Engineering Commons^™

Investigations Regarding The Pumping Process Of Wet-Mix Shotcrete Improvement And Upgrading Of Underground Traffic Structures, Johannes Flotzinger, Maria Thumann, Florian Steindl, Florian Mittermayr, Benedikt Lindlar, Wolfgang Kusterle

Shotcrete for Underground Support XIV

Workability is a physical property of fresh concrete, which can’t be described with only one single parameter or measured with one single test method. Pumpability and sprayability plays an important role for wet-mix sprayed concrete. The material must be conveyed through the pipe without changing its properties and mix proportion. The mix should leave the nozzle in a uniform stream intermixed homogeneously with the accelerator.

When concrete is pumped through a pipe, a thin layer of paste is lubricating the wall of the pipe. The interaction of the lubricating layer and the pipe wall is of great importance for pumpability. …

Untersammelsdorf Tunnel – Challenges, Special Measures And Use Of Special Shotcrete For Tunneling In Lacustrine Clay, Matthias Beisler, Johannes Benedikt, Sebastian Höser, Hanns Wagner, Klaus Berger

Shotcrete for Underground Support XIV

The 665 m long, twin-track Untersammelsdorf Tunnel is being built in the course of the construction of the Koralmbahn line between Graz and Klagenfurt. The tunnel is located in extremely challenging subsoil conditions consisting of silty to fine sandy lacustrine deposits. The developed tunneling concept provided wide-ranging special underground engineering measures as piling, jet grouting and temporary struts and represents a unique construction method to date. Accordingly, numerous challenges arose in the design phase, which could be verified by carrying out extensive trials and investigations in the preparatory period or for which fallback levels had to be provided for the …

Plastic Shrinkage Properties Of Natural Fiber Reinforced Shotcrete, Kyong-Ku Yun, Yoon-Sik Baek, Seung-Yeon Han, Yong-Gon Kim

Shotcrete for Underground Support XIV

Recently, natural hemp fibers have been developed for use in wet or dry mix shotcrete instead of conventional synthetic fibers made from petroleum. Synthetic fibers, which is mainly in polypropylene, has been used for controlling an initial shrinkage cracking in concrete, however, the effect was poor showing a severe plastic shrinkage cracking.

Plastic shrinkage cracking is a nonstructural crack that occurs due to the surface drying of concrete in a plastic condition due to rapid evaporation of bleeding water. The volume reduction due to plastic shrinkage and the resulting tensile stress exceeds the tensile strength of the concrete. In particular, …

Performance Improvement Of Shotcrete By Polymer Binder Modification, Klaus Bonin

Shotcrete for Underground Support XIV

Tunneling construction engineering cannot exist without sprayed concrete – whether it is in tunneling, mining or equivalent constructions. Underground construction is a vast field and will be of strategic urban importance in the future. On the one hand, many existing tunnels will need in short term repair work or enlargements, while there is huge demand for the construction of new ones.

Polymer-modified sprayed concrete is suitable for the most used wet shotcrete application, but, as it is also common to use dry shotcrete, it’s also possible to be used there.

The used polymer amount depends highly on the requirements, in …