A method for observing water distribution inside a rock sample using a splitting test

Abstract

The application discloses a method for observing water distribution in a rock sample by using a splitting test, and comprises the following steps: (1) drying the rock sample; (2) preparing a dyeing agent for soaking the rock sample, selecting a dyeing agent with high contrast with the original color of the rock and a proper dye mass concentration; (3) soaking the rock sample in the dyeing agent; (4) smearing the surface of the rock sample with paraffin; (5) placing the rock sample in a splitting test device to perform the splitting test; and (6) placing the rock sample split into two halves in a place with sufficient light and taking a photo for storage. The method can avoid the problems of a large amount of heat generated in a traditional cutting mode and a long time consumption of nuclear magnetic resonance imaging, thereby affecting the water distribution in the rock, and has the advantages of simple operation and the effect of directly observing the real water distribution in the rock sample.

Description

Technical Field

[0001] This invention belongs to the field of rock mechanics testing technology, specifically a method for observing the internal moisture distribution of rock samples using a splitting test. Background Technology

[0002] Water is the most significant factor affecting rock properties: it not only lowers the rock's elastic modulus and increases its Poisson's ratio, but also increases rock deformation and reduces its strength. Therefore, the interaction between water and rock has always been a hot topic in geotechnical engineering research. With in-depth research, scholars have found that water content alone is insufficient to evaluate the water content of rocks; the spatial distribution of water within the rock is also a crucial factor influencing its properties. Furthermore, the migration of water molecules within the rock is also considered an important factor affecting its mechanical properties. Therefore, a method is urgently needed to clearly observe the distribution and migration process of water within rocks.

[0003] However, as a hard material, it has always been difficult to visually observe the moisture distribution inside a rock sample, which severely limits experimental research on the influence of different moisture distributions on the mechanical behavior of rocks.

[0004] Currently, there are two main methods for observing the internal moisture distribution of rock samples: cutting the rock and using nuclear magnetic resonance imaging (NMR). Cutting rock samples typically involves mechanical cutting, where a cutting machine directly cuts the rock sample along the desired plane. This method is simple, but the friction between the cutting blade and the rock during cutting inevitably generates a large amount of heat. This high temperature causes the moisture inside the rock to evaporate, resulting in a discrepancy between the observed moisture distribution and the original sample. Clearly, this method cannot accurately represent the true moisture distribution within the rock. Nuclear magnetic resonance imaging (NMR) utilizes the NMR effect, which arises from the differences in the relaxation properties of atomic nuclei in different materials, to display the moisture distribution on a plane. While this method can indirectly obtain information about the moisture distribution inside the rock, it still has several limitations. First, this method can only project the three-dimensional moisture distribution onto a plane, and cannot show the moisture distribution on each plane. When the moisture distribution on every plane under the core projection is consistent, this method can accurately represent the internal moisture distribution of the rock. However, when the moisture distribution on different projected planes is inconsistent, the internal moisture distribution obtained by this method is obviously inconsistent with the actual situation. Secondly, since the water in the soaked sample easily evaporates into the air, it is necessary to observe the internal water distribution of the sample shortly after soaking. However, this method requires a large nuclear magnetic resonance imaging (NMR) scanner, which is often unavailable in geotechnical laboratories, necessitating visits to other laboratories, which clearly cannot meet the experimental requirements. Therefore, using NMR imaging also presents significant limitations and inconveniences. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for observing the internal moisture distribution of rock samples using a splitting test. This method is simple and practical, and can directly observe the true distribution of moisture inside the rock sample, which is beneficial to the study of its influence on the mechanical behavior of rocks.

[0006] The present invention solves the above-mentioned technical problems by means of the following technical solution:

[0007] This invention discloses a method for observing the internal moisture distribution of a rock sample using a splitting test, the method comprising the following steps:

[0008] (1) The rock sample was dried to remove the original moisture, and then the mass m of the dried rock sample was measured using an electronic balance. 干 ;

[0009] (2) Place the dried rock sample in a constant temperature and humidity chamber and cool it to room temperature;

[0010] (3) Select a small molecule dye that contrasts with the natural color of the rock, mix it with water to dissolve it and obtain a dyeing agent that contrasts with the natural color of the rock. The mass concentration of the dye in the dyeing agent is 5%-25%.

[0011] (4) Place the rock sample cooled to room temperature into the staining agent from step (3) to obtain the sample required for the experiment to study the effect of internal water distribution on rock mechanical behavior under different soaking time conditions. Then remove the sample, wipe it dry, and measure the mass m of the sample after soaking. 湿 Moisture content of rock samples

[0012] (5) Apply paraffin wax to the sample surface to form a paraffin film on the sample surface to prevent the sample moisture from evaporating into the air, and at the same time inhibit the migration of water molecules inside the rock sample from high concentration area to low concentration area.

