Mt ng lt xpMT NG CP CAO VIT NAMTm tt: Bi bo trnh by nghin cu v
mt ng lt v kh nng ng dng hiu qu cho xy dng giao thng Vit Nam. Thng
qua nhng phn tch v kt cu, vt liu v cng ngh cho thy mt ng lt l loi
mt ng t c nhiu u im v kh nng khai thc, tui th, kh nng ti to cao
trong s cc loi mt ng hin hnh. ng thi y cng l loi mt ng thch nghi tt
vi iu kin bin i kh hu v p ng c vi kch bn nc bin dng trong tng lai
khng xa cho iu kin Vit Nam.
1.Gii thiu m bo cht lng khai thc tt cho mt tuyn ng th cht lng mt
ng l yu t quan trng. Hin nay, loi kt cu mt ng c s dng kh a dng. T
nhng loi mt ng t t nhin cho n loi mt ng cp cao nh b tng xi mng (mt
ng cng), b tng asphalt (mt ng mm)
Mt ng cng c c u im ni bt nh kh nng chu lc cao, tui th khai thc
di. Mt ng mm li t c u im v tnh d thi cng, m thun khi khai thc v c
bit l gi thnh xy dng cnh tranh. V vy, hai loi mt ng ny c s dng hu
ht cc d n ng b cp cao.
Vit Nam, trong qu trnh pht trin c s h tng nhng nm gn y, hu ht cc
tuyn ng giao thng chnh u c xy dng bng lp mt btng asphalt. S d nh vy
l do trnh k thut ca cc nh thu trong nc ch yu quen thuc vi cng ngh
xy dng mt ng ny. V vy, lp mt btng asphalt l la chn s mt cho cc d n
xy dng ng mi v ci to nng cp cc tuyn ng b Vit Nam.
Tuy nhin, d dng nhn thy nhng nhc im c bn ca hai loi mt ng nu
trn. Th nht, nu nh mun n hi ca mt ng mm qu nh dn n kh nng chu lc
thp th mt ng cng li c mun n hi qu cao, gy xc khi chy xe v c bit l
gy nt khi khai thc. Th hai, mt ng mm tuy c tin thi cng nhanh so vi
mt ng cng nhng tui th khai thc li ngn (di 15 nm). Th ba, c hai loi
mt ng trn u l mt ng lin khi nn rt kh khn cho cng tc duy tu bo dng
cng nh ti s dng.
Trong nhng nm gn y, loi mt ng lt c nghin cu v p dng c hiu qu mt
s nc nh M, Anh, v nht l H Lan. Tuy loi mt ng ny c chi ph xy dng ban
u cha cnh tranh, nhng so vi mt ng cng v mt ng mm truyn thng , mt ng
lt li t c nhng u im ni bt v kh nng chu lc, chng nt, nhm v kh nng
thot nc. c bit, mt ng lt cn d dng duy tu, bo dng v tn dng gn nh hon
ton khi i tu. Bn cnh , mt ng lt cn to c m quan cng nh tng an ton
khi chy xe.
Vit Nam, lp mt lt mi ch c s dng lt va h hoc ng dnh cho ngi i b.
Trong khi nhu cu xy dng mt cng, sn bay, ng th cn kh ln. Hn na, mt s
th ven bin t min Trung tr vo, nht l khu vc TP. H Ch Minh, c d on l
s phi i mt vi nguy c nc bin dng cao do hin tng m ln ton cu. Do , mt
loi mt ng c th tn dng trit khi cn nng cao theo mc nc bin dng l nhu
cu c tht trong tng lai khng xa [1].Bi bo trnh by tng quan v mt ng
lt, nhng tiu chun lin quan n vt liu v kt cu p dng cho cc loi mt ng
cho giao thng th, GTVT ng b cao tc, mt ng sn bay, mt cng v khu cng
nghip. T xut kh nng p dng loi mt ng ny lm phong ph thm cc la chn
cho kt cu mt ng Vit Nam.
2. Vt liu v cng ngh sn xut vin lt.Vin lt (hay cn gi l gch lt) kh
a dng v chng loi v phng php sn xut ty thuc vo phm vi p dng v yu cu
cht lng. Vin lt c th c chia ra lm 3 nhm ch yu [2], gm:
Nhm gch lt t thin nhin: Loi ny c gia cng ch yu bng th cng t khi
t nhin. Cc vin lt thin nhin thng c cng rt cao, bn tt. Tuy nhin, loi
vin lt ny c kch thc v cht lng thay i trong phm vi kh rng.
