Method for arranging goaf-adjacent roadway in working face of protected seam under continuous mining

Abstract

Disclosed is a method for arranging a goaf-adjacent roadway in a working face of a protected seam under continuous mining. The method includes: calculating a range X1 of an ultimate stress equilibrium zone in lateral coal mass of a goaf; calculating a horizontal distance Xf from a boundary line of a stress-reduction zone to an edge of a coal pillar in a protective seam; comparing magnitudes of X1 and Xf to determine whether the width of the ultimate equilibrium zone is entirely within a range of the stress-reduction zone; calculating a distance L2 from a stress peak point of the coal pillar in the protective seam to an edge position of the coal pillar; calculating a periodic collapse step distance of an overlying surrounding rock in the protective seam; calculating a distance from a stress peak point in a compaction zone of the goaf in the protective seam to an edge of the goaf; determining a distance x' from a stress trough point in coal and rock mass beneath the protective seam to a stress peak position in the coal pillar zone; determining a position of the stress peak point in the coal seam based on the distance L2, and then determining an arrangement position for a goaf-adjacent roadway based on x', that is, arranging the goaf-adjacent roadway at the stress trough point in the coal and rock mass beneath the protective seam. According to the present disclosure, the reasonable position for arranging the goaf-adjacent roadway can be determined, thereby reducing the burst hazards of the goaf- adjacent roadway. 20 25 20 43 29 11 J un 2 02 5 A B S T R A C T 2 0 2 5 2 0 4 3 2 9 1 1 J u n 2 0 2 5 1 / 2 FIG. 1 FIG. 2 1 / 2 Calculate the range X1 of the ultimate stress equilibrium zone in the lateral coal mass of a goaf Calculate the horizontal distance Xf from the boundary line of the stress-reduction zone to the edge of the coal pillar Calculate the stress peak point L2 in the Calculate the distance L3 from the stress peak protected seam beneath the rock pillar point in the compaction zone of the goaf in the of the protective seam protective seam to the edge of the goaf Determine the distance x' from the stress trough point in the coal and rock mass beneath the protective seam to the stress peak position in the rock pillar zone Evaluate the rationality of the positional arrangement of the goaf-adjacent roadway in the protected seam FIG. 1 Earth's surface Protective seam L1 Protected seam FIG. 2 20 25 20 43 29 11 J un 2 02 5 2 0 2 5 2 0 4 3 2 9 1 1 J u n 2 0 2 5 C a l c u l a t e t h e r a n g e x o f t h e u l t i m a t e s t r e s s e q u i l i b r i u m z o n e i n t h e l a t e r a l c o a l m a s s o f a g o a f s t r e s s - r e d u c t i o n z o n e t o t h e e d g e o f t h e c o a l p i l l a r C a l c u l a t e t h e s t r e s s p e a k p o i n t L i n t h e C a l c u l a t e t h e d i s t a n c e L f r o m t h e s t r e s s p e a k o f t h e p r o t e c t i v e s e a m p r o t e c t i v e s e a m t o t h e e d g e o f t h e g o a f c o a l a n d r o c k m a s s b e n e a t h t h e p r o t e c t i v e s e a m t o t h e s t r e s s L L 1 P r o t e c t e d s e a m F I G . 2

Description

TECHNICAL FIELD The present disclosure relates to the technical field of safe mining of coal mines, in particular to a method for arranging a goaf-adjacent roadway in a working face of a protected seam under continuous mining. BACKGROUND Rock burst is a typical dynamic phenomenon in mines with significant hazards. This dynamic phenomenon instantaneously releases a large amount of elastic deformation energy accumulated in the coal and rock mass in an abrupt and violent manner, causing destruction to the coal and rock mass and producing intense vibrations. The dynamic force propels broken coal and rock into the excavation space of underground roadways, accompanied by loud noises, leading to equipment damage, underground roadway destruction, and casualties. The traditional method for mining non-continuous single working faces of a protective seam requires leaving coal pillars of considerable width between the working faces of the protected seam to ensure that the working faces of the protected seam remain within the effective protection range of the protective seam. However, this arrangement method conflicts with the arrangement method suitable for coal seams prone to rock bursts, which suggests arranging narrow coal pillars. That is, when narrow coal pillars are left in the working faces of the protected seam to achieve continuous mining, the risk of rock burst disasters is relatively low. For multi-seam mining, the upper protective seam is mined first, causing the coal seams below, located within the effective pressure relief range, to be in a protected state, which can effectively reduce the burst hazards in the subsequently mined lower coal seams. At present, substantial research has been conducted on the pressure relief effect after mining the upper protective seam, but relatively little research has