Method and device for constructing equivalent pipeline flow model for underground water solute transport of intersecting fractures

Abstract

The invention discloses a method and a device for constructing an equivalent pipeline flow model for underground water solute transport of intersecting fractures, and belongs to the technical field of underground water pollution prevention and control and risk management and control. The method comprises the following steps: determining an intersection fracture groundwater solute migration conceptual model according to an intersection fracture typical condition, selecting a groundwater solute migration spatio-temporal evolution correlation characteristic variable, obtaining a groundwater solute migration mathematical control equation, and obtaining a groundwater solute migration spatio-temporal evolution numerical simulation system; and obtaining a crack groundwater solute transport equivalent dispersion quantitative model and a corresponding equivalent permeability and equivalent circular tube seepage section quantitative model, and further establishing a groundwater solute transport equivalent pipeline flow model. The method can provide powerful support for rapid prediction and early warning of large-scale complex medium groundwater pollution and effective risk management and control.

Description

Technical Field

[0001] The present invention belongs to the technical field of prediction, early warning and risk control of groundwater pollution in complex media, and specifically relates to a method and device for constructing an equivalent pipeline flow model of solute migration in intersecting fractured groundwater. Background Art

[0002] At present, in the prediction, early warning and risk assessment of groundwater solute pollution in fractured complex media, in order to obtain accurate and reliable results, the use of discrete fracture network numerical simulation system to simulate and evaluate groundwater pollution status and environmental risks is a commonly used quantitative method. However, in order to achieve accurate and reliable numerical simulation, it is necessary to comprehensively consider many influencing factors and complex evolution processes, especially the solute migration process of each fracture at a large scale and refinement, which is time-consuming, computationally resource-consuming, and even difficult to complete. In addition, there is a large uncertainty in the modeling and prediction of complex medium groundwater systems. The use of Monte Carlo and other methods for uncertainty assessment requires hundreds or thousands of numerical simulation tests, with huge or even unacceptable computational costs and low efficiency. Therefore, there is an urgent need for a practical, efficient, fast and reliable method for constructing a quantitative model of solute pollutant migration in intersecting fractured groundwater. Summary of the invention

[0003] The purpose of the present invention is to provide a method and device for constructing an equivalent pipeline flow model of solute transport in intersecting fractured groundwater, so as to solve the problems of large uncertainty in quantitative results, high cost and low efficiency in the prediction, early warning and risk control of groundwater pollution in complex fractured media in the prior art.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] In a first aspect, the present invention provides a method for constructing an equivalent pipeline flow model for groundwater solute transport in intersecting fractures, comprising:

[0006] Step A: Determine the conceptual model of the spatiotemporal evolution of groundwater solute transport in intersecting fractures under typical conditions and obtain the corresponding typical feature set, i.e., the typical condition framework, select the characteristic variables associated with the spatiotemporal evolution of groundwater solute transport (including solute concentration), obtain the mathematical control equations of groundwater solute transport in fractured media, and obtain the numerical simulation system of the spatiotemporal evolution of groundwater solute transport in fractured media;

[0007] Step B: Select the number of inlets and outlets of the intersecting fissures for groundwater seepage in the intersecting fissures respectively;

[0008] Step C: Determine the set of control parameters (hydraulic conductivity, diffusion and dispersion parameters, etc.) for the temporal and spatial evolution of groundwater solute transport V = [v1, v2, ..., v k ], select the range of each control parameter to form the control parameter range set U = [u1,u2,…u k ];

[0009] Step D: Select the change level of each control parameter, where the two end points of each control parameter change interval are mandatory level values, and the minimum change level of each control parameter is 2; obtain the basic typical scenario sampling of the spatiotemporal evolution of groundwater solute migration under a given condition framework based on the orthogonal test method or the full combination of control parameters, and generate the corresponding different control parameter value combinations of each typical scenario, i.e., parameter combinations;

[0010] Step E: Obtain the calculated values ​​of the characteristic variables associated with the fracture network topology structure corresponding to each basic typical scenario;

[0011] Step F: Based on the numerical simulation system of the spatiotemporal evolution of groundwater solute transport, obtain the simulated values ​​of the associated characteristic variables corresponding to each basic typical scenario and the calculated values ​​of each related associated characteristic variable (including head difference, intersection line inlet and outlet flow, etc.)

