Device and Method for Measuring Rock Moisture Diffusion Coefficient Based on Diffusion-Adsorption Coupling

Abstract

The present invention provides a device and method for measuring the humidity diffusion coefficient of rocks based on diffusion-adsorption coupling, belonging to the field of geotechnical engineering testing. The present invention realizes long-term, continuous and automatic monitoring of the humidity diffusion test process through a hanging weighing method, and obtains the weight change of the specimen in real time during the humidity diffusion process; through a strain acquisition system, it monitors the strain of the specimen in real time, overcomes the problem of untimely monitoring under the condition of a long test cycle, and proposes a test method for accurately determining the diffusion position by monitoring the strain in order to calculate the humidity diffusion coefficient; through a servo control system, it simulates different temperature and humidity environments of the surrounding rock; through an intelligent sensing film, it solves the problem of test interruption after the strongly expansive specimen disintegrates due to humidity influence, and synchronously monitors the strain of the specimen. A calculation method for the humidity diffusion coefficient based on diffusion-adsorption coupling is proposed to more accurately obtain the humidity diffusion coefficient of rocks, which is particularly suitable for geotechnical bodies with strong expansibility and disintegration properties.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering tests, and particularly relates to a device 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 error, 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 a device and method for measuring the moisture diffusion coefficient of rocks based on diffusion-adsorption coupling, especially for 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 assessment 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 of the rock specimen during the moisture diffusion process, more accurately capture the micro-strain caused by moisture diffusion to determine the diffusion position; by means of making a remolded sample through a small amount of sampling 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:

[0007] 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;

[0008] The main body box is divided into a test area, a control area, an adjustment area, and a water tank area by a partition board;

[0009] 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;

[0010] 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 sensors;

[0011] The temperature and humidity servo regulation system includes a temperature sensor, a humidity sensor, an evaporator, a water tank, and a blower; wherein, the temperature sensor and the humidity sensor are arranged in the test area; the water tank is arranged in the water tank area for storing liquid water for humidity regulation; the evaporator consists of two 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 blower is arranged on the side of the upper part of the evaporator facing the test area, and air outlets are distributed on the partition board between the test area and the adjustment area; the upper heating area of the evaporator realizes temperature regulation through heating, and the lower heating area realizes humidity regulation through heating and evaporating water bodies. With the cooperation of the blower, the humid and hot air enters the test area through the air outlets to realize the temperature and humidity regulation during the test process;

[0012] 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, the hanging weigher, 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 the weight data of the hanging 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.

[0013] Furthermore, the intelligent sensing film is made of a flexible water-proof material, and 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.

[0014] Furthermore, the intelligent sensing film is evenly divided into several zones along the axial direction, and two groups of strain sensors are arranged in each zone and are arranged opposite to each other along the radial direction, which are used to monitor the axial strain of the test piece to accurately determine the diffusion position.

[0015] Furthermore, the hanging weigher is a tension and compression type weighing sensor, and three hanging weighers are evenly distributed on the top of the test area of the main box.

[0016] 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, and 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.

[0017] Furthermore, when the humidity in the test area of the main box reaches the set value, the computer clears the weight value of the hanging 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.

[0018] 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, and includes the following steps:

[0019] Step 1: Core samples are taken from the rock to be tested 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;

[0020] 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; 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 zones 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 encapsulation of the rock specimens is completed.

[0021] Step 3: Take 3 rock specimens encapsulated 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.

[0022] 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 specimens collected by the strain collector and the weight of the rock specimens collected by the hanging weighing device no longer change within 24 hours after a certain moment, the test ends. The test period is from the start of the test to this moment.

[0023] 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.

[0024] Furthermore, in Step 1, the rocks to be detected include rocks without clay minerals and rocks with clay minerals; for rocks without clay minerals, 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 rocks from which it is difficult to drill complete original rock specimens, 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.

[0025] Furthermore, in Step 5, for rocks without clay minerals, the humidity diffusion coefficient is:

[0026]

[0027] 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 it is monitored that the strain at a certain point starts to increase from 0, it indicates that the humidity has diffused to this position.

