Embed Size (px)
Citation preview
Information Circular 8741
Results of Research To DevelopGuidelines for Mining Near Surfaceand Underground Bodies of Water
By Clarence O. Babcock and Verne E. Hooker
UNITED STATES DEPARTMENT OF THE INTERIOR
Ct;cil D. Andrus, Secretary
BUREAUOF MINES
Thispublicationhasbeencatalogedasfollows:
Babcock, Clarence 0Results of research to develop guidelines for mining near
surface and underground bodies of water / by Clarence O.Babcock and Verne E. Hooker. [Washington]: United StatesDepartment of the Interior, Bureau of Mines, 1977.
17p. : ill., diagrams; 26 em. (Information c..ircular . Bureau ofMines; 8741)
1. Mine water. '2. Mine drainage. 3. Coal mines and mining.I. Hooker, Verne E., joint author. II. United States. Bureau ofMines. III. Title. IV. Series: United States. Bureau of Mines.Information circular. Bureau of Mines; 8741.
TN23.U71 no. 8741 622.06173
U.S. Dept. of dle- Int. Library
CONTENTS
Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Surface waters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Total extraction mining... . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . .Partial extraction mining.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Roomand pillar..............................................Minimum depth of cover '. . ...Pillar dimensions for first workings....................
Panel and pillar.............................................Safety zones......................................................
Surface, waters... . . . . . . . . . . . . . '. . . . . . . . . . ... . . . . . . . . . . . . . . . . . . .Structures retaining water ~.......................
Underground waters . . . '0''.. . . . . . . . . .'.. . . . . . . . . . . . . . . ~ . . . . . . . . . . .Minemaps.........................................................
Surfacefeatures.............................................Undergroundfeatures.........................................
Property boundary barrier pillars '. .. . . . .. ... ..... ... ... . ... .. ..Abandoned workings, abandoned areas, and adjacent mines...........Oil and gas well pillars ' ' ~ '.Shaft and vertical opening barrier pillars........................Mining under abandoned flooded workings ~..
Appendix... .. .. . .. . ... .. ... ... e.. .. . .. . .. .... .. . ... ....ILLUSTRATIONS
1.2.3.
Safety zone beneath body of surface' water. ..... . . .. .'... . .. . . . . . . . . . . .Safety ,zone beneath dam and impounded body of surface water.; ,..Drill pattern for safe advance through coal with unknown
inundation hazards ......TABLES
1..2.3.4.5.6.7.
feet. . . . . . . .".. . . . . . . . .feet. . '. . . . . . . . . . . . . . . .fee t . . . . . . . . . . . . . . . . . .feet. . . . . . . . . . . . . . . . . .
fee t . . . . . . . . . . . . . . . . .feet. . . . . . . . . . . . . . . . .feet.................
Minimum pillar widths for pillar heights of 3
Minimum pillar' widths for pillar heights of 4Minimum pillar widths for pillar heights of 6
Minimum pillar widths for pillar heights of 8
Minimum pillar widths for pillar heights of 10
Minimum pillar widths for pillar heights of 12
Minimum pillar. widths ~or pillar heights of 14
Page
112233348999
11111112131416161617
1011
15
5566778
SPECIAL NOTE
The section on mine maps (pages 11-13) is synopsized
from existing Federal regulations (30 CFR75.12(0). Thissection is included to emphasize the importanc~ of mine
maps in relation to mining under or near bodies.g! ,wll1:~rand
is not intended as an additiona~ mapping requirement or as aproposed amendment to current regulations.
Panel and pillar mining,' being useddn the United
Kingdom, is not yet extensively used in"the United States .
This system which works well in deep coal, hassmuch less
application herej particu1arlYiin the eastern.part,Cif the
couI).trywberethePbiggest.tonnageisrelatively shallow.The' panel width used has been so wide .that only deepr.coal
can qualify for mining by this method. However, if thismethod is imported) as the longwal1 method 'Was iiithe past,
so~eguide1i~e~~or. its use,wil:1 ~e available. The methodshou.~?fin? ~ewhere..the' coal'is.,iatthenecessarysc1iepth,because higher recoveryispossible'thannthroOD1-"'and- .pill.ar met-Wods.
RESULTSOF RESEARCHTO DEVELOP GUIDELINESFOR MININGNEAR SURFACE AND UNDERGROUNDBODIESOF WATER
by
Clarence O. Babcock 1and Verne E. Hooker2
ABSTRACT
This Bureau of Minespublication present$ guidelines for mining ..nearsurface and underground bodies of water .The guidelines were based on infor-mationdeveloped under contract in three phase$ of study, as follows:(1) Collection and documentation of data from worldwide sources; (2) appli-cation of existing guidelines, foreign, Federal, and State, to case.historiesof previous iIlundations; an~ (3) development o£recomnended guidelines forunderground coal mining near bodies of wateraime9 at inaximum efficient utili-zation of underground coal resources consistent with miriimizing. inundationhazards. While the contract guidelines were for the mining of coal seams,they may also be. used for mining any tabular sedimentary mineral deposit.Tables are given fo~ the determination of the size of coal pillars need~d;for other bedded d~posits, similar table$ could be determined based on "theirstrength properties.
INTRODUCTION
The need for practical safety guidelines when mining near bodies of wateris growing because of increasing mineral demands and an increasing number ofwater impoundments near mineral- resources. Accordingly., the Bureau of Minesgenerated a program for the development of poteritial recommended guidelinesfor mining in close proximity to bodies of water. The objective wa~ maximumefficient utilization of underground coal resources consistent with minimiz-ing inundation hazards.
