Method for acquiring mechanical properties in whole direct coal stretching process based on molecular simulation

Abstract

The invention provides a molecular simulation-based method for acquiring mechanical properties of a whole direct coal stretching process. The method comprises the following steps: acquiring structural information, density and moisture content of various coal samples in a coal seam prone to dynamic disasters; constructing molecular structure super-unit cells of the coal sample based on the structure information, density and moisture content of the coal sample; carrying out uniaxial stretching simulation calculation on the molecular structure superunit cells of the coal sample; drawing a uniaxial tensile stress-strain curve of the coal sample according to a uniaxial tensile simulation calculation result; analyzing the mechanical properties of the coal sample in the whole direct stretching process based on the uniaxial stretching simulation calculation result and the uniaxial stretching stress-strain curve of the coal sample; based on the mechanical properties of various coal samples in the whole direct stretching process, the influence of different structural information, density and moisture content of the coal samples on the mechanical properties of the coal samples is obtained; the method has the beneficial effect that the mechanical property of the coal sample in the whole direct stretching process can be obtained; the method is suitable for the field of accurate determination of coal rock mechanical properties.

Description

Technical Field

[0001] The present application relates to the field of accurate determination of mechanical properties of coal and rock, and specifically to a method for obtaining mechanical properties of coal during the entire direct tensile process based on molecular simulation. Background Art

[0002] Studies have confirmed that coal rock mass will undergo tensile failure in coal mine dynamic disasters. Therefore, the determination of mechanical properties such as coal tensile strength is of great significance for the mechanism exploration and prevention of dynamic disasters. However, the experimental determination of direct tensile strength of coal rock mass is relatively difficult. There are problems such as complex operation process, high equipment precision requirements, low experimental success rate, and difficulty in accurately detecting stress and strain data after reaching the maximum peak. Scholars often use the Brazilian splitting method to indirectly obtain the tensile mechanical properties and damage evolution of coal rock. The results of this indirect experimental determination are prone to be biased, resulting in large measurement errors of mechanical properties. Therefore, there is an urgent need for a method that can accurately characterize the direct tensile mechanical properties of coal.

[0003] With the progress of molecular dynamics theory, the increase of computer computing power and the development of refined characterization of coal's physical and chemical structure, the precise construction of coal rock molecular structure models and molecular dynamics simulation of related mechanical properties have developed rapidly, laying a foundation for dynamic simulation of coal scratches, stiffness matrix, cutting, and uniaxial compression and tension. It is an important method to explore the mechanical properties of coal from the microscopic molecular level. The above simulation methods have certain advantages in the study of coal mechanical properties, but there are still problems such as the difficulty in constructing coal molecular structure models, the large demand for molecular dynamics simulation computing power, and the inadequate analysis of simulation results, especially the inadequate analysis of post-peak strength of tensile failure. Summary of the invention

[0004] In order to solve one of the above-mentioned technical defects, the present application provides a method for obtaining the mechanical properties of coal during the entire direct stretching process based on molecular simulation.

[0005] The present application provides a method for obtaining the mechanical properties of coal during the entire direct stretching process based on molecular simulation, including:

[0006] Obtain structural information, density and moisture content of various coal samples in coal seams prone to dynamic disasters;

[0007] The molecular structure supercell of the coal sample is constructed based on the structural information, density and moisture content of the coal sample;

[0008] The uniaxial tensile simulation calculation of the molecular structure supercell of the coal sample was carried out;

[0009] The uniaxial tensile stress-strain curve of the coal sample is drawn according to the uniaxial tensile simulation calculation results;

[0010] Based on the uniaxial tensile simulation calculation results and the uniaxial tensile stress-strain curve of the coal sample, the mechanical properties of the coal sample in the whole process of direct tensile were analyzed;

[0011] Based on the mechanical properties of various coal samples during the whole process of direct stretching, the influence of different structural information, density and moisture content of coal samples on the mechanical properties of coal samples were obtained.

[0012] Preferably, the structural information of the coal sample includes:

[0013] The atomic number ratio of C, H, O, N and S elements in the coal sample;

[0014] Chemical shift of C element in coal samples, and distribution of aliphatic carbon, aromatic carbon and carboxyl carbon;

[0015] The attribution of C, N and S elements in coal samples;

[0016] The structures of aromatic and aliphatic side chains contained in coal samples;

[0017] Distribution of nanopore sizes in coal samples.

