CA1130823A - Longwall mining method designed to alleviate the earth pressure at the working face - Google Patents
Longwall mining method designed to alleviate the earth pressure at the working faceInfo
- Publication number
- CA1130823A CA1130823A CA339,914A CA339914A CA1130823A CA 1130823 A CA1130823 A CA 1130823A CA 339914 A CA339914 A CA 339914A CA 1130823 A CA1130823 A CA 1130823A
- Authority
- CA
- Canada
- Prior art keywords
- face
- ore bed
- tunnel
- working face
- earth pressure
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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- Lining And Supports For Tunnels (AREA)
Abstract
LONGWALL MINING METHOD DESIGNED
TO ALLEVIATE THE EARTH PRESSURE
AT THE WORKING FACE
Abstract of the Disclosure In order to improve the efficiency of longwall mining while avoiding any danger of face fall, it is proposed to form in the ore bed lying ahead of the working face or the ground over- or underlying the ore bed a tunnel which extends over the whole extent of face width. Such tunnel formation is effective to disperse the stress envelope formed around the face region thereby to reduce the face earth pressure. Further reduction of the earth pressure can be effected as required by injecting high-pressure liquid into the ore bed region lying between the working face and the tunnel.
TO ALLEVIATE THE EARTH PRESSURE
AT THE WORKING FACE
Abstract of the Disclosure In order to improve the efficiency of longwall mining while avoiding any danger of face fall, it is proposed to form in the ore bed lying ahead of the working face or the ground over- or underlying the ore bed a tunnel which extends over the whole extent of face width. Such tunnel formation is effective to disperse the stress envelope formed around the face region thereby to reduce the face earth pressure. Further reduction of the earth pressure can be effected as required by injecting high-pressure liquid into the ore bed region lying between the working face and the tunnel.
Description
1~3~8;Z3 BACKGROUND OF T~E INVENTION
....
This invention relates generally to longwall mining methods which are used in coal and the like underground rnines and more particularly to those designed to alleviate the earth pressure developing around the working face.
In longwall mining, an excessive earth pressure lS often met in the vicinity of the workinq face particularly in cases where the depth of mining is substantially increased and tends to cause bulging collapse of the working face, thus impairing the mining efficiency. In coping with such situations, it has been usual in practice to take measures such as of increasing the pressure-hearing capacity of the support structure, adding protecting devices thereto, or restricting the entrance of mine workers to the working area for safety of mining operation.
SUMMARY OF THE INVENTION
.
Under the circumstances, the present invention is intended to make any measures conventionally taken, in the longwall mining, for prevention of face bulging collapse practically needless or to minimize the need for taking such conventional safety measures.
According to the present invention, there is provided a new longwall mining method designed to alleviate the earth pressure developing around the working face and characterized i in that it comprises the steps of forming in the unmined ore bed lying ahead of the longwall working place in the direction of excavation at the level of the working place a tunnel which extends over the whole width of the working face and between two face gateways formed on the opposite sides of the unmined ore bed in order to disperse the stress envelope initially formed , - . ,~
sd/ - , -2-.'. ' : ~
. -- ' .
' 1136~8;~3 around the working place and then excavatiny that region o~
the ore bed which lies between the working face and the tunnel.
The above and other ~eatures and advantages of the present invention will become apparent froJn the following description when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
-In the drawings:
Fig. 1 is a diagrammatic plan view, in longitudinal cross-section, illustrating a longwall mining face;
; Fiq. 2 is a cross-sectional side elevation taken along the line II-II in Fig. l;
Fig. 3 is a view similar to Fig. 1, illustrating an embodiment of the present invention as applied to the mine face of Fig. l;
Fig. 4 is a view similar to Fig. 2, ta~en along the line IV-IV in Fig. 3;
Fig. 5 is a view similar to Figs. 1 and 3, illustrating another embodiment of the invention which includes a different formation of tunnels in the unmined ore bed;
Fig. 6 is a view similar to Figs. 1, 3 and 5, illustrat-ing a further embodiment of the invention which includes yet ' another tunnel formation in the unmined ore bed;
Figs. 7 and 8 are views similar to Figs. 2 and 4, i illustrating further embodiments of the present invention which include tunnels formed in the ground overlying the ore bed to be excavated and the ground underlying the latter, respectively;
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113~:)823 Fig. g is a view similar to Figs. 1, 3, 5 and 6, illustrat ing the working face of Fig. 1 further embodying the second aspect of the mining method of the present invention; and Fig. 10 is a longitudinal cross section taken along ~he line X - X in Fig. 9.