It should be emphasizet! that an .empirical approach to data collection wasused in developing these recommendations. The basic engineering concepts aresound; however, when there is sufficient engineering data or mining experienceavailable, these conservative recommendations should be modified. Furtherresearch is under consideration to refine the engineering conditions on whichthe recommendations are based. . .
lMlning Engineer.2Superv1sory geophysicist.Both authors are with the Denver Mining Research Center,
Denver, 0010.Bureau of Mine,s~
2
Two contracts on the subject were initiated in May 1975 and completed in Septem-ber 1976.3 Results of the contracts were/evaluated and compilec1by the authors intoa single comprehensive set of recommended technical guidelines relative to surfacewaters, surface structures, and abandoned workings.
These recommended guidelines cover total extraction by longwall or retreat pil-
lar robbing, partial, extraction by roo~a~d~illar, partial extraction by panel min-ing, and a combination of these methods. SOuiia of the ~ortarit variables involvedare the solid rock cover above the coal seam(s), allowable tensile strain at the bot-tom of the water body, the number of seams that may be mined or restricted, and theallowable proximity of faults, old workings, etc.
SURFACE WATERS
Total Extraction Minin~
A total extractionmining system is defined as the extractionof the whole min-able thickness of a coal seam or other bedded mineral deposit over a large enougharea so that the lateral dimensions in:any direction are equal to or greater thanthe depth of mining. The method of extraction, whether by longwall, continuous, orconventional mining, is'not relevant to this definition.
, ~ ~ ~- ~ ~ ~
The followingg~idelines are recommended With respect to totai,extraction min-
ing. These guidelines,require the establisluniarii":-DY.. drilling or ot:herwise--of thethickness of solid rock cover above the proposed total extractionwortdngs. If itis desired to have oVer"yingmateria1(s) otherthanso11d rock coVer included in theminimum depth stipulat1okf;.itis necessary to demonstratethe nattire and permeabil-ity of such materi81s. . Where' theword "coal" or:i:"seam'" is used, it also applies to
any biadded ~ m1neraldepo~~t..- -- - - - - -
1. Any single~eamofc=pal beneathor in thevicinityof anybody; of .surface'water may be totally extracted,whether by longwall JDinin,g or by pUlar-robbing, pro-vided tha~ far ~ each I-foot thickness of coUile~'to be extracted; a miniDnun'of 60feet of solid strata cover exiSts betWeen the proposedworkings and the bed of thebody of surface water. . .~
2. Where more than one seam of coal exists, all may be worked by total extrac-tion provided that for each 1 foot of the. aggregate coal and rock thickness of all
seams to be.extracted,a minimum thickness of 60 feet of solid strata cover exists
between the' proposed workings in the uppermost' s~am and ~~e bed of the body of
3 Skel~~y .an.~I.()Y.(lIa;!,isl!urg, ..fa .') . Guide~in:stor'Mining .N"ear Stli-ft.:c~.~at.ers(qQtractHO?5?987).,' BUMines Open Fi1eRept.29~77 ,1977, 190 pp.;~vai~ablefor consult~tiQ~/~t the B';1reau of Mil}:s libr.ariesinDen'ler,Colo.,. 'l'wi~.Cities,Minn., PittsburglL; Pa.,Spokane, Wasn., and'Carbondale,."Ill~;at the CentralLibrary, U.S. Department of the Interior, Washington, D..C.; at thelf.brari.es of
the Morgantown Energy.~search Center--ERDA,Morgantown, W. Va., and the TrainingFacility--MESA, Bec1:Cley, w..'Va.; and from.the National Technical Information .ServicE!, SpI'ingfield~'Va., PB 264 728/AS. .
K. Wardell and Partners (Newcastle, United Kingdom)~ Guidelines for Min.ing NearSurface Waters (COntract 00252021). BuMines Open $ile Rep~..3Q-77, 1977, .59 pp.;available for consultation at the Bureau of Mines. librari~fI .i.n D.e,nver, Colo.,Twin Cities, Minn., Pittsburgh, Pa., Spokane,..Wash., and Carb~ndale,~l1~<; at theCentral Library, U.S. Departmentof the Interior,Washington, D.C.; at thelibraries of the Morgantown Energy Researcn Centar--ERDA,Mg.rgan~()WD,~ W.ya., andthe Training Facility--MESA, Beckley, W. Va.; and tx-om the National Te,.chni.c~lInformationServic~, Springfi~ld, Va., PB 264 7291As.
3
surface water. When subsidence observations have been carried out and satis-
factory calculations of surface tensile strain can be made, any number ofseams may be mined by total extraction provided that the maximum cumUlative,
calculated4 tensile strain beneath a body for surface water will nowhereexceed 8.75 mm/m (0.875 percent). . .
3. Where a single seam has already been mined by total extraction inaccordance with the provision that for each I-foot thickness of mineral and
rock extracted, a minimum of 60 feet of solid strata cover should exist, no
other underlying seam should be mined by total extraction. Where the coverbetween the two seams is 60 times (or greater) the extractable thickness of
the lower seam, such a lower seam should be mined by partial extraction--in
accordance with the subsequent guidelines here stipulated--as though the upper
seam represented a body of surface water.
4. Where wash or other natural or artificial deposits, which may be .
highly permeable or which when wet may flow, exist between bedrock and the bedof a body of surface water, these should be excluded from the thickness of
solid strata mentioned, except where it has been demonstrated that such wash
or other deposits would not be likely to flow when wet and could be consideredas impermeable.
