CN113216967A - Opposite safe mining method for adjacent working faces under shallow-buried short-distance room-and-pillar type goaf - Google Patents
Opposite safe mining method for adjacent working faces under shallow-buried short-distance room-and-pillar type goaf Download PDFInfo
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Abstract
The invention discloses a method for oppositely and safely mining adjacent working faces under a shallow-buried short-distance room-column type goaf, which comprises the following steps: s1, based on FLAC3DCalculating a numerical value to obtain the stability of the coal pillar of the top room-and-pillar type goaf; s2, simultaneously mining and single-working-face mining different opposite distances of adjacent working faces under the room-and-column type goaf based on the stability of the coal pillars of the top room-and-column type goaf to obtain a side supporting pressure superposition effect and the stability of the coal pillars between the faces; and S3, acquiring opposite mining timing sequence plans and methods of adjacent working faces based on the stability of the coal pillars of the top room-and-column type goaf, the side supporting pressure superposition effect and the stability of the coal pillars between the faces. The invention can make safe adjacent working face opposite mining time sequence planning and provide a safe and reliable adjacent working face opposite mining method.
Description
Technical Field
The invention relates to the technical field of coal mining, in particular to a method for oppositely and safely mining adjacent working faces under a shallow-buried short-distance room-pillar type goaf.
Background
Most coal seams in Jurassic coal fields in northern Shaanxi have shallow parts within 300m, the top coal seam is about 100m from the earth surface generally and is called as a shallow coal seam, the main coal seam is 3-5 layers generally, the coal seam spacing is 6-40 m generally, the middle coal seam is mainly used and belongs to a shallow short-distance coal seam group, in the early stage of the last century in 90 years, part of mines adopt a room-and-column type to mine the top coal seam, a large number of room-and-column type goafs are formed, a wall type mining method is gradually popularized in the later stage, a large number of wall type goafs are formed, and potential safety hazards are brought to lower coal seam. At present, most of coal seams at the top of a mine in a coal field are basically mined, lower coal seam mining is gradually started, the mining belongs to 'mining under shallow-buried short-distance coal seam group goaf', because the coal seam spacing is small, the mining of the lower coal seam is greatly influenced by the goaf of the upper coal seam, a left coal pillar and an interval rock stratum structure, particularly, the mining is carried out under a room-and-pillar type goaf, the large-area collapse of the room-and-pillar type goaf is easily caused, strong mine pressure disasters and toxic and harmful gas overrun are caused, and the mining is a general technical problem in mining under the shallow-buried short-distance room-and-pillar type goaf; meanwhile, due to the mining history, in the process of mining the lower coal seam under the room-and-pillar type goaf by part of adjacent mines, the special technical problem of opposite mining of adjacent working faces of the adjacent mines is faced because the production systems of the adjacent mines are independent.
In the opposite mining process of adjacent working faces of adjacent mines, the advanced supporting pressures of the two working faces are possibly superposed, the influence of the lateral supporting pressures of the working faces on an inter-face coal pillar is stronger than that of single-seam mining, and disasters such as sudden collapse of an upper room-and-pillar type goaf and instability of the inter-face coal pillar in the opposite mining process of the two working faces are easily caused, so that safety accidents such as the bracket of the two working faces of a lower coal seam is pressed down, harmful gas in the room-and-pillar type goaf is gushed into the working faces and the like are caused.
In addition, in the prior art, a great deal of research is carried out on the stability of the coal pillars of the mining and stoping roadway with the single working face under the shallow-buried short-distance goaf, the distribution rule of the advanced supporting pressure of the single working face and the like, and a lot of beneficial results are obtained, but the stability analysis of the coal pillars between faces in the opposite mining process of adjacent working faces, the stability prejudgment of the upper room pillar type goaf and the superposition effect of the supporting pressure of the surrounding rocks in opposite mining of the two working faces are not involved, and the technology is still in the technical blank in the opposite safe mining technology of the adjacent working faces.
Disclosure of Invention
Aiming at the problems, the invention provides a safe mining method for opposite directions of adjacent working faces under a shallow-buried short-distance room-and-pillar type goaf, which aims to solve the technical problems in the prior art, can make safe opposite mining time sequence plans of the adjacent working faces and provide a safe and reliable opposite mining method for the adjacent working faces.
In order to achieve the purpose, the invention provides the following scheme: the invention provides a method for oppositely and safely mining adjacent working faces under a shallow-buried short-distance room-column type goaf, which comprises the following steps:
s1, based on FLAC3DCalculating a numerical value to obtain the stability of the coal pillar of the top room-and-pillar type goaf;
s2, simultaneously mining and single-working-face mining different opposite distances of adjacent working faces under the room-and-column type goaf based on the stability of the coal pillars of the top room-and-column type goaf to obtain a side supporting pressure superposition effect and the stability of the coal pillars between the faces;
and S3, acquiring opposite mining timing sequence plans and methods of adjacent working faces based on the stability of the coal pillars of the top room-and-column type goaf, the side supporting pressure superposition effect and the stability of the coal pillars between the faces.
