A device for controlling the moisture content of sandy mudstone based on the principle of positive and negative pressure

Abstract

This invention provides a moisture content control device for sandy mudstone based on the principle of positive and negative pressure, including a wide-temperature-range constant temperature chamber, a temperature control device, and a moisture content regulation unit. During operation, the intelligent temperature control device first adjusts the temperature to allow the sandy mudstone to air dry until the gravity transmitted by the electronic gravity sensor no longer changes. On one hand, an external remote control starts an intelligent humidifier and a rotary vacuum pump, causing water vapor to flow from the negative pressure chamber through the pores of the sandy mudstone in the sample fixing stage to the positive pressure chamber under the influence of positive and negative pressure, thus increasing the moisture content of the sandy mudstone. On the other hand, the electronic gravity sensor transmits real-time data, calculating the moisture content and rate of the sandy mudstone sample according to a pre-set formula program. Simultaneously, when the moisture content of the sandy mudstone sample reaches the set value for the required test, the program automatically stops, and the wide-temperature-range constant temperature chamber returns to normal.

Description

Technical Field

[0001] This invention relates to the field of experimental technology for controlling the moisture content of sandy mudstone, and in particular to a device for controlling the moisture content of sandy mudstone based on the principle of positive and negative pressure. Background Technology

[0002] Moisture content is a crucial factor influencing the physical and mechanical properties of sandy mudstone. Sandy mudstone is a type of rock composed of clay and clastic minerals, with a high content of hydrophilic clay minerals such as montmorillonite. This gives it significant water absorption and swelling characteristics. In geotechnical engineering, changes in the moisture content of sandy mudstone have a substantial impact on its mechanical properties and are a significant factor leading to engineering accidents. In slope engineering, changes in the moisture content of sandy mudstone affect its shear strength. When the moisture content increases, the shear strength decreases, easily triggering slope instability, landslides, and other geological disasters, posing a serious threat to engineering construction and the surrounding environment. The traditional "soaking-drying" method has revealed serious limitations when treating sandy mudstone. During soaking, a large amount of water rushes into the pores, and clay minerals such as montmorillonite expand upon contact with water, causing changes in the internal structural stress of the rock. During drying, water is rapidly lost, and minerals shrink. This drastic volume change makes sandy mudstone extremely prone to disintegration, severely damaging its original structure. As a result, it is impossible to accurately obtain its true physical and mechanical properties at different moisture contents, which greatly affects the research and evaluation of sandy mudstone in engineering applications.

[0003] The commonly used experimental instruments for controlling the moisture content of sandy mudstone on the market are mainly drying ovens, rapid moisture analyzers, high-frequency moisture detectors, and capacitive sensor moisture meters.

[0004] Key issue ①: Traditional oven drying tests only consider that high temperatures can dry sandy mudstone, without considering the precise temperature for drying. If the temperature is too high, some bound water in the sandy mudstone may be released prematurely, resulting in an overestimation of the moisture content. If the temperature is too low, the drying time may be too long, or even the sandy mudstone may not be completely dried.

[0005] Key issue ②: Different types of sandy mudstone, such as montmorillonite sandy mudstone and kaolinite sandy mudstone, have different mineral compositions, particle sizes, and pore structures, which will affect the form (such as adsorbed water, bound water, and free water) and content of water. For example, montmorillonite sandy mudstone has strong water absorption and swelling properties, and its water content and distribution pattern are significantly different from those of kaolinite sandy mudstone. These characteristics need to be considered when measuring water content.

[0006] Key Issue ③: Sample size and shape affect the rate and uniformity of moisture evaporation. Larger samples evaporate moisture relatively slowly, potentially requiring longer drying times or stronger detection signals for accurate moisture content measurement. Irregularly shaped samples can lead to non-uniformity in instrument detection; for example, when using a capacitive sensor moisture meter, an irregular shape may cause uneven electric field distribution, affecting the measurement of the dielectric constant.

[0007] Key issue 4: Most of these instruments are used for measurements in a relatively stable laboratory environment, and rarely consider the complex working conditions of sandy mudstone in actual engineering environments, such as wet-dry cycles, freeze-thaw cycles, and positive and negative pressure changes.

[0008] CN 119086878 A: A device and method for testing the hydrophysical properties of soil and rock samples under wet-dry cycling; the device achieves full automation of the wet-dry cycling and monitoring processes through an electronic control system, reducing the impact of manual intervention on test accuracy. The wet-dry cycling system can effectively simulate the natural phenomenon of alternating wet and dry conditions. This technical solution is suitable for accurate testing of single sandy mudstone samples under wet-dry cycling conditions, but it cannot simulate the complex working conditions of multiple sandy mudstone samples under wet-dry cycling, freeze-thaw cycles, temperature, and positive and negative pressure.

[0009] CN 107782640 A: A method for detecting water content uniformity and calculating diffusion coefficient of rock specimens based on digital images; This method introduces digital image technology into the detection of water content uniformity and calculation of diffusion coefficient of rock specimens. By acquiring color difference images of the sample surface during the humidity diffusion process, MATLAB is used to identify and extract color grayscale values ​​and calculate variance to analyze water content uniformity, realizing a quantitative description of the water content distribution of rocks. It can not only determine water content uniformity, but also establish a quantitative relationship through regression analysis of pixel grayscale values ​​and water content. However, it may not be effective in detecting water content uniformity for rocks such as sandy mudstone with extremely small pores or special water absorption.

