Pressure relief boundary quantification method based on surface dynamic settlement and coal wall stress dynamic evolution

Abstract

The invention relates to a pressure relief boundary quantification method based on surface dynamic settlement and coal wall stress dynamic evolution, and belongs to the technical field of pressure relief boundary quantification, and the method comprises the following steps: S1, collecting a coal sample of a protected layer of a specific mine, carrying out desorption experiments under different constant load conditions, determining a stress value corresponding to gas rapid desorption, and determining a stress value corresponding to gas rapid desorption; setting the pressure relief critical stress value as a pressure relief critical stress value of the protected coal seam; s2, determining the deformation value of the overlying strata according to the relationship between the pressure relief value and the stress-strain of the overlying strata; s3, determining a mining overlying strata surface settlement value according to the coal seam mining thickness and the overlying strata deformation value; s4, determining the stress distribution rule of the whole overlying strata according to the dynamic settlement rule of the overlying strata surface, and delimiting the evolution rule of the pressure relief boundary based on the definition of the pressure relief boundary; and S5, analyzing the convergence time criterion of the dynamic time function of ground surface settlement, substituting the convergence time criterion into the dynamic evolution function of the three-dimensional pressure relief boundary of the overlying strata, and finally determining the spatial position of the convergence of the pressure relief boundary.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pressure relief boundary quantification, and relates to a pressure relief boundary quantification method based on surface dynamic settlement and coal wall stress dynamic evolution. BACKGROUND

[0002] After coal seam mining, three zones will be formed in the vertical direction of overburden rock, and the crushing degree of overburden rock in the three zones is quite different, and the stress distribution of overburden rock changes with time, which makes it difficult to determine the protection range of adjacent protected layers. At present, the existing methods mainly determine the pressure relief range of overburden rock through the "Coal and Gas Outburst Prevention and Control Details", empirical formula, theoretical derivation, similar simulation and numerical simulation, but the overburden rock generally needs to be stable for about one year after mining, and the pressure relief range will change accordingly during this period, in addition, after a certain period of mining, some underground tunnels will no longer exist due to the stop of mining, which makes it more difficult to determine the stress evolution of overburden rock through underground measurement. Therefore, based on surface settlement, scientifically determining the pressure relief range and the convergence position of the pressure relief boundary of overburden rock at different times is a feasible way to determine the stress evolution of overburden rock through the ground.

[0003] On the other hand, for a specific coal seam in a mine, when the coal seam is relieved to a certain extent, the coal seam will absorb a large amount of gas desorption and migration, so that the protected layer is effectively protected. Therefore, it is particularly important to select an appropriate pressure relief value to determine the pressure relief range. At present, whether the roof and floor unloading expansion reaches 0.003 is mainly used to determine whether the pressure relief is effective in the coal mine site. This method is of great significance to determine the protection range of the pressure relief boundary, but the pressure relief value is the most direct indicator to determine the protection range of overburden rock. However, it is difficult to directly determine the stress value of overburden rock, which leads to few methods for determining the pressure relief boundary through the pressure relief value in the field.

[0004] Therefore, there is an urgent need for a pressure relief boundary convergence position quantification method based on surface dynamic settlement. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a pressure relief boundary quantification method based on surface dynamic settlement and coal wall stress dynamic evolution, which can determine the convergence position of the pressure relief boundary by surface settlement inversion of the stress distribution of overburden rock after mining, and provide a basis for accurate determination of the protection range of the protected layer and accurate arrangement of the pressure relief gas extraction borehole during mining and after mining.

[0006] To achieve the above purpose, the present application provides the following technical scheme:

[0007] A pressure relief boundary quantification method based on surface dynamic settlement and coal wall stress dynamic evolution, comprising the following steps:

[0008] S1: Collect coal samples from the protected seam of a specific mine and conduct desorption experiments on adsorbed gas under different constant load conditions to determine the stress value corresponding to rapid gas desorption, and set it as the critical stress value for decompression of the protected coal seam;

[0009] S2: Based on the relationship between the unloading value and the stress-strain of the overburden rock, the deformation value of the overburden rock is determined;

[0010] S3: Determine the surface settlement of overburden caused by mining based on the coal seam mining thickness and overburden deformation value;

[0011] S4: According to the dynamic settlement law of the overburden surface, determine the stress distribution law of the entire overburden based on the definition of the unloading boundary and determine its evolution law;

[0012] S5: Analyze the convergence time criterion of the dynamic time function of surface settlement, substitute it into the dynamic evolution function of the three-dimensional unloading boundary of the overburden, and finally determine the spatial position of the convergence of the unloading boundary.