[0013] (6) Place the rock sample in the splitting test device, design the splitting surface of the rock sample as the sample surface that needs to be observed in the study, start the splitting test device to split and cut the splitting surface to obtain the splitting surface of the rock sample.

[0014] (7) After the splitting test, the rock sample split into two halves is placed in a well-lit place and its split surface is photographed. By observing the photograph, the true distribution of water inside the rock sample can be obtained. The influence of water inside the rock on the mechanical behavior of the rock can be studied by using the rock water content data and the water distribution data inside the rock.

[0015] In step (6), the splitting surface can be designed in two ways: one is along the axial direction of the rock core, and the other is along the radial direction of the rock core.

[0016] In step (7), the color of the soaked rock sample is used to observe the water distribution inside the rock sample. Specifically, the inside of the rock is divided into a wet zone, a transition zone, and a dry zone. The wet zone is the same color as the soaking liquid, which is completely soaked in water. Near the boundary of the wet zone, the color of the soaking liquid becomes lighter and lighter as you move away from the wet zone, until it becomes the original color of the rock, indicating that the concentration of water molecules is constantly decreasing. This area is the transition zone, which is proof of water molecule migration. The area that retains the original color of the rock indicates that water molecules have not yet migrated in and is called the dry zone.

[0017] Compared with the prior art, the method of the present invention has the following advantages:

[0018] (1) The method of the present invention avoids the large amount of heat generated by the traditional cutting mode and the long time required for nuclear magnetic resonance imaging, which affects the distribution of water inside the rock. It is simple to operate and can achieve the effect of directly observing the true distribution of water inside the rock sample.

[0019] (2) The splitting test used in this invention allows for flexible selection of the surface to be observed in the research, breaking the limitation of traditional methods that can only select the plane of a specific rock sample, and fully meeting the needs of experimental research.

[0020] (3) Because the color of the staining agent used to soak the rock sample is significantly different from the color of the rock itself, the wet and dry boundary zone inside the rock can be clearly seen. The water molecule concentration gradient of the rock sample can also be seen intuitively from the depth of the staining agent color. This is of great significance for in-depth research on the influence of different water distributions on the mechanical behavior of rocks.

[0021] (4) The method of the present invention can be completed in the same laboratory from the end of the immersion of the rock sample to the end of the test and the taking of the picture. It only takes a few minutes. Compared with the traditional method, the method of the present invention can greatly reduce the time of rock sample exposure to air, thereby avoiding the problem of the rock sample being exposed to air for too long and affecting the distribution of moisture.

[0022] (5) The method of the present invention only requires a simple splitting test device, which is widely applicable, simple to operate, and convenient to use. Attached Figure Description

[0023] Figure 1(a) shows a device suitable for splitting the axial splitting surface of a rock sample, with its steel pressure bar aligned with the axial direction of the rock sample.

[0024] Figure 1(b) shows a device suitable for splitting the radial splitting surface of a rock sample, wherein the steel pressure bar is in the same radial direction as the rock sample.

[0025] Figure 2 This is a schematic diagram of the rock sample before and after the splitting test in Embodiment 1 of the present invention.

[0026] Figure 3 This is a schematic diagram of the rock sample before and after the splitting test in Embodiment 2 of the present invention.

[0027] In the diagram: 1—Steel pressure bar; 2—Rock sample; 3—Split test device; 4—Wet zone; 5—Transition zone; 6—Dry zone. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0029] This invention discloses a method for observing the internal moisture distribution of a rock sample using a splitting test, comprising the following specific operational steps:

[0030] (1) Place rock sample 2 in a forced-air drying oven and dry it at 105℃ for 48 hours to remove the original moisture in the rock sample. Then, use an electronic balance to measure the mass m of the dried rock sample. 干 ;

[0031] (2) Place the dried rock sample in a constant temperature and humidity chamber and cool it to room temperature;

[0032] (3) Select a small molecule dye that contrasts with the natural color of the rock, mix it with water to dissolve it and obtain a dyeing agent that contrasts with the natural color of the rock. The dye mass concentration in the dyeing agent is 5%-25%, and this concentration is selected according to the depth of the natural color of the rock.

