Geotechnical Challenges of Bridge Approach Embankments and Foundations in Poor Ground – Lessons Learnt from RMS Projects

Dr AHM Kamruzzaman (Zaman), FIEAust CPEng NER RPEQ, Specialist Geotechnical Engineer, RMS

Abstract

Construction of bridge approach embankments over soft clays causes significant geotechnical challenges in terms of large total and differential settlements, lateral movements, and high excess pore-water pressures. In addition, project design requirements are to meet stringent post construction and differential settlements for the whole design life of structures. Soft ground improvement measures are often needed to fulfil such settlement requirements. Several bridge approach embankments were built recently over soft clays with thickness up to 28 m, and ground improvement techniques with or without Prefabricated Vertical Drain (PVD) were used depending on soft clay thickness, construction time and settlement requirements. RMS faces various challenges on constructing these embankments such as excessive settlement and longer preloading time than those predicted. Furthermore, construction of bored piles for bridges through poor ground (such as soft clay, sandy gravelly clay, weak rock) resulting in pile hole instability is another emerging issue for RMS. Based on the integrity test results on a few recent projects, it was ascertained that bored piles failed the integrity requirements often due to cracking, necking, formation of weak concrete and soft toe. These geotechnical issues are the main causes for delay in construction, increase in maintenance costs and technical risks to the RMS assets.

This presentation explores some important design and construction issues for settlement prediction of bridge approach embankments on soft clays and integrity of bored pile foundations on weak materials from lessons learnt at RMS projects.

About Dr AHM Kamruzzaman (Zaman)

Dr AHM Kamruzzaman (Zaman) is a Specialist Geotechnical Engineer with Roads and Maritime Services (RMS), and a Fellow and Chartered Professional Engineer in Australia. He has over 24 years of working experience in public, consulting, construction and research industries in the provision of providing geotechnical specialist advice and the management of technical risk in major infrastructure, tunnelling and building projects both in Australia and Singapore. Over the years, he has held a number of prominent roles such as a Principal Geotechnical Peer Reviewer, Geotechnical Manager, Principal Geotechnical Engineer, Team Leader, Independent Verifier, Senior Geotechnical Engineer and Research Fellow.

Since 2007, Zaman has worked on a number of major RMS highway upgrading projects such as: Ballina Bypass, Pimlico to Teven, Banora Point, Sapphire to Woolgoolga, Hunter Expressway, Oxley Highway to Kempsey, Nambucca Heads to Urunga, Warrell Creek to Nambucca Heads, Foxground to Berry, Grafton Bridge and WestConnex. He has also worked on many deep excavations and tunnelling projects in Singapore from 2002 to 2006 including Land Transport Authority (LTA) circle line projects C823, C824, C853, 851A, Nicoll Highway collapse reconstruction and Common Service Tunnel.

Zaman has obtained his PhD from the National University of Singapore and written over 50 technical papers including several RMS specifications/technical directions (e.g. Deep Soil Mixing, Concrete Injected Columns and Bored Pile Testing) on various geotechnical issues. His field of specialization includes: soft soil, ground improvement, pile foundation on weak rock and deep excavation. Zaman is also an editorial panel member of Journal of Ground Improvement, ICE.

Venue location

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