ABSTRACT
The design of gravity walls is covered by Section 9 of Eurocode 7 Part 1, ‘Retaining structures’, whose contents are as follows:
§9.1 General (6 paragraphs) §9.2 Limit states (4) §9.3 Actions, geometrical data and design situations (26) §9.4 Design and construction considerations (10) §9.5 Determination of earth pressures (23) §9.6 Water pressures (5) §9.7 Ultimate limit state design (26) §9.8 Serviceability limit state design (14)
A gravity wall is a structure whose self-weight (including any backfill on its base) plays a significant role in the support of the retained material. Such walls are usually made of stone or concrete and have a base footing (with or without heel), a ledge, and – when necessary – a buttress. [EN 1997-1 §9.1.2.1]
Structures composed of elements of both gravity and embedded walls are called ‘composite’ in Eurocode 7. These include earth structures reinforced by tendons, geotextiles, or grouting and structures with multiple rows of ground anchorages or soil nails. Composite walls should be designed according to the rules discussed here and in Chapter 12. [EN 1997-1 §9.1.2.3]
Section 9 of EN 1997-1 applies to structures which retain ground (soil, rock, or backfill) and water, where ‘retained’ means ‘kept at a slope steeper than it would eventually adopt if no structure were present’. [EN 1997-1 §9.1.1(1)P]
Annex B.3 of Eurocode 7 Part 2 provides outline guidance on the depth of investigation points for retaining structures, as illustrated in Figure 11.1. (See Chapter 4 for guidance on the spacing of investigation points.)
The recommended minimum depth of investigation, za, for excavations where the groundwater table is below formation level is the greater of:
†i.e. weaker strata are unlikely to occur at depth, structural weaknesses such as faults are absent, and solution features and other voids are not expected.
