الفهرس 
LITERATURE REVIEWOnly 14 pages are availabe for public view
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Abstract
The use of tunnels in urban areas has gained much popularity in recent
years in transportation and in infrastructure projects especially in heavily
populated cities, where the available areas above-ground are limited.
Tunneling is a relatively complicated engineering problem. The degree of
complexity gets higher when two tunnels are closely spaced, which is a
typical case used in transportation or in infrastructure projects.
The main objective of this research was to develop a numerical model to
study the behavior of twin tunnels constructed using open face machines in
stiff clayey soils. The numerical analysis results were compared with field
measurements to investigate the possibility of efficient back analysis of
tunneling projects using such techniques and to validate the applicability of
the numerical model used in this research for future cases with similar
tunneling and geological conditions. An extensive parametric study was
also performed to identify the main variables that govern the behavior of
twin tunnels and to quantify their impact on tunnel and ground behavior.
The study validated the concept of using stress release factor to simulate
three dimensional soil arching at tunnel face and ground relaxation prior to
lining installation. The study also provided an assessment of zone of stress
disturbance around twin tunnels constructed in stiff clay in addition to
estimates of associated displacements and lining straining actions. The
results of the parametric study were used to develop an estimate of the
separation distance between twin tunnels beyond which interaction
between tunnels is expected to be of minor influence.
Kevwords:- twin tunnels, stiff clay, numerical modeling, Flac5.0,
settlement, displacement fields, stress and strain fields, case history.