A calculation method and system for mining-induced stress under the action of load transfer in a rock stratum structure

Abstract

The present invention belongs to the technical field of mining-induced stress calculation, and discloses a method and system for calculating mining-induced stress under the action of load transfer of rock strata structures. This method determines the basic mechanical parameters of each overlying rock stratum of the working face through boreholes near the working face, and determines whether a loose layer arch is formed in the overlying rock strata according to the formation conditions of the loose layer. According to the key stratum theory, based on the stiffness and strength criteria, basic information such as the thickness and position of the key strata in the overlying rock strata of the working face is judged. At the same time, based on the rock breaking line and the virgin stress line, the bearing structure characteristics and corresponding dimensions of the overlying rock strata are obtained, a mechanical model of mining-induced stress under the action of load transfer of rock strata structures is established, the components of mining-induced stress of coal and rock strata during the mining of the working face are analyzed, and an analytical expression of mining-induced stress of coal and rock strata is obtained. The present invention calculates the mining-induced stress of coal and rock strata according to the structural characteristics of the overlying rock strata, clarifies the stress distribution of the coal body in front of the working face, and has guiding significance for the safe production of coal mines.

Description

Technical Field

[0001] The present invention belongs to the technical field of calculation of mining-induced stress in coal mines, and particularly relates to a method and system for calculating mining-induced stress under the action of load transfer of rock stratum structures. Background Technique

[0002] The quantitative determination of mining-induced stress is the basis for preventing and controlling coal mine dynamic disasters such as rock bursts, mine tremors, coal and gas outbursts, and dynamic water inrusions. At present, methods such as on-site measurement, experimental simulation, and theoretical analysis are mainly used to determine mining-induced stress. The existing on-site measurement is to arrange stress gauges in the roadways on both sides of the working face for real-time monitoring to obtain the distribution law of mining-induced stress, determine the position and magnitude of the peak stress, but it can only determine the real-time stress distribution during the mining process of the working face and cannot determine the mining-induced stress of the working face in advance. The existing experimental simulation is to establish an experimental model according to the geological and mining conditions of the working face and analyze the stress distribution law during the mining process of the working face, but it cannot quantitatively determine the distribution data of mining-induced stress. The existing theoretical analysis method mathematically homogenizes the overlying strata of the working face, does not consider the occurrence characteristics of each stratum and the transfer effect of mining-induced stress in the rock stratum structure, and there is a large deviation between the determined distribution characteristics of mining-induced stress and the engineering practice. Previous studies have shown that key strata, loose layer arches and other rock stratum structures exist in the overlying strata of the working face; during the mining process of the working face, the movement, deformation, fracture and movement of the rock stratum structure control the distribution characteristics and evolution law of mining-induced stress, and affect the transfer effect of mining-induced stress. Therefore, it is necessary to propose a method for calculating mining-induced stress under the action of load transfer of rock stratum structures. According to the geological and mining conditions, a mechanical model is established considering the key stratum structure and the loose layer arch structure to realize the quantitative calculation of mining-induced stress. Summary of the Invention

[0003] In order to overcome the problems existing in the related technologies, the disclosed embodiments of the present invention provide a method and system for calculating mining-induced stress under the action of load transfer of rock stratum structures.

[0004] The technical solution is as follows: A method for calculating mining-induced stress under the action of load transfer of rock stratum structures includes the following steps:

[0005] Step1, obtaining the basic mechanical parameters of the overlying strata of the working face based on the boreholes near the working face;

[0006] Step2, based on the formation conditions of the loose layer arch, determining whether a loose layer arch is formed above the working face according to the ratio of the rise to the span of the loose layer arch and the relationship between the span of the loose layer arch and the mining width of the working face;

[0007] Step3, according to the key stratum theory, based on the stiffness and strength criteria, obtaining the basic information of the position and thickness of the key strata in the overlying strata of the working face through key stratum discrimination software;

[0008] Step 4: Obtain the overlying strata bearing structure characteristics and dimensions based on the strata fracture line, virgin stress line, and all straight lines of the top and bottom interfaces of each stratum.

[0009] Step 5: Establish a mechanical model of mining-induced stress under the action of strata structure load transfer, analyze the components of mining-induced stress in coal and rock strata during the working face mining, and obtain the analytical expression of mining-induced stress in coal and rock strata.

[0010] In Step 1, the basic mechanical parameters of the overlying strata of the working face include: the thickness of the key stratum, the tensile strength of the key stratum, the distance between the bottom interface of the key stratum and the top interface of the coal seam, the thickness and burial depth of the coal seam, the thickness of each stratum in the bedrock, the fracture angle, and the lithology.

[0011] In Step 2, determine whether a loose layer arch is formed above the working face, including: core sampling and preservation on the surface or underground in the coal mining area, and drawing a comprehensive columnar diagram of the borehole. According to the comprehensive columnar diagram of the borehole, determine the thickness, burial depth, thickness of each stratum in the bedrock, and lithology of the coal seam in the coal mining area; use a borehole logging analyzer to drill holes above the roof of the working face roadway, and draw a fracture evolution diagram of the peephole through the depth of the peephole in the peephole result to obtain the strata fracture angle; obtain the formation conditions of the loose layer arch through the characteristics of the arch height-span ratio of the loose layer arch and the relationship between the span of the loose layer arch and the mining width of the working face. When the sum of the arch height and thickness of the loose layer arch is less than the thickness of the loose layer, a loose layer arch is formed, otherwise it cannot be formed.

[0012] In Step 3, through the key stratum discrimination software, obtain the basic information of the position and thickness of the key stratum in the overlying strata of the working face, including:

[0013] By taking cores from the strata, conducting uniaxial compression, uniaxial tension, and triaxial compression experiments on the obtained specimens to determine the mechanical parameters, obtain the basic mechanical parameters of each stratum, and use the key stratum discrimination method. Based on the basic mechanical parameters, conduct key stratum discrimination through the comprehensive columnar diagram of the borehole to obtain the position of the key stratum and the distance between the bottom interface of the key stratum and the top interface of the coal seam.

[0014] The key stratum discrimination method includes: assuming that there are strata in the overlying strata of the stope, , are the loads of the and strata on the first stratum; is the fracture distance of the and strata. According to the stiffness criterion and strength criterion for discriminating key strata, if , then this key stratum is the main key stratum; if , then this key stratum is the sub-key stratum.

[0015] In Step 4, the characteristics and dimensions of the overlying strata bearing structure are obtained, including: determining the strata fracture line through the edge position of the goaf in the working face and the strata fracture angle, determining the virgin stress line according to the edge position of the loose layer arch span, and determining the straight lines where the top and bottom interfaces of each stratum are located based on the burial depth of each stratum. The four straight lines form a closed figure to obtain the morphological characteristics and dimensions of the overlying strata bearing structure.

