CN115341902A - Water-retaining coal mining method for lateral closed curtain of surrounding rock of coal mine working face - Google Patents
Water-retaining coal mining method for lateral closed curtain of surrounding rock of coal mine working face Download PDFInfo
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Abstract
The invention discloses a lateral closed curtain water-retention coal mining method for surrounding rocks of a coal mine working face, which comprises the steps of determining a mining influence range boundary of a thick hard sandstone aquifer and a position of the thick hard sandstone aquifer in a water diversion fracture zone height range according to acquired well field geological data, mining subsidence data of a mining area at the periphery of a well field and water diversion fracture height exploration data; according to the well field exploitation design, a closed curtain is constructed in the water-bearing layer of the thick hard rock layer of the boundary of the mining area or the panel area and around the stoping face, and the closure of the closed curtain is realized on the stoping face; and carrying out stoping operation on the stope face in the closed curtain. In the mining-induced fracture of the stable area behind the working face, the lateral water diversion fracture is plugged by directional horizontal long drilling grouting, the time and space characteristics of the mining overburden rock damage development of the working face are fully utilized, the grouting is carried out by utilizing the fracture generated by the movement of the mining-induced rock stratum, and the lateral water diversion channel of the rock stratum aquifer is plugged greatly.
Description
Technical Field
The invention belongs to the technical field of coal mining safety, and particularly relates to a water-retaining coal mining method for a lateral closed curtain of surrounding rock of a coal mine working face.
Background
With the increase of coal mining depth in China, more and more coal mines are exposed to a high water pressure mining environment, the Monshana mining area is used as one of important energy bases in China, when a Jurassic Yanan coal seam is mainly mined, thick hard water-rich rock strata are always formed on the Jurassic Yanan coal seam, and when the Jurassic Yanan coal seam is mined in a high-strength mode, the water damage prevention and control problem of the thick rock strata is faced. The prior mine water disaster prevention and control technology usually adopts the measures of pre-dredging before mining, increasing the drainage capacity and the like, and has the defects that: the purpose of in-situ water resource protection is difficult to achieve; in addition, in the existing rock stratum pore grouting, the pore throat is small, water can bypass, but slurry is difficult to pass through, so that the problem of pore grouting of a pre-mining structure water interception curtain is difficult to realize, water continuously enters a working face along a water guide crack after a strong water-rich rock stratum is mined and broken, the water is a main source of water burst of a mine, a coal mine needs to continuously drain water to maintain the safety of an underground operation space, huge drainage cost is spent, and a large amount of water resource waste is caused. Therefore, how to efficiently transform the mining permeability of the huge thick rock stratum has great significance for mine water control.
Disclosure of Invention
Aiming at the defects and shortcomings in the prior art, the invention provides a lateral closed curtain water-retention coal mining method for surrounding rock of a coal mine working face, which is characterized in that a fracture generated by the movement of a mining rock stratum is utilized for grouting, pore grouting is changed into fracture grouting, the water passing section of a rock stratum aquifer is greatly reduced, the permeability is reduced, the lateral peripheral dynamic supply of the rock stratum aquifer is effectively cut off, the mine water inflow is greatly reduced, the technical problem that a water-inrush large channel in a water-diversion fracture zone is difficult to block in the prior art is solved, and the purpose of reducing the mine water inflow of the huge thick rock stratum aquifer is achieved
In order to achieve the purpose, the invention adopts the following technical scheme:
a lateral closed curtain water-retention coal mining method for surrounding rocks of a coal mine working face comprises the steps of determining the mining influence range boundary of a thick and hard sandstone aquifer and the position of the thick and hard rock aquifer in the height range of a water flowing fracture zone according to acquired well field geological data, mining subsidence data of a mining area around a well field and water flowing fracture height exploration data; according to the well field exploitation design, a closed curtain is constructed in the water-bearing layer of the thick hard rock layer of the boundary of the mining area or the panel area and around the stoping face, and the closure of the closed curtain is realized on the stoping face; and carrying out stoping operation on the stope face in the closed curtain.
