Expansive soil cutting atmospheric influence depth analysis method based on fracture dominant flow

Abstract

The invention discloses an expansive soil cutting atmospheric influence depth analysis method based on fracture dominant flow, which comprises the following steps: describing moisture movement in saturated-unsaturated soil in a matrix domain through a Richards equation, and calculating to obtain moisture content and water head distribution at different time steps; combining the power exponent relationship between the volume flux density of the fracture dominant flow and the macropore volume water content with a kinematic wave model, establishing a kinematic wave equation representing the kinematic characteristics of the water in the fracture domain, solving the kinematic wave equation, and determining the atmospheric influence depth dc of the fracture domain; through a Green-Ampt model, describing water exchange between a matrix domain and a fracture domain, calculating a wetting front depth and an infiltration rate, and determining an atmospheric influence depth dm of the matrix domain; and combining the fracture domain atmospheric influence depth dc and the matrix domain atmospheric influence depth dm to obtain the expansive soil cutting atmospheric influence depth da. According to the method, the influence of engineering disturbance and natural rainfall on the water infiltration depth can be comprehensively analyzed, and the atmospheric influence depth can be accurately calculated.

Description

Technical Field

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

[0002] Expansive soils are widely distributed around the world, especially in Hubei, Henan, Guangxi, Yunnan and other provinces in my country, due to their unique shrinkage and swelling characteristics, posing a major challenge in railway engineering design and construction. Expansive soils are distributed over an area of ​​more than 100,000 square kilometers in my country. This type of soil is highly sensitive to changes in humidity and heat in the environment. Water absorption and swelling will cause significant expansion deformation and force impact on the roadbed structure and upper track structure, posing a threat to the operation safety and stability of high-speed railways. The design of high-speed railways has extremely strict requirements for the control of foundation deformation. In expansive soil areas, especially low-fill and shallow-cut roadbeds, their smoothness is easily affected by the deformation of the expansive soil foundation. Although existing design theories and methods recommend the use of a variety of measures such as replacement filling, drainage, composite foundation, pile mesh structure, pile-board structure, etc. to deal with the deformation problem of expansive soil foundations, and propose suggestions for optimizing pile length and pile spacing to reduce the amount of roadbed surface uplift, these solutions often lead to a significant increase in project costs.

[0003] The current calculation methods mainly focus on the expansion and contraction deformation of expansive soil under the action of overlying loads, but the consideration of the moisture changes and deformation process in the road cut is not sufficient. This makes it difficult to meet the precise requirements of high-speed railway ballastless track for millimeter-level deformation control. In addition, although the environmental effects of expansive soil road cuts and the progressive deformation of their structures have been studied both at home and abroad, the research on the water penetration characteristics in the cracks and the depth and range of the water field rebalance process is still insufficient, especially the lack of methods for accurately calculating the depth of the impact of the flow of expansive soil cracks on the atmosphere.

[0004] In terms of atmospheric influence depth analysis of expansive soil cuttings, existing technical solutions mainly rely on empirical formulas and simplified physical models to predict the deformation behavior of expansive soils. These methods usually treat expansive soils as homogeneous and isotropic media, ignoring the effects of cracks and pore structures 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 effects of seasonal water changes on the performance of expansive soils. (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 effect of water on the performance of expansive soil to a certain extent, it fails to fully consider the effect of soil cracks on the path and rate of water migration, resulting in limited prediction accuracy; (2) Empirical formula method: These methods are usually based on a large amount of field observation data, and empirical formulas that reflect the expansion and contraction characteristics of expansive soils are obtained by fitting. However, these formulas are often limited to 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 the depth analysis 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 soils 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. (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 the existing technical conditions, due to the conservative or rough estimation of the atmospheric influence depth, 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 mesh 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, comprising:

[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 water 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 of the fracture domain d c and the atmospheric influence depth d 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 water content and water head distribution at different time steps are calculated, including:

[0014] Determine the total water head H in saturated-unsaturated soil.