[0010] CN 212159647 U: A device for monitoring the characteristics of rock moisture content change under rainfall conditions; the resistivity of rock samples is measured by a digital bridge, conversion device and electrodes, and the data is processed by a computer. It can obtain information on the change of rock moisture content in real time during rainfall simulation. However, it cannot obtain accurate data on the moisture content of some sandy mudstones, and there is an error in the determination of the moisture content of sandy mudstones. Summary of the Invention

[0011] The purpose of this invention is to provide a device for controlling the water content of sandy mudstone based on the principle of positive and negative pressure, which can effectively control the water content and rate of water content in sandy mudstone. To achieve the above-mentioned technical features, this invention achieves its purpose as follows:

[0012] A device for controlling the moisture content of sandy mudstone based on the principle of positive and negative pressure includes a wide-temperature-range constant temperature chamber and a temperature control device.

[0013] The wide-temperature-range constant temperature chamber is equipped with a moisture content control unit, which includes a sample fixing stage. The sample fixing stage is provided with an installation groove adapted to the shape of the sandy mudstone sample, and the installation groove is connected to a positive pressure chamber and a negative pressure chamber on both sides of the sample fixing stage. The positive pressure chamber is connected to the mist outlet of a humidifier, and the negative pressure chamber is connected to the air inlet of a vacuum pump. The top of the sample fixing stage, the positive pressure chamber, and the negative pressure chamber are provided with sealing covers. An electronic gravity sensor is provided below the sample fixing stage, and the electronic gravity sensor is connected to a calculation and data processing unit.

[0014] The temperature control device is installed on the wide-temperature-range constant temperature chamber and is used to adjust the temperature inside the chamber.

[0015] The positive pressure chamber and the negative pressure chamber are respectively connected to the mist outlet of the humidifier and the air inlet of the vacuum pump through a pressure stabilization and balance port.

[0016] The vacuum pump is equipped with a check valve at its inlet.

[0017] The wide-temperature-range constant temperature chamber is equipped with a temperature lock cover, which has a handle for easy opening and closing.

[0018] The bottom of the wide-temperature-range constant temperature chamber is provided with a platform, and the top of the platform is provided with a buffer layer. The electronic gravity sensor is installed on the top of the buffer layer.

[0019] A method for using a moisture content control device for sandy mudstone based on the principle of positive and negative pressure includes the following steps:

[0020] S1: Install the moisture content control unit in the wide-temperature range constant temperature chamber;

[0021] S2: Check the airtightness of each component of the moisture content control unit, and check whether the temperature control device, electronic gravity sensor, humidifier and rotary vacuum pump are working properly;

[0022] S3: Open the wide-temperature zone constant temperature chamber and place the sandy mudstone sample in the mounting slot on the sample fixing platform;

[0023] S4: According to the different working conditions of sandy mudstone, close the wide temperature zone constant temperature chamber, adjust the temperature in the wide temperature zone constant temperature chamber through the temperature control device, connect the electronic gravity sensor to the calculation and data processing unit, collect and transmit sandy mudstone data, and record the initial mass of sandy mudstone as m.

[0024] S5: The temperature in the wide-temperature-range constant-temperature chamber is controlled at room temperature using a temperature control device. The sandy mudstone on the sample fixing stage is air-dried until the data recorded by the electronic gravity sensor no longer changes, indicating that the sandy mudstone is completely air-dried. Its mass is recorded as m0. The humidifier and vacuum pump are then activated to allow water vapor to enter the negative pressure chamber from the positive pressure chamber through the pores of the sandy mudstone in the sample fixing stage, increasing the water content of the sandy mudstone. After positive pressure humidification and negative pressure assisted water vapor infiltration, the total mass of the sandy mudstone and its internal water content at a certain moment is m. t The mass of water is mw = m t -m0, then the formula for calculating the moisture content ω is:

[0025]

[0026] The initial gravity G0 of the sandy mudstone sample was measured using an electronic gravity sensor before the experiment. Using the gravity calculation formula G = mg, the following can be obtained: At a certain measurement moment after the positive and negative pressure action and humidification process are completed, the electronic gravity sensor measures the total gravity G of the sandy mudstone and its water content at that moment. t We can obtain mt = Gt / g, and then we can use m0 and m t Substituting the expression into the moisture content calculation formula, we get:

[0027]

[0028] This allows for the direct use of real-time measurements from electronic gravity sensors, computing and data processing units to calculate the water content and rate of change of sandy mudstone at different stages.