The invention also has the following technical characteristics:
the method specifically comprises the following steps:
step 1, acquiring geological data of a well field, mining subsidence data of a mining area around the well field and height exploration data of a water flowing fracture, and determining a mining influence range boundary of a thick hard sandstone aquifer and a position of the thick hard sandstone aquifer in a height range of a water flowing fracture zone according to the acquired data;
step 2, arranging a first mining working face in the direction of a vertical main roadway in a water-bearing layer of a thick hard rock stratum on one side of the boundary of a mining area or panel according to the well field mining design; determining the layout position of a first boundary lateral curtain of the first mining working face according to the plane position of the first mining working face;
step 3, carrying out stoping operation on the first mining working face, and constructing a first boundary lateral curtain to a stoping line in the stoping operation process of the first mining working face, wherein in the trend of the first mining working face, the top end of the first boundary lateral curtain and the mining working face of the first mining working face always keep a certain lag distance D;
step 4, according to the method from the step 2 to the step 3, the mining operation of the first continuous working face, the construction of a second boundary lateral curtain for lateral water interception and seepage prevention of the first continuous working face, the mining operation of the second continuous working face, the construction of a third boundary lateral curtain for lateral water interception and seepage prevention of the second continuous working face, the mining operation of the third continuous working face and the construction of a fourth boundary lateral curtain for lateral water interception and seepage prevention of the third continuous working face are completed in sequence;
in the construction process, the top end of the second boundary lateral curtain and the mining working surface of the first continuous working surface, the top end of the third boundary lateral curtain and the mining working surface of the second continuous working surface, and the top end of the fourth boundary lateral curtain and the mining working surface of the third continuous working surface are always kept at a certain lag distance D;
and 5, carrying out hydraulic fracturing and grouting transformation on the horizontal well by utilizing the horizontal long drill hole, sequentially connecting blank sections among the first boundary lateral curtain, the second boundary lateral curtain, the third boundary lateral curtain and the fourth boundary lateral curtain to form closed curtain interception on a mining area or panel area, and then sequentially stoping a stope face in the closed curtain.
Furthermore, the horizontal distance between the plane of the first boundary lateral curtain and the lateral boundary of the first mining face close to the first boundary curtain is S, and S meets the following conditions:
wherein the content of the first and second substances,
r is the boundary of the mining influence range of the aquifer of the thick and hard sandstone, and the unit is m;
δ is the formation movement angle in degrees;
k is the vertical stress peak coefficient;
c is the cohesion of the coal body and has the unit of MPa;
p 0 the unit is the supporting strength of the coal side, and is kPa;
m is the mining thickness and the unit is m;
f is the friction factor of the contact surface of the coal seam and the coal seam roof or the coal seam floor;
H m the unit is m, which is the coal seam burial depth;
gamma is the average volume force of the overburden and has the unit of kN/m 3 。
Further, the hysteresis distance D =2L to 3L, and L is determined by the following formula:
in the formula (I), the compound is shown in the specification,
alpha is the rotation angle of the thick and hard sandstone rock beam of the mining working face, and the unit is DEG,
R t the tensile strength of the thick and hard sandstone rock beam of the mining working face is MPa,
q is the uniform load of the thick and hard sandstone rock beam of the mining working face, the unit is Mpa,
h is the thickness of the thick hard sandstone rock beam of the mining working face, and the unit is m;
and L is the periodic breaking step distance of the thick and hard sandstone rock beam of the mining working face, and the unit is m.
Further, the boundary R of the mining influence range of the thick and hard sandstone aquifer in the step 1 is determined by the following formula:
R＝H/tanδ
in the formula (I), the compound is shown in the specification,
r is the boundary of the mining influence range of the aquifer of the thick and hard sandstone, and the unit is m;
h is the vertical distance between the top plate of the aquifer of the thick and hard sandstone and the top plate of the coal seam, and the unit is m;
δ is the formation movement angle in degrees.
Further, the operation parameters of the hydraulic fracturing in the step 5 comprise: the fracturing fluid is active water fracturing fluid, the propping agent is quartz sand with the thickness of 4-12 m 3 The injection displacement is 6-12 m 3 Min, average sand ratio of 10-30％。
Furthermore, the grouting material in the step 5 comprises 10-40% of cement, 60-90% of fly ash and an activator by mass percentage.
