Simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil

Abstract

The invention provides a simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil. The simple evaporation system comprises a weighing sensor, a sample preparation cylinder outer cylinder, a soil sample, a chassis, a first tensiometer, a second tensiometer, a third tensiometer, a wireless transmitting collector, a power transmitting module, a power receiving module, a transparent organic glass box and an evaporation control system. According to the simple evaporation system for rapidly measuring the hydraulic parameters of the unsaturated soil, the initial saturation state of the bottom of a sample can be accurately judged according to the measured value of the bottom tensiometer, and the measurement and calculation errors are reduced by comparing the measured values of the bottom plate tensiometer with the measured values of the other two height tensiometers; a temperature and humidity control system is adopted to accurately and actively control the evaporation rate of the sample surface; the soil sample and the sample preparation cylinder are connected by adopting a special glue solution, and the soil sample can be evaporated in a thermal environment and cannot be separated from the sample preparation cylinder under the action of strong cementation, so that the overall structure uniformity of the soil sample in the whole test process is maintained.

Description

Technical Field

[0001] The invention relates to the technical field of geotechnical engineering tests, and in particular to a simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil. Background Art

[0002] The accurate determination of hydraulic parameters of unsaturated soil is an important basis for seepage calculation and analysis in geotechnical engineering. Hydraulic parameters of unsaturated soil usually include soil-water characteristic curve and permeability coefficient curve. Usually, the method for determining hydraulic parameters of unsaturated soil is to use pressure plate instrument and other equipment to grade the matrix suction of unit sample, and determine the soil-water characteristic curve of soil after the suction reaches equilibrium; and use permeameter and other equipment to measure the unsaturated permeability coefficient of unit sample. However, this method usually needs to wait for a long time for suction equilibrium to obtain hydraulic parameters of unsaturated soil, which is time-consuming and laborious, and the soil-water characteristic curve and unsaturated permeability system of soil sample need to be measured separately in two equipments. In order to shorten the test time, a simple evaporation method has been developed in recent years. The simple evaporation method is usually carried out by using a simple evaporation system. Sensors such as tensiometers and weighing balances are installed in the simple evaporation system to measure the changes of soil matrix suction and water content in real time. Because the simple evaporation method has a short test time (for example, clay can complete the evaporation test within 10 days under normal circumstances), and the soil-water characteristic curve and unsaturated permeability coefficient can be obtained simultaneously in the same simple evaporation system, this method has been increasingly favored by scholars studying unsaturated soil in recent years.

[0003] At present, the existing simple evaporation system usually installs two tensiometers at different heights of the sample, and then places the sample tube on a weighing balance for free evaporation. During the evaporation process, the readings of the weighing balance are recorded regularly to infer the changes in the moisture content of the sample. Then, the suction value of the sample during the evaporation process is obtained through the tensiometer data. Finally, the soil-water characteristic curve of the sample can be drawn through the sample moisture content and suction values ​​recorded at different times, and the unsaturated permeability coefficient of the sample can be obtained by calculation.

[0004] However, the existing simple evaporation system has four defects: First, when using the simple evaporation method, it is assumed that the initial state of the bottom of the sample is a completely saturated state, and the moisture content (suction) is linearly distributed along the height of the sample, and then the sample begins to evaporate freely after being placed in the simple evaporation system. However, the existing simple evaporation system only installs tensiometers at two heights of the sample, and can only measure the suction values ​​of the sample at these two heights, and cannot determine the initial saturation state of the bottom of the sample, nor can it determine whether the initial suction values ​​measured by the two tensiometers are linearly related to the suction values ​​at the bottom of the sample; second, the existing simple evaporation system cannot actively control the evaporation rate of the sample. If the evaporation rate of the test is not controlled, on the one hand, the test time will be uncontrollable, and on the other hand, the measurement error of samples of different soil types will increase, because if the same evaporation rate is used for different soils, the inside of the sample soil will be hot. Under the action of gradient, cracks are easily generated, resulting in uneven internal moisture distribution, which affects the continuity of the test data and increases the calculation error; third, in the existing simple evaporation system, during the evaporation of the soil sample, the surrounding walls of the soil sample will be separated from the inner wall of the sample preparation tube under the action of the thermal environment, forming shrinkage cracks, which will cause huge test errors; fourth, the tensiometer in the existing simple evaporation system needs to be connected to a power source other than the weighing balance through a cable. Since the cable and the weighing balance cannot be separated, the weighing balance reading will be affected during the evaporation of the sample, thereby affecting the test measurement accuracy. In general, the existing simple evaporation system has problems such as the inability to determine the hydraulic gradient of the sample in the initial state, the inability to actively control the evaporation rate of the sample, the easy separation of the soil sample and the sample preparation tube wall during the evaporation process to produce shrinkage cracks, and the sensor cable affecting the measurement accuracy, which greatly increases the measurement error of the hydraulic parameters of unsaturated soil.

