He so an toan va khoi liforng cat khai thac Tai bis song dong bang sdng Ciiu Long
Safety factor and volume of sand mining in waterfront Melcong delta
Ngay nhan bai: 17/02/2017 Ngay sifa bai: 20/3/2017 Ngay chap nhan dang: 5/4/2017
TOIH TAT
Cat la mot loai khodng san cd gia tri trong nganh xiy dUng. Viec khai thac cat da gay ra nhieu vu sat 16 nghiem trong. Tac dong cua viec khai thac cat tdi he so an toan bd sdng phai du^c xem xet dac biet. Nghien edu anh hiidng cua khai thac cat tdi he s6 an toan trf do liia chon sU Lhay doi dia hinh long sdng phd hap dung de tinh he s6 an toan, Fs va khoi liit^ng khai thac cat, Ben cgnh do, viec xac dinh siic khang cat khong thoat nUdc va phdOng phap tinh h^ so an toan Fs ciing difdc xem xet.
Tii khda: Khai thac eat
ABSTRACT
Sand is a valuable mineral in the construction industry. Sand mining has caused serious landslides. The impact of sand extraction on the river bank safety factor should be considered in particular. Study the impact of sand mining on the safety factor from in order to select appropriate riverbed topographic variety to calculate the safety factor, Fs and sand mining volumes. In addition, the determination of the undrained cutting resistance and the method of calculatmg the Fs safety factor are also considered.
Key words: Sand mining.
ThS. Nguyin Van DufOng
Giang vien - Khoa Xay ddng, Triidng Dai hoc Thu DSu Mot ThS. Tran Van Phfi
Giang vifin - Khoa Xay diing, Trddng Dai hoc Thu Dau Mpt ThS. Phii Thi Tuyet Nga
Gi^ng viin - Khoa X5y diing, TrifcJng Dgi hoc Thii Dau Mpt
Nguyen Van Ditdng, Tran Van Phe Phu Thj Tuyet Nga
l.GlCrt THIEU
Viee khai thac cat da lay di mot lUong cat Idn da trd n§n piio bien tren cac song d nudc ta Viec khai thac cat mang mgt sot dac tfiem nhu sau cJiin ra theo mua, theo chieu d^i va chieu rgng song. Ngay nay, viee khai thac cat dien ra mot each phdc tap va kho kiem soat. Do dd yeu eau ve kiem soat khoSng mue nude, chieu sau cue han va gdc dde euc han phai dam bao nghi§m ngat.
Vi mat khai thac cat c^n phSi mo phong sU thay doi dia hinh Idng song vi tinh toan khoi lUOng khai thac. Tieu ciiuan cCia dc qu6c gia da de cap den he sd an toan cho m^i dde. Cae nha khoa hoc tren the gidi cung CO rat nhieu nghien ctfu lien quan den tae ddng eua "khai thac cat tdi dia hinh bdsdng. mdt sd edng trinh tieu bieu: O. Millet (2011)11]; D.
Padmalal (2008) [2]; Luo et al (2007) [3].
GeoStudio- mdt chuong trinh thifong mai kha pho bien trong phan tich eac bai toan i\in quan den dia ky thuSt ehiJa dLfng cich tinh theo c^c tac gi3. Mdi tSe giii thda man eSe dieu kien can bSng khac nhau Vi^c nghi#n cilu sU thay fioi dia hinh long sdng. nham tim ra sUthay doi dia hinh long sdng phu hop, giup tinh toan he sd an toan Fs vi khdi luong khai thac eat.
2. LLTA C H O N PHl/ONG P H A P TiNH H | s 6 AN T O A N FS 2.1 PhUCng phap can being gidi han
Theo tieu c h u I n FHWA-NHI-06-088 ciia My di xuat bdi fJaresh et al. 2006. Tren nen dat yeu thdng thucfng xay ra khi ke bi lun xudng, dat vung ^nh hUdng xung quanh trdi.
