluid and a temperature control device for controlling the temperature of the water bath circulating fluid, and the temperature control device can control the temperature of the water bath circulating fluid to be -30-50°C.

[0011] Preferably, the water bath circulating fluid is silicone oil.

[0012] Preferably, it also includes a salt data acquisition instrument and a computer, the computer having a triaxial test software, the pressure volume controller is connected to the data acquisition instrument, and is used to transmit the data collected by the pressure volume controller to the data acquisition instrument, the data acquisition instrument is connected to the computer, and the triaxial test software can analyze and process the data in the data acquisition instrument.

[0013] Preferably, a thermal insulation layer is provided outside the triaxial pressure chamber.

[0014] Compared with the prior art, the present invention has achieved the following technical effects:

[0015] The invention provides a saline soil freeze-thaw creep measuring device. The temperature of the saline soil sample can be adjusted by a water bath circulating fluid of a temperature-controlled water bath device, so that the saline soil sample can repeatedly undergo a freezing and thawing process. In the freezing and thawing process, a creep test is performed on the saline soil sample through a triaxial pressure chamber, a data acquisition component and a pressure-volume controller, and the changes in the physical, mechanical and chemical properties of the saline soil under the action of the freeze-thaw cycle are measured. The device is used to study the creep characteristics and laws of the saline soil during the freeze-thaw cycle changes, simulate the mechanical behavior and deformation process of the saline soil sample during the freeze-thaw cycle through numerical calculation, predict the freeze-thaw creep characteristics of the saline soil under different conditions, and provide theoretical support for engineering design and numerical analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 This is a schematic diagram of the structure of the freeze-thaw creep measurement device for saline soil.

[0018] In the figure: 1-temperature controlled water bath device; 2-water bath circulating fluid inlet pipeline; 3-water bath circulating fluid outlet pipeline; 4-shell; 5-saline soil sample; 6-annular gap; 7-insulation layer; 8-axial loading device; 9-temperature sensor; 10-underwater load sensor; 11-pore water pressure sensor; 12-displacement sensor; 13-pressure volume controller; 14-data acquisition instrument; 15-computer. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The purpose of the present invention is to provide a saline soil freeze-thaw creep measurement device to solve the problems existing in the above-mentioned prior art, to study the changes in the physical and mechanical properties of saline soil under the action of freeze-thaw cycles, and to improve the efficiency and accuracy of saline soil freeze-thaw creep measurement.

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] The present invention provides a device for measuring freeze-thaw creep of saline soil. Figure 1As shown, it includes a temperature-controlled water bath device 1, a triaxial pressure chamber, a data acquisition component and a pressure-volume controller 13. The triaxial pressure chamber includes a shell 4 and an axial loading device 8 and a confining pressure device located in the shell 4. A saline soil sample 5 wrapped by a rubber membrane is placed at the center of the shell 4, and an annular gap 6 is provided between the rubber membrane and the inner wall of the shell 4. The axial loading device 8 is located at the top of the saline soil sample 5 and is used to apply a load to the saline soil sample 5. The confining pressure device can pressurize the saline soil sample 5 to achieve the confining pressure condition; the temperature-controlled water bath device 1 is connected to the shell 4 and is used to transport a water bath circulating fluid with a specific temperature to the annular gap 6; the data acquisition component is placed in the shell 4 and is used to monitor the temperature, displacement, pore water pressure and axial force of the saline soil sample 5; the data acquisition component, the temperature-controlled liquid bath device, the axial loading device 8 and the confining pressure device are all connected to the pressure-volume controller 13 by signal, and the pressure-volume controller 13 can control the temperature, confining pressure, axial force and applied axial load of the saline soil sample 5 according to the data collected by the data acquisition component. The temperature-controlled water bath device 1 is connected to the triaxial pressure chamber through a water bath circulating liquid inlet pipe 2 and a water bath circulating liquid outlet pipe 3, and both the water bath circulating liquid inlet pipe 2 and the water bath circulating liquid outlet pipe 3 are heat-insulating pipes to ensure temperature stability. The water bath circulating liquid of the temperature-controlled water bath device 1 can adjust the temperature of the saline soil sample 5, so that the saline soil sample 5 can repeatedly undergo freezing and thawing processes, and during the freezing and thawing process, the saline soil sample 5 is subjected to a creep test through the triaxial pressure chamber, the data acquisition component and the pressure-volume controller 13, and the changes in the physical, mechanical and chemical properties of the saline soil under the action of freeze-thaw cycles are measured, so as to study the creep characteristics and laws of the saline soil during freeze-thaw cycle changes, simulate the mechanical behavior and deformation process of the saline soil sample 5 during the freeze-thaw cycle through numerical calculation, predict the freeze-thaw creep characteristics of the saline soil under different conditions, and provide theoretical support for engineering design and numerical analysis. The pressure volume controller 13 includes a microprocessor, a stepper motor, a gearbox, a hydraulic cylinder and a pressure sensor. The liquid (usually airless water) in the hydraulic cylinder is pressurized and displaced by moving the piston. The piston is connected to one end of the screw rod, the nut is fixedly connected to the hydraulic cylinder, the nut is threadedly connected to the screw rod, and the other end of the screw rod is connected to the stepper motor and the gearbox that reciprocate on the linear guide rail. The pressure sensor is connected to the internal space of the hydraulic cylinder for real-time monitoring of the output pressure value. The microprocessor starts the stepper motor according to the instruction, the stepper motor drives the gearbox, the gearbox drives the screw rod to rotate, and the screw rod pushes the piston to move and compress the liquid (usually airless water) in the cylinder, so that the liquid (usually airless water) produces a volume change, thereby generating a continuous pressure. The pressure sensor feeds back the current pressure value to the microprocessor, so that the microprocessor can control the working state of the motor to reach the target pressure value.