[0029] Let ω1 be the water content of the sandy mudstone at time t1, and ω2 be the water content of the sandy mudstone at time t2, then:

[0030]

[0031] The rate of change of water content, v, can be expressed as:

[0032]

[0033] Substituting the expressions for ω1 and ω2, we get:

[0034]

[0035] After simplification, we get:

[0036]

[0037] Measured by a gravity sensor, let G0 be the gravity corresponding to the dry weight of sandy mudstone, G t1 The total weight of the sandy mudstone and its internal water content at that moment, Gt2 If the total weight of the sandy mudstone and its internal water content is at that moment, then the expression for the rate of change of water content v is:

[0038]

[0039] A method for controlling the moisture content and its rate of change in sandy mudstone based on a positive and negative pressure principle includes the following steps:

[0040] By adjusting the humidification capacity of the humidifier and the pressure in the positive pressure chamber, the amount of water vapor entering the pores of sandy mudstone can be precisely controlled. Based on the pore structure and target moisture content of the sandy mudstone, the working power of the humidifier and the pressure value of the positive pressure chamber can be set. For sandy mudstone with smaller pores, the humidification capacity can be appropriately reduced and the positive pressure increased, so that water vapor can slowly and fully penetrate into the pores, avoiding pore blockage or uneven moisture distribution caused by excessive or rapid water vapor.

[0041] Preliminary experiments were conducted to determine the moisture absorption curves of different types of sandy mudstone under different positive pressures and humidification rates. Based on this, the positive pressure humidification process was precisely controlled in the formal experiment, thereby achieving effective control over the increase in moisture content. The air inlet of the vacuum pump was connected to the negative pressure chamber. By adjusting the pumping speed of the vacuum pump and the pressure inside the negative pressure chamber, the migration speed and discharge rate of water vapor in the sandy mudstone were controlled. When it was necessary to accelerate moisture penetration, the pumping power of the vacuum pump was increased to enhance the negative pressure effect, so that water could flow more quickly from the positive pressure chamber to the negative pressure chamber through the pores of the sandy mudstone under the drive of the pressure difference. This ensured that the interior of the rock was fully moistened and the moisture was evenly distributed, while avoiding moisture residue and improving the accuracy and completeness of moisture content measurement.

[0042] The wide-temperature-zone constant temperature chamber connects to an external temperature control device, enabling precise temperature control at different stages. During the air-drying stage, the temperature is controlled within a suitable range, slightly higher than room temperature, to accelerate moisture evaporation and allow the sandy mudstone to reach a fully air-dried state as quickly as possible, accurately obtaining the dry weight m0. During the moisture content increase stage, an appropriate temperature is selected based on the characteristics of the sandy mudstone and the target moisture content. For some sandy mudstones with enhanced water absorption at higher temperatures, the temperature can be appropriately increased to promote moisture absorption, but excessively high temperatures should be avoided to prevent changes in the internal structure or mineral composition of the rock. Through precise temperature control, supplemented by positive and negative pressure, effective control of moisture content is achieved.

[0043] An electronic gravity sensor located beneath the sample fixing stage monitors the changes in the mass of the sandy mudstone in real time and transmits the data to the computing and data processing unit. During the experiment, the system calculates the real-time moisture content ω and moisture content v rate of change based on gravity changes, and records gravity data at regular intervals. If the rate of change in moisture content deviates from the expected range, parameters such as positive pressure, negative pressure, or temperature can be adjusted in a timely manner. When the calculated moisture content or the rate of change in moisture content does not match the preset value, the system automatically adjusts the operating parameters of the humidifier, vacuum pump, or temperature control device. If the rate of increase in moisture content is too fast, the humidifier's humidification capacity is reduced or the positive pressure chamber pressure is decreased. If the rate of increase in moisture content is too slow, the vacuum pump's pumping power is appropriately increased or the temperature is raised.

[0044] The present invention has the following beneficial effects:

[0045] 1. The apparatus of this invention precisely controls the temperature within a wide-temperature-range constant-temperature chamber using a temperature control device, providing stable and precisely adjustable temperature conditions to ensure that the rock sample remains within the set temperature environment during the experiment. When studying the characteristics of rock moisture content variation, different temperatures significantly affect the evaporation and diffusion rates of water, as well as the physicochemical properties of the rock. Precise temperature control eliminates the interference of temperature fluctuations on experimental results, enabling researchers to accurately investigate the interaction between rock and water at specific temperatures, thus improving the accuracy and reliability of experimental data.

[0046] 2. The device of this invention utilizes the principle of positive and negative pressure to rapidly introduce water vapor into the pores of sandy mudstone, thereby increasing the water content of the sandy mudstone to the desired experimental water content. Under positive pressure, water can more effectively penetrate into the pores and fissures of the rock, ensuring sufficient internal wetting and making the water content measurement results more reflective of the rock's true water absorption. Negative pressure helps accelerate the expulsion of water from the rock, promoting rapid migration and diffusion of water within the rock, avoiding water residue, and thus improving the accuracy and completeness of water content measurement. For example, in simulating the wetting of rocks by reservoir water in the drawdown zone of a riverbank, positive pressure can simulate water pressure pushing water deeper into the rock; when studying the drainage characteristics of rocks, negative pressure can simulate the suction force during natural drainage or evaporation, ensuring sufficient water expulsion.