[0028] Furthermore, in Step 5, for the original rock specimens and remolded specimens containing clay minerals, the humidity diffusion coefficients are respectively expressed as:

[0029]

[0030]

[0031] In the formula, and respectively represent the humidity diffusion coefficients of the original rock specimens and remolded specimens containing clay minerals; is the adsorption rate constant; 、 are respectively the porosities of the original rock blocks and the remolded rock specimens.

[0032] Furthermore, the calculation method of the adsorption rate constant is as follows:

[0033]

[0034] Wherein, is the moisture adsorption amount of the specimen at adsorption equilibrium; is the instantaneous moisture adsorption amount of the specimen before equilibrium;

[0035] The integral form of

[0036]

[0037] Where:

[0038]

[0039]

[0040] 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 interval and the adsorption rate constant is obtained by fitting.

[0041] Advantages of the present invention:

[0042] (1) The measurement 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.

[0043] (2) A method that precisely captures 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 rock specimens. Compared with the traditional one-dimensional model, it can more precisely monitor the humidity diffusion process in rocks and determine the diffusion position, and is applicable to engineering evaluations under complex geological conditions.

[0044] (3) Four key factors, namely rock mineral type, porosity, temperature, and humidity, are considered, and an empirical formula for the humidity diffusion coefficient with multi-factor coupling is established, reducing the process of long-term and repeated tests. It can more comprehensively reflect the multi-factor influence in the humidity diffusion process, improve the accuracy of the humidity diffusion coefficient, avoid the limitations of a large number of tests and complex calculations in traditional methods, and is particularly applicable to rocks with significant differences in mineral type and pore structure, achieving the rapid acquisition of the humidity diffusion coefficient.

[0045] (4) The problem of difficult acquisition of complete rock cores in traditional methods is solved. 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 is particularly applicable to geotechnical bodies with strong expansibility and disintegration properties, such as metamorphic swelling rocks and expansive soils.

[0046] In summary, the measuring device and method of the present invention avoid cumbersome operations and specimen disintegration through fully automated non-destructive tests, achieving real-time monitoring and precise 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; are particularly applicable to strongly expansive and disintegrating rocks that are difficult to sample, predict the time-dependent deformation characteristics of surrounding rocks, evaluate the stability of surrounding rocks, and provide efficient and accurate support for engineering design and maintenance. Description of the Drawings

[0047] Figure 1 It is a schematic diagram of the overall structure of the measuring device described in the present invention.

[0048] 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 clear display of the internal structure).

[0049] 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 clear display of the internal structure).

[0050] Figure 4 It is a schematic diagram of the structure of the hanging basket.

[0051] Figure 5 It is a schematic diagram of the structure of the intelligent sensing film.

[0052] 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 suspension 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. Specific implementation manners

[0053] The specific implementation manners of the present invention will be described in detail below in combination with the technical solutions and the drawings.

[0054] 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.

[0055] 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.

[0056] The self-weighing system includes a suspended weighing device 2, a suspension connecting rod 3, and a suspension basket 4 that are connected in sequence; among them, 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 suspension basket in real time.

[0057] The strain acquisition system includes an intelligent sensing film 5 and a strain collector 6; among them, 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.

[0058] The temperature and humidity servo adjustment system includes a temperature sensor 9, a humidity sensor 10, an evaporator 11, a water tank 12 and a fan 13; wherein 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 adjustment; the evaporator 11 is composed of two upper and lower heating zones, which are respectively located in the adjustment area 103 and the water tank area 104, wherein the upper heating zone is located in the upper part of the water tank 12, and the lower heating zone is in contact with the water tank 12; a fan 13 is provided on the upper part of the evaporator 11 facing the test area, and air outlets 14 are distributed on the wet and hot isolation plate 17 between the test area 101 and the adjustment area 103; the upper heating zone of the evaporator 11 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 wet and hot air enter the test area through the air outlet to realize temperature and humidity adjustment during the test.

[0059] The control system includes a computer 15 and a servo controller 16; wherein the servo controller 16 is arranged in the control area 102, connected to the computer 15, the suspended weighing device 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 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 and temperature and humidity control.

[0060] The structure of each component is described in detail below to facilitate further understanding of the present invention.

