Chuyen de Thi Cong

Cng ngh thi cng cc khoan nhi v t-ng barret

Gvhd : gs. Ts. Ks & Kts L kiu

1

B xy dng

Tr-ng i hc kin trc HN

Mn hc

Vt liu, kt cu v cng ngh thi cng

Chuyn

Cc khoan nhi

v t-ng barret

Gio Vin HD : GS.TS.ks & kts. l kiu

Hc vin TH : Nguyn Hng Quang

Lp : CH03K-HKT

H ni 04-2004

Ni dung



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Trang

1. Gii thiu chung 1

2. Cc dng cc khoan nhi ph bin

v ph-ng php thi cng cc khoan nhi 2

3. Quy trnh cng ngh thi cng cc khoan nhi 4

4. Thi cng cc barrette 24

Thi cng cc khoan nhi

I- Gii thiu chung :



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Trong hon cnh hin nay, nh cao tng ra i l mt h qu tt yu

ca vic tng dn s th, thiu t xy dng v gi t cao. Th loi

cng trnh ny cho php c nhiu tng hay nhiu khng gian s dng

hn, tn dng -c mt t nghiu hn, cha -c nhiu ng-i v hng

ho hn trong cng mt khu t. Nh cao tng c th c xem l C

my to ra ca ci hot ng trong nn kinh t th. Tuy nhin khng

nn coi chng mt cch n gin l s gia tng khng gian xy dng

theo chiu cao trn mt din tch t xy dng hn ch m chng c

nhng yu cu kh nghim ngt cn phi tun th trong qu trnh thit

k v thi cng.

Mt b phn ht sc quan trng trong cc cng trnh xy dng ni

chung v nh cao tng ni ring l mng cng trnh. Mt cng trnh bn

vng, c n nh cao, c th s dng an ton lu di ph thuc rt

nhiu vo cht l-ng mng ca cng trnh. Cc khoan nhi l mt trong

nhng gii php mng -c p dng kh ph bin xy dng nh cao

tng trn th gii v Vit Nam vo nhng nm gn y, bi cc khoan

nhi p ng -c cc c im ring bit ca nh cao tng nh- :

- Ti trng tp trung rt ln chn cc ct nh.

- Nh cao tng rt nhy cm vi ln, c bit l ln lch, v ln s

gy tc ng rt ln n s lm vic tng th ca ton b to nh.

- Nh cao tng th-ng -c xy dng trong khu vc ng dn c-,

mt nh c sn kh dy. V vy vn chng rung ng v chng ln

m bo an ton cho cc cng trnh ln cn l mt c im phi c

bit l-u trong xy dng loi nh ny.

Ngoi nhng -u im ca cc khoan nhi l tho mn -c cc yu

cu trn, thi cng cc khoan nhi cn trnh -c ting n qu mc, hn

na nu s dng mng Barrette (Mt dng c bit ca cc khoan nhi)

lm cc tng hm cho loi nh ny s rt d dng v c rt nhiu thun

li, cng trnh gim -c ti trng do ly i lp t cc tng hm chim

ch, mt khc c tng hm th nh cao tng s tng n nh khi chu

lc ngang, ng thi cng trnh c thm din tch s dng.

II- C c dng cc khoan nhi ph bin v c c ph-ng ph p thi cng cc

khoan nhi :

1- Cc dng cc khoan nhi :

- Cc nhi n gin tit din hnh tr v khng thay i trn sut



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chiu su ca cc.

- Cc nhi m rng y : Cc c hnh tr khoan bnh th-ng nh-ng

khi gn n y th dng gu c bit m rng y h khoan, cng c

th s dng mt l-ng nh thuc n m rng y. Ng-i ta cng c

th m rng nhiu t bng khoan hoc thuc n trn sut chiu di thn

cc. Cc -c m rng y v cc

-c m rng nhiu t thn cc

s tng sc chu ti hn nhiu so vi

cc thng th-ng.

- Cc Barrette : y l mt loi

cc nhi c tit din hnh ch nht,

ch L, ch I, ch H thc cht l

nhng bc t-ng su trong t bng

b tng ct thp. Cc ny c sc

chu ti rt ln ti a n 6000T v

rt -u vit khi xy dng nhng nh

c nhiu tng hm v n l t-ng c

chng sp l quanh nh, va l t-ng c chng n-c cho cc tng hm (

thi cng ni phn sau)

2- Cc ph-ng php thi cng cc khoan nhi :

Trn th gii c rt nhiu thit b v cng ngh thi cng cc khoan

nhi nh-ng c 2 nguyn l -c s dng trong tt c cc ph-ng php thi

cng l :

- Cc khoan nhi c s dng ng vch

- Cc khoan nhi khng dng ng vch

2-1. Cc khoan nhi c s dng ng vch :

Loi ny th-ng -c s dng khi thi cng nhng cc nm k st

vi cng trnh c sn hoc do nhng iu kin a cht dc bit. Cc

khoan nhi c dng ng vch thp rt thun li cho thi cng v khng

phi lo vic sp thnh h khoan, cng trnh t b bn v khng phi s

dng dung dch Bentonite, cht l-ng cc rt cao.

Nh-c im ca ph-ng php ny l my thi cng ln, cng knh,

khi my lm vic th gy rung v ting n ln v rt kh thi cng i vi



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nhng cc c di trn 30m.

2-2. Cc khoan nhi khng dng ng vch:

y l cng ngh khoan rt ph bin. u im ca ph-ng php

ny l thi cng nhanh, m bo v sinh mi tr-ng v t nh h-ng n

cc cng trnh xung quanh.

Ph-ng php ny thch hp vi loi t st mm, na cng na

mm, t ct mn, ct th hoc c ln si c ht t 20-100mm.

C 2 ph-ng php dng cc khoan nhi khng s dng ng vch:

a- Ph-ng php khoan thi ra (phn tun hon):

My o s dng gung xon ph t, dung dch Bentonite -c

bm xung h gi vch h o. Mn khoan v dung dch -c my

bm v my nn kh y t y h khoan ln -a vo b lng lc tch

dung dch Bentonite ti s dng.

Cng vic t ct thp v b tng tin hnh bnh th-ng.

- u im : Ph-ng php ny c gi thit b r, thi cng n gin,

gi thnh h

- Nh-c im : Tc khoan chm, cht l-ng v tin cy ch-a

cao.

b- Ph-ng php khoan gu :

Theo cng ngh khoan ny, gu khoan th-ng c dng thng xoay

ct t v -a ra ngoi. Cn gu khoan c dng ng-ten, th-ng l 3

on truyn -c chuyn ng xoay t my o xung gu nh h thng

rnh.

Vch h khoan -c gi n nh nh dung dch Bentonite. Qa trnh

to l -c thc hin trong dung dch Bentonite. Trong qu trnh khoan

c th thay cc gu khc nhau ph hp vi nn t o v khc

phc cc d tt trong lng t.

- u im : Thi cng nhanh, vic kim tra cht l-ng d dng thun

tin, m bo v sinh mi tr-ng v t nh h-ng n cc cng trnh ln

cn.

- Nh-c im : Phi s dng cc thit b chuyn dng gi t, gi

thnh cc cao.

Ph-ng php ny i hi quy trnh cng ngh rt cht ch, cn b

k thut v cng nhn phi thnh tho, c thc t chc k lut cao.



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Do ph-ng php ny khoan nhanh hn v cht l-ng m bo hn

cc ph-ng php khc, nn hin nay cc cng trnh ln Vit Nam ch

yu s dng ph-ng php ny bng cc thit b ca c (Bauer), Italia

(Soil-Mec) v ca Nht (Hitachi).

III- Quy trnh cng ngh thi cng Cc khoan nhi :

Quy trnh cng ngh thi cng cc khoan nhi bao gm cc cng

on :

- Cng tc chun b

- Cng tc nh v tim cc

- Cng tc h ng vch khoan v bm dung dch Bentonite

- Xc nhn su h khoan v x l cn lng y h cc

- Cng tc chun b v h lng thp

- Lp ng b tng

- Cng tc b tng v rt ng thp

- Kim tra cht l-ng cc

1- Cng tc chun b :

vic thi cng cc khoan nhi t hiu qu cao th ngoi vic phi

chun b cc loi thit b thi cng cn thit phi iu tra kh nng vn

chuyn, p dng cc bin php ngn nga ting n v chn ng, ... cn

phi tin hnh iu tra y cc mt v tnh hnh phm vi chung quanh

hin tr-ng.

Cn ch my khoan thuc loi thit b ln rt nng nn nht thit

phi iu tra y v ph-ng n v l trnh vn chuyn. Phi m bo

phi c din tch hin tr-ng lp dng thit b, ngoi ra cn phi

thc hin vic x l gia c mt -ng v nn t trong khu vc thi cng

thuan tin cho cng vic lp dng thit b v xe c i li.

Phi c cc bin php hn ch tc hi ca ting n v chn ng.

Cc bin php gim ting n nh- sau :

- Gim ting n t ng c n : ch h-ng pht ra ting n v t

chp ht m ng c n.

- in kh ho ngun ng lc : dng ng c in thay th cho

my n , my nn kh.

- Xy t-ng bao quang hin tr-ng : hiu qu ca vic cch m bng

t-ng ph thuc rt nhiu vo cao v cht liu lm t-ng. Nu t-ng



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lm bng vt liu cch m th hiu qu rt cao.

Cn ch xc nhn chng loi v v tr ca cc vt kin trc ngm

v xem xt kh nng gy nh h-ng n khu vc v cng trnh ln cn

c bin php x l thch hp.

2- nh v v tr t cc :

Phi dng my kinh v xc nh v tr t cc. Vic nh v -c

tin hnh trong thi gian dng ng vch, c th nhn thy ng vch c

tc dng u tin l m bo c nh v tr cc. Trong qu trnh ly t ra

khi lng cc cn khoan s -c -a ra -a vo lin tc nn tc dng th

hai ca ng vch l m bo khng cho sp thnh pha trn v cc

khng b lch ra khi v tr.

T mt bng nh v mng cc ca nh lp h thng nh v v l-i

khng ch cho cng trnh theo to . Cc l-i nh v ny -c chuyn

di v c nh vo cc cng trnh ln cn hoc lp thnh cc mc nh

v. Cc mc ny -c ro chn bo v chu o v lin tc kim tra

phng x dch do va chm v ln.

3- Cng tc h ng vch, khoan v bm dung dch Bentonite :

ng vch l mt ng thp c -ng knh ln hn -ng knh gu

khoan khong 10cm, ng vch di khong 6m -c t phn trn

ming h khoan nh ln khi mt t khong 0,6m



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ng vch c nhim v :

- nh v v dn h-ng cho my khoan

- Gi n nh cho b mt h khoan v chng sp thnh phn trn h

khoan

- Bo v t , thit b khng ri xung h khoan

- Lm sn tm v thao tc buc ni v lp dng ct thp, lp

dng v tho d ng b tng.

Sau khi b tng cc nhi xong, ng vch s -c rt ln v thu

hi li.

Cc ph-ng php h ng vch:

- Ph-ng php rung: L s dng loi ba rung thng th-ng, t



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su khong 6 mt phi mt khong 10 pht, do qu trnh rung di nh

h-ng n ton b khu vc ln cn nn khc phc hin t-ng trn,

tr-c khi h ng vch, ng-i ta o sn mt h su t 2,5 n 3 m ti v

tr h cc vi mc ch bc b lp cng trn mt t gim thi gian ca

ba rung xung cn khong 2-3 pht.

- Ph-ng php p: L s dng my p p ng vch xung su

cn thit. Ph-ng php ny chu -c rung ng nh-ng thit b cng

knh, thi cng phc tp v nng sut thp.

- S dng chnh my khoan h ng vch: y l ph-ng php

ph bin hin nay. Ng-i ta lp vo gu khoan thm mt ai st m

rng h o khoan n ht su ca ng vch th dng cn cu hoc

my o -a ng vch vo v tr v h xung cao trnh cn thit, dng

cn g nh ln ng vch iu chnh thng ng. Sau khi t ng

vch xong phi chn cht bng t st v nm ng vch khng dch

chuyn -c trong qu trnh khoan.

a. Cng tc khoan to l:

Qu trnh ny -c thc hin sau khi t xong ng vch tm. t

ly ra khi lng cc -c thc hin bng thit b khoan c bit, u

khoan ly t c th l loi gung xon cho lp t st hoc l loi thng

cho lp t ct. im c bit ca thit b ny l cn khoan: Cn c dng

ng ten gm 3 ng lng vo nhau v truyn -c chuyn ng xoay, ng

trong cng gn vi gu khoan v ng ngoi cng gn vi ng c xoay

ca my khoan. Cn c th ko di n su cn thit.



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Trong khi khoan do cu to nn t thay i hoc c khi gp d vt i

hi ng-i ch huy khoan phi c kinh nghim x l kp thi kt hp

vi mt s cng c c bit nh- mi khoan ph, mi khoan ct, gu

ngom, ba my...

