This report presents the findings of the monitoring programme undertaken by GHD at Snake Hill (SH1 RP 144/11.34), a road slip site which was stabilised using graded gravel column drains.
Monitoring of pore water pressures was undertaken using piezometers, inclinometers were monitored to determine deformation, and computer simulated back analysis was undertaken.
This report discusses the results of the monitoring programme, and asserts that the column drains have provided effective positive subsurface drainage to the failure planes, resulting in the stabilisation of the site.
It also discusses the typical cost of methods for the stabilisation of deep-seated road failures driven by high pore water pressures, and finds that column drains are comparatively cost-effective.
Keywords: underslip stabilisation, graded gravel column drains, high pore water pressure, inclinometer, piezometer, deep-seated road failure, cost effectiveness, Snake Hill, SH1