Coal rock creep seepage coupling model construction method and system

Abstract

This invention discloses a method and system for constructing a coupled model of coal and rock creep and seepage, relating to the field of coal and rock mechanics. The method includes: calculating effective stress based on synchronous coal and rock creep and seepage data; constructing a coal and rock creep constitutive model based on the effective stress; establishing an initial seepage sub-model based on measured permeability using Darcy's law; bidirectionally coupling the coal and rock creep constitutive model with the initial seepage sub-model to form a basic set of coupled variables; constructing continuous phase field variables based on the basic set of coupled variables; using these variables to characterize the gradual evolution of coal and rock from a complete state to a fractured state to determine the crack evolution region; and simultaneously correcting the coal and rock creep damage state and seepage channel state to obtain a spatial phase field crack evolution field. This invention is applicable to the quantitative characterization of abrupt changes in seepage capacity under long-term loading of coal and rock, achieving the effect of improving the physical consistency and predictive stability of the model.

Description

Technical Field

[0001] This invention relates to the field of coal and rock mechanics, and in particular to a method and system for constructing a coupled model of coal and rock creep and seepage. Background Technology

[0002] In studies on underground coal and rock engineering, coalbed methane extraction, and deep energy storage, creep deformation of coal and rock under long-term load, pore pressure, and seepage can alter the pore and fracture structure, thereby affecting permeability evolution. Related technologies typically obtain data such as axial strain, volumetric strain, pore pressure difference, and flow rate through triaxial creep seepage tests, and establish creep seepage analysis models based on the effective stress principle, constitutive equations, and Darcy's law. At the same time, permeability is corrected by combining damage mechanics or statistical fracture parameters to describe the multi-field response law of coal and rock from compaction and stable creep to accelerated damage stages.

[0003] Existing modeling methods often treat creep damage variables and permeability correction coefficients as time series or empirical functions. When cracks inside the sample are still in the dispersed propagation stage, the slow changes in seepage capacity can be reflected by continuous parameter updates. However, when coal and rock undergo local rupture and form through-flow channels under long-term effective stress and pore pressure feedback, the spatial connectivity of the cracks will cause the macroscopic permeability to exhibit a nonlinear characteristic of transitioning from gradual change to sudden increase. If the model still describes the seepage state with a single continuous update rule, it is difficult to simultaneously express the correspondence between crack spatial evolution, damage seepage zone connectivity determination, and macroscopic permeability transition. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a method for constructing a coupled model of coal and rock creep seepage to solve the problem that it is difficult to couple and characterize the sudden changes in permeability caused by the penetration of cracks due to coal and rock creep damage.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for constructing a coupled model of coal and rock creep and seepage, comprising: acquiring raw data of coal and rock creep and seepage from a coal and rock sample, and determining the volumetric creep strain and measured permeability based on the raw data of coal and rock creep and seepage to obtain synchronous data of coal and rock creep and seepage; calculating the effective stress based on the synchronous data of coal and rock creep and seepage, constructing a constitutive model of coal and rock creep based on the effective stress, and establishing an initial seepage sub-model based on the measured permeability using Darcy's law, and bidirectionally coupling the constitutive model of coal and rock creep and the initial seepage sub-model to form a basic set of coupled variables; constructing continuous phase field variables based on the basic set of coupled variables, and using the continuous phase field variables to characterize the change of coal and rock from a whole state to a fractured state. The gradual evolution of the state determines the coal and rock crack evolution region, and simultaneously corrects the coal and rock creep damage state and seepage channel state to obtain the spatial phase field crack evolution field; the spatial phase field crack evolution field identifies the damage seepage region, and based on the percolation theory, it is determined whether the damage seepage region forms a through seepage path. According to the judgment result, the macroscopic permeability update rule is switched between continuous gradual update mode and percolation abrupt update mode to generate an initial coupled model of creep seepage; based on the synchronous data of coal and rock creep seepage, the undetermined parameters in the initial coupled model of creep seepage are inverted, and after the parameters are determined, iterative solutions are performed until the preset convergence conditions are met to generate a coupled model of coal and rock creep seepage.

[0007] As a preferred embodiment of the coal-rock creep-seepage coupling model construction method of the present invention, the specific steps for obtaining synchronous coal-rock creep-seepage data are as follows: The coal and rock samples were sized and sealed, and then loaded into the preset creep and seepage test state. After the test state stabilized, the start time of the synchronous test was determined. Using the start time of the synchronous test as the time reference, the deformation response, loading response, pore pressure response and seepage response of the coal and rock samples during the creep seepage process are continuously recorded according to the sampling interval, and a corresponding time stamp is configured for each test response, and the raw data of coal and rock creep seepage are output. The raw data of coal and rock creep is subjected to benchmark subtraction and time alignment. The volumetric creep strain is calculated based on the processed deformation response, and the measured permeability is calculated using Darcy's law based on the processed pore pressure response and seepage response, thus obtaining synchronous data of coal and rock creep.

[0008] As a preferred embodiment of the coal-rock creep-seepage coupling model construction method of the present invention, the specific steps of calculating the effective stress based on the synchronous data of coal-rock creep-seepage and constructing the coal-rock creep constitutive model based on the effective stress are as follows: The pore pressure response in the synchronous data of coal and rock creep is smoothed by differential pressure, and the processed pore pressure response is matched with the loading response at the corresponding sampling time. Then the effective stress corresponding to the coal and rock skeleton is calculated. By using effective stress as the creep driving input and volumetric creep strain in the synchronous data of coal and rock creep and seepage as the response constraint, a temporal correspondence between effective stress and volumetric creep strain is established to obtain the creep state sequence. The effective stress is written into the input layer of the creep constitutive model, the creep state at the previous sampling time is written into the creep state cache layer, the volumetric creep strain is written into the creep response output layer, and the creep state update chain is configured according to the creep state update order to obtain the coal and rock creep constitutive sub-model.

[0009] As a preferred embodiment of the coal and rock creep-seepage coupling model construction method of the present invention, the specific steps for establishing the initial seepage sub-model based on measured permeability using Darcy's law are as follows: Write the measured permeability from the synchronous data of coal and rock creep into the seepage state node, and read the inlet pore pressure and outlet pore pressure at the same sampling time to calculate the seepage pressure difference. Write the seepage pressure difference, measured permeability and seepage basic parameters into the Darcy seepage calculation node to generate the initial seepage mapping relationship. The initial seepage mapping relationship is written into the mapping layer of the seepage model, the pressure difference is configured as the seepage driving input, the measured permeability is configured as the seepage state variable, the seepage response is configured as the seepage output variable, and the seepage state update chain is configured according to the Darcy seepage update order to obtain the initial seepage sub-model.

[0010] As a preferred embodiment of the coal and rock creep-seepage coupling model construction method of the present invention, the specific steps of bidirectionally coupling the coal and rock creep constitutive model with the initial seepage sub-model to form a basic set of coupling variables are as follows: The creep state output of the coal and rock creep constitutive model is connected to the permeability state of the initial seepage sub-model to form the first coupling path from creep to seepage. The current creep state output by the coal and rock creep constitutive model is used as the permeability correction input and written into the initial seepage sub-model. The seepage state of the initial seepage sub-model is updated according to the Darcy seepage update order. The pore pressure state output of the initial seepage sub-model is connected to the effective stress input of the coal and rock creep constitutive model to form a second coupling path from seepage to creep. The pore pressure state output by the initial seepage sub-model is written into the coal and rock creep constitutive model as the effective stress correction input to update the effective stress state of the coal and rock creep constitutive model. The consistency of the states of the first and second coupling paths is verified at the same sampling time, and the verified effective stress state, creep state, seepage state and feedback state are bound according to the sampling time to obtain the basic coupling variable set.