[0013] Furthermore, step S1 specifically includes the following steps:

[0014] S11: Apply hydrostatic pressure until the axial stress reaches the original formation pressure;

[0015] S12: Reduce the confining pressure until it is equal to the true formation stress value;

[0016] S13: performing methane adsorption until a saturated adsorption equilibrium state is reached;

[0017] S14: Unload the confining pressure and determine the cumulative desorption amount of gas;

[0018] S15: Repeat steps S11-S14 to measure the cumulative desorption amount of gas at different pressure relief values ​​until the inflection point of the rapid desorption amount of gas is determined, thereby determining the critical stress value of rapid desorption.

[0019] Furthermore, step S2 specifically includes the following steps:

[0020] S21: Classify the three zones of overburden in the vertical direction into layered overburden structure, massive overburden structure and scattered overburden structure, and extract the stress and strain characteristics of the three types of structures;

[0021] S22: Use elastic, plastic or viscous elements in series or parallel to describe the stress-strain relationship of three types of structures;

[0022] S23: For the bulk overburden structure, the fracture strain ratio and effective compressibility coefficient are introduced to establish a quantitative relationship between the amount of fracture closure and the degree of compaction difficulty of the bulk overburden. Considering the distribution of damage variables of the bulk overburden, a compaction-damage fracture constitutive model of the bulk overburden is established.

[0023] For massive overburden structures, the massive overburden structures are divided into rocks and cracks. It is assumed that the deformation of the massive overburden is mainly due to the time-dependent compaction of the cracks, and the intact rock itself is in the elastic stage. The two are correlated to construct a constitutive model of the massive structure.

[0024] For layered overburden structure, based on the classic layered structure Drucker-Prager yield criterion, the influence of the anisotropy of the layered overburden is considered and the classic constitutive law is modified.

[0025] S24: Based on the stress-strain relationship of the overburden, the overall stress-strain characteristics of the overburden are described by connecting three types of structures in series. The series characteristics of the three types of structures in the vertical direction are analyzed, and the quantitative relationship of the total stress and strain of the three types of structures in series is established.

[0026] Furthermore, step S3 specifically includes the following steps:

[0027] S31: Calculate the stress value of each rock layer respectively, subtract the deadweight of the overburden rock to determine the stress of each rock layer of the overburden rock, and obtain the stress distribution of the entire overburden rock;

[0028] S32: Determine the deformation value of each rock layer under specific stress conditions based on the stress-strain relationship, and superimpose them in a cumulative manner to obtain the distribution law of the overburden unloading expansion;

[0029] S33: Based on the coal seam thickness, mining height, and overburden expansion, a surface settlement model of the overburden from the mining layer upward is established;

[0030] S34: The constitutive models of the three types of structures are microelementized based on rock layers;

[0031] S35: Calculate the loads at the interfaces of each rock layer within the three types of structures based on the bulk density and thickness of the overburden rock;

[0032] S36: Substitute the load and the elastic modulus of each rock layer into the rock constitutive model of each structure in the overburden rock to obtain the unloading expansion of each rock layer, integrate it in the vertical direction, and obtain the cumulative conduction characteristics of the overburden rock's overall unloading expansion;

[0033] S37: Use the coal seam mining height minus the overburden expansion due to pressure relief to obtain the surface settlement law of the overburden, form a function of mining stress and surface settlement, mining height, and overburden strength, and determine the quantitative relationship between surface settlement and overburden mining stress.

