Báo cáo thực tập - Nguyễn Thanh Ngân

7/30/2019 Bo co thc tp - Nguyn Thanh Ngn

1/15

TRNG I HC THY LIKHOA CNG TRNH

BO CO THC TP CHUYN NGNH A K

THUT XY DNG

Gio vin hng dn: PGS.TS. Trnh Cng VnH tn hc vin: Nguyn Thanh NgnLp: 20KT11-CS2M s hc vin: 128605860012

Tp. H Ch Minh 2013


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Bo co: Thc tp chuyn ngnh a k thut xy dng

SVTH: Nguyn Thanh Ngn, MSSV: 128605860012 Trang 2


3/15


LI M U

Vng Mn - X No tng i thp v bng phng, nm trong vng Tysng Hu, c hnh thnh do nhng hot ng tn kin to cng vi s bi tch

ph sa sng Hu v ph sa bin. Ch thy vn, thy lc ca vng rt phctp. y l vng t c khai khn tng i sm, h thng knh rch phttrin kh tt phc v cho vic giao thng v ti tiu ca vng ny.

Vng Mn - X No b chia ct bi mng li knh rch chng cht.Ngun cp nc ngt cho vng d n l sng Hu vi lu lng bnh qun macn vo khong 1200 m/s, lu lng bnh qun ma l vo khong 7000 m/s.

Tuy khu vc d n thuc cc tnh Hu Giang, Kin Giang v Thnh phCn Th thuc BSCL nm h lu vng chu th sng Mekong c nhiuthun li, nhng cng tn ti nhiu kh khn hn ch v iu kin t nhin, linh hng bi ch thu vn, cc khai thc t thng lu v dao ng cathy triu bin ng-bin Ty. Mt khc nn t khu vc tng i yu, khnng chu ti km, i hi c phng php thi cng hp l m bo cht lngcng trnh v tic kim chi ph u t. Vic lp d n thy li Mn- X Noc nghin cu mt cch kh k lng ca cc t chc, cc nh nghin cukhoa hc thuc nhiu lnh vc khc nhau.

Cc hng mc chnh ca d n thy li Mn - X No bao gm xydng hon chnh 113km bao kt hp lm ng giao thng nng thn c b

mt c gia c bng b tng hoc cp phi; xy dng h thng cng gm 52cng cp 1 (c khu 10-20m) v cng cp 2 (c khu t 3 n 16m), honchnh h thng knh cp 2 v knh ni ng; cp nc sch nng thn

Do nn a cht yu v phc tp, nn vic kho st v thit k c quantm. Gii php u tin c a ra l, dng mng cc b tng ct thp truyn ti trng xung lp t c s chu ti ln hn, nhng phng php nylm tng chi ph u t. Gii php c chn l dng cc xi mng t thay thcc b tng ct thp, cng ngh thi cng bng phng php phc va xi mngvi p lc cao. Phng php ny va thch hp thi cng trong iu kin thc t

vi khng gian nh, v kinh t.


Vng tiu d n Omon-Xano


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PHN NI DUNG

PHN 1: GII THIU V D N THY LI OMON-XANO

1.1. Tn d n: D n khp kn tuyn , cng vng Mn - X No giai

on 1, tnh Hu Giang, Kin Giang, Thnh ph Cn Th thuc D n: Qun lthy li phc v PTNT vng ng bng sng Cu Long (WB6).

1.2. a im xy dng: tnh Hu Giang, Kin Giang v Thnh ph CnTh.

1.3. Hnh thc u t: Xy dng mi.

1.4. Ch u t : Ban Qun l d n u t v Xy dng Thy li 10 -B Nng nghip v Pht trin nng thn.

1.5. Hnh thc qun l thc hin d n: Ch u t trc tip qun lthc hin d n.

1.6. Nhim v cng trnh:

- Kim sot l c nm cho khong 45.430 ha t t nhin, m bo sn

xut nng nghip n nh, bo v vn cy n qu v h thng h tng c s.


Vng tiu d n Omon-Xano


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- Phc v ti, tiu, x phn, ngn mn, ly ph sa ci to t cho 38.800ha t nng nghip.

- Kt hp cp nc dn sinh, pht trin giao thng thy b, to nn dnc, ci thin mi trng trong khu vc.

