A method for analyzing atmospheric impact depth in expansive soil cuttings based on fracture-dominated flow

Abstract

The present invention discloses a method for analyzing the atmospheric influence depth of expansive soil cuttings based on fractured dominant flow, comprising: describing the water movement in saturated-unsaturated soil in the matrix domain by using the Richards equation, and calculating the moisture content and water head distribution at different time steps; combining the power exponential relationship between the volume flux density of the fractured dominant flow and the water content of the macropore volume with a motion wave model, establishing a motion wave equation representing the motion characteristics of water in the fracture domain, solving the motion wave equation, and determining the atmospheric influence depth d in the fracture domain. c The Green-Ampt model is used to describe the water exchange between the matrix domain and the fracture domain, calculate the wetting front depth and infiltration rate, and determine the atmospheric influence depth d in the matrix domain. m ; Set the atmospheric influence depth d in the fracture domain c and the atmospheric influence depth d in the matrix domain m Combined with the above, the atmospheric influence depth d of expansive soil cutting is obtained. a The present invention can comprehensively analyze the effects of engineering disturbance and natural rainfall on water infiltration depth and accurately calculate the atmospheric influence depth.

Description

Technical Field

[0001] The invention relates to the technical field of expansive soil cutting engineering, and in particular to a method for analyzing the atmospheric impact depth of an expansive soil cutting based on fracture dominant flow. Background Art

[0002] Expansive soils, due to their unique shrinkage-on-wet expansion properties, are widely distributed globally, particularly in provinces such as Hubei, Henan, Guangxi, and Yunnan in my country, posing a significant challenge to railway engineering design and construction. Expansive soils cover over 100,000 square kilometers in my country. This soil type is highly sensitive to environmental changes in moisture and heat, and its water absorption and expansion can significantly impact the roadbed and upper track structures, posing a threat to the operational safety and stability of high-speed railways. High-speed railway design requires extremely stringent control of foundation deformation. In expansive soil areas, especially low-fill and shallow-cut roadbeds, the smoothness of the roadbed is highly susceptible to deformation of the expansive soil. While existing design theories and methods recommend various measures to address deformation in expansive soil foundations, such as replacement fill, drainage, composite foundations, pile grids, and pile-slab structures, and suggest optimizing pile length and spacing to minimize roadbed surface uplift, these solutions often result in significant increases in project costs.

[0003] Current calculation methods primarily focus on the expansion and contraction of expansive soils under overlying loads, but inadequately consider the moisture variations and deformation processes within the cutting. This makes it difficult to meet the precise millimeter-level deformation control requirements of high-speed ballastless track. Furthermore, while research on the environmental effects of expansive soil cuttings and the progressive deformation of their structures has been conducted both domestically and internationally, insufficient research has been conducted on the water penetration characteristics within cracks and the impact of depth and range on the rebalancing of the water field. In particular, there is a lack of methods for accurately calculating the depth of atmospheric impact of flow in expansive soil cracks.

[0004] In terms of the depth analysis of atmospheric influence on expansive soil cuttings, existing technical solutions mainly rely on empirical formulas and simplified physical models to predict the deformation behavior of expansive soil. These methods usually treat expansive soil as a homogeneous and isotropic medium, ignoring the influence of cracks and pore structure on water migration and stress distribution. For example, commonly used models include expansion and contraction prediction models based on water balance theory, and empirical formulas that consider the influence of seasonal water changes on the performance of expansive soil. (1) Water balance model: This model predicts the volume change of soil caused by changes in atmospheric conditions by calculating the water migration inside the expansive soil layer. Although this model considers the influence of water on the performance of expansive soil to a certain extent, it fails to fully consider the influence of soil cracks on the water migration path and rate, resulting in limited prediction accuracy; (2) Empirical formula method: These methods are usually based on a large amount of field observation data, and obtain empirical formulas reflecting the expansion and contraction characteristics of expansive soil by fitting. However, these formulas are often limited by specific regions and specific conditions, and are difficult to be widely applied to expansive soil cuttings under different geological and climatic conditions.

