CN110705087A - Construction method of rock discrete element sample containing closed stress - Google Patents
Construction method of rock discrete element sample containing closed stress Download PDFInfo
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- CN110705087A CN110705087A CN201910919882.4A CN201910919882A CN110705087A CN 110705087 A CN110705087 A CN 110705087A CN 201910919882 A CN201910919882 A CN 201910919882A CN 110705087 A CN110705087 A CN 110705087A
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Abstract
The invention discloses a method for constructing a rock discrete element sample containing closed stress, which can construct the rock discrete element numerical value sample containing the closed stress by adjusting boundary conditions and model parameters, and comprises the following steps: establishing a calculation area; generating a non-cemented particle sample; assigning a linear contact model; eliminating particle interaction inside the sample; applying confining pressure; imparting a parallel bond contact pattern; self-balancing the sample; the internal stress distribution of the sample was measured. The method is simple, convenient and feasible, effectively solves the problems that the rock internal sealing stress cannot be reserved and is difficult to accurately measure from the angle of numerical test, and provides an effective technical means for further researching the influence of the rock internal sealing stress on the mechanical behavior of the rock internal sealing stress.
Description
Technical Field
The invention relates to a geotechnical engineering numerical calculation method, in particular to a rock discrete element sample construction method containing closed stress, and belongs to the field of geotechnical engineering numerical calculation.
Background
Rock is a natural geological material which is quite common in nature, on one hand, the components of the rock are quite complex, and on the other hand, the macro-micro physical mechanical properties of the rock are easily and obviously influenced by the action of an external environment. Due to the existence of geological structure action, temperature action and chemical action in the natural environment, the rock mass with complex components is easy to generate obvious incongruous deformation, so that the closed stress existing in a self-balancing state can be generated in the rock mass. The engineering problems of rock burst, water inrush, collapse, nonlinear creep and the like in rock mass engineering are considered to be in strong connection with the sealing stress in the rock mass. In recent years, engineering construction gradually progresses to deep underground, and in the in-situ deep rock mass, because the rock mass is often subjected to complex geological environments such as high heat, high osmotic pressure, high disturbance and the like, sealing stress is very remarkable in the rock mass, and the influence caused by the sealing stress in the rock mass is not negligible. In the deep rock mass excavation process, along with the removal on external constraint boundary, the inside closed stress of rock mass releases with the form of strain energy gradually, consequently, the inside closed stress of rock mass is difficult to the retention, also is difficult to by the precision measurement simultaneously for further research closed stress is absorbed into the predicament to the influence of rock mass mechanics nature.
The discrete unit method is widely applied to research of rock mechanical properties, can greatly save indoor test resources and well ensure controllability of test variables and sample consistency by adopting the discrete unit method to carry out a numerical test, and can continuously and accurately measure the evolution process of microstructure variables in the sample in the process of carrying out the numerical test. Therefore, the deep research on the sealing stress in the rock by adopting the numerical test based on the discrete unit method is a better scientific attempt. At present, many researchers have used a parallel cementing contact model to characterize the microstructure characteristics of the rock, and have obtained better results, but few researchers have tried to use numerical tests to study the construction of rock samples containing closed stress. In view of the existing documents and patents, a complete set of closed stress-containing rock sample numerical model construction method is still lacking, so that a simple and feasible closed stress-containing rock discrete element sample construction method is needed.
Disclosure of Invention
The invention aims to provide a construction method of a rock discrete element sample containing sealing stress, aims to freeze the sealing stress in the rock sample from the angle of a numerical test, solves the problems that the sealing stress in the rock cannot be reserved and is difficult to accurately measure and the like, and provides an effective technical means and a scientific thought for researching the influence of the sealing stress on the mechanical properties of the rock.