[0012] Step G: Collect all parameter combinations and corresponding simulated values ​​or calculated values ​​of associated characteristic variables to form a basic data set for modeling;

[0013] Step H: obtaining a preset number of scenario samples based on the preset scenario sampling number and the control parameter variable, obtaining a data enhancement scenario parameter combination, obtaining a data enhancement scenario simulation value or a calculated value of the associated characteristic variable corresponding to each scenario through the numerical simulation system and related calculations, and combining the data enhancement scenario parameter combination and the data enhancement scenario simulation value or the calculated value as a modeling enhancement data set;

[0014] Step I: Based on the modeling basic data set or the modeling basic data set and the modeling enhanced data set, respectively, a numerical simulation system is used to obtain the time-varying value of the average concentration of groundwater solutes at each outlet, and the corresponding equivalent dispersivity and equivalent average flow velocity are inverted according to the change value, and the equivalent permeability is obtained based on the equivalent average flow velocity and the corresponding hydraulic gradient; based on the digital modeling method, according to the modeling data set and the equivalent dispersivity and the equivalent permeability values, a quantitative model of the equivalent dispersivity and the equivalent permeability and the control parameter is established and optimized;

[0015] Step J: Validate the constructed quantitative model using a modeling enhancement data set or a collection of modeling enhancement data that has not been used in quantitative modeling and / or typical scenario physical model test data, where the model validation at least includes an equivalent dispersion quantization model;

[0016] Step K: Establish an equivalent pipeline flow conceptual model, determine the equivalent seepage cross-sectional area of ​​each pipeline in each scenario according to the basic modeling data set and the import and export flow rates of the corresponding scenarios and the equivalent average flow rate, and then establish a quantitative model of the equivalent seepage cross-sectional area of ​​each pipeline and the control parameter based on the basic modeling data set and the equivalent seepage cross-sectional area of ​​each pipeline and the digital modeling method;

[0017] Step L: For specific application scenarios, obtain the geometric parameters of intersecting fractures, establish a discrete fracture network model, obtain the structural parameters of the intersecting fracture network, and determine whether the typical feature set meets the given typical condition framework. If so, determine the distribution of each pipeline and the length of each pipeline based on the structural parameters of the intersecting fracture network, the characteristics of the intersecting fracture seepage field, and the equivalent pipeline flow conceptual model; further determine the values ​​of each related control parameter, and determine the equivalent pipeline cross-sectional area, the corresponding permeability of the permeable medium and the corresponding diffusion parameter based on the equivalent diffusion quantification model, the equivalent permeability quantification model, and the equivalent pipeline seepage cross-sectional area quantification model, and then establish the corresponding specific intersecting fracture groundwater solute transport equivalent pipeline flow model.

[0018] Furthermore, in step A, the conceptual model of the spatiotemporal evolution of groundwater solute migration under typical conditions is determined and the corresponding typical feature set, i.e., the typical condition framework, is obtained, including: determining the characteristics of the fracture morphology, determining the number of intersection lines and the number of inlets and outlets, determining the characteristics of the fracture surface, determining the characteristics of the topological structure of the fracture intersection, determining the characteristics of the change in the width of the groundwater seepage fracture, determining the characteristics of the groundwater flow state, and determining the characteristics of the change in the groundwater head in the fracture.

[0019] Furthermore, in step A, the characteristic variables associated with the spatiotemporal evolution of groundwater solute transport include: groundwater solute pollutant concentration, groundwater infiltration velocity, change in groundwater solute concentration at fracture intersections, and average groundwater solute concentration at fracture intersections; in step E, the characteristic variables associated with the fracture network topological structure include the mean value of each fracture network topological structure parameter and its value distribution, and the structural parameters include the number of inlet intersections, the number of outlet intersections, the equivalent seepage path length, intersection length, intersection position, and fracture disk diameter.

[0020] Furthermore, in step H, the preset number of scenario samples is obtained based on the preset scenario sampling number and the control parameter variables, including: selecting the number of random sampling, determining or selecting the random distribution type and corresponding distribution parameters applicable to each control parameter variable, completing the random number generation of the control parameter variables and thus forming a new parameter combination scenario.

