CN110765572A - Continuous discontinuous numerical simulation method for single triaxial test of almond-shaped basalt - Google Patents
Continuous discontinuous numerical simulation method for single triaxial test of almond-shaped basalt Download PDFInfo
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Abstract
The invention relates to a continuous discontinuous numerical simulation method for a single triaxial test of almond-shaped basalt, which comprises the following steps: obtaining macro and micro structural features of the core sample and a statistical model of the almond body; establishing a fine model capable of simulating rock structure characteristics based on the statistical model of the almond body; and carrying out rock single triaxial test numerical simulation on the fine model by using a continuous discontinuous numerical method, and revealing the damage mechanism of the rock and the influence of the almond body on the rock fracture behavior from the macro-micro perspective. The simulation method can reveal the damage mechanism and the influence of the almond body on the mechanical property and the rupture behavior from the macro-microscopic perspective.
Description
Technical Field
The invention relates to the technical field of rock mechanics and engineering, in particular to a continuous and discontinuous numerical simulation method for an almond-shaped basalt single triaxial test.
Background
As a natural heterogeneous geological material, various defects (such as microcracks, bedding, holes, joints, faults and the like) inevitably develop in the rock. The instability destruction of rock engineering is often a dynamic evolution process in which the primary defects are continuously closed, cracked, expanded and communicated under the action of load and finally cause material destruction, and is closely related to the evolution law of cracks. Therefore, developing the fracture characteristics, mechanism and evolution rule detection of the rock with defects is a basic scientific problem for accurately revealing the pregnancy disaster mechanism of underground engineering, scientifically predicting the disaster approach mode and effectively preventing and treating disasters, and has important theoretical value and practical significance.
The influence of defects such as cracks and holes on the strength, deformation characteristics and fracture evolution rules of the rock or rock-like material is researched by adopting various test technologies, and the influence of various factors including geometrical parameters (quantity, inclination angle, length, shape and the like), mechanical properties (whether filling, filling type and the like exist, stress state and the like of the defects on the rock fracture mechanism is analyzed. However, although the testing method can intuitively obtain the mechanical characteristics and behavior characteristics of the rock and partially reveal the failure mechanism, the method is difficult to deeply reveal the inherent evolution law and mechanism of deformation failure, and has the defects of complex operation, high cost, long period and the like. With the rapid development of computational rock mechanics, the numerical simulation has the advantages of strong repeatability, accuracy and the like, and is widely used for researching macro-micro mechanics characteristics and fracture mechanisms of rocks, wherein the numerical simulation mainly comprises numerical methods of continuity (FEM, FDM, XFEM, RFPA and the like) and discontinuity (DEM, DDA and the like). As is known, the continuous numerical method cannot truly represent the initial defects in the brittle rock and capture the newly formed discontinuous structure in the fracture process, and the traditional discontinuous medium numerical simulation method cannot well simulate the evolution process from continuous to discontinuous.
Basalt is a typical volcanic eruption rock, and usually contains heterogeneous bodies such as pores and almond bodies. The great coupling factors in the basalt diagenesis process cause the geometric parameters and physical and mechanical parameters of almond bodies or holes to generate remarkable variability, such as: the almond body content can range from almost 0% to 100%, the diameter can span many orders of magnitude (from tens of microns to a few millimeters, even centimeter-sized), the shape can range from slender to spherical, and these differences tend to have important effects on the mechanical properties of the rock and the fracture mechanism. In addition, the overall discreteness and variability of the indoor test results are large, and the test and analysis difficulty of the test is increased to a certain extent. Therefore, the numerical method is more necessary to develop the single triaxial mechanical test research of the almond-shaped basalt.
Disclosure of Invention
The invention provides a continuous and discontinuous numerical simulation method for a single triaxial test of almond-shaped basalt, which lays a solid foundation for accurately recognizing and scientifically mastering the mechanical response and the fracture mechanism of underground engineering surrounding rock and can also provide reference for understanding the mechanical behavior of other rocks with defects and controlling the stability of an engineering rock mass.