[0005] Therefore, it is necessary to provide a simple evaporation system for quickly measuring the hydraulic parameters of unsaturated soil to solve the above technical problems. Summary of the invention

[0006] The present invention provides a simple evaporation system for quickly measuring the hydraulic parameters of unsaturated soil, which solves the problems of the existing simple evaporation system, such as the inability to determine the hydraulic gradient of the sample in the initial state, the inability to actively control the evaporation rate of the sample, the easy separation of the soil sample and the sample preparation tube wall during the evaporation process to produce shrinkage cracks, and the influence of the sensor cable on the measurement accuracy, which greatly increases the measurement error of the hydraulic parameters of unsaturated soil.

[0007] In order to solve the above technical problems, the present invention provides a simple evaporation system for quickly measuring the hydraulic parameters of unsaturated soil, comprising: a weighing sensor, an outer cylinder of a sample preparation cylinder, a soil sample, a chassis, a first tension meter, a second tension meter, a third tension meter, a wireless transmission collector, a power transmission module, a power receiving module, a transparent organic glass box and an evaporation control system; The weighing sensor is fixedly installed at the bottom of the transparent organic glass box, the chassis is arranged on the top of the weighing sensor, the outer cylinder of the sample preparation tube is placed on the chassis, the soil sample is arranged inside the outer cylinder of the sample preparation tube, and glue is arranged between the soil sample and the outer cylinder of the sample preparation tube; The evaporation control system is arranged at the top inside the transparent organic glass box, the first tension meter is arranged in the middle of the chassis, the second tension meter is arranged on one side of the outer surface of the outer cylinder of the sample preparation tube, and the third tension meter is arranged on the other side of the outer surface of the outer cylinder of the sample preparation tube. One side of the first tension meter, the second tension meter and the third tension meter are all fixedly connected with tension meter cables, the wireless transmitting collector is arranged on one side of the tension meter cables, one end of the three tension meter cables is commonly fixedly connected with cables, the power receiving module is arranged at one end of the cables, the power transmitting module is arranged on one side of the power receiving module, one side of the power transmitting module is fixedly connected with a power transmitting module wire, a bracket is arranged on the surface of the power transmitting module wire, and a fixed support is fixedly connected to the bottom of the bracket; The evaporation control system comprises an evaporation control system bottom plate, a supporting metal plate, heat dissipation holes, an evaporation control chamber, a fan, a heater, a humidifier and a temperature and humidity sensor.

[0008] Preferably, a spiral groove is provided on the surface of the top of the chassis, and a water discharge and inlet hole is opened on one side of the surface of the chassis.

[0009] Preferably, the supporting metal plate is arranged at the bottom of the evaporation control system base plate, the heat dissipation holes are opened at the bottom of the supporting metal plate, the evaporation control chamber is arranged at the top of the evaporation control system base plate, and the fan, heater, humidifier and temperature and humidity sensor are respectively arranged at the top inside the evaporation control chamber.

[0010] Preferably, the outer cylinder of the sample preparation tube is a hollow cylinder, and an external thread is provided at the bottom for matching and installing with the chassis. The inner diameter of the outer cylinder of the sample preparation tube is larger than the outer diameter of the soil sample. The gap distance between the inner wall of the outer cylinder of the sample preparation tube and the soil sample is 2~5mm. After the soil sample is prepared and saturated in the compactor and saturation cylinder, it is moved into the center position of the inner part of the outer cylinder of the sample preparation tube and placed upright.

[0011] Preferably, the material of the outer cylinder of the sample preparation cylinder is required to use metal that does not deform in a hot environment, such as stainless steel and aluminum alloy, to prevent shrinkage cracks from forming on the side walls of the soil sample during evaporation.

[0012] Preferably, the glue is specially made of epoxy resin material, which can bond with the soil sample but not flow into the pores of the soil sample, and the glue can bond well to the inner wall of the outer cylinder of the sample preparation tube. After the glue is cured, it will be bonded to the soil sample and the outer cylinder of the sample preparation tube as one. Through the bonding effect of the glue, the soil sample is prevented from separating from the side wall in a hot environment to form shrinkage cracks, thereby solving the measurement and calculation errors caused by the problem of shrinkage cracks around the soil sample.

