I I I I I KHOA HOC - CONG NGH6
PHAN TiCH Sir KHAC NHAU VE TINH TOAN SDTC CHjU TAI CUA COC DON THEO DAT NEN GiffA COC DONG VA COC KHOAN NHOI
THEO 22TCN 272-05
Tom tdt: Bai bao trinb bay khdi nidm, ca s d I'f' thuyit tinh todn sO-c chiu tdi theo dat nin cCia CQC ddng va cgc khoan nhdi. TCr do, tac gid phdn tich, so sanh sy khac nhau g/da cac phwang phdp tinh, thyc hi$n cac vi du minh j hga cho bai loai cgc tren vd dua ra kit ludn, "'_
khuyin cao cho nguai lam cdng tdc thiit ki. | ru- khda: Cgc ddng, cgc khoan nhdi, tinh todn J
sire chju tdi theo dit nin. 7 Summary: This article presents the concept, !
the theoretical basis for calculating the bearing capacity of the piles and the drill stuffed piles. ^ From there, the author analyzes, compares ' the differences between calculation methods, performs illustrations for the two types of piles 4 and makes conclusions, recommendations for ^ designers.
Keywords: Closed pile, drill stuffed pile, calculation of bearing capacity In soil. A
LDATVANB^
Hipn nay, mdng cgc ddng va khoan nhoi la hai lopi d u g e s u dung chu yeu trong t h i l t k l , xdy dung cac cdng trinh giao thdng vd xay dung. Tfnh todn sde chju tdi d i i v d i hai lopi mdng ndy tuang doi phuc tap, phu thudc n h i l u vdo d i i u kidn dja c h i t , loai d i t , cae Idp dja lang md cgc xuyen qua, dja chat mui cgc, c h i l u sau, kich thudc coc, phuong phdp tinh todn v.v... vd rat hay n h i m l l n . Cpc ddng va cpc khoan nhoi cd bidn phap thi edng, khoang cdch gida cae cgc khdc nhau, phuo-ng phdp thi nghiem xdc djnh sue chju tai khac nhau nen linh toan sue chju tai theo ddt n i n cung nhieu diem khdc nhau. Vipc Idm rd s u khac nhau v l tinh todn sue chiu tdi cua cpc don theo d l l n i n gii>a cpc ddng va cgc khoan n h l i theo 22TCN 272-05 Id dieu c i n thiet.
2. MOT s 6 KHAI NI$M c a BAN
Mdng cpc Id kieu mdng sau tuong d i i manh d u g c chdn toan bd hay mdt p h i n trong d i t , dyj^ac thi cdng bang ddng, khoan, khoan xoan, xdi thuy luc hay cdc phuang phap khac vd nd cd duge kha nang chju tai t d dat xung quanh vd hay t d dja tang d i t hay dd bdn
mm
PGS. TS. PHAM V A N T H O A N Vidn Ky thupt cdng trinh dpc bi|t d u d i mui cpc. Mdng sau la mdng ma sue ehing cOa nd cd d u g c bang truyen tai trpng tdi d i t hay da tpi ao sau ndo dd bdn d u d i k i t c l u bang k h i nang chju lipc tpi day, s g dfnh bam hay ma sat, hope d hai. Mdng ddc lap la mdng d d dan le cac p h i n khac nhau cua mgt c l u kidn k i t d u p h i n d u d i . Mdng nay dugc gpi la mdng cd d l . Cgc c h I n g Id cgc ma toan bd khi nang chju lue ehu y i u ed d u g c t u sde khang cCia v|t lieu mdng md trdn dd mui cpc l u a vao. Cpc ma sal 1^
cgc md loan bd kha nang chju luc chu yeu cd duoc t u sue khdng eua dat bao quanh dge than cpc du-crc chdn trong dat. Cgc xidn la cgc ddng ed gdc nghieng so vdi phuang t h i n g ddng de tpo ra sde khdng cao han doi vdi tdi trgng ngang. To hgp cpc chong vd cpc ma sat la cgc cd d u g e kha nang chiu luc t d t l hep eua d sde chju d mui cgc va sde khang bao quanh dge than cpc. Cgc ddng la loai cpc dugc c h i t^o s i n bang BTCT, thdp, go, be tdng, sau dd s u dung cdc t h i l t bj (chu yeu la bUa hay vdt ndng khdc) de dua cgc xuydn sdu x u i n g cdc Idp nen d i t d dd sau mong m u l n . Cgc khoan n h l i Id mdt k i l u mdng sau d u g c chdn todn bd hay mpt phan trong dat vd dugc thi cdng bang cdch do be tdng t u a i trong ho khoan trudc d d cd hope khdng c d e l t thep. Cgc khoan c6 d u g e kha nang chju tai t d d l l xung quanh va l u dia tang dat hay dd phia d u d i mOi cgc. Cpc khoan cung thudng d u g c eoi n h u la ede gieng ehim, gieng chim khoan, cgc khoan hay try khoan.