[0061] like Figure 1 As shown, the main box 1 is a rectangular box, which is divided into a test area 101, a control area 102, an adjustment area 103 and a water tank area 104 by a wet and hot isolation plate 17; the main box 1 is provided with a front cover, which can be opened to place test pieces, connect transmission lines and other test preparations, and the front cover is provided with a handle 19 and an observation window 18, which can be used to open the front cover and observe the shape of the test piece.

[0062] like Figure 2 As shown, the self-weighing system includes a hanging weighing device 2, a hanging connecting rod 3 and a hanging basket 4; the details are as follows:

[0063] The hanging weighing device 2 is a tension and compression weighing sensor. Three hanging weighing devices 2 are evenly distributed on the top of the test area to measure the weight changes of the three test pieces synchronously. The lower end of the hanging weighing device 2 is connected to the hanging connecting rod 3 by a thread, which is convenient for disassembly to place the test piece, etc. The hanging connecting rod 3 is a hollow metal cylindrical rod body, the top end of which is connected to the hanging weighing device 2, and the bottom end is fixed to the hanging basket 4; 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 scale 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, reducing the influence on the weight data of the test pieces after moisture absorption.

[0064] 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:

[0065] As Figure 5 shown in the figure, the intelligent sensing film 5 is made of a flexible water-proof material, and its structural design aims to simultaneously meet multiple functions such as water-proof, slightly restricting the test piece, 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 for the transmission line 20 connecting the strain sensor and the strain collector 6 to pass through, and can shrink to reduce the pore, and at the same time, it is further sealed with sealant during the test to avoid 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 in 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.

[0066] The sealing ring 7 is an annular elastic rubber ring, which is installed between the open end of the intelligent sensing film 5 and the rock test piece 21 to avoid water vapor from entering the interior.

[0067] The strain collector 6 is arranged in the control area 102, and is used for collecting the strain data from the strain sensors and connecting with the servo controller through the transmission line 20 to realize further data transmission.

[0068] 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.

[0069] The temperature and humidity adjustment system includes a temperature sensor 9, a humidity sensor 10, an evaporator 11, a water tank 12 and a fan 13; specifically as follows:

[0070] As Figure 2 shown in the figure, the temperature sensor 9 and the humidity sensor 10 are installed on one side of the test area 101, and are used for real-time monitoring of the temperature and humidity in the test area 101, and transmitting the monitored data 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.

[0071] The water tank 12 is arranged in the water tank area 104 and is used for storing liquid water for humidity adjustment.

[0072] As Figure 3 shown, the evaporator 11 is arranged in the regulation 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 body above the evaporator, with the air outlet facing the test area. Dense round holes are distributed on the humid heat isolation plate 17 between the test area and the regulation area, serving as the air outlet 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 body through heating, and the lower heating area adjusts the humidity inside the box body by heating and evaporating the water body. With the cooperation of the fan, the humid hot air enters the test area through the air outlet to achieve the temperature and humidity adjustment during the test process.

[0073] The control system includes a computer 15, a servo controller 16, and transmission lines; specifically as follows:

[0074] 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 specimen during the test process; 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 specimen 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.

[0075] 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.

[0076] A method for measuring the rock moisture diffusion coefficient based on diffusion-adsorption coupling, which is realized by using the above-mentioned measuring device, includes the following steps:

[0077] Step 1: Drill core samples from the rock to be tested and prepare a number of rock specimens with the same size; place the rock specimens in the hanging basket 4 inside the main body box 1, set the temperature of the main body box to continuously dry the rock specimens until the weight of the rock specimens no longer changes;

[0078] More specifically, the rock to be tested includes rocks without clay minerals and rocks containing clay minerals; for rocks without clay minerals, original rock specimens are obtained by drilling core samples; for rocks containing clay minerals, original rock specimens and remolded specimens are prepared respectively. The remolded specimens are formed by grinding the original rock to the required particle size and pressing without adding binders. During the pressing process, the density and compactness of the remolded specimens are the same as those of the original rock;

[0079] Step 2: Divide the dried rock specimens into multiple strain test areas of equal height evenly according to each partition 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 each partition of the intelligent sensing film 5 respectively. The transmission lines on the strain sensors extend out from the elastic wire threading holes 8 at the closed end of the intelligent sensing film. Thus, the encapsulation of the rock specimens is completed.

