19 June 2001
SR-11: SCOUR PROTECTION FOR STEEL PILE SUPPORTED
Problem: Serious erosion of seabed material has occurred around a marine
structure as a result of wave action and/or strong current.
Description of Repairs: Two methods are available for scour protection:
Riprap Placement: Replace the lost foundation material by dumping stones
randomly into place. If stone riprap is not available, use bags of synthetic fiber
woven water-permeable material filled with concrete. On sandy seabeds, a filter
fabric may be required under the riprap or bags to prevent scour through the
individual units (see Figure 8-11). The materials most commonly used are
commercially available synthetic fiber, non-woven fabrics weighing between 269
and 405 grams per square meter (8 and 12 ounces per square yard,) or woven
fabrics weighing between 169 and 236 grams per square meter (5 and 7 ounces
per square yard.)
Steel Sheet Piles: Drive steel sheet piling around structure to protect soil around
the bearing piles (see Figure 8-11). The decision to replace the lost foundation
material under the structure should be based on the strength of the exposed
Application: A careful evaluation should be performed to determine if: (1) any
settlement of the structure has occurred due to the scour, or (2) suitable bearing
capacity exists within the remaining structural foundation to support the loading.
Selecting either scour protection technique should ensure that suitable structural
integrity exists before beginning the repairs.
Future Inspection Requirement: Normal inspection requirements will generally
suffice. If riprap is used, annual underwater inspection will be required to ensure
that material is not lost.