3. SCPC CHjU T A I C O A c p c D O N THEO D A T N^N C a che lam vipc eua mdng cpc: Mdng cgc khi lam vipc la s u t u a n g tac dong thdi giua d c bd phgn d u thdnh len mdng: S u t u a n g lae gida cpc vd dit;
cgc va cpc (hipu ung nhdm); giua dat vd be mdng;
giua cge va be mdng.Trong qua trinh khai thac va s u dyng, mdng cpc cd the bi phd hogi theo mpt trong cac dang sau:
• Nen dat tot, vat lieu cpc bj phd hoai (vd, giy, kdo ddt...);
• Vdt lipu cpc tot, nen khdng dCi sde chju tdi vd bi phd hoai (lun, chuyen vj Idn cOa mdng);
S6 3 nam 2018 I
KHOA HOC - C O N G N G H E MMKgg Bd mdng khdng du b i n vd bj phd hopi do u l n
ndt, cpc chge thung dai, ept ehgc thung be, ddi bj cat trdn t i l t didn nghieng.
Sue chju tai cua mdng cpc phu thugc vdo cdc bg phdn cau thdnh Idn mdng bao g I m be mdng, cgc trong mdng, s l l u g n g cge, bd trf cpc vd n i n d i t . Sde chju tai dgc tryc ciia cgc d u g c phan lam hai loai:
Sue chiu tai theo vpt lidu (P^) vd sde chju tai theo dat nen (P^^), Ddi vdi sue chju tdi cua cgc theo vat lieu, sde chju tai cgc hpn (P^,) se d u g c linh toan dua tren c u d n g dd cgc hpn eua vat ligu (vdi cge thep la c u d n g do gidi hpn chay cua thep f^, edn vdi cgc be tdng, c u d n g do cue han t h u d n g la cudng dd thf nghidm d ngay t h d 28 trdn m i u t m trdn f^.
D i i vdi s u e chiu tai eua cpc theo d i t n i n , cgc t r u y i n tdi trpng t d cdng trinh bdn trdn xuong nen dat phia dudi theo mdt trong hai d c h : Sue khdng xung quanh cge Q^ (gdm ma sdt thdnh bdn va lue dfnh cua d i t va cge) la phan Igc gida d i t xung quanh cpc vdi didn tfch thanh ben cua cge. Sue khang mui Qp Id phan luc cua d i t mui cgc len dau cge. Sue chiu tai cue hpn eua cgc theo d i t ndn d u g c chia thanh sue khang ben va sue khang mut n h u sau: Q^ = Q^ + Qp- Nhieu nghien c u u cho thay r i n g , sue khdng ben dat cgc hpn rat nhanh d ehuyen vj khoang 3 - 5mm. Sde khdng mui dgt cue hpn rat chdm, d u d i tdc dyng cua tai trgng, chuyen vi cua cpc r l t nhd, do do sde khdng miji m d i chf huy dgng mdt phan nhd (trong khi dd, sue khang ben eua cpc da kha Idn).
