A pressure plate instrument for fully automatic water volume measurement and recording and its use method

Abstract

This application discloses a fully automatic pressure plate instrument for measuring water volume and its usage method. The pressure plate instrument includes a pressure chamber system, a loading system, an automatic bubble flushing system, an inlet and outlet drainage system, and a control system. In this application, the control system automatically controls the various actions of the aforementioned pressure chamber system, loading system, automatic bubble flushing system, and inlet and outlet drainage system. After the test soil sample is installed, it can automatically complete all the remaining operations of the soil-water characteristic curve mapping test, which greatly reduces the degree of manual intervention in the test process, reduces the intensity of manual work, and also greatly reduces the impact of human operation errors on the test results.

Description

Technical Field

[0001] The present application belongs to the technical field of geotechnical engineering test instruments, and specifically relates to a pressure plate instrument for fully automatic water volume measurement and recording and a method for using the same. Background Art

[0002] Unsaturated soil is a multiphase mixture, consisting of a solid phase, a liquid phase, a gas phase and a water-gas interface (also called a shrinkage membrane). The two sides of the shrinkage membrane are gas phase and liquid phase respectively. The membrane has surface tension and is in a tension equilibrium state under the long-term action of gas phase pressure and liquid phase pressure. The study of the relationship between the gas and liquid phases in the equilibrium state is of great significance to the study of mechanics, permeability, deformation, etc. of unsaturated soil. The difference between the gas phase pressure and the liquid phase pressure of unsaturated soil is the matrix suction, and the ratio of water to soil volume in unsaturated soil is the volume moisture content. The volume moisture content decreases with the increase of matrix suction. For soils with the same properties, the relationship between matrix suction and volume moisture content is certain, and the relationship curve between matrix suction and volume moisture content is called the soil-water characteristic curve. This curve reflects the water holding capacity of the soil and has a high status in determining important parameters such as unsaturated strength and unsaturated permeability coefficient.

[0003] The pressure plate instrument is the most commonly used device for studying soil-water characteristic curves. The working principle of this device is to place the soil sample on a clay plate, which is only permeable to water but not air within a certain pressure range. The soil sample and clay plate are placed in a sealed cylinder, and air pressure is applied in the cylinder. Due to the effect of the gas phase pressure, the water in the soil is gradually discharged through the clay plate. Only by accurately measuring the volume of the discharged water can the volumetric water content be calculated. The matrix suction is equal to the applied air pressure value, and the soil-water characteristic curve can be drawn.

[0004] The traditional method of conventional pressure plate instrument is to manually blow air with an ear bulb or use a roller to drive the bubbles to the gas collecting device during the bubble flushing process in the pipeline. This process needs to be completed manually and at a fixed time, which seriously affects the test efficiency. Whether the bubble flushing is completed depends on visual observation and cannot be automatically identified. When measuring the drainage volume, the water level height is read by the naked eye through the scale tube, which seriously reduces the test accuracy. When recording and processing data, it is necessary to rely on the experimenter to read and record the readings at regular intervals every day, which seriously consumes manual labor.

[0005] There are also some new devices in the prior art that have upgraded the conventional pressure plate instruments for automation. Among them, "A fully automatic diffusion bubble scour measuring instrument for unsaturated soil testing (CN104034385A)" adopts a pressure-volume controller and a precision water pressure sensor to flush bubbles, "A fully automatic unsaturated soil-water characteristic curve pressure plate instrument (CN111257201A)" and "A soil-water characteristic curve pressure plate instrument with improved bubble scour structure (CN111257200A)" use a peristaltic pump circulating water flow path to flush bubbles, and "A fully automatic measurement system for a complete soil-water characteristic curve (CN108507931A)" adopts a stepping motor, a pressure sensor and a pressure-volume controller to achieve automatic control and measurement.

[0006] But there are still the following shortcomings:

[0007] 1. The water level is measured by a water pressure gauge, and the accuracy is generally in the order of ±1-5mm, which still has a large system error;

[0008] 2. The pipeline bubble flushing process is open-loop control, that is, after the scheduled flushing, manual inspection is still required to confirm whether there are any bubbles left. However, it is difficult for the human eye to identify tiny bubbles, and there is still a large random error;

[0009] 3. The bubble discharge path is long during the pipeline bubble flushing process, which makes it difficult to discharge the bubbles;

[0010] 4. The pipeline filling and drainage process before and after the test still needs to be manually controlled;

[0011] 5. During the test, some switch valves still need to be opened or closed manually.

[0012] This shows that the prior art still has certain defects. Summary of the invention

[0013] The present application provides a pressure plate instrument for fully automatic water volume measurement and recording and a method of using the same to solve at least one of the above-mentioned technical problems.

[0014] The technical solution adopted in this application is:

[0015] In the first aspect, the present application provides a pressure plate instrument for fully automatic water volume measurement, which includes a pressure chamber system, the pressure chamber system includes a pressure chamber for loading a test soil sample and a loading system connected to the pressure chamber for applying pressure to the test soil sample, and also includes a control system, through which the loading action of the loading system is automatically controlled, and also includes an automatic bubble flushing system, the automatic bubble flushing system includes a left-side measuring tube, a right-side measuring tube and a flushing pump, the left-side measuring tube, the right-side measuring tube, the flushing pump and the permeable base of the pressure chamber form a circulation path, and the water squeezed out of the test soil sample during the dehumidification measurement process enters the circulation path, the left-side measuring tube and the right-side measuring tube are used to collect and read the water discharge of the test soil sample during the dehumidification measurement process and read the water absorption during the moisture absorption measurement process; the automatic bubble flushing system also includes a first exhaust member, a first exhaust member, a second exhaust member, a first ... Two exhaust components, an air intake and exhaust assembly and an air collecting device, the first exhaust component is connected to the space above the liquid level inside the left measuring tube, the second exhaust component is connected to the space above the liquid level inside the right measuring tube, the air collecting device is arranged on the circulation passage and is located between the left measuring tube and the right measuring tube, the air collecting device includes a water storage chamber, the water storage chamber is connected to the circulation passage, the air intake and exhaust assembly includes an air intake and exhaust pipe and an air pump, the air intake and exhaust pipe is connected to the space above the liquid level inside the water storage chamber, the air pump is used to control the opening and closing of the air intake and exhaust assembly and to discharge bubbles through the air intake and exhaust assembly or to inhale gas into the water storage chamber so that the liquid level inside the water storage chamber is at a preset standard height; the automatic bubble flushing system is connected to the control system, and the automatic bubble flushing system is controlled by the control system.