[0034] Further, step S4 specifically includes the following steps:

[0035] S41: Dynamic analysis of surface dynamic settlement is carried out, dynamic time function is introduced, and the dynamic evolution law of surface settlement is obtained;

[0036] S42: Substitute the dynamic evolution law of surface settlement into the stress calculation function to obtain the stress distribution function of the overburden at different times;

[0037] S43: Based on the definition of the pressure relief boundary, the stress distribution function is substituted to obtain the distribution characteristics of the pressure relief boundary at different mining times;

[0038] S44: Based on the quantitative relationship between surface settlement and overburden mining stress, combined with the definition of the unloading boundary, the functional relationship between the overburden unloading boundary and surface settlement is obtained;

[0039] S45: Introducing the dynamic function of surface settlement, the corresponding relationship between surface dynamic settlement and the expansion of the overburden pressure relief boundary of the goaf is derived;

[0040] S46: Calculate the distribution and expansion path of the overburden unloading boundary in the goaf, analyze the influence of overburden lithology, mining height, coal seam inclination, coal seam burial depth, and mining time on the expansion law of the unloading boundary, and reveal the expansion characteristics of the overburden unloading boundary in the goaf from the perspective of dynamic surface settlement above the well;

[0041] S47: Analysis of the damage law of coal and rock mass under the combined action of cyclic load and constant load;

[0042] S48: Obtain rock life curves under different time and amplitude conditions by fitting statistical prediction methods to predict the long-term strength of overburden rocks;

[0043] S49: Combining the definition of the overburden stress relief boundary with the stress distribution law of the coal walls on both sides, the time required for the coal body near the stress concentration location to be damaged, deteriorated, and finally destroyed is calculated. This allows the spatial location of the overburden stress relief boundary outside the overburden to be determined at different times, revealing the extension characteristics of the overburden stress relief boundary on both sides of the goaf.

[0044] S410: based on the change of the pressure relief position of the overburden in the goaf at different times, deduce the temporal evolution law of the movement rate of the pressure relief position of the overburden in the goaf;

[0045] S411: For the overburden pressure relief boundary on both sides of the goaf, based on the overburden pressure relief critical value, the change of the overburden pressure relief critical position is determined by the evolution law of the stress distribution of the coal wall on both sides over time, and finally the movement rate of the overburden pressure relief boundary on both sides of the goaf is obtained;

[0046] S412: The time-space functions of the goaf and the overburden stress relief boundaries on both sides are combined to obtain the movement rate of the stress relief boundaries at different positions of the overburden. The stress distribution of the overburden after coal seam mining is used as the initial condition and substituted into the time-delay evolution model of the overburden stress relief boundary to determine the allometric expansion characteristics of the overburden stress relief boundary as it changes with time.

[0047] S413: Based on a specific time range of overburden decompression gas extraction, determine the three-dimensional spatial position and evolution of the overburden decompression boundary during the decompression gas extraction period.

[0048] Furthermore, in step S5, a virtual time step is calculated during the surface settlement calculation process as a way of applying a time difference, and the variation value is calculated according to the following steps to obtain the convergence position of the pressure relief boundary:

[0049] S51: Input the surface settlement dynamic function when the initial time is 0, call the calculation method of the pressure relief boundary, and save the stress tensor and strain tensor and the spatial position of the pressure relief boundary at time 0;

[0050] S52: Virtually calculate a time step, call and save the stress tensor, strain tensor and the position of the stress relief boundary space again;

[0051] S53: Subtract the previously saved value from the saved value, and the difference is the first-order variation of the mining-induced overburden stress tensor, strain tensor and unloading boundary;

[0052] S54: According to the positive or negative value of the variation value, the stability of the model is judged, thereby determining the convergence space position of the pressure relief boundary.

[0053] The beneficial effects of the present invention are:

[0054] 1. Based on the pressure relief boundary, the pressure relief range and degree of overburden can be divided more accurately, thus providing a reliable basis for the graded prevention and control of coal and gas outbursts.

[0055] 2. Selecting an appropriate pressure relief value can break through the method of using pressure relief expansion as a direct parameter on site, and provide a new idea for the scientific prevention and control of coal seams and gas outbursts.

[0056] 3. It breaks through the traditional measurement method and can directly use the uphole parameters to invert the downhole parameters, providing reliable parameters for the accurate determination of the location of gas in the goaf based on ground drilling, and improving the accuracy of pressure relief gas extraction.

