THIET KE CHONG NEO CAP CHO CAC LO KHAI THAC BANG NOC PHANG TRONG MO HAM LO
able bolt is one of supports for tunneling construction, i Nowadays, it is widely used at underground coal mines.
However, the acknowledgement about its mechanism and designation is limited. This article refers to the problems , about the designation of cable bolts for longwall flat roof at ' underground mines
1. Dat va'n de
Ke't ca'u neo va neo cap da dugc SLf dung tCf lau de chd'ng giCf cac dudng Id ehuan bi va Id khai thac. Neo cap cd ca'u tao tCf cac sgi thep duge ghep lai vdi nhau. Thdng thudng, sd sgi cap duge ben vdi nhau la sd le, thudng la 5 hoac 7 sgi, tuy theo tCfng trudng hgp cu the. Khi ke't hgp vdi vua bgm vao trong Id neo, kha nang dinh ke't eua neo cap tang len do sdi cap cd dien tfch be mat tie'p xue ldn hdn so vdi cdt thep ddn thdng thudng, nen hieu qua chd'ng giuf cao hdn.
Hien nay, viee suf dung ke't ca'u neo cap trong cac budng cdt edn ban ehe. u Viet Nam v l n SLf dung ket eau chd'ng giu"
khung gd, khung thep truyen thd'ng. Gan day viec sCf dung be tdng phun, neo hoac ke't hgp giu'a be tdng phun va neo trong chd'ng giu' da cd hieu qua nha't djnh. Tuy nhien, hien nay da phan cac md thudng SLf dung ke't ca'u neo vdi cdt neo bang thep ke't hgp vdi be tdng phun chd'ng giur cho cac dudng Id dao trong da. Viec bd sung hoac suf dung ke't cau neo cap se cd hieu qua chd'ng giu" cao hdn rat nhieu. Bai bao nay gidi thieu viec thie't ke neo cap d cac dudng Id khai thac trong cac md than ham Id.
2. Ca'u tao va cd che lam viec cua neo cap
Ca'u tao ciia mdt neo cap bao gdm mdt bd sgi cap dai, dau cap dygc bd chat vdi nhau va cho phep neo dugc lap dat va xoay dugc, d phan than cap cd cac tam de tang cCfng eho cap va d l dieu chinh trong qua trinh lap dat. De tien lgi, d dudi neo cd Id hdng de bgm vu'a va tam dem de khi bgm vUa thi vufa khdng the bj day ngygc trd lai. Dau neo cung dugc thiet ke de viec lap dat cac tam thep dem va cac thie't bj dieu chinh khac d be mat ngoai mdt each d l dang.
He thd'ng cae tam buldng va dai dc cung dugc sCf dung de chd'ng lai sy djch chuyen cua phan dau cap.
NCS. TRAN TUAN MINH Trudng Dai hoc Mo Moskva
(LBNga)
Hinh 1. Bo cap e6 7 sgi, mat eat ngang eua neo cap va vua, neo cap trong thue the chdng giCt
Cap va bd cap mem de udn nen khd thi cdng. De lam cCfng bd cap tren, chieu dai bd cap va dau cap thudng phai them chi tie't tang cCfng hoac nut cCfng. Chi tiet tang cCfng cd chieu dai tUdng t y nhu chieu dai cua thdi chat deo, eho phep thyc hien d l dang trong qua trinh lap dat. Mat khac, chi tie't tang cCfng lam nhiem vu ngan can sy dich ehuyen cua neo trong qua trinh lap dat.
TUdng t y nhy cac neo khac, neo cap lam viec dya tren cac nguyen ly sau:
- Nguyen ly treo:
Vdi nguyen ly treo, trudng hgp dgn gian nhat la neo treo cac khd'i da bj tach rdi sap do vao Idp da ben vCfng ben tren ndc, tCf dd se lam eho ndc Id dn dinh tranh dugc sap do hinh 3.
KHCNM SO 8/2010* CNKT HAM LO
Ne'u pha buy ndc Id d dang vdm thi khi dd cac tru than se mang mdt phan tai trgng, cac neo cap ehi cd tac dung de treo giiJf trgng lygng cCia khd'i da ben dudi vdm sap 60 (hinh 4).
Chieu cao cCia vdm sap 60 phu thude vao chieu rdng budng, vao dieu kien dia chat, tac ddng cua Cfng sua't thing dung va nam ngang tac ddng cCia cdng tac khai thac md. Rd rang, chieu dai va sd lUdng neg cap se phu thugc vao chieu cao eCia vdm pha huy va dygc xac dinh dya vao chieu cao vdm pha huy (hinh 4).
