W. H. Ting, Consulting Engineer, Kuala Lumpur
The sparging of air as a ground treatment is of interest within the context of the introduction of air into subsurface soil as a ground improvement procedure. The authors may be interested to know that Professor Shunta Shiraishi presented a paper ‘Tiny air bubbles prevent seismic liquefaction of ground’ at the Geotech-Year 2000 Conference: on Developments in Geotechnical Engineering, held at the Asian Institute of Technology, Bangkok, Thailand, in November 2000.
The introduction of air bubbles as a general ground improvement procedure is attractive, as it is known that normally partly saturated soils (containing air in the soil voids) have higher strength and lower permeability when compared with fully saturated soils. There remains the practical problem of developing an efficient process whereby the appropriate air bubbles are permanent and well distributed. The authors' contribution is a step in the right direction.
Authors' reply
We are grateful to Dr Ting for his helpful comment about the potential use of unsaturated soil for prevention of liquefaction. We are also grateful to Arthur Penman for a similar comment.
The method suggested by Professor Shiraishi is, as we understand, to form horizontal bands of unsaturated soil by the application of positive air pressure and suction in adjacent boreholes. As part of our investigation into methods for generating unsaturated barriers, we are currently trying this approach in a laboratory tank test.
