Analysis method for the crack propagation process of rock and concrete considering seepage corrosion

Abstract

The present invention relates to the technical field of rock mass engineering, and discloses an analysis method for the crack propagation process of rocks and concrete considering seepage corrosion. The method includes: generating m×n grid points, and assigning specified labels to different grid points to respectively represent soluble substances, insoluble substances, pores, water, etc.; simulating the flow of water in cracks and the diffusion of solutes; by analyzing whether there is liquid in the front, rear, left, and right directions of the solid during the calculation, it can be determined whether the solid particles will exfoliate and migrate; calculating the water flow impact force borne by the movable solid particles based on the Bernoulli equation, and calculating the moving rate of the solid particles based on Newton's second law. The method proposed by the present invention can more efficiently and accurately carry out the crack propagation of brittle materials such as rocks and concrete under the action of seepage, and can provide guidance for the analysis of sudden water inrush during tunnel excavation, the evolution process of seepage water during operation, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of rock mass engineering, and particularly relates to a method for analyzing the crack propagation process of rocks and concrete considering seepage corrosion. Background Technique

[0002] Affected by complex geological conditions, underground projects such as tunnels are likely to encounter great challenges due to groundwater during construction and service periods, such as sudden water inrush during construction and water leakage during service. The occurrence of problems such as sudden water inrush and water leakage is related to the existence of groundwater around the tunnel, and also related to seepage channels such as cracks in the tunnel surrounding rock and tunnel lining concrete. When groundwater seeps in the cracks of the surrounding rock and lining concrete, some soluble substances in the surrounding rock and concrete (such as soil in the surrounding rock and calcium hydroxide in the concrete) will dissolve in water and gradually migrate out of the cracks with the flow of water. It should be noted that materials such as surrounding rock and concrete are usually composed of a variety of components, including some substances that are insoluble in water. After all the water-soluble substances in the vicinity are dissolved, these water-insoluble substances will be in a movable state, and then will move due to the impact of water flow and gradually migrate out of the cracks. It can be seen that factors such as the dissolution of soluble substances and the migration of movable solids may lead to a gradual increase in the crack width of the surrounding rock and concrete, and further deteriorate the situations such as sudden water inrush during tunnel construction and water leakage during tunnel service.

[0003] Although daily inspections can provide guidance for formulating the timing of relevant prevention and control measures for sudden water inrush during tunnel construction and water leakage during tunnel service. However, it should also be noted that daily inspections usually require a large amount of manpower and material resources, and the construction timing of relevant treatment measures is mostly determined by experience, and there will inevitably be situations where the construction timing is too early or too late. Taking treatment measures too early may face phenomena such as increased costs and material waste, and taking treatment measures too late will seriously affect the construction and operation safety of the tunnel. If a theoretical analysis method can be used to predict and analyze the crack propagation process of tunnel surrounding rock, lining, etc., the treatment decision-making level of risk prevention and control measures during tunnel construction and operation can be significantly improved, and thus the construction and operation costs can be reduced.

[0004] At present, certain progress has been made in the analysis of the evolution process of seepage channels in tunnel surrounding rock and lining concrete. For example, in Document 1 (Shen Linfang, Lv Qianwen, Liu Wenlian, Zhang Jiaming, Yang Hongzhong, Li Ze. Numerical calculation study on the seepage characteristics of three-dimensional rock fractures under the coupling action of stress-seepage-corrosion [J / OL]. Chinese Journal of Geotechnical Engineering. https: / / link.cnki.net / urlid / 32.1124.TU.20240318.1005.005), a numerical calculation model for the coupling mechanism of stress-seepage-corrosion in three-dimensional rock fractures was established, and the influence of factors such as seepage velocity, normal stress, and corrosion reaction rate on the evolution law of fracture seepage characteristics was discussed; in Document 2 (Wang Zhiliang, Zhang Yue, Shen Linfang, et al. A coupled seepage-corrosion model for fractures in the interfacial transition zone of concrete considering the influence of microstructure [J]. Engineering Mechanics, 2021, 38(6): 133-142.), a coupled seepage-corrosion model for fractures in the interfacial transition zone of concrete considering the influence of microstructure was established. However, it should be noted that currently these models cannot consider the influence of factors such as the migration of movable solids, which leads to a large difference between the analysis results and the actual situation and is not conducive to the safety analysis of tunnel construction and operation. Summary of the Invention

