Shear wave velocity monitoring of collapsible loessic brickearth soil

Gunn, David; Nelder, L.M.; Jackson, Peter; Northmore, Kevin; Entwisle, David; Mildowski, A.E.; Boardman, D.I.; Zourmpakis, A.; Rogers, C.D.F.; Jefferson, I.; Dixon, N.. 2006 Shear wave velocity monitoring of collapsible loessic brickearth soil. Quarterly, 39 (2). 173-188.

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Metastable loessic brickearth comprises a stiff fabric structure with inter-particle interactions different to those normally associated with clay-sized or silt-sized particle fabrics. Laboratory samples loaded near in situ moisture contents exhibited little consolidation and relatively high shear wave velocities, which changed in response to sample flooding. In situ hydro-collapse caused non-monotonic changes in the velocity of shear waves through loessic brickearth that was subjected to simple flooding and to flooding while under additional surface loading. Hydro-collapse in situ resulted in an overall reduction of up to 50% in the shear wave velocity. A conceptual model of brickearth structure based on SEM images is presented to explain the process of collapse and its effect on shear wave velocity. These indicate a transition from a relatively low-density, high-stiffness fabric to the higher-density, lower-stiffness fabric during structural collapse of the loessic brickearth. The collapse process disrupts clay bridge-bonds that hold individual and aggregated clay-coated silt sized particles in an open packed structure, and which are absent in a more closely packed collapsed structure. These studies provide information for geohazard research and the development of shear wave velocity and other geophysical tools to assess soil collapse potential in situ.

Item Type: Publication - Article
Programmes: BGS Programmes > Other
ISSN: 1470-9236
Additional Keywords: Density, Engineering properties, Geophysics, Load tests, Shear-wave behaviour ; Soils
NORA Subject Terms: Earth Sciences
Date made live: 16 Jul 2007 13:14 +0 (UTC)

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