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What are buttress dams?
A buttress dam consists of water retaining sloping membrane or deck on the upstream which is supported by a series of buttresses at right angles to the axis of the dam. The upstream water retaining sloping membrane may be in the form of a reinforced concrete slab or a series of arches or thickened buttress heads. At the upstream end a cutoff is provides to prevent or reduce the seepage of water.
Buttress dams [1]
By
Mansoureh Hasanzadeh
Ports and Maritime Organization of Iran, Coasts and Ports Department
The challenge of maximizing dredging efficiency is still remains as a dilemma in port management and brings about unforeseen costs annually. While among many environmental and safety rules which are addressed and executed in marine waters, there’s no exact direction about dumping dredged sediments. It’s obvious that dredging operations to deepening shipping channel and increasing draft should be done temporarily. On the other hands, the dumping of picked sediment (both contaminated and clean) supposed to be done based on comprehensive technological aspects. Whereas, a cost dredging and crucial environmental consequences are worryingly high.Initial surveys reveals that the availability of information on target marine area should be as enough as its need to make big necessary data which should be drawn.
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By
Ghalndarzadeh A., Akbari N., Fakher A. from University of Tehran
ABSTRACT
Seismic behavior of quay walls is one of major concerns in earthquake geotechnical engineering field. Among different types of quay walls such as caisson and concrete block walls, deck and pile structures and anchored flexible walls the behavior of flexible walls looks more complicated. In the presented research, a series of shaking table tests were carried out in order to understand the seismic behavior of anchored flexible quay walls. The models were fully instrumented to monitor their behavior during shakings. Displacement of the wall, accelerations in the backfill, excess pore pressures in the soil, bending moment in the wall and tension of tie-rods were measured. By making different relative densities for the backfill and the foundation, different failure modes were observed. It is concluded that the performance of an anchored quay wall is strongly influenced by the occurrence of liquefaction.
Keywords: Anchored flexible quay wall, liquefaction, softening, failure modes
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The immersed tube method for underwater crossing involves the following basic construction steps:
(i) Prefabricating long tunnel units (steel shell or concrete) in a dry-dock or shipyard
(ii) Floating and towing the units with removable bulkhead to the site
(iii) Immerse the units in a pre-dredged trench
(iv) Connect the units one by one
(v) Covering the completed tunnel with backfill
One of the major effects of angle of approaching velocities of ships is its influence of the energy to be absorbed by the fender system. Consider several ships berth on the same pier at the same speed but with different angle of approach, though their kinetic energies are the same, the amount of energy absorbed by fender differs. The amount of energy absorbed by fender is :