Lw igUu^t
ih1: Co che pile hoai dien hinh dang cung triiot tron Tinh toan 6n dinh dUa vao he sd an toan:
04.2017 lillJilllBl! 79
Bdng 1 : Hi so Fs cua eae tac gia PP Spencer Morqens Price
GLE Spencer Morqens Price
GLE
ronqPP Can Banc Gidi Han L = 4 0 m H(m)
14.56
18.65 Fs 2.131 2.131 2.131 1.803 1803 1.803 Ti!/Bangi chothSy phUOng phap Spencer cho ket q u i he so Fs thap nhat. Oe thien ve an toan trong tinh toan chon gia tri nguy hiem nhSt de phan tich.
K(!t luan: SCf dung phuong p h i p Spencer d l phan tieh nghien ciiu.
K^tqua nay phii hop vdi nghien cuU ciia E Spencer 1967 v4 eung trifgt tron trong phSn tich dn dinh mai dde
2.2 PhUcmg phap phSn ttlT hiiiu han
Oe tinh tocin he sd an toan ta chi can tinh toan uing suat-biln dang vdi e-q) giSm dSn thi sd lUdng cac phan to d^o tang dan (bSng each chia c-ip cho k) va dSn tdi chd mai dat dde mat dn dinh khi ehuyin vi cCia diem khao sat tren mat mai doc tang manh. H§ sd an toan cua mai dat 1^ he sd k lam eho ehuyin vi eiia mat mai dSt tang vd eCing Idn.
C o n t r o l p o i n t
Hinh 2: Mo hinh trong PP Phan TilHuu Han - PhUOng phap e-(p gieim
Bdng 2: Hf PhUcAig
phap Ko Tronq lue
Ko Tronq lue
d Fs eCia cac PP tronq PP Phan TCr HCTu Han L=;4Qm H(m) 14.56 18.65
Fs 2 235 2.131 1.933 2.072 - TCf Bang 2 cho thay phuong phap KD cho ket qua hi so Fs thap nhat.
Oe thien v l an toan trong tinh toan ehon gia tn nguy hiem nhat de phan tieh.
K^t luan: SCr dung phuong phap Ko trong tinh toan 2.3 Lua chon phUcfng phap tfnh he so an toan Fs Bdng 3: He so Fs cua PP Spencer va PP Ko Phu'Ong
phap Ko Spencer
Ko Spencer
L=40m H(m) 14.56 18.65
Fs 2.235 2.307 1.933 1.803
- Hai phuong phcip tren dUa ra k i t qu3 tifOng duong, phuong phap Spencer don gian trong yeu t d dau vao vh phuong p h i p phan tich, Hon nCra phuong phap nay dem lai c i i nhin trUc quan cho ngudi ky sif.
Ket ludn: SCf dung phuong phap Spencer trong tinh toan 3.PHANT[CHBAITOAN
3.1 LUa chon dang thay doi dja hinh SLidung dia chat Vinh Long
Dieu kien L=40 m, H=l 0 m, WL=Om vi AH=>4.56m.
Sir dung 2 phuong phap: PP Spencer vi PP Ko d l xac dinh h^ sd an toan dn djnh b d sdng.
+Dang 1: Ha Idng sdng thay ddi theo hudng vudng gdc.
+Dang 2: Ha Idng sdng thay ddi theo hudng tSng dd dde.
Dudng eong mJu do la kich thUde vh hinh dang cung trugt trong
- TU Bing 3 cho thay phUOng phap Spencer cho ket qua he sd Fs thap n h a t Ge thien ve an toan trong tinh toan ehon gia tri nguy hiem nhat de phan tieh.
Hinh S: H&so an toan vS cung triiot theo hifdng tSng do doc bing PP Spencer [Fs=2.292) Bdng 4:6anq k i t qua so sanh he sd Fs
Phuong phap ban dau ha vuonq qdc
tSng dd doc
CBGH 1 PTHH Fs 3.275 2.726 2 292
3.295 2.457 2.437
aF5%
061 -10.95
5.95 - Nhan xet'
He sd an toan ban dau cCia 2 PP: PP Spencer v PP Kola gan b i n g nhau.
