Discrete-continuous coupling-based concrete faced rockfill dam construction process simulation method

Abstract

The invention discloses a concrete faced rockfill dam construction process simulation method based on discrete-continuous coupling. A continuous model is constructed according to the size and material parameters of a concrete faced rockfill dam; simulating graded loading and staged water storage processes through the continuous model, and setting boundary conditions for the continuous model; determining a discrete domain range, a rockfill material contact model and mesoscopic material parameters; constructing a Brick discrete element particle set outside the continuous model, performing pre-balance calculation on the Brick discrete element particle set to enable the average unbalance ratio of the Brick discrete element particle set to reach 1 * 10 <-5 >, and storing a balance result in a binary format; the construction process is simulated, and in the coupling process, a finite difference method is adopted to simulate the rock-fill dam body which is not coupled in the early stage; and when entering a loading step of a coupling region, importing a Brick discrete element particle set, and establishing discrete-continuous coupling model calculation. By combining the continuous model and the discrete model, the simulation result is more accurate.

Description

Technical Field

[0001] The invention belongs to the technical field of numerical simulation of water conservancy engineering structures, and particularly relates to a construction process simulation method of a face rockfill dam based on discrete-continuous coupling. Background Art

[0002] With the rapid increase in the demand for water resources and the increasing difficulty of energy development in social development, the construction of reservoir dams in various countries around the world is developing towards high-scale development, and the hydrological, topographical, geological and other dam construction conditions are becoming more and more complex. Among them, the face rockfill dam is often used as a recommended dam type for pumped storage power stations and water conservancy and hydropower projects due to its low cost and good durability and impermeability. It is developing towards a 300m dam height. However, at the same time, as a granular accumulation structure composed of a large amount of rockfill materials, the deformation state of the face rockfill dam is affected by the microscopic mechanical behavior of rockfill materials such as crushing and anisotropy. Its overall structure shows mechanical characteristics such as discontinuity and strong contact dissipation, which is prone to engineering problems such as dam deformation exceeding expectations and damage to anti-seepage structures. In this regard, it is urgent to deepen the understanding of the deformation characteristics of rockfill materials in order to accurately predict the deformation state of face rockfill dams and serve the safety state analysis and control of rockfill dams. Summary of the invention

[0003] The purpose of the present invention is to provide a method for simulating the construction process of a concrete face rockfill dam based on discrete-continuous coupling, and to make the simulation result more accurate by combining a continuous model with a discrete model.

[0004] The technical solution adopted by the present invention is a construction process simulation method of a face rockfill dam based on discrete-continuous coupling, which is specifically implemented in the following steps: Step 1, construct a continuous model according to the size and material parameters of the concrete face rockfill dam; Step 2, simulating the process of graded loading and staged water storage through a continuous model and setting boundary conditions for the continuous model; Step 3, determine the discrete domain range, rockfill contact model and mesoscopic material parameters; Step 4: construct a Brick discrete element particle set with the same volume as the discrete domain outside the continuous model, and perform a pre-balance calculation on the Brick discrete element particle set so that the average imbalance ratio of the Brick discrete element particle set reaches 1×10 -5 , the balancing results are stored in binary format; Step 5, simulate the construction process. During the coupling process, the finite difference method is used to simulate the rockfill dam body that is not coupled in the early stage. When entering the loading step of the coupling area, the pre-balanced Brick discrete element particle set is imported to quickly establish the discrete-continuous coupling model calculation.

[0005] The present invention is also characterized in that: In step 1, the dimension parameters of the panel rockfill dam are the dimension parameters of the cross section of the panel rockfill dam. The cross section of the panel rockfill dam consists of the dam body contour line and the foundation contour line, wherein the dam body contour line parameters include the dam body height, dam crest width, dam body slope ratio, and toe plate size; the foundation contour line parameters include the upstream and downstream heights of the foundation and the length of the original ground line.

[0006] In step 1, the material parameters of the face rockfill dam include the material constitutive models and macroscopic mechanical parameters of the foundation, toe plate, face plate and different partitions of the rockfill dam.

[0007] In step 2, the boundary condition is set specifically as follows: the bottom of the continuous model is set as a fixed boundary of the continuous model.

[0008] In step 3, the discrete domain range is determined as follows: the construction process is simulated by using the graded loading method, the settlement distribution cloud map of the panel rockfill dam under various levels of load is calculated, and the discrete domain is set at the maximum settlement position, representative partition, and area with large deformation gradient.

[0009] In step 3, a linear contact model is used to reflect the microscopic characteristics of rockfill materials.