Description of the Preferred Embodiments .
Referring first to Figs. 1 and 2, which diagrammatically illustrate a longwall mining area, reference numeral 2 indicates an ore bed such as a coal or rock salt seam; and 1 indicates the longwall mining face of the ore bed 2 being excavated in the direction of arrows P. Reference numeral 3 indicates face gate-ways formed on the opposite sides of the ore bed 2 being ex-cavated. In such underground working area, a stress envelope develops as indicated by the chain-dotted lines Al because of the presence of the mined-out opening or void 4. As is known, the stress envelope Al represents the zone of heavy stress concentration formed around the void under ground pressure and is a factor which can cause bulging collapse at the working face la while on the other hand exerting unwanted forces upon mining machines in use with the result that the mining efficiency is reduced and the machine loads heavily increased. In the example illustrated, the mined-out opening ~ is left unfilled allowing - free rock fall and, as with this case, even in cases where the mined-out opening is filled as excavation proceeds, the state of balance of earth pressure must be more or less broken compared to its state before excavation and there exists at all times an open space extending along the working face over the whole width .t~
thereof that is required for mining operation. Because of these facts, the stress envelope developing around the work ing face is substantially limited in radius of curvature ir~e-.
.' ,, '~
, . - ~ ~ .
' :
113Q8;23 spective of whether the mined-out area is filled immediately or left unfilled.
The mining method of the present invention is advantageously applicable to a longwall mining face which is subject to an excessive ground pressure as described above. S~ecifically, as seen in Figs. 3 and 4, there is formed in the unmined ore bed 2 lying ahead of the working area 1 in the direction of excavation P at least one elongate void or tunnel 5 which extends over the whole width w of the working face. Such pressure-releasing tunnel or tunnels 5 are ordinarily formed substantiallyin parallel to the working face la and extend between the face gateways 3, formed on the opposite sides of the unmined ore bed
....
This invention relates generally to longwall mining methods which are used in coal and the like underground rnines and more particularly to those designed to alleviate the earth pressure developing around the working face.
In longwall mining, an excessive earth pressure lS often met in the vicinity of the workinq face particularly in cases where the depth of mining is substantially increased and tends to cause bulging collapse of the working face, thus impairing the mining efficiency. In coping with such situations, it has been usual in practice to take measures such as of increasing the pressure-hearing capacity of the support structure, adding protecting devices thereto, or restricting the entrance of mine workers to the working area for safety of mining operation.
SUMMARY OF THE INVENTION
.
Under the circumstances, the present invention is intended to make any measures conventionally taken, in the longwall mining, for prevention of face bulging collapse practically needless or to minimize the need for taking such conventional safety measures.
According to the present invention, there is provided a new longwall mining method designed to alleviate the earth pressure developing around the working face and characterized i in that it comprises the steps of forming in the unmined ore bed lying ahead of the longwall working place in the direction of excavation at the level of the working place a tunnel which extends over the whole width of the working face and between two face gateways formed on the opposite sides of the unmined ore bed in order to disperse the stress envelope initially formed , - . ,~
sd/ - , -2-.'. ' : ~
. -- ' .
' 1136~8;~3 around the working place and then excavatiny that region o~
the ore bed which lies between the working face and the tunnel.
The above and other ~eatures and advantages of the present invention will become apparent froJn the following description when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
-In the drawings:
Fig. 1 is a diagrammatic plan view, in longitudinal cross-section, illustrating a longwall mining face;
; Fiq. 2 is a cross-sectional side elevation taken along the line II-II in Fig. l;
Fig. 3 is a view similar to Fig. 1, illustrating an embodiment of the present invention as applied to the mine face of Fig. l;
Fig. 4 is a view similar to Fig. 2, ta~en along the line IV-IV in Fig. 3;
Fig. 5 is a view similar to Figs. 1 and 3, illustrating another embodiment of the invention which includes a different formation of tunnels in the unmined ore bed;
Fig. 6 is a view similar to Figs. 1, 3 and 5, illustrat-ing a further embodiment of the invention which includes yet ' another tunnel formation in the unmined ore bed;
Figs. 7 and 8 are views similar to Figs. 2 and 4, i illustrating further embodiments of the present invention which include tunnels formed in the ground overlying the ore bed to be excavated and the ground underlying the latter, respectively;
~. !;
' . .