[0016] In Step 5, the analytical expressions of the mining-induced stress of the coal and rock strata are obtained, including:

[0017] Taking the intersection point of the central axis of the goaf and the top interface of the coal seam as the origin, a rectangular coordinate system is established, with the top interface of the coal seam as the axis and the central axis of the goaf as the axis; establishing a calculation model of the mining-induced stress under the action of the load transfer of the strata structure; obtaining respectively represent the mining-induced stress expressions of the arch foundation section of the loose layer arch, the section of the main key stratum, the section of the sub-key stratum, and the section of the coal seam:

[0018] ;

[0019] ;

[0020] ;

[0021] (1)

[0022] In the formula, is the span of the loose layer, is the distance from the intersection point of the bottom interface of the loose layer and the strata fracture line to the peak stress position, is the arch thickness of the loose layer arch, is the strata fracture angle, are all undetermined coefficients, respectively represent the soft rock thickness between the loose layer and the main key stratum, the thickness of the main key stratum, the soft rock thickness between the main key stratum and the sub-key stratum, the thickness of the sub-key stratum, and the soft rock thickness between the sub-key stratum and the coal seam, respectively represent the mining-induced stress of the arch foundation section of the loose layer arch, the mining-induced stress of the arch foundation section of the loose layer arch, the mining-induced stress of the section of the main key stratum, the mining-induced stress of the section of the main key stratum, the mining-induced stress of the section of the sub-key stratum, the mining-induced stress of the section of the sub-key stratum, the mining-induced stress of the section of the coal seam, the mining-induced stress of the section of the coal seam, where They are the intersection points of the straight line where the arch base of the loose layer is located, the straight line where the top interface of the main key layer is located, the straight line where the top interface of the sub-key layer is located, the straight line where the top interface of the coal seam is located and the peak stress line. is the distance from the location to the rock fracture line, is a mathematical constant, the base of the natural logarithm function, They are respectively the arch base of loose layer, main key layer, sub-key layer and original rock stress of coal seam.

[0023] Furthermore, the establishment of a mining stress calculation model under the action of rock layer structure load transfer includes: obtaining the inner envelope of the loose layer arch according to the loose layer arch axis equation and The relationship is:

[0024] (2)

[0025] In the formula, is the functional relationship expression between the vertical coordinate and horizontal coordinate of the envelope line in the loose layer, is the lateral pressure coefficient, The arch height is for the loose layer;

[0026] The mining stress at the loose layer arch base is transferred from the loose layer overlying the loose layer arch and the weight of the loose layer arch. The transferred stress on the FG section of the loose layer arch base is half of the weight of the loose layer and the loose layer arch. Deadweight and loose layer rock strata in the arch The difference in self-weight gives formula (3);

[0027] (3)

[0028] In the formula, is the load transfer coefficient of loose layer, is the thickness of the loose layer overlying the loose layer arch, It is the bulk density of loose layer.

[0029] Furthermore, the establishment of a mining stress calculation model under the load transfer effect of the rock structure also includes:

[0030] The mining stress of the main key layer under the load transfer of loose layer arch is transferred from the overlying rock layer to the main key layer. , loose layer arch transfer stress , Overlying rock stratum self-weight stress It consists of three parts: the overlying rock strata transfer stress Loose layer inner arch and Half of the self-weight and loose layer arch transfer stress is the stress of the loose layer arch FG section, and the self-weight stress of the overlying rock layer for Part of the dead weight, we get formula (4):

[0031] (4)

[0032] In the formula, It is the loose layer arch-main key layer load; The average bulk density of the soft rock between the main key layer and the loose layer.

[0033] According to the equivalent relationship of mining stress in the IJ section of the main key layer, formula (5) is obtained;

[0034] (5)

[0035] The boundary conditions and continuity conditions of mining stress distribution in the loose layer arch FG section and the main key layer IJ section are listed from left to right, and formula (6) is obtained:

[0036] (6)

[0037] The coefficients to be determined in formula (1) can be obtained by combining formula (2) and formula (6) , and the analytical expressions of mining stress in the loose layer arch foundation FG segment and the main key layer IJ segment were obtained.

[0038] Furthermore, the establishment of a mining stress calculation model under the load transfer effect of the rock structure also includes:

[0039] The mining stress of the sub-key layer under the load of the main key layer is transferred from the overlying rock layer , the main key layer transfers stress , Overlying rock stratum self-weight stress It consists of three parts: the overlying rock strata transfer stress Overlying rock Half of the deadweight of the part; the main critical layer transfers stress The stress of the IJ section of the main key layer and the self-weight stress of the overlying rock layer for Part of the dead weight, we get formula (7):

[0040] (7)

[0041] In the formula, is the load transfer coefficient between the main key layer and the sub-key layer, is the average bulk density of the soft rock between the sub-key layer and the main key layer;

[0042] According to the equivalent relationship of mining stress in the PQ section of the sub-critical layer, formula (8) is obtained;

[0043] (8)

[0044] The boundary conditions and continuity conditions of mining stress in the PQ section of the subcritical layer are listed from left to right, and formula (9) is obtained:

[0045] (9)

[0046] By combining formula (7) and formula (9), we can solve the coefficients in formula (1) , and the analytical expression of mining stress in the IJ section of the sub-critical layer is obtained.

[0047] Furthermore, the establishment of a mining stress calculation model under the load transfer effect of the rock structure also includes:

[0048] The mining stress of the coal seam ahead of the working face under the action of sub-critical layer load is transferred from the overlying rock layer , Sub-critical layer transfer stress , Overlying rock stratum self-weight stress It consists of three parts; the stress transmitted by the overlying rock is Half of the deadweight of the part; subcritical layers transfer stress is the stress of the sub-critical layer PQ section, and the self-weight stress of the overlying rock layer for Part of the dead weight, we get formula (10):

[0049] (10)

[0050] In the formula, is the load transfer coefficient between sub-critical layer and coal seam, is the bulk density of the soft rock between the coal seam and the sub-critical layer;

[0051] According to the equivalent relationship of mining stress in the UV section of coal seam, formula (11) is obtained:

[0052] (11)

[0053] The boundary conditions and continuity conditions of mining stress in the UV section of the coal seam are listed from left to right, and formula (12) is obtained;

[0054] (12)

[0055] By combining formula (10) and formula (12), we can obtain the coefficients to be determined in formula (1): , and the analytical expression of mining stress in UV section of coal seam is obtained.

[0056] Furthermore, the establishment of the mining stress calculation model under the action of rock layer structure load transfer also includes: according to the load three-band model, when the mining width is less than the set value, there is no loose layer arch above the working face, and when the sub-critical layer is first broken, according to the mining stress of the coal wall of the working face, formula (13) is obtained;

[0057] (13)

[0058] In the formula, All are undetermined coefficients;

[0059] Coal mining stress is transferred from the overlying rock layer , Overlying rock stratum self-weight stress The overburden rock stratum transfer stress is transferred from the rock stratum self-weight stress within the rock stratum fracture line. Half of the self-weight of this part of the rock stratum is transferred to the goaf through the underlying rock stratum. Therefore, the transfer stress of the UV section of the coal seam is Half of the deadweight of the part, the deadweight stress of the overlying rock The stress on the coal seam is transferred from the deadweight stress of the overlying rock strata outside the rock fracture line. for Part of the dead weight, we get formula (14):

[0060] (14)

[0061] It represents the average bulk density of all rock layers above the coal seam;

[0062] According to the coal seam UV The equivalent relationship between the mining stress and the segment dynamic stress is obtained by formula (15):

[0063] (15)

[0064] The boundary conditions and continuity conditions of mining stress in the UV section of the coal seam are listed from left to right, and formula (16) is obtained:

[0065] (16)

[0066] In the formula, It is the mining stress from the boundary of coal seam goaf to the peak stress line when no loose layer arch is formed above the working face. It is the mining stress from the peak stress line to the original rock stress line when no loose layer arch is formed above the working face;

[0067] By combining formula (14) and formula (16), we can solve the unknown coefficients in formula (13): , and the analytical expression of mining stress in UV section of coal seam is obtained.

