• Defining nailing

Soil nailing system involves reinforcing (not post-tensioning method) the ground by installing and executing steel rebars close together (nails or reinforcing nails), which are subsequently anchored into the slurry. To ensure the continuity of the stabilized wall during the progress of its construction from top to down, the excavation wall is shotcrete. This system is commonly used to stabilize natural slopes or excavations. Under certain conditions, the earthen wall nailing system is a suitable solution from the point of view of technical feasibility, construction costs and execution time in comparison with the ground anchor system, which is another conventional retaining system (top-down). This technique is also used for excavation in soil-like materials (eg, soft rock or aerated rock).

Another application of the passive reinforcement system is in landslide stabilization. In this case, the reinforcement system (nail, nailing or passive nails) is implemented in a pattern close to each other and almost perpendicular to the slip bed and is exposed to shear forces due to the movement of the sliding mass. A structure can be divided into permanent or temporary structures based on its service life or intended time of use. A structure with a service life of 18 months or less is known as a temporary structure and a structure with a longer service life is known as a permanent structure. If a structure was originally intended as a temporary structure (for example, an excavation temporary maintenance system) but its construction is delayed so that the excavation remains without a reinforcement and maintenance system for more than 18 months, the structure should be constructed as a permanent structure.

  • Background

Origin of nailing wall

The origin of the nailing wall can be related to the retaining system of underground rock drilling known as the New Austrian tunneling method (Rabcewicz, 1964a, 1964b, 1965). This method involves the implementation of a passive steel reinforcement system in rock bolt. The combined system of passive and shotcrete reinforcing steels has also been used since the late 1960s (Lang, 1961) to stabilize rock slopes. Stabilization of rock slopes is used. This technique relies on the tensile strength of reinforcing steels under relatively small deformations in the ground and surrounding soil. This system is upgraded by shotcrete connectivity. If a combination of passive and shotcrete reinforcing steels is used instead of rock in the soil, it is called nailing.

One of the first applications of the soil nailing system was in 1972 for a railway widening project near Versailles, France, where an 18-meter-high sandy roof was stabilized using a nailing system. Because this method was cost-effective and had a shorter construction time (Rabejac and Toudic, 1974) than other conventional systems, the use of soil nailing systems became common in France and other parts of Europe.

The first use of the nailing system in Germany dates back to 1975 (Stocker et al., 1979). The first major research project on wall nailing in Germany performed from 1975 to 1981 at the University of Kalsruhe and the Boer construction company. The research program included full-scale experiments of laboratory walls with different arrangements and the development of analysis and design methods. (Gässler and Gudehus, 1981; Schlosser and Unterreiner, 1991) .

In France, the Clouterre research program began in 1986 with public-private partnerships. The purpose of this study was to perform full-scale experiments, study and monitor structures in operation and numerical simulations (Schlosser, 1983; Clouterre, 1991).

History of Application and Development in the United States

The first use of a nailing wall system in North America was for temporary maintenance of excavated excavation in Vancouver, Washington, and Mexico City in the late 1960s and early 1970s. One of the first applications in the United States was to maintain a 13.7-meter-deep foundation drilling system in dense lake silt sand for the development of the Good Samaritan Hospital in Portland-Oregon in 1976 (Byrne et al, 1998).

According to reports, the construction of this protective system took about half the time and 85% of the cost of conventional drilling maintenance systems.

In 1989, the Oregon Department of Roads and Transportation, as the first application of a soil nailing system, installed an 8-meter wall at the bridge abutment (end-slope removal). In 1988, a 12.2-meter double-layered wall was built along Interstate 78, near Alton, Pennsylvania. Each row of walls with a height of 6.1 meters with a horizontal displacement of 3 meters, was made of very aerated rocks.

The use of nailing stabilized walls has increased in the United States over the past decade, mainly for the following reasons;

  1. This system is technically feasible.
  2. In most cases, it is economical compared to conventional retaining walls that are performed from top to down in permanent and temporary excavations.

Design engineers are becoming more familiar with soil nailing technology. Most nailed stabilized walls are still used as temporary retaining structures, but the use of a nailed system as a permanent structure has increased in the last ten years.

The development of knowledge and application of the soil nailing system owes much to the efforts of the US Highway Administration’s R&D department. The first documents on soil nailing were published by the U.S. Department of Highway Research and Development (Elias and Juran, 1991). The purpose of this document was to disseminate information to US highway consulting engineers and users who used the technique as a buffer system in transit projects.

These efforts paved the way for further research and development activities in the United States. In 1993, the U.S. Highway Authority paid for the translation of the French text “Implementation of the Soil Nailing System” into English. In 1994, the “Monitoring the Earth Wall Nailing System” was published (Porterfield et al, 1994). From 1996 to 1998, the U.S. Department of Highways and State Consulting Engineers supported all workshops nationwide to provide executive guidance for the nailing system. The documents collected from 103 experiments were presented as a preliminary design guide and subsequently developed as a design guide (Byrne et al., 1998).

The U.S. Department of Highways has also established various research projects in academic societies.

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