CN117948143A - Roof fracturing method for coal mine working face in initial mining stage - Google Patents
Roof fracturing method for coal mine working face in initial mining stage Download PDFInfo
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Abstract
The invention discloses a method for fracturing a roof of a coal mine working face in an initial mining stage, and relates to the technical field of coal mining. The method for fracturing the roof of the coal mine working face in the initial mining stage comprises the following steps of: s1: determining the position of a key layer to be fractured above the coal seam; s2: determining the vertical height of the key layer; s3: determining the vertical height of the top end and the bottom end of the fracturing line from the coal seam; s4: determining the breaking step distance of the rock stratum, wherein the midpoint of the breaking step distance is positioned in the range of horizontal projection of the fracturing line on the working surface; s5: determining the drilling angle and depth of a fracturing line; s6: and determining the breaking time according to the vertical height of the top end of the fracturing line from the coal seam, the vertical height of the bottom end of the fracturing line from the coal seam and the advancing speed of the working face. The method for fracturing the roof of the coal mine working face in the initial mining stage can clearly determine the fracturing position of the key layer and the fracturing time of the key layer, improves the fracturing efficiency of the roof of the coal mine working face in the initial mining stage, and further ensures the safety of underground mining.
Description
Technical Field
The invention relates to the technical field of coal mining, in particular to a method for fracturing a roof of a coal mine working face in an initial mining stage.
Background
In the initial mining stage of the coal mine working face, roof deep hole blasting or hydraulic fracturing technology is adopted to treat the overburden layer of the coal seam, so that the initial collapse of the overburden layer is effectively promoted, and safe production is ensured, wherein the design of the technical parameters related to roof fracturing is a key factor for determining the pressure relief effect.
In the related technology, the design of the related technical parameters of roof fracturing in the initial mining stage of the working face mostly adopts engineering analogy method, namely, depending on the experience of technicians, a pressure relief scheme in the initial mining stage of a certain A mine working face is directly moved to a certain B mine working face to be implemented in the initial mining stage, or the roof of an overlying hard thick layer is directly presplit, a certain blindness exists for the layer fracturing range, the roof fracturing work is often finished, but the position of the working face to be advanced cannot be determined, the overlying hard and difficult-to-collapse rock stratum is broken, and then a large-area roof overhang behind the working face is caused.
The situation directly causes that the roof fracturing technology has poor fracture control effect on the hard and difficult-to-collapse rock stratum covered on the working face in the initial mining stage, so that underground mine pressure is seriously developed, particularly for rock burst mines, the fracture of the hard and difficult-to-collapse rock stratum covered on the working face in the initial mining stage directly influences underground anti-impact safety, and even part of mines are broken and collapsed for promoting the hard and difficult-to-collapse rock stratum covered on the working face, the working face cannot be temporarily stopped from stoping, and workers are arranged to enter the vicinity of the working face to repeatedly perform roof pre-fracturing construction, so that the operation risk is increased, and the cost is wasted.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the related art to some extent.
Therefore, the embodiment of the invention provides a method for fracturing the roof of the coal mine working face in the initial mining stage, which can determine the fracturing position of the key layer and the fracturing time of the key layer, improve the fracturing efficiency of the roof of the coal mine working face in the initial mining stage and further ensure the safety of underground mining.
The method for fracturing the roof of the coal mine working face in the initial mining stage comprises the following steps:
s1: determining the position of a key layer to be fractured above the coal seam;
s2: determining the vertical height of the key layer;
S3: determining the vertical height of the top end of the fracturing line from the coal seam and the vertical height of the bottom end of the fracturing line from the coal seam;
s4: determining a fracture step of a formation According to the breaking step/>Determining the position of the fracturing line and the breaking step/>The midpoint of (2) is located in the range of horizontal projection of the fracturing line on the working surface;
s5: determining the drilling angle and depth of the fracturing line according to the vertical height of the fracturing line and the horizontal projection position of the fracturing line on the working surface;
S6: and determining the breaking time according to the vertical height of the top end of the fracturing line from the coal seam, the vertical height of the bottom end of the fracturing line from the coal seam and the advancing speed of the working face.
