A numerical simulation-based micro-analysis method for mechanical properties of geotextile-reinforced soil medium

Abstract

The application discloses a geotextile bag rock-soil medium mechanical property mesoscopic analysis method based on numerical simulation and relates to the technical field of environmental geotechnical engineering. A geotextile bag grid in a three-dimensional space is constructed, model boundary node coordinates of a to-be-tested geotextile bag are searched, a solid calculation model of the to-be-tested geotextile bag is established in combination with a surface structure, random-size spherical particles are generated according to a preset porosity, initial equilibrium of the particle system is realized by using a density scaling method, average stress inside the spherical particles is calculated, movement of the spherical particles in the particle system is controlled through a preset time step, the particle system is cyclically calculated based on stress, an optimal particle system is obtained, relevant contact models are set, position constraints of the spherical particles are removed by using a servo method, a new composite system is formed, a triaxial compression process is simulated, and three groups of deviatoric stress and strain relationship curves are obtained. The application is helpful to simulate mechanical responses of the geotextile bag under different load conditions and further evaluate engineering performances of the geotextile bag.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental geotechnical engineering, and particularly relates to a geotextile bag rock-soil medium mechanical property meso-analysis method based on numerical simulation. BACKGROUND

[0002] The geotextile bag is an engineering material for protecting and reinforcing the soil and rock bank slope. In recent years, the geotextile bag has become a widely used flexible revetment technology in bank slope engineering due to its high strength, easy material acquisition, weather resistance, environmental protection and other characteristics. The geotextile bag material is usually made of high-strength synthetic fiber, and a stable protective layer is formed by filling a certain gradation of soil and stone bulk material, thereby constructing a composite material that meets the strength and deformation requirements. A plurality of geotextile bags can be stacked and arranged together to form a flexible slope according to different bank line shapes and slope requirements, so as to adapt to different terrain changes and soil settlement.

[0003] The filling material of the geotextile bag is a discrete body with complex meso-features and dense particle arrangement, and its mechanical properties and bearing capacity are affected by many factors such as gradation, particle size and surface shape. In addition, the outside of the geotextile bag is constrained by the bag material, so the overall strength characteristics and bearing capacity of the geotextile bag are much higher than those of a single bulk material. However, the shape of the geotextile bag varies, and there is currently no perfect method to characterize the mechanical properties of the geotextile bag rock-soil medium.

[0004] Due to the difficulties in studying the mechanical properties of the geotextile bag through field tests and laboratory tests, the numerical simulation method has become an effective research means. The numerical simulation method can simulate the mechanical behavior of the geotextile bag under external force by establishing an appropriate mathematical model, so as to approach the mechanical response characteristics of the real material. Compared with the traditional test method, the numerical simulation method has the advantages of strong sample repeatability and controllable cost, and can provide a scientific basis for the design and engineering application of the geotextile bag.

[0005] When describing the mechanical properties of the geotextile bag during service through numerical simulation, the conventional continuous numerical simulation method performs well in describing the mechanical response of the geotextile bag material. However, since the filling material of the geotextile bag is usually granular and has complex meso-features such as particle contact, friction and slip, these meso-features have an important influence on the mechanical behavior of the geotextile bag. The traditional continuous numerical simulation method is difficult to accurately describe the mechanical behavior of these meso-features, and has certain limitations in analyzing the deformation and failure of the filling medium in the bag. Therefore, the discrete-continuous coupling simulation analysis method can be used to better study the mechanical properties such as strength and deformation of the geotextile bag.

[0006] In the analysis of the mechanical characteristics of the soil bag using the discrete-continuous coupling simulation method, the construction of a fine numerical model in accordance with the actual situation is a key technology. For the soil bag, on the one hand, the external flexible deformation needs to be considered, and on the other hand, the internal filling medium not only needs to match the real shape and gradation of the soil and stone bulk material, but also needs to set a suitable contact model, and then a numerical test is carried out by applying a load to simulate the mechanical response of the soil bag under different load conditions, and then the engineering performance of the soil bag is evaluated.

[0007] Therefore, how to provide a numerical simulation-based micro-analysis method for the mechanical characteristics of the soil bag rock-soil medium, estimate the equivalent strength parameters of the soil bag during the service process, and provide a theoretical basis for the determination of the macro-mechanical parameters of the soil bag, is a problem that needs to be solved by those skilled in the art. SUMMARY

[0008] Therefore, the present application provides a numerical simulation-based micro-analysis method for the mechanical characteristics of the soil bag rock-soil medium, which can solve the problems in the prior art.

[0009] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0010] A numerical simulation-based micro-analysis method for the mechanical characteristics of the soil bag rock-soil medium, comprising the following steps:

[0011] S1, determining a soil bag to be tested, and establishing a soil bag grid in a three-dimensional space according to the soil bag to be tested;

[0012] S2, coordinate positioning of the grid points and the grid structure of the soil bag grid in the three-dimensional space, and retrieving the model boundary node coordinates of the soil bag to be tested;

[0013] S3, based on the model boundary node coordinates of the soil bag to be tested, and in combination with the surface structure of the soil bag to be tested, an entity calculation model of the soil bag to be tested is established;

[0014] S4, generating randomly sized spherical particles in the entity calculation model of the soil bag according to a predetermined porosity, obtaining an initial particle system of the filling medium, and realizing the initial equilibrium of the particle system by using a density scaling method;

[0015] S5, using the finite calculation range of the entity calculation model of the soil bag and the size of the generated spherical particles, setting a plurality of tangent measuring circles, judging the contact form between the particle systems, and calculating the average stress inside all the measuring circles; the movement of the spherical particles in the particle system is controlled by a predetermined time step;