Coc trong d i t set. Khi thi cdng cpc, d i t set bi xao dpng, khi do sue khang eat khdng thoat nude cCia d i t set tam thdi giam xuong. Tuy nhidn, sau mgt thdi gian ddi (cpc nghi) dp Igc n u d e Id rdng d u se tidu tdn dan. 0 da so d i t set se ed hipn t u g n g sde khdng d t phyc h i i mdt hoac todn p h i n theo thdi gian. Vdi d l l dinh bao hda n u d e , nen s u dung sue khdng d l khdng thodt n u d e S^ de d u bao sue chju tdi cue han cua cgc vi ngay khi cd tai trgng tde dung, loan bg lai trpng se do dp luc n u d e lo rong t i l p nhan (vdi d i t set bao hda, ap Igc n u d e Id rdng d u tieu tan r l t cham, hay eoi n h u khdng tidu tan). Do v|y, vdi dat dfnh, thdi d i l m nguy h i l m n h l t chfnh la ngay sau khi thi edng xong, n u d e ehua kjp thoat dl.
Cpc trong dat cat. Cgc ddng (hay dp) t h u d n g lam chat dat xung quanh cgc, dan d i n s g lun syt cCia dat xung quanh, hd s l dp lue ngang K^ se tang Idn, dong thdi s d e khdng d t cua d l l se t i t han. Tinh chat cDa dat tot Idn Idm eho sue chiu tai cua cpc cao han.
I So 3 nam 2018
Khi tai trpng dat d i n eye han, d l l d mui cge se bj phd hoai theo mat trugt sau. Mat trugt sau nay hinh vdng cung bat dau t u mui cgc, dl xuong d u d i khoang 2-3,5D, sau do vdng len trdn khodng 2-8d (D - d u d n g kfnh cua ege). Pham vi mat trugt phu thu^c vdo lopi dat d Idn c|kn mui cgc. Neu la d i t dinh thi mat trugt nhd (xuIng d u d i va len tren khoang 2-2,5D), cdn vdi d t chgt thi mpt trugt ddi han (xuong d u d i khoang 3-3,50, len trdn khoang 6-1OD). N l u cgc lam viee trong nhdm, khi tdi trpng dat cue han, dat d d u d i mui cpc edn bj pha hoai sdu han. Chfnh vi t h i md h l u h i t eae tieu c h u l n d l u ydu d u c h i l u sdu khao sat t i i t h i l u phdi Idn han dp sdu mOi cge khoang 2-3,5D.
Sue chju tdi ngang cua mdng cgc Id sde chju d l c h I n g lai chuyen vj ngang do luc ngang va md men gay Ipt tae dyng tai dinh mdng. D i i vdi mdt mdng dan, sde khang theo phuang ngang cd t u 3 thanh p h i n : Ap lgc ddt theo phuang ngang, lue d t d chdn mdng vd dp luc d miji cpc phan bo khdng d i n g d l u . Ap lgc dat theo phuang ngang Id sde khang ngang chu y i u d i i vdi cpc ddi.
V d i cpc khoan n h l i cd s d dyng dung djch giu on djnh thanh lo khoan ma day id khoan khdng Q\xac ve sinh spch se mCin khoan trude khi do be tdng thi sde khdng mui se gidm di r l t n h i l u . Cdn n l u thi cdng khdng giij" thanh bang dung djch, cd I h l trong qud trinh d l bd tdng cd nhdng tang cue set bj Id hay bj Id vach thi lam chat lugng bd tdng giam. Cdn n l u d l bd tdng qud thda nude, n u d e se bj dat set xung quanh hut 1dm gidm sde khdng d t cua d i t nay.