5. Where a fault which might connect mine workings with a body of sur-
face water and which has a vertical displacement. greater than 10 feetJ or an
intrusive dike having a width greater than 10 feet, is known to exist or ismet with during development, no seam should be totally extracted within50 feet horizontally o~ either side of such fault or dike.
Partial Extraction Mlnin~
A partial extraction system is one in which designated pillars are delib-
erately left unworked for the purpose of giving more or less permanent supportto the overlying strata and the land surface. Two such systems are the room-and-pillar' first working and the panel-and-pilla~ system.
. Room and Pillar
In the room-and-pillar system of mining about 50 percent of the coal is
recovered by two intersecting sets of parallel entries, usually nearly per-
pendicular to one another. The result is a checkerboardlike array of pillarswhich. systematically support the roof rock. In the following discussion the
term "first working" means~hat the' coal is mined by driving the entries, as
opposed to "secondary workings" in whicb the coal left in the pillars is minedto increase recovery.
Minimum Depth of Cover
A minimum thickness of solid strata cover should be left above the coal
seam. Both the height and width of the entries and the characteristics of
4Calculation procedure is given in the appendix.
4
the roof beds are significant parameters with respect to expected roof. col~lapse:;: height.
The separate provisions with respect to drifts and tunnels are stip-ulated because the practicability and cost ()~., suppor.ting and maintaining themwould be generally acceptable. In room-and-pillar entries, however, the costof permanent supports. would be exceptionally high and their maintenance wouldbe generally impracticable.
The following guidelines are recommended with respect toa minimum depthof solid strata forroom-and-pillar working~.
1. No entry should be driven in any coal seam lying beneath or in thevicinity of any body of surface water where ..t;het.otalthickne.ss of solidstrata cover above the seam is less than 5 times the maximum entry width (5s)
or 10tifues the maxiplumentry height (lOt),.whichever is the greater. Whereat least.one competent bed of sandstone or sim,ilarmaterialis present withinthe solid strata and has/.athickness at least 1.75.times.ti:lemaxilnum entrywidth, mining at'alessercover than 55 or 10t::1IlCI.Ybe consider~.
2. In the caseof drifts or tunnels beneatn or in thevic:in.ity ()f the
body of surface water d:rIyen through the strata for the purpos.e of gainingaccess to.a coalsea1:!:J.,theprovision of lQt::.(),:'5sshQtlld alsq'.!ipply unlessdrif.ts ortunne];s.a:petperinanently. Stlpp():pted;:anda,:'e. sQm.!iintaine4. In. thelatter event,howeye,:'., .there should bea minimum solid,rockcover of 1.75times the maximumdrift or tunnel width.
Pillar Dimensions fot-First WorkinRs
The results of observing'the behavior of mine pillars underground,with,
respect .to stability, of laboratory testiI).g of ,coal samples, andoftheo-retical considerati,ons.wereconibined to establish the size ofcoa,lpillarsneeded for safetyasfuI).ctions o.fcoal "thickness, depthbelO'! surface of thecoal seam, and theroOpl ~idthused. In accordaI).ce.~th theresu,.lts.,thefol-lowing guidelines are proposed with respect to pillar dimensions for room-and-
pillar first workings. " ,
1. Whereroom-and-pillar firstworkingi~tQbecarried. out beneath orin the vicinity oj; anY'J£bo(ly of surface water and at cover depth .greater. thanthe stipulatedminimum, ,.theminimum width of. pillar should be determinedinaccordance withee/tables1 through 1..6 An exception:is madewhere;specificlocal, data ,(includi~grelevflnt andcomp.arable.mining experience) exist whichdemonstrate that a lesser.widthcould be used with..safety.
6Tablesinclude seams thicknesses of 3, 4,6, 8, 10, 12, and 14 feet. Ifother seam thicknessdata are required, the tabulated value, W.,.c.!in£beobtained by trial and error or numericalmethods from the equation«W+R)/W)21.5D = 10001 /H' + 20 (W/H)2,whereW,R,H, andDja:p~pi.llar width,room width, seam thickness, and depth from surface,respectlyely.
5
2. Where an upper seam has been mined by room-and-pi11ar first workingin accordance with these guidelines, underlying seams should not be mined--
whether by total or partial extraction--except by considering the upper seamas though it were the base of the 5urfa~e body of water. .
3. Where pillar widths are determined in accordance with th~se provi-sions, the calculated pillar loading should not exceed the allowable 10ad-
bearing capacity of the immediate roof and/or floor beds.
TABLE 1. - Minimum pillar widths for pillar heights of 3 feet. feet
NOTE.--The figures -in this table in no way exclude the application of totalextraction mining at the appropriate solid strata cover and seamthickness.
TABLE 2. - Minimum pillar widths for pillar heights of 4 feet. feet
NOTE.--The figures in this table in no way exclude the application of total
@xtractton mining at the appropriate solid strata cover and seamthickness.
