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Controls on the geotechnical response of sedimentary rocks to weathering.

de Vilder, S.J. and Brain, M.J. and Rosser, N.J. (2019) 'Controls on the geotechnical response of sedimentary rocks to weathering.', Earth surface processes and landforms., 44 (10). pp. 1910-1929.


Weathering reduces the strength of rocks and so is a key control on the stability of rock slopes. Recent research suggests that the geotechnical response of rocks to weathering varies with ambient stress conditions resulting from overburden loading and/or stress concentrations driven by near-surface topography. In addition, the stress history experienced by the rock can influence the degree to which current weathering processes cause rock breakdown. To address the combined effect of these potential controls, we conducted a set of weathering experiments on two sedimentary lithologies in laboratory and field conditions. We firstly defined the baseline geotechnical behaviour of each lithology, characterising surface hardness and stress-strain behaviour in unconfined compression. Weathering significantly reduced intact rock strength, but this was not evident in measurements of surface hardness. The ambient compressive stress applied to samples throughout the experiments did not cause any observable differences in the geotechnical behaviour of the samples. We created a stress history effect in sub-sets of samples by generating a population of microcracks that could be exploited by weathering processes. We also geometrically modified groups of samples to cause near-surface stress concentrations that may allow greater weathering efficacy. However, even these pronounced sample modifications resulted in insignificant changes in geotechnical behaviour when compared to unmodified samples. The observed reduction in rock strength changed the nature of failure of the samples, which developed post-peak strength and underwent multiple stages of brittle failure. Although weakened, these samples could sustain greater stress and strain following exceedance of peak strength. On this basis, the multi-stage failure style exhibited by weaker weathered rock may permit smaller-magnitude, higher-frequency events to trigger fracture through intact rock bridges as well as influencing the characteristics of pre-failure deformation. These findings are consistent with patterns of behaviour observed in field monitoring results.

Item Type:Article
Keywords:Unconfined compression, Rock strength, Stress history, Failure style, Rockfall, Rock bridges
Full text:(AM) Accepted Manuscript
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Publisher statement:This is the accepted version of the following article: de Vilder, S.J., Brain, M.J. & Rosser, N.J. (2019). Controls on the geotechnical response of sedimentary rocks to weathering. Earth Surface Processes and Landforms 44(10): 1910-1929., which has been published in final form at This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.
Date accepted:25 March 2019
Date deposited:02 April 2019
Date of first online publication:29 March 2019
Date first made open access:29 March 2020

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