[0013] Preferably, the upper surface of the first tensiometer is flush with the upper surface of the chassis, the bottom surface of the soil sample is located on the spiral groove of the chassis, the excess water in the soil sample due to saturation can freely drip into the spiral groove of the chassis and be discharged through the water inlet and outlet, the upper surface of the first tensiometer and the bottom surface of the soil sample are in close contact, and the initial saturation state of the bottom of the soil sample can be determined by the real-time measurement of the suction value by the first tensiometer, the second tensiometer and the third tensiometer respectively pass through the side wall openings of the outer cylinder of the sample preparation cylinder and are in close contact with the surface of the soil sample, the second tensiometer and the third tensiometer are used to measure the matrix suction at two heights during the evaporation process of the soil sample in real time, and the second tensiometer and the third tensiometer are used to measure the matrix suction at two heights during the evaporation process of the soil sample in real time. The installation positions of the third tensiometer on the soil sample are respectively at / and / positions of the soil sample height. When the suction values ​​measured by the first tensiometer, the second tensiometer and the third tensiometer are linear gradients, they can be used as the starting point for the evaporation test. The cables of the first tensiometer, the second tensiometer and the third tensiometer are all connected to the wireless transmitter collector, which is placed and fixed on the weighing sensor. The function of the wireless transmitter collector is to collect the suction data of the first tensiometer, the second tensiometer and the third tensiometer in real time, and transmit them wirelessly to the computer software for data storage through the internally arranged wireless transmission module using the Internet of Things ZigBee protocol.

[0014] Preferably, the wireless transmitting collector is connected to the power receiving module through the cable, and the power transmitting module can be suspended directly above the power receiving module by being fixed by the bracket and the fixed support. The vertical distance between the power receiving module and the power transmitting module is 2~10mm. The power transmitting module is connected to an external regulated power supply through the wire. The power transmitting module generates electromagnetic induction under the excitation of the external power supply, and uses the coil in the transmitting module to generate current, which is then wirelessly transmitted to the power receiving module. The power receiving module can simultaneously power the wireless transmitting collector, the first tension meter, the second tension meter and the third tension meter, thereby ensuring that the external power supply can provide contactless power supply to all power-requiring components on the weighing sensor in real time, solving the problem of cables affecting measurement results caused by wired power supply.

[0015] Preferably, the evaporation control system is installed and fixed at the top center position of the transparent organic glass box, the evaporation control system is cylindrical, and its outer diameter is the same as the outer diameter of the outer cylinder of the sample preparation tube, the bottom plate of the evaporation control system is located at the lower part of the evaporation control chamber, and the upper part of the evaporation control chamber is fixed to the transparent organic glass box with threads, the evaporation control chamber is a hollow cylinder, the heater and the humidifier are symmetrically installed inside the evaporation control chamber, the fan is installed between the heater and the humidifier, the fan controls the wind speed and temperature of the air discharged from the evaporation control chamber, the heater generates high temperature in the evaporation control chamber, and the humidifier controls the humidity of the air discharged from the evaporation control chamber, the fan, the heater and the humidifier are all provided with knob switches, and the knob switches are all arranged outside the transparent organic glass box, and the wind speed of the fan, the temperature and humidity of the air in the chamber can be arbitrarily adjusted by steplessly adjusting the knob switch, and the hot air generated in the evaporation control chamber can be discharged through the heat dissipation holes, and then evenly diffused to the surface of the soil sample.

[0016] Preferably, the surface of the soil sample is 30 to 150 mm away from the bottom plate of the evaporation control system. The temperature and humidity sensor is installed in the evaporation control chamber to monitor the temperature and humidity of the air in the evaporation control chamber in real time. According to the type of soil sample used in the simple evaporation test and the test duration requirements, the fan, heater and humidifier in the evaporation control chamber can be adjusted arbitrarily, and the air environment temperature and humidity required for the test are achieved through the joint action of the three, thereby accurately controlling the evaporation rate of the soil sample.

