KHOA HOC - CONG NGHE t t t i
HGHIEN Cmi AP DUNG PHtfdNG PHAP
THONG KE DANH GIA MUfC DO BIEN DONG KHI THI CONG LdP CAPPHOlDADAMIJIviETNAM
T S . B O I T U A N ANH Trudng Dai hoc GTVT PGS.TS NGUYEN QUANG P H O C
Trudng Dgi hoc GTVT
T 6 M T A T ; Bai bao trinh bay k i t qua nghien c d u xae dinh dp tech chuan cua cac chi tigu c o ban n h y thanh phan cap phoi, dp hao mdn. chf so CBR, gidi hgn chay, chi so deo, ham l y p n g hat thoi dgt, dp chat dam nen, tich s6 d§o khi thi cong cac Idp d p phoi da dSm d Vigt Nam g i n day.
T I P k h o a : dp Igch c h u i n , thanh p h i n c i p phoi, chi so CBR, d p p h l l da dam.
ABSTRACT: The article presents the results of the study determining the standard deviation of basic technical parameters of crushed stone grades using for pavement construction In Vietnam such as graded composition, Los Angeles abrasion, California Bearing Ratio, liquid limit, plasticity index, elongation and flakiness index, compacted density, PP index.
K e y w o r d s : Standard deviation, graded composition, CBR, crushed stone grades.
IDATV^NDE
c i p phoi da dam d y p e s d dung pho b i l n eho k i t e i u mat d y d n g 6 to hien nay do dgt d y p e nhdng y u diem n h i t djnh ve chat l y p n g va thi eong. Tuy nhign, ehat l y p n g d p phoi da dam thi cdng tren cdng trinh t h y e le dang la van de e i n tiep tuc d y a c quan tam. Trong qua trinh t h y e hign d y an, do tac dgng
I So 4 nam 2020
bdi n h i l u y l u t l nen chat l y p n g thi cong Idp d p phoi da dam se khdng ddng deu, c h ! dap dng d y p e ygu c l u thiet k l d pham vl n h i t djnh, N h i l u nghign edu trgn t h i gidi tap trung danh gia anh h y d n g s y d i n g d i u , dp lech ehuan cua cae thdng sl/ehi tieu trong qua trinh thi cdng d i n c h i t l y p n g khai thae cua mat d y d n g .
Khi thi cdng, mdc do dap dng t h i l t k l , dp lech chuan cua cae thdng so phu thupe vao trinh dp thi eong, loai vat lieu, d i l u kign khi hau thdi tilt,..,va d y a c nghign cdu rut ra t d ehuoi d y an da thye hign. Tren t h i gldl, nghign cdu anh h y d n g cua viec dam bao va kiem soat c h i t l y p n g thi edng d i n dac tryng khai thae eua mat d y d n g da d y p e phat t r i i n manh nhdng nam gan day. K i i m soat dp dong deu thi edng n h i m nang eao tuoi thg, chat l y p n g phuc vu eua mat d y d n g la d n t h i l t nhyng it d y p e quan tam nghign c d u ehuygn sau d Viet Nam,
Bai bao trinh bay k i t qua nghien edu t h i n g ke xac djnh dp lech chuan eua eac thdng so trong qua trinh thi cdng eac Idp cap phoi da dam; t d do de x u i t bg so lieu do Igch chuan trong d l l u kign Viet Nam lam c a s d cho phan tich anh h y d n g cua quan ly va kiem soat chat l y p n g QA/QC den dac tryng khai thac k i t d u mat d y d n g .
