Vấn đề dự báo thời gian ổn định không chống của công trình ngầm sau khi đào

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The term "stand-up tmte'is used Hist time in Lauffefs lock mass

dassifKatkm (1958) In relatkm to the so called 'effedis/B unsupported

span" and then modified by Bieniawski (1973). Until now the

stand-up time Is a useful parameter in rock mechanics and tunnel

design. It affects the selection of excavation method, excavation

cyde, the nxk reinforcement method and time to Install rock support.

In other words, the sland-up time Is a tunctkm not only of rock mass

properties but also of excavation technique. Because c/assificaSon

methods are based on rock mass quality empirical evaluation

through specific parameters, however, the determination of the rock

mass properties to evaluate rock mass quality and also the

sjand-up time Is very difficult in In-s'itu. Therefore, the development

of mathematk:al models Is necessary and has great meaningful to

estimate the stand-up time in the tunneling. This articte presents a

theoretical solution for determination of the stand-up time or 'rock

mass failure-time of geo-hazards'

GS. TS. NGUYEN QUANG PHlCH

Hdl Cdng tilnh ngim VI0t Nam

Bien t$p: TS. Pham Minh Di>c

1.D|tvin de

Trong thuc t l xiy dung cac cdng trinh ngim

dan dung v l khai thie mo ham 16. hipn tuang

phi huy khoi d l (trie va. trdc Id. sap Id, trupl

Id...) thudng cd thi xay ra vio thdi dilm nhat

djnh sau khi die nlu khdng tien hinh gia cd khIi

d l hole lap dung ket cau chlng hap 1;^ v l kip

thdi Thdi dilm niy phu thupc vio kich thudc

khoang khdng gian trdng ehua dupe gia cl ,

chlng dd, vio cic die dilm dia chit v l cic tinh

chit ca hpc cua khIi dl . Khoang thdi gian k l tir

khi die khoang trlng nhung ehua gia co, chlng

dd eho din khi xay ra phi huy thudng dupe gpi

la thdi gian In ffinh khing chlng (the stand-up

time), hay thdi gian luu khong. Khai nipm niy

xuat hien diu tien trong eich phan loai khIi d l

cua Lauffer (1958) [1] v l sau nay trong each

phln lopi ciia Bieniawski (1973) [1]. Trong eac

cleh phln loai d6, mli lien quan giOa thdi gian

In dinh khdng chlng v l khiu dp khdng chlng

hCru hipu (chieu rpng hc|c khoing eleh tir

guang dap den kit eau chlng) duac si? dung

d l xiy dyng hay tinh toin t l chirc chu ky dio,

sao cho kit ciu chlng tam phai duac hoan

chinh trudc thdi diem ed the xay ra phi huy.

M|c dCi cic phuang phip niy dang dupe sir

dyng phi biln d Ao v l tren thi gidi, nhung eung

phai thiy rang mdi lien hp neu tren ciia cac tic

gia diu mang tinh kinh nghiem, theo danh gia

ehu quan, khdng duac xiy dung trdn ea sd Up

luan v|t ly chat che. Cung vi v|y, xic dinh thdi

gian In i^nh khdng chlng II vin d l ludn dupe

quan tim trong ITnh vuc ea hpe d l v l xiy dyng

cdng trinh ngim. Xle dinh thdi gian In dinh

khdng chdng eung ding nghTa vdi xic dinh thdi

gian xay ra tai bien dia chit (rock mass failure￾time of geo-hazards).

Bii viet niy gidi thipu mpt Idi gill 1;^ thuyit

xac ^nh thdi gian dn d[nh khdng chlng hay thdi

gian on the xay tai biln dja chit trong xiy dyng

cdng trinh ngam.

2. IWo hinh bai toan va cac dilu kipn v l

khdi da

Trong khdi d l ludn tin tai cac m|t phln each

khac nhau. Su cd mat cua chiing din din tinh

chit luu biln v l ea hpc, tire II su phy thupc cua

cie tinh chat ca hpc vio thdi gian. Thuc t l eung

chirng minh dilu nay qua su phIt triln djch

chuyin, bien dang v l eac hipn tupng phi hOy,

xay ra trong khIi da sau khi dio, chlng gift

khoang khdng gian ngam, theo thdi gian. Tinh

chit luu biln eiia khIi da duac md phong bdi

cac md hinh luu biln, dupe nhilu nhi khoa hpc

de xuit [2].

Trong bai niy, tlnh chit ca hpc ciia khdi d l

phy thupc vie thdi gian dupe md phpng bing

KHCNM SC 7/2015' CNKT HAM LO