JRC Technical report: Assembling the ground model and the derived values

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 2 - Assembling the ground model and the derived values

The Ground Model is defined in the second generation of Eurocode 7 as a ‘site-specific outline of the disposition and character of the ground and groundwater based on results from ground investigations and other available data’. It is a compilation of data including maps, plans, sections, and reports that capture objective information across the zone of influence - including rockhead & structural geology, superficial geology and geomorphology, seismicity, hydrogeological conditions and geotechnical & geochemical conditions. The Ground Model is an illustration based on derived values of ground properties - obtained by theory, correlation, or empiricism from test results or field measurements - and interpolation between factual data, including the distribution of the geotechnical units within the zone of influence. Derived values presented in the Ground Investigation Report (GIR) are the source for representative values of ground properties to be used in ultimate and serviceability limit state verifications.

In the second generation Eurocode 7, the concept of the zone of influence is sensibly widened, after environmental and seismic aspects have become central in planning the Ground Investigation and processing the results. This guideline addresses the process of assembling the Ground Model, highlighting the importance of progressively upgrading it with an increase in knowledge of the ground within the zone of influence of the specific structure.