[0016] S6, in the process of spherical particle movement, the particle system is calculated cyclically according to the error rate between the average stress in the particle system and the target stress, the updated particle size and the average stress of the particle system are judged and deleted for the edge particles, and the updated optimal particle system is obtained;

[0017] S7, the contact between the particles in the entity calculation model of the updated geotextile bag and the contact between the particles and the geometric boundary of the entity calculation model of the geotextile bag are set as linear contact models, and the contact modulus, stiffness ratio and friction coefficient are used to simulate the physical and mechanical properties of the geotextile bag body material and the filling soil body;

[0018] S8, the servo method of measuring circle is used to control the particle system, so as to ensure the effective contact between the geotextile bag body material and the filling soil body and the filling soil body, delete the measuring circle servo, release the position constraint of the spherical particle, and form a new composite system;

[0019] S9, the hoop direction confining pressure of the entity calculation model of the geotextile bag is set, and a specific speed is given in the Z direction to simulate the triaxial compression process, and three groups of deviatoric stress and strain relationship curves are calculated;

[0020] S10, the strength characteristics of the geotextile bag are analyzed according to the Mohr stress circle, and the equivalent macroscopic strength parameters of the geotextile bag are calculated.

[0021] The above method, optionally, S1 includes the following contents:

[0022] According to the shape and size of the to-be-measured geotextile bag, the number of grid nodes, the number of units, the grid point coordinates and the unit composition parameters are determined, and the geotextile bag grid is constructed; according to the shape of the geotextile bag, the number of grid nodes and the number of units are determined.

[0023] The above method, optionally, S2 includes the following steps:

[0024] S201, according to the known node coordinates, all units are searched to search the edges of each unit;

[0025] S202, all given nodes are traversed to determine the boundary of the model;

[0026] S203, according to the geometric shape of the geotextile bag and the grid density, the positions of the grid points are distributed, and the unit direction is checked to ensure that the stress direction of each grid is consistent.

[0027] The above method, optionally, S3 includes the following steps:

[0028] S301, according to the grid position, calling the function library of FLAC3D6.0, using shell structure unit to represent the surface structure of the geotextile bag, creating a three-dimensional geotextile bag entity calculation model;Set the initial attribute parameters of the geotextile bag body material;At the same time, the geotextile bag ring element is grouped;

[0029] S302, set the damping attribute of the geotextile bag unit;Fix the speed of the geotextile bag unit node, and constrain the position of the geotextile bag body material.

[0030] The above method, optionally, S4 includes the following steps:

[0031] S401, according to the preset porosity, generate random size spherical particles in the entity calculation model of the geotextile bag, the centers of all spherical particles are located in the entity calculation model of the geotextile bag;Give the density and damping attribute of the spherical particle, to simulate the filling soil particles;At the same time, the intersection number of spherical particles and geotextile bag boundary is judged by using ray method, the spherical particles outside the geotextile bag model are deleted, and the remaining spherical particles constitute the initial particle system of the filling medium;

[0032] S402, using density scaling method, time step mode is automatic mode, cycle preset times, delete the spherical particles that escape from the target range in the balance process.

[0033] The above method, optionally, S5 includes the following steps:

[0034] S501, according to the finite calculation range of the entity calculation model of the geotextile bag and the generated particle size, set a regular measuring circle in the initial particle system, the radius R of the measuring circle is 6 times the maximum particle radius, and a plurality of tangent measuring circles are set in the geotextile bag model according to the measuring circle radius;

[0035] S502, compare the center distance between spherical particles, the distance between spherical particles and geotextile bag model boundary and the radius of spherical particles, determine the contact between particles and particles and particles and wall in the particle system, and calculate the total number of contacts;

[0036] S503, set the contact between spherical particles and spherical particles and the contact between spherical particles and geotextile bag model boundary as linear contact model, the attribute parameters of the contact model include normal stiffness and tangential stiffness;Traverse all contacts between the particle system, calculate the distance between any contact and the measuring circle;

[0037] S504, using PFC3D6.0 platform to carry out iterative calculation on the particle system, realizing the free movement of the particles.

[0038] The above method, optionally, the specific content of S9 is:

[0039] The circumferential confining pressure of the entity calculation model of the geotextile bag is respectively 100 kPa, 200 kPa and 300 kPa, the upper and lower walls are created in the z direction by using the PFC6.0 platform, and a certain speed is given in the opposite direction to load, simulating the triaxial compression process; the displacement and stress in the axial and lateral directions are monitored until the entity calculation model of the geotextile bag appears shear failure; the stress is calculated according to the force on the loading plate, and the stress data is recorded; at the same time, the axial strain is calculated according to the position information and initial size of the loading plate, and the strain data is recorded; according to the recorded stress and strain data, three groups of deviatoric stress and strain relationship curves are calculated by changing the confining pressure of the entity calculation model of the same geotextile bag; finally, the strength characteristics of the geotextile bag are analyzed according to the Mohr stress circle, and the equivalent macroscopic strength parameters of the geotextile bag are calculated.

[0040] The method described above, optionally, further comprises S11, the monomer geotextile bag unit adopts the parameters obtained by S10, and the engineering characteristics of the entity calculation model of the geotextile bag are further analyzed by combining multiple geotextile bag units in an interleaved arrangement.

[0041] The method described above, optionally, the specific content of S11 is:

[0042] According to the actual engineering geotextile bag structure, the entity calculation models of multiple geotextile bags are combined in an interleaved arrangement, the macroscopic equivalent strength parameters of the monomer geotextile bag unit obtained by S10 are adopted, a flexible revetment structure is constructed, and the engineering characteristics of the geotextile revetment structure are further analyzed.

