Rock humidity diffusion coefficient measuring device and method based on diffusion-adsorption coupling

Abstract

The invention provides a rock humidity diffusion coefficient measuring device and method based on diffusion-adsorption coupling, and belongs to the field of geotechnical engineering testing. According to the invention, long-term, continuous and automatic monitoring of the humidity diffusion test process is realized through a suspension type weighing mode, and the weight change of a test piece in the humidity diffusion process is obtained in real time; the strain of the test piece is monitored in real time through the strain acquisition system, the problem that monitoring is not timely under the condition of a long test period is solved, and a test method for accurately determining the diffusion position in a strain monitoring mode so as to calculate the humidity diffusion coefficient is provided; different temperature and humidity environments of the surrounding rock are simulated through a servo control system; the problem that the test is interrupted after the strong-expansibility test piece is disintegrated due to the influence of humidity is solved through the intelligent sensing film, and the strain of the test piece is synchronously monitored. The method for calculating the humidity diffusion coefficient based on diffusion-adsorption coupling is provided, the humidity diffusion coefficient of the rock is more accurately obtained, and the method is particularly suitable for rock-soil bodies with high expansibility and disintegration.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering tests, and particularly to an apparatus and method for measuring the moisture diffusion coefficient of rocks based on diffusion-adsorption coupling. Background Art

[0002] The moisture diffusion coefficient of rocks is an important physical quantity describing the moisture diffusion rate in rocks, which is significantly affected by factors such as environmental temperature and humidity, its own mineral type and porosity. By measuring the moisture diffusion coefficient, the bearing capacity and stability of rocks under complex conditions can be predicted, providing a basis for engineering design and maintenance, especially for geotechnical engineering containing expansive clay minerals.

[0003] Currently, research on equipment and methods for moisture diffusion tests, especially for rock masses with significant expansibility and difficult to obtain complete specimens, is still relatively scarce. The currently commonly used method for measuring the moisture diffusion coefficient is to experimentally measure the change in moisture absorption of rocks under different humidity conditions, and calculate the moisture diffusion coefficient in combination with the mass and volume of the specimens. However, these methods usually assume that moisture diffusion is only driven by the concentration gradient, ignoring the influence of adsorption on the diffusion process. Especially for rocks containing clay minerals, the surface adsorption of water molecules will significantly change the effective diffusion path and further affect the pore structure and permeability through mineral expansion, resulting in the difficulty of accurately capturing the moisture diffusion behavior by traditional methods. In addition, traditional methods often rely on cumbersome operations such as slicing, drying, and multiple weighings, which not only have complex procedures and long test cycles, but may also affect the accuracy of data due to specimen disintegration or human errors, and it is difficult to monitor the long-term and continuous moisture diffusion process while maintaining the integrity of the specimens, thus limiting the ability to further explore key characteristics such as internal deterioration characteristics of the specimens.

[0004] Therefore, it is particularly important to provide an apparatus and method for measuring the moisture diffusion coefficient of rocks based on diffusion-adsorption coupling, especially applicable to expansive rocks containing clay minerals with low strength and easy to disintegrate, to more accurately describe the moisture diffusion behavior, thereby improving the accuracy and applicability of moisture diffusion coefficient tests and providing a scientific basis for engineering stability evaluation and support design. Summary of the Invention

[0005] To solve the problems of inaccurate testing, cumbersome operation, long testing cycle, and inability to monitor in real time in the determination of the rock moisture diffusion coefficient in the prior art, the present invention provides a device and method for determining the rock moisture diffusion coefficient based on diffusion-adsorption coupling. The present invention adopts an intelligent sensing film and an automatic data acquisition function to realize the real-time monitoring of the axial deformation and moisture absorption amount of the rock specimen during the moisture diffusion process, and more accurately captures the micro-strain caused by moisture diffusion to determine the diffusion position; by taking a small amount of samples to prepare remolded samples for testing, the cumbersome and repetitive processes such as slicing, drying, and weighing in the traditional method are avoided, and a method for determining the rock moisture diffusion coefficient based on diffusion-adsorption coupling is proposed, which can more accurately obtain the moisture diffusion coefficient of the rock and is particularly suitable for geotechnical bodies with strong expansibility and disintegration. Through the present invention, a scientific basis can be provided for the stability evaluation and support design of various engineering rock masses, and the testing efficiency and accuracy are significantly improved.

[0006] To achieve the above object, the technical solution adopted by the present invention is: A device for determining the rock moisture diffusion coefficient based on diffusion-adsorption coupling, comprising a main body box, a self-weight system, a strain acquisition system, a temperature and humidity servo regulation system, and a control system; The main body box is divided into a test area, a control area, an adjustment area, and a water tank area by a partition; The self-weight system includes a suspended weighing device, a suspension link, and a suspension basket connected in sequence; wherein, the suspended weighing device is arranged at the top of the test area in the main box body to weigh the specimen placed in the suspension basket in real time; The strain acquisition system includes an intelligent sensing film and a strain collector; wherein, the intelligent sensing film is a cylindrical structure with one end open and the other end closed, and strain sensors are arranged on its inner wall; the strain collector is arranged in the control area and is connected to the strain sensor; The temperature and humidity servo regulation system includes a temperature sensor, a humidity sensor, an evaporator, a water tank, and a fan; wherein, the temperature sensor and the humidity sensor are arranged in the test area; the water tank is arranged in the water tank area and is used for storing liquid water for humidity regulation; the evaporator consists of upper and lower heating areas, which are respectively located in the adjustment area and the water tank area, wherein the upper heating area is located above the water tank, and the lower heating area is in contact with the water tank; a fan is arranged on the side of the upper part of the evaporator facing the test area, and air outlets are distributed on the partition between the test area and the adjustment area; the upper heating area of the evaporator adjusts the temperature by heating, and the lower heating area evaporates the water body by heating to adjust the humidity. With the cooperation of the fan, the humid and hot air enters the test area through the air outlets to realize the temperature and humidity regulation during the test process; The control system includes a computer and a servo controller; among them, the servo controller is arranged in the control area and is connected to the computer, a suspended weigher, a strain collector, a temperature sensor, a humidity sensor, an evaporator and a fan, and is used to receive computer instructions to control the test process, receive the weight data of the suspended weigher, the strain data of the strain collector, the temperature data of the temperature sensor, the humidity data of the humidity sensor and transmit them to the computer for data processing. The computer controls the evaporator and the fan through the servo controller according to the collected temperature data and humidity data to realize temperature and humidity regulation.

