KHAO SAT VA DANH GIA MOT SO PHlTONG PHAP BO TRI TAM MO, TRU CAU BANG MAY TDDT
ThS. NCS. HO THI LAN HUONG Bd mon Trdc dia
Khoa Cdng trinh
Tru&ng Dgi hpc Giao thdng Van tdi
Tdm tdt: Bdng phuang phdp udc tinh do .chinh xdc chgt che theo nguyen ly sd binh phuang nhd nhdt, bdi bdo khao sdt vd ddnh gid do chinh xdc cua cdc phuang phdp giao hgi
trong bd tri mo, tru cong trinh cdu, lir do dua ra cdc kit lugn vi do chinh xdc cdng nhu pham vi dp dung cua timg phuang phdp.
Summary:By the method of fine estimated accuracy in accordance with the principles of least squares, the paper survey and evaluate the accuracy of method in synodic in setting out abutment, piers of bridges, from which make conclusions about the accuracy and the applicability of each method.
I. DAT VAN DE
Bd tri tam md, tru cau la cdng viec rat quan trgng trong cdng tac xay dung cdng trinh cau. Do chinh xac tam md tru cau lien quan den do chinh xac va dn djnh tdng the ciia cdng trinh cau. Do vj tri dac biet ciia md, trii can ma khi sii- dung may toan dac dien tir (TDDT) de bd tri, chi thuc hien dugc bang cac phirong phap giao hdi. Trong pham vi bai bao nay se khao sat va danh gia do chinh xac, neu pham vi irng dung ciia cac phuong phap giao hdi trong bd tri tam md tru cau.
II. NOI DUNG
1. Cac phuong phap giao hoi trong bd tri tam md tru cau a. Phinrug phdp giao hgi gdc thudn
Tam mo tru ciu P dugc xac djnh tir hai diem 1, 2 ciia ludi khdng che bang each dat 2 gdc bang Pi;
P2 (hinh 1). Do chinh xac cua phuong phap bd tri P phu thugc do chinh xac bd tri gdc bang Pi va gdc
bing p.. CX12 .,' ~ ^ . P
M
eht sm" y 1
S^-FS^ (1)
Hinh 1. So' dd phirong phdp giao hdi gdc thudn
Tap chi KHOA HQC GIAO THONG VAN TAI So 29 - 03/2010 137
b. Phuong phap giao hoi canh
Tir hai diem 1. 2 ciia ludi khdng che bo tri khoang each S|, S2 bing may TDDT, giao cua 2 khoang each nay chinh la diem P can tim (hinh 1).
Do chinh .xac ciia phuang phap phu thugc vao do chinh xac bo tri khoang each ngang S| va S2 va dirge tinh theo cac cdng thiic:
i
(2) M ghe
2 2 m c. + m ^
"1 2 y sin y c. Phirang phdp giao hpi goc - canh
Day la phuang phap ngoai thuc te thudng dugc ap dung khi bd tri tam md tru cau bang may TDDT, 2 may dat ddng thdi tai 2 diem ciia ludi khong che, bd tri ddng thdi gdc P;; P2 va canh Si; S2, giao ciia 2 hudng bd tri chinh la diem P can tim.
Do chinh xac bd tri gdc tinh theo cdng thirc (1). do chinh .xac bd tri canh tinh theo cdng thirc (2), do chinh xac ciia phirong phap:
(3)
in
gc
m X m ght ghe
2 _^ 2 m -^-m
2ht ghe (I. Phuong phdp giao hgi nghich gdc - canh
Phirong phap giao hdi nghjch la mdt trong nhQ-ng phuo-ng phap xac djnh diem giao hdi cho do chinh xac tuong ddi cao. Tuy nhien trudc day chi dugc sir dung de tang day ludi khdng che mat bang thoa man cho yeu cau do ve chi tiet ban dd dja hinh vi viec tinh toan kha phirc tap.
Nhung hien nay img dung chuang trinh giao hdi nghjch ciia may toan dac dien tu da cai tien triet de van de tinh toan cua phuong phap nay vi the pham vi img dung ciia phuang phap dugc md rdng.
- Dat may TDDT tai diem P (hinh 2) ngam den diem ciia ludi khdng ehl 1, 2 (toi thilu 2 diem, tdi da 5 diem), do gdc P va canh Si. ST. Sau khi nhap vao dii cac dir lieu yeu cau (chilu cao may, chieu cao giro-ng, tga do 1, 2) may se tinh ra tga do diem P.