The method for fracturing the roof of the coal mine working face in the initial mining stage can clearly determine the fracturing position of the key layer and the fracturing time of the key layer, improves the fracturing efficiency of the roof of the coal mine working face in the initial mining stage, and further ensures the safety of underground mining.
In some embodiments, in step S3, the stride is brokenThe calculation formula of (2) is as follows:
；
in the method, in the process of the invention, Is the thickness of a key layer above a coal layer,/>Is the ultimate tensile strength of a key layer above a coal layer,/>And uniformly distributing load to key layers above the coal seam.
In some embodiments, the step size is determined by the step sizeHeight from top of key layer/height from top of key layer of coal layerFor comparison, ifThe horizontal projection of the fracturing line on the working surface covers the non-production coal wall of the working surface from the cutting holeIs defined by the range of (2); if/>The horizontal projection of the fracturing line on the working surface covers the non-production coal wall/>, which is away from the cutting hole of the working surface, on the working surfaceIs a position of (c).
In some embodiments, ifHorizontal projection of one end of the fracturing line on the working surface and spacing/>, between the working surface and a cut-off non-production coal wallFor/>Horizontal projection of the other end of the fracturing line on the working surface and spacing/>, between the working surface and the cut-off non-production coal wallFor/>; If/>Horizontal projection of midpoint of fracturing line on working surface and spacing/>, between working surface and cut-off non-production coal wallFor/>。
In some embodiments, the break opportunity includes a time to start breaking and a time to end breaking, where the calculation formula of the time to start breaking is:
；
the calculation formula of the time for ending the breaking is as follows:
；
in the method, in the process of the invention, Is the vertical height of the bottom end of the fracturing line from the coal seam,/>Is the vertical height of the top end of the fracturing line from the coal seam,/>Is the working surface propelling speed.
In some embodiments, in step S2, the height of the top of the key layer from the coal seam, i.e., the vertical height of the top of the fracture line from the coal seam, and the height of the bottom of the key layer from the coal seam, i.e., the vertical height of the bottom of the fracture line from the coal seam.
In some embodiments, in step S2, the determined vertical height of the top end of the fracture line from the coal seam and the determined vertical height of the bottom end of the fracture line from the coal seam are checked to determine the vertical height of the fracture line.
In some embodiments, comparing the location of occurrence of the high-energy microseismic of the adjacent working face during initial mining with the determined location of the key layer, and if the location of occurrence of the high-energy microseismic of the adjacent working face during initial mining falls within the key layer on the coal seam, the key layer is accurate; if the positions of the adjacent working surfaces where the high-energy microseisms occur during the initial mining do not fall into the key layers on the coal seam, the key layers are required to be checked and confirmed.
In some embodiments, the location of a critical layer to be fractured above the coal seam is calculated according to formation critical layer theory.
In some embodiments, the boreholes are run in a direction perpendicular to the coal wall, and the borehole spacing is 2 times the fracture radius.
Drawings
FIG. 1 is a schematic flow chart of a method for fracturing a roof of a coal mine working face in an initial mining stage according to an embodiment of the invention.
Fig. 2 is a schematic diagram of the positions of the fracturing lines in the method for fracturing the roof of the coal mine working face in the initial mining stage according to the embodiment of the invention.
FIG. 3 is a schematic illustration of another location of a fracture line in a roof fracture method for a face of a coal mine at an initial stage of mining according to an embodiment of the present invention.
FIG. 4 is a schematic illustration of another location of a fracture line in a roof fracture method for a face of a coal mine at an initial stage of mining according to an embodiment of the present invention.
FIG. 5 is a schematic cross-sectional view of a borehole fracturing in a roof fracturing method of a face of a coal mine at an initial stage of mining according to an embodiment of the present invention.
Fig. 6 is a schematic plan view of a borehole fracturing in a method for fracturing a roof of a coal mine working face at an initial mining stage according to an embodiment of the present invention.