Ha Idng sdng theo phUong phap tang dd doc nguy hiem han ha vudng gdc va mo phdng g^n thUc t l han.
Kfch thudc va hinh dang eung trUcft trong PP Ko gan gidng vdi PP Spencer.
K i t ludn: SiJr dung dja hinh thay doi theo hudng tang gdc dde.
3.2 Xac cRnh sdc khdng cdt khong thodt nudc trong phan tich on djnh
• TUthinghiemcatcSnh hien trudng.
- Theo ti§u chuan ASTM D2573, sCfc khang cat khong thoat nUdc sdng Su duoc lay tUthi nghiem cat canh hien trudng phai duac dieu chinh theo mot he sd kinh nghiem / j . vdi gia tri Sut, va gia tn nay md^ dUa vao tinh toan dn dinh. V6i 5^, = f^^-^ufv
• SLIC khang cat khdng thoat nUdc sCr dyng chi sd PI.
- Theo Worth and Houlsby 1985 gia tri sUc khang eSt khdng thoat nude sdng 5u dUoe eho bdi:
- ^ = 0.129+0.00435P1
• SUc khang cat khdng thoat nude sil dyng t h i nghiem e^t dat true tiep trong phdng
Tai dd sau ztrong dat.
S„(DS)=o„tg(p+c
• So sdnh sUc khang eSt khdng thoat nude SutinhtUchisdd^oPlva t h i nghiem eat dat trUc t i l p , t h i nghiem dt dnh
Tinh Vinh Long 70
Bang 6: Gia trt so sanh
0 10 2 0 3 0 . 4 0 50 6 0 70 Su suy diSn ( k N / m 2 )
Hinh 6: Bsea 66 bieu dien %, suy dien V3 S. cat canh song Co Chien Bdng 5: qia tri so sanh
SddUiieu Ty sd GTTB TJ'SOR' Ty so COV
S„ theo PI 14 0.828 0.988 0.12
Su cdt d^ttrijfc tiep 14 0404 0.944 0.42 - Tinh TrS Vinh
50
0 20 , 40 60 Su suy dien {kN/m2)
Hinh 7: Bieu 36 bieu dien Su suy dien va S» cat canh tinh Tra Vinh.
Sd dU lieu T^ sd GTTB T y s o R ' T^ sd COV
S. theo PI 11 0 958 0.988 0.04
Su cat dat true t l l p 11 0.611 0.944 0.28
• Nhan xet
+ T U bieu do bieu dien dUdng Su cho thay dUdng Su tinh theo PI gan sat vdi dudng 1:01
-l-Trj sd GTTB cua gia t n Su tinh theo PI gan ti&m can bang 1 han Su tinh theo dt d i t true tiep. Nen gia tri Su tinh theo P[ chinh xac hon Su tinh theo eat d i t trUc tiep
4-Tri sd R2 cua gia tri Su tinh theo PI gan bSng 1 hon gia tri tinh theo cSt dat true tiep. Do dd do bien ddng cUa cae gia trj Su tinh theo PI dao ddng khdng n h i l u nen k i t qua tin cay han tinh theo cat dat true t i l p
+ T r i sd COV cCia Su tinh theo PI nhd han khi tinh theo dt d i t trUc t l l p Do dd dd lech chuan cua dc gia trj trong Su tinh theo PI nhd hon. Do do ket qua tinh theo PI tin cay hOn
Kit luan: Chon PP tinh todn sUc khang cSt Su theo PI 4. TfNH T O A N H E s d CHO T I N H VINH LONG 4.1 Dieu kien ^ a chat, thijy van