1 S12
Hinh 2. So' dd phuong phdp giao hdi nghich gdc - canh
138 Tap chi KHOA HQC GIAO THONG VAN TAI S6 29 - 03/2010
- Cac yeu td can tinh la:
+ Do chenh lech gitra tga do thuc te va tga do thiet ke ciia diem P.
Ry = yp - ypik
- Dat doan Rx, Ry theo hudng true tga do se .xac djnh dugc diem cin bo tri Po.
- Do chinh xac ciia phuong phap:
M ghngc Trong dd: inni = ms
m r
^ n , + m n .
•^'p s , . s .
sm y . 2
(4)
De cd dieu kien kiem tra va nang cao do chinh xac cua phuang phap, nen do den nhieu diem.
2. Khao sat do chinh xac cac phirong phap giao hoi trong bd tri va kiem tra tam md tru cau
Udc tinh do chinh xac bd tri cac tru Pi, P2, Pj tir cac diem khdng che 1, 2, 3 ... tren bd sdng bang may TDDT do chinh xac do gdc 3 " ; do chinh xac do canh 2-i-2ppm; ket qua ghi d bang 2.
Khao sat do chinh xac ciia cac phuong phap giao hdi bang each tir 3 diem ciia ludi khdng che thi cdng I, 2, 3 bd tri cac tru Pi, P2, P3 lan lugt theo cac phirong phap tren vdi khoang each theo phuong dgc cau thay ddi (100m; 250m; 400m), tga do cac diem ghi trong bang 1.
Hinh 3. Sa dd bd Iri Idm md iru cdu bdng cdc phuang phdp giao
Tap chi KHOA HQC GIAO THONG VAN TAI « So 29 - 03/2010 139
Ten diem 1 2
Bdng 1.
Toa do diem khong che X(m)
495.9706 300.6865 100.9370
Y(m) 336.5750 379.7504 369.7421
Toa do diim Ten diem
Pi P2 P5
hrdi vd loa tdm md Iru cdu (diem thiet ki) Toa do diem thiet ke
X(m) 300.6865 300.6865 300,6865
Y(m) 479.7504 629.7504 779.7504
Ten diem
P|
P2 P,
" Bdng 2. Sai sd vi tri diim Giao hoi tir 2 diem cua LKC GHG
5.3 7.4 12.7
GHC 3.9 4.0 5.4
GHG-C 2.9 3.4 4.3
GHN 2.7 3.8 5.4
bd tri bdng cdc PP giao hdi lir 2 vd 3 diim LKC Giao hoi tir 3 diem cua LKC GHG
3.0 6.4 11,9
GHC 2.8 3.7 5.2
GHG-C 1,8 2.5 3.2
GHN 1,9 3.3 5.1 Ghi chu: GHG - Giao hdi gdc; GHC - Giao hdi cgnh; GHG-C - Giao hdi gdc canh: GHN - Giao hoi nghich: LKC - Ludi khdng che
Du kien bd tri bang may TDDT cd do chinh xac do gdc bang 3 ' 2-i-2ppmD, Sai sd vj tri diem dugc thdng ke d bang 2.
dd chinh xac do canh
• Pi
Dl>3
G H G GIIC GHG-C GHN G I I C GlIG-C GIIN
GIAO HOI TU 2 DIEM Cl A Ll 01 KHONGCHE
GIAO i i g i r r 2 D I E M C U A L U O I KHONG CHE
Hinh 4. Dd thi sai sd v; tri diim bd Iri bdng phuong phdp giao hdi lir 2 vd 3 diim Tir ket qua khao sat tren cd the riit ra nhting nhan xet sau;
- Vdi khoang each Idn. khi bd tri bang 3 diem do chinh xac khdng tang len nhieu so vdi bo tri tir 2 diem (tang khoang 30% -^ 40% vdi khoang canh 100m; den 400m chi tang nhd hon 10%
trir bd tri bang phuong phap gdc canh).
- Phirang phap giao hdi gdc cho do chinh xac kem nhat. khoang cac cang xa do chinh xac
cang kem vii do bien ddng Idn, , - Phuong phap giao bdi gdc - canh cho do chinh xac cao nhat;
(Xem tiip trang 149)