Salah Sadek

Shear Strength of Fiber-Reinforced Sands

Soil reinforcement using discrete randomly distributed fibers has been widely investigated over the last 30 years. Several models were suggested to estimate the improvement brought by fibers to the shear strength of soils. The objectives of this paper are to (1) supplement the data available in the literature on the behavior of fiber-reinforced sands; (2) study the effect of several parameters which are known to affect the shear strength of fiber-reinforced sands; and (3) investigate the effectiveness of current models in predicting the improvement in shear strength of fiber-reinforced sand. An extensive direct shear testing program was implemented using coarse and fine sands tested with three types of fibers. Results indicate the existence of a fiber-grain scale effect which is not catered for in current prediction models. A comparison between measured and predicted shear strengths indicates that the energy dissipation model is effective in predicting the shear strength of fiber-reinforced specimens in reference to the tests conducted in this study. On the other hand, the effectiveness of the predictions of the discrete model is affected by the parameters of the model, which may depend on the test setup and the procedure used for mixing the fibers.

Evaluation of the seismic hazard of Lebanon

This paper presents the results of a study undertaken todetermine the seismic hazard of Lebanon. The seismic hazard evaluation wasconducted using probabilistic methods of hazard analysis. Potential sourcesof seismic activities that affect Lebanon were identified and the earthquakerecurrence relationships of these sources were developed from instrumentalseismology data, historical records, and earlier studies undertaken toevaluate the seismic hazard of neighboring countries. The sensitivityof the results to different assumptions regarding the seismic sources in theLebanese segment and choice of the attenuation relationship wasevaluated. Maps of peak ground acceleration contours, based on 10percent of probability of exceedance in 50 years and 100 years time spans,were developed.

Compliance factors within a GIS‐based framework for landfill siting

The complex process of siting landfills involves a number of stakeholders with varying perspectives and priorities. The constraints which must be met by any potential landfill site are numerous and diverse. In this paper a GIS‐based decision‐aid tool and framework are presented as a robust alternative for analysing large sets of complex data of varying nature in a quick and reliable manner. The approach devised is flexible. It allows the siting criteria, the associated importance factors, and site compliance levels, to be easily varied by means of drop‐down menus embedded in ArcGIS, to reflect local and regional priorities and concerns. The case of Lebanon has been used to illustrate potential uses of the tool and methodology, which could be implemented in any other context for which the base data are available. The necessary data coverages were obtained and/or developed from Lebanese country‐wide sources, coupled with field surveys. Two basic scenarios were simulated for demonstration purposes: the first incorporates an engineering and infrastructure compliance priority, while the second focuses on environmental concerns and associated indicators.

Quantification of Model Uncertainty in Shear Strength Predictions for Fiber-Reinforced Sand

AbstractSeveral models have been suggested to estimate the improvement brought by fibers to the shear strength of fiber-reinforced sands. To date, the effectiveness and reliability of these models have not been the subject of a comprehensive evaluation. The objectives of this paper are to (1) compile the experimental data available in the literature on the behavior of fiber-reinforced sands into a comprehensive state-of-the-art database, (2) quantify the model uncertainty and bias of current strength prediction models for fiber-reinforced sands, and (3) provide insight regarding possible modifications that could be made to the formulation of available models to improve their predictive effectiveness and reduce their model uncertainty. Two models that are considered to present the best available approaches to predicting sand-fiber shear strength were evaluated, namely, the “energy-based” model and the “discrete” model. The energy-based model was found to underestimate the measured friction coefficient on a...

Temporal variation of leachate quality in seawater saturated fills

Many waste fills are located along the coast, often encroaching into the sea, and are consequently subjected to seawater intrusion. Although previous investigations have demonstrated the beneficial effects of moisture addition on biodegradation processes, these studies have not considered the potential effects of seawater intrusion into a sea fill. In this study, a preliminary laboratory-scale experiment was conducted to evaluate the potential effects of seawater intrusion on biodegradation processes and leachate quality. Chemical analysis was performed on leachate samples for a period of 230 days to study the temporal variation of leachate quality in the early stages of refuse decomposition. Leachate samples were collected weekly and several parameters were monitored including pH, COD, TOC, TDS, EC, chlorides, sulfates, orthophosphates, nitrates, ammoniacal nitrogen, hardness, and heavy metals. Chemical concentration levels were related to biological activity within the test cells, and the results indicate that salt water could delay MSW biodegradation.