[0005] In summary, the existing technologies for analyzing the depth of atmospheric influence on expansive soil cuttings have the following major defects: (1) Ignoring the influence of fractured dominant flow: The existing technologies generally ignore the role of fractures in water migration and stress response in expansive soils. The neglect of fractured dominant flow leads to the inability to accurately predict the deformation behavior of the cutting when analyzing water infiltration, evaporation and soil expansion behavior. This defect makes the model unable to effectively reflect the dynamic changes of expansive soil under actual geological conditions, thereby affecting the safety and economy of the design; (2) The analysis model is overly simplified: The current technical solutions often use overly simplified models to predict the behavior of expansive soils. These models fail to fully consider the heterogeneity and anisotropy of expansive soils. In addition, the neglect of microstructures such as fractures and pores leads to a large deviation between the prediction results and the actual situation, which cannot meet the requirements of high-precision design. Requirements; (3) Low prediction accuracy: Due to the failure to fully consider the influence of fissure water, the existing technology has low accuracy in predicting the deformation behavior of expansive soil road cuttings under different climatic conditions, which directly affects the reliability of engineering design and increases the difficulty and cost of subsequent maintenance; (4) High cost: Under existing technical conditions, due to the conservative or rough estimation of the depth of atmospheric influence, in order to ensure the safety of the project, overly conservative measures are often taken during the design, such as the use of high-cost solutions such as composite foundations and pile net structures, which not only increases the construction cost but also prolongs the construction period; (5) Limited applicability: Most of the existing technical solutions are based on empirical data and observation results in specific areas, and their universality and scope of application are limited. For expansive soil areas with complex geological conditions or developed fissures, these methods may not be able to provide accurate predictions and analysis. Summary of the Invention

[0006] In view of this, the purpose of an embodiment of the present invention is to provide a method for analyzing the atmospheric influence depth of expansive soil road cuttings based on fracture dominant flow, by comprehensively analyzing the effects of engineering disturbance and natural rainfall on the water infiltration depth, and combining the water migration characteristics of the fracture domain and the matrix domain, to accurately calculate the atmospheric influence depth.

[0007] The embodiment of the present invention is achieved as follows:

[0008] A method for analyzing the atmospheric impact depth of expansive soil cuttings based on fracture dominant flow includes:

[0009] The Richards equation is used to describe the water movement in saturated and unsaturated soil in the matrix domain, and the moisture content and hydraulic head distribution at different time steps are calculated.

[0010] The power exponential relationship between the volume flux density of the fracture dominant flow and the water content of the macropore volume is combined with the motion wave model to establish a motion wave equation representing the motion characteristics of water in the fracture domain. The motion wave equation is solved to determine the atmospheric influence depth d in the fracture domain. c .

[0011] The Green-Ampt model is used to describe the water exchange between the matrix domain and the crack domain, calculate the wetting front depth and infiltration rate, obtain the water distribution and migration path, and determine the atmospheric influence depth d in the matrix domain. m .

[0012] The atmospheric influence depth d of the fracture domain c and the atmospheric influence depth d in the matrix domain m Combined with the above, the atmospheric influence depth d of expansive soil cutting is obtained. a .

[0013] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil cuttings based on fracture dominant flow, the Richards equation is used to describe the water movement in saturated-unsaturated soil in the matrix domain, and the moisture content and head distribution at different time steps are calculated, including:

[0014] Determine the total hydraulic head H in saturated-unsaturated soils.

[0015] Take a tiny parallelepiped in the soil and establish the continuity equation based on the law of conservation of mass Where ρ is the density of water, υ x 、υ y 、υ z represent the flow velocities in the x, y, and z directions respectively, and θ is the volumetric water content.

[0016] According to Darcy's law, the flow velocity υ in the continuity equation is x 、υ y 、υz Expressed in terms of permeability coefficient and total water head, we can obtain

[0017] Transform the right side of the continuity equation into a function of the water storage rate S and the total water head H The continuity equation is transformed into the Richards equation describing the water movement in saturated-unsaturated soil in the matrix domain:

[0018] According to the hydraulic head boundary conditions, the Richards equation is solved by the finite difference method or the finite element method to obtain the water content and hydraulic head distribution at different time steps.

[0019] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil road cuttings based on fracture dominant flow, the total water head of the saturated zone soil H1 = h1 + z1, and the total water head of the unsaturated zone soil H2 = h2 + z2, wherein h1 is the pressure head, z1 is the vertical coordinate of the saturated zone relative to the reference plane, h2 is the capillary pressure head, and z2 is the vertical coordinate of the unsaturated zone relative to the reference plane.

[0020] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil cuttings based on fracture-dominated flow, atmospheric pressure is taken as the reference plane in determining the total water head in saturated-unsaturated soil.

