Preface 
Rock support is an element of vital importance to ensure safety of the underground space we build. Shotcrete is today used as support in almost all underground structures, and the support strength depends of material properties, rock surface conditions, how the shotcrete is applied, and of vibration from blasting ort other. It is known that fresh concrete is affected by vibrations and it is important to clarify these effects on shotcrete in conjunction with blasting. The issue of curing time and distance to blasts is central in order to judge when and where next blast round can be performed. Excess margins due to uncertainty of how shotcrete is affected tend to result in more expensive facilities and longer construction time. Possible damage of the shotcrete support may affect the safety. To improve the understanding of how vibrations affect young and hardened shotcrete, laboratory analyses and numerical finite element analyses were carried out. The resulting laboratory work was then used as input to a numerical model for calibration purpose. Thereafter, the numerical model was used to calculate load cases with different distances to the source of vibration and varying curing time for the shotcrete. These were then compared to actual cases from projects built. The laboratory tests were performed at the KTH Betongbyggnad laboratory in model scale. The research was performed by the doctorate student Ms Lamis Ahmed at the Royal Institute of Technology (KTH) in Stockholm, Sweden. The work was supervised by Professor Anders Ansell, and resulted in a licentiate exam. Since additional research is needed in order to understand these mechanisms, this is planned and should result in a PhD exam. The Rock Engineering Research Foundation, BeFo, have together with Formas financed this work which was completed in 2012. The researcher was supported by an advisory group consisting of Mikael Hellsten from BeFo, Jonas Holmgren, Anders Bodare and Richard Malm from KTH. 
Stockholm in December 2012 
Per Tengborg