Rock mineral scale thermal damage quantitative evaluation method and system

Abstract

The invention discloses a rock mineral scale thermal damage quantitative evaluation method and system, and relates to the field of high-temperature geotechnical engineering, and the method comprises the steps: obtaining a rock sample surface image, segmenting the rock sample surface through a classification and regression algorithm, and determining the contour image of each mineral component of rock; establishing a rock numerical model based on a parallel bonding model PBM and a smooth joint model SJM, and determining the total bonding number among particles; the rock numerical model is heated and cooled, a rock hot crack distribution image after heating-cooling is obtained, and the number of microcracks in the rock sample is determined; obtaining a new contour of each mineral after heating-cooling according to the rock hot crack distribution image, and determining the internal crack area of each mineral and the internal crack area of the whole rock sample; according to the total bonding number among the particles, the number of microcracks in the rock sample, the crack area in each mineral and the crack area in the whole rock sample, the damage degree of the whole rock sample and the damage degree of each mineral are accurately evaluated.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature geotechnical engineering, and in particular to a method and system for quantitatively evaluating thermal damage at a rock mineral scale. Background Art

[0002] In deep underground projects such as mining, transportation, and water conservancy, rock masses are often exposed to high temperatures, which can cause uneven thermal expansion of minerals in the rock mass and produce cracks, which in turn affects the stability of the rock mass project.

[0003] At present, the damage evaluation of temperature-induced rock cracks is often carried out by microscopic observation, and the length, width and area of ​​microcracks are statistically analyzed, and the damage degree is evaluated by comparing with that before high temperature. Limited by the strict experimental conditions of in-situ high-temperature microscopic observation, different rock samples are often heated to the set temperature and then cooled for observation. However, this method is inevitably affected by the discreteness of the sample, and thus cannot accurately reflect the damage caused by temperature. Numerical simulation has become an effective means to explore rock temperature damage due to its repeatability. The interior of the rock is composed of different minerals, and each type of mineral is affected by temperature to different degrees. Existing studies usually use the random distribution of the mineral crystal model (Grain based model, GBM) to establish a rock numerical model. However, this modeling method does not take into account the real mechanical behavior of the rock, which leads to deviations between the simulation results and the actual situation. It is difficult to accurately reflect the real mineral crystal structure of the rock, such as the exact morphology and distribution characteristics of the mineral crystals in the rock, and thus it is difficult to accurately evaluate the damage degree of various minerals. Summary of the invention

[0004] The present invention provides a method and system for quantitatively evaluating thermal damage at the scale of rock minerals, which is used to solve the above-mentioned problem existing in the prior art, that is, how to accurately evaluate the damage degree of various minerals in the prior art. The present invention provides a method for quantitatively evaluating thermal damage at the scale of rock minerals, which comprises: Obtain the surface image of the rock sample, segment the surface of the rock sample through classification and regression algorithms, and determine the contour image of each mineral component of the rock; According to the obtained contour images of each mineral component of the rock, a numerical model of the rock mesostructure is constructed, and particles are used to fill the inside of the contour of the numerical model of the rock mesostructure; According to the numerical model of the rock mesostructure after particle filling, the parallel bond model PBM and the smooth joint model SJM are selected to simulate the interaction within and between minerals respectively to construct a rock numerical model. According to the constructed rock numerical model, the microscopic mechanical parameters and thermodynamic parameters are assigned to the particles filled in the mineral contour and the contact between the particles to determine the total bonding amount between the particles; The constructed rock numerical model is heated and cooled to obtain the rock thermal crack distribution image after heating-cooling, and the number of microcracks in the rock sample is determined; the damage degree of the entire rock sample is obtained based on the ratio of the number of microcracks in the rock sample to the total number of bonds between particles; According to the rock thermal crack distribution image, the new contours of each mineral after heating-cooling are determined, and the crack area in each mineral and the crack area in the entire rock sample are obtained; according to the damage degree of the entire rock sample, the damage degree of each mineral is obtained by combining the ratio of the crack area in each mineral and the crack area in the entire rock sample.