Preferably, the specific calculation step of the coal pillar stability of the top room-and-pillar goaf of S1 includes:
s1.1, based on the FLAC3DCalculating numerical values to obtain a room-and-column goaf coal column vertical stress distribution rule;
s1.2, constructing a room-and-column goaf coal column load calculation model;
s1.3, based on the room-and-column type goaf coal pillar load calculation model, obtaining average stress and coal pillar ultimate strength on the room-and-column type goaf coal pillar;
s1.4, based on the average stress and the coal pillar ultimate strength of the room-and-column goaf coal pillars, obtaining the safety coefficient of the room-and-column goaf coal pillars, namely the stability of the top room-and-column goaf coal pillars according to the vertical stress distribution rule of the room-and-column goaf coal pillars;
s1.5, based on the room and column type goaf coal pillar safety coefficient, constructing a physical similar material model, wherein the physical similar material model is used for displaying the state of the room and column type goaf coal pillar and verifying the accuracy of the stability calculation of the top room and column type goaf coal pillar.
Preferably, the average stress P on the pillar of the room and pillar type goaf is specifically:
wherein gamma is the average volume weight of the overlying strata, H is the buried depth, L is the length, a is the width of the coal pillar, and b is the width of the coal room.
Preferably, the coal pillar ultimate strength σsThe method specifically comprises the following steps:
in the formula, σcThe uniaxial compressive strength of the coal pillar, h the height of the residual coal pillar, a1 the width of the residual coal pillar, and n the width-to-height ratio of the coal pillar.
Preferably, room and pillar type goaf coal pillar safety coefficient kfThe method specifically comprises the following steps:
in the formula, p is the average stress on the coal pillar of the room-and-pillar type goaf, sigmasThe ultimate strength of the coal pillar.
Preferably, the specific steps of S2 are:
s2.1, FLAC based on S13DNumerical calculation results are obtained, and the distribution characteristics of lateral support pressure and the inter-surface coal pillar stress evolution law of simultaneous mining of different opposite distances of adjacent working surfaces and mining of a single working surface are obtained;
s2.2, constructing an inter-surface coal pillar load calculation model based on the distribution characteristics of lateral support pressure of simultaneous mining and single-working-surface mining of different opposite distances of adjacent working surfaces and the inter-surface coal pillar stress evolution law;
s2.3, based on the inter-surface coal pillar load calculation model, obtaining the average stress at the top of the coal pillar and the inter-surface coal pillar safety coefficient; and the average stress at the top of the coal pillar and the safety coefficient of the coal pillar between the surfaces are respectively used for representing the superposition effect of the lateral support pressure and the stability of the coal pillar between the surfaces.
Preferably, the average stress P of the top of the coal pillarZThe method specifically comprises the following steps:
wherein a is the width of the coal pillar, H1Is the thickness of bedrock, gamma1Is the average volume weight of bedrock, H2Is the thickness of the soil layer, gamma2Is the average volume weight of soil layer, alpha1Is the breaking angle of bedrock, alpha2Is a soil layer breaking angle.
Preferably, the safety coefficient k of the interplanar coal pillarsfzThe method specifically comprises the following steps:
in the formula, σsIs the ultimate strength of the coal pillar, pzThe maximum stress of the coal pillar between the surfaces.