[0016] By adopting the above-mentioned structure, it is possible to realize fully automatic water intake and drainage control, fully automatic bubble flushing, and fully automatic bubble flushing result detection of the circulation path of the present application, which greatly improves the efficiency of water intake and drainage and bubble flushing and can directly eliminate the influence of manual errors on the accuracy of test results compared to manual operation or bubble flushing operation that requires manual review.

[0017] Moreover, in the above scheme, the left measuring tube and the right measuring tube in the automatic bubble flushing system actually integrate the functions of flushing cycle and water volume measurement, and there is no need to set up additional water volume measuring devices / structures to detect the water discharge volume of the test soil sample in the dehumidification measurement and the water absorption volume of the test soil sample in the dehumidification measurement process, which simplifies the equipment structure and reduces the difficulty of the test. At the same time, in the present application scheme, the length of the bubble discharge path is shortened by setting an air collecting device between the left measuring tube and the right measuring tube, which is more convenient for collecting and discharging bubbles. In addition, compared with the use of a pressure-volume controller for bubble flushing, the use of the above structure can save a lot of equipment costs while ensuring the bubble flushing effect to ensure the accuracy of the test results. It is particularly suitable for experimental teaching, and is also suitable for the transformation and upgrading of traditional pressure plate instruments, further reducing the test cost.

[0018] As a preferred embodiment of the present application, the automatic bubble flushing system also includes an intake and exhaust control component, which includes a first solenoid valve connected to the first exhaust component and a second solenoid valve connected to the second exhaust component, the first solenoid valve is used to control the opening and closing of the first exhaust component, and the second solenoid valve is used to control the opening and closing of the second exhaust component.

[0019] In the above scheme, each valve is automatically controlled by the control system. That is to say, when the pressure plate instrument in this application is used to conduct soil-water characteristic curve mapping tests, there is no need for manual participation in the operation of each valve during the entire long test cycle, which saves a lot of manpower and can avoid test failure or extension of the test process due to human operating errors.

[0020] As a preferred embodiment of the present application, a first ultrasonic rangefinder is provided at the top of the left measuring tube, a second ultrasonic rangefinder is provided at the top of the right measuring tube, and a third ultrasonic rangefinder is provided at the top of the gas collecting device. The first ultrasonic rangefinder is used to measure the liquid level inside the left measuring tube and transmit the liquid level information to the control system, the second ultrasonic rangefinder is used to measure the liquid level inside the right measuring tube and transmit the liquid level information to the control system, and the third ultrasonic rangefinder is used to measure the liquid level inside the water storage chamber and transmit the liquid level information to the control system.

[0021] Preferably, the above-mentioned first, second and third ultrasonic rangefinders all adopt high-precision ultrasonic rangefinders with a ranging accuracy of 0.2mm and a ranging resolution of 0.1mm. Compared with traditional manual naked eye readings / water level gauges or pressure sensors or float measurements, they can more accurately measure the liquid level of the left measuring tube, the right measuring tube and the water storage chamber inside the gas collecting device, which is beneficial to ensure the accuracy of the test results.

[0022] As a preferred embodiment of the present application, it also includes a water intake and discharge system, which includes a water pump and a water storage tank, the water pump is connected to the water storage chamber and the water storage tank respectively, and the water pump injects the water in the water storage tank into the circulation path or extracts the water in the circulation path into the water storage tank under the control of the control system; the left measuring tube is also provided with a first bottom liquid level sensor, a first middle liquid level sensor, and a first upper liquid level sensor, and the right measuring tube is also provided with a second bottom liquid level sensor, a second middle liquid level sensor, and a second upper liquid level sensor.

[0023] In the above scheme, by setting up the above-mentioned multiple liquid level sensors, the changes in the liquid level height inside the left and right measuring tubes can be more accurately grasped during the test, which is convenient for more accurate control of the water inlet and outlet actions and the forward and reverse switching of the flushing pump during the bubble flushing process, thereby improving the bubble flushing efficiency and flushing effect.

[0024] As a preferred embodiment of the present application, the permeable base has a left inlet and drain port facing the left side of the measuring tube and a right inlet and drain port facing the right side of the measuring tube. The permeable base is connected in the circulation passage through the left inlet and drain port and the right inlet and drain port. A left solenoid valve is provided at the left inlet and drain port to control the opening and closing of the left inlet and drain port, and a right solenoid valve is provided at the right inlet and drain port to control the opening and closing of the right inlet and drain port. The left solenoid valve and the right solenoid valve are controlled by the control system.

[0025] As a preferred embodiment of the present application, a clay plate for carrying a test soil sample and a downward pressure component for transferring a vertical load to the test soil sample are arranged inside the pressure chamber, the clay plate is arranged on the upper part of the permeable base, the downward pressure component includes an upper pressure cover, a T-shaped permeable stone and an annular metal sheet, the interior of the upper pressure cover is provided with an internal flow channel that vertically penetrates the upper pressure cover, the upper part of the upper pressure cover is provided with an inlet of the internal flow channel, and the side of the upper pressure cover facing the T-shaped permeable stone is provided with an outlet of the internal flow channel; an upper pressure cover solenoid valve is also provided at the inlet of the internal flow channel, and the upper pressure cover solenoid valve can close or open the inlet of the internal flow channel.

[0026] By adopting the above structure, when the dehumidification measurement test is formally carried out, the T-shaped permeable stone arranged on the top of the test soil sample can be saturated with water through the internal flow channel arranged inside the upper pressure cover before the consolidation operation. By setting the upper pressure cover solenoid valve, the internal flow channel can be closed during the consolidation operation, thereby preventing the water in the test soil sample from being pressurized and discharged into the T-shaped permeable stone on the top during the consolidation process, ensuring that all the water discharged during the consolidation process enters the measuring tube, thereby overcoming the problem of inaccurate measurement of consolidation drainage, and thus facilitating the measurement accuracy of drainage during subsequent dehumidification measurements.