[0005] Optionally, the constructed rock numerical model is heated and cooled, and a rock thermal crack distribution image after heating-cooling is obtained to determine the number of microcracks in the rock sample, specifically including: Selecting particles with a preset width from the outer boundary of the rock numerical model as thermal boundaries, determining the area to be tested, and using thermal pointers to obtain the temperature of the area to be tested; By iteratively adjusting the temperature of the thermal boundary, when the preset temperature rise threshold is reached, the temperature is kept constant, and iterative mechanical calculations are performed to control the uniform distribution of the temperature field until no new thermal cracks are generated. The cooling process is simulated by adjusting the temperature drop amplitude of the thermal pointer.

[0006] Optionally, obtaining the damage degree of the entire rock sample according to the ratio of the number of microcracks in the rock sample to the total number of bonds between particles specifically includes: The damage degree of the entire rock sample is obtained using the following formula: ; in, N 1 is the number of microcracks in the rock sample, N is the total amount of bonding between particles in the rock sample before heating-cooling treatment.

[0007] Optionally, the damage degree of each mineral is obtained according to the damage degree of the entire rock sample, in combination with the ratio of the crack area in each mineral to the crack area in the entire rock sample, specifically including: The damage degree of each mineral is obtained using the following formula: ; in, A 0 is the crack area within a mineral grain, A 1 is the total area of ​​microcracks in the rock sample, N 1 is the number of microcracks in the rock sample, N is the total amount of bonding between particles in the rock sample before heating-cooling treatment.

[0008] Optionally, after obtaining the contour images of each mineral component of the rock, an RGB image of the entire rock sample is generated, and the RGB image of the entire rock sample is converted into a grayscale image, and then the contours of each mineral component of the rock are filled with color.

[0009] Optionally, the micromechanical parameters include the effective stiffness of the linear contact part, the normal-to-tangential stiffness ratio, the particle friction coefficient, the effective stiffness of the parallel bonding part, the tensile strength and the cohesion; the thermodynamic parameters include the linear expansion coefficient, the specific heat capacity, the thermal conductivity and the thermal resistance.

[0010] Optionally, after obtaining the entire rock sample and the degree of damage of each mineral, annotations are made in the contour image of each mineral component of the rock.