[0043] Through the technical solution described above, compared with the prior art, the present application provides a geotextile rock-soil medium mechanical property microscopic analysis method based on numerical simulation, which has the following beneficial effects:

[0044] 1) The method is based on a discrete-continuous coupled simulation method to construct a three-dimensional space model of the geotextile bag in accordance with the actual situation, adopts a shell element to simulate the geotextile bag body material, a ball particle to simulate the filling soil, and sets different microscopic mechanical parameters, estimates the equivalent strength of the geotextile bag during service through triaxial compression test, and further determines the macroscopic equivalent strength parameters of the geotextile bag;

[0045] 2) In the method, the shell structure element of FLAC3D6.0 is used to simulate the geotextile bag body material, and the ball particle in PFC3D6.0 is used to simulate the filling material, which ensures the microscopic structure of the geotextile bag body material and the filling soil particles; at the same time, the particle system servo method controlled by the measuring circle is adopted, which reduces the problem of long calculation time caused by large model and many internal particles, and makes the simulation result more true and reliable. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on the provided drawings.

[0047] Figure 1 A flow chart of a geotextile bag rock-soil medium mechanical property microscopic analysis method based on numerical simulation is disclosed in the present application.

[0048] Figure 2 A triangular mesh geotextile bag node unit diagram is disclosed in the embodiments of the present application; wherein 2a is a triangular network, and 2b is a mesh unit.

[0049] Figure 3 A typical geotextile bag body material contour mesh diagram is disclosed in the embodiments of the present application; wherein 3a is a front view, 3b is a top view, and 3c is a side view.

[0050] Figure 4 A microscopic particle structured geotextile bag filling material is disclosed in the embodiments of the present application.

[0051] Figure 5 A geotextile bag model internal measurement circle arrangement diagram is disclosed in the embodiments of the present application.

[0052] Figure 6 A geotextile bag composite system calculation model schematic diagram is disclosed in the embodiments of the present application.

[0053] Figure 7 A geotextile bag composite system triaxial compression simulation diagram is disclosed in the embodiments of the present application.

[0054] Figure 8 A geotextile bag composite system triaxial compression internal change diagram is disclosed in the embodiments of the present application.

[0055] Figure 9 A geotextile bag model deviatoric stress-strain curve diagram is disclosed in the embodiments of the present application.

[0056] Figure 10 A geotextile bag model Mohr strength envelope diagram is disclosed in the embodiments of the present application.

[0057] Figure 11 A combined geotextile bag slope protection structure form design diagram is disclosed in the embodiments of the present application. DETAILED DESCRIPTION

[0058] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0059] In the present application, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations, the term "include", "contain" or any other variant thereof is intended to cover non-exclusive containing, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitation, the element defined by the sentence "including a…" does not exclude the presence of other identical elements in the process, method, article or equipment including the element.

[0060] Referring to Figure 1 The present application discloses a numerical simulation-based geotextile bag rock-soil medium mechanical property meso-analysis method, comprising the following steps:

[0061] S1, determining a to-be-tested geotextile bag, using Ansys software to establish a geotextile bag grid in a three-dimensional space according to the to-be-tested geotextile bag;

[0062] S2, performing coordinate positioning on the grid points and grid structures of the geotextile bag grid in the three-dimensional space, retrieving the model boundary node coordinates of the to-be-tested geotextile bag, and checking the unit direction at the same time, so as to ensure that the stress direction of each grid is consistent;

[0063] S3, based on the model boundary node coordinates of the to-be-tested geotextile bag, combining the surface structure of the to-be-tested geotextile bag to establish an entity calculation model of the to-be-tested geotextile bag, first calling the function library of FLAC3D6.0, using shell structure elements to generate a calculation model of the geotextile bag body material, and simultaneously restraining the triangular grid position to prevent the deformation of the bag body material;

[0064] S4, generating round spherical particles of random sizes in the entity calculation model of the geotextile bag according to a preset porosity, obtaining an initial particle system of the filled medium, realizing the initial equilibrium of the particle system by using a density scaling method, setting initial contact parameters, simulating the filled soil body, and using the PFC3D6.0 platform to carry out mechanical calculation to equilibrium, so as to realize the equilibrium of the initial particle system;

[0065] S5, using the finite calculation range of the entity calculation model of the geotextile bag and the generated spherical particle size, a plurality of tangent measurement circles are set in the initial particle system using the PFC3D6.0 platform, the contact form between the particle systems is judged, and the average stress inside all the measurement circles is calculated; the motion of the spherical particles in the particle system is controlled through a preset time step to realize the free motion of the spherical particles;

[0066] S6, during the motion of the spherical particles, the particle system is calculated repeatedly according to the error rate between the average stress inside the particle system and the target stress, the updated particle size and the average stress of the particle system are judged and deleted for the edge particles to obtain an updated optimal particle system;

[0067] S7, setting the contact between the particles inside the updated entity calculation model of the geotextile bag and the linear contact model between the particles and the geometric boundary of the entity calculation model of the geotextile bag, the contact modulus, stiffness ratio and friction coefficient are used to simulate the physical and mechanical properties of the geotextile bag body material and the filled soil body;

[0068] S8, using the servo method of the measurement circle to control the particle system, ensuring the effective contact between the geotextile bag body material and the filled soil body and the inside of the filled soil body, reasonably simulating the mechanical behavior of the geotextile bag, and ensuring accurate simulation of the interaction between the geotextile bag and the filled soil body; deleting the measurement circle servo, releasing the position constraint of the spherical particles, and forming a new composite system;

[0069] S9, setting the hoop direction confining pressure of the entity calculation model of the geotextile bag to be 100kPa, 200kPa and 300kPa respectively, and giving a specific speed loading in the Z direction, creating an upper wall and a lower wall in the z direction using the PFC6.0 platform, and giving a certain speed in the opposite direction to load, simulating the triaxial compression process, monitoring the displacement and stress in the axial and lateral directions until the geotextile bag model appears shear failure; according to the force on the loading plate and the calculation formula, the force is converted into stress, and the stress data is recorded; at the same time, the position information and the initial size of the loading plate are used to calculate the axial strain, and the strain data is recorded; according to the recorded stress and strain data, the confining pressure of the same geotextile bag model is changed to calculate three groups of deviatoric stress and strain relationship curves;

[0070] S10, according to the Mohr stress circle, the strength characteristics of the geotextile bag are analyzed, and the equivalent macroscopic strength parameters of the geotextile bag are calculated.

