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Self-drilling bars for tight spot micropiling 30 May 2013
Minova News Release
Self-drilling bars within the extensive range of the Minova MAI range of foundation and stability control products are moving beyond their traditional applications in underground construction and are being used also as micropiles. Vital to the protection of infrastructure above underground excavations, the expanded use of the SDA self-drilling bars provide efficient underpinning of the foundations of buildings and for stabilizing ground around excavations particularly in hard-to-reach sites with limited working space.
Self-drilling bars used applied as micropiles in tight spots

Self-drilling bars used applied as micropiles in tight spots

SDA micropiles can be installed in every ground type and can withstand, reliably, both tension and compression loads of up to 2,750kN in tension and up to 1,910kN in compression. The hollow-bar design of the self-drilling system offers a single action for drilling and grouting. As an efficient method of stabilizing the subsoil, micropiling is becoming an ever more important method for preventing settlement of foundations for the long term.
Conventional micropiling has several major limitations. These include the time-consuming multi-step installation process, the fixed length of reinforcement or their complicated extension, and their design for just compression forces and not for tension, being limited by the load capacity of their connections and pile-caps.
Minova MAI SDA hollow-bars overcome these limitations and make the installation faster and more efficient with their one-step process. The bar is drilled into the ground and cement grout is injected through the hollow rod in one operation. During drilling, the grout stabilizes the borehole to prevent it collapsing. Once installed to the required length and after full hardening, the grout transfers the load from the bar into the surrounding soil. The simultaneous grouting ensures full and uniform coverage of grout along the full length of micropile. Extension couplings provides lengthening of the micropiles and the bearing capacity of the connection remains the same as of the bars.
Comparatively small-scale drilling equipment can be used to install the SDA bars as micropiles in tight spaces or with limited headroom. With little vibration or noise, the drilling process itself causes minimal stress on the surrounding structures.
In diverse ground conditions, from gravel, sand, or clay, or on sites with insufficient structural integrity, the Minova SDA self-drilling bars as micropiles are versatile in their application, quick and reliable in their installation, and compatible with conventional drilling equipment. Once installed, they are an effective means of preventing settlement and helping to increase soil stability.
References
Ground preparation at Semmering Base Tunnel - TunnelTalk, February 2013
War on terror heraldsshotcrete breakthrough - TunnelTalk, June 2012

           

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