[0027] As a preferred embodiment of the present application, it also includes an equipment box, and the automatic bubble flushing system is arranged inside the equipment box; the control system is a PLC touch screen programming all-in-one machine, and the equipment box is provided with the PLC touch screen programming all-in-one machine.

[0028] In a second aspect, the present application also provides a method for using a pressure plate instrument for fully automatic water volume measurement, which is based on the above-mentioned pressure plate instrument for fully automatic water volume measurement, and includes the following steps:

[0029] Step 1: Place the test soil sample: open the top cover of the pressure chamber, install the permeable base and clay plate in place, and place the saturated test soil sample on the clay plate; after the test soil sample is placed, connect the pressure chamber to the loading system;

[0030] Step 2: Automatic water filling of the pipeline: The control system controls the water inlet and outlet system to extract water from the water storage tank and inject it into the circulation path until the liquid level inside the left and right measuring tubes reaches the specified height;

[0031] Step 3, automatic bubble flushing: the control system controls the automatic bubble flushing system to act multiple times to discharge the bubbles in the circulation path;

[0032] Step 4, automatic bubble detection: During the automatic bubble flushing process, the control system controls the first ultrasonic rangefinder and the second ultrasonic rangefinder to monitor the liquid level in the left and right measuring tubes after each flushing action is completed and calculates the sum of the liquid level in the left and right measuring tubes. When the difference between the sum of the liquid level in the left and right measuring tubes of two adjacent flushing actions is When the bubble flushing is less than 0.2mm, it is determined that the bubble flushing is completed, otherwise continue to repeat step 3;

[0033] Step 5: Automatic measurement and recording of dehumidification water volume: The control system controls the first ultrasonic rangefinder and the second ultrasonic rangefinder to measure the liquid level inside the left and right measuring tubes, and the sum of the liquid level in the two measuring tubes is recorded as , the control system controls the loading system to apply air pressure to the inside of the pressure chamber , the control system controls the execution of step 3 and step 4 every j hours. When the pressure drop is less than 0.2 mm, it is determined that the test soil sample has completed drainage and reached suction balance. The control system controls the first ultrasonic rangefinder and the second ultrasonic rangefinder to measure the liquid level inside the left and right measuring tubes, and the sum of the liquid level in the two measuring tubes is recorded as The control system is based on the soil porosity ratio e and the initial total volume of the soil sample input in advance. and the measured displacement =( - ) ,in To measure the cross-sectional area of ​​the pipe, the test soil sample is automatically calculated below Volume moisture content =e-(1+e) / , the control system controls the loading system to gradually increase the air pressure applied to the pressure chamber and records it as , , ..., , and repeat the above measurement and recording operation to obtain the volumetric water content at each level of gas pressure;

[0034] Step 6, automatic measurement and recording of water volume during moisture absorption measurement: the control system controls the loading system to gradually reduce the air pressure applied to the inside of the pressure chamber, and the volume water content of the test soil sample at each level of air pressure during the moisture absorption measurement process is calculated by referring to the calculation method in step 5;

[0035] Step 7: drawing soil-water characteristic curves. The control system draws soil-water characteristic curves of the test soil sample during the dehumidification process and the moisture absorption process according to the data obtained in Steps 5 and 6.

[0036] Step eight, after completing step seven, the water in the circulation path is completely extracted and transported to the water storage tank by controlling the water inlet and outlet system through the control system.

[0037] As a preferred embodiment of the present application, the above-mentioned automatic bubble flushing specifically includes: first, the control system controls the first solenoid valve to close, the second solenoid valve, the left solenoid valve, and the right solenoid valve to open, and controls the flushing pump to rotate forward to drive the water in the circulation path to flow forward, so that the liquid level in the left measuring tube begins to drop, and the liquid level in the right measuring tube begins to rise, a part of the bubbles are driven to the right measuring tube and discharged through the second exhaust member, and a part of the bubbles are driven to the gas collecting device and gathered in the space above the liquid level inside the water storage chamber, and wait until the liquid level inside the left measuring tube drops to trigger the first bottom liquid level sensor or the liquid level inside the right measuring tube rises to trigger the second top liquid level sensor. The control system controls the second solenoid valve to close, the first solenoid valve, the left solenoid valve, and the right solenoid valve to open, and controls the flushing pump to reversely drive the water in the circulation path to flow in the opposite direction, so that the liquid level in the right measuring tube begins to drop, and the liquid level in the left measuring tube begins to rise, and part of the bubbles are driven to the left measuring tube and discharged through the first exhaust member, and part of the bubbles are driven to the gas collecting device and gathered in the space above the liquid level in the water storage chamber, until the liquid level in the right measuring tube drops to trigger the second bottom liquid level sensor or the liquid level in the left measuring tube rises to trigger the first top liquid level sensor to complete a complete bubble flushing action, and this is repeated n times;

[0038] The automatic bubble detection specifically includes: the control system controls the air pump to rotate forward or reverse according to the measurement result of the third ultrasonic rangefinder so that the liquid level in the water storage chamber is maintained at the standard scale line, and the liquid level in the left and right measuring tubes is measured by the first and second ultrasonic rangefinders respectively. , And calculate + Then, the bubble flushing action is completed again and the liquid level in the left and right measuring tubes is measured again. , And calculate + , then calculate =|( + )-( + )|, if >0.2mm, repeat the bubble flushing action until <0.2mm.

[0039] As a preferred embodiment of the present application, the specific operation of automatic water filling of the above-mentioned pipeline includes controlling the first solenoid valve, the second solenoid valve, the left solenoid valve, and the right solenoid valve to open through the control system, and controlling the water pump to draw water from the water storage tank and input it into the circulation path until the liquid level inside the left measuring tube and the right measuring tube rises to trigger the first middle liquid level sensor and the second middle liquid level sensor.

[0040] Due to the adoption of the above technical solution, the beneficial effects achieved by this application are as follows:

[0041] 1. In the present application, the control system is used to automatically control the various actions in the aforementioned pressure chamber system, loading system, automatic bubble flushing system and water supply and drainage system, and all remaining operations of the soil-water characteristic curve mapping test can be automatically completed after the installation of the test soil sample is completed, which greatly reduces the manual participation in the test process, reduces the manual work intensity, and also greatly reduces the impact of manual operation errors on the test results.

