chuong 3.PDF

109 CHUONG XUYEN TIEUCHUAN 3.THINGHIEM CHUONG THiNeHTFM xuYENilEucxuAru(sPT) 3.1 crorrHrf;u 3.1.1 ttcUYEttt-Y Trong thi nghi€mxuydn ti€u chudn(SPT-Standard PenetrationTest),ta d6ng mdt ong ldy mdu (kich thudc ti6u chudn) vdo ddt dudi nang lucrngd6ng tiOu chudn Ta ddm sd nh6tdap dd ong m5u ngdpvho ddt m6t doanld 30 cm 2L.I C HS S p r Nam 1902, cdng ty C.R Gow thi nghi€m SPT ddu tiOn v6i dng lfy m6u duong kfnh 2,54 cm (1"), que ta dd d4p SPT n4ng 50 kg Ddn ndm 1922, thf nghiOmb6t ddu r6ng rii & Bic M! c6ng ty Gow s6t nhApvdo cdng ty Raymond Concrete Prie H i n h3 G i i n S P T n h Nam 1927,thi nghiOmSPTduo.c chudnhoi{nhu hi€n (dng ldy mdu 2", qui ta 63,6kg) Nam 1948,Terzaghi vd Peck md ti chi tidt thi nghi€m SPT cudn sdch "Co hoc ddt"- Ly thuydt vi Thuc ti6n" Til d6 cho ddn nhirng ndm 199511996,SPT tr& thinh thi nghiCmphd th6ng nhdt & B6c M! Tuy nhi€n, tdt ca c6c nhd khoa hoc o Bic M! deu cho rang,day ld thf nghiOmbi c6c nhh thdu lam dung nhdt (theonghla,nh6 nOnkdt hqp cDngthi nghiOmCPT, hodc DMT hoic thf nghiOmkh6c, thi, vi qu6 quen thu6cvd c6 sdnthidt bi, ngudi ta lai chi tien hdnh SPT) 110 THfNGHICM DATHIENTRUdNG VALfNGDUNG TRoNGPHAN TICHNENMONG 3.2.NQtDUNG THiNGHrEru spr 3.2.1 CACrHANHPHANC(,arHtEr B! Thidt bi SPT gdm c6: thidt bi khoan tao 16 (c6 thd ld khoan gudng xo6n, ho6c khoandung dich), dng lAy mAu (hinh 3.2), quhta Neu khoan tao 16 gifr thinh bang dung dich luAn chuydn (bentonite),thi dung dich phii c6 ty tdi thidu le 1,05,vd 16khoan ludn luon phii ddy dung dich Nen han chd ding dng casinggifr thinh Ndu c6 dilng casing, d|y cira casingphAi c6ch vi rri ddp SPTir nhdt 1,5m 6ng lay m5u (dang bd doi) c6 dulng kfnh le 30,8 mm (1,5"), dudng kfnh ngolri50,8mm (2,0") Qui ta ndng63,6 kg ( laO lbs) vd roi & d6 cao76,2 cm (30") ddu cit thAn5ng ddu tr€n Hinh 3.2 Ong lay miu SPT Hinh 3.3 Di't ong (sau bd d6i) 3.2.2 rRiNHTu rHi NGHTEM l) Khoantao 16ddn dd sAuthf nghi€m 2) Ldp dng ldy m6u vio cdn, dua xudng d6y hd khoan 3) Cho roi qui ta xudng ddu cdn a DQp6ng xuy€n dd ngap 15 cm Ta kh6ng cdn dem sd nhiit dApndy; a Dap tidp, ddm sd nhr{tdap Nr dd dng xuyOndu-o.c15 cm (t} cm rhf 15 ddn cm thti 30); Ddm sd nh6t N, dd dng xuy€n tidp 15 cm nfra (tii cm thri 30 ddn cm thft 45); Kdt qui criathi nghi€mli N = N, + N, Nhu vay, N