[0021] Furthermore, in step J, if the modeling enhancement data set is used in the quantitative model modeling, a preset number of scenario samples are generated again based on the control parameter variables to obtain a data enhancement scenario parameter combination, and the data enhancement scenario simulation value or calculated value of the associated characteristic variable corresponding to each scenario is obtained through the numerical simulation system and related calculations. The data enhancement scenario parameter combination and the data enhancement scenario simulation value or calculated value are combined as the regenerated modeling enhancement data set.

[0022] Furthermore, in step K, the digital modeling method includes: a statistical analysis modeling method and a machine learning modeling method; the statistical analysis modeling method includes establishing a multivariate regression statistical model of the associated characteristic variables and all their controlled parameter factors and a multivariate regression statistical model of the associated characteristic variables and their main controlled parameter factors.

[0023] Furthermore, the multivariate regression statistical analysis modeling method includes: establishing a multivariate regression statistical model and directly giving the specific parameters of each pipeline, and establishing a multivariate regression statistical model and obtaining the average values ​​and distributions of the parameters of the pipeline flow model based on the multivariate regression statistical model, and then assigning an average value to the diffusion or randomly assigning a diffusion parameter to each pipeline.

[0024] Furthermore, in step K, establishing the equivalent pipeline flow conceptual model includes:

[0025] Keep the total flow rate of the fracture inlet equivalent, the total flow rate of the fracture outlet equivalent, the average solute concentration change characteristics of each inlet equivalent, and the average solute concentration change characteristics of each outlet equivalent;

[0026] Establish the connection characteristics of the pipelines between the inlet and outlet of the intersecting fractures, including whether they pass through the center point or the center area of ​​the fracture, and whether the solutes in each pipeline are mixed through the center point or the center area of ​​the fracture and the degree of mixing;

[0027] Determine the number of equivalent pipes used for each inlet intersection line and the number of equivalent pipes used for each outlet intersection line of intersecting fracture groundwater;

[0028] Determine the generalization method of the equivalent infiltration path imposed on the equivalent pipe between the inlet and outlet of the fractured groundwater and the corresponding calculation method of the equivalent hydraulic gradient.

[0029] Furthermore, in step L, the establishment of a discrete fracture network model includes: a deterministic discrete fracture network model and a randomly distributed parameter discrete fracture network model.

[0030] In a second aspect, the present invention provides a device for constructing an equivalent pipeline flow model for groundwater solute transport in intersecting fractures, comprising:

[0031] The module for constructing the conceptual model of solute transport in intersecting fracture groundwater is used to select the associated characteristic variables of the groundwater environment and construct the conceptual model of the spatiotemporal evolution of the corresponding groundwater environment system under the framework of typical conditions;

[0032] A numerical simulation module for intersecting fracture generation and solute migration, for obtaining control parameter variables that affect the spatiotemporal evolution of associated characteristic variables based on the spatiotemporal evolution conceptual model, the numerical model and the numerical simulation system, and obtaining simulated or calculated values ​​of associated characteristic variables in typical scenarios;

[0033] The module for constructing the equivalent parameter quantitative model of fracture solute transport pipeline flow is used to obtain different typical scenarios composed of different control parameter combinations of the groundwater environment system according to the given preset number of typical scenarios, and to establish the equivalent parameter quantitative model of fracture solute transport pipeline flow, including statistical model and machine learning model;

[0034] The module for constructing and applying the equivalent pipeline flow model for solute transport in intersecting fractures is used to construct the conceptual model of equivalent pipeline flow for solute transport in groundwater in intersecting fractures, and supports the application of the equivalent pipeline flow model for solute transport in groundwater in intersecting fractures at different scales.

[0035] Based on the above technical solution, the embodiments of the present invention can at least produce the following technical effects:

[0036] The method for constructing an equivalent pipeline flow model for solute transport in intersecting fractured groundwater provided by the present invention systematically solves key problems such as the equivalent diffusion of the basic structural units of the fracture network based on the topological structure of 3D random DFNs. At the same time, it provides and establishes an effective and reliable model for estimating key parameters of pollutant transport and diffusion processes at field scales of tens to hundreds of meters, and proposes a way and method for effectively upscaling modeling of pollutant transport in fractured media. It can efficiently realize the rapid and reliable prediction of the spatiotemporal distribution of solute pollutants in intersecting fractured groundwater in different application scenarios under the premise of meeting a given condition framework, significantly improve the accuracy, efficiency and practicality of the evaluation and prediction of the spatiotemporal evolution state of groundwater pollution in complex media and the spatiotemporal distribution of pollutants, and can provide strong support for the rapid prediction, early warning and effective risk control of groundwater pollution in complex media at larger scales. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0038] Figure 1 is the best fitting curve of each test data in the embodiment of the present invention;

