67 diforc on dinh bang cU&ng vdi lieu cot soi ve dac tmh bien dang cua Nghien culU thUc nghiem or

diforc on dinh bang gia cU&ng vdi vat lieu cot soi

Experimantal study on deformation characteristics of liquefied stabilized soil reinforced by fiber material prepared at laboratory and field

Duorng Quang Hung

T o m t a t I 1 - D a t v a n d e Bai bao nay trinh bay nghien cihi siTkhac nhau giij'a dieu kien bao

Afidng trong phong vdi ngoai hien trudng cOa m l u t h i nghiem la hon htfp dat cot soi ve ket qud ba true cua chung, nham sang to kha nang sul dung h§n hcip dat vdi cot sOi va xi mang lam vat lieu dat dap. Mot loai t h i nghiem nen ba true co ket khong thoat nUdc (CU tests) difcrc thuc hien cho ca hai loai mSudat chay on djnh (liquefied stabilized soil - LSS) du'dc tron vdi vat lieu cot soi ham lUffng 0 va 20 kg/m^ lan luot tai tuoi 28 va 56 ngay bao dudng, dadi da dang cac dieu kien n h u la toe do bien dang khong doi, Ung suat lech khdng doi (thi' nghiem triing li^g suat mot phan), va toe do bien dang dUOc thay doi trong suot qua trinh gia tdi don dieu. Hai loai mau nay lan (Udt dUOc chuan bj va b i o dudng trong phong thi' nghiem va dUOc taeh ra tir nen dat mo hinh duoc lam ngoai hien trudng theo phUtfng phap taeh lay m l u khdi (block sampling). DUa vao ket qua t h i nghiem, nghien cilu da i i m ra rang ultg dung LSS dUtrc trpn vdi vat lieu cdt scri lam vat lieu lap if cong trudng se cho ra duoc nen dat cd t i n h d^o dai hon.

TUkhoa: Bat chdy on dmh, vat heu cot sal, bao duong trong phong va hien Irudng, tinh chdt cat ba true

Abstract

In this study, the difference in triaxial shear property of Liquefied Stabilized Soil (LSS) mixed with fiber material cured in laboratory and at field was investigated AseriesofConsolidated-Undramedtriaxial compression tests under the conditions al constant strain rate, constant deviator stress (partial creep test), and changed strain rale dunng monotonic loading have been earned out for bolii specimens of LSS mixed with fiber material amount of 0 and 20 kqlmi prepared by trimming LSS retrieved from a model ground by block sampling and cured in laboratory at curing time of 28 and 55 days,

respectively. Based on the test results, it was found that the application of LSS mixed with fiber material as a bac!<filling material to construction sites enables lo create a ground with the Improved ductile charateristic.

Key words: Uquefied Stabilized Soil, Fiber Material, Cured in Laboratory and at field, Triaxial Shear Property

TS. Duo^ig Quang Hiing Bo mon K4I cau BTCT-CD. Khoa Xdy d\

Email: hungl2l903@yahoo.com BT. 0912.472 670

Ngay nhan bai:

Ngay sira bai Ngay duy|t dang:

Tai Nhat Ban, LSS dup'c sir dung r l l pho biin nhu la phuang phap lai che. LSS 6' day la d i l dup'c trdn vdi nu'd'c (hoae nudc biin) va chit on dmh la xi mang dac biet sau dd duac tai sir dung nhu la vat lieu lip [1-2] Tuy nhien eae nghien ciru chi ra ring LSS the hien ung m cudng dd kem deo dai va don ban nlu lang cudng do bo'i lang ham luang XI mang. D l eai thien duac tinh dec dai eiia LSS, Kohata va cac ddng su da phat triin mdl phuang phap gia cudng bdi Iron vat heu c i l sgi vao hdn hap [5-9]. Vat lieu cot sp'i dup'c cae nha nghien eiru sir dyng dup'c tai chi lir eae loai bao p h i thai va dup'c nghiin thanh sai nho. Mgi loai eae thi nghiem nen ba true da dup'c thuc hien. K i l qua chl ra ring linh chit deo dai ciia LSS Iron vdi vat lieu edt sgi la duae cai thien.

