Utveckling av principer för dimensionering av spiling – etapp1

When the rock mass strength capacity is exceeded due to weak rock mass quality with weakness zones or limited rock cover an adapted and customized pre-support in the form of spiling (piles or bolts) is needed to secure the rock excavation. However, according to a recently completed feasibility study funded by BeFo, the knowledge of how spiling should be designed is incomplete. The design of spiling differs, and different calculation methods, elementary cases and load cases have been used for the same expected behaviour of the rock mass. Principles and guidelines, both nationally and internationally, are lacking for the design of spiling. Several studies have previously been conducted in which spiling has been analysed numerically and the ground considered as a continuum. However, specific questions such as under which geological conditions spiling pipes can be be used, or when the interaction between the spiling bolts and the rock mass can be accounted for has not been studied scientifically and is currently primarily based on empirical data and how it has been done in previous projects. To obtain a safe design where the prevailing uncertainties are considered in a more stringent way in the design, it is important that a deeper knowledge in the field of rock mechanics is achieved for these issues. The overall aim of the present project is to develop rock mechanical principles for the design of spiling for different geological conditions and contribute to the development of knowledge in the industry in this field, which in the future can form the basis for national guidelines on the subject – something that has been requested by the Swedish Transport Administration.