[0017] Compared with the related art, the simple evaporation system for quickly measuring the hydraulic parameters of unsaturated soil provided by the present invention has the following beneficial effects: The invention provides a simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil. By installing a tensiometer at the bottom of a sample and at two heights, the initial saturation state of the bottom of the sample can be accurately determined by the measured value of the bottom tensiometer, and the accurate starting time of the simple evaporation test can be accurately determined by comparing the measured values ​​of the bottom plate tensiometer and the tensiometers at the other two heights, thereby reducing the measurement and calculation errors. A special temperature and humidity control system is adopted to accurately and actively control the evaporation rate of the sample surface, and a suitable evaporation rate can be selected according to the characteristics of different types of soil bodies to carry out the test, thereby ensuring the matching of the thermal gradient and the moisture gradient inside the sample soil body, and avoiding the occurrence of uneven moisture distribution caused by the reflux of moisture in the sample. A special glue is adopted to connect the soil sample and the sample preparation tube, and under the strong bonding effect, the soil sample can evaporate in a hot environment without being separated from the sample preparation tube, thereby maintaining the overall structural uniformity of the soil sample during the entire test process, avoiding the occurrence of shrinkage cracks, and greatly reducing the test error. A contactless power supply system is adopted to separate the sensor cable installed on the sample from the external power supply, thereby avoiding the influence of the cable disturbance on the sample evaporation process, thereby reducing the test error. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A cross-sectional schematic diagram of a simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil provided by the present invention; Figure 2 for Figure 1 A schematic diagram of a chassis cross section is shown; Figure 3 for Figure 1 Schematic diagram of the evaporation control system shown; Figure 4 for Figure 3 The schematic diagram of the bottom plate structure of the evaporation control system shown; Figure 5 For Figure 1 The schematic diagram of the top view of the outer cylinder of the sample preparation cylinder is shown.

[0019] Numbers in the figure: 1. weighing sensor, 2. outer cylinder of sample preparation cylinder, 3. soil sample, 4. glue, 5. chassis, 501. spiral groove, 502. water inlet, 6. first tension meter, 7. second tension meter, 8. third tension meter, 9. tension meter cable, 10. wireless transmitter collector, 11. cable, 12. power transmitter module, 13. power receiver module, 14. bracket, 15. power transmitter module wire, 16. fixed support, 17. transparent plexiglass box, 18. evaporation control system, 1801. evaporation control system bottom plate, 1802. supporting metal plate, 1803. heat dissipation hole, 1804. evaporation control chamber, 1805. fan, 1806. heater, 1807. humidifier, 1808. temperature and humidity sensor. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with the accompanying drawings and implementation modes.

[0021] Please refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 ,in, Figure 1 A cross-sectional schematic diagram of a simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil provided by the present invention; Figure 2 for Figure 1 A schematic diagram of a chassis cross section is shown; Figure 3 for Figure 1 Schematic diagram of the evaporation control system shown; Figure 4 for Figure 3 The schematic diagram of the bottom plate structure of the evaporation control system shown; Figure 5 for Figure 1 A simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil comprises: a weighing sensor 1, an outer cylinder of a sample preparation tube 2, a soil sample 3, a chassis 5, a first tension meter 6, a second tension meter 7, a third tension meter 8, a wireless transmitting collector 10, a power transmitting module 12, a power receiving module 13, a transparent organic glass box 17 and an evaporation control system 18; The weighing sensor 1 is fixedly installed at the bottom of the transparent organic glass box 17, the chassis 5 is arranged on the top of the weighing sensor 1, the outer cylinder 2 of the sample preparation tube is placed on the chassis 5, the soil sample 3 is arranged inside the outer cylinder 2 of the sample preparation tube, and a glue 4 is arranged between the soil sample 3 and the outer cylinder 2 of the sample preparation tube; The evaporation control system 18 is arranged at the top inside the transparent organic glass box 17, the first tension meter 6 is arranged in the middle of the chassis 5, the second tension meter 7 is arranged on one side of the outer surface of the outer cylinder 2 of the sample preparation tube, and the third tension meter 8 is arranged on the other side of the outer surface of the outer cylinder 2 of the sample preparation tube. One side of the first tension meter 6, the second tension meter 7 and the third tension meter 8 are all fixedly connected with tension meter cables 9, the wireless transmitting collector 10 is arranged on one side of the tension meter cables 9, and one end of the three tension meter cables 9 is commonly fixedly connected with a cable 11, the power receiving module 13 is arranged at one end of the cable 11, the power transmitting module 12 is arranged on one side of the power receiving module 13, and one side of the power transmitting module 12 is fixedly connected with a power transmitting module wire 15, and a bracket 14 is arranged on the surface of the power transmitting module wire 15, and a fixed support 16 is fixedly connected to the bottom of the bracket 14; The evaporation control system 18 includes an evaporation control system base plate 1801 , a supporting metal plate 1802 , heat dissipation holes 1803 , an evaporation control chamber 1804 , a fan 1805 , a heater 1806 , a humidifier 1807 and a temperature and humidity sensor 1808 .

[0022] The top surface of the bottom plate 5 is provided with a spiral groove 501 , and one side of the bottom plate 5 surface is provided with a water inlet and outlet hole 502 .