Mt s loi my khoan cc nhi ph bin :



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b. Dung dch Bentonite:

Bentonite l loi t st c kch th-c ht nh hn t st kaolinite

nn ng-i ta th-ng dng t st Bentonite ch to bn khoan. Dung

dch st Bentonite c hai tc dng chnh:

- Gi cho thnh h o khng b sp nh dung dch chui vo khe nt

quyn vi ct ri to thnh mt mng n hi bc quanh thnh vch h

gi cho ct v cc vt th vn khng b ri v ngn khng cho n-c thm

thu qua vch.

- To mi tr-ng nng nng t vn khoan ni ln mt trn

tro ra hoc ht khi h khoan.

Cc c tnh k thut ca bt Bentonite :

- m 9- 11%

- tr-ng n 14- 16 ml/g

- Khi l-ng ring 2,1T/m3

- pH ca keo vi 5% 9,8 - 10,5

- Gii hn lng Aherberg > 400- 450

- Ch s do 350-400



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- lt sng c 100: 98-99%

- tn trn sng c 74: 2,2-2,5%

c. Bn khoan :

Bn khoan l dung dich Bentonite bao gm n-c, st Bentonite, t

st thng th-ng, xi mng v cht ph gia

Cc thng s k thut ch yu ca dung dch Bentonite -c khng

ch nh- sau:

- Hm l-ng ct < 5%

- Dung trng 1,01-1,1

- nht 32-34giy

- pH 9,5-11,7

- Liu l-ng trn 30-50 kg Bentonite/m3

Do dung dch Bentonite c tm quan trng c bit vi cht l-ng

h khoan do phi cung cp dung dch Bentonite to thnh p lc d-

gi cho thnh h khoan khng sp. Cao trnh dung dch Bentonite t nht

phi cao hn cao trnh mc n-c ngm t 1-2m, thng th-ng nn gi

cho cao trnh dung dch Bentonite cch mt trn ca ng vch l 1m,

ng-i ta c th t thm ng bao pha ngoi ng vch tng thm cao

trnh v p lc ca dung dch Bentonite nu cn thit.

Trong qu trnh khoan, chiu su ca h khoan c th uc tnh nh

cun cp hoc chiu di cn khoan. xc nh chnh xc hn ng-i ta

dng mt qu di y bng -ng knh khong 5cm buc vo u th-c

dy th xung y o chiu su h o v cao trnh b tng trong qu

trnh . Trong sut qu trnh o, phi kim tra thng ng ca cc

thng qua cn khoan. Gii hn nghing cho php ca cc khng v-t

qu 1%.

4. Xc nhn su h khoan v x l cn lng y h cc:

a. Xc nhn su h khoan:

Khi tnh ton ng-i ta ch da vo mt vi mi khoan kho st a

cht tnh ton su trung bnh cn thit ca cc nhi. Trong thc t

thi cng do mt ct a cht c th thay i, cc a tng c th khng

ng u gia cc mi khoan nn khng nht thit phi khoan ng nh-

su thit k qui nh m cn c s iu chnh.

Trong thc t, ng-i thit k ch qui nh a tng t y cc v khi

khoan y cc phi ngp vo a tng t y cc t nht l mt ln



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-ng knh ca cc. xc nh chnh xc im dng ny khi khoan

ng-i ta ly mu cho tng a tng khc nhau v on cui cng nn

ly mu cho tng gu khoan.

Ng-i gim st hin tr-ng xc nhn t d-c chiu su yu cu,

ghi chp y , k c bng chp nh mu khoan lm t- liu bo co ri

cho dng khoan, s dng gu vt vt sch t ri trong y h

khoan, o chiu sau h khoan chnh thc v cho chuyn sang cong on

khc.

b. X l cn lng y h khoan:

nh h-ng ca cn lng i vi cht l-ng cc : Cc khoan nhi

chu ti trng rt ln nn ng li d-i y h khoan bn t hoc

bentonite dng bn nho s nh h-ng nghim trng ti kh nng chu

ti ca mi cc, gy st ln cho kt cu bn trn, lm cho cng trnh b

dch chuyn gy bin dng v nt. V th mi cc u phi -c x l

cn lng rt k l-ng.

C 2 loi cn lng:

- Cn lng ht th: Trong qu trnh to l t ct ri vi hoc khng

kp -a ln sau khi ngng khoan s lng xung a h. Loi cn lng

ny to bi cc ht -ng knh t-ng i to, do khi lng ng

xung y th rt kh moi ln.

- Cn lng ht mn: y l nhng ht rt nh l lng trong dung

dch bentonite, sau khi khoan to l xong qua mt thi gian mi lng dn

xung y h.

Cc b-c x l cn lng:

- B-c 1: X l cn lng th_ i vi ph-ng php khoan gu sau

khi l t n su d nh m khng -a gu ln vi m tip tc

cho gu xoay vt bn t cho n khi y h ht cn lng mi thi.

i vi ph-ng php khoan l phn tun hon th xong khi kt thc

cng vic to l phi m bm ht cho khoan chy khng ti 10 pht,

n khi bm ht ra khng cn thy t ct mi ngng v nhc u khoan

ln.

- B-c 2: X k cn lng ht mn: b-c ny -c thc hin tr-c khi

b tng. C nhiu ph-ng php x l cn lng ht mn:



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+ Ph-ng php thi ra dng kh nn: Dng ngay ng b tng

lm ng x l cn lng. Sau khi lp xong ng b tng ng-i ta lp u

thi ra ln u trn ca ng. u thi ra c 2 ca, mt ca -c ni

vi ng dn thu hi dung dch bentonite v bn t t y h khoan

v thit b lc dung dch, mt ca khc -c th ng kh nn 45, ng

ny di khong 80% chiu di ca cc.

Khi bt u thi ra, kh nn -c

thi lin tc vi p lc 7kg/cm2 qua

-ng ng 45 t bn trong ng b

tng. Khi kh nn ra khi ng 45 s

quay tr li thot ln trn ng to

thnh mt p lc ht y h -a dung

dch bentonite v cn lng theo ng

b tng n thit b lc v thu hi dung

dch. Trong sut qu trnh thi ra ny

phi lin tc cp b dung dch bentonite

m cao trnh v p lc ca bentonite

ln h mng khng thay i. Thi gian

thi ra th-ng t 20-30 pht. Sau khi

ngng cp kh nn, ng-i ta th dy o

su. Nu lp bn lng



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bm ra. Khi dung dch ny t ch tiu sch v lng t yu cu

10cm th ngng bm v kt thc cng on lun chuyn bentonite ny.

5- Cng tc chun b v h lng thp:

Trong cc cc khoan nhi th-ng cc nh thit k ch t ct thp

ti 1/3 chiu di ca cc nh-ng cng c cc thit k ca Nht hoc mt

s n-c khc li t ct thp xung tn y.

Ct thp -ng buc sn thnh tng lng vn chuyn v t ln gi

gn h khoan, sau khi kim tra y h khoan nu lp bn ct lng d-i

y h



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Khi h ct thp phi tin hnh rt cn thn t t gi cho lng thp

lun thng ng trnh va chm lng thp vo thnh h khoan lm sp

thnh gy kh khn cho vic no vt thi ra.

m bo dy ca lp b tng bo v th-ng gn mt ngoi

Ct thp ch mt dng c nh v Ct thp bng b tng, bng cht do

hoc hn thm tai thp trn hay thp bn vo mt ngoi lng thp. C ly

theo chiu di ca dng c nh v ct thp th-ng t 3-6m v trnh

lch tm s l-ng dng c nh v mi mt ct l t 4-6 ci.

6- Lp ng b tng :

Tu theo ph-ng php x l cn lng, ng b tng c th -c

lp ngay sau khi khoan h xong lm cng vic thi ra y h khoan

nh-ng cng c th -c lp ch b tng sau khi x l cn lng.

ng b tng l ng thp dy khong 3mm -ng knh t 25-

30cm -c ch to thnh tng on c cc mun c bn l 0,5m; 1,0m;

1,5m; 2,0m; 2,50m; 3,00m; 5,00m; 6,00m c th t hp lp rp tu

theo chiu su ca h khoan.

C 2 cch ni ng hin nay l ni bng ren v ni bng cp. Cch

ni bng cp -c s dng rng ri hn nhanh hn v d thao tc hn.

Ch ni th-ng c giong cao su ngn dung dch bentonite thm nhp

vo ng v -c bi m tho lp -c d dng.

ng b tng -c lp dn tng on t d-i ln trn. lp ng

-c thun tin ng-i ta s dng mt h gi c bit qua ming h

vch, trn gi c 2 na vnh khuyn c bn l, ming ca mi on ng

c -ng knh to hn v khi th xung th b gi li trn 2 na vnh

khuyn . V th ng b tng -c treo vo ming h vch qua gi

c bit ny. Khi na vnh khuyn trn gi sp xung s to thnh

mt hnh trn m kht ly thn ng b tng. y d-i ca ng b

tng -c t cch y h khoan 20cm trnh b tc ng do t

d-i y h khoan nt li.

7- Cng tc b tng v rt ng vch:

Sau khi kt thc thi ra h khoan v t lng thp cn phi tin

hnh b tng ngay v lu bn ct s tip tc lng nh h-ng n

cht l-ng ca cc.



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V nguyn tc b tng cc khoan nhi l b tng d-i n-c

bng ng dn, cho nn t l cp phi b tng phi ph hp vi do,

dnh, d chy trong ng dn m khng hay b gin on, th-ng ng-i ta

dng loi b tng do c st 13-18cm. T l ct khong 45%, l-ng

xi mng trn 370kg/m3. T l n-c xi mng nh hn 50%. Th-ng ng-i

dng b tng si v b tng si d chy hn b tng dm.

tng c-ng mt s tnh cht ca b tng v thun li trong thi

cng ng-i ta c th cho vo b tng mt s cht ph gia nh- cht tng

kh, cht gim n-c hoc cht ng rn chm.

a- Hnh thc ng dn dng b tng:

C 2 loi : Loi y y v loi c van tr-t

+ Loi y y l loi ng dn c mt np y d-i y. y np

li v cho ng dn t t chm xung y h, lc ny trong ng dn

khng c n-c. Sau tin hnh b tng vo v nhc ng dn ln, ci

np s ri ra v l-u li y h. Ng-i ta cng c th s dng mt nt

bc t vo ng ngn cch gia b tng v dung dch bentonite

trong ng , sau khi nhc ng ln nt bc s ri ra v ni ln mt

bentonite trn ming cc v -c thu hi.

+ Ph-ng php van tr-t: y ng dn vn h, cng nh- ph-ng

php trn, ng-i ta t t -a ng dn xung cch y h khoan khong

10-20cm. Tr-c khi b tng cho van tr-t vo trong ng st ti

mt dung dch bentonite, sau nh trng l-ng b tng -c lin

tc m y n-c trong ng dn ra ngoi.

b- Tc v thi gian b tng:

Nu qu trnh b tng b gin on th d sinh ra s c t cc

nn b tng phi tht lin tc, mt khc nu phn b tng tr-c

vo giai on s ninh th s tr ngi cho vic chuyn ng ca b tng

tip theo trong ng dn.

Tc b tng nn c gng cng nhanh cng tt. Ph-ng php

thng dng l cho trc tip b tng t xe vn chuyn qua mng vo trong

phu ca ng dn, tuy vy nu qu trnh qu nhanh cng s c vn

l to ma st ln gia b tng v thnh h khoan gy l t lm gim

cht l-ng b tng. Kinh nghim cho thy tc b tng thch hp l

khong 0,6m3/pht.

Thi gian b tng 1 cc ch nn khng ch trong 4 gi, v m b



18

tng u tin s b y ni ln trn cng nn m b tng ny nn c

ph gia ko di ninh kt m bo khng b ninh kt tr-c khi kt thc

hon ton vic b tng cc . Ngoi ra phi ch l theo ph-ng

php ng dn th khong 1,5 gi t khi bt u trn b tng phi

cho k ht.

c- su cm ng dn vo trong b tng v cao v-t ln ca b

tng trn u cc:

Trong qu trnh b tng, ng -c rt ln dn bng cch tho

b dn tng on ng sao cho ng lun lun ngp trong va b tng t

2-9m mc ch y b tng t y ng dn ra, b tng dng dn ln

khng cho dung dch bentonite v bn ct pha trn ln vo b tng.

Mt khc nu ng dn cm vo b tng qu su th b tng phn

y ca ng chy khng thng v s lm cho b tng trong phu u

ng dn b trn ra ngoi v ri t do vo tronhg l lm km cht l-ng b

tng v lm gim rt nhiu kh nng gi thnh t ca dung dch

bentonite.

phn trn u cc khi b tng d-i n-c th khng th trnh

khi bn, cn lng ln vo trong b tng lm gim cht l-ng ca b

tng do vy m bo an ton ng-i ta th-ng b tong cc v-t ln

mt o so vi cao ca thit k khong 50cm.

kt thc qu trnh b tng, phi xc nh -c cao trnh ca

b tng v cao trnh tht ca b tng cht l-ng tt. Vic quyt nh thi

im ngng b tng s do nh thu xut v gim st hin tr-ng

chp thun.

d- Rt ng vch:

Lc ny cc gi , sn cng tc, treo ct thp vo ng vch u

-c tho d. ng vch -c ko ln t t bng cn cu v phi ko

thng ng trnh x dch tim u cc. C th phi gn thm mt thit

b rung vo ng vch vic rt ng vch -c d dng.