[0068] Another object of the present invention is to provide a system for calculating mining stress under the action of rock layer structure load transfer, the system implements the method for calculating mining stress under the action of rock layer structure load transfer, the system comprises:

[0069] Mechanical parameter obtaining module, which obtains the basic mechanical parameters of the overlying strata of the working face based on the boreholes near the working face;

[0070] Loose layer arch formation module, which determines whether a loose layer arch is formed above the working face based on the formation conditions of the loose layer arch, according to the ratio of the arch rise to the span of the loose layer arch and the relationship between the span of the loose layer arch and the mining width of the working face;

[0071] Key layer position and thickness obtaining module, which obtains the basic information of the position and thickness of the key layers in the overlying strata of the working face based on the key layer theory, the stiffness and strength criteria, and through the key layer discrimination software;

[0072] Overlying strata bearing structure characteristics and dimensions obtaining module, which obtains the bearing structure characteristics and dimensions of the overlying strata based on the fracture lines of the strata, the virgin stress lines, and all the straight lines of the top and bottom interfaces of each stratum;

[0073] Coal and rock stratum mining-induced stress analytical expression obtaining module, which is used to establish a mining-induced stress mechanical model under the action of the load transfer of the rock stratum structure, analyze the components of the mining-induced stress of the coal and rock strata during the mining of the working face, and obtain the analytical expression of the mining-induced stress of the coal and rock strata.

[0074] Combining all the above technical solutions, the beneficial effects of the present invention are as follows: The present invention collects the mechanical parameters of each stratum of the boreholes near the working face; determines whether a loose layer arch is formed above the working face according to the formation conditions of the loose layer arch, discriminates the position of the key layer according to the key layer theory research and the key layer position discrimination conditions for the overlying strata; obtains the bearing structure characteristics and dimensions of the overlying strata according to the fracture lines of the strata; establishes a mining-induced stress mechanical model under the action of the load transfer of the rock stratum structure, analyzes the components of the mining-induced stress of the coal and rock strata during the mining of the working face, and obtains the analytical expression of the mining-induced stress of the coal and rock strata. The peak stress and the stress influence range of the mining-induced stress of the coal and rock strata are clarified. The present invention calculates the mining-induced stress of the coal and rock strata according to the bearing structure characteristics of the overlying strata, clarifies the stress distribution of the coal body in front of the working face, and has guiding significance for the safe production of coal mines.

[0075] Furthermore, the present invention establishes a mining-induced stress calculation model under the action of the load transfer of the rock stratum structure, obtains the analytical expressions of the mining-induced stress of the loose layer arch, the main key layer, the sub-key layer, and the coal seam above, and clarifies the peak stress and the stress influence range of the mining-induced stress of the coal and rock strata. The research can provide a theoretical basis for the determination of the mining-induced stress of the working face.

[0076] A calculation method of mining-induced stress under the action of load transfer of rock stratum structure provided by the present invention can achieve quantitative calculation of mining-induced stress. On the one hand, it can realize the reasonable layout of the working face and roadway, optimize the size of coal pillars, and improve the recovery rate of coal resources; on the other hand, it can achieve accurate prevention and control of coal and rock dynamic disasters, avoid excessive prevention and control, and reduce the prevention and control cost. At present, the determination of mining-induced stress mainly adopts methods such as on-site measurement, experimental simulation and theoretical analysis. The existing on-site measurement can only determine the real-time stress distribution during the mining process of the working face and cannot determine the mining-induced stress in advance. The existing experimental simulation cannot achieve quantitative determination of the data of mining-induced stress distribution. The characteristics of mining-induced stress distribution determined by the existing theoretical analysis method deviate greatly from the engineering practice. A calculation method of mining-induced stress under the action of load transfer of rock stratum structure is based on considering the load transfer of key stratum structure and loose stratum arch structure, and conducts quantitative calculation of mining-induced stress according to the geological and mining conditions of the working face, making up for the deficiencies of lag, inability to quantify and mathematical homogenization in the existing determination of mining-induced stress.

[0077] In the present invention, the quantitative determination of mining-induced stress is the basis for the prevention and control of coal mine dynamic disasters such as rock bursts, mine tremors, coal and gas outbursts, and dynamic water inrusions. At present, the determination of mining-induced stress mainly adopts methods such as on-site measurement, experimental simulation and theoretical analysis. The existing on-site measurement method can only monitor the mining-induced stress in real time and cannot predict it in advance. The existing experimental simulation can analyze the evolution law of mining-induced stress but cannot quantitatively determine it. The existing theoretical analysis adopts the idea of mathematical homogenization and ignores the influence of rock stratum structure on the transfer of mining-induced stress. A calculation method of mining-induced stress under the action of load transfer of rock stratum structure can, on the one hand, conduct quantitative calculation of mining-induced stress according to specific geological and mining conditions, and on the other hand, consider the load transfer of rock stratum structure, making up for the deficiency of the idea of mathematical homogenization.

[0078] The mining-induced stress of the working face and overlying strata is mainly determined by on-site measurement, experimental simulation and theoretical analysis, etc. On-site measurement can obtain the real-time stress distribution but cannot predict the mining-induced stress. Through experimental simulation, the evolution law of mining-induced stress can generally be determined, but the mining-induced stress cannot be accurately determined. The existing theoretical analysis leads to a large deviation between the calculation result and the engineering site due to model mathematical homogenization and ignoring the influence of rock stratum structure on mining-induced stress. A calculation method of mining-induced stress under the action of load transfer of rock stratum structure is based on considering the load transfer of key stratum structure and loose stratum arch structure, and conducts quantitative calculation of mining-induced stress according to the geological and mining conditions of the working face, making up for the deficiencies of lag, inability to quantify and mathematical homogenization in the existing determination of mining-induced stress. Brief Description of the Drawings

[0079] The drawings here are incorporated into the specification and form a part of this specification, showing embodiments in line with the present disclosure, and are used together with the specification to explain the principles of the present disclosure;

[0080] Figure 1It is the flowchart of the calculation method of mining-induced stress under the load transfer of the rock stratum structure provided by the embodiment of the present invention;

[0081] Figure 2 It is the mechanical model diagram of the calculation of mining-induced stress under the load transfer of the rock stratum structure provided by the embodiment of the present invention;

[0082] Figure 3 It is the curve diagram of the mining-induced stress distribution of coal and rock strata under the advancement of the working face by 70 m provided by the embodiment of the present invention;

[0083] Figure 4 It is the curve diagram of the mining-induced stress distribution of coal and rock strata under the advancement of the working face by 85 m provided by the embodiment of the present invention;

[0084] Figure 5 It is the comprehensive borehole columnar diagram drawn by the embodiment of the present invention. Specific Embodiments

[0085] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe the specific embodiments of the present invention in detail with reference to the accompanying drawings. Many specific details are set forth in the following description to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0086] The innovation of the present invention lies in: the quantitative determination of mining-induced stress in the present invention is the basis for preventing and controlling coal mine dynamic disasters such as rock bursts, mine tremors, coal and gas outbursts, and dynamic water inrusions. Currently, the determination of mining-induced stress mainly uses methods such as on-site measurement, experimental simulation, and theoretical analysis. The existing on-site measurement is to deploy stress gauges in the roadways on both sides of the working face for real-time monitoring and obtain the distribution law of mining-induced stress, determine the peak stress position and magnitude, but it can only determine the real-time stress distribution during the mining process of the working face and cannot determine the mining-induced stress of the working face in advance. The existing experimental simulation is to establish an experimental model according to the geological and mining conditions of the working face and analyze the stress distribution law during the mining process of the working face, but it cannot realize the quantitative determination of the mining-induced stress distribution data. The existing theoretical analysis method mathematically homogenizes the overlying strata of the working face and does not consider the occurrence characteristics of each stratum and the transfer effect of mining-induced stress in the rock stratum structure, and the determined mining-induced stress distribution characteristics deviate greatly from the engineering practice. Previous studies have shown that there are key strata, loose layer arches and other rock stratum structures in the overlying strata of the working face; during the mining process of the working face, the movement, deformation, fracture, and movement of the rock stratum structure control the distribution characteristics and evolution law of mining-induced stress and affect the transfer effect of mining-induced stress. Therefore, it is necessary to propose a calculation method of mining-induced stress under the load transfer of the rock stratum structure. According to the geological and mining conditions, a mechanical model is established considering the key stratum structure and the loose layer arch structure to realize the quantitative calculation of mining-induced stress.