The invention discloses the following technical effects:
the invention can be based on FLAC3DNumerical calculation, theoretical analysis and physical simulation find the distribution characteristics of lateral supporting pressure and the evolution rule of the stress of the coal pillar between the surfaces when different opposite distances of the adjacent working surfaces under the room-and-column type goaf are exploited simultaneously and exploited on a single working surface, determine the stability of the coal pillar between the surfaces, further formulate safe and reliable opposite exploitation time sequence planning of the adjacent working surfaces, and provide a safe and reliable opposite exploitation method of the adjacent working surfaces.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a flow chart of a method of the present invention;
FIG. 2 is a model for calculating the load bearing of the pillars in the room and pillar type goaf according to the present invention;
FIG. 3 is a coal pillar load calculation model of the present invention;
FIG. 4 illustrates the relationship between the mining planes of the two working faces in accordance with an embodiment of the present invention;
FIG. 5 is a cross-section taken through the middle of 2206 face of an embodiment of the present invention;
FIG. 6 is a cross-section of the middle portion of a 2201 face according to an embodiment of the present invention;
FIG. 7 is a cross-sectional view of the trend of the two working surfaces interacting with each other according to the embodiment of the present invention;
FIG. 8 shows an embodiment of the present invention 2-2 toThe distribution rule of the vertical stress of the coal pillar during coal seam mining;
FIG. 9 shows the physical simulation result of the stability of the pillars in the room and pillar type goaf according to the embodiment of the present invention;
FIG. 10 shows the two working surfaces facing each other at a distance of 60m before the bearing pressures begin to overlap in accordance with an embodiment of the present invention;
FIG. 11(a) is a schematic diagram of the pillar stress between mining faces at a facing distance of 60m according to an embodiment of the present invention;
fig. 11(b) is a schematic diagram of the stress of the coal pillars between the simultaneous mining faces at the facing distance of 34m according to the embodiment of the present invention;
FIG. 11(c) is a schematic diagram of the stress of the coal pillar between the mining faces with the same advancing distance of 28m in opposite directions according to the embodiment of the invention;
FIG. 11(d) is a schematic view of the interplane pillar stresses of the facing simultaneously-propelled working surfaces side by side according to an embodiment of the present invention;
FIG. 11(e) is a schematic diagram of the stress of the coal pillars between the mining faces under the condition that the working faces are opposite and simultaneously pushed and staggered by 10m according to the embodiment of the invention;
FIG. 11(f) is a schematic diagram of the interfacial pillar stress of only 2206 working face pushing working face side by side according to an embodiment of the present invention;
FIG. 11(g) is a schematic diagram of the stress of a coal pillar between two mining surfaces of 2206 working surfaces which are pushed to stagger by 10m according to an embodiment of the invention,
FIG. 11(h) is a schematic diagram of the stress of a coal pillar between a 2206 working face propulsion staggered lower mining face of 20m according to the embodiment of the invention;
FIG. 12 illustrates the maximum vertical stress of the coal pillar between the faces of two faces simultaneously opposing mining and only 2206 faces mining according to an embodiment of the present invention;
FIG. 13 shows the maximum vertical stress at 30m width of an interplanar coal pillar according to an embodiment of the present invention;
FIG. 14 shows a 30m coal pillar between two working faces facing each other according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Referring to fig. 1-3, the invention provides a method for oppositely and safely mining adjacent working faces under a shallow-buried short-distance room-and-pillar type goaf, which comprises the following steps:
s1, based on FLAC3DNumerical value calculates, acquires top room column formula collecting space area coal pillar stability, and concrete step is:
s1.1, based on the FLAC3DNumerical calculation is carried out to obtain the distribution rule of the vertical stress of the coal pillar of the room and column type goaf, the maximum vertical stress borne by the coal pillar of the room and column type goaf is determined, and the room and column is analyzedStability of the coal pillar in the gob.
S1.2, building a room-and-column type goaf coal column load calculation model, wherein the room-and-column type goaf coal column load calculation model is shown in figure 2 on the assumption that a top plate supported by a room-and-column type goaf coal column is intact and does not fall off, and the whole weight of an overlying rock layer acts on the coal column.
S1.3, based on the room-and-column type goaf coal pillar load calculation model, obtaining average stress and coal pillar ultimate strength on the room-and-column type goaf coal pillar;
the average stress on the room-and-column goaf coal pillars is specifically as follows:
in the formula, p is the average stress on the coal pillar of the room-and-pillar type goaf, and is MPa; gamma is the average volume weight of overburden stratum, kN/m3(ii) a H is the buried depth, m; l is the length of the coal pillar of the room-and-pillar type goaf, m; a is the width of a coal pillar in a room-and-column goaf, m; b is the width of the coal room, m.
The coal pillar stability is related to the strength of the coal body and the size of the coal pillar, and the ultimate strength of the coal pillar is usually calculated by adopting a Bieniwski formula:
in the formula, σsThe ultimate strength of the coal pillar is MPa; sigmacThe uniaxial compressive strength of the coal pillar is MPa; h is the height of the residual coal pillar, m; a is1M is the width of the residual coal column; n is the width-height ratio of the coal pillar, and when a/h is more than 5, n is 1.4; when a/h < 5, n is 1.