Hinh 8: Ban do khao sat viing sat Ici song Co thien-Vinh Long Bang 7: Xac dmh tinh chat cCia dat tren sdnq Cd Chien
Tinh ch^t
- Oac tinh
-Chieu sau.h(m) - D 6 a m t u n h i e n : W ( % ) - Dung trong tU nhien' y„
(q/cm') - O g b a o h d a ' G ( % ) - Gidi han ehSy. LL (%) -Gidihand&o:PL(%) -Chi sd deo: PI (%) - Gdc ma sat trong: tp -Luc k i t dinh. c(kPa)
Ldp d ^ t 1
Dat dap a set, cat (Trang thai nifa cUng) 0 - - 2
59.9 15.9 97.5 49.9 29.8 20.1 2.4 9.1
L^pdfit l a i set mau s3m den [Trang thai chay)
- 2 ^ - 8 44.5 17.1 9 6 9 36.9 21 8 15.1 4.2 10.5
. Ldp ait 2 Dat biJn,
(Trang thSi mem) -8 -I- -30
48.3 16.7
96.3 43.1 24.7 18.4 3.4 11.2
Hinh 9: Ket qua ciia sifc khang ck khfing tiioit nUdc song ciia dat set bao hoa (a) Thi nghiem cat dnh vi (b) Thi nghi#m CPT
A ^ K>J —I—thap nhat y <> —CH cao nhat
l _ _ H ^ — d t a h i u
I8-Oct 6-May 22-Nov 10-Jun Ngay (m/d/yy)
Hinh 10: Bieu do khoang muc nuoc song tram My Thuan cao nhhat va thap nhat theo nga]
m20B
Nhan x e t : Khoang mUe nUde sdng dao ddng tU 0.85m d i n 4 53m Ket luan: Chon khoang mUe nudc song tU Om den 6 m.
4.2 IVld phdng tinh toan trUcfng hop chtfa tai +Cac be rdng mai sdng thay doi la 20 m, 40 m, 60 m va 90 m, -J-Chilu sdu ban dau H=10m.
-H IVlue nudc sdng thay ddi tUOm den 6 m -l-Phuang ph^p phan tieh - Phuong phap Spencer
Hinh 11: Mo liinh tinli toan dn dmh mai dot tinh Vinh Long cliua tai
• Ket qua phan tich he sd an toan Fs Hinh 12 Bieu do he so an toan Fs Tinh Vinh Long thua lai
- Can cU vao bieu dd quan he giCla c h i l u sSu va he sd an toan Fs (Hinh 12) eho thay.
-f- Khi chieu sau tang thi he so an toan Fs giam -I- Khi khodng mUc nUdc sdng tang thi h^ sd an toan Fs giam -l-Khi b l rdng mai dde g i i m thi he sd an toan Fs giSm,
• K i t qu3 Ht, Ung vdi cac L khac nhau
Bdng 8: K i t qua He. Ung v tSi Fs=1 1
c L khSc nhau ciia Tinh Vinh Long cd
WL Om 1 m 2 m 3 m 4 m 5 m 6 m
L.=20m 28.78 24 20 1882 15 84 12,34 10,00
H L=40m
39.50 37.58 35.19 30.15 24.57 19 80 17.63
«
L=60m 51.24 49.57 47.05 44.21 37.36 29.59 26.32L=90m J 69.31 68.09 66.21 63.38 57.22 48.58 41.64
0 2 WL 4 6
Hinh 13: Bieu do Ha Ifng vdi car Lkhknhau ciia Tinh Vinh Longed tai Fs-1,1 - Can cil vao bieu dd quan he giOa chieu sHu cue han va k h o i n g muc nude sdng (Hinh 13) eho thay:
-l-Khi cung mdt khoing mUc nude sdng nieu be rong mai doc gi^m thi ehieu sau cUc han g i i m .
-fKhi ciing mot b l rpng mai song nieu khoing mUc nudc sdng tang thi chieu sau cUc han g i i m .