In order to achieve the purpose, the specific technical scheme of the invention is as follows:
a method for constructing a rock discrete element sample containing closed stress comprises the following steps:
a. establishing a calculation area: a calculated area slightly larger than the sample size is established.
b. Generating a non-cemented particle sample: and establishing a corresponding particle generation area according to the sample appearance size parameters, establishing a rigid wall body along the boundary of the particle generation area, filling small particles into the area according to the specified pore ratio, and constructing to obtain the non-cemented particle sample.
c. Assigning a linear contact model: and setting the contact models between the wall and the particles and between the particles as linear contact models, and setting parameters of the linear contact models and other physical property parameters.
d. Eliminating particle interaction inside the sample: the particles in the sample can move freely under the action of unbalanced contact force until the contact force of the particles in the sample is gradually reduced and approaches a specified value.
e. Applying confining pressure: according to a given confining pressure value, a confining pressure is applied in a mode that the peripheral wall of the sample is gradually moved to the center position of the sample, so that certain contact stress is generated inside the sample.
f. Imparting a parallel bond contact pattern: and setting a contact model between particles in the sample as a parallel cementation model, and setting parameters of the parallel cementation contact model to form intergranular cementation which can resist damage among the particles so as to freeze contact stress generated in the sample.
g. Self-balancing of a sample: setting the movement speed of particles in the sample to be zero, deleting the wall body around the sample, continuously enabling the particles in the sample to move freely, and gradually enabling the whole sample to enter a self-balancing state.
h. Measuring the internal stress distribution of the sample: and constructing a measuring ball at the center of the sample after self-balancing, and measuring to obtain the stress tensor of the position.
Further, in step b, the radius of the small particles used for filling the particle area should be less than or equal to one fiftieth of the shortest side length of the sample.
Further, in the step c, the parameters of the linear contact model specifically include wall-to-particle normal contact stiffness, wall-to-particle tangential contact stiffness, wall-to-particle friction coefficient, particle-to-particle normal contact stiffness, particle-to-particle tangential contact stiffness, and particle-to-particle friction coefficient, and the other physical property parameters include particle density, gravitational acceleration, and damping coefficient.
Further, in step d, the standard for eliminating the particle interaction inside the sample is that the contact force of the particles inside the sample is zero.
Further, in step e, the standard of the confining pressure application completion is that the stress value of the peripheral wall body is equal to the given confining pressure value.
Further, in the step f, the parameters of the parallel bond model specifically include the effective young modulus of the bond between the particles, the bond cohesion between the particles, the bond tensile strength between the particles, and the internal friction angle of the bond between the particles.
Further, in the step g, the ratio of the sum of the unbalanced forces of the whole particles to the external force applied to the whole particles is less than 0.0005.
Compared with the prior art, the invention has the following beneficial technical effects:
1. the invention provides a method for constructing a rock discrete element sample containing closed stress, which is used for constructing the rock discrete element sample containing the closed stress on the basis of a discrete unit method.
2. In the method, the discrete element sample is pre-pressed by applying confining pressure, and the magnitude of the sealing stress in the subsequent sample can be interfered by adjusting the magnitude of the confining pressure, so that the controllability of the sealing stress in the sample construction process is ensured.
3. According to the method, the characteristic that the parallel cementation model has the breaking strength is utilized, the contact acting force between the particles is frozen into the interparticle cementation, on one hand, the effect that the parallel cementation model can well reflect the mechanical behavior characteristics of the rock is fully exerted, and on the other hand, the influence of the mechanical behavior of the rock with the sealing stress can be well reflected from a microscopic layer.
Drawings
FIG. 1 is a flow chart of a method for constructing a rock discrete element sample containing closed stress.
Fig. 2 is a graph of a rock discrete element value sample provided by an embodiment of the invention.
Fig. 3 is a distribution diagram of particle contact action categories inside a rock discrete element sample provided by an embodiment of the invention.
Fig. 4 is a graph showing the relationship between confining pressure and the internal stress component value of the sample according to the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clear, the following description will be made of specific embodiments of the present invention with reference to the accompanying drawings and examples.
A method for constructing a rock discrete element sample containing closed stress comprises the following steps:
a. establishing a calculation area: a rectangular parallelepiped calculation region of 0.2 m length, 0.2 m width and 0.4 m height was created.
b. Generating a non-cemented particle sample: establishing a cylindrical particle generation area with the radius of the bottom surface of 0.05 m and the height of 0.2 m according to the external dimension parameters of the sample, establishing a rigid wall body along the boundary of the particle generation area, and filling small particles into the area according to a specified pore ratio to construct and obtain a non-cemented particle sample;
in the present invention, the porosity ratio of the sample is 0.35, the radius of the small particles used is in the range of 0.003-0.004 m, and the number of the whole particles of the sample is 4732, and the sample of the non-cemented particles is obtained as shown in FIG. 1.
