AGS - Engineers Australia

Australian Geomechanics Society and Australasian Tunnelling Society (ATS) EVENT INDIVIDUAL MEMBERSHIP WESTERN AUSTRALIA CHAPTERS AGS WA AND ATS WA TECHNICAL PRESENTATION Deep Sewer Tunnels Presented by Dr John Endicott, Executive Director-‐ Geotechnical, AECOM, Hong Kong In 1994 Contracts were let to use TBMs to drive five tunnels between 90m and 140m below sea level as Stage 1 of a scheme for transportation of sewage under the harbor of Hong Kong. A sixth tunnel was built by drill and blast. In 1996 the first Contractor stopped work and a protracted Arbitration followed based on an argument that it was impossible to proceed due to the need to reduce the inflow of water. A settlement was agreed in favour of Government. Work continued under Replacement Contracts. In 1999 residents at Tseung Kwan O were alarmed at settlement of the ground more than 1km from the tunnel. Nearby, in recently reclaimed land, subsidence of more than one metre was reported and drawdown of ground water was observed as far as 2kms from the tunnel. Lessons learned from the experience on Stage 1 were put into practice for Stage 2A. More geological information was provided including horizontal directional coring for about 5kms, some 29% of the length of the tunnels. A geological model was developed on a Geographical Information System (GIS) that included data from over 100,000 archived and project specific boreholes. Geological risk, normally 100% for the Contractor, was shared by the Employer. In particular the drilling and grouting for stemming the inflow of ground water was paid by re-‐measurement. Estimates for quantities of drilling, grouting and temporary support and estimates for the construction period were developed making use of performance data from Stage 1 tunnels captured in a Tunnel Data Management System comprising gigabytes of data. Stage 2A tunnels are under construction using the drill and blast method and are nearing the last break-‐through. The contract specified pre-‐excavation grouting. A development during construction has been the use of colloidal silica instead of micro-‐fine cement for grouting fissures in the rock. Colloidal silica is more expensive material than micro-‐fine cement but less of it is needed therefore the cost of grouting is within expectations. THE PRESENTER John Endicott has specialized in ground engineering since obtaining his PhD in 1970 at Cambridge University using a centrifuge to model failure of slopes. Since 1975 he has been based in Hong Kong working primarily in South East Asia. He has been in charge of AECOM’s Hong Kong office with, at times, over 500 geotechnical and tunnelling staff. He has been involved in many projects including many underground railway projects, over 100 underground railway stations, as well as highway tunnels and water tunnels. He was also the Project Design Director for the reclamation of Chek Lap Kok International Airport in Hong Kong as well as extensive other reclamations and construction on soft ground. Relevant to this lecture, he was engaged in 1996 as one of Hong Kong Government’s experts in arbitration concerning the Stage 1 deep sewer tunnel construction contracts. The arbitration was settled in favour of Government. He was then involve with the procurement options, and later he was the Director in charge of the geotechnical investigation and tunnel design, for 20kms of stage 2A deep sewer tunnels beneath the harbor which are nearing completion. These tunnels are notable because unusually the Employer accepted a large part of the geological risk by paying for all the ground treatment on a re-‐measurement basis. Two Universities, Hong Kong University and Hong Kong University of Science and Technology have appointed him Adjunct Professor and he has been recognized as an Industry Leader by being the first Hong Kong Engineer to deliver the biennial Lumb Lecture, Hong Kong’s equivalent to the Rankine Lecture. THE DETAILS
WHEN COST AGS/EA Member: FREE Non Member: $30.00 REFRESHMENTS th
Tuesday 9 September 2014 5.30pm Light Refreshments 6.00pm Presentations WHERE Engineers Australia Auditorium 712 Murray Street West Perth, WA 6005 REGISTRATION Register online at: https://events.engineersaustralia.org.au/ei/get
demo.ei?id=1943&s=_9VC0Z5CEE You are invited to join the Speaker for dinner after the talk (pay your own way) at: Black Tom’s, 27 Ord Street, West Perth. CPD Engineers Australia members participating in AGS and AusIMM technical sessions can record attendance on their personal Continuing Professional Development (CPD) logs. Members should refer to Engineers Australia CPD policy for details on CPD types, requirements and auditing guidelines.

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