been carried out on the goaf-adjacent roadways of the protected seam during continuous mining, which fails to meet the needs of safe mining of coal mines. SUMMARY The objective of the present disclosure is to provide a method for arranging a goaf-adjacent roadway in a working face of a protected seam under continuous mining. According to the method, the reasonable position for the arrangement of the goaf-adjacent roadway can be 2025204329   11 Jun 2025 determined, thereby reducing the burst hazards of the goaf-adjacent roadway and ensuring the safe mining of coal mines. To achieve the above objective, the present disclosure provides a method for arranging a goaf-adjacent roadway in a working face of a protected seam under continuous mining. The method includes the following steps: S1, calculating the range of an ultimate stress equilibrium zone in the lateral coal mass of a goaf, with the calculation formula as follows: = mA in rfcyH+Co / tan^ol %1    2tan^o    Co / tan o+Pz / A_|, where H represents the thickness of a coal seam, measured in meters (m); xr represents the width of an ultimate equilibrium zone, measured in meters (m); represents the mining height of the coal seam; <p0 represents the internal friction angle of the coal seam, reflecting the magnitude of the internal friction force between the particles within the coal and rock mass; represents the stress concentration factor of the coal mass; represents the average density of a rock stratum; Co represents the cohesion of the coal mass; Px represents the lateral constraint force of the goaf in a protected seam on a coal pillar; represents the scale factor; S2, calculating the horizontal distance x, from the boundary line of a stress-reduction zone to the edge of a coal pillar in a protective seam, with the calculation formula as follows: hf xf = —-J— sm a + L 0, f sin(a+5)           0 where x, represents the horizontal distance from the boundary line of the stress-reduction zone to the edge of the coal pillar, measured in meters (m); hf represents the depth of a roadway relative to the floor of the coal seam, measured in meters (m); represents the dip angle of the coal seam; 8 represents the stress transmission angle of the floor; L0 represents the length of the working face of the coal seam, measured in meters (m); S3, comparing magnitudes of x± and x, to determine whether the width of the ultimate equilibrium zone is entirely within the range of the stress-reduction zone, where when xx < X,, it indicates that the roadway is entirely arranged within the stress-reduction zone, and no burst hazards will occur; when x 1 > X,, it indicates that the roadway is not entirely arranged within the stress-reduction zone, and care should be taken to avoid arranging the roadway outside the range of the stress-reduction zone; S4, calculating the distance from a stress peak point of the coal pillar in the protective seam to 2025204329   11 Jun 2025 the edge position of the coal pillar, with the calculation formula as follows: mA 2     1   tan^0’ where m' represents the mining height of the protective seam; L2 represents the distance from the stress peak point of the coal pillar in the protective seam to the edge position of the coal pillar; Lt represents the width of a coal pillar zone in the protective seam, measured in meters (m); S5, calculating the periodic collapse step distance of an overlying surrounding rock in the protective seam, with the calculation formula as follows: L = \^ W J 3q ’ where LW represents the periodic collapse step distance of the overlying surrounding rock in the protective seam, measured in meters (m); represents the tensile strength of a roof rock stratum, measured in Pascals (Pa); ' H represents the height of the roof rock stratum, measured in meters (m); q represents the pressure exerted by an overlying rock stratum on the roof rock stratum, measured in Pascals (Pa); S6, calculating the distance from the stress peak point in a compaction zone of the goaf in the protective seam to the edge of the goaf, with the calculation formula as follows: L 3 = 2.5LW, where L3 represents the distance from the stress peak point in the compaction zone of the goaf in the protective seam to the edge of the goaf, measured in meters (m); S7, determining the distance from the stress trough point in the coal and rock mass beneath the protective seam to the stress peak position in the coal pillar zone, with the calculation formula as follows: ‘ = l3+l2 2 ’ where ' represents the distance from the stress trough point in the coal and rock mass beneath the protective seam to the stress peak position in the coal pillar zone, measured in meters (m); and S8, based on L2 obtained in S4, namely the distance from the stress peak point of the coal pillar 2025204329   11 Jun 2025 in the protective seam to the edge position of the coal pillar, and since the position of the coal pillar is fixed, determining the position of the stress peak point in the coal seam firstly; then, based on x' obtained in S7, namely the distance %' from the stress trough point