[0057] 4. It improves the convenience of determining the stress distribution and unloading boundary of the overburden. Compared with other methods that are limited by the space in the well, it is more convenient to measure the surface settlement on the surface, which can more easily obtain the stress and unloading boundary distribution of the overburden.

[0058] Other advantages, objectives, and features of the present invention will be described in detail in the following description. A person skilled in the art will readily understand the advantages and features of the present invention after reading the description. The present invention is highly recognized within the industry and can be used as a guide through the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0060] Figure 1 A technical roadmap for the stress distribution and displacement accumulation transmission characteristics of overburden rocks caused by mining in inclined coal seams;

[0061] Figure 2 A technical roadmap for the time-lag expansion mechanism of overburden unloading boundary driven by asymmetric stress;

[0062] Figure 3 This is the flow chart of the variational criterion of the time increment method. DETAILED DESCRIPTION

[0063] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0064] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention. The illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed to meet actual production needs, and the component layout may also be more complex.

[0065] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the embodiments of the present invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring the embodiments of the present invention.

[0066] Example 1:

[0067] like Figure 1 、 Figure 2 and Figure 3 As shown, the present invention provides a method for quantifying the unloading boundary based on the dynamic evolution of surface dynamic settlement and coal wall stress, which is characterized by comprising the following steps:

[0068] Step 1: Collect coal samples from the protected seam of a specific mine and conduct desorption experiments under different constant load conditions to determine the stress value corresponding to rapid gas desorption, which is set as the critical stress value for decompression of the protected coal seam. The critical stress value for decompression specifically includes the following steps:

[0069] (1) Hydrostatic pressure is first applied until the axial stress reaches the original formation pressure. The confining pressure is then reduced until it equals the true formation stress. Methane adsorption is then performed until saturated adsorption equilibrium is reached. The confining pressure is then released and the cumulative gas desorption volume is determined.

[0070] (2) Repeat the experiment in (1) to measure the cumulative desorption of gas at different pressure relief values ​​until the inflection point of rapid gas desorption is determined, thereby determining the critical stress value for rapid desorption.

[0071] Step 2: Determine the deformation value of the overburden based on the stress-strain relationship between the unloading value and the overburden. The stress-strain relationship is the stress-strain relationship of the three vertical zones of the overburden. This step mainly includes the following steps:

[0072] (1) The layered intact structure, blocky fracture structure and scattered structure of the three zones are classified and hypothesized, and the stress-strain characteristics of the three types of structures are extracted. The stress-strain relationship of the three types of structures is described by connecting elastic, plastic or viscous elements in series or in parallel. Then, based on the stress-strain relationship of the overburden, the overall stress-strain characteristics of the overburden are described by connecting the three types of structures in series as a whole.

[0073] (2) The crack strain ratio and effective compressibility coefficient are introduced to establish a quantitative relationship between the closure amount of cracks in the bulk overburden and the degree of compaction difficulty. Considering the distribution of damage variables in the bulk overburden, a compaction-damage fracture constitutive model of the bulk overburden is established. The massive overburden structure is divided into rock and cracks. It is assumed that the deformation of the massive overburden is mainly due to the time-dependent compaction of the cracks, and the intact rock itself is in the elastic stage. The two are correlated to construct a constitutive model of the massive structure. For layered overburden, based on the classic Drucker-Prager yield criterion for layered structure, the influence of the anisotropy of the layered overburden is considered and the classic constitutive model is modified. The vertical series characteristics of the mining-induced layered structure, masonry beam structure and bulk structure are analyzed, and a quantitative relationship of the total stress and strain of the three types of structures in series is established.

[0074] (3) Determine the surface settlement of the overburden caused by mining based on the coal seam mining thickness and the overburden deformation value. For the surface deformation value, the unloading cumulative deformation method is used to substitute it into the aforementioned stress-strain relationship. Its main features include the following steps.

[0075] 1) First, calculate the stress value of each rock layer separately. Then, subtract the deadweight of the overburden to determine the stress of each rock layer. This can then determine the stress distribution of the entire overburden. Based on the stress-strain relationship, determine the deformation value of each rock layer under specific stress conditions. Then, cumulatively superimpose the deformation values ​​to obtain the distribution pattern of the overburden unloading expansion. Based on the coal seam thickness, mining height, and overburden unloading expansion, a surface settlement model of the overburden from the mining layer upward is established.

