: B l T f ! m HOM NAY
trdng quan if) chat iirang thi corig tang ham nha cao tang
uai tro tu uan doc lap cho chii dau tir
rs. Nguyen Sy HUng*
Tom tit: Thi cdng nha cd tang ham da cd ttf lau tren thigidi, nd trd thanh pho bien va la thdng le khi xay dtfng nha nhiSu tang. Tuy nhien, d Wit Nam, viec thi cdng nha cd tang ham la mpt phan khd, phtfe tap han nhiiu so vcA kit cau ben tren cda cong trinh. Tap chi Xay dtfng va Bd thi ky nay gidi thieu cdng ddc gia v4 mdt so nguyen nhan thudng gap trong quan iy chat lugng dli edng tang ham nha cao tang, ttf do neu ien vai trd tU van ddc lap cho chu dau tU.
TQkhoa: Quan iychatlUOng, thi cdng, tang ham.
Summary: Constructing buildings with basements has been conducted for a long time in the worid. It is becoming popular and a regulation when building any multi storey buildings. However, in Vietnam, the construction of a high rise building with basement is a difficult part, which is more complicated than constructing the above-ground structure In this issue, the Construction and Urban magazine v/ould like to state the usually-meet causes In quality management in constructing the basement of a high-rise building, and raise the role of independent consultancy for the client
Key words: Quality management, Contructing, basements Nhan ngay 20/4/2015, chinh stfa ngay 25/4/2015, chap nhin dang ngay 04/5/2015.
1. Mot so vi du va nguyen nhan thudng gap trong quin ty chat lUtfng thi cong tang him nha cao ting
V
ao then ky mdi xuat hien nha cao ting cd tang ham dViet Nam, trong nhQng nam 1990, dau nhQng nam 2000, ty le cac cfing trinh gap sy co rat nho. Ly do l i phln ldn d c cfing trinh tren dUdc d c nha tUvan, nha thiu thi cong nudc ngoai nhieu kmh nghiem quin ly trong sufit qua trinh xay dung cfing trinh. Vf du: Cao oe Metropolitan va cao oc Ocean Place (Quan 1, Tp^ Hfi Chi Minh) vdi phuong an dao md, chong giQ tfianh vach hfi dao; cao 6c Pacific Palace (LyThudng Kilt Ha Nfii) vdj phuang i n thi cong Top-Down, thi cfing dong thdi ca ting him v i tang cao, efi tQ 2 din 5 ting ham nhUng hau nhU khfing cd sU co ding kl, khfing gay Inh hudmg xlu den cdng trinh xung quanh.^ Tuy nhien, d n g ve sau, sU tham gia cija cac dan vj thiet kl, thi cdng Vigt Nam ngiy cang nhilu, khfing phai dan vj nao cung cd du nang lyc, kinh nghigm va do vay ty le cong trinh g|p sy cd phln him cung tang Ien. Co the ke ra d day mot vai dan chOng nhiKThi cfing Thap ngan hang diu tuphattnen Viet Nam (194Tran Quang Khai, Ha Nfii) gap sUco nUdc bun cit chiy tQ dp sau -12,5m vao day ho mdng; thi cdng tang ham cao 6c
Cao 6c Pacific Palace Duang Ly Thuang Kiet HaNoi) Pacific gay sup do Vien Khoa hoc xa hdi vung Nam Bfi; thi cong tang ham cao de Saigon Residences (11D Thi Sach, Quan 1, Tp.
Ho Chf Minh) lam syt nen khu dat chung cU Cosaco;... X'.