2. PHlTdNG PHAP NGHIEN Cmi
2.1 D o lech chuan va n g h i e n c d u d o lech c h u a n cac t h o n g s o khi thi c o n g cap p h o i da dam Dp Igch chuan, hay dp Igch tieu e h u i n (Standard Deviation) la mgt dgi lypng t h i n g kg md ta dung d l do mde do phan tan cua mgt tap d y llgu da d y p e lap thanh bang tan so. Dp lech ehuan cdn d y p e s d dung khi tinh sai s l chuan, Khi l i y dp lech e h u i n ehia cho can bac hai cua so lypng quan sat trong tap d y llgu, se ed gia trj cua sai so ehuan. Do lech chuan do tinh b i l n ddng eua gia tri mang tinh thong kg. Nd eho t h i y s y chenh lech v l gia tri cua tdng thdi d i i m danh gia so vdi gia tri trung binh. Do Igch chuan la thong so quan trpng n h i t khi danh gia dp d i n g d i u cua qua trinh thi eong. Tigu c h u i n AASHTO R9 danh gia dp ddng d i u eua qua trinh thi cdng b i n g bleu do kiem soat da d y p e d y a vao quy trinh thi eong cua My [3].
De xae djnh dp lech ehuan eua mgt b i l n X c i n tinh toan t h i n g kg t d chuol so lieu thi nghiem, kiem dinh du ldn qua trinh thi cong eae d y an. Nghien cdu nay t d so lieu kiem djnh, thi nghiem d 24 d y an ldn, mdi d y an lai ed n h i l u dogn do Trydng Dgi hpc GTVT ea s d Ha Ngi, phan hieu thanh pho Ho Chi Minh va Vien KHCN GTVT thye hign nam 2013-2017. Cae d y an deu la eac t u y i n d y d n g 6 td eao
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f t t t t KHOA HOC - CONG NGHE
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toe, d y d n g cap cao d y p e cac dan vj ehuygn nghiep thi cong trai deu ea 3 mien Bac, Trung, Nam dam bao tinh dai dien,
Vgt llgu thi nghiem trong nghign c d u do lech chuan d y p e lay t d eae h i dao kiem djnh tai hien trydng eae d y an trong va sau qua trinh thi edng. Cac thdng s l d y p e lya chpn theo TCVN 8859-2011 eho 2 logi d p p h l l da dam logi I va ll;
thanh phan cap p h l l CPDD37.5 va CPDD25: Thanh p h i n c i p phoi, dp hao mon Los-Angeles (LA), chi s l CBR, gidi hgn ehay Wl, chi s l deo lp, h^m lypng hgt thoi det, dp chat dam nen K, tich s l deo PP.
S d dung cac tigu c h u i n hign hanh de thi nghiem cac thdng s l , 2.2 P h y a n g phap nghien c d u va t r i n h t y tinh toan
Ddi vdi m i l d y an, cdng tac t h i l t ke hdn hpp CPDD khae nhau, thanh phan c i p phdi, cac chi tigu ca ly,...
khong g l l n g nhau. Tuy nhign hien nay tat ca cac d y an v i n chi l i y TCVN8859-2011 de bien sogn ehi
dan ky thuat ma c h y a cd nhdng quy djnh rigng eho tdng d y an nhy d i i vdi bg tong nhya; v i du c h y a quy djnh thanh p h i n d p p h l l phai trong gidl hgn d y d n g t h i l t kg cong try dung sai (JMF+dung sai) ma ehi gldl han trong d y d n g bao tlgu ehuan la dgt yeu e i u , cac chi tlgu khae cung t y a n g t y . Nhy vgy bai bao s d dung tieu e h u i n TCVN8859-2011 d l kiem soat mdc do b i l n ddng cho eae d y an [4].
T i t ca cae thdng s l e i n danh gia mdc dp b i l n dgng d y p e phan tieh vdi gia tri tuygt doi. Viee tinh toan c d mau toi t h i l u n theo cdng thdc sau:
Trong do: Z^^^ la hg so tinh t d phan phdi ehuan, b i n g 1.96 khi a=5%
a la dp Igch chuan tong the, d y a theo nghien edu tryde hogc nghign c d u tham dd.