• K i t q u i he sd ha do sau cUc han vdi eac be rdng m i l khac nhau B^ngg
WL Om I m 2 m 3 m 4 m S m 6 m
KetquaRoUnq vdi cae Lkhac nhau cua Tinh Vinh Long ehUa tai Rcr
L=20m 1.88 142 0 88 0,58 0.23 0 00
L=40m 2 95 2 76 2.52 2.01 1.46 0 98 0 76
L=60m 412 3 96 3.71 3.42 2.74 1.96 1 63
L=90m 5.93 5 81 5 62 5.34 4.72 3.86 316
- Can cilvho b i l u do quan h^ giCfa chieu sau eUchan va khoing mUc nude sdng (Hinh 14) cho thay:
-t-Khi eiing mdt khoing mUe nUdc sdng n i l u be rong mai dde giam thi he sd ha do sSu cUe han g i i m .
-l-Khi cung mdt b l rdng mai sdng nieu khoang miic nude sdng tang thi he sd ha dd sau cUc han giam.
• K i t q u i acting vdi cae Lkhac nhau eda Tinh Vinh Long chus co t i i Bing 10: K i t qua Ot.Ung vdi dc Lkhac nhau cCia Tinh Vinh Long chUa e d t i i
WL Om I m 2 m 3 m 4 m 5 m 6 m
• '~.-..i O r L=20m
55.21 50.43 43.25 38.38 31 68 26 57
L=a40m 4464 43.21 41.34 37.01 31.56 25.33 23.78
L=^nL. _ 40.50 39.56 38.10 36,38 31.91 26,25 23.69
J,=99m 37.60 37.11 36.34 35.15 32.45 28.36 24,83
-L=20m -L=40m L=60m -L=90 m
0 2 W L 4 6
Hinh 15: Bieu do Oa ung v6i cac L khac nhau cila Tinh Vinh Long chua <d tii - Can cU v i o b i l u dd quan h^ giijra gde dde cue han va khoing mUc nUdc sdng (Hinh 15} cho t h a y
-l-Khi khoing mucnudc sdng tang thi gdc dde cUc han g i i m . -I-Vdi WL=3.8m la khoing mUc nUdc sdng cUc han mh d dd gdc 6dc cUc han khdng phu thudc vao b l rdng mai dde.
+Kh\ khoing muc nUdc sdng nhd hon khoing mue nudc song cue han vdi be rdng m i l doc tang thi gdc dde cUc han g i i m .
4-Khi khoing mUc nude song Idn han khoang miie nUde sdng cUc han vdi be rdng mai thay ddi thi gdc dde cue han khdng ddi
4.3 Ap dung k i t q u i nghien cOti
• Kiem tra he sd an toan bd sdng hien tai Quy trinh x i c dinh
0 2 WL4 6
Hinh 14: Bieu do Ru dug vdi cSc L khac nhau cda Tinh Vinh Long chifa co li\
Thong s& d&u vao H, WL, L, dia ehdt, tai trong
K i 4 m t r a H ^ 1 0 m , W L s 6 m , 2 0 m £ L £ 9 0 m
raim tra vCing dia ehdt Khdng
' ^ ° ^ C h u « t i n h ^ to^n duoc Khdng
thda
V f n h L o n g
Tim khoang L gan nhat
Np K h o n g t a i
SO dMng bilu d6 12a, b, c, d
l i n lirol vdi L=20, 40, 60, 90 m
Co tai
SO d u n g b i l u d 6 4 31a, b. c, d l a n l i i p t v o i L = 2 0 , 4 0 . 60, 9 0 m
L J
Ngi s u y F s t h e o H , W L
y^b~
^
N$i suy Fs theo L toan khdi li^ong cat khai thdc
Thong so dku v^o WL, L, Mktl, Hkt, dja ehdt, tai trong trpng K i e m h a H a i O m , W L £ 6 m , ;
i
m S L £ 9 0 m ' Thoa I K i l m tra vCing dia ehdt
Khdng thda
C h u ^ tinh . todn d u ^ c
VTnh Long
Tim khoang L gan nhat
Khdng tai C6 tai
Sir dgng biSu So dijng bieu do 13 do 13
NOi suy Her theo L, WL
J
Tinh todn khoi lu'o'ng cat 4.4 Tinh khdi iKomg cat khai thac
Cdng thUe tinti khdi lugng c i t khai t h i c V = l^t, x H > ; ( B - 2 x L ) x l Kilm tra d i l u ki§n dn dinh
rif(H„<hi„)then(h^=0 1 - > ^ > , 4 f H , < H „ < H i J t h e n ( H . = h i , - 4 . , ) ^ V = H « x ( B - 2 x L ) x 1 ( D
[if(H„>hi,,)then{h^=4.,-h^,) J 4.5 K i l m nghiem ket qud phan tich Bang 1 1 : K i t qua h§ sd an toan eua eae vu sat Id Thdi gian
23/01 /2014 13/01 /2013 19/05 /2013
fiia d i l m Xa An Binh, H. Long Hd Khdm 6, Phudng 5 Khdm 6, Phudng 5
H (m) .
