NGHIEN ciru-TRAODOI /
XAC DINH LUG CAN X6l DAT THEO CHI SO TiCH PHAN DO BEN QUA DAT KHI THI CONG DAT BANG MAY X6l
DETERMINATION OF DIGGING RESISTANCE, BASED UPON INTEGRAL INDEX OF SOIL STRENGTH IN EARTH
PREPARATION WITH DIGGING MACHINE
TS. Nguyin Danh Son Trudng Dai hgc C6ng nghiep TP. H6 Chi Minh
TOM T A T
Bdi bdo dua ra cdc cdng thirc gidi tich de xdc dinh luc cdn xai ddt theo chi sd tich phdn do ben cua ddt, sd va dap cua mat do ke khi thi cdng ddt bdng mdy xai. Diiu ndy, trdnh ditgc cdc khuyet diem cua cdc phuang phdp xdc dinh luc cdn xai ddt dua trin cdc cdng thuc thuc nghiem chua diing hang loat cdc he sd kinh nghiem.
Dd so sdnh ket qud tinh todn ly thuyet vdi kit qud thuc nghiem ddi vai cdc mdy xai ddt. Sai sd khdng vuat qud 16%.
Cdc cdng thuc dua ra cd thi dung de phdn tich dinh luang vd dinh tinh luc cdn xai ddt, tuy thugc vdo cdc yiu td dnh hucmg din chi sd tich phdn do ben cua ddt.
Tir khda: Mdy xai ddt; Luc cdn.
ABSTRACT
The paper come up with analytic formulas to determine resistance from digging based upon integral.
Index of soil strength - numbers of impact of densimeter during earth work by digging machine. This approach lead to avoid some drawbach condition from other method, wich are offen emperical and experimentally related.
Comparison of results from this approach and from theoritical and experiments are conducted wich headed to a tolerance within 16%.
Proposed formulas from this method can be used for quantiative and qualitative analysis of resistance from digging and depens on how variation of integral index of sod strength.
Keywords: Digging machine; Digging resistance.
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NGHIEN cuu-TRAODOI
l . D A T V A N D E
Cach tinh toan luc can dua tren cac cong thiic thuc nghiem chiia dung hang loat cac he s6 kinh nghiem. Cac tinh toan nay chi diing vdi cac dilu kien ma tai do cac he s6 nay dugc xac d i n h [ l ] .
Cac luc can ciia dat co t h i dugc xac dinh tren ca sd cac phuang phap ca hgc moi trudng lien tuc, ca biet la moi trudng co dinh bam. Dilu nay cho phep tranh dugc nhugc diem tren. Cac luc can trong trudng hgp nay xac dinh qua ling suat phap a va img suat tiep T phat sinh tren cac be mat tiep xiic cua ludi cat vdi dat. Ung suat phap tren b l mat tilp xiic ciia ludi cat vdi dat xac dinh tren CO sd ly thuyit tinh hgc ciia moi trudng lien tuc c6 luc dinh bam va ma sat [3].
2. GIAI QUYET VAN D £
D I xudt so d6 tinh toan luc can tac dung len rang ciia may xdi nhu tren hinh 1. Cong thuc de xac dinh ung suat phap tren be mat tiep xiic cua rang xdi con sac vdi dat co dang:
G - (K, -I) C^cotgp+K,y N/m' (I)
O day, so hang dau cua ve phai cong thiic xac dinh ung suat do luc bam cua dat con so hang thii hai la ung suat do trgng lugng cua dat.
Cac ky hieu sir dung trong cong thiic: C^: Luc bam giua cac phan tir dat, N/m^,
p - goc ngi ma sat ciia dat, y, khoi lugng rieng cua dat, N / m \ K^: He so giai tich, phu thugc vao goc xdi a, goc ngi ma sat p va goc ngoai ma sat 5 cua dat.
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Hinhl: Sa dd luc cdn tdc dung len rdng cua mdy xdi.
Cong thirc dimg vdi loai dat co ton tai bat dang thiic 5 < p. Doi vdi cac goc khac nhau he so K, dugc xac dinh bang phuang phap giai tich theo cac cong thuc rieng, dang cua chiing dugc xac dinh bang tri so ciia goc xdi a va cac goc ma sat.
Doi vdi cac goc xdi thoai a < 55" tri so K, dugc xac dinh theo cong thuc:
1 - sin p cos la
^ ' = l - s i n p • (y Doi vdi cac goc xdi Idn a > 55" dac biet khi ludi bi ciin, (goc ciin ky hieu la a^) tri so K, dugc xac dinh theo cong thuc:
cos^(cos(5+-Jsin^ / ? - s i n ^ 5 „ K,= ^ - i i^ e" (3)
l - s i n / 7
Trong do: r|=(2a -JI+8+ a r c s i n l ^ ) t g p , (4) s i n p Chi s6 cua so mG r\ cung phu thupc vao cac goc ma sat, goc xai a, goc ciin a^ciia luoi xaiva nhiSu thong so khac.
