Nicolas Nerincx's scientific contributions

The treatment of soils with binders (lime and cement) is common practice in the field of road and railway earthworks. So far the use of treated soils for dams and dikes is unusual. The CFBR working group on dams (and dikes) in hard backfill and treated soils (mirror group of Icold Technical Committee P - Committee on cemented embankment dams) has been working for several years on the development of these techniques applied to dams and dikes, considering the mechanical improvements made by the treatment at the design stage. For this purpose, one of the objectives of the WG is to define design and justification criteria for these new types of structures. To this end, research work has been undertaken to better understand the mechanical behavior of the treated materials used on a large scale. From a database of laboratory and in-situ test results for lime treated loess, two numerical modeling approaches of gradually increasing complexity were conducted in parallel in order to define the stability conditions depending on cure time, particularly at the young age, of a typical 30 m height dam built with this type of material. Using PLAXIS and FLAC numerical modelling software, the mechanical behavior of the structure was simulated by considering: - layered construction effects; - the variations of mechanical and rheological properties with the cure time; - various types of elasto-plastic behavior (Mohr-Coulomb, Modified Cam-Clay, Plastic Soil Hardening model and Hardening Soil Model); - the generation and dissipation of pore pressures. This article presents the studies carried out as well as the technical locks encountered. The results obtained by the modelling methods, and their limits, are exposed and compared. As a conclusion, the communication summarizes the progress of the knowledge following the work described before, as well as the general lessons learned from this unprecedented modelling work.

Lime treatment is a well-known technique of earthworks, for earthworks execution, soil improvement and stabilization. Its applications are mainly roads, railways, airports and platforms construction. In addition, some positive past experiences of lime treatment were related to solve erosion problems of dispersive and non-cohesive soil in hydraulic structures. The interest of the dams and dikes community regarding this technique is currently growing. During the last decade, the benefits of lime treatment according appropriate treatment technologies were shown at the laboratory and on site. This communication deals with the performance reached by lime treated soils and associated design requirements and application. It reviews the most significant recent results in terms of improved mechanical strength, resistance to internal erosion and resistance to surface erosion. It is still unusual to evaluate the resistance of a dam or dike to overflowing. We present the results of the overflowing test campaign carried out in 2018 on three earth structures, which compares the surface erosion resistance of treated and untreated soil. The last part of the paper deals with the dikes and dams design perspectives opened by soil treatment. These results are analyzed in the light of the reassessment of the consequences of climate change on hydrology, and the assessment of floods, leading to unplanned overflows during the design phase.

Nowadays, lime-treatment of silty and clayey soils is frequently used to build linear transportation infrastructures. Use of this technology in the context of hydraulic structures is gaining strong interest. It has indeed be demonstrated, thanks to former R&D works, that lime-treated soils can successfully fulfill a series of relevant functions as far as dams and levees are concerned : slope stability, low permeability, resistance to surface and internal erosion. Lab experiments and full-scale field measurements, completed by a careful review of existing infrastructures worldwide, substantiate this statement. As part of the recent DigueELITE R&D project, the overflow resistance of a levee made with a lime-treated soil has been measured on a structure built on the Vidourle river (France). One of the outcomes of the project was the development of a measuring device for in-situ evaluation of surface erosion, together with the corresponding test protocols and subsequent analysis. With this setup , it was possible to demonstrate that the lime-treated soil was 5 to 10 times more resistant to overtopping than the same untreated soil, with a maximum improvement in the most sensitive zones (crest and toe). After a brief recall of the impact of lime-treatment on relevant soil properties, this article presents:-The results of the overflow trials on the full scale levees, and their interpretation,-The consequences of the findings of the DigueELITE project in terms of levee and small dam design, including cost analysis,-The overall project conclusions and further mid-and long-term perspectives.

As part of the recent DigueELITE R&D project, the overflow resistance of a levee constructed of lime-treated soil was measured on a structure on the Vidourle river in France. One of the outcomes was the development of a measuring device for the in-situ evaluation of surface erosion, together with the corresponding test protocols and subsequent analysis. It was possible to demonstrate that the lime-treated soil was 5 to 10 times more resistant to overflowing than natural untreated soil, with a maximum improvement in the most sensitive zones (crest and toe). The authors describe the results of the overflow trials on the full-scale levees, and their interpretation, as well as resulting recommendations from the project in terms of levee and small dam design, and a cost analysis.