S1.4, based on the average stress and the coal pillar ultimate strength of the room-and-column goaf coal pillars, obtaining the safety coefficient of the room-and-column goaf coal pillars, namely the stability of the top room-and-column goaf coal pillars according to the vertical stress distribution rule of the room-and-column goaf coal pillars;
according to the ultimate strength theory, when the stress peak value born by the coal pillar exceeds the ultimate strength of the coal pillar, the coal pillar is unstable and easy to damage, and when the stress peak value born by the coal pillar is smaller than the ultimate strength of the coal pillar, the coal pillar is stable, and the safety coefficient of the stability of the coal pillar is the ratio of the ultimate strength of the coal pillar to the vertical stress born by the safety coefficient. According to a large amount of practical experience, when the coal pillar safety coefficient is greater than 2, the coal pillar is more stable, and then the formula for calculating the average stress and the coal pillar ultimate strength on the coal pillar in the goaf is stepped on through the room-and-column type, and the formula for calculating the coal pillar safety coefficient in the room-and-column type goaf can be obtained as follows:
in the formula, kfThe safety coefficient of the coal pillar of the room-and-column goaf is shown, and p is the average stress on the coal pillar of the room-and-column goaf, and is MPa; sigmasThe ultimate strength of the coal pillar is MPa.
S1.5, based on room and column type collecting space area coal pillar factor of safety, establish the similar material model of physics, the similar material model of physics adopts room and column type exploitation top coal seam for the reliability of the room and column type collecting space area coal pillar situation of show directly perceived verifies numerical calculation and theoretical analysis, and right top room and column type collecting space area coal pillar stability calculates and carries out the accuracy verification.
And S2, based on the stability of the coal pillars of the top room-and-column type goaf, simultaneously mining and single-working-face mining on different opposite distances of adjacent working faces under the room-and-column type goaf to obtain lateral support pressure distribution characteristics, an inter-face coal pillar stress evolution rule, a lateral support pressure superposition effect and inter-face coal pillar stability.
Under the premise that most of the pillars of the room-and-pillar type goaf at the top of S1 are stable, the restriction factor of opposite safe mining of the adjacent working faces of the lower coal seam is converted into the stability of the pillars between the two working faces, and the main factor influencing the stability is the influence of the superposition effect of the lateral bearing pressures of the two working faces on the pillars between the two working faces in the opposite mining process of the adjacent working faces.
The specific calculation processes of the distribution characteristics of the lateral support pressure and the stress evolution law of the coal pillars between surfaces, the superposition effect of the lateral support pressure and the stability of the coal pillars between surfaces are as follows:
s2.1, FLAC based on S13DAnd (3) obtaining the distribution characteristics of the lateral support pressure and the stress evolution rule of the coal pillars between the surfaces by the numerical calculation result and the simultaneous mining of different opposite distances of adjacent working surfaces and the mining of a single working surface, and obtaining the following basic rules:
the first and adjacent working faces are mined simultaneously: when the opposite distance is reduced to a certain distance, the superposition effect of the advanced supporting pressure of the two working surfaces and the maximum vertical stress of the coal pillar between the two working surfaces is obvious. And the stress superposition effect is continuously enhanced along with the decrease of the opposite distance of the two working surfaces to the side-by-side position. The two working faces are staggered for a certain distance behind the shoulders, the maximum vertical stress of the coal pillar between the faces is further increased, but the increase amplitude is obviously reduced. Then, the maximum vertical stress of the coal pillars between the planes is basically kept unchanged along with the increase of the staggered distance.
And secondly, mining the single working face with the adjacent working faces facing each other: when the two working faces are opposite and simultaneously exploited, the advance supporting pressure and the maximum vertical stress of the coal pillar between the working faces are superposed, one working face suspends exploitation, and the other working face rapidly advances. As the facing distance is reduced to the side-by-side position, the stress superposition effect is obviously weakened compared with that of mining with two working faces facing simultaneously. After the coal pillars are abreast, one-stop-one mining is continuously kept, and the maximum vertical stress of the coal pillars between the surfaces does not rise after increasing to a certain value along with the continuous increase of the staggered distance.
According to the evolution law, the maximum vertical stress of the coal pillar between the front and the rear of the two working faces in a side-by-side mode can reach the peak value when the adjacent working faces of the lower coal seam are exploited oppositely and simultaneously and the single working face is exploited through the FLAC3D numerical calculation. Therefore, if the coal pillar between the two working face side-by-side positions is stable, the safety of mutually influenced sections of opposite mining of adjacent working faces can be ensured.
S2.2, constructing an inter-surface coal pillar load calculation model based on the distribution characteristics of lateral support pressure of simultaneous mining and single-working-surface mining of different opposite distances of adjacent working surfaces and the inter-surface coal pillar stress evolution law, as shown in FIG. 3;
s2.3, based on the inter-surface coal pillar load calculation model, obtaining the average stress at the top of the coal pillar and the inter-surface coal pillar safety coefficient; and the average stress at the top of the coal pillar and the safety coefficient of the coal pillar between the surfaces are respectively used for representing the superposition effect of the lateral support pressure and the stability of the coal pillar between the surfaces.
