The International Information Center for Geotechnical Engineers

Wednesday, 21 November 2012 14:40

An unusual Application of Soil Nails

The Problem: 

A 30 m high unstable slope along the Kaminisiquia River in Thunder Bay, Canada, with urban infrastructure and residences at the top.

An Economical Engineered Solution: 

Percussion installation of these 35 mm diameter steel nails to 12 m depths on a 1 to 1.5 m grid is very fast – no drilling or grouting. Since the nails are inserted perpendicular to the failure surface, they are designed in bending and shear, not the usual tension. Very effective with a great deal of resistance against deep failures. For shallow failures above 1 to 2 m, the nails are widened with special plates to deal with a flow failure mode around a stiff nail. Instead of the conventional shotcrete, the facing is designed with roots, 15 to 30 cm deep depending on the slope angle. Installation is using light equipment working on the slope. A sacrificial corrosion allowance ensures a 75 year design life. This ‘soil nail and root technology’ is suitable for slopes up to 45 degrees.

The soil nail stabilization design.

The Kaministiquia River Site in Canada.

The nails are installed with a spider-like excavator using percussion for very fast installation.

The soil nails have special heads to stop shallow flow slides.

One of the stabilized sites: the nails are completely out of site and maintenance free.

Reference: 

Fabius, M. and Tozer S. 2006. Case Study: Innovative Soil Nail Stabilization of a 100 foot High Urban Slope. 31st Annual Deep Foundations Institute Conference, Washington DC. (DFI 2006 Special Recognition Award for Outstanding Project).

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Read 6493 times Last modified on Wednesday, 21 November 2012 14:43

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