Sau khi rt ng vch phi lp ct vo h cc nu cc su, lp h thu

bentonite v ro chn tm bo v cc.

Khng -c php rung ng hoc khoan cc khc trong vng 24 gi

k t khi kt thc b tng cc trong phm vi 5 ln -ng knh ca

cc.



19

8- Kim tra cht l-ng cc khoan nhi :

Vic kim tra cht l-ng thi cng cc khoan nhi ni chung phi

thc hin trc tip ti hin tr-ng, do s phc tp trong thi cng, gi

thnh cng nh- tnh cht quan trng ca cc khoan nhi i vi cng

trnh nn yu cu kim tra giai on ch to cc phi ht sc nghim

ngt, t l l-ng cc kim tra nhiu v nu c mt s sai st no trong

qu trnh ch to gy h- hng s rt kh sa hoc nu khc phc th chi

ph s rt ln.

Kt qu nghin cu cho thy : nguyn nhn gy h- hng cc khoan

nhi rt a dng nh-ng phn ln cc khuyt tt l do cng ngh thi cng

khng thch hp gy ra v vy cn phi kim tra cht ch ton b cc

cng on thi cng cc.

Tuy vy, sau khi b tng vic kim tra cht l-ng cc vn cn

thit nhm pht hin cc khuyt tt v x l nhng cc b h- hng. i

t-ng ca vic kim tra cc khoan nhi l cht l-ng ca nn t v cht

l-ng ca bn thn cc. Vn kim tra c 2 ch tiu ny c nhiu

ph-ng php thc hin bng cc cng c hin i, c th phn ra 2

ph-ng php c bn l ph-ng php tnh v ph-ng php ng.

a- Kim tra bng ph-ng php tnh :

* Ph-ng php gia ti tnh : y l ph-ng php ph bin v ng

tin cy kim tra kh nng chu ti ca cc. Tu theo yu cu c th

ng-i ta c th xc nh kh nng chu nn, chu ko hay chu y ca

cc. V i t-ng gia ti c th s dng cc vt nng cht ti hoc s

dng khoan neo xung t. C 2 quy trnh nn tnh -c s dng trong

thc t l :

+ Quy trnh th nghim nn chm vi ti trng khng i nh

gi ng thi kh nng chu ti v tc ln ca cc theo thi gian. Th

nghim cc theo quy trnh ny i hi nhiu thi gian, c th ko di

nhiu ngy.

+ Quy trnh tc chuyn dch khng i nhm mc ch duy nht

l ng gi kh nng chu ti ca cc. Th nghim theo quy trnh ny ch

ko di 3-5 gi.

Ngoi 2 quy trnh trn ng-i ta cn p dng mt s quy trnh gia ti

khc nh- quy trnh th nghim nhanh vi gia ti khng i, quy trnh th

nghim cn bng...



20

Nh-c im c bn ca ph-ng php ny l gi thnh rt cao v

cng tc chun b th nghim i hi nhiu thi gian.

* Ph-ng php khoan ly mu li cc: Dng my khoan ly cc

mu hnh tr c -ng knh 50-150 mm cc su khc nhau dc sut

chiu di thn cc 3 v tr cch u nhau trn mt ct ngang ca cc.

u im ca ph-ng php ny l c th xc nh chnh xc cht

l-ng b tng ca cc nh-ng nh-c im l chi ph ly mu kh ln. Khi

khoan 3 l cho mi cc nu khoan ht c chiu di th chi ph khoan xp

x gi thnh cc.

* Ph-ng php siu m: y l ph-ng php rt ph bin v nh n

c th pht hin cc khuyt tt ca b tng ng thi da vo s t-ng

quan gia tc truyn sng v c-ng b tng ta c th bit -c

c-ng b tng m khng phi ly mu hay ph hu kt cu.

Ng-i ta t 2 ng thp c -ng knh 80mm vo lng thp vi

chiu di ng bng chiu su h o v i xng nhau qua trc ca cc

tr-c khi tin hnh b tng. Sau ny, khi kim tra cht l-ng ca cc

th -a u thu v u pht siu m vo 2 ng thp trn v lun -c gi

cng mt cao trnh, sng siu m s qut theo tit din ca cc. Bng

cch ny ng-i ta nh gi -c cht l-ng b tng nm gia 2 l khoan.

kim tra cht ch hn cht l-ng cc c th khoan hoc t sn t 3-

5 l trn mi cy cc th nghim. C th s dng ph-ng php siu m

m u thu v u pht cng -c gn trn mt thanh ch to bng vt

liu cch m.

Ph-ng php siu m cho kt qu kh chnh xc, ng tin cy, gi

thnh th nghim khng qu cao, nhiu n-c quy nh s cc phi th

nghim theo ph-ng php ny l 10% s cc.

b- Kim tra bng ph-ng php ng:

* Ph-ng php o m di : Nguyn l l s dng l thuyt t hin

t-ng m di : Ng-i ta g mt ba vo u cc, mt thit b ghi gn

ngay trn u cc ghi cc hiu ng v m di, kt qu o c s -c

my tnh x l v cho ra kt qu v cht l-ng cc.

Ph-ng php ny n gin, tc kim tra rt nhanh c th t ti

300 cc/ngy nh-ng nh-c im c bn ca ph-ng php ny l

chnh xc ch t yu cu vi su 20m tr li (ph-ng php bin dng

nh).



21

* Ph-ng php rung : Cc th nghim -c rung c-ng bc vi bin

khng i trong khi tn s rung c thay i trong mt di kh rng.

Tn s cng h-ng ghi -c s cho ta bit cc khuyt tt ca cc nh- tit

din b gim yu, c-ng b tng thay i...

Ph-ng php ch mi p dng ch yu Php bi th nghim kh

phc tp v i hi ng-i phn tch nh gi kt qu phi c trnh

cao, nhiu kinh nghim.

* Ph-ng php bin dng ln : Theo ph-ng php ny, xung chn

ng -c to bi ba c trng l-ng ln (15-20 T) huy ng ton

b kh nng chu ti ca t nn. Trong th nghim ch cn 2-3 nht ba

l nh-ng cc phi t dch chuyn cn thit. Ng-i ta ghi sng gia

tc v sng bin dng cho mi nht ba. Kt qu s -c x l bng cc

ch-ng trnh my tnh. Do nng l-ng s dng trong th nghim rt ln

nn trong thc t c th pht hin -c khuyt tt ca cc su

khng hn ch.

Nh-c im ca ph-ng php ny l thit b ca ba nng v cng

knh mt khc do lc xung ng ln c th lm hng cc.

* Ph-ng php tnh ng (Statnamic): Nguyn l l p dng nguyn

tc hot ng ca ng c tn la : thit b th nghim -c gn vo u

cc cng vi thit b gy n to ra phn lc trn u cc. Khi n, cc

thng s v gia tc, bin dng v chuyn v u cc s -c thit b th

nghim ghi li v nh cc ph-ng trnh v truyn sng s cho ta biu

quan h gia ti trng tc dng v chuyn v, t s xc nh -c ti

trng gii hn ca cc.

IV. Thi cng cc barret

Qui trnh thi cng cc barret v c bn ginh hn- thi cng cc khoan nhi, ch khc l thit b thi cng o h v hnh dng lng ct thp. Thi cng cc khoan nhi th dng l-i khoan hnh ng trn v lng ct thp hnh ng trn, cn thi cng cc baret th dng loi gu ngom hnh ch nht v lng ct thp c tit din hnh ch nht Cc cng vic thi cng cc barret nh- sau:

I- o h cc:

1. Thit b o h:



22

C th ni, hin nay thit b o h cc bart rt a dng. n-c ngoi, mi tng cng ty chuyn nghip c th c cc loi ring. Tuy nhin, ni chung th cc loi gu ngom o h c tit din hnh ch nht vi cnh ngn t 0,60m n 1,50m, cnh di t 2,00m n 4,00m ( phn ln l 3,00m ), cn chiu cao th c th t 6,00m n 12,00m. Thit b o c loi gu ngom o loi t st v loi ct. Cn khi cn ph dng loi u ph vi nhng bnh xe rng c-a c ln c gn l-i kim c-ng, mt loi thit b ca hng Bachy Soletanche ( Php ). Xem nh ca gu o cc barrette km y.

Ta c th hnh dung kch th-c ca gu o vi t l l ng-i ng cnh trong hnh.

Chun b h

o:

m bo cho gu o ng v tr v xung thng, cn phi lm nh- sau: o bng tay mt h c tit din ng bng kch th-c tit din cc bart v

su khong 0,80m n 1,00m. t vo h o ni trn mt khung c bng thp ch to sn. Nu khng c khung c bng thp ch to sn, th c th bng b tng hoc xy bng gch tt vi xi mng mc cao. Sau khi b tng cc xong th b khung c bng st ming h ra hoc p phn b tng hoc gch xy c nh h-ng ny i ( lp b tng dy khong 14cm, hoc lp gch dy khong 20m ). Cn ch thm rng m bo k thut , th phi c cng nhn iu khin



23

thit b thnh tho v tay ngh cao.

Ch to dung dch bentonite ( bn khoan ):

Dung dch bentonite dng gi cho thnh h o ca cc bart khng b st l.

a. Tnh cht dung dch bentonite mi ( tr-c khi dng ): Bentonite bt -c ch to sn trong nh my, th-ng ng thnh tng bao 50kg ( ging nh- bao xi mng ). Hin nay n-c ta phi nhp bentonite t n-c ngoi, ch yu t c do cng ty ERBSLOH ch to. Tu theo yu cu k thut khoan, o v tnh cht a tng, m ho tan t 20kg n 50kg bt bentonite vo 1 mt khi n-c.

Mt dung dch mi, tr-c lc s dng phi c cc c tnh sau y:

- Dung trng nm trong khong t 1,01 n 1,05 ( tr tr-ng hp loi bn st c bit, c th c dung trng n 1,15 ).

- nht Marsh > 35 giy. - tch n-c d-i 30 cm khi. - Hm l-ng ct bng 0. - -ng knh ht d-i 3mm. b. S dng v s l dung dch bentonite ( bn khoan ):

Qu trnh ch to, s dng, thu hi, x l v ti to s dng dung dch bentonite ( dung dch khoan, bn khoan ) -c thc hin nh- sau: Ch to dung dch bentonite mi gm: Cc bao bentonite mi gm:

- Cc bao bentonite bt -c cha trong kho ( bao ) hoc trong sil (bt).

- Ch to dung dch bentonite: + C th dng phu trn n gin. + C th dng my trn.

Th-ng trn 20kg n 50kg bt bentonite vi 1 mt khi n-c ( tu

theo yu cu ca thit k ). Ngoi ra, theo yu cu k thut c th, m c

th cho thm vo dung dch mt s cht ph gia mc ch lm cho n

nng thm, khc phc kh nng vn cc ca bt bentonite, tng thm

st hoc ng-c li gim st bng cch chuyn n thnh th lng,

chng li s nhim bn ca n bi xi mng hoc thch cao, gim pH

ca n hoc tng ln, gim tnh tch n-c ca n, v.v Sau dung dch khoan mi -c cha vo b cha bng thp, b cha xy gch, b cha bng cao su c khung thp hoc bng sil ( tu tng iu kin c th m s dng loi b cha no ). S dng dung dch bentonite mt cch tun hon. Trong khi khoan



24

hoc o h phi lun lun y dung dch khoan trong h. Dung dch khoan ny l dung dch mi. Gu o xung su n u th phi b xung ngay dung dch khoan cho y h. Trong khi o dung dch khoan bentonite b nhim bn ( do t, ct ) lm gim kh nng gi n nh thnh h, do phi thay th. lm vic , phi ht bn bn t h khoan, o ln -a v trm x l. C th dng loi bm chm t y h o hoc bm ht c mng lc trn mt t. Dung dch khoan -c -a v trm x l. Cc tp cht b kh i, cn li l dung dch khoan nh- mi ti x dng.