Mean stress P at the top of the coal pillarZThe method specifically comprises the following steps:
in the formula, pzThe average stress of the coal pillars between surfaces is MPa; a is the width of the coal pillar, m; h1Is the thickness of the bedrock, m; gamma ray1Is the average volume weight of bedrock, kN/m3；H2Is the soil thickness, m; gamma ray2Is the average volume weight of soil layer, kN/m3；α1Is the breaking angle of bed rock, °; alpha is alpha2Is the soil layer breaking angle.
The safety coefficient of the interplanar coal pillars is as follows:
in the formula, σsThe ultimate strength of the coal pillar is MPa; the unit is; p is a radical ofzThe maximum stress of the coal pillar between the surfaces is MPa.
And S3, acquiring opposite mining timing sequence plans and methods of adjacent working faces based on the stability of the coal pillars of the top room-and-column type goaf, the side supporting pressure superposition effect and the stability of the coal pillars between the faces.
After the stability of the coal pillars in the room-and-pillar type goaf is mastered, numerical calculation, theoretical analysis and physical simulation are carried out. The lateral bearing pressure distribution characteristics and the inter-surface coal pillar stress evolution law of simultaneous mining of different opposite distances of adjacent working surfaces and single-working-surface mining under the room-and-pillar type goaf are disclosed, and the criterion for determining the stability of the inter-surface coal pillars is provided.
According to the research, a safety-based adjacent working face opposite mining time sequence plan is formulated, and a safe and reliable adjacent working face opposite mining method is provided: in the opposite mining process of adjacent working faces, along with the reduction of the opposite distance, the maximum vertical stress of the coal pillars between the faces has an obvious rising inflection point, at the moment, one working face is temporarily stopped mining, the other working face continues to accelerate, and the influence time of the superposed stress is shortened as much as possible. Along with the increase of the staggered distance between the continuous propulsion working face and the temporary stoping working face, when the maximum vertical stress of the coal pillar between the faces is not increased and basically keeps stable, the stoping working face recovers mining, the two working faces are staggered and accelerated to propel simultaneously, the two working faces are separated from the mutual influence area as soon as possible, and the safety of the two working faces after being staggered is ensured.
Referring to fig. 4-14, in this embodiment, taking the mining situation of two adjacent mines in the nakedfish city as an example, the 2206 working face and the 2201 working face belong to different mines respectively, and the two working faces are adjacent opposite mining working faces.
2-2 coal seams are mined on 2206 working faces and 2201 working faces, the thickness of each coal seam is 6.41-7.96, the mining height is 6.5m, the average burial depth is about 120m, and a long-wall comprehensive mechanized coal mining method is adopted; 2-2 Coal bed top 2-2 toThe coal seam is mined, the thickness of the coal seam is 1.52-3.42 m, and the average thickness is 3.2 m. The small part at the position 5-8 m above the 2206 working surface is 2-2 toMost of the coal-house pillar type goafs are long-wall goafs, the section meeting the 2201 working face is the long-wall goaf, and due to the fact that overlying strata above the long-wall goaf are fully collapsed, large-area collapse disasters can not happen generally when the 2206 working face is mined.
2 is arranged at the position 5-8 m above the 2201 working surface-2 to6m room-and-column goaf is reserved in the coal seam mining process. Because the stability of the coal pillars in the room and pillar type goaf is not clear, the two working faces mine mutually influencing sections in opposite directions, and the 2201 working face has the possibility of causing a large-area collapse disaster of the room and pillar type goaf, so that huge potential safety hazards exist. The width of the coal pillar (mine boundary coal pillar) between the two working faces is 23-51 m, and the width of the coal pillar at the opposite mining influence section is about 30 m.
On 19/6 of 2020, 2206 faces have advanced to 710m, 2201 faces have advanced to 220m, and the production locations of the two faces are 360m apart. The mining plane position relationship of the two working faces is shown in FIG. 4, the working face strike section 2206 is shown in FIG. 5, the working face strike section 2201 is shown in FIG. 6, and the section inclination of the mutual influence section of the two working faces is shown in FIG. 7.
By applying the technical scheme of the invention, opposite mining time sequence plans of the 2206 working face and the 2201 working face are formulated, and safe mining before and after the two working faces meet is ensured.
1. Analysis 2-2 toCoal bed room column type collecting space area coal column stability.
(1) And (3) calculating the numerical value of the stress distribution rule of the coal pillars in the room-and-column goaf:
FLAC3Dnumerical calculation gives-2 toAfter the coal seam is mined, the maximum concentrated stress of the coal pillar in the room pillar area is about 7MPa, which is about 3.7 times of the stress of the original rock. 2-2 toThe vertical stress distribution of the coal seam mining tendency section is shown in FIG. 8, and the concentrated stress of a coal pillar (15m) between working faces reaches 8 MPa; the vertical stress of the coal pillars in the room pillar area is 6-8 MPa, and the vertical stress of the coal pillars at the position close to the working face and in the middle of the room pillar area is larger. The maximum vertical stress of the coal pillar in the room column area is less than the uniaxial compressive strength (19.5MPa), so the coal pillar in the room column area is stable.
