CN110761791B - Method for upward repeated mining of hollow coal seam by accumulated water among coal pillars in freezing cutter pillar type residual mining area - Google Patents
Method for upward repeated mining of hollow coal seam by accumulated water among coal pillars in freezing cutter pillar type residual mining area Download PDFInfo
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- CN110761791B CN110761791B CN201911122440.3A CN201911122440A CN110761791B CN 110761791 B CN110761791 B CN 110761791B CN 201911122440 A CN201911122440 A CN 201911122440A CN 110761791 B CN110761791 B CN 110761791B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C41/00—Methods of underground or surface mining; Layouts therefor
- E21C41/16—Methods of underground mining; Layouts therefor
- E21C41/18—Methods of underground mining; Layouts therefor for brown or hard coal
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- E—FIXED CONSTRUCTIONS
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- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F15/00—Methods or devices for placing filling-up materials in underground workings
Abstract
The invention discloses a method for repeatedly mining a hollow coal seam by accumulated water among coal pillars in a freezing cutter-pillar type residual mining area in an ascending mode, and belongs to the technical field of coal mining. On the basis of judging the ascending mining feasibility of the kick-out coal seam and detecting the distribution conditions of the coal pillar group and the dead zone group of the cutter-post type residual mining zone, the invention uses the left coal pillar as a partition of accumulated water among the coal pillars of the cutter-post type residual mining zone, and utilizes the artificial refrigeration technology to freeze the accumulated water among the coal pillars of the dead zone in a segmented manner, so that the water in a liquid phase becomes ice with certain bearing capacity, the space of the dead zone is filled, the whole dead zone and the left coal pillar are connected into a whole through freezing, and then the special mining method for mining the kick-out coal seam on the kick-out coal seam is carried out. Compared with the traditional column-side paste filling mining, the invention does not need to treat accumulated water among coal columns in the knife column type residual mining area, greatly reduces the engineering quantity, and does not need to set a ground grouting material mixing station for mixing filling slurry, pumping and other work; is beneficial to recovering mineral resources and promotes the sustainable development of the mineral resources.
Description
Technical Field
The invention relates to a method for repeatedly mining a pedaled empty coal seam in an ascending way by accumulated water among coal pillars in a freezing column type residual mining area, relates to the technical field of coal mining, and is mainly suitable for safe mining of the pedaled empty coal seam on the column type residual mining area.
Background
With the acceleration of the socialist modernization process, the contradiction between the limitless increase of the demand of coal and the limitless renewable resource is severe day by day, which requires that the resource recovery rate is improved and a saving-type mining area is built, so that the re-mining of residual coal is gradually paid attention to people.
Under the influence of early mining, some coalbeds capable of being mined are abandoned above a plurality of goafs in the existing production mining areas or mines, the abandoned coal reserves are considerable, and the upward mining of the residual mining areas of the coal mines becomes more and more the focus of attention of people along with the improvement of mining technologies. However, due to the influence of early mining, the integrity and stability of the goaf coal seam and the floor rock stratum in the residual mining area are damaged and destroyed in different degrees, which may cause mine disasters and affect safe production. Thus, the prerequisites for upgoing mining are: the feasibility evaluation and judgment are carried out on whether the safety mining of the overhead coal seam on the residual mining area can be carried out, except for a conventional uplink mining feasibility judgment method of the residual mining area, such as a three-belt judgment method, a surrounding rock balance method, a ratio judgment method, a mathematical analysis method and the like, the Chinese patent CN101109283B quantitatively judges the feasibility of the uplink mining of the overhead coal seam from the perspective of an interlayer rock stratum structure; the Chinese patent CN103147737A provides a method for detecting a damage rule of overburden rock in upward mining, discloses a spatial-temporal evolution rule of overburden rock damage in the upward mining process, solves the problem of reasonably determining the arrangement of an upward mining working face and a roadway, and ensures the safety of upward mining. The upward mining feasibility judgment of each pedaled empty coal seam is based on the thickness and the stability of the stratum between layers, the upward mining feasibility of the pedaled empty coal seam in the residual mining area is judged and evaluated in advance through calculation and analysis, and engineering practice is guided.
The coal pillar group of the cutter-pillar type residual mining area, the overlying goaf coal seam and the coal seam floor rock layer form a whole, so the stability of the coal pillar group of the cutter-pillar type residual mining area restricts the safe upward mining of the goaf coal seam. In addition, the cutter pillar type residual goaf between the left coal pillar groups is gradually filled with underground water, so that the coal pillars and surrounding rocks are softened, and the stability of the overhead mining is influenced.
Therefore, a method for enhancing the stability of the coal pillar group in the tool post type residual mining area under the hollow coal seam is urgently needed to be found, the problem of water accumulation among the remaining coal pillars can be solved, and the safety mining of the hollow coal seam is ensured.
