Ahmed Benamar

Electrokinetic remediation of dredged sediments from Le Havre Harbour

ABSTRACT Dredging is necessary for the development of the harbours and the maintenance of their activities. Dredging sediments, when polluted, present an effective and durable contamination risk of the ecosystems. The electromigration process is a promising decontamination technique for removal of ionised or ionisable substances contained in the sediment. An experimental study which aimed at investigating the efficiency of this technique is performed for three samples of sediments dredged in three basins in the port of Le Havre (France). The results show a decrease of the electric current in the sample during the process, highlighting the saturation of the electromigration potential. The extracted solution volume increases with electric power and the electrodes material is also the parameter controlling the electrokinetic process.

Effects of Fine Particles on the Suffusion of Cohesionless Soils. Experiments and Modeling

Internal erosion has long been a major problem associated with earthen structures, and its field investigation has been limited because of its complexity. Laboratory experiments provide a potential insight into the induced processes. Soils suitable to suffusion involve an easy movement of fine particles between the coarse ones. In this study, suffusion experiments were performed on a laboratory column packed with different sand–fines mixtures and subjected to controlled flow conditions. The mixtures are made of Fontainebleau sand (NE34) and fines (kaolinite or illite or silt). The initiation and the progression of soil suffusion were investigated for soil mixtures, and the hydraulic conductivity variation was derived from pressure measurements. Attempts are made to assess the influence of the type and content of fine particles on mixtures suffusion. The results show that among the tested fine particles, illite exhibits a great resistance against suffusion. Fine content increase involves less suitability to suffusion till a threshold value. Recorded pressures indicate that detachment of fines may be followed by clogging in the soil matrix, leading to a decrease of hydraulic conductivity. Furthermore, analytical solutions of simplified mathematical model based on the mass conservation of eroded particles (Govindaraju et al., J Hydrol 172:331–350, 1995) were used to simulate the recorded soil suffusion curves, and the model performance was evaluated. Comparisons between numerical and experimental results indicated a quite good agreement, and allowed the estimation of the model parameters.

Citric Acid-Enhanced Electroremediation of Toxic Metal-Contaminated Dredged Sediments: Effect of Open/Closed Orifice Condition, Electric Potential and Surfactant

Abstract Citric acid (CA), a widely used eco-friendly electrolyte, can be employed as an agent for enhancing toxic metal (TM) removal from contaminated dredged sediment using electrokinetic (EK) technology. In this study, dredged harbor sediments co-contaminated by TMs were subjected to enhanced EK treatment using a mixture of chelating agent (CA) and surfactant as an additive in the processing fluids. Several control conditions that may influence the efficiency of TM removal were tested, including open/closed sediment chamber orifices, electric potential gradients (0.5, 1.0, and 1.5 V cm−1), and electrolyte surfactant. Tween 20 (4 mmol L−1) was used as a surfactant within the electrolyte to investigate the extent of TM removal in sediment with high organic matter content. The results showed that an open orifice led to a greater electro-osmotic flow (EOF) with moderate TM removal. In contrast, a closed orifice with a nonionic surfactant electrolyte allowed the highest removal of TMs from the matrix. Moreover, increasing the electric potential gradient led to a higher EOF under the open orifice condition, but no significant increase in TM removal was observed owing to a higher accumulation of TMs in the middle of the matrix, caused by the opposite direction of EOF and electro-migration of metal-citrate complexes.

Assessment of the vulnerability index of small dams to natural hazards: case study

Abstract Assessing the vulnerability of small dams to natural hazards (earthquake, rainfall, snow, and wind) is an important task. In many emergency situations, after an earthquake or a major flood, the diagnostic task requires quickness and efficiency. But hydraulic structure owners lack expertise and are led to engage less experienced engineers. For this purpose, a standard methodology is required, allowing the managers to quickly assess the small dam vulnerability for assisting engineers in their diagnosis. In this context a simple and useful method was developed through this chapter that aims to assess the vulnerability index of small dams, taking into account all influential parameters, where the most important are mainly related to environmental location, earth structure, and operation conditions. This approach allows making decisions about the rehabilitation to be conducted after such analysis. Degradation mechanisms of small dams detected in the area of concern were analyzed as a practical example for which the vulnerability index was assessed and rehabilitation recommendations were suggested to lower this index.

Optimization of the maintenance strategies of roads in Morocco: calibration study of the degradations models of the highway development and management (HDM-4) for flexible pavements

ABSTRACT The Highway Development and Management 4 (HDM-4) model was developed by the World Bank and used for pavements management system. An approach of the adaptation to local conditions is therefore required by adjusting the calibration factors, with the consideration of the context in which they are to be applied. The aim of the present work is to suggest these calibration factors for predicting the deterioration (structural cracking, ravelling, potholes and their resultant roughness) of roads in Morocco. The careful choice of such maintenance work planning is based on the result of these models. This study is based on the exploitation of road database, obtained from visual inspections and measurements performed by the National Center of Road Study and Research. The monitoring covered 6 years and concerned 55 test sections located on the Moroccan territory. Four kinds of structures were analysed involving different pavement bodies, constituting materials and thicknesses. The used method is based on a statistical analysis using equations implemented in HDM-4 models. The calibration process of the pavement behaviour was performed by a linear regression between the predicted values and observed values. Thereafter, the calibration factors for the initiation and the propagation of each damage in the models were determined. The obtained results allow us performing a quite good calibration for a pertinent use of HDM-4 in the local context.

Solid Particles Transport in Porous Media: Experimentation and Modelling

Solid particle detachment, transport and deposition in natural or artificial porous media have been the subject of an intense research effort in the last four decades. Particle-facilitated contaminants transport, accidents due to internal erosion in the hydraulic structures and permeability decreases of the oil wells, drinking water supply or artificial recharge of the aquifers, aroused a growing interest. In this study, results of two laboratory experimental systems for tracer tests in columns are presented. System 1 concerns step-input injection method where two studies were realized. The first study is devoted for studying deposition kinetics (Kdep) of the Suspended Particles (SP) and the second for evaluation the porous medium damage (clogging and release). However, system 2 concerns the pulse injection method whose aim was to study the SP deposition kinetics. The interpretation and analysis of the Break-Through Curves (BTCs) were obtained using the analytical and numerical solution of convection–dispersion equation (1D) including a source term (deposition and release term). Using system 2 results showed a decrease of the deposition kinetics coefficient with flow velocity until a critical velocity where Kdep decreases. For high injected volumes of the SP in system 1, the permeability decreases occurs throughout of the entrance of the porous medium.

Contribution of the transport of suspended particles to the internal erosion in soils: Particle migration in porous media

ABSTRACT An experimental study which aimed at investigating the transport behaviour of suspended particles in saturated porous media is presented. A short-pulse technique was used for measuring particle recovery and collision efficiencies in two porous media (silica gravel and glass beads). Breakthrough curves (BTCs) were measured on-line and well described by analytical solution of an advective-dispersive equation with a first-order deposition kinetic. The effects of hydrodynamic and gravity forces on particle transport and deposition rate were delineated. Results show particles travelling faster than the conservative tracer. The recovery rate of the suspended particles decreased with decreasing flow rate, and the deposition rate presents unexpected changes, depending on the flow rate.