(2) Theoretical analysis of the stability of the pillars in the room-and-pillar goaf:
according to 2-2 toMining parameters and geological conditions of coal bed room column region, and average volume weight gamma of overlying strata1＝25kN/m3Thickness H131.5m, average bulk density of soil layer gamma220kN/m3, soil layer thickness H255 m. The length L of the pillar in the room and pillar type mining is 6m, the width a of the pillar is 6m, and the width b of the coal room is 6 m. Stress P of original rock0＝γ1H1+γ2H2＝1.9MPa。
The average stress on the coal pillar of the room-and-pillar type goaf is 7.6MPa, which is consistent with the numerical calculation result (7MPa) and is 4 times of the original rock stress.
The width-to-height ratio of the coal pillar in the room-and-pillar type goaf is about 1.9, n is 1, and the uniaxial compressive strength of a coal bed is 19.5MPa on average. The parameters are substituted into calculation, and the ultimate strength of the coal pillar is 25.82 MPa.
The safety coefficient of the coal pillar of the room-and-pillar type goaf is calculated to be 3.4 and is more than 2, so 2-2 toAnd the coal pillar of the coal bed room column type goaf is stable and consistent with the numerical calculation result.
(3) Physical simulation of the stability of the pillars in the room-and-column goaf:
physical simulation results show that-2 toAfter the pillar type mining of the coal seam, the top plate of the goaf does not collapse, the top plate is kept stable under the support of the pillars of the pillar region, the data of the measuring points arranged on the pillars are analyzed, the pillar region pillars have small deformation, and the pillars of the pillar type goaf are stable, as shown in fig. 9. The reliability of numerical calculation and theoretical analysis is further verified.
2. The simultaneous mining of 2206 face and 2201 face at different facing distances and the mining of 2206 face only side bearing pressure superposition effect are disclosed, and the stability of coal pillars between faces is analyzed.
(1)FLAC3DNumerical calculation reveals the lateral support pressure distribution characteristics and the inter-face coal column stress evolution law of 2206 working face and 2201 working face opposite-direction simultaneous mining and only 2206 working face mining.
The numerical calculation shows that when the opposite distance between the two working surfaces is about 60m, the advanced supporting pressures of the two working surfaces start to be superposed, as shown in fig. 10, but the influence of the lateral supporting pressure on the coal pillar between the two surfaces is small; when the facing distance of the two working surfaces is 28m, the lateral supporting pressure has a large influence on the coal pillar between the surfaces, and the maximum vertical stress of the coal pillar between the surfaces has an obvious rising inflection point. And the two mining modes of simultaneous mining of two working faces and mining of only 2206 working face and temporary stopping of mining of 2201 working face have larger difference of maximum vertical stress of coal pillars between the two working faces, as shown in figure 11.
Comparing two simulation results of only 2206 working face mining and two working faces mining simultaneously in opposite directions, the change rule of the maximum vertical stress of the coal pillar between the faces is shown in fig. 12, and it can be known that:
when the distance between the two working faces is 30m, the maximum vertical stress of the coal pillar between the faces is reduced by about 4% after the mining of 2201 working faces is stopped;
only 2206 working surfaces are pushed, and when the two working surfaces are staggered by 14m, the stress of the coal pillar between the two working surfaces reaches the maximum and is 9.12 MPa; after the staggered distance is more than 20m, the maximum vertical stress of the coal pillars between the surfaces does not rise any more. At the moment, the distance between the two working surfaces is 2 cycles to obtain a step distance, and the movement of the top plate is basically stable.
FLAC3DThe numerical calculation also yields twoWhen the working faces are mined oppositely and staggered by 10m at the same time, the vertical stress of the coal pillars between the faces is the largest, 9.41MPa, which is far less than the compressive strength of the coal bed, and the coal pillars between the faces are stable. When only 2206 working faces are pushed to stagger by 10m, the maximum coal pillars between the faces is 9.08MPa, and the pressure reduction effect is obvious.
(2)2206 and 2201 working faces are oppositely mined and the stability of the coal pillar between the front face and the rear face is analyzed in a side-by-side mode.
Before and after the 2206 working face and the 2201 working face are mined side by side, the width of a coal pillar between the faces is about 30m, and the stability of the coal pillar at the moment is analyzed by adopting a theory, so that the method is very important for making opposite safe mining time sequence plans of the two working faces.
