Recent Innovations in Soil Nailing for Temporary Works

Temporary work designs on major infrastructure projects often require innovative solutions to solve construction challenges in high-consequence environments. This paper describes two techniques of soil nailing recently used for the temporary support of road and rail infrastructure in greater Melbourne. In the first example, hollow-bar soil nails utilizing a sacrificial cutting tool and continuous oversupply of grout were used to provide support to various excavations across two major projects. The hollow-bar technique was used in predominantly friable (or more granular) embankment fills where side wall collapse of the drill hole may otherwise have occurred using a conventional air-track drilling approach without casing. In the second example, a nominal amount of tensioning was applied to otherwise conventional solid-bar soil nails supporting an excavation next to an operational rail corridor. The tensioning was used in combination with two stages of grouting to minimize construction-induced movements associated mostly with relaxation and slippage, with the aim of meeting strict track tolerances. To the authors’ knowledge, the two techniques described in this paper have not been readily used in the Melbourne market. They allowed for retaining walls to be constructed in an economical manner while minimizing the risk of movement and instability in high-consequence environments (road and rail). For each example, performance monitoring of the retaining walls is discussed along with observations from testing and construction. Discussion on potential limitations of such techniques for permanent works applications is also provided.