Underground reservoir coal pillar stability assessment method and device

Abstract

The invention discloses an underground reservoir coal pillar stability evaluation method and device. The method comprises the following steps: establishing a coal rock creep constitutive model about an underground reservoir coal pillar; based on the coal rock creep constitutive model, performing creep simulation calculation on the coal pillar after a certain time of coal mining to obtain a time-varying relationship of the stress of the coal pillar and a time-varying relationship of the strain of the coal pillar after a certain time of coal mining; and judging the stability of the coal pillar according to the change relation of the stress of the coal pillar along with the time and the change relation of the strain of the coal pillar along with the time. According to the method, the coal rock creep constitutive model is established, simulation is carried out based on the coal rock creep constitutive model, the influence of coal rock creep on the stress of the coal pillar is fully considered, and the stability of the coal pillar can be accurately evaluated.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, and in particular to a method, apparatus, electronic device, and storage medium for assessing the stability of coal pillars in underground reservoirs. Background Technology

[0002] A coal mine underground water reservoir is formed by connecting discontinuous protective coal pillars left during mining through artificial dams, creating a complete enclosed space in the goaf, and constructing water inlet and outlet facilities and pipelines. Coal mine underground water reservoirs can be connected by artificial channels between the same coal seam, different coal seams, or even multiple mining areas, thereby achieving unified storage and utilization of mine water. Simultaneously, corresponding extraction and recharge projects are constructed on the surface, forming a distributed underground water reservoir system.

[0003] Current methods and technologies for designing coal pillars in underground reservoirs mainly rely on field practice and experience. This approach suffers from significant limitations, involves substantial calculations, and lacks scientific rigor and practicality. Therefore, to address these issues, numerical simulation methods are needed to study the deformation and long-term stability of coal pillars in actual underground reservoir construction. This will provide valuable references for the design of coal pillars in underground reservoirs.

[0004] However, the geological environment of coal mines is complex, and many factors affect the stability of coal pillars. In particular, the creep law of coal and rock is complex, and existing technologies, relying solely on engineering experience, cannot accurately calculate the creep characteristics of coal and rock. Therefore, the current technology for assessing the stability of coal pillars is inaccurate. Summary of the Invention

[0005] Therefore, it is necessary to provide a method, device, electronic equipment, and storage medium for assessing the stability of coal pillars in underground reservoirs, addressing the technical problem of inaccurate assessment of coal pillar stability in existing technologies.

[0006] This invention provides a method for assessing the stability of coal pillars in underground reservoirs, comprising:

[0007] Establish a coal and rock creep constitutive model for coal pillars in underground reservoirs;

[0008] Based on the coal and rock creep constitutive model, creep simulation calculations were performed on the coal pillar after a certain period of coal seam mining to obtain the relationship between the stress and time of the coal pillar and the relationship between the strain and time of the coal pillar after a certain period of coal seam mining.

[0009] The stability of the coal pillar is evaluated based on the relationship between the stress and strain of the coal pillar over time.

[0010] Furthermore, the evaluation of the stability of the coal pillar based on the relationship between the stress and time and the strain of the coal pillar over time includes:

[0011] Based on the relationship between the strain of the coal column and time, the displacement of the coal column and time are determined.

[0012] Based on the relationship between the stress of the coal pillar and time, the plastic zones on both sides of the coal pillar and the distribution status indicators of the plastic zones are determined.

[0013] Determine the water-induced influence index of the plastic zone on the reservoir side. The two sides of the coal pillar include the reservoir side and the roadway side. The plastic zone on the reservoir side is the plastic zone on the reservoir side of the coal pillar.

[0014] The stability of the coal pillar is evaluated based on the relationship between displacement and time, the relationship between stress and time, the distribution index of the plastic zone, and / or the index of the influence of water.

[0015] Furthermore, the evaluation of the stability of the coal pillar based on the displacement-time relationship, the stress-time relationship of the coal pillar, the plastic zone distribution index, and / or the water-affected index includes:

[0016] The coal pillar is divided into segments, the stress state of each segment is extracted, the stress moiré envelope diagram of each segment is calculated based on the stress state of each segment, and the stability of the coal pillar is evaluated based on the stress moiré envelope diagram of each segment.

[0017] Furthermore, the plastic zone distribution index includes: the proportion of the plastic zone in the entire coal pillar and the proportion of the elastic zone in the entire coal pillar. The evaluation of the stability of the coal pillar based on the displacement versus time relationship, the stress versus time relationship, the plastic zone distribution index, and / or the water-affected index includes:

[0018] The stability of the coal pillar is evaluated based on the proportion of the plastic zone and the proportion of the elastic zone in the entire coal pillar.

[0019] Furthermore, the determination of the plastic zone distribution state index includes:

[0020] After a preset creep time, the areas on both sides of the coal pillar with a development depth exceeding a preset depth threshold are designated as plastic zones, and the remaining areas of the coal pillar are designated as elastic zones.

[0021] Calculate the proportion of the plastic zone in the entire coal pillar and the proportion of the elastic zone in the entire coal pillar.

[0022] Furthermore, the water-affected index is the coal pillar water head value. The evaluation of the stability of the coal pillar based on the displacement-time relationship, the stress-time relationship, the plastic zone distribution index, and / or the water-affected index includes:

[0023] The stability of the coal pillar is evaluated based on the water head value of the coal pillar.

[0024] Furthermore, the assessment of the stability of the coal pillar based on the coal pillar water head value includes:

[0025] The maximum head that the coal pillar can withstand is calculated as the ultimate head value.