[0007] Furthermore, the intelligent sensing film is made of a flexible water-proof material. Its open end is used to place the test piece, so that the test piece is in contact with the humidity environment, and a sealing ring is installed between the test piece and the open end to prevent water vapor from entering the interior; an elastic threading hole is provided at the center of the closed end of the intelligent sensing film. One end of the transmission line is connected to the strain sensor arranged on the inner wall of the intelligent sensing film, and the other end is connected to the strain collector through the elastic threading hole.

[0008] Furthermore, the intelligent sensing film is evenly divided into several zones along the axial direction. Two groups of strain sensors are arranged in each zone and the two groups of strain sensors are arranged opposite to each other along the radial direction, and are used to monitor the axial strain of the test piece to accurately determine the diffusion position.

[0009] Furthermore, the suspended weigher is a tension and compression type weighing sensor, and three suspended weighers are evenly distributed on the top of the test area of the main box.

[0010] Furthermore, the hanging basket includes a connecting beam, side frames and a hollow platform; both ends of the connecting beam are respectively connected to one side frame. The side frames are rectangular structures composed of metal sheets. A plurality of evenly distributed hollow cylindrical metal rods are fixedly connected to the bottom edge of the side frames to form a hollow platform for placing the test piece, and can timely slide the formed liquid water along the metal rods of the hollow platform to reduce the influence on the weight data of the test piece after moisture absorption.

[0011] Furthermore, when the humidity in the test area of the main box reaches the set value, the computer clears the weight value of the suspended weigher and then continues to collect data to avoid the influence of the attached water on the surface of the hanging basket and the hanging connecting rod on the water absorption of the test piece in a high humidity environment.

[0012] A method for measuring the humidity diffusion coefficient of rock based on diffusion-adsorption coupling, which is realized by using the above-mentioned device for measuring the humidity diffusion coefficient of rock based on diffusion-adsorption coupling, includes the following steps: Step 1: Core samples are taken from the rock to be detected and prepared into several rock test pieces with the same size; the rock test pieces are placed in the hanging basket in the main box, and the temperature of the main box is set to continuously dry the rock test pieces until the weight of the rock test pieces no longer changes; Step 2: Divide the dried rock specimens into multiple strain test areas of equal height evenly according to the respective partitions of the intelligent sensing film; place the rock specimens into the intelligent sensing film with the ends of the rock specimens aligned with the open ends of the intelligent sensing film, insert the sealing ring between the rock specimens and the intelligent sensing film, and make each strain test area of the rock specimens correspond to the strain sensors in the respective partitions of the intelligent sensing film. The transmission lines on the strain sensors extend out from the elastic wire-passing holes at the closed ends of the intelligent sensing film. Thus, the packaging of the rock specimens is completed. Step 3: Take 3 rock specimens packaged in Step 2 and place them in the hanging baskets in the main body box respectively, and connect the transmission lines of the strain sensors to the corresponding strain collectors. Step 4: Set the constant temperature and constant humidity in the test area of the main body box, and the data acquisition time interval of the strain collector according to the environment where the original rock is located. When the deformation amount of the rock specimen collected by the strain collector and the weight of the rock specimen collected by the hanging scale do not change within 24 hours after a certain moment, the test ends. The test period is from the start of the test to this moment. Step 5: Based on the diffusion-adsorption coupling method, decompose the humidity diffusion process into a diffusion term driven by the concentration gradient and an adsorption term caused by the adsorption of moisture on the rock surface, and calculate the rock humidity diffusion coefficient.

[0013] Further, in Step 1, the rocks to be detected include rocks without clay minerals and rocks with clay minerals; for rocks without clay minerals, the original rock specimens are prepared by drilling rock cores; for rocks with clay minerals, they are divided into those from which complete original rock specimens can be drilled and those from which it is difficult to drill complete original rock specimens. For the latter, the original rock is ground to the required particle size and pressed into remolded specimen without adding binder. During the pressing process, the density and compactness of the remolded specimen are the same as those of the original rock.

[0014] Further, in Step 5, for rocks without clay minerals, the humidity diffusion coefficient is: In the formula, is the equilibrium concentration at steady state, that is, the ratio of the weight of the specimen after diffusion to the dry weight of the specimen; is the time required to reach steady state; is the maximum distance of humidity diffusion, which is determined by the position where the rock specimen generates strain. When the strain at a certain point starts to increase from 0, it indicates that the humidity has diffused to this position.

[0015] Further, in Step 5, for the original rock specimens and remolded specimens with clay minerals, the humidity diffusion coefficients are respectively expressed as: In the formula, and respectively represent the humidity diffusion coefficients of the original rock specimen containing clay minerals and the remolded specimen; is the adsorption rate constant; , are the porosities of the original rock block and the remolded rock specimen respectively.