[0042] 2. In this application, the water intake and discharge process of the circulation path, the bubble flushing process, and the water volume measurement process in the test have achieved closed-loop control. No human participation is required in the entire bubble flushing process and water volume measurement process, which not only saves manpower but also directly avoids manual operation / reading errors that lead to reduced accuracy of test results.

[0043] 3. In the above scheme, the left and right measuring tubes integrate the functions of water volume measurement and water storage flushing during the test, simplifying the equipment structure, eliminating the need to further reduce the control difficulty of the test equipment, facilitating the programming and modification of the equipment automation control program, and are particularly suitable for experimental teaching. In addition, the cost of the equipment components used in the above scheme is relatively low, which can greatly reduce the equipment cost while ensuring the same measurement accuracy.

[0044] 4. In the present application, when the dehumidification measurement test is formally carried out, the T-shaped permeable stone arranged on the top of the test soil sample can be saturated with water through the internal flow channel arranged inside the upper pressure cover before the consolidation operation. By setting the upper pressure cover solenoid valve, the internal flow channel can be closed during the consolidation operation, thereby preventing the water in the test soil sample from being pressurized and discharged into the T-shaped permeable stone on the top during the consolidation process, ensuring that all the water discharged during the consolidation process enters the measuring tube, thereby overcoming the problem of inaccurate measurement of consolidation drainage, and thus facilitating the measurement accuracy of drainage during subsequent dehumidification measurements.

[0045] 5. In the present application, the length of the bubble discharge path is greatly shortened by arranging the gas collecting device and the air inlet and outlet assembly on the circulation path between the left and right measuring tubes. Compared with the prior art that simply relies on the opening of the measuring tube to discharge bubbles, the difficulty of bubble removal is greatly reduced, which is conducive to improving the bubble flushing efficiency to save flushing time, thereby shortening the test cycle and improving the test efficiency. In addition, by controlling the liquid level in the water storage chamber of the gas collecting device at the standard scale line, the amount of water in the circulation path except the left and right measuring tubes can be kept constant, thereby ensuring the accuracy of reading the water discharge during the dehumidification measurement process and the water absorption during the moisture absorption measurement process by measuring the water level changes of the left and right measuring tubes. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0047] Figure 1 A schematic diagram of the overall structure of a pressure plate instrument for fully automatic water volume measurement in an example;

[0048] Figure 2 This is a schematic diagram of the structure of the left measuring tube in an example;

[0049] Figure 3 This is a schematic diagram of the structure of the right measuring tube in an example;

[0050] Figure 4 A schematic diagram of the connection structure between a flushing pump and a first exhaust member and a second exhaust member in an example;

[0051] Figure 5 A schematic diagram of the connection structure of the gas collecting device and the inlet and outlet pipes, the air pump, the water pump, and the water storage tank in an example;

[0052] Figure 6 is a schematic diagram of the structure of a pressure chamber system in an example;

[0053] Figure 7 It is a schematic diagram of the coordination structure between the upper pressure assembly and the test soil sample in an example;

[0054] Figure 8 This is a schematic diagram of the equipment box and central control system in an example.

[0055] List of parts and reference numerals:

[0056] 11 left measuring tube, 111 first ultrasonic distance meter, 112 first bottom liquid level sensor, 113 first middle liquid level sensor, 114 first top liquid level sensor, 12 right measuring tube, 121 second ultrasonic distance meter, 122 second bottom liquid level sensor, 123 second middle liquid level sensor, 124 second top liquid level sensor, 13 flushing pump;

[0057] 21 first exhaust component, 22 first solenoid valve, 23 second exhaust component, 24 second solenoid valve, 25 inlet and outlet pipes, 26 air pump;

[0058] 3 gas collecting device, 31 water storage chamber, 311 standard scale line, 32 third ultrasonic rangefinder;

[0059] 4 pressure chamber, 41 clay plate, 42 permeable base, 421 left inlet and outlet, 422 right inlet and outlet, 423 left solenoid valve, 424 right solenoid valve, 43 upper gland, 431 internal flow channel, 44 T-type permeable stone, 45 annular metal sheet, 46 upper gland solenoid valve, 47 ring knife, 48 quick-connect interface, 49 test soil sample;

[0060] 51 water pump, 52 water storage tank;

[0061] 6 equipment boxes, 61 PLC touch screen programming all-in-one machine. DETAILED DESCRIPTION

[0062] In order to more clearly illustrate the overall concept of the present application, a detailed description is given below in an illustrative manner in conjunction with the accompanying drawings.

[0063] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below. It should be noted that the embodiments of the present application and the features in each embodiment may be combined with each other without conflict.

[0064] In addition, in the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "top", "bottom", "inside", "outside", "axial", "radial", "circumferential", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0065] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0066] In the present application, unless otherwise clearly specified and limited, a first feature "above" or "below" a second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments or examples.

[0067] Reference Figure 1-8 As shown, the present application first provides a fully automatic water volume measurement and recording pressure plate instrument, which includes a pressure chamber 4 system, a loading system, an automatic bubble flushing system, a water inlet and outlet system and a control system. In the present application scheme, the control system automatically controls various actions in the aforementioned pressure chamber 4 system, the loading system, the automatic bubble flushing system and the water inlet and outlet system, and can automatically complete all remaining operations of the soil-water characteristic curve mapping test after the installation of the test soil sample is completed, which greatly reduces the manual participation in the test process, reduces the manual work intensity, and also greatly reduces the impact of manual operation errors on the test results.

