Fully automatic pressure plate instrument for soil-water characteristic curve of unsaturated soil

Abstract

Fully automatic pressure plate instrument for soil-water characteristic curve of unsaturated soil. It includes a control cabinet and a main test cabinet. The main test cabinet is provided with a pressure chamber, a pressure chamber base, an axial pressure mechanism, an automatic flushing bubble mechanism, an evaporation compensation mechanism, and a confining pressure mechanism. The automatic flushing bubble mechanism is provided with a peristaltic pump and a double-layer graduated measuring tube for flushing; the evaporation compensation mechanism is provided with a double-layer graduated measuring tube for evaporation; the main test cabinet is a transparent cover cabinet, and an electronic constant temperature and humidity device is fixed inside the transparent cover cabinet; the axial pressure mechanism and the confining pressure mechanism are respectively provided with automatic pressure regulating valves; the front end of the control cabinet is provided with a touch-type industrial control computer. The pressure plate instrument is provided with a fully automatic bubble flushing mechanism, an evaporation compensation mechanism, an automatic pressure regulating mechanism, and a constant temperature and humidity mechanism, which can greatly improve the acquisition accuracy of soil-water characteristic curve test data, and the test data is more real and objective, and at the same time, the degree of automation is high and the controllability is good.

Description

Technical Field

[0001] The invention relates to soil-water characteristic curve test equipment, and in particular to an unsaturated soil-water characteristic curve pressure plate instrument provided with a fully automated bubble flushing mechanism, an evaporation compensation mechanism, an automatic pressure regulating mechanism, and a constant temperature and humidity mechanism, which enables a high degree of automation in soil-water detection and high test data accuracy. Background Art

[0002] The matrix potential of soil water (or soil water suction) varies with the soil water content. The relationship curve is called the soil-water characteristic curve, which mainly refers to the relationship curve between the matrix suction formed in unsaturated soil and the water content or saturation in the soil. It reflects the water holding capacity of the soil under the action of matrix suction. The soil-water characteristic curve can effectively determine the shear strength, permeability, diffusion characteristics, volume strain, etc. of unsaturated soil. Therefore, it occupies an important position in unsaturated soil mechanics. The experimental research on the soil-water characteristic curve often uses the soil-water characteristic curve pressure plate instrument.

[0003] At present, the shortcomings of the soil-water characteristic curve pressure plate instrument are:

[0004] 1. The bubble flushing structure cannot be fully automatic, the operation is troublesome, and the existing bubble flushing structures are mostly simple and the flushing is not thorough;

[0005] 2. Due to the long process of unsaturated soil test, under certain air temperature and humidity, the water in the test will evaporate to a certain extent. The existing experimental equipment lacks consideration of evaporation, which affects the accuracy of the test data.

[0006] 3. The sample is pressurized manually, and the test process lasts for a long time, so there are problems such as slow pressure relief and inability to automatically replenish air pressure;

[0007] 4. The existing equipment lacks constant temperature and humidity test condition control, so during a long test cycle, different temperature and humidity conditions will cause large errors in the soil and water test data. Summary of the invention

[0008] The purpose of the present invention is to solve the above-mentioned technical problems and to provide a fully automatic unsaturated soil-water characteristic curve pressure plate instrument. The pressure plate instrument is provided with a fully automatic bubble flushing mechanism, an evaporation compensation mechanism, an automatic pressure regulating mechanism, and a constant temperature and humidity mechanism, which can greatly improve the collection accuracy of soil-water characteristic curve test data, and the test data is more real and objective, and at the same time has a high degree of automation and good controllability.

[0009] The technical solution of the present invention is:

[0010] A fully automatic unsaturated soil-water characteristic curve pressure plate instrument, comprising a control cabinet and a main test cabinet arranged on the control cabinet, wherein a pressure chamber, a pressure chamber base, an axial pressurizing mechanism, and a confining pressure pressurizing mechanism are arranged in the main test cabinet, wherein the pressure chamber is arranged on the pressure chamber base, and a clay plate is also pressed between the pressure chamber and the pressure chamber base, a groove is formed on the pressure chamber base, and a base water storage cavity is formed between the clay plate and the pressure chamber base, wherein the pressure chamber is used to press a test soil sample, wherein the axial pressurizing mechanism is provided with an axial pressurizing device, and an axial pressure is applied to the test soil sample by the axial pressurizing device, wherein the confining pressure pressurizing mechanism is used to provide confining pressure to the interior of the pressure chamber, and the moisture in the soil sample is discharged through the clay plate with air blocking and water passing function under the action of the axial pressure and the confining pressure, and the base water storage cavity is used to collect the moisture squeezed out of the test soil sample, and the water discharge is read by the water pressure sensor after circulating through the flushing mechanism;

[0011] A microcontrol unit MCU embedded control system is arranged in the control cabinet, and the axial pressurizer and the confining pressure pressurizing mechanism also include switch devices respectively, and the microcontrol unit MCU embedded control system is connected with the switch devices of the axial pressurizer and the confining pressure pressurizing mechanism, and the axial pressurizer and the confining pressure pressurizing mechanism are controlled by the microcontrol unit MCU embedded control system;