[0011] The present invention provides a rock mineral scale thermal damage quantitative evaluation system, comprising: The acquisition module is used to acquire the surface image of the rock sample, segment the surface of the rock sample through classification and regression algorithms, and determine the contour image of each mineral component of the rock; A rock mesostructure numerical model construction module is used to construct a rock mesostructure numerical model based on the acquired contour images of each mineral component of the rock, and to fill the contour of the rock mesostructure numerical model with particles; The rock numerical model module is used to construct a rock numerical model by simulating the interaction between minerals and minerals by selecting the parallel bond model PBM and the smooth joint model SJM according to the numerical model of the rock mesostructure after particle filling; The total bonding number determination module is used to assign microscopic mechanical parameters and thermodynamic parameters to the particles filled in the mineral contour and the contact between the particles according to the constructed rock numerical model, and determine the total bonding number between the particles; The whole rock sample damage degree determination module is used to heat and cool the constructed rock numerical model, obtain the rock thermal crack distribution image after heating-cooling, and determine the number of microcracks in the rock sample; according to the ratio of the number of microcracks in the rock sample to the total bonding number between particles, the damage degree of the whole rock sample is obtained; The module for determining the damage degree of each mineral is used to determine the new contours of each mineral after heating-cooling according to the rock thermal crack distribution image, and obtain the crack area in each mineral and the crack area in the entire rock sample; according to the damage degree of the entire rock sample, combined with the ratio of the crack area in each mineral and the crack area in the entire rock sample, the damage degree of each mineral is obtained.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention provides a method for quantitatively evaluating thermal damage at the scale of rock minerals. The method segments the acquired rock sample surface image through classification and regression algorithms, and can accurately obtain the contours of each mineral component of the rock; then, according to the contour images of each mineral component of the rock, a numerical model of the rock mesostructure is constructed, and particles are used to fill the interior of the contour of the numerical model of the rock mesostructure, and a preliminary model construction result can be obtained; according to the filled numerical model of the rock mesostructure, by selecting the parallel bond model PBM and the smooth joint model SJM to simulate the interaction between the interior of the mineral and between the minerals respectively, the real mineral crystal structure of the rock can be accurately reflected, and then the The method can reflect the real mineral crystal structure of the rock, such as the shape, size, distribution of the grains and the interaction between the grains; at the same time, by applying different temperatures to the rock numerical model, it is possible to evaluate the influence of high temperature at the same mineral position, thus avoiding the influence of the discreteness of the real rock; at the same time, the present invention obtains the damage degree of the entire rock sample according to the ratio of the number of microcracks in the rock sample to the total number of bonds between the particles, and then obtains the damage degree of each mineral through the damage degree of the entire rock sample and the extraction of thermal cracks inside each mineral. It can accurately evaluate the difficulty of crack initiation and damage of various minerals under high temperature, realize the quantitative evaluation of thermal damage at the rock mineral scale, and improve the accuracy of damage degree evaluation of various minerals. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0014] Figure 1 A flow chart of a method for quantitatively evaluating thermal damage at the rock mineral scale provided by an embodiment of the present invention; Figure 2 A schematic diagram of rock and mineral contour extraction and numerical model construction provided by an embodiment of the present invention; Figure 3 The rock thermal crack distribution diagram after being acted on at different temperatures provided by the embodiment of the present invention; Figure 4 A schematic diagram of extracting mineral contours of rocks containing thermal cracks after being acted on at different temperatures provided by an embodiment of the present invention; Figure 5 A distribution diagram of the degree of damage of rock minerals after being acted on at different temperatures provided by an embodiment of the present invention; Figure 6 This is a graph showing the changing trend of the degree of damage to the rock as a whole and various minerals as the temperature increases, provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] The technical solution of the present invention and how the technical solution of the present invention solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present invention will be described below in conjunction with the accompanying drawings.

[0017] Figure 1 : is a flow chart of a method for quantitatively evaluating thermal damage at rock mineral scale provided by an embodiment of the present invention. Figure 1 As shown, this embodiment shows a method for quantitatively evaluating thermal damage at the rock mineral scale, including: S1: Obtain the surface image of the rock sample, segment the surface of the rock sample through classification and regression algorithms, and determine the contour image of each mineral component of the rock.

[0018] For example, the rock sample surface photo is cropped to cut off the non-rock sample part to facilitate the subsequent extraction of rock mineral contours. Figure 2 As shown in (a); In this embodiment, potassium feldspar is taken as an example. After the potassium feldspar mineral in the cropped picture is selected and circled, the outline of the potassium feldspar mineral is extracted, and an RGB image of the outline is generated. By converting the RGB image into an 8-bit grayscale image, the outline of the potassium feldspar is filled with color, thereby avoiding the influence of the potassium feldspar mineral boundary on the extraction of the remaining minerals. Finally, the outline of the potassium feldspar is extracted and filled with color, as shown in FIG. Figure 2 as shown in (b).

[0019] Repeat the above operations to complete the extraction and color filling of the mineral outlines of plagioclase, quartz and mica in turn, and obtain the outlines of all minerals in the rock sample, such as Figure 2 As shown in (c), the rock mineral outline RGB image is vectorized and saved as a DXF file.

[0020] S2: Based on the acquired contour images of each mineral component of the rock, a numerical model of the rock mesostructure is constructed, and particles are used to fill the interior of the contour of the numerical model of the rock mesostructure.

[0021] Exemplarily, the mineral components in step S1 can be grouped. Taking potassium feldspar as an example, according to the DXF file of the potassium feldspar mineral outline, small particles are used to fill the outline and complete the grouping; repeat the above operation to complete the outline particle filling and grouping of plagioclase, quartz and mica minerals in turn.

