- © 2016 The Mineralogical Society
Halloysite-rich soils derived from in situ weathering of volcanic materials support steep stable slopes, but commonly fail under triggers of earthquakes or rainfall. Resulting landslides are slide-flow processes, ranging from small translational slides to larger rotational failures with scarps characteristic of sensitive soils. Remoulding of failed materials results in high-mobility flows with apparent friction angles of 10–16°. The materials characteristically have high peak-friction angles (∼25–37°), low cohesion (∼12–60 kN m−2) and plasticity (plasticity index ∼10–48%), and low dry bulk density (∼480–1,080 kg m−3) with small pores due to the small size of the halloysite minerals. They remain saturated under most field conditions, with liquidity indexes frequently >1. Remoulded materials have limited cohesion (<5 kN m−2) and variable residual friction angles (15°–35°). Halloysite mineral morphology affects the rheology of remoulded suspensions: tubular minerals have greater viscosity and undrained shear strength than spherical morphologies.