Nguygn nhin cua nhCmg sU cd trgn trude hit la do cfing vile thiet kl, thi edng phan ham la mot phan khd, phQc tap hdn nhieu Sd vdi ket cau ben trgn cda edng trinh. Cy the hdn, dat la mpt loai vat ligu ty nhien rat khfi dU doan, hon nOa nude nglm trong dat gay ra d c tie dpng thudng la bat Ipi va phQc tap cho qua trinfi thi cfing. Su tuang tic cdng trinh - dat nen cung thay ddi lien tuc tnang sudt qua trinh thi cfing. Vile lay di mdt luang dit ldn gay ra sy bien dang, thay ddi nghigm trpng mfii trQdng dia ky thuat cho ci vCing xung quanh hd dio, giy ra d c tic dfing bit lpi cho cae cong trinh xung quanh, dac biet trong dilu kiln xiy chen d do thi, d c nguyin nhan tren cd t h i gpi la nguyin nhan ve mat ky thuat. Ben eanh do, viec dam bio chit luong phan tang ham doi hdi sy phdi hap, thdng nhlt va dong bp tit cao ei!ia tat ca eae khau tQ khao sat thietke, till cong, thinghiem quan trac Chfnh s^r yeu kem ve nang luc cOa mdt trong nhQhg khau tren, hay sy phoi hc^ giua d c khiu khong an khdp se dan tdi sUtruc trie, tham d|{
sued, nguygn nhin niy cd t h i gpi la nguyin nhan ve mat quan ^.jj
2. Cong tac khao sat >.' Khi thi cfing dio hd dao siu, ttang thai dng suit trong n ^
dat thay doi, dat nen se bien dang dan tdt khi nang mat dn d | f TQdd ed t h i gay ra d e hiln tupng nhutudng hd dao bj c h i ^ vj, hd mong trong dit set eo t h i bj bye day do mit khi nang OT tai tae ddng ngUdc lln trin. Thgm vao do, nU6c nglm trongi®
4 8 HOC V £ N cm BO QUAlM LY XAY D J N G VA D 6 THI
Nudc ngam trong dat gdy ra cdc tde dgng thudng Id bdt igi vd ph dc tgp
cung ia mfit y l u ^ giy ra trang t h i i m i t dn ^nh. Neu diy hd dao nain trorig d i t d t viec bdm ha mUc nUdc nglm ed the gay ra xdi ngam ddng thdi cd the gay lun eho vdng d i t xung quanh. Neu day ho dao nam trong dat set phfa tren [(sp dat chQa nude ed ap cd the xiy ra hign tupng bye diy. Mdt sd vj tri xiy dyhg ed t h i co d c tui bun hay d c via d t ed nUde xen kep hoac d c khu vyc gin sdng CO nUdc chiy gpi l i bay dia chat neu khfing phat hign va khic ehl nhQng biy nay eung de dan den syco.
^ Be phyc vu tfnh toan thiet ke, lip bien phap thi cong phan ham, cong tac khio sat dia chat d n chuygn biet hem so vdi d e cong trinh khong cd tang him, eung d p nhieu so lieu diu vao cho d e phln m i m tfnh toan nhu Plaxis, Geoslope. Vi vay, ngay tQ diu d n xie djnh rd d e hang muc, yeu d u , d e ehi tilu thi nghiem cQa cfing tie khao sat ^ a dilfc
- Dau tien d n phii tien hanh khao sat sd bo de d l ra giai phap tudng chan hc^ ly, an toan v i kinh te. Giai doan tiep theo d n t i l n hanh khio sat thi nghiem chuyen biet cho thilt k l thi cfing dao hd mdng sau.
- Pham vi, dp sau khio sat dua vao kich thQdc ho dao, phuong an nen mdng, ddng thdi phai dya vao dilu kien dja chat cdng trinh cua dja dilm xay dyng; khdng dUdc bd sdt d e bay dja chat - Kit qui khao sat cho bilt rd d u tao dia tang, tfnh chat ca l;^ eua dit, d e kit qua thi nghiem nen ba tnjQ thf nghiem nen ed ket, thf nghigm xae dinh he sd tham eua dat I p lye
nUde 16 rong, d c thf nghigm hien trQdng. Danh gia dupc Idil nang bung nen day hd dao, khi nang tniang nd dan hoi eua dat danh gii Inh hudng eua thi cong dao ho mdng sau doi vdi cdng trinh can k l .