[0021] In a preferred embodiment of the present invention, in the above-mentioned method for analyzing the atmospheric influence depth of expansive soil cuttings based on fracture dominant flow, the power exponential relationship between the volume flux density of fracture dominant flow and the water content of the macropore volume is combined with the motion wave model to establish a motion wave equation representing the motion characteristics of water in the fracture domain, and the motion wave equation is solved to determine the atmospheric influence depth d in the fracture domain. c include:

[0022] Establish the power exponential relationship between the volume flux density q of the fracture dominant flow and the volume water content w of the macropores: q = kw n , where k is the empirical coefficient and n is the power exponent.

[0023] Combined with the motion wave model, the basic equation of motion wave is established Where t is time and z is depth.

[0024] Substituting the power exponential relationship representing the dominant flow characteristics of the fracture into the basic equation of the motion wave, the motion wave equation is obtained:

[0025] Solve the motion wave equation to obtain the depth and speed of the wetting front advance, and determine the atmospheric influence depth d of the fracture domain. c .

[0026] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil cuttings based on fracture dominant flow, the motion wave equation is solved to obtain the depth and speed of the wetting front advance, and the atmospheric influence depth d of the fracture domain is determined. c include:

[0027] During the advancement stage of the moist front, the rate of change of moisture content behind the moist front with time is 0, that is, Solving the mass balance equation The water volume flux density q in the macropore domain is also 0, and the wetting front wave velocity is expressed as Relationship between the depth and time of arrival of the wetting front

[0028] During the drainage front advancement stage, the surface rainfall intensity is s When the time drops to 0, the surface moisture content also drops to 0, and the functional relationship of the drainage front advancement process is obtained: d (t)=z0+kw n (tt s ), the functional relationship of the tail front formation, where z0 is the initial wetting front position, t s It's time for the rain to stop.

[0029] During the weakening phase of the moist front, at a specific depth z i At this point, the volume flux density q decreases with time t, forming a tail front, and the change is q(t) = q i exp(-α(tt i )), where t i This is when the moist front begins to weaken.

[0030] Determine the atmospheric influence depth d in the fracture domain c , including the relationship between the wave velocity of the moist front, the depth reached by the moist front and the time, the functional relationship of the advancement process of the drainage front, and the changes in the tail front during the weakening stage of the moist front.

[0031] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil cuttings based on fracture-dominated flow, for flat-plate viscous layer flow, the power exponential relationship between the volume flux density q and the macropore volume water content w is q∝w 3 .

[0032] For viscous saturated flow in pipes, the power exponential relationship between the volume flux density q and the macropore volume water content w is q∝w 2 .

[0033] For viscous saturated flow in pipes, the power exponent n in the power exponential relationship between volume flux density q and macropore volume water content w is greater than 2.

[0034] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil cuttings based on fracture dominant flow, the Green-Ampt model is used to describe the water exchange between the matrix domain and the fracture domain, calculate the wetting front depth and infiltration rate, obtain the water distribution and migration path, and determine the atmospheric influence depth d of the matrix domain. m include:

[0035] Establish the Green-Ampt model, the basic equation is Among them, θ i is the initial water content of the soil, θ s is the saturated water content of soil, f is the soil pressure head before the wetting front, K s is the saturated permeability of the soil, F is the cumulative infiltration volume, and t is the time.

[0036] Calculating the wetting front depth

[0037] Calculate infiltration rate

[0038] The depth of the moistening front z calculated according to the Green-Ampt model f and the infiltration rate i, determine the water distribution and migration path in the matrix domain and the crack domain.

[0039] Based on the rainfall duration and intensity, calculate the maximum wet front depth z at the end of the rainfall max .

[0040] The maximum wetting front depth z max As the atmospheric influence depth d m .

[0041] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil cuttings based on fracture dominant flow, the maximum wetting front depth z is adjusted according to the drainage and evaporation effects in the later period of rainfall. max .

[0042] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the aforementioned method for analyzing the atmospheric impact depth of expansive soil cuttings based on fractured dominant flow is implemented.

[0043] The beneficial effects of the embodiments of the present invention are:

[0044] The present invention analyzes water migration in the fracture domain, considers the stress unloading effect caused by engineering disturbance, and uses a motion wave model to describe and calculate the water migration process in the fracture domain, thereby determining the atmospheric influence depth of the fracture domain. The present invention also adopts a matrix domain water migration analysis, and through the saturated-unsaturated seepage calculation controlled by the Richards equation, examines the water infiltration depth (dm) in the matrix domain, considering the influence of soil pore structure and particle properties on water propagation. For water exchange between the two domains, the Green-Ampt model or other models are used to process the water exchange between the fracture domain and the matrix domain, optimizing the overall understanding of water migration. Under certain conditions, the pressure head boundary condition can also be used to more accurately simulate this exchange process.