Lime treatment of silty and clayey soils is a well-know and widely applied technique in transport infrastructure works (roads, highways, airfields, railways…). But the use of lime treated soils in a hydraulic context is less developed. However, some examples were reported and detailed testimonials of applications of this technique, realized from the 1970s, can be found, mostly in the United States, South of Africa, Asia and Australia. During the last decade, the benefits of lime treatment were evidenced for the enhancement of mechanical properties and stability of earthen structures, for the resistance to internal and external erosion of treated materials, and for the possibility to maintain low permeability. An experimental earthfill dike was built, in the frame of the French research program "DigueELITE" and successfully tested against surface erosion and real scale overflow. Thanks to this experience and also to the large amount of results collected since 2005, it becomes possible to provide recommendations for the use of lime treated soils in the design of earthfill dikes and small earth dams resistant to mechanical and hydraulic stresses. After a brief description of the most outstanding hydraulic structures using lime-treated components, the paper gives an overview of the performance of soil-lime mixes, as highlighted in recent years, and discusses the resulting benefits for the design and construction of dikes and small dams.

The R&D project "DigueELITE" is working on new concepts of dikes and low earthdams, based on an existing and established technique in the field of earthworks for road or railways infrastructures : soil treatment with lime. The R&D DigueELITE project started in 2013 on the following basis: a high level know-how on soil treatment and a new approach of designing overflow resistant dikes or (low) dams. The project includes laboratory studies, engineering, experimental dike realisation and in-situ real scale tests. Namely, a new device for assessment of dike and earthfill overflow dam overflow resistance has been applied on the experimental dike built in 2015. The results of the researches and the laboratory and in situ tests make clear the main benefits of lime treatment in the frame of dikes and earthfill dams.: - Limiting the need of valuable materials (depending on site conditions), such as clean sand, gravels, fill soils . . . - Allowing, under defined circumstances, overflow, leading to cost reduction compared to other type of overflow protection such as rip rap, stone mattresses . . . Overflow resistance may also lead to reduced freeboard, - Simplifying the typical cross section, with limitation of complex filter and drain system, - Possible grass covering over the whole embankment, as there is no need anymore for surface protection - depending on the site conditions - Possible slope steepening - Lower built-up (thanks to steeper slopes), what is of crucial importance in inhabited areas. - Global cost reduction, material transport reduction and decrease of nuisances : damage on existing road network, noise, dust. . . . Taking advantage of those benefits, the engineer may change significantly the design of such structures. Under defined circumstances, it is now possible to design "overflow resistant dikes" and "low submersible dams". Those completely new concepts are very relevant answers to new challenges, such as valuable soil scarcity, available built-up areas, and even climate change with more frequent floods, of possibly higher peak flows.

Soil treatment with cement or lime is used in hydraulic works since for a few decades. Since 10 years, the feedback from existing structures and in-depth studies of treated soils behavior make this technique more and more interesting for designers and owners who intend to take advantage of treated soils performance. This paper describes first the treated soil as a material: treatable soils, performance, mixing and compaction. It relates then the benefits of soil treatment for small dams. Current studies about soil treated dams, carried out in the context of the ICOLD Committee P are described. Soil treated dams are for now a concept, not completely validated yet, unlike dikes and low dams in treated soils. Studies include laboratory tests in order to select or develop a proper soil model for treated soil, and also engineering efforts to preliminary design such dams, e.g. dams with upstream watertightness system The paper also addresses the dikes topic, describing the results of the French R&D project DigueELITE about lime treated soils, and the new in-situ overtopping test. Main result of that project is that soil treatment gives to soil good resistance against surface erosion compared to non treated soil. This comes in addition to already demonstrated internal erosion resistance of treated soil. Finally, feedback from existing structures is given, such as canal, zoned dam, dike and temporary cofferdam.

The treatment of silty and clayey soils with lime (calcium oxide or hydroxide) is a technique widely used for soils improvement and stabilization, and applied in the context of roads, highways, railways, platforms construction. However the principles of lime treatment for hydraulic earthen structures remain barely applied or even forgotten (European case). If existing testimonials (levees, dams, mainly in US and Australia) are evidences that show effectiveness and durability of lime-treated structures, there was a necessity to evaluate a series of unknown characteristics and relevant properties of lime-treated soils for an application in hydraulic context, through laboratory studies and full-scale experiments. This paper relates results of several research programs, and focuses on a multi-scale approach for assessment of lime-treated soils properties, relevant for hydraulic earthen structures : laboratory testing and full-scale lime-treated embankments. The conferred soil properties can lead to innovative earthfill dams and dikes designs by addressing some of the typical designer's problems, such as stability, watertightness, internal erosion, surface protection and flood control.