[0047] 3. The device of the present invention achieves precise control of water content and its rate of change through a real-time monitoring and feedback adjustment mechanism, ensuring that the water content of sandy mudstone changes at a predetermined rate to meet experimental or engineering requirements. Attached Figure Description

[0048] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0049] Figure 1 A schematic diagram of the external structure of a sandy mudstone moisture content control device based on the principle of positive and negative pressure, provided for an embodiment of the present invention;

[0050] Figure 2 An internal structural diagram of a sandy mudstone moisture content control device based on the principle of positive and negative pressure, provided for an embodiment of the present invention;

[0051] Figure 3 This is a front view of the installation structure of the positive pressure chamber, negative pressure chamber, and electronic gravity sensor provided in an embodiment of the present invention;

[0052] Figure 4 This is a top view of the installation structure of the positive pressure chamber, negative pressure chamber, and electronic gravity sensor provided in an embodiment of the present invention;

[0053] Figure 5 This is a diagram showing the state of a sandy mudstone sample when the sealing cover is opened and placed, as provided in an embodiment of the present invention.

[0054] Figure 6 This is a schematic diagram of a vacuum pump structure provided in an embodiment of the present invention;

[0055] In the figure: 1. Wide-temperature zone constant temperature chamber; 2. Temperature control device; 3. Temperature lock cover; 4. Handle; 5. Sample fixing stage; 6. Positive pressure chamber; 7. Negative pressure chamber; 8. Pressure stabilization and balance port; 9. Electronic gravity sensor; 10. Gravity sensing protective chamber; 11. Shock-absorbing pad; 12. Humidifier; 13. Mechanical and electrical equipment protective pad; 14. Vacuum pump; 15. Vacuum pump rotor; 16. Air inlet; 17. Air outlet; 18. Check valve; 19. Support; 20. Sealing cover; 21. Sandy mudstone sample. Detailed Implementation

[0056] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0057] To achieve the above-mentioned technical features, the objective of this invention is as follows:

[0058] See Figure 1-6 A moisture content control device for sandy mudstone based on the principle of positive and negative pressure includes a wide-temperature-range constant temperature chamber 1 and a temperature control device 2. The wide-temperature-range constant temperature chamber 1 is equipped with a moisture content control unit, which includes a sample fixing platform 5. The sample fixing platform 5 has an installation groove 5a adapted to the shape of the sandy mudstone sample 21, and the installation groove 5a is connected to a positive pressure chamber 6 and a negative pressure chamber 7 on both sides of the sample fixing platform 5. The positive pressure chamber 6 is connected to the mist outlet of a humidifier 12, and the negative pressure chamber 7 is connected to the air inlet 16 of a vacuum pump 14. A sealing cover 20 is provided on the top of the sample fixing platform 5, the positive pressure chamber 6, and the negative pressure chamber 7. An electronic gravity sensor 9 is installed below the sample fixing platform 5 and is connected to a calculation and data processing unit. The temperature control device 2 is installed on the wide-temperature-range constant temperature chamber 1 and is used to regulate the temperature inside the wide-temperature-range constant temperature chamber 1.

[0059] The sandy mudstone moisture content control device provided in this embodiment firstly features a mounting groove 5a on the sample fixing platform 5 that matches the shape of the sandy mudstone sample 21. This allows for precise placement of the sandy mudstone sample, ensuring a stable position during the experiment. This locking and positioning prevents shaking or displacement from affecting the experimental results. (See...) Figure 4 , Figure 5 Secondly, the mounting groove 5a is connected to the positive pressure chamber 6 and negative pressure chamber 7 on both sides of the sample fixing stage 5, and the sealing cover plate 20 serves as a sealing component to completely cover the sample fixing stage 5, the positive pressure chamber 6 and the negative pressure chamber 7 to prevent water vapor leakage. When the system is running, the gas in the positive pressure chamber 6 can be evenly distributed inside the mounting groove 5a on the sample fixing stage 5, thereby ensuring that the gas in the entire system flows in an orderly manner only through the positive pressure chamber 6, the mounting groove 5a and the negative pressure chamber 7 as channels during positive and negative pressure operation, maintaining the sealing and pressure stability of the system, and forming a complete gas passage. During operation, water is first supplied to the humidifier 12 to the predetermined water level through the water supply unit. The airtightness of the positive pressure chamber 6 and negative pressure chamber 7 connected to the outside is checked, and the sandy mudstone sample is placed in the installation slot 5a. Then, the temperature lock cover 3 of the wide-temperature zone constant temperature chamber 1 is closed, and the program controls the temperature control device 2 to maintain the temperature in the wide-temperature zone constant temperature chamber 1 at a suitable temperature, allowing the sandy mudstone to be air-dried or oven-dried. The data is then transmitted to the calculation and data processing unit via the electronic gravity sensor 9 for calculation, and the dry weight and natural moisture content of the sandy mudstone are recorded. The temperature in the wide-temperature zone constant temperature chamber 1 is adjusted to room temperature by the temperature control device 2, and the humidifier 12 and vacuum pump 14 are started. According to the principle of positive and negative pressure, water vapor is transferred from the positive pressure chamber 6 through the pores of the sandy mudstone in the sample fixing stage 5 to the negative pressure chamber 7, thereby increasing the water content of the sandy mudstone. Finally, based on the gravity of the sandy mudstone at each stage transmitted to the computing unit by the electronic gravity sensor 9, the water content of the sandy mudstone and the water content rate at different stages can be calculated by the processing unit, thereby effectively monitoring the changes in the water content of the sandy mudstone.