[0023] The supporting metal plate 1802 is arranged at the bottom of the evaporation control system base plate 1801, the heat dissipation hole 183 is opened at the bottom of the supporting metal plate 1802, the evaporation control chamber 1804 is arranged at the top of the evaporation control system base plate 1801, and the fan 1805, heater 1806, humidifier 1807 and temperature and humidity sensor 1808 are respectively arranged at the top inside the evaporation control chamber 1804.

[0024] The outer tube 2 of the sample preparation tube is a hollow cylinder, and an external thread is provided at the bottom for matching and installing with the chassis 5. The inner diameter of the outer tube 2 of the sample preparation tube is larger than the outer diameter of the soil sample. The gap distance between the inner wall of the outer tube 2 of the sample preparation tube and the soil sample 3 is 2-5 mm. After the soil sample 3 is prepared and saturated in the compactor and the saturation cylinder, it is moved into the center position of the inner part of the outer tube 2 of the sample preparation tube and placed upright.

[0025] The material of the outer tube 2 of the sample preparation tube is required to be a metal that does not deform in a hot environment, and stainless steel and aluminum alloy are used to prevent shrinkage cracks from forming on the side wall of the soil sample 3 during evaporation.

[0026] The glue 4 is specially made of epoxy resin material, which can be bonded to the soil sample 3 but does not flow into the pores of the soil sample 3, and the glue 4 can be well bonded to the inner wall of the outer tube 2 of the sample preparation tube. After the glue 4 is cured, it will be bonded to the soil sample 3 and the outer tube 2 of the sample preparation tube as a whole. Through the bonding effect of the glue 4, the soil sample 3 is prevented from separating from the side wall in a hot environment to form shrinkage cracks, thereby solving the measurement and calculation errors caused by the problem of shrinkage cracks around the soil sample.

[0027] The upper surface of the first tensiometer 6 is flush with the upper surface of the chassis 5, and the bottom surface of the soil sample 3 is located on the spiral groove 501 of the chassis 5. The excess water in the soil sample 3 due to saturation can freely drip into the spiral groove 501 of the chassis 5 and be discharged through the water discharge port 502. The upper surface of the first tensiometer 6 and the bottom surface of the soil sample 3 are in close contact, and the initial saturation state of the bottom of the soil sample 3 can be determined by the real-time measurement of the suction value of the first tensiometer 6. The second tensiometer 7 and the third tensiometer 8 respectively pass through the side wall openings of the sample preparation tube outer cylinder 2 and are pressed against the surface of the soil sample 3. The second tensiometer 7 and the third tensiometer 8 are used to measure the matrix suction at two heights during the evaporation process of the soil sample 3 in real time. The second tensiometer 7 and the third tensiometer 8 are used to measure the matrix suction at two heights during the evaporation process of the soil sample 3 in real time. The third tensiometer 8 is installed at the 1 / 3 and 2 / 3 positions of the height of the soil sample 3 respectively. When the suction values ​​measured by the first tensiometer 6, the second tensiometer 7 and the third tensiometer 8 are linear gradients, they can be used as the starting point of the evaporation test. The cables 9 of the first tensiometer 6, the second tensiometer 7 and the third tensiometer 8 are all connected to the wireless transmitter collector 10, and the wireless transmitter collector 10 is placed and fixed on the weighing sensor 1. The function of the wireless transmitter collector 10 is to collect the suction data of the first tensiometer 6, the second tensiometer 7 and the third tensiometer 8 in real time, and transmit them wirelessly to the computer software for data storage through the internal wireless transmission module using the Internet of Things ZigBee protocol.

[0028] The wireless transmitting collector 10 is connected to the power receiving module 13 through the cable 11. The power transmitting module 12 can be suspended above the power receiving module 13 by fixing it with the bracket 14 and the fixed support 16. The vertical distance between the power receiving module 13 and the power transmitting module 12 is 2-10 mm. The power transmitting module 12 is connected to the external regulated power supply through the wire 15. The power transmitting module 12 generates electromagnetic induction under the excitation of the external power supply, and uses the coil in the transmitting module to generate current, which is then wirelessly transmitted to the power receiving module 13. The power receiving module 13 can simultaneously power the wireless transmitting collector 10, the first tension meter 6, the second tension meter 7 and the third tension meter 8, thereby ensuring that the external power supply can provide contactless power supply to all power-requiring components on the weighing sensor 1 in real time, solving the problem of the cable affecting the measurement result caused by the wired connection power supply.

