Rock-Engineering Design and NTC2018: Some Open Questions

The Italian technical standard of construction (NTC-2018) defines the standards for designing, building and testing all kinds of constructions, considering their performances in terms of mechanical resistance, stability and durability. These standards give us the general safety criteria, stating that the effect of actions and material characteristics must be included in the design. Moreover, NTC-2018 transposes requirements suggested in the EN Eurocodes (EN 1990 - EN 1999). For what it concerns geotechnical structures, since 2010, EN-1997 Geotechnical Design (EC7) has been the reference design code for construction in the EU. What about rock engineering designs? Since rock mechanics is a branch of geotechnics, rock-engineering constructions should be designed following EC7 and NTC-2018 requirements. However, their applicability is not obvious, since the use of partial factors in design calculation is not allowed due to lack of proper partial factors or since there are no precise indications about the processing of data coming from new analysis techniques (e.g. remotely sensed data). For rock masses, partial factors may be applied to joint strength but they cannot be used for joint orientation or spacing. As a consequence, statistical approaches, together to detailed geomechanical surveys (traditional and/or non-contact) are more suitable for these parameters. In this paper, the authors analysed some open questions in national and European regulations related to rock-engineering design.