Tuy nhien, chua ed b i t ky mol nghien euu nao ve LSS dup'c gia cuo'ng vdl vat lieu cdt sg'i tai hien trudng, va sy khae nhau Irong linh ehil biln dang giu'a LSS duo'c gia cudng vdi vat lieu cdt sp'i duae bao dudng trong phdng va ngoai hien truilng duae bao cao.

Nghien ciru nay thue hidn mdl md hinh nen dit lip vdi vat lieu la LSS dug'c gia cudng vdi vai lieu cdt sg'i ham luang 0 va 20 kg/m^ trong ba hd dao. Cting thai diim, cac mau cting dup'c due va bao duang trong phdng thi nghiem Mgt logt cae thi nghiem CU co kit dang hudng, ap suit hieu qua 98 kPa duac thuc hien Iren thiit bj nen ba tryc (TC tests) duo'i diiu kien khac nhau eiia ldc do biin dang mdl true cho cac m i u duac liy lir hien trudng (In-situ LSS) va trong phdng thi nghiem (Indoor LSS). Dua vao kit qua thi nghiem, su khac nhau trong dae tinh biin dang eiia LSS hien trudng va LSS trong phdng se dugc phan tich,

2, Thi nghiem 2.1. Vat lieu thi nghiem

Trong nghien ciru nay, NSF-CLAY duac sir dyng la vat lieu goe. Tinh c h i l vat ly dugc ghi Irong bang 1. Chit on dinh XI mang dugc sir dyng la loai xi mang dac biet ten la Geoset 200 san xult bdi Cdng ty xi mang Taiheiyo, Vat lieu col sgi la bao p h i thai duge nghiin thanh dgng sgi bdng.

Bang 1 Tinh chat vat ly ciia NSF-CLAY Density of particle Ps (g/cm^) Liquid iimit WL (%) Piastic Limit Wp (%) Plasticity Index Ip

2.762 60.15 35 69 24.46 2.2. Phuvng phap trdn

Thdng thudng ed hai phuang phap trdn LSS dugc sij' dyng cho d i t dao Itr nln d i l tu nhien ed chira luang Idn hat mm la biin set va set chay. Trong nghien ciru nay, de d i

SO 37 - 2020

67

KHOA HOC & CONG NGHE

L=1000mm

Nonwoven geotextile filter

Direct dnve iiiotot

-DBI poi^

•Load cell PiDximeter LOT Tians ducer far pore

oierpressiiie Trare dice r for cell pressure

Hinh 1 . Mo hinh ho dao Hinh 2. Thiet bi thi nghiem

dang chuan bi, phuang phap loai biin la dugc sCr dung. Nhu vay nude dugc them vao d i t de diiu chinh khii luang the tieh eiia biin, sau dd chit on dinh xi mang se duac trdn ciing.

Mpt loat thi nghiem trgn duac thuc hien bdi thay doi khii lugng the tich ciia biin va ham lugng ciia chit on dmh xi mang. Gia tri chay, dd set, ty le bleeding va cudng do chiu nen ciia m l u dugc xac djnh cho mdi mlu LSS d luoi 28 ngay bao duang. Nhu vay cac gia Iri dat dugc se cho ra dugc mgt ty le Iron lieu chuin cho nghien cuu nay.

2.3. Chuin bi miu

Dua Iren kit qua thiil k i ty lg Iron tieu chuin [8], trong nghien eiru nay, ly Id bleeding la thip ban 1%, ham lugng chit on djnh xi mang la SOkg/m'' va khoi lugng t h i lich cua LSSla1.280g/cm^

M i u duac chuin bj bdi Iron chat on dinh xi mang irong dat biin bang may trdn lay de dieu chinh ty trong. Thi nghiem ly trgng duac Ihuc hien bdi do khoi lugng ciia bun dugc due trong khudn vtra AE lieu chuin Sau khi dat dugc ty trong mong muon, vat heu col sgi dugc them vao va Iron tiip blng may Iron tay. Thi nghiem chay dugc lam theo lieu chuin JHS A313 - Japan Highway Public Corporation "Testing Method for Air Mortar and Air IVlilk, 1,2 cylinder sample" d i xae dinh dp chay cua LSS. De tao mdt nen d i l lap md hinh, LSS luai dugc Iron vai col sgi vdi ham lugng lin lugt la 0, 20 kg/m^, sau dd duge d i vao ba h i dao s i n nhu hinh ve 1. Mdl lo'p va dja ky thuat dugc phii len ho dao trude khi do LSS de tranh LSS thim vao nin d i l . Sau khi do, b l mai LSS dugc phii bdi mdl lo'p polymer d i bao dudng ngoai hien Irudng.

