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 …

Shotcrete In Tunnelling In Frozen Ground, Ludger Speier, Heiner Klönne

Shotcrete for Underground Support XI

The use of shotcrete in tunnelling in frozen ground will be presented for an actual project. There are specific demands on the mixture of shotcrete and the construction because of the frozen ground. The basics for the design especially the safety concept and the experiences made during construction will be presented.

Construction Placement, Hardened Properties And Durability Of Shotcrete With Highly Functional Fly Ash, Kunihiro Yuno, Chikanori Hashimoto, Mitsuhiro Ishii, Hiroyuki Mizuguchi

Shotcrete for Underground Support XI

Shikoku Electric Power Co., Inc. has developed the technology to manufacture a brand name “Finash” about 12 years ago, by sorting and classifying coal ash generated in coal fired power plants. “Finash” is highly functional fly ash (HFA) is produced by removing irregular coarse particles. It is important for the production of HFA to minimize the variation in quality of coal ash with sophisticated classification technique and extracting good-quality spherical fine particles. The specific surface of HFA is more than 5000 cm2/g. It is now widely utilized as concrete admixture for general civil engineering structures and buildings in Japan.

When …

Determination Of Energy Absorption Capabilities Of Large Scale Shotcrete Panels, Ellen C. Morton, Ernesto Villaescusa, Alan G. Thompson

Shotcrete for Underground Support XI

The Western Australian School of Mines (WASM) has developed a facility for the static testing of full scale ground support elements. The test facility consists of several stiff steel frames used to support the sample and a screw feed jack is used to load the sample. A large scale punch test method has been developed to evaluate various shotcrete mix designs at different curing times. The shotcrete is sprayed on to a sandstone substrate containing an isolated disc that is centrally located. The test sample is placed on to the sample frame and restrained on all sides. The disc is …

Technical And Commercial Evaluation Of Modified Shotcrete In Tunnel Construction, Erik Iglesias Dr.-Ing., Tu Volker Wetzig Dipl.-Ing., Jürgen Bezler, Mareike Xia Dipl.-Ing.

Shotcrete for Underground Support XI

Rebound is a significant factor when evaluating the quality and performance of a construction site using shotcrete. Rebound modifies the characteristics of shotcrete and must be disposed of. Thus a reduction in rebound becomes both a technical and a commercial objective.

Based on many years of experience with polymers in mortar applications, different polymer modified systems were developed for shotcrete applications and investigated in extensive full size trials. The investigations fully confirmed expectations as regards a reduction in rebound. At the same time the recently developed polymer has a retardant effect, giving the concrete other improved properties. Parallel to the …

Experiences With Polymer-Modified Shotcrete, Gerhard Pittino, Robert Galler, Klaus Bonin, Jürgen Bezler

Shotcrete for Underground Support XI

Adhesive mortar for tiles can be significantly improved by modification. Why should sprayed concrete not benefit similarly for various applications? This question has been investigated through large-scale tests in a tunnel cross passage, in an access gallery of a salt mine and in a mining gravity shaft. In-situ tests are necessary because the sprayed concrete mix and the process engineering have a significant influence on the quality of the sprayed concrete. The fresh concrete properties and the properties of the sprayed concrete like early strength development, the ability to creep, adhesion, density and resistance to abrasion are all investigated.