[0012] As an improvement, the pressure plate instrument is also provided with an automatic flushing bubble mechanism, which is provided with a peristaltic pump and a double-layer graduated measuring tube for flushing. The peristaltic pump, the double-layer graduated measuring tube for flushing and the base water storage cavity of the pressure chamber base constitute a water circulation flow path, which is driven by the peristaltic pump, and bubbles are discharged through the double-layer graduated measuring tube for flushing, and the squeezed water in the base water storage cavity is flushed with bubbles. The peristaltic pump also includes a switch device, and the microcontroller unit MCU embedded control system is connected to the switch device of the peristaltic pump, and the peristaltic pump is controlled by the microcontroller unit MCU embedded control system;

[0013] As an improvement, the pressure plate instrument is further provided with an evaporation compensation mechanism, the evaporation compensation mechanism and the automatic flushing bubble mechanism share a peristaltic pump, the evaporation compensation mechanism is provided with a double-layer graduated measuring tube for evaporation, the double-layer graduated measuring tube for evaporation, through the conduit and the peristaltic pump, forms a water circulation flow path, and the water of the evaporation compensation mechanism and the water of the automatic flushing bubble mechanism circulate synchronously;

[0014] As an improvement, the main test cabinet is a transparent cover cabinet, and an electronic constant temperature and humidity device is fixed on the rear wall inside the transparent cover cabinet. The electronic constant temperature and humidity device is connected to the micro control unit MCU embedded control system, and the temperature and humidity inside the transparent cover cabinet are automatically controlled by computer software. The pressure plate instrument realizes constant temperature and humidity conditions during the test process by setting a closed transparent cover cabinet and the electronic constant temperature and humidity device, so as to obtain more accurate test data;

[0015] As an improvement, the axial pressurizer and the confining pressure pressurizing mechanism are respectively connected to an automatic pressure regulating valve through an air guide pipe, and are respectively connected to an external air source through the air guide pipe through the automatic pressure regulating valve. The automatic pressure regulating valve includes a switch device, and the switch device of the automatic pressure regulating valve is respectively connected to a microcontroller MCU embedded control system. The automatic pressure regulating valve is controlled by the microcontroller MCU embedded control system, thereby controlling the pressure of the axial pressurizer and the confining pressure pressurizing mechanism;

[0016] As an improvement, a touch-type industrial control computer is arranged at the front end of the control cabinet, the microcontroller unit MCU embedded control system is connected to the touch-type industrial control computer, and the pressure plate instrument is controlled and operated by the touch-type industrial control computer.

[0017] Furthermore, the axial pressurizing mechanism comprises a reaction force frame, the axial pressurizer comprises an axial loading cylinder fixed to the bottom of the reaction force frame, and a piston rod on the axial loading cylinder, the piston rod is connected to a lifting platform, the pressure chamber base is arranged on the lifting platform, the upper part of the reaction force frame is provided with an axial compression connecting rod and a displacement sensor, the axial compression connecting rod passes downward through the upper part of the pressure chamber, and the lower end is sequentially connected to the axial load sensor and the ball head, and is pressed on the test soil sample through the upper pressure plate and the permeable stone, a sealing structure is arranged between the axial compression connecting rod and the pressure chamber, the confining pressure pressurizing mechanism is connected to the side wall of the pressure chamber through the air guide pipe and is in conduction with the pressure chamber, during the test, the test soil sample is pressed into the pressure chamber, the axial pressurizer applies axial pressure to the test soil sample through the axial compression connecting rod, and at the same time, the confining pressure pressurizing mechanism applies confining pressure to the inside of the pressure chamber, and the water squeezed out of the test soil sample penetrates into the water storage cavity of the base through the clay plate;

[0018] Further, the automatic flushing bubble mechanism includes a peristaltic pump structure, a double-layer graduated measuring tube for flushing, and a measuring tube water storage base. The peristaltic pump structure includes a first water inlet end, a first water outlet end, and a peristaltic pump. The peristaltic pump drives the water to flow from the first water inlet end to the first water outlet end. The double-layer graduated measuring tube for flushing is fixed on the measuring tube water storage base. The double-layer graduated measuring tube for flushing includes a first measuring tube inner tube and a first measuring tube outer tube arranged on the same axis line. The upper end of the first measuring tube outer tube is higher than the upper end of the first measuring tube inner tube. The first measuring tube inner tube is A sealing cover is provided at the upper end of the outer tube, and a plurality of air holes are provided on the sealing cover. The measuring tube water storage base includes a water inlet hole and a water storage cavity. One end of the water inlet hole is communicated with the lower end of the inner tube of the first measuring tube, and the other end is communicated with the base water storage cavity of the pressure chamber base through a third conduit. One end of the water storage cavity of the measuring tube water storage base is communicated with the lower end of the outer tube of the first measuring tube, and the other end is communicated with the first water inlet end of the peristaltic pump structure through the first conduit. The first water outlet end of the peristaltic pump structure is communicated with the base water storage cavity of the pressure chamber base through a second conduit.