[0011] As a preferred embodiment of the coal-rock creep-seepage coupling model construction method of the present invention, the specific steps of constructing continuous phase field variables based on the basic coupling variable set and using the continuous phase field variables to characterize the gradual evolution of coal and rock from an intact state to a fractured state and determine the coal-rock crack evolution region are as follows: The basic set of coupled variables is mapped to the spatial computational grid of the coal and rock samples, and a phase field update interface is configured for each grid to obtain the set of spatially coupled grids. The current phase field driving quantity is generated based on the effective stress state and creep state corresponding to the spatially coupled grid, and the current phase field driving quantity is locked by taking the larger value of the historical field value at the previous sampling time to obtain continuous phase field variables. Using the continuous phase field variables at the previous sampling time as initial values, the current continuous phase field variables are updated grid by grid according to the historical field locking results. The process of the continuous phase field variables changing from the complete threshold interval to the damage transition threshold interval and then to the fracture threshold interval is recorded as the gradual evolution process of coal and rock. The grids that reach the fracture threshold interval are marked as crack grids, and adjacent crack grids are connected and merged according to the spatial adjacency relationship to obtain the coal and rock crack evolution region.

[0012] As a preferred embodiment of the coal-rock creep-seepage coupling model construction method of the present invention, the specific steps for simultaneously correcting the coal-rock creep damage state and seepage channel state to obtain the spatial phase field crack evolution field are as follows: Using the coal and rock crack evolution region as the correction range, the creep state at the current sampling time is mapped to the corresponding spatial coupling grid, and the continuous phase field variable is converted into a phase field damage level and compared with the damage level corresponding to the creep state to obtain the coal and rock creep damage state. Using the coal and rock crack evolution region as the channel correction range, the seepage state at the current sampling moment is mapped to the corresponding spatial coupling grid, and the continuous phase field variables are converted into channel open level and then updated to obtain the seepage channel state. By configuring the same spatial index and time index for the creep damage state and seepage channel state of coal and rock under the same sampling time and the same spatial coupling grid, and binding them to the corresponding continuous phase field variables according to the spatial coupling grid, the spatial phase field crack evolution field is obtained.

[0013] As a preferred embodiment of the coal and rock creep seepage coupling model construction method of the present invention, the specific steps for generating the initial creep seepage coupling model are as follows: Using the spatial phase field crack evolution field as input, the continuous phase field variables are converted into crack damage markers, and the seepage channel state is converted into channel open markers. The spatial location that simultaneously has crack damage markers and channel open markers is marked as the damage seepage location, thus obtaining the damage seepage marker map. A three-dimensional 26-adjacent template was used to perform connectivity search on the damage seepage marker map, and isolated markers were removed after merging adjacent damage seepage locations to obtain the damage seepage region. Using the damaged seepage area as the permeability judgment object, the inflow boundary and outflow boundary of the coal and rock sample are used as the penetration judgment boundary, and the damaged seepage area that simultaneously contacts the inflow boundary and outflow boundary is marked as the penetration seepage path to obtain the penetration judgment result. Based on the breakthrough judgment result, the macroscopic permeability update rule is switched between continuous gradual update mode and permeability sudden change update mode. The updated macroscopic permeability is written into the initial seepage sub-model, and the breakthrough judgment result is written into the coal and rock creep constitutive sub-model to correct the creep damage variable, so as to obtain the initial coupled model of creep seepage.

[0014] As a preferred embodiment of the coal-rock creep-seepage coupling model construction method of the present invention, the specific steps for generating the coal-rock creep-seepage coupling model are as follows: Based on synchronous data of coal and rock creep and seepage, an inversion sample sequence is generated according to the sampling time. Huber robust residual labeling is performed on the inversion sample sequence. The labeled inversion sample sequence is written into the parameter interface of the creep seepage initial coupling model to obtain parameter inversion constraints. Based on parameter inversion constraints, a synchronous inversion target for volumetric creep strain deviation and measured permeability deviation is established. The undetermined parameters in the initial coupled creep-seepage model are solved in a hierarchical inversion order of creep parameters first, seepage parameters follow, and coupling parameters are fine-tuned to obtain a definite parameter set. The determined parameter set is written into the initial coupled model of creep seepage and parameter locking is performed. The initial coupled model of creep seepage after parameter locking is iteratively solved according to the bidirectional coupling path. After the convergence conditions are met in two adjacent iterations, the model encapsulation container is written to obtain the coupled model of coal and rock creep seepage.

[0015] Secondly, the present invention provides a coal and rock creep-seepage coupling model construction system, including: a data synchronization module, used to acquire the original coal and rock creep-seepage data of coal and rock samples, and determine the volumetric creep strain and measured permeability based on the original coal and rock creep-seepage data to obtain synchronized coal and rock creep-seepage data; The coupled modeling module is used to calculate the effective stress based on synchronous data of coal and rock creep and seepage, construct a coal and rock creep constitutive sub-model based on the effective stress, and establish an initial seepage sub-model based on measured permeability using Darcy's law. The coal and rock creep constitutive model and the initial seepage sub-model are bidirectionally coupled and associated to form a basic set of coupled variables. The phase field evolution module is used to construct continuous phase field variables based on the basic coupling variable set. The continuous phase field variables are used to characterize the gradual evolution of coal and rock from the intact state to the fractured state, determine the coal and rock crack evolution region, and simultaneously correct the coal and rock creep damage state and seepage channel state to obtain the spatial phase field crack evolution field. The permeability update module is used to identify the damaged seepage region based on the spatial phase field crack evolution field, and to determine whether the damaged seepage region has formed a through seepage path based on permeability theory. Based on the judgment result, it switches the macroscopic permeability update rule between continuous gradual update mode and permeability abrupt update mode to generate the creep seepage initial coupling model. The inversion solution module is used to perform parameter inversion on the undetermined parameters in the initial coupled model of creep seepage based on synchronous data of coal and rock creep seepage, and to perform iterative solution after the parameters are determined until the preset convergence conditions are met, thereby generating the coupled model of coal and rock creep seepage.

[0016] The beneficial effects of this invention are as follows: by identifying the damaged seepage region based on the spatial phase field crack evolution field, and judging whether it has formed a through seepage path based on the permeability theory, the macroscopic permeability update rule is switched between the continuous gradual update mode and the permeability abrupt update mode, realizing the synchronous mapping between the crack connectivity state and the permeability evolution mode. This enables the model to update the seepage channel and damage variables when creep damage accumulates to the point of channel penetration. It is suitable for the quantitative characterization of the abrupt process of seepage capacity under long-term loading of coal and rock, and achieves the effect of improving the physical consistency and predictive stability of the model. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart of the method for constructing a coupled model of coal and rock creep and seepage.

[0019] Figure 2 A schematic diagram of the system for constructing a coupled model of coal and rock creep and seepage.

[0020] Figure 3 Flowchart for constructing a constitutive model of coal and rock creep.

[0021] Figure 4 A flowchart for forming the basic set of coupled variables. Detailed Implementation

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0024] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0025] Reference Figures 1-4 As an embodiment of the present invention, this embodiment provides a method for constructing a coal and rock creep-seepage coupling model, including the following steps: S1. Obtain the original data of coal and rock creep permeability of coal and rock samples, and determine the volumetric creep strain and measured permeability based on the original data of coal and rock creep permeability to obtain synchronous data of coal and rock creep permeability.

[0026] S1.1. The coal and rock samples are sized and sealed, and the samples are loaded into the preset creep and seepage test state. After the test state is stable, the start time of the synchronous test is determined.

[0027] Furthermore, the end faces of the coal and rock samples are flattened, and the diameter, height, and mass of the coal and rock samples are measured to form the dimensional calibration parameters of the coal and rock samples. According to the dimensional calibration parameters of the coal and rock samples, the coal and rock samples are placed in the clamping cavity of the creep flow test device, and the coal and rock samples are sealed and clamped by the sealing sleeve and the end pressure head. Loads are applied according to the axial loading path, the confining pressure loading path, and the pore pressure loading path respectively, so that the coal and rock samples enter the creep flow test state. When the axial load, confining pressure, pore pressure, and flow response all reach the stable condition, the current sampling time is determined as the synchronous test start time.