[0022] S3: Based on the numerical model of the rock mesostructure after particle filling, the parallel bond model PBM and the smooth joint model SJM are selected to simulate the interactions within and between minerals respectively to construct a rock numerical model.

[0023] For example, the parallel bond model (PBM) is used inside the minerals, and the smooth joint model (SJM) is used between the minerals to complete the modeling, such as Figure 2 as shown in (d).

[0024] S4: Based on the constructed rock numerical model, the microscopic mechanical parameters and thermodynamic parameters are assigned to the particles filled in the mineral contour and the contact between the particles to determine the total amount of bonding between the particles.

[0025] Exemplarily, mesoscopic mechanical parameters and thermodynamic parameters can be assigned to the particles filled in the mineral contour and the contacts between the particles; the mesoscopic mechanical parameters may include, for example, the effective stiffness of the linear contact part, the normal-tangential stiffness ratio, the particle friction coefficient, the effective stiffness of the parallel bonding part, the tensile strength and the cohesion, etc.; the thermodynamic parameters may include, for example, the linear expansion coefficient, the specific heat capacity, the thermal conductivity and the thermal resistance, etc.; then, the total number of bonds between the particles before the heating-cooling treatment is obtained; in this embodiment, the total number of bonds is 20,576.

[0026] S5: Heat and cool the constructed rock numerical model to obtain the rock thermal crack distribution image after heating-cooling, and determine the number of microcracks in the rock sample; obtain the damage degree of the entire rock sample based on the ratio of the number of microcracks in the rock sample to the total number of bonds between particles.

[0027] Exemplarily, by selecting particles with a preset width from the outer boundary of the rock numerical model as the thermal boundary, for example, particles 1 mm away from the outer boundary can be selected as the thermal boundary, and the temperature of these areas can be monitored using a thermal pointer. By iteratively adjusting the temperature of the thermal boundary, heat conduction from the outside to the inside is achieved. Once the predetermined temperature rise threshold is reached, the temperature will be kept constant, and iterative mechanical calculations will be performed to control the uniform distribution of the temperature field until no new thermal cracks are generated. Adjust the cooling amplitude of the thermal pointer, set the internal high-temperature particles as the heat source for heat transfer, and then perform mechanical equilibrium calculations to simulate the cooling process.

[0028] The internal thermal crack distribution of the numerical specimens after being heated to 200℃, 400℃, 600℃ and 800℃ and cooled to room temperature is shown in Figure 2. Figure 3 shown.

[0029] After high temperature cooling, the number of thermal cracks in the rock sample is read. In this embodiment, the number of thermal cracks after high temperature cooling at 200°C, 400°C, 600°C and 800°C is 8, 96, 719 and 2805 respectively.

[0030] Optionally, the damage degree of the entire rock sample is obtained using the following formula: ; in, N 1 is the number of microcracks in the rock sample, N is the total amount of bonding between particles in the rock sample before heating-cooling treatment.

[0031] S6: According to the rock thermal crack distribution image, determine the new contour of each mineral after heating-cooling, and obtain the crack area in each mineral and the crack area in the entire rock sample; according to the damage degree of the entire rock sample, combined with the ratio of the crack area in each mineral and the crack area in the entire rock sample, obtain the damage degree of each mineral.

[0032] For example, since each mineral undergoes expansion or compression deformation under the action of the high temperature-cooling cycle, it is necessary to re-extract the mineral contour after high temperature-cooling to obtain the new contour of each mineral after deformation. Based on the crack distribution image after high temperature, combined with step S2, the new contour of each mineral after heating-cooling treatment can be obtained. The mineral contour extraction results in the rock sample after high temperature-cooling at 200℃, 400℃, 600℃ and 800℃ are as follows: Figure 4 Then the micro-crack area inside each mineral is obtained.

[0033] Optionally, according to the damage degree of the entire rock sample, combined with the ratio of the crack area in each mineral and the crack area in the entire rock sample, the damage degree of each mineral is obtained using the following formula: ; in, A 0 is the crack area within a mineral grain, A 1 is the total area of ​​microcracks in the rock sample, N 1 is the number of microcracks in the rock sample, N is the total amount of bonding between particles in the rock sample before heating-cooling treatment.