Nhm gch lt t gch t st nung (vt liu gm): Loi vt liu ny c kch thc
v cht lng ng u hn so vi vin lt. Tuy nhin, cng chu lc thp hn.
Nhm gch lt t gch BTXM: loi vin lt ny thng c c sn trong nh my.
Cht lng v chnh xc v kch thc ca vin lt c kim sot cht tr. Hnh dng, mu
sc ca vin lt c iu chnh theo nhu cu cu to, s lm vic v m quan ca cng
trnh nhm tng nhanh cng tui sm. Sau , vin lt c chuyn sang cc gi xp
tip tc dng h v lu tr. Nguyn l ny gn tng t nh qu trnh sn xut gch xy
BTXM. iu ny nhm mc ch tn dng dy chuyn sn xut gch xy sn xut gch
lt.
Dy chuyn sn xut hin i bao gm thit b my sn xut gch lt nhiu lp sn
xut vi cng xut ln. Tng t nh trn, hn hp BTXM kh c ln vo khun v rung
p vi tn s cao. Sau khi mt lp gch c c trn mt gi hon chnh, khun c tho
v mt lp ct mng c rc trn b mt gch chng dnh. Sau , lp gch tip theo c
c trc tip trn b mt lp trc . Qu trnh ny c tin hnh cho n khi 8 n 10
lp gch c c trn mi gi. Gi cha sau c di chuyn sang dy chuyn dng h v
lu tr. Hoc my c di chuyn trn ray sang v tr gi tip theo [3].
Yu cu k thut c bn ca vin lt BTXM c cp trong bng 1.
Bng 1. Yu cu k thut ca gch lt BTXM [4]3. Cc loi kt cu mt ng ltDo
cc u im ni bt ca mt ng lt nh nu trn, kt cu mt ng lt c th c p dng
cho nhiu loi cng trnh vi yu cu k thut v yu cu khai thc khc nhau.
Nhn chung, kt cu mt ng lt c b tr nh cc lp trong hnh 1.
Hnh1. Cc lp ca kt cu mt ng lt in hnh [5]Bng 2. Vt liu v chiu dy
cc lp trong kt cu mt ng lt [5,6]
Di lp nn gia c ca mt ng lt l tng t. Vt liu v chiu dy ca cc lp
trong kt cu mt ng lt c kin ngh trong bng 2.
Cc loi mt ng sau c p dng ph bin trn th gii v cng c th p dng hiu
qu Vit Nam.
3.1. Mt ng lt cho ng th
Hnh 2. i l Champs Elysee, Paris s dng mt ng ltKt cu mt ng lt cho
ng th c s dng kh ph bin thnh ph ca cc nc pht trin (hnh 2). u im ni
bt ca mt ng lt khi p dng cho ng th l tnh m quan, kh nng duy tu bo
dng, kh nng thit k thnh mt ng thm thng ng Bn cnh , khi p dng cho iu
kin Vit Nam loi mt ng cn c u im l duy tr c cao sau mi ln i tu mt
ng. Ngc li, trong trng hp cn nng cao mt ng th vic s dng mt ng lt li
c u im l tn dng c gn nh ton b lp mt lt. iu ny rt thch hp cho nhng
th ven bin nh TP. H Ch Minh ang b e da bi thy chiu v mc nc bin dng
(hnh 3)
Hnh 3. Ngp lt do thy triu TP. H Ch Minh3.2. Mt ng lt cho ng cao
tcVi kh nng chu c ti trng ln, khng b bin dng nt khi chu ti v ch thy
nhit thay i, nhm cao nn mt ng lt rt thch hp cho kt cu mt ng cao tc
chu ti trng nng (hnh 4). Vit Nam cha lm ch c cng ngh mt ng cng nn
trc mt vic p dng mt ng lt cho cc ng cao tc nhng khu vc ch thy nhit,
a cht phc tp v chu ti trng nng l bc qu ph hp.
Hnh 4. Mt ng lt ng cao tc.3.3. Mt ng lt cho sn bay, bn cng, khu
cng nghipYu cu c th ca mt sn bay, mt cng v ng khu cng nghip l va
chu ti trng ln, ng thi cng chu ti trng cc b rt cao. Kh nng h hng kt
cu mt d pht sinh trong qu trnh khai thc. V vy, vic p dng kt cu mt
ng lt c u tin s dng (hnh 5, 6, 7). Tng t nh mt ng th, mt sn bay v
bn cng iu kin Vit Nam nu c p dng mt ng lt s khc phc c tnh trng h
hng v kh duy tu bo dng. ng thi, cc sn bay v bn cng khu vc pha nam c
th nng dn cao lp mt theo mc nc bin dng m vn tn dng c gn nh ton b lp
vt liu mt lt.