[0010] Step 4 is as follows: Step 3 After determining the discrete domain position, set the selected grid to "Null" unit; Step 4.1, establish a discrete element model of the coupling part in a new file, and the discrete domain is a rectangle and larger than the discrete domain size in step 3; Step 4.2, establish Wall in the discrete domain. The x coordinate and width of Wall are consistent with those of Null cell, and its height is higher than that of Nall cell. Step 4.3, the prototype gradation of the rockfill material is expanded, and particles with a diameter of less than 5 cm are cut off; at the same time, the minimum particle size for particle crushing is set to 50 cm; Step 4.4, generate discrete particles that are all balls according to the grading, then set the common rockfill material shape as a template, fill the template with balls, and adjust the number of particles and smoothness; Step 4.5, using filled Clump particles to replace rockfill materials with a particle size greater than 50 cm, and replacing Clump with crushable Cluster particles; Step 4.6, setting the porosity of the rockfill material to 0.3-0.4; Step 4.7, the default contact setting is linear contact and the initial density, damping, normal stiffness, tangential stiffness and friction coefficient of the particles generated in the rectangular area are set; the gravitational acceleration is set so that the ratio of the average unbalanced force to the average contact force is less than 1×10 -5 Standard balance particles; Step 4.8, after calculating the equilibrium, initialize the particle displacement, velocity, and contact force, delete the Wall, and export the calculated Brick as a binary file.

[0011] Step 5 is as follows: Step 5.1, before reaching the coupling position, the construction simulation is carried out according to the graded structure, and the calculation termination condition for each layer is that the ratio of the sum of the average unbalanced force and the average contact force is less than 1×10-5; Step 5.2, when the coupling position is reached, select the large strain mode, set the coupling domain, and the coupling domain is larger than the established Brick range; the surface in contact with the continuous domain is set as Wall-Zone, and the front and back are set as Wall; Step 5.3, import the pre-balanced Brick into the coupling position, delete the redundant particles and perform discrete-continuous coupling calculation; Step 5.4, repeat the above loading process until the construction is completed, thus realizing the construction process simulation of the concrete face rockfill dam.

[0012] The beneficial effects of the present invention are: 1. The construction process simulation method of the face rockfill dam based on the discrete-continuous coupling method of the present invention can be extended to other civil engineering and geotechnical engineering fields. Based on the external particle introduction method, the ratio of the sum of the average unbalanced force and the average contact force is less than 1×10 -5 The coupled model of the panel rockfill dam can be used to simulate the construction process. The step-by-step loading of the dam and the phased water storage process can be considered in the actual construction. It can effectively simulate the nonlinear behavior of rockfill materials and reflect the complex mechanical properties in actual engineering. It can analyze the dynamic response of the dam body under different construction stages and external loads to help understand the mechanical behavior during construction and water storage. Physical model tests are often very cost-effective and time-consuming. The use of discrete-continuous coupling simulation is not limited by laboratory tests and is flexible and scalable. It can simultaneously consider the microscopic interaction between particles and the macroscopic response of the overall structure to provide more accurate simulation results. During the simulation, the settlement, displacement and stress distribution of the dam body can be monitored in real time, providing important data support for the construction process.

[0013] 2. This invention gives full play to the advantages of two types of numerical simulation methods. It can not only obtain the structural properties of rockfill dams such as macroscopic deformation and stress in a large continuous domain, but also analyze the microscopic deformation mechanism of rockfill materials in a discrete domain, achieving a good balance between macroscopic and microscopic analysis and computational efficiency. The research results have important reference value for understanding and predicting the mechanical behavior of rockfill dams during operation, optimizing design and construction control, and ensuring dam safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1It is a schematic diagram of the coupling model of different parts of the face rockfill dam in the construction process simulation method of the face rockfill dam of the present invention; Figure 2 It is a dam body material partition diagram of the maximum cross section of the face rockfill dam in the face rockfill dam construction process simulation method of the present invention; Figure 3 It is a schematic diagram of the loading sequence of the face rockfill dam in the construction process simulation method of the face rockfill dam of the present invention; Figure 4 It is a particle gradation curve of rockfill material in the construction process simulation method of a face rockfill dam of the present invention; Figure 5 It is a schematic diagram comparing the dam body deformation of the continuous model and the continuous-discontinuous coupling model in the construction process simulation method of the face rockfill dam of the present invention; Figure 6 It is a schematic diagram comparing the measured settlement value of the ES2 measuring line with various calculated values ​​when the water storage is completed in the construction process simulation method of the concrete face rockfill dam of the present invention; Figure 7 It is a schematic diagram comparing the dam body stress of the continuous model and the continuous-discontinuous coupling model in the construction process simulation method of the face rockfill dam of the present invention; Figure 8 It is a schematic diagram of the force chain distribution in the discrete domain of different parts of the dam body in the construction process simulation method of the face rockfill dam of the present invention; Fig. 9 It is a schematic diagram of the variation trend of the second invariant of the partial fabric tensor in the construction process simulation method of the face rockfill dam of the present invention; Fig.10 It is a schematic diagram of the sliding contact ratio variation process of different parts of the face rockfill dam in the face rockfill dam construction process simulation method of the present invention; Fig.11 It is a schematic diagram of normal contact distribution in the method for simulating the construction process of a face rockfill dam of the present invention; Fig.12 It is a schematic diagram of two-dimensional statistical distribution of average normal contact force of rockfill materials at different positions and at different times in the construction process simulation method of a face rockfill dam according to the present invention; Fig.13 It is a schematic diagram of two-dimensional statistical distribution of average tangential contact force of rockfill materials at different positions and at different times in the construction process simulation method of a face rockfill dam according to the present invention; Fig.14 It is a schematic diagram of the change of coordination numbers of rockfill materials at different positions during service life in the method for simulating the construction process of a face rockfill dam according to the present invention. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0016] Example 1 The method for simulating the construction process of a concrete face rockfill dam based on discrete-continuous coupling disclosed in this embodiment is specifically implemented according to the following steps: Step 1: Build a continuous model based on the size and material parameters of the face rockfill dam. The modeling objects include the concrete face, transition layer (2A), cushion layer (3A), main rockfill area (3BⅠ, 3BⅡ), secondary rockfill area (3C), and dam foundation cover layer. The model takes into account the stages of dam filling and water storage. Step 2, simulating the graded loading and phased water storage process through a continuous model and setting boundary conditions for the continuous model; in this embodiment, graded loading is used to simulate the dam filling, concrete panel pouring and water storage process, and the entire dam body construction and water storage process is divided into 31 levels; the dam body construction process is divided into 27 levels; the 28th level is the concrete panel pouring; the water storage period is the 29th-31st level loading, and each loading is 35m water load.