[0060] Furthermore, the positive pressure chamber 6 and the negative pressure chamber 7 are connected to the mist outlet of the humidifier 12 and the air inlet 16 of the vacuum pump 14, respectively, through the pressure stabilizing and balancing port 8. The pressure stabilizing and balancing port 8 serves as a transitional connecting pipe to connect the humidifier and other components together, ensuring smooth transmission of gas and liquid between the various components to balance the internal pressure of the system and thus balance the air pressure.

[0061] Furthermore, the air inlet 16 of the vacuum pump 14 is equipped with a check valve 18. When the vacuum pump 14 stops working or the system pressure fluctuates, the check valve 18 can effectively prevent gas backflow and maintain the vacuum or low pressure state in the system.

[0062] Furthermore, the wide-temperature zone constant temperature chamber 1 is equipped with a temperature lock cover 3, which has a handle 4 for easy opening and closing.

[0063] Furthermore, the bottom of the wide-temperature zone constant temperature chamber 1 is provided with a platform 11, and the top of the platform 11 is provided with a buffer layer, and the electronic gravity sensor 9 is installed on the top of the buffer layer.

[0064] Furthermore, a gravity sensing protective chamber 10 is provided around the electronic gravity sensor 9. The gravity sensing protective chamber 10 is designed as a sealed structure, with sealant or special sealing processes used at the edges of each layer of material to prevent dust, moisture, or other impurities from entering the chamber and causing damage to the electronic gravity sensor. The innermost layer uses rubber shock-absorbing material, which can effectively absorb the vibration energy transmitted to the protective chamber from the outside. The middle layer is an anti-interference material, using a metal shielding mesh, which can reflect and absorb electromagnetic waves to prevent external electromagnetic interference signals from affecting the normal operation of the electronic gravity sensor and ensure the accuracy of its measurement data. The outermost layer is made of high-temperature and low-temperature resistant materials, using ceramic fiber composite materials, which can maintain stable physical and chemical properties in a wide temperature range environment, protecting the internal sensor and other materials from the effects of temperature changes and maintaining the overall structural integrity of the protective chamber.

[0065] In one implementation, the outer shell of the wide-temperature-range constant temperature chamber 1 is made of stainless steel, the insulation layer is made of polyurethane, and the inner liner is made of aluminum alloy. A high-precision temperature sensor is installed inside the chamber to monitor the internal temperature in real time. The sensor transmits the temperature signal to the control system, which compares the preset temperature value with the actual monitored temperature. When the temperature deviates from the set value, the control system will activate the heating or cooling device to adjust it.

[0066] In one implementation method, in this embodiment, the heating device in the temperature control device 2 uses electric heating, converting electrical energy into heat energy. Its power can be selected and adjusted according to the size of the chamber and the required heating rate. The refrigeration system is based on the compressor refrigeration principle, achieving heat transfer and temperature reduction through the circulation of refrigerant in components such as the evaporator and condenser. This advanced refrigeration system can achieve efficient cooling over a wide temperature range and possesses good temperature stability and rapid response capabilities. A circulating fan is installed inside the chamber to promote air circulation. A reasonable air duct design ensures uniform air distribution within the chamber, avoiding localized excessively high or low temperatures.

[0067] In one implementation method, the temperature lock cover 3 is made of polyurethane insulation material, which has a large number of tiny pores inside, greatly increasing the thermal resistance of heat transfer and further reducing the heat transfer rate through the temperature lock cover, thus enhancing the insulation effect and helping to maintain a constant internal temperature and improve experimental accuracy. When the vacuum pump 14 is working, the temperature lock cover 3 is closed to prevent pressure imbalance between the inside and outside of the chamber. Even though the temperature lock cover 3 is closed when the vacuum pump 14 is working, constant temperature can still be maintained during the experiment. This mainly relies on the ventilation system integrated into the temperature control device. This ventilation system is carefully designed and closely connected to the internal environment of the wide-temperature-range constant temperature chamber 1. When the vacuum pump 14 is running, the gas pressure and composition inside the chamber change. The ventilation system can accurately monitor these changes and dynamically adjust according to preset temperature and gas concentration parameters. Through efficient gas circulation and heat exchange mechanisms, it ensures that while maintaining stable pressure inside the chamber, the impact of heat generated by the vacuum pump or changes in gas composition is minimized. Even with the vacuum pump running continuously, the ventilation system can consistently provide a stable temperature environment inside the constant temperature chamber, ensuring that the temperature inside the chamber remains within the set range. This guarantees that the entire experimental process is not affected by temperature fluctuations, thus ensuring the accuracy and reliability of the experimental results.