[0019] The evaporation compensation mechanism includes a measuring tube water passing base, and a double-layer graduated measuring tube for evaporation fixed on the measuring tube water passing base. The peristaltic pump structure also includes a second water inlet end and a second water outlet end. The evaporation compensation mechanism and the automatic flushing bubble mechanism share the peristaltic pump, and the water is driven to flow from the second water inlet end to the second water outlet end through the peristaltic pump. The double-layer graduated measuring tube for evaporation includes a second measuring tube inner tube and a second measuring tube outer tube arranged on the same axis line. The upper end of the second measuring tube outer tube is higher than the upper end of the second measuring tube inner tube. A sealing cover is arranged on the upper end of the second measuring tube outer tube. A plurality of air holes are arranged on the sealing cover. The measuring tube water passing base includes a water inlet hole and a water passing cavity. One end of the water inlet hole is connected to the lower end of the second measuring tube inner tube, and the other end is connected to the second water outlet end of the peristaltic pump structure through a fourth conduit. One end of the water passing cavity is connected to the lower end of the second measuring tube outer tube, and the other end is connected to the second water inlet end of the peristaltic pump structure through a fifth conduit.

[0020] Furthermore, the measuring tube water storage base and the measuring tube water flow base are respectively provided with water pressure sensors, and the water pressure sensors are connected to the microcontroller unit MCU embedded control system, and the water liquid change amount of the measuring tube water storage base and the measuring tube water flow base is respectively obtained through the microcontroller unit MCU embedded control system.

[0021] Furthermore, the automatic pressure regulating valve includes a reduction motor, a connecting piece, a pressure regulating valve, a fixed rod, and a precision guide rail. The reduction motor is provided with a switch device. The precision guide rail is vertically arranged on the fixed rod. The pressure regulating valve is fixedly arranged on the fixed rod. The reduction motor is slidably arranged on the precision guide rail. The pressure regulating valve includes a tightening shaft of the pressure regulating valve. The reduction motor includes an output shaft. The output shaft of the reduction motor is connected to the tightening shaft of the pressure regulating valve through a connecting piece. When the reduction motor rotates forward, it drives the tightening shaft of the pressure regulating valve to tighten the pressure regulating valve, so that the pressure of the pressure regulating valve increases. At the same time, the tightening shaft of the pressure regulating valve drives the reduction motor to move downward along the precision guide rail to reduce the speed. When the motor reverses, the output shaft of the reduction motor drives the pressure regulating valve to tighten the rotating shaft and loosen the pressure regulating valve. At the same time, the pressure regulating valve tightens the rotating shaft to drive the reduction motor to move upward along the precision guide rail, so that the pressure of the automatic control valve is reduced. The pressure regulating valve is provided with a pressure sensor, and the pressure sensor is connected to the microcontroller unit MCU embedded control system. When the pressure value of the pressure regulating valve becomes smaller, the microcontroller unit MCU embedded control system starts the reduction motor to rotate forward to increase the pressure. When the pressure value of the pressure regulating valve becomes larger, the microcontroller unit MCU embedded control system starts the reduction motor to reverse and reduce the pressure, thereby controlling the pressure value of the automatic pressure regulating valve to a constant value.

[0022] Flushing process:

[0023] Open the sealing cover on the double-layer graduated measuring tube for flushing, and pour airless water into the double-layer graduated measuring tube for flushing from the top to fill the inner tube of the first measuring tube, fill the water level of the outer tube of the first measuring tube to the initial water level value, cover the sealing cover, and start flushing through the microcontroller unit MCU embedded control system. The system will automatically start the peristaltic pump, and the airless water passes through the outer tube of the first measuring tube, the water storage cavity, and the first conduit in sequence, and flows into the peristaltic pump from the first water inlet end. Driven by the peristaltic pump, the airless water passes through the first water outlet end and the second conduit in sequence and enters the base water storage cavity of the pressure chamber base. The airless water drives the squeezed water in the base water storage cavity to flow out through the third conduit, and enters the inner tube of the first measuring tube through the water inlet hole of the measuring tube water storage base. The water in the inner tube of the first measuring tube gradually increases and overflows. The overflowing water enters the outer tube of the first measuring tube downward, and the bubbles in the water are discharged upward through the air holes of the sealing cover. The water in the outer tube of the first measuring tube continues to circulate according to this process until there are no more bubbles discharged from the double-layer graduated measuring tube for flushing, and then the flushing is stopped.

[0024] After the test starts, do not change the amount of water in the automatic flushing bubble mechanism and keep the initial amount of water unchanged. During the test, the system can be flushed at any time as needed, because the water in the inner tube of the first measuring tube is always full. The increase in the water volume in the outer tube of the first measuring tube is the water content of all the squeezed out test soil samples during the test.

[0025] The sealing cover is used to seal the water in the double-layer graduated measuring tube for flushing and reduce evaporation.