[0017] Step 3, determine the discrete domain range, rockfill contact model and mesoscopic material parameters; Step 4: To speed up the calculation process, a pre-balance strategy is used to generate rockfill particles. A Brick discrete element particle set with the same volume as the discrete domain is constructed outside the continuous model. The Brick discrete element particle set is pre-balanced to make the average imbalance ratio of the Brick discrete element particle set reach 1×10 -5 , the balance results are stored in binary format, which is convenient for subsequent quick import; Step 5, simulate the construction process. During the coupling process, the finite difference method is used to simulate the rockfill dam body that is not coupled in the early stage. When entering the loading step of the coupling area, the pre-balanced Brick discrete element particle set is imported to quickly establish the discrete-continuous coupling model calculation.

[0018] The present invention can better simulate the construction and water storage process of the face rockfill dam, as well as the macro- and micro-mechanical behaviors such as the crushing and sliding of the rockfill material granular body, realize the cross-scale correlation between the face rockfill dam and the rockfill material, and further reveal the evolution mechanism of the micro-mechanical properties of different parts of the face rockfill dam during its service life. It has important theoretical significance for mastering the mechanical properties of the rockfill material and feeding back the deformation behavior of the rockfill dam.

[0019] Example 2 On the basis of Example 1, in step 1, the dimension parameters of the panel rockfill dam are the dimension parameters of the cross section of the panel rockfill dam. The cross section of the panel rockfill dam consists of the dam body contour line and the foundation contour line, wherein the dam body contour line parameters include the dam body height, dam crest width, dam body slope ratio, and toe plate size; the foundation contour line parameters include the upstream and downstream heights of the foundation and the length of the original ground line. In this embodiment, the normal water storage level of the panel rockfill dam is 2005.00m, the verified flood level is 2008.00m, and the total storage capacity is 620 million m3. The dam crest elevation is 2010.00m, the maximum dam height is 139.00m, the dam crest length is 424.00m, and the dam crest width is 10m.

[0020] Example 3 On the basis of Example 1, Figure 2 As shown in Figure 1, in step 1, the material parameters of the face rockfill dam include the material constitutive models and macroscopic mechanical parameters of the foundation, toe plate, face plate and different partitions of the rockfill dam. The concrete face plate adopts a linear elastic model, and the Young's modulus is 2.84×10 4 MPa, Poisson's ratio is 0.2; rockfill and foundation cover are considered as nonlinear materials, and the Duncan-Zhang EB model is adopted. The model parameters are shown in Table 1: Table 1

[0021] In step 2, the boundary conditions are set as follows: the bottom of the continuous model is set as the fixed boundary of the continuous model. Since the bedrock is below the overburden, its deformation is considered negligible, so the bottom of the model is set as a fixed boundary, normal constraints are applied on both sides, and the upstream water pressure is applied as a surface force on the panel and the upstream foundation surface.

[0022] Example 4 Based on Example 1, in step 3, the discrete domain range is determined as follows: Figure 3 As shown in the figure, the construction process is simulated by the graded loading method, and the settlement distribution cloud map of the face rockfill dam under various levels of load is calculated, and the discrete domain is set at the maximum settlement position, representative partition, and the position of the area with large deformation gradient. In step 3, the linear contact model is used to reflect the microscopic characteristics of the rockfill material.

[0023] The linear contact model consists of a linear model and a damping model. The linear component calculates the linear force. , the damper model calculates the damping force . and can be decomposed into the normal component and the tangential component , the relationship between the two and the relative displacement is as follows: (1) Where: is stiffness; , are the normal and tangential relative displacements between spheres or between sphere and wall, respectively.

[0024] Normal component of the damping force With tangential component The relationship with the relative translation speed is as follows: (2) Where: and is the mass of the spheres in contact with each other (if one side is a wall, =0); , is the damping ratio; , is the relative translation speed between spheres or between the sphere and the wall.