" : '' `
'~, . ' .
sdJI~' -3-.
113~:)823 Fig. g is a view similar to Figs. 1, 3, 5 and 6, illustrat ing the working face of Fig. 1 further embodying the second aspect of the mining method of the present invention; and Fig. 10 is a longitudinal cross section taken along ~he line X - X in Fig. 9.
Description of the Preferred Embodiments .
Referring first to Figs. 1 and 2, which diagrammatically illustrate a longwall mining area, reference numeral 2 indicates an ore bed such as a coal or rock salt seam; and 1 indicates the longwall mining face of the ore bed 2 being excavated in the direction of arrows P. Reference numeral 3 indicates face gate-ways formed on the opposite sides of the ore bed 2 being ex-cavated. In such underground working area, a stress envelope develops as indicated by the chain-dotted lines Al because of the presence of the mined-out opening or void 4. As is known, the stress envelope Al represents the zone of heavy stress concentration formed around the void under ground pressure and is a factor which can cause bulging collapse at the working face la while on the other hand exerting unwanted forces upon mining machines in use with the result that the mining efficiency is reduced and the machine loads heavily increased. In the example illustrated, the mined-out opening ~ is left unfilled allowing - free rock fall and, as with this case, even in cases where the mined-out opening is filled as excavation proceeds, the state of balance of earth pressure must be more or less broken compared to its state before excavation and there exists at all times an open space extending along the working face over the whole width .t~
thereof that is required for mining operation. Because of these facts, the stress envelope developing around the work ing face is substantially limited in radius of curvature ir~e-.
.' ,, '~
, . - ~ ~ .
' :
113Q8;23 spective of whether the mined-out area is filled immediately or left unfilled.
The mining method of the present invention is advantageously applicable to a longwall mining face which is subject to an excessive ground pressure as described above. S~ecifically, as seen in Figs. 3 and 4, there is formed in the unmined ore bed 2 lying ahead of the working area 1 in the direction of excavation P at least one elongate void or tunnel 5 which extends over the whole width w of the working face. Such pressure-releasing tunnel or tunnels 5 are ordinarily formed substantiallyin parallel to the working face la and extend between the face gateways 3, formed on the opposite sides of the unmined ore bed
2. The formation of pressure-leasins tunnel or tunnels, however, may be determined as desired in accordance with the surround-ing conditions, including the ground condition around the work-ing area and the state of stress envelope Al, the ore bed 2 being excavated or the over- and underlying grounds 6 and 7.
Various tunnel formations other than that shown in Figs. 3 and - 4 are illustrated in Figs. 5 to ~. Shown in Fig. 5 are voids or tunnels 5 which are more or less inclined to the working face la instead of being parallel thereto and extend through the unmined ore bed 2 as with the case of Figs. 3 and 4.
Fig. 6 illustrates a tunnel formation similar to that of Fig. 5 except that the tunnels 5 in this formation is inclined in a direction opposite to those in the formation of Fig. 5.
Fig. 7 illustrates another tunnel formation in which tunnels 5 are formed in the overlying ground 6 at a level slightly above the ore bed region 2 to be excavated. Reference numeral 3a ; indicates raises driven upwardly from each of the face gateways
Various tunnel formations other than that shown in Figs. 3 and - 4 are illustrated in Figs. 5 to ~. Shown in Fig. 5 are voids or tunnels 5 which are more or less inclined to the working face la instead of being parallel thereto and extend through the unmined ore bed 2 as with the case of Figs. 3 and 4.
Fig. 6 illustrates a tunnel formation similar to that of Fig. 5 except that the tunnels 5 in this formation is inclined in a direction opposite to those in the formation of Fig. 5.