FIG. 7 is a schematic illustration of yet another cross-section of a borehole initiation in a method of roof initiation at a face of a coal mine in an initial mining stage according to an embodiment of the present invention.
Fig. 8 is a graph of monitoring microseismic frequency in a roof fracturing method of a coal mine working face at an initial mining stage according to an embodiment of the present invention.
Fig. 9 is a graph of monitoring microseismic energy in a roof fracturing method of a coal mine face at an initial mining stage according to an embodiment of the present invention.
FIG. 10 is a table showing the thrust of the face in the roof fracturing method of the face in the initial mining stage according to the embodiment of the present invention.
Reference numerals:
a coal seam 1; a key layer 2; a fracturing line 3.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
As shown in fig. 1 to 10, the method for fracturing the roof of the working face of the coal mine in the initial mining stage according to the embodiment of the invention comprises the following steps: s1: determining the position of a key layer 2 to be fractured above the coal seam 1; s2: determining the vertical height of the key layer 2; s3: determining the vertical height of the top end of the fracturing line 3 from the coal bed 1 and the vertical height of the bottom end of the fracturing line 3 from the coal bed 1; s4: determining a fracture step of a formationAccording to the breaking step/>Determining the position of the fracture line 3 and breaking step/>The midpoint of (2) is located within the range of the horizontal projection of the fracturing line 3 on the working surface; s5: determining the drilling angle and depth of the fracturing line 3 according to the vertical height of the fracturing line 3 and the horizontal projection position of the fracturing line 3 on the working surface; s6: and determining the breaking time according to the vertical height of the top end of the fracturing line 3 from the coal bed 1, the vertical height of the bottom end of the fracturing line 3 from the coal bed 1 and the pushing speed of the working surface.
According to the method for fracturing the top plate of the coal mine working face in the initial mining stage, the position of the key layer 2 is determined, the vertical height of the fracturing line 3 and the horizontal position of the fracturing line 3 on the working face are determined to determine the position and the fracturing depth of the fracturing line 3, the timely and effective collapse of the key layer 2 under the normal pushing of the working face is ensured by defining the fracturing time of the key layer 2, the overhanging behind the working face is eliminated, repeated top plate presplitting construction when personnel enter the vicinity of the working face is avoided, the top plate fracturing efficiency of the key layer 2 of the coal mine working face in the initial mining stage is improved, underground anti-impact safety is ensured, and underground mining safety is further ensured.
In some embodiments, in step S3, the stride is brokenThe calculation formula of (2) is as follows:
equation 1: ；
in the method, in the process of the invention, For the thickness of the key layer 2 above the coal layer 1, it can be obtained by drilling in the stope,/>The ultimate tensile strength of the key layer 2 above the coal layer 1 is obtained by laboratory testThe uniform load applied to the key layer 2 above the coal layer 1 can be calculated.
The numerical value of the breaking step distance is accurately calculated through the formula 1, a basis is provided for determining the horizontal position of the fracturing line 3, and the accuracy of the position of the fracturing line 3 is ensured.
In some embodiments, as shown in FIGS. 2, 3, and 4, the step size is determined for a breakHeight from top of key layer 2 from coal seam 1/>For comparison, if/>The horizontal projection of the fracturing line 3 on the working surface covers the non-production coal wall/>, which is away from the cutting hole of the working surface, on the working surfaceIs defined by the range of (2); if/>The horizontal projection of the fracturing line 3 on the working surface covers the non-production coal wall/>, which is away from the cutting hole of the working surface, on the working surfaceIs a position of (c).
The fracture height of the rock layer above the coal layer 1 gradually increases along with the advancement of the working surface, wherein the fracture height of the rock layer above the coal layer 1 is about half of the advancement distance of the working surface, and the fracture step distance is calculatedHeight from top of key layer 2 from coal seam 1/>By contrast, the coverage area of the horizontal projection of the fracturing line 3 on the working surface is ensured, and then the pre-fracturing range of the fracturing line 3 after drilling is ensured, if/>During specific construction, the requirement that the horizontal projection of the fracturing line 3 on the working surface covers the working surface and is away from the cut non-production coal wall/>, of the working surfaceThe inclination angle of the fracturing line and the initial point of drilling are not required to be forced, and the specific construction environment and the specific construction conditions are selected.