Dung dch sau khi -c x l phi c cc c tnh sau y:

- Dung trng d-i 1,2 ( tr loi dung dch nng c bit ). - nht Marsh nm gia 35 v 40 giy. - tch n-c d-i 40 cm khi. - Hm l-ng ct ti a 5%.

o h cc bart bng gu ngom:

Dng loi kch th-c gu o thch hp m bo -c kch th-c h o ng vi kch th-c cc bart theo thit k. Gu o phi th ng c nh h-ng t sn. H o phi m bo ng v tr v thng ng. Hin nay c thit b kim tra kch th-c hnh hc v thng ng ca h khoan, h o ( v d ti Vin Khoa hc cng ngh v Giao thng vn ti ). Trong lc o, phi cung cp th-ng xuyn dung dch bentonite ( bn khoan ) mi, tt vo y h o. Mt khc, mc cao ca dung dch bentonite trong h o bao gi cng phi cao hn mc n-c ngm ngoi h o ti thiu 2,00m. Dung dch bentonite -c tun hon v x l trong h o th-ng xuyn c dung dch bentonite tt, sch, mi. Phi m bo cho kch th-c hnh hc ( tit din v chiu su ) h o ng thit k v khng b st l thnh h. Mun vy, phi m bo cho dung dch bentonite thu hi ch cha cn lng t ct d-i 5%. ng thi cng c th kim tra thng ng v hin t-ng st l h o th-ng xuyn mt cch o-n gin bng dy di vi u dy l qu di nng.

Khi o n su thit k, phi tin hnh thi ra bng n-c c p lm sch y h. C th dng loi bm chm ht cn lng bng t ct nh ln. Cn ct to, cui si, vn th dng gu ngom vt sch ri -a ln. L-ng cn lng th-ng rt kh vt sch -c hon ton, do trong thc t c th cho php chiu dy lp cn lng d-i y h o nh thua 10cm. kim tra chiu dy lp cn lng c th dng dy di vi qu nng ng-i o c th cm nhn -c hoc dng thit b o bng ph-ng php chnh lch in tr kiu CZ.IIB do Trung Quc mi ch to.



25

Ch l vic thi ra y h o rt quan trng v ht sc ht sc cn thn. Do phi s dng thit b chuyn dng, thch hp v ng-i thc hin phi c tay ngh thnh tho, c kinh nghim v c tinh thn trch nhim. m bo -c y h cng sch th sc chu ti ca cc cng tt. Sau khi o xong h cc bart, phi kim tra li ln cui cng kch th-c hnh hc ca n. Kch th-c cnh ngn ca tit din ch -c php sai s 5cm, kch th-c cnh di ca tit din ch -c php sai s 10cm, chiu su h ch -c php sai s trong khong 10cm v nghing ca h theo cnh ngn ch -c sai s trong khong 1% so vi chiu su h o.

II- Ch to lng ct thp v th vo h o cho cc bart:

Sai s cho php v kch th-c hnh hc ca lng ct thp nh- sau:

- C li gia cc ct thp dc: 1mm; - C li gia cc ct thp ai: 2mm; - Kch th-c cnh ngn tit din: 5mm; - Kch th-c cnh di tit din: 10mm; - di tng cng ca lng ct thp: 50mm.

Chiu di ca mi on lng thp, tu theo kh nng ca cu, th-ng di t 6m n 12m. Ngoi vic phi t hp lng ct thp nh- thit k, tu tnh hnh thc t, nu cn, cn c th tng c-ng cc thp ai cho ( c -ng knh ln hn ct ai ) gng lng ct thp thp li cho chc chn, khng b xc xch khi vn chuyn. Khi th tng on lng ct thp vo h o sn cho cc bart, phi cn chnh cho chnh xc, phi thng ng v khng -c va chm vo thnh h o. Ni cc on lng ct thp vi nhau khi th xong tng on c th dng ph-ng php buc ( nu cc ch chu nn ) v dung ph-ng php hn in ( nu cc chu c lc nn, lc un v lc nh ). Ch :

- Khi th tng on lng ct thp xung h o, phi c cc thanh thp nh hnh kho ngng gi vo ming h n khi ri xung h.

- Trong tr-ng hp nh ca lng ct thp nm d-i mt t, hoc nm d-i mc ca dung dch betonite, th phi c du hiu bit -c v tr ca lng ct thp.

III- cc btng bart:

Sau khi vt sch y h ( dung dch bentonite ), trong khong thi gian khng qu 3 gi, phi tin hnh btng. btng bng ph-ng php va dy hay cn gi l btng trong n-c.



26

Cp phi btng thng th-ng nh- sau: Dng ct liu nh (1 x 2cm hoc 2 x 3cm ) bng si hay dm; ct vng khoang 45%, t l n-c trn ximng khong 50%; dng l-ng xi mng PC30 khong 370 n 400kg cho mi mt khi b tng. st ca btng trong khong t 13 n 18cm. C th dng thm ph gia nh-ng phi thn trng. Tr-c khi btng phi lp -ng cong b tng cho mt cc bart, theo tng t btng mt. Mt -ng cong btng c t nht 5 im phn b u n trn chiu di cc.

btng bng phu hoc mng nghing ni vi ng dn. ng dn lm bng kim loi, c -ng knh trong ln hn 4 ln -ng knh ca ct

liu ht v th-ng ln hn hay bng 120mm. ng dn -c t hp bng cc loi ng c chiu di khong 2 n 3m, -c ni vi nhau rt kht bng ren, nh-ng ng thi d tho lp. Tr-c khi btng vo phu hay mng nghing, phi c nt tm ( bng va ximng ct -t ) u ng dn. Khi btng y p phu, trong l-ng btng s y nt va xung dng btng chy lin tc xung h cc. Lm nh- vy trnh cho btng b phn tng.

ng btng c chiu di ton b bng chiu di cc. Tr-c lc btng n chm y, sau -c nng ln khong 15cm dng btng ( sau khi b nt tm ) chy lin tc xung y h cc v dng dn ln trn. Khi btng t d-i y h dng ln dn dn, th cng rt ng dn btng dn dn ln, nh-ng phi lun m bo cho ng dn ngp trong btng t-i mt on t 2 n 3m. Lm nh- vy btng khng b phn tng v sau khi ninh kt xong th btng khng b khuyt tt. Tc btng khng -c chm qu hay nhanh qu, tc hp l nht l 0,60 mt khi/pht. Khng nn bt u btng vo ban m m nn bt u b tng cho mi cc vo bui sng sm. Phi lin tc khng -c ngh cho xong tng cc trong mt ngy. Phi th-ng xuyn theo di ghi chp mc cao ca mt btng t-i dng ln sau mi xe t ( mch ) b tng vo h cc. Phi tnh -c khi l-ng btng cn thit xong cho mi cc; nh- vy c th ch ng -c trong vic chun b s xe btng cn thit mt cch hp l, y v kp thi. Khi l-ng btng thc t th-ng nhiu hn khi l-ng btng tnh ton ( theo kch th-c hnh hc ca h o cho cc ) l khong t 5% n 20%. Nu qu 20% th phi bo cho thit k kim tra li.

Mt s iu cn ch thm v qu trnh btng cc bart:



27

Khi b tng n vi ba mt nh cc th u ng dn btng ch cn ngp trong b tng t-i khong 1m. Nn b tng cao hn mc nh cc l thuyt khong 5cm. Khi rt ng dn ra khi cc phi nh nhng, t t trnh cho btng b xo trn. Phi m bo cho lp btng bo v ct thp dy hn hay ti thiu l 7cm. Ch -c o h cc bn cnh h ang btng cc vi iu kin: + Khong cch gia hai mp cnh cc bart ln hn hay bng 2b ( trong b l cnh ngn ca tit din cc ). + Btng cc xong trn 6 ting ng h ( v sau 6 gi th btng cc mi cng cn thit ). Chiu cao gii hn ct u cc ( on btng xu li ct thp cu to vo i cc ) tnh t gia mt phng u cc theo l thuyt v u cc lc kt thc l: + 0,3 ( Z + 1 ), khi cao l thuyt ca mt phng u cc nm chiu su Z (m) d-i mt sn cng tc, nh hn 5m. + Bng 0,8m khi cao l thuyt ca mt phng u cc nm chiu su d-i mt sn cng tc, ln hn 5m. Chiu cao ti thiu ct u cc -c xc nh bi ng-i thi cng sao cho btng u cc thc t l tt. - Khi o h thi cng cc v lc btng cc phi ch khng -c thc hin khi trong chiu su ca cc c dng n-c ngm ang chy v n s lm st l thnh h v hng btng. Trong tr-ng hp ny phi bo cho t- vn thit k x l. C th x l bng cch h ng vch bng thp.

Kim tra cht l-ng btng cc bart:

Quy trnh m bo cht l-ng thi cng cc bart, cng ging nh- cc

khoan nhi, thc hin theo TCXD 206 : 1988 - Cc khoan nhi - yu cu

v cht l-ng thi cng. Khi btng ninh kt xong ( sau 28 ngy ) th

kim tra cht l-ng bng ph-ng php khng ph hu.

C nhiu ph-ng php kim tra cht l-ng btng cc. Ph-ng

php ph bin nht v m bo tin cy hn c - ph-ng php siu m

truyn qua. Nh ph-ng php siu m truyn qua, ng-i ta pht hin

-c cc khuyt tt ca btng trong thn cc mt cch t-ng i chnh

xc. 1- Nguyn l cu to thit b kim tra siu m truyn qua:

Thit b kim tra cht l-ng btng cc nhi, cc bart, t-ng trong

t, v.v theo ph-ng php siu m truyn qua c s cu to nh- sau:



28

- Mt u o pht sng dao ng n hi ( xung siu m ) c tn s

truyn sng t 20 n 100kHz;

- Mt u o thu sng: u pht v u thu -c iu khin ln

xung ng thi nh h thng cp ti in v nm trong hai ng ng

y n-c sch.

- Mt thit b iu khin cc dy cp -c ni vi cc u o cho

php t ng o chiu su h u o;

- Mt b thit b in t ghi nhn v iu chnh tn hiu thu -c;

- Mt h thng hin th tn hiu;

- Mt h thng ghi nhn v bin i tn hiu thnh nhng i l-ng

vt l o -c;

- C cu nh tm cho hai u o trong ng o.

Ph-ng php kim tra

Cc b-c tin hnh nh- sau:

- Pht xung siu m t mt u o t trong ng o ng y n-c sch v truyn qua btng cc

- Thu sng siu m mt u o th 2 t trong ng o khc cng cha y n-c sch, cng mc vi u pht

- o thi gian truyn sng gia hai u o trn sut chiu di ca ng t sn, t u cc n chn cc

- Ghi s bin thin ca tn hiu thu -c - Nh sng siu m truyn qua m thit b c th ghi li ngay

tnh hnh truyn sng qua be tng ca cc v cc khuyt tt

ca b tng cc

t-ng trong t

Thi cng t-ng trong t thc cht l thi cng t-ng barrette, nhng panel ( mt on t-ng khong 2.4 mt ) -c ni lin nhau qua cc giong chng thm to thnh mt bc t-ng trong t bng b tng ct thp V c bn thi cng t-ng trong t cng ging nh- thi cng cc barrette. Trnh t thi cng t-ng trong t bng ph-ng php b tng ti ch -c thc hin nh- sau:

o h cho panen ( barrette ) u tin

B-c 1 : Dng gu o thch hp o mt phn h n chiu su thit

k . Ch o n u, phi cung cp kp thi dung dch bentonite n



29

, cho y h o, g- cho thnh h o khi b st l

B-c 2 ; o phn h bn cnh, cch phn h u tin mt gii t.

Lm nh- vy khi cung cp dung dch bentonite vo h s khng lm

l thnh h c

o nt phn t cn li ( o trong dung dch bentonite ) hon thnh

mt h cho panel u tin theo thit k.

H lng ct thp, t giong chng thm v b tng cho panel

barret u tin

Cc b-c thc hin nh- sau:

B-c 4 : H lng ct thp vo h o sn, trong dung dch bentonite .

Sau t giong chng thm CWS vo v tr

B-c 5 : b tng theo ph-ng php va dng, thu hi dung dch

bentonite v trm x l

B-c 6 : Hon thnh b tng cho ton b panel th nht

o h cho panel barret tip theo v tho ton b g lp giong

chng thm

Cc b-c thc hin nh- sau: B-c 7 : o mt phn h su n ct thit k y Panel ( o trong dung dch bentonite ). Ch o cch panel u tin mt di t

B-c 8 : o tip n st Panel s 1

B-c 9 : G b g lp giong chng thm bng gu o khi cnh ca

panel s 1, nh-ng giong chng thm CWS vn nm ti ch tip gip

gia 2 panel

H lng ct thp,t giong chng thm v b tng cho panel

barret th hai

B-c 10 : H lng ct thp xung h o cha y dung dch

bentonite . Sau t b g lp vi giong chng thm CWS vo v tr

B-c 11: b tng theo ph-ng php va dng nh- panel s 1

B-c 12 : Tip tc o h cho panel th- 3 pha bn kia ca panel s

1. Thc hin vic h lng ct thp, t b g lp cng giong chng

thm v b tng cho panel th 3 ging nh- thc hin cho cc panel

tr-c

Tip tc tin hnh theo qui trnh thi cng nh- vy hon thnh ton

b bc t-ng trong t theo thit k

Kim tra cht l-ng b tng dng ph-ng php siu m ging nh-



30

kim tra cc barrette.

Ngoi ra cn kim tra cht l-ng chng thm n-c qua t-ng.