Depth, feet Room width16 feet 18 feet 20 feet 22 feet 24 feet
100 12 13 14 - -
150 15 16 16 17 18200 17 18 19 20 20.250 19 20 21 22 22300 20 21 22 23 24350 22 23 24 25 26400 23 24 25 26 27450 25 26 27 28- 29500 26 27 28 28 30550 27 28 29 30 31600 28 28 30 31 32
Depth, feet Roomwidth-16 feet 18 feet 20 feet 22 feet 24 feet
100 14 15 16 - -
150 17 18 19 20 21200 20 21 22 23 24250 23 24 25 26 . 27300 25 26 27 28 29350 27 28 29 30 31400 29 30 31 32 33450 30 31 33 34 35500 32 33 34 35 36550 33 34 36 37 38600 35 36 37 38 39
6
TABLE 3. ~ Minimum pillar widths for pillar hei~hts of 6 feet. feet
NOTE.--The figures in this table in no way exclude the application of total
extraction mining at the appropriate solid "strata cover and seamthickness. .
TABLE 4. - Minimum pillar widths for pillar hei~hts of 8 feet. feet
NOTE.--The figures in this t~ble in noway exclude the application of total
extraction mining at the appropriate solid strata cover and seamthickness.
Depth, feet,' . Room width
16 feet 18 feet 20 feet 22.feet 24 feet
100 l 19 20 - -
150 22 24 25 . 26 27200 26 28 29 30 32250 30 31 33 34 35300 33 35 36 37 38350 36 37 39 40 41400 39 40' 41 43 44450 4L 42 44 4.5 46500 43 45 46 .47 48550 45 47 48 49 51600 47 49 50 51 53
Depth, feet Room wid th
16 feet 18 feet 20 feet 22 feet 24 feet
100 2il. 22 24 - -
150 27 29 30 32 33200 33 34 36 37 38250 37 39 40 42 43300 I,
'41 43 44 46 47350 45 '47 48 .4.9 51400 48 50 .51 53 54450 51 .53 55 56 57'500 54 56 57 59 60550 57 59 60 62 63600 60 61 63 64 66
.'
7
TABLE 5. - Minimum pillar widths for pillar heights of 10 feet. feet
NOTE.--The figures in this table in no way exclude the application of totalextraction mining at the appropriate solid strata cover and seamthickness.
TABLE 6. - Minimum pillar widths for pillar heights of 12 feet. .feet
NOTE.--The figures in this table in no way exclude the application of totalextraction mining at the appropriate solid strata cover and seamthickness.
Depth, feet Room width16 feet 18 feet 20 feet 22 feet 24 feet
100 24 26 27 - -
150 32 34 35 37 38200 39 40 42 43 45250 44 46 48 49 51300 49 51 53 54 56350 54 56 57 59 60400 58 60 6i 63 64450 62 64 65, 67 68 .500 66 67 69 70 72550 69 71 72 74 75600 72 74 76 77 79
Depth, feet Room width16 feet 18 feet 20 feet 22 feet 24 feet
150 . 37 39 40 42 44200 45 46 48 50 51250 51 53 55 57 58300 57 59 61 63 64350 63 65 66 68 70400 68 .70 71 73 75450 73 74 76 78 79500 77 79 80 . 82.. 84550 81 83 84 86 88600 85 87 88 90 91650 88 90 92 94 . 95700 92 94 95 97 99720 93 95 97 98 100
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
8
TABLE 7. - Minimum pillar widths for pillar hei~hts of. 14 feet, feet
NOTE. --The figu:res in this."table in no way exclude the applicati:onof totalextraction mining at the appropriate solid strata cover and seamthickness. .
Panel arid Pillar
The panel-and-pillar system is defi:ned to be one in which a beddeddeposit is totally extracted from panels which are of such width in relation
to their depth that the main strata can span anyone of them with littledeflection. Individual extraction panels are separated by abutment. pillars
designed to sustain the load of the main strata overlying a group. of suchpanels and pillars. The minerals from the panels may be extracted by long-
wall mining, or. the panels may ~irst be mined by room and pillar. and the
piltars may subsequently be taken by either continuous or conventional miningmethods.
The following guidelines are recommended with respect to panel-and-
pillar mining beneath and in the vicinity of bodies of surface water.
..
Depth. feet Roomwidth16 feet 18 feet 20 feet 22 feet 24 feet
150 41 43 45 47 48200 51 53 54 56 58250 58 60 62. 64 66300 66 67 .69 71 73350 72 74 76 77 79400 78 80 81 83 85'450 83 85 87 88 90500 88 90 92 . 93 95550 93 95 96 98 100600 97 99 101 103 104650 102 103 105 107 108700 106 107 109 III 113
. 750 109 III 113 115 116800 113 115 116 119 120840 116 118 l2G 121 123
9
1. Where. the panel-and-pillar system is to be carried out beneath or inthe vicinity of any body of surface water, there should be a minimum solidstrata cover thickness of 270 feet or 3p, where p is the width of the panel,whichever 1s greater. .
2. The widths of extraction panels should not exceed one-third the depthof mining, and the widths of pillars between extraction panels should be 15times their height or one-fifth the depth of mining, whichever is. greater.
3. Where more than one seam is to be mined by this system, the panelsand pillars in all seams sh9uldbe superimposed in the vertical direction withthe panel widths being determined from the depth to the uppermost seam andthe pillar widths being determined by reference to the thickest and/or deep-est seam, whichever would give the greater dimension. .
4. Where the panel-aud-pillar system of mining has been employed in anupper seam, it should not be permissible to mine by total extraction in anyunderlying seam. except by considering the upper one as though. it were the baseof the surface body of water.
Safety Zones
From observed behavior of rock strata and soil above mined-oqt regions,a zone is known to exist that will most likely fail if mined, causing flood-ing of the workings and damage to the surface and to surface structures. Fromrock mechanics considerations the approximate shape and extent of this zone.can be identified. If no risk can be taken, obviously no mining is possible.For many cond~tions of mining, no damage is likely to occur and mining shouldbe permitted. .
