A method for freezing open-pit mine end-wall coal pressing

Abstract

The present invention discloses a method for freezing mining of coal pressure at the end wall of an open-pit mine, which includes constructing a frozen soil wall: the frozen soil wall includes a protective frozen soil wall and a supporting frozen soil wall; pursuing mining; and continuing pressure walling: the pressure walling is divided into initial pressure walling and comprehensive pressure walling. The present invention utilizes freezing to change the mechanical properties of the rock mass, improves the strength of the end wall, and provides effective support for end wall mining, and is particularly suitable for open-pit coal mines in cold areas with large water content at the end wall. The double-layer frozen soil wall design not only strengthens the freezing effect, but also provides alternating cover for pressure walling in stages, thereby reducing the difficulty of on-site construction management. The freezing equipment and cold transfer medium are common in the market, easy to obtain, easy to operate, low in solution cost, and good in effect. The low ambient temperature in the northern part of China in winter further reduces the cost of the solution. Pursuit mining ensures timely mining of the coal pressure at the end wall, while realizing the recovery of the refrigeration equipment. Implementing pressure walling in stages can not only ensure the efficiency of pressure walling, provide support force for the end wall in time, but also reduce the difficulty of on-site construction.

Description

Technical Field

[0001] The invention relates to a method for mining end-wall compressed coal, in particular to a freezing type mining method for mining end-wall compressed coal in an open-pit mine. Background Art

[0002] The overall shape of the open-pit mine is an inverted trapezoid. Due to the requirements for the stability of the end wall, the slope angle of the end wall should not be too large, which causes a large amount of coal compression on the end wall. The mining of compressed coal on the end wall has always been an important research topic in the field of open-pit mining. Especially for open-pit mines with thick and extremely thick coal seams, improving the recovery rate of compressed coal on the end wall is of great significance to improving the recovery rate of the overall mine. In recent years, experts and scholars have explored ways to increase the mining rate of compressed coal on the end wall by adjusting the open-pit mining process, such as mining by leaning against the wall, and have achieved certain results. However, no matter how the process is improved, the inherent stability of the rock mass on the end wall is always an important factor restricting the mining of compressed coal. Summary of the invention

[0003] In view of the problems existing in the above-mentioned prior art, the present invention provides a freezing mining method for compressed coal at the end wall of an open-pit mine, which freezes the rock mass at the end wall, fundamentally improves the strength of the end wall, enhances the stability of the end wall, and provides a guarantee for mining compressed coal at the end wall.

[0004] To achieve the above object, the present invention provides the following technical solution: a method for freezing mining of open-pit coal at the end of the open-pit mine, comprising the following steps:

[0005] Construct frozen soil walls: frozen soil walls include protective frozen soil walls and supporting frozen soil walls;

[0006] Along the direction from the spoil dump to the mining area, on the plane of the first stripping step above the end coal seam roof, 2-3 rows of freezing holes are drilled vertically downwards at intervals to form a protective frozen soil wall; the row spacing is 3-5 times the diameter of the freezing holes themselves, and the spacing between adjacent freezing holes in the same row is 1-2 times their own diameters; along the direction from the spoil dump to the mining area, on the plane of 1-2 stripping steps above the protective frozen soil wall, freezing columns are arranged vertically downwards at intervals to form a supporting frozen soil wall; the freezing columns are surrounded by multiple freezing holes; cooling pipes are installed in all freezing holes. The cooling pipes are three-layer steel pipes with a sealed bottom, and two passages are formed inside. The cold transfer medium is loaded inside the passages, and all cooling pipes are connected to the cooling compressor unit through pipelines;

[0007] Pursuit mining: After the construction of the frozen soil wall is completed, the end wall mining face is arranged at the end wall position close to the spoil dump to mine the end wall pressure coal; during the initial mining, the protective frozen soil wall within the three to five days' advancement range of the end wall mining face is first stopped from cooling, the cooling pipe is recovered, and the end wall stripping material where the protective frozen soil wall is located is 1-2m close to the supporting frozen soil wall. At the same time, the excavation equipment is used to peel off the end wall stripping material where the protective frozen soil wall is located, and the pressure coal below is mined, and the supporting frozen soil wall is retained in the process; with the continuous mining of the end wall pressure coal, when there is only one day's advancement left for the end wall mining face, the protective frozen soil wall within the advancement range of the next day's end wall mining face is stopped from cooling in advance, and so on and so forth, and the range of stopping cooling for the protective frozen soil wall always precedes the one-day advancement of the front wall mining face;

[0008] Continuous pressure: pressure is divided into initial pressure and comprehensive pressure;

