Marine structures are defined as a human made structures which are constructed for the purpose of port facilities
and/or protecting the coastline, This research focus on studying and analyzing the stability of an important type of
marine structure which is: concrete block quay wall, optimum design and stability of pre-cast concrete blocks quay
walls consists of 15 row of blocks numbered respectively from bottom to top using the hollow blocks instead of
solid ones by obtaining the resulting benefits of this replacement is investigated. Therefore, four stages of
optimization under stability considerations have been adequated as. GEO5 software had been used for the purpose
of determining the factors of safety against overturning and sliding for all structure and at each block interface and
also determining the bearing pressures exerted by the quay wall to the existing ground for structural elements under
all load combinations for all stages of optimization and using these pressures in hansen's equations for studying the
stability of the block quay wall against (bearing capacity). SLOPE/W software had been used also for studying the
stability of block quay walls against slip failure. The results show that the critical stage of optimizations is opt.(2),
reducing the backfill internal angle of friction (φ) from 40˚ to 30˚, reduces the factors of safety against Bearing
capacity and slip failure and Increasing the subsoil cohesion parameter (c), improves the bearing capacity factor of
safety.