[0071] Further, S1 includes the following contents:

[0072] According to the shape and size of the to-be-tested geotextile bag, the number of grid nodes, the number of units, the coordinates of the grid points and the unit composition parameters are determined, and the geotextile bag grid is constructed; according to the shape of the geotextile bag, the number of grid nodes and the number of units are determined.

[0073] Further, S2 comprises the following steps:

[0074] S201, according to the known node coordinates, traversing all the elements to search the edges of each element;

[0075] S202, traversing all given nodes to determine the boundary of the model;

[0076] S203, according to the geometric shape of the geotextile bag and the grid density, distributing the position of the grid points, while checking the element direction to ensure that the stress direction of each grid is consistent.

[0077] Specifically, for the grid point coordinates in three-dimensional space, each grid point has three components, namely x, y and z coordinates; for the element composition parameters, the geotextile bag is composed of triangular elements, each element has 3 nodes, and the node number of each element is given in counterclockwise order to ensure the consistency of the element direction, as shown in Figure 2 .

[0078] Specifically, as shown in Figure 2 b, in S202, for any triangular element (numbered ii), assuming it is composed of three nodes i, k and m, then i and k, k and m, m and i need to be considered respectively. If a certain edge has not been recorded, give the current edge a number and record the node numbers of the two endpoints of the edge; if the current edge has been recorded, discard the current edge. Finally, find the number of all non-repeating edges and record the node numbers corresponding to the two endpoints of each edge to ensure the uniqueness of each edge.

[0079] Specifically, in S203, first, set the left boundary initial value of the model to x min =10000000.0, the right boundary initial value to x max =-10000000.0, the front boundary initial value to y min =10000000.0, the back boundary initial value to y max =-10000000.0, the upper boundary initial value to z max =-10000000.0, and the lower boundary initial value to z min =10000000.0. Further, traverse the coordinates of all nodes. If the coordinate values x c , y c , z c of the cth node satisfy x c <x min , replace x min with x c , if x c >x maxx max is replaced by x c ; similarly, if y c < y min , y min is replaced by y c ; if y c > y max , y max is replaced by y c ; if z c < z min , z min is replaced by z c ; if z c > z max , z max is replaced by z c . After the traversal is completed, the boundary of the model can be obtained. The left boundary of the model is x=x min , the right boundary is x=x max , the front boundary is y=y min , the back boundary is y=y max , the lower boundary is z=z min , and the upper boundary is z=z max .

[0080] Specifically, in S204, by calculating the difference of node coordinates, two edge vectors can be obtained, and then the cross product of the two edge vectors is calculated by cross multiplication to obtain the normal vector of the triangle. Without loss of generality, it is assumed that the node coordinates of the i-th triangular element are (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3). Two edge vectors are obtained by calculating the difference of node coordinates, wherein the coordinates of vector a are (Vx1, Vy1, Vz1), and the coordinates of vector b are (Vx2, Vy2, Vz2).

[0081] The edge vector a and the edge vector b are calculated by using formulas (1) and (2) respectively.

[0082]

[0083]

[0084] Further, the normal vector c (Vx, Vy, Vz) of the triangular element is calculated by using the cross product formula (3).

[0085]

[0086] Further, the length of the normal vector is calculated by using formula (4).

[0087]

[0088] Furthermore, the unit normal vector is calculated using formula (5):

[0089]

[0090] Furthermore, the centroid coordinates of any triangular element are derived using formula (6):

[0091]

[0092] Furthermore, the direction of the force on the triangle is calculated according to formula (7) to ensure that the direction of the force on the triangular element is consistent with the normal vector.

[0093]

[0094] Further, see Figure 3 As shown, S3 includes the following steps:

[0095] S301. Based on the mesh location, call the function library of FLAC3D 6.0, use shell structural elements to represent the surface structure of the geotextile bag, and create a three-dimensional solid calculation model of the geotextile bag; set the initial property parameters of the geotextile bag material, with the modulus along the normal direction being 5.0 × 10⁻⁶. 6 Pa, tangential modulus is 0, thickness is 0.0005 m, density is 930 kg / m³ 3 Simultaneously, the geotextile bags are grouped into circumferential units;

[0096] S302. Set the damping properties of the geotextile unit to ensure the effectiveness of local damping of the structural unit; fix the velocity of the geotextile unit nodes to constrain the position of the geotextile material.

[0097] Further, see Figure 4 As shown, S4 includes the following steps:

[0098] S401. Generate spherical particles of random size within the solid calculation model of the geotextile bag according to the preset porosity. The center of all spherical particles is located within the solid calculation model of the geotextile bag. Assign density and damping properties to the spherical particles to simulate the filling soil particles. The damping coefficient of the spherical particles is 0.1, and the porosity is 0.4. At the same time, use the ray method to determine the number of intersections between the spherical particles and the boundary of the geotextile bag. Delete the spherical particles outside the geotextile bag model. The remaining spherical particles constitute the initial particle system of the filling medium.

