Page - 1128 - in Book of Full Papers - Symposium Hydro Engineering

normal conditions during the operation of structures ageing will usually affect the performance requirements, and then later affect the safety if corrective measures are not taken.“ [4] A similar definition is used by the USSD: „The aging of dams, constructed of earth and rockfill material, as defined herein is due to time-related changes in the properties of the materials of which the structure and its foundation are composed.“ [5] In [6] the term ageing is related to natural processes, whilst damage is considered to be originated in man-made activities. Since also natural events may lead to damage, this distinction may not be valid for all kind of deterioration processes, which have to be considered in the context of embankment dams. Typical ageing processes for embankment dams are listed below:  Rooting of sealings/barriers of embankment dams with an increase of permeability  Rooting of filter elements with an decrease of permeability  Freezing-thawing-circles and drying of soils and natural sealings leading to cracks  Particle breakage by saturation or stresses  Upcoming woody vegetation close to or on the embankment  Changing of design fundamentals such as hydrology (climate change) or design risk level which outdates the performance and required safety of the dam  Sedimentation of reservoirs  Etc. 3. LIFE CYCLE CONSIDERATIONS The consideration of life-cycle management of engineering structures is more and more showing practical relevance. Generally, phase models are established as shown in Fig. 1 and Fig. 2. In practice usually the phases design, construction and operation/maintenance are considered. For supervision and documentation, usually annual reports are prepared on the behalf of the owner [7] [8]. In the context of life cycle management the service life span of dams plays an important role. Life span and ageing interact. The stronger the ageing effects, the shorter the life span of an embankment dam. For embankment dams a life span of 50 to 100 years may be assumed [9]. 1128