[0028] It should also be noted that the creep flow test conditions are set according to the target test conditions, including axial load, confining pressure, inlet pore pressure, outlet pore pressure, and temperature, and are formed after each loading condition reaches the preset target value and remains stable.

[0029] S1.2. Using the start time of the synchronous test as the time reference, continuously record the deformation response, loading response, pore pressure response and seepage response of the coal and rock sample during the creep seepage process according to the sampling interval, and configure a corresponding time mark for each test response to output the raw data of coal and rock creep seepage.

[0030] Furthermore, taking the start time of the synchronous test as time zero, sampling times are generated sequentially according to the sampling interval; at each sampling time, the deformation response, loading response, pore pressure response, and seepage response of the coal and rock sample are recorded respectively; the sampling times are configured as deformation response time markers, loading response time markers, pore pressure response time markers, and seepage response time markers respectively; the deformation response, loading response, pore pressure response, and seepage response of the coal and rock sample are written in the order of sampling times, and the raw data of coal and rock creep seepage are output.

[0031] S1.3. The original coal and rock creep data are subjected to benchmark subtraction and time alignment processing. The volumetric creep strain is calculated based on the processed deformation response, and the measured permeability is calculated using Darcy's law based on the processed pore pressure response and seepage response to obtain synchronous coal and rock creep data.

[0032] Furthermore, using the deformation response, pore pressure response, and seepage response corresponding to the start time of the synchronous test as the subtraction benchmark, the initial offset is subtracted point by point from the deformation response, pore pressure response, and seepage response in the original coal and rock creep data. According to the deformation response time marker, pore pressure response time marker, and seepage response time marker, the subtracted deformation response, subtracted pore pressure response, and subtracted seepage response are aligned to the same sampling time. The volumetric creep strain is calculated based on the subtracted deformation response, and the measured permeability is calculated using Darcy's law based on the subtracted pore pressure response and subtracted seepage response, thus forming synchronous coal and rock creep data.

[0033] It should also be noted that Darcy's law is a classical seepage relationship that describes the flow rate of a fluid in a porous medium as being directly proportional to the permeability, pressure difference, and flow cross-sectional area, and inversely proportional to the fluid viscosity and seepage length. It is used to calculate the measured permeability based on the seepage pressure difference between the inlet and outlet pore pressures formed by the subtracted pore pressure response, and the subtracted seepage response.

[0034] S2. Calculate the effective stress based on the synchronous data of coal and rock creep and seepage, construct a coal and rock creep constitutive model based on the effective stress, and establish an initial seepage sub-model based on the measured permeability using Darcy's law. Couple the coal and rock creep constitutive model with the initial seepage sub-model in two directions to form a basic set of coupled variables.

[0035] S2.1 Perform differential pressure bilateral smoothing on the pore pressure response in the synchronous data of coal and rock creep, match the processed pore pressure response with the loading response at the corresponding sampling time, and then calculate the effective stress corresponding to the coal and rock skeleton.

[0036] Furthermore, the inlet and outlet pore pressures are extracted from the pore pressure response in the synchronous coal and rock creep data at each sampling time. The pore pressure responses at adjacent sampling times are used as bilateral references to smooth the instantaneous fluctuations in the inlet and outlet pore pressures. The smoothed pore pressure response is then matched point-by-point with the loading response according to the sampling time. The loading response is converted into the total stress of the coal and rock sample, and the pore pressure is subtracted from the total stress to calculate the effective stress corresponding to the coal and rock skeleton. The expression is as follows: ; in: It is the first The effective stress corresponding to the coal and rock skeleton at each sampling time, in Pa; It is the first The total stress of the coal and rock sample obtained from the loading response at each sampling time is expressed in Pa. is the Biot effective stress coefficient, used to characterize the degree of influence of pore pressure on the effective stress of the coal and rock skeleton, and is dimensionless; It is the first The inlet orifice pressure after differential pressure bilateral smoothing at each sampling time, in Pa; It is the first The outlet orifice pressure after differential pressure bilateral smoothing at each sampling time is expressed in Pa. It is the first Each sampling time; It is an indicator for differential pressure bilateral smoothing; It is the sampling time sequence number.

[0037] S2.2. Using effective stress as the creep driving input and volumetric creep strain in the synchronous data of coal and rock creep and seepage as the response constraint, establish the temporal correspondence between effective stress and volumetric creep strain to obtain the creep state sequence.

[0038] Furthermore, using the sampling time as an index, the effective stress is read point by point from the effective stress corresponding to the coal and rock skeleton, and the volumetric creep strain at the same sampling time is read point by point from the synchronous data of coal and rock creep. The effective stress at the same sampling time is configured as the creep driving input, and the volumetric creep strain at the same sampling time is configured as the response constraint. According to the order of sampling time, the effective stress, volumetric creep strain and the creep state at the previous sampling time are bound point by point to form a temporal correspondence between the effective stress and the volumetric creep strain, and the creep state sequence is obtained.

[0039] S2.3. Write the effective stress into the input layer of the creep constitutive model, write the creep state at the previous sampling time into the creep state cache layer, write the volumetric creep strain into the creep response output layer, and configure the creep state update chain according to the creep state update order to obtain the coal and rock creep constitutive sub-model.

[0040] Furthermore, the effective stress in the creep state sequence is written into the input layer of the creep constitutive model according to the sampling time, the creep state corresponding to the previous sampling time is written into the creep state cache layer, and the volumetric creep strain at the same sampling time is written into the creep response output layer. According to the order of sampling time, the creep state of the previous sampling time in the creep state cache layer is read first, then the effective stress in the input layer of the creep constitutive model is read, and then the volumetric creep strain is used as the response constraint to check the creep state at the current sampling time. The creep state at the current sampling time is written back to the creep state cache layer to form a creep state update chain and obtain the coal and rock creep constitutive sub-model.

[0041] It should also be noted that the specific training of the coal and rock creep constitutive model is as follows: using the creep state sequence as the source of training samples, the effective stress, the creep state at the previous sampling time, and the volumetric creep strain are read in the order of sampling time. The effective stress and the creep state at the previous sampling time are input into the coal and rock creep constitutive model, and the volumetric creep strain is used as the response constraint to invert and solve the creep parameters in the coal and rock creep constitutive model. During the inversion and solution process, the deviation between the volumetric creep strain output by the coal and rock creep constitutive model and the volumetric creep strain in the synchronous data of coal and rock creep and seepage is compared one by one. After the deviation meets the convergence condition, the creep parameters are locked, and the training of the coal and rock creep constitutive model is completed.

[0042] S2.4 Write the measured permeability from the synchronous data of coal and rock creep into the seepage state node, and read the inlet pore pressure and outlet pore pressure at the same sampling time to calculate the seepage pressure difference. Write the seepage pressure difference, measured permeability and seepage basic parameters into the Darcy seepage calculation node to generate the initial seepage mapping relationship.

[0043] Furthermore, using the sampling time as an index, the measured permeability, inlet pore pressure, and outlet pore pressure at the same sampling time are read from the synchronous data of coal and rock creep. The measured permeability is written into the seepage state node according to the sampling time. The seepage pressure difference at the same sampling time is determined based on the pore pressure difference between the inlet and outlet pore pressures. The seepage pressure difference, measured permeability, coal and rock sample length, coal and rock sample cross-sectional area, and fluid viscosity are written into the Darcy seepage calculation node. The Darcy seepage calculation node calculates the seepage response at the same sampling time according to Darcy's law, based on the measured permeability, coal and rock sample cross-sectional area, seepage pressure difference, fluid viscosity, and coal and rock sample length. The sampling time, seepage pressure difference, measured permeability, and seepage response are mapped point by point to generate the initial seepage mapping relationship.