[0099] S402. Using the density scaling method, with the time step mode set to automatic, the system loops a preset number of times to delete spherical particles that escape from the target range during the balancing process.

[0100] Specifically, according to the preset porosity, random size ball particles are generated in the geotextile bag model, and the centers of all the ball particles are located in the geotextile bag model; further, the density and damping properties of the ball particles are endowed to simulate the filling soil particles. The damping coefficient of the ball particles is 0.1, and the porosity is 0.4; at the same time, the number of intersection points of the ball particles and the geotextile bag boundary is judged by using the ray method, the ball particles outside the geotextile bag model are deleted, and the remaining ball particles constitute the initial particle system of the filling medium. By using the density scaling method, the time step is 1.0, which is helpful for the rapid balance of the ball particles, the time step mode is modified to the automatic mode, in which the time step is related to the stiffness of the initial particle system, and the initial balance of the particle system is realized by circulating 5000 times, and the particles escaping from the target range in the balance process are deleted.

[0101] Further, referring to Figure 5 As shown in the figure, S5 includes the following steps:

[0102] S501, according to the finite calculation range of the solid calculation model of the geotextile bag and the generated particle size, a regular measuring circle is set in the initial particle system, the radius R of the measuring circle is 6 times the maximum particle radius, and a plurality of tangent measuring circles are set in the geotextile bag model according to the measuring circle radius;

[0103] S502, comparing the center distance between the ball particles, the distance between the ball particles and the geotextile bag model boundary and the radius of the ball particles, determining the contact between the particles in the particle system and the wall, and calculating the total number of contacts;

[0104] S503, setting the contact between the ball particles and the ball particles and the contact between the ball particles and the geotextile bag model boundary as a linear contact model, the attribute parameters of the contact model include normal stiffness and tangential stiffness, wherein the normal stiffness represents the relationship between the normal force and the normal displacement, and the tangential stiffness represents the relationship between the shear stress increment and the shear displacement; all contacts between the particle systems are traversed to calculate the distance between any contact and the measuring circle;

[0105] S504, using PFC3D6.0 platform to iteratively calculate the particle system to realize the free movement of the particles.

[0106] Specifically, in S501, according to the geometric boundary restriction of the geotextile bag model, a closed geometric region is obtained. The calculation range corresponding to the geometric region is obtained according to the coordinates of the geometric region of the geotextile bag model, and in the three-dimensional case, the calculation range of the geotextile bag model can be expressed as [xx min ,xx max ],[yy min ,yy max ],[zz min ,zzmax ], where xx min = -100000, xx max = 100000; yy min = -100000, yy max = 100000; zz min = -100000, zz max = 100000. For each measurement circle, its center coordinates are obtained, the number of measurement circles along the x-axis direction is nx = (xx max - xx min ) / (2*R), the number of measurement circles along the y-axis direction is ny = (yy max - yy min ) / (2*R), and the number of measurement circles along the z-axis direction is nz = (zz max - zz min ) / (2*R). For the center of any measurement circle, a ray is extended horizontally along the right direction, and the number of intersection points of the ray and the geometric boundary of the geotextile model is calculated. If the number of intersection points of the ray corresponding to any measurement circle and the boundary is 0 or even, it is removed; otherwise, it is retained; the screened measurement circles are all within the geometric boundary of the geotextile model.

[0107] Specifically, in S502, for any two spherical particles, when the distance between the centers of the spherical particles is less than or equal to the sum of their radii, it indicates that there is contact between the two spherical particles, i.e., particle-to-particle contact; similarly, if the distance from the center of any spherical particle to the boundary of the geometric region of the geotextile model is not more than the particle radius, it indicates that the particle is in contact with the model boundary, i.e., particle-to-wall contact.

[0108] Specifically, in S503, the coordinates of the pth contact are (x1, y1, z1), and the center coordinates of the jth measurement circle are (x0, y0, z0).

[0109] According to formula (8), the distance dd between any particle system and any measurement circle center is calculated:

[0110]

[0111] All contacts between the particle systems are traversed, the stress tensor inside the measurement circle is calculated, and the average stress inside the measurement circle is solved by the stress tensor.

[0112] According to formula (9), the average stress inside any measurement circle is calculated

[0113]

[0114] Solve the average stress inside all the measuring circles, calculate the average value inside the particle system, and obtain the average stress σs of the particle system.

[0115] Specifically, referring to Figure 7 As shown in S504, the particle system is iteratively calculated by using the PFC3D6.0 platform, the motion of the spherical particles in the particle system is controlled through a preset time step (10000), the changes of the contact force, particle position and velocity inside the particle system (ball-ball, ball-facet) are realized, the stress field inside the particle system is changed, and finally the free motion of the particles is realized. Among them, the target stress trr=10kPa.

[0116] According to formula (10), the difference sss1 between the average stress inside the measuring circle after the particle motion and the target stress (trr) is calculated step by step:

[0117]

[0118] The size of the spherical particles inside the measuring circle is changed by calculating the difference.

[0119] According to formula (11), the error rate sss2 between the average stress inside the particle system after the particle motion and the target stress is calculated:

[0120] sss2= (σ s -trr) / trr (11)

[0121] According to sss1 and sss2, the updated particle size and the average stress of the particle system are judged and deleted for the edge particles, and the above process is repeated to obtain the updated optimal particle system.