Th-ng gp l hin t-ng thm chung quanh khu vc tm giong. Cha

bng ph-ng php bm va epoxy c p lc epoxy lp y nhng ch

thm.

B Xy dng

H-ng dn k thut phng nga s c thi cng h o trong vng t yu

H Ni - 2006

2

Li ni u

H-ng dn k thut ny do Vin Khoa hc Cng ngh Xy dng bin son, V Khoa hc cng ngh ngh, B Xy dng ban hnh.

H-ng dn k thut phng nga s c thi cng h o trong vng t yu

1. Phm vi p dng 1.1 H-ng dn ny p dng cho cng tc thi cng cc h o cng trnh dn dng v

cng nghip trong vng c mt hoc nhiu lp t yu trong phm vi t mt t n ba ln su h o.

1.2 H-ng dn bao gm cc yu cu k thut i vi cc cng tc kho st a k

thut, thit k bin php thi cng, thi cng, cng tc quan trc a k thut trong qu trnh thi cng nhm phng nga s c cho h o, cho kt cu mng v phn ngm bn trong h o v cc cng trnh ln cn h o.

3

2. Gii thch t ng Trong h-ng dn ny, cc t ng d-i y -c hiu nh- sau

2.1 t yu: l t loi st c tnh nn ln cao, kh nng chu ti rt thp. Mt hoc

mt s tnh cht vt l, bn v bin dng ca loi t ny nm trong khong gi tr th-ng gp nh- sau y: a) Tnh cht vt l:

- h s rng e > 1

- st B > 1 b) bn:

- sc mang ti tiu chun RH < 0,05MPa

- sc khng ct khng thot n-c Cu< 0,005 MPa;

- sc khng xuyn tiu chun N30 < 4 ba/30cm;

- sc khng xuyn tnh qc < 0,8 MPa; c) Tnh cht bin dng:

- h s nn ln a1-2 > 0,005 MPa-1 ;

- mun bin dng E < 2,0 MPa. 2.2 Mt n nh thnh (mi) h o: l hin t-ng st l, tr-t thnh (mi) h o.

2.3 Ln mt t xung quanh h o: l hin t-ng b mt t quanh h o b ln,

nt khi thi cng h o.

2.4 y tri y h o: l hin t-ng y h o b tri ln so vi cao o.

2.5 H- hng kt cu mng v phn ngm bn trong h o l hin t-ng: a) phn u cc ca mng cng trnh b chuyn dch khi v tr thi cng tr-c

khi o; b) cc kt cu hoc b phn kt cu nh- lp b tng lt, bn mng thi cng

trong h o b nt, vnh lm gim hoc mt kh nng lm vic theo yu cu ca thit k.

2.6 H- hng cng trnh ln cn h o: l hin t-ng ln, dch chuyn, nt v bin

dng ca kt cu v cng trnh ln cn xung quanh h o khi b nh h-ng ca qu trnh thi cng h o.

2.7 Cng tc quan trc a k thut l cng tc theo di, o c nh k, x l, biu din v l-u gi cc s liu quan trc a k thut thu -c.

3. s c th-ng gp v nguyn nhn s c khi thi cng h

o

3.1 S c th-ng gp khi thi cng h o trong vng t yu: a) mt n nh thnh (mi) h o; b) ln b mt t xung quanh h o;

4

c) y tri y h o; d) h- hng kt cu mng v cc b phn ngm xy dng bn trong h o v

cc cng trnh ln cn h o. 3.2 Nguyn nhn ch yu gy s c khi thi cng h o:

a) dch chuyn ca cc lp t yu t bn ngoi vo pha trong h o; b) h mc n-c ngm, tng p lc n-c d-i y h o.

4. Cc yu cu v bin php phng nga s c

4.1 Yu cu chung 4.1.1 H o cn -c coi nh- mt hng mc cng trnh c lp v phi -c thc

hin theo trnh t cht ch: kho st a k thut; thit k bin php thi cng; thi cng v quan trc a k thut trong qu trnh thi cng; hon cng v nghim thu h o.

4.1.2 Trong tr-ng hp c nhiu h o trn cng mt bng, cn thit k bin php thi

cng tng th cho cc h o nhm hn ch nh h-ng gia chng vi nhau. 4.1.3 Nh thu thit k cn -a ra nhng gii php thit k hp l hoc phi c nhng

khuyn co cn thit nhm trnh nhng nh h-ng bt li ca qu trnh thi cng h o. Trong tr-ng hp c th, cn hn ch ti a vic h su y mng v y cc phn ngm ca cng trnh.

4.2 Yu cu i vi cng tc kho st a k thut

Ngoi nhng quy nh v cng tc kho st xy dng theo quy nh hin hnh, vic kho st a k thut phc v thi cng h o cn l-u nhng yu cu sau: a) phi xc nh cc thng s cu to a tng, c bit ch trng quy lut

phn b theo din, theo chiu su ca cc tng t yu; b) xc nh cc tnh cht c l ca t phi ph hp vi m hnh v ph-ng php

tnh ton -c s dng trong thit k bin php thi cng; c) xc nh iu kin a cht thy vn, c bit s tn ti, c im v ng

thi ca cc tng cha n-c.

4.3 Yu cu i vi thit k bin php thi cng 4.3.1 u tin bin php thi cng h o vi mi dc t nhin cho cc tr-ng hp mt

bng thi cng rng, khng c cc cng trnh xy dng lin k. Trnh t thi cng

th-ng l : o t n su an ton, thi cng mt phn kt cu mng (cc), o t n su thit k, thi cng tip phn kt cu cn li v lp t hon cng h o.

4.3.2 Cn t chc thi cng o th vi cc quan trc a k thut ph hp la chn

bin php k thut thi cng thch hp. Khi chn bin php thi cng h o vi mi dc t nhin, cn xc nh dc mi h o bng s liu kho st a k thut hoc bng thc nghim ti hin tr-ng.

4.3.3 Khi khng c kh nng thi cng o t vi mi dc t nhin, c th p dng

bin php thi cng vi cc gii php chng gi thnh h o sau: a) t-ng c vn thp;

5

b) t-ng c bng cc t xi mng; c) t-ng c bng cc b tng ct thp c sn hoc khoan nhi; d) t-ng b tng ct thp trong t.

4.3.4 Khi p dng bin php chng gi thnh h o bng t-ng c, cn xc nh cc thng s k thut ca t-ng c nh- v tr, su, kch th-c tit din ngang, h thng kt cu neo v chng t-ng c (nu cn), yu cu kh nng chng thm ca t-ng c (nu cn).

4.3.5 Cc thng s cn xc nh khi tnh ton v thit k bin php thi cng bao gm:

- h s an ton chng tr-t t thnh h o;

- ln, ln khng u b mt t xung quanh h o;

- chuyn v ca h thng t-ng c;

- gi tr ng sut, bin dng ca thanh chng, neo t-ng c (nu c);

- cc thng s lin quan n n nh y h o (tr s nng tri y h o, gi tr p lc n-c tc dng d-i y h o, v.v...);

- l-u l-ng n-c chy vo h mng, mc h thp mc n-c ngm;

- d bo kh nng gy h- hng i vi cc cng trnh ln cn h o. 4.3.6 Khi thit k bin php thi cng cn l-u :

a) khi c nhiu h o trn mt bng, phi -a ra trnh t thi cng -u tin nh- thi cng cc h o su tr-c, cc h o nng sau;

b) phi ch r nhim v cng tc quan trc a k thut trong qu trnh thi cng; c) bin php x l cc tnh hung c du hiu xy ra s c.

4.3.7 Thit k bin php thi cng phi -c nh thu thi cng xy dng thm tra v ph duyt tr-c khi thi cng.

4.4 Yu cu i vi cng tc thi cng 4.4.1 Thi cng o t phi tun th thit k bin php thi cng -c ph duyt. 4.4.2 Phi o u tng lp trn ton b din tch h o, trnh o su cc b. 4.4.3 Hn ch ti a vic gia ti xung quanh h o, khng tp trung cc ph-ng tin

thi cng trn b mt quanh h o, phi vn chuyn t o ra xa phm vi h o.

4.4.4 Phi lp u tng lp trn c din tch h o. Phi kp thi chn lp cht ct vo

cc khong trng rt c, hn ch ti a ln khi t trn mt gy h- hng cng trnh ln cn khu vc rt c.

4.4.5 Trong qu trnh thi cng, nh thu thi cng xy dng phi quan st, pht hin cc

biu hin bt th-ng trong qu trnh o v kp thi bo co cho Ch u t-. Khi cn thit, phi tm dng thi cng theo di v x l.

4.5 Yu cu i vi cng tc quan trc a k thut 4.5.1 Ph-ng n quan trc a k thut -c nh thu thi cng xy dng thit lp v

phi -c Ch u t- chp thun.

6

4.5.2 Ph-ng n quan trc a k thut cn ch r cc thng s, s l-ng v v tr cn

o c quan trc; cc thit b dng c o v ph-ng php lp t, ly s liu; chu k o; ph-ng php x l, biu din, gii thch v nh gi s liu; cc gi tr quan trc cnh bo nguy c s c.

4.5.3 Cc thng s a k thut cn quan trc trong qu trnh thi cng h o c th

l:

- ln ca mt t quanh khu vc o ;

- chuyn v ngang ca thnh h o ;

- mc n-c v mc thy p ca cc tng cha n-c ;

- p lc n-c l rng ;

- chuyn v ca t-ng c, bin dng ca h neo hoc h thanh chng ;

- ln v h- hng kt cu ca cng trnh ln cn.

5. X l tnh hung khi c du hiu s c

5.1 Khi xut hin cc gi tr quan trc cnh bo c du hiu s c, nh thu thi cng xy dng cn bo ngay vi Ch u t-. Trong tr-ng hp cn thit, c th tm ngng thi cng v c bin php x l thch hp.

5.2 Cc bin php k thut c th p dng nhm ngn nga pht sinh s c c th l:

a) gim ti trn khu vc ln cn h o nh- di chuyn t tha, cc vt t-, ph-ng tin thi cng ra xa h o;

b) san lp li phn h o; c) gim dc thnh (mi) h o; d) gia c-ng cc h neo hoc kt cu chng thnh h o; e) gim thiu bm, ht h thp mc n-c ngm; f) gim thiu cc hot ng thi cng gy chn ng mnh ti cc khu vc ln

cn nhng, p cc, hot ng vn chuyn bng cc xe ti nng. 5.3 Sau khi thc hin mt hoc mt s trong cc bin php nu trn v kt qu quan

trc cho thy s c -c ngn chn, cn xc nh nguyn nhn, iu chnh thit k bin php thi cng.

5.4 Trong tr-ng hp xy ra s c, cn thc hin cc cng vic theo quy nh hin

hnh v qun l s c cc cng trnh xy dng.

6. Nghim thu h o

6.1 Nghim thu h o thc hin theo quy nh hin hnh nh- i vi mt hng mc cng trnh.

6.2 Cn c nghim thu h o bao gm:

a) bo co kho st a k thut phc v thi cng h o (nu c); b) thit k bin php thi cng h o -c duyt;

7

c) bn v hon cng cc kt cu bn trong h o tr-c v sau khi thi cng h o;

d) bo co quan trc a k thut trong qu trnh o; e) bo co x l tnh hung khc phc s c (nu c).

Ch-ng 3

Thi cng tng hm bng cng ngh top down

I. T ng quan:

Mt trong nhng vn c bn khi thi cng tng hm nh cao tng l gii php n nh thnh h o trong qu trnh thi cng. Trong thc t c nhiu ph-ng php gi thnh h o tu thuc vo su h o, iu kin a cht, mt bng thi cng gii php kt cu...

Vi cng trnh Trung tm thng mi v vn phng cao cp, phn ngm thp nht (y i) nm su 14.30m (13.3m so vi mt t). T-ng tng hm b tng ct thp dy 800mm -c s dng t-ng chn cho h o trong qu trnh thi cng phn ngm. Vn t ra l lm th no gi vch h o trong sut qu trnh thi cng phn ngm. Cc ph-ng php -c s dng nhiu n-c ta bao gm: khoan neo t-ng vo t (Anchors - tiebacks), chng trc tip ln thnh h o v ph-ng php mi Top-Down. Vi thc t cng trnh Trung tm thmg mi v vn phng cao cp c chiu su tng hm tng i ln, tin hnh thi cng phn ngm mt cch an ton, nhanh chng v tin li, ta s dng ph-ng php thi cng mi theo cng ngh TOP DOWN.

Hnh nh v cng ngh thi cng Top Down trn th gii:

Tm hiu gii php thi cng neo ta thy c mt s hn ch:

+ Thi cng neo phc tp.

+ Ph thuc vo cc cng trnh ln cn.

+ Ph thuc iu kin a cht cng trnh.

+ Chi ph v gi thnh v mt s nh-c im ca n.