Dau cap
Mdt nguyen 1^ lam viec cCia neo cap nu'a la nguyen Iv/- dam mang tai (hinh 5). Chieu rdng cCia ram phu thugc vao kha nang mang tai cua tru than (hinh 6).
Chieu rdng cCia budng dygc xac dinh theo cdng thufc cCia Wilson va nd phu thugc vao do ben cCia cac tru than (Wilson 1972).
C^c neo ic^ cap
Chi tiet tang cCfng Nut He thong
bao boc
Chi tiet tang cCfng
Cac nut neo Doan cap
phong ra
Cac nut neo Hinh 2.. Neo cap va cac yeu tdcau thanh neo cap
Vung noc {i CO cau true -=••
on dinh. ,-.
Cac neo cap
Hinh 3. Khdi bj tach rdi ra duge neo glut bdi eac neo cap
Vung noc 6n (Jlnh
\ . t
Cac neo
Tru than 1
Hinh 4. Vdm ap luc ehi tiet eho trudng hgp pha huy dang vdm
- Nguyen ly dam mang tai:
Dam sap
—' do ngay lap tijfc
Hinh 5. Kfch thude cua vung pha huy trong tru than, (B^ - ket qua eua chieu rgng 16 do hoat dgng khai dao; yp^- vung pha huy tru than 1;
yp2 -vung pha huy tru than 2)
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Hinh 6. Neo cap surdung de bo sung tao dam mang tai giam kha nang chju tai eho tru than va neo cap surdung ket hgp vdi ludi thep chdng giOt
dudng 16 n6e phang trong thue ti' Khi pha buy phat then rdng sang hai ben cija ndc Id thi viec sCf dung cap bd sung (hinh
KHCNM SO 8/2010* CNKT HAM LO
Cac nut
^ . .
Nut cap nghieng Cap giira cac nut
Cap nghieng ' Nut giOr ong noi
Cac tam mang tai
Hinh 7a. Doan cap lien tue Hinh 7b. Dam cap ba doan b)
gngij nst
f'^ Hinh 8. Luge dd than cap eua mgt nua cap chju tai. Hinh 8b. Luge dd cua mgt nua cap, '"^^ ' quan sat cae tai trgng tTnh phat trien khi c6 tam dem phia dudi noc
7) la dieu can thie't. Cap mang tai bd sung nay dygc tao nen tCf cac sgi cap lien tuc (hinh 7a) hoac dugc tao nen tCf 3 doan cap (hinh 7b) tuy theo dieu kien thi cdng cu tlie.
Cac tai trgng phat trien dd'i vdi mdt bd cap cd the dugc xac djnii ddn gian bang cac tai trgng tTnh tac dung len cap. Gidi thieu gian 66 ddn gian eae loai tai trgng cCia mdt nijfa bd cap (hinh 8).
3. Tinh toan cac thong so cua neo - Do cumg cua he thong cap
Do cung cua neo cap dygc xac djnh bang chieu dai doan neo khdng cd vu'a trong Id khoan va cac dac tfnh bie'n dang ciia cap. Tuy nhien, phan bie'n dang dan dai trong phan chat deo cua cap se anh hudng de'n do cung va eung phai dygc xem xet. Cac dac tfnh bie'n dang cua cap do 3 yeu td la do cCfng trong che tao, dac tfnh dan hdi va sy dan dai. Do cufng trong che tao la cd dinh, yeu td xoay trdn thudng la do boat ddng quay trong qua trinh
lap dat, ye'u td dan hdi phu thude mdt phan vao cae md dun dan hdi cCia vat lieu cap. Md dun dan hdi cCia thep khoang 203,4GPa. Tuy nhien, md dun dan hdi ciia cap cdn phu thugc vao cdng nghe che tao cap.
Do eCfng cCia cap dugc xac djnh thee cdng thCfc sau (Maryland va American Iron 1985):
K = E. A/L (1) Trong dd: o r ;
K - Do cufng cCia cap (kN/cm)
A - Dien tfch mat cat ngang cap (cm^) L - Chieu dai doan cap ty do (cm) E - Md dun dan hdi cCia cap (GPa)
Md dun dan hdi, chieu dai, dien tfch, tie't dien va do cufng cCia cap dygc xac dinh tCf tai trgng lap dat. Do cufng ciia cap dygc xac djnh tCf viec SLf dung thf nghiem keo tut cap dygc lap dat trong da't da ndc cac dudng Id.