[0039] Figure 2 is a bar graph comparing the predicted value of equivalent diffusivity by regression with the experimental fitting value in the embodiment of the present invention;

[0040] Figure 3 It is a conceptual model of equivalent pipeline flow of cross-fracture solute transport in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0042] This embodiment provides a practical and feasible dimensionality reduction generalization modeling method and parameter assignment model for quantifying the transport of groundwater pollutants in a disk fracture network, making it possible to efficiently and quickly calculate the solute transport in larger-scale fractured bedrock groundwater.

[0043] 1. Establishment of a conceptual model for the spatiotemporal evolution of solute transport in intersecting fractures

[0044] 1) Determine the crack morphology: disc morphology;

[0045] 2) Determine the number of intersections and inlets and outlets: one in and one out;

[0046] 3) Determine the characteristics of the fracture surface: smooth;

[0047] 4) Determine the topological structural characteristics of the intersection of the cracks: including random intersection positions, rotatable intersections, intersection sizes within the diameter of the crack disk, and arbitrary intersection angles;

[0048] 5) Determine the width variation of different cracks for groundwater seepage: 1-5cm;

[0049] 6) Determine the characteristics of groundwater flow regime: Darcy flow;

[0050] 7) Determine the characteristics of groundwater head changes in the fracture: according to the regional groundwater hydraulic gradient of 0.1%-1%;

[0051] 2. Mathematical control equations for groundwater solute transport in intersecting fractures and selection of numerical simulation system

[0052] Governing equations:

[0053]

[0054] Saturated hydraulic conductivity K f [LT -1 ]:

[0055]

[0056] Where: is a two-dimensional gradient operator defined on the crack plane, b is the equivalent gap width [L], μ is the hydrodynamic viscosity coefficient (ML -1 T -1 ); p is the fluid density (ML -3 ); g is the acceleration due to gravity (LT -2 ); and Z f are the pressure head and elevation head in the fracture [L], Γ f is the volumetric fluid exchange rate (L -3 T).

[0057] When only convection and diffusion processes are considered, the two-dimensional transport governing equation is given as follows:

[0058]

[0059] Where: C f is the concentration in the crack [ML -3 ],u f is the fluid flux [LT -1 ], D f is the hydrodynamic diffusion coefficient of the fracture [LT -2 ].

[0060] Select DfnWorks and PFLOTRAN integrated numerical simulation system.

[0061] 3. Construction of equivalent diffusion multivariate regression statistical model for groundwater solute transport in intersecting fractures

[0062] (1) Equivalent dispersion identification method

[0063] Whether reducing the disk model to a one-dimensional pipe flow model or performing numerical calculations on a coarse mesh, obtaining the equivalent dispersion value at the outlet is the key to solving the above problems. This equivalent parameter reflects the comprehensive dispersion effect of the solute due to the complex velocity distribution and seepage path differences in the two-dimensional plane of the fracture. Using the one-dimensional ADE equation analytical solution, the equivalent dispersion and equivalent average velocity are obtained by fitting the average solute concentration process line at the fracture outlet:

[0064]

[0065] The initial and boundary conditions are as follows:

[0066] C(x,0)=0x≥0; C(0,t)=C0t≥0; C(∞,t)=0t≥0

[0067] Where C is the solute concentration (ML -3 ); x represents the distance between the observation point and the pollution source (L); t is the time (T); Co is the initial concentration (ML-3 );υ represents the average flow velocity of the seepage path (L / T); D L Representative diffusion coefficient (LT -2 ), whose value is equal to the product of the diffusion coefficient α(L) and the average flow velocity υ. In this embodiment, α obtained by fitting the equivalent penetration curve is used. eq , while maintaining is consistent with the estimated average V in the respective Lagrangian percolation region. In addition, to ensure the subsequent application of α eq The spatial coordinates of the key computing nodes remain unchanged, and d in With d ot The sum represents .