[0045] By comprehensively analyzing water migration and their interactions within the fissure and matrix domains, the present invention can more accurately predict the atmospheric influence depth of expansive soil cuttings. This method not only overcomes several shortcomings of existing technologies, such as neglecting the impact of fissure flow and oversimplifying models, but also provides a cost-effective, highly accurate solution, which is of great significance for improving the design and construction quality of expansive soil cutting projects. Furthermore, while improving prediction accuracy, the present invention can also be adjusted to specific geological and climatic conditions, demonstrating strong adaptability and broad application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 Schematic diagram of calculation boundary conditions for excavation cutting in the atmospheric influence depth analysis method for expansive soil cutting based on fracture dominant flow of the present invention;

[0048] Figure 2 Schematic diagram of the flat plate flow model structure in the atmospheric impact depth analysis method for expansive soil cuttings based on fracture-dominated flow of the present invention;

[0049] Figure 3 Schematic diagram of the structure of the circular tube flow model in the atmospheric impact depth analysis method for expansive soil cuttings based on fracture-dominated flow of the present invention;

[0050] Figure 4 Schematic diagram of the structure of the water movement wave model in the atmospheric influence depth analysis method for expansive soil cuttings based on fracture dominant flow of the present invention;

[0051] Figures 5a to 5eSchematic diagram of the water exchange process between two domains during rainfall in the atmospheric impact depth analysis method for expansive soil cuttings based on fracture dominant flow of the present invention;

[0052] Figure 6 This is a schematic diagram of a calculation example of a medium-width crack in the atmospheric influence depth analysis method for expansive soil cuttings based on crack dominant flow in the present invention. DETAILED DESCRIPTION

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0054] The present invention aims to solve the technical problem of accurately measuring the depth of atmospheric influence in expansive soil cutting projects. In the prior art, the influence of the dominant flow in the fracture on water migration and the change of the properties of the expansive soil is not fully considered, resulting in a low prediction accuracy of the depth of atmospheric influence. Therefore, the present invention proposes a method for comprehensively analyzing the influence of engineering disturbance and natural rainfall on the depth of water infiltration, and accurately calculating the depth of atmospheric influence by combining the water migration characteristics of the fracture domain and the matrix domain. The purpose of the present invention is to provide an analysis method that can overcome the limitations of the existing technology, with high precision, economic efficiency and strong adaptability, to guide the design and construction of expansive soil cutting projects and improve the quality and safety of the project. Through the present invention, the deformation behavior of expansive soil cuttings under different climatic conditions can be more accurately evaluated, providing a reliable basis for engineering design, reducing construction risks, reducing later maintenance costs, and achieving the sustainable development of expansive soil cutting projects.

[0055] Please refer to Figures 1 to 6 The first embodiment of the present invention provides an atmospheric influence depth analysis method for expansive soil cuttings based on fractured dominant flow, which includes: describing the water movement in saturated-unsaturated soil in the matrix domain by using the Richards equation, and calculating the moisture content and head distribution at different time steps; combining the power exponential relationship between the volume flux density of the fractured dominant flow and the water content of the macropore volume with the motion wave model to establish a motion wave equation representing the motion characteristics of water in the fracture domain; solving the motion wave equation to determine the atmospheric influence depth d in the fracture domain. c The Green-Ampt model is used to describe the water exchange between the matrix domain and the crack domain, calculate the wetting front depth and infiltration rate, obtain the water distribution and migration path, and determine the atmospheric influence depth d in the matrix domain. m ; Set the atmospheric influence depth d in the fracture domain c and the atmospheric influence depth d in the matrix domain mCombined with the above, the atmospheric influence depth d of expansive soil cutting is obtained. a .

[0056] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil cuttings based on fracture dominant flow, the Richards equation is used to describe the water movement in saturated-unsaturated soil in the matrix domain, and the moisture content and head distribution at different time steps are calculated, including: determining the total water head H in the saturated-unsaturated soil; taking a small parallelepiped in the soil body, and establishing a continuity equation based on the law of conservation of mass. Where ρ is the density of water, υ x 、υ y 、υ z represent the flow velocity in the x, y, and z directions respectively, and θ is the volumetric water content; according to Darcy's law, the flow velocity υ in the continuity equation is x 、υ y 、υ z Expressed in terms of permeability coefficient and total water head, we can obtain

[0057] Since the volumetric water content is a function of the capillary pressure head, which is in turn a function of time, the compressibility of water is neglected and the right side of the continuity equation is transformed into a function of the water storage rate and the head. The water storage rate represents the amount of stored water released by the compression of the soil skeleton when the head drops by one unit. The right side of the continuity equation is transformed into a function of the water storage rate S and the total head H. The continuity equation is transformed into the Richards equation describing the water movement in saturated-unsaturated soil in the matrix domain:

[0058] like Figure 1 As shown, according to the hydraulic head boundary conditions, the Richards equation is solved by the finite difference method or the finite element method to obtain the water content and hydraulic head distribution at different time steps.