[0029] The evaporation control system 18 is installed and fixed at the top center position of the transparent organic glass box 17. The evaporation control system 18 is cylindrical, and its outer diameter is the same as the outer diameter of the sample preparation tube outer tube 2. The evaporation control system bottom plate 1801 is located at the lower part of the evaporation control chamber 1804. The upper part of the evaporation control chamber 1804 is fixed to the transparent organic glass box 17 with threads. The evaporation control chamber 1804 is a hollow cylinder. The heater 1806 and the humidifier 1807 are symmetrically installed inside the evaporation control chamber 1804. The fan 1805 is installed between the heater 1806 and the humidifier 1807. 5 controls the wind speed and temperature of the air discharged from the evaporation control chamber 1804, the heater 1806 generates high temperature in the evaporation control chamber 1804, the humidifier 1807 controls the humidity of the air discharged from the evaporation control chamber 1804, the fan 1805, the heater 1806 and the humidifier 1807 are all provided with knob switches, and the knob switches are all arranged outside the transparent organic glass box 17. The wind speed of the fan, the temperature and humidity of the air in the chamber can be arbitrarily adjusted by steplessly adjusting the knob switch. The hot air generated in the evaporation control chamber 1804 can be discharged through the heat dissipation holes 1803, and then evenly diffused to the surface of the soil sample 3.

[0030] The surface of the soil sample 3 is 30~150mm away from the bottom plate 1801 of the evaporation control system. The temperature and humidity sensor 1808 is installed in the evaporation control chamber 1804, which can monitor the temperature and humidity of the air in the evaporation control chamber 1804 in real time. According to the type of soil sample used in the simple evaporation test and the test duration requirements, the fan 1805, the heater 1806 and the humidifier 1807 in the evaporation control chamber 1804 can be adjusted at will. Under the joint action of the three, the air environment temperature and humidity required for the test are achieved, thereby accurately controlling the evaporation rate of the soil sample 3.

[0031] The working principle of a simple evaporation system for quickly measuring hydraulic parameters of unsaturated soil provided by the present invention is as follows: During operation, first, the weighing sensor 1 is used to measure the change of the mass of the soil sample thereon in real time. The gap distance between the inner wall of the outer cylinder 2 of the sample preparation tube and the soil sample 3 is 2-5mm. After the soil sample is prepared and saturated in the compactor and the saturation cylinder, it is moved into the center position of the inner side of the outer cylinder of the sample preparation tube and placed upright. In order to prevent the side wall of the soil sample 3 from generating shrinkage cracks during the evaporation process, after the soil sample 3 is placed in the outer cylinder 2 of the sample preparation tube, glue 4 is poured into the gap between the outer cylinder 2 of the sample preparation tube and the soil sample 3 to bond with the soil sample 3 but does not flow into the pores of the soil sample 3. The glue 4 can be well bonded to the inner wall of the outer cylinder 2 of the sample preparation tube. After the glue 4 is solidified, it will be bonded to the soil sample 3 and the outer cylinder 2 of the sample preparation tube as a whole. Through the bonding effect of the glue 4, the soil sample 3 can be prevented from separating from the side wall in a hot environment to form shrinkage cracks, which well solves the measurement and calculation errors caused by the problem of shrinkage cracks around the soil sample in the existing simple evaporation system.

[0032] The function of the wireless transmitting collector 10 is to collect the suction data of the first tension meter 6, the second tension meter 7 and the third tension meter 8 in real time, and transmit the suction data to the computer software for data storage through the internal wireless transmitting module using the Internet of Things ZigBee protocol. The wireless transmitting collector 10 is connected to the power receiving module 13 through the cable 11, and the power transmitting module 12 is connected to the external voltage-stabilized power supply through the wire 15. The power transmitting module 12 generates electromagnetic induction under the excitation of the external power supply, and uses the coil in the transmitting module to excite and generate current, which is then wirelessly transmitted to the power receiving module 13. The power receiving module 13 can simultaneously supply power to the wireless transmitting collector 10, the first tension meter 6, the second tension meter 7 and the third tension meter 8, thereby ensuring that the external power supply can provide contactless power supply to all power-requiring components on the weighing sensor 1 in real time, solving the problem of the cable affecting the measurement results caused by the wired connection power supply in the existing simple evaporation system.