Alternatively, ifThe midpoint of the horizontal projection of the fracturing line 3 on the working surface is positioned at the distance/>, from the working surface cut to the non-production coal wallIs positioned at or away from the face cut-off non-production coal-upper wall/>From a location near to it.
In some embodiments, ifHorizontal projection of one end of the fracturing line 3 on the working surface and spacing/>, between the working surface and the cut-off non-production coal wallFor/>Horizontal projection of the other end of the fracturing line 3 on the working surface and spacing/>, between the working surface and the cut-off non-production coal wallFor/>; If/>Horizontal projection of midpoint of fracturing line 3 on working surface and spacing/>, of working surface cut-off non-production coal wallFor/>。
At the position ofWhen the coal wall is cut with the working face, the distance between the two end points of the fracturing line 3 and the non-production coal wall can be clearly determined, and the position of the fracturing line 3 can be determined through the vertical height of the fracturing line 3, namely the thickness of the key layer 2, so that the inclination angle and the length of the fracturing line 3 can be calculated, and the coal wall is obtained at the/>During drilling, the drill hole can be selected at the position of the working face open-cut hole according to the construction environment, so that the distance between the midpoint of the fracturing line 3 and the working face open-cut non-production coal wall is ensured to meet/>And the inclination angle of the fracturing line 3 is not required, and the inclination angle and the length of the fracturing line 3 can be calculated after the drilling position is determined.
In some embodiments, the break opportunity includes a time to start breaking and a time to end breaking, where the calculation formula of the time to start breaking is:
Equation 2: ；
the calculation formula of the time for ending the breaking is as follows:
Equation 3: ；
in the method, in the process of the invention, Is the vertical height of the bottom end of the fracturing line 3 from the coal seam 1,/>For the vertical height of the top end of the fracturing line 3 from the coal seam 1,/>Is the working surface propelling speed.
With the advancement of the working surface, the fracture height of the rock layer above the coal layer 1 is gradually increased, wherein the fracture height of the rock layer above the coal layer 1 is about half of the advancement distance of the working surface, when the working surface is advanced to 2 times the vertical height of the bottom end of the fracturing line 3 from the coal layer 1, the fracture height of the rock layer above the coal layer 1 reaches the bottom of the key layer 2, the key layer 2 starts to fracture, and when the working surface is advanced to 2 times the vertical height of the top end of the fracturing line 3 from the coal layer 1, the fracture height of the rock layer above the coal layer 1 reaches the top of the key layer 2, and the fracture of the key layer 2 is ended.
In some embodiments, in step S2, the height of the top of the key layer 2 from the coal seam 1, i.e., the vertical height of the top of the fracturing line 3 from the coal seam 1, and the height of the bottom of the key layer 2 from the coal seam 1, i.e., the vertical height of the bottom of the fracturing line 3 from the coal seam 1.
The fracturing line 3 is ensured to cover the whole key layer 2 in the vertical direction of the coal seam 1 so as to ensure the fracturing effect on the key layer 2.
In some embodiments, in step S2, the determined vertical height of the top end of the fracturing line 3 from the coal seam 1 and the vertical height of the bottom end of the fracturing line 3 from the coal seam 1 are checked to determine the vertical height of the fracturing line 3.
By checking the position of the key layer 2, the accuracy of the key layer 2 is ensured, and then the cracking effect of the key layer 2 is ensured.
In some embodiments, comparing the position of occurrence of the high-energy microseismic of the adjacent working face during the initial mining with the determined position of the key layer 2, and if the position of occurrence of the high-energy microseismic of the adjacent working face during the initial mining falls into the key layer 2 on the coal seam 1, the position of the key layer 2 is accurate; if the position of the adjacent working face where the high-energy microseismic occurs during the initial mining does not fall into the key layer 2 on the coal seam 1, the position of the key layer 2 needs to be checked and confirmed.