Tuy nhidn, xi mang trong cge nhoi se cd phan dng hda hgc vdi d l l set xung quanh, han nua, thanh cua cge nhoi t h u d n g s i n sui han cge e h l tao san, do do sde khdng ben d u g c cdi thien mdt phan. Doi vdi cgc khoan nhoi, vide khoan Id se lam d i t cdt ( d d thdnh ho vd ddy ho) rdi rpe han, do dd sde chiu lai cua cpc giam di.
Vdi cpc nhoi mui dat vdo da, ed hai ly do khien sue khang mui khdng dang ke: Mpc dO t i n g S\a chat Id dd nhung do qud trinh khoan, s g tiep xuc gida dd va cgc khdng bao gid la hodn hdo (dac biet la khi s d dyng dung djch d l I n djnh thdnh). Dudi tai trgng cdng trinh, dp lun phai nho han do ICin cho phep (thudng la r l t nhd). D u d i dg lun nhd do, sue khang mui ehl d u g c huy dpng mgt phan nhd do d u d n g kinh cgc n h l i r l t Idn. N h u vdy. cgc chong chi t h u d n g gap vdi cpc bd tdng d p eao hay cgc thdp. Chijng ta chu yeu gap lopi cpc hdn hgp ma sat va c h l n g Id pho b i l n nhlt.
mm
I I I I I KHOA HOC - C O N G NGHE
4. s y K H A C N H A U T R O N G TlNH TOAN SiSC CHjU T A I COC B 6 N G VA CQC KHOAN NHdl THEO 22TCN 272-05
s i r c K H A N G
(SlJC CHIU T A I ) LOAIBAT C O C B 6 N G COC KHOAN N H O I Cac ioai dat
Su>c chju tai C9C ttieo dSt nen
(I + II)
+ •••+ 'Pqsi'islK, (vi^c xac dinli q ; q^, xem ben diidi)
^•••+v„q.A.
{vi$c xac ^nti q ; q^, xem ben duui)
I. Sit'C ktidng mdi coc
Ptiu-cng ph^p thi nghi€m SPT Phu'O'ng piiap a Cat, flat rdi 0 , 0 3 8 A - A ' , „
"' D " *
« , = 0 , 4 J V „ ^
0 , 7 7 . 1 o g , „ i i ? ^ | | J V
-f Neu N < 60 thi q = 0,064.N - • N e u N > 6 0 t h i qp = 3,8 + Neu Dp > 1.27m tiii pliai tinti:
1,27
Set dc ioai, bCin dSo
Cat, dat rii\
CSt, ak rai
?,-0,3JV„„
0 , 7 7 . 1 o g , J ^
q^-NJ^F^<A:
760 sl,0 naD, + l(Ob
a-0,007UO,0021.-^sO,015
*-l,45.,/2^;0,5<;*sl,5
PhiFcng phap X Phu'dng phap X
Khong x6t Kiiong xet
•9S„
Khong xetPhiKwig phap thi nghiem CPT Phuvng phap thi nghiem CPT Khong xet
<i,' 1,1+1,2 Khdng xet
mm
S6 3 nam 2018 I JKHOA H O C - C O N G NGHE # # # # #
s i f c K H A N G
(SIJC CHIU TAl)
LOAI DAT
CQC E>6NG C p c KHOAN N H 6 |II. Sijc khang thdn cgc
Set cac lopi
Set cdc lopi
Cat, d i t rdi
Set cac lopi
Phuo-ng phap a Phuang phap a
Khdng xet Khdng xdt
= 9.5„
q^, = a, 5„,Phuo'ng phdp P Phuo-ng phap P
=iSxj;
Khdng xdt•P'^:
Khdng xetPhuo'ng phap K Phuo'ng phdp X
Khdng xet Khdng xet
q^=X.[o'^ + lS\
Khdng xetPhucng phap thi nghidm SPT Phucng phap Reese and Wright 1977
q^,=0,m\9N
+ N l u N < 53 thi q^, = 0,0028.N + N l u 5 3 < N < 1 0 6 t h i q^, = 0,00021.(N-53) + 0,15g,, =0,0019JV
Khdng xdtPhuong phap thi nghiem CPT Phuo'ng phap thi nghidm CPT
«>,-f„-
Khdng xet
Khdng xdt
trong dd: A : dipn tich xung quanh cua mui cgc (mm^);