[0033] (4) Place the rock sample cooled to room temperature into the staining agent from step (3) to obtain the sample required for the experiment to study the effect of internal water distribution on rock mechanical behavior under different soaking time conditions. Then remove the sample, wipe it dry, and measure the mass m of the sample after soaking. 湿 Water content of rock samples

[0034] (5) Apply paraffin wax to the sample surface to form a paraffin film on the sample surface to prevent the sample moisture from evaporating into the air, and at the same time inhibit the migration of water molecules inside the rock sample from high concentration area to low concentration area.

[0035] (6) Place the rock sample in the splitting test device 3. Design the splitting surface of the rock sample to be the sample surface to be observed in the study. There are two types of splitting surfaces: one is designed along the axial direction of the rock core, and the other is designed along the radial direction of the rock core. If the splitting surface of the rock core is in the axial direction, select the splitting test device in Figure 1(a) for the test, that is, the steel pressure bar 1 is designed along the axial direction of the rock sample 2; if the splitting surface of the rock core is in the radial direction, select the splitting test device in Figure 1(b) for the test, that is, the steel pressure bar 1 is designed along the radial direction of the rock sample 2; by starting the splitting test device, the splitting surface of the rock sample is split and cut, thus obtaining the splitting surface of the rock sample.

[0036] (7) After the splitting test, place the rock sample split into two halves in a well-lit place and take pictures of the split surface. By observing the pictures, the wet and dry boundary zone inside the rock sample can be clearly seen. The water molecule concentration gradient of the rock sample can also be intuitively seen from the depth of the rock sample color. The influence of water content data and water distribution data inside the rock sample on the mechanical behavior of the rock can be studied using the rock water content data and related data. The specific operation is as follows: the inside of the rock is divided into a wet zone, a transition zone and a dry zone. The wet zone is the same color as the soaking liquid. The wet zone is completely soaked in water. Near the boundary of the wet zone, the color of the soaking liquid becomes lighter and lighter as you move away from the wet zone until it becomes the original color of the rock. This indicates that the water molecule concentration is constantly decreasing. This area is the transition zone, which is proof of water molecule migration. The area that retains the original color of the rock indicates that water molecules have not yet migrated in. This area is called the dry zone.

[0037] The soaking time described in this invention can be set according to research needs, and can be used to study the influence of the distribution of internal water in rocks on the mechanical behavior of rocks under different soaking time conditions.

[0038] The following are embodiments of the present invention:

[0039] Example 1: A grayish-white limestone sample was completely immersed in water for 3 hours. A splitting test was used to observe the water distribution on the longitudinal section ABCD inside the sample (e.g., Figure 2 As shown in the figure, the method includes the following specific operation steps:

[0040] 1. Measure the dimensions of the rock sample using vernier calipers, then place the rock sample in a drying oven at 105℃ for 48 hours. Measure the mass (m) of the dried rock sample using an electronic balance. 干 ;

[0041] 2. Place the dried rock sample in a constant temperature and humidity chamber and cool it to room temperature;

[0042] 3. A small red molecule pigment was selected and mixed with water as the staining agent for soaking the limestone sample. Since the original color of the rock sample was relatively light, a lower concentration of staining agent was chosen to obtain better observation results; therefore, the dye mass fraction in the staining agent was set at 10%.

[0043] 4. Immerse the limestone sample in red dye, ensuring the dye level is higher than the sample height. After 3 hours, remove the sample to obtain the specimen required for the study. Wipe it dry and measure the mass (m) of the sample after immersion. 湿 Water content of rock samples

[0044] 5. Coat the surface of the limestone sample with paraffin wax to form a paraffin wax film on the sample surface;

[0045] 6. Place the limestone sample in the splitting test apparatus shown in Figure 1(a). According to the sample surface to be observed, place two vertical steel pressure bars on the upper and lower sides of surface ABCD, and then carry out the splitting test. The limestone sample will split along surface ABCD.

[0046] 7. After the splitting test, it can be observed that the surface area of ​​the sample turns dark red, which is the wet zone 4, completely soaked in water. From the wet zone towards the core of the rock sample, the red color of the rock sample gradually fades, from dark red to light red, until it completely turns back to the original grayish-white of the rock, indicating that the water molecule concentration is constantly decreasing. This area is the transition zone 5, which is evidence of water molecule migration. The core of the rock sample still retains the original grayish-white color of limestone, which is the area where water molecules have not yet entered, and is called the dry zone 6. In addition, it can be observed that the boundaries of the dry zone 6, the transition zone 5, and the wet zone 4 are all rounded rectangles.

[0047] 8. Place the rock sample split into two halves in a well-lit area and take a picture. The actual distribution of moisture inside the rock sample can be observed through the photo.