Vi nhng hn ch trn em quyt nh la chn thi cng bng cng ngh TOP DOWN. Vi cng ngh TOP DOWN c mt s -u im v hn ch nh- sau:

*/. u im:

+ Li dng h sn tng trn thi cng lm h chng thnh h o.

+ H chng n nh tt trong qu trnh thi cng.

+ Rt ngn thi gian thi cng.

*/. Hn ch:

+ Thi cng phn ngm su kh khn cho cng tc vn chuyn t v vt liu khc.

+ My mc yu cu hin i.

i vi nhng cng trnh c nn t tt, c th gia c-ng nn t bng cch m cht v lt va xi mng, xy gch trc tip ln nn t theo hnh dng ca sn, s-n thay cho h coppha v gio chng khi thi cng phn sn tng ngm.

Ph-ng php TOP-DOWN l ph-ng php thi cng t-ng i mi vi n-c ta. Kt cu t ct mt t tr xung v li dng h dm - sn ca cc tng hm lm h

thng chng t-ng tng hm thay cc h thanh chng thng th-ng. Tuy nhin cng ngh TOP DOWN cn nhiu hn ch v cng tc o t v vn chuyn t t tng hm ln trn, nht l i vi cc tng hm su nh- cng trnh ny (do my mc v ph-ng tin thi cng cn hn ch).

1.1. Thit b phc v thi cng:

- Phc v cng tc o t phn ngm gm: my o t loi nh (my con cua),

my san t loi nh, my lu nn loi nh, cc cng c o t th cng, my khoan

- Phc v cng tc vn chuyn: hai cn trc COBELCO 7045 phc v chuyn t, vt liu, thng cha t, xe ch t t .

- Phc v cng tc khc: hai my bm, hai thang thp t ti hai li ln xung, h thng n chiu sng, in chiu sng d-i tng hm, khoan, my hn...

- Phc v cng tc thi cng b tng: trm bm b tng, xe ch b tng th-ng phm, cc thit b phc v cng tc thi cng b tng khc.

- Ngoi ra tu thc t thi cng cn c cc cng c chuyn dng khc. 1.2. Vt liu:

a. B tng:

Do yu cu thi cng gn nh- lin tc, do nu ch b tng tng trn c-ng mi tho vn khun v o t thi cng tip phn d-i th thi gian thi cng ko di. m bo tin nn chn b tng cho cc cu kin t tng 1 xung tng hm l b tng c ph gia tng tr-ng c-ng nhanh c th cho b tng t c-ng chu lc sau t ngy (theo thit k cng trnh ny l 7 ngy). Cc ph-ng n (xem

ph lc 6).

b. Vt liu khc:

- Khi thi cng sn - dm tng hm th nht (ct - 4.0m), tin hnh o bc mt lp t c chiu dy 1,7m (n ct 2,2m) t hp mt lp gio chng dm, sn.

- Khi thi cng phn ngm c th gp cc mch n-c ngm c p nn ngoi vic b tr cc trm bm thot n-c cn chun b cc ph-ng n vt liu cn thit kp thi dp tt mch n-c.

- Cc cht chng thm nh- va Sika hoc nh t-ng Laticote hoc sn Insultec.

Tit din cu kin ct chng v dm sn + dm chng ging nh- sau:

x x

y

y

x

y

x

y

y

x x

t it d in d m c hn h

y

t it d in c t t m & c t c n h

t d d m ph I40.

t it d in d m bin .

d m ph

bul n g

in h c h t

c h i t it l in kt d m bin v o t n g d ia phr a g m b n g in h c h t . t l 1/ 10

s n g ia c n g

c h : kho n g c c h c c in h c h t 30 c m

kho n g c c h c c bu l n g 60 c m

t n g d ia phr a g m

s n g ia c n g

in h c h t

bul n g

II. Quy trnh thi cng Top Down cho phn ngm:

Cc giai on thc hin:

II.1. Giai on 1: Thi ct cc ct chng bng thp hnh.

Giai on ny -c thc hin ngay t qu trnh thi cng cc khoan nhi. Trong cc ct ny c cc ct l c nh s dng vnh vin cho cng trnh v c nhng ct ch l gii php chng tm chng gi t-ng trong t, sau khi thi cng phn ngm xong th s ct b i. II.2. Giai on 2: Thi cng tng ngm 1.

III. trnh t thi cng top - down cho phn ngm cng trnh

i vi cng trnh ny, trnh t thi cng -c lm theo cc b-c sau: II.1. Giai on 1: Thi cng cc ct chng bng thp hnh :

Ph-ng n chng theo ph-ng ng l dng cc ct chng bng thp hnh ,

trong cc ct ny c nhng ct l c nh, c nhng ct l tm thi khi thi cng

phn ngm xong ta s ct b i.

Cc ct ny di 17 m , c tit din :

Ct -c cm su vo cc khoan nhi 2m.

Cng on ny -c thc hin nh- sau:

- nh v li tim ct trn mt t sau khi thi cng xong cc nhi ngay d-i chn ct. - Dng cn trc h t t ct thp hnh xung lng h khoan , tay cn trc khng dch chuyn m ch cun tang cp trnh chm ct vo thnh h khoan - Rung lc hoc dng cn trc n ct thp sao cho ngp su trong b tng cc khong 1m - Chnh li trc thng ng ca ct thp cho trng vi trc ct v c nh ct thng ng bng h chng tm - b tng vo h sao cho lm y thm h o khong 1m - ct lm y phn cn li ca h khoan - Bo v trnh va chm vo ct thp Ct thp sau khi chn vo cc nhi ch cn nh ln trn mt t 2m ( nh ln khi sn 1m ) . Cn trc phc v thi cng loi ct ny dng lun cu COBELCO 7045 phc v thi cng khoan nhi. Cc thng s cu u tho mn vic cu lp ct thp di 17m.

x x

y

y

c n h c n h c n h c n h c n h c n h c n h c n h c n h

c n h c n h c n h c n h c n h c n h c n hc t t m c t t m

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h c n h c n h c n h c n h c n h c n h c n h c n h c n h c n h c n h c n h c n h c n h c n h

c n h

c n h

c t t m c t t m

c t t m c t t m c t t m c t t m c t t m c t t m c t t m c t t m c t t m


c

t t

m

c

t t

mc

t

tm

c

t t

mc

t

tm

c

t t

m

c

t t

m

c

t t

mc

t

tm

c

t t

mc

t

tm

c

t t

m

c

t t

mc

t

tm

c t t m

c t t mc t t m

c t t m

c t t m

c t t m

c t t m

c t t m

mt b n g c t c h n g b n g t hp hn h.

a

b

c

d

e

f

g

h

i

k

l

m

1 2 3 4 5 6 7 8 9 10 11 12 13

a

b

c

d

e

f

g

h

i

k

l

m

14

1 2 3 4 5 6 7 8 9 10 11 12 13 14

II.1. Giai on 1: Thi cng o t v chng gi t-ng vy tng hm -1 .

Giai on ny gm cc b-c sau y:

1) Thi cng o t: Ct sn tng hm 1 nm su 4,2m. Nh-ng lp

ghp cc dm sn v dm chng ging ta cn phi o su thm 1m na, vy chiu

su o t giai on 1 l ct 5,2m ( so vi mt t l su 4,2m).

- 1.0

-5.2

b c e f g h k la m

Cn t r c t h p1

giai on ny t-ng lm vic dng cng xon, nh-ng ta thy rng phn

cngxon l rt nh so vi chiu su 22m ca t-ng vy, khng cn chng .

Mi lung o rng 6m. My o i theo ph-ng dc nh, li phn t quanh ct thp hnh v st t-ng o bng th cng.

t o -c ln xe BEN t vn chuyn ra khi cng tr-ng. Khi l-ng t cn o:

V = ho Fh o = 4,2 36 65 x 1,5 = 14742m3 H s 1,5 l h s ni ln kh nng tng -c din tch s dng my o

- Dung my o gu nghch E vi cc thng s sau thc hin cng tc o t. + Dung tch gu: q = 0.25m

+ Bn knh o: R = 5m

+ Chiu cao t: H = 2.2m

+ Trng l-ng my: Q = 5.1T

+ B rng my: b = 2.1 m

+ Chiu su o t ln nht: Ho = 3.5m

+ Thi gian 1 chu k tck = 20 s

- Cng sut my o:

)/( 3 hmKNK

KqN tgck

t

d

Trong : + K = 1.2: h s y gu ph thuc vo loi t + Kt = 1.1: h s ti ca t + Nck = 3600/Tck

+ Tck = tck Kvt Kquay = 20 1.1 1 = 22 s + tck = 20 khi gc quay 90

o + Kvt = 1.1 khi t ln thng + Kq = 1 khi gc quay l 90

o Nck = 3600/22 = 163.63 (m3/h)

Ktg = 0.8: h s s dng thi gian. Vy:

)/3(7.358.063.1631.1

2.125.0 hmKN

K

KqN tgck

t

d

S ca my phc v cng tc o t thi cng tng ngm -1:

n = 14742/(35,7 8) = 52 (ca).

Khi l-ng t o th cng l: V = 4700(m2)*4,2 14742 = 4998m3

H ng d i c huyn c a my o t

mt b n g t h i c n g o t t h i c n g t n g hm -1



c

t t

m

c

t t

mc

t

tm

c

t t

mc

t

tm

c

t t

m

c

t t

m

c

t t

mc

t

tm

c

t t

mc

t

tm

c

t t

m

c

t t

mc

t

tm

c t t m

c t t mc t t m

c t t m

c t t m

c t t m

c t t m

c t t m

c n h c n h c n h c n h c n h c n h c n h c n h c n h

c n h c n h c n h c n h c n h c n h c n hc t t m c t t m

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h

c n h c n h c n h c n h c n h c n h c n h c n h c n h c n h c n h c n h c n h c n h c n h c n h

c n h

c n h

c t t m c t t m

2). Lp h dm sn v dm chng ging:

Thi cng giai on ny cn ch rng: cc dm tm c tc dng chng ging phi

-c lp thp hn cc dm sn mt khong bng chiu cao dm sn, c iu ny l

th mi hon thin -c vic lp cc dm sn sau ny.

- 1.0

-5.2

- 4.2: c t hm -1

d m s n d m c h n g

c t c n h c t tm

- 1.0

-5.2

b c e f g h k la m

- 4.2: c t hm -1

Cn t r c t h p2

II.2. Giai on 2: Thi cng o t v chng gi t-ng vy tng hm - 2 .

giai on ny trnh t v cch thi cng hon ton ging nh- giai on thi

cng tng hm 1.

1) Thi cng o t: Ct sn tng hm 2 nm su ct 7,8m. Nh-ng lp

ghp cc dm sn v dm chng ging ta cn phi o su thm 1m na, vy chiu

su o t giai on 1 l ct 8,8m ( so vi mt t l su 7,8m).

Khi o t giai on ny cn ch rng, su ny xe Ben khng xung

d-i hm -c, m ta phi dng cn trc thp cu nhng thng t t ln xe Ben

sn trn mt t.

Khi l-ng t cn o:

V = ho Fh o = 3,6 36 65 x 1,2 = 10109 m3 H s 1,2 l h s ni ln kh nng tng -c din tch s dng my o


+ Bn knh o: R = 5m



+ B rng my: b = 2.1 m



- Cng sut my o:

)/( 3 hmKNK

KqN tgck

t

d




o Nck = 3600/22 = 163.63 (m3/h)


)/3(7.358.063.1631.1

2.125.0 hmKN

K

KqN tgck

t

d


n = 10109/(35,7 8) = 36 (ca).

Khi l-ng t o th cng l: V = 4700(m2)*3,6 14742 = 2178m3

- 1.0

-5.2

b c e f g h k la m

- 4.2: c t hm -1 - 4.2: c t hm -1

-9.8

Cn t r c t h p3


Cch lp hon ton t-ng t nh- i vi dm sn tng 1.

- 1.0

-5.2

b c e f g h k la m

- 4.2: c t hm -1

-8.8

-7.8: c t hm -2

- 4.2: c t hm -1

-7.8: c t hm -2

Cn t r c t h p4

o t n su ny th p lc t v p lc n-c tc dng ln 1m b rng

ca t-ng vy ti cao mc sn tng 1 l N = 13,57Tn. Phn tch h bng

ph-ng php Phn t hu hn tm chuyn v ca t-ng vy.

S phn tch nh- sau.

Kt qu phn tch nh- sau:

TABLE: Joint Displacements

Joint OutputCase CaseType U1 U2 U3 R1 R2 R3

Text Text Text m m m Radians Radians Radians

21 DEAD LinStatic 1.11E-05 6.64E-07 -1.53E-05 2.87E-07 2.53E-06 1.36E-06


Ta thy rng nh t-ng vy (21) c chuyn v l 1.11E-05m, chuyn v t-ng ti

su sn tng hm 2 l 1.22E-05m. Nh- vy chuyn v ny rt nh, chng t

ph-ng n chng t-ng nh- vy ti thi im ny l hp l.

II.3. Giai on 3: Thi cng o t v chng gi t-ng vy tng hm - 3 .