The invention provides a continuous discontinuous numerical simulation method for a single triaxial test of almond-shaped basalt, which comprises the following steps:
the method comprises the following steps: obtaining macro and micro structural features of the core sample and a statistical model of the almond body;
step two: establishing a fine model capable of simulating rock structure characteristics based on the statistical model of the almond body;
step three: and carrying out rock single triaxial test numerical simulation on the fine model by using a continuous discontinuous numerical method, and revealing the damage mechanism of the rock and the influence of the almond body on the rock fracture behavior from the macro-microscopic viewpoint.
Preferably, the first step includes:
performing a polarizing microscope test on the rock core sample, and determining the structure, the particle size and the mineral composition of the rock core sample;
and determining the spatial distribution, the shape and the geometric dimension of the almond bodies in the core sample through electronic computed tomography scanning, and then determining a statistical model of the almond bodies.
Preferably, the first step includes:
performing a polarizing microscope test on the rock core sample, and determining the structure, the particle size and the mineral composition of the rock core sample;
measuring and counting two-dimensional geometric parameters of the almond body on the surface of the core sample to obtain corresponding surface almond body statistics; the two-dimensional shape of the almond body is an ellipse, and the two-dimensional geometric parameters comprise: a length of a major axis, an azimuth of the major axis, and a ratio of minor axis to major axis; wherein the azimuth angle of the major axis is defined as: the included angle between the long axis direction and the horizontal direction;
and obtaining a statistical model of the almond body by the surface almond body statistical combination probability distribution simulation method.
Preferably, the second step comprises:
determining a model size of the fine model;
generating a random ellipse by adopting a Monte Carlo technology according to the statistical model of the almond body;
setting a positional relationship between the ellipses to determine the fine model.
Preferably, the setting of the positional relationship between the ellipses includes:
setting no overlap between the ellipses, and if not, appointing a new centroid coordinate again;
and setting no overlap between the ellipse and the model boundary, and if not, appointing a new centroid coordinate again.
Preferably, the third step is: and importing the geometric figure of the fine model into continuous discontinuous numerical simulation software to obtain a numerical model capable of simulating the rock structure characteristics.
Preferably, the numerical model is divided into 3-node finite element triangular units in the continuous and discontinuous numerical simulation software, and 4-node bonding crack unit grids are embedded between the edges of the adjacent triangular units.
Preferably, the constitutive relation and the destruction criterion of the numerical model are:
the mechanical analysis of the triangular units adopts a linear elastic continuous medium theory, the normal repulsive force generated between the contact pairs of the triangular units is solved by adopting a distributed contact force penalty function method based on a potential function, and the tangential frictional force is calculated by adopting a coulomb friction law;
the progressive failure of the bonded crack units adopts a maximum tensile stress failure criterion and an M-C failure criterion, and the bonded crack units can yield and break in a pull failure mode, a shear failure mode or a pull-shear mixed failure mode based on local stress and crack relative displacement.
Preferably, the boundary conditions of the numerical model are: the axial loading is realized by applying vertical displacement rates with opposite directions and the same magnitude to the upper end and the lower end, and confining pressure corresponding to an indoor test is respectively applied to the left boundary and the right boundary.
Preferably, the mesoscopic parameters input by the numerical model are as follows: the elasticity parameter of the triangular unit, the strength parameter of the bonding crack unit and the penalty value.
One or more technical solutions provided in the present application have at least the following technical effects or advantages:
the method can obtain macro-micro structural features of the rock and the development rule of the almond body before mechanical test, establish a fine model capable of truly reflecting the complex structural features of the rock, develop relevant rock single triaxial test numerical simulation by using a continuous-discontinuous (FDEM) numerical method, explore the deformation destruction features and the fracture evolution process of the almond-shaped basalt, reveal the damage mechanism and the influence of the almond body on the mechanical properties and the fracture behavior of the almond-shaped basalt from the macro-micro perspective, lay a solid foundation for accurately confirming and scientifically mastering the mechanical response and the fracture mechanism of the underground engineering surrounding rock, and provide reference and reference for understanding of the mechanical behavior of other rocks with defects.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention.