Furthermore, the height of the water flowing fractured zone in the step 1 can be dynamically determined by combining the working resistance monitoring of the hydraulic support and the well-earth microseismic monitoring.
Compared with the prior art, the invention has the beneficial technical effects that:
(1) According to the method, the mining-induced fracture is formed near the stope surrounding rock through stoping on the working face, then, the lateral water flowing fracture is plugged through directional horizontal long drilling grouting in the mining-induced fracture of the stable area behind the working face side by utilizing the mining-induced permeability difference of different subareas of the stope surrounding rock, the time and space characteristics of the mining overburden rock damage and development of the working face are fully utilized, grouting is carried out by utilizing the fracture generated by the movement of the mining-induced rock stratum, and a closed curtain is constructed around the stope working face along with the mining process, so that the lateral water flowing channel of the rock stratum water-bearing layer is plugged greatly, the regional transformation of the permeability of the huge thick rock stratum water-bearing layer can be realized, the in-situ protection of water resources is achieved, the mine water inflow is reduced remarkably, and a large amount of drainage cost is saved.
(2) The method has the advantages of simple operation, strong adaptability and low construction cost, is beneficial to ecological civilized construction of the coal mine area, and has strong popularization and application values.
Drawings
FIG. 1 is a schematic view of the face mining side curtain layout of the present invention;
FIG. 2 is a schematic cross-sectional view of the face of the present invention showing the inclination of the mining side curtains;
FIG. 3 is a plan view of a thick hard rock roof dynamically broken with face mining;
FIG. 4 is a broken cross-sectional view of a rock beam for thick hard rock formation;
fig. 5 is a schematic view of mining lateral curtain grouting of a mining zone (panel).
The invention is described in detail below with reference to the drawings and the detailed description.
Detailed Description
The present invention is not limited to the following embodiments, and all equivalent changes based on the technical solutions of the present invention fall within the protection scope of the present invention.
Technical terms related to the present invention are explained as follows:
thick hard sandstone aquifer: refers to a sandstone layer which is permeable to water and gives a considerable amount of water, and has large thickness and mechanical strength.
First mining working face: refers to the first face to be recovered that is placed at the zone or panel boundary of a field mining design.
First successive working surfaces: the method is characterized in that the method is a working face which is arranged at the boundary of a mining area or a panel area of a well field mining design and needs to be mined after the first mining working face is mined. By analogy, the second continuous working face is the working face which needs to be stoped after the stoping of the first continuous working face is completed, the third continuous working face is the working face which needs to be stoped after the stoping of the second continuous working face is completed, and the first stoping working face, the first continuous working face, the second continuous working face and the third continuous working face in the scheme are arranged according to the positions shown in the attached figure 5.
Mining working face: for example, in the present embodiment, when the extraction work is performed on the first working face, the first continuous working face, the second continuous working face, and the third continuous working face arranged, the working face on which the extraction work is performed is referred to as a mining working face.
Solid coal side: and connecting the laneways on the side far away from the goaf in the working face.
Mining influence scope: the mining of the coal seam of the lower working face can cause the damage of the upper rock stratum in a certain range, the junction position of the upper rock stratum and the complete rock stratum is a mining influence boundary, and the area in the mining influence boundary belongs to the mining influence range.
And (3) connecting a lateral curtain: the lateral curtain is constructed on one side of the continuous working face for protecting the continuous working face, and the construction of the lateral curtain is carried out along with the mining of the coal mine working face in the scheme, and belongs to a mining lateral curtain.
Tendency: the straight line drawn downwards along the layer perpendicular to the strike line is called the inclined line, and the direction of the projection line on the horizontal plane is called the inclination.
The trend is as follows: the intersection line of the coal bed face and the horizontal plane is called the strike line, and the directions pointed by the two ends are called the strike.
Other faces to be stoped in the closed curtain: the continuous coal mining working face is a working face which is positioned in a closed curtain and is required to be subjected to coal mining in an area formed by enclosing a first mining working face, a first continuous working face, a second continuous working face and a third continuous working face.
The present invention will be described in further detail with reference to examples.