[0025] The microscopic contact model parameters of rockfill materials are shown in Table 2: Table 2

[0026] Example 5 Based on Example 1, step 4 is specifically as follows: Step 3: After determining the location of the discrete domain, set the selected mesh as a "Null" element to indicate that it will be replaced by the discrete element model; Step 4.1, establishing a discrete element model of the coupling part in a new file, the discrete domain is a rectangle and is larger than the discrete domain size in step 3. Following the above modeling process, this embodiment determines three coupling areas of the main rockfill area, the secondary rockfill area and the cushion area, all of which are located in the 13th level loading layer; Step 4.2, establish Wall in the discrete domain. The x coordinate and width of Wall are consistent with those of Null cell, and its height is higher than that of Nall cell. Step 4.3, the prototype gradation of rockfill is expanded to achieve a good balance between the calculation speed and simulation accuracy of the numerical simulation, and particles with a diameter of less than 5 cm are cut off; at the same time, considering that large particles will be broken, the minimum particle size for particle breakage is set to 50 cm. The particle gradation curve is as follows: Figure 4 As shown; Step 4.4, generate discrete particles that are all balls according to the grading, then set the common rockfill material shape as a template, fill the template with balls, adjust the number of particles and smoothness, and simulate the real rockfill material shape as much as possible; Step 4.5, using filled Clump particles to replace the rockfill with a particle size greater than 50 cm, and replacing Clump with crushable Cluster particles, to simulate the size and crushing performance of the rockfill in turn; Step 4.6, setting the porosity of the rockfill material to 0.3-0.4; for the three-dimensional discrete element model, the reasonable porosity of the sample should be 0.3-0.4. In this embodiment, the porosity is set to a fixed value of 0.35.

[0027] Step 4.7, the default contact setting is linear contact and the initial density, damping, normal stiffness, tangential stiffness and friction coefficient of the particles generated in the rectangular area are set; the gravitational acceleration is set so that the ratio of the average unbalanced force to the average contact force is less than 1×10 -5 Standard balance particles; Step 4.8, after calculating the equilibrium, initialize the particle displacement, velocity, and contact force, delete the Wall, and export the calculated Brick as a binary file.

[0028] Example 6 Based on Example 1, step 5 is specifically as follows: Step 5.1, before reaching the coupling position, follow Figure 1 The construction simulation is carried out according to the grading shown in the figure. The calculation termination condition for each layer is that the ratio of the average unbalanced force to the sum of the average contact force is less than 1×10 -5 ; Step 5.2, when the coupling position is reached (13 layers), select the large strain mode and set the coupling domain, which is larger than the established Brick range; the surface in contact with the continuous domain is set as Wall-Zone, and the front and back walls are set to ensure that the particles will not be squeezed out; Step 5.3, import the pre-balanced Brick into the coupling position, delete the redundant particles and perform discrete-continuous coupling calculation; Step 5.4, repeat the above loading process until the construction is completed, thus realizing the construction process simulation of the concrete face rockfill dam.

[0029] Through the above method, not only can the deformation coordination between the inactivated part and the lower dam body be ensured, but also the deformation value of the unconstructed part in the concrete face rockfill dam model is not affected by the settlement of the dam body below it, which better solves the filling process simulation of the discrete-continuous model of the concrete face rockfill dam.

[0030] In combination with Examples 1-6, in order to further analyze the simulation results, the present invention uses the following method to perform post-processing analysis on the discrete-continuous coupling model of the concrete face rockfill dam as a supplementary explanation of the present invention: 1) In order to verify the calculation accuracy of the discrete-continuous coupling method in the deformation of the concrete face rockfill dam, the coupling model of the 3BⅡ area is taken as an example, and the simulation results of the continuous model and the discrete-continuous coupling model are compared and analyzed. The deformation of the dam body during the completion period and the water storage period is shown in Figure 2. Figure 5 As shown. It can be seen from the figure: ① The maximum settlement of both models during the completion period occurred in the secondary rockfill area at 1 / 2 of the dam height. The maximum settlement of the continuous model was 48.46 cm, and the maximum settlement of the coupled model was 47.22 cm. Since the quality of the rockfill in area 3C is slightly lower than that in area 3BⅡ, the settlement contour of the dam body is slightly tilted downstream; ② For the displacement along the river, the upstream dam body moves upstream, and the downstream dam body moves downstream. At the same time, due to the application of the panel, the upstream dam slope at the 1 / 2 dam height position moves slightly downstream, but the displacement value and range are small; ③ The maximum displacement along the river to the upstream side of the continuous model is 3.97 cm, and that of the coupled model is 4.03 cm, located at 1 / 3 of the dam height. The maximum downstream displacement of the continuous model to the downstream side is 8.00 cm, and that of the coupled model is 8.21 cm, located at 1 / 2 of the dam height; ④ Compared with the completion period, the water storage period caused a significant change in the deformation of the dam body: the settlement value of the dam body increased after water storage, and the position was closer to the downstream side. The maximum settlement values ​​of the continuous model and the coupled model were 48.50 cm and 47.48 cm, respectively. After water storage, the downstream displacement of the dam body increased, which was manifested as a decrease in the displacement on the upstream side and an increase in the displacement on the downstream side. The maximum downstream displacement of the continuous model and the coupled model to the upstream side was 2.49 cm and 3.06 cm, respectively, and the maximum downstream displacement to the downstream side was 14.50 cm and 12.93 cm, respectively. Through the above analysis, it can be seen that the coupling model has little effect on the deformation calculation results of the rockfill dam, and only has a certain impact on the settlement calculation results near the coupling area.