[0023] In the embodiment of the present invention, it is further preferred that the data acquisition component includes a temperature sensor 9, an underwater load sensor 10, a displacement sensor 12 and a pore water pressure sensor 11. The temperature sensor 9, the underwater load sensor 10 and the pore water pressure sensor 11 are all arranged in the saline soil sample 5 to monitor the temperature, axial force and pore water pressure of the saline soil sample 5. The displacement sensor 12 is arranged on the axial loading device 8, and the displacement sensor 12 is used to monitor the displacement value generated when the axial loading device 8 applies a load to the saline soil sample 5. The temperature sensor 9 is used to test the temperature state of the saline-alkali soil sample during the freeze-thaw change process; the built-in underwater load sensor 10 has a range of not less than 25kN and an accuracy of not less than 0.1% of the full scale, and is used to directly measure the axial force of the saline-alkali soil sample; a 25mm linear displacement sensor 12 is used to measure the axial deformation of the saline-alkali soil sample, and the accuracy is not less than 0.1% of the full scale; the range selection of the pore water pressure sensor 11 generally corresponds to the maximum confining pressure value adopted, and the accuracy is 0.1% of the full scale.

[0024] In the embodiment of the present invention, it is further preferred that the temperature-controlled water bath device 1 includes a water bath circulating fluid and a temperature control device for controlling the temperature of the water bath circulating fluid, and the temperature control device can control the temperature of the water bath circulating fluid to -30-50°C, the temperature control resolution is 0.01°C, and the global temperature control accuracy is ±0.1°C, which can improve the temperature test accuracy. The temperature-controlled water bath device 1 adopts PID temperature control technology, and can set the freezing temperature and melting temperature, as well as the number of freeze-thaw cycles (usually ranging from one to dozens of times) according to demand. The freeze-thaw cycle process is to first keep the saline soil sample 5 at the set freezing temperature for a certain period of time (such as 12-24 hours) to fully freeze the soil sample, and then keep it in the set melting temperature environment for a certain period of time (such as 12-24 hours) to allow the soil sample to completely melt. After the freeze-thaw cycle, the water content of the soil sample may change due to water migration. The volume will also expand or shrink. Generally, saline soil will expand in volume when frozen, which is due to the formation of ice crystals. After multiple freeze-thaw cycles, the particle composition of the soil sample may change due to the loss or agglomeration of fine particles, resulting in an increase in the porosity of the soil. Freeze-thaw cycles affect the distribution and migration of salt in the soil. During the freezing process, salt migrates with water and gathers at the freezing front, and redistributes when it melts. Therefore, the freeze-thaw creep measurement device for saline soil can be used to study the changes in the physical, mechanical and chemical properties of saline soil under the action of freeze-thaw cycles, which can provide a deep understanding of the freeze-thaw characteristics of saline soil and provide a scientific basis for engineering design, construction and maintenance.