Example 1
According to the technical scheme, as shown in figures 1 to 5, the thickness of a main mining coal seam 1 of a certain coal mine is 8m, the burial depth is 650m, the coal seam belongs to a nearly horizontal coal seam, a thick hard rock stratum aquifer is reserved 180m above the coal seam, a thick hard rock stratum is reserved on a roof, the lithology of the thick hard rock stratum is mainly medium and thin sandstone, thin sandstone and mudstone interbedded layers, a fully-mechanized top coal mining process is adopted, the hydrogeology type is complex, and the water inflow of a nearby mine on the periphery is 2000m 3 H is used as the reference value. The first mining working face of the mine is 1800m long, the mining plan is divided into four panels, and the water disaster treatment work of the thick and hard rock stratum of the coal mine needs to be carried out.
The embodiment provides a lateral closed curtain water-retention coal mining method for surrounding rock of a coal mine working face, which comprises the following steps:
step 1, acquiring geological data of a well field, mining subsidence data of a mining area around the well field and height exploration data of a water flowing fracture, and determining a mining influence range boundary of a thick hard sandstone aquifer and a position of the thick hard sandstone aquifer in a height range of a water flowing fracture zone according to the acquired data;
in the conventional well logging, the well field geological data and the mining subsidence monitoring data are obtained by comprehensively surveying mainly through various means such as drilling, earthquake, geophysical well logging, geological and hydrogeological, sampling test, pumping test, surface water and underground water dynamic long-term observation and the like, wherein the well field geological data and the mining subsidence monitoring data mainly comprise a rock stratum moving angle, a distance between a top plate of a water bearing layer of a thick hard rock stratum and a top plate of a coal bed, a height of a water diversion fissure zone, a position of a water bearing layer of the thick hard rock stratum in the water diversion fissure zone and a coal bed burial depth,
in the embodiment, the rock stratum movement angle determined according to the mining subsidence monitoring data is 82 degrees, the distance between the top plate of the water-bearing layer of the thick hard rock stratum and the top plate of the coal seam is 220m, the height of a water-flowing fractured zone formed after the mining of the working face is stable is 220m, and the layer position of the water-bearing layer of the thick hard rock stratum in the water-flowing fractured zone is 180 m-220 m. Coal seam buried depth H m =650m; the mining thickness is m =8m;
step 2, arranging a first mining working face in the direction of a vertical main roadway in the water-bearing layer of the thick hard rock stratum on one side of the boundary of the mining area or the panel area according to the well field mining design; determining the layout position of a first boundary lateral curtain of the first mining working face according to the plane position of the first mining working face;
step 3, carrying out stoping operation on the first mining working face, and constructing a first boundary lateral curtain to a stoping line in the stoping operation process of the first mining working face, wherein in the trend of the first mining working face, as shown in fig. 1, the top end of the first boundary lateral curtain and the mining working face of the first mining working face always keep a certain lag distance D;
step 4, according to the method from the step 2 to the step 3, the mining operation of the first continuous working surface, the construction of a second boundary lateral curtain for lateral water interception and seepage prevention of the first continuous working surface, the mining operation of the second continuous working surface, the construction of a third boundary lateral curtain for lateral water interception and seepage prevention of the second continuous working surface, the mining operation of the third continuous working surface and the construction of a fourth boundary lateral curtain for lateral water interception and seepage prevention of the third continuous working surface are completed in sequence;
in the construction process, the top end of the second boundary lateral curtain and the mining working surface of the first continuous working surface, the top end of the third boundary lateral curtain and the mining working surface of the second continuous working surface, and the top end of the fourth boundary lateral curtain and the mining working surface of the third continuous working surface are always kept at a certain lag distance D;
wherein the hysteresis distance D =2L to 3L, and L is determined by the following formula:
in the formula (I), the compound is shown in the specification,
alpha is the rotation angle of the thick and hard sandstone rock beam of the mining working face, and the unit is DEG,
R t the tensile strength of the thick and hard sandstone beam of the mining working face is expressed in MPa,
q is the uniform load of the thick and hard sandstone rock beam of the mining working face, the unit is Mpa,
h is the thickness of the thick hard sandstone rock beam of the mining working face, and the unit is m;
and L is the periodic breaking step distance of the thick and hard sandstone rock beam of the mining working face, and the unit is m.