[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 get

[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 cutting based on fracture dominant flow, the total water head H of the saturated zone soil 1 =h 1 +z 1 , the total water head H of the unsaturated zone soil 2 =h 2 +z 2 , where h 1 is the pressure head, z 1 is the vertical coordinate of the saturation zone relative to the reference plane, h 2 is the capillary pressure head, z 2 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 dominant flow, in determining the total water head in saturated-unsaturated soil, the atmospheric pressure is taken as the reference plane.

[0021] In a preferred embodiment of the present invention, in the above-mentioned method for analyzing the atmospheric influence depth of expansive soil road cutting based on fracture dominant flow, the power exponential relationship between the volume flux density of fracture dominant flow and the water content of large pore 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 of the fracture domain. c include:

[0022] Establish the power exponential relationship between the volume flux density q of the fracture dominant flow and the water content w of the macropore volume: 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 Among them, t is time and z is depth.

[0024] Substituting the power exponential relationship representing the fracture dominant flow characteristics 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 moist 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 road cutting 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 in 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 over time is 0, that is, Solving the mass balance equation The water volume flux density q in the macropore domain is also 0. The wetting front wave velocity is expressed as Relationship between the depth and time 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 advancement process of the drainage front is obtained: d (t) = z 0 +kw n (tt s ), the functional relationship of the tail front formation, where z 0 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 the 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 dominant flow, for flat 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 a pipe, 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 a pipe, the power exponent n>2 in the power exponential relationship between the volume flux density q and the macropore volume water content w.

[0034] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil road cutting 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 soil moisture content, θ s is the saturated water content of soil, f is the soil pressure head in front of 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 the infiltration rate

[0038] The wetting front depth 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 fracture 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 road cutting 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 comprises 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 above-mentioned atmospheric influence depth analysis method for expansive soil cuttings based on fracture dominant flow is implemented.

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

[0044] The present invention analyzes the water migration in the fracture domain, considers the stress unloading effect caused by engineering disturbance, uses the motion wave model to describe and calculate the water migration process in the fracture domain, and then determines the atmospheric influence depth of the fracture domain; adopts the matrix domain water migration analysis, and investigates the water infiltration depth (dm) of the matrix domain through the saturated-unsaturated seepage calculation controlled by the Richards equation, and considers the influence of the soil pore structure and particle characteristics on water propagation; for the 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, optimize the overall understanding of water migration, and under certain conditions, the pressure head boundary condition can also be used to more accurately simulate this exchange process.

[0045] By comprehensively analyzing the water migration and interaction between the fissure domain and the matrix domain, the present invention can more accurately predict the atmospheric influence depth of expansive soil cuttings. It not only overcomes many defects of the prior art, such as ignoring the influence of fissure flow and oversimplifying the model, but also provides an economical, efficient and high-precision solution, which is of great significance for improving the design and construction quality of expansive soil cutting projects. In addition, while improving the prediction accuracy, the present invention can also be adjusted according to specific geological and climatic conditions, showing strong adaptability and wide 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 drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

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

[0048] Figure 2 It is a schematic diagram of the structure of a flat plate flow model in the atmospheric influence depth analysis method for expansive soil cuttings based on fracture dominant flow of the present invention;

[0049] Figure 3 It is a schematic diagram of the structure of the circular tube flow model in the atmospheric influence depth analysis method of expansive soil cutting based on fracture dominant flow of the present invention;

[0050] Figure 4 It is a schematic diagram of the structure of the water movement wave model in the atmospheric influence depth analysis method of expansive soil cutting based on fracture dominant flow of the present invention;

[0051] Figure 5a to Figure 5e It is a schematic diagram of the water exchange process between two domains during rainfall in the atmospheric impact depth analysis method of expansive soil cutting based on fracture dominant flow of the present invention;

[0052] Figure 6 It 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 of the present invention. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 here can be arranged and designed in various different configurations.