- Trong lUdng v u n g da't da sap do Trudng hgp neo treo (hinh 3):
Trgng lugng cCia khd'i vat lieu nay cd the duoc xac dinh tCfcdng thCfc sau:
F„ = B.H3.Y (2) Trong dd:
F„ - Trgng lugng ciia khd'i da tren mdt ddn vi chieu dai (kN/m)
B - Chieu rdng ciia dydng Id (m).
Ha- Khoang each tCf ndc Id than de'n mat phang pha buy tren cung (chieu cao vung pha hu:/) (m).
7 - Trgng lygng the tich da (kN/m^)
Trudng hgp sap do dang vdm (hinh 4):
Trgng lygng cCia khd'i vat lieu trong vdm ed the dugc xae djnh tCf cdng thCfc sau:
K = 'lB.H^r (3)
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Trong dd:
F„ - Trgng lugng CLia khd'i da ben dydi vdm ap lye (kN/m).
Ha - Chieu cao vdm ap lye (m).
y - Trong lygng the tfch da (kN/m^).
- Chieu cao da't da sap 60 gay tai trgng (Kha nang mang tai/mang neo): Chap nhan chieu cao Idp da't da sap do gay ra tai trgng tTnh.
Terzaghi (1946) da dya ra dudoan tai trgng tac dung len cac ke't ca'u chd'ng giu" tren cd sd chat lugng khd'i da va khau do cdng trinh ngam.
Unal (1984) da xac djnh chieu cao gay tai trgng tTnh eho eac dudng Id trong cac md than theo cdng thCfc:
^100-RMR
B, = B + Y,, + Y
/ / = 5
100
(4)Trudng hgfp dam mang tai:
Kha nang mang tai cCia tru than bi anh hudng bdi cae dieu kien khac nhau nhu chieu rong ciia cae budng (hinh 5)Theo Wilson (1972) chieu day tru than dygc xac dinh theo cac dieu kien sau:
Khi nen Id eCfng vung:
r \ w = 2 — In q
F P + (^n (5) Khi nen - ndc ed bieu hien dan hdi
w = m
F =
P + (^n - 1 (6)
Trong dd
1 , ( ^ - 1 )
1
'tgyfk
Dugc tfnh bang radian.
tgy/Ic m - Chieu davia (m)
q - Tai trgng pha buy (t/m^).
p - Lye hinh thanh ben ria tru than dugc gidi han de'n gia trj 0 t/m^.
a„ - Do ben nen dgn true ciia than.
k - He sd Cfng sua't ba chieu; k = 1+ sincp/l- sin cp.
(p - Gdc ma sat trong (do).
TCf nhung cdng thCfc (5), (6) xac djnh dUdc do Idn cua vung bie'n dang pha hiiy. D6 thi (9) xae dinh gdc ma sat trong la 35°. Hieu qua cua khoang trdng khai dao hay chieu rdng cua budng cd the dugc xac djnh bang cdng thCfc sau:
P2
m
Trong dd:
B - Chieu rdng cCia budng dUdc khai dao (m) Ypi - Vung pha hCiy cho tru 1 (m)
Yp2 - Vung pha hCiy cho tru 2 (m)
Trudng hgp dam nghieng gia cdtang cudng:
Y, = T.sina (8) X, = H- Tcosa (9) Trong dd:
T - Thanh phan Iyc keo.
H - Thanh phan Iyc keo nam ngang.
Yr - Thanh phan phan lye thing dCfng.
X,. - Thanh phan phan Iyc nam ngang.
a - Gdc nghieng cua cap.
- Chieu dai neo cap
Chieu dai cua cap la van de quan trgng nha't trong thie't ke he thd'ng neo cap. Chieu dai cap phu thugc vao cac dieu kien dja chat, bien dang djch ehuyen, cdng nghe thi edng va eac yeu cau khac. Thdng thudng, chieu dai cCia neo cap trong cac dudng Id ehuan bj thudng tCf 3,7m - 4,9m. Tuy nhien, chieu dai neo nhd nha't phai ngoai vung da bj pha buy. Tuy nhien, cd rat nhieu mat pha buy phat trien d phfa tren ke't ca'u chd'ng tam nen nhieu trudng hgp can chieu dai neo Idn hgn. Cac vung tiem an nguy hiem nay ed the la mdt khd'i da dang hop hay be mat dang cung trdn, phu thude vao dang pha buy cCia ndc dudng Id nhu hinh 3 va 4.