[0059] Specifically, the solution steps include: dividing the soil area into grids and discretizing time into small time steps; setting the moisture content and head distribution at the initial moment; setting boundary conditions, such as rainfall infiltration and evaporation; and at each time step, using the discretized equations for iterative calculations to update the moisture content and head values of each grid node until the predetermined simulation time is reached.

[0060] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil road cuttings based on fracture dominant flow, the total water head of the saturated zone soil H1 = h1 + z1, and the total water head of the unsaturated zone soil H2 = h2 + z2, wherein h1 is the pressure head, z1 is the vertical coordinate of the saturated zone relative to the reference plane, h2 is the capillary pressure head, and z2 is the vertical coordinate of the unsaturated zone relative to the reference plane.

[0061] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil cuttings based on fracture-dominated flow, atmospheric pressure is taken as the reference plane in determining the total water head in saturated-unsaturated soil.

[0062] Specifically, the pressure below the free water surface is greater than one atmosphere, and the pressure above the free water surface is less than one atmosphere. If atmospheric pressure is taken as the reference plane, the total water head of the saturated zone soil is H1 = h1 + z1, and the total water head of the unsaturated zone soil is H2 = h2 + z2.

[0063] In a preferred embodiment of the present invention, in the above-mentioned method for analyzing the atmospheric influence depth of expansive soil cuttings based on fracture dominant flow, the power exponential relationship between the volume flux density of fracture dominant flow and the water content of the macropore volume is combined with the motion wave model to establish a motion wave equation representing the motion characteristics of water in the fracture domain, and the motion wave equation is solved to determine the atmospheric influence depth d in the fracture domain. c Including: establishing the power exponential relationship q=kw between the volume flux density q of the fracture dominant flow and the water content w of the macropore volume n , where k is the empirical coefficient and n is the power exponent; combined with the motion wave model, the basic equation of motion wave is established Where t is time and z is depth. Substituting the power exponential relationship representing the dominant flow characteristics of the fracture into the basic equation of the motion wave, the motion wave equation is obtained: Solve the motion wave equation to obtain the depth and speed of the wetting front advance, and determine the atmospheric influence depth d of the fracture domain. c .

[0064] Specifically, the movement of water in macroporous media is complex, and Darcy's law, based on empirical statistical principles, is inappropriate for describing water flow within these pores. For expansive soils containing fractures, the formation of these fractures creates a loose layer of medium at the surface, and water movement within these fractures exhibits a dominant flow pattern. The presence of these fractures allows water to penetrate the underlying soil layers at a faster rate. Only by examining the water flow characteristics can we understand the impact of fractures on water migration and slope stability.

[0065] Regarding the seepage characteristics of fractured areas, we can adopt a method from micro to macro, extending the flat plate flow model and the circular tube flow model to a macro fracture flow model.

[0066] Through a large number of experiments and regression analysis based on statistical laws, it is concluded that there is a power exponential relationship between the volume flux q density of the fracture dominant flow and the volume water content w of the macropores.

[0067] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil cuttings based on fracture dominant flow, the motion wave equation is solved to obtain the depth and speed of the wetting front advance, and the atmospheric influence depth d of the fracture domain is determined. c Including: During the advancement stage of the moist front, the rate of change of moisture content behind the moist front with time is 0, that is, Solving the mass balance equation The water volume flux density q in the macropore domain is also 0, and the wetting front wave velocity is expressed as Relationship between the depth and time of arrival of the wetting front During the drainage front advancement stage, the surface rainfall intensity is s When the time drops to 0, the surface moisture content also drops to 0, and the functional relationship of the drainage front advancement process is obtained: d (t)=z0+kw n (tt s ), the functional relationship of the tail front formation, where z0 is the initial wetting front position, t s is the moment when rainfall stops; during the weakening stage of the moist front, at a specific depth z i At this point, the volume flux density q decreases with time t, forming a tail front, and the change is q(t) = q i exp(-α(tt i )), where t i is the moment when the moist front begins to weaken; determine the atmospheric influence depth d of the fracture domain c , including the relationship between the wave velocity of the moist front, the depth reached by the moist front and the time, the functional relationship of the advancement process of the drainage front, and the changes in the tail front during the weakening stage of the moist front.