[0016] Furthermore, the calculation method of the adsorption rate constant is as follows: wherein, is the moisture adsorption amount of the specimen at adsorption equilibrium; is the instantaneous moisture adsorption amount of the specimen before equilibrium; The integral form of is: In the formula, is the weight of the rock specimen at time is the weight of the rock specimen at equilibrium, is the initial dry weight of the rock specimen; the weight is recorded every , and the adsorption rate constant is obtained by fitting.

[0017] Advantages of the present invention: (1) The measuring device and method of the present invention do not require cumbersome operations such as slicing, drying, and multiple manual weighings, realizing a non-destructive test method with full-process real-time and automated monitoring, effectively preventing the specimen from disintegrating during the test, and providing a basis for further testing other physical and mechanical properties of the specimen after the test.

[0018] (2) A method for accurately capturing the humidity diffusion behavior in the axial direction is considered, and a one-dimensional humidity diffusion model is established, which can more accurately reflect the humidity diffusion characteristics of the rock specimen. Compared with the traditional one-dimensional model, it can more precisely monitor the diffusion process of humidity in the rock and determine the diffusion position, and is applicable to engineering evaluations under complex geological conditions.

[0019] (3) Considering four key factors, namely rock mineral type, porosity, temperature, and humidity, an empirical formula for the humidity diffusion coefficient with multi-factor coupling is established, reducing the process of long-term and repeated experiments, being able to more comprehensively reflect the multi-factor influence in the humidity diffusion process, improving the accuracy of the humidity diffusion coefficient, avoiding the limitations of a large number of experiments and complex calculations in traditional methods, being particularly applicable to rocks with significant differences in mineral types and pore structures, and achieving the rapid acquisition of the humidity diffusion coefficient.

[0020] (4) Solved the problem of difficult acquisition of complete rock cores in traditional methods. This method only needs to take a small amount of rock blocks and then test the porosity and mineral type to achieve the prediction of the humidity diffusion coefficient and deformation, avoiding a large amount of sampling work, and being particularly applicable to geotechnical bodies with strong expansibility and disintegration properties, such as metamorphic expansive rocks and expansive soils, etc.

[0021] In summary, the measurement device and method of the present invention avoid cumbersome operations and specimen disintegration through fully automated non-destructive tests, achieve real-time monitoring and accurate capture of the diffusion position; describe the humidity diffusion behavior based on diffusion-adsorption coupling, and are applicable to complex geological conditions; quickly calculate the humidity diffusion coefficient through an empirical formula with multi-factor coupling, reducing the test workload; being particularly applicable to strongly expansive and disintegrating rocks that are difficult to sample, predicting the time-dependent deformation characteristics of surrounding rocks, evaluating the stability of surrounding rocks, and providing efficient and accurate support for engineering design and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure of the measurement device described in the present invention.

[0023] Figure 2 It is a schematic diagram of the internal structure of the test area of the main box (the top plate, front cover, and side plates of the test area are removed for clearly showing the internal structure).

[0024] Figure 3 It is a schematic diagram of the internal structure of the control area and adjustment area of the main box (the top plate, side plates, and back plate of the control area are removed, and the side plates and back plate of the adjustment area are removed for clearly showing the internal structure).

[0025] Figure 4 It is a schematic diagram of the structure of the hanging basket.

[0026] Figure 5 It is a schematic diagram of the structure of the intelligent sensing film.

[0027] In the figure: 1 main body box; 101 test area; 102 control area; 103 adjustment area; 104 water tank area; 2 suspended weighing device; 3 suspension connecting rod; 4 suspended basket; 401 connecting beam; 402 side frame; 403 hollow platform; 5 intelligent sensing film; 6 strain collector; 7 sealing ring; 8 elastic wire passing hole; 9 temperature sensor; 10 humidity sensor; 11 evaporator; 12 water tank; 13 fan; 14 air outlet; 15 computer; 16 servo controller; 17 humidity and heat isolation board; 18 observation window; 19 handle; 20 transmission line; 21 rock specimen. Detailed implementation manners

[0028] The following describes the detailed implementation manners of the present invention in combination with the technical solutions and the drawings.

[0029] As Figures 1 to 3 shown, a device for measuring the humidity diffusion coefficient of rock based on diffusion-adsorption coupling includes a main body box 1, a self-weighing system, a strain acquisition system, a temperature and humidity servo adjustment system, and a control system.

[0030] The main body box 1 is divided into a test area 101, a control area 102, an adjustment area 103, and a water tank area 104 by a humidity and heat isolation board 17.

[0031] The self-weighing system includes a suspended weighing device 2, a suspension connecting rod 3, and a suspended basket 4 connected in sequence; wherein, the suspended weighing device 2 is arranged at the top of the test area 101 in the main box body to weigh the specimen placed in the suspended basket in real time.

[0032] The strain acquisition system includes an intelligent sensing film 5 and a strain collector 6; wherein, the intelligent sensing film 5 is a cylindrical structure made of flexible water-proof material for placing the specimen, one end of which is open to make the specimen contact with the humidity environment, and a sealing ring 7 is installed between the specimen and the open end to prevent water vapor from entering the interior; the other end of the intelligent sensing film is closed, and an elastic wire passing hole 8 is provided in the center. One end of the transmission line is connected to the strain sensor arranged on the inner wall of the intelligent sensing film, and the other end is connected to the strain collector 6 through the elastic wire passing hole 8; the strain collector 6 is arranged in the control area 102 and is used for collecting the strain data from the strain sensor.