Fig. 7 illustrates another tunnel formation in which tunnels 5 are formed in the overlying ground 6 at a level slightly above the ore bed region 2 to be excavated. Reference numeral 3a ; indicates raises driven upwardly from each of the face gateways
3 (not shown in this fiyure) into the overlying ground 6 for ~;~
- 5 - ~
~' . ~
.. ~ - .
113~823 ',:.
....
.
tunnel driving. A further tunnel formation is shown in Fig. 8 ~hich includes tunnels 5 driven in the underlying ground 7 at -~
a level slightly below the ore bed 2 by way of winzes 3b driven downwardly from the face gateways.
As the result of formation of such voids or pressure-releasing tunnels 5, the stress envelope Al initially formed around the working area l is dispersed as indicated by the chain-dotted lines A2 in Fig. 4. In this manner, the earth pressure in the vicinity of the working face la is widely reduced and the danger of bulging collapse eliminated. Subsequently, the ore bed 2 is ~excavated until the working face la reaches an appropriate position advanced beyond the first tunnel 5.
Such mining operation is repeated progressively so that at all times ore excavation is effected efficiently under reduced ground pressure.
According to the second aspect of the present invention, in cases where no satisfactory reduction in earth pressure is obtainable at the working face la just by digging tunnels 5 in the manner described above, a multitude of njection holes are drilled in that region of unmined ore bed 2 which lies between the working face la and the first tunnel 5 and, it desired, also in the next ore-bed region extending between the first ;~
and second tunnels, as indicated at B in Figs. 9 and 10, in advance of actual excavation, and high-pressure liquid of low cost such as high-pressure water i5 injected into such injection holes 8. The drilling of injection holes 8 may be advanced from the working place 1, either one or both of the gateways 3 and/or the neighboring tunnel or tunnels 5. Further, not only the number and length of injection holes 8 but their angle of inclination to the horizontal or to the direction of the widt~
, :
113~823 of working face la or to the length of face gateways 3 or that of tunnels S can be determined as desired in accordance with the conditions of ore bed 2 and over- and underlying grounds 6 . .
and 7. In this mining method, the injection of high-pressure liquid is intended to convert the energy of ground compression ,: . ., = _- = _ into that of plastic strain to further reduce the earth pressure in the ore bed 2 being excavated by utilizing the characteristic of an ore bed that its ultimate breaking strength is generally reduced with rise of its water content. Within the ore bed 2 injected with high~pressure liquid, there arise plastic and flow deformations and the energy held in the bed 2 is converted from its initial elastic form into an inert one so that the danger of bulging collapse at the working face la is effectively eliminated. It will be appreciated, therefore, that the safety in underground minins operations can be materially increased by repeating the driving of tunnel 5, injection of high-pressure liquid into ore bed 2 and its excavation successively in that order.
As will be apparent from the foregoing description, the longwall mining method of the present invention has among others the advantages that the earth pressure at the working face la can be fully reduced to enable safe excavation involving no ., .
bulging collapse and that the ground resistance to machine excavation is widely decreased to enable mining operation with substantially improved efficiency.
-~, .
. . _ . ~
: ,. ~ :
:~ .. : : :
: : :~ :'.::
:., :. :
- 5 - ~
~' . ~
.. ~ - .
113~823 ',:.
....
.
tunnel driving. A further tunnel formation is shown in Fig. 8 ~hich includes tunnels 5 driven in the underlying ground 7 at -~
a level slightly below the ore bed 2 by way of winzes 3b driven downwardly from the face gateways.
As the result of formation of such voids or pressure-releasing tunnels 5, the stress envelope Al initially formed around the working area l is dispersed as indicated by the chain-dotted lines A2 in Fig. 4. In this manner, the earth pressure in the vicinity of the working face la is widely reduced and the danger of bulging collapse eliminated. Subsequently, the ore bed 2 is ~excavated until the working face la reaches an appropriate position advanced beyond the first tunnel 5.
Such mining operation is repeated progressively so that at all times ore excavation is effected efficiently under reduced ground pressure.
