The Mont-Saint-Michel Project has been carried out to restore the maritime characteristics to those that existed before 1995. Attempts have been made to use marine sediments that are produced as construction waste every year for purposes such as the construction of pavements and driveways; however, it is difficult to directly use the sediments for these purposes. Hence, methods to stabilize marine sediments have recently been developed. The purpose of this paper is to propose a new approach to sediments stabilization; in this approach, pozzolan and alkali-activated binders, are used. The freeze-thaw test and wet-dry test are conducted to determine the durability of the sediments and examine their suitability for use as construction material. The binders are prepared by alkali activation using pozzolan, and different amounts of the binders are mixed with marine sediments named "la tangue". The surfaces of one group of sediments are treated by a substance containing liquid glass. We compare the durability properties and deformation behaviors of two different types of specimens, by conducting tests and taking into consideration climatic conditions around northern France. The sediments stabilized by surface treatment showed high durability properties. The possibility of using them as construction sediments is discussed.

International audienceThe Mont-Saint-Michel Project has been carried out to restore the maritime characteristics that existed before 1995. Attempts have been made to use marine sediments e.g. in the construction of pavements and driveways. Hence, methods to stabilise marine sediments have recently been developed. A new approach to sediment stabilisation is here proposed by using pozzolan and alkali-activated binders. Freeze-thaw and wet-dry tests are conducted to determine the durability of the sediments and to examine their suitability for use as construction material. The binders are prepared by alkali activation using pozzolan, and different amounts of the binders are mixed with marine sediment. The surfaces of one group of sediments are treated by a substance containing liquid glass. We compare the durability properties and deformation behaviours of two different types of specimen, by conducting tests and taking into consideration climatic conditions. The sediments stabilised by surface treatment showed high durability properties

Ecosystem conservation has become one of the purposes in river management as well as flood mitigation and water resources management, and understanding of river flow and morphology in a stream with vegetation becomes important. Recently 2D depth averaged analysis is familiar even in a stream with vegetation by taking account of form drag due to vegetation. However, the shear stress in vegetated area is not properly described because the resistance law due to bed roughness is not reasonably modified in vegetated area. In this study, we discussed the bed roughness boundary layer in flow with non-submerged vegetation to deduce a reasonable relation between U and u* in vegetated area toward improving the analysis of sediment transport. The results show that the modification of resistance law using by thickness, velocity distribution in that layer was found to bring significant improvement of accurate estimation of shear velocity and subsequently the sediment transport. The proposed modification is improved by 2D depth averaged analysis based on this concept, and its application is certificated through flume experiment.

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