ld so nhrlt ddp dd ong xuyOnducr c 30 cm, & Vi0,tNam, chring ta k;f hi€u ld N30.Tuy nhi6n, day ld kf hi€u sai, c6c nudc phucrngTay sE hidu lh n[ng luong thuc md dng lAy mdu nhAn duo.c tai c6c cdng trinh Vi€t Nam chi ld 307o (xem p h d n3 ) 4) Rft 6ng lay m6u l6n, bd d6i v) thu ldy m6u ddt, dem vd thf nghiOmrrongphdng CHIJONG 3.THfNGHIEM XUYEN TIEUCHUAN 111 5) L4p lai cdc budc I d€n4 Thubng, ta crl thf nghiOm1,5m sAumdt ldn 6) Ndu dd dap qur{ 100 nh6t dAp rdi m} dng xuyOnvAn chua qua duo.c 30 cm thi ta cfrngdirngthf nghiOmlai - 3.2.3 CHUANHOASO DOC Trong tdt ca c6c thi nghiOm hi€n trudng, St'I ld m6r nhlrng thi nghi6m kh6ngchfnh xdc nhat Ndu hai ngudi kh6c nhau, sfr dung hai thiet bi kh6c nhau, rhf nghi€mldn cAn tr€n ndn ddng nhdt, thi kdt qui N thd khiic ddn hcrn l1OVo (tuynhi€n,Nuosd xdp xi nhau,ndu ta bidt chfnh x6c ndnglugng hiOuqui) Nang lucrngtoln phdn bria roi li: E = 63,6 kg x 0,762m - 4g,4 kgm Tuy nhi€n, nang luong E nhy kh6ng hodn to)n chuydnt6i dng ldy mdu Su mdt mdtndnglugng xhy cdc phdnchfnh sau: Mdt mi{t nang lucrngdo ma s6t gifra bfa roi vdi truc dAn hu6ng; ma siit gifra diy k6o vdi rdng roc Mdt mdt nang luong ngudi thi nghidm (loai bria k6o blng ddy qua rdng roc): Khi thi day dd bfia roi, ngudi thf nghi€m kh6ng thi tu mh v6n hoi niu day lai (so vdng day, mdr cong di nhat).Doi vi nguyOnnhanndy mh ndng lugng mdt ddn hon207o Mat mdt nang luong ma s6tgifraddt 16khoanv6i cdn xuy6n,v.v Bing 3.1 tr)nh biy nanglugng hiOuqui trung binh thong k6 m6t sd nudc c6c nudcdangph6t tridn, thiet bi SPTphd bien v6n ld loai nhAn(donut),sir dung dAy k6o trOnrdng roc Vdi loai ndy, c6,cnudc ti€n tien, ndng luong hieu qui li 45+65To,it c6cnudc dang phrit tridn, so ndy chic cdn tdi hcrn.Hcn nfra, gi/atritrong bAnglI gi6tri trung binh, d6, ndu c6 thi nghiCmSPTm) nang luong hi€u qu| chi co 20o/o thi cflngkhong phAididu la (nhu vay, ndu N = 40, ru&ngld ddr rdt tdt, nhtmg thuc l) ddtxdu vi N,oo= 40 201 I0O= [], vd Noo=40 Z0l 60 = l3) Tai Vi€t Nam, chfng ta chuac6 thong k0, nhung dd an ro)n, c6 thd tam ldy nang lugng hlru ich til khoAng 30 d€n55Vo BAng3.7 NEng luong hi6u qui (y") crja m6t so ttridt bi SpT Loai SPT Loai nhSn (donut) D6y+;56q to" B5cMV AE Nhat o/ Anh Tu d6no Loai an toin (safetv) D6v+rdnqroc Tu d6no 70+80 80 +100 50 bU 78 Do d6, ta