Tunnelling in Fault zones - Problems and Solutions

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Abstract

When tunnelling through fault zones with large overburden depth, large displacements are frequently observed. Whether this causes problems very much depends on the approach used. Challenges are the prediction of the expected displacements prior to excavation in order not to violate the clearance profile, as well as choosing support characteristics compatible with the strains.
Shotcrete linings can sustain a strain of approximately 0.5% to 1% without failure. Strain above this value inevitably leads to failure of the lining and a loss of resistance, causing additional displacements. A criterion for a critical overburden depth for closed linings has been developed. As an improvement to open slots, yielding elements have been developed, allowing large strains and controlled development of support resistance. The development of the displacements, as well as the rheological behaviour of the supports must be considered. Using standard grouted bolts, a potential that the “fresh” grout is sheared due to the initially large strain rates exists. Special bolt designs allow for a higher strain tolerance.
Quality monitoring and up-to-date data evaluation is of crucial importance, allowing the prediction of changes in the ground conditions ahead of the face. With the help of empirical relations, the development of the displacements for different advance rates and supports can be predicted.
Original languageEnglish
Pages (from-to)49-56
Number of pages8
JournalTunel
Volume25
Issue number3
Publication statusPublished - 2016

Keywords

    ASJC Scopus subject areas

    • Engineering(all)

    Fields of Expertise

    • Sustainable Systems

    Treatment code (Nähere Zuordnung)

    • Application

    Cooperations

    • NAWI Graz

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