Disclosure of Invention
The invention aims to provide a method for repeatedly mining a pedaled empty coal seam in an ascending manner by accumulated water among coal pillars of a freezing knife-pillar type residual mining area, which effectively solves the problem that a knife-pillar type residual mining area coal pillar group is locally instable instantaneously in the pedaled empty coal seam ascending mining process.
According to the special mining method, on the basis of judging the ascending mining feasibility of the kick-out coal seam and detecting the distribution conditions of the coal pillar group and the dead zone group of the tool post type residual mining zone, the remaining coal pillars are used as partitions of water accumulated among the coal pillars of the tool post type residual mining zone, the water accumulated among the coal pillars of the dead zone is frozen in a segmented mode by using an artificial refrigeration technology, liquid-phase water is made into ice with certain bearing capacity, the space of the dead zone is filled, the whole dead zone and the remaining coal pillars are connected into a whole through freezing, and then the kick-out coal seam is mined on the kick-out coal seam.
The invention provides a method for upward repeated mining of a hollow coal seam by accumulated water among coal pillars in a freezing cutter-pillar type residual mining area, which comprises the following steps of:
(1) judging the feasibility of upward mining of the overlying and empty coal seam on the cutter column type residual mining area;
(2) the distribution conditions of a coal pillar group and an empty area group of a tool post type residual mining area under a pedaled coal seam are explored and found out by combining original geological and technical data of a mine, and distribution form graphs of the coal pillar group and the empty area group of the tool post type residual mining area are drawn to guide safe production; detecting the accumulated water height, the accumulated water quantity and the water quality of the dead zone of the tool post type residual mining area by combining mine production data;
(3) excavating a stoping roadway of the pedaled empty coal seam, and arranging a working surface of the pedaled empty coal seam;
(4) arranging a freezing station in an air return roadway of the pedaled empty coal seam, and carrying out saline water conveying and loop pipeline erection in the roadway;
(5) vertically drilling holes in a pedaled empty coal seam stoping roadway from top to bottom, arranging roadway drilling holes, putting the roadway drilling holes into accumulated water in a goaf of a residual mining area, and arranging freezing pipelines, wherein the drilling holes in the roadway always lead the current freezing area, and the freezing pipelines are arranged in the goaf between the next coal pillars in advance to perform pre-freezing and cooling work, so that the freezing speed is improved; when the area of the empty area between the coal pillars is too large and the accumulated water is too much, performing bottom plate auxiliary drilling construction on the bottom plate of the working face from top to bottom;
(6) the freezing station arranged in the step (4) starts to refrigerate, the accumulated water in the empty area between the coal pillars at the end part of the knife-pillar type residual mining area enters an active freezing period, the accumulated water is gradually frozen, and the ice body frozen by the accumulated water in the unfilled empty area is fully abutted by utilizing the characteristic of volume expansion of the water during freezing, so that the bottom plate rock stratum of the hollow coal seam is supported, and meanwhile, the side protection effect is realized on the coal pillars in the knife-pillar type residual mining area; the freezing pipelines are arranged in the auxiliary drilling holes of the bottom plate of the working face, the pipelines are timely removed when accumulated water between the coal pillars of the knife-pillar type residual mining area is basically frozen, the frozen pipelines are placed in the accumulated water and left in the frozen ice body, and finally the frozen pipelines are withdrawn through the drilling holes of the roadway after the ice body is melted, so that the pushing of the working face is prevented from being interfered;
(7) after water accumulation in the lower coal pillars of the recovery working surface of the pedaled empty coal seam is frozen, the recovery working surface is pushed forwards under the support, the recovery working surface is pushed section by section, when the working surface is pushed to the front 3-8m of the boundary line of the empty area between the next pre-frozen coal pillars, the pushing of the working surface is stopped, meanwhile, the freezing work in the step (6) reduces the refrigerating capacity and enters a passive freezing period, and the frozen ice blocks are kept not to be thawed;
(8) repeating the steps (5), (6) and (7), wherein the accumulated water in the goaf between the next coal pillars close to the working surface in the step (7) enters an active freezing period, so that the accumulated water in the goaf is frozen and solidified and forms a whole together with the left coal pillars, the residual mining area top floor and the surrounding rock, a supported stable environment is provided for the pushing of the working surface of the overlying pedaled empty coal seam, the working surface of the pedaled empty coal seam is continuously pushed forward, and the coal resources of the pedaled empty coal seam are gradually mined;
(9) along with the advance of the working surface, arranging a return air roadway of a freezing station for reinforcing support, gradually caving a transportation roadway on the other side along with the advance of the working surface, advancing the accumulated water freezing working of a goaf ahead of the advance of the working surface, starting an active freezing period of the accumulated water in the goaf between the 4 th coal pillars, finishing the refrigeration of the goaf between the coal pillars at the end part of a residual mining area, slowly and naturally thawing ice, and withdrawing a pipeline in accumulated water after the ice melts; then the working face is circularly operated, and the accumulated water in the empty areas among the coal pillars of at least three residual mining areas is in a frozen state while the working face is pushed.
