A method for controlled blasting, slotting, roof caving, and dam construction in high-level roadways during longwall retreat mining of thick to extra-thick coal seams.

Abstract

A method for controlled blasting and roof caving in high-level roadways during longwall retreat mining of thick to extra-thick coal seams involves excavating a high-level roadway for controlled blasting and roof caving within the high-level roof of the coal seam. Before mining, deep holes are drilled within the high-level roadway, arranged in multiple rows along its length. Each row of holes is divided into multiple sections along the cross-sectional direction of the high-level roadway. After the protective supports are moved or before the start of coal release in thick to extra-thick coal seams, each row of deep holes is blasted in a single, large-area, micro-differential blasting operation according to its sections, controlling the blasting and roof caving to construct a roof dam within the goaf. This invention determines the construction location of the high-level roadway, the method for designing the depth of the boreholes above the roadway, the method for determining the width of the roof dam, and the distance between two roof dams.

Description

Technical Field

[0001] This invention belongs to the field of mining technology, and specifically relates to a method for controlled blasting, slotting, roof caving, and dam construction in high-level roadways using the longwall retreat method for mining thick to extra-thick coal seams. Background Technology

[0002] When there is hard, thick overburden in the upper roof, the failure to collapse in time or the large-scale unsupported goaf after collapse will inevitably induce roof rockburst or mine tremors caused by the sudden fracture of the hard, thick overburden. For thin to medium-thick coal seams of 3.49m and below, based on the theory of roof cutting and pressure relief, controlled blasting is used to cut the roof and dam it in the goaf 5-15m away from the goaf roadway. This cuts off the roof and loosens the rock dam to support the roof, thereby releasing or transferring the ground pressure. This method has been successfully used to control the ground pressure and uneven surface subsidence in the goaf roadway of Jixi Mining Group. For thick to extra-thick coal seams of 3.5m and above, controlled blasting is carried out by drilling multiple rows of medium-deep or deep holes in the goaf and between the shield supports or roof caving supports. This is not only very unsafe and inconvenient, but also causes serious interference between the charging line and the coal mining movement. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for controlled blasting and slotting roof caving and dam construction in high-level roadways of longwall retreat mining of thick to extra-thick coal seams, so as to determine the construction position of the high-level roadway overlying the coal seam for controlled blasting and slotting roof caving construction, and to realize the design of the depth of the borehole in the upper part of the roadway, the design of the width of the roof dam construction, and the design of the distance between the two roof dam constructions.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for controlled blasting and roof caving in high-level roadways during longwall retreat mining of thick to extra-thick coal seams involves excavating a high-level roadway for controlled blasting and roof caving in the high-level roof of the coal seam. Before mining, deep holes are drilled in the high-level roadway, and multiple rows of blast holes are set along the length of the high-level roadway. Each row of blast holes is divided into multiple sections along the cross-sectional direction of the high-level roadway. After the shield support is moved or before the start of coal release in thick to extra-thick coal seams, each row of blast holes is blasted in a single large-area micro-differential blast according to the sections to control the blasting and roof caving, thereby piling up a roof dam in the goaf.

[0006] Furthermore, along the length of the elevated roadway, 2 to 10 rows of blast holes are blasted in one go; along the cross-sectional direction of the elevated roadway, each row of blast holes has 15 deep holes in 7 sections. Section 1 has 2 deep holes, perpendicular to the floor of the elevated roadway and located below the floor, with a spacing of no more than 0.5m; Section 2 has 2 deep holes symmetrically located outside and parallel to Section 1, at a distance of 1m from Section 1; Section 3 has 2 deep holes... Drill holes downwards at -75° along the bottom of the elevated roadway; drill two deep holes at -60° along the bottom of the elevated roadway in section 4; drill two deep holes at -45° on the sidewall in section 5; drill two deep holes horizontally on the sidewall above the two deep holes in section 5; drill three deep holes in section 7, with the middle deep hole perpendicular to the top of the elevated roadway and located above the top of the elevated roadway, and the two deep holes on both sides diagonally upwards along the top corner of the elevated roadway.

[0007] Furthermore, the height of the elevated roadway from the goaf roof is determined based on H = coal seam thickness / (k-1), where the loosening coefficient k is taken as 1.4. To ensure that the blast holes do not penetrate the goaf roof, the vertical depth of the deep holes in sections 1 to 4 from the floor of the elevated roadway is 3 to 5 meters shorter than H. Then, the drilling depth design formula is based on the roof cutting and pressure relief theory.