d la sai s l tuygt ddi hoae dp chym, t h y d n g l i y b i n g (10-12)% a Nghidn edu dp lech chuan da d y p e thye hien d n h i l u bang Hoa Ky, trong d i l u kien Viet Nam chya ed nghign c d u tham dd ngn sau khi tinh toan dp lech ehuan t d cae so llgu kiem soat Igi s l mau t i l thilu, Trinh t y eae b y d e tinh toan: (1) Ma hda d y an de dam bao khach quan, khong lam phat tan thdng tin kiem djnh; (2) T d eac k i t qua kiem dinh phan thanh 2 logi: CPDDl v^
CPDDIl; (3) Lgp bang cac thdng s l d n k i i m soat; (4) Loai bd eac sai s l tho, nhdng s l lieu b i t thydng theo tigu chuan ASTM E178; (5) S d dung phan m i m phan tich thong kg Minitab18 d l tinh toan dO lech ehuan; (6) K i i m tra Igi s l m i u t i i thieu d l dam bao nguygn tac t h i n g ke.
3. K I T QUA NGHIEN Cmi
3.1 Ket qua gia trj trung binh Vci do lech c h u a n cua cac thong so S d dung phan mem MinltabIS d y p e Hinh 3 . 1 , mpt s l b i l u do phan tieh thong kd eua Idp c i p phoi da dam 0^^^=37.5 loai II
a) Sang 19mm Histogram of CBR (%)
b) Do mai mdn LA Histogiam of Dg ch|t K (%)
e) Chi so CBR d) Do chdt dim nen K Hinh 3.1. Biiu dd phan tieh thing k§ CPBD 37.5 loai II
Bisfmm
S6 4 nam 2020 IKHOA HOC - CONG NGHE g g t i
Tu'ang t y Hinh 3.2 mpt s6 bieu do phan tich thSng i<e cua l&p cap phci fla dam D =26 loai I
H i s t o g r a m o f 2S i Histogram o f CBR (%)
b) Chi SO CBR
H b t o g r a m o f Tfch PP
c) Do chat dim nen K d) Tich s6 deo PP
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Hinh 3.2. Bieu dd phan tich thing ke CPDD 25 loai I Bang 3.1. Ket qua tinh toan gia tri trung binh va do lech chuan cua cac thong so
TT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Th6ng s6
Sang SOrnrn Sang 37.5mm Sang 25mm Sang 19mm Sang 9.5mm Sang 4.75mm Sang 2.36mm Sang 0.425mm Sang 0.075mm Do mai mon LA Chi s6 CBR Gidi han chay WL Chi so dec Ip Luomg hat thoi det Do chat dam nen K Tich so dec PP
Don vi
%
%
%
% %
%
%
%
%
%
%
%
%
%
%
%
C P D D n Trung
binh 100 98.87
-
76.39 53.96 36.71 25.31 12.31 6.89 25.7 111.3 18.95 4.82 8.76 9 9 36.59
Do If ch chuan
-
3.08
- 6.05 7.04 7 6.46 4.08 3.11 7.66 16.12 2.95 1.64 4.06 1.55 22.62
N 3 3 1 331
-
3 3 1 3 3 1 3 3 1 3 3 1 3 2 9 3 3 1 2 7 4 2 7 0 2 7 8 2 8 9 2 4 1 2 7 2 2 9 0
CPDD I Trung
binh
-
100 90.86 80.34 56.61 39.38 27.78 14.08 7.25 25.01 119.8 17.67 4.07 8.27 98.7 2 7
D$ Ifch chuin
- -
4.65 6.49 5.73 5.03 4.14 2.65 2.83 6.27 10.41 3.06 1.67 4 1.04 21.42
N
5 0 6 5 0 6 5 0 6 5 0 6 5 0 6 5 0 6 5 0 6 5 0 6 5 0 6 4 5 9 3 8 6 4 1 9 3 8 5 4 6 0 5 0 6
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CSUEHI • « •
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f f M t t KHOA HOC - CONG NGHE
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Vdl gia tri d = 0,12 a xac djnh d y p e so mau toi thieu la 267, s l lypng m l u N d Bang 3.1 eho t h i y so m l u da thye hien ldn han s l m l u t i l t h i l u , nhy vay dam bao ydu eau, Nhipng nhan xet rut ra tip k i t qua p h a n t i c h t h o n g ke thi c o n g cac l d p CPDD:
- C a ban eae ehi tigu kiem soat khi thi cong cap p h i i da dam deu trong tigu ehuan ky thuat, d y p e the hign b i n g gia tn trung binh d i u khdng v y p t qua gidi hgn. Tuy nhign cdn n h i l u diem n i m sat hoae v y p t qua cgn tieu ehuan, dieu nay t h i hign mpt so d y an thi edng khong dam bao ygu e l u ;
- Xu h y d n g l y p n g hgt thd deu it, I h l hien l y p n g Ipt qua cac sang trgn 4.75mm deu Idn han gia trj trung binh eua tigu chuan, dieu ngy cd the do eae nguygn nhan khi dam nen da bi v d d i n den lypng hgt to it di;
- Xu h y d n g hgt mjn cung t h i l u , cy the tgi eae mat sang 2.36mm va 0.425mm, c i p phoi dl sat can d y d i , d y d n g trung binh ludn nhd han gia tn trung binh trong tlgu chuan. Dieu nay d i n tdi ldp e l p p h i i da dam d i m nen ed b l mat khdng l l l n lac, ed hign t y p n g nhieu d ^ to d b l mat, khi lu eung sg bi cac d y d n g ran ngang;
- L y p n g hgt lot qua sang 0,075mm lai cd xu h y d n g n h i l u , t h i hign d y d n g trung binh luon ldn han gia trj trung binh trong tigu ehuan. Cap p h l l l i n cae hat set, byl lam giam chat l y p n g chung, dieu nay eung t h i hign qua chi so deo, tich PP va gidl hgn ehay n h i l u d y an khdng dat ygu e l u ky thugt;
- Ham l y p n g hat thoi det, dp mai mdn LA c a ban deu dgt ydu eau;
- Chi s6 CBR cua ea cap p h l l da dam loai I va logi ll ca ban eung
deu dat ygu eau ldn han 100%, ea biet CO mpt so vj tri khong dat gidl han nay;
- Dp chat d i m nen eung c a ban dat yeu e l u ldn han 98%, Tuy nhien do thanh phan cap p h l l khong dam bao, lypng hgt set nhieu nhy phan tich d trgn ngn mot so vj tri khdng dam bao dp chat. Can giam sat chat che thanh p h i n cap phoi d l dam bao dp chat d i m nen [8];
3.2 IJng d u n g k i t qua n g h i e n c d u va p h y c n g phap m o p h o n g Monte Carlo xac d j n h mo d u n dan hoi M, l d p cap p h o i da dam Khi t h i l t k l k i t eau mat d y d n g theo 22TCN274-01 mo dun dan hoi M^ va he so Idp a d y p e xae djnh
theo cac toan do phu thudc vao chi s l CBR, Nghign edu d Phap nam 2014 [6] da k i l n nghj quan he ngy phuc vu thiet k l k i t eau mat dydng theo AASHTO va p h y a n g phap ea hpc thye nghigm.
M^ = 91.226 + 0 , 0 1 7 x(CBR)^
Trong do : Mr la md dun dan hoi cap p h l l da dam (Mpa) va chi so CBR cua e l p p h l l da dam (%), Sau khi da ed d y p e gia trj trung binh va dp lech chuan CBR eae ldp cap phoi da dam d tren s d dyng cdng thdc mo phdng Monte Carlo de xac djnh Mr tinh toan : - Cap p h l l da dam 2 • Gia tn trung binh CBR=111.3%, dp lech chuin 16.12%
= ilk. "^:
160«) 20000 2W0O ZEDOO 320 K) 360 W) 4OO0O . W W 48000
hilnh 3.3. Bleu dd mo phong Monte Carlo xac dinh Mr lop cap phoi da dam II
Hinh 3.4. Bieu d6 mo phong Monte Carlo xac djnh Mr lap cip phoi di dam I
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KHOA HOC - C O N G NGHE MMMA
- Cap phdi da dam 1 : Gia trj trung binh CBR=119.8%, dp igch chuan 10.40%
S y dung phan m i m Crystal Ball 11.1.2 md phong 5000 lan xae djnh d y p e bieu do phan b l Mr cua ldp cap p h l l da dam 2 nhy Hinh 3.3.