[0034] For example, the damage degree of each mineral in the rock sample after high temperature cooling at 200°C, 400°C, 600°C and 800°C is as follows: Figure 5 As shown in the figure, the damage degree of the rock sample as a whole and various minerals after high temperature cooling changes with the increase of temperature, such as Figure 6shown.

[0035] The above is a method for quantitatively evaluating thermal damage at the scale of rock minerals provided by one or more embodiments of this specification. Based on the same idea, this specification also provides a corresponding system for quantitatively evaluating thermal damage at the scale of rock minerals, including: The acquisition module is used to acquire the surface image of the rock sample, segment the surface of the rock sample through classification and regression algorithms, and determine the contour image of each mineral component of the rock; A rock mesostructure numerical model construction module is used to construct a rock mesostructure numerical model based on the acquired contour images of each mineral component of the rock, and to fill the contour of the rock mesostructure numerical model with particles; The rock numerical model module is used to construct a rock numerical model by simulating the interaction between minerals and minerals by selecting the parallel bond model PBM and the smooth joint model SJM according to the numerical model of the rock mesostructure after particle filling; The total bonding number determination module is used to assign microscopic mechanical parameters and thermodynamic parameters to the particles filled in the mineral contour and the contact between the particles according to the constructed rock numerical model, and determine the total bonding number between the particles; The whole rock sample damage degree determination module is used to heat and cool the constructed rock numerical model, obtain the rock thermal crack distribution image after heating-cooling, and determine the number of microcracks in the rock sample; according to the ratio of the number of microcracks in the rock sample to the total bonding number between particles, the damage degree of the whole rock sample is obtained; The module for determining the damage degree of each mineral is used to determine the new contours of each mineral after heating-cooling according to the rock thermal crack distribution image, and obtain the crack area in each mineral and the crack area in the entire rock sample; according to the damage degree of the entire rock sample, combined with the ratio of the crack area in each mineral and the crack area in the entire rock sample, the damage degree of each mineral is obtained.

[0036] For the specific definition of the rock mineral scale thermal damage quantitative evaluation system, please refer to the definition of the rock mineral scale thermal damage quantitative evaluation method above, which will not be repeated here. Each module in the above-mentioned rock mineral scale thermal damage quantitative evaluation system can be implemented in whole or in part by software, hardware and their combination. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0037] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of the present invention.

Claims

1. A method for quantitative evaluation of thermal damage at rock mineral scale, characterized in that: include: Obtain the surface image of the rock sample, segment the surface of the rock sample through classification and regression algorithms, and determine the contour image of each mineral component of the rock; According to the obtained contour images of each mineral component of the rock, a numerical model of the rock mesostructure is constructed, and particles are used to fill the inside of the contour of the numerical model of the rock mesostructure; According to the numerical model of the rock mesostructure after particle filling, the parallel bond model PBM and the smooth joint model SJM are selected to simulate the interaction within and between minerals respectively to construct a rock numerical model. According to the constructed rock numerical model, the microscopic mechanical parameters and thermodynamic parameters are assigned to the particles filled in the mineral contour and the contact between the particles to determine the total bonding amount between the particles; The constructed rock numerical model is heated and cooled to obtain the rock thermal crack distribution image after heating-cooling, and the number of microcracks in the rock sample is determined; the damage degree of the entire rock sample is obtained based on the ratio of the number of microcracks in the rock sample to the total number of bonds between particles; According to the rock thermal crack distribution image, the new contours of each mineral after heating-cooling are determined, and the crack area in each mineral and the crack area in the entire rock sample are obtained; according to the damage degree of the entire rock sample, the damage degree of each mineral is obtained by combining the ratio of the crack area in each mineral and the crack area in the entire rock sample.