^ - Phli xac ^ n h sy biln ddi tinh chit ca ly eua d i t do sy thay ddi trang thai Qng suit d tucmg ho dao va myc nude nglm, dae biet eho nhQng loai d i t nhudit lun Udt dat truong nd, dat yeu bio hoa...
- Khio sit d n lam rfi d c die tnmg cua nudc ngam, bao gdm quy luat phan bd ting chQa nudc; chieu sau myc nudc; toe dp van ddng, hudng van dpng, he so tham, ngudn bd sung va dieu ki?n thoat nudc NhQhg so lieu nay l i can cQquan trpng de thiet ke biln phap khdng ehe anh hudng cQa nUdc ngam.
- Cdng tie khio sat edn phii chu y den d c cfing trinh d n ke hiln hQu, npi dung bao gfim kieu iffit d u cwig trinh, kilu dang nen mdng, chieu sau day mdng, hien trang kit d u edng trinh va sy Inh hudng d till cd bdi sy tac dpng nhu chin ddng, thay ddi muc nudc ngam, sy bien doi tinh chit eua d i t do qua trinh thi edng. Ngoii la, d n chu y din d e dang d n g Hinh nglm nhU dudng ong, dudng day d p , bdi ehung ctiiu inh huisng va ed tfie gay trd ngai cho thi cfing.
- Ngoii nhQng npi dung ve ^ a chit cdng trinh, hd sd kit qua khio sit d n phii neu rd dieu kign mat bang, eic kiln nghj ve gill phap diong dd, nhQng nguygn tic ti'nh toan thiet k^ gill phap khdng ehe nUde nglm.Tuy nhien, trong nhieu trUdng hc^
nhigm vu khao sat dja chit ehua dap Qng dupc d c yai d u eho phln him, dan d ^ bao d o khio sat tfiilu so lieu,vfdy:Thi^
thong tin quan trie mUc nUdc nglm tin cay, thieu thf nghigm piezcwneter de theo dfii mUe nUde nglm va do ap lyc nudC 16 rong; thieu d c so ligu thf nghiem nen ba true d l cd thfing so sQc chdng d t d a dat d trang thai thoat nUdc v i khfing thoat nUdt;
thieu so lieu tin ay v l lich sQ ung suit cua dit nen qua th&ig so ap luc tiln CO k i t thieu d c thf nghiem hiai m/dng de doi chilu vdi so lieu ^ i nghiem trong phong nham ed dupc gia trj thiet ke.
- Bao d o khio sat con nang ve cung d p so lieu ma thieu diQc nang dubio, khuyen nghj.
Hign tai con thieu nhQng ky sU chuyen nganh dia 1^ thuat gloi trong Tnh vUc xay dUng cfing trinh do Viet Nam chua xem trpng diing mQc chuygn nganh nay, vi the chat lUcmg cdng tac khao sit khfing eao. Ngoai ra, ehu diu tU cung chua coi trpng dung mQc t i m quan trong cua khao sat ngn han ehe kinh phi.
Do vay, khd d dUdc kit qua khio sat tin dy, chat lUcmg eaa ThUe te, chu trpng eong tie khao sat sg giup tilt kiem dUoc rat nhieu chi phf do thilt ke thQa hoac sU eo eong trinh. Nlu khio sat kem chat lupng se din d&i thilt ke va bign phap thi eong khdng phu hc^.
