DESIGN NOTE

DESIGN NOTEProject:Saldanha GMQ Ext. FEL31113Date:29/10/2012Section:Quay wall options assessmentNote No.:1113/QW/001 Rev00Status Draft Compiled by: WGD Checked by: - Page 6 / 6knots4. Reinforced Concrete Deck with Steel Tubular Bearing PilesAssessment CriteriaAbility to meetfunctional requirementsCommentsHeavy lift loading on a deck structure is a concernAvailability of skills:Satisfactory – Local marine piling skills are availableConstructabilityMaintainabilityEase of DeepeningCost and ValueConstructionprogrammeEnvironmental ImpactAvailability of materials:Extent of temporary works:Contractors site camp:Risk associated with unknownground conditions:Interaction with existing wallAccess for maintenance:Localisation and repairability ofdamage:From -6.5mCD to -11.5mCDCapital Cost:Maintenance and OperationalCost:Duration:All materials can be locally procuredMinimal – Pile headstocks and deck support, casting yard for precast deckelementsMinimal – Small footprint required mostly pile stock pile, and spoil stock pilefrom existing sheet pile removalHigh – very hard layers and very soft layers pose potential design, cost andduration risks to a piling solutionExtensive – Requires complete removal of existing wall as well as extensiveexcavation for the revetment slope – Construction of a return wall requiredfor the tie in at the existing blockwall GMQEasy access to face of structure and deck top, limited access to underside ofdeckDeck easy to repair, damage to pile is much harderCutting slope and installing revetment after construction of the deck isdifficult therefore will construct to -11.5mCD atR 1 200 000/m (ROM -40 to +50% quay wall only construction cost, itemscommon to all walls types excluded i.e. quay furniture, paving, berth pocketdredging etc – Not to be used to calculate project costs - for comparisonpurposes only)Medium – Anode replacement, serviceability repairs to cracking deckconcrete, revetment maintenance± 22 Months Slow - Speed of construction is slow – with option foracceleration through the mobilisation of additional piling rigs (additionalcost) – Number of interfaces with excavation, pile driving, precast beam andpanel placing and insitu concreting of deckSignificant – Installation of the wall requires the removal and disposal of ±40 000m³ of material -- Revetment is a positiveSEE FIGURE 6:The deck on piles option provides an alternative to the material intensive gravity options. The piling risks associated with the sheet pile are stilla concern. However the use of steel tubular piles allows for grabbing out or chiselling through the tube to progress through the harder layers.This option also requires the full removal of the existing wall and extensive dredging to create the revetment slope.The heavy lift requirement for the deck structure results in heavy beams, a thick deck and a close pile spacing, which result in higherconstruction costs and a longer construction programme.