[0054] The present invention aims to solve the technical problem of accurately measuring the atmospheric influence depth in expansive soil cutting projects. In the prior art, the influence of the dominant flow in the fissure on water migration and the change of the properties of the expansive soil is not fully considered, resulting in low prediction accuracy of the atmospheric influence depth. Therefore, the present invention proposes a method for comprehensively analyzing the influence of engineering disturbance and natural rainfall on the water infiltration depth, and accurately calculating the atmospheric influence depth by combining the water migration characteristics of the fissure domain and the matrix domain. The object of the present invention is to provide an analysis method that can overcome the limitations of the prior art, has high precision, is economical and efficient, and has strong adaptability, so as 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, a reliable basis can be provided for engineering design, construction risks can be reduced, and later maintenance costs can be reduced, so as to achieve 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 road cuttings based on fracture dominant flow, which includes: describing the water movement in saturated-unsaturated soil in the matrix domain by Richards equation, and calculating the water content and water head distribution at different time steps; combining the power exponential relationship between the volume flux density of fracture dominant flow and the water content of large pore volume with the 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 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 depth of atmospheric influence in the fracture domain dc and the atmospheric influence depth d m Combined 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 road cutting 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 water content and water head distribution at different time steps are calculated, including: determining the total water head H in the saturated-unsaturated soil; taking a tiny 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 get

[0057] Since the volumetric water content is a function of the capillary pressure head, which is in turn a function of time, ignoring the effect of water compressibility, the right side of the continuity equation is transformed into a function of water storage rate and water head. The water storage rate represents the amount of stored water released due to the compression of the soil skeleton when the water head drops by one unit. The right side of the continuity equation is transformed into a function of water storage rate S and 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:

[0058] like Figure 1 As shown, according to the hydraulic head boundary condition, 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, evaporation, etc.; 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 cutting based on fracture dominant flow, the total water head H of the saturated zone soil 1 =h 1 +z 1, the total water head H of the unsaturated zone soil 2 =h 2 +z 2 , where h 1 is the pressure head, z 1 is the vertical coordinate of the saturation zone relative to the reference plane, h 2 is the capillary pressure head, z 2 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 dominant flow, in determining the total water head in saturated-unsaturated soil, the atmospheric pressure is taken as the reference plane.

[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 the atmospheric pressure is taken as the reference plane, the total water head H of the saturated zone soil is 1 =h 1 +z 1 , the total water head H of the unsaturated zone soil 2 =h 2 +z 2 .

[0063] In a preferred embodiment of the present invention, in the above-mentioned method for analyzing the atmospheric influence depth of expansive soil road cutting based on fracture dominant flow, the power exponential relationship between the volume flux density of fracture dominant flow and the water content of large pore 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 of the fracture domain. c Including: 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 q = kw n , where k is the empirical coefficient and n is the power index; 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 moist front advance, and determine the atmospheric influence depth d of the fracture domain. c .

[0064] Specifically, in macroporous media, the movement law of water is relatively complex, and Darcy's law based on empirical statistical laws is not applicable to describing the flow of water in macropores. For expansive soils with cracks, a layer of dispersed medium is formed on its surface due to the formation of cracks, and the movement law of water in the cracks of cracked soil shows the characteristics of a dominant flow. Due to the existence of cracks, water can penetrate into the lower soil layer at a faster rate. Only by starting from the water flow characteristics can we figure out the impact of cracks on water migration and slope stability.

[0065] Regarding the seepage characteristics of the fracture zone, a method from micro to macro can be used, extending the flat plate flow model and the circular tube flow model to the 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 road cutting 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 in 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 over time is 0, that is, Solving the mass balance equation The water volume flux density q in the macropore domain is also 0. The wetting front wave velocity is expressed as 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 advancement process of the drainage front is obtained: d (t) = z 0 +kw n (tt s ), the functional relationship of the tail front formation, where z 0 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 the 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 As shown in the figure, the basic equation of the kinematic wave model is the mass balance equation based on the conservation of matter. The solution of the kinematic wave equation also depends on the relationship between the model variables. The discussion on the characteristics of water movement in the fracture zone has resulted in the relationship between the volume flux density of water movement in the macropore domain and the water content of the flow. The kinematic wave equation can be solved by combining it with the basic equation of the kinematic wave model.

