Kuala Lumpur city is sitting on Karstic limestone geology with
high ground water table. The Special Features of Karstic limestone
include cliffs, pinnacles, cavities, collapsed cavities and
sinkholes. Overlying these Karstic limestones is loose alluvium
from previous tin mining activities.
Due to the nature of the soil condition, much
thought and planning was channeled towards the selection of
a construction method that would have minimal negative impact
on the geological
condition of the soil.
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Some Features of Karstic Limestone
Bedrock
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It is known that the tunnel boring machine is
the most advanced and cost effective method used in the construction
of tunnel in Europe. However, TBMs come in a variety of shapes,
sizes, using a variety of technology according to need. For
SMART, after much research, study and survey, the Slurry Shield
TBM was opted for. This machine is designed to overcome problems
of groundwater drawdown which has been identified as the root
cause of incidences of sinkhole appearance.
In terms of cost, the slurry shield machine
is not different from any other type of TBM but unlike other
types, the slurry shield machine is designed to create a pressured
shield made up of bentonite and air pressure.
This pressured shield is able to counter balance
the pressures of the groundwater and loose soil acting on
the face of the boring machine.
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