Fig. 1 is a schematic flow chart of a continuous discontinuous numerical simulation method for a single triaxial test of almond-shaped basalt according to an embodiment of the present application;
FIG. 2 is a pictorial view of an almond-shaped basalt drill core in accordance with an embodiment of the present application;
fig. 3(a) is a characteristic diagram (polarization micrograph) of a macro-microscopic structure of the almond-shaped basalt provided by the embodiment of the application;
fig. 3(b) is a macro-microscopic structural feature diagram (CT scan diagram) of the almond-shaped basalt provided in the embodiment of the present application;
FIG. 4 is a graph of statistical results of geometric parameters of an almond body according to an embodiment of the present application;
FIG. 5 is a diagram of an FDEM numerical model of almond-shaped basalt according to an embodiment of the present application;
FIG. 6 is a stress-strain curve diagram of almond-shaped basalt under different confining pressures, provided by an embodiment of the present application;
FIG. 7 is a diagram of the destruction mode of almond-shaped basalt under different confining pressures according to an embodiment of the application;
fig. 8 is a diagram of the fracture evolution process of an almond-shaped basalt numerical test sample under uniaxial loading provided by the embodiment of the application.
Detailed Description
For further understanding of the present invention, the present invention will be described in more detail below with reference to the specific drawings and an embodiment of the continuous-discontinuous numerical method of the single triaxial test of almond-shaped basalt.
Taking the construction of a certain hydropower station as an example, an underground plant area is mainly located in a basalt stratum, the problem of high stress cracking of surrounding rocks in the excavation process caused by huge engineering scale, complex geological conditions, medium and high ground stress and the like is obvious, the damage modes of hard and brittle rock masses such as rib spalling, cracking relaxation and the like are widely disclosed, and great challenges are brought to the stability control of the surrounding rocks on site. The basalt bodies of the underground powerhouse can expose large-scale faults, dislocation zones, joint surfaces and other geological structures, and the almond-shaped basalt generally has a fine-scale almond body structure and has obvious influence on the mechanical properties and the fracture mechanism of rocks. Therefore, the deep research on the influence of the almond body on the basalt fracture evolution rule and the damage mechanism has important significance for accurately recognizing the underground plant surrounding rock damage mode, mastering the fracture evolution characteristics and predicting the damage degree, and can also provide reference for understanding of the mechanical behavior of other rocks with defects.
The method comprises the following specific steps:
the method mainly comprises three parts, S1: and obtaining macro and micro structural features of the rock and statistical rules of the almond body. S2: and establishing a fine model capable of truly reflecting the complex structural characteristics of the rock. S3: relevant rock single triaxial test numerical simulation is carried out by utilizing continuous-discontinuous (FDEM) numerical software (Irazu), and the damage mechanism and the influence of the almond body on the rupture behavior are revealed from the macro-microscopic perspective. The method comprises the following specific steps:
s1: firstly, macro-micro structural features and statistical rules of the almond body of a rock are obtained before mechanical loading, and development features of the almond body are revealed;
s101: the drilled core was collected from the underground powerhouse cavern group project site, about 50mm in diameter, see fig. 2.
S102: the rock slices ground to a length × width × thickness of 30 × 20 × 0.03mm were observed with a Leitz-ORTHOPLAN polarizing microscope in Germany to identify the mineral structure, particle size and mineral composition.
As shown in FIG. 3(a), the rock has an almond-shaped structure, wherein the almond body accounts for about 20 to 25%, is mostly elliptical and round, has a size of 0.6 to 4mm, is mostly chlorite as a mineral component, is slightly filled with quartz, and is accompanied by a large number of microcracks. The matrix has a grain-space hidden structure, and the mineral components mainly comprise anorthite, aphanite, common pyroxene, a small amount of chlorite and the like; the labrador is in a self-shaped lath shape, and the long diameter is 0.02-0.3 mm; the pyroxene is in the form of particles with the particle diameter of 0.01-0.04 mm; the vitreous is a cryptocrystalline aggregate, is a non-crystallized substance in the spray process of the lava, is dark brown, and is difficult to distinguish under a mirror.