[0068] In one implementation, in this embodiment, the humidifier 12 and the vacuum pump 14 are respectively installed on the top of the electromechanical equipment protective pad 13. The electromechanical equipment protective pad 13 is made of multi-layer composite materials. The top layer is made of rubber material with certain elasticity and wear resistance, which directly contacts the bottom of the electromechanical equipment, providing a soft support surface, reducing friction and hard contact between the equipment and the pad, and preventing the bottom of the equipment from being scratched or worn during operation. The middle layer is made of fiber material with good shock absorption performance, mainly responsible for absorbing and dispersing the vibration energy generated by the electromechanical equipment during operation. The bottom layer is a high-strength plastic board with high strength and stability, which aims to provide a stable support foundation for the entire protective pad, ensuring that the pad will not deform or shift excessively when bearing the weight and vibration of the equipment, and can produce a buffering effect during equipment operation, reducing the impact of vibration and impact on the equipment.

[0069] A method for using a moisture content control device for sandy mudstone based on the principle of positive and negative pressure includes the following steps:

[0070] S1: Install the moisture content control unit in the wide temperature range constant temperature chamber 1;

[0071] S2: Check the airtightness of each component of the moisture content control unit, and check whether the temperature control device 2, electronic gravity sensor 9, humidifier 12 and rotary vacuum pump 14 are working properly.

[0072] S3: Open the wide temperature range constant temperature chamber 1 and place the sandy mudstone sample 21 into the mounting slot 5a on the sample fixing stage 5;

[0073] S4: According to the different working conditions of sandy mudstone, close the wide temperature zone constant temperature chamber 1, adjust the temperature in the wide temperature zone constant temperature chamber 1 through the temperature control device 2, connect the electronic gravity sensor 9 to the calculation and data processing unit, collect and transmit sandy mudstone data, and record the initial mass of sandy mudstone as m.

[0074] S5: The temperature in the wide-temperature zone constant temperature chamber 1 is controlled at room temperature by the temperature control device 2. The sandy mudstone on the sample fixing stage 5 is air-dried until the data recorded by the electronic gravity sensor 9 does not change, that is, the sandy mudstone is completely air-dried, and its mass is recorded as m0. The humidifier 12 and vacuum pump 14 are started to allow water vapor to enter the negative pressure chamber 7 from the positive pressure chamber 6 through the pores of the sandy mudstone in the sample fixing stage 5, thereby increasing the water content of the sandy mudstone. After positive pressure humidification, negative pressure assisted water vapor infiltration and other operations, the total mass of the sandy mudstone and the water contained inside it at a certain moment is m0. t The mass of water is mw = m t -m0, then the formula for calculating the moisture content ω is:

[0075]

[0076] The initial gravity G0 of the sandy mudstone sample was measured before the experiment using an electronic gravity sensor (9). The gravity was calculated using the formula G = mg. At a certain measurement moment after the positive and negative pressure action and humidification process are completed, the electronic gravity sensor 9 measures the total gravity G of the sandy mudstone and its water content at that moment. t We can obtain mt = Gt / g, and then we can use m0 and m t Substituting the expression into the moisture content calculation formula, we get:

[0077]

[0078] In this way, the water content and rate of sandy mudstone at different stages can be calculated in real time by directly using the real-time measurement data of the electronic gravity sensor (9) and the computing and data processing unit.

[0079] Let ω1 be the water content of the sandy mudstone at time t1, and ω2 be the water content of the sandy mudstone at time t2, then:

[0080]

[0081] The rate of change of water content, v, can be expressed as:

[0082]

[0083] Substituting the expressions for ω1 and ω2, we get:

[0084]

[0085] After simplification, we get:

[0086]

[0087] Measured by a gravity sensor, let G0 be the gravity corresponding to the dry weight of sandy mudstone, G t1 The total weight of the sandy mudstone and its internal water content at that moment, G t2 If the total weight of the sandy mudstone and its internal water content is at that moment, then the expression for the rate of change of water content v is:

[0088]

[0089] A method for controlling the moisture content and its rate of change in sandy mudstone based on a positive and negative pressure principle includes the following steps:

[0090] By adjusting the humidification capacity of the humidifier 12 and the pressure inside the positive pressure chamber 6, the amount of water vapor entering the pores of sandy mudstone can be precisely controlled. Based on the pore structure and target moisture content of the sandy mudstone, the working power of the humidifier 12 and the pressure value of the positive pressure chamber 6 are set. For sandy mudstone with smaller pores, the humidification capacity is appropriately reduced and the positive pressure is increased so that water vapor can slowly and fully penetrate into the pores, avoiding pore blockage or uneven moisture distribution due to excessive or rapid water vapor.

[0091] Preliminary experiments were conducted to determine the moisture absorption curves of different types of sandy mudstone under different positive pressures and humidification rates. Based on this, the positive pressure humidification process was precisely controlled in the formal experiment, thereby achieving effective control over the increase in moisture content. The air inlet 16 of the vacuum pump 14 was connected to the negative pressure chamber 7. By adjusting the pumping speed of the vacuum pump 14 and the pressure inside the negative pressure chamber 7, the migration speed and discharge rate of water vapor in the sandy mudstone were controlled. When it was necessary to accelerate the infiltration of moisture, the pumping power of the vacuum pump 14 was increased to enhance the negative pressure effect, so that moisture could flow more quickly from the positive pressure chamber 6 to the negative pressure chamber 7 through the pores of the sandy mudstone under the drive of the pressure difference, ensuring that the interior of the rock was fully moistened and the moisture was evenly distributed, while avoiding moisture residue and improving the accuracy and completeness of moisture content measurement.