phii chudn hod N vd m6t gi6 tri c6 cirng nang luong hieu qui cd,c nudcti6n tidn, ngudi ta coi 607olit nang luong htru ich trung b)nh Do d6, thudng quy ddiN vd N60(60% nang lucrnghfru ich) -a 112 THfNGHIEM DATHIENTRUONG VAUNGDUNG TRONG PHANTICHNENMONG Ngoii ra, ctng m6t loai dat, ndu Noo= l0 tai I m, thi tai 30 m, Nuoc6 thd l6n t6i 20 D6ld do, tai 30 m, 6p luc ngangl6n hon rdt nhidu so vdi tai I m, d6, cdn phAi ddp nhidu nhr{tdAphon Nhu vAy,ta cdn hai loai h€ s6 chulinho6 chinh nhu du6riddy: N'uo=NuoxC,u=NxCuxC* (3.1) (Nuo=NxCu) ( 3.2) d6 N'uo cdn duoc kf hiOu ld (N,)uoi C (hay n,) - h9 sd hi€u qui: tr r \ _ " h " 6 day En- nlng lugng hi6u qui c6 thuc c[rathidt bi; 60 - nangluong hiOuqui ti6u chudn(6OVo); O nu6c ta, c6 thd tam lay C, = 0,5 + 0,9; Khi thidt bi tiOn tidn hon, ta c6 thd lay C, cao hcrn; CN- h0 sd d0 sdu.Tuy nhiOn,c6 nhidu tdc gih dd nghi c6c hOsd C" (gdn gidng nhau)nhu sau: Liao & Whitman(1986):C* = (0,9576/ o'un)o' (3.3) Peck(1974): CN= 0,77 log(20I l,O5 / o'"0) (3.4) Skempton(1986): CN=2/(l+o'"0) ( 3.5) o dAy o'uo- rlng suAthfru hiOutheo phuongdrfng,bar (= kglcmz) C* phucrngtr)nh (3.3) don giin, nhung ndu dd sAunh6 hon m thi nen dirngphuongtrinh (3.4) hoac (3.5) vi phuongtrinh (3.3) cho C* kh6 lcrn Ngodi ra, Bowles( 1996)cdn dd nghi c6c h0 sd khdc (qr, r'l:,I+), ruy nhi€n,ci{c h€ sd niy kh6ng quan so vdi C" vi C": Tz = min(1,0; 0,03L + 0,7) vdi L ld chidudii cdn I: = 1,0vdi 6ng lay mAukhOngc6l6p l6t ; = 0,9 voi dng ldy mdu c6l6p l6t, ddt c6t rdi ; = 0,8 v6i dng ldy mAu c6 l6p l6t, ddt c6t chat hodc ddt s6t Io = 1,0n6u 16khoanc6 dudngkfnh 60 + 120 mml' / = 1,05ndu 16khoanc6 dudngkfnh 150mm ; = l,15 nOu16khoanc6 dudns kfnh 200 mm cHuoNG 3.THINcHtFM XUYEN TteUCHUAN 113 3.3.UocriruncAc cni ,nEu co LVcOasAr DUATRENKETQUA SPT Tir thi nghidm SPT, ta c6 thd du b6o rat nhidu chi ti6u co ly, vi sd luong cdc phuongph6p thidt kd m6ng (m6ng n6ng, m6ng coc) dua truc tiep tr0n SPT lb nhidu nhAt(so v6r c\c thf nghiOmhi€n trudng kh6c) Tuy nhi6n, c6c tuctngquan nhy, cfrng nhu nhirng ring dung thiei ke r;in m6ng, c5 dd tin cAy nh6 ba lf chinh sau: a Nang lucrnghfru hi€u cira thidt bi SPTkh6ng bidt o Thf nghi€mSFrIle dQng,trong d6, da sd cdc chi ti0u co l! ld chi ti€u tinh a SPTra dbi duo.c 70 nam thi ngudi ta m6i b6t ddu quan tAm