A^: didn tich xung quanh eua cgc d ldp dat t h u i (mm^);
i: so Idp d i t ma cgc xuydn qua; (p ^. hd s l sue khang d i i vdi kha nang chju tai cua mui cpc; (p ^;. he so sde khdng doi v d i kha nang chju tai cua thdn cpc; o^: dng s u i t Igc t h i n g dung huu hieu (MPa); D - d u d n g kinh cgc; N: so dem SPT do durfc (Bua/300mm); N^^: s l dern SPT gan mui coc da hieu ehinh cho ap lgc t i n g phu' ~N '• so bi5a d i m trung binh dpc theo than cpc;
a: chieu rdng cpc; D = D - dudng kinh mui cge; D^
= Z- C h i l u sau chdn epe trong Idp d l l chju luc cuoi cung; S^: cudng dp khang d t khdng thodt nude cua d i t set, tra todn d l ; a : hp s l k i t dinh, phu thudc vao tdng lopi dat, ehieu sdu chdn ege D^^, cudng dp khdng d t khdng thoat nude, tra todn d l ) : A : he s l thuc nghidm, A = 0,4; qp: sue khang dan vj d l u ege danh djnh (MPa), d u g c xae djnh theo d c phuang phap thue nghiem SPT (thf nghipm lieu chuan d i i vdi d i t
m^m
# # # # # KHOA H O C - C 6 N G NGHE
rdi); Q^: tdi trgng danh c^nh do mui epe chju (kN); q : sde khdng ma sat dan vj danh (^nh than epe d idp dat tiid i (MPa), d u g c xdc dinh theo phuang phap thuc nghiem A cho dat dinh; so dem SPT (N) do dugc (BUa/300mm); hp s l khd nang chju tai (NJ Id tham s l tinh toan trung gian theo cdng thdc d bang; hd so giam sue khdng mui cpc cua cpc khoan dudng kinh Idn (F^) la tham so tinh toan trung gian theo cdng fridc d bang; dp xuydn eua epe khoan trong t i n g chju lue c u l i cCing (Z); sde khdng dan vj dau cpc (q^) d u g c xdc djnh theo cdc phuang phdp thgc nghipm SPT (thi nghigm xuyen ddng tieu c h u l n cho d i t rdi- phuang phap cua Reese and Wright 1977 ICiy theo lopi dat, theo edng thdc d bang; sue khang ma sdt dan vj thdn cgc (q^) dugc xdc dinh theo phuang phap thuc nghidm a cho d i t dinh tuy theo logi d i t , theo cdng thue d bang; hp so k i t dfnh ( a ) , phu thudc vao tdng lopi d i t , cudng dp khang d t khdng thodt nude, Tieu c h u l n 22TCN272^5, la he so thuc nghipm; hp so kinh nghipm (K)- Chgn A^= 0.9 theo "Phuang phap k i l m tra vipc thi edng cdc cge va ddnh gid khd ndng chju tdi cOa chUng trong vd sau khi ddng epe vdo d l l " ; cudng dp khdng d t khdng thodt nude trung binh (SJ; q_,^: gid trj tnjng binh cua q^ trdn todn bd ehieu sau yD dudi mui cgc; q ^ : gid tri trung binh cua q^ trdn toan bd khoang each 8D ben tren mui epe. L^:
c h i l u sdu d i n d i l m giua khoang chieu ddi tai diem xem xdt (mm); D,: c h i l u rdng hope dudng kinh cpc (mm); f^,: sde khang ma sat dan vj thdnh I n g cue bd l i y t d thi nghidm CPT tai d i l m xem xet (MPa); a^,: ehu vl cgc tai d i l m xem xdt (mm); h; khodng chieu ddi tai diem xem xet (mm).