D6i voi cac goc ma sat thoai thi tri s6 K,=l,5 - 4, con d5i vai cac goc ma sat Ion han thi K,=
15-20 tijy thuoc vao cac goc a , p, 8.
2014
Thanh phan ngang ciia luc can xdi dugc xac dinh tren ca sd phan tich so d6 luc can tac dung len rang cua may xdi (xem hinh 1).
Xet mgt phan tii dien tich ciia bl mat rang xdi, thanh phin luc phap tuyIn dN dugc xac dinh theo hi so cua ung sudt phap a:
dN=G.dl.dz, (5) Trong do: dl = —^— dy
sina
Luc tong hgp dQ cua cac img suat phap va ling suat tiep tren dien tich dl.dz dugc xac djnh bang cong thirc;
d Q - ^ (6) cos 6 dQ = a.dy.a (7)
sin a. cos 5
Ta CO thanh phan ngang cua lire can xai;
dW ^dQsin(a+d) (S)
fjA,c!.dy.dz (14)
"^ sina.cosS Sau khi bien doi lugng giac ta co:
dW^ =(l+tg5.cotga)a.dy.dz (10) hay
dW^^=A,.(7.dy.dz.
Trong do:
A, = l+tgS.cotga (11) He s6 A| nen sir dung khi a > 25". D6i vdi cac gia tri a nho nen su dung cong thuc xuat phat tij su gidi han chilu dai cua rang xdi:
dfV ^A/=o.dy.dz (12) Trong do:
A/ =sina +tgd.cotga (13) Thanh phSn ngang ciia lire can xdi tac dung len bl mat rang xdi ta xac dinh bang tich phan sau:
TAP
Trong do: h: Chieu sau xdi, m; b: Chieu rgng ludi xdi, m.
Sau khi thay gia tri cua a tir cong thiic (1) vao cong thirc (14) va tich phan ta dugc:
W^^^=A/K-l)cotgp.C^b.h +0.5A^K^.j.b.h' (15) Khi bo qua khoi lugng ciia dat dugc tach ra tren be mat rang xdi, chang han khi thi thi cong dat rat ran ta c6:
W_^^^A,(K-I)cotgp.C^b.h (16) O day, cac he so A^va K^ dugc xac dinh bang phuang phap giai tich theo cac cong thiic tren.
Cac ky hieu con lai ciing da dugc dua ra d trudc.
Cac he so K, khong phai la ham lien tuc cua goc xdi va cac goc ma sat ciia dat, cho nen khi phan tich anh hudng cua goc xdi den tri so W^
thi he so K|phu thugc vao gdc xdi a nen xac djnh theo cac cong thitc rieng doi vdi moi viing cua a da neu d tren (doi vdi a <45-50"va doi vdi a > 55").
Cong thiic giai tich de tinh toan luc can xdi dat tren co sd chi so tich phan dp ben cua dat - so va dap cua mat do ke (C^^) c6 thi nhan dugc Uen CO sd cac phu thugc tuang ung giua Cg va C^^
dugc xac dinh bang bieu thirc sau:
c.-^„.c„. a 7)
ci day: K^: He so tu'ong quan thir nguyen, cho bilt bao nhieu dan vi luc bam tinh bang MPa ling vdi mgt Ian va dap cua mat do ke (MPa/s6 va dap); C: So va dap ciia mat do ke.
Tri so ciia he so Kg dugc xac dinh bang thuc nghiem, K3 = 0,01-0,015 MPa/ va dap.
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NGHIEN ciiu-TRAO00!
Tren ca sd van de xem xet d tren ta co cong thuc d6i vdi cac loai dat cimg chac:
fV_^^ =A^(K,-l)cotgp.K^ C,^. b.h +0,5A^,.y.b.h' (18) Cac luc can tac dung d cac be mat ciin va d cac mat ben cua rang xdi khi can thiet thi xac dinh rieng biet theo phuang phap tuong tu'. Mo hinh da dua ra cho phep tinh cac luc can tac dung len rang xdi, khi gia thiet rang goc ngoai ma sat cua dat 5 luon luon nho hon go ngi ma sat p ciia no.
