A NON-SPLIT METHOD FOR EXTRACTION OF COAL PILLARS BY CONTINUOUS MINER

FIELD OF INVENTION
[001] The present subject matter described herein, relates to a method of underground coal mining for extraction of coal. More particular, to a method for extraction of coal pillars through Continuous Miners used in mass production technology.
BACKGROUND AND PRIOR ART AND PROBLEM IN PRIOR ART
[002] In mining operations in India, opencast mining is the most prevalent method for extraction of coal. It is known that underground coal mining demands high technical expertise, and a higher gestation period, therefore opencast mining is more preferred for extracting coal deposits at shallow to moderate depths. However recently, there has been a considerable increase in the production from opencast mines meeting a majority of the country's demand for coal. As a result, underground coal mining contributes to only 5%-10% coal production from the coal reserves.
[003] It is known in the field of coal mining that the thick coal seam is located at greater depth in the mines and the use of conventional methods of underground mining cannot meet the safety standards & efficiency requirement to produce coal at a mass level from such deep coal reserves. Considering the risks associated with underground coal mining, the international safety standards are set as Loss Time Injury Frequency Rate (LTIFR) per 2,00,000 man-hours to be less than 1.0. The governing authorities have also shown a preference for underground mining to extract the deep-seated coal in order to increase coal production but are facing challenges such as lack of safe mining method & technology. A Continuous Miner (CM) is one of the known coal mining equipment that can be equipped to boost the coal production from greater depths. It reduces the exposure of mining personnel from the hazardous zone, increases productivity and can work in difficult conditions, even in the absence of a long stretch of continuous deposition.
[004] Conventionally, the Split & Fender method is used for extraction of pillars from the underground coal mines through CM. In this method of depillaring, galleries ( also referred to as splits) are driven at the middle portion of the pillar thus, dividing the pillar into two equal halves and leaving a thick strip of coal having dimensions as 6 m to 10 m i.e. a fender (between the gallery and goaf). When the split reaches the limit of the pillar, the continuous miner is pulled back and it further cuts into the fender removing most of the width portion of the fender and known as a slice. However, a small section of coal is usually left at the end of the slice that is known as a snook. This procedure is repeated a number of times so the miner retreats back to the original panel galleries while removing most of the coal from the fender. This process usually includes extraction of other pillars in a straight line across the width of the panel with one row of pillars in the same direction. The aforementioned procedure is again repeated and further splits and fenders are formed parallel to the prior created splits and fenders until the whole panel has been removed by a row wise extraction of pillars.
[005] The split and fender method is preferably suitable for comparatively larger pillars wherein the size of fender has a sufficient Factor of Safety (FoS). The main disadvantage associated with this method is that the mining personnel need to enter into the split after disturbing the core of the pillar where the FoS is less than 1.0 (which can undergo catastrophic failure without much warning). Further, the spilt requires a support, thus increasing the cost and time taken to extract the pillar. Also, due to the relatively small size of the pillars the resultant fenders are narrow, i.e. 6.0 m in width with a height of 4 to 4.5 m. Thus, the split and fender method can only be preferably applied where the pillar size is greater than 30.0 m. Since in India, most of the reserves are under shallow cover with a seam depth of up to 150 m having a pillar size of 25 m x 25 m (measured from centre to centre) it becomes necessary that the FoS must be above 1.0 to ensure the safety of personnel and machinery during such mining operations. A low FoS as seen in the conventional method creates chances of potential hazards for the mining personnel & machinery deployed for the extraction of coal in the panel against chances of overriding of the fender or remnant pillar resulting in falling of roof extending during the ongoing working mining operations. Also, there is a probability of risk of failure of the Fender against the abutment load from the goaf edge and that could lead to multiple fatalities or a major loss of machinery.
[006] Therefore, in order to overcome the limitations of the existing provisions, there is a need in the art to provide a method suitable for extraction of coal from underground coal mines using continuous miner technology, which is more efficient and ensures safety of personnel and machinery during the mass extraction of coal pillars.
OBJECTS OF THE INVENTION
[007] It is therefore the object of the invention to overcome the aforementioned and other drawbacks in prior art used for extraction of pillars from underground coal mines during mining.
[008] The principal objective of the present invention is to develop a method, which is more efficient and has a higher factor of safety (FoS) for mining of coal pillars having size below 30.0 m preferably.
[009] Another object of the present invention is to develop a method, which is cost effective and economic simultaneously being suitable to the geological structural configurations of the coal mines.