Hnh 5. Mt sn bay quc t Hng Kng [8]
Hnh 7. ng khu cng nghip4. Cng ngh thi cng lp ltMt trong nhng kh
khn ln nht ph bin rng ri vic ng dng mt ng lt Vit Nam l h thng tiu
chun v vt liu v thit k kt cu cha c xy dng, v c bit l qu trnh thi
cng kh c gii ha. Tuy nhin, thi gian gn y nhng thit b c gii cho php
tc thi cng lp lt c th so snh c vi tc thi cng mt ng cng hin hnh c p
dng [9]. y s l tin tt cho vic thc y s dng mt ng lt Vit Nam.
Hnh 8. Thit b lt Tiger Stone5.nh gi hiu qu kinh t ca mt ng ltNu
so snh mt cch tng i chi ph xy dng gia mt ng lt v mt ng cng hin hnh
th gi thnh gn nh tng ng. Tuy nhin, vic p dng mt ng lt cho php cng
xng ha c vic sn xut vin lt nn cht lng c kim sot v kh n nh. ng thi
chi ph duy tu bo dng v nht l chi ph i tu mt ng lt r hn nhiu. V vy,
chi ph u t cho c vng i s dng ca mt ng lt hon ton cnh tranh vi mt ng
cng truyn thng.
6. Kt lun, kin nghT phn tch trn c th a ra cc kt lun v kin ngh
sau cho mt ng lt khi p dng Vit Nam
+ Chu c ti trng ln nn rt thch hp cho kt cu mt ng cao tc, mt cng,
mt ng sn bay, mt ng khu cng nghip...
+ Khng b nt khi chu ti trng v khi ch thy nhit thay i.
+ Tui th cao nn mc d chi ph u t xy dng ban u ln nhng chi ph khai
thc hng nm v c vng i hon ton cnh tranh c vi mt ng truyn thng.
+ C kh nng thit k thnh kt cu mt ng thm (thot nc thng ng).
+ D dng duy tu bo dng, c bng bin php th cng ln c gii.
+ To c nhm ph hp nn m bo tt an ton chy xe.
+ C m quan cao do rt thch hp cho mt ng ni th, khu dn c, ni cng
cng.
+ Kh nng tn dng cc vt liu ph thi khi ch to mt s vin lt nn c tnh
thn thin vi mi trng cao.
+ c bit, loi mt ng ny c th ti tn dng trit khi nhu cu thay i cao
mt ng t ra.
+ Cc nghin cu y v ton din hon chnh cng ngh sn xut vin lt, quy
trnh thit k v cng ngh thi cng mt ng lt cn sm c quan tm c th p dng
cho cc d n xy dng ng trong nhng nm tip theo Vit Nam.\.
Ti liu tham kho[1]o Vn ng (2009). Vt liu "xanh" v bn vng - xu
hng pht trin xy dng. Tp ch khoa hc cng ngh xy dng[2]Phm Minh Phc
(2010).Nghin cu, tnh ton kt cu mt ng b tng gch lt v kh nng ng dng
cho iu kin Vit Nam. Lun vn thc s khoa hc k thut. Trng i hc Giao
thng vn ti.[3]Raymond S. Rollings (1983). Concrete block pavement.
Technical report GL - 83 - 3. Geotechnical laboratory. U. S Army
Enginneer Waterways Experiment Station.[4]ASTM C936 (2001).
Standard specification for solid concrete interlocking paving
units. American society for Testing and Materials.[5]BS 7533 - 1
(2001). Pavements constructed with clay, natural stone or concrete
pavers, Part 1; Guide for the structural design of heavy duty
pavements constructed of clay pavers or precast concrete paving
blocks. British Standard.[6]BS 7533 - 3 (2005). Pavements
constructed with clay, natural stone or concrete pavers, Part 3;
Code of practice for laying precast concrete paving blocks and clay
pavers for flexible pavements. British Standard.[7]Heavy duty
pavement- The structural design of heavy duty pavement for ports
and other industries.[8]Case study in engineered interlocking
concrete pavement. Hong Kong International Airport.[9]Paving
machine- Tiger stone