[0026] The stability of the coal pillar is evaluated based on the comparison between the coal pillar water head value and the ultimate water head value.

[0027] This invention provides a device for assessing the stability of coal pillars in underground reservoirs, comprising:

[0028] The model building module is used to build a coal and rock creep constitutive model for coal pillars in underground reservoirs;

[0029] The simulation module is used to perform creep simulation calculations on the coal pillar after a certain period of coal seam mining based on the coal and rock creep constitutive model, and to obtain the relationship between the stress and strain of the coal pillar after a certain period of coal seam mining.

[0030] The evaluation module is used to evaluate the stability of the coal pillar based on the relationship between the stress and time of the coal pillar and the relationship between the strain and time of the coal pillar.

[0031] This invention provides an electronic device, comprising:

[0032] At least one processor; and,

[0033] A memory communicatively connected to at least one of the processors; wherein,

[0034] The memory stores instructions that can be executed by at least one of the processors, which enable the at least one processor to perform the underground reservoir coal pillar stability assessment method as described above.

[0035] The present invention provides a storage medium that stores computer instructions, which, when executed by a computer, are used to perform all the steps of the underground reservoir coal pillar stability assessment method as described above.

[0036] This invention establishes a coal-rock creep constitutive model for coal pillars in underground reservoirs. Based on this model, creep simulation calculations are performed on the coal pillar after a certain period of coal seam mining. The stress and strain of the coal pillar change over time after a certain mining period are obtained. The stability of the coal pillar is then evaluated based on these stress and strain changes over time. This invention, by establishing a coal-rock creep constitutive model and conducting simulations based on it, fully considers the influence of coal-rock creep on the stress of the coal pillar. It proposes a method for evaluating the stability of reservoir dams with creep characteristics, further improving the safety and reliability of reservoir dams and ensuring the safe operation of underground reservoir storage spaces. Attached Figure Description

[0037] Figure 1 This is a flowchart illustrating the workflow of a method for assessing the stability of coal pillars in an underground reservoir, according to an embodiment of the present invention.

[0038] Figure 2 This is a flowchart illustrating the process of a method for assessing the stability of coal pillars in an underground reservoir, according to another embodiment of the present invention.

[0039] Figure 3 A three-dimensional model of an example of the present invention;

[0040] Figure 4 The location of a monitoring point is an example of this invention;

[0041] Figure 5 The displacement versus time relationship of each monitoring point in a coal pillar is an example of this invention;

[0042] Figure 6 A flowchart illustrating the workflow of a method for assessing the stability of coal pillars in an underground reservoir, representing the preferred embodiment of the present invention.

[0043] Figure 7 This is a schematic diagram of coal pillar partitioning according to an embodiment of the present invention;

[0044] Figure 8 This is a Mohr envelope diagram of the stress distribution in a coal pillar according to an embodiment of the present invention.

[0045] Figure 9 This is a schematic diagram of an underground reservoir coal pillar stability assessment device according to an embodiment of the present invention;

[0046] Figure 10 This is a schematic diagram of the hardware structure of an electronic device according to the present invention. Detailed Implementation

[0047] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. Identical components are indicated by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, while the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0048] like Figure 1 The diagram shown is a flowchart of a method for assessing the stability of coal pillars in an underground reservoir according to an embodiment of the present invention, including:

[0049] Step S101: Establish a coal and rock creep constitutive model for the coal pillar of the underground reservoir;

[0050] Step S102: Based on the coal and rock creep constitutive model, perform creep simulation calculations on the coal pillar after a certain period of coal seam mining to obtain the relationship between the stress and time of the coal pillar and the relationship between the strain and time of the coal pillar after a certain period of coal seam mining.

[0051] Step S103: The stability of the coal pillar is evaluated based on the relationship between the stress and time of the coal pillar and the relationship between the strain and time of the coal pillar.

[0052] Specifically, this invention can be applied to electronic devices with processing capabilities.

[0053] Coal creep refers to the phenomenon that strain increases with time when stress remains constant.

[0054] (1) Stress relaxation and creep are exactly opposite processes. It mainly refers to the phenomenon that stress changes over time when strain does not change.

[0055] (2) Long-term strength refers to the strength of a rock against failure under long-term load. Since long-term load causes creep in rocks, creep strength is often used as long-term strength.

[0056] (3) Elastic aftereffect refers to the phenomenon that when a fixed load is applied to a material within its elastic range, the elastic deformation slowly increases over time.

[0057] The present invention first performs step S101 to establish a coal and rock creep constitutive model for the coal pillar of the underground reservoir.

[0058] Specifically, a coal-rock creep model is first selected, and then a coal-rock creep constitutive model for the coal pillar of the underground reservoir is established. Commonly used coal-rock creep constitutive models include elastic element models, plastic element models, elastoplastic element models, Newtonian fluid models, viscoelastic models, and viscoplastic models.

[0059] In this embodiment, the Cvisc model is preferably selected as the coal creep model. This is because the Cvisc model can effectively reflect the rheological characteristics of general soft and hard rocks; therefore, the Cvisc model is chosen to simulate the creep of the coal pillar.

[0060] In underground reservoirs, coal pillars can also be referred to as coal pillar dams. By obtaining relevant parameters from the constitutive equations of the coal pillars and substituting them into the constitutive equations, and using methods such as FLAC... 3D The software establishes a 3D calculation model of the coal pillar in the underground reservoir, which serves as a constitutive model for coal and rock creep.