1) Thi cng o t: Ct sn tng hm 3 nm su ct 11,4m. Nh-ng ct

sn tng hm 3 l mt trn ca i mng b, vy khng phi lp dm sn na m

l lp cc h dm chng ging tm. Vy su cn o l -11,4m.

- 4.2: c t hm -1

-7.8: c t hm -2

- 4.2: c t hm -1

-7.8: c t hm -2

b c e f g h k la m

- 1.0

-5.2

-8.8

-11.4

Cn t r c t h p5

Khi l-ng t cn o bng my:

V = ho Fh o = 2,6 36 65 x 1,2 = 7301 m3 H s 1,2 l h s ni ln kh nng tng -c din tch s dng my o


+ Bn knh o: R = 5m



+ B rng my: b = 2.1 m



- Cng sut my o:

)/( 3 hmKNK

KqN tgck

t

d




o Nck = 3600/22 = 163.63 (m3/h)


)/3(7.358.063.1631.1

2.125.0 hmKN

K

KqN tgck

t

d


n = 7301/(35,7 8) = 26 (ca).

Khi l-ng t o th cng l: V = 4700(m2)*2,6 7301 = 4920 m3.


- 4.2: c t hm -1

-7.8: c t hm -2

- 4.2: c t hm -1

-7.8: c t hm -2

b c e f g h k la m

- 1.0

-5.2

-8.8

-11.4

Cn t r c t h p6

o t n su ny th p lc t v p lc n-c tc dng ln 1m b rng ca

t-ng vy ti cao mc sn tng 1 l N1 = 13,57tn, ti cao mc sn tng hm

2 l N2 = 18,8 tn. Phn tch h bng ph-ng php Phn t hu hn tm chuyn

v ca t-ng vy.

S phn tch nh- sau.









su sn tng hm 2 (21) l 3.44E-05m, chuyn v t-ng ti su sn tng

hm 3 (23) l 3.5E-05m. Nh- vy chuyn v ny rt nh, chng t ph-ng n

chng t-ng nh- vy ti thi im ny l hp l.

II.4. Giai on 4: Thi cng o t v chng gi t-ng vy tng I

m ng.

1) Thi cng o t: Ct y nm su ct 14,1m. Nh-ng phi c lp btng

lt dy 20 cm , vy su cn o l ct -14,3m.


n = (2,0*36*65)/(35,7 8) = 16 (ca).

Khi l-ng t o th cng l: V = 4700(m2)*2,6 4680 = 4710 m3.

- 4.2: c t hm -1

-7.8: c t hm -2

- 4.2: c t hm -1

-7.8: c t hm -2

b c e f g h k la m

- 1.0

-5.2

-8.8

-11.4

-14.3

Cn t r c t h p7

o t n su ny th p lc t v p lc n-c tc dng ln 1m b rng ca

t-ng vy ti cao mc sn tng 1 l N1 = 13,57tn, ti cao mc sn tng hm

2 l N2 = 18,8 tn, ti cao mc sn tng hm 3 l N3 = 20,45 tn.

Phn tch h bng ph-ng php Phn t hu hn tm chuyn v ca t-ng

vy.

S phn tch nh- sau:





17 APLUC LinStatic 3.05E-05 2.01E-06 -2.40E-05 -8.86E-08 9.10E-06 1.56E-06

19 APLUC LinStatic 5.67E-05 1.69E-06 -4.51E-05 8.75E-08 5.28E-06 2.47E-06




su sn tng hm 2 (29) l 5.67E-05m, chuyn v t-ng ti su sn tng

hm 3 (21) l 6.89E-05m, chuyn v t-ng ti su nh i (23) l 6.99E-05m.

Nh- vy chuyn v ny rt nh, chng t ph-ng n chng t-ng nh- vy l hp

l.

II.5. Giai on 5: Thi cng btng l t dy 20 cm.

Cn m nn tht k v s l chng thm s b tr-c khi btng lt.

Th tch btng lt cn l: V = 4700*0,2 = 940m3.

- 4.2: c t hm -1

-7.8: c t hm -2

- 4.2: c t hm -1

-7.8: c t hm -2

b c e f g h k la m

- 1.0

-5.2

-8.8

-11.4

-14.3

-11.4: c t hm -3

c t t mc t c n h

bt n g l t

d y 20 c m

bt n g l t

d y 20 c m

bt n g l t

d y 20 c m

Cn t r c t h p8

II.6. Giai on 6: Thi cng l p dng ct thp v btng I m ng

b.

Gm cc b-c nh- sau: - Truyn ct xung tng ngm th ba. - Ph 70cm btng u cc, v sinh ct thp ch u cc v ct thp hnh cm vo cc. - Chng thm i cc bng mt s ph-ng php: pht va b tng, bi tum hoc thu

tinh lng. - b tng lt y i. - t ct thp i cc v hn thp bn lin kt ct thp hnh, ct thp ch ca ct. - b tng i cc. - Thi cng chng thm cho sn tng hm. Cng vic trc c chuyn l-i trc chnh cng trnh xung tng hm l ht sc

quan trng cn phi -c b phn trc c thc hin ng vi cc sai s trong gii hn cho php. Mun vy phi bt buc s dng cc loi my hin i nh-: my o thu chun NI.030 ca c, my NA 824 ca Thu s hoc my c chnh xc t-ng -ng (my chiu ng lade).

Vic ph u cc v v sinh ct thp phi -c thc hin nhanh chng, m bo yu cu: sch, k, m bo tnh lin kt ca b tng vi ct thp v tnh lin tc gia cc phn. Ngay sau phi t chc ngay vic chng thm i v b tng lt, trnh qu lu trong mi tr-ng m, xm thc gy kh khn cho vic thi cng v cht l-ng mi ni khng m bo.

i vi nn t l ct bi cht va th ph-ng php pht thy tinh lng -c -u tin

v n nng cao kh nng chu lc ca t nn va c kh nng chng thm ngn

n-c ngm chy vo h mng

- 4.2: c t hm -1

-7.8: c t hm -2

- 4.2: c t h m -1

-7.8: c t hm -2

- 1.0

-5.2

-8.8

-11.4

-14.3

b c e f g h k la m

Cn t r c t h p9

t t r n bt n g

Sb-92B

II.7. Giai on 7: Thi cng l p dng h ct chnh v ct li, v ch ca cng

trnh.

- 4.2: c t hm -1

-7.8: c t hm -2

-11.4: c t hm -3

- 4.2: c t hm -1

-7.8: c t hm -2

-11.4: c t hm -3

- 1.0

-5.2

-8.8

-11.4

-14.3

b c e f g h k la m

Cn t r c t h p10

i m n g t h i c n g xo n g

II.8. Giai on 8: Thi cng l p dng ton b dm ca sn tng hm -2.

- 4.2: c t hm -1

-7.8: c t hm -2

-11.4: c t hm -3

- 4.2: c t hm -1

-7.8: c t hm -2

-11.4: c t hm -3

- 1.0

-5.2

-8.8

-11.4

-14.3

b c e f g h k la m

Cn t r c t h p11

II.9. Giai on 9: Thi cng l p dng ton b dm ca sn tng hm - 1.

- 4.2: c t hm -1

-7.8: c t hm -2

- 4.2: c t hm -1

-7.8: c t hm -2

-11.4: c t hm -3

- 4.2: c t hm -1

-7.8: c t hm -2

-11.4: c t hm -3

- 4.2: c t hm -1

-7.8: c t hm -2

- 1.0

-5.2

-8.8

-11.4

-14.3

b c e f g h k la m

Cn t r c t h p12

II.10. Giai on 10: Thi cng l p dng ton b dm ca sn tng trt.

- 4.2: c t h m -1

-7.8: c t hm -2

- 4.2: c t h m -1

-7.8: c t hm -2

-11.4: c t h m -3

0.00

- 4.2: c t h m -1

-7.8: c t hm -2

-11.4: c t h m -3

0.00

- 4.2: c t h m -1

-7.8: c t hm -2

- 0.8 - 0.8- 1.0

-5.2

-8.8

-11.4

-14.3

b c e f g h k la m

Cn t r c t h p13

II.11. Giai on 11: Thi cng btng ct, li, v ch d-i tng hm - 3 v

sn tng hm -2.

- 1.0

-5.2

-8.8

-11.4

-14.3

b c e f g h k la m

Cn t r c t h p14

t t r n bt n g

Sb-92B


sn tng hm - 1.

- 1.0

-5.2

-8.8

-11.4

-14.3

b c e f g h k la m

Cn t r c t h p15

t t r n bt n g

Sb-92B


sn tng trt.

- 1.0

-5.2

-8.8

-11.4

-14.3

b c e f g h k la m

Cn t r c t h p16

t t r n bt n g

Sb-92B

- 0.80.00

Nh- vy kt thc qu trnh thi cng phn ngm.

1

Vi - Tnh to n t-ng trong t

I. Tng quan v la chn ph-ng php tnh t-ng trong t

Hin nay c rt nhiu ph-ng php -a ra tnh ton t-ng trong t c

cc thanh neo nh-:

- Ph-ng php Sachipana (Nht bn);

- Ph-ng php n hi c xt n ma st gia t v t-ng chn (Quy phm

thit k mng cng trnh xy dng ca Nht bn);

- Ph-ng php c xt n nh h-ng ca lc trc thanh chng cc tng thanh

chng theo tin trin ca vic o t;

- Ph-ng php S gia;

- Ph-ng php phn t hu hn ( trn nn n hi, PTHH trn bn mng n

hi, PTHH c xt quan h ca t vi t-ng chn);

- Ph-ng php B.N.Gimoskin cho php tnh ton c xt n lin kt mt pha

ca kt cu vi nn;

- Ph-ng php ca Blium-Lomeier xem p lc t pha tr-c t-ng l phn b

u, cng cng ca n phn b pha d-i

thun li v n gin trong vic xc nh p lc ln t-ng chn ta dng

ph-ng php Sachipana gn ng ca Nht Bn, vi ph-ng php ny tnh Lc

trc thanh chng v Mmen thn t-ng khng bin i theo qu trnh o t.

Mt s gi nh -a ra tnh ton nh- sau:

+ Trong t c tnh dnh, thn t-ng -c xem l n hi di v hn.

+ Phn lc chng h-ng ngang ca t bn d-i mt o chia lm hai vng:

Vng do t ti p lc t b ng c cao l; Vng n hi c quan h -ng

thng vi bin dng ca thn t-ng.

+ Sau khi khi lp t chng th xem chng nh- bt ng.

+ Sau khi lp t tng chng d-i th xem tr s lc trc ca tng chng trn

khng thay i, cn thn t-ng t d-i ln vn duy tr v tr nh- c.

Ph-ng php gii gn ng ch dng hai ph-ng trnh cn bng tnh:

Y = 0

MA = 0

Y = - 0)..(2

1..

2

1

2

1. 0

221

1

mmkmokokm

k

mki xxhxhhxWxvNN

Vi = -

Suy ra:

Nk = .h0.xm + .h0k2/2 - W.xm

2/2 v.xm - 1

1

k

iN - .h0k.xm/2 + .xm2/2 (1)

03

)...(22

...

)3

(.2

1.

6

1.

2

1)()(

2

00

02

0

321

1

mmkmk

m

k

kmmmkkkmik

k

iA

xxh

lxxh

xh

hxWxvxhNxhNM

(2)

2

Thay (1) vo (2) ta -c:

(W - )xm3/3 (.h0k/2 v/2 W.hkk/2 + x.hkk/2- .h0k/3) xm

2 -

- (.h0k v .h0k/2).hkk.xm [

1

1

1

1

..k k

ikkiki NhhN +.h0k2(hkk h0k/3)/2] = 0

(2a)

Vi: - p lc tnh ch ng tc dng ln trn mi mt di t-ng (theo

chiu cao t-ng).

- p lc tnh ca t tc dng ln trn mi mt di theo chiu cao t-ng.

w - p lc n-c.

wx + v tr s p lc t pha b ng

xm chiu su t-ng trong t ti thiu trong tng giai on o t.

T-ng -c cm vo cc lp t nh- sau:

- Lp t lp: c chiu dy 1,2 m

- Lp St do cng: c chiu dy 4,6 m v = 18,2 kN/m3, c = 19, = 13o

- Lp St pha do mm: c chiu dy 3,4 m v = 17,5 kN/m3, c = 5, = 11o

- Lp St pha do chy: c chiu dy 3,6 m v = 18,5 kN/m3, c=10, = 16o

- Lp Ct pha do: c chiu dy 6,7 m v = 19,2 kN/m3, c = 25, = 18o

- Lp Ct bi cht va: c = 19 kN/m3, = 30o

II. Xc nh s tnh ca t-ng trong t:

S tnh ton t-ng trong t -c th hin t qu trnh thi cng sau:

- o t n su - 3,4 m (k t mt t) th ta t mt t cy chng th

nht (tng qut th cy chng y c th l neo, sn tng hm btng ct

thp hoc h cc thanh chng bng thp hnh).

