- TiOOlUll IUQ'Ilgdan vi qua d~p
4. M6t s6 nh(in xet khi eh(Jn kieh thzrereca him ella d(ip
Thea dieu ki~n (4-1), chieu rQng B Clla d~p 006 ooAt khi n < 0 (mai thuqng Clla d~p nghieng "e phia thuqng lUll); tuy OOien n~u chQn n<O khong phil hgp vai
dieu ki~n xay d\lfig, nen t6t ooAt chi chQn n = 0 (mai thuqng lUll th~g dUng). Ngaai ra thea dieu ki~n (4-1), n~u thuqng luu khong co nuac (H = 0, 1]= 0) thi chieu rQng B cua d~p se 006 han truang hgp d~p co nuac. Ngum ta uac tiOO kh6i luqng d~p khi 1] = 0,1 006 han khi 1] =0,5 khaang 10%; tiOO ta{m nay cha ta thAy r~g, kh6i luqng d~p ph\! thuQc OOieu vaa tri s6 1]. Vi v~y vi~c lam giam ap I\l'c dAy n6i duo; day d~p la bi~n phap de giam B rAt co hi~u qua va co y nghia kiOO
t~Ian.
Thea dieu ki~n (4-2), chieu rQng B cua d~p se 006 di khi n tang dAn len, da 19i d\!ng dugc trQng luqng kh6i nuac phia thuqng lUll tac d\lfig len mai d~p (l\l'c P) .. Dieu nay ngugc I\li vo; dieu ki~n (4-1).
Nhu v~y vi~c tang n lqi v~ m~t 6n dinh OOungh~i v~ m~timg suAt; d~ giai quy~t mau thuful nay, d6i v(ri d~p Ian nguCrita phai ti~n haOOgiai hai toan kinh t~ v~ chQn chi~u r(lng B cho ~p (gia thi~t nhi~u n va tinh B theo cac di~u ki~n (4-1) va (4-2) d~ chQn dugc tri s6 B 006 ooAt); Tuy OOienv(ri cac d~p 006 (chi~u cao khoang 2 -;.3m tra xu6ng) co th~ chQntheo kiOOnghi~m.
M(lt s6 truang hgp d~c trung:
Gia sir chQn~p co n = 0 (mai thugng lUllthfu1gdimg), Yb =2,4T/m3:
N~u 11=0,5; theo ( 4-2) ta xac diOOdugc B = 0,75H va theo ( 4-1) ta xac dinh dugc B = 0,73H
N~u 11 =0,1 theo ( 4-2) ta xac diOOdugc B = 0,62H va theo ( 4-1) ta xac diOOdugc B = 0,66H
4.2.2. ChQn m,t cit th,!c cua d~p khong triln
M~t c~t Iy thuy~t chi co y nghia v~ m~t chiu h;rc.E>~phil hgp v(ri di~u ki~n sir d\lllg (thao nu6'c, giao thOng, quan Iy...) ta cAnch~ ~o I~i m~t c~t Iy thuy~t. M~t c~t sir d\lllg th\lc t~ gQila m~t c~t th\lc clla d~p.
M~t dt ngang clla d~p khong tran thuang chQnd~ng hiOOthang, mai thugng co th~ chQnd~g thfu1gdimg ho~c nghieng.
- TiOOtoan va chQncao triOOdiOOd~p co the tiOOva chQnOOud~p dAt. - Chi~u r(lng diOOd~pdugc chQn d\la vao chi~u cao d~p, di~u ki~n thi cong, yeu cdu giao thong tren m~t ~p ... noi chung khong nen chQnB 006 han 2m, ngoai ra cAnb6 tri h~ th6ng Ian can phong hQ,dim chi~u sang...
- B6 tri h~ th6ng hanh lang trong than d~p: V6'i cac d~p Ian cAnb6 tri hanh lang trong than d~p d~ ki~m tra kha nang lam vi~c clla d~p, d~ sira chua, b6 tri thi~t bi thoat nu6'c...
4.2.3. ChQn m,t cit th\fc cua d~p triln
Khi thi~t k~, roy vao timg lo~i d~p, quy mo, chi~u cao d~p... d~ chQn dugc cac d~g m~t c~t tran hgp lY- Ngoai ra tren diOOd~p con co the b6 tri Clra van, cira phai de di~u ti~t nu6'c. Chuang triOOchi gi(ri thi~u cac d~p khong co cira van, cira phai.
Cao triOOdiOOtuang ben, m6 giua nen Idy b~ng cao triOOdiOOd~p phAn khong trani:I2 ben d~p tran.