1.7. Quy m cng trnh:- Cc cng trnh c p dng cng ngh mi, trong c 6 cng dngp x lan b tng dng bn dm, 1 cng truyn thng v 3 cng dng p tr.

- Ca van s dng cho cc cng trnh gm dng ca van clape v t ng,khung ca v ci trc bng thp khng r, bn mt bng composite.

- Cu giao thng qua cng trnh: Cu ti trng H8T, b rng 4,5m, nhpbin v nhp gia bng BTCT, c s dng dm cu d ng lc.

- Qun l h thng cng trnh bao gm: Nh qun l im ti 2 cng trong10 cng : b tr ti cng p v cng l 62C.

PHN 2. THIT K X L NN BNG PHNG PHP PHT VA XIMNG P LC CAO

2.1. Thit k mng ban u: theo n v t vn kho st, thit k lCng ty C phn T vn Xy dng Thy li II (HECII) cho bit th nn mng

ban u cc cng ny c thit k bng cc b tng ct thp. Qua so snh giaphng php s dng cc b tng ct thp vi phng php pht va p lc caoth thy hiu qu kinh t ca phng php pht va p lc cao c gi thnh thpv cht lng p ng c yu cu k thut ca d n.

2.2. L do chuyn i sang gii php pht va xi mng:

Qua ti liu Bo co kho st a cht cho thy khu vc d n Mn -X No t rt yu nu a ra bin php thi cng cc b tng ct thp s tn kmcho Ch u t v cng trnh l nhng h thng cng thot nc tc dng ngthi ln h nn t yu.

So vi mt s gii php x l nn hin c, gii php pht va xi mng cu im l kh nng x l su (n 50m), thch hp vi cc loi t yu (t ctth cho n bn yu), thi cng c c trong iu kin nn ngp su trong nchoc iu kin hin trng cht hp, trong nhiu trng hp a li hiu qukinh t r rt so vi cc gii php x l khc.

V vy gii php gia c nn bng cng ngh pht va cao p (cn gi lJet grounting) c chn thay th cc b tng ct thp.

2.3. Gii php thit k:

Gii php x dng cc xi mng t c ng knh 600mm.



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Quan nim tnh ton cc xi mng t theo 3 quan im: Quan im xemcc xi mng t lm vic nh cc; Quan im xem cc cc v t lm vic ngthi v Tnh ton theo c 2 quan im trn (Phn mm dng tnh ton: Plaxis)

Hin nay, vic tnh ton sc chu ti v bin dng ca nn gia c bng cct - xi mng ang cn l vn tranh ci. Mt s nh khoa hc kin ngh tnh

ton nh i vi cc cng, s khc li ngh tnh ton nh i vi nn thinnhin, c tc gi li ngh tnh ton sc chu ti nh i vi cc cng, cn

bin dng th tnh ton theo nn. S d cn nhiu nhng quan im tri ngcnhau l v bn thn vn rt phc tp, cn phi c nhiu cng trnh nghin cul thuyt v thc nghim lm sng t vai tr mang ti ca cc, ca t nn xungquanh cc, ngha l xem cc v nn cng ng thi lm vic. Theo chng ti,vn s n gin hn nhiu nu quan nim nn t yu c gia c l mtnn mi, c tnh cht c l mi. R rng l, trc khi gia c, nn thin nhin lmt nn t yu vi cc tnh cht c l khng p ng c yu cu xy dng.

Sau khi gia c, cc ch tiu c l thay i mt cch ng k nh m, h srng gim, khi lng th tch, lc dnh, gc ma st trong tng nh cc qu trnhnn cht c hc, c kt v tc dng ca cc phn ng ho l gia xi mng v tnn trong qu trnh gia c. V vy, vic tnh ton sc chu ti v ln ca nnsau gia c c th tnh nh i vi nn thin nhin. Tuy nhin, cn phn bit haitrng hp l trng hp thi cng nhanh v trng hp thi cng chm.

a. Trng hp thi cng chm:

Khi gia c nn, tc l tc dng mt ti trng ngoi vo nn t (titrng l khi lng vt liu xi mng a vo nn) gy ra qu trnh nn chtc hc (do th tch vt liu xi mng chim ch th tch l rng trong t), qutrnh c kt ca t nn (do ht nc lm ng cng va xi mng, thot nc dop lc hu hiu tng, p lc nc l rng gim) v cc phn ng ho l ca ximng, t vi mi trng t yu. Cc qu trnh ny xy ra ng thi ngay saukhi bt u gia c nn nhng kt thc vo cc thi im khc nhau. Qu trnhnn cht c hc s kt thc ngay sau khi hon thnh gia c. Qu trnh c kt cat nn v tc dng ho l ca xi mng vi t nn s kt thc mun hn v sau

bao lu s kt thc th cn phi c nghin cu chi tit. Do vy, nu sau khi giac mt thi gian, khi m qu trnh c kt v cc phn ng ho l ca mi trng

kt thc, mi xy dng cng trnh th r rng l, nn t gia c tr thnhmt nn mi, ng sut trong nn gia c c phn b li, tnh cht c l cann thay i vi cc gi tr mi.

b. Trng hp thi cng nhanh:

Trng hp thi cng nhanh, ngha l, sau khi qu trnh gia c nn kt thcth tin hnh xy dng cng trnh ngay. Lc ny, ch c qu trnh nn cht chc l kt thc, cn qu trnh c kt v cc phn ng ho l ca mi trng vntip din. Tuy nhin, qu trnh nn cht c hc mi l ch yu, m qu trnh ny

th kt thc ngay sau khi gia c. Do vy, vic tnh ton nn, theo chng ti,vn c th tin hnh nh i vi trng hp thi cng chm, nhng c lu n



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tc dng ca qu trnh c kt v phn ng ho l ca mi trng cncha kt thc, bng cch a thm vo p lc gy ln mt tr s no ca "plc gia c" do trng lng vt liu xi mng gy ra. Tr s ny c th c tnh

bng 1/2 "p lc gia c". Mt s nh chuyn mn c th thc mc, khi tnh nhvy th khi lng xi mng a vo nn mt i u ? Ti sao li khng a

ton b ti trng ny vo gi tr p lc gy ln ca cng trnh m li ch avo mt gi tr no ? Thc ra, vic a thm vo tr s p lc gy ln mt gitr bng 1/2 "p lc gia c" cng ch mang tnh quy c da vo cc phn tchc s phng php lun ca vn . Chng ti cho rng, khi lng ct - ximng - vi a vo nn c th coi l mt ti trng ngoi. Di tc dngca ti trng ny, trong nn t s xut hin ng sut ph thm z gy bin dngnn (c theo phng dc v phng ngang). Tr s ca ng sut ph thm bng :

z = s + U

Trong ,- s: ng sut hu hiu do ht t tip thu

- U: ng sut trung tnh do nc tip thu

Cng vi thi gian, ng sut hu hiu tng ln, ng sut trung tnh gimi, nhng bt k thi im no trong nn t vn tn ti mi tng quan trn.Trong trng hp thi cng chm, cc qu trnh nn cht c hc, c kt v phnng ho l gia xi mng v mi trng kt thc. Khi ton b ti trngngoi (lng ct - xi mng - vi) do ht t tip thu (z = s ), ng sut trung

tnh b trit tiu (U=0), bin dng nn t tr s n nh, nn c nncht hon ton, tr thnh mt nn mi. Trong trng hp thi cng nhanh, chqu trnh nn cht c hc l kt thc, cn qu trnh c kt v cc phn ng hol gia xi mng, vi v nn cha kt thc, nn t ch bin dng mt phn, phncn li vn tip tc din ra cng vi qu trnh nn ln do ti trng cng trnh xydng.

Nh vy, c th quy c, mt na lng xi mng truyn cho ht tlm nn b bin dng, tng ng vi qu trnh nn cht c hc kt thc; cnmt na lng xi mng s vn tip tc gy ra bin dng nn, tng ng vi qu

trnh c kt v tc dng ho l gia xi mng, vi v t nn. Do , khi tnh lncng trnh cn thm vo tr s p lc gy ln mt gi tr bng mt na khilng xi mng a vo nn. Vi quan nim nh vy, ln ca nn sau gia cc th c tnh bng phng php cng ln tng lp.