[0068] In one example, referring to Figure 1-Figure 3 As shown, the automatic bubble flushing system mainly includes a left measuring tube 11, a right measuring tube 12 and a flushing pump 13. The left measuring tube 11, the right measuring tube 12, the flushing pump 13 and the permeable base 42 of the pressure chamber 4 form a circulation path. The water squeezed out of the test soil sample during the dehumidification measurement process enters the circulation path. The flushing pump 13 drives the water flow in the circulation path to perform bubble flushing. After that, the water discharge during the dehumidification measurement process and the water absorption during the moisture absorption measurement process of the test soil sample are read through the left measuring tube 11 and the right measuring tube 12. Specifically, a first ultrasonic rangefinder 111 is provided at the top of the left measuring tube 11, and a second ultrasonic rangefinder 121 is provided at the top of the right measuring tube 12. The first ultrasonic rangefinder 111 is used to measure the liquid level inside the left measuring tube 11 and transmit the liquid level information to the control system. The second ultrasonic rangefinder 121 is used to measure the liquid level inside the right measuring tube 12 and transmit the liquid level information to the control system. Continue to refer to Figure 4 and Figure 5As shown, it also includes a first exhaust member 21, a second exhaust member 23, an air intake and exhaust pipe assembly and an air collecting device 3. The first exhaust member 21 is connected to the space above the liquid level inside the left measuring tube 11, and the second exhaust member 23 is connected to the space above the liquid level inside the right measuring tube 12. The air collecting device 3 is arranged on the circulation passage and between the pressure chamber 4 and the right measuring tube 12. The air collecting device 3 includes a water storage chamber 31, which is connected to the circulation passage. The air intake and exhaust assembly includes an air intake and exhaust pipe 25 and an air pump 26. The air intake and exhaust pipe 25 is connected to the space above the liquid level inside the water storage chamber 31. The air pump 26 is used to control the opening and closing of the air intake and exhaust pipe 25 and to discharge gas through the air intake and exhaust pipe 25 or to inhale gas into the water storage chamber 31 so that the liquid level inside the water storage chamber 31 is at a preset standard height. A third ultrasonic rangefinder 32 is provided on the top of the gas collecting device 3. The third ultrasonic rangefinder 32 is used to measure the liquid level inside the water storage chamber 31 and transmit the liquid level information to the control system. During the flushing process, some bubbles are discharged through the first exhaust member 21 and the second exhaust member 23, and the other part is stored in the space above the liquid level inside the water storage chamber 31. Preferably, continue to refer to the same Figure 4 and Figure 5 As shown, the automatic bubble flushing system in this example also includes an air intake and exhaust control component, which includes a first solenoid valve 22 connected to the first exhaust member 21 and a second solenoid valve 24 connected to the second exhaust member 23. The first solenoid valve 22 is used to control the opening and closing of the first exhaust member 21, and the second solenoid valve 24 is used to control the opening and closing of the second exhaust member 23. Figure 5 As shown, it also includes a water inlet and outlet system, which includes a water pump 51 and a water storage tank 52. The water pump 51 is connected to the water storage chamber 31 and the water storage tank 52 respectively. The water pump 51 injects the water in the water storage tank 52 into the circulation path or extracts the water in the circulation path into the water storage tank 52 under the control of the control system; Figure 2 and Figure 3 As shown, the left measuring tube 11 is also provided with a first bottom liquid level sensor 112, a first middle liquid level sensor 113, and a first upper liquid level sensor, and the right measuring tube 12 is also provided with a second bottom liquid level sensor 122, a second middle liquid level sensor 123, and a second upper liquid level sensor. Figure 6 As shown, the permeable base 42 has a left inlet and outlet 421 facing the left measuring tube 11 side and a right inlet and outlet 422 facing the right measuring tube 12 side. The permeable base 42 is connected in a circulation passage through the left inlet and outlet 421 and the right inlet and outlet 422. A left solenoid valve is provided at the left inlet and outlet 421 to control the opening and closing of the left inlet and outlet 421, and a right solenoid valve is provided at the right inlet and outlet 422 to control the opening and closing of the right inlet and outlet 422. The left solenoid valve and the right solenoid valve are controlled by a control system.

[0069] By adopting the above structure, the water intake and drainage process of the circulation path, the bubble flushing process, and the water volume measurement process in the test in the present application realize closed-loop control. No human intervention is required in the entire bubble flushing process and the water volume measurement process, which not only saves manpower but also directly avoids the reduction of the accuracy of the test results caused by manual operation / reading errors. At the same time, in the above scheme, the left measuring tube 11 and the right measuring tube 12 integrate the functions of water volume measurement and water storage flushing in the test process, simplifying the equipment structure, eliminating the need to further reduce the control difficulty of the test equipment, and facilitating the programming and modification of the equipment automation control program, which is particularly suitable for experimental teaching. In addition, the cost of the equipment components used in the above scheme is relatively low, which can greatly reduce the equipment cost while ensuring the same measurement accuracy.

[0070] In the above scheme, the length of the bubble discharge path is greatly shortened by arranging the gas collecting device and the air intake and exhaust components on the circulation passage between the left measuring tube and the right measuring tube. Compared with the prior art that simply relies on the measuring tube opening to discharge bubbles, the difficulty of bubble removal is greatly reduced, which is beneficial to improving the bubble flushing efficiency to save flushing time, and further beneficial to shortening the test cycle and improving the test efficiency.

[0071] Preferably, the left measuring tube 11 and the right measuring tube 12 are made of transparent organic glass and scale paper is pasted on the tube wall, the water storage chamber 31 is provided with a standard scale line 311, and the first ultrasonic rangefinder 111, the second ultrasonic rangefinder 121, and the third ultrasonic rangefinder 32 installed on the left measuring tube 11 and the right measuring tube 12 are brass nickel-plated shells and threaded designs, so that they can be conveniently sealed with the left and right measuring tubes and the gas collecting device 3 through the threaded structure at the top of the left and right measuring tubes and the top of the gas collecting device 3, and the ranging accuracy is 0.2mm and the resolution is 0. .1mm, the use of a high-precision ultrasonic rangefinder can greatly improve the accuracy of water level measurement compared to the existing human eye observation readings or water level gauges / pressure sensors / floating balls to measure water level height, and by controlling the liquid level in the water storage chamber 31 of the gas collecting device 3 at the standard scale line 311, the amount of water in the circulation path except the left measuring tube 11 and the right measuring tube 12 can be kept constant, which can further ensure the accuracy of reading the drainage amount during the dehumidification measurement process and the water absorption amount during the moisture absorption measurement process by measuring the water level changes of the left measuring tube 11 and the right measuring tube 12. It also saves a lot of manual intervention, reduces the labor intensity, and can also reduce the errors caused by manual intervention.