[0048] Example 2: A red sandstone sample was immersed in water to half its height for 10 hours. A splitting test was used to observe the water distribution in the cross-sections α and β inside the sample (e.g., Figure 3 As shown in the figure, the method includes the following specific operation steps:

[0049] 1. Measure the dimensions of the sandstone sample using vernier calipers, then place the sample in a forced-air drying oven at 105℃ for 48 hours. Measure the mass (m) of the dried rock sample using an electronic balance. 干 ;

[0050] 2. Place the dried rock sample in a constant temperature and humidity chamber and cool it to room temperature;

[0051] 3. A small blue molecule dye was selected and mixed with water as the staining agent for soaking the rock sample. Since the rock itself is quite dark, a dye with a higher viscosity was chosen to obtain better observation results; therefore, the dye mass fraction in the staining agent was set at 20%.

[0052] 4. Immerse the limestone sample in blue dye until the dye reaches half the height of the sample. After 10 hours, remove the sample to obtain the required specimen. Wipe it dry and measure the mass m of the sample after immersion. 湿 Water content of rock samples

[0053] 5. Apply a layer of paraffin wax to the surface of the sandstone sample to form a paraffin wax film on the sample surface;

[0054] 6. Place the limestone sample in the splitting test apparatus. According to the sample surface to be observed, place two curved steel pressure bars on the upper and lower sides of the limestone sample, and then perform the splitting test. The limestone sample will split along surface α. Repeat the above operation to split surface β.

[0055] 7. After the splitting test, it can be observed that the surface β below the soaking line is dark blue, indicating that this plane is a wet zone 4 completely soaked in water. From the wet zone 4 towards the core of the rock sample, the red color of the rock sample gradually fades, changing from dark red to light red, and eventually completely turning back to the original grayish-white of the rock. This indicates that the water molecule concentration is continuously decreasing, and this area is a transition zone 5, which is evidence of water molecule migration. The surface α above the soaking line is the original red color of sandstone, indicating that this longitudinal section is a dry zone 6 where water molecules have not yet entered.

[0056] 8. Place the rock sample split into two halves in a well-lit area and take a picture. The actual distribution of moisture inside the rock sample can be observed through the photo.

[0057] The above description is only a preferred embodiment of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of this patent application are included in the scope of this patent application.

Claims

1. A method for observing the internal moisture distribution of a rock sample using a splitting test, characterized in that, The method includes the following steps: (1) The rock sample is dried to remove the original moisture in the rock sample, and then the mass m of the dried rock sample is measured using an electronic balance. 干 ; (2) Place the dried rock sample in a constant temperature and humidity chamber and cool it to room temperature; (3) Select a small molecule dye that contrasts sharply with the natural color of the rock, mix it with water to dissolve it and obtain a dyeing agent that contrasts sharply with the natural color of the rock. The mass concentration of the dye in the dyeing agent is 5%-25%. (4) Place the rock sample cooled to room temperature into the staining agent of step (3) to obtain the sample required for the experiment to study the effect of internal water distribution on rock mechanical behavior under different soaking time conditions. Then take it out, wipe it dry, and measure the mass m of the sample after soaking. 湿 Water content of rock samples ; (5) Apply paraffin wax to the sample surface to form a paraffin film on the sample surface to prevent the sample moisture from dissipating into the air, and at the same time inhibit the migration of water molecules inside the rock sample from high concentration area to low concentration area. (6) Place the rock sample in the splitting test device, design the splitting surface of the rock sample as the sample surface that needs to be observed in the study, start the splitting test device to split and cut the splitting surface to obtain the splitting surface of the rock sample, and design the splitting surface in two ways: one is designed along the axial direction of the rock core, and the other is designed along the radial direction of the rock core. (7) After the splitting test, place the rock sample split into two halves in a bright place and take pictures of its split surface. By observing the pictures, the true distribution of water inside the rock sample can be obtained. The influence of water inside the rock on the mechanical behavior of the rock can be studied by using the rock water content data and the water distribution data inside the rock. The color of the rock sample after soaking is used to observe the water distribution inside the rock sample. The specific operation is as follows: the inside of the rock is divided into a wet zone, a transition zone and a dry zone. The wet zone is the same color as the soaking liquid. Near the boundary of the wet zone, the color of the soaking liquid becomes lighter and lighter as it moves away from the wet zone until it becomes the original color of the rock. This indicates that the concentration of water molecules is constantly decreasing. This area is the transition zone, which is proof of water molecule migration. The area that retains the original color of the rock indicates that water molecules have not yet migrated in. This area is called the dry zone.

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