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This paper presents some recent technological developments in deep mixing for the offshore sector. Deep mixing methods comprise in-situ soil treatment technologies where binding materials are added and blended with the original soils in order to improve their mechanical properties. The MIxed Drilled Offshore Steel (MIDOS) pile is introduced in this paper, which takes advantage of such deep mixing technologies. The comparison between the API approach and CPT-based methods for the prediction of the pile capacity are provided to validate the capability of the MIDOS pile as a foundational element for oil&gas structures in different geological conditions. The theoretical calculations are intended for initial estimation of pile sizing only and are not intended as a detailed design method.

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.

This paper reports on an experimental investigation on the behaviour of small-diameter piles, commonly referred\ud to as micropiles. This particular type of deep foundation is frequently used in many barely accessible Italian\ud mountainous areas, often characterised by complex ground profiles composed of mixtures of coarse soils with some\ud fine matrix elements including cobbles and large-diameter boulders. In such ground conditions, the lack of reliable\ud site and laboratory geotechnical investigations providing an accurate soil mechanical description and conservative\ud approaches for micropile design often lead to significant underestimation of the vertical ultimate load. In order\ud to improve micropile design in such geological contexts, a new field trial investigation involving tension and\ud compression load tests on micropiles up to failure was set up in a selected test site located in the Italian alpine region.\ud From interpretation of the load tests carried out so far, the reliability of commonly used calculation methods for\ud estimating bearing capacity is discussed. As a result, a new approach for a more suitable calculation of the mobilised\ud shaft and base resistance of micropiles bored in highly coarse soils is tentatively propos

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