[0026] Evaporation compensation principle:

[0027] The evaporation compensation mechanism is started synchronously with the automatic flushing bubble mechanism, that is, when the flushing process starts, the sealing cover on the upper end of the outer tube of the second measuring tube of the double-layer graduated measuring tube for evaporation is opened, and airless water is poured in to fill the inner tube of the second measuring tube, and the water level of the outer tube of the second measuring tube is filled to the initial water level value, and then the sealing cover is covered to reduce water evaporation. Similar to the evaporation compensation mechanism, the water circulation flow of the evaporation compensation mechanism is synchronously started through the microcontroller unit MCU embedded control system. The water circulation flow of the evaporation compensation mechanism is an internal circulation flow. Since the evaporation compensation mechanism and the water in the measuring tube of the automatic flushing bubble mechanism have the same running speed, they circulate synchronously. In the same time period, the evaporation amount of water in the evaporation compensation mechanism is the same as the evaporation amount of water in the automatic flushing bubble mechanism. The evaporation amount of water in the evaporation compensation mechanism is obtained by the water amount difference in the evaporation compensation mechanism. By supplementing the automatic flushing bubble mechanism with the water evaporation amount, the accurate water amount in the automatic flushing bubble mechanism is obtained.

[0028] The fully automatic unsaturated soil-water characteristic curve pressure plate instrument of the present invention has the following beneficial effects:

[0029] 1. Adopting fully automated bubble flushing mechanism, cyclically flushing bubbles, eliminating bubbles more thoroughly and making the test data more accurate;

[0030] 2. Evaporation compensation is used to eliminate evaporation errors during the test, making the test data more accurate and true;

[0031] 3. The water pressure gauge is used to automatically collect water volume data, which can eliminate the reading error of human eyes;

[0032] 4. Automatic pressure regulating mechanism is used to ensure constant pressure value during long test process, and the automatic pressure regulating mechanism can maintain the pressure value unchanged when power is off or other external factors suddenly interfere;

[0033] 5. The constant temperature and humidity hood mechanism can avoid errors in soil and water test data caused by temperature and humidity changes.

[0034] 6. The test process basically adopts an automated mode, which is easy to operate and has high data collection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 , which is a stereoscopic diagram of the fully automatic unsaturated soil-water characteristic curve pressure plate instrument of the present invention;

[0036] Figure 2 ,for Figure 1 A three-dimensional diagram of the evaporation compensation mechanism and the automatic flushing bubble mechanism of the illustrated embodiment;

[0037] Figure 3 ,for Figure 1 Partial structure of the illustrated embodiment Figure 1 ;

[0038] Figure 4 ,for Figure 1 A three-dimensional diagram of the automatic pressure regulating valve of the illustrated embodiment;

[0039] Figure 5 ,for Figure 1 Gas circuit diagram of the illustrated embodiment. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with embodiments:

[0041] Example:

[0042] A fully automatic unsaturated soil-water characteristic curve pressure plate instrument, comprising a control cabinet 1, and a main test cabinet 12 arranged on the control cabinet, wherein a pressure chamber 3, a pressure chamber base 4, an axial pressurizing mechanism 5, and a confining pressure pressurizing mechanism 2 are arranged in the main test cabinet, wherein the pressure chamber 3 is arranged on the pressure chamber base 4, and a clay plate 42 is also pressed between the pressure chamber and the pressure chamber base, a groove is formed on the pressure chamber base, and a base water storage chamber 41 is formed between the clay plate and the pressure chamber base, wherein the pressure chamber is used to press a test soil sample 43, wherein the axial pressurizing mechanism 5 is provided with an axial pressurizer, and an axial pressure is applied to the test soil sample by the axial pressurizer, and the confining pressure pressurizing mechanism is used to provide confining pressure to the interior of the pressure chamber, and the moisture in the soil sample is discharged through the clay plate with air blocking and water passing function under the action of the axial pressure and the confining pressure, and the base water storage chamber is used to collect the moisture squeezed out of the test soil sample, and the water pressure sensor reads the water discharge after circulating through the flushing mechanism;

[0043] The control cabinet 1 is provided with a microcontroller MCU embedded control system, and the axial pressurizer and the confining pressure pressurizing mechanism also include switch devices respectively, and the microcontroller MCU embedded control system is connected to the switch devices of the axial pressurizer and the confining pressure pressurizing mechanism, and the axial pressurizer and the confining pressure pressurizing mechanism are controlled by the microcontroller MCU embedded control system;

[0044] The pressure plate instrument is also provided with an automatic flushing bubble mechanism 6, and the automatic flushing bubble mechanism 6 is provided with a peristaltic pump 61 and a double-layer graduated measuring tube 62 for flushing. The peristaltic pump 61, the double-layer graduated measuring tube 62 for flushing and the base water storage chamber 41 of the pressure chamber base constitute a water circulation flow path, and the bubbles are discharged through the double-layer graduated measuring tube for flushing by the peristaltic pump, and the squeezed water in the base water storage chamber is flushed with bubbles. The peristaltic pump also includes a switch device, and the microcontroller unit MCU embedded control system is connected to the switch device of the peristaltic pump, and the peristaltic pump is controlled by the microcontroller unit MCU embedded control system;

[0045] The pressure plate instrument is also provided with an evaporation compensation mechanism 9, which shares a peristaltic pump with the automatic flushing bubble mechanism. The evaporation compensation mechanism is provided with a double-layer graduated measuring tube 91 for evaporation, which forms a water circulation flow path through a conduit and the peristaltic pump. The water of the evaporation compensation mechanism and the water of the automatic flushing bubble mechanism circulate synchronously.