[0005] The purpose of the present invention is to provide an analysis method for the fracture propagation process of rock and concrete considering seepage corrosion to solve the technical problems mentioned in the background art.

[0006] To achieve the above purpose, the following technical solutions are adopted:

[0007] An analysis method for the fracture propagation process of rock and concrete considering seepage corrosion, the method includes:

[0008] Generate m×n grid nodes in the X and Y directions and assign specified labels to each grid node to represent soluble substances, insoluble substances, pores, and water;

[0009] Simulate the flow of water in the fracture and the diffusion of solutes;

[0010] Specify the water flow direction, set calculation parameters, and carry out the analysis of the fracture propagation process of rock and concrete.

[0011] Furthermore, generate m×n grid points in the X and Y directions by the following method:

[0012] Determine the number of material growth directions and number them, set the number of grid cells in the length and width directions of the model as m and n respectively, divide the model into a fracture zone and a solid phase zone, and set the number of grid cells, growth probability pg, and percentage of soluble substances psol in the length and width directions of the solid phase zone;

[0013] Generate random numbers corresponding to the number of lattice nodes in the solid phase region, and use the lattice node where the random number not exceeding the growth probability pg is located as the initial soluble solid node;

[0014] Taking the initial soluble solid node as the center, generate 8 random numbers corresponding to 8 different growth directions respectively. If the random number is greater than the set value, it is determined that growth occurs in the corresponding direction, otherwise there is no growth. Repeat this process until the number of soluble solid nodes reaches the set value.

[0015] Furthermore, during the process of analyzing the crack propagation process of rocks and concrete, by analyzing whether there is liquid in the front, back, left, and right directions of solid particles, determine whether the solid particles are peeled off and migrate:

[0016] If the current solid particle is not at the inlet and outlet positions and there is liquid in all four directions, it is determined that the current solid particle has been peeled off and migrates out of the crack with the flow of groundwater;

[0017] If the current solid particle is not at the inlet and outlet positions and there is no liquid in at least one of the four directions, it is determined that the current solid particle does not migrate;

[0018] If the current solid particle is at the inlet and outlet positions and there is liquid in all three directions, it is determined that the current solid particle has been peeled off.

[0019] Furthermore, during the process of analyzing the crack propagation process of rocks and concrete, if there is liquid in any one of the front, back, left, and right directions of the hole, it is determined that the hole is filled with solution.

[0020] Furthermore, during the process of analyzing the crack propagation process of rocks and concrete, calculate the pressure borne by the boundary points of the solid particle in the water-facing direction through the following formula:

[0021]

[0022] In the formula: f i is the water flow impact force borne by the i-th node on the water-facing side of the solid particle; ρ is the density of water; v is the fluid velocity of the fluid adjacent to the i-th node on the water-facing side of the solid particle;

[0023] Superimpose the impact forces borne by each point on the water-facing side to obtain the total force borne by the solid particle;

[0024] Based on Newton's second law, obtain the moving rate of the solid particle in the crack.

[0025] Furthermore, during the process of analyzing the crack propagation process of rocks and concrete, according to the size l of the movable solid s and the width of the seepage channel, determine whether the movable solid can pass through the seepage channel, where the size l of the movable solids The calculation formula is as follows:

[0026]

[0027] Where: x and y are the maximum dimensions of the movable solid in the X and Y directions respectively.