In the scheme, the accumulated water in the dead zone of the tool post type residual mining area is not communicated with the underground river, the long-term water volume of the accumulated water is basically unchanged, the accumulated water is replenished by a small amount of underground water and is lost in a small scale, and the total water volume is in a dynamic stable state.
In the above scheme, the selection and arrangement of the freezing equipment of the freezing station refer to the construction experience of the conventional freezing method tunnel, and the equipment selection provides the following reference scheme:
the refrigerator selects an SKD136.1.H type screw unit, the working condition refrigerating capacity of a single unit is designed to be 116960Kcal/h, and the power of a single motor is 114KW;
② each refrigerator IS assembled with a brine circulating pump (IS 150-125 and 315 are selected), and a single refrigerator has a flow of 200m3H, motor power 37KW;
thirdly, an IS 150-125-315B type cooling water circulating pump IS selected as a freezing station cooling water circulating pump, and the flow of each cooling water circulating pump IS 173m3And h, the motor power is 18.5 KW.
Wherein the brine circulating pump and the cooling water circulating pump are both additionally provided with a standby device
In the scheme, when each freezing pipeline is placed in the cutter post type residual mining area accumulated water, a series of temperature sensors are tied to the pipelines and are placed together with the pipelines, the pipelines are evenly distributed in the cutter post type residual mining area accumulated water, and the temperature of the accumulated water (frozen ice) in the goaf is monitored in real time.
In the above scheme, the feasibility determination method in step (1) is as follows: the method combines the traditional three-belt discrimination method, the surrounding rock balance method, the ratio discrimination method, the mathematical analysis method and the quantitative discrimination method to comprehensively discriminate the feasibility of the upward mining of the coal seam covered and empty on the cutter-column type residual mining area.
In the scheme, the width and the height of the cutter post type residual mining area space group and the coal post group under the kick-off coal bed are checked and cleaned through the original geological and technical data of the mine in the step (2), the distribution direction, the size and the volume of the cutter post type residual mining area space group are accurately detected through the three-dimensional laser scanner, and meanwhile the depth, the distribution range and the volume of accumulated water in the coal post space area are detected.
In the scheme, the open-cut holes of the pedaled empty coal seam are arranged above the explored cutter-pillar-type residual mining area end coal pillars in the step (3), the mining roadway and the working face are arranged on the pedaled empty coal seam, the air return roadway is widened by 1.0-1.2 times on the original design size, and the subsequent freezing station is convenient to arrange.
In the scheme, the selection of the type, power and number of the freezing equipment in the step (4) is determined according to the cold quantity required for completely freezing accumulated water after the cutter-column-type residual mining area goaf detected in the step (2) is filled with accumulated water, and the brine circulating system selects CaCl2The solution is used as refrigerant (CaCl)2The freezing point of the solution is lower than 8-10 ℃ of the designed salt water temperature, the specific gravity is not higher than 1.27), and a cooling water circulating system naturally cools through a cutting water pool. The freezing station related parameter indexes are as follows:
refrigerant: the preparation method of the Freon comprises the steps of R-22,
refrigerating machine oil: hanzhong HBR-B03 refrigerator oil (or other products with the same effect),
temperature of frozen brine: an active period: -20 ℃ to-25 ℃, maintenance period (extinction period): the temperature is minus 15 ℃ to minus 20 ℃,
average temperature after accumulated water is frozen: at the temperature of minus 8 ℃ to minus 12 ℃,
freezing saline water conveying pipe: a low temperature resistant flexible metal tube.
After the freezing parameters are determined, the trial operation of the equipment is carried out, and the whole system is formally constructed after running without errors.
In the scheme, the roadway drilling in the step (5) is performed in a manner of drilling vertically right above accumulated water among the explored cutter column type coal pillars in the residual mining area in order to reduce the workload of drilling; the auxiliary drilling of the working face is performed by obliquely drilling the bottom plate of the working face of the hollow coal seam from top to bottom, the auxiliary drilling is generally arranged in the middle area of the working face, the hole inclination angle theta is 10-60 degrees, the drilling depth H is determined by the thickness H of the stratum between layers and the drilling inclination angle theta, and the number of the drilling holes is determined by the cold demand, the volume of accumulated water and the freezing radius of a freezing pipeline. And (3) putting a freezing pipeline into the accumulated water between the coal pillars of the cutter-pillar type residual mining area through drilling, wherein the freezing pipeline forms a group of closed loops in the accumulated water between the coal pillars of the cutter-pillar type residual mining area, and the brine circulation is carried out to replace heat in the accumulated water so as to freeze the accumulated water into ice.
In the scheme, the uniaxial compressive strength of the frozen accumulated water between the coal pillars in the step (6) is 3 MPa-6 MPa according to laboratory actual measurement, and the tensile strength is 1/2 of the compressive strength, and is close to the strength of the gangue slurry filling material used in paste filling mining at the present stage under the confining pressure action exerted by the coal pillars.