[0046] The main test cabinet 12 is a transparent cover cabinet, and an electronic constant temperature and humidity device 8 is fixed on the rear wall inside the transparent cover cabinet. The electronic constant temperature and humidity device is connected to the micro control unit MCU embedded control system, and the temperature and humidity inside the transparent cover cabinet are automatically controlled by computer software. The pressure plate instrument realizes constant temperature and humidity conditions during the test process by setting a closed transparent cover cabinet and the electronic constant temperature and humidity device, so as to obtain more accurate test data;

[0047] like Figure 5 The axial pressurizer and the confining pressure pressurizing mechanism are respectively connected to an automatic pressure regulating valve 7 through an air guide pipe, and are respectively connected to an external air source 71 through the air guide pipe through the automatic pressure regulating valve. The automatic pressure regulating valve includes a switch device, and the switch device of the automatic pressure regulating valve is respectively connected to a micro control unit MCU embedded control system. The automatic pressure regulating valve is controlled by the micro control unit MCU embedded control system, thereby controlling the pressure of the axial pressurizer and the confining pressure pressurizing mechanism. Figure 5 Among them, 77a is a drying filter, 77b is a pressure regulating valve, 77c is a pressure gauge, and 77d is an electromagnetic reversing valve;

[0048] A touch-type industrial control computer 11 is disposed at the front end of the control cabinet 1 , and the microcontroller unit MCU embedded control system is connected to the touch-type industrial control computer, and the pressure plate instrument is controlled and operated by the touch-type industrial control computer.

[0049] The axial pressurizing mechanism 5 includes a reaction force frame 51, and the axial pressurizer includes an axial loading cylinder 52 fixed to the bottom of the reaction force frame, and a piston rod 53 on the axial loading cylinder, the piston rod is connected to a lifting platform 54, and the pressure chamber base 4 is arranged on the lifting platform 54. The upper part of the reaction force frame 51 is provided with an axial compression connecting rod 55 and a displacement sensor 56. The axial compression connecting rod passes downward through the upper part of the pressure chamber, and the lower end is connected to the axial load sensor 57a and the ball head 57b in sequence, and is pressed on the test soil sample through the upper pressure plate 57c and the permeable stone 57d. A sealing structure is provided between the axial compression connecting rod and the pressure chamber, and the confining pressure pressurizing mechanism 2 is connected to the side wall of the pressure chamber through an air guide pipe and communicated with the pressure chamber. During the test, the test soil sample is pressed into the pressure chamber, and the axial pressurizer applies axial pressure to the test soil sample through the axial compression connecting rod. At the same time, the confining pressure pressurizing mechanism applies confining pressure to the inside of the pressure chamber, and the water squeezed out of the test soil sample penetrates into the base water storage cavity through the clay plate;

[0050] Further, the automatic flushing bubble mechanism 6 includes a peristaltic pump structure, a double-layer graduated measuring tube 62 for flushing, and a measuring tube water storage base 63. The peristaltic pump structure includes a first water inlet end, a first water outlet end, and a peristaltic pump 61. The peristaltic pump drives the water to flow from the first water inlet end to the first water outlet end. The double-layer graduated measuring tube 62 for flushing is fixed on the measuring tube water storage base 63. The double-layer graduated measuring tube 62 for flushing includes a first measuring tube inner tube 62a and a first measuring tube outer tube 62b arranged on the same axial line. The upper end of the first measuring tube outer tube is higher than the upper end of the first measuring tube inner tube. The upper end of the outer tube of the first measuring tube is provided with a sealing cover 64, and the sealing cover is provided with a plurality of air holes. The measuring tube water storage base includes a water inlet hole and a water storage cavity. One end of the water inlet hole is connected with the lower end of the inner tube of the first measuring tube, and the other end is connected with the base water storage cavity 41 of the pressure chamber base through a third conduit 65. One end of the water storage cavity of the measuring tube water storage base is connected with the lower end of the outer tube of the first measuring tube, and the other end is connected with the first water inlet end of the peristaltic pump structure through a first conduit 66. The first water outlet end of the peristaltic pump structure is connected with the base water storage cavity of the pressure chamber base through a second conduit 67.

[0051] The evaporation compensation mechanism 9 includes a measuring tube water-passing base 92 and a double-layer graduated measuring tube 91 for evaporation fixed on the measuring tube water-passing base. The peristaltic pump structure also includes a second water inlet end and a second water outlet end. The evaporation compensation mechanism and the automatic flushing bubble mechanism share the peristaltic pump, and the peristaltic pump drives the water to flow from the second water inlet end to the second water outlet end. The double-layer graduated measuring tube 91 for evaporation includes a second measuring tube inner tube 91a and a second measuring tube outer tube 91b arranged on the same axis. The second measuring tube inner tube 91a and the second measuring tube outer tube 91b are arranged on the same axis. The upper end of the second measuring tube outer tube is higher than the upper end of the second measuring tube inner tube. The upper end of the second measuring tube outer tube is provided with a sealing cover 93, and the sealing cover is provided with a plurality of air holes. The measuring tube water passing base includes a water inlet hole and a water passing cavity. One end of the water inlet hole is connected to the lower end of the second measuring tube inner tube, and the other end is connected to the second water outlet end of the peristaltic pump structure through a fourth conduit 94. One end of the water passing cavity is connected to the lower end of the second measuring tube outer tube, and the other end is connected to the second water inlet end of the peristaltic pump structure through a fifth conduit 95.