[0028] Furthermore, in the process of analyzing the crack propagation process of rock and concrete, Ca 2+ and OH - diffusion follows steady-state diffusion, and the calculation formula is as follows:

[0029]

[0030] Where: J is the diffusion flux; D diffuse is the diffusion coefficient; is the concentration gradient along the x-axis direction, and the negative sign is used to ensure that the diffusion direction is consistent with the concentration reduction direction.

[0031] Furthermore, in the process of analyzing the crack propagation process of rock and concrete, based on the Ca(OH) 2 dissolution rate function to characterize the dissolution of Ca 2+ and OH - , the expression form of the Ca(OH) 2 dissolution rate function is:

[0032]

[0033] Where: v dissolve is the dissolution rate function; k dissolve is the dissolution rate; K eq is the chemical equilibrium constant; C(Ca 2+ ) is the concentration of Ca 2+ in the solution; C(OH - ) is the concentration of OH - in the solution.

[0034] Furthermore, in the process of analyzing the crack propagation process of rock and concrete, the volume of the lattice node gradually decreases with the dissolution of Ca(OH) 2 , and the calculation formula for the volume evolution of the lattice node is:

[0035]

[0036] Where: V w is the dimensionless volume corresponding to the substance concentration at the solid-liquid interface; A 0 is the reaction surface area; M is the molar volume of Ca(OH) 2 ; t is the time.

[0037] Further, in the process of analyzing the crack propagation process of rocks and concrete, when Ca in the crack solution 2+ and OH - all come from the dissolution of Ca(OH) 2 , and the dissolution rate and diffusion rate are the same at the solid-liquid interface, the dissolution process of Ca(OH) 2 is expressed as:

[0038]

[0039] In the formula: C w is the product of the ion concentrations of Ca 2+ and OH - at the solid-liquid interface, C w = C(Ca 2+ )·C(OH - ) 2 ; n is the normal direction pointing from the solid phase to the liquid phase; α is the reaction order.

[0040] Further, the transport of Ca(OH) 2 in concrete cracks is controlled by convection and diffusion, and the calculation formula is as follows:

[0041]

[0042] In the formula: C is the solute concentration; D diffuse is the solute diffusion coefficient; u is the velocity vector; is the gradient operator.

[0043] Further, the semi-bounce-back format is used to calculate the fluid node distribution function at the model boundary near the solid or along the fluid direction, and the non-equilibrium extrapolation format is used to calculate the fluid node distribution function at the inlet and outlet positions.

[0044] The beneficial effects of the present invention are:

[0045] The method proposed by the present invention can more efficiently and accurately carry out the propagation of cracks in brittle materials such as rocks and concrete under seepage action, and can provide guidance for the analysis of sudden water inrush during tunnel excavation, the evolution process of seepage water during operation, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Shows the characteristics and analysis flow chart of a method for analyzing the crack propagation process of rocks and concrete considering seepage corrosion according to an embodiment of the present invention.

[0047] Figure 2 Shows a schematic diagram of the lattice Boltzmann D2Q9 model according to an embodiment of the present invention.

[0048] Figure 3Shows a flowchart for generating the solid-phase region of rock or concrete fractures according to an embodiment of the present invention.

[0049] Figure 4 Shows a schematic diagram of exfoliable fine aggregates in the internal region according to an embodiment of the present invention.

[0050] Figure 5 Shows a schematic diagram of exfoliable fine aggregates at the inlet (or outlet) according to an embodiment of the present invention.

[0051] Figure 6 Shows a diagram of the initial state of fractures according to an embodiment of the present invention.

[0052] Figure 7 Shows a diagram of the state of fractures at the nth calculation step according to an embodiment of the present invention.

[0053] Figure 8 Shows a diagram of the state of fractures at the (n + m)th calculation step according to an embodiment of the present invention. Detailed implementation manners

[0054] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0055] The following combines the drawings and embodiments to further describe in detail the specific implementation manners of the present invention.