[0033] The temperature and humidity servo regulation system includes a temperature sensor 9, a humidity sensor 10, an evaporator 11, a water tank 12, and a fan 13; among them, the temperature sensor 9 and the humidity sensor 10 are arranged in the test area 101; the water tank 12 is arranged in the water tank area 104 and is used to store liquid water for humidity regulation; the evaporator 11 consists of two upper and lower heating zones, which are respectively located in the regulation area 103 and the water tank area 104, wherein the upper heating zone is located above the water tank 12, and the lower heating zone is in contact with the water tank 12; a fan 13 is arranged on the upper part of the evaporator 11 facing the test area side, and air outlets 14 are distributed on the humid and heat isolation plate 17 between the test area 101 and the regulation area 103; the upper heating zone of the evaporator 11 adjusts the temperature by heating, and the lower heating zone adjusts the humidity by heating and evaporating the water body. With the cooperation of the fan, the humid and hot air enters the test area through the air outlet to achieve the temperature and humidity regulation during the test process.

[0034] The control system includes a computer 15 and a servo controller 16; among them, the servo controller 16 is arranged in the control area 102 and is connected to the computer 15, the hanging weigher 2, the strain collector 6, the temperature sensor 9, the humidity sensor 10, the evaporator 11, and the fan 13, and is used to receive computer instructions to control the test process and temperature and humidity parameters, receive the weight data of the hanging weigher, the strain data of the strain collector, the temperature data of the temperature sensor, and the humidity data of the humidity sensor, and transmit them to the computer for data processing and temperature and humidity regulation.

[0035] The following is a detailed description of the structures of each component to facilitate further understanding of the present invention.

[0036] As Figure 1 shown, the main body box 1 is a cuboid box body, which is divided into a test area 101, a control area 102, a regulation area 103, and a water tank area 104 by a humid and heat isolation plate 17; a front cover is provided on the main body box 1. After opening, test preparation work such as placing specimens and connecting transmission lines can be carried out. A handle 19 and an observation window 18 are provided on the front cover, which are used to open the front cover and observe the shape of the specimens.

[0037] As Figure 2 shown, the self-weighing system includes a hanging weigher 2, a hanging connecting rod 3, and a hanging basket 4; specifically as follows: The hanging weigher 2 is a pull-press weighing sensor. Three hanging weighers 2 are evenly distributed at the top of the test area to synchronously measure the weight changes of three specimens. The lower end of the hanging weigher 2 is connected to the hanging connecting rod 3 by a thread, which is convenient for disassembling to place specimens, etc.; the hanging connecting rod 3 is a hollow metal cylindrical rod body, its top end is connected to the hanging weigher 2, and its bottom end is fixedly connected to the hanging basket 4; as Figure 4As shown in the figure, the middle position at the top of the hanging basket 4 is the connecting beam 401. The hanging connecting rod 3 is fixedly connected to the middle position of the connecting beam 401 and is connected to the hanging weighing device 2. Both ends of the connecting beam 401 are respectively connected to one side frame 402. The rectangular side frame is a metal sheet with a certain width. A plurality of evenly distributed hollow cylindrical metal rod bodies are fixedly connected to the bottom of the side frame 402 to form a hollow platform 403 for placing test pieces, and can timely slide the liquid water formed by high humidity along the rod bodies to reduce the influence on the weight data of the test pieces after moisture absorption.

[0038] The strain acquisition system includes an intelligent sensing film 5, a sealing ring 7, a strain collector 6, and a transmission line 20; specifically as follows: As Figure 5 shown, the intelligent sensing film 5 is made of a flexible water-repellent material, and its structural design aims to simultaneously meet multiple functions such as water isolation, slight restraint of test pieces, and real-time monitoring; one end of the intelligent sensing film 5 is open for the test piece to contact the humidity environment, and the other end is provided with an elastic wire-passing hole 8, which is used to allow the transmission line 20 connecting the strain sensor and the strain collector 6 to pass through, and can shrink to reduce the pore size. At the same time, during the test, it is further sealed with sealant to prevent water vapor from entering the interior; the intelligent sensing film 5 is evenly divided into several zones along the axial direction, and two groups of strain sensors are embedded on the inner side of each zone and the two groups of strain sensors are arranged opposite to each other along the radial direction for monitoring the axial strain of the test piece to accurately determine the diffusion position.

[0039] The sealing ring 7 is an annular elastic rubber ring installed between the open end of the intelligent sensing film 5 and the rock test piece 21 to prevent water vapor from entering the interior.

[0040] The strain collector 6 is arranged in the control area 102 for collecting strain data from the strain sensors and is connected to the servo controller through the transmission line 20 to realize further data transmission.

[0041] The transmission line 20 is a cable that can transmit digital signals carrying temperature, humidity, deformation, etc., and at the same time plays the role of supplying power to each part of the measuring device.

[0042] The temperature and humidity regulation system includes a temperature sensor 9, a humidity sensor 10, an evaporator 11, a water tank 12, and a fan 13; specifically as follows: As Figure 2 shown, the temperature sensor 9 and the humidity sensor 10 are installed on one side of the test area 101 for real-time monitoring of the temperature and humidity in the test area 101, and the monitored data is transmitted to the servo controller 16 through the transmission line to start the evaporator and the fan to work, realizing the servo change of automatically adjusting the computer preset temperature and humidity.

[0043] The water tank 12 is arranged in the water tank area 104 for storing liquid water for humidity regulation.

[0044] AsFigure 3 As shown, the evaporator 11 is arranged in the adjustment area 103 and the water tank area 104, divided into upper and lower heating areas, and can operate independently for heating. The upper heating area is exposed above the water tank, and the lower heating area is in contact with the water in the water tank; a fan 13 is installed on one side of the box above the evaporator, with the air outlet facing the test area. The humid and hot isolation board 17 between the test area and the adjustment area is distributed with dense round holes, which are the air outlets 14. The evaporator 11 and the fan 13 are both connected to the servo controller 16 through transmission lines. The upper heating area of the evaporator adjusts the temperature inside the box through heating, and the lower heating area adjusts the humidity inside the box by heating and evaporating the water body. With the cooperation of the fan, the humid and hot air enters the test area through the air outlet to achieve the temperature and humidity adjustment during the test.

