| Heterogeneities in various forms and scales often control the mechanisms and
locations of failure and deformation, and the factor of safety of saprolitic
slopes. This paper presents a critical review of field scale heterogeneities
and their roles in controlling the stability of saprolitic slopes. In
particular corestones and relict joints are analysed, with emphasis on
characterization and possible instability modes. Abnormal flow patterns,
fast build-up and/or chaotic distribution of pore water pressure are the
most common causative factors of landslides. As heterogeneities are often
responsible for the occurrence of such localized abnormalities, realistic
models incorporating effects of these features can help predict how and
where abnormal flow/pressure patterns may develop. Potential pitfalls during
ground investigation in landslide prone slopes are elucidated and effective
investigation strategies to avoid these pitfalls are recommended.
The uncertainties, for example, in distribution and volumetric percentage of
corestones and in delineating zonal boundaries, require continuous upgrading
of the engineering geological model during the construction stage of site
investigations. Such uncertainties can be reduced in a cost-effective manner
by recording drill penetration rates during installation of soil nails and
horizontal drains. A better understanding of the interactions among the
heterogeneities, the matrix and the engineering geological environment as a
whole should enable the significance of discrete features in stability to be
more consistently assessed, thereby providing a more rational basis for
investigation and design practice in saprolitic profiles. |