Cimg Ihdl diem. LSS luai cung duge diic trong cac khudn lieu ehuan dudng kinh 5 cm va chilu cao 10 em, tren be mat se dugc phii 1 Igp film polymer va duge bao dudng dudi dp I m khdng khi va nhiel dp trong phdng khoang 20°C.

Sau thai gian bao duang lin lugt 28 va 56 ngay, ca hai loai mlu hien trudng va Irong phdng dugc dua vao tiin trinh thi nghiem CU.

2 4. Phuvng phap thi nghiem

Thill bj nen ba true duge t h i hien tren hinh ve 2. D l

logi bd duae sai so thi nghiem do ldi tiep xiie lai dinh va Chan mlu (bedding error), mdl cap do biin dang eye bd LDT (Local Deformation Transducer) [10] dugc gin vao mat ben CLia mlu d l do biln dang dge tryc. Khi gia tri LTD vugt qua ngudng thi gia trj ehuyen vj dge true se nhan gia trj eiia proximeter va dial gauge va tu dpng diiu chinh sai so. Trong thi nghiem nay, mpt md la s i dugc si> dyng cho thiil bj gia tai cd kha nang dilu khien chuyin vj dgc trye vdi dd ehinh xae cgc cao va loai bd dugc sai s i (backlash) khi dao chiiu hudng ciia lai trong Toan bd qua trinh thi nghiem dugc diiu khien tu ddng bing mdt phln mim s i .

Thi nghiem CU duge Ihuc hien eho i l l ca cae m l u LSS Irong phdng va LSS hien trudng a tuoi bao duang 28 va 56 ngay. Sg bao hda miu dai dugc bing phuang phap ehan khdng, nude dugc khu khi ehay qua mlu dudi ap luc ngugc 196 kPa. Sau khi co k l l dang hudng suit 12 gid dudi ap luc hdng hieu qua 98 kPa, mlu dugc chuyen sang liin trinh nen ba tryc, De nghien ctru linh chai eudng dp va anh hUo'ng Irung irng suit tdi LSS, Ihi nghiem Iheo nguyen ly gay biln dang dgc true eho miu va xac djnh biin doi irng suit ciia mlu vai hai Irudng hap gia lai duac phan biet nhu hinh ve 3 va 4. Truo'ng hgp 1 Jcase 1) ia ap dyng cac vdng lap nhd gid tai/gia tai Irong tiln trinh gia tai dan digu va ldc dp bien dang mpt tryc 0.054%/phut (EQ). Trong truo'ng hap 2 (ease 2), Irting irng sua! (C) duac ap dung trong qua trinh gia tai va ngay truac khi thay doi tic dp bien dang mdl true (Eo -* C -» Eo -» C -• IOEO ^ C ^ EQ). SLP thay doi t i e do bien dang dpe tryc duge thue hien trong pham vi khoang 1% {£a=1%).

3. K i t qua thi nghiem va phan tich 3.1 Dac diem mdi quan he iJng suit vai bien dang

Hinh 5 t h i hien cae modul biin dang. Modul biln danq ban ddu EQ dugc djnh nghTa nhu dp cirng ban dlu tronq biln dang nhd ban Eg=0.002%. Modul bien dang E^^^ tronq tiio luyen cua dudng cong q~£g, nd the hien finh phi tuyen eua linh ehat bien dang Irong quan hg q-E^. Modul bidn danq E dugc djnh nghTa khi gia lai va dd lai Irong siidi qua trinh n^*"