3. Cong t i e thiet k^ lap bien phap tiii cdng O day, cong tac thilt k l kit d u d a don vj tU vin thiet k l va bien phap thi cdng cua nha thau dupc xem xet ehung. Sddi nhu vay vi dac thu cua tang him la kit d u va bign phap thi cfing gan kit rat chat che v ^ nhau, mpt bp phan vQa cd t h i ddng vai tro la kit clu chju lUc cho cfing trinh vQa dfing vai trd la kit d u bien phap, vf du nhutudng ba ret Khi thiit kl, ddn v\ tUvan thiet ke da ed djnh hudng trUdc ve phUdng i n thi cdng va de Mjit phuang i n thi eong chinh, tQ do nha thiu lay lam cd sd de lap phUdng an thi eong ehi t i l t
Ddn vi tu vin thilt ed the lam d e nhigm vy: Lap nhiem vy khao sat dja chat v i thiet ke cfing trinh v i de xuat bien phap thi cong De co t h i lam tot nhigm vu thQ nhlt ngUcfi thiet ke phai am hilu v l dia ky thuat vcfi ting him nha cao tang, sy am hieu phii 6 mQc do cliuyen sau.
Vdi nhigm vu thQ hai, ddn vj tfiilt k l eong trinh ho mdng sau phii dua vao dieu kien dia chat mdi trudng xung quanh ho mdng, yeu d u thilt ke cua kit d u chinh va dieu kiln thi cdng de xac djnh phUdng an thiet ke. PhUdng an thilt klcdng trinh hd mdng sau phai bao gom cae npi dung nhu kit d u d d phUdng i n dao dat ha mUc nUde nglm, bao ve mfii tnidng, bio ve d c d n g trinh xung quanh, quan trac Viec tfnh toan thilt keva phan
> X n V DMNG S. DO T H 4 9
VANDE
I
tich d n g trinh hd mdng siu phai tiln hanh theo d e tieu chuan, quy dinh liln quan cQa Nha nude va Thanh phd
Pliuc^g i n thiet ke vQa phai dam bio ve mat ky thuit tinh khi thi v i tinh kinh t l . Wil thilt k l h i tfiong ha mQc nUde ngam, d n xet den d e anh hUdng bat ldi den d c cdng trinh xung quanh. NgUdi thilt k l cung phai d l ra ylu d u ky thuat tiii edng, thi nghiim hign trudng va ylu eau quan trac; d c gidi han cho phep v l chuyin dieh, biln dang, gradient thuy lUc Dan vi thilt klcdng trinh phii theo doi trong thdi gian thi cdng, kjp thcrt nam bat finh hinh tiii eong tai hign tnidng, khi phat hien hiln trang thUc t l khdng khdp vdi bao d o khao sat hoac xult hien hiln tupng bit thudng phii kjp thdi cCing chQ dau tu, ddn vj khao s i t thi cfing, giam sat quan trie nghien cQu d l giai quylt trudng hc^ d n thilt can bd sung ylu cku khio sat va sua chQa thilt kl.
Nhtfng sai sotthudnggapdoi vdi donvithietkeia:
- Khfing nam vQng d c kien thQe ve dia Iq^ tiiuat nen IQng tung khi lap nhiem vu khao sit dia chat hau qui bao d o khao sat khong datygu d u , cdthe phli khao sat lai hole khio sat bd sung.
- Cae tfnh toan thilt ke thudng chf thign ve dy bao chuyen vi, biln dang ban than tUdng hd dio bang d c h nhap cac sd ligu dia chat kit d u vao d e phan mim tfnh toan (thudng la Plaxis) ma ehua co sy phan tfch, hieu ehinh d c so Ifgu diu vao, sy lUa chpn hpp ly cac mfi hlnh ft'nh toin trong phan mim, sU dU bio khoing biln thign giOakltqui ti'nh toan va thue te. Viee kiem tra diy trfii, buc mong, eat chiy do bdm ha mUe nUde ngam thudng sasii hoac thim chf khfing kiem tra, thucmg thilu sUdUbio luin eho phln dit xung quanh ho dao cung nhupham vi anh hUdng eua ho dao den mfii trUdng dia chat cfing trinh xung quanh.
