Grout Density Monitoring

In the past, the successful completion of an offshore pile grouting operation was assessed by bringing grout samples from the pile-sleeve annulus to the surface, using either divers or surface return grout lines. These methods are vulnerable to the weather, to damage by pile driving operations and can require the use of divers.These limitations prompted the development of nuclear techniques to remotely monitor the quality of the grout in-situ in the pile-sleeve annulus.

The Hard Wire grout monitoring system provided for piled platforms comprises an array of fixed gauges installed at monitoring points, either on the pile sleeve or on the wall of an insert pile. The data is transmitted to the surface by cable. The nuclear gauges record and measure the density of grout arriving at the monitoring point and allow a rapid assessment of the structural capabilities of the grouted connection even before the grout has gained strength. This system has been installed on numerous structures world wide.

The system comprises a radioactive source and a detector and the grout passes through a measurement gap between them. As the density of the grout increases, the signal received by the detector is attenuated in proportion to the increase in grout density. The system is calibrated to convert this change in the signal to provide a measurement of the grout density.

A further system was developed for use on template structures and jackets using drilled piles. The gauge is attached to a length of armoured cable and is deployed using a deck-mounted winch. This system may be used in any situation where the gauge can be suspended or supported in the annulus to be monitored, for example a pile/soil or pile/sleeve annulus. This system allows the instrument to be recovered and reused.

The ROV deployed system is an adaptation of the winch-deployed version. A gauge is mounted on the manipulator arm of a remotely operated vehicle. The subsea probe communicates with a computer on the surface via the ROV umbilical. The system is highly flexible because it is not dedicated to any specific vehicle. This system was first used in the North Sea and Gulf of Mexico and is now industry-standard worldwide, where quality assurance is required.

Foundocean can provide advice on all types of grout monitoring systems and also design and construct the necessary monitoring equipment to suit all types of platforms and templates.

ROV deployed density probe in pile annulus