[0009] The first wall compaction is during the end wall compaction coal mining process, which lags behind the end wall mining face by 20-30m and starts the wall compaction inner drainage from the spoil dump. The upper surface of the first wall compaction is flush with the upper surface of the protective frozen soil wall; the comprehensive wall compaction is to build a complete spoil dump according to the designed height after the first wall compaction; at the beginning of the comprehensive wall compaction, the progress of the first wall compaction and the inner drainage work line is delayed by three to four days, the refrigeration of the supporting frozen soil wall freezing pipes is stopped and the cooling pipes are recovered, and then a complete spoil dump is built. With the implementation of the comprehensive wall compaction, when there are still two days of progress left for the first wall compaction and the inner drainage work line, the cooling of the supporting frozen soil walls within the progress range of the next two days of the first wall compaction and the inner drainage work line is stopped in advance, and so on and so forth, and the range of stopping cooling of the supporting frozen soil walls is always two days ahead of the progress of the first wall compaction and the inner drainage work line at the front end.

[0010] Furthermore, adjacent rows of freezing holes in the protective frozen soil wall are arranged in a staggered manner.

[0011] Furthermore, the freezing hole has a diameter of 20-50 cm.

[0012] Furthermore, the spacing between adjacent freezing columns in the supporting frozen soil wall is 1.2-1.4 times of their own diameters, and the spacing between adjacent freezing holes is 5-10 cm greater than their own diameters.

[0013] Furthermore, the cold transfer medium is high-concentration salt water.

[0014] Furthermore, the end wall mining working face advances 5-10m per day.

[0015] Furthermore, the bottom of the freezing hole is ultra-deep, with the coal seam floor reaching 2-3 m.

[0016] Compared with the prior art, the present invention utilizes freezing to change the mechanical properties of the rock mass, improves the strength of the end wall, and provides effective support for the mining of the end wall. It is particularly suitable for open-pit coal mines in cold areas where the water content of the end wall is relatively high. The double-layer frozen soil wall design not only strengthens the freezing effect, but also provides alternating cover for the staged pressure wall, reducing the difficulty of on-site construction management. Freezing equipment and cold transfer media are common in the market, easy to obtain, easy to operate, low in cost and effective. The low ambient temperature in northern China in winter further reduces the cost of the solution. Pursuit mining ensures the timely mining of the end wall pressure coal and realizes the recovery of the refrigeration equipment. The staged implementation of pressure wall can not only ensure the efficiency of pressure wall, provide support for the end wall in time, but also reduce the difficulty of on-site construction. The overall plan is closely connected with open-pit mining, does not affect open-pit mining, and the staff are more familiar with the process, which is convenient for construction in the mining area. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the frozen soil wall arrangement of the present invention;

[0018] Figure 2 This is a schematic diagram of the pursuit mining and subsequent pressure pressing of the present invention;

[0019] Figure 3 This is a schematic diagram of the freezing column structure of the present invention;

[0020] In the figure: 1- supporting frozen soil wall; 2- protecting frozen soil wall; 3- end wall coal seam; 4- the first stripping step; 5- freezing hole; 6- spoil dump; 7- mining area; 8- freezing column; 9- end wall mining working face; 10- initial wall compression; 11- full wall compression. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings.

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The present invention provides a technical solution, comprising the following steps:

[0024] Construct frozen soil wall: The frozen soil wall includes a protective frozen soil wall 2 and a supporting frozen soil wall 1; Figure 1 and Figure 2As shown, along the direction from the spoil dump 6 to the mining area 7, on the plane of the first stripping step 4 above the top plate of the end wall coal seam 3 of the open-pit mine, close to the bottom line of the slope of the previous step, 2-3 rows of freezing holes 5 are drilled vertically downward at intervals, and multiple rows of freezing holes 5 form a protective frozen soil wall 2; the row spacing is 3-5 times the diameter of the freezing holes 5 themselves, preferably, adjacent rows of freezing holes 5 are arranged in a staggered manner, and the spacing between adjacent freezing holes 5 in the same row is 1-2 times their own diameter. The function of the protective frozen soil wall 2 is to freeze the upper part of the end wall rock mass of the end wall coal seam 3, provide short-term cover for the end wall mining process, prevent local end wall landslides, and cooperate with the supporting frozen soil wall 1 to provide support and cover for the staged wall compression.

[0025] Along the direction from the spoil dump 6 to the stope 7, on the plane of 1-2 stripping steps above the protective frozen soil wall 2, near the bottom line of the upper step slope, frozen columns 8 are arranged vertically downward at intervals to form a supporting frozen soil wall 1; Figure 3 As shown, the freezing column 8 is surrounded by a plurality of freezing holes 5. Preferably, the freezing column 8 is surrounded by 30-50 freezing holes 5. The spacing between adjacent freezing columns 8 is 1.2-1.4 times of their own diameters, and the spacing between adjacent freezing holes 5 is 5-10 cm greater than their own diameters. In areas with soft soil, 2-3 rows of supporting freezing walls 1 can be arranged side by side, which can be determined according to the strength and stability requirements of the freezing holes 5 to ensure the freezing effect. The function of the supporting frozen soil wall 1 is to freeze the end wall rock mass, increase the end wall strength, and provide the main support force for subsequent end wall mining.

