JRC Technical report: Determination of representative values from derived values for verification with limit states with EN 1997

With the adoption of the 2nd Generation of Eurocode 7 'Geotechnical design', Member States will need to implement new procedures in many different topics, not considered in the first generation, such as (1) the assessment of Representative values, (2) the Ground Model, (3) the use of Reliability methods, and (4) the implementation of design in the execution phase. CEN Technical Committee 250/Sub-Committee 7 (TC 250/SC 7) therefore decided to produce a suite of four guidelines, one for each of the most relevant new aspects.
These guidelines were prepared by four task groups within SC 7 and other outstanding experts in European geotechnical engineering, and are being published as a series of JRC Technical Reports. The aim of this series is to clarify the new concepts and methods in the transition from the first to the second Generation of Eurocode 7, and provide geotechnical engineers with didactic background material that could not be presented in the Eurocode. SC 7 officially presented the guidelines at the seminar 'Development of second generation of Eurocode 7' (Paris, 21-22 October 2024). 

Guideline 1 - Determination of representative values from derived values for verification with limit states with EN 1997

This guideline summarizes the global process of designing geotechnical structures, as given in the second generation of Eurocode 7, and highlights the step where the designer must determine representative values for limit state verifications based on ground investigation data.
The text explains the different concepts related to the ground property values, including measured, derived, representative, nominal, indicative, characteristic, design and best estimate values.
The guideline provides the reader with procedures for determining representative values in special cases, which are common in practice - e. g. dealing with limited samples, with depth-dependent properties, and data from different sources. Five examples are presented and solved, covering various aspects such as different geotechnical structures and limit states, different number of derived values, different distribution function, and independent and depth-dependent ground properties.
This guideline is an essential tool for designers to understand how to determine representative values for the design and verification of geotechnical structures, in accordance with the procedures outlined in the second generation of Eurocode 7.