[0018] More preferably, the constructing of the molecular structure supercell of the coal sample based on the structural information, density and moisture content of the coal sample comprises: drawing a molecular structure plane model of the coal sample based on the structural information of the coal sample, and polymerizing the molecular structure plane model of the coal sample based on the density and moisture content of the coal sample to obtain a molecular structure supercell of the coal sample;

[0019] Drawing the molecular structure plane model of the coal sample based on the structural information of the coal sample specifically includes:

[0020] Aromatic hydrocarbons were plotted based on their structures contained in the coal samples;

[0021] Based on the atomic number ratio of C, H, O, N and S elements in the coal sample, alkane chains are added to the aromatic hydrocarbons according to the structure of the aliphatic side chains contained in the coal sample to obtain complete aromatic hydrocarbons;

[0022] Drawing heterocycles according to the attribution of N and S elements in the coal sample specifically includes: adding a benzene ring and a five-membered ring, and modifying one C atom in the benzene ring and the five-membered ring to a N atom or an S atom, respectively, to obtain a heterocycle;

[0023] According to the attribution of C elements in the coal samples, the complete aromatic hydrocarbons and heterocyclic rings are connected, and the structure of the ring cluster is adjusted to obtain the molecular structure planar model of the coal samples.

[0024] Preferably, the uniaxial stretching simulation calculation of the molecular structure supercell of the coal sample specifically includes:

[0025] The molecular structure supercell of the coal sample is geometrically optimized and energy minimized to obtain a molecular structure supercell model of the coal sample.

[0026] Applying a preset number of tensile stresses to the molecular structure supercell model of the coal sample along a preset direction, and measuring the strain amount of the molecular structure supercell model of the coal sample in the preset direction each time the tensile stress is applied;

[0027] Output the tensile stress applied each time, the strain of the molecular structure supercell model of the corresponding coal sample, and the molecular structure supercell model of the corresponding coal sample after each tensile stress is applied.

[0028] More preferably, the analysis of the mechanical properties of the coal sample during the whole direct stretching process based on the uniaxial stretching simulation calculation results and the uniaxial stretching stress-strain curve of the coal sample specifically includes:

[0029] The pores and surface areas of the molecular structure supercell model of the coal sample are calculated each time tensile stress is applied, and a relationship diagram between stress and pores and surface areas is drawn based on the calculation results;

[0030] Obtain the pore and surface areas corresponding to different stresses from the stress, pore and surface area relationship diagram;

[0031] The tensile strength corresponding to different strain stages is obtained from the uniaxial tensile stress-strain curve of the coal sample.

[0032] Preferably, the alkane chain comprises a methyl group, an ethyl group, a carboxyl group, an oxygen-containing functional group, or a hydroxyl group.

[0033] Preferably, when the structural information and moisture content of the coal samples are the same, the formula for the influence of different densities of the coal samples on the tensile strength of the coal samples is:

[0034] σ=-3.838+3.675ρ;

[0035] Where σ is the peak stress of coal tensile failure, in GPa; ρ is the supercell density of coal, in cm 3 / g.

[0036] In this application, the direct stretching simulation of nanoscale coal becomes a reality through the construction of molecular structure supercells and dynamic simulation (i.e., uniaxial stretching simulation calculation) of coal samples, thereby obtaining the mechanical properties of coal samples during the entire direct stretching process, especially the mechanical properties of the direct stretching post-peak stage. It solves the problem that the cause analysis of mine power disaster accidents in the prior art is mainly based on compression and shear failure, and tensile failure is easily ignored. It also solves the problem that the direct and indirect stretching measurement of coal rock mass in the prior art is difficult, the measurement results are inaccurate, and the mechanism of coal mine power disasters is not clearly explained. At the same time, it solves the problems of difficulty in constructing coal molecular structure models, large molecular dynamics simulation computing power requirements, and inadequate analysis of simulation results. Based on the mechanical properties of various coal samples during the entire direct stretching process, the influence of internal factors such as structural information, density, and water content of coal samples on the mechanical properties of coal samples during the entire direct stretching process can be obtained, providing a theoretical basis for the mechanism of mine power disasters.

[0037] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or understood by practicing the present application. The purpose and other advantages of the present application can be realized and obtained by the contents indicated in the written description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0039] Figure 1 A schematic flow chart of an implementation method of a method for obtaining mechanical properties of coal during the entire direct stretching process based on molecular simulation provided in this application;

[0040] Figure 2 The molecular structure supercell diagram of long flame coal provided for this application;

[0041] Figure 3 The molecular structure supercell diagram of the long flame coal with a moisture content of 1wt% to 5wt% provided in this application;

[0042] Figure 4 The molecular structure supercell diagram of coking coal provided for this application;

[0043] Figure 5 The molecular structure supercell diagram of anthracite provided for this application;

[0044] Figure 6 for Figure 1 A schematic diagram of a process for drawing a molecular structure plane model of a coal sample based on the structural information of the coal sample in the embodiment;

[0045] Figure 7 for Figure 1 A schematic diagram of a process for carrying out uniaxial stretching simulation calculation on a molecular structure supercell of a coal sample in the embodiment;

[0046] Figure 8 Uniaxial tensile stress-strain curve of the coal sample provided for this application;

[0047] Fig. 9 for Figure 8 The molecular structure supercell model of the coal sample corresponding to the ad-th tensile stress applied in the pre-peak stage;

[0048] Fig.10 for Figure 8 The peak value in the figure is the molecular structure supercell model of the coal sample after the e-th tensile stress is applied;

[0049] Fig.11 for Figure 8 The molecular structure supercell model of the coal sample corresponding to the fkth application of tensile stress in the post-peak stage;

[0050] Fig.12 for Figure 7 A schematic flow chart of an implementation method of analyzing the mechanical properties of a coal sample during the entire direct stretching process based on the uniaxial stretching simulation calculation results and the uniaxial stretching stress-strain curve of the coal sample in the embodiment;

[0051] Fig.13 Stress vs. pore and surface area graph provided for this application;

[0052] Fig.14 A graph showing the relationship between peak tensile stress at failure and density provided for this application. DETAILED DESCRIPTION

[0053] In order to make the technical solutions and advantages in the embodiments of the present application more clearly understood, the exemplary embodiments of the present application are further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than an exhaustive list of all the embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0054] Figure 1 A schematic diagram of an implementation method of a method for obtaining the mechanical properties of coal during the entire direct stretching process based on molecular simulation provided in this application is shown in FIG. Figure 1 As shown, in order to solve the above problems, a method for obtaining the mechanical properties of coal during the whole direct stretching process based on molecular simulation is provided in the embodiment of the present application, including:

[0055] Obtain structural information, density and moisture content of various coal samples in coal seams prone to dynamic disasters;

[0056] The molecular structure supercell of the coal sample is constructed based on the structural information, density and moisture content of the coal sample;

[0057] The uniaxial tensile simulation calculation of the molecular structure supercell of the coal sample was carried out;

[0058] The uniaxial tensile stress-strain curve of the coal sample is drawn according to the uniaxial tensile simulation calculation results;

[0059] Based on the uniaxial tensile simulation calculation results and the uniaxial tensile stress-strain curve of the coal sample, the mechanical properties of the coal sample in the whole process of direct tensile were analyzed;

[0060] Based on the mechanical properties of various coal samples during the whole process of direct stretching, the influence of different structural information, density and moisture content of coal samples on the mechanical properties of coal samples were obtained.

[0061] In this application, the direct stretching simulation of nanoscale coal becomes a reality through the construction of molecular structure supercells and dynamic simulation (i.e., uniaxial stretching simulation calculation) of coal samples, thereby obtaining the mechanical properties of coal samples during the entire direct stretching process, especially the mechanical properties of the direct stretching post-peak stage. It solves the problem that the cause analysis of mine power disaster accidents in the prior art is mainly based on compression and shear failure, and tensile failure is easily ignored. It also solves the problem that the direct and indirect stretching measurement of coal rock mass in the prior art is difficult, the measurement results are inaccurate, and the mechanism of coal mine power disasters is not clearly explained. At the same time, it solves the problems of difficulty in constructing coal molecular structure models, large molecular dynamics simulation computing power requirements, and inadequate analysis of simulation results. Based on the mechanical properties of various coal samples during the entire direct stretching process, the influence of internal factors such as structural information, density, and water content of coal samples on the mechanical properties of coal samples during the entire direct stretching process can be obtained, providing a theoretical basis for the mechanism of mine power disasters.

[0062] Furthermore, the structural information of the coal sample includes:

[0063] The atomic number ratio of C, H, O, N and S elements in the coal sample;

[0064] Chemical shift of C element in coal samples, and distribution of aliphatic carbon, aromatic carbon and carboxyl carbon;

[0065] The attribution of C, N and S elements in coal samples;

[0066] The structures of aromatic and aliphatic side chains contained in coal samples;

[0067] Distribution of nanopore sizes in coal samples.

[0068] Specifically, the atomic number ratio of C, H, O, N and S elements in the coal sample can be determined by GB / T476-2001 "Elemental Analysis Method for Coal" to determine the mass fraction of the main elements C, H, O, N, S in the coal sample, and divided by the relative atomic mass of each element to obtain the H / C, O / C, N / C and S / C atomic number ratios of the coal sample.

[0069] The chemical shift of the C element in the coal sample can be measured by a nuclear magnetic resonance spectrometer to obtain the distribution of aliphatic carbon, aromatic carbon and carboxyl carbon in the C element.

[0070] The attribution of C, N and S elements in coal samples can be obtained by measuring the chemical state spectrum of C, N and S elements in coal samples by X-ray photoelectron spectrometer. These include: the content of aromatic carbon, alkane carbon, carbon-oxygen single bond, carbonyl carbon and carboxyl carbon in C element, the content of pyridine, pyrrole, quaternary nitrogen and nitrogen oxides in N element, and the content of mercaptan, thiophenol, sulfide, thiophene, sulfoxide, sulfone and other contents in S element.

[0071] The structure of aromatic hydrocarbons and aliphatic side chains contained in coal samples can be obtained by measuring the transmittance of surface functional groups in coal samples by Fourier infrared spectroscopy; the structure of aliphatic side chains includes methyl, ethyl, carboxyl, oxygen-containing functional groups and hydroxyl groups. The transmittance of surface functional groups is divided into regions for analysis: 700-900cm -1 The aromatic ring substitution region is the structure of aromatic hydrocarbons contained in the coal sample, 1000~1800cm -1 The oxygen-containing functional group area is the structure of oxygen-containing functional groups contained in the coal sample, 2800~3000cm -1 The aliphatic region is the structure of the aliphatic side chain contained in the coal sample, 3000~3600cm -1 The hydrogen bonding area is the structure of the hydroxyl groups contained in the coal sample. The spectra of the four areas are subjected to peak fitting and quantitative analysis, and the stretching vibration area ratios of aromatic hydrocarbons and aliphatic side chains are calculated to add aromatic hydrocarbons and aliphatic side chains in the construction of the molecular structure planar model.

[0072] The distribution of nanopore size in coal samples can be determined by low-temperature liquid nitrogen adsorption to measure the distribution of tiny pores with diameters ranging from 2 to 50 nm in coal samples.

[0073] In this application, the structural information of coal samples, including physical and chemical structural information, is accurately determined by methods such as coal industrial analysis, coal element analysis methods, nuclear magnetic resonance spectrometer, X-ray photoelectron spectrometer, Fourier transform infrared spectroscopy, and low-temperature liquid nitrogen adsorption, providing a basis for the construction of molecular structure supercells of coal samples. In this application, the distribution of nanopore sizes in coal samples is obtained, solving the problem that centimeter sizes are mostly used in the prior art and are not accurate enough.

[0074] Figure 2The molecular structure supercell diagram of the long flame coal with a moisture content of 1wt% to 5wt% provided in this application, Figure 3 The molecular structure supercell diagram of long flame coal containing water provided in this application, Figure 4 The molecular structure supercell diagram of coking coal provided in this application, Figure 5 The molecular structure supercell diagram of anthracite provided for this application is as follows: Figure 2-5 As shown, the coal samples may be different coal samples such as long flame coal, coking coal, anthracite, etc., and different coal samples correspond to different structural information.

[0075] Furthermore, the molecular structure supercell of the coal sample is constructed based on the structural information, density and moisture content of the coal sample, including:

[0076] Based on the structural information of the coal sample, the Visualizer module in the Materials Studio software was used to draw the molecular structure planar model of the coal sample. Based on the density and moisture content of the coal sample, the Amorphous Cell module was used to polymerize the molecular structure planar model of the coal sample to obtain the molecular structure supercell of the coal sample. The rationality of the molecular structure supercell of the coal sample was tested according to the distribution of nanopore size in the coal sample.

[0077] Figure 6 for Figure 1 A schematic diagram of a process for drawing a planar model of the molecular structure of a coal sample based on the structural information of the coal sample in the embodiment, as shown in FIG. Figure 6 As shown, the molecular structure plane model of the coal sample is drawn based on the structural information of the coal sample, specifically including:

[0078] According to the atomic number ratio of C, H, O, N and S elements in the coal sample, the chemical formula of the molecular structure plane model of the coal sample is obtained; the chemical formula of the molecular structure plane model of the coal sample is: C x H y O z NS, where the atomic number ratios of H / C, O / C, N / C, and S / C of the coal sample are: y / x, z / x, 1 / x, 1 / x, respectively;

[0079] Draw aromatic hydrocarbons according to the structure of aromatic hydrocarbons contained in the coal sample; specifically, add benzene rings, and then add naphthalene, anthracene / phenanthrene and polycyclic aromatic hydrocarbon structures according to the structure of aromatic hydrocarbons;

[0080] Based on the atomic number ratio of C, H, O, N and S elements in the coal sample, an alkane chain is added to the C atom of the aromatic hydrocarbon according to the structure of the aliphatic side chain contained in the coal sample to obtain a complete aromatic hydrocarbon; the alkane chain includes methyl, ethyl, carboxyl, oxygen-containing functional group and hydroxyl group;

[0081] According to the attribution of N and S elements in the coal sample, a heterocycle is drawn, specifically including: adding a benzene ring and a five-membered ring, respectively modifying one C atom in the benzene ring and the five-membered ring to an N atom or an S atom to obtain a heterocycle; specifically, the attribution of the N element is mainly pyridine, and the attribution of the S element is mainly thiophene, so the heterocycles obtained are pyridine and thiophene heterocycles;

[0082] According to the attribution of C element in coal sample, the complete aromatic hydrocarbons and heterocyclic rings are connected, and the structure of ring cluster is adjusted to make the bond length and bond angle of the connection between aromatic hydrocarbons and heterocyclic rings reasonable, so as to obtain the molecular structure planar model of coal sample.

[0083] In the present application, a molecular structure planar model is first constructed according to the structural information of the coal sample, and then a molecular structure supercell is constructed according to the density and water content, so that the obtained molecular structure supercell can more accurately reflect the physical and chemical information of the coal sample.

[0084] Figure 7 for Figure 1 A schematic diagram of a process for performing uniaxial stretching simulation calculation on the molecular structure supercell of a coal sample in the embodiment is shown in FIG. Figure 7 As shown, further, the uniaxial stretching simulation calculation of the molecular structure supercell of the coal sample specifically includes:

[0085] The Geometry Optimization and Anneal calculation programs in the Forcite Calculation module were used, the force field was set to the compass force field, i.e., CurrentForcefield=>"COMPASSⅡ", and the number of simulation steps was set to 100,000 to achieve the balance requirement, to achieve the geometric optimization and energy minimization of the molecular structure supercell of the coal sample, and to obtain the molecular structure supercell model of the coal sample;

[0086] A preset number of tensile stresses are applied to the molecular structure supercell model of the coal sample along a preset direction, and the forces applied in other directions are all 0, and the strain amount of the molecular structure supercell model of the coal sample in the preset direction is measured each time the tensile stress is applied; specifically, the preset number of tensile stresses can be ten times;

[0087] Output the tensile stress applied each time, the strain of the molecular structure supercell model of the corresponding coal sample, and the molecular structure supercell model of the corresponding coal sample after each tensile stress is applied.

[0088] Figure 8 The uniaxial tensile stress-strain curve of the coal sample provided for this application is as follows: Figure 8 As shown, specifically, the uniaxial tensile stress-strain curve of the coal sample can be plotted according to the tensile stress applied each time and the corresponding strain of the molecular structure supercell model of the coal sample. Figure 8Here, ak represents the 1st to 10th times of applying tensile stress, respectively. The tensile stress applied at the ath time (i.e., the 1st time) is 0 GPa.

[0089] Fig. 9 for Figure 8 The molecular structure supercell model of the coal sample corresponding to the ad-th tensile stress applied in the pre-peak stage; Fig.10 for Figure 8 The peak value in the figure is the molecular structure supercell model of the coal sample after the e-th tensile stress is applied; Fig.11 for Figure 8 Molecular structure supercell model of the coal sample after the fkth tensile stress is applied in the post-peak stage.

[0090] Fig.12 for Figure 7 A schematic flow chart of an implementation method of analyzing the mechanical properties of a coal sample during the entire direct stretching process based on the uniaxial stretching simulation calculation results and the uniaxial stretching stress-strain curve of the coal sample in the embodiment, Fig.13 The stress, pore and surface area relationship diagram provided for this application, such as Fig.12 and Fig.13 As shown, further, the mechanical properties of the coal sample in the whole process of direct stretching are analyzed based on the uniaxial stretching simulation calculation results and the uniaxial stretching stress-strain curve of the coal sample, specifically including:

[0091] Through the Atom Volume & Surface module, the Connolly surface task was selected, and the grid resolution was set to 0.015 nm. The pores and surface areas of the molecular structure supercell model of the coal sample were calculated each time tensile stress was applied, and the relationship between stress and pores and surface areas was plotted based on the calculation results.

[0092] Obtain the pore and surface areas corresponding to different stresses from the stress, pore and surface area relationship diagram;

[0093] The tensile strength corresponding to different strain stages is obtained from the uniaxial tensile stress-strain curve of the coal sample, specifically including: the stress-strain change trend in the pre-peak stage, the peak stress and strain, and the residual tensile capacity in the post-peak stage.

[0094] like Figure 8 As shown, the pre-peak stage presents obvious linear characteristics, and the post-peak stage presents obvious strain softening characteristics, but the post-peak stage still has a tensile strength of about 70% of the uniaxial tensile strength.

[0095] In the present application, the changes of coal samples during the whole process of direct stretching can be simulated to obtain the mechanical properties during the whole process of direct stretching, especially the post-peak stage, which solves the problems in the prior art that the experimental measurement of direct stretching is relatively difficult, the operation process is complicated, the equipment precision requirements are high, the experimental success rate is low, and it is difficult to accurately detect stress and strain data after reaching the maximum peak.

[0096] In the specific implementation process, the coal samples can be different coal samples such as long flame coal, coking coal, anthracite, etc. Different coal samples correspond to different structural information. The density can be 1.15, 1.20, 1.25, 1.30, 1.35 and 1.40 g / cm 3 The moisture content can be 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 wt%. Based on the different structural information, density and moisture content of the coal samples, any combination is made to analyze the mechanical properties of the coal samples during the whole direct stretching process, and the influence of different structural information, different density and different moisture content of the coal samples on the mechanical properties of the coal samples can be obtained.

[0097] Fig.14 The relationship between the tensile failure peak stress and density provided for this application is as follows: Fig.14 As shown in the figure, further, when the structural information and moisture content of the coal samples are the same, the influence formula of different densities of the coal samples on the tensile strength of the coal samples is:

[0098] σ=-3.838+3.675ρ;

[0099] Where σ is the peak stress of coal tensile failure, in GPa; ρ is the supercell density of coal, in cm 3 / g; The fitting degree of the formula for the influence of different densities of coal samples on the tensile strength of coal samples is: R 2 =0.956.

[0100] The fitting degree of the formula for the influence of different densities of coal samples on the tensile strength of coal samples in this application is 0.956, indicating that the fitting degree of the formula is high and can well reflect the influence of density on the tensile strength of coal samples.

[0101] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0102] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for obtaining the mechanical properties of coal during the whole direct tensile process based on molecular simulation, characterized in that: include: Obtain structural information, density and moisture content of various coal samples in coal seams prone to dynamic disasters; The molecular structure supercell of the coal sample is constructed based on the structural information, density and moisture content of the coal sample; The uniaxial tensile simulation calculation of the molecular structure supercell of the coal sample was carried out; The uniaxial tensile stress-strain curve of the coal sample is drawn according to the uniaxial tensile simulation calculation results; Based on the uniaxial tensile simulation calculation results and the uniaxial tensile stress-strain curve of the coal sample, the mechanical properties of the coal sample in the whole process of direct tensile were analyzed; Based on the mechanical properties of various coal samples during the whole process of direct stretching, the influence of different structural information, density and moisture content of coal samples on the mechanical properties of coal samples were obtained.

2. The method for obtaining the mechanical properties of coal during the whole direct tensile process based on molecular simulation according to claim 1 is characterized in that: The structural information of the coal sample includes: The atomic number ratio of C, H, O, N and S elements in the coal sample; Chemical shift of C element in coal samples, and distribution of aliphatic carbon, aromatic carbon and carboxyl carbon; The attribution of C, N and S elements in coal samples; The structures of aromatic and aliphatic side chains contained in coal samples; Distribution of nanopore sizes in coal samples.

3. The method for obtaining the mechanical properties of coal during the whole direct tensile process based on molecular simulation according to claim 2 is characterized in that: The method of constructing a molecular structure supercell of the coal sample based on the structural information, density and moisture content of the coal sample comprises: drawing a molecular structure plane model of the coal sample based on the structural information of the coal sample, and polymerizing the molecular structure plane model of the coal sample based on the density and moisture content of the coal sample to obtain a molecular structure supercell of the coal sample; Drawing the molecular structure plane model of the coal sample based on the structural information of the coal sample specifically includes: Aromatic hydrocarbons were plotted based on their structures contained in the coal samples; Based on the atomic number ratio of C, H, O, N and S elements in the coal sample, alkane chains are added to the aromatic hydrocarbons according to the structure of the aliphatic side chains contained in the coal sample to obtain complete aromatic hydrocarbons; Drawing heterocycles according to the attribution of N and S elements in the coal sample specifically includes: adding a benzene ring and a five-membered ring, and modifying one C atom in the benzene ring and the five-membered ring to a N atom or an S atom, respectively, to obtain a heterocycle; According to the attribution of C elements in the coal samples, the complete aromatic hydrocarbons and heterocyclic rings are connected, and the structure of the ring cluster is adjusted to obtain the molecular structure planar model of the coal samples.

4. The method for obtaining the mechanical properties of coal during the whole direct tensile process based on molecular simulation according to claim 1 is characterized in that: The uniaxial stretching simulation calculation of the molecular structure supercell of the coal sample specifically includes: The molecular structure supercell of the coal sample is geometrically optimized and energy minimized to obtain a molecular structure supercell model of the coal sample. Applying a preset number of tensile stresses to the molecular structure supercell model of the coal sample along a preset direction, and measuring the strain amount of the molecular structure supercell model of the coal sample in the preset direction each time the tensile stress is applied; Output the tensile stress applied each time, the strain of the molecular structure supercell model of the corresponding coal sample, and the molecular structure supercell model of the corresponding coal sample after each tensile stress is applied.

5. The method for obtaining the mechanical properties of coal during the whole direct tensile process based on molecular simulation according to claim 4 is characterized in that: The mechanical properties of the coal sample in the whole process of direct tension are analyzed based on the uniaxial tension simulation calculation results and the uniaxial tension stress-strain curve of the coal sample, specifically including: The pores and surface areas of the molecular structure supercell model of the coal sample are calculated each time tensile stress is applied, and a relationship diagram between stress and pores and surface areas is drawn based on the calculation results; Obtain the pores and surface areas corresponding to different stresses from the stress, pore and surface area relationship diagram; The tensile strength corresponding to different strain stages is obtained from the uniaxial tensile stress-strain curve of the coal sample.

6. The method for obtaining the mechanical properties of coal during the whole direct tensile process based on molecular simulation according to claim 3 is characterized in that: The alkane chain includes a methyl group, an ethyl group, a carboxyl group, an oxygen-containing functional group, and a hydroxyl group.

7. The method for obtaining the mechanical properties of coal during the whole direct tensile process based on molecular simulation according to claim 5 is characterized in that: When the structural information and moisture content of coal samples are the same, the formula for the influence of different densities of coal samples on the tensile strength of coal samples is: σ=-3.838+3.675ρ; Where σ is the peak stress of coal tensile failure, in GPa; ρ is the supercell density of coal, in cm 3 / g.

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