den vidc chudn hod so doc, d6, rdt nhidu tuong quan thuc nghiOm(md ngly v6n dang dirng) lai lay so doc th0 N (chuachudnh6a)dd lim thudc 3.3.1 DANHGtACAcrirunCHArvAr lY DUArRENKErQUASpr 3.3.1.1.Ddnh gi6 dQ chet tudng d6i cfra dd'trdi dga tran ket qui SPT Terzaghivh Peck (1967) ddu ti6n dua tudng quan D,-N (khongchuiin ho6) nhu 6bhng3.2: B6ng 3.2.DO chit tuong doi D, 0+4 4+10 10+30 30+50 >50 D,(%l i.1E, 15+35 35+65 65+85 + 10 TrangthSi rdt roi roi chit vrja chdt rdt chdt N Saud6, Gibbs v) Holtz (1979) chrlngminh r5ng, D, cbn phu thudc vdo cap ring suAt(o',0) - dAy chinh le kh6i ni€m hd sd dQ sAuC,u- nhiOn,hic d6 khrli ni€m C,u chuaphd bidn nOnGibbs vh Holtz dua dd thi & hinh 3.4 Kulhawy vh Mayne (1990) trich d6n phuongtrinh phrlc tap (3.6) tir Marcusonvd Bieganousk/,trong d6, D, phu thu6c vdo cAp rlng sudt (6',o), cdp phdi hat (qua h0 sd ddngnhdt Cu= D6s/D,o) vd lich sir ring sudt (OCR): D , ( V o ) = 2+ (3.6) Ngodi ra, Kulhawy vh Mayne (1990) cbn trich d6n phuongtr)nh (3.7) (tuong tu phuongtr\nh 2.2 cira CPT), d6 strdung s6 doc chudn hod N'u.,: TNOHT 114 THfNGHIEM oATHIENTRUdNG VAIAG DUNG TRoNGPHAN T[cHNENM6NG D I )ocR0'tr(1,2+0,05log(t/ 100) too+ 25togD50 d6 ( 3.7) Dro- kfch thu6c trung binh cira thhnhphdn hat, mm; OCR- h€ sd qu6 cd kdt (o'./o'"0), r - tudi cira ddt, nam Trong phuong trinh (3.7), ta c5 tfnh ddn ydu td gid ho6 (tudi ctra dAt), dai luong nhy goi l) Co vi bang: ( 3.8) Ce=1,2+ 0,05 log(t/ 100) N^n o O O o CL o rf I ah z oa o, L an o N 'Dr (i6) 90 DHinh 3.4 Quan h6 D,-N fng su6t(Gibbsvi Holtz, 1979) 3.3.1.2.Diinh gi6 trang th6i crja di't dinh dua tr6n ket qui SpT Tucrngquan gifra LI (dO s€t - liquidity index - cbn kf hi6u lh B) ducr c trinh bhy o bAng 3.3 Tuy nhi6n, d6 tin cay cira bAng ndy kh6ng cao l5m, v) c6c ddt c6 d6 nhay cAmkh6c s0 c6 tucrngquan khdc di BAng3.3 Trang th5icfra dft dinh (Szechyvi Varga, 1978) N^n 30 LI >0,5 0,25+0,5 0+0.25 -0,5+Q < -0,5 Tranq th5i mem d6o c(tno nlla ctirnq cf-fno rat r5n -r CHUONG 3.THINGHIEM XUYEN TIEUCHUAN 115 3.3.2.DANHGIAT1NH BIE-N DANGC(|AOAr O{E TRCNXEr OUASPr 3.3.2.1 D6nhgi6 m6dunbidn dangcia c6t drlatr6n ket qui SpT Mddunbiendangcirac6tc6 thdx6cdinhsob6 nhusau: (3.e) E=kNuo,bar d6 k = voi ddtc6tlAn bui, s6t; k = l0 v6i ddt c6t sachcd kdt thulng; k = 15 vdi dAtc6t sachqu6 