[0076] 2) The constitutive models of the above three types of structures are further microelementized based on rock layers. The loads at the interfaces of each rock layer within the three types of structures are calculated based on the bulk density and thickness of the overburden. The loads and parameters such as the elastic modulus of each rock layer are then substituted into the rock constitutive models within each overburden structure to obtain the unloading expansion of each rock layer. By integrating in the vertical direction, the cumulative conduction characteristics of the overburden's overall pressure relief expansion are obtained. The surface settlement law of the overburden is then obtained by subtracting the pressure relief expansion of the overburden from the coal seam mining height. This function is formed by the mining stress and parameters such as surface settlement, mining height, and overburden strength, and the quantitative relationship between surface settlement and overburden mining stress is determined.

[0077] Step 4: Based on the dynamic settlement law of the overburden surface, determine the stress distribution law of the entire overburden, and based on the definition of the unloading boundary, delineate the evolution law of the unloading boundary. Specifically, it includes the following steps:

[0078] (1) Dynamic analysis of surface dynamic settlement is performed, and a dynamic time function is introduced to obtain the dynamic evolution law of surface settlement. Then, the stress distribution function of the overburden at different times can be obtained by substituting it into the stress calculation function. Based on the definition of the unloading boundary, the stress distribution dynamic function is substituted to obtain the distribution characteristics of the unloading boundary at different times.

[0079] (2) Based on the quantitative relationship between surface settlement and overburden mining stress, combined with the definition of the relief boundary, the functional relationship between the overburden relief boundary and surface settlement is obtained. Subsequently, the dynamic surface settlement functions such as Logistics and Knothe are introduced to derive the corresponding relationship between surface dynamic settlement and the expansion of the overburden relief boundary of the goaf. The distribution law and expansion path of the overburden relief boundary of the goaf are calculated by programming, and the influence of factors such as overburden lithology, mining height, coal seam inclination, coal seam burial depth, and mining time on the expansion law of the relief boundary are analyzed. The expansion characteristics of the overburden relief boundary of the goaf are revealed from the perspective of surface dynamic settlement above the well.

[0080] (3) Analyze the damage law of coal rock mass under the combined action of cyclic load and constant load. By fitting the statistical prediction method, the rock life curve under different time and amplitude is obtained, and then the long-term strength of the overburden is predicted. Combining the definition of the overburden unloading boundary and the stress distribution law of the coal wall on both sides, the time required for the coal body near the stress concentration position to be damaged, deteriorated and finally destroyed is calculated, thereby determining the spatial location of the outer unloading boundary of the overburden at different times and revealing the expansion characteristics of the overburden unloading boundary on both sides of the goaf.

[0081] (4) Based on the changes in the overburden unloading position of the goaf at different times, the evolution law of the movement rate of the overburden unloading position of the goaf is deduced over time. For the overburden unloading boundary on both sides of the goaf, the overburden unloading critical value is also used as the basis. The changes in the overburden unloading critical position are determined by the evolution law of the stress distribution of the coal wall on both sides over time, and finally the movement rate of the overburden unloading boundary on both sides of the goaf is obtained. The time-space function of the goaf and the overburden unloading boundary on both sides are combined to obtain the movement rate of the overburden unloading boundary at different positions. The overburden stress distribution after the completion of coal seam mining is used as the initial condition and substituted into the overburden unloading boundary time-lag evolution model to determine the heterogeneous expansion characteristics of the overburden unloading boundary during mining. Finally, based on the specific time range of overburden unloading gas extraction, the three-dimensional spatial position and evolution of the overburden unloading boundary during the unloading gas extraction period are determined.

[0082] Step 5: Analyze the convergence time criterion of the dynamic time function of surface settlement, substitute it into the dynamic evolution function of the three-dimensional unloading boundary of the overburden, and finally determine the spatial location of the unloading boundary convergence. The time function convergence criterion is to calculate a virtual time step during the surface settlement calculation process as a way to apply a time difference. Based on this method, the corresponding variation value calculation program is written to obtain the convergence location of the unloading boundary. The specific steps are as follows:

[0083] (1) Input the surface settlement dynamic function when the initial time is 0, call the calculation method of the unloading boundary mentioned above, and save the stress tensor and strain tensor at time 0 and the spatial position of the unloading boundary.