It should be noted that, in the actual construction process, since the rectangular coal mine mining area surrounded by the first mining working face, the first continuous working face, the second continuous working face and the third continuous working face is in a mining area or panel, the geological conditions of the working faces are the same or similar, and therefore, the α and R in the above formula are the same or similar t Q and h are fixed values, which can be determined by the well field geological data obtained in the step 1 and mining subsidence data of the mining area around the well field, and the value range of alpha is 2-8 degrees according to experience.
In this example, α is 8 ° and the tensile strength R of the rock beam is t The height of the rock beam is 3.0MPa, the uniform load q of the rock beam is 0.1MPa, the thickness h of the rock beam is 40 m, then the periodic breaking step distance L =75.5m of the rock beam is obtained through the formula, the mining is followed, the lag distance D between the top end of the lateral curtain and the corresponding mining working face in the walking direction is 151 m-226.5 m, namely, as shown in figure 1, the distance between the top end of the first boundary lateral curtain and the mining working face of the first mining working face is kept to be 151 m-226.5 m all the time. By parity of reasoning, the mining working surface of the second boundary lateral curtain and the first continuous working surface, the mining working surface of the top end of the third boundary lateral curtain and the second continuous working surface, and the mining working surface of the top end of the fourth boundary lateral curtain and the third continuous working surface are all always 151 m-226.5 m apart,this has the advantage that: the method can ensure that the drill holes are distributed in the area behind the working face where overburden rock deformation is stable, avoid hole collapse and blockage of the drill holes and facilitate implementation of horizontal long drill hole grouting transformation.
As shown in fig. 4, the lag distance D =2L to 3L behind the working face is because the overburden deformation is already stable at a certain distance behind the working face according to practical operation experience, and the lag distance D =2L to 3L is more convenient for laying and grouting the horizontal long drill.
As a preferable scheme of this embodiment:
the horizontal distance between the plane of the first boundary lateral curtain and the lateral boundary of the first mining working face close to the first boundary curtain in the inclination of the first boundary lateral curtain is S, and the S meets the following conditions:
in the formula (I), the compound is shown in the specification,
r is the boundary of the mining influence range of the aquifer of the thick and hard sandstone, and the unit is m;
delta is the formation movement angle in degrees;
k is the vertical stress peak coefficient;
c is the cohesion of the coal body and has the unit of MPa;
p 0 the unit is the supporting strength of the coal side, and is kPa;
m is the mining thickness and the unit is m;
f is the friction factor of the contact surface of the coal seam and the coal seam roof or the coal seam floor;
H m the unit is m, which is the coal seam buried depth;
gamma is the average volume force of the overburden and has the unit of kN/m 3 。
In the above formula, delta, K, C,
p 0 、m、f、H m And gamma is a constant value and can be determined by the well field geological data obtained in the step 1 and mining subsidence data of the mining area around the well field.
The mining influence range boundary R of the thick and hard sandstone is determined by the following formula:
R＝H/tanδ
in the formula (I), the compound is shown in the specification,
r is the boundary of the mining influence range of the aquifer of the thick and hard sandstone, and the unit is m;
h is the vertical distance between the top plate of the aquifer of the thick and hard sandstone and the top plate of the coal seam, and the unit is m;
δ is the formation movement angle in degrees.
In the above formula, H and δ are constants, and can be determined by the well field geological data obtained in step 1 and mining subsidence data of the mining area around the well field.
In the embodiment, the movement angle of the rock stratum is 82 degrees, the vertical stress peak coefficient is 2.5 degrees, the cohesive force of the coal body is 0.5Mpa, the internal friction angle of the coal body is 20 degrees, the support strength of the coal side is 20kPa, the mining thickness is 8m, the friction factor of the contact surface of the coal seam and the coal seam top plate or the coal seam bottom plate is 0.3, the burial depth of the coal seam is 650m, the average volume force of the overlying rock stratum is 25kN/m & lt 3 & gt, and the horizontal distance between the boundary curtain and the lateral boundary of the mining area, namely 16.4m S-type structure is 25.3m is obtained through the above method; the mining influence range boundary R at the bottom plate of the aquifer of the thick and hard rock stratum is 25.3m.
