After winning a contract for an oil refinery construction project 25 miles west of Puerto La Cruz, on the Caribbean Coast in Venezuela, Weeks Marine needed to install 300 large diameter piles to within 2 cm of design location.
The piles are being installed in open ocean conditions from the shoreline to to a point 2 km offshore during an aggressive construction schedule. Additionally, Weeks' had to provide survey control for the installation of subsea pipeline, pipeline-end manifold (PLEM), and a monobouy with a steel pipe pile anchor system located 7 km offshore.
The solution that Weeks decided upon involved the use of a Trimbles Target:Pile system, consisting of application specific software and two 7400Dsi receivers. Subsequently, through further research, Trimble has replaced the 7400 series of receivers with the new MS750 receiver.
Project details
The piles were required for the installation of a heavy duty barge dock, a 2.1-km roadway/conveyor trestle and bulk materials handling pier, and two 7 km long subsea pipelines, PLEM, and monobouy. The installation was required for the export of petroleum products by a new refinery located on the Caribbean Coast in Jose, Venezuela. Weeks Marine was responsible for the engineering, procurement, and construction.
Trimbles Target:Pile system was installed on a Weeks 350-ton capacity derrick barge to provide centimeter-precise positions for the construction of the conveyor trestle and mooring dolphins.
To compliment the Target:Pile system, Weeks Marine also used a 4400 series GPS receiver as a base station, and a 4400 Total Station with a handheld TSC1. The 4400 Total Station was used to collect the as-built horizontal position of the piles, establish horizontal control points on survey
platforms for optical survey equipment, positioning barge anchors, and for quality checks against the separate digital GPS systems used by the pipelay barge and the dredge.
Operation
To place the 54-in. diameter concrete piles for the conveyor trestle and the 54-in. diameter steel piles for the mooring dolphins, Weeks Marine used a 300-ft long floating barge with a 350-ton crane. The floating barge has a piling template attached to one side that is lifted out of the water, with two of the spuds resting on the side of the barge for stability, as the barge is winched onto location.
Two GPS antennae, with ground planes, are on the barge and two are on the template. The winchman views the Target:Pile display and when the barge is roughly on location, the crane lowers the template. Once the spuds are set and the template is fairly level, Target:Pile's displays are used to monitor the hydraulic controls that are used to fine tune the position of the gates that will hold the pile.