[0084] (2) Let the model perform a virtual calculation for one time step, and then call and save the stress tensor, strain tensor and the spatial position of the stress relief boundary again.

[0085] (3) Subtract the previously saved value from the saved value, and the difference is the first-order variation of the mining-induced overburden stress tensor, strain tensor and unloading boundary.

[0086] (4) According to the positive and negative values ​​of the variational value, the stability of the model is judged, thereby determining the convergence space position of the unloading boundary.

[0087] Example 2:

[0088] An electronic device comprising a memory and a processor;

[0089] The memory is configured to store a computer program.

[0090] The processor is configured to implement the pressure relief boundary quantification method based on dynamic ground subsidence and dynamic evolution of coal wall stress according to the computer program when the computer program is executed.

[0091] Embodiment 3:

[0092] A computer readable storage medium, the storage medium has a computer program stored thereon, and the computer program, when executed by a processor, implements the pressure relief boundary quantification method based on dynamic ground subsidence and dynamic evolution of coal wall stress according to the computer program when the computer program is executed.

[0093] Embodiment 4:

[0094] A computer program product, characterized by comprising a computer program, the computer program, when executed by a processor, implements the pressure relief boundary quantification method based on dynamic ground subsidence and dynamic evolution of coal wall stress according to the computer program when the computer program is executed.

[0095] In the above embodiments, the description refers to "the present embodiment" to indicate that the specific features, structures or characteristics described in the embodiment are included in at least some embodiments, but not necessarily all embodiments. Multiple occurrences of "the present embodiment" do not necessarily all refer to the same embodiment.

[0096] In the above embodiments, although the present application has been described in conjunction with specific embodiments thereof, many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. For example, other storage structures (e.g., dynamic RAM (DRAM)) can use the embodiments discussed. Embodiments of the present application are intended to embrace all such alternatives, modifications and variations as can fall within the scope of the appended claims.

[0097] The computer readable storage medium in the present embodiment can be understood by those skilled in the art that all or part of the steps of the above-mentioned method embodiments can be completed by the hardware of the computer program. The foregoing computer program can be stored in a computer readable storage medium. The program, when executed, performs steps including the above-mentioned method embodiments; and the foregoing storage medium includes ROM, RAM, magnetic disc or optical disc and various media that can store program codes.

[0098] The electronic terminal provided in this embodiment includes a processor, a memory, a transceiver and a communication interface. The memory and the communication interface are connected to the processor and the transceiver and complete communication with each other. The memory is used to store computer programs, the communication interface is used for communication, and the processor and the transceiver are used to run computer programs so that the electronic terminal executes the various steps of the above method.

[0099] In this embodiment, the memory may include a random access memory (RAM), and may also include a non-volatile memory (non-volatile memory), such as at least one disk storage.

[0100] The above-mentioned processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, and discrete hardware components.

[0101] The present invention can be used in a wide variety of general-purpose or special-purpose computing system environments or configurations, such as personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, and distributed computing environments that include any of the above.

[0102] The present invention may be described in the general context of computer-executable instructions, such as program modules, executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, and the like that perform specific tasks or implement specific abstract data types. The present invention may also be practiced in distributed computing environments where tasks are performed by remote processing devices connected via a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media, including storage devices.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for quantifying the unloading boundary based on dynamic surface settlement and dynamic evolution of coal wall stress, characterized by: The following steps are involved: S1: Collect coal samples from the protected seam of a specific mine and conduct desorption experiments on adsorbed gas under different constant load conditions to determine the stress value corresponding to rapid gas desorption, and set it as the critical stress value for decompression of the protected coal seam; S2: Based on the relationship between the unloading value and the stress-strain of the overburden rock, the deformation value of the overburden rock is determined; S3: Determine the surface settlement of overburden caused by mining based on the coal seam mining thickness and overburden deformation value; S4: According to the dynamic settlement law of the overburden surface, determine the stress distribution law of the entire overburden based on the definition of the unloading boundary and determine its evolution law; S5: Analyze the convergence time criterion of the dynamic time function of surface settlement, substitute it into the dynamic evolution function of the three-dimensional unloading boundary of the overburden, and finally determine the spatial position of the convergence of the unloading boundary.