Through the position detection of the high-energy microseismic of the adjacent working face in the initial mining period, the key layer 2 of the working face is verified, the comparison is reliable, and the accuracy of the position of the key layer 2 is ensured.
In some embodiments, the location of the critical layer 2 to be fractured above the coal seam 1 is calculated according to formation critical layer 2 theory.
The rock stratum key layer 2 theory is the prior art, and the position of the key layer 2 can be accurately obtained according to the key layer 2 theory, so that the distance between the key layer 2 and the coal seam 1 can be determined through drilling.
And a plurality of rock layers are arranged above the coal bed 1, the first hard and difficult-to-collapse rock layer above the coal bed 1 is the key layer 2 according to the key layer 2 theory, and the position of the first hard and difficult-to-collapse rock layer above the coal bed 1 is calculated. Assuming that the first layer is a hard and hard formation, until the m-th layer is deformed in coordination with the first layer, and the (m+1) -th layer is not deformed in coordination with the first layer, the (m+1) -th layer is the (2) -th hard and hard formation. Because the first layer to the mth layer rock layer are in coordinated deformation, the curvature of each rock layer is the same, each rock layer forms a combined beam, and the load acting on the first layer hard rock layer can be derived according to the combined beam principle:
Equation 4: ；
in the method, in the process of the invention, To account for loading of the mth formation on the first hard, difficult to collapse formation; /(I)For the thickness of the ith formation,/>For the volume weight of the ith formation,/>Is the elastic modulus of the ith formation, where (i=1, 2, …, m),/>、/>、/>Obtained for field or laboratory testing.
Considering that the m+1st layer forms the load for the first hard and difficult-to-collapse rock layer:
equation 5: ；
because the (m+1) th layer is a hard and difficult-to-collapse rock layer, the deflection of the (m+1) th layer is smaller than that of the lower rock layer, the lower rock layer is not needed to bear the load of the upper rock layer, and the following steps are necessarily needed:
Equation 6: ；
Substituting formula 4 and formula 5 into formula 6 and simplifying the same can obtain:
Equation 7: ；
equation 7 is a formula for determining the position of the hard and difficult-to-collapse rock stratum. The height of the top of the first hard and difficult-to-collapse rock layer from the coal bed 1 is The height of the bottom of the first hard and difficult-to-collapse rock layer from the coal bed 1 is/>。
In some embodiments, the boreholes are run in a direction perpendicular to the coal wall, and the borehole spacing is 2 times the fracture radius.
The effective fracturing area of a single drilling hole is ensured, a plurality of drilling holes realize continuous fracturing of the key layer 2, and the fracturing effect of the key layer 2 is ensured.
Optionally, the drilling interval is 4 m-6 m.
The method for fracturing the top plate of the coal mine working face in the initial mining stage of the coal mine 309 in the rock burst is specifically described below by taking the effect of controlling the fracture of the top plate in the initial mining stage of the coal mine working face in the rock burst as an example.
The fully mechanized mining face is buried at a depth of about 640m, the working face of the south neighboring 308 is mined out, and the north side is solid coal. Comprehensively considering occurrence of the key layer 2 and a large-energy microseismic event in the initial mining process of the adjacent 308 working face, determining that a sixth roof above the coal seam 1 is an overlying first hard and difficult-to-collapse rock stratum and is used as a fracturing target rock stratum. And in the initial mining stage of the working face, a roof deep hole presplitting blasting technology is adopted to presplit the hard and difficult-to-collapse rock stratum covered on the first layer, so that the pressure relief and the danger relief of the local stope are realized.