[0092] The wide-temperature zone constant temperature chamber 1 is connected to the external temperature control device 2, which can precisely control the temperature at different stages. During the air-drying stage, the temperature is controlled within a suitable range slightly higher than room temperature to accelerate moisture evaporation and allow the sandy mudstone to reach a completely dry state as soon as possible, accurately obtaining the dry weight m0. During the moisture content increase stage, an appropriate temperature is selected according to the characteristics of the sandy mudstone and the target moisture content. For some sandy mudstones with enhanced water absorption at higher temperatures, the temperature can be appropriately increased to promote moisture absorption, but it is necessary to avoid excessively high temperatures that may cause changes in the internal structure or mineral composition of the rock. Through precise temperature control, assisted by positive and negative pressure, effective control of moisture content can be achieved.

[0093] An electronic gravity sensor 9 located beneath the sample fixing stage 5 monitors the changes in the mass of the sandy mudstone in real time and transmits the data to the computing and data processing unit. During the experiment, the system calculates the real-time moisture content ω and moisture content v rate of change based on gravity changes, recording gravity data at regular intervals. If the rate of change in moisture content deviates from the expected range, parameters such as positive pressure, negative pressure, or temperature can be adjusted promptly. When the calculated moisture content or rate of change in moisture content does not match the preset value, the system automatically adjusts the operating parameters of the humidifier 12, vacuum pump 14, or temperature control device 2. If the rate of increase in moisture content is too fast, the humidification capacity of the humidifier is reduced or the pressure of the positive pressure chamber is decreased; if the rate of increase in moisture content is too slow, the pumping power of the vacuum pump is appropriately increased or the temperature is raised. Through this real-time monitoring and feedback adjustment mechanism, precise control of the rate of change in moisture content is achieved, ensuring that the moisture content of the sandy mudstone changes at a predetermined rate to meet experimental or engineering requirements.

Claims

1. A method for controlling the moisture content and rate of change of sandy mudstone, comprising a sandy mudstone moisture content control device, wherein the sandy mudstone moisture content control device comprises a wide-temperature zone constant temperature chamber (1) and a temperature control device (2). The wide-temperature constant temperature chamber (1) is equipped with a moisture content control unit. The moisture content control unit includes a sample fixing stage (5). The sample fixing stage (5) is provided with an installation groove (5a) that is adapted to the shape of the sandy mudstone sample (21). The installation groove (5a) is connected to the positive pressure chamber (6) and the negative pressure chamber (7) provided on both sides of the sample fixing stage (5). The positive pressure chamber (6) is connected to the mist outlet of the humidifier (12). The negative pressure chamber (7) is connected to the air inlet (16) of the vacuum pump (14). The sample fixing stage (5), the positive pressure chamber (6) and the negative pressure chamber (7) are provided with sealing cover plates (20). An electronic gravity sensor (9) is provided below the sample fixing stage (5). The electronic gravity sensor (9) is connected to the calculation and data processing unit. The temperature control device (2) is installed on the wide temperature range constant temperature chamber (1) and is used to adjust the temperature inside the wide temperature range constant temperature chamber (1); Its features are, The method for controlling the water content and its rate of change in sandy mudstone includes the following steps: By adjusting the humidification capacity of the humidifier (12) and the pressure inside the positive pressure chamber (6), the amount of water vapor entering the pores of the sandy mudstone is controlled. Based on the pore structure and target water content of the sandy mudstone, the working power of the humidifier (12) and the pressure value of the positive pressure chamber (6) are set. For sandy mudstone with smaller pores, the humidification capacity is appropriately reduced and the positive pressure is increased so that the water vapor can slowly and fully penetrate into the pores, avoiding pore blockage or uneven water distribution due to excessive or rapid water vapor. Preliminary experiments were conducted to determine the water absorption curves of different types of sandy mudstone under different positive pressures and humidification amounts. Based on this, the positive pressure humidification process was controlled in the formal experiment, thereby achieving effective control over the increase in water content. The air inlet (16) of the vacuum pump (14) was connected to the negative pressure chamber (7). By adjusting the pumping speed of the vacuum pump (14) and the pressure inside the negative pressure chamber (7), the migration speed and discharge amount of water vapor in the sandy mudstone were controlled. When it was necessary to accelerate water penetration, the pumping power of the vacuum pump (14) was increased to enhance the negative pressure effect, so that water could flow from the positive pressure chamber (6) to the negative pressure chamber (7) more quickly through the pores of the sandy mudstone under the drive of the pressure difference, ensuring that the interior of the rock was fully moistened and the water was evenly distributed, while avoiding water residue and improving the accuracy and completeness of water content measurement. The wide-temperature zone constant temperature chamber (1) is connected to an external temperature control device (2) to precisely control the temperature at different stages. During the air-drying stage, the temperature is controlled within a suitable range slightly higher than room temperature to accelerate moisture evaporation and allow the sandy mudstone to reach a completely air-dried state as soon as possible, so as to accurately obtain the dry weight. During the stage of increasing water content, an appropriate temperature is selected based on the characteristics of sandy mudstone and the target water content. For some sandy mudstones with enhanced water absorption at higher temperatures, the temperature can be appropriately increased to promote water absorption, but excessively high temperatures should be avoided to prevent changes in the internal structure or mineral composition of the rock. Through precise temperature control, combined with positive and negative pressure, effective control of water content can be achieved. The electronic gravity sensor (9) located below the sample fixing stage (5) monitors the changes in the mass of sandy mudstone in real time and transmits the data to the calculation and data processing unit. During the experiment, the real-time water content is calculated based on the changes in gravity. and moisture content The rate of change is recorded by recording gravity data at regular intervals. Once the rate of change of moisture content is found to deviate from the expected range, the positive pressure, negative pressure or temperature parameters are adjusted in time. When the calculated moisture content or the rate of change of moisture content does not match the preset value, the control system automatically adjusts the working parameters of the humidifier (12), vacuum pump (14) or temperature control device (2). If the rate of increase of moisture content is too fast, the humidification amount of the humidifier is reduced or the pressure of the positive pressure chamber is reduced. If the rate of increase of moisture content is too slow, the pumping power of the vacuum pump is appropriately increased or the temperature is increased.