Chieu dai thfch hgp eCia neo dugc de xua't de xac dinh nhu sau:
L'= B^'(Lang vaBischoff 1982) (10)
L = B/3(Bienawski 1987) (11) Z = B
100- RMR\ (Unal 1984) (12)
da , 2 A 1 0 0 ;
Trong dd:
L - Chieu dai neo (m)
B - Chieu rdng dudng ham (khau do) (m) RMR - Chi sd chat lugng khd'i (Bieniawski, 1987).
- Chieu dai neo trong trudng hdp vdm sap dd:
Neo phai dii dai de neo giu' trong eac dieu kien dja chat, da't da khae nhau khi thi cdng dudng ham. Chieu dai neo cd the dugc tinh toan theo edng thCfc thyc nghiem cua Stillborg (1986) nhy sau:
L =1,4 + 0,1846 (13) Hoac tinh theo cdng thCfe:
L ' = B^'^ (14)
KHCNM SO 8/2010* CNKT H.^M LO
Trong dd: B - la chieu rdng eCia dudng ham (m) - Khoang each giufa cac neo:
Hinh 9 dd thj xac djnh khoang each neo vdi chieu rdng dudng Id 7,6m va trong lugng the tfch cua da 2,403T/ml
+ Khoang each giCfa cac neo theo cdng thufc thyc nghiem cCia Stillborg (1986):
a = 3 x e (15) e - Khoang each giCfa eac khe nCft gan nhau nha't
+ Khoang each giu'a eac neo theo Lang (1961):
a < L/2 vdi L - Chieu dai thanh neo (16) Chieu sau Idp bao phu, ft
1t.9 1,000 1,500
ro-
• o
"'32 c
'j2
>
s: zz
it:
dJ c
• a ro- c In
>
x:
ChCi dan:
Chieu davia, m
A - vung bie'n dang 3m -vung bie'n dang 1,8m - vung bie'n dang 2,4m
cua neo chd'ng lai phan Idp nhy sau:
n.y.AR
sy tach ldp trong dat da
T = - l-e .-(.tg(p)k.Dlr
k.{\- 'ygcp 1 -
-(,lg<p.k.LIR) ) (18)
r.R:
Trong dd:
T - Lye keo neo don vj.
cp - Gdc ma sat trong cua cac ldp da't da.
k - Ty sd giCfa ap Iyc ngang trung binh va ap Iyc thing dCfng trung binh.
R - Ban kfnh vung da dygc gia cudng.
A - Dien tfch vung gia tai cua mdt thanh neo (A = axa).
L - Chieu dai cua neo.
a - Khoang each giu'a cac neo.
c - Lye dfnh ke't giu'a cac Idp da.
D - Chieu cao vung dat da bi phan bd lai Cfng sua't.
n - He so phu thude vao thdi gian lap dat neo.
Y - Trgng lugng rieng eCia dam da mang tai.
Khoang each giCfa cac neo cap, ft
'<n3 T 3 :>.
•<[D
• o 3 -<(Ui
6 i-«
o
Khoang each giCfa cac neo cap, m Hinh 9. Do thj xae djnh vung bien dang
trong tru than
A- Noc dan hoi, B - noc cUng - Lye keo va kha nang chju tai cua neo:
+ Kha nang chju keo eCia neo theo Stillborg (1986) dugc xac dinh theo cdng thCfe:
T = 0,5 ^ 0,8 X T„eo (17)
Khi tao dygc vdm da gia cydng thi kha nang chiu tai eCia neo tfnh toan cd the dugc lay giam di tCf 0,5 ^ 0,8 kha nang mang tai thyc te cua neo.
Theo hudng dan ve thie't ke he thd'ng neo de tang kha nang mang tai, gia tai cho ke't ca'u da't da phan Idp phia tren ndc, Lang va Bischoff (1982) da dya ra cdng thCfc tfnh toan Iyc keo
Chu dan:
A- O- D-
4 neo 3 neo 2 neo
cap cap cap
Hinh 10. Dd thj mdi lien he giOta eae thanh phan ket cau chdng neo cap, ket qua chieu rgng khoang trdng B^ = 7,6m va trgng lugng khdi da y
= 2,403 T/m^ (McDonnelL 1995).