[0087] Example 1, as Figure 1 shown, a method for calculating mining-induced stress under the action of load transfer in a rock stratum structure provided by an embodiment of the present invention includes the following steps:

[0088] Step1, obtain the basic mechanical parameters of the overlying rock stratum of the working face based on the boreholes near the working face;

[0089] Step2, based on the formation conditions of the loose layer arch, determine whether a loose layer arch is formed above the working face according to the relationship between the arch rise-span ratio of the loose layer arch and the span of the loose layer arch and the mining width of the working face;

[0090] Step3, according to the key stratum theory, based on the stiffness and strength criteria, obtain the basic information of the position and thickness of the key strata in the overlying rock stratum of the working face through the key stratum discrimination software;

[0091] Step4, obtain the bearing structure characteristics and dimensions of the overlying rock stratum according to the rock stratum fracture line, the virgin stress line, and all the straight lines of the top and bottom interfaces of each rock stratum;

[0092] Step5, establish a mechanical model of mining-induced stress under the action of load transfer in the rock stratum structure, analyze the components of mining-induced stress in the coal and rock strata during the mining of the working face, and obtain the analytical expression of mining-induced stress in the coal and rock strata.

[0093] Exemplarily, in step Step1, the mechanical parameters of each rock stratum above the working face include the thickness of the key stratum, the tensile strength of the key stratum, the distance between the bottom interface of the key stratum and the top interface of the coal seam, the thickness and burial depth of the coal seam, the thickness of each rock stratum in the bedrock, the fracture angle, and the lithology. The mechanical parameters are determined by taking cores from the bedrock and conducting uniaxial compression, uniaxial tension, and triaxial compression experiments on the obtained specimens, so as to obtain the basic mechanical parameters of the key stratum; using the key stratum discrimination method, based on the basic mechanical parameters, conduct key stratum discrimination in the borehole comprehensive columnar diagram to obtain the position of the key stratum and the distance between the bottom interface of the key stratum and the top interface of the coal seam; using the borehole logging analyzer, draw the fracture evolution diagram of the peephole borehole to obtain the fracture angle of the bedrock.

[0094] In step Step2, determine whether a loose layer arch is formed above the working face according to the relationship between the arch rise-span ratio of the loose layer arch and the span of the loose layer arch and the mining width of the working face. When the sum of the arch height and thickness of the loose layer arch is less than the thickness of the loose layer, a loose layer arch is formed, otherwise it cannot be formed. The specific steps are as follows:

[0095] Drilling and coring on the surface or underground in the coal mining area is done, and a comprehensive columnar diagram of the borehole is drawn. Based on the comprehensive columnar diagram of the borehole, the thickness, burial depth, thickness of each rock layer in the bedrock and lithology of the coal seam in the coal mining area are determined. Using a borehole logging analyzer, a borehole is drilled above the top plate of the working face tunnel. By peeping at the borehole depth in the result, a peeping borehole fracture evolution diagram is drawn to obtain the rock formation fracture angle. The conditions for the formation of the loose layer arch are obtained by the relationship between the arch span ratio characteristics of the loose layer and the span of the loose layer arch and the mining width of the working face. When the sum of the arch height and thickness of the loose layer arch is less than the thickness of the loose layer, a loose layer arch is formed, otherwise it cannot be formed.

[0096] In step 3, the key layer identification software is used to obtain basic information such as the position and thickness of the key layer in the overlying rock formation on the working face. The mechanical parameters are determined by coring the rock formation and performing uniaxial compression, uniaxial tensile and triaxial compression tests on the obtained samples, thereby obtaining the tensile strength of each rock formation. The key layer identification method is used to identify the key layer in the comprehensive columnar diagram of the borehole based on the mechanical parameters of the bedrock, and the position of the key layer and the distance between the bottom interface of the key layer and the top interface of the coal seam are obtained.

[0097] The key layer identification method is based on the key layer theory, and the key layer is identified according to the strength criterion and the stiffness criterion to obtain the position of the key layer and the distance between the bottom interface of the key layer and the top interface of the coal seam.

[0098] The specific steps are: Layers of rock, , For the and The load of the first layer on the first layer; For the and The breaking distance of the rock layer is determined according to the stiffness criterion and strength criterion of the key layer. , then this key layer is the main key layer; if , then the key layer is a sub-key layer;

[0099] Exemplarily, in step 4, the bedrock breaking line is determined according to the bedrock breaking angle, and the straight lines where the top and bottom interfaces of each rock layer are located are determined by the buried depth of the top interface of each rock layer. The four straight lines form a closed figure to obtain the morphological characteristics and size of the overlying rock layer group.

[0100] For example, in step 5, a mining stress mechanical model under the action of rock layer structure load transfer is established, and the components of coal and rock layer mining stress during working face mining are analyzed to obtain an analytical expression of coal and rock layer mining stress. The specific steps are as follows:

[0101] The specific steps are as follows: A rectangular coordinate system is established with the intersection point of the central axis of the goaf and the top interface of the coal seam as the origin, the top interface of the coal seam as the axis, and the central axis of the goaf as the axis. A calculation model of mining-induced stress under the action of load transfer in the rock stratum structure is established. The present invention innovatively proposes to obtain The expressions of mining-induced stress for the FG section of the arch foundation of the loose layer, the IJ section of the main key stratum, the PQ section of the sub-key stratum, and the UV section of the coal seam are shown in formula (1).

[0102] ;

[0103] ;

[0104] ;

[0105] (1)

[0106] In the formula, is the span of the loose layer, is the distance from the intersection point of the bottom interface of the loose layer and the broken line of the rock stratum to the peak stress position, is the thickness of the arch of the loose layer, is the break angle of the rock stratum, are all undetermined coefficients, are respectively the thickness of the soft rock between the loose layer and the main key stratum, the thickness of the main key stratum, the thickness of the soft rock between the main key stratum and the sub-key stratum, the thickness of the sub-key stratum, and the thickness of the soft rock between the sub-key stratum and the coal seam, are respectively the mining-induced stress of the FG section of the arch foundation of the loose layer section, the mining-induced stress of the FG section of the arch foundation of the loose layer section, the mining-induced stress of the main key stratum section, the mining-induced stress of the main key stratum section, the mining-induced stress of the sub-key stratum section, the mining-induced stress of the sub-key stratum section, the mining-induced stress of the coal seam section, the mining-induced stress of the coal seam section, where are respectively the intersection points of the straight line where the arch foundation of the loose layer is located, the top interface of the main key stratum, the top interface of the sub-key stratum, and the top interface of the coal seam with the peak stress line, is the distance from this position to the broken line of the rock stratum, is a mathematical constant, that is, the base of the natural logarithm function, are respectively the original rock stresses of the arch foundation of the loose layer, the main key stratum, the sub-key stratum, and the coal seam.

[0107] Embodiment 2. As another embodiment of the present invention, during the working face mining process, the distribution of mining-induced stress in the coal and rock strata is comprehensively affected by the bearing structures in the bedrock and the loose layer. Based on the evolution mechanism of mining-induced stress under the action of load transfer, a calculation method for mining-induced stress under the action of the load transfer of the rock stratum structure is established, as follows Figure 1 shown.

