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Presented by: Jonathon Simons Sanjo Adeyemo

Taiwo Oshodi

An Investigation into the Geological Faults and Subsequent Construction Implications

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•Introduction to the Project

•Geological Conditions

•The Collapse

•Causes of Failure

•The Solutions

•Conclusions

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• Lane Cove Tunnel Collapse• Sydney Australia• Connecting the M2 Freeway at North Ryde to Gore Hill Freeway• AU$1.1billion contract Awarded to Theiss & John Holland Joint Venture

Source – Google Maps Data 2010

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• The Collapse Occurred on the 2nd November 2005

• The first collapse occurred at approx 01:40 am• 02:00 am a hole was observed approximately

4-5m wide and had undermined approximately 1-2m under the road

• 06:00 am, a secondary collapse was heard and the hole had widened to approximately 8-9m

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• Dangerously the hole compromised the stability of a neighbouring tower block

Damage to the unit block at 11-13 Longueville Road, Lane Cove

Source – Work Cover: New South Wales

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1. Geological conditions at the site

2. The large span width of the tunnel intersection

3. The proximity of the tunnel excavations to the ground surface

4. The nature of the tunnel roof support installations

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• Hawkesbury Sandstone & Ashfield Shale• Lane Cove Tunnel lies predominately in the low

strength Shale• Site Engineer classed the bedrock as having

low to very low strength• The Presence of a (doleritic) Dyke• Rock Mass Joints and Faults

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• Longueville Road retaining wall• Rock Bolting• Inadequate support system• Advancement of one side of the tunnel to quick• Specifications not adequate for region of tunnel

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• The tower block was evacuated and the road closed at 06:45

• The hole was then filled with concrete and then the voids filled with grout to finalise the stabilization

• Approximately 2750 cubic metres of concrete and grout were pumped into the collapsed area

SCHOOL OF CIVIL ENGINEERING The SolutionThe Solution

Pacific Highway Off-Ramp at south western corner of Kerslake Apartments. Void backfilling with concrete 3rd November 2005

Source – Work Cover: New South Wales

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• New foundations using piles

• Diverting the tunnel

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• Low Strength Shale• Presence of dyke• Jointing Failure• Retaining wall drilling• Poor rock stabilizing methods• Rock bolting not installed to specification

causing failure of the ground support system

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