ROCK MASS CHARACTERIZATION AND SPATIAL ESTIMATION OF GEOMECHANICAL PROPERTIES THROUGH GEOSTATISTICAL TECHNIQUES

This thesis deals with geostatistics, which is a branch of statistics focusing on spatial or spatiotemporal datasets, and explores its possible application to rock mechanics, with particular reference to wide areas, located in the Alpine context. The final objective of this work is the estimation (i.e. the prediction), through geostatistical techniques, of the geomechanical parameters determining the quality of rock masses, starting form punctual and scattered sampling locations.This thesis is a contribute in assessing how the rock mass features, in the Alpine geological context, can be regarded as regionalized variables, and the geostatistical tool can be used to foresee the spatial structure of rock masses. The main topic regards the estimation of rock mass properties, and their associated variations, at regional scale, through geostatistical techniques. The estimation consists in forecasting the behaviour and the values of a regionalized variable, in an area, starting form punctual and scattered measures. The main challenge is to understand if the geostatistical techniques, applied so successfully to local and specific problems, can be applied also at regional scale (i.e. considering very wide portion of territory), finding the best method useful to make estimation of that scale. Actually to have a tool able to predict the rock mass parameters at regional scale can be very useful in areas interested by the planning and construction of large-scale engineering works. The study areas, chosen to verify the applicability of geostatistical methods at regional scale, are both located in the Central Alps: the first is the Italian Alpine Valley named Valchiavenna (SO), while the second is in Switzerland, near the Grimselpass.The main innovative aspercts of this thesis, respect to the previous works, are: - the area involved in the estimations: very wide areas have been considered in order to verify if geostatistics give good results also at regional scale; - the geology of the site: hard rock masses outcropping on two different location of the Alpine chain have been investigated: the first one is in the Italian Central Alps and the second one in the Swiss Alps;- the starting measurements: data have been collected in situ using both direct and indirect measurements (i.e. geomechanical survey in Valchiavenna, combined with photogrammetric analysis at Grimsel test site).