[0108] Taking the intersection point of the coal seam top interface and the central axis of the goaf as the origin, a plane rectangular coordinate system is established. The thickness of the loose layer is , and the thickness, rise, and span of the loose layer arch are respectively . The thickness of the loose layer, the distance from the loose layer arch to the main key stratum, the thickness of the main key stratum, the distance from the main key stratum to the sub-key stratum, the thickness of the sub-key stratum, and the distance from the sub-key stratum to the coal wall are respectively , and the total height is . In the mechanical model, the load widths of the FG, IJ, PQ, and UV segments are respectively . When there is no loose layer arch formed in the overlying rock strata, the width of the UV segment is . The rock breaking angle is . The load transfer coefficients of the loose layer, the main key stratum, the sub-key stratum, and the coal seam are respectively . The mining-induced stress consists of the stress transferred by the masonry beam , the stress transferred by the overlying rock strata and the self-weight stress of the overlying rock strata . The mining-induced stress distribution functions of the loose layer arch arch base, the main key stratum, the sub-key stratum, and the coal seam are respectively , as shown in Equation (1):

[0109] ;

[0110] ;

[0111] ;

[0112] (1)

[0113] According to the equation of the loose layer arch axis, the relationship between the envelope line y in the loose layer arch and x is shown in Equation (2):

[0114] (2)

[0115] The mining-induced stress at the loose layer arch arch base is transferred from the overlying loose layer of the loose layer arch and the self-weight of the loose layer arch. Since the mechanical model is a symmetric load symmetric structure model, the stress transferred to the FG segment at the loose layer arch base is half of the self-weight of the loose layer and the loose layer arch, that is, the self-weight of the loose layer and the rock strata in the loose layer archThe difference in deadweight is innovatively proposed in the present invention, and formula (3) is obtained:

[0116] (3)

[0117] The mining stress of the main key layer under the load transfer of loose layer arch is transferred from the overlying rock layer to the main key layer. , loose layer arch transfer stress , Overlying rock stratum self-weight stress The overburden strata transfer stress Loose layer inner arch and Half of the self-weight and loose layer arch transfer stress Loose layer arch FG Segment stress, self-weight stress of overlying rock for Part of the dead weight, the present invention innovatively proposes, and obtains formula (4);

[0118] (4)

[0119] According to the equivalent relationship of mining stress in the IJ section of the main key layer, the present invention innovatively proposes formula (5):

[0120] (5)

[0121] The boundary conditions and continuity conditions of the mining stress distribution in the loose layer arch FG section and the main key layer IJ section are listed from left to right. The present invention innovatively proposes formula (6);

[0122] (6)

[0123] The coefficients to be determined in formula (1) can be obtained by combining formula (2) and formula (6) , and the analytical expressions of mining stress in the loose layer arch foundation FG segment and the main key layer IJ segment were obtained.

[0124] The mining stress of the sub-key layer under the load of the main key layer is transferred from the overlying rock layer , the main key layer transfers stress , Overlying rock stratum self-weight stress The overburden strata transfer stress Half of the weight of the QHNPI part of the overburden. The stress of the IJ section of the main key layer and the self-weight stress of the overlying rock layer for Part of the dead weight, the present invention innovatively proposes to obtain formula (7):

[0125] (7)

[0126] According to the equivalent relationship of mining stress in the PQ section of the sub-critical layer, the present invention innovatively proposes formula (8):

[0127] (8)

[0128] The boundary conditions and continuity conditions of the mining stress in the PQ section of the sub-critical layer are listed from left to right. The present invention innovatively proposes formula (9):

[0129] (9)

[0130] By combining formula (7) and formula (9), we can solve the coefficients in formula (1) , and the analytical expression of mining stress in the IJ section of the sub-critical layer is obtained.

[0131] The mining stress of the coal seam ahead of the working face under the action of sub-critical layer load is transferred from the overlying rock layer , Sub-critical layer transfer stress , Overlying rock stratum self-weight stress The overburden stratum transfer stress is Half of the deadweight of the part. Subcritical layers transfer stress is the stress of the sub-critical layer PQ section, and the self-weight stress of the overlying rock layer for Part of the dead weight, the present invention innovatively proposes to obtain formula (10):

[0132] (10)

[0133] According to the equivalent relationship of mining stress in the UV section of the coal seam, the present invention innovatively proposes formula (11):

[0134] (11)

[0135] The boundary conditions and continuity conditions of the mining stress in the UV section of the coal seam are listed from left to right. The present invention innovatively proposes formula (12):

[0136] (12)

[0137] By combining formula (10) and formula (12), we can obtain the coefficients to be determined in formula (1): , and the analytical expression of mining stress in UV section of coal seam is obtained.

[0138] When the mining width is small, there is no loose layer arch above the working face, and when the sub-critical layer is broken for the first time, the invention innovatively proposes the formula (13) based on the mining stress of the coal wall of the working face;

[0139] (13)

[0140] In the formula, All are undetermined coefficients.

[0141] Coal mining stress is transferred from the overlying rock layer , Overlying rock stratum self-weight stress The overburden rock stratum transfer stress is transmitted from the rock stratum self-weight stress within the rock stratum fracture line. Half of the self-weight of this part of the rock stratum is transmitted to the goaf through the underlying rock stratum. Therefore, the coal seam UV The transferred stress on the segment is Half of the deadweight of the part, the deadweight stress of the overlying rock The stress transmitted from the overlying rock formation outside the rock fracture line is the stress transmitted from the overlying rock formation. for Part of the dead weight, the present invention innovatively proposes to obtain formula (14):

[0142] (14)

[0143] According to the equivalent relationship of mining stress in the UV section of the coal seam, the present invention innovatively proposes formula (15):

[0144] (15)

[0145] The boundary conditions and continuity conditions of the mining stress in the UV section of the coal seam are listed from left to right. The present invention innovatively proposes formula (16):

[0146] (16)

[0147] By combining formula (14) and formula (16), we can solve the unknown coefficients in formula (13): , and the analytical expression of mining stress in UV section of coal seam is obtained.

[0148] It can be known from the above embodiments that the present invention is based on the key layer theory, and obtains the key layer position and layer thickness by performing key layer identification on the boreholes near the working face. At the same time, the morphological characteristics and size of the overlying rock strata group on the working face are determined according to the rock stratum breaking line, the straight lines where the top and bottom interfaces of each rock stratum are located, and the original rock stress line position. Finally, a mining stress mechanics model under the load transfer of the overlying rock structure is established, and the working face is obtained based on the model, and the peak stress of the coal rock stratum mining stress and the stress influence range are clarified. The present invention calculates the coal rock stratum mining stress according to the structural characteristics of the overlying rock strata, clarifies the stress distribution of the coal body in front of the working face, and the method designed by the present invention can reduce the loss of mining damage, which has a certain guiding significance for the safe and efficient mining of the working face.

[0149] Embodiment 3, an embodiment of the present invention provides a system for calculating mining stress under load transfer of rock formation structure, comprising:

[0150] The mechanical parameter obtaining module obtains the basic mechanical parameters of the overlying strata of the working face based on the boreholes near the working face;

[0151] The loose layer arch formation module determines whether a loose layer arch is formed above the working face based on the formation conditions of the loose layer arch, according to the ratio of the arch rise to the span of the loose layer arch and the relationship between the span of the loose layer arch and the mining width of the working face;

[0152] The key stratum position and thickness obtaining module obtains the basic information of the position and thickness of the key strata in the overlying strata of the working face based on the key stratum theory, based on the stiffness and strength criteria, through the key stratum discrimination software;

[0153] The overlying strata bearing structure characteristics and dimensions obtaining module obtains the overlying strata bearing structure characteristics and dimensions according to the strata fracture line, the virgin stress line, and all the straight lines of the top and bottom interfaces of each stratum;

[0154] The coal and rock strata mining-induced stress analytical expression obtaining module is used to establish a mining-induced stress mechanical model under the action of rock strata structure load transfer, analyze the components of the mining-induced stress of coal and rock strata during the mining of the working face, and obtain the coal and rock strata mining-induced stress analytical expression.