-Thieu sy phan tfch tiiau dao nhieu phUdng an de dUa ra phUdng an hpp h? nhatVidu nhUsQdung cQLarsen cho hfi dao qua sau (>10m), khfing d m cQlarsen vao ting d i t khfing tham nude, hay sQ dung tudng ba ret ehd hfi dao ndng gay ton kem.
Mfit so trudng hdp sddo tfnh toan sai din tdi dUbao sai.
- Nhi thau tU van thiet ke da dua ra biln phip ehinh eho thi cong, tuy nhiln viee lap nay tiiU^g mang tinh "ddi pho" thign v l dy bio gia tri kinh t l hdn la tfnh ky thuat do vay nhieu trudng hdp biln phap dua ra khdng hpp ly. Khi nha thiu dUa ra biln phip thi eong khae, tuvan thilt k l lai phai thiet ke lai d l phu hdp vdi bign phip mdi.
Ve phan d c nha thau thi cfing xay dyng, phan Idn ehUa cd du nang lUe va kinh nghiim d n thiet d l lip phUOng an bign phap thi eong hpp ly, khd khan khi giii quylt d e vin de cd lign quan den tinh toan, thilt ke he thong tudng chan phan ngam.
Ho thudng thug mdt ddn vj tU vin lip bien phap thi cdng, hoac tu lap va thug ddn vi tU vin tham tra lai. Luc nay cd t h i gap vin d l thay doi giii phap thi cong, thay ddi gtii phip thilt ke cfing trinh. Van de dinh gia ve Inh hudng vdi cfing trinh lan d n , phUdng an ky thuat thi cfing dao d i t hut nUde ho dio mfit each 1 an toan, hap \</: lip he tiifing quan trie, theo doi va phat hien kip I thdi nhQng dien biln bat lpi khi thi cdng la d c bai toan klid doi j vdi nha thiu; dae bigt nhieu nha thau ehUa coi trpng de ra cac giii phap xQ ly Iq? thuat dy kien khi ed nhiJng dien biln bit lai hoac khi bat dau xiy ra syco.
4. Cong tac thi cong, giam sat thi cong
Nhiem vu cCia nha thiu l i lap bign phap thi cong, thi eong theo dung bin ve thiet k l va bign phap thi cfing duac phe duyet dim bio chat lupng, khdi lupng, tien dfi, an toan lao dfing va vg sinh mfii trUdng. Nang lUc nha thau ddng vai trd die bigt quan trong trong viee dim bao chat luong eong trinh va ngin ngOa sU eo, do do nhi thiu phii hilu day du dieu kign ^ a chat tUdng tie eong trinh d i t nen, d c nguy cdcfi the gap phli khi nln dat mem yeu, myc nUdc nglm eao, eoi trpng dung mQe_ya kip thdi cfing tac giim sat thi cfing va giam'sat ticg{^Xh\eX k l ; Hdp tae chat ehe vdi t u van giam sat tU van thilt kedldam bao chat lUpng cfing trinh; Lap phUdng an de phong, ngan ngQa sy eo, khi sQcoxay ra, phoi hap vdi cae bgn lign quan han ehl tfii da hau qua tieu cQc
I
Mfit sd han che thudng gap cua nha thiu dan din khfing dam bio chit lupng, tham chf de xay ra syed thQdng la:
- Nha thiu lap ban thiet ke bign phip thi d n g khfing hpp ly, khdng tien lieu day dCi t l i trpng va tic dfing, tfnh toan so sii, khiem khuyet hoac dua vao kinh nghiem, dya vao phln mem trong khi khdng kiem soit dQOc ti'nh tin cay ciia kit qua, nham lan trong dinh gia tai va d i p Qng cCia dat
- Nang lye nha thau khfing dip Qng dUOC dieu kiln thi cfing;
Nhan sy va thilt bj cua nhi thiu thi rang khong dung, khfing khdp vdi hfi sa du thau eung nhu bign phip thi eong da duyet, thi cdng khong dung quy trinh;
- Tien dp gap gap, nhi thiu chay tfieo tien dp ngn khong dam bio dUpc chit luang.