Su chuyen tir trang thai img suat phang sang trang thai ung suat khong gian d nhirng vimg dap va nen theo mgi phuong dugc tinh den bang each nhan them he so tuong quan K^. Doi vdi cac ludi xdi CO chieu rgng b ciia chiing nho han dang ke so vdi chieu sau xdi h thi giiia img suSt dugc tinh toan theo cong thuc ly thuyet a^^ tren ca sd tmh hgc moi trudng lien tuc va cac tri so thuc nghiem a^^ CO moi quan he:
w,„-^^,a,, (19) Trong do: K^: He so tang ling suat, tinh den sir tang ling suat trong dat d cac dilu kien nen theo mgi phuang khi so sanh vdi bai toan phang.
Ciing vdi su thay doi ty s6 h ^ trong khoang
> 5-10 thi he s6 K^ = 1,5-7,5. Trudng hgp nay ddi vdi may xdi co mgt rang ta co:
W^=A^(K,-I)cotgp.K^.K^C^^ b.h+0.5A^.K^.y.b.h' (20) Su so sanh cac tinh toan dugc thuc hien vdi cac so lieu thir nghiem cac may xdi d i t cong nghiep lap tren may keo cua Nha may Treliabin (Lien bang Nga).
Cac thii nghiem dugc tiln hanh vdi dk loai III - A set. Rang xdi co chilu rgng tinh theo canh cat b, -0,06 met, chilu dai rang xdi 1^ = 0,25 met, goc sac p - 45". D^t co cac thong s6 sau: Loai dk:
A set: C^,g ^ 8-9; Goc ngoai ma sat 6 - 26"; Goc
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ngi ma sat p = 29"; Ty trgng y =17 KN/m^; Kg = 15000 N/m^. Vdi cac s6 lieu nay, ta se cd cong thirc tinh toan gSn dimg dudi day vdi cac goc xai a > 30^
Cong thirc d l tinh toan thanh phan luc can xdi tong cong theo phuong ngang cd dang:
W„,s- (^+^S^^^^SO-)(^r<^i'D-^-^+ ^rrb-h') (21) Trong do: Kj va K^: Cac he so tinh din cac tinh chat cua dat, tinh den su ton tai lire can a vimg bi cim ciia ludi xdi va ma sat d cac thanh ben cua ludi xdi.
Cac thi nghiem dugc tien hanh khi xdi d^t CO chieu sau xdi khac nhau vdi ciing goc xdi a
^ 55". Trong qua trinh tien hanh cac thir nghiem da ghi lai gia tri ciia thanh phan luc can xdi theo phuong ngang W^^. Luc can xdi toan phSn theo phuong ngang dugc tinh toan co k l din luc can do ludi bi ciin va luc can ma sat ciia cac mat ben ciia ludi xdi va gia lap rang xdi. Cac kit qua so sanh dugc dua vao bang 1.
Bdngl. So sdnh cdc ket qud tinh todn vdi cdc so lieu thu nghiem ve luc cdn cua mdy xdi
Chieu sau xai
h, m
0,7 0,9 1,1
Thanh phan lire can theo phuang ngang W^, KN
Thuc nghiem
65 115 130
Tinh toan ly thuyet 74,87 96,85 119
Sai so
15 16 10 D6i voi cac dieu kien da neu tren K = 105600 N/m^ va dap; (K, = K^.K^); IC^ = 1,75 _ j a i lirong khong t h i nguyen.
2014
3. KET LUAN
Tir bang 1 ta thay sai s6 giiia tinh toan ly thuyet va ket qua thuc nghiem trong tinh toan luc can xdi dat khong vugt qua 16%.
Su so sanh cac ket qua cho thay rang trong khuon kho gia thiet dat ra thi cac cong thiic dugc lap ra CO the diing de phan tich v l djnh lugng cung nhu ve dinh tinh luc can xdi dk khi thi cong dk bSng may xdi, tuy thugc vao cac yeu to anh hudng den chi so tich phan do ben ciia dat.*J*
Ngay nhan bai: 03/02/2014 Ngay phan bien: 19/3/2014
Tai liSu tham khao:
[1]. EanoBHeB B . H 3ejieHHH A . H . K e p o e H . A MauinHbi ajia seMJiflHMX pa6oT H3fl. MamuHocxpoeHHe, 1972.
[2]. BexpoB K). A, EajiaflHHCKHir B.A. MaiuHHbi juin ^eMJianbix pa6oT u^n. Bwcmaji uiKona, 1980.
[3]. CoKOJioBCKHii B.B.CxaTHJia cbinyneH cpcflbi HSa-FocyAapCTBeHoe HaAaxejiCTBO TCXHUKO- xeopeTHMecKOM jiHTepaxypbi, 1954.
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