[0031] To further verify the accuracy of the numerical simulation, the measured settlement at the ES2 survey line of the dam body was compared with the settlement calculation results of the continuous model, the 3A area coupling model, the 3BⅡ area coupling model and the 3C area coupling model. Figure 6As shown in the figure: ① The maximum settlement of the dam body is located at 1 / 2 of the dam height, and the settlement of the dam top and dam bottom is small, which is consistent with the actual distribution of settlement of the face rockfill dam; ② The calculated values ​​of the dam body settlement below 1 / 3 of the dam height of the four types of numerical models have a high degree of consistency, and this part is located at the lower side of the discrete domain; there are slight differences in the settlement values ​​of the upper and middle parts of the dam body, with the maximum difference being 2.52 cm; ③ The average absolute errors of the continuous model, 3A, 3BⅡ, and 3C coupled models with the measured values ​​are 0.75 cm, 1.82 cm, and 1.90 cm, respectively. m, 1.89cm, the calculated values ​​of the three coupling models are all smaller, this is because the establishment of discrete areas has strengthened the material properties of the rockfill materials in the nearby areas to a certain extent, resulting in a slight decrease in the settlement value; ④ The maximum differences between the calculated values ​​and the measured values ​​of the coupling models in Area 3A, Area 3BⅡ and Area 3C are 2.77cm, 2.84cm and 2.9cm respectively, accounting for 6.62%, 6.71% and 6.88% of the maximum settlement value, all of which appear near the coupling position at an elevation of 1967.10m. The above deformation behavior comparison analysis shows that: compared with the continuous model, the coupling model can also more accurately reflect the deformation law and deformation value of the face rockfill dam, and can be used as a simulation tool for the study of the microscopic characteristics of rockfill materials.

[0032] 2) In order to verify the calculation effect of the discrete-continuous coupling model, the 3BⅡ coupling model is taken as an example to compare it with the stress simulation results of the finite difference model. The principal stresses of the dam body during the completion period and the water storage period are as follows: Figure 7 As shown in the figure. It can be seen from the figure that: ① The principal stress contour lines of the continuous model and the coupling model are basically parallel to the dam slope, and show a gradual increase trend from the dam top to the dam foundation, and the principal stress extreme values ​​are all located at the bottom of the dam body. After water storage, the principal stress approaches upstream under the action of water load, which is in line with the stress distribution law of the dam body; ② The stress cloud diagrams of the continuous model and the coupling model have obvious changes in the material partitions of the rockfill dam, which is due to the obvious differences in the mechanical properties of the materials in different partitions; the stress contour lines of the coupling model are only tortuous near the discrete domain, and the cloud diagram distribution outside the discrete domain is consistent; ③ During the completion period, the minimum and maximum principal stress values ​​of the continuous model and the coupling model are 0.51MPa and 0.52MPa, respectively, both located at the bottom of the dam body, and the maximum principal stress values ​​are 2.56MPa and 2.64MPa, respectively; ④ During the water storage period, the stress on the upstream side of the dam body increases significantly, and the minimum principal stress of the continuous model and the coupling model increases to 0.53MPa and 0.55MPa, respectively. The maximum principal stresses are 6.68MPa and 6.20MPa respectively, located in the middle of the panel. It can be seen that water storage causes the panel pressure to increase rapidly, but has little effect on the internal stress of the dam body.

[0033] 3) Force chain information. Under load, adjacent particles of discrete elements come into contact and transmit contact force, forming force chains with different strengths. The force chains intersect with each other to form a network form, which is unevenly distributed in the particle system. The structural characteristics of the force chain reflect the non-uniformity and anisotropy of the contact force distribution inside the material, which is an important feature of the microstructure of granular materials. During the service of the face rockfill dam, the evolution process of the force chain of the rockfill material in different parts of the dam body is as follows: Figure 8 As shown in the figure. It can be seen from the figure that: ① During the construction period, the force chains in the 3A coupling area are evenly distributed and are mostly perpendicular to the left and right contact surfaces. When the dam body is completed, due to the weight of the upper filling dam body, the strong contact force chains are concentrated on the lower left side, and the number of activated force chains increases, and the maximum value of the force chain decreases. During the water storage period, since the coupling area is close to the upstream side and is greatly affected by water storage, its maximum value of the force chain increases significantly, and the number of strong contact force chains also increases, mostly distributed at the bottom of the area and perpendicular to the contact surfaces on both sides; ② With the increase of the dam body filling height, the number of vertical force chains in the 3BⅡ coupling area gradually increases, and the strength gradually increases. The strong contact force chain is distributed in a "tree-like" manner, that is, there are a large number of weak contact force chains in the upper part of the coupling area, and a small number of strong contact force chains with thicker force chains in the lower part; ③ The distribution and development of the force chain in the 3C coupling area are basically consistent with those in the 3BⅡ area, but because it is close to the downstream side, the water storage has little effect on its force chain changes, and no obvious changes like those in the 3BⅡ area have occurred.