[0061] Then, step S102 is executed. Based on the coal and rock creep constitutive model, creep simulation calculations are performed on the coal pillar after a certain period of coal seam mining to obtain the relationship between the stress and time of the coal pillar and the relationship between the strain and time of the coal pillar after a certain period of coal seam mining.

[0062] Specifically, such as Figure 3 As shown, a three-dimensional model is determined based on the topography of the coal mine field, the working face conditions, and the distribution of rock strata. FLAC 3D The software can perform creep simulation calculations on coal pillars based on a coal and rock creep constitutive model, obtaining stress and strain variation diagrams of the coal pillar after a certain period of coal seam mining (e.g., one, two, or three years). The purpose of using this software is primarily to analyze the effects of coal pillar changes over time. The coal pillar stress variation diagram illustrates the relationship between coal pillar stress and time, and the coal pillar strain variation diagram illustrates the relationship between coal pillar strain and time. The coal pillar in this example is a coal pillar from an underground reservoir.

[0063] Finally, step S103 is executed to evaluate the stability of the coal pillar based on the relationship between the stress and time of the coal pillar and the relationship between the strain and time of the coal pillar.

[0064] Since the relationship between coal pillar stress and time and the relationship between coal pillar strain and time are both obtained based on creep simulation calculations, the influence of coal and rock creep on coal pillar stress is fully considered based on the relationship between coal pillar stress and time and the relationship between coal pillar strain and time, and the stability of coal pillar can be accurately assessed.

[0065] This invention establishes a coal-rock creep constitutive model for coal pillars in underground reservoirs. Based on this model, creep simulation calculations are performed on the coal pillar after a certain period of coal seam mining. The stress and strain of the coal pillar over time are obtained, and the stability of the coal pillar is evaluated based on these relationships. This invention, by establishing and simulating a coal-rock creep constitutive model, fully considers the influence of coal-rock creep on the stress of the coal pillar, enabling accurate assessment of its stability.

[0066] like Figure 2 The diagram shown is a flowchart of a method for assessing the stability of coal pillars in an underground reservoir according to another embodiment of the present invention, including:

[0067] Step S201: Establish a coal and rock creep constitutive model for the coal pillar of the underground reservoir.

[0068] Step S202: Based on the coal and rock creep constitutive model, perform creep simulation calculations on the coal pillar after a certain period of coal seam mining to obtain the relationship between the stress and time of the coal pillar and the relationship between the strain and time of the coal pillar after a certain period of coal seam mining.

[0069] Step S203: Determine the displacement-time relationship of the coal pillar based on the relationship between the strain of the coal pillar and time.

[0070] Step S204: Based on the relationship between the stress of the coal pillar and time, determine the plastic zone and the distribution status index of the plastic zone on both sides of the coal pillar.

[0071] Step S205: Determine the water-induced influence index of the plastic zone on the reservoir side. The two sides of the coal pillar include the reservoir side and the roadway side. The plastic zone on the reservoir side is the plastic zone on the reservoir side of the coal pillar.

[0072] Step S206: The stability of the coal pillar is evaluated based on the relationship between the displacement and time of the coal pillar, the relationship between the stress of the coal pillar and time, the distribution state index of the plastic zone, and / or the index of the influence of water.

[0073] Specifically, step S201 is first executed to establish a coal-rock creep constitutive model for the underground reservoir coal pillar. Preferably, the relevant parameters of the underground coal pillar are substituted into the constitutive equations of the Cvisc model, and a model such as FLAC is used. 3D The software establishes a 3D calculation model of the coal pillar in the underground reservoir, which serves as a constitutive model for coal and rock creep.

[0074] Then, step S202 is executed. Based on the coal and rock creep constitutive model, creep simulation calculations are performed on the coal pillar after a certain period of coal seam mining to obtain the relationship between the stress and time of the coal pillar and the relationship between the strain and time of the coal pillar after a certain period of coal seam mining.

[0075] For example, using FLAC 3D The software performs creep simulation calculations on coal pillars based on the coal and rock creep constitutive model, and obtains the stress and strain changes of the coal pillars after a certain period of coal seam mining (such as one year, two years or three years).

[0076] Then, step S203 is executed to determine the displacement-time relationship of the coal pillar based on the relationship between the coal pillar strain and time.

[0077] Specifically, the coal pillar with underground water reservoir is divided into the reservoir side and the roadway side. During the simulation, three points—the reservoir side, the roadway side, and the center of the coal pillar—were selected for strain analysis. As a preferred method, the monitoring points on both sides of the coal pillar were chosen at half the height of the pillar. The locations of the monitoring points are as follows: Figure 4 As shown in the figure. Through simulation analysis, the relationship between displacement and time was obtained. The relationship between displacement and time is as follows: Figure 5 As shown.

[0078] Then, step S204 is executed to determine the plastic zone and its distribution status index on both sides of the coal pillar based on the relationship between the stress of the coal pillar and time.

[0079] Specifically, both sides of the coal pillar in the mine have a plastic zone of a certain width. In this step, the stress-time relationship of the coal pillar under different creep time conditions is first extracted. Specifically, the stress-time relationship of the coal pillar under different creep time conditions can be represented by a stress cloud diagram of the coal pillar. Then, the stress distribution pattern and evolution characteristics are comprehensively analyzed. Preferably, the stress distribution pattern and evolution characteristics are comprehensively analyzed.

[0080] Specifically, monitoring points can be set up at different locations to monitor the process during calculation, and the existing methods for determining the plastic zone can be used to identify the plastic zone.