[0072] In one example, referring to Figure 6As shown, a quick-connect joint is provided on the top cover of the pressure chamber 4, and a clay plate 41 and a ring knife 47 for carrying the test soil sample are provided inside the pressure chamber 4. The clay plate 41 is provided on the upper part of the permeable base 42, and the ring knife 47 limits and fixes the test soil sample on the clay plate 41. With this arrangement, during the test process without considering the consolidation conditions, the pressure chamber 4 can be quickly connected to the aforementioned loading system through the quick-connect joint, which facilitates the loading system to apply pressure to the inside of the pressure chamber 4, which is conducive to improving the test efficiency.

[0073] In another example, referring to Figure 7 As shown, a downward pressure assembly for transmitting vertical load to the test soil sample is also provided inside the pressure chamber, a clay plate 41 is provided on the upper part of the permeable base 42, and the downward pressure assembly and the ring knife 47 limit and fix the test soil sample on the clay plate 41, and the downward pressure assembly includes an upper pressure cover 43, a T-shaped permeable stone 44 and an annular metal sheet 45, and an internal flow channel 431 penetrating the upper pressure cover 43 in the vertical direction is provided inside the upper pressure cover 43, an inlet of the internal flow channel 431 is provided on the upper part of the upper pressure cover 43, and an outlet of the internal flow channel 431 is provided on the side of the upper pressure cover 43 facing the T-shaped permeable stone 44; an upper pressure cover solenoid valve 46 is also provided at the inlet of the internal flow channel 431, and the upper pressure cover solenoid valve 46 can close or open the inlet of the internal flow channel 431. With this arrangement, during the test process where consolidation conditions need to be considered, the upper gland 43 can directly transmit the vertical load applied by the axial load rod in the loading system to the test soil sample, and when the dehumidification measurement test is formally carried out, the internal flow channel 431 provided inside the upper gland 43 can be used to first saturate the T-shaped permeable stone 44 provided on the top of the test soil sample with water, and the upper gland solenoid valve 46 can be provided to close the internal flow channel 431 during the consolidation operation, thereby preventing water in the test soil sample from being trapped during the consolidation process. The water is discharged under pressure into the T-shaped permeable stone 44 at the top, ensuring that all the water discharged during the consolidation process enters the measuring tube, thereby overcoming the problem of inaccurate consolidation drainage measurement in the prior art, and thus helping to ensure the measurement accuracy of the drainage during the subsequent dehumidification measurement process; in the test process where the consolidation conditions do not need to be considered, the above-mentioned structure is adopted. After the internal flow channel 431 is filled with water, the barrier effect of the downward pressure component and the ring knife 47 can ensure that the moisture in the test soil sample can only be discharged through the permeable base 42 at the bottom, which is conducive to ensuring the measurement accuracy of the drainage during the dehumidification measurement process.

[0074] Reference Figure 1 and Figure 8As shown, the device also includes a device box 6, and the automatic bubble flushing system is arranged inside the device box 6; the control system is a PLC touch screen programming integrated machine 61, and the device box 6 is provided with a PLC touch screen programming integrated machine 61. Compared with the use of an MCU embedded control system, the use of the PLC touch screen programming integrated machine 61 can greatly reduce the equipment cost and save a lot of test programming design cycles, saving time costs.

[0075] Based on the above-mentioned pressure plate instrument for automatic water volume measurement, the present application also provides a method for using the pressure plate instrument for automatic water volume measurement to complete the soil-water characteristic curve mapping test in a simple and efficient manner, which mainly includes the following steps:

[0076] Step 1, placing the test soil sample: open the top cover of the pressure chamber 4, install the permeable base 42 and the clay plate 41 in place, and place the saturated test soil sample on the clay plate 41; after the test soil sample is placed, connect the pressure chamber 4 to the loading system.

[0077] Step 2: Automatically fill the pipeline with water: the control system controls the water inlet and outlet system to extract water from the water storage tank 52 and inject it into the circulation path until the liquid levels inside the left measuring tube 11 and the right measuring tube 12 reach the specified height; the specific operation includes controlling the first solenoid valve 22, the second solenoid valve 24, the left solenoid valve, and the right solenoid valve to open through the control system, and controlling the water pump 51 to extract water from the water storage tank 52 and input it into the circulation path until the liquid levels inside the left measuring tube 11 and the right measuring tube 12 rise to trigger the first middle liquid level sensor 113 and the second middle liquid level sensor 123.

[0078] Step three, automatic bubble flushing: the control system controls the automatic bubble flushing system to act multiple times to discharge the bubbles in the circulation path. Preferably, the specific operations include: first, the control system controls the first solenoid valve 22 to close, the second solenoid valve 24, the left solenoid valve, and the right solenoid valve to open, and controls the flushing pump 13 to rotate forward to drive the water in the circulation path to flow forward, so that the liquid level in the left measuring tube 11 begins to drop, and the liquid level in the right measuring tube 12 begins to rise, a part of the bubbles are driven to the right measuring tube 12, and discharged through the second exhaust member 23, and a part of the bubbles are driven to the gas collecting device 3 and gathered in the space above the liquid level inside the water storage chamber 31, and when the liquid level inside the left measuring tube 11 drops to trigger the first bottom liquid level sensor 112 and the liquid level inside the right measuring tube 12 rises to trigger the second top liquid level sensor 124, the control system controls the second solenoid valve 2 4 is closed, the first solenoid valve 22, the left solenoid valve and the right solenoid valve are opened, and the flushing pump 13 is controlled to reverse to drive the water in the circulation path to flow in the opposite direction, so that the liquid level in the right measuring tube 12 begins to decrease, and the liquid level in the left measuring tube 11 begins to increase. A part of the bubbles is driven to the left measuring tube 11 and discharged through the first exhaust member 21, and a part of the bubbles is driven to the gas collecting device 3 and gathered in the space above the liquid level in the water storage chamber 31, until the liquid level in the right measuring tube 12 decreases to trigger the second bottom liquid level sensor 122 and the liquid level in the left measuring tube 11 increases to trigger the first top liquid level sensor 114 to complete a complete bubble flushing action, and this is repeated n times, and the value of n can be freely set in the control system according to the test needs.