And 5, carrying out horizontal well hydraulic fracturing and grouting transformation by using the horizontal long drill hole, sequentially connecting blank sections among the first boundary lateral curtain, the second boundary lateral curtain, the third boundary lateral curtain and the fourth boundary lateral curtain to form closed curtain intercepting of a mining area or panel, and then sequentially stoping a stope face in the closed curtain.
The hydraulic fracturing principle is as follows: the ground high-pressure pump set is used for injecting large-displacement liquid into the stratum through the shaft, high pressure is suppressed at the bottom of the well, and when the pressure exceeds the bearing capacity of the stratum, a crack is formed in the stratum near the bottom of the well. And continuously injecting liquid carrying the propping agent, wherein the fracture gradually extends forwards, and the propping agent plays a role in propping the fracture, so that a sand-filled fracture with a certain size and high flow conductivity is formed, and the effects of weakening the mechanical property of the stratum and improving the permeability of the stratum are achieved.
In the embodiment, in the hydraulic fracturing operation, the fracturing fluid is active water fracturing fluid, the propping agent is quartz sand, and the sand adding strength of the fracturing section is 4-12 m 3 The injection displacement is 6-12 m 3 Min, the average sand ratio is 10-30%.
And 5, the grouting material comprises 10-30% of cement, 70-90% of fly ash and an exciting agent by mass percent.
In conclusion, the method disclosed by the invention utilizes the deformation and permeability zoning characteristics of the mining lateral overburden rock structure formed after the coal seam is mined out to perform grouting plugging on the lateral water flowing fractures generated by the movement of the rock stratum and plug the lateral supply channel of the sandstone aquifer from the in situ, so that the water flowing section of the sandstone aquifer is greatly reduced, and the permeability is reduced; and then with the mining area or the panel area as a unit, performing grouting transformation on the lateral sandstone aquifer roof on the periphery of the four working faces to finally form lateral closed curtain closure on the mining area and the panel area, effectively cutting off dynamic supply of roof water of the mining area around the sandstone aquifer, and greatly reducing water inflow of the mining area or the panel area so as to solve the technical problem that a vertical water inrush large channel in a water diversion fissure zone is difficult to block in the prior art.
The above-described implementation processes are merely examples for clearly illustrating the present application, and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should it be exhaustive of all embodiments. And obvious variations or modifications of this type are intended to be covered by the present invention.
Claims (8)
1. A lateral closed curtain water-retention coal mining method for surrounding rocks of a coal mine working face is characterized by comprising the steps of determining a mining influence range boundary of a thick hard sandstone aquifer and a position of the thick hard sandstone aquifer within a height range of a water flowing fracture zone according to acquired well field geological data, mining subsidence data of a mining area around a well field and water flowing fracture height exploration data; according to the well field mining design, a closed curtain is constructed in the water-bearing layer of the thick hard rock layer of the boundary of a mining area or a panel area and around a stoping face, and closed curtain interception is realized on the stoping face; and carrying out stoping operation on the stope face in the closed curtain.