As shown in fig. 5 and 6, the actual conditions of the working surface are combined 309Take 39.69m,/>Take 17.78m,/>Get 21.91m,/>Taking 5MPa. The target horizon is covered with a layer of sandy mudstone (rock layer 1 for short), a layer of fine sandstone (rock layer 2 for short), a layer of sandy mudstone (rock layer 3 for short) and a layer of coal (rock layer 4 for short), and the layers are divided into a plurality of layers of sandy mudstone (layer 4 for short)Take 1.53m,/>Take 25kN/m3,/>Taking 15GPa; /(I)Take 1.07m,/>Take 23kN/m3,/>Taking 23GPa; /(I)Take 1.15m,/>Take 25kN/m3,/>Taking 15GPa; /(I)Take 0.61m,/>Take 13kN/m3,/>Taking 3.4GPa. Calculating according to formula 1 to obtain breaking step distance/>=75.92m＜2/>=79.38M, i.e. the cleavage line needs to be covered/>A position of = 37.96m is just enough, where the open-cut eye width is about 10m.
As shown in fig. 7, the drilling hole depth of 56m, the inclination angle of 45 degrees and the explosive amount of 100kg are determined according to the drilling hole arrangement mode, the position of the key layer 2 to be fractured and the underground actual construction conditions.
According to 309 actual mining conditions of the working surface, calculated by the formula 2 and the formula 3, the condition that the fracturing target rock stratum starts to be broken when the working surface is pushed to be about 35.56m away from the coal wall behind the open-cut hole is displayed; when the working face is pushed to be about 79.38m away from the coal wall behind the open-cut hole, the fracturing target rock stratum is completely broken, and the projection position of the fracturing line 3 on the working face is within the range of about 28.38 m-49.60 m away from the coal wall behind the open-cut hole; considering 309 a face open cut width of about 10m, the fracturing target formation should actually begin to fracture after the face has advanced about 25.56 m; the fracturing target formation was completely fractured after approximately 69.38m of face advancement.
In order to verify the control effect of roof fracture on the roof fracture in the initial mining stage of the working face, microseismic monitoring data of the initial mining stage of the working face are collected and analyzed. As shown in fig. 8, from the viewpoint of the microseismic frequency, the microseismic frequency starts to rise after the working surface advances to 19.20m, the law of rising and then falling is presented, and the microseismic frequency is stabilized after the working surface advances to 74.40 m. As shown in fig. 9, the microseismic energy and the microseismic frequency show similar rules, and the microseismic energy which is pushed from the working surface to 19.20m as a whole is shown to rise and then fall, and is basically stable after being pushed to 74.40 m. At the same time, microseismic monitoring data shows that the first 4 th power event occurred since face recovery 309 when the face was advanced to 19.20m, at 9m in front of the face, i.e., at a distance of 38.20m from the face behind the open cut. The microseismic monitoring data can prove that the breaking activity of the first layer of hard thick-layer roof covering the stope begins to be aggravated after the working face is advanced to 19.20m, the first large-scale breaking occurs, and the breaking is started to be positioned at a distance of 38.20m from the coal wall behind the open-cut hole of the working face; thereafter, the roof of the first hard, difficult to collapse rock formation in the stope continues to fracture, and the fracture of the roof of the first hard, thick layer in the stope is substantially complete after the face has been advanced to 74.40 m. As shown in fig. 10, according to the actual pushing progress of 309 working surfaces, the time for starting breaking of the top plate of the first layer of hard thick layer covered on the stope is only 1 day earlier than the theoretical calculation result, the time for ending breaking is only 1 day earlier than the theoretical calculation result, and the position for starting breaking is within the manual control range of 28.38 m-49.60 m. Therefore, the invention provides a method for designing the top plate fracturing parameters of the initial mining stage of the underground working face of the coal mine, and the fracturing position and the fracturing time of the first hard and difficult-to-collapse stratum covered on the initial mining stage of the working face are accurately controlled.
In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; may be mechanically connected, may be electrically connected or may be in communication with each other; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.