[0044] S2.5. Write the initial seepage mapping relationship into the mapping layer of the seepage model, configure the pressure difference as the seepage driving input, configure the measured permeability as the seepage state variable, configure the seepage response as the seepage output variable, and configure the seepage state update chain according to the Darcy seepage update order to obtain the initial seepage sub-model.

[0045] Furthermore, the initial seepage mapping relationship generated in the previous step is written into the mapping layer of the seepage model according to the sampling time. The seepage pressure difference in the initial seepage mapping relationship is configured as the seepage driving input, the measured permeability in the initial seepage mapping relationship is configured as the seepage state variable, and the seepage response in the initial seepage mapping relationship is configured as the seepage output variable. According to the Darcy seepage update order, the seepage driving input at the same sampling time is read first, and then the seepage state variable at the same sampling time is read. Subsequently, the initial seepage mapping relationship is called through the mapping layer of the seepage model to calculate the seepage output variable. The seepage driving input, seepage state variable, and seepage output variable are written into the seepage state update chain according to the sampling time to obtain the initial seepage sub-model.

[0046] The initial seepage sub-model training is as follows: The inlet pore pressure, outlet pore pressure, measured permeability, and seepage response from the synchronous coal and rock creep seepage data are used as training samples. The inlet and outlet pore pressures are read at the sampling time to determine the seepage pressure difference. This pressure difference and measured permeability are input into the initial seepage sub-model, and the seepage response is used as the output constraint. The fundamental seepage parameters in the initial seepage sub-model are then inverted and solved. During the inversion process, the deviation between the seepage response output by the initial seepage sub-model and the seepage response in the synchronous coal and rock creep seepage data is compared point by point. Once the deviation meets the convergence condition, the fundamental seepage parameters are locked, completing the initial seepage sub-model training.

[0047] S2.6 Connect the creep state output of the coal and rock creep constitutive model to the permeability state of the initial seepage sub-model to form the first coupling path from creep to seepage. Write the current creep state output by the coal and rock creep constitutive model as the permeability correction input into the initial seepage sub-model and update the seepage state of the initial seepage sub-model according to the Darcy seepage update order.

[0048] Furthermore, the current creep state is read from the creep state output of the coal and rock creep constitutive sub-model according to the sampling time, and the current creep state is written into the permeability state of the initial seepage sub-model according to the same sampling time, forming the first coupling path from creep to seepage. The initial seepage sub-model uses the current creep state as the permeability correction input, matches it with the measured permeability in the initial seepage mapping relationship, and corrects the permeability changes caused by coal and rock pore compression and fracture expansion according to the current creep state, forming the corrected permeability at the same sampling time. The initial seepage sub-model reads the seepage pressure difference and the corrected permeability at the same sampling time according to the Darcy seepage update order, calculates the seepage response at the same sampling time, and writes the corrected permeability and seepage response back to the seepage state of the initial seepage sub-model.

[0049] S2.7 Connect the pore pressure state output of the initial seepage sub-model to the effective stress input of the coal and rock creep constitutive sub-model to form a second coupling path from seepage to creep. Write the pore pressure state output by the initial seepage sub-model as the effective stress correction input into the coal and rock creep constitutive sub-model to update the effective stress state of the coal and rock creep constitutive model.

[0050] Furthermore, the pore pressure state is read from the output terminal of the initial seepage sub-model at the sampling time, and written into the effective stress input terminal of the coal-rock creep constitutive sub-model at the same sampling time, forming a second coupling path from seepage to creep. The coal-rock creep constitutive sub-model uses the pore pressure state as the effective stress correction input, matches it with the loading response at the same sampling time, and subtracts the influence of pore pressure according to the effective stress calculation expression corresponding to the coal-rock skeleton to form the corrected effective stress. The coal-rock creep constitutive model writes the corrected effective stress into the effective stress state and drives the creep state update at the same sampling time with the corrected effective stress.

[0051] S2.8 Perform state consistency verification on the first coupling path and the second coupling path at the same sampling time, and bind the verified effective stress state, creep state, seepage state and feedback state according to the sampling time to obtain the basic coupling variable set.

[0052] Furthermore, using the sampling time as an index, the current creep state output by the coal and rock creep constitutive sub-model in the first coupling path, the permeability correction input received by the initial seepage sub-model, and the seepage state updated by the initial seepage sub-model are read first. Then, the pore pressure state output by the initial seepage sub-model in the second coupling path, the effective stress correction input received by the coal and rock creep constitutive model, and the effective stress state updated by the coal and rock creep constitutive model are read. The sampling time, time stamp, input source, output destination, and update order corresponding to the first and second coupling paths are checked item by item. If the sampling time is inconsistent, it is rematched to the same sampling time according to the aforementioned time stamp. If the input source or output destination is inconsistent, the current creep state, pore pressure state, seepage state, and effective stress state at the corresponding sampling time are read back. At the same sampling time, the verified effective stress state, creep state, seepage state, and feedback state are written into the same time sequence record to obtain the basic coupling variable set.

[0053] S3. Construct continuous phase field variables based on the basic coupling variable set, use the continuous phase field variables to characterize the gradual evolution of coal and rock from the intact state to the fractured state, determine the coal and rock crack evolution region, and simultaneously correct the coal and rock creep damage state and seepage channel state to obtain the spatial phase field crack evolution field.

[0054] S3.1 Map the basic set of coupled variables to the spatial computational grid of the coal and rock sample, and configure a phase field update interface for each grid to obtain the spatial coupled grid set.

[0055] Furthermore, a three-dimensional computational domain consistent with the shape of the coal and rock sample is established based on the diameter and height of the sample. This domain is then spatially discretized to form multiple spatial computational grids for bearing the effective stress state, creep state, seepage state, and continuous phase field variables. The effective stress state, creep state, seepage state, and feedback state are read from the basic coupled variable set according to the sampling time, and written into the corresponding spatial index and the spatial computational grid at the corresponding sampling time. A phase field update interface is configured for each spatial computational grid. This interface receives the effective stress state and creep state and outputs the phase field driving quantity required for updating the continuous phase field variables, forming a spatial coupled grid set.

[0056] S3.2. Generate the current phase field driving quantity based on the effective stress state and creep state corresponding to the spatially coupled grid, and lock the current phase field driving quantity with the historical field value at the previous sampling time by taking the larger value to obtain the continuous phase field variable.

[0057] Furthermore, the effective stress state under the same spatial index is read from the spatially coupled mesh set according to the sampling time, and the effective stress state is input into the phase field update interface; the creep state under the same spatial index is read according to the same sampling time, and the creep state is input into the phase field update interface; the phase field update interface calculates the current phase field driving quantity based on the stress intensity corresponding to the effective stress state and the deformation accumulation degree corresponding to the creep state, the expression of which is: ; in: It is the first The sampling time, the first The current phase field driving quantity of each spatial computation grid, dimensionless; It is the first The spatial location or spatial index corresponding to each spatial computation grid; It is the weighting coefficient corresponding to the stress strength term, which is obtained by inverting the fitting error between the effective stress term and the measured damage evolution results, and is dimensionless; It is the weighting coefficient corresponding to the creep deformation accumulation term, which is obtained by inverting the fitting error between the volume creep strain accumulation term and the measured damage evolution result, and is dimensionless; It is the first The sampling time, the first The equivalent stress intensity, calculated from the effective stress state, is given in Pa in a spatial computational grid. This is the characteristic stress corresponding to the coal and rock sample entering the damage evolution stage, with the unit being Pa; It is the first The sampling time, the first The cumulative volumetric creep strain of each spatial computational grid, dimensionless; It is the characteristic volumetric creep strain corresponding to the coal and rock sample entering the damage evolution stage, and is dimensionless; It is a volumetric item identifier used to indicate that the strain is a volumetric strain; It is a creep term identifier, used to indicate that the strain is a creep strain; It is the sequence number of the spatial computing grid; The current phase field driving quantity under the same spatial index is compared with the historical field value at the previous sampling time grid by grid, and the larger value is written into the historical field value at the current sampling time to obtain continuous phase field variables.

