KHOA HQC - CONG NGHE
Tap Chi GTVT 1+2/2011 I
DUNG BETONG DAM LAN LAM MAT DlICiNG OTO
PGS. NGUT. NGUYEN QUANG CHIEU
B
e tong dam lan, con goi la betong lu len (Roller Compacted Concrete, RCC) la loai betong dUdc sd dung ngay cang nhieu de xay dung cac dap thuy dien va xay dUng mat dadng d nudc ngoai tCr nhieu nam nay.d nudc ta tCr nam 2003 be tong dam lan (RCC) da dUdc ap dung de xay diing mpt so cac dap thuy dien d Tay Nguyen va mien Trung, gan day dUdc sif dung de xay di/ng thuy dien Sdn La vdi khoi lUdng Idn (Udc tinh khoang 4,4 trieu m^ RCC).
RCC phan biet vdi be tong xi mang truyen thong (be tong chan dong) bdi dp sut bang 0, ty le cot lieu cao va lUdng xi mang thap (vdi RCC lam dap). Cac dap thuy dien thudng la cong trinh khoi ldn, de giam SLf phat nhiet trong qua trinh hydrat hda xi mang va ha gia thanh san pham thudng sif dung cac chat dpn khoang vat nhU tro bay va thi cong theo phUdng phap rai tUng Idp.
Khi dung RCC de lam dudng oto thi phai tang lUdng xi mang va giam ty le nUdc/chat lien ket so vdi lam dap nudc vi Ung suat cd hpc do 6 to di qua cung nhu Ung suat nhiet deu Idn hdn.
Dung betong dam lan lam dUdng co nhieu ldi ich:
Betong dam lain la mpt tien bp ky thuat da va dang dUdc sir dung de lam mat dudng d nudc ngoai tu hang chuc nam nay. Dung betong dam lan de lam mat dudng thi cd the khac phuc dUdc cac nhUdc diem chinh cua mat dudng betong xi mang lam theo phUdng phap truyen thong vi:
- Cd the sir dung cac thie't bj thi cong thong dung nhu may san, may rai be tong nhUa, may lu, tram trpn da cap phoi.
- Toe dp thi cong nhanh, thdi gian bao dudng ng&n. Mat dUdng sau khi thi cdng xong cd the cho xe nhe chay dUdc ngay.
- Chat lupng betong dam lan xap xi bang chat lupng betong truyen thong.
- Do ham lUdng nUdc tha'p, lu len bang lu cha'n dpng cong sua't Idn dat dp chat cao nen khong can bo tri nhieu khe co dan phUc tap nhu vdi dudng betdng thudng.
Day la hudng nghien cUu thanh cong nham lam cho be tong xi mang thich hdp vdi mat dUdng dtd, ngupc vdi viec che tao cac thie't bj thi cong mat dudng betong hien dai, cdng sua't Idn, gia thanh rat d i t va chf thich hdp vdi cac xa Id Idn.
Tuy nhien loai mat dUdng nay khd thi cdng de dat dp bang phang cao nen chf dung lam Idp mat cho cac dudng dtd tU cap II trd xuong.
1. Yeu cau doi v6l vat lieu
Betdng dam lan gom cac chat lien ke't (xi mang, tro bay...), cdt lieu, nUdc va phu gia hdp thanh.
Cd hat Idn nha't cua cdt lieu D = 20mm la thich hdp. Khi mat dudng betong dam lan dupc r^i thanh
hai Idp thi cd hat Idn nha't cua Idp dudi cd the dung D = 40mm. Pham vi cap phdi cua cot lieu betdng dam lan cd the tham khao d bang 1. Khi rai thanh hai Idp, chieu day Idp dudi thudng lay bang 2/3 tdng chieu day, chieu day Idp tren bang 1/3 tdng chieu day nhung khdng nho hdn 8cm, cd hat Idn nha't cua cdt lieu Idp tren la 20mm.
Bing 1 Dirdng
kinh c3 hat
\6n nhat,
mm 20 40
Kich c9 16 sang, mm Sang 16 tron
40 1 25 1 20 1 10 1 5 1 2,5
Sang 16 vu6ng 0,6 T 0,3 1 0,15 Ty le % lot qua sang theo trpng li/c(ng
-- -- 90 100 65-77
90-100 50-65 30-45 21-35 - 35-50 25-40 19-32
10-20 7-15 10-20 7-15
5-10 8-10 Pham vi cap phdi thie't ke can cU vao ket qua thf nghiem trong phdng, dUa vao dp chat, cUdng dp va dp d i thi cdng de tim ra.