Claims (10)
1. The method for fracturing the roof of the coal mine working face in the initial mining stage is characterized by comprising the following steps of:
s1: determining the position of a key layer to be fractured above the coal seam;
s2: determining the vertical height of the key layer;
S3: determining the vertical height of the top end of the fracturing line from the coal seam and the vertical height of the bottom end of the fracturing line from the coal seam;
s4: determining a fracture step of a formation According to the breaking step/>Determining the position of the fracturing line and the breaking step/>The midpoint of (2) is located in the range of horizontal projection of the fracturing line on the working surface;
s5: determining the drilling angle and depth of the fracturing line according to the vertical height of the fracturing line and the horizontal projection position of the fracturing line on the working surface;
S6: and determining the breaking time according to the vertical height of the top end of the fracturing line from the coal seam, the vertical height of the bottom end of the fracturing line from the coal seam and the advancing speed of the working face.
2. The initial mining stage coal mine face roof fracturing method of claim 1, wherein in step S3, the fracturing step isThe calculation formula of (2) is as follows:
；
in the method, in the process of the invention, Is the thickness of a key layer above a coal layer,/>Is the ultimate tensile strength of a key layer above a coal layer,/>And uniformly distributing load to key layers above the coal seam.
3. The initial mining stage coal mine face roof fracturing method of claim 2, wherein the breaking steps are spaced apartHeight from top of key layer/height from top of key layer of coal layerFor comparison, if/>The horizontal projection of the fracturing line on the working surface covers the non-production coal wall/>, which is away from the cutting hole of the working surface, on the working surfaceIs defined by the range of (2); if/>The horizontal projection of the fracturing line on the working surface covers the non-production coal wall/>, which is away from the cutting hole of the working surface, on the working surfaceIs a position of (c).
4. A roof fracturing method of a face of a coal mine at an initial stage of mining according to claim 3, wherein ifHorizontal projection of one end of the fracturing line on the working surface and spacing/>, between the working surface and a cut-off non-production coal wallFor/>Horizontal projection of the other end of the fracturing line on the working surface and spacing/>, between the working surface and the cut-off non-production coal wallFor/>; If/>Horizontal projection of midpoint of fracturing line on working surface and spacing/>, between working surface and cut-off non-production coal wallFor/>。
5. The initial mining stage coal mine working face roof fracturing method of claim 1, wherein the fracturing opportunity comprises time for starting fracturing and time for ending fracturing, and a calculation formula of the time for starting fracturing is as follows:
；
the calculation formula of the time for ending the breaking is as follows:
；
in the method, in the process of the invention, Is the vertical height of the bottom end of the fracturing line from the coal seam,/>Is the vertical height of the top end of the fracturing line from the coal seam,/>Is the working surface propelling speed.
6. The method for roof fracturing of a coal mine working face in the initial mining stage according to claim 1, wherein in step S2, the height of the top of the key layer from the coal seam is the vertical height of the top of the fracturing line from the coal seam, and the height of the bottom of the key layer from the coal seam is the vertical height of the bottom of the fracturing line from the coal seam.
7. The method of roof fracturing of a face of a coal mine at an initial stage of coal mining according to claim 5, wherein in step S2, the determined vertical heights of the top end of the fracturing line and the bottom end of the fracturing line from the coal seam are checked to determine the vertical height of the fracturing line.
8. The initial mining stage coal mine face roof fracturing method of claim 6, wherein the positions of occurrence of high-energy microseisms of adjacent working faces during initial mining are compared with the determined positions of key layers, and if the positions of occurrence of high-energy microseisms of the adjacent working faces during initial mining fall into the key layers on the coal seam, the positions of the key layers are accurate; if the positions of the adjacent working surfaces where the high-energy microseisms occur during the initial mining do not fall into the key layers on the coal seam, the key layers are required to be checked and confirmed.
9. The method for roof fracturing of a coal mine working face in the initial mining stage according to claim 1, wherein the position of a key layer to be fractured above a coal seam is calculated according to a rock stratum key layer theory.
10. The method for fracturing a roof of a working face of a coal mine at an initial mining stage according to claim 1, wherein the drill holes are constructed in a direction perpendicular to a coal wall, and the drill hole spacing is 2 times the fracturing radius.
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