[0045] The control system includes a computer 15, a servo controller 16 and transmission lines; specifically as follows: As Figure 1 shown, the computer 15 is independent of the main body box 1 and is connected to the servo controller 16 inside the main body box 1 through a transmission line to control the test process and input the temperature and humidity instructions required for the test to each component of the measuring device, and can receive and process the strain data of the test piece during the test; to avoid the influence of the attached water on the surface of the hanging basket and the hanging connecting rod on the water absorption of the test piece in a high-humidity environment, it has the function of being able to clear the weight value and continue to collect data when the humidity in the test area reaches the set value.

[0046] As Figure 3 shown, the servo controller 16 is arranged in the control area 102, used to transmit computer instructions and receive and transmit test deformation data, and is connected to the computer 15 and each part of the measuring device through transmission lines.

[0047] A method for measuring the humidity diffusion coefficient of rock based on diffusion-adsorption coupling, which is realized by using the above-mentioned measuring device, includes the following steps: Step 1: Drill core samples from the rock to be tested and prepare several rock test pieces with the same size; place the rock test pieces in the hanging basket 4 inside the main body box 1, set the temperature of the main body box to continuously dry the rock test pieces until the weight of the rock test pieces no longer changes; More specifically, the rock to be tested includes rocks without clay minerals and rocks containing clay minerals; for rocks without clay minerals, original rock test pieces are drilled from the core; for rocks containing clay minerals, original rock test pieces and remolded specimens are respectively prepared. The remolded specimens are made by grinding the original rock to the required particle size and pressing without adding a binder. During the pressing process, the density and compactness of the remolded specimens are the same as those of the original rock; Step 2: Divide the dried rock specimens into multiple strain test areas of equal height evenly according to the respective zones of the intelligent sensing film 5; place the rock specimens into the intelligent sensing film 5 with the ends of the rock specimens aligned with the open end of the intelligent sensing film 5, insert the sealing ring 7 between the rock specimens and the intelligent sensing film 5, and make each strain test area of the rock specimens correspond to the strain sensors in the respective zones within the intelligent sensing film 5. The transmission lines on the strain sensors extend out through the elastic wire-passing holes 8 at the closed end of the intelligent sensing film. Thus, the packaging of the rock specimens is completed. Step 3: Take 3 rock specimens packaged in Step 2 and place them in the hanging baskets 4 inside the main body box respectively, and connect the transmission lines of the strain sensors to the corresponding strain collectors 6. Step 4: Set the constant temperature and constant humidity in the test area of the main body box, as well as the data acquisition time interval of the strain collector 6 according to the environment where the original rock is located. When the deformation amount of the rock specimens collected by the strain collector 6 and the weight of the rock specimens collected by the hanging weighing device 2 no longer change within 24 hours after a certain moment, the test ends, and the test period is determined to be from the start of the test to the end of this moment. Step 5: Based on the diffusion-adsorption coupling method, decompose the humidity diffusion process into a diffusion term driven by the concentration gradient and an adsorption term caused by the adsorption of moisture on the rock surface, and calculate the rock humidity diffusion coefficient. The specific process is as follows: Step 5.1: Establish an expression for the humidity diffusion coefficient Based on the diffusion-adsorption coupling method, decompose the humidity diffusion process into two parts, namely a diffusion term driven by the concentration gradient and an adsorption term caused by the adsorption of moisture on the rock surface. Based on this, the basic control equation for humidity diffusion is as follows: (1) In the formula: is the moisture concentration at a certain moment during the diffusion process, that is, the ratio of the weight of the absorbed moisture at a certain moment in the test to the dry weight of the rock specimens; is the equivalent humidity diffusion coefficient , where is the diffusion term driven by the concentration gradient, is the adsorption term caused by the adsorption of moisture on the rock surface; is the humidity diffusion time; is the Laplace operator, which is used to describe the diffusion behavior of humidity in one-dimensional space, , then formula (1) can be written as: (2) In the formula, starting from the exposed surface of the rock specimen in contact with the humidity environment, is the coordinate of the axial diffusion position. When the strain at a certain point is detected to start increasing from 0, it indicates that the humidity has diffused to this position.

[0048] Step 5.2: Calculate the rock humidity diffusion coefficient (1) Humidity diffusion coefficient of rocks without clay minerals For rocks without clay minerals, the adsorption term caused by water adsorption on the rock surface is not considered, and only the diffusion term is considered .

[0049] Determine the diffusion distance according to the position where the rock specimen generates strain: (3) In the formula, is the maximum distance of humidity diffusion; According to the one-dimensional form of Fick's law in formula (2), when reaching the stable condition, the concentration gradient is linearly distributed. Therefore, the diffusion term formula can be expressed as: (4) In the formula, is the equilibrium concentration when reaching the steady state, that is, the ratio of the weight of the specimen after diffusion to the dry weight of the specimen; is the time required to reach the steady state.

[0050] (2) Humidity diffusion coefficient of the original rock specimen containing clay minerals For the original rock specimen containing clay minerals, the adsorption term is further considered , combined with the Langmuir isotherm: (5) In the formula: is the moisture adsorption amount of the specimen at adsorption equilibrium, is the maximum adsorption amount, is the adsorption equilibrium constant.