c. Assigning a linear contact model: setting contact models between walls and particles and between particles as linear contact models, and setting parameters of the linear contact models and other physical property parameters;
in the present invention, the particle density was 2560 kg/m3The gravity acceleration is-9.8 m/s2The damping coefficient is 0.1; in addition, the linear contact model parameters are shown in the following table:
| parameters of linear contact model | Numerical value |
| Wall and particle normal contact stiffness (N/m) | 1×108 |
| Wall and particle tangential contact stiffness (N/m) | 1×108 |
| Coefficient of friction between wall and particles | 0.2 |
| Particle to particle normal contact stiffness (N/m) | 3×107 |
| Particle to particle tangential contact stiffness (N/m) | 3×107 |
| Coefficient of friction between particles | 0.577 |
d. Eliminating particle interaction inside the sample: the particles in the sample can move freely under the action of the unbalanced contact force until the contact force of the particles in the sample is gradually reduced and approaches to a certain designated value;
the standard for completion of the elimination of the particle interaction inside the sample is that the contact force of the particles inside the sample is zero.
e. Applying confining pressure: according to a given confining pressure value, confining pressure is applied in a mode that a peripheral wall of the sample gradually moves towards the center of the sample, so that certain contact stress is generated inside the sample; the standard of the applied confining pressure is that the stress value of the peripheral wall is equal to the given confining pressure value, and according to the method, the confining pressure application is carried out on the sample according to the confining pressure values shown in the following table:
| parameters of the sample | Example 1 | Example 2 | Example 3 |
| Confining pressure (Pa) | 1×106 | 2×106 | 3×106 |
f. Imparting a parallel bond contact pattern: setting a contact model between particles in the sample as a parallel cementation model, and setting parameters of the parallel cementation contact model to form intergranular cementation which can resist damage among the particles so as to freeze contact stress generated in the sample;
the parameters of the parallel bond contact model used are shown in the following table:
| parallel bond contact model parameters | Numerical value |
| Interparticle cementation effective Young's modulus (Pa) | 1×1010 |
| Interparticle cementing cohesion (Pa) | 5×1011 |
| Interparticle bond tensile Strength (Pa) | 1×1011 |
| Interparticle cementation internal friction angle (°) | 30 |
g. Self-balancing of a sample: setting the movement speed of particles in the sample to be zero, deleting the wall body around the sample, continuously enabling the particles in the sample to move freely, and gradually enabling the whole sample to enter a self-balancing state;
the whole sample reaches the self-balancing state judgment standard, namely the ratio of the sum of the overall unbalanced acting force of the particles to the external force borne by the whole particles is less than 0.0005, when the self-balancing state reaches, the contact action type distribution of the particles in the sample is shown in figure 3, and from the numerical test result, after the particles in the sample are bonded through a parallel cementing model and reach the self-balancing state, the contact action among the particles is not completely generated in a compression stress mode, and a certain tensile stress exists among partial particles.
h. Measuring the internal stress distribution of the sample: constructing a measuring ball at the center position of the sample after self-balancing, wherein the radius of the measuring ball is 0.04 m, and measuring to obtain the stress tensor of the position; the distribution situation of the internal stress of the sample is quantitatively described by respectively selecting and three stress components, the results of different embodiments are shown in fig. 4, and from the results of numerical tests, after the series of steps, a certain nonuniform sealing stress exists in the sample, and the final sealing stress can be regulated and controlled by changing the magnitude of the applied confining pressure.