[0068] (2) Typical scenario design of groundwater solute transport in intersecting fractures

[0069] In order to explore the influence of the geometric parameters of the disc-shaped crack on the equivalent dispersivity, a 7-factor mixed level L36 (2^5 3^2) orthogonal numerical model was constructed. The equivalent dispersivity and equivalent average velocity fitting results of 36 groups of models are shown in the table below. Here, the intersection length L- and the distance d- from the intersection to the center of the circle are normalized and divided by the diameter D and represented by Lr- and dr- respectively.

[0070] Table 1 Orthogonal test scenario design

[0071]

[0072] In order to more accurately estimate the influence of the other six control variables on the equivalent dispersion, the method of full combination of control variables is used to expand the sample data. The control variables D (100, 300, 500 cm) and θ (π / 2, 3π / 4, π) are set as the main control factors at 3 levels, Lr in (0.2,0.5), Lr ot (0.2,0.5), dr in (0.3,0.43) and dr ot (0.3, 0.43) were set as 2 levels respectively, and a total of 144 sets of numerical models were established after all control parameters were combined. The above 36 orthogonal test models and 144 models were regressed with 7 control parameters (control factors) to obtain the following equation: Equation (5) represents the statistical regression relationship between each control parameter (full factor) and the equivalent dispersion. Their R 2 It is 0.911, the equation fits the data well, and the full factor regression model shows a high degree of fit.

[0073]

[0074] 4. Numerical simulation verification of multivariate regression statistical model of groundwater solute transport in intersecting fractures

[0075] Sixteen new numerical models were added to verify the prediction ability and accuracy of the above regression equation, and the mean relative error (MRE) of the 16 verified models was calculated. The control parameter D was expanded to five levels from 100 cm to 500 cm, and θ was also increased to five levels (π, 8π / 9, 3π / 4, 11π / 18, π / 2). The levels of the other four control parameters were uniformly set to: dr in =0.43, dr ot =0.3, Lr in =0.5, Lr ot =0.2.

[0076]

[0077] y i is the true value; is the predicted value.

[0078] By applying the equivalent diffusivity simulation values ​​of the 16 groups of models and the predicted values ​​of the regression equation to obtain the MRE, the MRE was 12%. This shows that the full factor regression equation has a good predictive ability for interpolated data.

[0079] 5. Physical simulation test verification of typical scenarios of multivariate regression statistical model of groundwater solute transport in intersecting fractures

[0080] In addition, the reliability of the statistical prediction model was further verified through physical experiments under four different typical conditions (Exp. 1 to Exp. 4). Figure 1 The values ​​of the main parameters under each test condition are given. These four groups of tests respectively verify the influence of b, Q, θ, and L on the equivalent dispersivity. The distribution points of the solute concentration breakthrough process obtained by fitting the test with the ADE equation are Figure 1 The best fitting curves of each test data are shown. In addition, the above test parameters are substituted into formula (5) to obtain the regression equivalent diffusion prediction value, which is compared with the test fitting value. The results are shown in Figure 2As shown in the figure, compared with the physical test results, the equivalent dispersivity calculated by the regression equation has achieved a satisfactory agreement. It should be pointed out that: in Experiment 1 (Exp.1) and Experiment 2 (Exp.2), the flow velocity in the fracture is increased or decreased by changing the gap width and hydraulic gradient, respectively, when the average Reynolds number is small (<100). The spatial distribution characteristics of the flow velocity in the fracture plane have not changed, so the equivalent dispersivity result has not changed substantially. It can be seen from the results of Experiment 3 (Exp.3) that the angle has a significant effect on the dispersivity, which is highly consistent with the conclusion obtained by numerical simulation. Due to the limitations of the device structure, the values ​​of Lr1 (=0.12), dr and D in Experiment 4 (Exp.4) belong to parameter extrapolation for the regression model in this embodiment, and its equivalent dispersivity still agrees well with the regression equation (5), which proves that the full factor (all control parameters) regression equation has a good extrapolation ability.

[0081] 6. Construction of the conceptual model of equivalent pipeline flow for groundwater solute transport in intersecting fractures

[0082] An equivalent pipeline flow model is established. Through the center of the circle, the corresponding inlet and outlet pipeline model dispersions are the same, and k is the same. According to the equivalent dispersion, k and A statistical model, the equivalent pipeline model k, A in, A out and dispersion of each channel are calculated through known control parameters.

