dublin port tunnel xiaowei jin, xinni wang, mingqiu mao
TRANSCRIPT
Introductionin Dublin, Ireland connects to the M1, part of the M50 relieves surface road congestion in Dublin city centerthe twin tunnelsJune 2001–2006, €752 million
Geological condition
• Bedrock in the Dublin area is a thin to medium interbedded homogenous grey argillaceous limestone and calcareous shale.
• Over much of the city, it is overlain by glacial deposits, known as Dublin boulder clay.
Geological condition• Boulder Clay has a widespread
distribution across central Dublin.
• It has traditionally been divided into two strata, an upper Brown Boulder Clay and a lower Black Boulder Clay for engineering purposes, the upper unit being a weathered facies of the lower.
• These sediments can vary greatly in thickness, from a few metres to upwards of 20m.
• The till contains water-bearing lenses of sand and gravel.
ProblemsThe changing geology, boulder clay, limestone, clay, sands and gravels, can cause differential settlements
The excavation influences onto the adjacent roads
the diaphragm walls need to be supported as the depth of the excavation
A comprehensive drainage system is needed
Overview
• The tunnel is built in five section:
• Two bored section
• Two “cut and cover” section
• A specialised pipe jacked section
Solution1 TBM
• Two TBMs are adopted
TBM1
Progress per day 10 to 12m average
length 2.6km
geology Carboniferous limestone
Volume spoil excavated 0.5 million cubic meters
Solution1 TBM
• TBM2
Progress per day 2 to 3m average
length 800m
geology Dublin boulder clay
Volume spoil excavated 71,000 cubic meters
Solution2 Cut and Cover
The “cut and cover” sections:
-The southern section is 500m long at Fairview
-The northern section is 1500m from Whitehall Church to Shantalla
Solution2 Cut and Cover
To secure the sides of the excavation two separate measures are employed
-the construction diaphragm
-the use of a combination of soil nailing and shotcreting