cdkdt Ohya vd cdng su (1982)cho rang,th6ng qua kdt qui thi nghiOmxuy6n ti€u chudn SPT,ta c6 thd so bo du b6o modun bien dang nhu & hinh 3.5 Tuy nhien, nhu ta thdy trOnhinh v6, dd tin cdy cfia tuong quan khdng cao l6m Trong hinh v6, E du-o c k;i hicu le EpMr,d6 le mddun bidn dang xdc dinh thdng qua thf nghiOmPMT Vdi thf nghiem PMT ddt cdt, E duo,c coi li mddun bidn dang thodt nudc Trong hinh nhy, phucrngtrinh tuong quan l): E = 9,08 Nuoo'66, bar (3.10) Ngoii ra, ta cfrngc6 thd sft dung tudng quan M = Cr + C"N ctra Dric (Co hoc Ddt, V[ Cong Ngt NguyenVan D[ng) 500 * "i | tt 200 *.s.osNo'cE " $r too ^ - (no 320, rZ'O.46?, S.D,e6t-Spol i, I ] o :l o I a o y'r r/a go ? l o 20 Hinh 3.5 Modun bi6n dang cfra c5t Eo*"(Ohya) 100 200 Nuu THINGHICM VAI1NGDUNG TRONG PHANTICHNENMONG DATHIENTRUdNG 116 3.3.2.2 D6nhgi6 m6dundirnh6i t(c thdi crjas6t dua tr6n ket qui SPT Ohyavi c6ngsu (1982)cho rangmddunddn hdi tfc thdi E" ciras6tc6 thd tam tinh nhuhinh3.6: E" ^, (6 ddn 50) Nuoo'o' , bar ( 11 a ) (3.11b) Gi6 tri trung binh ld E" r 19,3N600'63 3.3.2.3.D6nh gi6 m6dun bi6n dqng cia s6t dr,ratr6n k6i qui SPT Stroud(1974)ki€n nghi c6chu6c tfnh m6dunbidn dangkhOngno h6ng nhu sau: M = 4,1 Noo ndu I (hay PI - chi sd d6o)>30 ' M - (8,6 - 0,15IP)N6o ndu I rar' a t is3ur.d -i; :i t O 9,o iq) x o (! OCR.O.58 Npo/dro 1 ' 1 21, a ' g i s , s , - s.D 3.82) \r/_f WN '/ { g } € {{ J: q < ,'7* ' ^*"e{"'sf to U' (O I -'6 / ffit"""Ln t s r o Nuo/ o'uo(o'"0do bbng bar) l rotq Hinh 3.8 Quan h6 OCR N(Kulhawy and Mayne, 1990) 118 THfNGHTeM DArH|EN TRUoNG vAIJNG DUNG TRoNG PHAN TfcHNENMONG K o o O l , lp o l o { n " ,r ? ? ? I +.I Ko z o o ro ?o 30 4,0 50 60 N/o'uo Hinh 3.9 Quan hQ Ko N (Kulhawy, 1989); o'"" tinh blng bar 3.3.4.DANHGIASUCKHANGCAr C(JAOAr OqINTRENrEr OUASPr 3.3.4.1.D6nh gi6 srlc khang cit cia ddt c6t drratr6n kdt qui SpT ThO so nhdt (vd cfing c6 dOtin cAy thdp nhdt) lI udc luong 50 Theo Peck vi c6ng su 41 Theo Meyerhof 45 rdt roi roi chdt vUa chdt rdt chat D6 chit tuong d6i II 12.9 TIEUCHUAN CHUONG 3.THINGHIEM XUYEN I BAng3.8 Sr?ckh6ng m0i q"(kPa),c6ch tinh SchmertmannSPT B6t6nq vd coc H Goc dnq th6p Ddts6t 67N 46N H6n hop s6t-bui-c6t;CAlrdl n h i d ub u i :B u i 3N 92N c6t 306 N 6N Da voi mdm; C6t l6n nhrduv6 sd hdn 345N 4N K,i hi6u I I z Loai dit Sau