[0080] Step 3: Take 3 rock specimens encapsulated in Step 2 and place them in the hanging baskets 4 in the main body box respectively, and connect the transmission lines of the strain sensors to the corresponding strain collectors 6.

[0081] Step 4: According to the environment where the original rock is located, 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. 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 scale 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.

[0082] 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:

[0083] Step 5.1: Establish an expression for the humidity diffusion coefficient

[0084] 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:

[0085] (1)

[0086] 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:

[0087] (2)

[0088] 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 monitored to start increasing, it indicates that the humidity has diffused to this position.

[0089] Step 5.2: Calculate the rock humidity diffusion coefficient

[0090] (1) Humidity diffusion coefficient of rocks without clay minerals

[0091] 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 .

[0092] Determine the diffusion distance according to the position where the rock specimen generates strain:

[0093] (3)

[0094] In the formula, is the maximum distance of humidity diffusion;

[0095] 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:

[0096] (4)

[0097] 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.

[0098] (2) Humidity diffusion coefficient of the original rock specimen containing clay minerals

[0099] For the original rock specimen containing clay minerals, the adsorption term is further considered , combined with the Langmuir isotherm:

[0100] (5)

[0101] In the formula: is the moisture adsorption amount of the specimen at adsorption equilibrium, is the maximum adsorption amount, is the adsorption equilibrium constant.

[0102] When reaching the stable state, , the adsorption amount reaches equilibrium. At this time, , is the instantaneous moisture adsorption 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 Derivation:

[0103] (6)

[0104] Also according to , where is the adsorption rate constant, substituting into (6) gives:

[0105] (7)

[0106] When reaching the steady state, , then the adsorption term can be simplified to:

[0107] (8)

[0108] Therefore, the influence of the adsorption term on the diffusion coefficient can be expressed through the adsorption rate equation as:

[0109] (9)

[0110] (3) Humidity diffusion coefficient of the remolded specimen of rock containing clay minerals

[0111] 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, which are respectively denoted as , , 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:

[0112] (10)

[0113] Based on formula (9), the humidity diffusion coefficient of the remolded specimen of rock containing clay minerals is obtained:

[0114] (11).

[0115] Furthermore, the calculation method of the adsorption rate constant is as follows:

[0116] (12)

[0117] Where is the moisture adsorption amount of the test piece at adsorption equilibrium; is the instantaneous moisture adsorption amount of the test piece before equilibrium;

[0118] The integral form of Equation (12) is:

[0119] (13)

[0120] Where:

[0121] (14)

[0122] (15)

[0123] In the formula, is the weight of the rock test piece at time is the weight of the rock test piece at equilibrium, is the initial dry weight of the rock test piece; the weight is recorded every and the adsorption rate constant .

[0124] Example 1

[0125] A roadway in a certain metal mine is located in a granite formation. The surrounding rock is mainly composed of quartz, feldspar and mica, and contains 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 roadway stability, and predict its bearing capacity and deformation characteristics in a complex humidity environment, it is necessary to carry out humidity diffusion tests to obtain relevant parameters to guide engineering design and maintenance. The specific method is as follows:

[0126] Step 1: Obtain representative granite rock blocks from different areas of the on-site mining area, make multiple cylindrical rock test pieces with a size of diameter 50mm and height 100mm, and place the rock test pieces into the main box 1; turn on the computer and the power of the main box, energize each part of the measuring device, set the drying temperature to 105°C, and carry out continuous drying to eliminate the free water in the rock test pieces until the weight value of the rock test pieces no longer changes.

[0127] Step 2: Divide the dried rock specimens into multiple strain test areas of equal height evenly according to each partition 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 each partition of the intelligent sensing film 5 respectively. The transmission lines on the strain sensors extend out from the elastic wire threading holes 8 at the closed end of the intelligent sensing film 5. Thus, the encapsulation of the rock specimens is completed.

[0128] Step 3: Take 3 rock specimens encapsulated in Step 2 and place them in the hanging baskets 4 in the main body 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.

