Twin tunnel interaction mechanism in kenny hill formation using finite element analysis
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Date
2018-06
Authors
Tan, Yih Ken
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Abstract
Urban tunnelling is becoming more popular due to the limitation of land use in
metropolis. However, urban tunnelling are always associated with difficulties and
involved with complex mechanism due to its interaction between tunnels and ground.
The volume loss during the tunnelling excavation has led to ground deformation which
may potentially damage the adjacent surface or subsurface structures. Thus, for large
scale underground construction like KVMRT, tunnel design with proper estimation of
ground deformation and realistic geotechnical simulation is essential. In this study, the
subsurface characterization of tunnel excavation section in Kenny Hill Formation was
conducted to develop 3D ground model, tunnel filtered model and ground section
through spatial interpolation of borehole data using Inverse Distance Weighted method
(IDW). Six greenfield ground sections were selected based on input of tunnel filtered
models configuration of tunnels and availability of tunnelling induced ground movement
data. The conceptual models for finite element modelling were developed based on the
soil profiles and corresponding soil parameters determined from ground sections. The
strength and stiffness parameters for Hardening Soil (HS) model were established using
data from site investigation, in situ and laboratory test and empirical correlation with
standard penetration test N numbers(SPT-N). The effectiveness of empirical correlation
is determined by back-analysis of twin tunnels excavation in 2D finite element analysis
using lining contraction method and verified with monitored ground movement data.
The numerical back-analysed results of twin tunnels excavation simulation using HS
parameters obtained from selected empirical correlation showed good agreement with
construction-monitored ground movements with application range of values of
contraction ratio from 0.3% to 0.92%.