The project site is underlain by superficial deposits of recent to sub-recent age alluvium with the upper soil stratum comprising very soft to soft marine clays (Halocene clay) of up to about 25m thick. The reclaimed area on swampy coastal land was pre-loaded with hydraulic sand fill and aided with pre-fabricated vertical drains (PVD) to accelerate the consolidation settlement. This paper presents the design considerations including the important factors for realistic prediction of consolidation settlement and fill embankment slope stability. Emphasis is placed on the monitoring data and their comparison with the design predictions.

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In the mid to end 2000, Vietnam embarked in the construction of a series of deep water ports along the Cai Mep Thi Vai river, in the province of Vung Tau, close to Ho chi Minh city. Those ports were partly built on the tidal plain and partly reclaimed from the river. Two such ports Cai Mep International Terminal (CMIT) and GEMALINK, close to the mouth of the river, were showing a clay layer with very poor mechanical property of respectively 36 and 42 m. It was not possible to reclaim the 6 m of sand fill needed to put the container yard above the 100 years flood, without some sort of reinforcement/consolidation of the clay layers; Two problems were encountered, one of stability at the edge of the reclaimed land, the other one of the bearing capacity and long term settlement. The initial solution along the edge envisaged by the client was a block of soil mixing, but both the cost and the time needed were not satisfactory and Ménard was invited by the EPC-contractor to propose an alternative solution. Such alternative, implemented successfully, consisted in increasing the shear capacity by forced consolidation of the clay using the Ménard Vacuum Consolidation. The case histories of the two projects will be presented.

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Pearl Jumeira is an artificial offshore land formation located in Jumeira Beach in the Arabian Gulf and is constructed from Dubai-sourced reclaimed sand and locally sourced rockworks. Reclaimed sand was dredged from known borrow pits in Dubai waters. The island will cover approximately 8.3 million square feet of land (fully serviced with all infrastructure requirements) consisting of more than 3.0 million square feet of residential villa plots and over 90,000 square feet of retail, community, and educational facilities. The current paper presents a geotechnical case study on this reclaimed island in terms of: The geotechnical design, the construction stages, and the ground investigation results. In the geotechnical design stage, soil properties of the reclaimed land were investigated to achieve the design bearing capacity and to assess the risk of liquefaction. In the geotechnical construction stage, soil improvement technologies such as vibro compaction and surface compaction were used. In the soil investigation stage, a set of soil tests were conducted in order to achieve the geotechnical design. These tests include Standard Penetration Test (SPT), Unconfined Compressive Strength Test (UCS), Piezocone Penetration Tests (CPTU), Zone Load Test, Particle Size Distribution (Sieve Analysis), etc.... The thickness of the reclamation fill varies across the site but is typically in the order of 10 m to 15 m and consists primarily of clean sand with lenses of silty materials. The materials below the pre-reclamation seabed comprise of layers of sand and silty materials of varying thicknesses, underlain by the Calcisiltite/Calcarenite bedrock between -10 m and -15 m Dubai Municipality Datum (DMD).

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The Tokyo Haneda Airport has been developed by land reclamation since 1931. When we look back its history, dredged soils have been effectively used at the offshore expansion project (1984–2007) and the D-runway project (2007–2010). In the offshore expansion project, a dredged clay deposit in ultra-soft state was converted into an airport island. Because of softness of the dreaded soil, continuity of the vertical drains under large consolidation settlement, as well as large lateral soil movement, had to be concerned. In the D-runway project, lightweight treated soils of dredged clay were effectively used to reduce earth pressure on the seawall. To efficiently conduct large-scale placement, pneumatic mixing method was very useful. At the joint structure between the reclamation and piled pier sections, air-foam treated lightweight soil was placed as backfill, because more lightness was strongly required to ensure the stability.

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Offshore land reclamation has become more challenging in recent years. One of reasons is the use of soft soil such as dredged clay slurry when there is lack of granular fill materials and the improvement of soft soil to meet the design requirements is challenging. Another reason is that the water depth in which land reclamation has to be carried out is getting deeper and deeper and the supply of a huge amount of fill materials becomes another challenge. In this paper, methods for land reclamation using clay slurry and the associated soil improvement methods are introduced. Case studies for land reclamation over ultra-soft soil are presented. Methods to use sewage sludge or other waste for land reclamation are also proposed. To overcome the difficulties in land reclamation in deep water, a new land reclamation method, NeuSpace, is also introduced.

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A new method is developed to improve the effectiveness of vacuum preloading on the consolidation of dredged fill in Wenzhou, China. This is achieved by adding some flocculants (floc) to the dredged fills while maintaining a certain level of vacuum pressure through prefabricated vertical drains (PVDs). The floc agent adopted in this study is a mixture of polyacrylamide (PAM) and calcium hydroxide (Ca(OH)2), which would dehydrate soil particles through changing the bound water into free water. The water states transformation occurs inside the soil particles, which would significantly mitigate the risk of clogging around PVDs and enhance the soil permeability, thereby improving the efficiency of consolidation. A number of laboratory tests are conducted to testify this method. Comparison between conventional vacuum preloading method and the proposed method demonstrates that, the new method achieves better improvement of dredged fill in a shorter period of time.

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