PHN 3. CNG NGH PHT VA P LC CAO P DNG CHO THIT KX L NN CC CNG THUC D N:

Cng ngh jet grouting l mt cng ngh trn su dng t (wet mixing).Hin nay nc ta cha c thut ng khoa hc ting Vit chnh thc gi tncng ngh ny. Tm thi, chng ti xut thut ng "khoan pht cao p",



8/15


phn bit vi cc cng ngh khoan pht s dng p sut thp hn (210 atm) vc ch nt bt c mt nc ta t nhiu nm nay.

Cng ngh khoan pht cao p (KPCA) c pht minh Nht Bn nm1970. Sau cc cng ty ca , c mua li pht minh trn v n naynhiu cng ty x l nn mng hng u th gii hin nay nh cng ty Layne

Christensen (M), Bauer (c), Keller (Anh), Frankipile (c) u c s dngcng ngh ny. Tri qua hn ba mi nm hon thin v pht trin, n naycng ngh ny c tha nhn rng khp, c kim nghim v a vo tiuchun cc nc pht trin trn th gii.

Khoan pht va cao p l mt qu trnh b tng ho t. Nh c tia ncv tia va phun ra vi p sut cao (200-400 atm), vn tc ln (100 m/s), cc

phn t t xung quanh l khoan b xi ti ra v ho trn vi va pht ngcng to thnh mt khi Xi mng-t ng nht - tm gi l xi mng-t.

Cng ngh thi cng cc xi mng t:

S dy chuyn thit b khoan pht va cao p (Jet-grouting)

Hin nay trn th gii c hai cng ngh c p dng ph bin l cngngh ca Chu u v cng ngh ca Nht Bn.



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Hin nay Vit Nam ph bin hai cng ngh thi cng cc xi mng t l:Cng ngh trn kh (Dry Jet Mixing) v Cng ngh trn t (Wet Mixing haycn gi l Jet-grouting)l cng ngh ca Nht Bn.

- Trn kh l qu trnh phun trn xi mng kh vi t c hoc khng ccht ph gia.

- Trn t l qu trnh bm trn va xi mng vi t c hoc khng ccht ph gia.

Mi phng php trn (kh hoc t) c thit b giy chuyn thi cng kthut, thi cng phun (bm) trn khc nhau.

Hin nay trn th gii pht trin ba cng ngh Jet-grouting: u tin lcng ngh S, tip theo l cng ngh T, v gn y l cng ngh D.

+ Cng ngh n pha S: Cng ngh n pha to ra cc cc xi mng tc ng knh va v nh 0,4 - 0,8m. Cng ngh ny ch yu dng thi cngnn t p, cc...

+ Cng ngh hai pha D: Cng ngh hai pha to ra cc cc xi mng t cng knh t 0,8 -1,2m. Cng ngh ny ch yu dng thi cng cc tngchn, cc v ho chng thm.

+ Cng ngh ba pha T: Pht ba pha l phng php thay th t m khngxo trn t. Cng ngh T s dng lm cc cc, cc tng ngn chng thm,c th to ra ct Soilcrete ng knh n 3m.

Hin nay Vit Nam, Trung tm Cng ngh My xy dng v C khthc nghim thuc Vin Khoa hc v Cng ngh Giao thng Vn ti nghincu v ch to thnh cng thit b iu khin v nh lng xi mng thi cngcc t gia c. Qua , Trung tm lm ch c vic ch to h iu khin,h nh lng v phun xi mng; t hp thit b thi cng cc gia c c ngdng thnh cng v cho hiu qu cao ti cng trng.

So vi sn phm cng loi ca CHLB c, thit b do Trung tm ch toc tnh nng k thut tng ng nhng gi thnh ch bng 30%. So vi thit

b ca Trung Quc, thit b c nhiu tnh nng u vit hn hn: Do s dng myc s l loi ba ng cc di chuyn bng bnh xch, nn tnh c ng cao, tc lm vic ca thit b khoan ln, nng sut gp 1,5-2 ln. c bit, t hp thit

b c trang b h thng iu khin hin i, ton b cc thao tc thi cng ccgia c c t ng ha theo cc chng trnh, cc s liu v lng xi mng sdng trn tng mt cc c hin th, lu gi v in thnh bng kt qu thi cngcho tng cc. y chnh l nhng ch tiu rt quan trng nh gi cht lngca thit b cng nh cht lng ca cc gia c c thi cng.

y l ln u tin trong nc ch to c t hp thit b thi cng ccgia c. Thit b c gi thnh thp, ph hp vi kh nng ti chnh ca cc n v

thi cng. Thit b cng c cc nh thu s dng thi cng ti sn bay TrNc.