[0069] In the stage of the advancement of the wet front, when the surface layer receives rainfall, a stable moisture content profile is formed behind the wet 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 obtain the volume flux density profile function behind the wet front. Considering the adsorption effect of the matrix domain, there is a maximum depth. Beyond this depth, macropore flow no longer occurs. This depth is Z * At the same time, solving the equation can obtain the moisture content profile behind the wetting front, the wave velocity of the wetting front, and the relationship between the depth and time reached by 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 is a functional relationship for the tail front, that is, the volume flux density decreases gradually, t i The moist front weakened after 10:00. 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 dominant flow, for flat 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 a pipeline, the power exponential relationship between the volume flux density q and the macropore volume water content w is q∝w 2 ; For viscous saturated flow in pipelines, the power exponent n>2 in the power exponential relationship between volume flux density q and macropore volume water content w.

[0073] Specifically, Figure 2 As shown in , at the microscopic level, for flat-plate viscous layer flow, the volume flux density and the volume water content of the macropore flow are in a cubic relationship. Figure 3As shown, for viscous saturated pipe flow, the volume flux density and the volume water content of large pore flow are in a quadratic relationship; for unsaturated pipe flow, the power of the 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 fracture morphologies, regression analysis of a large amount of experimental data, including water conductivity tests on undisturbed soils, various artificial fractured soils, and tests on mixed specimens containing complex large pores, shows 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 fracture morphologies, the variability and roughness of natural fractures, the curvature and volatility of fracture boundaries, and the connection between fractures.

[0075] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil road cutting 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 the Green-Ampt model, the basic equation is Among them, θ i is the initial soil moisture content, θ s is the saturated water content of soil, f is the soil pressure head in front of 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 the infiltration rate The 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 the 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 established according to the concept of dominant flow, assuming that when rainwater infiltrates, it first enters the soil through the dominant path of cracks. After the cracks are filled with water, the water on the soil surface and the side walls of the cracks begins to infiltrate the soil. The two-domain water exchange process mathematically describes the process of water infiltration from the soil surface and the side walls of the cracks into the soil.

[0077] The water exchange between the two domains during a rainfall process is as follows: Figure 5a to Figure 5eThe water exchange between the two domains is very complicated, but for a rainfall process, Figure 5c The situation shown is dominant, 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 kind of 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, an equal-width crack is used as an example for analysis: the shaded part is water. After the pipe is filled with water, the Green-Ampt model is used to obtain the solution of the radiation from the pipe sidewall to the matrix domain, and the corresponding y value at any time is solved. From this, the scope of the dominant flow on the matrix domain can be obtained, and this result can be superimposed on the existing seepage calculation results. The end of the pipe 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 solved.

[0080] The water exchange between the two domains can be solved by this analytical solution or empirical formula, or the boundary conditions can be imposed on the corresponding boundary of the matrix domain. The boundary condition is the pressure head boundary, and the head value is half the gap width. In the matrix domain seepage calculation, the effect of the dominant flow on the matrix domain can be shown.

[0081] In a preferred embodiment of the present invention, in the above-mentioned atmospheric influence depth analysis method for expansive soil road cutting 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, including 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 an expansive soil cutting based on fracture 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 an expansive soil cutting based on fracture dominant flow, which has the following effects:

[0084] 1. The present invention fully considers the influence of the fracture dominant flow, and accurately calculates the atmospheric influence depth by carefully analyzing the water migration characteristics of the fracture domain and the matrix domain. Compared with the existing technology, it can more accurately predict the deformation behavior of the expansive soil cutting under different climatic conditions, providing a more reliable basis for engineering design.

