ABSTRACT:

A new type of soil nailing, called sand anchors, was developed to stabilise old retaining walls. Sand anchors bear without grout due to the constrained dilatancy of a dense granular material between anchor rod and borehole wall. They protect the environment, preserve old monuments, provide additional drainage, the load can be applied immediately, they are removable and the cost is low. Their bearing effect is explained with the following example. The stabilisation of an old retaining wall with sand anchors, in co-operation with the company Bausanierungstechnik GmbH, is presented together with results of pullout tests. Finally some recommendations for applications of sand anchors in soil are given.

INTRODUCTION

Sand anchors can be applied in rock using sand and in soils using gravel, Wehr (1999). In both cases they may be installed as anchors or as nails, however only the application soil nailing is described herein. The name Ôsand anchorÕ will be kept. Old retaining walls often show large deformations. It may be concluded, that the wall does not have the required safety and is no more usable with increasing risk of further deformations. The installation of sand anchors stabilises the wall safely and cost effectively. Soil nailing of retaining walls was introduced in Germany some 15 years ago. Generally tensionless or pre-stressed rods are used in the soil to ensure the required safety of the wall and soil system against sliding or slipping. Sand anchors are part of the so-called "hidden soil nailing" with an enlarged nail head, which acts as load distribution element behind retaining walls. The main advantage is that the soil nail is not connected to the old retaining wall, which then just carries its own weight. The design uses the same safety philosophy as ordinary soil nailing, Gudehus (1990).

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