4. Cac phuang phap thiet ke theo kinh nghiem.
Cae phuong phap kinh nghiem ed ban deu dya vao cac thi nghiem tai cac cdng trinh d gan mat dat, nhung cdng trinh xay dyng dan dung KHCNM SO 8/2010* CNKT HAM LO
vdi Cfng sua't tac dung nhd. Chung khdng de cap de'n cac ye'u td Cfng suat mdi trydng trong khai thac md thydng gap va cac hien tydng bat thydng nhy hien tUdng nd da. Cac hien tydng nay ngydi ta da gap phai trong qua trinh khai thac md d Nam Phi (Piper 1985), dac biet la qua trinh khai thac Platinum va cdng nghiep khai thac kim cydng bang nhung gieng cd do sau Idn d Nam Phi. Theo kinh nghiem thie't ke cua US Corps of Engineers, cac thdng sd ciia neo cd the dUdc lay nhy trong bang 1.
Mdt phygng phap thiet ke nee khac trong da't da nCft ne vdi cac mufc dd va dieu kien nuft
ne khac nhau da dugc Famer va Shelton (1980) cdng bd. Ve cd ban, nd cung gidng nhy nhung thdng sd cCia US Corps of Engineer dua ra, nhLfng nd cdn them cac thdng sd ve sd lygng khe nCft, mat phan each va hydng cua khe nCft quan he vdi true dydng ham va viee thi cdng lap dat neo. Ke't qua phygng phap thie't ke nee ciia Famer va Shelton the hien trong bang 2.
Dya tren cd sd he thdng phan loai khd'i da cCia Bieniawski va cdng nghe thi cdng da gidi thieu viec sCf dung cac ket ca'u chd'ng giuf va yeu cau khd'i lydng ke't ca'u chd'ng giuf (bang 3).
Bang 1. Hudng din thiet keket eau chdng dudng ham theo US Corps of Engineers Thong so'
Chieu dai nho nhat cOa neo
Khoang each cac neo nho nha't
Quy luat kinh nghiem Gia tri ldn nhat
a) L = 2x a (a - khoang each cac neo)
b) L = 3x khoang each ngan nhat cCia khdi da sup do c) Cho nhuTng diem nam dinh ham
Chieu rong dudng ham B < 6m, L = 0,5B Chieu rong difdng ham B = 18-30m, L = 0,25B Chieu rong dudng ham B = 6-18m, L = 3 - 4,5m d) Cho nhCfng diem nam du6i
Chieu cao dLfdng ham < 18m, L lay nhLf (c) Chieu cao di/dng ham H > 18m, L = 0,2H Gia tri nho nhat
a) 0,5xL
b)1,5xchieu rong gidi han cOa cac khdi da mat dn djnh c) 0,9-1,2m
Bang 2. Kinh nghiem thiet ke he thdng ket cau neo trong khai dao nhQng dudng ham c6 chieu rgng < 15m (Famer va Shelton 1980).
So luong mat phan each
< 2 goc nghieng 0 - 45°
vdi phirang nam ngang
< 2 goc nghieng v|; = 45 - 90° vdi phuong nam ngang
< 3 vdi be mat phing, chCfa nLfdc
Chieu dai neo thiet ke L = 0,3B
a = 0,5L (Phu thuoc vao chieu day va Cfng sua't cCia dia tang) viec lap dat neo c6 the ke't hop ludi thep chdnq da roi 6 nhCfng noi c6 the.
Cho cac neo ben sudn.
L > h.sinv|/ (neu neo lap dat vuong goc vdi mat phan each).
L > h.tgvt/ (neu neo duoc lap dat song song).
L = 2a, a = 3 - 4x kfch thudc khdi da. Lap dat neo vuong goc vdi mat phan each trong khai dao sdf dung ke't hop vdi lifdi thep de chdng da roi.
Chu dan
Muc dfch cOa neo la tao ra mot dam mang tai Idn hdn chieu rpng ham
Lap dat neo noc nhU tren, neo hong chdng lai kha nang c6 the truot cua mat phan each.
Neo duoc lap dat nhanh sau khi khai dao de tranh hien tLfong da roi vao dudng ham.