[0058] The continuous phase field variables at the previous sampling time are used as the initial values ​​of the continuous phase field variables at the current sampling time. The historical field lock values ​​are read one by one according to the spatial index. When the historical field lock value is greater than the current initial value of the continuous phase field variable, the historical field lock value is written into the current continuous phase field variable. When the historical field lock value does not exceed the current initial value of the continuous phase field variable, the current initial value of the continuous phase field variable is retained, and the continuous phase field variable update of each spatial computing grid at the current sampling time is completed.

[0059] The updated continuous phase field variables are compared with the complete threshold interval. When the continuous phase field variables are within the complete threshold interval, the corresponding spatial computation grid is recorded as the complete state. The updated continuous phase field variables are compared with the damage transition threshold interval. When the continuous phase field variables enter the damage transition threshold interval, the corresponding spatial computation grid is recorded as the damage development state. The updated continuous phase field variables are compared with the fracture threshold interval. When the continuous phase field variables enter the fracture threshold interval, the corresponding spatial computation grid is recorded as the fracture state. The complete state, damage development state, and fracture state are recorded in the order of sampling time as the gradual evolution process of coal and rock.

[0060] The spatial computational grids that reach the fracture threshold interval are marked as crack grids, and adjacent spatial computational grids around the crack grids are retrieved according to spatial adjacency. The first crack grids identified are assigned connectivity identifiers. When adjacent spatial computational grids that also reach the fracture threshold interval are retrieved, the adjacent crack grids are assigned the same connectivity identifier. If multiple existing connectivity identifiers come into contact, they are merged into the same connected region. After all crack grids are retrieved, the spatial range corresponding to the connected region is taken as the coal and rock crack evolution region.

[0061] It should be noted that spatial adjacency is determined based on the spatial index relationship of spatial computation grids in the radial, circumferential, and height directions. When the index difference between two spatial computation grids in all three directions is no greater than 1 and they are not the same grid, they are determined to have a spatial adjacency relationship.

[0062] The complete threshold range is determined based on the stable fluctuation range of continuous phase field variables when the coal and rock sample has not yet shown obvious creep damage, crack propagation and abnormal permeability changes in the initial loading stage, and is used to indicate that the spatial computing grid is in a complete state; Based on the statistical results of the phase field variables when the volumetric creep strain growth rate of the coal and rock samples remained at a low level after axial load, confining pressure and pore pressure stabilized, the measured permeability did not show a continuous increase and the continuous phase field variables only experienced small disturbances, the range of the complete threshold interval was determined to be [0, 0.10]. Among them, 0.10 was taken from the upper envelope value of the stable segment of the continuous phase field variables in the initial stage of loading, that is, the upper limit of the engineering obtained by adding three times the standard deviation to the mean value of the phase field variables in this stage.

[0063] The damage transition threshold range is determined based on the range of continuous phase field variables when the coal and rock samples exhibit continuous creep deformation accumulation, microcrack initiation, and slow permeability change but have not yet formed a stable crack grid after the continuous phase field variables exceed the upper limit of the complete threshold range. It is used to represent the damage development state of the spatial computational grid. Based on the range of continuous phase field variables corresponding to the start of continuous accumulation of volumetric creep strain, the change of measured permeability from stable to slow change, but the crack mesh has not yet formed a stable connection, the range of damage transition threshold interval is determined to be (0.10, 0.80), where 0.10 is the statistical upper limit of the intact state, and 0.80 is the lower limit of the critical phase field variables before the crack mesh stabilizes.

[0064] The fracture threshold range is determined based on the range of continuous phase field variables corresponding to the stable occurrence of cracked meshes, the connection of adjacent cracked meshes, or the significant jump in macroscopic permeability, and is used to indicate that the spatial computational mesh is in a fractured state. The range of values ​​for the fracture threshold interval is determined to be [0.80, 1], based on the critical values ​​corresponding to when the continuous phase field variable reaches the point where local damage is irreversibly propagated, adjacent crack meshes begin to connect, and the measured permeability shows a significant jump. Here, 0.80 is the initial threshold for fracture state, and 1 is the normalized value of the complete fracture characterization value of the continuous phase field variable.

[0065] S3.3 Using the coal and rock crack evolution region as the correction range, the creep state at the current sampling time is mapped to the corresponding spatial coupling grid, and the continuous phase field variable is converted into a phase field damage level and compared with the damage level corresponding to the creep state to obtain the coal and rock creep damage state.

[0066] Furthermore, using the coal and rock crack evolution region as the correction range, according to the spatial index of the spatially coupled grid within the coal and rock crack evolution region, the creep state at the current sampling time and the continuous phase field variables under the same spatial index are read one by one, and the creep state at the current sampling time is written into the corresponding spatially coupled grid. Then, the continuous phase field variables are compared with the complete threshold interval, the damage transition threshold interval, and the fracture threshold interval respectively. When the continuous phase field variable is in the complete threshold interval, the phase field damage level is recorded as the complete level; when the continuous phase field variable is in the damage transition threshold interval, the phase field damage level is recorded as the damage development level; when the continuous phase field variable is in the fracture threshold interval, the phase field damage level is recorded as the fracture level. Then, the damage level corresponding to the creep state under the same spatial index is read, the phase field damage level is compared with the damage level corresponding to the creep state, and the corresponding spatially coupled grid is updated with the higher damage level to obtain the coal and rock creep damage state.

[0067] S3.4. Using the coal and rock crack evolution region as the channel correction range, the seepage state at the current sampling time is mapped to the corresponding spatial coupling grid, and the continuous phase field variables are converted into channel open levels and then updated to obtain the seepage channel state.

[0068] Furthermore, using the coal and rock crack evolution region as the channel correction range, the seepage state and continuous phase field variables under the same spatial index are read one by one according to the spatial index of the spatially coupled grid within the coal and rock crack evolution region. The seepage state at the current sampling time is written into the corresponding spatially coupled grid to make the seepage state correspond to the spatial position. Then, the continuous phase field variables are compared with the complete threshold interval, the damage transition threshold interval, and the fracture threshold interval respectively. When the continuous phase field variables are in the complete threshold interval, the channel opening level is recorded as an unopened channel level. When the continuous phase field variables are in the damage transition threshold interval, the channel opening level is recorded as a partially open channel level. When the continuous phase field variables are in the fracture threshold interval, the channel opening level is recorded as a fully open channel level. The channel opening level is written into the spatially coupled grid under the same spatial index, and the seepage state at the current sampling time is updated according to the channel opening level to obtain the seepage channel state.

[0069] S3.5 Configure the same spatial index and time index for the coal and rock creep damage state and seepage channel state under the same sampling time and the same spatial coupling grid, and bind them to the corresponding continuous phase field variables according to the spatial coupling grid to obtain the spatial phase field crack evolution field.

[0070] Furthermore, using the sampling time as the time index and the spatial index of the spatially coupled grid as the spatial index, the creep damage state of coal and rock under the same sampling time and the same spatially coupled grid is read; then the seepage channel state under the same sampling time and the same spatially coupled grid is read; the creep damage state of coal and rock is written into the same time index and the same spatial index position in the spatial field container, and the seepage channel state is written into the same time index and the same spatial index position in the spatial field container; subsequently, the continuous phase field variable is written into the same time index and the same spatial index position in the spatial field container, so that the creep damage state of coal and rock, the seepage channel state, and the continuous phase field variable are bound grid by grid in the spatially coupled grid to obtain the spatial phase field crack evolution field.