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PHN 4. THC T THI CNG PHT VA XI MNG TI HIN TRNG:

My bm va cao p kt hp thit b khoan ti hin trng cng

4.1. Phng php thi cng:

Cc xi mng t (hay cn gi l ct xi mng t, tr xi mng t), cthi cng to thnh theo phng php khoan trn su. Dng my khoan v ccthit b chuyn dng (cn khoan, mi khoan) khoan vo t vi ng knhv chiu su l khoan theo thit k (Cc c ng knh D = 600 mm, chiu di

cc L= 32m). t trong qu trnh khoan khng c ly ln khi l khoan m bph v kt cu, c cc cnh mi khoan nghin ti, trn u vi cht kt dnh



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(cht kt dnh thng thng l xi mng hoc vi, thch cao i khi c thmcht ph gia v ct). Phng php x l bng cc t - xi mng kh n gin:

bao gm mt my khoan vi h thng li c ng knh thay i tu thuctheo ng knh ct c thit k v cc xi l cha xi mng c gn my bmnn vi p lc ln ti 12 kg/cm2. Trong qu trnh khoan li c thit k

trn u t v xi mng, xi mng kh c phun nh lng lin tc v trn uto thnh nhng cc t - xi mng ng knh 600mm.

Qu trnh phun (hoc bm) cht kt dnh trn vi t trong h khoan,tu theo yu cu c th c thc hin c hai pha khoan xung v rt ln cami khoan hoc ch thc hin pha rt mi khoan ln. trnh lng ph ximng, hn ch xi mng thot ra khi mt t gy nhim mi trng thngthng khi rt mi khoan ln cch cao mt t t 0.5m n 1.5m ngi tadng phun cht kt dnh, nhng on cc 0.5m n 1.5m ny vn c phuny cht kt dnh l nh cht kt dnh c trong ng ng tip tc c phun

(hoc bm) vo h khoan.Khi mi khoan c rt ln khi h khoan, trong h khoan cn li t

c trn u vi cht kt dnh dn dn ng cng to thnh cc xi mng t.

4.2. Quy trnh thi cng:

Quy trnh thi cng cc ximng-t bng phng php Jet grouting thhin trong s sau y:

Bc 1: My khoan khoan to l xung ti cao trnh thit k.

Bc 2: Tin hnh pht va. Va c bm t my bm cao p qua hthng ng ng p lc n my khoan v pht ra theo phng ngang ti ucn khoan. Trong sut qu trnh pht va, cn khoan lun lun xoay v rt ln.Va pht va ph v kt cu va trn vi t xung quanh cn khoan to thnhcc ximng t.

S thi cng cc ximng t dng phng php Jet grouting

4.3. Mt s s c trong qu trnh thi cng:



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Trong khi thi cng cc th, nu gp s c th phi tm ngng pht va,nn a u pht xung di im tm ngng khong 0,5m, ch n khi khc

phc xong th tip tc bm v pht cho n khi hon thnh.

Nu thi gian tm ngng thi cng mt cc vt qu 24 ting ng h thphi lm li ton b cc .

Khi khoan cha n cao mi cc thit k, nu gp m ci khng thtip tc c th c th khoan cc th sang v tr bn cnh.

4.3.1. Khi lng n va ln bt thng (dng tro ngc b gim i),c th do mt s nguyn nhn sau:

- Trong qu trnh khoan pht gp hang rng trong lng t.

- rng ca t ln.

- T l nc/xi mng (N/X) cha ph hp.

- Khe h dc ng b bt kn.Bin php x l:

- Nu gp hang rng trong lng t, tin hnh cho my pht va ti chcho n khi va in y hang rng.

- Nu gp tng t c rng ln, c th: iu chnh li t l N/X choph hp (dung dch va c hn); Hoc thay i tc rt cn khoan.

- Nu khe h dc ng b bt kn, phi rt cn khoan ln v tin hnh vsinh cn khoan sch s. Dung dch va qu c cng c th lm bt khe h dccn khoan, trong trng hp ny cn iu chnh t l N/X cho ph hp (lm chodung dch long hn).