in the coal and rock mass beneath the protective seam to the stress peak position in the coal pillar zone, determining an arrangement position for a goaf-adjacent roadway, where the arrangement position is the position of the stress trough pointfor arranging the goaf-adjacent roadway, namely the optimal arrangement position. Furthermore, the calculation formulas for Px and A in S1 are respectively as follows: Pe = K HC, where represents the ratio of the elastic modulus of the coal seam to the elastic modulus of the rock stratum; represents the thickness of the coal seam, measured in meters (m); represents the lateral constraint factor, reflecting the degree of constraint between the coal seam and the surrounding rock; = / (1 - ), where represents the Poisson’s ratio. According to the present disclosure, the pressure relief range and angle of the upper protective seam after mining are calculated, thereby determining the reasonable arrangement position of the goaf-adjacent roadway in the protected seam. Then, the vertical stress is calculated based on the goaf-adjacent roadway position to verify the rationality of the roadway arrangement position. This provides the theoretical guidance for determining whether adjustments to the arrangement position of the goaf-adjacent roadway in the protected seam are needed during subsequent continuous mining in the mine. The present disclosure ensures the safe mining of coal mines, holds significant practical importance and substantial social benefits for the continuous and safe production of protective seam mining in the mine, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a workflow diagram of a method according to the present disclosure; FIG. 2 is a schematic diagram of the continuous mining of a protective seam according to the present disclosure; and FIG. 3 is a schematic diagram of the stress distribution around a goaf-adjacent roadway 2025204329   11 Jun 2025 according to the present disclosure. DETAILED DESCRIPTION The present disclosure is further illustrated below with reference to the accompanying drawings. As shown in FIG. 1, a method for arranging a goaf-adjacent roadway in a working face of a protected seam under continuous mining includes the following steps. In S1, the range of the ultimate stress equilibrium zone in the lateral coal mass of a goaf is calculated, with the calculation formula as follows: = mA in FfeyH+Cp / tan pl 1   2tan^O    CO / tanpO+Px / A ’ In the formula, H represents the thickness of a coal seam, measured in meters (m); xx represents the width of an ultimate equilibrium zone, measured in meters (m); represents the mining height of the coal seam; <p0 represents the internal friction angle of the coal seam, reflecting the magnitude of the internal friction force between the particles within the coal and rock mass; represents the stress concentration factor of the coal mass; represents the average density of a rock stratum; Co represents the cohesion of the coal mass; Px represents the lateral constraint force of the goaf in a protected seam on a coal pillar; represents the scale factor. In S2, the horizontal distance Xf from the boundary line of a stress-reduction zone to the edge of a coal pillar in a protective seam is calculated, with the calculation formula as follows: hf xf = —sm a + L 0. f sin(a+3)           0 In the formula, Xf represents the horizontal distance from the boundary line of the stressreduction zone to the edge of the coal pillar, measured in meters (m); hf represents the depth of a roadway relative to the floor of the coal seam, measured in meters (m); represents the dip angle of the coal seam; 8 represents the stress transmission angle of the floor; Lr represents the length of the working face of the coal seam, measured in meters (m). In S3, the magnitudes of xa and Xf are compared to determine whether the width of the ultimate equilibrium zone is entirely within the range of the stress-reduction zone; when xr < Xf, it indicates that the roadway is entirely arranged within the stress-reduction zone, and no burst hazards will occur; when xr> Xf, it indicates that the roadway is not entirely arranged within the stress-reduction zone, and care should be taken to avoid arranging the roadway outside the range of the stress-reduction zone. 2025204329   11 Jun 2025 In S4, as shown in FIGS. 2 and 3, the distance from the stress peak point of the coal pillar in the protective seam to the edge position of the coal pillar is calculated, with the calculation formula as follows: mA 2     1 tan^0’ In the formula, m' represents the mining height of the protective seam; L2 represents the distance from the stress peak point of the coal pillar in the protective seam to the edge position of the coal pillar; Lr represents the width of a coal pillar zone in the protective seam, measured in meters (m). In S5, the periodic collapse step distance of the overlying surrounding rock in the protective seam is calculated, with the calculation formula as follows: L = \^ W J 3q ’ In the formula, LW represents the periodic collapse