2. The method for quantifying the unloading boundary based on dynamic surface settlement and dynamic evolution of coal wall stress according to claim 1 is characterized by: Step S1 specifically includes the following steps: S11: Apply hydrostatic pressure until the axial stress reaches the original formation pressure; S12: Reduce the confining pressure until it is equal to the true formation stress value; S13: performing methane adsorption until a saturated adsorption equilibrium state is reached; S14: Unload the confining pressure and determine the cumulative desorption amount of gas; S15: Repeat steps S11-S14 to measure the cumulative desorption amount of gas at different pressure relief values ​​until the inflection point of the rapid desorption amount of gas is determined, thereby determining the critical stress value of rapid desorption.

3. The method for quantifying the unloading boundary based on dynamic surface settlement and dynamic evolution of coal wall stress according to claim 1 is characterized by: Step S2 specifically includes the following steps: S21: Classify the three zones of overburden in the vertical direction into layered overburden structure, massive overburden structure and scattered overburden structure, and extract the stress and strain characteristics of the three types of structures; S22: Use elastic, plastic or viscous elements in series or parallel to describe the stress-strain relationship of three types of structures; S23: For the bulk overburden structure, the fracture strain ratio and effective compressibility coefficient are introduced to establish a quantitative relationship between the amount of fracture closure and the degree of compaction difficulty of the bulk overburden. Considering the distribution of damage variables of the bulk overburden, a compaction-damage fracture constitutive model of the bulk overburden is established. For massive overburden structures, the massive overburden structures are divided into rocks and cracks. It is assumed that the deformation of the massive overburden is mainly due to the time-dependent compaction of the cracks, and the intact rock itself is in the elastic stage. The two are correlated to construct a constitutive model of the massive structure. For layered overburden structure, based on the classic layered structure Drucker-Prager yield criterion, the influence of the anisotropy of the layered overburden is considered and the classic constitutive law is modified. S24: Based on the stress-strain relationship of the overburden, the overall stress-strain characteristics of the overburden are described by connecting three types of structures in series. The series characteristics of the three types of structures in the vertical direction are analyzed, and the quantitative relationship of the total stress and strain of the three types of structures in series is established.

4. The method for quantifying the unloading boundary based on dynamic surface settlement and dynamic evolution of coal wall stress according to claim 1 is characterized by: Step S3 specifically includes the following steps: S31: Calculate the stress value of each rock layer respectively, subtract the deadweight of the overburden rock to determine the stress of each rock layer of the overburden rock, and obtain the stress distribution of the entire overburden rock; S32: Determine the deformation value of each rock layer under specific stress conditions based on the stress-strain relationship, and superimpose them in a cumulative manner to obtain the distribution law of the overburden unloading expansion; S33: Based on the coal seam thickness, mining height, and overburden expansion, a surface settlement model of the overburden from the mining layer upward is established; S34: The constitutive models of the three types of structures are microelementized based on rock layers; S35: Calculate the loads at the interfaces of each rock layer within the three types of structures based on the bulk density and thickness of the overburden rock; S36: Substitute the load and the elastic modulus of each rock layer into the rock constitutive model of each structure in the overburden rock to obtain the unloading expansion of each rock layer, integrate it in the vertical direction, and obtain the cumulative conduction characteristics of the overburden rock's overall unloading expansion; S37: Use the coal seam mining height minus the overburden expansion due to pressure relief to obtain the surface settlement law of the overburden, form a function of mining stress and surface settlement, mining height, and overburden strength, and determine the quantitative relationship between surface settlement and overburden mining stress.