In the scheme, the volume of the water frozen in the step (6) is expanded to 1.1 times of the original volume, water is accumulated between the cutter-post-type coal pillars in the goaf which are not connected with the roof, and when the distance between the water surface and the roof occupies 10% of the total height of the goaf, the frozen ice can be fully connected with the roof. When the accumulated water is less and the roof can not be connected, the ice accumulation amount is increased through manual water injection to enable the coal pillars to be connected, so that the empty area between the coal pillars of the whole tool post type residual mining area is filled, the advancing kicking-off coal seam floor rock stratum is supported, and in addition, the solid ice has a certain lateral supporting effect on the coal pillars of the tool post type residual mining area.
In the scheme, the stoping working face in the step (7) is pushed to the front 3-8m of the boundary line of the empty area between the coal pillars of the next tool post type residual mining area, namely the working face crosses the goaf between the coal pillars and the coal pillars, and the pushing distance of the working face of the kicked-off coal seam is [ (a + b) ± 5] m; wherein, the width of the empty area between the coal pillars is a, and the width of the coal pillars in the knife pillar type residual mining area is b.
In the scheme, the passive freezing period in the step (7) refers to a goaf over which the mining working face of the overlying goaf coal seam passes, the frozen ice blocks only need to maintain the existing frozen state, the temperature of circulating brine is raised to minus 20 ℃ to minus 15 ℃, and energy conservation and economy are achieved as much as possible.
In the scheme, the circulation work in the step (9) is the goaf over which the working face passes, the refrigeration work is stopped, the freezing loop is withdrawn after the ice is melted (when the withdrawal difficulty is high and potential safety hazards exist, withdrawal is not carried out without risk), and the freezing station is gradually moved forward along with the propulsion of the working face.
The invention has the beneficial effects that:
(1) the upward mining feasibility of the kick-off coal seam is judged on the basis of mine production data and exploration data, water accumulated between the coal pillars of the tool post type residual mining area is frozen by adopting a freezing method, liquid-phase water becomes solid ice after being frozen, the solid ice replaces filling materials to fill the whole dead zone of the tool post type residual mining area, the tool post type residual mining area coal pillar groups under the kick-off coal seam are sequentially laterally protected in a full filling mode, the kick-off coal resources are gradually mined, mineral resources are recovered, and the sustainable development of the mineral resources is promoted.
(2) Compared with the traditional column-side paste filling exploitation, the method has the advantages that accumulated water among coal columns in the cutter-column-type residual exploitation area does not need to be treated, the engineering quantity is greatly reduced, and a ground grouting material mixing station does not need to be set for mixing filling slurry, pumping and the like.
(3) The cutter post type residual mining area top bottom plate and the surrounding rock form a whole together when accumulated water among the coal pillars freezes into ice, so that a common bearing body is formed, and a more stable bottom plate environment is provided for the pushing of the working surface of the overlying and kicked-off coal seam.
Drawings
FIG. 1 is a schematic diagram of water accumulation freezing of a goaf adjacent to a coal pillar at the end of a cutter pillar type residual mining area.
Fig. 2 is a schematic diagram of a freezing station and freezing piping arrangement.
FIG. 3 is a schematic view of the working face propulsion of the overlying and kicked-off coal seam in the cutter-column type residual mining area.
In the figure: 1-climbing empty coal seam, 2-interlayer rock stratum, 3-drilling roadway and 4-cutter column type residual mining area coal column; 5-a currently frozen cutter column type residual mining area, 6-a cutter column type residual mining area subjected to pre-freezing, 7-a bottom plate auxiliary drilling hole, 8-a freezing station, 9-a salt water conveying pipe, 10-a salt water loop pipe, 11-a freezing pipe closed loop in accumulated water of the cutter column type residual mining area, 12-a pedaled empty coal seam mining area, 13-a pedaled empty coal seam mining working face, 14-an air return roadway and 15-a transportation roadway.
Detailed Description
The following examples are intended to illustrate and explain the present invention without limiting its scope.
In order to clearly understand the technical objects, characteristics and effects of the invention, the method for freezing the ascending re-mining of the pedaled empty coal seam by the accumulated water in the coal pillars of the goaf is further described in detail with reference to the attached drawings.