[0052] The measuring tube water storage base and the measuring tube water flow base are respectively provided with a water pressure sensor 96, and the water pressure sensor is connected to the micro control unit MCU embedded control system, and the water liquid change amount of the measuring tube water storage base and the measuring tube water flow base is respectively obtained through the micro control unit MCU embedded control system.

[0053] The automatic pressure regulating valve 7 includes a reduction motor 72, a connecting piece 73, a pressure regulating valve 74, a fixed rod 75, and a precision guide rail 76. The reduction motor is provided with a switch device. The precision guide rail is vertically arranged on the fixed rod. The pressure regulating valve is fixedly arranged on the fixed rod. The reduction motor is slidably arranged on the precision guide rail. The pressure regulating valve 74 includes a pressure regulating valve tightening shaft 74a. The reduction motor includes an output shaft. The output shaft of the reduction motor is connected to the pressure regulating valve tightening shaft through a connecting piece. When the reduction motor rotates forward, it drives the pressure regulating valve tightening shaft to tighten the pressure regulating valve, so that the pressure of the pressure regulating valve increases. At the same time, the pressure regulating valve tightening shaft drives the reduction motor to move along the precision guide rail. When the pressure regulating valve moves downward and the reduction motor reverses, the output shaft of the reduction motor drives the pressure regulating valve to tighten the rotating shaft and loosen the pressure regulating valve. At the same time, the pressure regulating valve tightens the rotating shaft to drive the reduction motor to move upward along the precision guide rail, so that the pressure of the automatic control valve is reduced. The pressure regulating valve is provided with a pressure sensor, and the pressure sensor is connected to the microcontroller unit MCU embedded control system. When the pressure value of the pressure regulating valve becomes smaller, the microcontroller unit MCU embedded control system starts the reduction motor to rotate forward to increase the pressure. When the pressure value of the pressure regulating valve becomes larger, the microcontroller unit MCU embedded control system starts the reduction motor to reverse and reduce the pressure, thereby controlling the pressure value of the automatic pressure regulating valve to a constant value.

[0054] Flushing process:

[0055] Open the sealing cover on the double-layer graduated measuring tube for flushing, and pour airless water into the double-layer graduated measuring tube for flushing from the top to fill the inner tube of the first measuring tube, fill the water level of the outer tube of the first measuring tube to the initial water level value, cover the sealing cover, and start flushing through the microcontroller unit MCU embedded control system. The system will automatically start the peristaltic pump, and the airless water passes through the outer tube of the first measuring tube, the water storage cavity, and the first conduit in sequence, and flows into the peristaltic pump from the first water inlet end. Driven by the peristaltic pump, the airless water passes through the first water outlet end and the second conduit in sequence and enters the base water storage cavity of the pressure chamber base. The airless water drives the squeezed water liquid in the base water storage cavity to flow out through the third conduit, and enters the inner tube of the first measuring tube through the water inlet hole of the measuring tube water storage base. The water liquid in the inner tube of the first measuring tube gradually increases and overflows. The overflowing water liquid enters the outer tube of the first measuring tube downward, and the bubbles in the water liquid are discharged upward through the air holes of the sealing cover. The water liquid in the outer tube of the first measuring tube continues to circulate according to this process until there are no more bubbles discharged from the double-layer graduated measuring tube for flushing, and then the flushing is stopped.

[0056] After the test starts, do not change the amount of water in the automatic flushing bubble mechanism and keep the initial amount of water unchanged. During the test, the system can be flushed at any time as needed, because the water in the inner tube of the first measuring tube is always full. The increase in the water volume in the outer tube of the first measuring tube is the water content of all the squeezed out test soil samples during the test.

[0057] The sealing cover is used to seal the water in the double-layer graduated measuring tube for flushing and reduce evaporation.

[0058] Evaporation compensation principle:

[0059] The evaporation compensation mechanism is started synchronously with the automatic flushing bubble mechanism, that is, when the flushing process starts, the sealing cover on the upper end of the outer tube of the second measuring tube of the double-layer graduated measuring tube for evaporation is opened, and airless water is poured in to fill the inner tube of the second measuring tube, and the water level of the outer tube of the second measuring tube is filled to the initial water level value, and then the sealing cover is covered to reduce water evaporation. Similar to the evaporation compensation mechanism, the water circulation flow of the evaporation compensation mechanism is synchronously started through the microcontroller unit MCU embedded control system. The water circulation flow of the evaporation compensation mechanism is an internal circulation flow. Since the evaporation compensation mechanism and the water in the measuring tube of the automatic flushing bubble mechanism have the same running speed, they circulate synchronously. In the same time period, the evaporation amount of water in the evaporation compensation mechanism is the same as the evaporation amount of water in the automatic flushing bubble mechanism. The evaporation amount of water in the evaporation compensation mechanism is obtained by the water amount difference in the evaporation compensation mechanism. By supplementing the automatic flushing bubble mechanism with the water evaporation amount, the accurate water amount in the automatic flushing bubble mechanism is obtained.