[0083] One of the applications of the regression model of this embodiment is to try to transform the convection-diffusion process in the crack surface of a two-dimensional disk into a one-dimensional circular tube problem while ensuring a high degree of accuracy.

[0084] A complete description of the one-dimensional convection-diffusion process also requires the determination of the equivalent permeability K eq Equivalent seepage cross-sectional area A eq , to ensure the conservation of mass between computing nodes, that is, the flow equivalence and diffusion effect are equivalent at the same time.

[0085] 7. Construction of statistical model of equivalent hydrodynamic parameters for pipeline flow model of groundwater solute transport in intersecting fractures

[0086] For the disk fissure, the equivalent average flow velocity per unit hydraulic gradient, that is, the equivalent permeability, is established, and the calculation formula is as follows:

[0087]

[0088] At the same time, according to the equivalent average flow velocity and total flow rate, the equivalent seepage cross-sectional area A is calculated. eq , and its calculation formula is as follows:

[0089]

[0090] The variance analysis was performed on the influencing factors of these two equivalent hydraulic parameters, among which b, dr and Lr had a significant effect on Keq The influence is significant, which is quite different from the traditional cubic law derived from parallel plates. eq The size of depends not only on the gap width, but also on other fracture geometric parameters, which indicates that if the a priori formula under ideal conditions is directly used in the process of dimensionality reduction and generalization, the solute transport results will be misestimated.

[0091] Select all factors and eq and A eq Performing multiple regression statistics, we obtain regression equations (9) and (10):

[0092]

[0093] R 2 =0.998

[0094]

[0095] R 2 =0.994

[0096] 8. Large-scale application of the equivalent pipe flow model for groundwater solute transport in intersecting fractures

[0097] In the application research of this embodiment, a larger-scale application case of the equivalent pipeline flow model of intersecting fracture groundwater solute transport was investigated: the seepage area was 20m x20m x 20m, and the typical feature set met the typical condition framework of the conceptual model of the spatiotemporal evolution of intersecting fracture groundwater solute transport given in this embodiment.

[0098] Specifically, the groundwater seepage in the fracture network is a steady flow, the inflow and outflow boundaries are both constant head boundaries, and the pollutant concentration at the inflow boundary is set to a constant concentration considering the continuous stable pollution source. The dispersion of each pipeline in the equivalent pipeline flow model is assigned a specific dispersion value calculated based on the statistical model obtained in the study of this embodiment.

[0099] The results show that the equivalent pipe flow model achieves high accuracy in terms of cross-sectional average concentration on the outflow boundary, compared with the numerical simulation results of pollutant transport in the discrete fracture network model. However, if no equivalent dispersion value is assigned to each pipe, the simulation results of pollutant concentration will have significant errors.

[0100] It is worth noting that on a computer equipped with an i9-12900k processor and 96GB RAM, it takes more than 5000 seconds to simulate solute transport in a disk-like fracture network with a domain length of 30 meters. In contrast, using the channelized fracture network model, the calculation time on a common laptop equipped with an i5-13500H processor and 32GB RAM is less than 5 seconds, indicating that its computational efficiency is more than 1000 times higher than conventional DFN numerical simulations.

[0101] This embodiment systematically solves key problems such as the equivalent diffusion of the basic structural units of the fracture network based on the topological structure of 3D random DFNs. At the same time, it provides and establishes an effective and reliable model for estimating key parameters of pollutant transmission and diffusion processes at field scales of tens to hundreds of meters, and proposes ways and methods for effectively upscaling modeling of groundwater pollutant migration in fractured media. It improves the accuracy, efficiency and practicality of quantifying the spatiotemporal evolution of complex groundwater pollutant migration in fractured media, provides strong support for groundwater pollution assessment and risk control, and has important practical value.

[0102] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of the present invention to be protected is defined by the attached claims and their equivalents.