[0008]

[0009] Determine the depth L of the 7 sections and 3 deep holes, where z is the acoustic impedance of the rock, and r e S is the borehole radius. t Where N is the tensile strength of the rock, and N is the height of the elevated tunnel.

[0010] Furthermore, based on D=2L'+B=2Hctg60+B, the width D of the dam to be built at the top and the horizontal depth L'=2Hctg60 of the deep holes for the blasting of the 5th and 6th sections from the sidewall of the high-level roadway are determined. Then, based on the lithology, direct drilling and field tests, the row spacing of each row of blast holes along the length of the roadway is determined.

[0011] Furthermore, the inclined spacing A between two adjacent top-mounted dams is 100-200m, where the closer the coal seam is to horizontal, the closer the spacing between the two top-mounted dams is to the lower limit; the closer the coal seam dip angle is to 30°, the closer the inclined spacing between the two top-mounted dams is to the upper limit.

[0012] Furthermore, for thin and medium-thick coal seams with a burial depth of less than 300m and a coal seam thickness close to or less than 3.49m, and extra-thick coal seams with a burial depth of less than 600m and a coal seam thickness greater than 8m, after controlled blasting, slotting, roof caving, and dam construction to eliminate rockburst and mine vibration, it is necessary to supplement the goaf area to prevent uneven surface subsidence.

[0013] Furthermore, for thin and medium-thick coal seams with a burial depth greater than 300m and a coal seam thickness close to or less than 3.49m, to extra-thick coal seams with a burial depth greater than 600m and a coal seam thickness greater than 8m, after controlling blasting, cutting grooves, releasing the top, connecting the top, and building dams to eliminate rockburst and mine vibration, it is basically unnecessary to supplement the goaf to prevent uneven surface subsidence.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] 1) After the roof collapse induced by the slotting method (110 method), the collapsed material is not easy to pile into a complete rockfill dam that reaches the roof, and the self-stabilizing ability of the rockfill dam is very poor. It must rely on the strong support of the supports in the roadway along the goaf. Even so, when the coal seam is buried at a depth of more than 600m, the non-coal ore body is buried at a depth of more than 900m, or the coal seam thickness is more than 3.5m, the slotting method (110 method) basically fails to control the ground pressure in the roadway (along the goaf), nor can it eliminate rockburst and mine tremor, let alone prevent uneven surface subsidence disasters.

[0016] This invention relies on a controlled blasting and roof cutting dam construction system with strict design requirements for dam width, location of the roof cutting construction roadway, and drilling depth. The blasted loose rock can be piled into a self-stabilizing roof dam. Not only does the blasting and roof cutting release a certain amount of ground pressure, but the self-stabilizing loose rock dam can also transfer residual ground pressure to the floor. Moreover, the blasted loose rock dam acts like a spring installed under the roof of the goaf, and with proper arrangement, it can prevent uneven settlement of the roof and the ground surface.

[0017] 2) Although existing literature describes the use of multiple rows of blast holes directly drilled under the suspended roof in goaf mining of thin to medium-thick coal seams (ore bodies) of 3.49m and below, and controlled blasting and jacking to allow the blasted loose rocks to be directly piled up in situ to form a loose rock dam of a certain width to support the roof, thus releasing and successfully transferring the roof pressure, drilling under the suspended roof in goaf mining of thick coal seams (ore bodies), especially in goaf mining of coal seams of 3.5m and above or extra-thick coal seams or non-coal ore bodies of 10m and above, is not only unsafe but also very inconvenient. The high-level roadway controlled blasting and jacking method for mining thick to extra-thick coal seams using the longwall retreat method of this invention can overcome the above problems. Attached Figure Description

[0018] Figure 1 This is a projection view of the goaf floor of the present invention, and also... Figure 2 View I-I in the middle.

[0019] Figure 2 This is a longitudinal projection view of the present invention, and also... Figure 1 View II-II in the middle.