According to the mining parameters and geological conditions of two working faces, the breaking angle alpha of the bedrock between the working faces1At 60 degrees and a soil layer breaking angle alpha2Is 67 degrees, and the coal pillar between the surfaces is a1Taking 30m, the average volume weight gamma of bedrock1Is 25kN/m3Average soil layer volume weight gamma2Is 20kN/m3Thickness of bedrock H144m, soil thickness H255m, the width-height ratio of the coal pillar between the surfaces is 4.4, and n is 1.
Respectively substituting the parameters into a coal pillar ultimate strength calculation formula and a coal pillar top average stress calculation formula to obtain:
the average stress of the coal pillar between the two working surfaces is 5.85MPa, and the ultimate strength of the coal pillar is 43.4 MPa. Receiving upper part 2-2 toThe influence of coal bed remaining pillars is taken as the stress peak coefficient to be 1.5, so that the maximum stress between working faces is 1.5 multiplied by 5.85 to 8.8MPa, which is 4.6 times of the original rock stress, and the maximum stress is consistent with the numerical calculation result. The safety coefficient between the two working surfaces is 4.9 by substituting the formula (5), and the stability of the coal pillar between the working surfaces can be judged.
(3) Physical simulation verifies the stability of the coal pillar 30m between the two working faces.
Physical simulation shows that when the coal pillar between the two working faces is 30m, the distribution rule of the vertical stress of the coal pillar is as shown in fig. 13. The peak value of the vertical stress of the coal pillar is 8.6MPa, which is far less than the uniaxial compressive strength of the coal bed, and the coal pillar is good in stability, as shown in figure 14, and is consistent with the results of numerical calculation and theoretical analysis.
3. And (4) reasonable opposite mining time sequence planning of the 2206 working face and the 2201 working face is established, and a safe and reliable mining method is provided.
According to the maximum stress rule of the coal pillar obtained by numerical simulation, when the distance between the 2206 working surface and the 2201 working surface is 28m, the maximum vertical stress of the coal pillar between the working surfaces has an inflection point, and the continuous propelling stress is obviously increased.
In order to ensure safe mining, when the opposite distance between the two working faces is 30m, the 2201 working face temporarily stops mining, so that the concentrated stress of the coal pillar can be reduced by about 4-5%, and meanwhile, the risk of local collapse of the goaf of the upper room pillar is avoided.
When the 2206 working face is pushed to the staggered distance which is more than 20m, the maximum vertical stress of the coal pillars between the working faces tends to be stable, the 2201 working face can recover mining after being separated from the obvious influence area, and the pushing speed of the two working faces should be increased at the same time.
According to numerical simulation, theoretical analysis and physical simulation, when the width of the coal pillar between the two working faces affecting each other and the stage face is about 30m, the stability can still be kept under the time sequence planning condition, and the two working faces can realize safe mining.
4. Engineering practice verification
The 2206 working face and the 2201 working face adopt the technical scheme of the invention, and through earth surface movement monitoring, mine pressure actual measurement of the two working faces and coal pillar monitoring between the faces, the earth surfaces of the two working faces do not collapse in large area, abnormal changes of the support load and gas components of the working faces do not occur, and the working faces are stable in advance of the pillar type goaf coal pillars. At present, the two working faces are safely mined, so that the opposite safe mining of the adjacent longwall working faces under the shallow-buried short-distance room pillar goaf is realized, the moving of the working faces and the long-time production halt are avoided, the remarkable economic benefit is obtained, and the reliability of the technical scheme of the invention is verified.
The invention discloses the following technical effects:
the invention can be based on FLAC3DNumerical calculation, theoretical analysis and physical simulation find the distribution characteristics of lateral supporting pressure and the evolution rule of the stress of the coal column between the surfaces when the different opposite distances of the adjacent working surfaces under the room-and-column type goaf are exploited simultaneously and the single working surface is exploited, determine the stability of the coal column between the surfaces, and further formulateAnd the safe and reliable opposite mining time sequence of the adjacent working faces is planned, and a safe and reliable opposite mining method of the adjacent working faces is provided.
The above-mentioned embodiments are only specific embodiments of the present invention, which are used for illustrating the technical solutions of the present invention and not for limiting the same, and the protection scope of the present invention is not limited thereto, although the present invention is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the present invention in its spirit and scope. Are intended to be covered by the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (8)
1. The opposite safe mining method for adjacent working faces under the shallow-buried short-distance room-and-pillar type goaf is characterized by comprising the following steps:
s1, based on FLAC3DCalculating a numerical value to obtain the stability of the coal pillar of the top room-and-pillar type goaf;
s2, simultaneously mining and single-working-face mining different opposite distances of adjacent working faces under the room-and-column type goaf based on the stability of the coal pillars of the top room-and-column type goaf to obtain a side supporting pressure superposition effect and the stability of the coal pillars between the faces;
and S3, acquiring opposite mining timing sequence plans and methods of adjacent working faces based on the stability of the coal pillars of the top room-and-column type goaf, the side supporting pressure superposition effect and the stability of the coal pillars between the faces.