[0051] When reaching the stable state, , the adsorption amount reaches equilibrium. At this time , is the instantaneous moisture adsorption amount of the specimen before equilibrium; the enhancement effect of the adsorption is reflected in the product of the adsorption rate and the adsorption equilibrium amount; since the adsorption process is related to the concentration gradient, formula (5) needs to be differentiated with respect to to obtain: (6) Also according to , where is the adsorption rate constant, substituting it into (6) gives: (7) When reaching the steady state, , the adsorption term can be simplified as: (8) Therefore, the influence of the adsorption term on the diffusion coefficient can be expressed through the adsorption rate equation as: (9) (3) Humidity diffusion coefficient of the remolded specimen of rock containing clay minerals Since the remolded specimen of rock is tested on the basis of destroying the original rock structure, there are certain differences in its porosity. To more accurately obtain the humidity diffusion coefficient close to the original rock, by measuring the porosity of the original rock block and the remolded specimen of rock, they are respectively denoted as , , and a scale factor is defined to characterize the porosity difference between the two. This scale factor reflects the relative difference in porosity between the original rock and the remolded specimen of rock: (10) Based on formula (9), the humidity diffusion coefficient of the remolded specimen of rock containing clay minerals is obtained: (11).

[0052] Furthermore, the calculation method of the adsorption rate constant is as follows: (12) where is the moisture adsorption amount of the specimen at adsorption equilibrium; is the instantaneous moisture adsorption amount of the specimen before equilibrium; The integral form of formula (12) is: (13) where: (14) (15) In the formula, is the weight of the rock specimen at time is the weight of the rock specimen at equilibrium, is the initial dry weight of the rock specimen; the weight is recorded every , and the adsorption rate constant is obtained by fitting.

[0053] Example 1 A roadway in a certain metal mine is located in a granite formation. The surrounding rock is mainly composed of quartz, feldspar, and mica, with almost no clay minerals. Its average air temperature and humidity are 25°C and 80%RH respectively. Although the rock in this mining area has high strength and a dense structure, under the long-term high-humidity environment, microcrack expansion and local deterioration may still occur on the surface of the surrounding rock. To evaluate the influence of humidity diffusion on the stability of the roadway and predict its bearing capacity and deformation characteristics under complex humidity environments, it is necessary to conduct humidity diffusion tests to obtain relevant parameters to guide engineering design and maintenance. The specific method is as follows: Step 1: Obtain representative granite rock blocks from different areas of the on-site mining area, prepare multiple cylindrical rock specimens with a diameter of 50 mm and a height of 100 mm, and place the rock specimens into the main box 1; turn on the computer and the power of the main box to energize all parts of the measuring device, set the drying temperature to 105°C, and conduct continuous drying to eliminate the free water in the rock specimens until the weight value of the rock specimens no longer changes.

[0054] Step 2: Evenly divide the dried rock specimens into multiple strain test areas of equal height according to the respective partitions of the intelligent sensing film 5; place the rock specimens into the intelligent sensing film 5 with the ends of the rock specimens aligned with the open end of the intelligent sensing film 5, insert the sealing ring 7 between the rock specimens and the intelligent sensing film 5, and make each strain test area of the rock specimens correspond to the strain sensors in the respective partitions of the intelligent sensing film 5. The transmission lines on the strain sensors extend out from the elastic wire-passing holes 8 at the closed end of the intelligent sensing film 5. Thus, the packaging of the rock specimens is completed.

[0055] Step 3: Take 3 rock specimens packaged in Step 2 and place them in the hanging baskets 4 in the main box 1 respectively, and connect the transmission lines of the strain sensors to the corresponding strain collectors 6 to complete the wiring work of the strain sensors.

[0056] Step 4: According to the environment where the granite rock blocks are located, set the temperature and humidity in the test area 101 of the main box to 25°C and 80%RH respectively, and set the data acquisition frequency of the strain collector 6 with an interval time of 10 min. When the deformation amount of the rock specimens collected by the strain collector 6 and the weight of the rock specimens collected by the hanging weighing device 2 no longer change within 24 h after 48 h, end the test, and the test period is 48 h.

[0057] Step 5: After the 48-h test is completed, the following relevant data are obtained: the initial weight of the rock specimens is 530 g, the final weight of the rock specimens is 534 g, the diffusion distance is 20 mm, and the humidity diffusion coefficient is calculated using formula (4) as m 2 / h.

[0058] Example 2 The surrounding rock of a certain underground metal mine roadway is metamorphic swelling rock, rich in clay minerals such as montmorillonite and kaolinite. Its average air temperature and humidity are 25°C and a constant humidity of 80%RH respectively. Due to the significant swelling and disintegration properties of this type of rock, the mineral types and their components vary greatly in different regions, and it is prone to softening, hydrolysis and volume expansion in a high-humidity environment, which will seriously affect the stability of the roadway. Although this rock shows strong deterioration characteristics after long-term exposure to a high-humidity environment, due to the relatively complete structure in some local areas, intact original rock specimens can still be drilled. In order to accurately evaluate the deformation aging characteristics of the surrounding rock under the action of humidity diffusion and provide a basis for engineering safety. The specific method is as follows: Step 1: Obtain representative intact swelling rock blocks from different regions of the on-site mining area, prepare multiple cylindrical rock specimens with a diameter of 50mm and a height of 100mm, and place the rock specimens in the main box 1. Turn on the computer and the power of the main box to energize all parts of the measuring device. Set the drying temperature to 105°C and carry out continuous drying to eliminate the free water in the rock specimens until the weight value of the rock specimens no longer changes.

[0059] Step 2: Evenly divide the dried rock specimens into multiple strain test areas of equal height according to the respective partitions of the intelligent sensing film 5; place the rock specimens in the intelligent sensing film 5 and align the ends of the rock specimens with the open end of the intelligent sensing film 5. Plug the sealing ring 7 between the rock specimens and the intelligent sensing film 5, and make each strain test area of the rock specimens correspond to the strain sensors in the respective partitions of the intelligent sensing film 5. The transmission lines on the strain sensors extend out from the elastic wire-passing holes 8 at the closed end of the intelligent sensing film 5. Thus, the packaging of the rock specimens is completed.