[0026] The diameter of the freezing hole 5 is 20-50cm, and the bottom of the ultra-deep end side coal seam 3 is 2-3m. Cooling pipes are installed in all freezing holes 5. The cooling pipes are three-layer steel pipes with a sealed bottom, and two through passages are formed inside. The cold transfer medium is loaded inside the passage, preferably high-concentration salt water, which can not freeze at -30℃ and has high cold transfer efficiency. All cooling pipes are connected to the cooling compressor unit through pipelines; through the cooling compressor unit, the cold medium is continuously input into the cooling pipe, so that the outside of the cooling pipe is frozen, and then the surrounding rock mass is frozen. After the freezing hole 5 is frozen, the diameter of the frozen soil column formed produces a "cross circle" to form a continuous frozen soil wall.

[0027] Pursuit mining: After the frozen earth wall is built, Figure 2 As shown, an end wall mining face 9 is arranged at the end wall position near the spoil dump 6 to mine the end wall compressed coal, and the mining direction is from the spoil dump 6 to the mining face 7; in order to provide flexible space for the initial construction, during the initial mining, the protective frozen soil wall 2 within the three to five days' advancement range of the end wall mining face 9 is first stopped from supplying cooling, the cooling pipe is recovered, and the end wall stripping material where the protective frozen soil wall 2 is located is simultaneously stripped by excavation equipment close to the supporting frozen soil wall 11-2m, and the compressed coal below is mined, and the supporting frozen soil wall 1 is retained during the process;

[0028] With the continuous mining of the end wall pressure coal, when there is one day's advancement left for the end wall mining working face 9, the protective frozen soil wall 2 within the advancement range of the next day's end wall mining working face 9 will be stopped from supplying cooling in advance. From then on, the protective frozen soil wall 2 will always stop supplying cooling in the range ahead of the one-day advancement of the front wall mining working face 9, thus realizing the mining method of the end wall pressure coal chasing the protective frozen soil wall 2. The range of stopping the cooling supply in advance of the later protective frozen soil wall 2, that is, the pursuit distance of the end wall mining working face 9 is kept within one-day advancement in order to reduce the excavation cost under the premise of ensuring the support strength. If the pursuit distance is too short, the rock mass around the frozen soil wall will be frozen too hard, and the excavation cost will be high. At the same time, the excavation process may affect the recovery of the cooling pipe and increase the cost; if the pursuit distance is too long, the frozen soil wall will easily melt, the strength will be reduced, and it will not play the due supporting role. The one-day advancement of the end wall mining working face 9 is generally 5-10m.

[0029] Continuous pressure: pressure is divided into initial pressure 10 and comprehensive pressure 11; Figure 2 As shown, the initial wall pressure 10 is carried out during the end wall coal mining process, lagging behind the end wall mining working face by 920-30m, and the inner wall pressure is started from the spoil dump 6. The upper surface of the initial wall pressure 10 is flush with the upper surface of the protective frozen soil wall 2; the initial wall pressure 10 inner discharge at the first time can provide support for the end wall; the main reason why the height of the initial wall pressure 10 is only flush with the upper surface of the protective frozen soil wall 2 is to ensure the efficiency of the soil discharge and wall pressure, and to ensure the first-time wall pressure to provide support.

[0030] The comprehensive pressure relief 11 is to lag behind the initial pressure relief 10 to build a complete dumping ground according to the designed height; at the beginning of the comprehensive pressure relief 11, the progress of the pressure relief inner drainage work line of the initial pressure relief 10 is delayed by three to four days, the refrigeration of the frozen pipes supporting the frozen soil wall 1 is stopped and the cooling pipes are recovered, and then the complete dumping ground is built. With the implementation of the comprehensive pressure relief 11, when there are two days of progress left in the pressure relief inner drainage work line of the initial pressure relief 10, the support frozen soil wall 1 within the progress range of the pressure relief inner drainage work line of the next two days will be stopped in advance, and so on, the support frozen soil wall 1 will always stop cooling the range of the cooling of the support frozen soil wall 1 ahead of the progress of the pressure relief inner drainage work line of the first pressure relief 10 for two days; with the advancement of the end wall mining working face 9, the continuous pressure relief is realized. The daily progress of the pressure relief inner drainage work line of the initial pressure relief 10 is generally 10-15m.