4. V l DU TlNH T O A N
V i dM 1. Tinh todn sue chju lai cgc dan BTCT due san theo d i t nen eua mdng try d u . Cho bilt, cpc cd kfch thudc t i l t didn vudng. canh a = 400 mm, mdng gom 4 hang va 7 cdt Tong so 28 cgc, kfdi Hiudc be mdng B x L x h = 8200 mm x 4600 mm x2000 mm. Dudng kinh mui cpc Dp = 0,0. Chieu dai mui epe Lm = 300 mm.
Chieu sau dogn epe trong Idp d l l chiu Igc c u l l cung Db = 2000 mm. Cpc xuyen qua eae Idp d i t nhu sau:
n
1 2 3 4
Ten io-p dat thv i (tinh tiF mat dat nen tr6> xuong
phia du'6i) 1 2 3 4
Loai dat
Cat piia set Cat iiat min S6t mem S6t cu'ng
Chilu day iop datthOi (L,-m)
5,0 4,0 4,0 Rat diy
Dac diem co*
iy cua dat nen theo tiFng iop
W.20 JV-25
«.«
S . 6 0 CT'v.0,20Afl>a
Hinh 1. VI dii tinh toan coc dong BTCT theo dit n4n
Ta co: A, - a ' - 400' = 160.000(mm')
Dign tich mat cSt ngang thSn cpc BTCT:A^ . a ' = 4 0 0 ' =160.000(mm');
• T i n h toan Sit'C t(hang m u i do'n vj q^
IViui CQC CO chieu dai i,„ = 300,00 (mm);
Du'O'ng i<inh mui cpc BTCT; Dp = 0,00 (mm);
Ap dgng phu'ang phap SPT, tinh tpan SLTC i<hang mui cpc ia dat set cijng tO cac cong thijc tren, ta c6:
?, =0,3 JV„^ =0,3.45,381-13,614(Afl»a) 0 , 0 3 8 J ) t J V ^ 0,038.2000.45,381
*' D ' 400 - 8,622 <13,614(Aff'a)
«, =8,622(MPa)
• T i n h t o a n si>c k h d n g do'n vj than cpc q,, Dipn tich xung quanh phan mui cpc:
A, -0.5.4a.^ll,*(0,5af -0,5.4.400.^300'-f(0,5.400)' .288444,102(mm')
Cpc BTCT xuygn qua 4 idp dat;
Chieu sau cpc trong idp dat thu' 1, 2, 3, 4 la I, = 5,0;
4,0; 4,0 va 2,0 (m);
Di§n tich be mat than cpc trong lap d^t thi> 1 la:
A„ - 4aJ, = 4.400.5000 = 8000000(mm')
Dien tich be mat than cpc trpng ldp dat t h i i 2 la:A,j = 4 a i j = 4.400.4000 - 6400000(mm')
Dien tich b^ mat than cpc trong i*p d i t thir 3 ia:A , - 4aA . 4.400.4000 - 6 4 0 0 0 0 0 ( ™ K ' )
m^
KHOA HOC - CONG NGH5 I I I I I Di§n tich be mat than cpc trong lap d^t thi> 4 ia:
• 4 , 4 - 4 a . ( D , - ; _ ) + A ^ . 4.400.(2000 - 300)-i. 288444,102 -3008444,102(mm')
Ap dyng phu'ang phap SPT va cong thCrc tr6n, ta c6 SLFC khang than cpc lap 1 (lap cat):
q„ = 0,0019. N = 0,0019.20 = 0,038 (IVIPa);
Siic khang than coc lap 2 (lap cat):
qs, = 0,0019. Af = 0,0019.25 = 0,0475 (MPa);
SLTC khdng than cgc lap 3 (lap set mem):
qs, = 0,0019. iV = 0,0019.40 = 0,076 (IVIPa);
SLFC khang than cpc lap 4 (iap s6t cu'ng):
qs„ = 0,0019. JV = 0,0019.60 = 0,114 (IVIPa);
5. XAC 0|NH CAC HE S6 SCfC K H A N G
Tra bang, ta c6:
sn
1 2 3 4
Lop dat Lopi L6p2 Lap 3 Lop 4
Xdc djnh
0,45X., 0,45\
0 , 5 0 \ 0,50X,; 0,70X.
