First, fully amphibious solution derisks site characterisation schedules

The challenge

One of the Maldives' largest infrastructure projects to date is the Greater Malé Connectivity Project, a 6.7 km road bridge and causeway that connects Malé to three islands. During the planning phase of this project, the developer asked us to conduct site characterisation, which would stretch from land to a water depth of 55 metres.

Typically for site characterisation work on land, a drilling rig is used, for nearshore waters a self-elevating platform (SEP) is best placed but in intertidal areas and extremely shallow waters neither of these can work continuously and logistics becomes an issue. In this case it would have meant:

• continuously swapping between the drilling rig and the SEP depending on the tide.

• continuously mobilising assets, and their crew which will result in significant downtime and avoidable safety exposure.

Solution

To avoid continuously changing between drilling rigs and SEPs with the changing tides, our unique intertidal drilling unit, the Fugro Amphibious Buggy (FAB), was used. The FAB, designed for marine geotechnical investigations in intertidal waters, was the perfect solution as it is able to work on dry land to a water depth of approximately 2.5 m.

During low tide, the FAB was able to drive between the geotechnical drilling locations, using its tracked pontoons, and operate as a regular drilling rig would. The FAB is jacked up to a safe height above the incoming tide water level like a SEP to be able to continue working through tidal changes.

Alternatively, during high tide the FAB was sailed to the location utilising the tracks as propellers, its legs would then be lowered to jack it up into position. This allowed us to continue data collection regardless of the changing tide.

Benefits of using the FAB:

• By having only one asset, that could easily be mobilised in the intertidal zone we cut down mobilisation time by 30%.

• The FAB is raised to a safe working height above water level considering tidal changes and weather conditions.

• The platform was able to accommodate a variety of geotechnical drill rigs. For this project, a nearshore / land drill rig was used.

Innovative highlight

With the FAB we were able to go where others could not go. Using only one asset, that could adapt to the changing tides, allowed us to continue working on both land and in the water, cutting down data acquisition time. By eliminating continuous swapping between assets, especially over the rocky terrain, we also minimised our HSE risk and reduced the impact on the environment.

Impact

Deploying the FAB proved to be a quick and efficient solution for intertidal areas. Allowing us to collect data in the challenging intertidal areas, where other assets would have struggled. The FAB eliminated continuous mobilisation, reducing the project cost by 20%.