10 December 2021

The 11th Lumb Lecture at HKU: Bridging the Gap between Theoretical and Actual Slope Performance by H.N. Wong

Posted by Dave Petley

The 11th Lumb lecture by H.N. Wong

The 11th Lumb Lecture at HKU: Bridging the Gap between Theoretical and Actual Slope Performance by H.N. Wong

Professor H.N Wong is the former head of the Geotechnical Engineering Office in Hong Kong, the agency charged with responsibility for slope management in the territory.  Last Friday he delivered the 11th Lumb Lecture at Hong Kong University, entitled “Bridging the Gap between Theoretical and Actual Slope Performance”.

The lecture is held every two years in memory of Professor Peter Lumb, who for 32 years was an academic in the Department of Civil Engineering, The University of Hong Kong.  He was a towering figure in geotechnical engineering in Hong Kong, and indeed globally, and much of the success in managing slopes in Hong Kong is built upon his work and that of his students.

In his lecture, H.N. Wong drew upon multiple examples from Hong Kong.  He highlighted the uncomfortable fact that the failure rate for engineered slopes is much higher than that of other engineered structures.  H.N. notes that one of the issues is that there is a large gap between theoretical and actual slope performance.  The lecture explores ways to both understand this issue and to address it.

The full synopsis is below.

The lecture has been posted online and can be viewed for free.  I thoroughly recommend it.

Synopsis: Bridging the Gap between Theoretical and Actual Slope Performance by H.N. Wong

Unlike other types of modern-day engineering structures, slopes that are engineered according to sound geoscience theories and meeting state-of-the-art standards still suffer from an appreciable chance of failure. This unsettling fact was not previously evident to the geotechnical community at large. It was also unfamiliar to the local practitioners during the formative years in the first one to two
decades of implementing the system for mandating the application of geotechnology in Hong Kong’s slope engineering. Despite this, the notable improvement in slope safety made at the time has rendered Hong Kong internationally reputable as a model of slope engineering in an urbanized setting. Yet, as time went by when more engineered slopes had been formed and their actual performance tested under heavy rains, the bitter lesson was learnt of the gap between theoretical and actual slope stability. The systematic landslide investigations and related technical development studies launched by the GEO since the mid-1990s has provided comprehensive findings on failures of engineered slopes and important insights into the causes. This has brought about enhanced understanding of the need and impetus for further improving the relevant slope engineering practices. While the experience and knowledge have emerged primarily from Hong Kong, it is relevant to urban slope engineering and landslide risk management elsewhere.

This Lecture aims to show, with reference to the available data and selected case histories, the extent and causes of the disparity between the theoretical and actual slope performance in Hong Kong. In this context, the key improvement measures adopted over the years with some degree of success in bridging the gap will be explained. This will illustrate the importance of robust geotechnical design and holistic landslide risk management. Cautioning against complacency particularly in the wake of the new challenges that may arise from climate change, the Lecturer will also discuss issues yet to be addressed and some possible solutions.