Claims (7)
1. A method for constructing a rock discrete element sample containing closed stress is characterized by comprising the following steps:
a. establishing a calculation area: establishing a calculation area slightly larger than the size of the sample;
b. generating a non-cemented particle sample: establishing a corresponding particle generation area according to the sample appearance size parameters, establishing a rigid wall body along the boundary of the particle generation area, filling small particles into the area according to a specified pore ratio, and constructing to obtain a non-cemented particle sample;
c. assigning a linear contact model: setting contact models between walls and particles and between particles as linear contact models, and setting parameters of the linear contact models and other physical property parameters;
d. eliminating particle interaction inside the sample: the particles in the sample can move freely under the action of the unbalanced contact force until the contact force of the particles in the sample is gradually reduced and approaches to a certain designated value;
e. applying confining pressure: according to a given confining pressure value, confining pressure is applied in a mode that a peripheral wall of the sample gradually moves towards the center of the sample, so that certain contact stress is generated inside the sample;
f. imparting a parallel bond contact pattern: setting a contact model between particles in the sample as a parallel cementation model, and setting parameters of the parallel cementation contact model to form intergranular cementation which can resist damage among the particles so as to freeze contact stress generated in the sample;
g. self-balancing of a sample: setting the movement speed of particles in the sample to be zero, deleting the wall body around the sample, continuously enabling the particles in the sample to move freely, and gradually enabling the whole sample to enter a self-balancing state;
h. measuring the internal stress distribution of the sample: and constructing a measuring ball at the center of the sample after self-balancing, and measuring to obtain the stress tensor of the position.
2. The method for constructing the rock discrete element sample containing the confining stress as claimed in claim 1, wherein in the step b, the radius of the small particles used for filling the particle area is less than or equal to one fiftieth of the shortest side length of the sample.
3. The method according to claim 1, wherein in step c, the parameters of the linear contact model specifically include wall-to-particle normal contact stiffness, wall-to-particle tangential contact stiffness, wall-to-particle friction coefficient, particle-to-particle normal contact stiffness, particle-to-particle tangential contact stiffness, and particle-to-particle friction coefficient, and the other physical property parameters include particle density, gravitational acceleration, and damping coefficient.
4. The method for constructing the rock discrete element sample containing the confining stress as claimed in claim 1, wherein in the step d, the criterion for eliminating the particle interaction inside the sample is that the contact force of the particles inside the sample is zero.
5. The method for constructing the rock discrete element sample containing the confining pressure as recited in claim 1, wherein in the step e, the standard of the confining pressure application completion is that the stress value of the peripheral wall is equal to the given confining pressure value.
6. The method for constructing the rock discrete element sample containing the sealing stress according to claim 1, wherein in the step f, the parameters of the parallel bond model specifically include the effective Young's modulus of the inter-particle bond, the bonding cohesion of the inter-particle bond, the tensile strength of the inter-particle bond, and the internal friction angle of the inter-particle bond.
7. The method for constructing the rock discrete element sample containing the confining stress as claimed in claim 1, wherein in the step g, the ratio of the sum of the unbalanced forces of the whole particles to the sum of the external forces applied to the whole particles is less than 0.0005.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112326524A (en) * | 2020-10-22 | 2021-02-05 | 中国石油大学(华东) | Rock pore permeability measurement method based on CT scanning image |
| CN113433150A (en) * | 2021-06-29 | 2021-09-24 | 北京科技大学 | Method for determining rock sealing stress |
| CN115389286A (en) * | 2022-08-23 | 2022-11-25 | 东北大学 | Deep rock mass closed stress construction method for physical model test |
| CN116337627A (en) * | 2023-05-30 | 2023-06-27 | 北京科技大学 | Determination method for real strength of rock by considering sealing stress |
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| CN103940666A (en) * | 2014-03-18 | 2014-07-23 | 中国矿业大学 | Determination method for mesoscopic parameters simulating mechanical properties of intermittent crack rock |
| US20180124328A1 (en) * | 2016-11-02 | 2018-05-03 | National University Of Defense Technology | Method for measurement and 3D reconstruction of precipitation particles based on orthogonal dual-view imaging |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112326524A (en) * | 2020-10-22 | 2021-02-05 | 中国石油大学(华东) | Rock pore permeability measurement method based on CT scanning image |
| CN113433150A (en) * | 2021-06-29 | 2021-09-24 | 北京科技大学 | Method for determining rock sealing stress |
| CN115389286A (en) * | 2022-08-23 | 2022-11-25 | 东北大学 | Deep rock mass closed stress construction method for physical model test |
| CN116337627A (en) * | 2023-05-30 | 2023-06-27 | 北京科技大学 | Determination method for real strength of rock by considering sealing stress |
| CN116337627B (en) * | 2023-05-30 | 2023-08-11 | 北京科技大学 | Determination method for real strength of rock by considering sealing stress |
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