S103: in order to accurately know the characteristics of spatial distribution, form, geometric dimension and the like of the almond body in the rock, a German Siemens SOMATOM sensing 40 CT machine is used for scanning a rock core sample, and a layer is scanned every 1mm from top to bottom along the height direction.
As shown in fig. 3(b), the internal defects of the rock have large overall difference, strong randomness and obvious heterogeneity, and the density, size, shape, direction distribution and the like of the almond body have no obvious rules.
S104: due to the high cost of CT scanning, it is difficult to scan a large number of samples. Therefore, the geometric parameters of the almond body on the surface of the cylindrical core sample are measured and counted to obtain a corresponding probability model. The almond body is approximately elliptical in a two-dimensional state, and the geometric parameters mainly comprise the length of a long axis, the azimuth angle of the long axis (defined as the included angle between the direction of the long axis and the horizontal direction), the ratio of a short axis to the long axis and the like.
As shown in fig. 4, about 2500 almond bodies having a major axis length of 1mm or more among 18 standard cylindrical samples (diameter 50mm, height 100mm) were analyzed, and the inclination angle of the major axis was uniformly distributed, the length was negatively exponential distributed (λ ═ 0.23, μ ═ 4.31mm, correlation coefficient 0.96), the minor axis/major axis was normally distributed (μ ═ 0.63, σ ═ 0.17, correlation coefficient 0.98), the areal density P20 was 0.012 pieces/mm 2, and the area ratio of the almond bodies was 14.66%.
S2: and establishing a two-dimensional fine model capable of truly reflecting the complex structural characteristics of the rock based on the statistical law of the almond body.
S201: determining the range of a research area, wherein the width multiplied by the height of the model is 50mm multiplied by 100mm, and the size of the model is consistent with that of an actual standard cylindrical sample;
s202: generating a group of random ellipses by adopting Monte Carlo technology (Monte Carlo) according to the statistical probability model of the geometric parameters of the almond body;
s203: the positional relationship between ellipses is analyzed based on boolean operations, no overlap is allowed between ellipses and model boundaries, otherwise new centroid coordinates are reassigned, all implemented in Matlab, and the results are shown in fig. 5 (a).
S3: relevant single triaxial experimental numerical simulations were carried out using continuous-discontinuous (FDEM) numerical software (Irazu) revealing its destruction mechanism and the effect of the almond mass on its rupture behavior from a macro-microscopic perspective.
S301: and (3) introducing the generated geometric figure into continuous-discontinuous (FDEM) numerical simulation software (Irazu), dividing the geometric figure into 3-node triangular finite elements, embedding 4-node bonding crack unit grids between the edges of adjacent triangular units, wherein the side length of each triangular unit is 1mm, and dividing the triangular unit into 22500 units.
The numerical model constitutive relation and the destruction criterion are as follows: the mechanical analysis of the triangular units adopts a linear elastic continuous medium theory, the normal repulsive force generated between the contact pairs of the triangular units is solved by adopting a distributed contact force penalty function method based on a potential function, and the tangential frictional force is calculated by adopting a Coulomb friction law. The crack unit is used for simulating progressive failure of the material, and mode I (tensile failure), mode II (shear failure) or I-II mixed mode (tensile-shear failure) yielding and breaking of the crack unit can occur based on local stress and relative crack displacement by adopting a maximum tensile stress failure criterion and an M-C failure criterion.
Boundary conditions of the model: the axial loading is realized by applying vertical displacement rates of 0.05m/s with opposite directions and the same magnitude at the upper end and the lower end. And applying confining pressure corresponding to the indoor test to the left and right boundaries respectively to carry out a single triaxial loading test, wherein the confining pressure range is 0-30 MPa. The operation is performed by adopting a plane strain model, and the time step length is 5 multiplied by 10-7ms. The axial stress and strain are calculated by the node force and displacement of the upper and lower load plates, and the lateral strain is calculated by monitoring the displacement of the node according to the middle local area (the width is about 10mm) of two side surfaces of the sample, as shown in fig. 5 (b).