Claims

1. A method for constructing an equivalent pipeline flow model for groundwater solute transport in intersecting fractures, characterized in that: include: Step A: Determine the conceptual model of the spatiotemporal evolution of groundwater solute transport in fractured groundwater under typical conditions and obtain the corresponding typical feature set, i.e., the typical condition framework; select the characteristic variables associated with the spatiotemporal evolution of groundwater solute transport; obtain the mathematical control equations of groundwater solute transport in fractured media; and obtain the numerical simulation system of the spatiotemporal evolution of groundwater solute transport in fractured media; Step B: Select the number of inlets and outlets of the intersecting fissures for groundwater seepage in the intersecting fissures respectively; Step C: Determine the set of control parameters V = [v1, v2, ..., v k ], select the range of each control parameter to form the control parameter range set U = [u1,u2,…,u k ]; Step D: Select the change level of each control parameter, obtain the basic typical scenario sampling of the spatiotemporal evolution of groundwater solute transport, and generate the corresponding different control parameter value combinations of each typical scenario, i.e., parameter combinations; Step E: Obtain the calculated values ​​of the characteristic variables associated with the fracture network topology structure corresponding to each basic typical scenario; Step F: Based on the numerical simulation system of spatiotemporal evolution of groundwater solute transport, obtain the simulated values ​​of the associated characteristic variables corresponding to each basic typical scenario and the calculated values ​​of each related associated characteristic variable; Step G: Collect all parameter combinations and corresponding simulated or calculated values ​​of associated characteristic variables to form a basic data set for modeling; Step H: obtaining a preset number of scenario samples based on a preset scenario sampling number and a control parameter variable, obtaining a data enhancement scenario parameter combination, obtaining a data enhancement scenario simulation value or a calculated value of an associated characteristic variable corresponding to each scenario through a numerical simulation system and related calculations, and combining the data enhancement scenario parameter combination and the data enhancement scenario simulation value or the calculated value as a modeling enhancement data set; Step I: Based on the modeling basic data set or the modeling basic data set and the modeling enhanced data set, respectively, a numerical simulation system is used to obtain the time-varying value of the average concentration of groundwater solutes at each outlet, and the corresponding equivalent dispersivity and equivalent average flow velocity are inverted according to the change value, and the equivalent permeability is obtained based on the equivalent average flow velocity and the corresponding hydraulic gradient; based on the digital modeling method, according to the modeling data set and the equivalent dispersivity and the equivalent permeability, a quantitative model of the equivalent dispersivity and the equivalent permeability and the control parameter is established and optimized; Step J: Validate the constructed quantitative model using a modeling enhancement data set or a collection of modeling enhancement data that has not been used in quantitative modeling and / or typical scenario physical model test data, where the model validation at least includes an equivalent dispersion quantization model; Step K: Establish an equivalent pipeline flow conceptual model, determine the equivalent seepage cross-sectional area of ​​each pipeline in each scenario according to the basic modeling data set and the import and export flow rates of the corresponding scenarios and the equivalent average flow rate, and then establish a quantitative model of the equivalent seepage cross-sectional area of ​​each pipeline and the control parameter based on the basic modeling data set and the equivalent seepage cross-sectional area of ​​each pipeline and the digital modeling method; Step L: For specific application scenarios, obtain the geometric parameters of intersecting fractures, establish a discrete fracture network model, obtain the structural parameters of the intersecting fracture network, and determine whether the typical feature set meets the given typical condition framework. If so, determine the distribution of each pipeline and the length of each pipeline based on the structural parameters of the intersecting fracture network, the characteristics of the intersecting fracture seepage field, and the equivalent pipeline flow conceptual model; further determine the values ​​of each related control parameter, and determine the equivalent pipeline cross-sectional area, the corresponding permeability of the permeable medium and the corresponding diffusion parameter based on the equivalent diffusion quantification model, the equivalent permeability quantification model, and the equivalent pipeline seepage cross-sectional area quantification model, and then establish the corresponding specific intersecting fracture groundwater solute transport equivalent pipeline flow model.

2. The construction method according to claim 1, characterized in that: In step A, the conceptual model of the spatiotemporal evolution of groundwater solute migration under typical conditions is determined and the corresponding typical feature set, i.e., the typical condition framework, is obtained, including: determining the fracture morphological characteristics, determining the number of intersection lines and the number of inlets and outlets, determining the fracture surface characteristics, determining the fracture intersection topological structure characteristics, determining the groundwater seepage fracture width variation characteristics, determining the groundwater flow state characteristics, and determining the groundwater head variation characteristics in the fractures.