Mat dudng betdng dam lan rai thanh hai Idp thi Idp dudi cd the trdn vao mpt lUdng tro bay thi'ch hdp.
Betdng dam lan sau khi trdn tro bay khdng chf giam dupc gia thanh ma cdn giam dUdc lUdng tda nhiet khi ddng cUng, cai thien dp d i khi thi cdng va cd tac dung chdng tha'm. Khi rai thanh hai Idp de dam bao cho hai Idp dinh chat nhau va du thdi gian lu len thi nen trpn them phu gia lam cham thdi gian ngung ke't.
Ty le phdi hdp cac thanh phan cua be tdng dam lan dupc xac djnh tren nguyen tac bao dam cUdng dp yeu cau va cd the lu len bang lu cha'n dpng. Cudng dp keo udn cua betdng trong phdng thi nghiem phai cao hdn cudng dp thiet ke tU 15 - 20%.
Khi trpn tro bay, lieu lupng tro bay bang 20% lieu lupng xi mang, ham lupng tdt nha't cua phu gia cham ngUng ket vao khoang 0,25 - 0,30% trpng lUdng khd cua xi mang -f tro bay.
2. PhUdng phap thiet ke
Viec ti'nh chieu day cua mat dudng betdng dam lan dupc tien hanh nhU vdi mat dUdng betdng thdng thudng trU nhOng quy djnh dudi day:
- Cudng dp thiet ke cua betdng dam lan khdng dUdc thap hdn quy dinh d bang 2
Bang 2 Cap giao thong
Cirdng do keo uon thiet lce(MPa) Mo dun dan hoi keo uon
E ( x l O ' M P a )
RCC FRCC
Dac biet nang
5 35 33
Nang 5 35 33
Vufa 4.5
33 31
Nhe 4.0 31 29 + RCC betdng dam lan (Roller Compacted Con- crete)
-h FRCC betdng dam lan trdn tro bay (Fly Ash Roller Compacted Concrete)
Viec thie't ke chieu day mat dudng RCC cung dupc tien hanh theo phUdng phap gan dung. Oau
:t^
•7Hd» 20HKHOA HQC - CONG NGHE
tien gia dinh chieu day ta'm betdng hj rdi tinh ufng sua't do tai trpng lap lai cua true banh xe gay ra Op - Neu Ung sua't nay khdng chenh lech so vdi cUdng dp keo udn cua betdng qua ± 5% thi lay chieu day gia djnh lam chieu day thiet ke. Neu khdng thi phai gia dinh lai hj va tinh lai cho den khi dat yeu cau. Chieu day gia djnh hj Ung vdi cac cap giao thdng khac nhau cho.d bang 3.
Bing 3
Cap giao thong
Chieu day gii dinh hi(cm) Rat nang
>26 Nang
24- 26
Vilfa 22-24
Nhe
<22
Chieu day nhd nha't cua mat dudng RCC li 18cm.
Mat dudng RCC dUdc hinh thanh nhd lu len hdn hdp be tdng khd cUng bang lu cha'n ddng va lu banh Idp. PhUdng phap thi cdng nay lam cho viec bd tri cac thanh truyen lUc va thanh chju keo khd khan.
Ngoai ra ke't qua xac djnh he sd co cho tha'y he sd co cua RCC tha'p hdn so vdi be tdng thudng khoang 30%. Vi vay mat dUdng RCC d nudc ngoai thdng thudng chf bd tri khe co vdi khoang each giOa cac khe tu 15 - 20m. Tat ca cac khe deu la khe co gia va khdng dat thanh truyen lUc.
3.Thi c6ng
Viec thi cdng mat dudng RCC dUdc tien hanh theo trinh tU sau:
- Chuan bj Idp mdng: De bao dam mat dUdng cd chieu day khdng ddi va dupc lu chat, Idp mdng
phai cd chat lUdng tdt, bao dam dp bSng phang va dp ddc ngang thiet ke. Can tudi am Idp mdng khi thi cdng d nhiet dp cao.
- Rai vi san: RCC dUdc rai thanh Idp chieu day tu 18 - 25cm sau khi lu chat. De tranh lam khe dpc nen cd gang rai tren toan chieu rdng mat dudng. Co the rai bang cac thiet bj sau: May rai be tdng diing van khudn trUdt; May san; May san ke't hdp may ui loai nhd; May rai be tong nhua...