[0034] 4) Quantitative analysis of fabric tensor. The force chain distribution can only qualitatively obtain the microscopic mechanical evolution characteristics of rockfill materials. In order to reveal this process more accurately, this paper introduces the fabric tensor coefficient to quantitatively describe the contact direction and the anisotropy of the contact force. The contact direction refers to the direction of the external normal line of the contact, and its anisotropy can be quantitatively described by the fabric tensor: (1) In formula (1): is a 3×3 second-order symmetric tensor; is the total number of contacts; is the contact normal unit vector, represent In the Cartesian coordinate system , , Components in 3 directions. Partial configuration tensor By the second invariant Quantifying anisotropy: (2) In formula (2): is the deviatoric stress tensor; when the two are coaxial is positive, otherwise it is negative.

[0035] During the service life of the concrete face rockfill dam, the change process of the second invariant of the mesostructure of the 3A, 3BⅡ and 3C coupling models is as follows: Fig. 9 As shown in the figure, "a" represents the dam construction process, "b" represents the panel construction process, and "c, d, e" are the first, second, and third phase water storage processes, respectively. It can be seen from the figure that: ① After each layer of dam filling, the anisotropic state of the rockfill materials in each part will increase significantly, and then the particle system will be adjusted to disperse and spread the upper pressure, so that the anisotropy degree will be reduced; ② Compared with the impact of dam filling, the 3A area is more significantly affected by the panel construction and reservoir water storage, and this area is closer to the upstream dam surface. The first water storage water level is lower than the elevation of the coupling part, so it has little impact on the micro-structure changes. With the increase of water storage water level, the degree of structural anisotropy in the 3A area fluctuates violently; ③ Compared with the impact of dam filling, the micro-structures of 3BⅡ and 3C areas are less affected by water storage, and the panel construction and water storage also have little impact on them; ④ The closer to the upstream side, the longer the time required for each equilibrium of the block stone system and the overall equilibrium. The above-mentioned analysis on the anisotropy of the mesostructure of rockfill materials is consistent with the empirical knowledge and the actual laws of the dam body, and accurately reveals the evolution process of the mesostructure of rockfill materials during the service of the concrete faced rockfill dam.

[0036] 5) Quantitative analysis of sliding contact In order to quantitatively describe the micromechanical behavior characteristics and energy evolution law of rockfill materials during construction, this paper introduces the concept of sliding contact fraction. The sliding contact here refers to the contact situation where the contact force reaches the maximum value and sliding adjustment occurs. This section uses the sliding contact fraction (%) is defined as: (3) In formula (3): is the number of sliding contacts; is the total number of contacts.

[0037] Fig.10The evolution process of the sliding contact ratio of each coupled part of the dam body during service, "a, b, c, d, e" in the figure have the same meaning as above. It can be seen from the figure that: ① The sliding contact ratio trends of the three models are basically the same as their structural anisotropy trends. During the construction of each layer of rockfill, the anisotropy degree first increases rapidly and then gradually decreases. The two can verify each other. The sliding adjustment of particles reduces the structural anisotropy degree of the region; ② The overall trend of the sliding contact ratio in different parts is the same. The change in the 3A area is a sudden increase and a sudden decrease, followed by slight fluctuations until equilibrium is reached. This is due to the special shape of the 3A cushion area, the horizontal size of the area is smaller than the vertical size, the stress conditions are complex, and the particles are not easy to adjust, which is manifested as small fluctuations, so the equilibrium time is also long. When each layer is loaded, the sliding contact ratio of the 3BⅡ area increases rapidly, but the downward slope is relatively gentle. The growth slope and the decrease slope of the sliding contact ratio in the 3C area are both relatively gentle, and the equilibrium time is short, which shows that the particle balance adjustment in the 3C area is rapid and easy to reach equilibrium.

[0038] 6) Analysis of the evolution law of contact direction. There are a large number of random contact relationships between rockfill materials. By statistically analyzing a certain amount of contact information, we can obtain the overall and deterministic contact change law. This paper mainly analyzes the distribution of microstructures such as contact direction, normal contact force, and tangential contact force. The contact direction distribution of 3A, 3BⅡ and 3C coupling areas is as follows: Fig.11 As shown in the figure: ① The contact direction of the 3A area has obvious anisotropy during the construction period, completion period and water storage period, and its main contact direction is parallel to the lower left to the upper right, which is mainly restricted by the body shape of the 3A area; after water storage, it still shows obvious anisotropy, and the main direction changes slightly. ② The contact direction distribution of the 3BⅡ area changes slightly and is approximately spherical; as the construction progresses, the rockfill is further compacted, its anisotropy decreases, and the main direction changes slightly; water storage significantly increases the anisotropy of the material in this area, and the main direction is slightly adjusted. ③ The contact direction of the 3C area is basically approximately spherical and approximately isotropic in the three stages; at the completion, due to the uneven pressure due to the proximity of the coupling area to the downstream, there are certain changes in the direction distribution; the contact direction changes more significantly during water storage, and the main direction changes from the upper right to the upper left, which is because the contact in this direction is generated to resist the water pressure.