[0122] Further, the specific content of S9 is:

[0123] The circumferential confining pressure of the entity calculation model of the geotextile bag is set to 100kPa, 200kPa and 300kPa, respectively, and the upper and lower walls are created in the z direction by using the PFC6.0 platform, and a certain speed is given in opposite directions for loading, simulating the triaxial compression process; the displacement and stress in the axial and lateral directions are monitored until the entity calculation model of the geotextile bag appears shear failure; the stress is calculated according to the force on the loading plate, and the stress data is recorded; at the same time, the position information and initial size of the loading plate are used to calculate the axial strain, and the strain data is recorded; according to the recorded stress and strain data, by changing the confining pressure of the same entity calculation model of the geotextile bag, three groups of deviatoric stress-strain curves are calculated; finally, the strength characteristics of the geotextile bag are analyzed according to the Mohr stress circle, and the equivalent macroscopic strength parameters of the geotextile bag are calculated.

[0124] Further, S11 further analyzes the engineering properties of the entity calculation model of the geotextile bag by combining multiple geotextile bag units in an interlaced arrangement using the parameters obtained by S10.

[0125] Further, the specific content of S11 is:

[0126] According to the actual engineering geotextile bag structure, the entity calculation model of multiple geotextile bags is combined in an interlaced arrangement, the macro equivalent strength parameters of the single geotextile bag unit obtained by S10 are used, a flexible revetment structure is constructed, and the engineering properties of the geotextile revetment structure are further analyzed.

[0127] Specifically, respective parameters are assigned for particle-particle contact and particle-wall contact; the contact model between the filling material soil bodies is set as linear contact, wherein the contact modulus (emod) is set to 1.0e7, the stiffness ratio (kratio) is set to 2.0, and the friction coefficient (fric) is set to 0.3; the contact model between the filling soil body spherical particles and the geotextile body material is also set as linear contact, and the relevant contact parameters are empirically valued.

[0128] The servo method of measuring circles controls the granular system, ensures effective contact between the geotextile body material and the filling soil body and the interior of the filling soil body, reasonably simulates the mechanical behavior of the geotextile bag, and ensures accurate simulation of the interaction between the geotextile bag and the filling soil body; the displacement, velocity and contact force of the filling soil body spherical particles are cleared, then the measuring circle servo is deleted, the position constraint of the spherical particles is released, a new composite system is formed, and see Figure 6 .

[0129] Specifically, triaxial compression tests are carried out on the geotextile composite model. The confining pressure in the hoop direction of the geotextile composite model is set to 100kPa, 200kPa and 300kPa respectively, then the upper and lower rigid walls are created using the PFC6.0 platform, and a certain loading rate 0.001 is set in the z direction to move inward relative, until the model yields and fails, to simulate the strength deformation of the geotextile composite model under triaxial compression, and further calculate the macro equivalent mechanical strength parameters of the geotextile bag.

[0130] The equivalent macroscopic strength parameters of the geotextile bag were calculated. The real-time dimensions of the specimen were obtained using the position coordinates of the upper and lower rigid walls. The axial strain of the specimen was determined by calculating the ratio of the difference between the real-time dimensions and the initial dimensions before loading to the initial dimensions. Furthermore, the axial stress of the geotextile bag composite model was obtained by dividing the force recorded by the loading plate by the contact area. Further, the difference between the axial stress and the radial stress was calculated to obtain a deviatoric stress-strain relationship curve. By changing the confining pressure of the same geotextile bag model, three sets of deviatoric stress-strain relationship curves were plotted. Finally, the strength characteristics of the geotextile bag were analyzed based on the failure Mohr stress circle and strength envelope. The macroscopic equivalent strength parameters of the geotextile bag were determined by the common tangent of the failure stress circle under the ultimate limit state.

[0131] Among them, the center of the Mohr stress circle at failure is radius is Where σ1 represents axial stress and σ3 represents radial stress. The slope of the external tangent of the Mohr stress circle under the ultimate limit state of the geotextile bag can be used to estimate the internal friction angle of the geotextile bag model as φ = 23.37°; based on the intercept of the external tangent with the y-axis, the cohesion of the geotextile bag model is calculated as c = 102.61 kPa.

[0132] Specifically, based on the actual geotextile structure of the project, multiple geotextile models are combined in a staggered arrangement. The macroscopic equivalent strength parameters of the individual geotextile units obtained by S6 are used to construct a flexible revetment structure, providing reliable protection for the project. The safety and stability of the geotextile revetment structure can be further analyzed.

[0133] In one specific embodiment of the present invention, a bank slope project uses geotextile bags for bank protection. Each geotextile bag is 1m long, 1m wide, and 0.3m thick. The filling material inside the geotextile bags is excavated on-site and consists of soil or a soil-rock mixture that does not contain humus. The filling rate is not less than 75%. Figure 3 The outline of the geotextile bag shown is used for design and fabrication, wherein the geotextile bag material is woven into a triangular grid. Figure 2 b), the grid size is 0.05m * 0.05m ( Figure 2 (b) Because the filling material inside geotextile bags is a bulk medium such as soil or soil-rock mixture, it is very difficult to evaluate the mechanical properties of geotextile bag composite media using macroscopic calculation models, which makes it difficult to judge the design and construction of geotextile bag revetments. Therefore, this invention proposes a microscopic numerical simulation method for the mechanical properties of geotextile bag soil-rock media based on discrete-continuous coupling analysis, which can estimate the equivalent strength parameters of geotextile bags during service. The steps are as follows:

[0134] (1) Use Ansys software to create a three-dimensional geotextile mesh, such as... Figure 2 As shown, where, Figure 2 'a' represents a triangular network.Figure 2 b is the grid unit. The size of a single triangular grid is 0.05m*0.05m, a total of 5168 grid nodes and 2586 grid units are needed, and the local grid of the geotextile bag model is shown in Figure 2 a.