36
35
33 L , (in)' 61 2
77
66
•»|WL-«
im] . 3.75
4.66
4.01 Fs 1.048
1.073
1.094
Can c i i vao Bang 11 he sd an t o i n Fs cOa c;
u s a t l d d i e n r a k h i h e s d a n toanFs<1.1 B i n g 12; Ket qua t i n h toan khoi lUOng cat T h i n cat
CC-TQ.l CC-TQ 2 CC-TQ.3 CC-TQ.4 CC-TQ.5
B(m) ,, 580 880 580 780 580
. Hkt (m) 4.18 3.67 3.33 2 4.42
V{m3/ml tham do 2090.43 2936.24 1675.32 1385.21 2123.57
V(m3/m) 2090 2936 1665 1400 2210 Cin cU vao Bdng 12 K i t q u i tinh t o i n khdi luang eat so udi k i t qua khdi lUOng tham dd cho t h i y khSi lugng tham do va tinh t o i n gan bang nhau.
5. K£T LUAN
Vifc tinh t o i n he sd an toan v i khdi tuong c i t khai thac l i viee can t h i l t va quan trong, dieu do d i m b i o do on ^ n h cua bd song, cung n h u han c h i sat Id b d sdng.
Thdng qua v i d u phia tr§n eho thay phuong phap Spencer la phuang phap phCi hcjp de tinh t o i n he sd an t o i n Fs v i tinh sUc khang cat khdng t h o i t nude Su theo ehi sd deo PI l i p h t i h g p v d i ket q u i SutU thf nghiem dt c i n h .
Thdng qua b i n g k i t q u i h f sd a n t o a n c u a c i c v u s a t l d t h o t h l y dia hinh Idng sdng thay ddi theo hUdng tang do doc la phiJ hgp dien bien Idng sdng thucte.
Thdng qua b i n g k i t q u i tinh toan khdi lucfng cat cho thay cdng thiic tfnh t o i n khdi lugng cat l i gan bSng vdi khoi lugng eat t h i m dd.
TAILIEUTHAMKHAO
[1] O.Millet, 2011, River erosion,lanclslides and slope development in Gota River Mt.TTies/s, Chalmers University Of Technology.Sweden.
[2] D Padmalal, 2008. Environmental Impact Of Sand Mining: A Case Study In Ttie River Catchments Of Vembanad Lake, Southwest India,
[3] Luo.X L. E.¥ Zeng, R V. Ji, C.P.Wang, 2007. Effects of in-channel sand excavation on Itie hydrology of thePeari River Delta, China > u m o / D ^ H f i / n ? t o 3 y W i 2 J 0 - 2 J 9 .
[4] Spencer. E, 1967. A method of analysis of Ihe stability of embankments assuming parallel interslicefoicei.Geotedimque, 17(1): 11-26
[5] Worth, C. P. and Houlsby, 6. T. (1985)." Soil Mechanics-Property Characterization and analysis praceduies.'Proceedings.ll* International Conference on Soil Mechanics and Foundation Enginearing,VoLl, San Francisco, pp.1-55.
04.2017 BWIiffEiOl 8 5