[0039] 7) Analysis of the evolution law of normal contact force. In order to quantitatively describe the normal contact force between particles, this study transforms the three-dimensional contact information into two-dimensional contact information by averaging, so as to use the currently mature two-dimensional structural analysis method. Bathurst et al. derived the normal contact force distribution structural tensor, and used the second-order Fourier expansion formula to fit and quantitatively analyze the normal contact force distribution, and obtained the average normal contact force distribution function as follows: (4) In formula (4): is the average normal contact force; is the Fourier fitting coefficient of the normal contact force; is the principal direction of the anisotropy of the normal contact force.

[0040] The two-dimensional statistical distribution of the normal contact force of rockfill is as follows: Fig.12 The blue line is shown in the figure, and the red line is the fitting value. The evolution law of the normal contact force during the service of the rockfill is analyzed from the perspectives of coupling position and period. Fig.12 It can be seen that: ① The anisotropy of the 3A area changes slightly. Since the rockfill in this area is close to the upstream dam slope, the normal contact force is mostly parallel to the upstream dam slope. During water storage, the main direction of the normal contact force is still parallel to the upstream dam slope, but the water load increases the normal contact force perpendicular to the dam slope, which slightly reduces its anisotropy; ② When the filling is completed, the average normal contact force distribution in the 3BⅡ area is close to isotropy. With the progress of construction and water storage, the average normal contact force value increases, the direction remains basically stable, and gradually presents a "peanut shape"; ③ With the progress of construction, the anisotropy of the 3C area decreases slightly, and the main direction of the normal contact force is to the upper right, which may be due to the nature of the rockfill in the 3C area.

[0041] 8) Analysis of the evolution law of tangential contact force. In order to quantitatively describe the evolution law of tangential contact force of particle systems, Bathurst et al. derived the tangential contact force tensor, used the second-order Fourier expansion formula to fit and quantitatively analyze the tangential contact force distribution, and the average tangential contact force distribution function as follows: (5) In formula (5): is the average tangential contact force; is the Fourier fitting coefficient of the tangential contact force; is the principal direction of the anisotropy of the tangential contact force.

[0042] The evolution law of tangential contact force during the service life of rockfill materials is analyzed from the perspectives of coupling position and period. The two-dimensional statistical distribution of the average normal contact force of rockfill materials is shown in the figure. Fig.13 The blue line is shown in the figure, and the red line is the fitting value. Fig.13 It can be seen that: as the construction progresses, the deviation angle of the 3BⅡ discrete area has obvious changes and fluctuations. Although the average tangential contact force of the other discrete areas has certain fluctuations and adjustments at different times, the average tangential contact force value remains basically unchanged and the direction remains basically stable.

[0043] 9) Quantitative analysis of compaction evolution of rockfill materials. The coordination number, also known as the average contact number, is an important indicator of material compaction. ,in is the number of contacts in the model that are active (normal contact force is greater than zero), is the total number of particles in the model. The increase in coordination number indicates that the internal voids of the rockfill material decrease and the compaction degree is further improved. On the contrary, it indicates that the internal voids of the rockfill material increase. In order to understand the changes in compaction degree at different positions during the service of the rockfill material, coordination number monitoring points are arranged at the center of the 3A, 3BⅡ and 3C discrete domains to observe the tension or compression of the parts. During the service of the face rockfill dam, the changes in the coordination number of the rockfill material at different positions are shown in the figure. Fig.14 shown.

[0044] (1) The evolution of the coordination number in the 3A region is as follows: ① The compaction degree of the rockfill in the coupling region shows an increasing trend as the dam body is filled, which is consistent with the actual trend of the project; during the construction period, the coordination number in the coupling region fluctuates greatly, which may be due to the narrow width of the 3A region, resulting in poor force chain transmission. ② The panel construction has little effect on the change of the coordination number in the 3A region, and the value increases slightly. ③ During the water storage period, when the water load is slightly higher than the elevation of the discrete domain, the particles in the 3A coupling region adjust, causing the coordination number to increase sharply.

[0045] (2) The evolution of the coordination number in the 3BⅡ area is as follows: ① The compaction degree of the rockfill in the coupling area shows an increasing trend as the dam body is being filled, but its growth rate is smaller than that in the 3A area; ② The slab construction has no effect on the compaction degree of the rockfill, which is due to the small load of the slab itself and the fact that the 3BⅡ area is far from the upstream; ③ During the impoundment period, the coordination number in the coupling area increases slightly, which is due to the continuous compaction of the rockfill in the coupling area caused by the water load.

[0046] (3) The evolution of the coordination number in the 3C region is as follows: ① The compaction degree of the rockfill in the coupling region is generally stable as the dam body is filled. This is because the 3C region is close to the downstream dam slope and the upper rockfill has little effect on its compaction effect. ② The application of the face plate has no obvious effect on the coordination number of the 3C coupling region. The 3C region is far away from the upstream, and the face plate construction has no effect on the compaction degree of this area. ③ During the water storage period, the change pattern of the coordination number of the rockfill is consistent with that of the 3BⅡ region.