The microscopic parameters input by the model are as follows: mainly comprising elastic parameters (E, ν and rho) of triangular units and strength parameters (c, phi and f) of quadrilateral bonding crack unitst、GfEtc.) and penalty values (P)n、Pt、Pf). In general, the energy of rupture Gf1Fracture toughness K measured by three-point bending test or estimated by tensile strengthIcCalculated to obtain the breaking energy Gf2About 10Gf1Penalty value (P)n、Pt、Pf) The elastic modulus is 10-100 times, and other parameters refer to test results. The model is composed of two materials, namely a matrix and an almond body, the homogeneity is isotropic, the matrix refers to the test result (pure matrix), and the parameter of the almond body is properly weakened relative to the matrix. Continuously carrying out trial and error check on the basis of initial parameters, and obtaining reasonable results when the results (stress-strain curve, macroscopic mechanical parameters, characteristic strength, damage characteristics and the like) obtained by numerical simulation are basically consistent with the test resultsSee table 1 for mesoscopic parameters of (a).
TABLE 1 Almond basalt FDEM microscopic parameters
As shown in fig. 6, the initial compaction stage of all numerical value samples is not obvious, and the mechanical behavior of the curve before the peak is expressed as linear characteristic; the curve near the peak is in a sawtooth shape, the platform of the peak is obvious, and the stress after the peak falls off. Along with the increase of confining pressure, the fluctuation range of the curve near the peak value is continuously increased, the stress after the peak falls slowly, and the feature is gradually changed from brittleness to ductility. In conclusion, the stress-strain curves obtained by numerical simulation and indoor test have good consistency in regularity and numerical value.
As can be seen in Table 2, the mechanical parameters obtained by numerical simulation are basically consistent with the test results, which shows that the microscopic parameters selected by the numerical model have better reliability and can better reflect the main mechanical behavior of the almond-shaped basalt.
TABLE 2 Almond basalt Macro-mechanics parameters
As shown in FIG. 7, the specimen fails under uniaxial loading in the form of a split fracture, with multiple longitudinal tensile cracks intersecting each other throughout the specimen. 0<σ3When the pressure is less than or equal to 10MPa, the whole sample is cracked and damaged, mainly by tension cracks and secondarily by shear cracks. Increases with confining pressure (10)<σ3Less than or equal to 30MPa), the tensile crack is restrained, the main body forms an inclined shearing or conjugate shearing fracture surface which forms an angle of 60-70 degrees with the horizontal direction from the upper right corner to the lower left corner, the shear fracture is taken as the main part, and the tensile crack develops locally. The fracture form of the numerical value sample is consistent with the test result, and the damage characteristics of the basalt can be well reflected.
S302: after the numerical calculation is completed, the crack propagation and stress field evolution characteristics in the numerical samples under different confining pressures are analyzed in detail, and the damage mechanism and the influence of the almond body on the fracture behavior are revealed from the macro-micro perspective.
As shown in fig. 8(a), the slope of the axial stress-strain curve at the initial stage of loading was substantially constant and free from microcracks. Sigma obtained by strain inflection point of crack body with increasing loadci62.99MPa, sigmaci/σfIs 0.47, and the test result (. sigma.)ci/σf0.45) at which point yield cracks begin to appear and increase significantly, thereafter increasing substantially linearly, the lateral stress-strain curve begins to appear nonlinear, and the specimen progresses into the crack propagation stabilization phase. σ obtained by volume strain inflection point as loading continuescd123.24MPa, sigmacd/σfIs 0.92, and the test result (. sigma.)cd/σf0.90) at which the cumulative yield crack increases sharply, the axial stress-strain curve deviates from linearity, and the specimen proceeds into the crack unstable propagation stage. Once the stress reaches the peak strength (134.40MPa), the stress drops rapidly, the yield crack growth rate reaches the maximum, the fracture crack develops rapidly, and the brittle fracture is obvious. The residual stress is 0, the number of microcracks is not changed, the ratio of the number of tensile and shear fracture cracks is about 5:1, and the tensile cracks are taken as the main.