[0129] Step 4: According to the environment where the granite rock blocks are located, set the temperature and humidity of the test area 101 of the main body 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 scale 2 no longer change within 24 h after 48 h, end the test, and the test period is 48 h.

[0130] Step 5: After the 48-h test ends, obtain the relevant data: 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 by formula (4) as m 2 / h.

[0131] Example 2

[0132] 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. Since this type of rock has significant expansibility and disintegration properties, the mineral types and their components in different regions vary greatly, and it is prone to softening, hydrolysis and volume expansion in a high-humidity environment, which will seriously affect the roadway stability. 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:

[0133] Step 1: Obtain representative intact swelling 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, place the rock specimens into the main box 1, turn on the computer and the power of the main box, 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.

[0134] Step 2: Evenly divide the dried rock specimens into multiple strain test areas of equal height according to each partition of the intelligent sensing film 5; place the rock specimens into the intelligent sensing film 5 and align the ends of the rock specimens 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 respectively correspond to the strain sensors in each partition 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.

[0135] Step 3: Take 3 rock specimens packaged in Step 2 and place them respectively in the hanging baskets 4 in the main box 1, and connect the transmission lines of the strain sensors to the corresponding strain collectors 6 to complete the wiring work of the strain sensors.

[0136] Step 4: According to the environment where the metamorphic swelling rock is located, set the temperature and humidity of 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 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 scale 2 no longer change within 24 h after 60 h, the test is ended, and the test period is 60 h.

[0137] Step 5: After the 60-h test is ended, the following relevant data are finally obtained: the initial weight of the rock specimens is 500 g, the final weight of the rock specimens is 512.5 g, the diffusion distance is 80 mm, the adsorption equilibrium constant h -1 , and the humidity diffusion coefficient is calculated to be m 2 / h by using formula (9).

[0138] Example 3

[0139] The surrounding rock of a deep mine roadway 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 device and method for measuring the humidity diffusion coefficient based on remolded samples 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:

[0140] 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 put the remolded specimens into the main box 1 for drying to eliminate the free water in the specimens until the weight value of the specimens no longer changes.

[0141] Step 2: Divide the dried remolded specimens evenly into multiple strain test areas of equal height according to the respective partitions of the intelligent sensing film 5; put the remolded specimens into the intelligent sensing film 5 and align the ends of the remolded specimens with the open end of the intelligent sensing film 5. Then plug 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 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 encapsulation of the remolded specimens is completed.

[0142] Step 3: Take 3 remolded specimens encapsulated in Step 2 and place them in the hanging baskets 4 in the main box 1 respectively. Then connect the transmission lines of the strain sensors to the corresponding strain collectors 6 to complete the wiring work of the strain sensors.

[0143] 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 with an interval time of 10min. 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 24h after 72h, end the test, and the test period is 72h.

[0144] Step 5: After the 72h 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, the adsorption equilibrium constant s -1 , the porosity of the original rock fragments is 0.28, the porosity of the remolded specimens is 0.22, and the humidity diffusion coefficient is calculated using formula (11) as m2 / h.

