Citation

Dykes A. Landslides 2008; 5(4): 417-429.

Copyright

(Copyright © 2008, Holtzbrinck Springer Nature Publishing Group)

DOI

10.1007/s10346-008-0136-1

PMID

unavailable

Abstract

The morphological characteristics of bogflows, bog bursts and other types of peat failures suggest that the tensile strength of peat may have had a significant influence on their occurrence and development. This paper describes a method for the determination of peat tensile strength utilising small block samples (100 mm × 100 mm, up to 60 mm thick) in a newly developed laboratory apparatus. The results, demonstrating good reproducibility and being consistent with published data, were applied to a case example. The stability of a recent 35,000-m 3 bogflow on Maghera Mountain, Co. Clare, Ireland, was analysed using a standard limit equilibrium technique. The breaking stress (i.e. maximum tensile strength) of the acrotelm peat at the Maghera bogflow was 5.35 kPa (range 2.9-7.6 kPa). Using this value to represent the overall strength of the acrotelm in the model, analyses showed that even above the crest of an escarpment, the acrotelm was strong enough to contain a large volume of low or zero-strength lower catotelm peat within the blanket bog upslope from the escarpment. Furthermore, simple analysis of single blocks of peat at the upslope edge of a retrogressively developing failure established the size of blocks that should develop, i.e. 3-4 m. The floating acrotelm rafts observed in the Maghera bogflow, typically up to around 3 m, were broadly consistent with this analysis. This paper therefore presents for the first time quantitative evidence of the importance of the acrotelm tensile strength in bogflows and a new method for routinely obtaining tensile strength data.