[0056] An embodiment of the present invention provides an analysis method for the fracture propagation process of rock and concrete considering seepage corrosion, as Figure 1 shown. This method includes the following steps:

[0057] 1) Use a random growth algorithm to generate m×n lattice points in the X and Y directions, and assign specified labels to different lattice points to respectively represent soluble substances, insoluble substances, pores, water, etc.

[0058] 2) Based on the lattice Boltzmann method, use the D2Q9 and D2Q5 models respectively to simulate the flow of water in fractures and the diffusion of solutes. The D2Q5 model is a simplified form of the D2Q9 model, and the D2Q5 model lacks the four directions from 5 to 8 (taking Figure 2 as an example).

[0059] 3) Specify the flow direction of water, set relevant calculation parameters, and carry out an analysis of the fracture propagation process of rock and concrete.

[0060] Figure 3 Shows the flow chart for generating the solid phase region of rock or concrete fractures according to an embodiment of the present invention. Taking Figure 3 as an example, in the generation of lattice points based on the random growth algorithm:

[0061] First, determine the number of material growth directions and number them. For a two-dimensional model, there are 8 growth directions for material points. The nodes can be numbered according to the naming rule of first line then point and counterclockwise direction, such as Figure 2 . Design the number of grids in the length and width directions of the model as m and n respectively. Divide the model into a fracture zone and a solid phase zone, and set the number of grids, growth probability pg, and percentage of soluble substances psol in the length and width directions of the solid phase zone.

[0062] Secondly, generate random numbers corresponding to the number of lattice nodes in the solid phase zone. The nodes where the random numbers not exceeding the growth probability pg are located are regarded as the initial soluble solid (or hole) nodes, and the number of initial soluble solid (or hole) nodes should not exceed the set value.

[0063] Finally, taking the initial soluble solid (or hole) node as the center, generate 8 random numbers corresponding to 8 different growth directions respectively. If the random number is greater than a certain value, it is considered that growth occurs in the corresponding direction, otherwise it does not grow. Repeat this process until the number of soluble solid (or hole) nodes reaches the set value.

[0064] In an exemplary embodiment, during the process of specifying the water flow direction, setting relevant calculation parameters, and analyzing the rock and concrete fracture propagation process, by analyzing whether there is liquid in the four directions of the front, back, left, and right of the solid, it can be determined whether the solid particles will exfoliate and migrate.

[0065] 1) If there is solution in all four directions, it is considered that the solid particle has exfoliated and will migrate out of the crack with the flow of groundwater, such as Figure 4 , otherwise, it is considered that the solid particles will not migrate.

[0066] 2) For the solid particles at the inlet and outlet positions, there are only three directions that may be in contact with water. If the solid particles at this position are in contact with water in three directions, it is considered that they have exfoliated, such as Figure 5 .

[0067] In an exemplary embodiment, during the process of analyzing the rock and concrete fracture propagation process, if there is liquid in any one of the four directions of the front, back, left, and right of the hole, it is determined that the hole is filled with solution.

[0068] In an exemplary embodiment, during the process of specifying the water flow direction, setting relevant calculation parameters, and analyzing the process of rock and concrete crack propagation, movable solids move due to the force generated by the impact of water flow. Based on Bernoulli's equation, when ignoring the height change in the seepage direction, the calculation method for the pressure borne by the boundary point of the solid particle in the water-facing direction is as follows:

[0069]

[0070] In the formula: f i is the water flow impact force borne by the i-th node on the water-facing side of the solid particle; ρ is the density of water; v is the fluid velocity of the fluid adjacent to the i-th node on the water-facing side of the solid particle.

[0071] By superimposing the impact forces borne by each point on the water-facing side, the total force borne by the solid particle can be obtained, and the calculation method is as follows:

[0072] F = Σf i

[0073] In the formula: F is the total water flow impact force borne by the solid particle.

[0074] The movement rate of the solid particle in the crack can be obtained based on Newton's second law.

[0075] In an exemplary embodiment, during the process of specifying the water flow direction, setting relevant calculation parameters, and analyzing the process of rock and concrete crack propagation, if the size l of the movable solid s is not greater than the width w of the seepage channel, it is considered that the movable solid can pass through the seepage channel, otherwise it cannot. The calculation method for the size of the movable solid is as follows:

[0076]

[0077] In the formula: x and y are the maximum sizes of the movable solid in the X and Y directions respectively.

[0078] In an exemplary embodiment, during the process of specifying the water flow direction, setting relevant calculation parameters, and analyzing the process of rock and concrete crack propagation, the diffusion of Ca 2+ and OH - obeys steady-state diffusion, that is, the mass of the diffusing substance passing through a unit area perpendicular to the diffusion direction per unit time is proportional to the concentration gradient at this cross-section:

[0079]

[0080] In the formula: J is the diffusion flux; D diffuse is the diffusion coefficient; is the concentration gradient along the x-axis direction, and the negative sign is to ensure that the diffusion direction is consistent with the direction of concentration decrease.

[0081] In an exemplary embodiment, during the process of specifying the water flow direction, setting relevant calculation parameters, and analyzing the rock and concrete crack propagation process, Ca(OH) 2 The dissolution rate function can be expressed in the following form:

[0082]

[0083] In the formula: v dissolve is the dissolution rate function; k dissolve is the dissolution rate; K eq is the chemical equilibrium constant; C(Ca 2+ ) is the Ca 2+ concentration in the solution; C(OH - ) is the OH - concentration in the solution.

[0084] It should be noted that most of the Ca 2+ and OH - in the solution come from the dissolution of Ca(OH) 2 . When the remaining part is very small and can be ignored, at this time, the Ca(OH) 2 dissolution rate function can be used to characterize the dissolution of Ca 2+ and OH - . It can be understood that when there are other soluble substances in the solution, the dissolution of these soluble substances in the solvent will produce Ca 2+ and OH - . On the basis of applying the above-described Ca(OH) 2 dissolution rate function to characterize the dissolution of Ca 2+ and OH - , the dissolution rate functions of other soluble substances can be added to characterize the dissolution of Ca 2+ and OH - together.

[0085] This is only an example of the present invention. In other embodiments, some soluble substances in the rock are not necessarily Ca(OH) 2 . For example, if the soluble substance is compound A, the dissolution rate function of A is used to characterize the dissolution of ions in the solution, but the difference is only the replacement of the dissolution rate function, and other analysis methods are the same.

[0086] The dissolution of Ca(OH) 2 causes its volume to gradually decrease. The calculation method of the node volume evolution is as follows:

[0087]

[0088] In the formula: V wis the dimensionless volume corresponding to the substance concentration at the solid-liquid interface; A 0 is the reaction surface area; M is the molar volume of Ca(OH) 2 .

[0089] In an exemplary embodiment, during the process of specifying the water flow direction, setting relevant calculation parameters, and analyzing the rock and concrete crack propagation process, it is assumed that Ca 2+ and OH - in the crack solution all come from the dissolution of Ca(OH) 2 , and the dissolution rate and diffusion rate at the solid-liquid junction are the same. Then the dissolution process of Ca(OH) 2 can be expressed as

[0090]

[0091] where: C w is the ion concentration product of Ca 2+ and OH - at the solid-liquid interface, C w = C(Ca 2+ )·C(OH - ) 2 ; n is the normal direction pointing from the solid phase to the liquid phase; α is the reaction order. For the dissolution of Ca(OH) 2 , α is taken as 1.

[0092] In an exemplary embodiment, during the process of specifying the water flow direction, setting relevant calculation parameters, and analyzing the rock and concrete crack propagation process, the transport of Ca(OH) 2 in the concrete crack is mainly controlled by convection and diffusion, and is specifically described as:

[0093]

[0094] where: C is the solute concentration; D diffuse is the solute diffusion coefficient; u is the velocity vector; ▽ is the gradient operator.

[0095] In an exemplary embodiment, during the process of specifying the water flow direction, setting relevant calculation parameters, and analyzing the rock and concrete crack propagation process, the fluid node distribution function at the boundary of the model near the solid or along the fluid direction is calculated using the semi-bounce-back format, and the fluid node distribution function at the inlet and outlet positions is calculated using the non-equilibrium extrapolation format.

[0096] Next, the embodiments of the present invention will be further described in combination with specific cases to illustrate the feasibility and progressiveness of the present invention.

[0097] Based on the random growth algorithm, a seepage-corrosion model is established as Figure 6In the figure, the upper light-colored area represents the fluid, the lower pale yellow area represents the soluble concrete binder, and the lower dark area represents the insoluble substances such as fine aggregates.

[0098] The number of grids in the length and width directions of the model are 100 and 50 respectively, and the number of grid points are 101 and 51 respectively. Among them, the widths of the initial seepage area and the solid area are 20 and 30 grids respectively. Assuming that the concrete is composed of soluble substances such as Ca(OH) 2 and insoluble substances such as fine aggregates, the number of nodes representing the soluble substances should account for 46.13% of the total number of solid nodes, and Ca(OH) 2 accounts for 20% of the cement hydration products. It can be known that the Ca(OH) 2 content represented by each soluble solid node is 6.0465×10 -4 nmol / (0.01mm) 2 . In the model, other calculation parameters are shown in the following table.

[0099] Table 1 Parameters of the seepage corrosion model

[0100]

[0101] Through calculation, the development state of the concrete crack at the nth calculation step can be obtained as Figure 7 , and the development state at the (n + m)th calculation step is as Figure 8 . It can be seen that this model can calculate the evolution trend of concrete fissures under different analysis steps. By calculating the actual time represented by each analysis step, the prediction of the fissure development state after a certain time of seepage corrosion in the actual situation can be obtained.

[0102] The evolution analysis of rock fissures under seepage-corrosion conditions is similar to that described in this case, but there are differences in the calculation parameters, so it will not be elaborated here.

[0103] The above embodiments are only used to illustrate the present invention, rather than to limit the present invention. Those of ordinary skill in the relevant technical fields can also make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention, and the patent protection scope of the present invention should be defined by the claims.

Claims

1. A method for analyzing the crack expansion process of rock and concrete considering seepage and dissolution, characterized in that: include: Generate m×n grid nodes in the X and Y directions, and assign designated labels to each grid node to characterize soluble matter, insoluble matter, pores, and water; Simulate the flow of water in fractures and the diffusion of solutes; Specify the direction of water flow, set calculation parameters, and analyze the crack expansion process in rock and concrete; In the process of analyzing the crack expansion process of rocks and concrete, we can determine whether the solid particles are peeling off or migrating by analyzing whether there is liquid in the front, back, left, and right directions of the solid particles: If the current solid particles are not at the inlet or outlet and there is liquid in all four directions, it is determined that the current solid particles have been peeled off and migrated out of the cracks with the flow of groundwater; If the current solid particle is not at the inlet or outlet position and there is no liquid in at least one of the four directions, it is determined that the current solid particle does not migrate; If the current solid particle is at the inlet and outlet positions and there is liquid in all three directions, it is determined that the current solid particle has been peeled off; In the process of analyzing the crack expansion process of rock and concrete, the pressure on the boundary points of solid particles in the water-facing direction is calculated by the following formula: Where: f i is the water flow impact force on the i-th node on the water-facing side of the solid particle; ρ is the water density; v is the fluid velocity of the fluid near the i-th node on the water-facing side of the solid particle; The total force on the solid particles is obtained by superimposing the impact forces on each point on the water-facing side. The movement rate of solid particles in the cracks is obtained based on Newton's second law.

2. The method for analyzing the crack expansion process of rock and concrete considering seepage and dissolution as claimed in claim 1, characterized in that: Generate m×n grid points in the X and Y directions by the following method: Determine the number of material growth directions and number them, set the number of grids in the length and width directions of the model to m and n respectively, divide the model into the fracture area and the solid phase area, set the number of grids in the length and width directions of the solid phase area, the growth probability pg and the percentage of soluble matter psol; Generate a random number corresponding to the number of grid nodes in the solid phase region, and use the grid node where the random number does not exceed the growth probability pg as the initial soluble solid node; With the initial soluble solid node as the center, 8 random numbers are generated corresponding to 8 different growth directions. If the random number is greater than the set value, growth will occur in the corresponding direction. Otherwise, no growth will occur. This cycle will be repeated until the number of soluble solid nodes reaches the set value.

3. The method for analyzing the crack expansion process of rock and concrete considering seepage and dissolution as claimed in claim 1, characterized in that: In the process of analyzing the crack expansion process of rock and concrete, if there is liquid in any of the four directions of the hole, namely, front, back, left, and right, it is determined that the hole is filled with solution.

4. The method for analyzing the crack expansion process of rock and concrete considering seepage and dissolution as claimed in claim 1, characterized in that: In the process of analyzing the crack propagation process of rock and concrete, the movable solid size l s and the width of the seepage channel determine whether the movable solid can pass through the seepage channel. The movable solid size l s The calculation formula is: Where: x and y are the maximum dimensions of the movable solid in the X and Y directions respectively.

5. The method for analyzing the crack expansion process of rock and concrete considering seepage and dissolution as claimed in claim 1, characterized in that: In the process of analyzing the crack propagation process of rock and concrete, Ca 2+ and OH - The diffusion of obeys steady-state diffusion, and the calculation formula is as follows: Where: J is the diffusion flux; D diffuse is the diffusion coefficient; C is the solute concentration; is the concentration gradient along the x-axis, and the negative sign is used to ensure that the diffusion direction is consistent with the direction of concentration decrease.

6. The method for analyzing the crack expansion process of rock and concrete considering seepage and dissolution as claimed in claim 5, characterized in that: In the process of analyzing the crack propagation process of rock and concrete, the Ca(OH)2 dissolution rate function is used to characterize the Ca 2+ and OH - The dissolution rate function of Ca(OH)2 is expressed as: Where: v dissolve is the dissolution rate function; k dissolve is the dissolution rate; K eq is the chemical equilibrium constant; C(Ca 2+ ) is the Ca in the solution 2+ concentration; C(OH - ) is the OH in the solution - concentration.

7. The method for analyzing the crack expansion process of rock and concrete considering seepage and dissolution as claimed in claim 6, characterized in that: In the process of analyzing the crack expansion process of rock and concrete, the volume of the lattice node gradually decreases as Ca(OH)2 dissolves. The volume evolution calculation formula of the lattice node is: Where: V w is the dimensionless volume corresponding to the substance concentration at the solid-liquid interface; A0 is the reaction surface area; M is the molar volume of Ca(OH)2; t is time.

8. The method for analyzing the crack expansion process of rock and concrete considering seepage and dissolution as claimed in claim 6, characterized in that: In the process of analyzing the crack expansion process of rock and concrete, when the Ca in the crack solution 2+ and OH - All of them come from the dissolution of Ca(OH)2, and the dissolution rate and diffusion rate at the solid-liquid interface are the same. The dissolution process of Ca(OH)2 is expressed as: Where: C w is Ca at the solid-liquid interface 2+ and OH - The ion concentration product, C w =C(Ca 2+ )·C(OH - ) 2 ; n is the normal direction from the solid phase to the liquid phase; α is the reaction order.

9. The method for analyzing the crack expansion process of rock and concrete considering seepage and dissolution as claimed in claim 8, characterized in that: The transport of Ca(OH)2 in concrete cracks is controlled by convection and diffusion, and the calculation formula is as follows: Where: C is the solute concentration; D diffuse is the solute diffusion coefficient; u is the velocity vector; is the gradient operator.

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