[0135] (2) According to the grid position, the function library of FLAC3D6.0 is called, the shell structure unit is used to represent the surface of the geotextile bag, and the three-dimensional geotextile bag model is created, as shown in Figure 3 , wherein, Figure 3 a is the front view, Figure 3 b is the plan view, Figure 3 c is the side view; the triangular grid position is constrained, the geotextile bag unit is set to be undamped, the velocity of the geotextile bag model unit node is fixed, and the bag body material is prevented from deforming. At the same time, the initial parameters of the geotextile bag body material are set, the modulus along the normal direction is 5.0*106Pa, the modulus along the tangential direction is 0, the thickness is 0.0005m, and the density is 930kg / m 3 .

[0136] (3) In the geotextile bag model, random size spherical particles are generated according to the porosity and particle size, the damping coefficient of the spherical particles (ball) is set to 0.1, and the porosity is 0.4; the spherical particles outside the geotextile bag model are deleted, and the filled soil body is simulated, as shown in Figure 4 . The inter-particle contact is set to a linear contact model, the linear contact modulus (emod) is set to 1.0e7, the stiffness ratio (kratio) is set to 2.0, the friction coefficient between the spherical particles is set to 0.3, and the equilibrium calculation function of PFC6.0 is used to calculate the geotextile bag model to the equilibrium state.

[0137] (4) According to the finite calculation range of the geotextile bag model and the particle size generated in the model, a plurality of tangent measurement circles are set in the initial particle system using the PFC3D6.0 platform, as shown in Figure 5 ; the contact form between the particle systems is judged, the average stress inside all the measurement circles is calculated; the motion of the spherical particles in the particle system is controlled through a preset time step to realize the free motion of the spherical particles; at the same time, during the motion of the spherical particles, the particle system is calculated repeatedly according to the error rate between the average stress inside the particle system and the target stress (trr=10kPa), the updated particle size and the average stress of the particle system are judged and deleted for the edge particles to obtain the optimal particle system after updating.

[0138] (5) Set the contact model inside the filling soil body and the contact model between the filling soil and the geotextile bag as linear contact models, wherein the contact model between the filling soil bodies is linear contact, the contact modulus (emod) is set to 1.0e7, the stiffness ratio (kratio) is set to 2.0, and the friction coefficient (fric) is set to 0.3; the contact model between the filling soil round ball particles and the geotextile bag body material is also set as linear contact, the contact modulus (emod) is set to 1.0e7, the stiffness ratio (kratio) is set to 2.0, and the friction coefficient (fric) is set to 0.3. Through the servo method of measuring the circular controlled particle system, the geotextile bag and the filling soil and the filling soil inside are in good contact, so as to ensure that the mechanical behavior in the simulation process can reasonably simulate the interaction between the geotextile bag and the filling soil. Then, the displacement, velocity and contact force of the filling soil round ball particles are cleared, the measuring circle is deleted, and the position constraint of the round ball particles is cancelled, to form a new composite system, as shown in Figure 6 .

[0139] (6) Set the hoop direction confining pressure of the geotextile bag model to 100 kPa, 200 kPa and 300 kPa respectively, create the upper and lower walls in the axial compression direction by using the PFC6.0 platform, and give a certain speed in the opposite direction for loading, so as to simulate the triaxial compression process, as shown in Figure 7 and Figure 8 . Monitor the displacement and stress in the axial compression direction until the geotextile bag model is damaged; convert the force into stress according to the force on the loading plate and the calculation formula, and record the stress data; at the same time, calculate the strain by using the position information and the initial size of the loading plate, and record the strain data; according to the recorded stress (major principal stress) and strain data, calculate the three groups of deviatoric stress and strain relationship curves by changing the confining pressure of the same geotextile bag model, as shown in Figure 9 . Finally, analyze the strength characteristics of the geotextile bag according to the Mohr stress circle, and calculate the equivalent macroscopic strength parameters of the geotextile bag. According to the Mohr strength envelope Figure 10 , the internal friction angle φ of the geotextile bag model is estimated to be 23.37°, and the cohesion C is estimated to be 102.61 kPa.

[0140] (7) Combine multiple geotextile bag structures in a staggered arrangement, and set the macroscopic mechanical parameters of the single geotextile bag according to the above strength parameters, which are used for revetment reinforcement engineering, and the arrangement form of the slope protection geotextile bag is as shown in Figure 11 .

[0141] For the sake of clarity, the components and steps of the examples have been described above generally in terms of their functionality, without reference to the specific manner in which they are implemented. Whether such functionality is implemented in hardware or software depends on the particular application and design constraints imposed on the overall system. Skilled artisans can implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

