Department of Civil Engineering, University of Bradford, Bradford, West Yorkshire, BD7 1DP, UK.
Microbiological effects on slope stability: an experimental analysis
Article first published online: 14 JUN 2006
Volume 41, Issue 3, pages 423–435, June 1994
How to Cite
MEADOWS, A., MEADOWS, P. S., WOOD, D. M. and MURRAY, J. M. H. (1994), Microbiological effects on slope stability: an experimental analysis. Sedimentology, 41: 423–435. doi: 10.1111/j.1365-3091.1994.tb02004.x
- Issue published online: 14 JUN 2006
- Article first published online: 14 JUN 2006
- Manuscript received 17 March 1993; revision accepted 14 October 1993
A natural, pure quartz sand has been seeded with the bacterium Pseudomonas atlantica and the fungus Penicillium chrysogenum, and angles of avalanche and repose have been measured under water using a laboratory clinometer. The lowest angles of avalanche occur in freshly packed clean sediment (control), with the seeded sediments having higher values. Among the latter, the lowest angles of repose occur in the bacterial seeded sediments, and the highest in the fungal seeded sediments. The largest differences between the angle of avalanche and angle of repose occur in the bacterial seeded and media control sediments. The smallest differences occur in the fungal seeded sediment. In most cases the second angle of avalanche is lower than the first angle of avalanche, whilst the second angle of repose is higher than the first angle of repose.
The bacteria bind particles together with their extracellular polymeric material, while the fungus binds particles by holding them together with a network of hyphal filaments. In the bacterial seeded sediment growth is uniform over the sediment surface. In the fungal seeded sediment growth occurs as discrete colonies separated by bare sediment, and the fungal hyphae penetrate the sediment to a significant depth. On avalanching, the fungal colonies move down the slope with the hyphal filaments trailing behind them in the sediment. Overall, both the bacterium and the fungus increase slope stability. However, the fungal colonies maintain slope stability after avalanching more effectively than does the uniform bacterial growth. The results are discussed in relation to the wide range of biological effects that stabilize flat sediments and to laboratory and field studies on the stability of sediment slopes.