[0081] In some embodiments, the stress in the coal pillar gradually increases from the goaf towards the interior of the coal pillar, reaches its maximum within a certain width, and then begins to decrease towards the center of the coal pillar. This width can be identified as the plastic zone.

[0082] After determining the plastic zone, the distribution status indicators of the plastic zone can be determined. The distribution status indicators of the plastic zone include the proportion of the plastic zone in the entire coal pillar and the proportion of the elastic zone in the entire coal pillar.

[0083] In one embodiment, determining the plastic zone distribution state index includes:

[0084] After a preset creep time, the areas on both sides of the coal pillar with a development depth exceeding a preset depth threshold are designated as plastic zones, and the remaining areas of the coal pillar are designated as elastic zones.

[0085] Calculate the proportion of the plastic zone in the entire coal pillar and the proportion of the elastic zone in the entire coal pillar.

[0086] Specifically, by calculating the state of the coal pillar after three years of continuous creep, the distribution of its plastic zone is obtained. Specifically, the areas on both sides of the coal pillar with a development depth exceeding a preset depth threshold are designated as plastic zones, and the remaining areas are designated as elastic zones.

[0087] This embodiment distinguishes between the plastic region and the elastic region to determine the distribution state index of the plastic region.

[0088] Then, step S205 is executed to determine the water-affected index of the plastic zone on the reservoir side. The two sides of the coal pillar include the reservoir side and the roadway side. The plastic zone on the reservoir side is the plastic zone on the reservoir side of the coal pillar.

[0089] Specifically, numerical simulations were used to analyze the strain, stress, and creep characteristics of the plastic zone of the coal pillar. This revealed that under long-term water immersion, the bottom of the coal pillar is more prone to failure. In this step, the distribution of the plastic zone of the coal pillar under long-term creep conditions was first determined; then, the evolution law of the plastic zone and the influence of water on the plastic zone of the reservoir-side coal pillar were obtained. Further analysis showed that the plastic zone exhibits a trapezoidal distribution, with a larger area at the bottom and a smaller area at the top.

[0090] Finally, step S206 is executed to evaluate the stability of the coal pillar based on the relationship between the displacement and time of the coal pillar, the relationship between the stress of the coal pillar and time, the distribution state index of the plastic zone, and / or the index of the influence of water.

[0091] This embodiment analyzes the displacement, strain, stress, and creep characteristics of the plastic zone of a coal pillar through numerical simulation, providing a method for studying the long-term stability of creep-induced coal pillars. It offers a useful reference for the design of coal pillars in underground reservoirs, and can provide relatively accurate quantitative results for the design of coal pillars in underground mines. The calculation accuracy is high, which is conducive to ensuring the safety of coal pillars in underground reservoirs. It has guiding significance for the safe construction and operation of underground reservoirs and has important theoretical significance and engineering practice value.

[0092] Displacement is the manifestation of accumulated strain during the stress process of a coal pillar, reflecting the sum of elastic and plastic deformation throughout the entire stress process. Therefore, the stability of the coal pillar can be evaluated based on the relationship between displacement and time.

[0093] In one embodiment, the evaluation of the stability of the coal pillar based on the displacement-time relationship, the stress-time relationship of the coal pillar, the plastic zone distribution index, and / or the water-affected index includes:

[0094] The coal pillar is divided into segments, the stress state of each segment is extracted, the stress moiré envelope diagram of each segment is calculated based on the stress state of each segment, and the stability of the coal pillar is evaluated based on the stress moiré envelope diagram of each segment.

[0095] Specifically, the coal pillar is divided into segments, the stress state of each segment is extracted, and the stress Mohr envelope diagram of each segment is obtained as a standard for evaluating the stability of the coal pillar.

[0096] The stress state of each segment on the coal pillar can be extracted using existing methods, such as from a coal-rock creep constitutive model or through field measurements. The values ​​extracted from the coal-rock creep constitutive model and the values ​​obtained from field measurements can be mutually verified.

[0097] The stress state of the coal pillar was evaluated using the Mohr envelope, and it was found that the middle of the coal pillar was the most stable, while the sides were the least stable.

[0098] By analyzing the relationship between the stress state and failure criteria of a coal pillar, the Mohr envelope is used to evaluate the stress state of the coal pillar, thereby assessing its stability.

[0099] In some embodiments, evaluating the stability of the coal pillar based on the stress Mohr envelope diagram of each segment includes:

[0100] If the distance between the stress state of the coal pillar and the envelope is greater than a preset distance threshold, the stability of the coal pillar is judged to be good; if the distance between the stress state of the coal pillar and the envelope is less than the distance threshold but they are not tangent or intersecting, the stability of the coal pillar is judged to be average, and the possibility of deterioration in stability is relatively high; if the stress state of the coal pillar is tangent or intersecting the envelope, the coal pillar has been destroyed, and the stability of the coal pillar is judged to be poor.

[0101] The stress state can be represented by a Mohr circle, and the distance between the center of the circle and the envelope, minus the radius of the circle, is the distance between the two.

[0102] Rock strength theory uses the stress state of a rock as a parameter to study its relationship with rock failure. The closer the stress state is to the ultimate stress state, the higher the probability of failure. Among many strength theories, the Mohr-Coulomb strength theory is one of the most widely used strength theories in rock mechanics, with high acceptance and strong practicality.

[0103] In this embodiment, the Mohr envelope is used to evaluate the stress of the coal pillar in order to obtain a reliable assessment of the stability of the coal pillar.