tinh Q, u21Qn tU phuong trinh (1.24) vd (1.25), cdch tfnh crla Schmertmann, cdn c6 thOmkh6i niOmsricchiu tii huy dQng,d6ld: Vdi coc b€t6ngvd H: Qr,a= Q, + Qn/3 (3"23) Vdi coc 6ng th6p: Qr,a= Q, + Qn/2 (3.24) Vd stic chiu tii cho ph6pdu-o c coi le: [Ql = Qh,/z Nhu vdy, theo c6ch tinh nhy, h€ sd an toln cho s(rckh6ng bdn ld Fr = 2, vh h€ sd an todn cho sfc kh6ngmfri lI Fn= x = cho coc bdtdngvd coc H; Fn = x = cho coc 6ng th6p 3C h i d us A u n g d m d i Ndu chidu sAung)m cira doan coc lop ddt chiu tii (dat tdt) l)r dir l6n, th) sric kh6ng b€n vd mfri sE duoc tinh to6n nhu & phdn 3.5.2.1vd 3.5.2.2.Tuy nhi€n,neu chidu sAungdmkh6ngdfr, thi sfc kh6ngmfri sd bi giim di Ta goi Do (actual) l) chidu sAu nghm thuc (cira coc vho lop ddt t6t), ve Dc (critical)ld chidu sAunghrncdn thidt D phq thuOcvdo loai dat nhu bing 3.9 Trong bing, B ld duongkinh coc Bdng 3.9 Chiiu siu ngim cdn thidt D^/B K,i hi6u Loai dit Odts6t z Cetdt nhidubui:Bui H6nhooset-bui-c5t: C r i t c :N < ^ N=13-29 I N>30 12 Dri voi mdm: C6t ldn nhiduv6 so, hdn o Khi ltlp ddt o mfli coc xdu hcn lcrpddt b€n tr€n (hiem thidt kd nhu vAy) th) ta c khdng cdn hi€u chinh srlcchiu tAi tfnh du-o 9.TNOHT 130 THfNGHTFM DAr HteNTRIJdNG VAUNcDUNG TRONG PHANThH NENMONG KHI LOP oAT O MUI CoC TdT uoN LoP DAT gEN TREN vA: N6u D ncD (hinh3.18a),thi phii hi€u chinhnhu sau: D^ -gtc) =9r-c go * O;,Ot t= *[r,-.*ftte,-q*)] (3.2s) (3.26) d6 9o- srlckh6ng mfri hiOuchinh; qr"- srlckh6ng mfri tinh m[t phan lop nhu & ba6c 3.5.2.2; qr- srlckh6ng mfri (chua hi€u chinh) tinh mfii coc nhu bu6c 3.5.2.2; { - sfc khr{ngbOnhi€u chinh cira phAncoc lcrpdat tdt doan cudi coc; {" - srlckh6ng b6n (chua hiou chinh) cria cirng phdn coc nhu tfnh f, Trong phuong trinh (3.25) (3.26), ci go vi f, ddu nh6 hon gi6 tri chua higu chinh (q, v) f,") a) b) Hinh 3.18 Hi6u chinh sfc kh6ng Niu D n>D (hinh 3.18b),thi phii hi€uchinh nhu sau: fir-c-p= +0,5(q.o-q,.)] !*[or 9co d6 e.z7) f,r.-o - srlc kh6ng bcn hi€u chinh cho doan coc tt didm LC (mat phan lop, tfc ld layer change)tdi didm D; - srlckhdng b€n chua hi6u chinh cho doan LC-D; fior-c_o q.o - sfc kh6ng mfri rinh tai didm D (kh6ng hi0ir chinh) Sfc khdng mfri qokh6ng cdn hiOuchinh 121 TIEUCHUAN 3.THtNGHIqM XUYEN CHUONG 3.6.QUANHEGruACPTVA SPT Quan h0 gifra kdt qui CPT vd SPTkh0ng phAi