[0079] Step 4, automatic bubble detection: During the automatic bubble flushing process, the control system controls the first ultrasonic rangefinder 111 and the second ultrasonic rangefinder 121 to monitor the liquid level in the left measuring tube 11 and the right measuring tube 12 after each flushing action is completed and calculates the sum of the liquid level in the left measuring tube 11 and the right measuring tube 12. When the difference between the sum of the liquid level in the left measuring tube 11 and the right measuring tube 12 in two adjacent flushing actions is When the bubble flushing is less than 0.2 mm, it is determined that the bubble flushing is completed, otherwise, step 3 is repeated. Preferably, the specific operation includes: the control system controls the air pump 26 to rotate forward or reverse according to the measurement result of the third ultrasonic rangefinder 32 so that the liquid level in the water storage chamber 31 is maintained at the standard scale line 311, and the liquid level in the left measuring tube 11 and the right measuring tube 12 are measured by the first ultrasonic rangefinder 111 and the second ultrasonic rangefinder 121 respectively. , And calculate + Then, the bubble flushing action is completed again and the liquid level in the left measuring tube 11 and the right measuring tube 12 is measured again. , And calculate + , then calculate =|( + )-( + )|, if >0.2mm, repeat the bubble flushing action until <0.2mm

[0080] Step 5: Automatic measurement and recording of dehumidification water volume: The control system controls the first ultrasonic rangefinder 111 and the second ultrasonic rangefinder 121 to measure the liquid level inside the left measuring tube 11 and the right measuring tube 12, and records the sum of the liquid level in the two measuring tubes as , the control system controls the loading system to apply air pressure to the inside of the pressure chamber 4 , the control system controls the execution of step 3 and step 4 every j hours (the j value can be freely set in the control system according to the test needs). When the test soil sample is less than 0.2 mm, it is judged that When the drainage is completed and the suction balance is achieved, the control system controls the first ultrasonic rangefinder 111 and the second ultrasonic rangefinder 121 to measure the liquid level inside the left measuring tube 11 and the right measuring tube 12, and the sum of the liquid level in the two measuring tubes is recorded as The control system is based on the soil porosity ratio e and the initial total volume of the soil sample input in advance. and the measured displacement =( - ) ,in The cross-sectional area of ​​the test tube is automatically calculated. Volume moisture content =e-(1+e) / , the control system controls the loading system to gradually increase the air pressure applied to the inside of the pressure chamber 4 and is recorded as , , ..., , and repeat the above operation to obtain the volumetric water content at each level of gas pressure;

[0081] Step 6, automatic measurement and recording of water volume during moisture absorption measurement: the control system controls the loading system to gradually reduce the air pressure applied to the inside of the pressure chamber 4, and the volume water content of the test soil sample at each level of air pressure during the moisture absorption measurement process is calculated by referring to the calculation method in step 5;

[0082] Step 7: drawing soil-water characteristic curves. The control system draws soil-water characteristic curves of the test soil sample during the dehumidification process and the moisture absorption process according to the data obtained in Steps 5 and 6.

[0083] Step eight, after completing step seven, the water in the circulation path is completely extracted and transported to the water storage tank 52 by controlling the water inlet and outlet system through the control system.

[0084] By adopting the above method, the fully automatic air pressure control, fully automatic water inlet and outlet control, fully automatic bubble scouring control, fully automatic bubble scouring result detection control, fully automatic water volume measurement and recording control and automatic drawing of the final soil-water characteristic curve of the pressure plate instrument are realized, and the whole process of the soil-water characteristic curve test except the installation of the test soil sample is automated. Compared with the existing manual measurement and manual review test process, it greatly saves manpower and improves the test efficiency. In addition, the automated control during the test process can directly eliminate the influence of manual operation errors on the accuracy of the test results, which is beneficial to improving the surveying and mapping accuracy of the soil-water characteristic curve.

[0085] Anything not described in this application can be achieved by adopting or drawing on existing technologies.

[0086] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0087] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A pressure plate instrument for full-automatic water volume measurement, comprising a pressure chamber system, the pressure chamber system comprising a pressure chamber for loading a test soil sample and a loading system connected to the pressure chamber for applying pressure to the test soil sample, and also comprising a control system, through which the loading action of the loading system is automatically controlled, characterized in that: It also includes an automatic bubble flushing system, which includes a left-side measuring tube, a right-side measuring tube and a flushing pump. The left-side measuring tube, the right-side measuring tube, the flushing pump and the water-permeable base of the pressure chamber form a circulation path. The water squeezed out of the test soil sample during the dehumidification measurement process enters the circulation path. The left-side measuring tube and the right-side measuring tube are used to collect and read the water discharge amount of the test soil sample during the dehumidification measurement process and read the water absorption amount during the moisture absorption measurement process; The automatic bubble flushing system also includes a first exhaust member, a second exhaust member, an air intake and exhaust assembly and an air collecting device, wherein the first exhaust member is in communication with the space above the liquid level inside the left measuring tube, the second exhaust member is in communication with the space above the liquid level inside the right measuring tube, the air collecting device is arranged on the circulation passage and is located between the left measuring tube and the right measuring tube, the air collecting device includes a water storage chamber, the water storage chamber is in communication with the circulation passage, the air intake and exhaust assembly includes an air intake and exhaust pipe and an air pump, the air intake and exhaust pipe is in communication with the space above the liquid level inside the water storage chamber, the air pump is used to control the opening and closing of the air intake and exhaust assembly and to discharge bubbles through the air intake and exhaust assembly or to inhale gas into the water storage chamber so that the liquid level inside the water storage chamber is at a preset standard height; The automatic bubble flushing system is connected to the control system, and the automatic bubble flushing system is controlled by the control system.

2. The pressure plate instrument for fully automatic water volume measurement as claimed in claim 1, characterized in that: The automatic bubble flushing system also includes an intake and exhaust control component, which includes a first solenoid valve connected to the first exhaust component and a second solenoid valve connected to the second exhaust component, the first solenoid valve is used to control the opening and closing of the first exhaust component, and the second solenoid valve is used to control the opening and closing of the second exhaust component.

