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GEOTECHNICAL
CPD course on some old geotechnical failure incidents in Hong Kong
By Mr Vince KONG

The GE Division organised a two-day CPD course, titled "Some old geotechnical failure incidents in Hong Kong". Various honourable speakers from Geotechnical Engineering Office (GEO) and consultants were invited to give informative presentations on previous geotechnical failure incidents in Hong Kong, particularly the lessons learned and related subsequent changes in the standards and procedures.

The types of old geotechnical failure incidents reported including blasting related failures, sea-wall/reclamation failures, trench excavation failures, tunnel related failures and slope related failures. Despite the incidents presented were termed "old" some of them occurred several decades ago, and their significance and impact on engineering and statutory requirements cannot be neglected at present.

In reviewing previous failures, the most common causes of failure were misinterpretation of geological data in design office, poor site quality control and safety supervision. For instance, a blasting related failure occurred in Shau Kei Wan, 1991 and a tunnel related failure occurred in Causeway Bay, 1983. The possible cause of these two failures was due to misinterpretation of ground investigation data, leading to an improper construction instruction on site.

In addition, examples were given on post-incident investigation. Sea-wall/reclamation failures occurred on Junk Bay Controlled Tip and Ma On Shan Area 77, and a tunnel related failure showed us how to conduct a detailed study on a geotechnical failure which included proper reviewing of relevant aerial photographs and desk study information together with sensitivity check on soil parameters. The conclusion drawn from the findings might help in preventing similar failure in the future.

Reviewing historical documentaries, we will learn more on the advancement in statutory requirements in geotechnical field and engineering advancement in the aftermath of failure incidents. In the review of the past failures on trench and deep excavation, excessive settlements or even a collapse of excavation were reported to have occurred in most cases. Regarding slope related failures, a comprehensive review was carried out from 1960s to the present. The government departments made several notable evolutions in geotechnical control and supplemented with various publications in advocating appropriate design guidance, and public awareness on maintenance and safety.

In attending this informative two-day course, it is important for us to have good appreciation on the rationale underlying current practices and to prevent similar failures to occur based on the lesson learnt from previous failure incidents.


Souvenir presentation to Ir Ken K S Ho, the speaker on old slope failures in Hong Kong


Presentation by Ir Y S Au Yeung

Workshop on excavation and lateral support works
By Ir Albert HO

On 17 March 2007, the GE Division and HKGES jointly organised a workshop on excavation and later support (ELS) works at the Hong Kong Productivity Council with the support from the ST Division, the Association of Geotechnical and Geoenvironmental Specialist (Hong Kong) and City University of Hong Kong. The workshop was a continuation of the seminar held in June 2005 and aimed to train local engineers to carry out ELS design by using CIRIA Report C580 "Embedded retaining walls - guidance for economic design".

The CIRIA Report C580 outlines a design framework in consideration of soil-structure interaction analyses by using limit state partial factor approach. The Report C580, in conjunction with some modifications, was considered applicable to ELS works in Hong Kong by the building authority. The authority also actively supported the C580 design approach by promoting a two-year trial period since 6 January 2005. Recently, the trial period has been extended for three more years.

The workshop invited Dr Andy Pickles of Geotechnical Consulting Group, Ir James Sze of Ove Arup & Partners Hong Kong Ltd and Ir Rupert Leung of Hyder Consulting Ltd, to share their valuable experiences and insightful opinions from the trial use of the C580 design approach in local and East Asia projects. Ir Stephen Y C Lee of the Buildings Department and Ir Dr Thomas Lam of the Geotechnical Engineering Office were also invited to present the authorities requirements on design, construction and monitoring issues associated with the ELS works using the C580 approach. During the discussion session, Dr S L Chiu and Dr Axel Ng of Maunsell Aecom shared with the audience their experiences in using software Plaxis for ELS designs.

The workshop provided a forum for the exchange of further experience in the design of ELS by limit state and partial factor approach as well as checking requirements. In-depth discussions were held on the use of numerical analyses for ELS designs.

Over 300 practitioners attended the workshop. The response was again overwhelming when compared with the seminar two years ago. It was hoped that the workshop would encourage more practitioners to adopt and try this alternative approach to ELS design.


Speakers and organising committee of the workshop


Speaker at ELS workshop

The 13th annual dinner
By Ir Ringo YU

The GE Division held its 13th annual dinner on 23 March 2007 at the Hong Kong Convention and Exhibition Centre. There were a total of 29 tables with some 340 participants attending, which was a record as compared to all the past Division's annual dinners.

It was our honour to invite Mr Cheung Hau-wai, JP, Director of Buildings Department, to join us as the guest of honour and give a speech on issues affecting local geotechnical engineering professionals. It was noted that the number of registered geotechnical engineers on the government lists, two years after the implementation of the legislation, was merely about 70 in March 2007. This was low considering that there were over 500 qualified geotechnical engineers in Hong Kong. Mr Cheung also briefed the audience about the planned introduction of minor works in the Buildings Ordinance which would remove significant administrative burdens to less complex works.

Our Chairman, Ir Albert Ho, gave a presentation on the difficulties faced by the geotechnical engineering profession. Ir Ho noted that there was some upturning of construction works in past years but the competitions on fee were severe. He opined that the present competition was not a healthy one and urged the industry to review our strategy in bidding and get rewarded for what we did, such that adequate resources could be invested to nurture the young ones and to maintain sustainable development of our industry.

This year's annual dinner also celebrated the 20th anniversary of the establishment of the Division. Past Division Chairmen were invited to join this relaxed and enjoyable event. For the first time, the Division invited a musical band, comprising six members from Civil Engineering and Development Department, to provide entertainment to all the participants. Their singing was well received.

Taking this opportunity, prizes were awarded to the winners of the competitions organised by the Division in 2006/07.

The Division would finally like to thank the generous sponsorship and support for the lucky draws and table prizes, which included contributions from GEO, Arup, GCG, Fraser, Maunsell, Halcrow, LMM, China-Geo, Geotech, Fugro, Victor Li, C M Wong, Gammon, Lambeth, Jacobs, ESA, Henry Chan, Shun Yuen and Konwall.


President of the HKIE (left 3rd) with our Past Division Chairmen


Ir Albert Ho, the Chairman (R), presenting souvenir to Mr C K Mak, JP

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