- Ap Ive thftm duai day d~p W, (Hinh 4.6)
l: G T6ng cac Ilfc th~ng dUng tac d\ffig len m{lt cAt tinh toano
l:G=G+W2- W,
bh nbh bh bh
~G =y,-+y--aIY-=-(YI +yn-aly)
2 2 2 2
(4-3)
Y, Yl - TrQng luqng rieng Clla nuac va Clla v~t li~u lam d~p.
a, _H~ s6 ap IlfCthilm con l(li do tac d"mg can traClla mang ch6ng thllm.l:Mo _ T6ng momen clla cac IlfCd6i vai trQng tam clla m{lt dt tinh toano l:Mo _ T6ng momen clla cac IlfCd6i vai trQng tam clla m{lt dt tinh toano
bh(~-nbJ ~M = yh2 •h +a y bh .~ _ y nbh (~_ nbJ _ y bh ._~2_~
023126 223 12 3
(4-4)
(4-5)Thay cac tri s6 l:G va l:Mo vao cong thuc (4-2) va lily dilu trir truac s6 h(lllg thu Thay cac tri s6 l:G va l:Mo vao cong thuc (4-2) va lily dilu trir truac s6 h(lllg thu hai ta co Ung sullt amep thuqng luu day d~p 0' khi h6 day nuac.
0'= h[ YI(1-n)+ yn(2 - n)- aly - y ~:]
f)~th6a man di~u ki~n t(li mep thuqng luu d~p khong sinh ra Ung suilt keo, ruc la
0' = 0 ta tim duQ'c chi~u r(mg day d~p.
b= h
2'1-(1- n)+ n(2 - n)- 0.1
y
(4-6)
Kh6i luqng cong trinh se nh6 nhilt khi bi~u thUc trong Clm Clla cong thuc (4-6) d(lt tri s6 ClfCd(li. Lily d(lo ham clla bi~u thuc do theo n va cho biing khong ta duQ'c:
2-2'1- n=--Y-
2
(4-7)
Neu Yl = 2,4 T/ml (be tong), Y = 1T/ml (nuac) thi n = - 0,2 nghla la mai thuqng luu d~p co d(\ d6c nguQ'c. M{lt cAt d~p nhu v~y gay kho khan khi thi cong va co th~
(4-8)
(4-9)phat sinh ling sudt keo tren m(it h<;ilUll d~p khi d~p vila thi cong xong hay khi thao phat sinh ling sudt keo tren m(it h<;ilUll d~p khi d~p vila thi cong xong hay khi thao C<;iUh6, do do ngum ta thuang IdYn=O.
Khi mai thuQllg lUll th~ng dUng thi chi~u rQng b la:
b= h
~~ -a1
N6u a, =0,5, y, =2,4 T/ml (be tong), y = I T/ml (nuac) thi b=0,73h. N6u co bi~n phap giam ap Ivc thdm an~n b~ng khong (al=0) thi b =0,65h. Ta thdy r~ngtrm'mg hgp khong co ap Ivc thdm chi~u rQng day d~p b nh6 han truang h9P co ap Ivc thdm duai n~n va kh6i IUQllgv~t li~u lam d~p co th6 giam (10
+25)%. Vi v~y cful thi6t phai co cae bi~n phap cong trinh d6 giam ap Ivc thdm duai day d~p.