3. The pressure plate instrument for fully automatic water volume measurement as claimed in claim 1, characterized in that: A first ultrasonic rangefinder is provided at the top end of the left measuring tube, a second ultrasonic rangefinder is provided at the top end of the right measuring tube, and a third ultrasonic rangefinder is provided at the top of the gas collecting device. The first ultrasonic rangefinder is used to measure the liquid level inside the left measuring tube and transmit the liquid level information to the control system, the second ultrasonic rangefinder is used to measure the liquid level inside the right measuring tube and transmit the liquid level information to the control system, and the third ultrasonic rangefinder is used to measure the liquid level inside the water storage chamber and transmit the liquid level information to the control system.

4. The pressure plate instrument for fully automatic water volume measurement as claimed in claim 1, characterized in that: It also includes a water inlet and outlet system, which includes a water pump and a water storage tank. The water pump is connected to the water storage chamber and the water storage tank respectively. Under the control of the control system, the water pump injects the water in the water storage tank into the circulation path or extracts the water in the circulation path into the water storage tank; The left measuring tube is also provided with a first bottom liquid level sensor, a first middle liquid level sensor, and a first upper liquid level sensor, and the right measuring tube is also provided with a second bottom liquid level sensor, a second middle liquid level sensor, and a second upper liquid level sensor.

5. The pressure plate instrument for fully automatic water volume measurement as claimed in claim 1, characterized in that: The permeable base has a left inlet and outlet facing the left measuring tube and a right inlet and outlet facing the right measuring tube. The permeable base is connected in the circulation passage through the left inlet and outlet and the right inlet and outlet. A left solenoid valve is provided at the left inlet and outlet to control the opening and closing of the left inlet and outlet, and a right solenoid valve is provided at the right inlet and outlet to control the opening and closing of the right inlet and outlet. The left solenoid valve and the right solenoid valve are controlled by the control system.

6. The pressure plate instrument for fully automatic water volume measurement as claimed in claim 1, characterized in that: The interior of the pressure chamber includes a clay plate for carrying a test soil sample and a downward pressure component for transmitting a vertical load to the test soil sample. The clay plate is arranged on the upper part of the permeable base. The downward pressure component includes an upper pressure cover, a T-shaped permeable stone and an annular metal sheet. The interior of the upper pressure cover is provided with an internal flow channel that vertically penetrates the upper pressure cover. The upper part of the upper pressure cover is provided with an inlet of the internal flow channel, and the side of the upper pressure cover facing the T-shaped permeable stone is provided with an outlet of the internal flow channel; an upper pressure cover solenoid valve is also provided at the inlet of the internal flow channel, and the upper pressure cover solenoid valve can close or open the inlet of the internal flow channel.

7. The pressure plate instrument for fully automatic water volume measurement as claimed in claim 1, characterized in that: It also includes an equipment box, and the automatic bubble flushing system is arranged inside the equipment box; the control system is a PLC touch screen programming all-in-one machine, and the equipment box is provided with the PLC touch screen programming all-in-one machine.

8. A method for using a pressure plate instrument for fully automatic water volume measurement, characterized in that: The pressure plate instrument for fully automatic water volume measurement according to claim 1 comprises the following steps: Step 1: Place the test soil sample: open the top cover of the pressure chamber, install the permeable base and clay plate in place, and place the saturated test soil sample on the clay plate; after the test soil sample is placed, connect the pressure chamber to the loading system; Step 2: Automatic water filling of the pipeline: The control system controls the water inlet and outlet system to extract water from the water storage tank and inject it into the circulation path until the liquid level inside the left and right measuring tubes reaches the specified height; Step 3, automatic bubble flushing: the control system controls the automatic bubble flushing system to act multiple times to discharge the bubbles in the circulation path; Step 4, automatic bubble detection: During the automatic bubble flushing process, the control system controls the first ultrasonic rangefinder and the second ultrasonic rangefinder to monitor the liquid level in the left and right measuring tubes after each flushing action is completed and calculates the sum of the liquid level in the left and right measuring tubes. When the difference between the sum of the liquid level in the left and right measuring tubes of two adjacent flushing actions is When the bubble flushing is less than 0.2mm, it is determined that the bubble flushing is completed, otherwise continue to repeat step 3; Step 5: Automatic measurement and recording of dehumidification water volume: A first ultrasonic rangefinder is provided at the top of the left measuring tube, a second ultrasonic rangefinder is provided at the top of the right measuring tube, and a third ultrasonic rangefinder is provided at the top of the gas collecting device. The control system controls the first ultrasonic rangefinder and the second ultrasonic rangefinder to measure the liquid level inside the left measuring tube and the right measuring tube, and the sum of the liquid level in the two measuring tubes is recorded as , the control system controls the loading system to apply air pressure to the inside of the pressure chamber , the control system controls the execution of step 3 and step 4 every j hours. When the test soil sample is less than 0.2 mm, it is judged that When the drainage is completed and the suction balance is achieved, the control system controls the first ultrasonic rangefinder and the second ultrasonic rangefinder to measure the liquid level inside the left and right measuring tubes, and the sum of the liquid level in the two measuring tubes is recorded as The control system is based on the soil porosity ratio e and the initial total volume of the soil sample input in advance. and the measured displacement =( - ) ,in The cross-sectional area of ​​the test tube is automatically calculated. Volume moisture content =e-(1+e) / , the control system controls the loading system to gradually increase the air pressure applied to the pressure chamber and records it as , , ..., , and repeat the above measurement and recording operation to obtain the volumetric water content at each level of gas pressure; Step 6, automatic measurement and recording of water volume during moisture absorption measurement: the control system controls the loading system to gradually reduce the air pressure applied to the inside of the pressure chamber, and the volume water content of the test soil sample at each level of air pressure during the moisture absorption measurement process is calculated by referring to the calculation method in step 5; Step 7: drawing soil-water characteristic curves. The control system draws soil-water characteristic curves of the test soil sample during the dehumidification process and the moisture absorption process according to the data obtained in Steps 5 and 6. Step eight, the pressure plate instrument for fully automatic water volume measurement also includes an inlet and outlet water system. After completing step seven, the inlet and outlet water system is controlled by the control system to extract all the water in the circulation path and transport it to the water storage tank.

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