Surface Waters
The following guidelines are recommended with respect to safety zonesaround and beneath bodies of surface water.
. 1. Where any body of surface water is present above the potential mineworkings, a safety zone around such body of surface water should extend 200feet horizontally from the high-water mark, or perimeter of the water body,and vertically downward from this .point to a depth of 350 feet, then outwardat an angle of dip of 650 as shown in figure 1.
2. If mining is considered within such a safety zone, it should be inaccordance with the guidelines for mining beneath surface waters.
3. The width of such a safety zone may be increased or decreased if .local observations and/or experience justify.
Structures Retaining Water
Since there is always some risk thatdamage will occur to surface struc-tur@s by mining, no mining should be done in a safety zone beneath and around
10
..~
I
~.~~~~j ... .. .",..~....
:{??}~~?i W~~~~~~~~~~~~~~~~~~~t::.:. . . . . . . . . . . . . .':'::::::::::::~~~~~~~~~~~HiE ~HHHfHHHHr',','. "".'.' ".' ... '::""' '":":':":-:':"":":".:.:.:.:.:.:..:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:. :.:.:.:.:.:.:.:.:.:.:.:.:.:.:.: .:.:.:.:.:.:.:. ::: :::::::::::.
'. ':::::':':":""~':.:-:.::.:.:.:.:.:. :.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:. :.:.:.:.:.:. :.:.:.:.:. :.:.:.:.:. :.:.: :::. .:::::::.'.' .' o. . 0"'"N I '''.."...,, :...'.'.'.' '...'.'.'...'.'.'.'.'.'.'.'.'.'.'.'...'.'...'.'.'.'.'.'.'...'.'. '.'.'.'.'.'.'.':: '::.. Norm.oIorno ':"."~ '.' '10''':t tl ":":.~ :-'..:0:':.:.:':':':.:':':.:':':.:.:':':':':':':':':':':':':.:.:.:.:.:.:.:.:.:.:.: .:.:.:.:.:.:.:. ::~: ::: ext Act,' Onex roc on .'. ,,: .:'" r, t d':.:.:.:::::..:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.: .:.:.:.:.:.:.:. ::: ::::::. ' tt dpermIt e..." .:. ...:, "'''''' perml e
.,::.::.~.::..:.::::::::::::::::::::::::::...' . . . . . ""."':~:::::::::::::::::::::::::: 0::::::::::::::: :::: ~m:::::::.'::"':'''''. ',:.." '...'.'...' '.'.' Zoneof no,'.'.'...'.'...'.'.'.'.'.'.''.'.'.'.'.'.'.'. ::: ::'::::::::::.
...:::-::::':.:::.:' :':-:.: :~:.:.:.:.:.:.:.:.:.:.~extra ct ion :.:.:.:.:.:.:.:.:.:.:.:.:.:.,':':':':':.:':' ::: :::::::::::::::::.,,,'::,:'::::".-::'".:.' :'. ":.:':':':':':.:':':':"'. , - .':':-:':.:':.:':.:':':':':' :.:.:.:.:.:.:.: :."" ..:::::::::::::::::.
, ,:,::.:..:-::::-,::.:..,:..,:::':-'':.':': .:.:.:.:.: .:.:.:.:.:. :.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.: .:.:.:.: .:.:. :.:.: '.:.:.:.:.:.:.:.: '::::'. ~::...:::::::::: :::.:',,:.:.:.::'.-:::::::~5°..,,",::' :.:.:.:-:.:.:.:. :.:.:.:.:.:-:.:.:.:.:.:.:.:.:. :.:.:.:.:.:. :':':':':':':':.:':'. ':.:.:.:.:.:.:.:.:. "'. ::65~ ::::::::::::::,. '. " . '. . ...y '..' . . . -. . . . -. . .. . -. . . . . . . . . . . . . . . . . . . . . . . . .., . . . . . . . .. "" "'''''''' """'"
::::.:.::.::::,:.::.::::.::'.::'.':::':' :.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:..:.:.:.:.:.:.:.:.:.:.:.: :.:.:.:.:.:.:.:.:.:. ::::::::::::::::::::::::":",:::':-':':::':-'.:.::'.:.:,:::-:-:.:.:-::.:.:.:.:.:-:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.: -:.:.:.:.:.:.:.:.:.: .:.:.:.:.:.:.:.:' .:.:.:.:.:.:.:.:. :.:. :::::::::::::; ::::::: ::.:::.:::.:,:.:.:::::,:.':-:::-:.:-.:::.:.:::..:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.: :.:.: .:':':':':':':':'. '::::::: f::::::::::f::: '
':'::..:.::':::::.::.:..::,,::.::.:::::.':.:.:.:.:.:.:-:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:~:.:.:.:.:.:.:. .:.:.:.:.:.:.:.:.:.:.:'...':::::::::::::::::::::':''':':':'':':':'':':':::'::.'.'.'.'.~.'.'.'.'.' '~'~.'~".".' 't'~' . . ~,:.:.:,.~. . . . .. . .. . :"':':':'" ..::::::::...:::::::,
iltl'111111';!!!~~!!::~!!!~j!!IiII'II\ltlli;:(fl
Surface water r- 2001---1
\I
0--'-
-x- Whichever is larger
FIGURE 1. . Safety zone beneath body of surface water~
a structure where its failure would cause loss of life, property damage, or
damage to water supplies needed for the public welfare. If the consequences
of structural failure are not, severe, mining may be undertaken.