[0060] Step 3: Take 3 rock specimens packaged in Step 2 and place them in the hanging baskets 4 in the main box 1 respectively, and connect the transmission lines of the strain sensors to the corresponding strain collectors 6 to complete the wiring work of the strain sensors.

[0061] Step 4: According to the environment where the metamorphic swelling rock is located, set the temperature and humidity of the test area 101 in the main box to 25°C and 80%RH respectively, and set the data acquisition frequency of the strain collector 6 at an interval of 10 minutes. When the deformation amount of the rock specimens collected by the strain collector 6 and the weight of the rock specimens collected by the hanging weighing device 2 no longer change within 24 hours after 60 hours, end the test, and the test period is 60 hours.

[0062] Step 5: After the 60-hour test is over, the following relevant data are finally obtained: the initial weight of the rock specimens is 500g, the final weight of the rock specimens is 512.5g, the diffusion distance is 80mm, and the adsorption equilibrium constant h -1 , and the humidity diffusion coefficient is calculated by formula (9) to be m 2 / h.

[0063] Example 3 The surrounding rock of a roadway in a deep mine is strongly swelling argillaceous rock, rich in clay minerals such as illite and chlorite. Its average air temperature and humidity are 25°C and a constant humidity of 80%RH respectively. However, due to its strong disintegration property, it is difficult to drill complete original rock specimens. In this case, traditional sampling and slicing methods cannot meet the test requirements, and the influence of humidity diffusion behavior on roadway stability is crucial. Therefore, it is necessary to adopt a humidity diffusion coefficient measurement device and method based on remolded specimens to determine the humidity diffusion coefficient and diffusion distance, so as to evaluate the deterioration characteristics and engineering risks of the surrounding rock in a long-term high-humidity environment. The specific method is as follows: Step 1: Obtain representative swelling rock fragments from different areas of the on-site mining area. After grinding them into powder, use a pressing process to press the powder into several cylindrical remolded specimens with a diameter of 50mm and a height of 100mm. Then place the remolded specimens in the main box 1 and dry them to eliminate the free water in the specimens until the weight value of the specimens no longer changes.

[0064] Step 2: Uniformly divide the dried remolded specimens into multiple strain test areas of equal height according to each partition of the intelligent sensing film 5; place the remolded specimens in the intelligent sensing film 5 and align the ends of the remolded specimens with the open end of the intelligent sensing film 5. Stuff the sealing ring 7 between the remolded specimens and the intelligent sensing film 5, and make each strain test area of the remolded specimens correspond to the strain sensors in each partition of the intelligent sensing film 5 respectively. The transmission lines on the strain sensors extend out from the elastic wire-passing holes 8 at the closed end of the intelligent sensing film 5. Thus, the encapsulation of the remolded specimens is completed.

[0065] Step 3: Take 3 remolded specimens encapsulated in Step 2 and place them in the hanging baskets 4 in the main box 1 respectively, and connect the transmission lines of the strain sensors to the corresponding strain collectors 6 to complete the wiring work of the strain sensors.

[0066] Step 4: Set the temperature and humidity in the test area 101 of the main box to 25°C and 80%RH respectively, and set the data acquisition frequency of the strain collector 6 at an interval of 10 minutes. When the deformation amount of the remolded specimens collected by the strain collector 6 and the weight of the remolded specimens collected by the hanging scale 2 no longer change within 24 hours after 72 hours, end the test, and the test period is 72 hours.

[0067] Step 5: After the 72-hour test ends, finally obtain the relevant data: the initial weight of the remolded specimens is 490g, the final weight of the remolded specimens is 505g, the diffusion distance is 90mm, and the adsorption equilibrium constant s -1, the porosity of the original rock fragments is 0.28, and the porosity of the remolded specimen is 0.22. The humidity diffusion coefficient calculated by formula (11) is m 2 / h.

[0068] As described above, the above are the preferred specific embodiments of the present invention. However, the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A device for measuring the rock moisture diffusion coefficient based on diffusion-adsorption coupling, characterized in that: It includes a main box, a self-weighing system, a strain acquisition system, a temperature and humidity servo adjustment system and a control system; The main box is divided into a test area, a control area, a regulation area and a water tank area; The self-weighing system comprises a hanging weighing device, a hanging connecting rod and a hanging basket connected in sequence; wherein the hanging weighing device is arranged at the top of the test area in the main box body, and weighs the test piece placed in the hanging basket in real time; The strain collection system includes an intelligent sensing membrane and a strain collector; wherein the intelligent sensing membrane is a cylindrical structure with one end open and the other end closed, and a strain sensor is arranged on its inner wall; the strain collector is arranged in the control area and connected to the strain sensor; The temperature and humidity servo adjustment system includes a temperature sensor, a humidity sensor, an evaporator, a water tank and a fan; wherein the temperature sensor and the humidity sensor are arranged in the test area; the water tank is arranged in the water tank area; the evaporator is composed of two upper and lower heating zones, which are respectively located in the adjustment area and the water tank area, wherein the upper heating zone is located in the upper part of the water tank, and the lower heating zone is in contact with the water tank; a fan is arranged on the upper part of the evaporator facing the test area, and air outlets are arranged on the partition between the test area and the adjustment area; the upper heating zone of the evaporator realizes temperature adjustment by heating, and the lower heating zone realizes humidity adjustment by heating and evaporating water, and cooperates with the action of the fan to let the hot and humid air enter the test area through the air outlet to realize temperature and humidity adjustment; The control system includes a computer and a servo controller; wherein the servo controller is arranged in the control area, connected to the computer, the suspended weighing device, the strain collector, the temperature sensor, the humidity sensor, the evaporator and the fan, and is used to receive computer instructions to control the test process, receive weight data from the suspended weighing device, strain data from the strain collector, temperature data from the temperature sensor, and humidity data from the humidity sensor and transmit them to the computer for data processing. The computer controls the evaporator and the fan through the servo controller according to the collected temperature data and humidity data to achieve temperature and humidity regulation.