[0104] In one embodiment, the plastic zone distribution index includes: the proportion of the plastic zone in the entire coal pillar and the proportion of the elastic zone in the entire coal pillar. The evaluation of the stability of the coal pillar based on the displacement versus time relationship, the stress versus time relationship, the plastic zone distribution index, and / or the water-affected index includes:

[0105] The stability of the coal pillar is evaluated based on the proportion of the plastic zone and the proportion of the elastic zone in the entire coal pillar.

[0106] Specifically, the proportion of the plastic zone and the elastic zone in the entire coal pillar are used as a standard for evaluating the stability of the coal pillar.

[0107] In some embodiments, the evaluation of the stability of the coal pillar based on the proportion of the plastic zone and the proportion of the elastic zone in the entire coal pillar includes:

[0108] If the ratio of the width of the plastic zone to the width of the coal pillar is greater than the preset plastic zone ratio threshold, the coal pillar is considered to have poor stability; if the ratio of the width of the plastic zone to the width of the coal pillar is less than or equal to the preset plastic zone ratio threshold, the coal pillar is considered to have good stability.

[0109] If the ratio of the elastic zone width to the coal pillar width is greater than the preset elastic zone ratio threshold, the coal pillar stability is assessed as good; if the ratio of the elastic zone width to the coal pillar width is less than or equal to the preset elastic zone ratio threshold, the coal pillar stability is assessed as poor.

[0110] Specifically, the higher the proportion of the plastic zone width to the coal pillar width, the worse the coal pillar stability; conversely, the lower the proportion of the plastic zone width to the coal pillar width, the better the coal pillar stability. Similarly, the higher the proportion of the elastic zone width to the coal pillar width, the better the coal pillar stability; conversely, the lower the proportion of the elastic zone width to the coal pillar width, the worse the coal pillar stability. In practical applications, specific analysis should be conducted based on the actual site conditions.

[0111] This embodiment uses the proportion of the plastic zone and the proportion of the elastic zone in the entire coal pillar to obtain a reliable assessment of the stability of the coal pillar.

[0112] In one embodiment, the water-affected index is the water head value of the coal pillar. The evaluation of the stability of the coal pillar based on the displacement-time relationship, the stress-time relationship, the plastic zone distribution index, and / or the water-affected index includes:

[0113] The stability of the coal pillar is evaluated based on the water head value of the coal pillar.

[0114] Specifically, the weakening range of the coal pillar increases as it spreads through the plastic zone, pores, and fissures to a larger area of ​​the dam body. Therefore, determining the hydraulic head that the coal pillar can withstand is used as a standard for evaluating its stability.

[0115] The water head value of the coal pillar can be determined based on on-site measurement data or by using existing water head value measurement methods.

[0116] This embodiment uses the water head value of the coal pillar to reliably assess its stability. This evaluation method is highly practical, simple to operate, and provides excellent guidance for engineering practice.

[0117] In one embodiment, the step of judging the stability of the coal pillar based on the coal pillar water head value includes:

[0118] The maximum head that the coal pillar can withstand is calculated as the ultimate head value.

[0119] The stability of the coal pillar is evaluated based on the comparison between the coal pillar water head value and the ultimate water head value.

[0120] Specifically, based on the functional relationship between the limiting hydraulic head value and the size of the plastic zone of the coal pillar, and taking into account the width of the plastic zone of the coal pillar and factors of seepage mechanics, the limiting hydraulic head value is calculated. The stability of the coal pillar can be judged by comparing the coal pillar hydraulic head value with the limiting hydraulic head value.

[0121]

[0122] Where: h w —The critical hydraulic head value for seepage in a coal pillar, in meters;

[0123] p—water pressure value, MPa;

[0124] B—width of the coal pillar, in meters;

[0125] Y—width of the plastic zone of the coal pillar, in meters;

[0126] ρ—Density of flowing water, kg / m³ 3 ;

[0127] g n —Acceleration due to gravity, g n =10m / s 2 .

[0128] Then, the relationship between the water head value of the coal pillar and the limit water head value is compared. If the water head value of the coal pillar is less than the limit water head value, the stability of the coal pillar is judged to be good. Otherwise, if the water head value of the coal pillar is greater than or equal to the limit water head value, the stability of the coal pillar is judged to be poor, that is, the coal pillar is unstable.

[0129] like Figure 6 The diagram shown is a flowchart of a method for assessing the stability of coal pillars in an underground reservoir, according to a preferred embodiment of the present invention, including:

[0130] Step S601, Selection of coal and rock creep constitutive model;

[0131] Step S602: Use FLAC3D software to establish a 3D calculation model to perform creep simulation calculations on the coal pillar;

[0132] Step S603: Determine the relationship between strain and time;

[0133] Step S604: Analyze the stress distribution changes caused by creep;

[0134] Step S605: Analyze the changes in the distribution of the plastic zone caused by creep;

[0135] Step S606, Stability Assessment: Based on the numerical simulation of coal pillar creep characteristics, a comprehensive assessment of the stability of the coal pillar within the mining area is conducted.

[0136] In step S601, commonly used constitutive models for coal and rock creep include elastic element models, plastic element models, elastoplastic element models, Newtonian fluid models, viscoelastic models, and viscoplastic models. In this method, the Cvisc model is selected for coal and rock creep simulation because it effectively reflects the rheological characteristics of general soft and hard rocks.

[0137] Determining the creep model is the basis and foundation for 3D modeling in step 2.