[0010] These and other objects and advantages of the present subject matter would be apparent to a person skilled in the art after consideration of the following detailed description taken into consideration with accompanying drawings in which preferred embodiments of the present subject matter are illustrated.
SUMMARY OF THE INVENTION
[0011] One or more drawbacks of the conventional systems based on existing coal mining technology or similar technologies are overcome, and additional advantages are provided through a non- split method for extraction of coal pillars using Continuous Miner as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be a part of the claimed disclosure.
[0012] In an embodiment of the present subject matter, a non-split mining method for extraction of coal pillars by Continuous Miner, comprising of determining the size of a pillar in underground coal mine, sequencing of pillars for extraction, and cutting a pillar into a series of slices directed into level gallery followed by a push from dip gallery direction, wherein each slice having a minimum width of 3.5 m is cut at an angle of a from gallery and at a minimum distance of 3.0 m from the dip gallery of the pillar. A first slice is cut from a first edge of the pillar, a second slice and a third slice are cut in a parallel orientation to the first slice, a fourth slice is cut from a second edge of the pillar, a fifth slice and a sixth slice are cut in a parallel orientation to the fourth slice, and a seventh slice is cut from a third edge of the pillar, and an eight slice and a ninth slice are cut in a parallel orientation to the seventh slice.
[0013] In another embodiment of the present subject matter, a snook portion has a minimum area preferably between 5% to 10% of the original pillar size and a pre-determined width to height ratio of w:h.
[0014] In yet another embodiment of the present subject matter, the value of the angle a is 45o.
[0015] In yet another embodiment of the present subject matter, the sequencing of pillars is in a straight line for caving of the roof in the dip direction.
[0016] In yet another embodiment of the present subject matter, the sequencing of extraction of pillars is in a straight line for inducing regular caving of the roof in the dip direction.
[0017] In yet another embodiment of the present subject matter, the size of the pillar is less than 30.0 m (centre to centre).
[0018] In yet another embodiment of the present subject matter, left side of the pillar forms the first edge.
[0019] In yet another embodiment of the present subject matter, the left corner portion and bottom horizontal side of the pillar forms the second edge.
[0020] In yet another embodiment of the present subject matter, right side of the pillar forms the third edge.
[0021] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
[0022] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter, and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods or structure in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0024] Figure 1 illustrates a flow diagram representing steps involved in the non-split mining method in accordance with an embodiment of the invention;
[0025] Figure 2 illustrates a schematic view of the extraction of coal by non-split mining method using a Continuous Miner in accordance with an embodiment of the invention;
[0026] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
[0027] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein are not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the appended claims.
[0028] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a",” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0030] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0031] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0032] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
[0033] The present subject matter describes a method for extraction of coal pillars through continuous miners used in mass production technology. The method comprises extraction of coal pillars from underground coal mine by cutting slices from a pillar using continuous miner first into the direction of level gallery followed by driving a push out (hereinafter referred to as a “snook”) in the direction of dip gallery into the pillar. A straight line of extraction of pillars is maintained during the extraction of coal and use of such a straight line sequencing of pillars allows caving of the roof in the dip direction thus ensuring that no mining personnel is exposed to goaf or dangerous portions during the continuous mining operation. The cutting of a slice is done at an inclination of predetermined angle a from working level. The snook is also made out from the dip at an inclination of angle a from the dip direction.
[0034] As illustrated in Figure 1 and Figure 2, the non-split mining method for extraction of coal pillars by continuous miner comprises of steps where first size of the pillar is determined 101 inside the underground coal mine. It is checked whether the pillar size is less than 30.0 m or not as the non-split method is suitable for small pillar sizes i.e. below 30.0 m. Further, after determination 101 of the size of a pillar the pillars to be extracted are sequenced 102 in a straight line for caving of the roof in the dip direction. The sequencing 102 of pillars is followed by cutting of 103 a pillar into a series of slices directed into level gallery followed by a push 104 from dip gallery direction, wherein each slice having a minimum width of 3.5 m is cut at an angle of a from gallery and at a minimum distance of 3.0 m from the dip gallery of the pillar 201. The value of angle a is pre-determined and has a minimum value of 45o. The cutting of slices is also referred as driving into the pillar.
[0035] During the process of cutting of a pillar, a first slice 202 is cut from a first edge 211 of the pillar 201, where left side of the pillar 201 forms the first edge 211. Then, a second slice 203 and a third slice 204 are cut from the first edge 211 in a parallel orientation to the first slice 202. Such a series of cutting 103 of slices further includes cutting of a fourth slice 205 from a second edge 212 of the pillar 201, where left corner portion and bottom horizontal side of the pillar form the second edge 212. Then, a fifth slice 206 and a sixth slice 207 are cut from the second edge in a parallel orientation to the fourth slice 205.