[0060] The present invention has been described in detail above. The above description is only a preferred embodiment of the present invention and should not limit the scope of implementation of the present invention. That is, any addition, reduction or replacement of general technical means made according to the scope of this application should still fall within the scope of the present invention.

Claims

1. A fully automatic unsaturated soil-water characteristic curve pressure plate instrument, which includes a control cabinet and a main test cabinet arranged on the control cabinet, wherein the main test cabinet is provided with a pressure chamber, a pressure chamber base, an axial pressurizing mechanism, and a confining pressure pressurizing mechanism, wherein the pressure chamber is arranged on the pressure chamber base, and a clay plate is also pressed between the pressure chamber and the pressure chamber base, a groove is formed on the pressure chamber base, and a base water storage cavity is formed between the clay plate and the pressure chamber base, wherein the pressure chamber is used to press a test soil sample, and the axial pressurizing mechanism is provided with an axial pressurizer, through which the axial pressurizer applies axial pressure to the test soil sample, and the confining pressure pressurizing mechanism is used to press the pressure chamber. The part provides confining pressure, and the moisture in the soil sample is discharged through the clay plate with air-blocking and water-passing functions under the action of axial pressure and confining pressure. The base water storage cavity is used to collect the moisture squeezed out of the test soil sample, and the water pressure sensor reads the water discharge after circulating through the flushing mechanism. A microcontrol unit MCU embedded control system is arranged in the control cabinet, and the axial pressurizer and the confining pressure pressurizing mechanism also include switch devices respectively. The microcontrol unit MCU embedded control system is connected with the switch devices of the axial pressurizer and the confining pressure pressurizing mechanism, and the axial pressurizer and the confining pressure pressurizing mechanism are controlled by the microcontrol unit MCU embedded control system, which is characterized in that: The pressure plate instrument is also provided with an automatic flushing bubble mechanism, which is provided with a peristaltic pump and a double-layer graduated measuring tube for flushing. The peristaltic pump, the double-layer graduated measuring tube for flushing and the base water storage cavity of the pressure chamber base constitute a water circulation flow path, which is driven by the peristaltic pump, and the bubbles are discharged through the double-layer graduated measuring tube for flushing, and the squeezed water in the base water storage cavity is flushed with bubbles. The peristaltic pump also includes a switch device, and the microcontroller unit MCU embedded control system is connected to the switch device of the peristaltic pump, and the peristaltic pump is controlled by the microcontroller unit MCU embedded control system; The pressure plate instrument is also provided with an evaporation compensation mechanism, which shares a peristaltic pump with the automatic flushing bubble mechanism, and is provided with a double-layer graduated measuring tube for evaporation, which forms a water circulation flow path through a conduit and the peristaltic pump, and the water of the evaporation compensation mechanism and the water of the automatic flushing bubble mechanism circulate synchronously; The main test cabinet is a transparent cover cabinet, and an electronic constant temperature and humidity device is fixed on the rear wall inside the transparent cover cabinet. The electronic constant temperature and humidity device is connected to the micro control unit MCU embedded control system, and the temperature and humidity inside the transparent cover cabinet are automatically controlled by computer software. The pressure plate instrument realizes constant temperature and humidity conditions during the test process by setting a closed transparent cover cabinet and the electronic constant temperature and humidity device, so as to obtain more accurate test data; The axial pressurizer and the confining pressure pressurizing mechanism are respectively connected to an automatic pressure regulating valve through an air guide pipe, and are respectively connected to an external air source through the air guide pipe through the automatic pressure regulating valve. The automatic pressure regulating valve includes a switch device, and the switch device of the automatic pressure regulating valve is respectively connected to a microcontroller MCU embedded control system. The automatic pressure regulating valve is controlled by the microcontroller MCU embedded control system, thereby controlling the pressure of the axial pressurizer and the confining pressure pressurizing mechanism; A touch-type industrial control computer is arranged at the front end of the control cabinet, and the microcontroller unit MCU embedded control system is connected to the touch-type industrial control computer, and the pressure plate instrument is controlled and operated by the touch-type industrial control computer.

2. The fully automatic unsaturated soil-water characteristic curve pressure plate instrument according to claim 1 is characterized in that: The axial pressurizing mechanism comprises a reaction force frame, the axial pressurizer comprises an axial loading cylinder fixed to the bottom of the reaction force frame, and a piston rod on the axial loading cylinder, the piston rod is connected to a lifting platform, the pressure chamber base is arranged on the lifting platform, the upper part of the reaction force frame is provided with an axial compression connecting rod and a displacement sensor, the axial compression connecting rod passes downward through the upper part of the pressure chamber, and the lower end is connected in sequence to the axial load sensor and the ball head, and is pressed on the test soil sample through the upper pressure plate and the permeable stone, a sealing structure is arranged between the axial compression connecting rod and the pressure chamber, the confining pressure pressurizing mechanism is connected to the side wall of the pressure chamber through the air guide pipe and is in conduction with the pressure chamber, during the test, the test soil sample is pressed into the pressure chamber, the axial pressurizer applies axial pressure to the test soil sample through the axial compression connecting rod, and at the same time, the confining pressure pressurizing mechanism applies confining pressure to the inside of the pressure chamber, and the moisture squeezed out of the test soil sample penetrates into the water storage cavity of the base through the clay plate.