4.3.2. Khi dng tro ngc ln bt thng (dng tro ngc qumnh): th cn phi xem xt li cc thng s khoan pht hoc phng phpthi cng. Dng tro ngc ln bt thng c th do nhiu nguyn nhn:

- Trong qu trnh khoan pht gp phi m ci.

- rng ca t b.

Bin php x l:- Nu gp phi m ci, c th dng mi khoan dng ba rung khoan

ph hoc khoan vng qua hn .

- Nu rng ca t b, khoan tip mt s l tip theo cng gp hintng dng tro ngc ln bt thng, cn phi tin hnh kho st li a chttrong vng x l, iu chnh thit k cho ph hp.



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PHN 5. NHNG NHN XT V GP CA HC VIN NHM CITHIN NHNG VN TN TI TRONG THI CNG HOC NHNG BIHC M HC VIN C TH RT RA SAU CHUYN THC TP:

Mu lu th nghim cc xi mng t

Cng ngh trn su ni chung v cc xi mng t c p dng khph bin trn th gii nhng ch mi c p dng Vit Nam gn y.

Thc t vi cc nn ng p cao trn nn t yu; cng trnh yu cu

thi gian thi cng ngn; ln cn li nh; yu cu t nn c kt nhanh; titkim vt liu p khi vt liu ny khan him th gii php x l nn bng cc ximng t t ra kh hiu qu. V vy sp ti chng ta nn mnh dn ng dngcng ngh ny x l nn p trn t yu nht l cc on ng u cu.

Ngoi ra, ng dng cc xi mng t lm tng chn, vch tng hm, chngmt n nh mi dc cng t c hiu qu cao v kinh t - k thut.

Mt khi cng ngh ny tr nn ph bin th gi thnh xy lp s gim vu im ca phng php x l bng cc xi mng t cng c nng cao.

So vi mt s gii php x l nn hin c, cng ngh cc xi mng t cu im l kh nng x l su (n 50m), thch hp vi cc loi t yu (t ctth cho n bn yu), thi cng c c trong iu kin nn ngp su trong nchoc iu kin hin trng cht hp, trong nhiu trng hp a li hiu qukinh t r rt so vi cc gii php x l khc.(nu s dng phng php cc btng p hoc cc khoan nhi th rt tn km do tng t yu bn trn dy. Vimt trng hp p dng vi lp t dy 30m, th khi s dng phng phpcc- t xi mng tit kim cho mi mng xi l khong 600 triu ng.

u im ni bt ca cc xi mng t l:

- C th p dng cho mi loi t khc nhau.



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- C th thi cng trong khng gia hn ch.

- Trong thi cng t to ra ting n, chn ng.

- C kh nng vt qua gii hn bn di nn, hoc khng lm nhhng n cc cng trnh ln cn.

- C th thc hin gia cng theo phng xin, phng ng, phngngang, trn hay di mc nc ngm.

- Tc thi cng nhanh so vi cc phng php x l khc.

- Khng cn duy tu, bo dng cho cng trnh sau khi x l.

- Gia c cho cc cng trnh ngm, cc cng trnh ang s dng.

- X l bt k su no m khng cn o n cao trnh x l m chcn to h khoan c ng knh t 150 200mm.

- Gim thiu xo trn n mi trng xung quanh phm vi x l.- Ci thin ng k sc chu ti ca cng trnh.



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PHN KT LUN

Qua phn tch cng ngh thi cng tr t xi mng bng cng ngh JetGrouting cho thy y l gii php mang nhiu tnh u vit cho cng tc x

l ln nn ng p cao trn t yu trong iu kin va x l ln trit nhng phi va m bo c cc iu kin thc t ca cng trnh nh: khngnh hng n giao thng, khng nh hng n cc cng trnh ln cn, thigian thi cng ngn...

Sau chuyn thc tp, nhng kin thc v cng ngh thi cng tr xi mngt bng Jet Grouting rt b ch v th v, l c s ph v tt cng tc nghincu v thc tin sau ny.

Qua y ti cng rt cm n thy PGS.TS. Trnh Cng Vn, Cng ty Cphn T vn Xy dng Thy li II ht lng ch dn tn tnh v gip tihon thnh tt chuyn thc tp.


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Báo cáo thực tập - Nguyễn Thanh Ngân