Phan tich ket cau bo phan cong tdc caa thiQt bj khoan - phan - tron coc xi mang ddt PGS.TS Nguyin H6ng Ngdn', ThS Huynh Cdng Ldn", ThS Trdn Cdng TriS 'Bd mdn Cd gidi hda Xi nghiep Xdy dflng, Khoa Cd khi, Trfldng Dai hpc Bdeh khoa TR HCM ^Bd mdn May Xay dflng, Khoa Cd khi, Trfldng Dai hpc Giao thdng Vdn tdi TP HCM TOM TAT Bdi viet trinh bdy scf lUdc vi gidi phdp xii ly nin ddt yiu bdng cgc xi mdng ddt Phdn tich dnh hudng cua kit cdu bg phdn ldm viic din chdt lUdng cgc xi mdng ddt Tii dUa kit cdu ldm viec phii hdp vdi diiu kien tU nhiin cua Viet Nam, dong thdi, dUa cdc thong so ky thudt cua cong nghi cgcxi mdng ddt dp dung nhiing diiu kien ddt khdc I DAT VAN DE TONG QUAN VE CQC XI M A N G DAT Nhilu cdng trinh xdy dflng cua nfldc ta 2.1 Gidi thieu chung dfldc thflc hiln trln nln dat ylu Di xdy dflng can phdi tiln hdnh xfl ly nln mdng cho hilu qua Cpc xi mang dat (hay cdn gpi Id cpt xi va tilt kilm, phu hpp dilu kiln kinh t l - ky thudt mang dat, tru xi mdng dat) - (Deep soil mixing cu thi Mdt nhflng phfldng phdp xfl ly nln columns, soil mixing pile), la mdt cpc hinh tru yeu hilu qua Id dung cpc xi mdng dat khdng cd cdt trdn tao thdnh bdi hdn h ^ dflpc trdn diu gifla thep dat nguyin trang vdi xi mang dfldc phun xuong nln dat bdi thilt bi khoan - phun Cdng nghe thi cdng tao cpc xi mdng dat dflpc dp dung d nfldc ta chfla Idu, nhilu van dl Qud trinh thi cdng tao thdnh cpc xi mang vl ly ludn vd thflc tiln van cdn chfla dflpc nghiln dat dung phfldng phdp khoan trdn sdu Sfl dung cflu day du, dac bilt la nhflng nghiln cflu vl kit mdy khoan vd cdc thilt bi chuyin dflng (can cau cua bd phdn lam viec - mdt nhflng ylu khoan, mui khoan ), khoan vdo dat vdi dfldng td anh hfldng ldn nhat din chat Iflg'ng cua cpc xi kinh vd chilu sdu Id khoan theo thilt kl Dat mang ddt qud trinh khoan khdng dfldc lay lln khoi lo khoan ma bi phd vd kit cau, dfldc cdc canh mui Vdi nhflng xu thi dd, viec nghien cflu gidi khoan nghiln tdi, trdn diu vdi chat kit dinh (chat quylt van dl vl kit cdu cua bd phdn lam viec d l kit dinh thdng thfldng Id xi mang hoac vdi, thach phu hdp vdi dilu kiln tfl nhien cua nfldc ta la hit cao ddi cd thlm chat phu gia va cat), sflc can thilt TAP CHf CO KHf VlfiT NAM • Sd 03 (Thang nam 2012) Qua trinh phun (hoac bdm), chat kit dinh dl trdn vdi dat hd khoan, theo ylu cau cd thi dfldc thflc hiln d cd hai pha khoan xudng vd rut lln cua mui khoan hoac chi thflc hiln d pha rut mui khoan lln De trdnh ldng phi xi mdng, han chi xi mang thodt khdi mat dat, gdy d nhiem mdi trfldng, thdng thfldng, rut mui khoan lln each dp cao mat dat tfl 0,5 1,5m ngfldi ta dflng phun chat kit dinh, nhflng doan cpc 0,5 1,5m ndy van dfldc phun day du chat kit dinh Id nhd chat kit dinh cd dfldng dng tilp tuc dflpc phun (hodc bdm) vdo hd khoan Khi mui khoan dflpc rut lln khdi hd khoan, hd khoan cdn lai dat da dflpc trpn deu vdi chat kit dinh dan dan ddng cflng, tao cpc xi mang dat Hiln cd cdng nghe trdn khd (Dry Jet Mixing) vd cdng nghe trdn fldt (Wet Mixing hay cdn gpi la Jet - Grouting): - Trdn khd Id qud