Unit
- Marine construction domain: encompasses structures built in coastal waters, harbours, estuaries, and open seas including ports, jetties, seawalls, offshore platforms, and submarine pipelines.
- Environmental loads: waves, currents, tides, storm surges, and seismic activity impose dynamic forces that are significantly higher than terrestrial loads, requiring specialised design approaches.
- Corrosion challenge: the splash zone and submerged zone create aggressive electrochemical conditions that accelerate deterioration of steel and concrete; protective systems like cathodic protection and coatings are essential.
- Geotechnical variability: seabed soils range from rock to soft clays and sands; bearing capacity and settlement predictions are complicated by water saturation and dynamic loading.
- Access constraints: construction equipment must be transported by barge or helicopter; work is often tide-dependent and weather-sensitive, limiting productive windows.
- Regulatory framework: projects require permits under maritime law, environmental protection acts, and navigation safety codes; non-compliance can halt construction.
- Typical failure modes: scour around foundations, fatigue cracking from wave loading, concrete degradation from chloride ingress, and instability from poor soil-structure interaction.
- Life-cycle perspective: marine structures have high maintenance costs; design for inspectability, repair, and decommissioning is a core requirement from the outset.
- Material selection: marine concrete uses high cement content, low water-cement ratio, and supplementary cementitious materials to resist chloride penetration; steel grades with improved toughness and weldability are specified for low-temperature service.
- Construction methods: pile driving via impact or vibratory hammers, installation of prefabricated caissons, and use of jack-up barges or floating cranes are common; underwater concreting with tremie pipes ensures monolithic placement in deep water.
- Environmental considerations: projects must manage dredging impacts, noise from piling affecting marine mammals, and turbidity from excavation; mitigation measures include silt curtains, bubble curtains, and seasonal work windows to protect spawning cycles.
- Health and safety: working over water requires fall protection, life jackets, emergency rescue boats, and dive teams for underwater inspections; confined spaces in cofferdams and caissons demand strict gas monitoring and ventilation protocols.
- Quality control underwater: non-destructive testing using ultrasonic thickness gauging, cathodic potential surveys, and ROV-based visual inspections verify weld integrity, coating condition, and concrete cover; acceptance criteria follow class society rules.
Process Flow
- Stage 1 - Concept definition: Identify functional requirements such as berthing capacity, vessel dimensions, and operational loads.
- Stage 2 - Site appraisal: Conduct hydrographic surveys, geotechnical boreholes, and metocean studies to characterise the environment.
- Stage 3 - Preliminary design: Select structural typology and material, perform initial stability checks, and determine foundation requirements.
- Stage 4 - Detailed engineering: Complete structural analysis, detail reinforcement or steel connections, specify corrosion protection, and prepare construction drawings.
- Stage 5 - Construction planning: Sequence marine operations, mobilise plant, install temporary works, and execute the permanent works under a quality plan.
- Stage 6 - Commissioning and handover: Test systems, verify performance criteria, document as-built conditions, and transfer to operations team.
Quick Revision
- Marine construction deals with structures in coastal and offshore environments subject to wave, current, and corrosion loads.
- Site access and geotechnical conditions are fundamentally different from land-based projects.
- A six-stage process from concept to handover ensures systematic delivery.