5. The method for quantifying the unloading boundary based on dynamic surface settlement and dynamic evolution of coal wall stress according to claim 1 is characterized by: Step S4 specifically includes the following steps: S41: Dynamic analysis of surface dynamic settlement is carried out, dynamic time function is introduced, and the dynamic evolution law of surface settlement is obtained; S42: Substitute the dynamic evolution law of surface settlement into the stress calculation function to obtain the stress distribution function of the overburden at different times; S43: Based on the definition of the pressure relief boundary, the stress distribution function is substituted to obtain the distribution characteristics of the pressure relief boundary at different mining times; S44: Based on the quantitative relationship between surface settlement and overburden mining stress, combined with the definition of the unloading boundary, the functional relationship between the overburden unloading boundary and surface settlement is obtained; S45: Introducing the dynamic function of surface settlement, the corresponding relationship between surface dynamic settlement and the expansion of the overburden pressure relief boundary of the goaf is derived; S46: Calculate the distribution and expansion path of the overburden unloading boundary in the goaf, analyze the influence of overburden lithology, mining height, coal seam inclination, coal seam burial depth, and mining time on the expansion law of the unloading boundary, and reveal the expansion characteristics of the overburden unloading boundary in the goaf from the perspective of dynamic surface settlement above the well; S47: Analysis of the damage law of coal and rock mass under the combined action of cyclic load and constant load; S48: Obtain rock life curves under different time and amplitude conditions by fitting statistical prediction methods to predict the long-term strength of overburden rocks; S49: Combining the definition of the overburden stress relief boundary with the stress distribution law of the coal walls on both sides, the time required for the coal body near the stress concentration location to be damaged, deteriorated, and finally destroyed is calculated. This allows the spatial location of the overburden stress relief boundary outside the overburden to be determined at different times, revealing the extension characteristics of the overburden stress relief boundary on both sides of the goaf. S410: based on the change of the pressure relief position of the overburden in the goaf at different times, deduce the temporal evolution law of the movement rate of the pressure relief position of the overburden in the goaf; S411: For the overburden pressure relief boundary on both sides of the goaf, based on the overburden pressure relief critical value, the change of the overburden pressure relief critical position is determined by the evolution law of the stress distribution of the coal wall on both sides over time, and finally the movement rate of the overburden pressure relief boundary on both sides of the goaf is obtained; S412: The time-space functions of the goaf and the overburden stress relief boundaries on both sides are combined to obtain the movement rate of the stress relief boundaries at different positions of the overburden. The stress distribution of the overburden after coal seam mining is used as the initial condition and substituted into the time-delay evolution model of the overburden stress relief boundary to determine the allometric expansion characteristics of the overburden stress relief boundary as it changes with time. S413: Based on a specific time range of overburden decompression gas extraction, determine the three-dimensional spatial position and evolution of the overburden decompression boundary during the decompression gas extraction period.

6. The method for quantifying the unloading boundary based on dynamic surface settlement and dynamic evolution of coal wall stress according to claim 1 is characterized in that: In step S5, a virtual time step is calculated during the surface settlement calculation process as a way of applying a time difference. The variation value is calculated according to the following steps to obtain the convergence position of the pressure relief boundary: S51: Input the surface settlement dynamic function when the initial time is 0, call the calculation method of the pressure relief boundary, and save the stress tensor and strain tensor and the spatial position of the pressure relief boundary at time 0; S52: Virtually calculate a time step, call and save the stress tensor, strain tensor and the position of the stress relief boundary space again; S53: Subtract the previously saved value from the saved value, and the difference is the first-order variation of the mining-induced overburden stress tensor, strain tensor and unloading boundary; S54: According to the positive or negative value of the variation value, the stability of the model is judged, thereby determining the convergence space position of the pressure relief boundary.

7. An electronic device, characterized in that: including memory and processor; The memory is used to store computer programs; The processor is configured to implement the unloading boundary quantification method based on surface dynamic settlement and dynamic evolution of coal wall stress as described in any one of claims 1 to 6 when executing the computer program.

8. A computer-readable storage medium, characterized in that The storage medium stores a computer program, and when the computer program is executed by the processor, the unloading boundary quantification method based on surface dynamic settlement and dynamic evolution of coal wall stress as described in any one of claims 1 to 6 is implemented.

9. A computer program product, characterized in that: The method comprises a computer program which, when executed by a processor, implements the method for quantifying the unloading boundary based on dynamic surface settlement and dynamic evolution of coal wall stress as claimed in any one of claims 1 to 6.

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