[0145] As described above, the above is a preferred specific embodiment 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, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. A method for measuring the moisture diffusion coefficient of rock based on the coupling of diffusion and adsorption, characterized in that, This method is implemented by using a device for measuring the moisture diffusion coefficient of rock based on the coupling of diffusion and adsorption. The device includes a main body box, a self - weighing 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; The self - weighing system includes a suspended weighing device, a suspension connecting rod, and a suspension basket connected in sequence. Among them, the suspended weighing device is arranged at the top of the test area in the main box body to weigh the test piece placed in the suspension basket in real time; The strain acquisition system includes an intelligent sensing film and a strain collector. Among them, 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 connected to the strain sensors. The intelligent sensing film is evenly divided into several partitions along the axial direction, and two groups of strain sensors are arranged in each partition and are arranged opposite to each other along the radial direction for monitoring the axial strain of the test piece; The temperature and humidity servo - regulation system includes a temperature sensor, a humidity sensor, an evaporator, a water tank, and a fan. Among them, 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 consists of two upper and lower heating areas, which are located in the adjustment area and the water tank area respectively. 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 water to adjust the humidity. With the cooperation of the fan, the humid and hot air enters the test area through the air outlets to achieve temperature and humidity regulation; 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, the suspended weighing device, the strain collector, the temperature sensor, the humidity sensor, the evaporator, and the fan. It is used to receive computer instructions to control the test process, receive the weight data of the suspended weighing device, 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. 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; The method for measuring the moisture diffusion coefficient of rock includes the following steps: Step 1: Drill a core sample from the rock to be tested and prepare several rock test pieces of the same size. Place the rock test pieces in the suspension basket, set the temperature of the main body box, and continuously dry the rock test pieces until the weight of the rock test pieces no longer changes; Step 2: Evenly divide the dried rock test pieces into multiple strain - testing areas of equal height according to the partitions of the intelligent sensing film. Put the rock test pieces into the intelligent sensing film, align the end of the rock test piece with the open end of the intelligent sensing film, plug the sealing ring between the rock test piece and the intelligent sensing film, and make each strain - testing area of the rock test piece correspond to the strain sensors in each partition of the intelligent sensing film respectively. The transmission lines on the strain sensors extend out from the elastic wire - passing holes at the closed end of the intelligent sensing film. Thus, the packaging of the rock test piece is completed; Step 3: Take 3 rock specimens encapsulated in Step 2 and place them in the hanging baskets in the main 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 of the main box test area, as well as the data acquisition time interval of the strain collector according to the environment where the original rock is located. End the test when the deformation amount of the rock specimen collected by the strain collector and the weight of the rock specimen collected by the suspended weighing device at a certain moment no longer change within 24 hours after that 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.

2. The method for measuring the moisture diffusion coefficient of rock based on diffusion-adsorption coupling according to claim 1, wherein In the said Step 1, the rocks to be detected include rocks without clay minerals and rocks with clay minerals; for rocks without clay minerals, original rock specimens are prepared by drilling cores; for rocks with clay minerals, they are divided into those from which complete original rock specimens can be drilled and those from which complete original rock specimens are difficult to drill. For the rocks from which complete original rock specimens are difficult to drill, the original rock is ground into the required particle size and pressed into remolded specimens without adding binder. During the pressing process, the density and compactness of the remolded specimens are the same as those of the original rock.

3. The method for measuring the moisture diffusion coefficient of rock based on diffusion-adsorption coupling according to claim 2, wherein For rocks without clay minerals, the humidity diffusion coefficient is expressed as: 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 moisture 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 moisture has diffused to this position.

4. The method for measuring the rock moisture diffusion coefficient based on diffusion-adsorption coupling according to claim 3, characterized in that For the original rock specimens with clay minerals and the remolded rock specimens, the humidity diffusion coefficients are respectively expressed as: In the formula, and represent the humidity diffusion coefficients of the original rock specimens and the remolded specimens containing clay minerals, respectively; is the adsorption rate constant; and are the porosities of the original rock blocks and the remolded rock specimens, respectively.

5. The method for measuring the rock moisture diffusion coefficient based on diffusion-adsorption coupling according to claim 4, wherein The adsorption rate constant The calculation method is as follows: Among them, 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 is as follows: Wherein: 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 time, and the adsorption rate constant is obtained by fitting.

6. The method for determining the humidity diffusion coefficient of rock based on diffusion-adsorption coupling according to claim 1, characterized in that The intelligent sensing film is made of a flexible water-proof material. Its open end makes the specimen contact with the humidity environment, and a sealing ring is installed between the specimen and the open end; at the center of the closed end of the intelligent sensing film, there is an elastic wire-passing hole. One end of the transmission line is connected to the strain sensor on the inner wall of the intelligent sensing film, and the other end is connected to the strain collector through the elastic wire-passing hole.

7. The method for measuring the moisture diffusion coefficient of rock based on diffusion-adsorption coupling according to claim 1, wherein The hanging type weighing device is a tension-compression type weighing sensor, and three hanging type weighing devices are evenly distributed on the top of the test area of the main box.

8. The method for measuring the moisture diffusion coefficient of rock based on diffusion-adsorption coupling according to claim 1, characterized in that 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 frame is a rectangular structure composed of metal sheets. A plurality of evenly distributed hollow cylindrical metal rods are fixedly connected to the bottom edge of the side frame to form the hollow platform.

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