[0020] Figure 3 This is an enlarged view of the borehole layout and detonation sections for controlled blasting in high-level roadways according to the present invention. Figure 2 View III-III in the middle. Detailed Implementation

[0021] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0022] After longwall retreat mining in horizontal to gently inclined coal mines, large areas of continuous goaf are formed. When there is hard, thick overburden in the upper roof, the failure to collapse in time or the large area of ​​unsupported goaf after collapse will inevitably induce roof rockburst or mine tremors caused by the sudden fracture of the hard, thick overburden. For thin and medium-thick coal seams of 3.49m and below, controlled blasting and caving can be carried out directly in the goaf 5-15m away from the goaf roadway to cut the roof and build a dam. This cuts off the roof and loosens the rock dam to support the roof, thereby releasing or transferring the ground pressure and successfully controlling the ground pressure and uneven surface subsidence in the goaf roadway. For coal seams of 3.5m and above, and even extra-thick coal seams, multiple rows of medium-deep or deep holes are drilled in the goaf and between the shield supports or roof caving supports to carry out controlled blasting and caving. This is not only very unsafe and inconvenient, but also causes serious interference between the charging line and the coal movement.

[0023] Therefore, this invention provides a method for controlled blasting, slotting, roof caving, and dam construction in high-level roadways using the longwall retreat method for mining thick to extra-thick coal seams. It determines the construction location of the high-level roadway, the method for designing the depth of the boreholes in the upper part of the roadway, the method for determining the width of the roof dam, and the distance between the two roof dams.

[0024] Specifically, such as Figure 1 , Figure 2 and Figure 3 In the high-level roof of coal seam 1, a high-level roadway 3 was excavated using controlled blasting and roof caving. Clearly, high-level roadway 3 is parallel to the strike of the longwall retreat mining area. Before mining, the high-level roadway 3 was constructed according to... Figure 3 Deep blasting holes 5 are drilled, that is, multiple rows of deep holes 5 are arranged along the length of the high-level roadway 3; and each row of deep holes 5 is divided into multiple sections along the cross-sectional direction of the high-level roadway 3.

[0025] After the protective support 6 is moved or before the coal release begins in thick to extra-thick coal seams, according to Figure 3 In the middle section, a single large-area micro-differential blasting is performed on each row of deep holes 5, controlling the blasting groove and roof release, thereby achieving the desired effect within the goaf 4 according to... Figure 1 and Figure 2 2. Piling up to form a dam with the top piled up.

[0026] In this invention, a coal seam 1 with a thickness of 3.5 to 7.99 m is defined as a thick coal seam, and a thickness of 8 m or more is defined as an extra-thick coal seam.

[0027] In this invention, the high-level roof of coal seam 1 refers to the roof rock layer located above coal seam 1 and relatively far from coal seam 1.

[0028] In this invention, large-area micro-delay blasting refers to the detonation of blast holes distributed 360° along the roadway cross-section in a micro-delay sequence according to each section, with 2 to 10 rows of 360° distributed blast holes detonated each time along the length of the roadway. Depending on the need for blasting vibration reduction, a delay of 10 to 25 microseconds can be implemented for every 2 to 5 rows.

[0029] In an embodiment of the present invention, 2 to 10 rows of blast holes are arranged along the length of the elevated roadway 3, and each row of blast holes is as follows: Figure 3 Along the cross-sectional direction, each row of deep holes 5 has 15 deep holes 5 in 1 to 7 sections.

[0030] More specifically, 1 section with 2 deep holes, i.e. Figure 3 The two No. 1 holes are perpendicular to the bottom plate of the elevated roadway 3 and located below the bottom plate of the elevated roadway 3, with a general spacing of no more than 0.5m; the two deep holes No. 5 in the two sections are... Figure 3 The two #2 holes are symmetrically located outside the two deep holes 5 in section 1, parallel to the two deep holes 5 in section 1, and generally 1m away from the two deep holes 5 in section 1; the two deep holes 5 in section 3 are... Figure 3 Two boreholes, number 3, were constructed downwards at a -75° angle from the bottom of the elevated roadway 3; two deep boreholes, number 5, were constructed in section 4. Figure 3 Two boreholes, number 4, were constructed downwards at a -60° angle along the bottom of the elevated roadway 3; two deep boreholes, number 5, were constructed in section 5. Figure 3 Two holes #5 were drilled downwards at a -45° angle into the wall; two deep holes #5 were drilled in section 6. Figure 3 Two holes #6 were drilled horizontally on the wall above the two deep holes #5 in section 5; the three deep holes #5 in section 7 were... Figure 3 Of the three No. 7 holes, the middle one deep hole 5 is perpendicular to the top plate of the high-level tunnel 3 and located above the top plate of the high-level tunnel 3, while the two deep holes 5 on both sides are constructed obliquely upward along the top corner of the high-level tunnel 3.