A, 0.30 0,80 0,80 0,80
H|s6
0,36 0,36 0,40 0,40:0,56
Lo^i dSt cat pha, (p_
C«min,(p..
S6t ni>a a>ng, tp,„, s a cOng, <p„=0,56
• Tinh toan sire chju tai cua cpc theo dat nen Theo c6ng thCrc ta co:
e , = <P,M, =0,56.8,622.288444,102 . 1392700,427(W) = 1392,700(W)
!2, = ^(?;,„^„A„)-0,36.0,038.8000000
•10,36.0,0475.6400000 + 0,40.0,076.6400000
•i-0,40.0,114.3008444,102.550625,051(W) .550,625(JW)
Sifc chju tai cua cpc theo dat n^n:
P = Q + Q = 1392,7 •!• 550,625= 1943,325 (kN)
dn p s
Vi du 2. Tfnh tpan si>c chju tdi cpc khpan nh6i theo dat n^n cua mong trg cau. Chp biet, cpc cc duang kinh D = 1000 mm, m6ng g6m 06 cpc, kich thu'o'c be mong B x L x h = 7600 mm x 4600 mm x 2000 mm.
Coc xuyen qua cac lap dat nhu' sau:
TT
1 2 3
4
T§ni6TJdatthi>
i (tinh lit m^t m6ngtroxu6ng phia du'o'i)
1 2 3
4
Loai dat
Cat m|n Catiiattlio Set ni^a ci>ng Set cu'ng
Chieu day i»pditthi>
i(L-Tn) 5,0 4,0 4,0
RatdJy.Z
= 2,0 (m) fiac diem CO iy cua dat nen theo
tLpng iop N, = 27 N, = 30 Nj = 50;
S. = 0,3;
a = 0,42 N,'=60;
S. = 0,5;
a = 0,35
Ta cd:
Cpc khoan nhil cd dudng kinh D = 1000 (mm);
Dien tfch tilt dien cpc:
4 = £ ^ = lili500l.785000,00(™^)
Hinh 2. Vi dy tinh todn cge khoan nhdi theo dit nin
• Tinh toan sde khang mui San vj q^
IVlui CQC cd chieu dai 1^ = 0,00 (mm);
Du'dng kinh mfli cpc khoan nhoi Dp = D = 1000 (mm);
Dien tieh xung quanh eua mQi coc:
A , = 2 ^ i ) i „ + 5 £ l = 2.3,14.1000.0 + ^ : l i ^ 5 5 2 l
" 4 4 -785000,00(mm^)
Ap dung phuang phap a tinh toan cho dat set cijng to c^c cong thtjc tren, ta co:
I s6 3 nam 2018
# * # # # KHOA HOC - C O N G N G H f e = l,45.j2S^ = 1,45.^2.0,5 = 1,45;
0 , 5 < i = l,45<l,5
<2 = 0,0071+0,002I.-' = 0,0071+0,0021.^^ = 0,0113 <0,015 1000
' 12,fl.Dp + 760i 12.0,0113.1000 + 760.1,45 ' iV,=6.fl + 0 , 2 . - U 6 . f l + 0 , 2 . ^ ^ 1 = 8,40<9
I D) [ lOOOj 9p - -W, S„ F, - 8,4.0,5.0.614 = 2,5Z{MPa) < AMPa
' Tinh toan sire khang d e n v| than cgc q^
Cge khoan nhoi xuyen qua 4 ldp d i t ;
C h l l u sau cpc trong Idp d i t thd 1, 2, 3, 4 la I, = 5,0;
4,0; 4,0 v a 2 , 0 ( m ) ;
Dien tieh be mpt than epe trong Idp dat t h d 1 la:
A^, = 2 j r J ) i , = 2.3,14.1000.5000 = 31400000(mm')
Didn lich b l mat than cpc trong ldp d i t thd 2 la:
4 ^ =2 j r i ) 4 = 2.3,14.1000.4000 = 25120000(mm') Didn tfch be mat than cpc trong idp dat t h d 3 la:
A,3 = 2 j r i J ij = 2.3,14.1000.4000 = 25120000(77im') Didn tich be mpt than ege trong Idp d i t thd 4 la;
A,4 = 2 j r i > ^ = 2.3,14.1000.2000 = 1256a000(mm^) Ap dung cac edng thdc theo phuang phap Reese and Wright 1977); (5 phuang phap a ) , ta ed:
Sde khang thdn cgc Idp 1 (Idp eat):
q^, = 0,0028.N = 0,0028 27 = 0,0756 (MPa);
Sde khang than coc Idp 2 (Idp eat):
q ^ = 0,0028.N = 0.0028.30 = 0,0840 (MPa);
Sue khang than cpc Idp 3 (Idp sdt nda cdng):
9.3 = «3-5«3 = 0,3.0,42 = 0 , I 2 6 ( M / ' a ) Sue khang than cpc Idp 4 (Idp sdt cdng):
9.4 =«4'5„4 = 0 , 5 . 0 , 3 5 = 0 , 1 7 5 ( A f f a )
• Xac djnh cac hd so sde khang Tra bang 5.13, ta cd:
sn
1 2 3 4
Lop dat Lopi L*p2 Ldp 3 Lop 4
Hfsi
0,45 0,45 0,65 0,65, 0,55
Loai 6k
Cat mjn, (p^
cat hat the, ?)„
S6t nOa cu'ng, (p^
Setci>ng, (p^p=0,55
• Tinh toan s u ^ chju tai cua cgc theo dat n i n Theo edng thdc trdn, la cd:
e „ =?'.„9 A =0,55.2,58.785000 -1113915,00(/V) -1113,915(«V)
2 , - S ( ? ' , . , ? . 4 , ) - 0 , 4 5 . 0 , 0 7 5 6 . 3 1 4 0 0 0 0 0
•)-0,45.0,0840.25120000-1-0,650,126.25120000 -H0,65.0,175.12560000 - 5503792,00(W)
= 5503,792(/W)
SCi'c chju tai cua cpc theo d^t nen:
Pj„ = Q, -I- Q, = 1113,915-1- 5503,792 = 6617,707 (kN) 5. K^T LUAN
Tinh toan sijc chju t i i cua cpc dong va cpc khoan nhoi theo d4t nen ia cong viec thuang xuy&n nhirng phai phan biet ro rang trong thiet ke mong cpc mo try chu. Vipc chpn mpt phu'ang phap phu hop anil huang Idn dgn dp an toan, bipn phap thi cdng va gia thanh c6ng trinh. Trong thiet ke, r i t can cac chuyen gia CO nhi^u kinh nghigm va chuyen men sau trong ITnh v y c nSy va nen tinh toan theo nhieu phuang phap khac nhau de chpn d u a c ket q u i ho'p ly va tin cay nhat •
T A I LiEU THAM K H A O
1. Thiet k^ mo t n j mong cau theo 22TCN272- 05, TS. Pham Van Thoan, NXB Xay dung, 2015.
2. Tieu c h u i n thi^t ke cau 22TCN272-05, Bp GTVT, 2010.
>Q^Ii!I@
So 3 nam 2018 I