step distance of the overlying surrounding rock in the protective seam, measured in meters (m); represents the tensile strength of a roof rock stratum, measured in Pascals (Pa); H' represents the height of the roof rock stratum, measured in m; q represents the pressure exerted by an overlying rock stratum on the roof rock stratum, measured in Pascals (Pa). In S6, the distance from the stress peak point in a compaction zone of the goaf in the protective seam to the edge of the goaf is calculated, with the calculation formula as follows: L 3 = 2.5LW. In the formula, L3 represents the distance from the stress peak point in the compaction zone of the goaf in the protective seam to the edge of the goaf, measured in meters (m). In S7, the distance from the stress trough point in the coal and rock mass beneath the protective seam to the stress peak position in the coal pillar zone is determined, with a calculation formula as follows: X ‘ = L3+L2. 2 In the formula, ' represents the distance from the stress trough point in the coal and rock mass beneath the protective seam to the stress peak position in the coal pillar zone, measured in meters (m). 2025204329   11 Jun 2025 In S8, based on L2 obtained in S4, namely the distance from the stress peak point of the coal pillar in the protective seam to the edge position of the coal pillar, and since the position of the coal pillar is fixed, the position of the stress peak point in the coal seam is determined firstly; then, based on x' obtained in S7, namely the distance x' from the stress trough point in the coal and rock mass beneath the protective seam to the stress peak position in the coal pillar zone, an arrangement position is determined for a goaf-adjacent roadway. The arrangement position is the position of the stress trough point for arranging the goaf-adjacent roadway, namely the optimal arrangement position. Furthermore, the calculation formulas for Px and A are respectively as follows: Px = K HC. In the formula, represents the ratio of the elastic modulus of the coal seam to the elastic modulus of the rock stratum; represents the thickness of the coal seam, measured in meters (m); represents the lateral constraint factor, reflecting the degree of constraint between the coal seam and the surrounding rock. = / (1 - ). In the formula, represents the Poisson’s ratio. A protective seam mining mine once experienced rock burst phenomena in the goaf-adjacent roadway. There are potential burst hazards at the position of the mine’s goaf-adjacent roadway in the protected seam. The steps of the calculation method for determining the position of the goaf-adjacent roadway are as follows. (1) The mining height of the coal seam is 10 m, the Poisson’s ratio is 0.5, the internal friction angle is 20°, the stress concentration factor is 2, the average density of the rock stratum is 2.5 t / m3, the burial depth is 1200 m, the cohesion is 2 MPa, and the lateral constraint force is 0. The width of the ultimate equilibrium zone can be calculated as:  x1 = mA 2 tan ^o ln FfcyH+Co / tan^ol = Co / tan^o+Px / A 10 i Z2x2.5xl200+2 / tan20°' 2xtan20° k 2 / tan 20°      , = 22.75 . (2) The depth from the goaf to the floor of the coal seam is 10 m, the dip angle of the coal seam is 15°, the vertical stress transmission angle of the coal seam floor is 20°, and the minimum distance of the stress-reduction zone from the edge of the coal pillar can be calculated as: x^0 = . sin a + Lo = .10 osin 15° + 10 = 14.51 m. sin(a+3)           0 sin 35° (3) Since the calculated x1 is smaller than x^0, the mine’s ultimate equilibrium zone is not 2025204329   11 Jun 2025 entirely located within the range of the stress-reduction zone. It is necessary to locate the stress trough point to arrange the roadway, avoiding arranging the roadway outside the range of the stress-reduction zone. (4) The mining height of the working face of the protected seam is 4 m, the Poisson’s ratio is 0.5, the internal friction angle is 20°, and the width of the rock pillar zone is 5 m. The position of the stress peak point beneath the coal-rock pillar of the protective seam is determined as: m'A -:---- tan ^o = Lr — — = 2.5 m. 1    2 (5) The tensile strength of the roof rock stratum is 8.1 MPa, the height of the roof rock stratum is 20 m, and the pressure exerted by the overlying rock stratum on the roof rock stratum is 10 MPa. The periodic collapse step distance is calculated as: LW I °H2   z =^-=6 m. (6) With a periodic collapse step distance of 6 m, the distance from the stress peak point of the goaf in the protective seam to the edge of the goaf is calculated as: L3 = 2.5LW = 15 m. (7) The calculation formula for the position of the stress trough point in the coal and rock mass beneath the protective seam is: x‘ =      = 8.25m. (8) By arranging the goaf-adjacent roadway of the protected seam during continuous mining in this mine at a position 8.25 m from the edge of the coal pillar, the calculated stress is minimized, thereby minimizing the likelihood of rock burst events. The optimized roadway layout is reasonable.