- o t n su - 7m th t tip t cy chng th hai.

- o t n su -10,6m th t tip t cy chng th ba.

- V tip tc o t n su y i 13m kt thc qu trnh o t.

3

h n g c h n g 1

h n g c h n g 2

-2.20

-6.80

-10.20

-13.80

t l p

st d o c n g

st pha d o mm

st pha d o c h y

c t pha d o

c t bi c ht v a

-20.50

-7.5MNN

-1.00

c t y i

h n g c h n g 3

Ta thy rng: thc t cng trnh trn mt t xung quanh t-ng u -c

cht cc vt liu hoc ln tri xy dng, v c th c cc ph-ng tin nh i li

ln trn mt t h mng cng trnh, v th -c cht mt phn ti trng phn

b u q, gi thit q = 1 T/m2 = 10 kN/m2.

T-ng t-ng ko di l-ng t-ng chn n chiu cao h. T c th xc nh

cc tr s p lc t theo l thuyt p lc t Raikine, cn c vo mc n-c ngm

tnh ton p lc n-c, ly 1m theo chiu di thn t-ng tnh.

II.1. Tnh p lc ca t v n-c ln t-ng:

II.1.1. Tnh p lc t ch ng tc dng ln t-ng:

- su Z = 1,2 m:

2,1 1cdp = (q + .h) tan2(450 -

2

) 2c.tan(450 -

2

)

= (10 + 17 x 1,2) tan2(450) = 30,2 (KN/m2).

- su z = 3,4 m:

200214,3

2 /3,252

1345tan.19*2

2

1345tan.2,2*2,18 mKNpp cdcd

- su z = 5,8 m:

200228,5

3 /7,222

1345tan.19*2

2


- su z = 7,0 m:

4

200237

4 /7,282

1145tan.5*2

2


- su z = 9,2 m:

20027 42,9

5 /62,462

1145tan.5*2

2


- su z =10,6 m:

20022,9

4

6,10

6 /26,462

1645tan.10*2

2


- su z = 13,3 m:

20

0026,10

6

3,13

7 /55,592

1645tan.10*2

2


II.1.2. Tnh p lc n-c ngm:

Trong qu trnh thi cng, phi lun m bo -c mc n-c ngm thp hn

mt t o l 1m. Do s chnh p lc n-c s -c tnh nh- sau:

- Giai on 1: o n su - 3,4 m (so vi mt t) th mc n-c ngm t

nhin ang su - 6,5m, m bo iu kin thi cng t ra, do giai

on ny, p lc n-c ngm hai bn t-ng l cn bng nhau.

- Giai on 2: o t n su 7m (so vi mt t), h thp mc n-c

ngm bn trong lng t-ng xung 1m so vi mt t thi cng, do

chnh lch mc n-c su ny l mh 5,1 . p lc n-c -c tnh nh-

sau:

2/155,1*10. mKNhpw

- Giai on 3: o t n su 13,3 m (so vi mt t), h thp mc

n-c ngm bn trong lng t-ng xung 1m so vi mt t thi cng, do

chnh lch mc n-c su ny l mh 8,7 . p lc n-c -c tnh

nh- sau:

2/788,7*10. mKNhpw

II.1.3. Tnh p lc t b ng

- su 7m.

PP = .x.tan2(450 +

2

) + 2c.tan(450 +

2

)

= 17,5*x*tan2(450 + 2

110) + 2*5.tan(450 +

2

110)

= 25,75.x + 12,131.

Vy c, w7 = 25,75 v v7 = 12,131

5

III. Xc nh su chn t-ng, lc dc thanh chng v mmen thn

t-ng.

Khi xc nh chiu su t-ng trong t ngoi vic t-ng lm vic mt

cch bnh th-ng cn ch n vic h su thm ngn n-c. Tr s phn cm

su thm -c ly nh- sau:

Trong cht: 0,5 - 1m, trong bin cht v trong st cht: 0,75 1,5m,

trong st do v st do: 1,5 - 2m. Vi cng trnh ny, o t n ct 13,3m

(lp ct pha do) nn ta chn cm thm l xm.

Giai on I. o t n su -3,4m (tnh t mt t) v t hng

thanh chng th nht.

Sau khi o t n su 3,4m (so vi mt t), ta tin hnh t hng

chng th nht. Gi IN1 l lc dc trong thanh chng th nht. Ti thi im ny,

p lc t ch ng tc dng ln t-ng cn b, nn coi 01 IN .

Mmen un thn t-ng ti su ny l: TmKNmM I 75,65,671 .

Tip tc o t th p lc t ch ng tng dn v p lc t b ng

gim dn, do xut hin lc nn trong hng thanh chng ny.

Giai on II. o t n su -7m (tnh t mt t) v t hng

thanh chng th hai.

Ti giai on ny, gi lc dc trong hng chng th nht l IIN1

S thanh chng k = 1, hok = 7m, hkk = h1k = 3,6m, Nk = IIN1 . Dng cng thc

(2a) tm xm:

3

1(W - )xm

3 (2

1.h0k

2

1v

2

1W.hkk +

2

1x.hkk -

3

1.h0k) xm

2 -

- (.h0k v 2

1.h0k).hkk.xm [

1

1

1

1

..k k

ikkiki NhhN +2

1.h0k

2(hkk 3

1h0k)]

= 0

Xc nh cc h s ,, :

27 4 /7,43157,28 mKNppP wcda

= 1h

Pa = 7

7,43= 6,25 ; =

1

7

4

h

Pcd = 7

7,28= 4,1 ; = - = 6,25 4,1 = 2,15

3

1(25,75 4,1)xm

3 (2

16,25*7

2

112,131

2

125,75*3,6 -

3

12,15*7) xm

2 -

- (6,25*7 12,131- 2

1.2,15*7).3,6.xm [

2

16,25*72*(3,6

3

17)] = 0

7,22xm3 + 35,55*xm

2 86,74xm 194 = 0

xm3 + 4,93xm

2 12xm 26,87 = 0

Gii bng ph-ng php th dn, ta -c: xm 1 = 2,8 m

6

Dng cng thc (1) tm lc trc thanh chng th hai IIN 2 :

Nk = .h0k.xm + 2

1.h0k

2 - 2

1W.xm

2 v.xm - 1

1

k

iN - 2

1.h0k.xm +

2

1.xm

2 (1)

IIN1 = 6,25*7*2,8 +

2

16,25*72 -

2

125,75*2,82 12,131*2,8

- 2

1*2,15*7*2,8+

2

14,1*2,82 = 135,7 kN = 13,57 tn

=> Mmen un thn t-ng to su 7m l : TmM II 4,192 .

+X+X

Biu mmen ca tng BartGi tr lc dc ti hng neo 1

- 1.00q = 1 T/m2

-Y +Y

- 7.5

-Y +Y

2

IIIM = 19,4 Tm

1

IIM = 6,75 Tm

N = 13,57 t1

II

Biu ni lc thanh chng v thn t-ng ti giai on thi cng II

Giai on III. o t n su 10,6m (tnh t mt t) v t

hng chng th ba.

Vi k = 2; Nk = IIN1 = 135,7 kN; hok = 10,6 m, h1k = 7,2 m;

hkk = h2k = 3,6 m; Nk = IIIN 2 ; w; v; ; ; . Dng cng thc (2a) tm xm:

3

1(W - )xm

3 (2

1.h0k

2

1v

2

1W.hkk +

2

1x.hkk -

3

1.h0k) xm

2 -

- (.h0k v 2

1.h0k).hkk.xm [

1

1

1

1

..k k

ikkiki NhhN +2

1.h0k

2(hkk 3

1h0k)]

= 0

3

1(25,75- 4,1)xm

3 (2

16,25*10,6

2

112,131

2

125,75*3,6-

3

12,15*10,6)xm

2

- (6,25*10,6 12,131- 2

1.2,15*10,6).3,6.xm

- [135,7*7,2 135,7*3,6 + 2

16,25*10,62*(3,6

3

110,6)] = 0

7,22xm3 + 26,89xm

2 153,8xm 513,2 = 0

xm3 + 3,72xm

2 21,3xm 71,1 = 0


Dng cng thc (1) tm lc trc thanh chng IIIN 2 :

7

Nk = .hok.xm + 2

1.h0k

2 - 2

1W.xm

2 v.xm - 1

1

k

iN - 2

1.h0k.xm +

2

1.xm

2 (1)

=> IIIN 2 = 6,25*10,6*4,5 + 2

16,25*10,62 -

2

125,75*4,52 12,131*4,5 -

- 135,7 - 2

1*2,15*10,6*4,5 +

2

14,1*4,52 = 188,8 kN = 18,85 tn

=> Mmen un thn t-ng ti su 10,6m l: TM III 4,303 .

N = 13,57t1

II

N = 18,8t2

III

q = 1 T/m2

-Y +Y

- 7.5

-Y +Y

2

IIM = 19,4 Tm

1

iM = 6,75 Tm

+X+X

Biu mmen ca tng BartGi tr lc dc ti cc hng neo

- 1.00

3

IIIM = 30,4 Tm

Biu ni lc thanh chng v thn t-ng ti giai on thi cng III

Giai on IV. o t n su 13,3m (tnh t mt t) - kt thc

qu trnh o t.

Vi k = 3; Nk = IIN1 = 135,7 kN; Nk =

IIN 2 = 188,8 kN; hok = 13,3 m,

h1k = 9,9 m; h2k = 6,3m ; hkk = 2,7 m ; Nk = IIIN3 ; w; v; ; ; .

Dng cng thc (2a) tm xm:

3

1(W - )xm

3 (2

1.h0k

2

1v

2

1W.hkk +

2

1x.hkk -

3

1.h0k) xm

2 -

- (.h0k v 2

1.h0k).hkk.xm [

1

1

1

1

..k k

ikkiki NhhN +2

1.h0k

2(hkk 3

1h0k)]

= 0

3

1(25,75- 4,1)xm

3 (2

16,25*13,3

2

112,131

2

125,75*2,7-

3

12,15*13,3)xm

2

- (6,25*13,3 12,131- 2

1.2,15*13,3)*2,7*xm

- [(135,7*9,9 + 188,8*6,3) (135,7 + 188,8)*2,7 +

+ 2

16,25*13,32*(2,7

3

113,3)] = 0

7,22xm3 + 8,79xm

2 153,1xm 701 = 0

8

xm3 + 1,22xm

2 21,2xm 97,1 = 0


Dng cng thc (1) tm lc trc thanh chng IVN3 :

Nk = .hok.xm + 2

1.h0k

2 - 2

1W.xm

2 v.xm - 1

1

k

iN - 2

1.h0k.xm +

2

1.xm

2 (1)

=> IVN 2 = 6,25*13,3*5,64 + 2

16,25*13,32 -

2

125,75*5,642 12,131*5,64 -

- 135,7 - 2

1*2,15*13,3*5,64 +

2

14,1*5,642 = 204,5 kN = 20,45 tn

=> Mmen un thn t-ng ti su 13,3m l: => TmM IV 504 .

-Y +Y

2

IIM = 19,4 Tm

1

iM = 6,75 Tm

4

IVM = 50 Tm

+X+X

Biu mmen ca tng BartGi tr lc dc ti cc hng neo

- 1.00

3

IIIM = 30,4 Tm

N = 20,45t3

Iv

N = 13,57t1

II

N = 18,8t2

III

q = 1 T/m2

-Y +Y

- 7.5

Biu ni lc thanh chng v thn t-ng ti giai on thi cng IV

Xt thy, nu x = 5,64m th chn t-ng Diaphramg s nm trong lp Ct

pha do, m lp ny l lp yu, c N = 21. Nn ta phi ko di cho chn t-ng

nm trong lp Ct bi cht va (c N = 30) mt on l 2,5 m. Cc l do khc

cho s la chn ny l:

- Bn thn t-ng trong t khng chu ti trng ca cng trnh, m ch chu

trng l-ng bn thn v mt phn ti trng t cc sn tng hm.

- T-ng trong t khng -c php ln, bi nu xy ra ln th s ph v lin

kt gia n vi sn tng hm d-i cng, iu ny dn n n-c ngm s

thm thu vo hm

Vy tng di ca t-ng Diaphramg l: H = 22cm.

IV. Xc nh s b kch th-c tit din t-ng Diaphramg:

Cc kch th-c s b ca t-ng nh- sau:

- Chiu dy t-ng chn theo c s sau:

9

+ Theo yu cu chng thm.

+ T Mmen trong t-ng, ta tnh -c chiu cao lm vic ca t-ng (h0) thng

qua cng thc: h0 = bRn

M

A .

1. Vi b chiu rng ca di t-ng cn tnh ton.

Trong bi ton ny, chn b = 0,8m (theo chiu cao t-ng).

+ Cn c vo cng ngh v ph-ng tin thi cng thc t. Th-ng thi cng cp

t-ng bng gu ngom, c cc kch th-c gu: 600, 800, 1000mm.

+ Chn theo kinh nghim.

Chuyen de Thi Cong

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