Ground investigation

Annex B.3 of Eurocode 7 Part 2 provides outline guidance on the depth of investigation points for pile foundations, as illustrated in Figure 13.1. (See Chapter 4 for guidance on the spacing of investigation points.)

The recommended minimum depth of investigation below the base of the deepest pile, za, is the greatest of: ^ * bg za * 3Df za * 5m for piles

Figure 13.1. Recommended depth of investigation for pile foundations za> 5m

Figure 13.1. Recommended depth of investigation for pile foundations where bg is the smaller width of the pile group on plan and DF is the base diameter of the largest pile.

The depth za may be reduced to 2m if the pile foundation is built on competent strata1 with 'distinct' (i.e. known) geology. With 'indistinct' geology, at least one borehole should go to at least 5m. If bedrock is encountered, it becomes the reference level for za. [en 1997-2 §B.3(4)]

Greater depths of investigation may be needed for very large or highly complex projects or where unfavourable geological conditions are encountered. [EN 1997-2 §B.3(2)NOTE and B.3(3)]

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