Wood-cement-composite behaviour of beech circular hollow sections
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ORIGINAL ARTICLE
Wood‑cement‑composite behaviour of beech circular hollow sections Sebastian Hirschmüller1 · Seraphin Hubert Unterberger2 · Roman Marte3 · Jan‑Willem van de Kuilen4 Received: 15 October 2019 / Accepted: 5 November 2020 © The Author(s) 2020
Abstract Beech laminated veneer lumber (LVL) circular hollow sections for use as nails in temporary geotechnical soil nailing systems were developed within this research. For the soil wall stability, beside a sufficient load carrying capacity of the nail cross section, a load carrying connection between the cement annulus and the nail is necessary. As cement grout ensures the bond between the nails and soil for the mobilisation of a soil reinforcement effect, a reliable connection between cement and wood surface is required. Occurring shear forces must be transferred from the nail into the soil through the wood-cement interface similar to reinforced concrete. Pull-off tests on clear LVL specimens with different cement and wood surface modifications as well as the results of large-scale push-out tests are presented. The results reveal a sufficient short-term bonding strength between the cement annulus and the wooden member to transfer the geotechnical loads, but also highlight the necessity of further research on long-term behaviour.
1 Introduction Temporary soil nailing systems, or reinforced soil walls (RSW), are often used to stabilize excavation slopes. Typically, steel nails are drilled into the soil followed by filling up the annulus around the steel using cement grout. The cement protects the steel against corrosion and ensures the * Sebastian Hirschmüller sebastian.hirschmueller@th‑rosenheim.de Seraphin Hubert Unterberger [email protected] Roman Marte [email protected] Jan‑Willem van de Kuilen [email protected] 1
Department of Research and Development, Technical University of Applied Sciences Rosenheim, Hochschulstraße 1, 83024 Rosenheim, Germany
2
Institute of Construction and Material Sciences, Material Technology, University of Innsbruck, Technikerstraße 13, 6020 Innsbruck, Austria
3
Institute of Soil Mechanics, Foundation Engineering and Computational Geotechnics, Graz University of Technology, Rechbauerstraße 12, 8010 Graz, Austria
4
Civil, Geo and Environmental Engineering, TUM School of Life Sciences, Holzforschung München, Technical University of Munich, Winzererstraße 45, 80797 München, Germany
necessary connection between soil and nail. Afterwards a reinforced shotcrete layer is attached to protect the slope’s surface. Wood and engineered wood products have a long tradition as structural elements in geotechnical slope stabilizations and are still part of new constructions. It is an obvious but innovative approach to use biodegradable nails made of renewable materials for temporary soil nailing, rather than wasting valuable but primary energy intense raw materials such as tempered steel. The possibility of substituting temporary steel nails by laminated veneer lumber (LVL) hollow cross sections (Fig.
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