KHCNM SO 8/2010* CNKT HAM LO
Bang 3. Ky thuat khai dao va qua trinh lua chgn ket cau chdng tren cdsdRMR
Hinh dang: Vom mong ngUa, chieu rong 10m, ung suat dumg, ufng suat ngang = 25 Mpa, phiTdng phap khai dao, khoan va no min
Phan loai khoi da
Da rat tot loai 1 RMR: 81 - 100 Da tot loai II
RMR:'61 - 8 0
Da trung binh III RMR: 41 - 60
Da yeu loai IV RMR: 21 - 40
Da rat yeu loai V RMR < 20
Khai dao
Toan gifdng, tien do 3m Toan gi/cfng, Tie'n do 1 - 1,5m chong giuf co djnh phfa sau gu'dng 20m Gifdng tie'n trifdc va ha bac (chia gUdng) tie'n do 1,5 -3m. Chong tam ngay sau khi no min, chong co dinh sau gifdng^ 10m Gifdng tie'n trifdc va ha bac (chia gUdng) tien dp 1 - 1,5m. Chd'ng tam ngay sau khi nd min, chdng co' dinh sau gifdng tie'n tru'dc
ibm
Birdc dao 0,5 - 1,5m dao chia gifdng, lap dSt ket ca'u chdng ngay sau khi khai dao, be tdng phun cd the difdc lap dSt ngay sau khi nd min
Ket cau chdng Neo (d =20mm) neo
toan bd bien
Be tdng phun Cac khung thep - Khdng can chd'ng giif
- Khi can cd the cho phep suf dung neo diem Neo toan bd vdi chieu
dai 3m khoang each neo 2,5m cd the dung them lirdi thep He thd'ng cac neo dai 4m, khoang each neo 1,5 - 2m ben tifdng cd lirdi thep
He thd'ng cac neo dai 4 - 5m, khoang each neo 1 -1,5m ben tifdng cd lu'di thep
He thd'ng cac neo dai 5 -6m, khoang each neo 1 - 1,5m ben ti/dng cd lifdi thep.
Neo ca nen cdng trinh.
50 m m d nhOfng ndi can
thiet 50-100 mm va ben tudng
30mm
1 0 0 - 150mm va ben tu'dng 50mm
150-200mm 150 ben tu'dng va 50 dirdi nen
Khdng
Khdng
Khung chdng, bifdc chd'ng 1,5m
Yeu cau suf dung khung thep cifng bifdc 0,75' va khi phan life nen Idn thi dung vdm ngifdc
5. Ket luan va kien nghi
TCf ke't qua phan tich va mdt sd ehi dan thie't ke d tren cd the nhan tha'y rang, de thie't ke duge ke't ca'u neo cap cd hieu qua, dau tien can xae djnh rd va chfnh xac cd che lam viec ciia neo. Theo dd, can phai xac djnh cu the dieu kien dja chat tai khu vyc khai dao, tfnh toan xac djnh tai trgng tTnh tac dung len neo va cac tai trong cd the xua't hien trong qua trinh khai dao dudng Id khi khai thac. Khi tfnh toan cac gia thie't lam viec cua neo can tien hanh so sanh va kiem nghiem cae ke't qua thyc nghiem de chon ra cae thdng sd chieu dai neo, mat do neo phu hgp nha't. Can xem xet chi tie't hydng va mat do khe nCft cung nhu dieu kien nydc ngam khu vyc tfnh toan, lya chgn cap va chat lygng cap hgp 1^, trgng qua trinh thi cdng lap dat can thie't phai thCf tai dd'i vdi neo va tuan thCi nghiem ngat quy trinh lap dat neo. Neu cd hien tuong bat thydng nha't thiet phai dCfng viec lap dat va xem xet lai toan bd dieu kien thie't ke va lap dat tCf dau. Viee cang cap trong trydng hgp neo ddc lap va neo ke't hop vdi dam cap nha't thie't phai tie'n hanh theo dung trinh ty, tranh
tang tai dot ngdt d i n den dut cap, khdng dam bao dieu kien lam viec ciia neo. Khi sii" dung neo cap ke't hgp vdi vu'a be tdng can chu y den cap phdi vu'a xi mang de sao cho vu'a xi mang chui he't vao khoang khdng giiia cac sgi cap, tranh nudc xam thyc va an mdn cap va eac tam nut trong qua trinh sCr dung ke't ca'u./.
Tai lieu tham khao
1. US. Department of health and human servieesm. Proceedings: New technology for coal mine roof support, October 2000.
2. AT Hale, DM Grave, C sevume and Kle Bron, Strata control in tunnels and an evaluation of support units and systems currently used with a view to improving the affectiveness of support, stability and safety of tunnels, December 1998.
3. Alan Thompson, Curtin University of technology, WA school of mines, Kalgooriie, Western Australia, Performance of cable bolt anchors - An Update,
4. Maiek Bouteldja, Design of cable bolts using numerical modelling, Department of mining and metallurgical engineering, McGill University, Montreal, Canada, April 2000.
KHCNM S 6 8/2010* CNKT HAM LO