According to the second aspect of the present invention, in cases where no satisfactory reduction in earth pressure is obtainable at the working face la just by digging tunnels 5 in the manner described above, a multitude of njection holes are drilled in that region of unmined ore bed 2 which lies between the working face la and the first tunnel 5 and, it desired, also in the next ore-bed region extending between the first ;~
and second tunnels, as indicated at B in Figs. 9 and 10, in advance of actual excavation, and high-pressure liquid of low cost such as high-pressure water i5 injected into such injection holes 8. The drilling of injection holes 8 may be advanced from the working place 1, either one or both of the gateways 3 and/or the neighboring tunnel or tunnels 5. Further, not only the number and length of injection holes 8 but their angle of inclination to the horizontal or to the direction of the widt~
, :
113~823 of working face la or to the length of face gateways 3 or that of tunnels S can be determined as desired in accordance with the conditions of ore bed 2 and over- and underlying grounds 6 . .
and 7. In this mining method, the injection of high-pressure liquid is intended to convert the energy of ground compression ,: . ., = _- = _ into that of plastic strain to further reduce the earth pressure in the ore bed 2 being excavated by utilizing the characteristic of an ore bed that its ultimate breaking strength is generally reduced with rise of its water content. Within the ore bed 2 injected with high~pressure liquid, there arise plastic and flow deformations and the energy held in the bed 2 is converted from its initial elastic form into an inert one so that the danger of bulging collapse at the working face la is effectively eliminated. It will be appreciated, therefore, that the safety in underground minins operations can be materially increased by repeating the driving of tunnel 5, injection of high-pressure liquid into ore bed 2 and its excavation successively in that order.
As will be apparent from the foregoing description, the longwall mining method of the present invention has among others the advantages that the earth pressure at the working face la can be fully reduced to enable safe excavation involving no ., .
bulging collapse and that the ground resistance to machine excavation is widely decreased to enable mining operation with substantially improved efficiency.
-~, .
. . _ . ~
: ,. ~ :
:~ .. : : :
: : :~ :'.::
:., :. :
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A longwall mining method designed to alleviate the earth pressure developing around the working face, characterized in that it comprises the steps of forming in the unmined ore bed (2) lying ahead of the longwall working place (1) in the direction of excavation (P) at the level of the working place (2) a tunnel which extends over the whole width (w) of the working face (1a) and between two face gateways formed on the opposite sides of the unmined ore bed (2) in order to disperse the stress envelope (A1) initially formed around the working place (1) and then excavating that region of the unmined ore bed which lies between the working face (1a) and the tunnel (5).
2. A longwall mining method as claimed in claim 1, in which the tunnel (5) is so formed as to extend between two face gateways formed completely within and on the opposite sides of the unmined ore bed (2).
3. A longwall mining method as claimed in claim 1 or 2, in which a plurality of tunnels (5) are formed solely in the unmined ore bed (2) lying ahead of the working place (1) in the direction of excavation (P) and forming which tunnels without mining any ground surrounding the ore bed.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP148466/1978 | 1978-11-30 | ||
| JP14846678A JPS5575098A (en) | 1978-11-30 | 1978-11-30 | Long wall type method with reduced ground pressure on face working surface |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1130823A true CA1130823A (en) | 1982-08-31 |
Family
ID=15453370
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA339,914A Expired CA1130823A (en) | 1978-11-30 | 1979-11-15 | Longwall mining method designed to alleviate the earth pressure at the working face |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5575098A (en) |
| CA (1) | CA1130823A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU2013358812B2 (en) * | 2012-12-10 | 2016-01-21 | China University Of Mining And Technology | Solid-filling coal mining method with two pre-excavated tunnels for advancing |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58164656U (en) * | 1982-04-28 | 1983-11-02 | 株式会社日本製鋼所 | Wrist protection device for air blasting robots, etc. |
| CN105089668A (en) * | 2014-05-19 | 2015-11-25 | 梁捷 | Longwall working face coal-pillar-free mining method |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4084384A (en) * | 1976-09-13 | 1978-04-18 | Shosei Serata | Advanced slot stress control method of underground excavation |
-
1978
- 1978-11-30 JP JP14846678A patent/JPS5575098A/en active Granted
-
1979
- 1979-11-15 CA CA339,914A patent/CA1130823A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU2013358812B2 (en) * | 2012-12-10 | 2016-01-21 | China University Of Mining And Technology | Solid-filling coal mining method with two pre-excavated tunnels for advancing |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5738754B2 (en) | 1982-08-17 |
| JPS5575098A (en) | 1980-06-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |