Engineering and environmental aspects of offshore soil mixing

Abstract

The increasing number of near-shore and offshore projects for commercial, residential or energy-generation purposes has led to the accelerated development of marine construction technologies. Some of these methods have been conceived to improve the geotechnical properties of soft seabed deposits. Cutter soil mixing (CSM) is a recent deep mixing method for the stabilisation of soils. This mixing procedure was initially developed for on-shore projects, but a few near-shore applications have been carried out. The research in this paper is on the possible use of CSM as an environmentally friendly offshore ground improvement technique. A specific full-scale trial was performed simulating offshore conditions. The complete process and the main production parameters were continuously monitored during the installation sequence. A comprehensive monitoring and sampling campaign was conducted at the site, and laboratory analyses were carried out on the collected water samples to investigate the water quality throughout the test. Finally, unconfined compression tests were undertaken to determine the geomechanical performance of the improved soil achieved after 28 curing days. The results suggest how CSM may be regarded as a valid technology for improving the physical properties of seabed soils, limiting the risk of negative environmental impact on the surrounding water.