Report No. : GEO Report No. 204

Report Title : Study of Distress on Slope No. 11SW-D/FR1 below Stubbs Road Happy Valley (2007), 183 p.

Author : Fugro Scott Wilson Joint Venture

Abstract

This report presents the findings of a study of the distress observed on slope No. 11SW-D/FR1, which is located above the Hong Kong Sanatorium and Hospital (HKSH) at Happy Valley. The distress comprised cracked drainage channels and cracked and displaced shotcrete cover. The key objectives of the study were to document the site development history and field observations, and to establish the probable causes of the distress.

It is concluded that the distress on slope No. 11SW-D/FR1 is mainly related to water ingress into the old loose fill underlying the compacted fill cap within the upper half of the slope and build-up of water pressure in the compacted fill within the lower half of the slope. It is also partly associated with general progressive slope deterioration following reconstruction works in the late 1970's and the situation is exacerbated locally by tree root action arising from unplanned vegetation.

The key source of water ingress is probably related to leakage from stormwater drains in the upslope area, although direct surface infiltration through the vegetated areas and leakage from the sewer beneath Stubbs Road may also have played a contributory role in providing water ingress into the slope. The investigation has established that the potential build-up of significant transient groundwater pressure in the compacted fill in the lower slope portion and/or in the old loose fill underlying the compacted fill cap during severe rainfall is liable to constitute a potential hazard.

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