The followingaround and beneath
welfare.
guidelines are recommended with respect to safety zones
structures the survival of which is important to t~ public
I, Where any surface structur~ is impounding a substantial body of sur-face water and damage to t6at structure by mine subsidence effects could lead
to a risk of structural failure and prejudice to public safety, no mining
should be permitted within the safety zone of such a structure.
, 2. The perimeter of the structure requiring protection should be estab-lished by those responsible for its maintenance and safety. The safety zonearound the perimeter of protection should extend outward 200 feet in all direc-tions~ then downward for 350 feet~ and then outward at a dip of 65° from thehorizontal as shown in figure 2. This safety zone is designated as a zone ofnQ ext~actiQn. Figu~e 2 also shows the restriction on mining beneath theimpounded wate~.
Roomand pillar 5s or lOtPanel 3p or 270 ftTotoI extraction ,GOt
11
Impounded surface wat~r. 1<. 200'~
~ ;.{:~:~:~:::::::::::::::::':~:':;.~:::.~~::~::~~$~~~~:::"
~ 200'~ ~ .'::::::::::::::::::::::::::--:':::::":'::::'::':'~'::':::':"~::
":'::~~~::::/r:t~~~
l
:~~':::::::::::::::::::.. .. Q . .. . ",' ':" : :'::"':""':"':'.'."...'.'.::::~:~:~:::::::::::::::::::::::: ::;:-:'f:~:::'~:~::{::'""..:':-""'''':''''''''.."'.'.'.'.'.'.'.'.' ~9.~ .:...:...:.''.':'.'.'.':':'.':':'.'.'.'.'.'.'.'.'.':':'.'.'.'.'."'. .::...:..,
'..:::..:..:.::.::;.:.::::-::.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.: :.:.:.:.:.:::.:.:.:.:.:.:.:.:.:.: .:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:: :.:. ~..:'Norma I'... ".:. " ':" .'.'.'.'.'.'.'.'. '.'.'.'.'.'.'.'.'.'.'.'.'.'.'. '.'.'.'.' .'.'. .'.'.'.'.'.'.'.'.'. '.'.'.'.'.'.'. '.'.'.' .'.'.'.'.'.'.'.'.'.'.'.'.' .: ~"." '... ',' ,,'.' extraction.:.:::::.:.::::..% ::':'::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ::::::::::::::::::::::::::::::::: :::::::::::::::::::::::::::::::: ~~:-;:"!.'" .
tt d
Normal .: ':-:"" '...' ' ' "'.'.'. 0:.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.' .'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.' ". :,":"., perm I e. .':":'~':".:'0'::". :.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.'0'.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.: .:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:. :':':~:~~:""'\"extractlon:..:'"''10'"...~ ' '.'.' .:v>""Z... . . . . .. '.'.', '.'.'.'.'.'.'.'.','.'.'.'.'.'.'.. o~.:..:,,:.~.:,~.permitted ::.::::::.~.:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::'!>;::::'.one of.no::::, :::::::::::::::::::::::::::::::::10 ~::'::':~'::~:~~:~':"!.'::."""'''''''' '"'' .'.'.'.'.'.'.','.','.'.'.'.'.'.','.','.'.'.'.'.'.'.'.'.'.'.'. '.'.".ext ractlon'.'.' D .'.',','.'.',','.'.'.'.'.'.'.'. .~ ":".~'::'::":".~'::."
tflf\:::~\j~\\\?~t~:~l:~!~\~~II\I\I~ld\~~~\~\\I\i\~~\~\\ii\~\\I\\\\\\Ii~j~H.~iIA,,..~", --' '.'.~.~.'.'.protect dam .'.'.'.'.'.'.'.'.'.'.'.'.... 6
'5'10""""""""""" '..."'.'.'.'.'.'.'.'.'.'.'.':'.'. ..~:..' ..~...:.:::.::.::,:::.::.:.~::
. - ,.,',',',',',','.'.'.'.'.' ,~.~.~.~.:.:.:.:.:.:.:. :.:.:.:~::::::::::::::::::::::::::::' ..:.~!?,~~~:i::::::::i~~':'i~:~i;;::::',
Di(-
-x- Whichever Is larger
FIG~RE 2. - . Safety zone beneath dam C?ndimpounded body of surface water.
3. A greater or lesser distance than that specifiedin paragraph2 maybe used where local observations and/or experience so indicate.
UNDERGROUNDWATERS',
Mine Maps
The operator of a coal mine should have in a fireproof repository(located in an area on the surface of the mine chosen by the mine operator to
minimize the danger of.destruction by fire or other hazard) accurate, up-to-
datemapsof theminedrawnto scale. .
Surface Features
Surface features may be shown directly on the mine map, or on a trans-
parent or translucent sheet~ which, when overlain on a map of undergroundworkings, shows true and exact relatiol\s of surface features to mine workingsand excavations. Surface features to be shown include--
1.2.3.
Nameand address of the mine.Scale and orientation of the map.
Boundary lines and names of all surface property owners.
Room'and pillar 5s or lOtPanel 3p or 210 f1Total extraction 60t
12
4.5.6.
Boundary lines of the coal rights pertaining to each mine.
All outcrop lines.
Topographic features such as hills, ravines, intermittent and
permanent streams, bodies of standing waters (with elevations and
estimateddepths). ' , ,
Location and identification of municipal subdivisions (State, county,
townships). ' ,
Location of all railroads and sidings, highways, and other roads.