[0138] In step S602, a three-dimensional model is determined based on the coal mine's topography, working face conditions, and rock strata distribution. (See...) Figure 3 FLAC 3D The software can perform creep simulation calculations on coal pillars using a computational model, obtaining stress and strain variation diagrams of the coal pillar after a certain period of coal seam mining (such as one, two, or three years). The main purpose of using this software is to analyze the effects of coal pillar changes over time.

[0139] In step S603, the coal pillar with underground water reservoir is divided into the reservoir side and the roadway side. During simulation and experimentation, three points—the reservoir side, the roadway side, and the center of the coal pillar—are selected for strain analysis. As a preferred method, the points on both sides of the coal pillar are selected at 1 / 2 of the coal pillar height. The positions of monitoring points A, B, and C are as follows: Figure 4 As shown, the location is between coal pillar water reservoir side 2, roadway side 3, and the center of coal pillar 1. Through simulation analysis, the relationship between displacement and time was obtained. The displacement-time relationship is as follows: Figure 5 As shown.

[0140] In step S604, there are plastic zones of a certain width on both sides of the coal pillar in the mine. In this step, the stress cloud map of the coal pillar under different creep time conditions is first extracted; then the stress distribution pattern and evolution characteristics are comprehensively analyzed. In one embodiment, the stress in the coal pillar gradually increases from the goaf towards the interior of the coal pillar, reaches its maximum within a certain width, and then begins to decrease towards the center of the coal pillar.

[0141] In step S605, the range of the plastic zone of the coal pillar in the mine determines the stability of the coal pillar. In this step, the distribution of the plastic zone of the coal pillar under long-term creep conditions is first determined; then the evolution law of the plastic zone of the coal pillar is obtained. The plastic zone of the coal pillar on the reservoir side is affected by water. It is further concluded that the plastic zone is larger at the bottom and smaller at the top, and has a "trapezoidal" distribution.

[0142] Step S606 can be divided into

[0143] (1) Selection of evaluation indicators

[0144] Combining steps S604 and S605, the stability of the coal pillar is mainly evaluated from the following three aspects when selecting evaluation indicators.

[0145] Coal pillar stress distribution index: Extract the average confining pressure and vertical stress on the coal pillar to obtain the segmented stress Mohr envelope diagram of the coal pillar, which serves as a standard for evaluating the stability of the coal pillar.

[0146] Plastic zone distribution index: The proportion of the plastic zone and the elastic zone in the coal pillar is used as a standard to evaluate the stability of the coal pillar.

[0147] The soaking effect of water is an indicator: water diffuses through the plastic zone, pores, and fissures of the coal pillar to a larger area of ​​the dam body, increasing the weakening range of the coal pillar. The water head that the coal pillar can withstand is used as a standard to evaluate its stability.

[0148] (2) Stability evaluation of coal pillar zones

[0149] In the stability evaluation of the coal pillar, the coal pillar is divided into 5 parts with an average width of 16m, and numbered I, II, III, IV, and V respectively, starting from the left side of the model. Figure 7 As shown.

[0150] Then, the horizontal and vertical stresses of each part are extracted to obtain the stress data of each coal pillar.

[0151] Finally, based on the extracted stress data for each part of the coal pillar, a Mohr envelope diagram of the stress distribution for each part of the coal pillar is drawn, such as... Figure 8 As shown, the stability of each part of the coal pillar can be determined from the stress distribution state. Figure 8 In the middle, the cohesion of the coal and rock mass C = 1.2 MPa, and the friction angle of the coal and rock mass is...

[0152] (3) Analyze the distribution of plastic state

[0153] The distribution of the plastic zone was obtained by calculating the state of the coal pillar after three years of continuous creep. Specifically, the areas on both sides of the coal pillar with a development depth exceeding a preset depth threshold were defined as the plastic zone, and the remaining areas were defined as the elastic zone.

[0154] (4) Analysis of the role of water:

[0155] Based on the functional relationship between the limiting hydraulic head and the size of the plastic zone of the coal pillar, and considering factors such as the width of the plastic zone of the coal pillar and seepage mechanics, the stability of the coal pillar can be judged.

[0156]

[0157] Where: hw —The critical hydraulic head value for seepage in a coal pillar, in meters;

[0158] p—water pressure value, MPa;

[0159] B—width of the coal pillar, in meters;

[0160] Y—width of the plastic zone of the coal pillar, in meters;

[0161] ρ—Density of flowing water, kg / m³ 3 ;

[0162] g n —Acceleration due to gravity, g n =10m / s 2 .

[0163] (5) Evaluation of the effect of reasonable coal pillar retention and evaluation of the dam retention effect by measuring water inflow and reservoir water storage and use.

[0164] In one example of the present invention, based on the water storage capacity and head value of the three reservoirs already constructed in Daliuta, and according to the relationship between the head value and the plastic zone, and combined with the actual water storage capacity and head value of the Daliuta reservoir, it can be determined that leaving an 80m coal pillar during the construction of Reservoir No. 4 can fully guarantee the safe and stable operation of the reservoir.

[0165] Based on the same inventive concept, such as Figure 9 The diagram shown is a schematic representation of an underground reservoir coal pillar stability assessment device according to an embodiment of the present invention, comprising:

[0166] Model building module 901 is used to build a coal and rock creep constitutive model for coal pillars in underground reservoirs;

[0167] Simulation module 902 is used to perform creep simulation calculations on the coal pillar after a certain period of coal seam mining based on the coal and rock creep constitutive model, and to obtain the relationship between the stress and time of the coal pillar and the relationship between the strain and time of the coal pillar after a certain period of coal seam mining.

