Reasons of common occurrence of "inadequate pile founding level" in piles of piers
The most severe load on piers usually is the horizontal load owing to berthing and mooring of large vessels. Design of piers is taken as an instance to illustrate the importance of adequate pile founding level. Because the widths of open berth piers are comparatively small so that they provide a short lever arm to counteract the moment persuaded by berthing loads. Furthermore the dead load of open berth piers are generally quite light and so the resisting moment provided by dead load of pier structures can't be sufficient to counteract the moment produced by berthing loads. To help in providing adequate resistance to overturning moment by the berthing load, soil resistance above bedrock contributes to stabilizing moment. For usually adopted marine piling type, which implies driven steel tubular piles with reinforced concrete infill, driven piles can at most be founded on top of rockhead surface. In case rockhead level is shallow (e.g.near shoreline), little soil cover can result in inadequate lateral resistance to the berthing load.