2. The rock moisture diffusion coefficient measuring device based on diffusion-adsorption coupling according to claim 1 is characterized in that: The smart sensing membrane is made of a flexible waterproof material, and its open end allows the specimen to contact the humidity environment, and a sealing ring is installed between the specimen and the open end; an elastic threading hole is provided in the center of the closed end of the smart sensing membrane, one end of the transmission line is connected to the strain sensor on the inner wall of the smart sensing membrane, and the other end is connected to the strain collector through the elastic threading hole.

3. The rock moisture diffusion coefficient measuring device based on diffusion-adsorption coupling according to claim 1 is characterized in that: The intelligent sensing film is evenly divided into a plurality of partitions along the axial direction. Two groups of strain sensors are arranged in each partition and the two groups of strain sensors are arranged opposite to each other along the radial direction to monitor the axial strain of the test piece.

4. The rock moisture diffusion coefficient measuring device based on diffusion-adsorption coupling according to claim 1 is characterized in that: The hanging weighing device is a tension-compression weighing sensor, and three hanging weighing devices are evenly distributed on the top of the test area of ​​the main box.

5. The rock moisture diffusion coefficient measuring device based on diffusion-adsorption coupling according to claim 1 is characterized in that: The hanging basket includes a connecting beam, a side frame and a hollow platform; the two ends of the connecting beam are respectively connected to a side frame, the side frame is a rectangular structure composed of metal sheets, and the bottom edge of the side frame is fixedly connected to a plurality of evenly distributed hollow cylindrical metal rods to form a hollow platform.

6. A method for determining the rock moisture diffusion coefficient based on diffusion-adsorption coupling, characterized in that: The method is implemented by using the rock moisture diffusion coefficient determination device based on diffusion-adsorption coupling as described in claim 3, and comprises the following steps: Step 1: Take a core sample from the rock to be tested and prepare it into a number of rock specimens of the same size; place the rock specimens in a hanging basket, set the temperature of the main box to continuously dry the rock specimens until the weight of the rock specimens no longer changes; Step 2: Divide the dried rock specimen into multiple strain test areas of equal height according to the partitions of the smart sensor membrane; place the rock specimen in the smart sensor membrane and align the end of the rock specimen with the open end of the smart sensor membrane, insert the sealing ring between the rock specimen and the smart sensor membrane, and make each strain test area of ​​the rock specimen correspond to the strain sensor of each partition in the smart sensor membrane, and the transmission line on the strain sensor extends from the elastic threading hole at the closed end of the smart sensor membrane, thus completing the packaging of the rock specimen; Step 3: Take three rock specimens packaged in step 2, place them in hanging baskets in the main box, and connect the transmission line of the strain sensor to the corresponding strain collector; Step 4: According to the environment of the original rock, set the constant temperature and constant humidity of the main box test area, as well as the data collection time interval of the strain collector The test is terminated when the deformation of the rock specimen collected by the strain collector and the weight of the rock specimen collected by the hanging weighing device do not change within 24 hours after the moment; Step 5: Based on the diffusion-adsorption coupling method, the humidity diffusion process is decomposed into a diffusion term driven by the concentration gradient and an adsorption term caused by water adsorbed on the rock surface, and the rock humidity diffusion coefficient is calculated.

7. The method for determining rock moisture diffusion coefficient based on diffusion-adsorption coupling according to claim 6 is characterized in that: In the step 1, the rocks to be tested include rocks without clay minerals and rocks containing clay minerals; for rocks without clay minerals, original rock specimens are prepared by drilling cores; for rocks containing clay minerals, they are divided into original rock specimens that can be drilled intact and original rock specimens that are difficult to drill intact. The original rock specimens that are difficult to drill intact are prepared by grinding the original rock to a desired particle size and pressing it into a reshaped sample specimen without adding a binder. During the pressing process, the density and compactness of the reshaped sample specimen are consistent with those of the original rock.

8. The method for determining rock moisture diffusion coefficient based on diffusion-adsorption coupling according to claim 7 is characterized in that: For rocks without clay minerals, the moisture diffusion coefficient is expressed as: In the formula, is the equilibrium concentration when steady state is reached, that is, the ratio of the weight of the specimen after diffusion to the dry weight of the specimen; is the time required to reach steady state; It is the maximum distance of humidity diffusion, which is determined by the position where the rock specimen generates strain. When the strain at a certain point increases from 0, it indicates that the humidity has diffused to that position.

9. The method for determining rock moisture diffusion coefficient based on diffusion-adsorption coupling according to claim 8 is characterized in that: For the original rock specimens and rock remolded specimens containing clay minerals, the humidity diffusion coefficients are expressed as: In the formula, and represent the moisture diffusion coefficients of the original rock specimens and remolded specimens containing clay minerals, respectively; is the adsorption rate constant; , are the porosity of the original rock block and the reshaped rock sample, respectively.

10. The method for determining rock moisture diffusion coefficient based on diffusion-adsorption coupling according to claim 9, characterized in that: The adsorption rate constant The calculation method is as follows: in, is the amount of water adsorbed by the specimen at adsorption equilibrium; is the instantaneous water adsorption of the specimen before equilibrium; The integral form of is: in: In the formula, yes The weight of the rock specimen at the time, is the weight of the rock specimen at equilibrium, is the initial dry weight of the rock specimen; Record the weight once and fit to get the adsorption rate constant .

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