[0033] The function of the fan 1805 is to control the wind speed and temperature of the air exhausted from the evaporation control chamber 1804, the function of the heater 1806 is to generate high temperature in the evaporation control chamber 1804, and the function of the humidifier 1807 is to control the humidity of the air exhausted from the evaporation control chamber 1804. The fan 1805, the heater 1806 and the humidifier 1807 are all provided with knob switches, and the knob switches are all arranged outside the transparent organic glass box. The wind speed of the fan, the temperature and humidity of the air in the chamber can be arbitrarily adjusted by steplessly adjusting the knob switches. The hot air generated in the evaporation control chamber 1804 can be discharged through the heat dissipation holes 1803, and then evenly diffused to the surface of the soil sample 3. The surface of the soil sample 3 is 100 meters away from the surface of the soil sample 3. The range from 30 to 150 mm from the bottom plate 1801 of the evaporation control system is a temperature and humidity sensor 1808 installed in the evaporation control chamber 1804, which can monitor the temperature and humidity of the air in the evaporation control chamber 1804 in real time. According to the type of soil sample used in the simple evaporation test (for example, clay, silt or sand) and the test duration requirement, the fan 1805, heater 1806 and humidifier 1807 in the evaporation control chamber 1804 can be adjusted arbitrarily. Under the joint action of the three, the air environment temperature and humidity required for the test are achieved, so that the evaporation rate of the soil sample 3 can be accurately controlled, avoiding the problem of uneven moisture distribution caused by excessive temperature gradient inside the soil sample, and reducing the test error.

[0034] Compared with the related art, the simple evaporation system for quickly measuring the hydraulic parameters of unsaturated soil provided by the present invention has the following beneficial effects: The invention provides a simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil. By installing a tensiometer at the bottom of a sample and at two heights, the initial saturation state of the bottom of the sample can be accurately determined by the measured value of the bottom tensiometer, and the accurate starting time of the simple evaporation test can be accurately determined by comparing the measured values ​​of the bottom plate tensiometer and the tensiometers at the other two heights, thereby reducing the measurement and calculation errors. A special temperature and humidity control system is adopted to accurately and actively control the evaporation rate of the sample surface, and a suitable evaporation rate can be selected according to the characteristics of different types of soil bodies to carry out the test, thereby ensuring the matching of the thermal gradient and the moisture gradient inside the sample soil body, and avoiding the occurrence of uneven moisture distribution caused by the reflux of moisture in the sample. A special glue is adopted to connect the soil sample and the sample preparation tube, and under the strong bonding effect, the soil sample can evaporate in a hot environment without being separated from the sample preparation tube, thereby maintaining the overall structural uniformity of the soil sample during the entire test process, avoiding the occurrence of shrinkage cracks, and greatly reducing the test error. A contactless power supply system is adopted to separate the sensor cable installed on the sample from the external power supply, thereby avoiding the influence of the cable disturbance on the sample evaporation process, thereby reducing the test error.

[0035] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A simple evaporation system for rapid measurement of hydraulic parameters of unsaturated soil, characterized in that: include: Weighing sensor, sample preparation tube outer tube, soil sample, chassis, first tension meter, second tension meter, third tension meter, wireless transmitter collector, power transmission module, power receiving module, transparent organic glass box and evaporation control system; The weighing sensor is fixedly installed at the bottom of the transparent organic glass box, the chassis is arranged on the top of the weighing sensor, the outer cylinder of the sample preparation tube is placed on the chassis, the soil sample is arranged inside the outer cylinder of the sample preparation tube, and glue is arranged between the soil sample and the outer cylinder of the sample preparation tube; The evaporation control system is arranged at the top inside the transparent organic glass box, the first tension meter is arranged in the middle of the chassis, the second tension meter is arranged on one side of the outer surface of the outer cylinder of the sample preparation tube, and the third tension meter is arranged on the other side of the outer surface of the outer cylinder of the sample preparation tube. One side of the first tension meter, the second tension meter and the third tension meter are all fixedly connected with tension meter cables, the wireless transmitting collector is arranged on one side of the tension meter cables, one end of the three tension meter cables is commonly fixedly connected with cables, the power receiving module is arranged at one end of the cables, the power transmitting module is arranged on one side of the power receiving module, one side of the power transmitting module is fixedly connected with a power transmitting module wire, a bracket is arranged on the surface of the power transmitting module wire, and a fixed support is fixedly connected to the bottom of the bracket; The evaporation control system comprises an evaporation control system bottom plate, a supporting metal plate, heat dissipation holes, an evaporation control chamber, a fan, a heater, a humidifier and a temperature and humidity sensor.

2. A simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil according to claim 1, characterized in that: The surface of the top of the chassis is provided with a spiral groove, and one side of the chassis surface is provided with a water discharge and inlet hole.

3. A simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil according to claim 1, characterized in that: The supporting metal plate is arranged at the bottom of the evaporation control system base plate, the heat dissipation holes are opened at the bottom of the supporting metal plate, the evaporation control chamber is arranged at the top of the evaporation control system base plate, and the fan, heater, humidifier and temperature and humidity sensor are respectively arranged at the top inside the evaporation control chamber.