[0025] In the embodiment of the present invention, it is further preferred that the water bath circulating fluid is silicone oil, which has a low freezing point and can still maintain good fluidity in a low temperature environment and effectively conduct heat.

[0026] In the embodiment of the present invention, it is further preferred that the freeze-thaw creep measurement device for saline soil also includes a data acquisition instrument 14 and a computer 15, the computer 15 has a triaxial test software, the pressure volume controller 13 is connected to the data acquisition instrument 14, and is used to transmit the data collected by the pressure volume controller 13 to the data acquisition instrument 14, the data acquisition instrument 14 is connected to the computer 15, and the triaxial test software can analyze and process the real-time data in the data acquisition instrument 14. The data acquisition instrument 14 adopts a USB 8-channel data acquisition instrument 14, which is specially used for sensors that may be used in geotechnical laboratories. The device provides eight completely independent channels and samples ultra-high resolution 24-bit data at the same time. The triaxial test software uses GDSLAB software, which can integrate existing and existing new test hardware to provide data acquisition and control for standard and advanced tests. At the same time, GDSLAB software can collect data from existing hardware and then replay the data through GDSLAB REPORTS software. It can be used to complete triaxial tests and data acquisition that meet international standards, and generate reports that meet national standards. The operator selects the test type from the menu (e.g. UU, CU, multi-stage, stress path, etc.) and then enters the test parameters such as confining pressure, back pressure, test rate and test termination conditions. The system automatically processes all data stored in the file.

[0027] It is further preferred in the embodiment of the present invention that a heat-insulating layer 7 is provided outside the triaxial pressure chamber.

[0028] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A device for measuring freeze-thaw creep of saline soil, characterized by: The invention comprises a temperature-controlled water bath device, a triaxial pressure chamber, a data acquisition component and a pressure-volume controller. The triaxial pressure chamber comprises a shell and an axial loading device and a confining pressure device located in the shell. A saline soil sample covered by a rubber membrane is placed at the center of the shell, and an annular gap is provided between the rubber membrane and the inner side wall of the shell. The axial loading device is located at the top of the saline soil sample and is used to apply a load to the saline soil sample. The confining pressure device can pressurize the saline soil sample to achieve a confining pressure condition. The temperature-controlled water bath device is connected to the shell and is used to transport a water bath circulating fluid of a specific temperature to the annular gap. The data acquisition component is placed in the shell and is used to monitor the temperature, displacement, pore water pressure and axial force of the saline soil sample. The data acquisition component, the temperature-controlled liquid bath device, the axial loading device and the confining pressure device are all connected to the pressure-volume controller by signal. The pressure-volume controller can control the temperature, confining pressure, axial force and applied axial load of the saline soil sample according to the data collected by the data acquisition component.

2. The device for measuring freeze-thaw creep of saline soil according to claim 1, characterized in that: The data acquisition component includes a temperature sensor, an underwater load sensor, a displacement sensor and a pore water pressure sensor.

3. The device for measuring freeze-thaw creep of saline soil according to claim 2, characterized in that: The temperature sensor, the underwater load sensor and the pore water pressure sensor are all arranged in the saline soil sample and are used to monitor the temperature, axial force and pore water pressure of the saline soil sample.

4. The device for measuring freeze-thaw creep of saline soil according to claim 2, characterized in that: The displacement sensor is arranged on the axial loading device, and is used to monitor the displacement value generated when the axial loading device applies a load to the saline soil sample.

5. The device for measuring freeze-thaw creep of saline soil according to claim 1, characterized in that: The temperature-controlled water bath device comprises a water bath circulating fluid and a temperature control device for controlling the temperature of the water bath circulating fluid. The temperature control device can control the temperature of the water bath circulating fluid to be -30-50°C.

6. The device for measuring freeze-thaw creep of saline soil according to claim 1, characterized in that: The water bath circulating fluid is silicone oil.

7. The device for measuring freeze-thaw creep of saline soil according to claim 1, characterized in that: It also includes a salt data acquisition instrument and a computer. The computer has a three-axis test software. The pressure volume controller is connected to the data acquisition instrument to transmit the data collected by the pressure volume controller to the data acquisition instrument. The data acquisition instrument is connected to the computer. The three-axis test software can analyze and process the data in the data acquisition instrument.

8. The device for measuring freeze-thaw creep of saline soil according to claim 1, characterized in that: A thermal insulation layer is arranged outside the triaxial pressure chamber.

Images