[0155] To further illustrate the relevant effects of the embodiments of the present invention, the following experiments are carried out.

[0156] The present invention provides a method for calculating mining-induced stress under the action of rock strata structure load transfer, including the following steps:

[0157] S101. Collect the borehole columns near the working face and the mechanical parameters of each stratum above the working face;

[0158] S102. Obtain the basic information such as the position and thickness of the key strata in the overlying strata of the working face through the key stratum discrimination software;

[0159] S103. Based on the strata fracture line, and comprehensively considering the key stratum discrimination results, obtain the overlying strata bearing structure characteristics and dimensions;

[0160] S104. Establish a mining-induced stress mechanical model under the action of rock strata structure load transfer, analyze the components of the mining-induced stress of coal and rock strata during the mining of the working face, and obtain the coal and rock strata mining-induced stress analytical expression.

[0161] The mechanical parameters of each stratum around the borehole include: the thickness of the key stratum, the tensile strength of the key stratum, the distance between the bottom interface of the key stratum and the top interface of the coal seam, the thickness and burial depth of the coal seam, the thickness of each stratum in the bedrock, the fracture angle, and the lithology.

[0162] Core samples are taken and preserved from surface or underground boreholes, and a comprehensive columnar diagram of the boreholes is drawn. Based on the comprehensive columnar diagram of the boreholes, the thickness, burial depth of the coal seam to be mined in the coal mining area, the thickness and lithology of each rock stratum in the bedrock are determined.

[0163] By taking cores from the bedrock and conducting uniaxial compression, uniaxial tension, triaxial compression and other experiments on the obtained specimens to determine the mechanical parameters, the basic mechanical parameters such as the tensile strength of the key stratum are obtained.

[0164] Using the key stratum discrimination method, based on the mechanical parameters of the bedrock, the key stratum is discriminated in the comprehensive columnar diagram of the boreholes, so as to obtain the position of the key stratum and the distance between the bottom interface of the key stratum and the top interface of the coal seam.

[0165] Using a borehole logging analyzer, boreholes are drilled above the roof of the working face roadway, and through the depth of the boreholes in the peep results, a peep borehole fracture evolution diagram is drawn to obtain the bedrock fracture angle.

[0166] After determining the borehole column of the working face and the strength of different rock strata in the column, according to the stiffness condition and strength condition formula, the position of the key stratum of the working face is discriminated by means of the key stratum discrimination method. The specific steps are as follows: Suppose there are rock strata in the overlying strata of the stope, is the load of the th and th rock strata on the first rock stratum, is the fracture distance of the th and th rock strata. According to the stiffness criterion and strength criterion for discriminating the key stratum, if , then this key stratum is the main key stratum; if , then this key stratum is the sub-key stratum. By means of the above key stratum position discrimination method, the position of the key stratum in the columnar diagram is obtained.

[0167] The bedrock fracture line is determined by the bedrock fracture angle, and the straight lines where the top interfaces and bottom interfaces of each rock stratum are located are determined by the burial depths of the top interfaces of each rock stratum. The four straight lines form a closed figure to obtain the morphological characteristics and dimensions of the overlying rock stratum group. The specific process is as follows: The bedrock fracture line is determined by the bedrock fracture angle, and the straight lines where the top interfaces and bottom interfaces of each rock stratum are located are determined by the burial depths of the top interfaces of each rock stratum. The four straight lines form a closed figure to obtain the morphological characteristics and dimensions of the overlying rock stratum group.

[0168] Finally, a mechanical model of mining-induced stress under the action of load transfer of the rock stratum structure is established, and based on this model, the distribution forms of mining-induced stress in the coal body ahead of the working face and the overlying rock strata during the mining of the working face are obtained. The specific process is as follows:

[0169] Taking the intersection point of the central axis of the goaf and the top interface of the coal seam as the origin, a rectangular coordinate system is established, and the top interface of the coal seam isx Axis, the central axis of the goaf is y Axis. Establish a calculation model of mining-induced stress under the action of load transfer in the rock stratum structure. Obtain They are respectively the arch foundation of the loose layer arch FG Section, the main key stratum IJ Section, the sub-key stratum PQ Section, coal seam UV The expression of mining-induced stress in the section is shown in formula (1).

[0170] Specific application example.

[0171] 1. Use numerical simulation software to establish a numerical model with a length of 250 m and a height of 150 m. Considering the boundary effect, 15 m coal pillars are reserved on both sides of the model. The parallel bond model is used as the constitutive model, and the microscopic parameters in the numerical simulation software are assigned by the empirical formula method (Table 1). Figure 2 This is the mechanical model diagram of the mining-induced stress calculation under the action of load transfer in the rock stratum structure proposed in this embodiment; by repeatedly debugging the mechanical parameters until the obtained macroscopic parameters are consistent with the actual parameters. Using the uniaxial compressive test as the calibration data. Among them, horizontal displacement constraint conditions are applied to the left and right boundaries of the model, and vertical displacement constraint conditions are applied to the bottom of the model. The minimum particle size is set to 0.15 m, and the particle size ratio is 1.5. A measuring line is arranged on the top interface of the main key stratum, the top interface of the sub-key stratum, and the bottom interface of the coal seam respectively. One measuring point is arranged every 5 m on each measuring line, with 49 measuring points on one measuring line and a total of 147 measuring points. During the mining process, 5 m is mined each time, and the total mining distance is 220 m. Through the numerical model, study the distribution of mining-induced stress in the coal and rock strata, and obtain the distribution trend of mining-induced stress on the coal seam, sub-key stratum, and main key stratum. Among them, when the working face advances 70 m and 85 m respectively, the mining-induced stress on the coal seam and the key stratum is respectively as Figure 3 , Figure 4 Shown. According to the fitting of the mining-induced stress distribution curve of the coal and rock strata on one side of the goaf, the final expression form of the coal and rock strata is obtained as follows. And by substituting specific parameters, the function of the mining-induced stress distribution law of the coal and rock strata is obtained.

[0172] (17)

[0173] Table 1 Mechanical parameters in the numerical model

[0174]

[0175] 2. The width of a certain working face in a certain mine is 2128 m, the strike advance length is 240 m, the ground elevation is +1040 - +1100 m, and the working face elevation is +530 - +650 m. Now, based on the geological data provided by the boreholes in the 7# working face of the 4-1 coal seam in this mine, determine the position and related information of the key strata in the overlying strata of a certain working face. The specific steps are as follows:

[0176] Core samples were taken from boreholes drilled on the surface of a certain working face area in the 4-1 coal seam, and a comprehensive borehole columnar diagram was drawn. Through the comprehensive borehole columnar diagram, it was determined that the thickness of the 4-1 coal seam mined in a certain working face was 10.7 m, the thickness and lithology of the rock strata in the bedrock; core samples were taken from the rock strata for physical and mechanical parameter tests to obtain the tensile strength of the rock strata. The thickness, lithology and position of the key strata of the rock strata at the engineering site are shown in Table 2.

[0177] Table 2 Measured data of rock strata at the engineering site

[0178]

[0179] A borehole logging analyzer was used to draw an evolution diagram of the broken position of the peephole by peeping the depth of the borehole, and the broken angle of the bedrock was obtained as 70°. According to the formation conditions of the loose layer arch, it was judged that there was no loose layer arch in the loose layer above the working face. According to the key stratum discrimination method, it was obtained that there were 4 key strata in the overlying strata of a certain working face, namely the fine sandstone sub-key stratum with a thickness of 10.33 m, the siltstone sub-key stratum with a thickness of 10.51 m, the fine sandstone sub-key stratum with a thickness of 13.47 m, and the fine sandstone main key stratum with a thickness of 48.02 m. Substituting the parameters of the overlying strata (Table 3) into the calculation, the peak value of the mining-induced stress of the coal body in front of the working face was obtained as 38.49 MPa, and the influence range was 163.98 m.