[0071] S4. Identify the damaged seepage region based on the spatial phase field crack evolution field, and determine whether the damaged seepage region forms a through seepage path based on the percolation theory. Based on the judgment result, switch the macroscopic permeability update rule between the continuous gradual update mode and the percolation sudden update mode to generate the creep seepage initial coupling model.

[0072] S4.1. Using the spatial phase field crack evolution field as input, the continuous phase field variables are converted into crack damage markers, and the seepage channel state is converted into channel open markers. The spatial location that simultaneously has crack damage markers and channel open markers is marked as the damage seepage location, and a damage seepage marker map is obtained.

[0073] Furthermore, using the spatial phase field crack evolution field as input, continuous phase field variables are read point by point according to the time index and spatial index. When the continuous phase field variable enters the damage transition threshold interval or the rupture threshold interval, the corresponding spatial position is marked as a crack damage marker. The seepage channel state is read according to the same time index and the same spatial index. When the seepage channel state reaches the channel opening condition, the corresponding spatial position is marked as a channel opening marker. When crack damage markers and channel opening markers exist simultaneously under the same time index and the same spatial index, the corresponding spatial position is determined as the damage seepage position, and the damage seepage position is written into the damage seepage marker map according to the spatial index for subsequent connectivity search and through seepage path judgment.

[0074] S4.2. A three-dimensional 26-adjacent template is used to perform connectivity search on the damage seepage marker map, and isolated markers are removed after merging adjacent damage seepage locations to obtain the damage seepage area.

[0075] Furthermore, using the damage seepage locations in the damage seepage marker map as the retrieval objects, each damage seepage location is read sequentially according to the spatial index, and a three-dimensional 26-adjacency template is used to retrieve surrounding adjacent spatial locations. When adjacent spatial locations are also damage seepage locations, the current damage seepage location and the adjacent damage seepage locations are written into the same disjoint-set connected set, and merged into a unified connected identifier through disjoint-set path compression. After completing the retrieval of all damage seepage locations, isolated markers that do not form a connected relationship with other damage seepage locations are removed, and the spatial range corresponding to the retained connected set is taken as the damage seepage region.

[0076] It should also be noted that the 3D 26 Adjacency Template is a neighborhood retrieval method in 3D spatial grids. Centered on the current spatial computing grid, it retrieves all 26 spatial computing grids adjacent to the current spatial computing grid through faces, edges, and corners, and is used to determine whether there is a continuous connection between adjacent spatial locations.

[0077] S4.3. Using the damaged seepage area as the permeability judgment object, the inflow boundary and outflow boundary of the coal and rock sample are used as the penetration judgment boundary, and the damaged seepage area that simultaneously contacts the inflow boundary and outflow boundary is marked as the penetration seepage path to obtain the penetration judgment result.

[0078] Furthermore, using the damaged seepage area as the permeability assessment object, the damaged seepage positions within the damaged seepage area are read one by one according to the spatial index; the damaged seepage positions located at the inflow boundary of the coal and rock sample are configured as inflow boundary contact marks, and the damaged seepage positions located at the outflow boundary of the coal and rock sample are configured as outflow boundary contact marks; when both inflow boundary contact marks and outflow boundary contact marks exist in the same damaged seepage area, the damaged seepage area is marked as a through seepage path; when the damaged seepage area only contacts the inflow boundary of the coal and rock sample or only contacts the outflow boundary of the coal and rock sample, the damaged seepage area is marked as a non-through seepage area, forming a throughness assessment result, which is used to distinguish whether the damaged seepage area is a through seepage path or a non-through seepage area.

[0079] It should also be noted that the continuity judgment result is the result of judging the connectivity status of the damaged seepage area, specifically including two situations: one is a continuous seepage path, which means that the same damaged seepage area is simultaneously in contact with the inflow boundary and outflow boundary of the coal and rock sample; the other is a non-continuous seepage area, which means that the damaged seepage area is not simultaneously in contact with the inflow boundary and outflow boundary of the coal and rock sample.

[0080] S4.4 Based on the connection judgment result, switch the macroscopic permeability update rule between the continuous gradual update method and the permeability sudden change update method, and write the updated macroscopic permeability into the initial seepage sub-model. Write the connection judgment result into the coal and rock creep constitutive sub-model to correct the creep damage variable and obtain the initial coupled creep seepage model.

[0081] Furthermore, the continuity status of the damaged seepage area is read based on the continuity judgment result, and the continuity status is used as the basis for switching the macroscopic permeability update rule; when the continuity judgment result is an unconnected seepage area, a continuous gradual update method is adopted, and the creep damage status and seepage channel status of coal and rock are read according to the sampling time. Based on the degree of damage expansion, the degree of damage level improvement, and the degree of channel opening level improvement, the macroscopic permeability at the previous sampling time is incrementally updated, so that the macroscopic permeability changes gradually with the internal damage of coal and rock and the opening of channels. When the breakthrough judgment result is a breakthrough seepage path, the permeability mutation update method is adopted. According to the connectivity range of the breakthrough seepage path connecting the inflow boundary and the outflow boundary, the channel opening level and crack connectivity of the damaged seepage location within the breakthrough seepage path are read, and the macroscopic permeability at the previous sampling time is updated by leap. Then, the updated macroscopic permeability is written into the permeability state end of the initial seepage sub-model, and the breakthrough judgment result is written into the creep damage variable end of the coal and rock creep constitutive sub-model. This makes the macroscopic permeability update result reflect the change in seepage capacity, and makes the creep damage variable reflect the impact of breakthrough rupture, thus obtaining the initial coupled creep seepage model.

[0082] It should also be noted that the continuous gradual update method refers to the continuous incremental update of macroscopic permeability based on the gradual development of the creep damage state and seepage channel state of coal and rock when a through seepage path has not yet been formed in the damaged seepage area. As the damage range expands, the damage level increases, and the degree of channel openness increases, the macroscopic permeability increases slowly from the previous sampling time, which is used to characterize the gradual change of coal and rock seepage capacity in the non-through stage.

[0083] The permeability abrupt renewal mode refers to the leap renewal of macroscopic permeability when a continuous seepage path has been formed in the damaged seepage area, based on the flow capacity of the continuous seepage path after connecting the inflow boundary and the outflow boundary; when crack damage and channel opening form a continuous seepage path, macroscopic permeability no longer changes slowly according to the accumulation of local damage, but increases suddenly according to the seepage capacity corresponding to the continuous seepage path.

[0084] S5. Based on the synchronous data of coal and rock creep seepage, perform parameter inversion on the undetermined parameters in the initial coupled model of creep seepage, and perform iterative solution after the parameters are determined until the preset convergence condition is met, thereby generating the coupled model of coal and rock creep seepage.

[0085] S5.1. Based on synchronous data of coal and rock creep and seepage, generate an inversion sample sequence according to the sampling time, perform Huber robust residual labeling on the inversion sample sequence, and write the labeled inversion sample sequence into the parameter interface of the creep seepage initial coupling model to obtain parameter inversion constraints.

[0086] Furthermore, using synchronous data on coal and rock creep and seepage as a benchmark, an inversion sample sequence is generated point by point according to the sampling time. Huber robust residual labeling is performed on the volumetric creep strain deviation and measured permeability deviation in the inversion sample sequence. When the deviation does not exceed the Huber robust residual threshold, it is labeled as a regular inversion sample. When the deviation exceeds the Huber robust residual threshold, it is labeled as a deweighted inversion sample. The labeled inversion sample sequence is written into the parameter interface of the creep seepage initial coupling model to obtain parameter inversion constraints.

[0087] It should also be noted that the Huber robust residual threshold is determined based on the residual distribution of volumetric creep strain deviation and measured permeability deviation in the inverted sample sequence.