In order to pursue high benefits, a certain mine firstly mines a No. 8 coal seam at the lower part by crossing a No. 6 coal seam with large gangue content in the early mining, the resource of a subsequent No. 8 coal seam is gradually exhausted, the No. 6 coal seam is re-mined, a 36703 working face is arranged in the No. 6 coal seam, the lower part of the working face is a 38502 cutter-post type goaf, a typical cutter-post type residual mining area is covered with a pedaled coal seam, a large amount of old goaf accumulated water is arranged in the goaf among the cutter-post type residual mining area coal pillar groups of the 38502 cutter-post type residual mining area, the accumulated water is not communicated with an underground river, and the water. The stability of the coal pillar group in the No. 8 coal seam 38502 cutter-pillar type residual mining area seriously restricts the safe ascending mining of the empty resources on the No. 6 coal seam 36703 working face. In view of the above situation, the following describes the implementation process of the present invention in detail with reference to the accompanying drawings, and the implementation steps are as follows:
step one, a 'three-belt' discrimination method, a surrounding rock balance method, a ratio discrimination method, a mathematical analysis method and a quantitative discrimination method (refer to the method described in an authorized patent CN 101109283B) are adopted to comprehensively discriminate the feasibility of the upward mining of the No. 6 mine kick-off coal seam 1. From the mine production data: the kick-off coal seam 1 is positioned in a bent subsidence zone of the interlayer rock stratum 2, the structural damage degree is small, and only integral movement is generated; thick and hard limestone capable of playing a role of balancing is arranged above the No. 8 coal seam tool post type residual mining area, and the stepping-empty coal seam 1 can be guaranteed not to have step dislocation; the mining influence multiple of the kicked-off coal seam No. 1 and No. 8 coal seams is 6.8; the necessary interlayer spacing for upward mining is 10.4m, which is obviously smaller than the thickness of 27.9m between the kick-off coal seam 1 and the No. 8 coal seam interlayer rock stratum 2; the upward mining of the kick-off coal seam 1 conforms to the mining situation of the quantitative determination method. In conclusion, the 36502 cutter column type residual mining area of the No. 8 mine coal seam is feasible to be used for upward mining of the overhead coal seam 1.
And step two, according to original geological and technical data of the mine, the width of a No. 8 coal seam 38502 cutter column type residual mining area coal column 4 group and the width of a cutter column type residual mining area empty area group are respectively 5m to 15m and 15m to 25m, and the height of each coal seam is 5.2 m. And precisely surveying the distribution position, size and volume of 38502 cutter-column type residual mining area coal column groups and cutter-column type residual mining area empty area groups by adopting a three-dimensional laser scanner, wherein the average distance between accumulated water among the cutter-column type residual mining area coal columns and a top plate is 0.8m by drilling.
And step three, starting to tunnel the return air roadway 14 and the transportation roadway 15 of the pedaled empty coal seam 1 above the cutter pillar type coal pillars at the end part of the residual mining area, which is proved in the step two, arranging the pedaled empty coal seam mining working face 13, and widening the return air roadway 14 by 1.0-1.2 times on the original design size, so that the subsequent freezing station 8 can be conveniently arranged.
Fourthly, arranging a freezing station 8 in an air return roadway 14 of the pedaled empty coal seam, and erecting a saline water pipeline in the roadway; the type, power and number of the freezing equipment are selected according to the volume of the dead zone of the cutter column type residual mining area and the volume of water accumulated between the coal columns of the cutter column type residual mining area, which are detected in the step (2), so that the freezing cold demand is determined, and the equipment selection scheme of the embodiment is as follows:
the refrigerator selects an SKD136.1.H type screw unit, the working condition refrigerating capacity of a single unit is designed to be 116960Kcal/h, and the power of a single motor is 114KW;
(II) each refrigerator IS assembled with a brine circulating pump (IS 150-125-3H, motor power 37KW;
thirdly, an IS 150-125-315B type cooling water circulating pump IS selected as a freezing station cooling water circulating pump, and the flow of each cooling water circulating pump IS 173m3And h, the motor power is 18.5 KW.
Wherein, the brine circulating pump and the cooling water circulating pump are both additionally provided with a standby device.
Selection of CaCl in brine circulating system2The solution is used as refrigerant (CaCl)2The freezing point of the solution is lower than 8-10 ℃ of the designed salt water temperature, the specific gravity is not higher than 1.27), and a cooling water circulating system naturally cools through a cutting water pool. The freezing station related parameter indexes are as follows:
refrigerant: the preparation method of the Freon comprises the steps of R-22,
refrigerating machine oil: hanzhong HBR-B03 refrigerator oil (or other products with the same effect),
temperature of frozen brine: an active period: -20 ℃ to-25 ℃, maintenance period (extinction period): the temperature is minus 15 ℃ to minus 20 ℃,
average temperature after accumulated water is frozen: at the temperature of minus 8 ℃ to minus 12 ℃,
the frozen brine conveying pipe is a low-temperature-resistant flexible metal pipe.
After the freezing parameters are determined, the trial operation of the equipment is carried out, and the whole system is formally constructed after running without errors.
The selection and arrangement of the freezing equipment of the freezing station refer to the construction experience of the conventional freezing method tunnel.