Location and identification of mine buildings and facilities.
Location of all utilities and pipelines.
Location and depth of holes drilled for oi:l.,gas, water, or geologicinformation that penetrate a workable seam.Location of all surface fans.
Location of mine openings.
The location and description of at least two permanent baseline
points coordinated with the underground "and surface 'mine traverses,and the location and description of at least two permanent elevationbench marks used in connection with establishing or referencing mine
elevation surveys. Location and description of a,pe~nent bench'
mark or monument near the main mine opening.
7.
8.
9.
10.
11.
12.
13.14.
Underground Features
Whether or not combined on the same sheet with surface features, at
least one set of maps showing underground features should be composed on the
, same scale. Pertinent information to be recorded on the mine map shouldinclude--
1.
2.
3.4.
Name and address of the mine.
Scale and orientation of the map.Boundary lines of coal rights and owner identification.
Structure contours and dip of the coalbed being mined at notgreater than 10-foot elevation intervals.
5. Location of all drill holes that penetrate th~ mined bed.6. All shaft, slope, drift, and tunnel openings and auger",:and strip-
mined areas of the bed being mined.7. Location of all ventilation fans.
8. Location and exact extent of adjacent active or abandoned under-
ground workings above, below, or in the same seam. If abandoned
workings are knoWn to exist in an area, but exact extent is notknown, it should be so indi~ated.
9. Up-to-date locations of active work areas, worked-out areas, andabandoned areas.
10. Locations of entries and aircourses with direction of airflow
indicated by arrow.
Jl.. Location of all escapeways.12. Location and exact extent of
or fluid like materials which
peatJ etc.).
13. Location and elevation of any body of water dammed or held back inany portion of the mine.
all water pools, water-bearing strata,
tend -to flow when wet (quicksands,
-~-~ > c-"~ -~-~~c ~~~= ~_o~=~~=-"
" O' =~._,~,c~~ ~==~ --=~--
13
14. The elevation of tops and bottoms of. shafts and slopes, and thefloor at the entrance to drift and tunnel openings.The elevation of the floors at intervals of not more than 200 feetin--
15.
a. At least one entry of each working section and main and crossentries.The last line of open crosscuts of. each working section, and ofmain a.nd cross entries, before such sections and main and crossentries are abandonediRooms advancing toward or adjacent to property or boundary linesor adjacent mines.
b.
c.
16. 7he owner, agent, or manager of a mine should take all reasonablesteps to determine whether there is ~ any material below the surfacewhich could affect;; active, or soon .to be active, areas ,in a mine soas to cause danger to miners working in that mine. All factspertaining to such conditions should be presented to the manager.'
Property Boundary Barrier Pillars
To insure that. the mining of t.he coal seam by one company up to the propertyline does not favor that company over .another company that mines later, thefollowing guidelines are recomnended.
, ~
1. A boundary pillar of unmined coal should be left to the property line;it should be of ..a.width calculated by t4e equation Pb = 10 +2T+5D. Pb isthe pillar'width in feet, 10 is .~. co~si:811t ~afety factor;"; T is,'the thicknessof the bed in feet rou~dedto the next highest integer, and;J).isthedepth ofthe seam at the property line in.100-foot increments rounded to the next high-est integer. Th1s pillar width should be required on both sides of, the prop-erty line. When mining on one. side of the property line.has i~pproached closer-than would be permitted by this guideline, the ~dvancingworking shouldincrease its.property boundary barrier pillar,requirement~sothat.the ctDDUla-t~ve pillar size is equal to'-2 Pb. Where -faults are known to' occur, whichcoulcJ result in a connection between the abandoned and active wo*ings orwhich cou~d seriously weaken pillar stability and strength, additional pillarwidths should be used. This additional width'should be based on the experi-ence and judgment of the mine engineer and mine inspector..
2. Boundar,y barrier~pi1lars ~hould not be alteredfor 1ncreasedmineralrecover,y unless the mining proposalinsuresinspectionand certificationthatall of the affectedworkingsare free from hazardous accU]JIUlations of water,and the proposalhas-- -
a.b.c.
Been agreed to by the interested mining companies and superintendents.Been approved by the mine inspector.
Received approval from the responsible government regulatory ..agency.Considered eventuaL interconnection of the mining operations by -eHheraccident or development plan. - ~-
Considered, the development plans- from all affected mining.cgmpanies.
d.
e.
14
Abandoned WorkinRs~ Abandoned Areas~ and Ad;acent Mines
Water-filled mine openings, the presence of which is unknown or if knownthe e~tent of which is poorly defined, are of major concern to mine opeTators.The following guidelines are recommended with respect to these problems.
1. No mining should be permitted within 200 feet of any known or sus-pected abandoned workings (that are part of the present mine and/or otherprior mine) which cannot be inspected and certified free of dangerous accu-mulations of water. When these abandoned workings can be inspected and certi-fied as safe, mining can proceed to within the distance permitted by theProperty Boundary Barrier Pillar guidelines, or to within the distance cor-responding to a pillar width-to-thickness ratio of 10 to 1, whichever islarger. Where faults are known to occur that could impair the effectivenessof the pillar as a water barrier, additional pillar.width may be used asdetermined by the mine engineer and mine inspector. .