[0031] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0032] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any slight modification, equivalent substitution and improvement made to the above embodiment based on the technical essence of the present invention should be included in the protection scope of the technical solution of the present invention.

Claims

1. A method for freezing open-pit mine end-wall coal pressing, characterized in that: The following steps are involved: Constructing a frozen soil wall: The frozen soil wall includes a protective frozen soil wall (2) and a supporting frozen soil wall (1); Along the direction from the spoil dump (6) to the mining area (7), on the plane of the first stripping step (4) above the top plate of the end coal seam (3), 2-3 rows of freezing holes (5) are drilled vertically downwards in succession to form a protective frozen soil wall (2); the row spacing is 3-5 times the diameter of the freezing holes (5), and the spacing between adjacent freezing holes (5) in the same row is 1-2 times the diameter of the freezing holes (5); Along the direction from the spoil dump (6) to the mining area (7), on the plane of 1-2 stripping steps above the protective frozen soil wall (2), freezing columns (8) are arranged vertically downward at intervals to form a supporting frozen soil wall (1); the freezing columns (8) are surrounded by a plurality of freezing holes (5); Cooling pipes are installed in all freezing holes (5). The cooling pipes are three-layer steel pipes with sealed bottoms, and two passages are formed inside. Cold transfer medium is filled inside the passages. All cooling pipes are connected to the cooling compressor unit through pipelines. Chase mining: After the frozen soil wall is constructed, an end wall mining working face (9) is arranged at the end wall position near the spoil dump (6) to mine the end wall pressure coal; during the initial mining, the protective frozen soil wall (2) within the three to five days' advancement range of the end wall mining working face (9) is first stopped from supplying cooling, the cooling pipe is recovered, and the end wall stripping material where the protective frozen soil wall (2) is located is simultaneously stripped by excavation equipment close to the supporting frozen soil wall (1) by 1-2m, and the pressure coal below is mined, and the supporting frozen soil wall (1) is retained during the process; As the end wall coal is continuously mined, when there is one day's advancement left for the end wall mining working face (9), the protective frozen soil wall (2) within the range of the next day's advancement of the end wall mining working face (9) is stopped from supplying cooling, and the same is true from then on, and the range of stopping cooling of the protective frozen soil wall (2) is always ahead of the one-day advancement of the end wall mining working face (9); Continuous pressure: Pressure is divided into initial pressure (10) and comprehensive pressure (11); The first wall pressing (10) is to lag behind the end wall mining working face (9) by 20-30m during the end wall pressing coal mining process, and start the wall pressing inner drainage from the spoil dump (6), so that the upper surface of the first wall pressing (10) is flush with the upper surface of the protective frozen soil wall (2); the full wall pressing (11) is to lag behind the first wall pressing (10) and build a complete spoil dump according to the designed height; at the beginning of the full wall pressing (11), the progress of the wall pressing inner drainage work line is delayed by three to four days, and the support of the frozen soil wall is stopped. The freezing pipes of the earth wall (1) are refrigerated and the cooling pipes are recovered, and then a complete dumping ground is constructed. With the implementation of the comprehensive compression (11), when there are two days of advancement left in the first compression (10) compression inner drainage work line, the supporting frozen earth wall (1) within the advancement range of the next two days of the first compression (10) compression inner drainage work line will be stopped from supplying cold. From then on, the same logic is applied, and the range of stopping supplying cold to the supporting frozen earth wall (1) will always be two days ahead of the advancement of the first compression (10) compression inner drainage work line at the front end.

2. The open-pit mine end-wall compressed coal freezing mining method according to claim 1, characterized in that: Adjacent rows of freezing holes (5) in the protective frozen soil wall (2) are arranged in a staggered manner.

3. The open-pit mine end-wall compressed coal freezing mining method according to claim 1, characterized in that: The freezing hole (5) has a diameter of 20-50 cm.

4. The open-pit mine end-wall compressed coal freezing mining method according to claim 1, characterized in that: The spacing between adjacent freezing columns (8) in the supporting frozen soil wall (1) is 1.2-1.4 times of their own diameters, and the spacing between adjacent freezing holes (5) is 5-10 cm greater than their own diameters.

5. The open-pit mine end-wall compressed coal freezing mining method according to claim 1, characterized in that: The cold transfer medium is high-concentration salt water.

6. The open-pit mine end-wall compressed coal freezing mining method according to claim 5, characterized in that: The end wall mining working face (9) has a daily advancement rate of 5-10 m.

7. The open-pit mine end-wall compressed coal freezing mining method according to claim 1, characterized in that: The bottom of the freezing hole (5) is 2-3 m above the bottom plate of the ultra-deep end side coal seam (3).

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