And step five, according to the distribution position of the goaf group ascertained in the step two, vertically drilling holes from top to bottom at the position of a stoping roadway right above the corresponding goaf between the left coal pillars, lowering and arranging a saline water conveying pipe 9 and a saline water loop pipe 10 in the water of the cutter pillar type residual mining area through the roadway drilling holes 3, wherein the roadway drilling holes 3 always lead the currently frozen cutter pillar type residual mining area goaf 5, and meanwhile, arranging freezing pipelines in the next goaf between the coal pillars in advance to perform pre-cooling and freezing work, so that the formal freezing speed is improved. Because of the dead zone area is too big between the coal pillar, ponding is too much, from top to bottom at the working face bottom plate bores, sets up bottom plate auxiliary drilling 7, and bottom plate auxiliary drilling 7 is by kicking empty coal seam 1 working face bottom plate slope from top to bottom and bores, evenly arranges 3 bottom plate auxiliary drilling 7 to both sides by the working face middle zone, and drilling diameter 200mm, hole inclination angle alpha is 15.
And step six, the freezing station 8 arranged in the step four starts to refrigerate, accumulated water between the tool post type residual mining area coal posts at the end part enters an active freezing period, a freezing pipe closed loop 11 is frozen in the accumulated water discharged through the bottom plate auxiliary drilling hole 7, a pipeline is timely removed when the current frozen tool post type residual mining area goaf 5 is basically frozen, the freezing pipe closed loop 11 in the accumulated water of the tool post type residual mining area is discharged and remained in a frozen ice body, and finally the freezing pipe is withdrawn through the roadway drilling hole 3 after the ice body is melted, so that the interference on the propulsion of a working face is avoided. The ponding in the incomplete mining area dead zone 5 of present frozen tool post formula freezes gradually freezes, because the volumetric expansion rate that water freezes is 110%, can not connect the top completely when current ponding freezes, freeze and carry out appropriate amount supplementary water injection through tunnel drilling when going on, make the freezing while of ponding fully connect the top between the incomplete mining area coal pillar of tool post formula, play the supporting role to the bottom plate stratum of tunnelling pedal empty coal seam 1, solid-state ice also has certain side guard effect to the incomplete mining area coal pillar of tool post formula simultaneously.
The uniaxial compressive strength of the frozen accumulated water between the coal pillars is 3 MPa-6 MPa and the tensile strength is 1.5 MPa-3 MPa according to the actual measurement in a laboratory, and is close to the strength of the common gangue slurry filling material for paste filling mining at the present stage under the confining pressure action exerted by the coal pillars.
Seventhly, after the accumulated water in the lower coal pillar of the pedaled empty coal seam stoping working surface 13 is frozen, the pedaled empty coal seam stoping working surface is pushed forwards under the support of the frozen ice body, the stoping working surface 13 is pushed section by section, when the pedaled empty coal seam stoping working surface is pushed to the front of the boundary line of the next pre-frozen cutter post type residual mining area empty zone 6 by 3-8m, the pedaled empty coal seam stoping working surface 13 is stopped being pushed, the freezing work of the accumulated water in the coal pillar of the next cutter post type residual mining area is prepared, meanwhile, the pedaled empty coal seam stoping working surface is pushed to cross the frozen work of the accumulated water in the;
step eight, repeating the step five, the step six and the step seven, gradually freezing accumulated water in a dead zone between coal pillars close to the working surface in the step seven, so that the accumulated water between the coal pillars of the knife-pillar type residual mining area is frozen and solidified, and simultaneously, the frozen ice body accumulated water in the dead zone between the coal pillars of the knife-pillar type residual mining area, the remaining coal pillars, the top floor of the residual mining area and surrounding rocks form a whole together, thereby providing a stable working environment for the subsequent propulsion of the working surface of the overlying pedaled empty coal seam and gradually mining pedaled coal resources;
step nine, as shown in fig. 3, along with the propulsion of the coal seam mining working face 13, arranging a return air roadway of the freezing station 8 to strengthen support and prevent the roadway from collapsing. And (3) as the back mining working surface 13 of the pedaled empty coal seam is pushed, the accumulated water freezing working of the goaf is pushed ahead of the working surface, when the active freezing period of the accumulated water between the fourth coal pillar and the fifth coal pillar in the goaf begins, the goaf between the coal pillars at the end part of the residual mining area finishes refrigerating, and the pipeline is withdrawn after the frozen ice melts. Then the freezing station circularly works according to the above, the freezing station gradually moves forwards along with the advancing of the working surface, and the accumulated water in the empty area among the three cutter post type coal pillars in the residual mining area is in a frozen state while the working surface is advanced.