[0068] like Figure 4 Specifically, the basic equation of the kinematic wave model is a mass balance equation based on conservation of matter. Solving the kinematic wave equation also relies on the interrelationships between the model's variables. A discussion of the characteristics of water movement in fractured zones reveals a relationship between the volume flux density of water movement in macropores and the water content of the flow. Combining this with the basic equation of the kinematic wave model allows for the solution of the kinematic wave equation.

[0069] During the advancement of the wetting front, when the surface layer receives rainfall, a stable moisture content profile is formed behind the wetting front, the rate of change of moisture content with time is 0, and the volume flux density of water movement in the macropore domain is 0. At this time, the relationship between the simultaneous motion wave equation and the volume flux density of water movement in the macropore domain and the water content of the flow can be used to derive the volume flux density profile function behind the wetting front. Due to the adsorption effect of the matrix domain, there is a maximum depth. Beyond this depth, no macropore flow occurs. This depth is Z * At the same time, solving the equation can yield the moisture content profile behind the wetting front, the wave velocity of the wetting front, and the relationship between the depth and time of the wetting front.

[0070] During the advancement stage of the drainage front, as the surface rainfall intensity increases at t s When the time drops to 0, the surface moisture content also drops to 0. At this time, the functional relationship of the advancement process of the drainage front can be obtained.

[0071] During the weakening phase of the moist front, the i The boundary condition at the tail front is a functional relationship, that is, the volume flux density is gradually decreasing, t i The moist front weakened after a certain time. i The water movement process at depth is similar to the above two stages.

[0072] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil cuttings based on fracture-dominated flow, for flat-plate viscous layer flow, the power exponential relationship between the volume flux density q and the macropore volume water content w is q∝w 3 For viscous saturated flow in pipes, the power exponential relationship between volume flux density q and macropore volume water content w is q∝w 2 ; For viscous saturated flow in pipelines, the power exponent n in the power exponential relationship between volume flux density q and macropore volume water content w is greater than 2.

[0073] Specifically, such as Figure 2 As shown in , at the microscopic level, for flat viscous layer flow, the volume flux density and the volume water content of the macropore flow are in a cubic relationship. Figure 3 As shown in the figure, for viscous saturated pipe flow, the volume flux density and the volume water content of large pore flow are in a power-squared relationship; for unsaturated pipe flow, the power of the power-exponential relationship between the volume flux density and the volume water content of large pore flow is greater than 2.

[0074] At the macro level, for the combination of various crack morphologies, regression analysis of a large amount of experimental data, including water conductivity tests of original soil, various artificial cracked soils, and tests of mixed specimens containing complex large pores, concluded that the power exponent can well describe the relationship between volume flux density and large pore volume water content. The power exponent is generally between 2 and 3, which is the combined effect of multiple factors such as the combination of various crack morphologies, the variability and roughness of natural cracks, the curvature and volatility of crack boundaries, and the connection between cracks.

[0075] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil cuttings based on fracture dominant flow, the Green-Ampt model is used to describe the water exchange between the matrix domain and the fracture domain, calculate the wetting front depth and infiltration rate, obtain the water distribution and migration path, and determine the atmospheric influence depth d of the matrix domain. m Including: Establishing Green-Ampt model, the basic equation is Among them, θ i is the initial water content of the soil, θ s is the saturated water content of soil, f is the soil pressure head before the wetting front, K s is the saturated permeability of the soil, F is the cumulative infiltration volume, and t is the time; calculate the wetting front depth Calculate infiltration rate The depth of the moistening front z calculated according to the Green-Ampt model f and infiltration rate i, determine the water distribution and migration path in the matrix domain and crack domain; calculate the maximum wet front depth z at the end of rainfall based on rainfall duration and intensity. max The maximum wetting front depth z max As the atmospheric influence depth d m .

[0076] Specifically, the model is based on the concept of preferred flow, assuming that rainwater infiltrates the soil first through cracks, the preferred path. Once the cracks are filled with water, water from the soil surface and crack sidewalls begins to seep into the soil. The two-domain water exchange process mathematically describes how water from the soil surface and crack sidewalls infiltrates into the soil.

[0077] The water exchange between the two domains during a rainfall process is as follows: Figures 5a to 5e The water exchange between the two domains is very complex, but for a rainfall process, as shown in Figure 5c The situation shown is the dominant one, that is, as long as it is within the depth reached by the wetting front, the water exchange between the two domains can be regarded as the radiation of water from the macropore domain to the matrix domain.

[0078] For this radiation effect, the Green-Ampt model or other infiltration models can generally be used to obtain an analytical solution or empirical formula for the range of action of the dominant flow.

[0079] like Figure 6 As shown in the figure, a fracture of equal width is analyzed as an example. The shaded area represents water. After the pipe is filled with water, the Green-Ampt model is used to solve for the radiation from the pipe sidewall to the matrix domain. Solving for the corresponding y value at any time reveals the range of the dominant flow in the matrix domain, which can be added to the existing seepage calculation results. The pipe end is assumed to be a hemispherical region with a radius of r, and the equation for the radiation from this region to the matrix domain is also solved.

[0080] Water exchange between the two domains can be solved using either analytical or empirical solutions, or by applying boundary conditions to the corresponding boundaries of the matrix domain. The boundary condition is a pressure head boundary, where the head value is half the gap width. The matrix domain seepage calculation demonstrates the effects of the dominant flow on the matrix domain.

[0081] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil cuttings based on fracture dominant flow, the maximum wetting front depth z is adjusted according to the drainage and evaporation effects in the later period of rainfall. max .

[0082] A second embodiment of the present invention provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method for analyzing the atmospheric impact depth of expansive soil cuttings based on fractured dominant flow as described above is implemented.

[0083] The embodiment of the present invention aims to provide a method for analyzing the atmospheric impact depth of expansive soil cuttings based on fracture dominant flow, which has the following effects:

[0084] 1. This method fully considers the influence of dominant flow in fractures and accurately calculates the atmospheric influence depth by meticulously analyzing the water migration characteristics of fracture and matrix domains. Compared to existing technologies, it can more accurately predict the deformation behavior of expansive soil cuttings under different climatic conditions, providing a more reliable basis for engineering design.

[0085] 2. The present invention comprehensively considers the impact of engineering disturbance and natural rainfall on the water migration behavior of expansive soil cuttings. Through the comprehensive analysis of these two factors, a more comprehensive understanding of the water migration law of expansive soil is obtained, which improves the accuracy of prediction.

[0086] 3. This paper uses refined water migration models, including the kinematic wave model and the Green-Ampt model, to more accurately describe water migration in fracture and matrix domains. The application of these models makes the calculation of atmospheric influence depth more reliable and accurate.

[0087] 4. By more accurately predicting the deformation behavior of expansive soil cuttings, the present invention helps guide engineering design and construction, reduces engineering risks, and lowers subsequent maintenance costs, thereby improving engineering quality and safety.

[0088] 5. The method of the present invention is not only applicable to expansive soil cutting projects under different geological and climatic conditions, but can also be adjusted according to specific circumstances, showing strong adaptability and wide application potential.

[0089] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A method for analyzing the atmospheric impact depth of expansive soil cuttings based on fracture dominant flow, characterized in that: include: The Richards equation is used to describe the water movement in saturated and unsaturated soil in the matrix domain, and the moisture content and hydraulic head distribution at different time steps are calculated; The power exponential relationship between the volume flux density of the fracture dominant flow and the water content of the macropore volume is combined with the motion wave model to establish a motion wave equation representing the motion characteristics of water in the fracture domain. The motion wave equation is solved to determine the atmospheric influence depth d in the fracture domain. c Specifically, it includes: establishing the power exponential relationship between the volume flux density q of the fracture dominant flow and the water content w of the macropore volume , where k is the empirical coefficient and n is the power exponent; combined with the motion wave model, the basic equation of motion wave is established , where t is time and z is depth; substituting the power exponential relationship representing the dominant flow characteristics of the fracture into the basic equation of the motion wave, the motion wave equation is obtained Solve the motion wave equation to obtain the depth and speed of the wetting front advance and determine the atmospheric influence depth d of the fracture domain. c ; The Green-Ampt model is used to describe the water exchange between the matrix domain and the crack domain, calculate the wetting front depth and infiltration rate, obtain the water distribution and migration path, and determine the atmospheric influence depth d in the matrix domain. m , specifically including: establishing the Green-Ampt model, the basic equation is , where θ i is the initial water content of the soil, θ s is the saturated water content of soil, f is the soil pressure head before the wetting front, K s is the saturated permeability of the soil, F is the cumulative infiltration volume, and t is the time; calculate the wetting front depth ; Calculate infiltration rate ; Wetting front depth z calculated according to the Green-Ampt model f and infiltration rate i, determine the water distribution and migration path in the matrix domain and crack domain; calculate the maximum wet front depth z at the end of rainfall based on rainfall duration and intensity. max The maximum wetting front depth z max As the atmospheric influence depth d m ; The atmospheric influence depth d of the fracture domain c and the atmospheric influence depth d in the matrix domain m Combined with the above, the atmospheric influence depth d of expansive soil cutting is obtained. a .

2. The method for analyzing the atmospheric impact depth of expansive soil cuttings based on fracture dominant flow according to claim 1, wherein: The Richards equation is used to describe the water movement in the saturated-unsaturated soil in the matrix domain, and the moisture content and head distribution at different time steps are calculated, including: Determine the total hydraulic head H in saturated-unsaturated soils; Take a tiny parallelepiped in the soil and establish the continuity equation based on the law of conservation of mass , where ρ is the density of water, υ x 、υ y 、υ z represent the flow velocities in the x, y, and z directions, respectively, and θ is the volumetric water content; According to Darcy's law, the flow velocity υ in the continuity equation is x 、υ y 、υ z Expressed in terms of permeability coefficient and total water head, we can obtain , , ; Transform the right side of the continuity equation into a function of the water storage rate S and the total water head H , the continuity equation is transformed to obtain Richards equation describing the water movement in saturated-unsaturated soil in the matrix domain ; According to the hydraulic head boundary conditions, the Richards equation is solved by the finite difference method or the finite element method to obtain the water content and hydraulic head distribution at different time steps.

3. The method for analyzing the atmospheric impact depth of expansive soil cuttings based on fracture dominant flow according to claim 2, wherein: The total water head of the saturated zone soil is H1=h1+z1, and the total water head of the unsaturated zone soil is H2=h2+z2, where h1 is the pressure head, z1 is the vertical coordinate of the saturated zone relative to the reference plane, h2 is the capillary pressure head, and z2 is the vertical coordinate of the unsaturated zone relative to the reference plane.

4. The method for analyzing the atmospheric impact depth of expansive soil cuttings based on fracture dominant flow according to claim 2, wherein: In determining the total water head in saturated-unsaturated soil, atmospheric pressure is taken as the reference level.

5. The method for analyzing the atmospheric impact depth of expansive soil cuttings based on fracture dominant flow according to claim 1, wherein: The solution of the motion wave equation is used to obtain the depth and speed of the wetting front advance and determine the atmospheric influence depth d of the fracture domain. c include: During the advancement stage of the moist front, the rate of change of moisture content behind the moist front with time is 0, that is, , solve the mass balance equation , the volume flux density q of water movement in the macropore domain is also 0, and the wetting front wave velocity is expressed as , the relationship between the depth and time of the wetting front ; During the drainage front advancement stage, the surface rainfall intensity is s When the time drops to 0, the surface moisture content also drops to 0, and the functional relationship of the drainage front's advancement process is obtained: , the functional relationship of the tail front formation, where z0 is the initial wetting front position, t s It is the moment when the rain stops; During the weakening phase of the moist front, at a specific depth z i At , the volume flux density q decreases with time t, forming a tail front, and the change is , where t i It’s the moment when the moist front begins to weaken; Determine the atmospheric influence depth d in the fracture domain c , including the relationship between the wave velocity of the moist front, the depth reached by the moist front and the time, the functional relationship of the advancement process of the drainage front, and the changes in the tail front during the weakening stage of the moist front.

6. The method for analyzing the atmospheric impact depth of expansive soil cuttings based on fracture dominant flow according to claim 1, wherein: For flat plate viscous layer flow, the power exponential relationship between the volume flux density q and the macropore volume water content w is: ; For viscous saturated flow in pipes, the power exponential relationship between the volume flux density q and the macropore volume water content w is: ; For viscous saturated flow in pipes, the power exponent n in the power exponential relationship between volume flux density q and macropore volume water content w is greater than 2.

7. The method for analyzing the atmospheric impact depth of expansive soil cuttings based on fracture dominant flow according to claim 1, wherein: Adjust the maximum wet front depth z according to the drainage and evaporation effects in the later period of rainfall max .

8. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the method for analyzing the atmospheric impact depth of expansive soil cuttings based on fracture dominant flow according to any one of claims 1 to 7 is implemented.

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