[0088] S5.2. Based on parameter inversion constraints, establish synchronous inversion targets for volumetric creep strain deviation and measured permeability deviation. Solve the undetermined parameters in the initial coupled creep-seepage model according to the hierarchical inversion sequence of creep parameters first, seepage parameters follow, and coupling parameters fine-tuning, and obtain the determined parameter set.

[0089] Furthermore, based on the parameter inversion constraints, the inversion sample sequence after marking is read, and the volumetric creep strain deviation and measured permeability deviation are used as synchronous inversion targets. First, the seepage parameters and coupling parameters are fixed, and the creep parameters are solved by inversion. Then, the creep parameters are fixed, and the seepage parameters are solved by inversion. Finally, the coupling parameters are fine-tuned after the creep parameters and seepage parameters stabilize. During the inversion process, the predicted values ​​are compared with the corresponding values ​​in the synchronous data of coal and rock creep and seepage at each sampling time, and the influence of the weighted inversion samples is reduced by combining Huber robust residual marking to obtain a definite parameter set.

[0090] S5.3. Write the determined parameter set into the creep seepage initial coupling model and perform parameter locking. Iterate and solve the creep seepage initial coupling model after parameter locking according to the bidirectional coupling path. After the convergence conditions are met in two adjacent iterations, write the model encapsulation container to obtain the coal and rock creep seepage coupling model.

[0091] Furthermore, the determined parameter set is written into the creep parameter position, seepage parameter position, and coupling parameter position in the initial coupled model of creep seepage according to the parameter name, and parameter locking is performed; the seepage state of the initial seepage sub-model is updated according to the first coupling path, and the effective stress state of the coal and rock creep constitutive sub-model is updated according to the second coupling path; bidirectional coupling update is performed cyclically according to the sampling time, and the volumetric creep strain deviation and macroscopic permeability deviation in the output of adjacent iterations are compared round by round; when the volumetric creep strain deviation and macroscopic permeability deviation meet the convergence condition, the initial coupled model of creep seepage with locked parameters is written into the model encapsulation container to obtain the coupled model of coal and rock creep seepage.

[0092] It should also be noted that the convergence condition is that the volumetric creep strain deviation and macroscopic permeability deviation output by two adjacent iterations both enter the allowable error range, and the effective stress state, creep state and seepage state remain stable.

[0093] This embodiment also provides a coal and rock creep-seepage coupling model construction system, including: a data synchronization module, used to acquire the original coal and rock creep-seepage data of coal and rock samples, and determine the volumetric creep strain and measured permeability based on the original coal and rock creep-seepage data to obtain synchronized coal and rock creep-seepage data; The coupled modeling module is used to calculate the effective stress based on synchronous data of coal and rock creep and seepage, construct a coal and rock creep constitutive sub-model based on the effective stress, and establish an initial seepage sub-model based on measured permeability using Darcy's law. The coal and rock creep constitutive model and the initial seepage sub-model are bidirectionally coupled and associated to form a basic set of coupled variables. The phase field evolution module is used to construct continuous phase field variables based on the basic coupling variable set. The continuous phase field variables are used to characterize the gradual evolution of coal and rock from the intact state to the fractured state, determine the coal and rock crack evolution region, and simultaneously correct the coal and rock creep damage state and seepage channel state to obtain the spatial phase field crack evolution field. The permeability update module is used to identify the damaged seepage region based on the spatial phase field crack evolution field, and to determine whether the damaged seepage region has formed a through seepage path based on permeability theory. Based on the judgment result, it switches the macroscopic permeability update rule between continuous gradual update mode and permeability abrupt update mode to generate the creep seepage initial coupling model. The inversion solution module is used to perform parameter inversion on the undetermined parameters in the initial coupled model of creep seepage based on synchronous data of coal and rock creep seepage, and to perform iterative solution after the parameters are determined until the preset convergence conditions are met, thereby generating the coupled model of coal and rock creep seepage.

[0094] In summary, this invention identifies damaged seepage regions based on the spatial phase field crack evolution field and determines whether a through-flow path has formed based on permeability theory. It switches between a continuous gradual update mode and a permeability abrupt change update mode for macroscopic permeability update rules, thereby achieving synchronous mapping between crack connectivity and permeability evolution patterns. This enables the model to update seepage channels and damage variables when creep damage accumulates to the point of channel penetration. It is suitable for the quantitative characterization of abrupt changes in seepage capacity under long-term loading of coal and rock, and achieves the effect of improving the physical consistency and predictive stability of the model.

[0095] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for constructing a coupled model of coal and rock creep and seepage, characterized in that, include: Obtain raw data of coal and rock permeability from coal and rock samples, and determine the volumetric creep strain and measured permeability based on the raw data of coal and rock permeability to obtain synchronous data of coal and rock permeability; Effective stress is calculated based on synchronous data of coal and rock creep and seepage. A coal and rock creep constitutive model is constructed based on the effective stress. An initial seepage sub-model is established based on measured permeability using Darcy's law. The coal and rock creep constitutive model and the initial seepage sub-model are bidirectionally coupled and correlated to form a basic set of coupled variables. Based on the basic set of coupled variables, a continuous phase field variable is constructed. The continuous phase field variable is used to characterize the gradual evolution of coal and rock from an intact state to a fractured state, determine the crack evolution region of coal and rock, and simultaneously correct the creep damage state and seepage channel state of coal and rock to obtain the spatial phase field crack evolution field. Damaged seepage regions are identified based on the spatial phase field crack evolution field, and whether a through-seepage path is formed in the damaged seepage region is determined based on the permeability theory. Based on the determination result, the macroscopic permeability update rule is switched between the continuous gradual update mode and the permeability abrupt update mode to generate an initial coupled model of creep seepage. Based on synchronous data of coal and rock creep seepage, parameter inversion is performed on the undetermined parameters in the initial coupled model of creep seepage, and after the parameters are determined, iterative solution is performed until the preset convergence condition is met, thus generating the coupled model of coal and rock creep seepage.

2. The method for constructing a coupled coal-rock creep-seepage model as described in claim 1, characterized in that, The specific steps for obtaining synchronous data on coal and rock permeability are as follows: The coal and rock samples were sized and sealed, and then loaded into the preset creep and seepage test state. After the test state stabilized, the start time of the synchronous test was determined. Using the start time of the synchronous test as the time reference, the deformation response, loading response, pore pressure response and seepage response of the coal and rock samples during the creep seepage process are continuously recorded according to the sampling interval, and a corresponding time stamp is configured for each test response, and the raw data of coal and rock creep seepage are output. The raw data of coal and rock creep is subjected to benchmark subtraction and time alignment. The volumetric creep strain is calculated based on the processed deformation response, and the measured permeability is calculated using Darcy's law based on the processed pore pressure response and seepage response, thus obtaining synchronous data of coal and rock creep.

3. The method for constructing a coupled coal-rock creep-seepage model as described in claim 2, characterized in that, The steps for calculating the effective stress based on synchronous data of coal and rock creep and permeability, and constructing a constitutive model of coal and rock creep based on the effective stress, are as follows: The pore pressure response in the synchronous data of coal and rock creep is smoothed by differential pressure, and the processed pore pressure response is matched with the loading response at the corresponding sampling time. Then the effective stress corresponding to the coal and rock skeleton is calculated. By using effective stress as the creep driving input and volumetric creep strain in the synchronous data of coal and rock creep and seepage as the response constraint, a temporal correspondence between effective stress and volumetric creep strain is established to obtain the creep state sequence. The effective stress is written into the input layer of the creep constitutive model, the creep state at the previous sampling time is written into the creep state cache layer, the volumetric creep strain is written into the creep response output layer, and the creep state update chain is configured according to the creep state update order to obtain the coal and rock creep constitutive sub-model.