[0180] Five borehole stress gauges were arranged in the return air heading and the belt heading of the working face respectively, and the interval between each borehole stress gauge was 2 m. Whenever the working face advanced to within 0-5 m of the borehole stress gauge, the borehole stress gauge was removed and installed at a new measuring point 30 m in front of the farthest measuring point, so as to realize the stress monitoring during the whole process of working face mining. Part of the stress monitoring diagram is as Figure 5 shown.

[0181] The influence range of the mining pressure monitored on site was 161.1-173.9 m, and the peak stress was 37.45-40.23 MPa. The calculation results were basically consistent with the on-site measured results.

[0182] Table 3 Parameters of the overlying strata of the working face

[0183]

[0184] The above is only a relatively preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A calculation method for mining-induced stress under the action of load transfer in a rock stratum structure, characterized in that, The method comprises the following steps: Step 1, obtain the basic mechanical parameters of the overlying rock strata on the working face based on the drilling holes near the working face; Step 2: Based on the loose layer arch formation conditions, according to the loose layer arch rise-span ratio and the relationship between the loose layer arch span and the mining width of the working face, determine whether a loose layer arch is formed above the working face; Step 3, according to the key layer theory, based on the stiffness and strength criteria, the key layer identification software is used to obtain the basic information of the key layer position and thickness in the overburden stratum on the working face; Step 4: Obtain the bearing structure characteristics and dimensions of the overlying rock strata based on the rock fracture line, original rock stress line, and all straight lines at the top and bottom interfaces of each rock strata; Step 5, establish a mechanical model of mining stress under the action of rock layer structure load transfer, analyze the components of coal and rock layer mining stress during working face mining, and obtain an analytical expression for coal and rock layer mining stress; In step 5, the analytical expression of coal-rock mining stress is obtained, including: A rectangular coordinate system is established with the intersection of the central axis of the goaf and the top interface of the coal seam as the origin, the top interface of the coal seam as the x-axis, and the central axis of the goaf as the y-axis; a mining stress calculation model under the action of rock structure load transfer is established; Q1(x), Q2(x), Q3(x), and Q4(x) are obtained, which are the mining stress expressions of the loose layer arch base FG segment, the main key layer IJ segment, the sub-key layer PQ segment, and the coal seam UV segment respectively: In the formula, L is the span of the loose layer, M is the distance from the intersection point of the bottom interface of the loose layer and the broken line of the rock stratum to the peak stress position, δ is the arch thickness of the loose layer arch, α is the broken angle of the rock stratum, a1, b1, c1, d1, a2, b2, c2, d2, a3, b3, c3, d3, a4, b4, c4, d4 are all undetermined coefficients, h1, h2, h3, h4, h5 are the soft rock thickness between the loose layer and the main key stratum, the thickness of the main key stratum, the soft rock thickness between the main key stratum and the sub-key stratum, the thickness of the sub-key stratum, and the soft rock thickness between the sub-key stratum and the coal seam, respectively, Q 11 (x), Q 12 (x), Q 21 (x), Q 22 (x), Q 31 (x), Q 32 (x), Q 41 (x), Q 42 (x) are the mining-induced stresses of the FW section of the arch foundation of the loose layer arch, the WG section of the arch foundation of the loose layer arch, the IX section of the main key stratum, the XJ section of the main key stratum, the PY section of the sub-key stratum, the YQ section of the sub-key stratum, the UZ section of the coal seam, and the ZV section of the coal seam, respectively. Among them, W, X, Y, Z are the intersection points of the straight line where the arch foundation of the loose layer arch is located, the straight line where the top interface of the main key stratum is located, the straight line where the top interface of the sub-key stratum is located, and the straight line where the top interface of the coal seam is located and the peak stress line, x is the distance from this position to the broken line of the rock stratum, e is a mathematical constant, that is, the base of the natural logarithm function, and q1, q2, q3, q4 are the original rock stresses of the arch foundation of the loose layer arch, the main key stratum, the sub-key stratum, and the coal seam, respectively; The establishment of the mining stress calculation model under the load transfer of the rock layer structure includes: obtaining the relationship between the envelope y and x of the loose layer arch according to the loose layer arch axis equation: In the formula, y(x) is the functional relationship between the vertical coordinate and the horizontal coordinate of the envelope line in the loose layer, λ is the lateral pressure coefficient, and h0 is the arch height of the loose layer; The mining-induced stress at the arch foundation of the loose layer arch is transmitted from the overlying loose layer of the loose layer arch and the self-weight of the loose layer arch. The transmitted stress received by the FG section of the loose layer arch foundation is half of the self-weight of the loose layer and the loose layer arch, that is, the loose layer Q AEGB Self-weight and the rock layer Q in the loose layer arch DEF The difference in self-weight, and formula (3) is obtained; Where, K1 is the load transfer coefficient of loose layer, H0 is the thickness of loose layer overlying loose layer arch, γ1 is the bulk density of loose layer; H represents the total height of loose layer thickness, distance from loose layer arch to main key layer, thickness of main key layer, distance from main key layer to sub-key layer, thickness of sub-key layer, and distance from sub-key layer to coal wall; The establishment of a mining stress calculation model under the load transfer effect of rock structure also includes: Under the action of the arch load transfer in the loose layer, the mining stress of the main key stratum consists of three parts: the stress R2(x) transferred by the overlying strata, the stress S2(x) transferred by the loose layer arch, and the self-weight stress T2(x) of the overlying strata. The stress R2(x) transferred by the overlying strata is half of the sum of the self-weight of the inner arch Q AEG and Q EHIF in the loose layer. The stress S2(x) transferred by the loose layer arch is the stress of the FG section of the loose layer arch. The self-weight stress T2(x) of the overlying strata is the self-weight of Q FGJI in part, and formula (4) is obtained as follows: Where K2 is the load transfer coefficient of loose layer arch-main key layer; γ2 is the average bulk density of the main key layer and the soft rock between it and the loose layer; According to the equivalent relationship of mining stress in the main key layer IJ section, formula (5) is obtained; The boundary conditions and continuity conditions of mining stress distribution in the loose layer arch FG section and the main key layer IJ section are listed from left to right, and formula (6) is obtained: Formula (2)-Formula (6) are used to solve the unknown coefficients a1, b1, c1, d1, a2, b2, c2, d2 in Formula (1), and the analytical expressions of mining stress in the loose layer arch foundation FG section and the main key layer IJ section are obtained.

2. The mining-induced stress calculation method under the load transfer of the rock stratum structure according to claim 1, wherein, In step 1, the basic mechanical parameters of the overlying rock strata on the working face include: the thickness of the key layer, the tensile strength of the key layer, the distance between the bottom interface of the key layer and the top interface of the coal seam, the thickness and burial depth of the coal seam, the thickness of each rock layer in the bedrock, the fracture angle and lithology; In step Step 2, it is determined whether a loose layer arch is formed above the working face, including: drilling and coring on the surface of the coal mining area or underground construction ground, and drawing a comprehensive columnar diagram of the boreholes; according to the comprehensive columnar diagram of the boreholes, the thickness, burial depth, thickness of each rock layer in the bedrock and lithology of the coal seam mined in the coal mining area are determined; using a borehole logging analyzer, a borehole is drilled above the roof of the working face tunnel, and the borehole depth in the peek result is used to draw a peek borehole fracture evolution diagram to obtain the rock layer fracture angle; the loose layer arch formation conditions are obtained through the relationship between the loose layer arch span ratio characteristics and the loose layer arch span and the working face mining width. When the sum of the loose layer arch height and thickness is less than the loose layer thickness, a loose layer arch is formed, otherwise it cannot be formed.