2. The method for quantitatively evaluating thermal damage at the rock mineral scale according to claim 1, characterized in that: The step of heating and cooling the constructed rock numerical model, obtaining a rock thermal crack distribution image after heating-cooling, and determining the number of microcracks in the rock sample specifically includes: Selecting particles with a preset width from the outer boundary of the rock numerical model as thermal boundaries, determining the area to be tested, and using thermal pointers to obtain the temperature of the area to be tested; By iteratively adjusting the temperature of the thermal boundary, when the preset temperature rise threshold is reached, the temperature is kept constant, and iterative mechanical calculations are performed to control the uniform distribution of the temperature field until no new thermal cracks are generated. The cooling process is simulated by adjusting the temperature drop amplitude of the thermal pointer.

3. The method for quantitatively evaluating thermal damage at rock mineral scale according to claim 1, characterized in that: The damage degree of the entire rock sample is obtained according to the ratio of the number of microcracks in the rock sample to the total number of bonds between particles, specifically including: The damage degree of the entire rock sample is obtained using the following formula: ； in, N 1 is the number of microcracks in the rock sample, N is the total amount of bonding between particles in the rock sample before heating-cooling treatment.

4. The method for quantitatively evaluating thermal damage at rock mineral scale according to claim 3, characterized in that: The damage degree of each mineral is obtained according to the damage degree of the entire rock sample, combined with the ratio of the crack area in each mineral and the crack area in the entire rock sample, specifically including: The damage degree of each mineral is obtained using the following formula: ； in, A 0 is the crack area within a mineral grain, A 1 is the total area of ​​microcracks in the rock sample, N 1 is the number of microcracks in the rock sample, N is the total amount of bonding between particles in the rock sample before heating-cooling treatment.

5. The method for quantitatively evaluating thermal damage at rock mineral scale according to claim 1, characterized in that: After obtaining the contour images of each mineral component of the rock, an RGB image of the entire rock sample is generated, and the RGB image of the entire rock sample is converted into a grayscale image, and then the contours of each mineral component of the rock are filled with colors.

6. The method for quantitatively evaluating thermal damage at rock mineral scale according to claim 1, characterized in that: The microscopic mechanical parameters include the effective stiffness of the linear contact part, the normal-to-tangential stiffness ratio, the particle friction coefficient, the effective stiffness of the parallel bonding part, the tensile strength and the cohesion; the thermodynamic parameters include the linear expansion coefficient, the specific heat capacity, the thermal conductivity and the thermal resistance.

7. The method for quantitatively evaluating thermal damage at rock mineral scale according to claim 1, characterized in that: After obtaining the damage degree of the entire rock sample and each mineral, marking is performed in the contour image of each mineral component of the rock.

8. A rock mineral scale thermal damage quantitative evaluation system, characterized in that: include: The acquisition module is used to acquire the surface image of the rock sample, segment the surface of the rock sample through classification and regression algorithms, and determine the contour image of each mineral component of the rock; A rock mesostructure numerical model construction module is used to construct a rock mesostructure numerical model based on the acquired contour images of each mineral component of the rock, and to fill the contour of the rock mesostructure numerical model with particles; The rock numerical model module is used to construct a rock numerical model by simulating the interaction between minerals and minerals by selecting the parallel bond model PBM and the smooth joint model SJM according to the numerical model of the rock mesostructure after particle filling; The total bonding number determination module is used to assign microscopic mechanical parameters and thermodynamic parameters to the particles filled in the mineral contour and the contact between the particles according to the constructed rock numerical model, and determine the total bonding number between the particles; The whole rock sample damage degree determination module is used to heat and cool the constructed rock numerical model, obtain the rock thermal crack distribution image after heating-cooling, and determine the number of microcracks in the rock sample; according to the ratio of the number of microcracks in the rock sample to the total bonding number between particles, the damage degree of the whole rock sample is obtained; The module for determining the damage degree of each mineral is used to determine the new contours of each mineral after heating-cooling according to the rock thermal crack distribution image, and obtain the crack area in each mineral and the crack area in the entire rock sample; according to the damage degree of the entire rock sample, combined with the ratio of the crack area in each mineral and the crack area in the entire rock sample, the damage degree of each mineral is obtained.

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