The design of rock support to resist rockburst damage involves a proper definition of the seismic activity centre, identification of likely modes of failure, determination of trigger levels for failure, and the determination of support survival limits to hold ejected rock in place. This paper deals with damage assessment and the use of damage records to determine damage trigger levels and support survival limits.
Die Bemessung von Felsankerungen im gebirgsschlagsgefahrdeten Gebirge umfasst eine genaue Beschreibung des seismischen Aktivitatszentrums, Feststellung der Bruchmechanismen, Bestimmung der Ursache des Verbruches und die Überlebensgrenze von Einbaumitteln. Dieser Artikel behandelt die Schadenprognose und die Anwendung der Erkenntnisse von Schadenfallen in der Bestimmung Von Belastungs- und Schadengrenzen.
La conception du soutènement de la roche pour resister des coups de toit doit comprendre une definition precise du centre d'activite sismique et de la façon de rupture. On doit aussi determiner le niveau d'intensite sismique pour rompre le massif rocheux et la resistance du soutènement aux charges dynamiques. Cet article sert à evaluer les degats sismiques et leurs effets sur le soutènement.
The problem of containing rockburst damage is highly complex and only an integrated approach including risk assessment, strategic and tactical measures, in situ monitoring and proper ground control will provide acceptable solutions. Despite rapid progress in microseismic monitoring, the complexity of issues still forces us to adopt empirical approaches, to revert to conceptual and analytical models in an effort to identify new hypotheses, and to follow an observational design approach. A rationale for designing support systems to resist rockburst damage involves a proper definition of seismic activity centres, identification of likely modes of failure at the target, the determination of the trigger levels for rock fracturing and rock ejection, and the determination of support survival limits to either maintain a continuous rockmass by reinforcement or to retain and hold broken and ejected rock in place. Starting from a given, well defined seismic activity centre in terms of magnitude and source location, this paper deals primarily with damage prediction and support selection to contain rockburst damage.. St. John and Zahrah (1987) presented a comprehensive study on the aseismic design of subsurface excavations and underground structures subjected to seismic loading from natural and artificial sources. They reviewed the seismic environment and how structures are designed against earthquake hazards. Fundamentally, a design consists of estimating a design magnitude based on an empirical, site specific attenuation relationship defining the intensity of the ground motion anticipated at the site at some distance from the seismic source. Next, the damage caused by these dynamic influences has to be understood. From the perspective of support design, three damage mechanisms are to be considered: I. self-actuated ejection of fractured rock (strain burst or buckling with seismic source inside the failure mechanism) II. ejection of part of a fractured, broken or jointed rock mass (driven by inertia or stress waves) III. displacement of broken rock with gravity as the dominant driving force component (seismically triggered falls of ground or enhanced gravity condition) Finally, a support system must be found to contain or survive this damage. The conventional design approach as outlined above essentially consists of (1) the identification of the potential failure mode and (2) a comparison of the available resistances or capacity with the driving forces or demand (including dynamic components). Conventional design rationale cannot be directly adopted and empirical approaches must be used. The fundamental components of engineering design must, however, be incorporated implicitly into such empirical designs.