2. The method for safe mining of the opposite direction of the adjacent working face under the shallow-buried short-distance room-and-pillar goaf is characterized in that the specific calculation step of the coal pillar stability of the S1 top room-and-pillar goaf comprises the following steps:
s1.1, based onThe FLAC3DCalculating numerical values to obtain a room-and-column goaf coal column vertical stress distribution rule;
s1.2, constructing a room-and-column goaf coal column load calculation model;
s1.3, based on the room-and-column type goaf coal pillar load calculation model, obtaining average stress and coal pillar ultimate strength on the room-and-column type goaf coal pillar;
s1.4, based on the average stress and the coal pillar ultimate strength of the room-and-column goaf coal pillars, obtaining the safety coefficient of the room-and-column goaf coal pillars, namely the stability of the top room-and-column goaf coal pillars according to the vertical stress distribution rule of the room-and-column goaf coal pillars;
s1.5, based on the room and column type goaf coal pillar safety coefficient, constructing a physical similar material model, wherein the physical similar material model is used for displaying the state of the room and column type goaf coal pillar and verifying the accuracy of the stability calculation of the top room and column type goaf coal pillar.
3. The opposite safety mining method for the adjacent working faces under the shallow-buried short-distance room and pillar type goaf according to claim 2, characterized in that the average stress P on the coal pillar of the room and pillar type goaf is specifically as follows:
wherein gamma is the average volume weight of the overlying strata, H is the buried depth, L is the length, a is the width of the coal pillar, and b is the width of the coal room.
4. The method for safely exploiting the opposite directions of the adjacent working faces under the shallow-buried short-distance room-and-pillar type goaf according to claim 2, wherein the ultimate strength sigma of the coal pillar issThe method specifically comprises the following steps:
in the formula, σcIs the uniaxial compressive strength of the coal pillar, h is the height of the residual coal pillar, a1The width of the residual coal pillar is shown, and n is the width-height ratio of the coal pillar.
5. The opposite safety mining method for the adjacent working faces under the shallow-buried short-distance room and pillar type goaf according to claim 2, characterized in that the safety coefficient k of the room and pillar type goaf coal pillarfThe method specifically comprises the following steps:
in the formula, p is the average stress on the coal pillar of the room-and-pillar type goaf, sigmasThe ultimate strength of the coal pillar.
6. The method for safe mining of the adjacent working face under the shallow-buried short-distance room-and-pillar type goaf in the opposite direction as claimed in claim 1, wherein the specific steps of S2 are as follows:
s2.1, FLAC based on S13DNumerical calculation results are obtained, and the distribution characteristics of lateral support pressure and the inter-surface coal pillar stress evolution law of simultaneous mining of different opposite distances of adjacent working surfaces and mining of a single working surface are obtained;
s2.2, constructing an inter-surface coal pillar load calculation model based on the distribution characteristics of lateral support pressure of simultaneous mining and single-working-surface mining of different opposite distances of adjacent working surfaces and the inter-surface coal pillar stress evolution law;
s2.3, based on the inter-surface coal pillar load calculation model, obtaining the average stress at the top of the coal pillar and the inter-surface coal pillar safety coefficient; and the average stress at the top of the coal pillar and the safety coefficient of the coal pillar between the surfaces are respectively used for representing the superposition effect of the lateral support pressure and the stability of the coal pillar between the surfaces.
7. The method for safely mining the opposite direction of the adjacent working face under the shallow-buried short-distance room-and-pillar type goaf according to claim 6, characterized in that the average stress P at the top of the coal pillarZThe method specifically comprises the following steps:
wherein a is the width of the coal pillar, H1Is the thickness of bedrock, gamma1Is the average volume weight of bedrock, H2Is the thickness of the soil layer, gamma2Is the average volume weight of soil layer, alpha1Is the breaking angle of bedrock, alpha2Is a soil layer breaking angle.
8. The method for oppositely and safely mining the adjacent working faces under the shallow-buried short-distance room-and-pillar type goaf according to claim 6, wherein the safety coefficient k of the coal pillar between the facesfzThe method specifically comprises the following steps:
in the formula, σsIs the ultimate strength of the coal pillar, pzThe maximum stress of the coal pillar between the surfaces.
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