68

TAP CHi KHOA HOC K I E N T B U C - X A Y D U H G

Tdc dp bien dang mgt tnic khong ddi =£'0

Bien dang mgt true, £•(%) Hinh 3. Tru'dng htfp thi nghiem 1

1

s

_a-

x;

"s an

•0

. /

1 /

Eo x ^ l - j r ^

I / Eo:Modul bien dang ban d3.u / / EianModul bien dang tangent u Eeq.modul bien dang tutrag ducmg

BiSn dang mdt true, e^ (%) Hinh 5. Djnh nghta cac modul bien dang

tai dan dieu, Egq trong hieu chinh triing irng suat duge tinh loan ttr dudng die ciia diim giai ban dudi va trung diem Irong dudng thing ndi dilm da tai va diem giao trong dudng cong q-Eg khi gia tai lai. Egq the hien su thay doi ciia c l p dd pha hogi khi chju cat [11,12].

Hinh 6 the hien kit qua Ihi nghiemlrud'ng hgp 1 Irong quan h$ gitra irng suit lech q^^ax va Eg vai thai gian bao dud'ng khae nhau cua LSS hien trudng duge gia cuo'ng vo'i vai lieu cit sgi ham lugng 20 kg/m^(Pc-20). Kit qua ciia LSS hign Irudng 6' tuoi 84 ngay vo'i cting diiu kien thi nghiem duac the hien a day chf de cung c l p them thdng lin, nghien cuu cu the se duge thuc hien trong thai gian tdi. Cae gia trj cd duge tir dudng eong q~£a ciia thi nghiem CU dudi ap lgc hdng hieu qua 98 kPa. Kit qua the hien ring EQ va q^^^ ciia mlu Pc-0 la giam a luoi 56 ngay, tuy nhien v l long I h i cac gia Irj nay cd xu hUo'ng lang d luoi 84 ngay. Gia tri q^iax lang theo thdi gian bao dudng la do hieu qua ciia xi mang tang cudng dp Iheo thai gian da dugc b i l l d i n . Tuy nhien gia trj qmax ciia mlu Pc-20 giam d' luoi 84 ngay mac dii gia trj EQ ciia nd lang. Hien lugng nay la do dilu kidn thai l i i i ngoai trdi, nhigt dp ngoai tro'i gin thdi gian bao duang 84 ngay la duo'i O^C. Nhu vay cd the dp am da anh hUo'ng d i n cudng dp eiia miu. Thuc vay, nhO'ng anh huang nay se c l n dugc thgc hien eae nghidn eiru lilp theo trong Ihdi gian io'i.

3.2. Modul bien dang E,an

Hinh 7 the hidn kit qua thi nghiem trudng hgp 1 trong quan he giO'a E,an/Eo va q/q^ax cua ca Pe-0, 20 indoor LSS va in-siiu LSS l i lugt tai thdi gian bao dud'ng 28 ngay va 56 ngay. Cac gia trj cd dugc tir dudng cong q-Cg ciia Ihi nghiem

lech,

q(kPa)

/A' \

''/\. \ 'A \ /

!/—^ ^Triing img suat

Bien dang mgt true, £<, (%) Hinh 4. Tru'dng hdp thi nghiem 2

Ngay bao duong Hinh 6a. Quan he giu'a qmax~ ngay bao du'dng

6D0

soo

^ 400

m 300

200

100

V

\ . / "

.. J-

s X /

x/

/ - . /

f^iilTl -•-Pc-O 1 -4-Pc-201 Ngay bao dirong

,

Hinh 6b. Quan he giO'a Eo~ ngay bao du'dng

CU dudi ap luc hdng hieu qua 98 kPa. Hinh ve chi ra ring toe dp giam Eian/Eo ciia mau indoor LSS va in-situ LSS cd khung hudng tuang l u 6' ca hai miu Pc-0 va Pc-20 6' tuoi bao du&ng 28 ngay va 56 ngay, Nhin chung, d i l dugc xir ly blng xi mang da dugc bao eao ring tinh phi luyin trong dudng eong irng suit bien dang giam khi lang thai gian bao dudng [3]. Tuy nhien, trong nghien ciru nay l i e dp giam cua Eian/Eo eiia miu d tuoi 56 ngay ia rdng ban so vdi tuoi 28 ngay. Do vay, k l l qua thi nghiem trong nghien eiru nay dudng nhu linh phi tuyen tang khi lang thdi gian bao dud'ng Nhu vay linh c h i l nay cin dugc nghien eiru cy t h i han trong thai gian idi.