3. The fully automatic unsaturated soil-water characteristic curve pressure plate instrument according to claim 1 is characterized in that: The automatic flushing bubble mechanism comprises a peristaltic pump structure, a double-layer graduated measuring tube for flushing, and a measuring tube water storage base. The peristaltic pump structure comprises a first water inlet end, a first water outlet end, and a peristaltic pump. The peristaltic pump drives the water to flow from the first water inlet end to the first water outlet end. The double-layer graduated measuring tube for flushing is fixed on the measuring tube water storage base. The double-layer graduated measuring tube for flushing comprises a first measuring tube inner tube and a first measuring tube outer tube arranged on the same axis line. The upper end of the first measuring tube outer tube is higher than the upper end of the first measuring tube inner tube. The first measuring tube outer tube is A sealing cover is provided at the upper end of the tube, and a plurality of air holes are provided on the sealing cover. The measuring tube water storage base includes a water inlet hole and a water storage cavity. One end of the water inlet hole is connected with the lower end of the inner tube of the first measuring tube, and the other end is connected with the base water storage cavity of the pressure chamber base through a third conduit. One end of the water storage cavity of the measuring tube water storage base is connected with the lower end of the outer tube of the first measuring tube, and the other end is connected with the first water inlet end of the peristaltic pump structure through the first conduit. The first water outlet end of the peristaltic pump structure is connected with the base water storage cavity of the pressure chamber base through a second conduit.

4. The fully automatic unsaturated soil-water characteristic curve pressure plate instrument according to claim 3 is characterized in that: The evaporation compensation mechanism includes a measuring tube water passing base and a double-layer graduated measuring tube for evaporation fixed on the measuring tube water passing base. The peristaltic pump structure also includes a second water inlet end and a second water outlet end. The evaporation compensation mechanism and the automatic flushing bubble mechanism share the peristaltic pump, and the water is driven to flow from the second water inlet end to the second water outlet end through the peristaltic pump. The double-layer graduated measuring tube for evaporation includes a second measuring tube inner tube and a second measuring tube outer tube arranged on the same axial line. The upper end of the second measuring tube outer tube is higher than the upper end of the second measuring tube inner tube. A sealing cover is provided on the upper end of the second measuring tube outer tube, and a plurality of air holes are provided on the sealing cover. The measuring tube water passing base includes a water inlet hole and a water passing cavity. One end of the water inlet hole is communicated with the lower end of the second measuring tube inner tube, and the other end is communicated with the second water outlet end of the peristaltic pump structure through a fourth conduit. One end of the water passing cavity is communicated with the lower end of the second measuring tube outer tube, and the other end is communicated with the second water inlet end of the peristaltic pump structure through a fifth conduit.

5. The fully automatic unsaturated soil-water characteristic curve pressure plate instrument according to claim 4 is characterized in that: The measuring tube water storage base and the measuring tube water flow base are respectively provided with water pressure sensors, and the water pressure sensors are connected to the microcontroller unit MCU embedded control system, and the water liquid changes of the measuring tube water storage base and the measuring tube water flow base are respectively obtained through the microcontroller unit MCU embedded control system.

6. The fully automatic unsaturated soil-water characteristic curve pressure plate instrument according to claim 1 is characterized in that: The automatic pressure regulating valve comprises a reduction motor, a connecting piece, a pressure regulating valve, a fixed rod, and a precision guide rail. The reduction motor is provided with a switch device. The precision guide rail is vertically arranged on the fixed rod. The pressure regulating valve is fixedly arranged on the fixed rod. The reduction motor is slidably arranged on the precision guide rail. The pressure regulating valve comprises a tightening shaft of the pressure regulating valve. The reduction motor comprises an output shaft. The output shaft of the reduction motor is connected to the tightening shaft of the pressure regulating valve through a connecting piece. When the reduction motor rotates forward, it drives the tightening shaft of the pressure regulating valve to tighten the pressure regulating valve, so that the pressure of the pressure regulating valve increases. At the same time, the tightening shaft of the pressure regulating valve drives the reduction motor to move downward along the precision guide rail. The reduction motor During reversal, the output shaft of the reduction motor drives the tightening shaft of the pressure regulating valve to loosen the pressure regulating valve. At the same time, the tightening shaft of the pressure regulating valve drives the reduction motor to move upward along the precision guide rail, so that the pressure of the automatic control valve is reduced. The pressure regulating valve is provided with a pressure sensor, and the pressure sensor is connected to the microcontroller unit MCU embedded control system. When the pressure value of the pressure regulating valve becomes smaller, the microcontroller unit MCU embedded control system starts the reduction motor to rotate forward to increase the pressure. When the pressure value of the pressure regulating valve becomes larger, the microcontroller unit MCU embedded control system starts the reduction motor to reverse and reduce the pressure, thereby controlling the pressure value of the automatic pressure regulating valve to a constant value.

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