CEN committee TC250 is currently working on an update of the Eurocodes. Subcommittee SC10,in charge of updating EN 1990 (Basis of structural and geotechnical design has installed aworking group to produce a background document with the working title ‘Reliability Backgrounds of the Eurocodes’, with the intention to document and explain the reliability framework underlying all Eurocodes and the implementation of reliability aspects in them. As part of that effort, quantitative information on the inherent variability and uncertainty in loads, material properties and models is compiled. ISSMGE TC304 identified this as an opportunity to provide an overview of the relevant information available in the geotechnical literature such as the statistics of soil/rock properties. The EPRI TR 105000 report (Phoon et al. 1995) provided an overview of the statistics of inherent soil properties and measurement errors, but these statistics have not yet been updated systematically since 1995. Also, rock properties were not covered by the TR 105000 report. Other than soil/rock properties and measurement errors, there are also other important statistics, such as the statistics of transformation uncertainties and model factors.

The current technical report has the following features:

1. It serves as an update for the TR 105000 report on the statistics of inherent soil properties. Chapter 1 compiles the site specific statistics for univariate soil properties. Chapter 3 compiles the random field parameters (e.g., the scales of fluctuation) for spatial variability of soils. Many of the statistics are new.

2. It contains statistics that are not covered by the TR 105000 report. Chapter 1 compiles the site specific statistics for some rock and rock mass properties. Chapter 2 compiles the site specific correlations between soil/rock properties. Chapter 5 compiles the statistics for transformation uncertainties.

3. Chapter 4 compiles the statistics of geotechnical design model factors . Chapter 6 reviews methods that determine the characteristic value defined by the Eurocode 7. Chapter 7 reviews some numerical evidences for the worst case scale of fluctuation.