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

[0086] 3. The present invention adopts a refined water migration model, including a motion wave model and a Green-Ampt model, to more accurately describe the water migration process in the fracture domain and the matrix domain. The application of this model makes the calculation of the 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, reduce engineering risks, and lower subsequent maintenance costs, thereby improving engineering quality and safety.

[0088] 5. The method of the present invention is not only applicable to expansive soil road 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 specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation 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 in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

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 the saturated-unsaturated soil in the matrix domain, and the water content and water 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 ; 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 ; The atmospheric influence depth of the fracture domain d c and the atmospheric influence depth d m Combined with the above, the atmospheric influence depth d of expansive soil cutting is obtained. a .

2. The method for analyzing the atmospheric influence depth of expansive soil cuttings based on fracture dominant flow according to claim 1, characterized in that: The Richards equation is used to describe the water movement in the saturated-unsaturated soil in the matrix domain, and the water content and water head distribution at different time steps are calculated, including: Determine the total water head H in saturated-unsaturated soil; 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 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 get 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: 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 influence depth of expansive soil cuttings based on fracture dominant flow according to claim 2, characterized in that: 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 influence depth of expansive soil cuttings based on fracture dominant flow according to claim 2, characterized in that: In determining the total water head in saturated-unsaturated soil, atmospheric pressure is taken as the reference.

5. The method for analyzing the atmospheric impact depth of expansive soil cuttings based on fracture dominant flow according to claim 1, characterized in that: 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, and the motion wave equation is solved to determine the atmospheric influence depth d in the fracture domain. c include: Establish the power exponential relationship between the volume flux density q of the fracture dominant flow and the water content w of the macropore volume: q = kw 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 Among them, t is time and z is depth; Substituting the power exponential relationship representing the fracture dominant flow characteristics 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 moist front advance, and determine the atmospheric influence depth d of the fracture domain. c .

6. The method for analyzing the atmospheric influence depth of expansive soil cuttings based on fracture dominant flow according to claim 5, characterized in that: The motion wave equation is solved to obtain the depth and speed of the wet front advance, and the atmospheric influence depth d of the fracture domain is determined. 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, Solving the mass balance equation The water volume flux density q in the macropore domain is also 0. The wetting front wave velocity is expressed as 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 advancement process of the drainage front is obtained: d (t) = z0 + kw n (tt s ), the functional relationship of the tail front formation, where z0 is the initial wet front position, t s It's the moment when the rain stops; During the weakening phase of the moist front, at a specific depth z i At the 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 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.

7. The method for analyzing the atmospheric influence depth of expansive soil cuttings based on fracture dominant flow according to claim 5, characterized in that: 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 a pipe, the power exponential relationship between the volume flux density q and the macropore volume water content w is q∝w 2 ; For viscous saturated flow in a pipe, the power exponent n>2 in the power exponential relationship between the volume flux density q and the macropore volume water content w.

8. The method for analyzing the atmospheric impact depth of expansive soil cuttings based on fracture dominant flow according to claim 1, characterized in that: 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 include: Establish the Green-Ampt model, the basic equation is Among them, θ i is the initial soil moisture content, θ s is the saturated water content of soil, f is the soil pressure head in front of the wetting front, K s is the saturated permeability of the soil, F is the cumulative infiltration, and t is the time; Calculating the Wetting Front Depth Calculate the infiltration rate The wetting front depth z calculated according to the Green-Ampt model f and the infiltration rate i, which determines the water distribution and migration paths in the matrix domain and the fracture domain; Based on the rainfall duration and intensity, calculate the maximum wet front depth z at the end of the rainfall max ; The maximum wetting front depth z max As the atmospheric influence depth d m .

9. The method for analyzing the atmospheric influence depth of expansive soil cuttings based on fracture dominant flow according to claim 8, characterized in that: According to the drainage and evaporation effects in the later period of rainfall, the maximum wet front depth z is adjusted. max .

10. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: 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 9 is implemented.

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