[0047] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0048] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0049] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A simulation method for the construction process of a concrete face rockfill dam based on discrete-continuous coupling, characterized in that: Follow the steps below to implement it: Step 1, construct a continuous model according to the size and material parameters of the concrete face rockfill dam; Step 2, simulating the process of graded loading and staged water storage through a continuous model and setting boundary conditions for the continuous model; Step 3, determine the discrete domain range, rockfill contact model and mesoscopic material parameters; Step 4: construct a Brick discrete element particle set with the same volume as the discrete domain outside the continuous model, and perform a pre-balance calculation on the Brick discrete element particle set so that the average imbalance ratio of the Brick discrete element particle set reaches 1×10 -5 , the balancing results are stored in binary format; Step 5, simulate the construction process. During the coupling process, the finite difference method is used to simulate the rockfill dam body that is not coupled in the early stage. When entering the loading step of the coupling area, the pre-balanced Brick discrete element particle set is imported to quickly establish the discrete-continuous coupling model calculation.

2. The method for simulating the construction process of a concrete face rockfill dam based on discrete-continuous coupling according to claim 1 is characterized in that: In the step 1, the dimension parameters of the panel rockfill dam are the dimension parameters of the cross section of the panel rockfill dam. The cross section of the panel rockfill dam consists of a dam body contour line and a foundation contour line, wherein the dam body contour line parameters include the dam body height, dam crest width, dam body slope ratio, and toe plate size; the foundation contour line parameters include the upstream and downstream heights of the foundation and the length of the original ground line.

3. The method for simulating the construction process of a concrete face rockfill dam based on discrete-continuous coupling according to claim 2 is characterized in that: In the step 1, the material parameters of the face rockfill dam include the material constitutive models and macroscopic mechanical parameters of the foundation, the toe plate, the face plate and different partitions of the rockfill dam.

4. The method for simulating the construction process of a concrete face rockfill dam based on discrete-continuous coupling according to claim 1 is characterized in that: In step 2, setting the boundary condition specifically includes: setting the bottom of the continuous model as a fixed boundary of the continuous model.

5. The method for simulating the construction process of a concrete face rockfill dam based on discrete-continuous coupling according to claim 1 is characterized in that: In step 3, the discrete domain range is determined specifically as follows: the construction process is simulated by the graded loading method, the settlement distribution cloud map of the face rockfill dam under various levels of load is calculated, and the discrete domain is set at the maximum settlement position, representative partition, and the position of the area with large deformation gradient.

6. The method for simulating the construction process of a concrete face rockfill dam based on discrete-continuous coupling according to claim 5 is characterized in that: In step 3, a linear contact model is used to reflect the microscopic characteristics of the rockfill material.

7. The method for simulating the construction process of a concrete face rockfill dam based on discrete-continuous coupling according to claim 1 is characterized in that: The step 4 is specifically as follows: After the discrete domain position is determined in step 3, the selected grid is set as a "Null" unit; Step 4.1, establishing a discrete element model of the coupling part in a new file, wherein the discrete domain is a rectangle and is larger than the discrete domain size in step 3; Step 4.2, establish Wall in the discrete domain. The x coordinate and width of Wall are consistent with those of Null cell, and its height is higher than that of Nall cell. Step 4.3, the prototype gradation of the rockfill material is expanded, and particles with a diameter of less than 5 cm are cut off; at the same time, the minimum particle size for particle crushing is set to 50 cm; Step 4.4, generate discrete particles that are all balls according to the grading, then set the common rockfill material shape as a template, fill the template with balls, and adjust the number of particles and smoothness; Step 4.5, using filled Clump particles to replace rockfill materials with a particle size greater than 50 cm, and replacing Clump with crushable Cluster particles; Step 4.6, setting the porosity of the rockfill material to 0.3-0.4; Step 4.7, the default contact setting is linear contact and the initial density, damping, normal stiffness, tangential stiffness and friction coefficient of the particles generated in the rectangular area are set; the gravitational acceleration is set so that the ratio of the average unbalanced force to the average contact force is less than 1×10 -5 Standard balance particles; Step 4.8, after calculating the equilibrium, initialize the particle displacement, velocity, and contact force, delete the Wall, and export the calculated Brick as a binary file.

8. The method for simulating the construction process of a concrete face rockfill dam based on discrete-continuous coupling according to claim 1 is characterized in that: The step 5 is specifically as follows: Step 5.1: Before reaching the coupling position, the construction simulation is carried out according to the level. The calculation termination condition for each layer is that the ratio of the sum of the average unbalanced force and the average contact force is less than 1×10 -5 ; Step 5.2, when the coupling position is reached, select the large strain mode, set the coupling domain, and the coupling domain is larger than the established Brick range; the surface in contact with the continuous domain is set as Wall-Zone, and the front and back are set as Wall; Step 5.3, import the pre-balanced Brick into the coupling position, delete the redundant particles and perform discrete-continuous coupling calculation; Step 5.4, repeat the above loading process until the construction is completed, thus realizing the construction process simulation of the concrete face rockfill dam.

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