3. The construction method according to claim 1, characterized in that: In step A, the characteristic variables associated with the spatiotemporal evolution of groundwater solute transport include: groundwater solute pollutant concentration, groundwater infiltration velocity, change in groundwater solute concentration at fracture intersections, and average groundwater solute concentration at fracture intersections; in step E, the characteristic variables associated with the fracture network topological structure include the mean value of each fracture network topological structure parameter and its value distribution, and the structural parameters include the number of inlet intersections, the number of outlet intersections, the equivalent seepage path length, intersection length, intersection position, and fracture disk diameter.

4. The construction method according to claim 1, characterized in that: In step H, the preset number of scenario samples is obtained based on the preset scenario sampling number and the control parameter, including: selecting the number of random sampling, determining or selecting the random distribution type and corresponding distribution parameters applicable to each control parameter, completing the random number generation of the control parameter to form a new parameter combination scenario.

5. The construction method according to claim 1, characterized in that: In step J, if the modeling enhancement data set is used in the quantitative model modeling, step H is repeated to use the data enhancement scenario parameter combination and the data enhancement scenario simulation value or calculated value collection as the regenerated modeling enhancement data set.

6. The construction method according to claim 1, characterized in that: In step K, the digital modeling method includes: a statistical analysis modeling method and a machine learning modeling method; the statistical analysis modeling method includes establishing a multivariate regression statistical model of the associated characteristic variables and all their controlled parameter factors and a multivariate regression statistical model of the associated characteristic variables and their main controlled parameter factors.

7. The construction method according to claim 6, characterized in that: The multivariate regression statistical analysis modeling method includes: establishing a multivariate regression statistical model and directly giving the specific parameters of each pipeline, and establishing a multivariate regression statistical model and obtaining the average value and distribution of each parameter of the pipeline flow model based on the multivariate regression statistical model, and then assigning an average value to the dispersion or randomly assigning a dispersion parameter to each pipeline.

8. The construction method according to claim 1, characterized in that: In step K, the establishment of an equivalent pipeline flow conceptual model includes: Keep the total flow rate of the fracture inlet and outlet equivalent, the average solute concentration change characteristics of each inlet equivalent, and the average solute concentration change characteristics of each outlet equivalent; Establish the connection characteristics of the pipelines between the inlet and outlet of the intersecting fractures, including whether they pass through the center point or the center area of ​​the fracture, and whether the solutes in each pipeline are mixed through the center point or the center area of ​​the fracture and the degree of mixing; Determine the number of equivalent pipes used for each inlet intersection line and the number of equivalent pipes used for each outlet intersection line of intersecting fracture groundwater; Determine the generalization method of the equivalent infiltration path imposed on the equivalent pipe between the inlet and outlet of the fractured groundwater and the corresponding calculation method of the equivalent hydraulic gradient.

9. The construction method according to claim 1, characterized in that: In step L, the establishment of a discrete fracture network model includes: a deterministic discrete fracture network model and a randomly distributed parameter discrete fracture network model.

10. A device for constructing an equivalent pipeline flow model of groundwater solute transport in intersecting fractures, used to implement the construction method according to any one of claims 1 to 8, characterized in that: include: The module for constructing the conceptual model of solute transport in intersecting fracture groundwater is used to select the associated characteristic variables of the groundwater environment and construct the conceptual model of the spatiotemporal evolution of the corresponding groundwater environment system under the framework of typical conditions; A numerical simulation module for intersecting fracture generation and solute migration, for obtaining control parameter variables that affect the spatiotemporal evolution of associated characteristic variables based on the spatiotemporal evolution conceptual model, the numerical model and the numerical simulation system, and obtaining simulated or calculated values ​​of associated characteristic variables in typical scenarios; The module for constructing the equivalent parameter quantitative model of fracture solute transport pipeline flow is used to obtain different typical scenarios composed of different control parameter combinations of the groundwater environment system according to the given preset number of typical scenarios, and to establish the equivalent parameter quantitative model of fracture solute transport pipeline flow, including statistical model and machine learning model; The module for constructing and applying the equivalent pipeline flow model for solute transport in intersecting fractures is used to construct the conceptual model of equivalent pipeline flow for solute transport in groundwater in intersecting fractures, and supports the application of the equivalent pipeline flow model for solute transport in groundwater in intersecting fractures at different scales.

Images