As shown in fig. 8(b) and (c), at the initial stage of loading (point I), the stress field in the sample is at a very low level, and is relatively uniform, the anisotropy is not obvious, and there are no microcracks. When the axial stress reaches sigmaci(Point II), the stress field is non-uniform, the stress level inside the almond body is low, local stress concentration begins to occur around the almond body, and the compressive stress of the left and right substrates is concentrated (maximum principal stress σ)1) Upper and lower end substrate tensile stress concentration (minimum principal stress σ)3) And the smaller the spacing between the almond bodies is, the more obvious the stress concentration is. Because the strength of the almond body unit is low, the local stress reaches the peak strength at the moment, and the almond body in the middle of the sample begins to yield.
When the axial stress reaches sigmacd(Point III), the stress field non-uniformity is more pronounced when the majority of the almond bodies are already presentHowever, because the almond body units are softer and require more post-peak deformation to separate, no fracture cracks are seen in the almond body. Significant compressive stress concentrations occur on the left and right sides of the almond body A, B, tensile stress concentrations occur at the upper and lower ends thereof, peak tensile strength of the matrix units is reached, part of the matrix crack units begin to yield in tension, tensile stress at the yield position is released, and the tensile stress concentration area migrates to the crack tip. At the moment, the yield cracks of the matrixes between the almond bodies A and C are already communicated, the matrixes between the almond bodies B and D are thicker, the tensile yield cracks are not communicated yet, but a tensile stress concentration strip is formed, and the continuous expansion of the cracks is facilitated.
Peak point sigmad(point IV) the compressive stress concentration degree of the edge of the almond body is increased, the concentration range is enlarged, the pulling crack between the almond bodies G, H begins to appear and form local through, the pulling crack with local through is also formed between A, C and E and between B, D, the pulling stress concentration continuously migrates to the tip, and the stress release appears at the cracking position; with the gradual loading and deformation development, the part of the crack units which are already yielding in the stress release area begin to break due to the opening and sliding of the crack units, and tensile and shear fractures are generated, so that the crack tips are still in the stress concentration area and continuously undergo the yielding and breaking evolution process of the cracks, and the stress field also changes between the stress concentration and release areas. Therefore, the evolution characteristics of the stress field have a significant influence on the crack initiation and propagation process, and in turn the formation of these new cracks will further change the distribution of the stress field.
At the rear section (point V) of the peak, a through tensile crack is formed between the almond bodies A and B, and a through tensile crack parallel to the loading direction is also formed between other almond bodies, mainly for the tensile damage of the matrix unit; then, the micro cracks are mutually overlapped, collected and combined, and penetrate through the inside of the almond body to continuously expand towards two ends.
The rock sample interpenetrates and coalesces into macroscopic fractures from local fractures, with multiple longitudinal macroscopic fracture planes penetrating the sample and eventually causing sample failure (point VI) and debris spallation, at which point the stress field has been released. The whole sample is split damage, the internal is matrix tension damage, almond body shearing or tension damage, and the damage form is basically consistent with the test picture.
Therefore, the FDEM numerical model which is established based on the statistical law of the almond body and considers the heterogeneity of the rock microstructure can well reproduce the progressive fracture process of the brittle rock.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only illustrative of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A continuous discontinuous numerical simulation method for an almond-shaped basalt single triaxial test is characterized by comprising the following steps:
the method comprises the following steps: obtaining macro and micro structural features of the core sample and a statistical model of the almond body;
step two: establishing a fine model capable of simulating rock structure characteristics based on the statistical model of the almond body;
step three: and carrying out rock single triaxial test numerical simulation on the fine model by using a continuous discontinuous numerical method, and revealing the damage mechanism of the rock and the influence of the almond body on the rock fracture behavior from the macro-microscopic viewpoint.