4. A simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil according to claim 1, characterized in that: The outer cylinder of the sample preparation cylinder is a hollow cylinder, and an external thread is arranged at the bottom for matching and installing with the chassis. The inner diameter of the outer cylinder of the sample preparation cylinder is larger than the outer diameter of the soil sample.

5. A simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil according to claim 1, characterized in that: The material of the outer cylinder of the sample preparation cylinder is required to be a metal that does not deform in a hot environment to prevent shrinkage cracks from forming on the side wall of the soil sample during evaporation.

6. A simple evaporation system for rapid measurement of hydraulic parameters of unsaturated soil according to claim 1, characterized in that: The glue is specially made of epoxy resin material, which can be bonded to the soil sample but does not flow into the pores of the soil sample, and the glue can be well bonded to the inner wall of the outer cylinder of the sample preparation cylinder.

7. A simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil according to claim 2, characterized in that: The upper surface of the first tensiometer is flush with the upper surface of the chassis, and the bottom surface of the soil sample is located on the spiral groove of the chassis. Excess water in the soil sample due to saturation can freely drip into the spiral groove of the chassis and be discharged through the water inlet and outlet. The upper surface of the first tensiometer is tightly attached to the bottom surface of the soil sample, and the initial saturation state of the bottom of the soil sample can be determined by the real-time measurement of the suction value by the first tensiometer. The second tensiometer and the third tensiometer respectively pass through the side wall openings of the outer cylinder of the sample preparation cylinder and are pressed against the surface of the soil sample. The second tensiometer and the third tensiometer are used to measure the matrix suction at two heights during the evaporation process of the soil sample in real time. The second tensiometer and the third tensiometer are used to measure the matrix suction at two heights during the evaporation process of the soil sample in real time. The three tensiometers are installed at / and / positions of the soil sample height respectively. When the suction values ​​measured by the first tensiometer, the second tensiometer and the third tensiometer are linear gradients, they can be used as the starting point of the evaporation test. The cables of the first tensiometer, the second tensiometer and the third tensiometer are all connected to the wireless transmitter collector, and the wireless transmitter collector is placed and fixed on the weighing sensor. The function of the wireless transmitter collector is to collect the suction data of the first tensiometer, the second tensiometer and the third tensiometer in real time, and transmit them wirelessly to the computer software for data storage through the internal wireless transmission module using the Internet of Things ZigBee protocol.

8. A simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil according to claim 1, characterized in that: The wireless transmitting collector is connected to the power receiving module through the cable. The power transmitting module can be suspended directly above the power receiving module by being fixed by the bracket and the fixed support. The vertical distance between the power receiving module and the power transmitting module is 2~10mm. The power transmitting module is connected to an external voltage-stabilized power supply through the wire. The power transmitting module generates electromagnetic induction under the excitation of an external power supply, and uses the coil in the transmitting module to generate current, which is then wirelessly transmitted to the power receiving module. The power receiving module can simultaneously power the wireless transmitting collector, the first tension meter, the second tension meter and the third tension meter.

9. A simple evaporation system for rapid measurement of hydraulic parameters of unsaturated soil according to claim 1, characterized in that: The evaporation control system is installed and fixed at the top center position of the transparent organic glass box. The evaporation control system is cylindrical, and its outer diameter is the same as the outer diameter of the outer cylinder of the sample preparation tube. The bottom plate of the evaporation control system is located at the lower part of the evaporation control chamber. The upper part of the evaporation control chamber is fixed to the transparent organic glass box with threads. The evaporation control chamber is a hollow cylinder. The heater and the humidifier are symmetrically installed inside the evaporation control chamber. The fan is installed between the heater and the humidifier. The fan controls the wind speed and temperature of the air discharged from the evaporation control chamber. The heater generates high temperature in the evaporation control chamber. The humidifier controls the humidity of the air discharged from the evaporation control chamber. The fan, the heater and the humidifier are all provided with knob switches. The knob switches are all arranged outside the transparent organic glass box. The wind speed of the fan, the temperature and humidity of the air in the chamber can be arbitrarily adjusted by steplessly adjusting the knob switch. The hot air generated in the evaporation control chamber can be discharged through the heat dissipation holes and then evenly diffused to the surface of the soil sample.

10. A simple evaporation system for rapidly measuring hydraulic parameters of unsaturated soil according to claim 1, characterized in that: The surface of the soil sample is 30 to 150 mm away from the bottom plate of the evaporation control system. The temperature and humidity sensor is installed in the evaporation control chamber to monitor the temperature and humidity of the air in the evaporation control chamber in real time. The fan, heater and humidifier in the evaporation control chamber can be adjusted arbitrarily according to the type of soil sample used in the simple evaporation test and the test duration requirements.

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