On the ultimate limit state design proof for laterally loaded piles

According to Eurocode 7, the geotechnical ultimate limit state (ULS) design proof can be provided by either a GEO-2 or a GEO-3 design equation. In offshore engineering applications a GEO-3 proof is usually carried out in the design of laterally loaded piles. In Germany a GEO-2 proof is required according to DIN 1054; this standard also describes a special procedure on how to do this. This paper compares the results of the different approaches. The p-y method, usually used for calculating the pile load-bearing behaviour, is validated with respect to German regulations (e.g. with DIN 4085 regarding ultimate bedding stresses). In general it was found that the p-y method can be used in ULS design. It is further shown that the special ULS design procedure described in DIN 1054 can yield erroneous results (i.e. depending on system parameters and loading type, admissible loads may be either too small or too large). The GEO-3 proof generally produces reasonable results, but here the actual level of safety depends on the soil parameters. This paper recommends a new and simple design procedure, which is a GEO-2 proof but also gives correct admissible pile head loads in all cases considered and allows for the consideration of soils with strength degradation.