[0036] The cutting 103 of the pillar 201 is further continued after sixth slice 207 where a seventh slice 208 is cut from a third edge 213 of the pillar, where right side of the pillar 201 forms the third edge 213. Further, an eighth slice 209 and a ninth slice 210 are cut from the third edge 213 in a parallel orientation to the seventh slice 208. The snook 214 having an area equivalent to 5% to 10% of the original pillar size with a pre-determined width to height ratio of w: h is further pushed has been cut out in the pillar 201, thus ensuring a judicious extraction of the snook portion 214.
[0037] The method has numerous associated advantages besides being safe, efficient and cost effective such as the lengths of cuts into the pillar are significantly reduced compared to pillar length in conventional methods, all cuts have to be nominally made at 45º to the dips and levels gallery, all cuts are pre-marked using survey pegs and direction lines and all mining personnel can be trained easily for strictly adhering to survey marks and directions.
[0038] In addition, there is an increased volumetric extraction of coal i.e. up to 70 % to 80 % of the coal reserves by using the non-split mining method for extraction of coal from deep seated underground coal mines. Further, the pillar remains stable. Whereas, in the conventional methods the pillar loses its stability due to two unstable fenders and such splitting damages the core of the pillar. In contrast, in the non- split mining method the extraction of the pillar does not require any form of splitting of the pillar, which keeps the pillar intact and stable.
[0039] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances, where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”
[0040] It will be further appreciated that functions or structures of a plurality of components or steps may be combined into a single component or step, or the functions or structures of one-step or component may be split among plural steps or components. The present invention contemplates all of these combinations. Unless stated otherwise, dimensions and geometries of the various structures depicted herein are not intended to be restrictive of the invention, and other dimensions or geometries are possible. In addition, while a feature of the present invention may have been described in the context of only one of the illustrated embodiments, such feature may be combined with one or more other features of other embodiments, for any given application. It will also be appreciated from the above that the fabrication of the unique structures herein and the operation thereof also constitute methods in accordance with the present invention. The present invention also encompasses intermediate and end products resulting from the practice of the methods herein. The use of “comprising” or “including” also contemplates embodiments that “consist essentially of” or “consist of” the recited feature.
[0041] Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/component of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.
[0042] Reference Numerals
Reference Numeral Description
201 Pillar
202 First slice
203 Second slice
204 Third Slice
205 Fourth Slice
206 Fifth Slice
207 Sixth Slice
208 Seventh Slice
209 Eight Slice
210 Ninth Slice
211 First Edge
212 Second Edge
213 Third Edge
214 Snook Portion

We claim:

1. A non-split mining method for extraction of coal pillars by Continuous Miner, the method comprising:
determining (101) the size of a pillar (201) in underground coal mine;
sequencing (102) of pillars (201); and
cutting (103) a pillar (201) into a series of slices directed into level gallery followed by a push (104) from dip gallery direction, wherein each slice having a minimum width of 3.5m is cut at an angle of a from gallery and at a minimum distance of 3.0 m from the dip gallery of the pillar (201),
characterized in that,
a first slice (202) is cut from a first edge (211) of the pillar, a second slice (203) and a third slice (204) are cut in a parallel orientation to the first slice (202),
a fourth slice (205) is cut from a second edge (212) of the pillar, a fifth slice (206) and a sixth slice (207) are cut in a parallel orientation to the fourth slice (205), and
a seventh slice (208) is cut from a third edge (213) of the pillar, and an eight slice (209) and a ninth slice (210) are cut in a parallel orientation to the seventh slice (208).
2. The method as claimed in claim 1, wherein a snook portion (214) has a minimum area equivalent to 5% to 10% of the original pillar size and a pre-determined width to height ratio of w:h.
3. The method as claimed in claim 1, wherein the value of the angle a is 45o.
4. The method as claimed in claim 1, wherein the sequencing (102) of pillars is in a straight line for caving of the roof in the dip direction.
5. The method as claimed in claim 1, wherein the size of the pillar (201) is less than 30.0m.
6. The method as claimed in claim 1, wherein left side of the pillar (201) forms the first edge (211).
7. The method as claimed in claim 1, wherein the left corner portion and bottom horizontal side of the pillar forms the second edge (212).
8. The method as claimed in claim 1, wherein right side of the pillar forms the third edge (213).