[0031] It is worth noting that in this invention: once the location of the high-level roadway 3 is determined, the depth design of the 1 to 7 deep holes 5 on the cross-section and the row spacing design of each row of blast holes along the length of the roadway can be designed accordingly based on the lithology, blast hole diameter and actual experience; if the row spacing is greater than 1 to 1.5m, in order to ensure the grooving effect of the 1 deep hole 5, it is necessary to add 1 to 2 rows of 1 deep holes 5 between the 2 rows of blast holes.

[0032] In this invention, the height of the high-level roadway 3 from the roof of the goaf 4 is determined according to H = coal seam thickness / (k-1), where the loosening coefficient k is taken as 1.4; in order to ensure that the deep hole 5 does not penetrate the roof of the goaf 4, the vertical depth of the deep holes 5 in sections 1 to 4 from the bottom of the high-level roadway 3 is 3 to 5m shorter than the above, so as to prevent blasting.

[0033] Then, the drilling depth design formula is based on the top-cutting and pressure-relief theory:

[0034]

[0035] Determine the depth L of the 7 sections and 3 deep holes 5, where z is the acoustic impedance of the rock, r e S is the borehole radius. t N represents the tensile strength of the rock, and N is the height of the high-level tunnel 3.

[0036] If H < 20-25m, it cannot be guaranteed that the safety of charging and detonating explosives in the high-level roadway 3 above the goaf can be ensured. H can be increased or the roof can be blasted in advance before coal mining. As the coal mining progresses, the blasted material will naturally collapse and pile up to form a dam.

[0037] In the implementation of this invention, the width D of the top-mounted dam 2 and the horizontal depth L' = 2Hctg60 of the deep hole 5 for the 5th and 6th blasting sections from the sidewall of the high-level roadway 3 are determined according to D = 2L' + B = 2Hctg60 + B.

[0038] In the implementation of this invention, the inclined spacing A between two adjacent top-mounted dams 2 is 100-200m. The closer the coal seam is to horizontal, the closer the spacing between the two top-mounted dams 2 is to the lower limit; the closer the dip angle of the coal seam is to 30°, the closer the inclined spacing between the two top-mounted dams 2 is to the upper limit. The specific spacing can be determined based on mechanical analysis or settlement observation.

[0039] This invention Figure 1 If the coal seam is 10.5m thick, dip angle is less than 10° and overlying strata are 600-1000m thick, it is recommended that the top-mounted dam 2 be about 30m wide, the distance between the top-mounted dam 2 and the upper coal pillar be about 20m, the distance between the small coal pillar in the goaf roadway be about 10m, and the inclination distance between the two top-mounted dams 2 be about 80-120m.

[0040] This invention Figure 2 If the coal seam is 10.5m thick, dip angle is less than 10° and overlying strata are 600-1000m thick, the height H of the high-level roadway 3 from the roof of the goaf 4 is about 28m, and the height N of the high-level roadway 3 is about 3.3m and the width B is about 3.5m.

[0041] In embodiments of the present invention, for thin to medium-thick coal seams with a burial depth of less than 300m and a coal seam thickness close to or less than 3.49m, to extra-thick coal seams with a burial depth of less than 600m and a coal seam thickness greater than 8m, after controlled blasting, cutting, roof excavation, and dam construction to eliminate rockburst and mine seismic activity, auxiliary filling of the goaf is generally not required to prevent uneven surface subsidence. For thin to medium-thick coal seams with a burial depth greater than 300m and a coal seam thickness close to or less than 3.49m, to extra-thick coal seams with a burial depth greater than 600m and a coal seam thickness greater than 8m, after controlled blasting, cutting, roof excavation, and dam construction to eliminate rockburst and mine seismic activity, auxiliary filling of the goaf is generally not required to prevent uneven surface subsidence. Whether or not goaf filling is required can be determined based on mechanical analysis or settlement observation.

[0042] In an embodiment of the present invention, along the length of the tunnel, 2 to 10 rows of 1 to 7 deep holes 5 distributed along the 360° cross-section of the tunnel are detonated simultaneously each time; by means of the downward blasting of the first section of dense deep holes 5 along the cross-section of the tunnel, the 2nd, 3rd, 4th, 5th and 6th deep holes 5 are detonated symmetrically and thrown symmetrically, thereby building a dam on the spot; then by means of the blasting of the 7 deep holes 5 in the roof, a roof-connecting dam is formed in a timely and strict manner, that is, a roof-connecting dam 2 controlled by the blasting and cutting of the groove.

