Introduction: Increasing environmental constraints, in regards of the traditional solution which ... more Introduction: Increasing environmental constraints, in regards of the traditional solution which consists in dumping dredged sediments at sea, has led to explore alternatives to manage fine dredged marine sediments [1], [2]. The use in road construction can be an interesting one as the consumption of materials in this domain is important [3] and resources are declining. In this context, the use of low polluted fine sediments (mainly composed of silt) from Dunkirk harbor (France) as sub-base layer material was investigated in the laboratory [4]. The evaluation of mechanical, as well as environmental performance of different mixtures has revealed the ability of fine dredged sediments to be used as sub-base layer material. In order to validate the performance of designed material at site scale, an experimental road was built in October 2005. This paper presents the first results of the study, which aims at monitoring the mechanical and environmental behavior of this road with time. Met...
Dams induce a potentially significant impact on the environment and society by changing ecosystem... more Dams induce a potentially significant impact on the environment and society by changing ecosystems, by populations' relocation upstream and especially by the presence of an imposed risk on populations located downstream. Although dam failures have a low probability, the main cause of accidents, near submersions by unexpected flood has been foundations failures (ICOLD 1993) due to problems of erosion, or insufficient shear strength along the rock discontinuities or the interface between dam and foundation. Among dam failures, 21% are related to lack of shear strength along the discontinuities of the foundations (ICOLD 1995). It is well known that rock, as soil, is a complex engineering material formed y natural process, which induces vertical and horizontal variability. Plus, the sliding process of a rock foundation discontinuity is a mechanism that mobilizes points shear properties of this discontinuity. The variability of shear properties averaged over the sheared discontinuities is less than that of their point shear properties. This is known as the average effect in spatial variability. These phenomena of spatial variability are not taken into account in the standards of stability analysis of dam foundations sliding or research work published in the literature. The aim of the thesis is to develop an analysis of the spatial variability of shear strength that takes into account the reduction of the variability by scaling up effect. This approach was developed in the context of the current state of the art. An experimental method, which aimed to investigate in a simple way the shear strength of joints, was suggested in the thesis and has been validated by comparative study with more than thirty direct shear tests on joints taken from a foundation of concrete gravity dam. It was developed a process to analyze the spatial variability of the shear strength of the joints using the input parameters of the model of Barton and Choubey (1977). This approach is based on the use of geo-referenced data on these parameters characterizing the family of discontinuity along a vertical borehole. To validate the relevance and applicability of this approach, we have implemented it in a case study of a rock dam foundation. Using finite element software, a study illustrates the relevance of the analysis of the spatial variability of the shear strength of the joints in the assessment of stability against rock dam foundations sliding. The results show that taking into account the spatial variability of shear parameters can increase the margin of safety measured through an increase in the safety factor and a significant decrease in the probability of failure.
Introduction: Increasing environmental constraints, in regards of the traditional solution which ... more Introduction: Increasing environmental constraints, in regards of the traditional solution which consists in dumping dredged sediments at sea, has led to explore alternatives to manage fine dredged marine sediments [1], [2]. The use in road construction can be an interesting one as the consumption of materials in this domain is important [3] and resources are declining. In this context, the use of low polluted fine sediments (mainly composed of silt) from Dunkirk harbor (France) as sub-base layer material was investigated in the laboratory [4]. The evaluation of mechanical, as well as environmental performance of different mixtures has revealed the ability of fine dredged sediments to be used as sub-base layer material. In order to validate the performance of designed material at site scale, an experimental road was built in October 2005. This paper presents the first results of the study, which aims at monitoring the mechanical and environmental behavior of this road with time. Met...
Dams induce a potentially significant impact on the environment and society by changing ecosystem... more Dams induce a potentially significant impact on the environment and society by changing ecosystems, by populations' relocation upstream and especially by the presence of an imposed risk on populations located downstream. Although dam failures have a low probability, the main cause of accidents, near submersions by unexpected flood has been foundations failures (ICOLD 1993) due to problems of erosion, or insufficient shear strength along the rock discontinuities or the interface between dam and foundation. Among dam failures, 21% are related to lack of shear strength along the discontinuities of the foundations (ICOLD 1995). It is well known that rock, as soil, is a complex engineering material formed y natural process, which induces vertical and horizontal variability. Plus, the sliding process of a rock foundation discontinuity is a mechanism that mobilizes points shear properties of this discontinuity. The variability of shear properties averaged over the sheared discontinuities is less than that of their point shear properties. This is known as the average effect in spatial variability. These phenomena of spatial variability are not taken into account in the standards of stability analysis of dam foundations sliding or research work published in the literature. The aim of the thesis is to develop an analysis of the spatial variability of shear strength that takes into account the reduction of the variability by scaling up effect. This approach was developed in the context of the current state of the art. An experimental method, which aimed to investigate in a simple way the shear strength of joints, was suggested in the thesis and has been validated by comparative study with more than thirty direct shear tests on joints taken from a foundation of concrete gravity dam. It was developed a process to analyze the spatial variability of the shear strength of the joints using the input parameters of the model of Barton and Choubey (1977). This approach is based on the use of geo-referenced data on these parameters characterizing the family of discontinuity along a vertical borehole. To validate the relevance and applicability of this approach, we have implemented it in a case study of a rock dam foundation. Using finite element software, a study illustrates the relevance of the analysis of the spatial variability of the shear strength of the joints in the assessment of stability against rock dam foundations sliding. The results show that taking into account the spatial variability of shear parameters can increase the margin of safety measured through an increase in the safety factor and a significant decrease in the probability of failure.
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Papers by Gérard Ballivy