trinh phun trdn xi mang khd vdi ddt cd hoac khdng cd chat phu gia #111^ A Hinh 2.2: Cac bUdc thi cdng trpn kho Thi cdng cdi tao nln dat ylu bang cpc xi mang dat theo phfldng phdp trdn khd theo cdc bfldc sau: - Dinh vi vd dfla thilt bi thi cdng vdo vi tri thilt kl; - Khoan dau phun trdn xudng day khdi dat can gia cd; - Bat dau qua trinh khoan trdn vd keo dan dau khoan lln din mieng Id; - Trdn fldt Id qud trinh bdm trdn vfla xi mang vdi - Ddng tat thilt bi thi cdng va chuyen sang vi tri dat cd hoac khdng cd chat phu gia mdi lUM V A t r ^ Hinh 2.1 Ddy chuyin thiet bi trdn khd Hinh 2.3: Ddy chuyin thiet bi trdn fldt TAP CHf CO KHf VlfiT NAM V Sd 03 (Thang nam 2012) cr^ 2.3 Ung dung Hinh 2.4; Cac buOc llii cong Iron not liiiih J 'J: LgL xi mang dat hjjan thicn, 2.2 Uu vd nhfldc dilm Mpt sd td hpp thilt bi dflpc trang bi h? thdng dilu khiln hi|n dai, todn bd cdc thao tdc thi Uu dilm ndi bdc cua cpc xi mdng ddt: cdng cpc gia cd dflpc tfl ddng hda theo cdc chfldng - Thi cdng nhanh, ky thudt thi cdng khdng phflc trinh, cdc sd li|u vl Iflpng xi mdng sfl dung tren tflng mit cpc dflpc hiln thi, lflu gifl vd in tap, ylu td rui ro thdp bdng kit qua thi cdng cho tflng cpc - Tilt Idem thdi gian thi cdng din hdn 50% Khi xdy dflng cdc cdng trinh cd tdi trpng khdng phdi chd due cpc vd dat du cfldng dp ldn trln nln dat ylu, cdn phdi cd cdc biln phdp - Hilu qud kinh t l cao, gid thdnh hdn nhilu so xfl ly dat nln bin dfldi mdng cdng trinh, nhat la nhflng khu vflc cd tang ddt ylu ddy cd hilu qua vdi phfldng dn khdc cao, dflpc dp dung cho cdc cdng trinh xdy dflng - Rat thich hpp cho cdng tdc xfl ly nln mdng cho giao thdng, thuy lpi, sdn bay, bin cang, cac cdng trinh d cdc khu vflc nln ddt ylu nhfl bdi bdi, ven sdng, ven biln Nd cd thi sfl dung de lam tfldng hdo chdng tham cho dl dap, gia cd dat xung quanh - Cd thi thi cdng dflpc nhflng dilu ki|n dfldng ham, dn dinh tfldng chdn, chdng trflpt dat mat bang chat hep, ngdp nfldc cho mdi ddc, gia cd nln dfldng, md cau dan - Khd nang xfl ly khd sdu (cd thi din 50m) So vdi mdt sd gidi phdp xfl ly nln hiln CO, cdng ngh| cpc xi mdng dat cd flu dilm Id kha Nhflpc dilm: nang xfl ly sdu, thich hprp vdi cdc loai dat ylu (tfl cat thd cho din bim ylu), thi cdng dfldc cd - Kha nang chdng xd ngang kim (do khdng cd cdt dilu kiln nln ngdp sdu nfldc hoac dilu kiln thep) neu chi dflng ddn le hiln trfldng chat hep, nhilu trfldng hpp, da dem lai sfl tilt kilm ddng k l so vdi cdc giai phap - Chat Iflpng cac cpc khac khd ddng diu (do xfl ly khdc (nlu sfl dung phfldng phap cpc bl tdng tinh chat dat nln vd qua trinh cap xi mang khdng ep hoac cpc khoan nhdi thi rat tdn kem tdng ddng nhat) ddt ylu ben trln day) - Qua trinh nghiln cflu vl cpc xi mang dat cdn chfla hoan thien TAP CHf CO KHf VIET NAM ••• ANH HUdNG CUA KET CAU BO PHAN L A M VlfiC DEN CHAT LU'ONG COC XI MANG DAT S6 03 (Thane nam 2012) Quy trinh lam chat dat nen: a) b) c) Hinh 3.1 Quy trinh ldm chat nen a) Khoan cat pha dat nen, d6ng thdi bom viia b) Cat nhuyen dat va trpn that deu vdi viia c) Tao mot h6n h