Hinh 8 ihe hien k i t qua thi nghiem truang hgp 2 trong quan he giu'a E,an/Eo va q/q,r,3x ciia ca Pc-0, 20 indoor LSS

SO 37 • 2020

69

KHOA HOC & CONG NGHE

•|~Pc-20 case2

Hinh 9. Quan he Etan'"logEa/THl

Bien dang mgt true, £a(-''^o) -b)

1 P c - 2 0 easel j , .*==*

—•— Indoor, 28day

—A— Indoor, 56day

—O— In-sitii,28ilay

—£i— ln.5itu,56day

Bien d^ng mdt true, ea(%) Hinh 8. Quan h e Et3n/Eo~q/qmax/TH2

Bi^n dang mot true, 1 Pc-20 case2]

a ( % )

—•—Indoor.2aday 1

—A—Indoof,S6day j

—O—In-situ.28day | -A-In-SIIU.56da) |

I " ''

• "^ ? \ t t ' • ' ••

: :-^Mi

o

^ ^ 2 t o Bien dgng mgt true, £a(%) Hinh 10. Quan he Etan~log Ea,TH2

70

TAP CHi KHOA HOC K I E N T R U C - X A Y D U N C

07 a 0.6 i 0,5

0,3 02

01 | p c

20 1

. .

—•—]iidoor,28day|

—*— Indoor,56day - o - I n - s i n i , 2 B d a y

~'^^~ In-situ, 56day 1 0.4 0.5 0.

Hinh 11. Quan he Eeq/Eg'^q/qm

va in-silu LSS la luot lai thai gian bao dudng 28 ngay va 56 ngay. Hinh ve ehi ra ring E^n/Eo ciia ca hai m i u indoor LSS va in-silu LSS deu tang tire thi ngay sau khi ap dyng dieu kidn Irting irng suit va khdi lao mdl toe dd biin dang mgt tmc khdng doi mai b i t ke a tuoi bao dud'ng 28 hay 56 ngay, sau do duai l i l n trinh gia t§i su giam E,an/Eo cd khung hUo'ng rgng han. Nhu vay dp cirng ed khung hudng tang dot biln lam thai ngay sau khi thay doi tie dp biin dang hoae ap dyng trting irng suit, Han nua, pham vi chi s i gia trj Eon/Eo - 1 co khung hudng rdng han Irong trudng hap Pc-20 so vdi Pe-0.

Do vay cd the kit luan ring pham vi tuyin tinh trong quan he q~Ea dud'i dieu kien thi nghiem tren la rpng ban khi vat ligu ell sgi duge Iron vao trong LSS b i t k l thdi gian bao dudng.

Ndi each khae, kit qua thi nghiem da lim ra rang nhd hieu qua gia cudng do trdn LSS vdi vat lieu sgi ma phgm vi tuyin iinh trong quan he q-E^a cua LSS ngoai hien truo'ng ngay sau khi lac dung Irting irng suit duac lang Ien.

Hinh 9 t h i hien su phy thude elp dp biln dang trong modul biln dang Eian eho d i n diem dinh Irong dud'ng cong q-Eg cua ea hai mlu Pc-0, Pc-20 indoor LSS va in-silu LSS d' luoi bao duang 28 ngay va 56 ngay trong truilng hgp 1. Hi nh ve chi ra ring dd cirng ban d l u ciia in-situ LSS co khung huang rgng ban so vdi indoor LSS Tuy nhien khdng ed su khac nhau dang k i trong sg phu thude elp dd biln dang eiia Etan-

Hinh 10 the hien su phu thudc clp dp biln dang Irong modul biin dang Eig,, trong Irudng hgp 2. Trong ca hai m l u indoor LSS va in-silu LSS, hinh ve chi ra ring Eian d l u tang tire thi ngay sau khi ap dung dilu kien trting irng suat ke ea trong elp dp biin dang c i i lo'n. Han nO'a, ed I h l quan sat dugc pham vi rdng ban cua Ejan tang gin td'i dp cirng ban dlu trong mlu Pc-20. Thue vay, suit qua trinh gia lai trude diem dinh trong dudng cong q~Ea dp cirng ciia LSS lang ngay sau khi ap dyng trting irng suit Iham tri trong phgm vl ciia cap dp bin dang elt lan 6' bit k^ luoi bao duang nao.