3. The mining-induced stress calculation method under the load transfer of the rock stratum structure according to claim 1, characterized in that, In step 3, the key layer identification software is used to obtain the basic information of the key layer position and thickness in the overburden strata on the working face, including: By coring the rock layer, the obtained samples are subjected to uniaxial compression, uniaxial tensile and triaxial compression tests to determine the mechanical parameters, and the tensile strength of each rock layer is obtained. The key layer identification method is used to identify the key layer in the borehole comprehensive columnar diagram based on the mechanical parameters of the bedrock, and the position of the key layer and the distance between the bottom interface of the key layer and the top interface of the coal seam are obtained. The key stratum discrimination method includes: assuming that there are k strata in the overlying strata of the stope, q 1|g+1 , q 1|g are the loads of the (g + 1)-th and g-th strata on the first stratum; l g+1 , l g are the breakage distances of the (g + 1)-th and g-th strata. According to the stiffness criterion for discriminating key strata, l g+1 > l g , and the strength criterion q 1|g+1 < q 1|g . If g = k, then this key stratum is the main key stratum; if g < k, then this key stratum is the sub-key stratum. In step 4, the characteristics and dimensions of the bearing structure of the overlying rock strata are obtained, including: determining the rock stratum breaking line through the edge position of the goaf area of the working face and the rock stratum breaking angle, determining the original rock stress line according to the edge position of the loose layer arch span, and determining the straight lines where the top and bottom interfaces of each rock stratum are located according to the buried depth of each rock stratum. The four straight lines form a closed figure to obtain the morphological characteristics and dimensions of the bearing structure of the overlying rock stratum.

4. The mining-induced stress calculation method under the load transfer of the rock stratum structure according to claim 1, wherein The establishment of a mining stress calculation model under the load transfer effect of rock formation structure also includes: Under the action of the main key stratum load, the mining-induced stress of the sub-key stratum consists of three parts: the stress R3(x) transmitted by the overlying strata, the stress S3(x) transmitted by the main key stratum, and the self-weight stress T3(x) of the overlying strata; the stress R3(x) transmitted by the overlying strata is half of the self-weight of part of the overlying strata Q HNPI of the overlying strata; the stress S3(x) transmitted by the main key stratum is the stress of the IJ section of the main key stratum, and the self-weight stress T3(x) of the overlying strata is Q IJQP part of the self-weight, and formula (7) is obtained: Where K3 is the load transfer coefficient between the main key layer and the sub-key layer, γ3 is the average bulk density of the sub-key layer and the soft rock between it and the main key layer; According to the equivalent relationship of mining stress in the PQ section of the sub-critical layer, formula (8) is obtained; The mining stress boundary conditions and continuity conditions of the sub-critical layer PQ section are listed from left to right, and formula (9) is obtained: By combining formula (7) to formula (9), we can solve the unknown coefficients a3, b3, c3, d3 in formula (1) and obtain the analytical expression of mining stress in the IJ section of the subcritical layer.

5. The mining-induced stress calculation method under the load transfer action of the rock stratum structure according to claim 1, characterized in that, The establishment of a mining stress calculation model under the load transfer effect of rock formation structure also includes: The mining-induced stress in front of the working face under the action of the sub-critical layer load consists of three parts: the stress R4(x) transmitted by the overlying strata, the stress S4(x) transmitted by the sub-critical layer, and the self-weight stress T4(x) of the overlying strata; the stress transmitted by the overlying strata is Q NPUO Half of the partial self-weight; the stress S4(x) transmitted by the sub-critical layer is the stress of the PQ section of the sub-critical layer, and the self-weight stress T4(x) of the overlying strata is Q PQVU Partial self-weight, and formula (10) is obtained: Where K4 is the load transfer coefficient between the subcritical layer and the coal seam, and γ4 is the bulk density of the soft rock between the coal seam and the subcritical layer; According to the equivalent relationship of mining stress in the UV section of coal seam, formula (11) is obtained: The boundary conditions and continuity conditions of mining stress in the UV section of the coal seam are listed from left to right, and formula (12) is obtained; By combining formula (10)-formula (12), we can solve the unknown coefficients a4, b4, c4, d4 in formula (1) and obtain the analytical expression of mining stress in the UV section of the coal seam.

6. The method for calculating mining-induced stress under the action of load transfer of rock stratum structure according to claim 1, characterized in that The establishment of the mining stress calculation model under the action of rock layer structure load transfer also includes: according to the load three-band model, when the mining width is less than the set value, there is no loose layer arch above the working face, and when the sub-critical layer is first broken, according to the mining stress of the coal wall of the working face, formula (13) is obtained; In the formula, a5, b5, c5, d5 are all unknown coefficients; when no loose layer arch is formed in the overlying rock layer, the width of the UV segment is n; The mining stress of the coal seam is composed of the transferred stress R5(x) of the overlying strata and the self-weight stress T5(x) of the overlying strata; the transferred stress of the overlying strata is transmitted from the self-weight stress of the strata within the rock breaking line. Half of the self-weight of this part of the strata is transmitted to the goaf through the underlying strata. Therefore, the transferred stress received by the UV section of the coal seam is Q AWPUO Half of the partial self-weight, the self-weight stress T5(x) of the overlying strata is transmitted from the self-weight stress of the overlying strata outside the rock breaking line, and the transferred stress R5(x) of the overlying strata received by the coal seam is Q UVBWP Partial self-weight, and formula (14) is obtained: γ5 represents the average bulk density of all rock layers above the coal seam; According to the equivalent relationship of mining stress in the UV section of coal seam, formula (15) is obtained: The boundary conditions and continuity conditions of mining stress in the UV section of the coal seam are listed from left to right, and formula (16) is obtained: where Q 51 (x) is the mining-induced stress of the part from the boundary of the goaf of the coal seam to the position of the peak stress line when no loose layer arch is formed above the working face, and Q 52 (x) is the mining-induced stress of the part from the position of the peak stress line to the position of the virgin rock stress line when no loose layer arch is formed above the working face; By combining formula (14)-formula (16), the unknown coefficients a5, b5, c5, d5 in formula (13) are solved, and the analytical expression of mining stress in the UV section of the coal seam is obtained.

7. A mining-induced stress calculation system under the action of load transfer in a rock stratum structure, characterized in that, The system implements the method for calculating mining stress under load transfer of rock formation structure as claimed in any one of claims 1 to 6, and the system comprises: Mechanical parameter acquisition module, which obtains the basic mechanical parameters of the overlying rock formation on the working surface based on the drilling holes near the working surface; The loose layer arch formation module determines whether a loose layer arch is formed above the working face based on the loose layer arch formation conditions and the relationship between the loose layer arch span ratio and the loose layer arch span and the working face mining width; The module for obtaining the position and thickness of the key layer can obtain the basic information of the position and thickness of the key layer in the overburden stratum on the working face through the key layer identification software according to the key layer theory and based on the stiffness and strength criteria; The module for obtaining the bearing structure characteristics and dimensions of the overburden strata is used to obtain the bearing structure characteristics and dimensions of the overburden strata according to the stratum fracture line, the original rock stress line, and all the straight lines at the top and bottom interfaces of each stratum; The module for obtaining the analytical expression of coal-rock mining stress is used to establish a mechanical model of mining stress under the action of rock structure load transfer, analyze the components of coal-rock mining stress during working face mining, and obtain the analytical expression of coal-rock mining stress.

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