2. The coal mine working face surrounding rock lateral closed curtain water-retention coal mining method according to claim 1, characterized by comprising the following steps:
step 1, acquiring geological data of a well field, mining subsidence data of a mining area around the well field and height exploration data of a water flowing fracture, and determining a mining influence range boundary of a thick hard sandstone aquifer and a position of the thick hard sandstone aquifer in a height range of a water flowing fracture zone according to the acquired data;
step 2, arranging a first mining working face in the direction of a vertical main roadway in a water-bearing layer of a thick hard rock stratum on one side of the boundary of a mining area or panel according to the well field mining design; determining the layout position of a first boundary lateral curtain of the first mining working face according to the plane position of the first mining working face;
step 3, carrying out stoping operation on the first mining working face, and constructing a first boundary lateral curtain to a stoping line in the stoping operation process of the first mining working face, wherein in the trend of the first mining working face, the top end of the first boundary lateral curtain and the mining working face of the first mining working face always keep a certain lag distance D;
step 4, according to the method from the step 2 to the step 3, the mining operation of the first continuous working face, the construction of a second boundary lateral curtain for lateral water interception and seepage prevention of the first continuous working face, the mining operation of the second continuous working face, the construction of a third boundary lateral curtain for lateral water interception and seepage prevention of the second continuous working face, the mining operation of the third continuous working face and the construction of a fourth boundary lateral curtain for lateral water interception and seepage prevention of the third continuous working face are completed in sequence;
in the construction process, the top end of the second boundary lateral curtain and the mining working surface of the first continuous working surface, the top end of the third boundary lateral curtain and the mining working surface of the second continuous working surface, and the top end of the fourth boundary lateral curtain and the mining working surface of the third continuous working surface are always kept at a certain lag distance D;
step 5, carrying out hydraulic fracturing and grouting transformation on the horizontal well by utilizing the horizontal long drill hole, sequentially connecting blank sections among a first boundary lateral curtain, a second boundary lateral curtain, a third boundary lateral curtain and a fourth boundary lateral curtain to form closed curtain interception on a mining area or panel area, and then sequentially stoping other to-be-stoped working faces in the closed curtain;
the first working face, the first continuous working face, the second continuous working face and the third continuous working face enclose to form a rectangular coal mine mining area.
3. The water-retaining coal mining method adopting the closed curtain on the lateral wall rock of the coal mine working face as set forth in claim 2, wherein the horizontal distance between the plane of the first boundary lateral curtain and the lateral boundary of the first mining working face close to the first boundary curtain in the inclination direction is S, and S satisfies the following condition:
in the formula (I), the compound is shown in the specification,
r is the boundary of the mining influence range of the aquifer of the thick and hard sandstone, and the unit is m;
δ is the formation movement angle in degrees;
k is the vertical stress peak coefficient;
c is the cohesion of the coal body and has the unit of MPa;
p 0 the unit is the supporting strength of the coal side, and is kPa;
m is the mining thickness and the unit is m;
f is the friction factor of the contact surface of the coal seam and the coal seam top plate or the coal seam bottom plate;
H m the unit is m, which is the coal seam buried depth;
gamma is the average volume force of the overburden and has the unit of kN/m 3 。
4. The coal mine working face surrounding rock lateral closed curtain water-retention coal mining method according to claim 2, wherein in the step 3 and the step 4, the lag distance D = 2L-3L, and L is determined by the following formula:
in the formula (I), the compound is shown in the specification,
alpha is the rotation angle of the thick and hard sandstone rock beam of the mining working face, and the unit is DEG,
R t the tensile strength of the thick and hard sandstone beam of the mining working face is expressed in MPa,
q is the uniform load of the thick and hard sandstone rock beam of the mining working face, the unit is Mpa,
h is the thickness of the thick hard sandstone rock beam of the mining working face, and the unit is m;
and L is the periodic breaking step distance of the thick and hard sandstone rock beam of the mining working face, and the unit is m.
5. The coal mine working face surrounding rock lateral closed curtain water retention coal mining method as claimed in claim 1, wherein the thick and hard sandstone aquifer mining influence range boundary R is determined by the following formula:
R＝H/tanδ
in the formula (I), the compound is shown in the specification,
r is the boundary of the mining influence range of the aquifer of the thick and hard sandstone, and the unit is m;
h is the vertical distance between the top plate of the aquifer of the thick and hard sandstone and the top plate of the coal seam, and the unit is m;
δ is the formation movement angle in degrees.
6. The coal mine working face surrounding rock lateral closed curtain water-retention coal mining method according to claim 2, wherein the operation parameters of the hydraulic fracturing in the step 5 comprise: the fracturing fluid is active water fracturing fluid, the propping agent is quartz sand, and the sand adding strength of the fracturing section is 4-12 m 3 The injection displacement is 6-12 m 3 Min, the average sand ratio is 10-30%.
7. The coal mine working face surrounding rock lateral closed curtain water-retention coal mining method as claimed in claim 2, wherein the grouting material in step 5 comprises 10-40% of cement, 60-90% of fly ash and an exciting agent by mass percentage.
8. The coal mining method of claim 2, characterized in that the height of the water flowing fractured zone in the step 1 can be dynamically determined by the combination of hydraulic support working resistance monitoring and well-earth microseismic monitoring.
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