Neu l i y dp tin cgy 95% thi gia tn Mr cua e l p phdi da dam 2 bang 212Mpa, I l y trdn 210MPa.
T y a n g t y n h y vay d i i vdl Idp cap phoi da dam logi I the hien d Hinh 3.4, md phong Monte Carlo 5000 lan d y p e b i l u d l phan bo Mr. N l u lay dp tin cgy 95% thi gia trj Mr cua ldp cap p h l l da dam loai I bang 271.30 lay trdn 270 Mpa,
4. KiT LUAN, KI£N NGHI
4.1. K i t luan- C a ban eac chi llgu k l l m soat khi thi cong cap phoi da dam deu trong tigu chuan ky thuat, d y a c t h i hien bang gia trj trung binh deu khdng v y p t qua gidi han. Tuy nhign cdn n h i l u diem nam sat hogc v y p t qua can tigu chuan, dieu nay the hien mdt so d y an thi cdng khdng dam bao ygu c l u ;
- Chi s l deo 1^, tich PP va gidi han chay Wl nhieu d y an khdng dat ygu c l u ky thuat do ham l y p n g eac hat set, bui (lypng hat lot qua sang
0,075mm) lam giam e h i t l y p n g ehung;
- Dp chat dam nen cung ca ban dgt ygu cau Idn han 98%. Tuy nhien do thanh phan cap phoi khdng dam bao, lypng hgt set n h i l u nhy phan tich d trgn ngn n h i l u vj tri khdng dam bao dp chat. C i n giam sat chat che thanh phan e l p p h l l de dam bao do chat d i m nen;
- Tong hpp lai ed the k i t luan chat l y p n g thi cdng Idp e l p phoi da dam loai I tot han ldp d p phdi da dam logi ll the hien bang cae ehi tieu ky thuat, do lech ehuan d i u t i t han. Dieu nay cd the do vigc k l l m soat cap p h l l , cong nghe thi edng.
4.2. K i l n nghj
- D l xuat d y p e gia trj md dun dan h i i dpng cua d p phdi da dam logi I la 270MPa, eiia ldp cap phdi da dam logi ll la 210MPa phue vu phan tich ket cau mat d y d n g theo p h y a n g phap ea hpc thye nghigm va AASHTO 1993.
~ Tdng b y d e nghign edu k i i m soat c h i t l y p n g thi edng b i n g bieu d l thong kg. Nghien edu he s l thanh toan pay factor d l xuat mdc thydng/phat va gidi hgn bdc bo khi thi cong ldp e l p p h l l da dam d Viet Nam, •
TAI UEU THAM KHAO
1. Transportation research board (2013), Practices for Unbound Aggregate Pavement Layers, NCHRP Report 445, Washington, D.C,
2. Federal Highway Administration (1995), Quality Assurance Procedures for Construction, FHWA FAPG-23 CFR 6378, 1995.
3. AASHTO R 9-05 (2018), Standard Practice for Acceptance Sampling Plans for Highway Construction.
4. Bp KHCN (2011).
TCVN8859-2011. Ldp mong d p phoi da dam trong ket d u ao d y d n g d to - Vat ligu, thi cdng va nghigm thu.
5. AASHTO (2015), M e c h a n i s t i c - E m p i r i c a l Pavement Design Guide- A Manual of Practice, ISBN:
ISBN: 978-1-56051-597-5 6. Adama D., Meissa F., Yves B., Farld B,, Alexandre M. (2017), Implementation of Resilient Modulus CBR relationship in Mechanistic- Empirical (M-E) Pavement Design, Revue du GAMES - Sciences Appllquees et de I'Ingenleur, ISSN 2312-8712.
7. Shabbir H. M., Wan S. K.
(2015), Estimation of Subgrade Resilient Modulus Using the Unconflned Compression Test, Final Report VCTIR 15-R12, Virginia-USA.
I So 4 nam 2020