ln tuy6n tfnh Ty so q'l N cdn phu thudcvdo t6n ddt (xem bing2.5) Trudc d6 (1986),RobertsonphAnloai dat 12 virng nhu & h\nh2.23; d6, quanh0 q, vh N lay theobing 3.10 Ngodi ra, vdi cdt, t! sd ndy cdn phu thu6c vlo dudng kinh trung binh cd hat D.r,, nhu hinh 3.19 Bdng 3.10.Tuong quan gifra GPT vd SPT theo Robertson - 1986 Tf so q, / Nuo T6n ddt Nh6m (GPTso v6i SPT) Ddt hat nhav cim Hltu co; bin s6t Set l6n bui A B u i b u i l n s t : s tn h i d ub u i o S t n h i d ub u i t i c a t b u i C a t n h i ub u i CAtnhidubuit6ic5t I vdt I 1.5 z z,c 10 cAt t6i s6ic6t 11 Ddt hat rdt c[tnq (qu6 cd kdt) 12 Cttll A citt rdt cfno (ou6 cd kdt) o I I z Q u a nh & h i n h I : ( 3.28) g.,/ N = 5,44 Droo''u (q.,do bang bar) Vdi dat chrlanhidu hat thi: (3.2e) g r / N = , - P o o %4l1 , - him lucrngtfch lfry hat lot qua shng0,074mm (shngsci200) d6 %.oro j _ - 132 THINGHIEM DATHI€NTRUdNG VAUNG DUNG TRONG PHAN TICH ruEru U6ruE to A a t I ,il ? F n o z a tt ,l/ii rl F ro o F rl z I c *Hi ! r Y4 ?)HT f Gffi F o_ ,/ l+ rl o.ooI o oI o.l Cd hat trung binh Duo(mm) Hinh 3.79.Tudng quan giira ket qui CpT va SpT t-o CHI/ONG 3.THINGHIEM XUYEN TIEUCHUAN 133 3.7.ViDU T1NHTOAN 3.7.1.v1 DU1:XAcDINHrfruncHArcO Hgc cOnoAr Cho kdt quAthf nghiOmSPTnhu bing 3.11.Trong d6: COt I le dO sAuthf nghidm, c6t 2ld s0 nh6t dap dd dng ldy mdu di duo.c 30 cm, cdt le kdt qui phAnloai ddt phdng til m6u ddt thu dugc Xdc dinh g6c q vi mddun bidn dang E Biet muc nudc ngdm tai 3,5 m Bdng3.11.Kdt qui ttri nghidmSPT z (m) N ddt N.o o'," (bar) 0.25 0.50 0,65 1,52 3,05 o 4,57 I 6,10 12 6,86 15 7.62 21 24 33 30 35 27 63 33 38 60 60 72 d.JU 9.14 9.91 10,67 11.43 12.19 13.72 14.48 15,24 16.00 bui roi 25,66 10 0,80 bui 14 0,86 37.77 chdt to 0,92 38.67 VLla 22 0,97 41.36 ZU 1.04 40.03 23 1.11 40,98 38,26 45,00 39,1 40,01 c5t h 0.74 chdt 18 1,18 Vtja 42 22 1,25 /chdt z3 17.53 114 cAt (rdt) 18.29 138 chbt 16.76 I Schmertmann 32,58 31,51 33,38 35,02 o 1,39 '1,46 o 40 40 1,53 1,60 43,94 48 r.ov /o 1.79 92 1.88 45.00 45.00 45.00 30,03 38,21 41,51 44,25 45,00 CQt4 lh sd doc SPThiOuchinh theo ndng lugng tiOuchudn 607o: Nuo=N.Cu Cho ring, ndng luong hfru fch c[rathf nghiOmSPTn]y ld 40Vo: 3Cu=40 160 COt5 le ring suAtbin th6n hfru hi6u Cgt 6lh g6c ma s6t tfnh theo cdng thrlc Schmertmann(phuongtrinh 3.16):