2. The method for continuous discontinuous numerical simulation of the almond-shaped basalt single triaxial test according to claim 1, wherein the first step comprises:
performing a polarizing microscope test on the rock core sample, and determining the structure, the particle size and the mineral composition of the rock core sample;
and determining the spatial distribution, the shape and the geometric dimension of the almond bodies in the core sample through electronic computed tomography scanning, and then determining a statistical model of the almond bodies.
3. The method for continuous discontinuous numerical simulation of the almond-shaped basalt single triaxial test according to claim 1, wherein the first step comprises:
performing a polarizing microscope test on the rock core sample, and determining the structure, the particle size and the mineral composition of the rock core sample;
measuring and counting two-dimensional geometric parameters of the almond body on the surface of the core sample to obtain corresponding surface almond body statistics; the two-dimensional shape of the almond body is an ellipse, and the two-dimensional geometric parameters comprise: a length of a major axis, an azimuth of the major axis, and a ratio of minor axis to major axis; wherein the azimuth angle of the major axis is defined as: the included angle between the long axis direction and the horizontal direction;
and obtaining a statistical model of the almond body by the surface almond body statistical combination probability distribution simulation method.
4. The continuous discontinuous numerical simulation method for the single triaxial test of the almond-shaped basalt according to claim 1, wherein the second step comprises:
determining a model size of the fine model;
generating a random ellipse by adopting a Monte Carlo technology according to the statistical model of the almond body;
setting a positional relationship between the ellipses to determine the fine model.
5. The method for continuous discontinuous numerical simulation of the almond-shaped basalt single triaxial test according to claim 4, wherein the setting of the positional relationship between the ellipses includes:
setting no overlap between the ellipses, and if not, appointing a new centroid coordinate again;
and setting no overlap between the ellipse and the model boundary, and if not, appointing a new centroid coordinate again.
6. The continuous discontinuous numerical simulation method for the single triaxial test of the almond-shaped basalt according to claim 1, wherein the third step is: and importing the geometric figure of the fine model into continuous discontinuous numerical simulation software to obtain a numerical model capable of simulating the rock structure characteristics.
7. The method for continuous and discontinuous numerical simulation of almond-shaped basalt single triaxial test according to claim 6, wherein the numerical model is divided into 3-node finite element triangular units in the continuous and discontinuous numerical simulation software, and 4-node bonding crack unit grids are embedded between the edges of the adjacent triangular units.
8. The method for continuous and discontinuous numerical simulation of the almond-shaped basalt single triaxial test according to claim 6, wherein the constitutive relation and the failure criterion of the numerical model are as follows:
the mechanical analysis of the triangular units adopts a linear elastic continuous medium theory, the normal repulsive force generated between the contact pairs of the triangular units is solved by adopting a distributed contact force penalty function method based on a potential function, and the tangential frictional force is calculated by adopting a coulomb friction law;
the progressive failure of the bonded crack units adopts a maximum tensile stress failure criterion and an M-C failure criterion, and the bonded crack units can yield and break in a pull failure mode, a shear failure mode or a pull-shear mixed failure mode based on local stress and crack relative displacement.
9. The continuous discontinuous numerical simulation method for the single triaxial test of the almond-shaped basalt according to claim 6, wherein the boundary conditions of the numerical model are as follows: the axial loading is realized by applying vertical displacement rates with opposite directions and the same magnitude to the upper end and the lower end, and confining pressure corresponding to an indoor test is respectively applied to the left boundary and the right boundary.
10. The method for continuous and discontinuous numerical simulation of the almond-shaped basalt single triaxial test according to claim 6, wherein the microscopic parameters input by the numerical model are as follows: the elasticity parameter of the triangular unit, the strength parameter of the bonding crack unit and the penalty value.
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| CN113420427A (en) * | 2021-06-07 | 2021-09-21 | 中国科学院武汉岩土力学研究所 | Rock structural surface shearing continuous-discontinuous numerical method under constant rigidity |
| CN117291083A (en) * | 2023-09-11 | 2023-12-26 | 湘潭大学 | Rock discrete element model building method, rock mechanics multi-scale computing method, system and medium |
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