2. The method for controlling the water content and its rate of change in sandy mudstone according to claim 1, characterized in that: The positive pressure chamber (6) and the negative pressure chamber (7) are respectively connected to the mist outlet of the humidifier (12) and the air inlet (16) of the vacuum pump (14) through the pressure stabilization and balance port (8).

3. The method for controlling the water content and its rate of change in sandy mudstone according to claim 2, characterized in that: The vacuum pump (14) is equipped with a check valve (18) at its air inlet (16).

4. The method for controlling the water content and its rate of change in sandy mudstone according to claim 1, characterized in that: The wide-temperature zone constant temperature chamber (1) is equipped with a temperature lock cover (3), and the temperature lock cover (3) is equipped with a handle (4) for easy opening and closing.

5. The method for controlling the water content and its rate of change in sandy mudstone according to claim 1, characterized in that: The bottom of the wide temperature range constant temperature chamber (1) is provided with a platform (11), and the top of the platform (11) is provided with a buffer layer. The electronic gravity sensor (9) is installed on the top of the buffer layer.

6. The method for controlling the water content and its rate of change in sandy mudstone according to any one of claims 1-5, further comprising a method of use, characterized in that, Includes the following steps: S1: Install the moisture content control unit in the wide temperature range constant temperature chamber (1); S2: Check the airtightness of each component of the moisture content control unit, and check whether the temperature control device (2), electronic gravity sensor (9), humidifier (12) and rotary vacuum pump (14) are working properly; S3: Open the wide temperature range constant temperature chamber (1) and place the sandy mudstone sample (21) in the mounting slot (5a) on the sample fixing platform (5); S4: According to the different working conditions of sandy mudstone, close the wide temperature zone constant temperature box (1), adjust the temperature in the wide temperature zone constant temperature box (1) through the temperature control device (2), connect the electronic gravity sensor (9) to the calculation and data processing unit, collect and transmit sandy mudstone data, and record the initial mass of sandy mudstone as m. S5: The temperature in the wide-temperature zone constant temperature chamber (1) is controlled at room temperature by the temperature control device (2), and the sandy mudstone on the sample fixing stage (5) is air-dried until the data recorded by the electronic gravity sensor (9) does not change, that is, the sandy mudstone has been completely air-dried, and its mass is recorded as follows. The humidifier (12) and vacuum pump (14) are activated, allowing water vapor to enter the negative pressure chamber (7) from the positive pressure chamber (6) through the pores of the sandy mudstone in the sample fixing stage (5), thus increasing the water content of the sandy mudstone. After positive pressure humidification and negative pressure assisted water vapor infiltration, the total mass of the sandy mudstone and its internal water content at a certain moment is... The mass of water, mw = - Then the moisture content The calculation formula is: The initial gravity of the sandy mudstone sample was measured before the experiment using an electronic gravity sensor (9). From the gravity calculation formula =mg, therefore we can get = At a certain measurement moment after the positive and negative pressure action and humidification process are completed, the electronic gravity sensor (9) measures the total gravity of the sandy mudstone and its water content at this time. We can obtain mt = Gt / g, and then... and Substituting the expression into the moisture content calculation formula, we get: In this way, the water content and rate of sandy mudstone at different stages can be calculated in real time by directly using the real-time measurement data of the electronic gravity sensor (9) and the computing and data processing unit. set up Is The water content of sandy mudstone at time, Is If the water content of the sandy mudstone is at a certain time, then: rate of change of moisture content It can be represented as: Will and Substituting the expression, we get: After simplification, we get: Measured by a gravity sensor, assuming It is the gravity corresponding to the dry weight of sandy mudstone. The total weight of the sandy mudstone and the water it contains at that moment. The rate of change of water content is the total weight of the sandy mudstone and its internal water content at that moment. The expression is: 。

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