Claims (10)
1. The method for upward repeated mining of the empty coal seam by accumulated water among the coal pillars of the freezing cutter-pillar type residual mining area is characterized by comprising the following steps of:
(1) judging the feasibility of upward mining of the overlying and empty coal seam on the cutter column type residual mining area;
(2) the distribution conditions of a coal pillar group and an empty area group of a tool post type residual mining area under a pedaled coal seam are explored and found out by combining original geological and technical data of a mine, and distribution form graphs of the coal pillar group and the empty area group of the tool post type residual mining area are drawn to guide safe production; detecting the accumulated water height, the accumulated water quantity and the water quality of the dead zone of the tool post type residual mining area by combining mine production data;
(3) excavating a stoping roadway of the pedaled empty coal seam, and arranging a working surface of the pedaled empty coal seam;
(4) arranging a freezing station in an air return roadway of the pedaled empty coal seam, and carrying out saline water conveying and loop pipeline erection in the roadway;
(5) vertically drilling holes in a goaf coal seam stoping roadway from top to bottom, arranging roadway drilling holes, putting the roadway drilling holes into accumulated water in a goaf, and arranging freezing pipelines; drilling holes in the roadway always lead to the current freezing area, and a freezing pipeline is arranged in the next coal pillar empty area in advance for pre-freezing and cooling, so that the freezing rate is improved; when the area of the empty area between the coal pillars is too large and the accumulated water is too much, performing bottom plate auxiliary drilling construction on the bottom plate of the working face from top to bottom;
(6) the freezing station arranged in the step (4) starts to refrigerate, the accumulated water in the empty area between the coal pillars at the end part of the knife column type residual mining area enters an active freezing period, the accumulated water is gradually frozen, and the ice body frozen by the accumulated water in the unfilled empty area is fully abutted by utilizing the characteristic of volume expansion of the water during freezing, so that the bottom plate rock stratum of the hollow coal seam is supported, and the side protection effect is generated on the coal pillars in the knife column type residual mining area; the freezing pipelines are arranged in the auxiliary drilling holes of the bottom plate of the working face, the pipelines are timely removed when accumulated water between the coal pillars of the knife-pillar type residual mining area is basically frozen, the frozen pipelines are placed in the accumulated water and left in the frozen ice body, and finally the frozen pipelines are withdrawn through the drilling holes of the roadway after the ice body is melted, so that the pushing of the working face is prevented from being interfered;
(7) after water accumulation in the lower coal pillars of the recovery working surface of the pedaled empty coal seam is frozen, the recovery working surface is pushed forward under the support of an ice body, the recovery working surface is pushed section by section, when the working surface is pushed to the front 3-8m of the boundary line of the empty zone between the next pre-frozen coal pillars, the pushing of the working surface is stopped, meanwhile, the freezing work in the step (6) reduces the refrigerating capacity and enters a passive freezing period, and the frozen ice blocks are kept not to be thawed;
(8) repeating the steps (5), (6) and (7), wherein the accumulated water in the goaf between the next coal pillars close to the working surface in the step (7) enters an active freezing period, so that the accumulated water in the goaf is frozen and solidified and forms a whole together with the left coal pillars, the residual mining area top floor and the surrounding rock, a supported stable environment is provided for the propulsion of the working surface of the overlying pedaled empty coal seam, the pedaled empty coal seam working surface continues to be propelled forwards, and the pedaled empty coal seam coal resources are gradually mined;
(9) along with the propulsion of the working face, arranging a return air roadway of the freezing station to strengthen support, and gradually caving the transportation roadway on the other side along with the propulsion of the working face; the accumulated water freezing work of the goaf advances from the working face, when the active freezing period of accumulated water between the fourth coal pillar and the fifth coal pillar in the goaf begins, the goaf between the coal pillars at the end part of the residual mining area finishes refrigerating, the ice starts to slowly and naturally thaw, and the pipeline in the accumulated water is retracted after the frozen body melts; then the working face is circularly operated, and the accumulated water among the coal pillars of at least three residual mining areas is in a frozen state while the working face is pushed.
2. The method for upward repeated mining of the empty coal seam by accumulated water among the coal pillars in the freezing cutter-column type residual mining area according to claim 1, is characterized in that: the accumulated water in the dead zone of the tool post type residual mining area is the accumulated water which is not communicated with the underground river, the long-term water volume of the accumulated water is basically unchanged, the accumulated water is supplemented by a small amount of underground water and simultaneously runs off in a small scale, and the total water volume is in a dynamic stable state.
3. The method for upward repeated mining of the empty coal seam by accumulated water among the coal pillars in the freezing cutter-column type residual mining area according to claim 1, is characterized in that: the feasibility judgment method in the step (1) comprises the following steps: the method combines the traditional three-belt discrimination method, the surrounding rock balance method, the ratio discrimination method, the mathematical analysis method and the quantitative discrimination method to comprehensively discriminate the feasibility of the upward mining of the coal seam covered and empty on the cutter-column type residual mining area.
4. The method for upward repeated mining of the empty coal seam by accumulated water among the coal pillars in the freezing cutter-column type residual mining area according to claim 1, is characterized in that: and (2) the widths and the heights of the cutter post type residual mining area empty area group and the coal post group under the kick-off coal bed are checked through investigating original geological and technical data of a mine, the distribution direction, the size and the volume of the cutter post type residual mining area empty area group are accurately detected by adopting a three-dimensional laser scanner, and the depth, the distribution range and the volume of accumulated water in the empty area between the coal posts are simultaneously detected.
