Field Study of a Soil Nailed Loose Fill Slope

Failures of loose fill slopes have caused severe losses of life and property in Hong Kong. One of the reasons for such destructive power of the failures is the liquefaction of the loose fills in static conditions due to the infiltration of rainwater. One possible cost effective solution in upgrading this type of slopes is the use of soil nails. However, a major problem in using soil nails is the lack of knowledge about soil nail behaviour if the loose fill liquefies. In order to fill the gap and ultimately explore the potential of using soil nails in upgrading thousands of loose fill slopes in Hong Kong, a comprehensive field program was launched. Soil nails were constructed in a highly instrumented loose fill slope, which was purposely built by end tipping method to simulate the old fill slope formation in Hong Kong. The test slope, subjected to various in situ tests and monitoring for a rain season, was eventually brought to failure under concurrent surcharging and simulated rainfall conditions. From this study, soil nails have concluded to fit for this purpose, provided that some design details are adequately considered.