- Chi^ quan tam dung mQc d i n vile bao ve cdng trinh xung quanh, ehua tiln ligu dupc d c tac ddng cQa viee ha mye nudc ngam trong ho mong;
- Sa suit ehCi quan trong wee cap nhit cac sd lieu quan trie, xQ ly cham khi co cae dau hieu xay ra sU eo.
Dpi ngiJ tU vin giim sat giam sit cdng tic thi cfing cCia nha thiu, t u vin cho nha thiu va eung giii quylt d e van d l gap phii trong qui trinh thi c6ng.TUvln giam sat l i mdt nhin to rit quan trpng trong viec dam bao chat lUpng edng trinh. Song, dpi ngu tUvIn giim sit cung gip mdt so vin de nhu
- Chuyen mfin ehua vQng vang va ft kinh nghiem thut te, chua chuyen nghigp, nhieu khi khdng phe chuln hit nhQng linh vuc d n duac giim sit, cho qua nhQhg khilm khuylt ma khfing d kiem toan; thieu kien quylt hoac thilu thfch Qng trong cac finh huong xQ ly, phd mac dem vi thi edng, khd ap dat doi vol nhi thiu thi cong trong viec dim bio va tuan thQ quy djnh, bign phap thi cfing da duyet
- Cong tae giam sat khfing kiem soit h i t chat lupng vat lieu do trong dat dan din chat iQpng khong dong deu tai cac vj ijf khac nhau trong mfit hang mue (tudng vach ham dang cpc bar- rete dd trong dat hoac sQdyng cpc khoan nhdi tilt dien nlio lam tudng chan);
5. Cong tac quan trie
Quan tfic dia ky thuat cd y nghla quan trpng trong vleC thi cong d c cfing trinh nglm la d e d n g trinh rat "nhay cim"
vdi sy thay ddi cae tfnh chit ed ly, thuj van ciia nln d i t Hieu rfi va nam ehae quy luit thay ddi dd tQ trUde khi khdi cfing thi cfing eong trinh la mpt trong cac y l u td dam bio vigc thi eong N J thanh edng cong trinh. Cac hang muc quan trac ca bin khi thi y cong phln ngam la kilm soat dp sau mye nUdc ngam, doip lyi: ^ nude 16 rdng bing piezometer, quan trac nghieng tudng chin bang inclinometer, quan trie nghiing lun ciia cfing trinh v i matj dat xung quanh hd dio, quan trie biln dang he tfidng thanh chdng,...
Quan trie dja ky thuat de dilu ha, khio sit md t i d e dilu kiln hign trUdng ban dau. Quan trie d l kiem chQng de gii djiih cda thiet kl, de dilu chinh thilt 1 ^ Quan trac d l kiem tra, giam sat d c anh hudng eCia thi edng, cac so ligu quan trie co the giiip eho ky su eo quyet ^ n h diing trong thi cfing ma khfing gap sU ed Quan trie cd t h i de kilm tra chit lupng thi cong, eanh bao sdm d c sU ed cd the xiy ra, dieu nay glUp ngUdi ky su cd quyet dinh kip thdi hoac sd tan, xQ ly gia ed nhQng khu vUc nguy cddl dim bio an toin lao dfing. Quan trie cd the cung cap d c bang chQng v l phap 1;^ trong cac tinh hudng xay ra tranh chap giOa nhi thau thilt kl, nhi thau thi eong, ehd diu tU, din cUxung quanh cdng trinh...
Nhuvay, cdng tie quan trie rat quan trpng khi thi cong ting ham, tuy nhien nhilu trudng hop do van de thieu kinh phf ma mdt so edng trinh khfing dude quan trie day dii cae hang myc, hoac cd trudng hdp nha thiu thi cdng va d c ben lign quan Id la, khfing cap nhat so ligu quan trie dan den bfi qua d c dau higu eanh bio sped
(cdn tiep ky sau)