Nhd hieu qua cOa gia cuo'ng do su trdn vat lieu col sgi Irong LSS Ihi pham vi cho dp cirng rgng han dugc tang len 3,3. Modul bidn dang Eg,

Hinh 11 the hien kit qua thi nghiem ciia Egg/Eo va q/qmaj, cua ea hai mlu Pc-0, Pe-20 indoor LSS vd in-situ LSS 6' luoi bao duang 28 ngay va 56 ngay, Cae gia trj cd duge l u dudng

cong q~£a eua thi nghigm CU duai ap luc hdng hieu qua 98 kPa. Nhtfng nghien ciru trudc ndi chung deu bao cao ring modul biin dang ban d i u cua d i l duae xir ly bang xi mang trong bien dang nhd la khdng phy thudc vao ap luc hdng hieu qua, thuc vay, Egq/Eodugc xem xet la chi so thay doi ciia c i p dp pha hoai do ciL d giai doan ban diu luc e l l lam m l u bj pha hoai cue bd, sau dd m l u bj pha hoai long I h i do dai e l l hinh thanh tir linh luy nhilu pha hoai e l l cyc bd. hien lugng nay la do cau triic vi md giii'a cac hat bi pha hoai, va sau dd gay ra su thay doi linh ehit dan hii ciia vat lieu. Hinh ve chl ra ring, ve long t h i , l i e do giam eiia Eeq/Eo ciia mlu Pc-20 cd khung hudng nhd ban so vdi Pc-0 trong Irudng hgp indoor LSS. Thuc vay, vai lieu cdt sai trong LSS da lam giam pha hoai cyc bd do c i t Tuy nhien trong trudng hgp in- situ LSS, toe dd giam ciia Egg/Eo eua mau Pc-20 d tuoi bdo dudng 56 ngay lai rpng han. Hien lugng nay cd the do anh hudng mdi Irudng bao dud'ng va tac ddng trong qua trinh lay m i u khdng nguydn ven. Vdi kit qua nay cln phai thuc hien eae nghien ciru cu the ban trong thdi gian tdi.

4. Ket luan

De nghien citu dac linh biln dang ciia LSS trdn vo'i vgt ligu c i l sgi dudi didu kien bao duang Irong phdng va hien Irudng, mdl loat cac thi nghiem nen ba tryc khdng Iho^t nude co k l l da dugc thue hien trong hai Irudng hgp ciia l i e dp biin dang doe true cho ca hai logi miu dugc taeh tir nin dat md hinh theo phuang phap taeh mau khdi va mlu duge bao duang Irong phdng, thdi gian bao duang lin lugt la 28 va 56 ngay. Cae kit luan sau day dugc dua ra dua tren kit qua Ihi nghem.

- Quan he Egq/Eo va q/q^ax cua ca hai m i u dugc bao dud'ng trong phong thi nghiem va ngoai hien Irudng t h i hien luang tu nhau. Han nO'a linh phi tuyln trong dud'ng cong q~Ea ciia LSS bj yeu di do hieu qua eiia gia cudng.

- Kit qua Ihi nghigm cung the hien ring viing tuyin linh rgng han ngay sau khi ap dung triing ung suit trong qua Irinh cit, dilu nay la do hieu qua gia cudng khi them vat iieu col sai trong LSS thi cdng ngogi hien Irudng,

- K i t qua nghien ciru nay cho them mot d i n chirng ring, sg irng dyng LSS Iron vdi vai heu cdt sgi cho nen d i l l i p ngoai hien trudng cd the tao ra mdl nin d i l vdi dat tinh deo dai duge eai thien./.

(Tai li^u tham khao & trang 73^

71