2. Locator boreholes should be drilled from the advancing face nearestto the abandoned mine through the 200-foot barrie~.pillar to determine thelocation of abandoned workings. The ~quipment and materials necessary toplug the borehole upon breakthrough must be available to the drill crew. Thewater head pressure or atmospheric conditions in the abandoned workings shouldbe determined. . . . .
. 3. Unless downhole instrumentation definitely established that no waterexists in the abandoned workings, even though pressure or gravity flow doesnot occur at breakthrough, the workings should be . assumed to be floOded. Ifit is subsequently determine.d that the abandoned workings are dry, mining mayproceed up to the limits of boundary barrier pillar (when approaching theproperty line) as defined by Pb = 10 +2T + 5D; or normal mining operationsshould be permitted when the property limits are not a factor to be consideredin this development. .
4. Water may .be drained f~omabandoned workings through a 4rift or augerentry, if possible, or from boreholes drilled from the surface. Water alsomay be drained thrdugh the 200-foot barrier pillar to the active~workings andpumped to the surface. This latter method is' potentially hazardous, hOW,ever,and should only be used under the direction of knowledgeable arid experiencedpersonnel. If permits are necessary to discharge the water on the surface,they will need to be procure~.
5. If the abandoned workings are not initially dry or drained of water,an effective safety barrier pillar should be sized by utilizing modeling tech-niques and unconfined compressive strength tests. For modeling, a factor ofsafe~y of 4 should be used in pillar design. Whenever the pressure head isequal to or greater than 5 atmospheres, consideration should be given todraining these workings. The permeability of the unmined barrier pillarshould also be determined for consideration of its effect 011.waterflow and
f.urther pillar development. Two proving headings.(for ventilation purposes),kept as narrow as possible and prot@ct@d byborehol@s~wotildbe a safe miningplan to utilizefor developing the barrier pillar up to the limits determined
r3T t w
Coal thickness = T
Number of holes required:: W~6T(next whole number)Hole length =7 TSafe advance:: 4TSafety pillar ::3TAngle'e :: ATAN"'w/(7T+d)w =width of old headings I if
if w is unknown, use w =
15
by this recommended testingprocedure. These headingsshould be limited to15 feet in 'Width. The min-ing crew should be alert forsigns of pillar instability.excessive water leakage.strong sulfur smell, orother indicators of water.and mininghal~ed orreevaluated as necessarY. ,
The permeability of the pil-lar can be reduced and its,strength increased by intro-duction- of grout or othercementing agents. -
6.. Whenever an.Yworkingplace approaches (1) withinlOt or Pb, whicheve~ is '
greatest, of abandonedareas in the mine as shownby surveys made and certi-fied by a registered engi-neef or sUfYeyorcand thearea cannot-be inspected. or(2) wit4in 200 feet of any ,
other known abandoned areasof the mine that cannot beinspected and that may con-tain dangerous accumulationsof water or gas, or .' .
(3) within 200 feet of knownworkings of an adjacent m1ne~a borehole configuration '
such as that shown infigure 3 should be drilledin advance of the workingface of such working placeand should be continuallymaintained in advance ofthe working face. (NOTE.--In figure 3, w is the widthof the smallest old open-ings, if known. Ifnotknown, w is the value of theseam thickness, T).
16
Oil and Gas WellPillars
Mining should not come closer to active oil and gas wells than150 feet in any direction). When these wells are abandoned, however, -theycan be sealed and the barrier pillar mined through, provided that the sealsare tested for leakage prior to mining.
Shaft and Vertical Opening Barrier Pillars
When these abandoned openings can be inspected and certified free ofhazardous accumula~ions of water, they can be mined through as in normal pil-lar recovery operations.
When mining in the area of any abandoned shafts, raises, or otheropenings that cannot be inspected and certified free of dangerous accumula-tions of water, a barrier pillar 300 feet in diameter should be left aroundthe opening, provided that a minimum of 100 feet of solid coal is left aroundthe abandoned opening. Where these openings can be inspected and certifiedsafe, a pillar of width-to-thickness ratio of 10.to 1 should be left aroundeach opening. When mining in the area of abandoned siopes and like openings,the guidelines for mining near abandonedworkings shouldbe followed.
Mining Under Abandoned Flooded Workings
Mining under flooded abandoned workings should conform to the 60t and
maximu~ tensile strain rules for total extraction, to the 5s or lOt rules for
room-and-pillar extraction, and to the 3p or 270-foot rules for panel-and-pillar extraction. .
17
APPENDIX
In the United Kingdom, numerous examples of total extraction beneath thesea have been examined in which no seawater passed into the mines.. The maxi-mum seabed tensile strain for each of these cases was calculated, and the
results ranged from 5.0 to 15.0 millimeters per meter (rom/m). On the basis
of this analysis, the National Coal Board has adopted a criterion of 10.0rom/m of calculated maximum tensile strain as governing the minimum depth for
total extraction. The expression used in the United Kingdom for calculating
maximum tensile strain E. , is
KS.axE. =1)
The value of Sillax with longwall ca.ving is normally taken as O.90t, and the
average value for K as 0.75 in the United Kingdom. Thus, the minimum depth
of cover required for safety, D.in is .
D.in = 67.5t,
where t is the thickness of the coal seam mined. For a limiting tensile
strain of 5.0 rom/m, the limiting depth for total extraction would be l35t;for a limiting tensile strain of 15.0 rom/m, the limiting depth would be 45t.
If experience in the United States results in recommended strain values
other than those used in the United Kingdom, these values may be used.
INT.-BU.OF MINE!i,PGH.,"A.ZZZZIJ