[0168] The evaluation module 903 is used to evaluate the stability of the coal pillar based on the relationship between the stress and time of the coal pillar and the relationship between the strain and time of the coal pillar.

[0169] This invention establishes a coal-rock creep constitutive model for coal pillars in underground reservoirs. Based on this model, creep simulation calculations are performed on the coal pillar after a certain period of coal seam mining. The stress and strain of the coal pillar over time are obtained, and the stability of the coal pillar is evaluated based on these relationships. This invention, by establishing and simulating a coal-rock creep constitutive model, fully considers the influence of coal-rock creep on the stress of the coal pillar, enabling accurate assessment of its stability.

[0170] In one embodiment, the step of evaluating the stability of the coal pillar based on the relationship between the stress and time of the coal pillar and the relationship between the strain and time of the coal pillar includes:

[0171] Based on the relationship between the strain of the coal column and time, the displacement of the coal column and time are determined.

[0172] Based on the relationship between the stress of the coal pillar and time, the plastic zones on both sides of the coal pillar and the distribution status indicators of the plastic zones are determined.

[0173] Determine the water-induced influence index of the plastic zone on the reservoir side. The two sides of the coal pillar include the reservoir side and the roadway side. The plastic zone on the reservoir side is the plastic zone on the reservoir side of the coal pillar.

[0174] The stability of the coal pillar is evaluated based on the relationship between displacement and time, the relationship between stress and time, the distribution index of the plastic zone, and / or the index of the influence of water.

[0175] In one embodiment, the evaluation of the stability of the coal pillar based on the displacement-time relationship, the stress-time relationship of the coal pillar, the plastic zone distribution index, and / or the water-affected index includes:

[0176] The coal pillar is divided into segments, the stress state of each segment is extracted, the stress moiré envelope diagram of each segment is calculated based on the stress state of each segment, and the stability of the coal pillar is evaluated based on the stress moiré envelope diagram of each segment.

[0177] In one embodiment, the plastic zone distribution index includes: the proportion of the plastic zone in the entire coal pillar and the proportion of the elastic zone in the entire coal pillar. The evaluation of the stability of the coal pillar based on the displacement versus time relationship, the stress versus time relationship, the plastic zone distribution index, and / or the water-affected index includes:

[0178] The stability of the coal pillar is evaluated based on the proportion of the plastic zone and the proportion of the elastic zone in the entire coal pillar.

[0179] In one embodiment, determining the plastic zone distribution state index includes:

[0180] After a preset creep time, the areas on both sides of the coal pillar with a development depth exceeding a preset depth threshold are designated as plastic zones, and the remaining areas of the coal pillar are designated as elastic zones.

[0181] Calculate the proportion of the plastic zone in the entire coal pillar and the proportion of the elastic zone in the entire coal pillar.

[0182] In one embodiment, the water-affected index is the water head value of the coal pillar. The evaluation of the stability of the coal pillar based on the displacement-time relationship, the stress-time relationship, the plastic zone distribution index, and / or the water-affected index includes:

[0183] The stability of the coal pillar is evaluated based on the water head value of the coal pillar.

[0184] In one embodiment, the step of judging the stability of the coal pillar based on the coal pillar water head value includes:

[0185] The maximum head that the coal pillar can withstand is calculated as the ultimate head value.

[0186] The stability of the coal pillar is evaluated based on the comparison between the coal pillar water head value and the ultimate water head value.

[0187] Regarding the apparatus in the above embodiments, the specific manner in which each module performs its operation has been described in detail in the embodiments related to the method, and will not be elaborated upon here.

[0188] like Figure 10 The diagram shown is a hardware structure schematic of an electronic device according to the present invention, comprising:

[0189] At least one processor 1001; and,

[0190] A memory 1002 is communicatively connected to at least one of the processors 1001; wherein,

[0191] The memory 1002 stores instructions that can be executed by at least one of the processors to enable the at least one of the processors to perform the underground reservoir coal pillar stability assessment method as described above.

[0192] Figure 10 Take processor 1001 as an example.

[0193] The electronic device may also include an input device 1003 and a display device 1004.

[0194] The processor 1001, memory 1002, input device 1003 and display device 1004 can be connected by a bus or other means. The figure shows an example of connection by a bus.

[0195] The memory 1002, as a non-volatile computer-readable storage medium, can be used to store non-volatile software programs, non-volatile computer-executable programs, and modules, such as the program instructions / modules corresponding to the underground reservoir coal pillar stability assessment method in this application embodiment, for example, Figure 1 , Figure 2 The method flow is shown. The processor 1001 executes various functional applications and data processing by running non-volatile software programs, instructions, and modules stored in the memory 1002, thereby realizing the underground reservoir coal pillar stability assessment method in the above embodiments.

[0196] The memory 1002 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created based on the use of the underground reservoir coal pillar stability assessment method, etc. Furthermore, the memory 1002 may include high-speed random access memory and may also include non-volatile memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device. In some embodiments, the memory 1002 may optionally include memory remotely located relative to the processor 1001, and these remote memories can be connected via a network to the apparatus performing the underground reservoir coal pillar stability assessment method. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0197] The input device 1003 can receive user clicks and generate signal inputs related to user settings and function control of the underground reservoir coal pillar stability assessment method. The display device 1004 may include display screens or other display devices.

[0198] When one or more modules are stored in the memory 1002 and are run by one or more processors 1001, the underground reservoir coal pillar stability assessment method in any of the above method embodiments is executed.