4. The method for constructing a coupled coal and rock creep-seepage model as described in claim 2, characterized in that, The initial flow sub-model is established based on measured permeability using Darcy's law. The specific steps are as follows: Write the measured permeability from the synchronous data of coal and rock creep into the seepage state node, and read the inlet pore pressure and outlet pore pressure at the same sampling time to calculate the seepage pressure difference. Write the seepage pressure difference, measured permeability and seepage basic parameters into the Darcy seepage calculation node to generate the initial seepage mapping relationship. The initial seepage mapping relationship is written into the mapping layer of the seepage model, the pressure difference is configured as the seepage driving input, the measured permeability is configured as the seepage state variable, the seepage response is configured as the seepage output variable, and the seepage state update chain is configured according to the Darcy seepage update order to obtain the initial seepage sub-model.

5. The method for constructing a coupled coal and rock creep-seepage model as described in claim 1, characterized in that, The specific steps for bidirectionally coupling the coal and rock creep constitutive model with the initial seepage sub-model to form a basic set of coupling variables are as follows: The creep state output of the coal and rock creep constitutive model is connected to the permeability state of the initial seepage sub-model to form the first coupling path from creep to seepage. The current creep state output by the coal and rock creep constitutive model is used as the permeability correction input and written into the initial seepage sub-model. The seepage state of the initial seepage sub-model is updated according to the Darcy seepage update order. The pore pressure state output of the initial seepage sub-model is connected to the effective stress input of the coal and rock creep constitutive model to form a second coupling path from seepage to creep. The pore pressure state output by the initial seepage sub-model is written into the coal and rock creep constitutive model as the effective stress correction input to update the effective stress state of the coal and rock creep constitutive model. The consistency of the states of the first and second coupling paths is verified at the same sampling time, and the verified effective stress state, creep state, seepage state and feedback state are bound according to the sampling time to obtain the basic coupling variable set.

6. The method for constructing a coupled coal and rock creep-seepage model as described in claim 5, characterized in that, The specific steps for constructing continuous phase field variables based on the basic coupling variable set, and using these continuous phase field variables to characterize the gradual evolution of coal and rock from an intact state to a fractured state and to determine the crack evolution region of coal and rock, are as follows: The basic set of coupled variables is mapped to the spatial computational grid of the coal and rock samples, and a phase field update interface is configured for each grid to obtain the set of spatially coupled grids. The current phase field driving quantity is generated based on the effective stress state and creep state corresponding to the spatially coupled grid, and the current phase field driving quantity is locked by taking the larger value of the historical field value at the previous sampling time to obtain continuous phase field variables. Using the continuous phase field variables at the previous sampling time as initial values, the current continuous phase field variables are updated grid by grid according to the historical field locking results. The process of the continuous phase field variables changing from the complete threshold interval to the damage transition threshold interval and then to the fracture threshold interval is recorded as the gradual evolution process of coal and rock. The grids that reach the fracture threshold interval are marked as crack grids, and adjacent crack grids are connected and merged according to the spatial adjacency relationship to obtain the coal and rock crack evolution region.

7. The method for constructing a coupled coal and rock creep-seepage model as described in claim 1, characterized in that, The process of simultaneously correcting the creep damage state and seepage channel state of coal and rock to obtain the spatial phase field crack evolution field involves the following steps: Using the coal and rock crack evolution region as the correction range, the creep state at the current sampling time is mapped to the corresponding spatial coupling grid, and the continuous phase field variable is converted into a phase field damage level and compared with the damage level corresponding to the creep state to obtain the coal and rock creep damage state. Using the coal and rock crack evolution region as the channel correction range, the seepage state at the current sampling moment is mapped to the corresponding spatial coupling grid, and the continuous phase field variables are converted into channel open level and then updated to obtain the seepage channel state. By configuring the same spatial index and time index for the creep damage state and seepage channel state of coal and rock under the same sampling time and the same spatial coupling grid, and binding them to the corresponding continuous phase field variables according to the spatial coupling grid, the spatial phase field crack evolution field is obtained.

8. The method for constructing a coupled coal-rock creep-seepage model as described in claim 7, characterized in that, The specific steps for generating the initial coupled model of creep seepage are as follows: Using the spatial phase field crack evolution field as input, the continuous phase field variables are converted into crack damage markers, and the seepage channel state is converted into channel open markers. The spatial location that simultaneously has crack damage markers and channel open markers is marked as the damage seepage location, thus obtaining the damage seepage marker map. A three-dimensional 26-adjacent template was used to perform connectivity search on the damage seepage marker map, and isolated markers were removed after merging adjacent damage seepage locations to obtain the damage seepage region. Using the damaged seepage area as the permeability judgment object, the inflow boundary and outflow boundary of the coal and rock sample are used as the penetration judgment boundary, and the damaged seepage area that simultaneously contacts the inflow boundary and outflow boundary is marked as the penetration seepage path to obtain the penetration judgment result. Based on the breakthrough judgment result, the macroscopic permeability update rule is switched between continuous gradual update mode and permeability sudden change update mode. The updated macroscopic permeability is written into the initial seepage sub-model, and the breakthrough judgment result is written into the coal and rock creep constitutive sub-model to correct the creep damage variable, so as to obtain the initial coupled model of creep seepage.

9. The method for constructing a coupled coal and rock creep-seepage model as described in claim 8, characterized in that, The specific steps for generating the coal-rock creep-seepage coupling model are as follows: Based on synchronous data of coal and rock creep and seepage, an inversion sample sequence is generated according to the sampling time. Huber robust residual labeling is performed on the inversion sample sequence. The labeled inversion sample sequence is written into the parameter interface of the creep seepage initial coupling model to obtain parameter inversion constraints. Based on parameter inversion constraints, a synchronous inversion target for volumetric creep strain deviation and measured permeability deviation is established. The undetermined parameters in the initial coupled creep-seepage model are solved in a hierarchical inversion order of creep parameters first, seepage parameters follow, and coupling parameters are fine-tuned to obtain a definite parameter set. The determined parameter set is written into the initial coupled model of creep seepage and parameter locking is performed. The initial coupled model of creep seepage after parameter locking is iteratively solved according to the bidirectional coupling path. After the convergence conditions are met in two adjacent iterations, the model encapsulation container is written to obtain the coupled model of coal and rock creep seepage.

10. A coal and rock creep-seepage coupling model construction system, based on the coal and rock creep-seepage coupling model construction method according to any one of claims 1 to 9, characterized in that, include: The data synchronization module is used to acquire the original data of coal and rock permeability of coal and rock samples, and to determine the volumetric creep strain and measured permeability based on the original data of coal and rock permeability, thereby obtaining synchronized data of coal and rock permeability. The coupled modeling module is used to calculate the effective stress based on synchronous data of coal and rock creep and seepage, construct a coal and rock creep constitutive sub-model based on the effective stress, and establish an initial seepage sub-model based on measured permeability using Darcy's law. The coal and rock creep constitutive model and the initial seepage sub-model are bidirectionally coupled and associated to form a basic set of coupled variables. The phase field evolution module is used to construct continuous phase field variables based on the basic coupling variable set. The continuous phase field variables are used to characterize the gradual evolution of coal and rock from the intact state to the fractured state, determine the coal and rock crack evolution region, and simultaneously correct the coal and rock creep damage state and seepage channel state to obtain the spatial phase field crack evolution field. The permeability update module is used to identify the damaged seepage region based on the spatial phase field crack evolution field, and to determine whether the damaged seepage region has formed a through seepage path based on permeability theory. Based on the judgment result, it switches the macroscopic permeability update rule between continuous gradual update mode and permeability abrupt update mode to generate the creep seepage initial coupling model. The inversion solution module is used to perform parameter inversion on the undetermined parameters in the initial coupled model of creep seepage based on synchronous data of coal and rock creep seepage, and to perform iterative solution after the parameters are determined until the preset convergence conditions are met, thereby generating the coupled model of coal and rock creep seepage.

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