Semi-Fexible Rafts: Design Span for Local Depressions.

(1) The information from the site investigation is used to establish the diameter for local depressions. For typical ground conditions, Table 13.1 may be used for guidance.

This table is based on over 40 years’ experience by the authors’ practice. Where exceptionally large depressions are anticipated, e.g. due to the presence of old mine workings, swallow-holes, pipes and sink holes, their size must be determined from first principles.

(2) The design span for local depressions is established from Fig. 13.5, based on the local depression diameter and the depth of compacted hardcore or granular fill.

Table 13.1 Design diameter for local depressions

Fig. 13.5 Design span of local depressions. For soil classifications see Table 13.1.