[0142] The foregoing description of the disclosed embodiments enables a person skilled in the art to implement or use the application. Numerous modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Therefore, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for microscopic analysis of the mechanical properties of geotextile soil and rock media based on numerical simulation, characterized in that, Includes the following steps: S1. Determine the geotextile bags to be tested, and establish a geotextile grid in three-dimensional space based on the geotextile bags to be tested; S2. Locate the grid points and grid structure of the geotextile in three-dimensional space, and retrieve the coordinates of the model boundary nodes of the geotextile to be tested. S3. Based on the model boundary node coordinates of the geotextile bag to be tested, and combined with the surface structure of the geotextile bag to be tested, establish the solid calculation model of the geotextile bag to be tested. S4. Generate spherical particles of random size in the solid calculation model of the geotextile bag according to the preset porosity to obtain the initial particle system of the filling medium, and use the density scaling method to achieve the initial equilibrium of the particle system. S5. Utilizing the limited calculation range of the geotextile bag's solid calculation model and the generated spherical particle size, set multiple tangent measurement circles to determine the contact form between the particle system and calculate the average stress inside all measurement circles; control the movement of the spherical particles within the particle system through a preset time step. S6. During the movement of the spherical particles, the particle system is cyclically calculated based on the error rate between the average stress inside the particle system and the target stress. Edge particles are judged and deleted based on the updated particle size and the average stress of the particle system to obtain the updated optimal particle system. S7. Set the contact between particles inside the updated geotextile bag solid calculation model and the contact between particles and the geometric boundary of the geotextile bag solid calculation model to be linear contact models. Use contact modulus, stiffness ratio and friction coefficient to simulate the physical and mechanical properties of geotextile bag material and filling soil. S8. The servo method of measuring circle control particle system is adopted to ensure effective contact between geotextile material and filling soil and between the filling soil and the interior of the filling soil. The measuring circle servo is deleted, the position constraint of the spherical particles is released, and a new composite system is formed. S9. Set the circumferential confining pressure of the geotextile bag's solid calculation model and apply a specific velocity loading in the Z direction to simulate the triaxial compression process and calculate three sets of deviatoric stress-strain relationship curves. The specific content of S9 is as follows: The circumferential confining pressures of the geotextile bag's solid calculation model were set to 100 kPa, 200 kPa, and 300 kPa, respectively. In the z-direction, upper and lower walls were created using the PFC6.0 platform and loaded at a certain speed towards each other to simulate the triaxial compression process. Monitor axial and lateral displacements and forces until shear failure occurs in the solid calculation model of the geotextile bag; calculate stress based on the force on the loading plate and record stress data; simultaneously calculate axial strain using the position information and initial dimensions of the loading plate and record strain data; based on the recorded stress and strain data, calculate three sets of deviatoric stress-strain relationship curves by changing the confining pressure of the solid calculation model of the same geotextile bag. S10. Analyze the strength characteristics of the geotextile bag based on the Mohr stress circle and calculate the equivalent macroscopic strength parameters of the geotextile bag.

2. The method for microscopic analysis of the mechanical properties of geotextile soil and rock media based on numerical simulation according to claim 1, characterized in that, S1 includes the following: Based on the shape and size of the geotextile bag to be tested, determine the number of grid nodes, the number of units, the grid point coordinates, and the unit composition parameters to construct the geotextile bag grid; based on the shape of the geotextile bag, determine the number of grid nodes and the number of units.

3. The method for microscopic analysis of the mechanical properties of geotextile soil and rock media based on numerical simulation according to claim 2, characterized in that, S2 includes the following steps: S201. Based on the known node coordinates, traverse all cells to search for the edges of each cell; S202. Traverse all given nodes to determine the boundary of the model; S203. Based on the geometry and grid density of the geotextile bag, distribute the grid points and check the unit orientation to ensure that the force direction of each grid is consistent.

4. The method for microscopic analysis of the mechanical properties of geotextile soil and rock media based on numerical simulation according to claim 1, characterized in that, S3 includes the following steps: S301. Based on the mesh location, call the function library of FLAC3D6.0, use shell structural elements to represent the surface structure of the geotextile bag, and create a three-dimensional solid calculation model of the geotextile bag; set the initial property parameters of the geotextile bag material; and group the circumferential elements of the geotextile bag. S302. Set the damping properties of the geotextile unit; fix the velocity of the geotextile unit nodes and constrain the position of the geotextile material.

5. The method for microscopic analysis of the mechanical properties of geotextile soil and rock media based on numerical simulation according to claim 1, characterized in that, S4 includes the following steps: S401. Generate spherical particles of random size in the solid calculation model of the geotextile bag according to the preset porosity. The center of all spherical particles is located in the solid calculation model of the geotextile bag. Assign density and damping properties to the spherical particles to simulate the filling soil particles. At the same time, use the ray method to determine the number of intersections between the spherical particles and the boundary of the geotextile bag. Delete the spherical particles outside the geotextile bag model. The remaining spherical particles constitute the initial particle system of the filling medium. S402. Using the density scaling method, with the time step mode set to automatic, the system loops a preset number of times to delete spherical particles that escape from the target range during the balancing process.

6. The method for microscopic analysis of the mechanical properties of geotextile soil and rock media based on numerical simulation according to claim 1, characterized in that, S5 includes the following steps: S501. Based on the limited calculation range of the geotextile bag's solid calculation model and the generated particle size, set regular measurement circles in the initial particle system. The radius R of the measurement circle is taken as 6 times the maximum particle radius. Based on the radius of the measurement circle, set multiple tangent measurement circles in the geotextile bag model. S502. Compare the center distance between spherical particles, the distance between spherical particles and the boundary of the geotextile bag model, and the radius of the spherical particles to determine the contact situation between particles and particles and between particles and walls in the particle system, and calculate the total number of contacts. S503. Set the contact between spherical particles and between spherical particles and the boundary of the geotextile bag model as a linear contact model. The property parameters of the contact model include normal stiffness and tangential stiffness. Traverse all contacts between the particle system and calculate the distance from any contact to the measurement circle. S504. The PFC3D6.0 platform is used to perform iterative calculations on the particle system to realize the free movement of the particles.

7. A method for microscopic analysis of the mechanical properties of geotextile soil and rock media based on numerical simulation according to any one of claims 1-6, characterized in that, It also includes S11, where the parameters obtained from S10 are used for individual geotextile bag units. By combining multiple geotextile bag units in an alternating arrangement, the engineering characteristics of the geotextile bag's solid calculation model are further analyzed.

8. The method for microscopic analysis of the mechanical properties of geotextile soil and rock media based on numerical simulation according to claim 7, characterized in that, The specific content of S11 is as follows: Based on the actual geotextile bag structure of the project, a solid calculation model of multiple geotextile bags is combined in an alternating arrangement. The macroscopic equivalent strength parameters of the individual geotextile bag unit obtained by S10 are used to construct a flexible revetment structure, and the engineering characteristics of the geotextile bag revetment structure are further analyzed.

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