Dublin Port Tunnel

Xiaowei Jin, Xinni Wang, Mingqiu Mao

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

Thank you!

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