Claims

1. A method for arranging a goaf-adjacent roadway in a working face of a protected seam under continuous mining, comprising the following steps:S1, calculating a range of an ultimate stress equilibrium zone in lateral coal mass of a goaf, with a calculation formula as follows:= mA in rfcyH+Co / tan^ol %1   2tan^o    Co / tan^o+Px / AJ,wherein H represents a thickness of a coal seam, measured in meters (m); x-r represents a width of an ultimate equilibrium zone, measured in meters (m); represents a mining height of the coal seam; <p0 represents an internal friction angle of the coal seam, reflecting an magnitude of an internal friction force between particles within coal and rock mass; represents a stress concentration factor of the coal mass; y represents an average density of a rock stratum; Co represents a cohesion of the coal mass; Px represents a lateral constraint force of the goaf in a protected seam on a coal pillar; represents a scale factor;S2, calculating a horizontal distance Xf from a boundary line of a stress-reduction zone to an edge of a coal pillar in a protective seam, with a calculation formula as follows:hfxf = —sin a + L0, f sin(a+5)           0wherein Xf represents the horizontal distance from the boundary line of the stress-reduction zone to the edge of the coal pillar, measured in meters (m); hf represents a depth of a roadway relative to a floor of the coal seam, measured in meters (m); represents a dip angle of the coal seam; 8 represents a stress transmission angle of the floor; L0 represents a length of a working face of the coal seam, measured in meters (m);S3, comparing magnitudes of xr and Xf to determine whether the width of the ultimate equilibrium zone is entirely within a range of the stress-reduction zone, wherein when xr< Xf, it indicates that the roadway is entirely arranged within the stress-reduction zone, and no burst hazards will occur; when xr> Xf, it indicates that the roadway is not entirely arranged within the stress-reduction zone, and care should be taken to avoid arranging the roadway outside the range of the stress-reduction zone;S4, calculating a distance from a stress peak point of the coal pillar in the protective seam to an edge position of the coal pillar, with a calculation formula as follows:2025204329   11 Jun 2025wherein m' represents a mining height of the protective seam; L2 represents the distance from the stress peak point of the coal pillar in the protective seam to the edge position of the coal pillar; Lr represents a width of a coal pillar zone in the protective seam, measured in meters (m);S5, calculating a periodic collapse step distance of an overlying surrounding rock in the protective seam, with a calculation formula as follows:L = \^ W J 3q ’wherein Lw represents the periodic collapse step distance of the overlying surrounding rock in the protective seam, measured in meters (m); represents a tensile strength of a roof rock stratum, measured in Pascals (Pa); ' represents a height of the roof rock stratum, measured in meters (m); represents a pressure exerted by an overlying rock stratum on the roof rock stratum, measured in Pascals (Pa);S6, calculating a distance from a stress peak point in a compaction zone of the goaf in the protective seam to an edge of the goaf, with a calculation formula as follows:L 3 = 2.5LW,wherein L3 represents the distance from the stress peak point in the compaction zone of the goaf in the protective seam to the edge of the goaf, measured in meters (m);S7, determining a distance from a stress trough point in coal and rock mass beneath the protective seam to a stress peak position in the coal pillar zone, with a calculation formula as follows:‘ = l3+l2 2 ’wherein ' represents the distance from the stress trough point in the coal and rock mass beneath the protective seam to the stress peak position in the coal pillar zone, measured in meters (m); andS8, based on L2 obtained in S4, namely the distance from the stress peak point of the coal pillar in the protective seam to the edge position of the coal pillar, and since a position of the coal pillar is fixed, determining a position of the stress peak point in the coal seam firstly; then, based on ' obtained in S7, namely the distance ' from the stress trough point in the coal and rock mass beneath the protective seam to the stress peak position in the coal pillar zone,2025204329   11 Jun 2025determining an arrangement position for a goaf-adjacent roadway, wherein the arrangement position is a position of a stress trough point for arranging the goaf-adjacent roadway, namely an optimal arrangement position.

2. The method for arranging a goaf-adjacent roadway in a working face of a protected seam under continuous mining according to claim 1, wherein calculation formulas for Px and A in S1 are respectively as follows:Pe = K HC,wherein represents a ratio of an elastic modulus of the coal seam to an elastic modulus of the rock stratum; represents the thickness of the coal seam, measured in meters (m); represents a lateral constraint factor, reflecting a degree of constraint between the coal seam and a surrounding rock; and= / (1 - ),wherein represents a Poisson’s ratio.

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