Claims

1. A method for controlled blasting and caving roof caving in high-level roadways of longwall retreat mining of thick to extra-thick coal seams, wherein a high-level roadway (3) for controlled blasting and caving roof caving is excavated in the high-level roof of the coal seam (1), and deep holes (5) are drilled in the high-level roadway (3) before coal mining, and multiple rows of deep holes (5) are arranged along the length of the high-level roadway (3); multiple sections are set in each row of deep holes (5) along the cross-sectional direction of the high-level roadway (3); after the shield support (6) is moved or before the start of coal mining of thick to extra-thick coal seams, each row of deep holes (5) is blasted in a large area at one time according to the sections, and controlled blasting and caving roof caving are carried out, thereby piling up a roof dam (2) in the goaf (4). in, Along the length of the elevated roadway (3), 2 to 10 rows of blast holes are blasted at once; along the cross-sectional direction of the elevated roadway (3), each row of blast holes is equipped with 15 deep holes (5) in 7 sections. Among them, the first section has 2 deep holes (5), which are perpendicular to the bottom plate of the elevated roadway (3) and located below the bottom plate of the elevated roadway (3), with a spacing of no more than 0.5m; the second section has 2 deep holes (5), which are symmetrically located outside the first section of 2 deep holes (5), parallel to the first section of 2 deep holes (5), and 1m away from the first section of 2 deep holes (5); the third section has 2 deep holes (5), which are 1m apart from the first section of 2 deep holes (5) along the elevated roadway (3). Drill holes at -75° downwards at the bottom of the tunnel (3); drill two deep holes (5) at -60° downwards along the bottom of the high-level tunnel (3); drill two deep holes (5) at -45° downwards on the sidewall; drill two deep holes (5) at the bottom of the sidewall above the two deep holes (5) in the 6th section; drill three deep holes (5) in the 7th section, with the middle one deep hole (5) perpendicular to the top plate of the high-level tunnel (3) and located above the top plate of the high-level tunnel (3), and the two deep holes (5) on both sides diagonally upwards along the top corner of the high-level tunnel (3); in accordance with H = Coal seam thickness / ( k -1) Determine the height of the high-level roadway (3) from the roof of the goaf (4), where the loosening coefficient is... k Take 1.4; In order to ensure that the deep hole (5) does not penetrate the roof of the goaf (4), the vertical depth of the deep holes (5) in sections 1 to 4 from the floor of the high-level roadway (3) is relatively large. H Shorten by 3-5m; then design the drilling depth based on the top-cutting and pressure-relief theory. Determine the depth of 7 segments and 3 deep holes (5) L In the formula, z For rock acoustic impedance, The radius of the borehole is... For the tensile strength of rock, N The height of the high-level tunnel (3); in accordance with Determine the width of the dam (2) constructed by the top of the dam. D The horizontal depth of the deep hole (5) at which the blasting begins in sections 5 and 6 from the sidewall of the high-level roadway (3). Then, based on the lithology, direct drilling data, and field tests, the spacing between each row of blast holes along the length of the roadway is determined. B The width of the high-level tunnel (3).

2. The high-level roadway controlled blasting, slotting, roof caving, and dam construction method for longwall retreat mining of thick to extra-thick coal seams according to claim 1, characterized in that, Inclined spacing between two adjacent top-supported dams (2) A The distance is 100~200m. The closer the coal seam is to the horizontal, the closer the distance between the two top-mounted dams (2) is to the lower limit; the closer the dip angle of the coal seam is to 30°, the closer the inclined distance between the two top-mounted dams (2) is to the upper limit.

3. The high-level roadway controlled blasting, slotting, roof caving, and dam construction method for longwall retreat mining of thick to extra-thick coal seams according to claim 1, characterized in that... For thin and medium-thick coal seams with a burial depth of less than 300m and a coal seam thickness close to or less than 3.49m, and extra-thick coal seams with a burial depth of less than 600m and a coal seam thickness greater than 8m, after controlled blasting, slotting, roof caving, and dam construction to eliminate rockburst and mine vibration, auxiliary filling of the goaf area is required to prevent uneven surface subsidence.

4. The method for controlled blasting, slotting, roof caving, and dam construction in high-level roadways using the longwall retreat mining method for thick to extra-thick coal seams according to claim 1, characterized in that... For thin and medium-thick coal seams with a burial depth greater than 300m and a coal seam thickness close to or less than 3.49m, to extra-thick coal seams with a burial depth greater than 600m and a coal seam thickness greater than 8m, after controlled blasting, slotting, roof caving, and dam construction to eliminate rockburst and mine vibration, no auxiliary filling of the goaf is required.

Images