[0199] This invention establishes a coal-rock creep constitutive model for coal pillars in underground reservoirs. Based on this model, creep simulation calculations are performed on the coal pillar after a certain period of coal seam mining. The stress and strain of the coal pillar over time are obtained, and the stability of the coal pillar is evaluated based on these relationships. This invention, by establishing and simulating a coal-rock creep constitutive model, fully considers the influence of coal-rock creep on the stress of the coal pillar, enabling accurate assessment of its stability.

[0200] One embodiment of the present invention provides a storage medium that stores computer instructions, which, when executed by a computer, are used to perform all the steps of the underground reservoir coal pillar stability assessment method as described above.

[0201] In the context of this disclosure, a storage medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. The storage medium can be a machine-readable signal medium or a machine-readable storage medium. Optionally, the storage medium can be a non-transitory computer-readable storage medium, such as a ROM, random access memory (RAM), compact disc ROM (CD-ROM), magnetic tape, floppy disk, and optical data storage device.

[0202] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for assessing the stability of coal pillars in underground reservoirs, characterized in that, include: Establish a coal and rock creep constitutive model for coal pillars in underground reservoirs; Based on the coal and rock creep constitutive model, creep simulation calculations were performed on the coal pillar after a certain period of coal seam mining to obtain the relationship between the stress and time of the coal pillar and the relationship between the strain and time of the coal pillar after a certain period of coal seam mining. The stability of the coal pillar is evaluated based on the relationship between the stress and strain of the coal pillar over time.

2. The method for assessing the stability of coal pillars in underground reservoirs according to claim 1, characterized in that, The evaluation of the stability of the coal pillar based on the relationship between the stress and strain of the coal pillar over time includes: Based on the relationship between the strain of the coal column and time, the displacement of the coal column and time are determined. Based on the relationship between the stress of the coal pillar and time, the plastic zones on both sides of the coal pillar and the distribution status indicators of the plastic zones are determined. Determine the water-induced influence index of the plastic zone on the reservoir side. The two sides of the coal pillar include the reservoir side and the roadway side. The plastic zone on the reservoir side is the plastic zone on the reservoir side of the coal pillar. The stability of the coal pillar is evaluated based on the relationship between displacement and time, the relationship between stress and time, the distribution index of the plastic zone, and / or the index of the influence of water.

3. The method for assessing the stability of coal pillars in underground reservoirs according to claim 2, characterized in that, The stability of the coal pillar is evaluated based on the relationship between displacement and time, the relationship between stress and time, the distribution state index of the plastic zone, and / or the index of the influence of water, including: The coal pillar is divided into segments, the stress state of each segment is extracted, the stress moiré envelope diagram of each segment is calculated based on the stress state of each segment, and the stability of the coal pillar is evaluated based on the stress moiré envelope diagram of each segment.

4. The method for assessing the stability of coal pillars in underground reservoirs according to claim 2, characterized in that, The plastic zone distribution index includes the proportion of the plastic zone in the entire coal pillar and the proportion of the elastic zone in the entire coal pillar. The stability of the coal pillar is evaluated based on the displacement-time relationship, the stress-time relationship, the plastic zone distribution index, and / or the water-affected index, including: The stability of the coal pillar is evaluated based on the proportion of the plastic zone and the proportion of the elastic zone in the entire coal pillar.

5. The method for assessing the stability of coal pillars in underground reservoirs according to claim 4, characterized in that, The indicators for determining the distribution state of the plastic region include: After a preset creep time, the areas on both sides of the coal pillar with a development depth exceeding a preset depth threshold are designated as plastic zones, and the remaining areas of the coal pillar are designated as elastic zones. Calculate the proportion of the plastic zone in the entire coal pillar and the proportion of the elastic zone in the entire coal pillar.

6. The method for assessing the stability of coal pillars in underground reservoirs according to claim 2, characterized in that, The water-affected index is the water head value of the coal pillar. The stability of the coal pillar is evaluated based on the relationship between displacement and time, the relationship between stress and time, the plastic zone distribution index, and / or the water-affected index, including: The stability of the coal pillar is evaluated based on the water head value of the coal pillar.

7. The method for assessing the stability of coal pillars in underground reservoirs according to claim 6, characterized in that, The evaluation of the stability of the coal pillar based on the coal pillar water head value includes: The maximum head that the coal pillar can withstand is calculated as the ultimate head value. The stability of the coal pillar is evaluated based on the comparison between the coal pillar water head value and the ultimate water head value.

8. A device for assessing the stability of coal pillars in underground reservoirs, characterized in that, include: The model building module is used to build a coal and rock creep constitutive model for coal pillars in underground reservoirs; The simulation module is used to perform creep simulation calculations on the coal pillar after a certain period of coal seam mining based on the coal and rock creep constitutive model, and to obtain the relationship between the stress and strain of the coal pillar after a certain period of coal seam mining. The evaluation module is used to evaluate the stability of the coal pillar based on the relationship between the stress and time of the coal pillar and the relationship between the strain and time of the coal pillar.

9. An electronic device, characterized in that, include: At least one processor; as well as, A memory communicatively connected to at least one of the processors; wherein, The memory stores instructions that can be executed by at least one of the processors to enable at least one of the processors to perform the underground reservoir coal pillar stability assessment method as described in any one of claims 1 to 7.

10. A storage medium, characterized in that, The storage medium stores computer instructions, which, when executed by the computer, are used to perform all the steps of the underground reservoir coal pillar stability assessment method as described in any one of claims 1 to 7.

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