Theo kinh nghiem nen rai vat lieu cao hdn chieu day thiet ke vai cm rdi dung lu cha'n ddng lu vai li/ot de vat lieu khdng phui ra. Sau dd dung may san hoan thien den chieu cao cudi cung rdi tie'p tuc lu bang lu cha'n ddng va lu banh Idp.
- L u / e n ; Cdng tac lu len anh hudng rat Idn de'n dp chat va dp bang phang cua mat dudng vi vay can dac biet chu y.
Cach lu len nhU sau: dau tien cho lu cha'n dpng (khdng rung) lu tren 1/3 chieu rdng len le dudng va 2/3 chieu rpng len Idp be tong rdi chuyen dan vao trong.
- Bio dudng: Phai lam tdt cdng tac bao dudng vdi nhOng npi dung sau:
-I- GiO am sau khi lu len bang phun hoac tudi niidc.
-I- Cudi ca thi cdng phai phun Idp nhu tUdng bao dudng va rai sdi. Lupng nhu tUdng vao khoang 600g/
m^ va sdi cd 4/ 6mm.
Hdn hdp RCC dUdc che tao d cac tram tron be tdng xi mang hoac tram cap phdi da gia cd xi mang.
Neu cd trpn tro bay thi phai trang bj them phiu chufa tro bay va phai khdng che chinh xac lieu lUdng. •
NGHIEN Cifu DE XUAT.
(Tie'p theo trang 49) tor Wireless Access in Vehicular Environments (WAVE) - Multi-channel Operation
Ve hinh thUc thu phi, de xua't td chUc thu phi theo kieu md phu hdp vdi dac diem giao thdng Viet Nam ma v i n dam bao chinh xac d mpt mUc dp nha't djnh.
Ve phUdng thUc thu phi, td chUc tram thu phi cd lan danh rieng ETC va lan hdn hdp (ETC/MTC), thuan tien cho viec quan ly va xd ly thu phi trong dieu kien mdi trUdng giao thdng da dang va ddng tien IUu thdng vSn chu yeu la tien mat.
IV. Ket luan
Bai viet dUa tren cd sd phan tich cac dac trUng kinh te ky thuat va kha nang phat trien cua hai he thdng DSRC, tU dd de xua't SLf dung lUa chpn tieu chuan cu the he thdng DSRC 5.8 GHz cho ITS Viet Nam nham ddng gdp vao viec hoan thien bd tieu chuan ITS Viet Nam hien dang dUdc khan trUdng tien hanh nghien cUu xay dUng, gdp phan day nhanh hdn qua trinh Ung dung ITS cho mang dudng cao tdc Viet Nam nham khai thac tdi da nang lUc cua mang dudng, thuc day phat trien kinh te, cdng nghe, giai quyet tdt hdn van de mdi trUdng...Tuy nhien trong giai doan dau, do Uu diem the RFID cua he thdng DSRC
915 MHz cd gia thanh tha'p, dap Ung dUdc nhu cau quan ly phUdng tien va thu phi, trUdc mat cung co ttie xem xet dUa he thdng nay vao Ung dung trong giai doan dau de cac chu xe quen dan vdi he thdng ETC, tien tdi ap dung DSRC 5.8 GHz khi dieu kien cho phep. •
V. Tai lieu tham khao
[1] Beau Roodell, M.lmran Haye "Development of a Low-Cost Interface between Cell Phones and DSRC- Based Vehicle Unit for Efficient Use of VII Infrastructure"
Department of Electrical and Computer Engineering.
University of Minnesota Duluth, July, 2009
[2] Lee Amstrong "Dedicate Short Range Communications (DSRC) at 5.9 GHz" Amstrong Consulting, Inc
[3] (DOT, 2007) US DOT, "National ITS Architec- ture Website", Oct 2007.
[4] (Fisher, 2007) W. Fisher, "Development of DSRC/WAVE Standards", IEEE 802.11-07/2045rO, June 2007.
[5] L.H.Lan "Bao cao tdng ket de tai KC 03.21"
University of Transport and communication. 2009 [6] Huang Wei " Giao trinh ITS dai cUdng" Dong- Nan University, July. 2008.
[7] Hajime Teshigahara "Introduction of ETC in recent Japan" Nomura Reseach Institute. 11/2010.
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