5. The method for upward repeated mining of the empty coal seam by accumulated water among the coal pillars in the freezing cutter-column type residual mining area according to claim 1, is characterized in that: and (3) arranging open cutting holes of the kick-off coal seam above the explored cutter-pillar-type residual mining area end coal pillars, arranging a stoping roadway and a working face in the kick-off coal seam, widening an air return roadway, and facilitating arrangement of a subsequent freezing station.
6. The method for upward repeated mining of the empty coal seam by accumulated water among the coal pillars in the freezing cutter-column type residual mining area according to claim 1, is characterized in that: selecting the type, power and number of the freezing equipment in the step (4), determining the cold quantity required for completely freezing accumulated water after the cutter column type residual mining area goaf detected in the step (2) is filled with the accumulated water, and selecting CaCl as the brine circulation system2The solution is used as a refrigerant, and a cooling water circulating system is naturally cooled by a cutting water pool; when each freezing pipeline is placed in the cutter post type residual mining area accumulated water, a series of temperature sensors are bound to the pipelines, are placed together with the pipelines and are arranged in the cutter post type residual mining area accumulated water, and the temperature of the accumulated water or the frozen ice in the goaf is detected in real time.
7. The method for upward repeated mining of the empty coal seam by accumulated water among the coal pillars in the freezing cutter-column type residual mining area according to claim 1, is characterized in that: in the step (5), in order to reduce the drilling workload, drilling the roadway in a vertical drilling mode right above the accumulated water in the coal pillars of the explored cutter pillar type residual mining area; the auxiliary drilling of the working face is performed by obliquely drilling the bottom plate of the working face of the hollow coal seam from top to bottom and is generally arranged in the middle area of the working face, the hole inclination angle theta is 10-60 degrees, the drilling depth H is determined by the thickness H of an interlayer rock stratum and the drilling inclination angle theta, and the number of the drilled holes is determined by calculating the cold requirement, the volume of accumulated water and the freezing radius of a freezing pipeline; and (3) putting a freezing pipeline into the accumulated water between the coal pillars of the cutter-pillar type residual mining area through drilling, wherein the freezing pipeline forms a group of closed loops in the accumulated water between the coal pillars of the cutter-pillar type residual mining area, and the brine circulation is carried out to replace heat in the accumulated water so as to freeze the accumulated water into ice.
8. The method for upward repeated mining of the empty coal seam by accumulated water among the coal pillars in the freezing cutter-column type residual mining area according to claim 1, is characterized in that: the uniaxial compressive strength of the frozen accumulated water among the coal pillars in the step (6) is 3-6 MPa, and the tensile strength is 1/2 of the compressive strength;
the volume of the water frozen in the step (6) is expanded to 1.1 times of the original volume, water is accumulated between the coal pillars of the cutter pillar type residual mining area which are not connected with the roof in the goaf originally, and when the distance between the water surface and the roof plate accounts for 10% of the total height of the goaf, the ice body frozen can be fully connected with the roof; when the accumulated water is less and the roof can not be connected, the freezing work is carried out, and meanwhile, the ice accumulation amount is increased through manual water injection to enable the freezing work to be connected with the roof, so that the empty area between the coal pillars of the whole tool post type residual mining area is filled, the supporting effect on the advancing kicking-off coal seam floor strata is achieved, and in addition, the solid ice has a lateral supporting effect on the coal pillars of the tool post type residual mining area.
9. The method for upward repeated mining of the empty coal seam by accumulated water among the coal pillars in the freezing cutter-column type residual mining area according to claim 1, is characterized in that: the stoping working face is pushed to the front 3-8m of a boundary line of an empty area between coal pillars of the next tool post type residual mining area, namely the working face crosses the goaf and the coal pillars between the coal pillars, and the pushing distance of the working face of the kicked-off coal seam is [ (a + b) ± 5] m; wherein, a is the width of the empty area between the coal pillars, and b is the width of the coal pillars of the knife-pillar type residual mining area;
the passive freezing period in the step (7) refers to a goaf which is crossed by the mining working face of the overlying goaf coal seam, the frozen ice blocks only need to be maintained in the existing frozen state, and the temperature of circulating brine is increased by 5-10 ℃.
10. The method for upward repeated mining of the empty coal seam by accumulated water among the coal pillars in the freezing cutter-column type residual mining area according to claim 1, is characterized in that: the circulation work in the step (9) is that the working face passes over the goaf, the refrigeration work is stopped, the freezing loop is withdrawn after the frozen body is melted, and the freezing station moves forward gradually along with the propulsion of the working face; when the withdrawal difficulty is high and potential safety hazards exist, withdrawal is carried out without taking risk.
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