Groundwater Resources in Lebanon: A Vulnerability Assessment

This paper presents a regional groundwater vulnerability assessment for Lebanon using the DRASTIC model coupled with a GIS‐based framework to prioritize protection efforts, whereby the most vulnerable areas to groundwater are targeted first, thus optimizing the allocation of financial and human resources. The objective of the study is to initiate a systematic approach to better manage and protect the countrys groundwater resources.

A New Apparatus for the Evaluation of Electro-Kinetic Processes in Hazardous Waste Management

Possible uses of electro-kinetics for hazardous waste site remediation are being investigated. This paper describes a new apparatus which has been specifically designed, fabricated, and assembled to evaluate the viability, feasibility, practicality, and potential costs of these conceivable techniques experimentally. Results of studies on the existence of electro-osmotic flow in compacted clay and the electro-kinetic barrier to contaminant transport are used to illustrate the types of information that can be obtained by the apparatus.

Pile driving by numerical cavity expansion

A cavity expansion procedure for the simulation of pile driving is presented and assessed in this paper. The analysis uses a non-linear finite-element model and the penetration of the pile into the soil is simulated by a radial opening of the soil around the pile. The case of a pile advanced by expansion will be compared to a similar pile subjected to computational driving (referred to, respectively, as ‘expanded’ and ‘driven’ piles for convenience). The state of stress and deformation, and the evolution of pore-water pressure in the soil will be monitored for the expanded and driven piles. Further computational driving will be applied to both cases and the pile response and soil resistance will be compared. The computational cost of advancing the pile by expansion will finally be investigated. Copyright

Geotechnical and environmental considerations in highway layouts: an integrated GIS assessment approach

Highway route layout design typically relies on aerial photographs, topographic maps and geologic maps. In this paper, a GIS platform, which incorporates the main digital data needed for evaluating route layouts, is used in a computer-based approach for highway layout assessment. Possible layouts are evaluated based on two sets of criteria. First, traditional evaluation criteria focussing on geometric design factors and impact on man-made features are considered. Next, the developed assessment framework builds on the GIS platform to generate specific environmental and geotechnical criteria for route layout evaluation. The developed approach integrates highway design, slope stability, and traffic noise modeling packages and specifically written codes with the GIS packages ARC/INFO and ArcView. A prototypical application of the assessment framework for a proposed highway south of the city of Beirut, Lebanon is presented. The results demonstrate the potential of the developed approach in incorporating new evaluation criteria at the route layout design stage and in automating the route layout assessment procedure.

Undrained shear strength characteristics of compacted clay reinforced with natural hemp fibers

Reinforcing clay with natural fibers is a common practice in various applications, such as the construction of steep slopes, repair of shallow slope failures, improving the performance of landfill covers, strengthening of roadbeds, etc. The reliance on this technique is on the rise as a result of the increasing demand for incorporating sustainable materials in construction. “Hemp” fibers are natural fibers derived from the plant Cannabis Sativa. Industrial Hemp is legally cultivated in a number of countries. Hemp is used in several industries, such as paper, textiles, clothing, biodegradable plastics, construction, body care products, food, medicine, and biofuel, in addition to applications in strengthening concrete and soils. The main objective of this paper is to investigate the potential use of natural Hemp fiber in improving the load response of compacted clays. A laboratory-testing program consisting of 18 unconsolidated undrained triaxial tests was designed for this purpose. Specimens of control clay and of clay mixed with Hemp fibers added at various fiber contents were prepared at a number of water contents and compacted using the standard proctor procedure. Specimens with diameters of 7.15 cm and heights of 14.3 cm were prepared at varying moisture contents (14%, 18%, and 20%) and mixed with fibers of 4 cm length at gravimetric contents ranging from 0.5% to 1.5%. Results show that improvements in shear strength of up to 100% could be realized for the Hemp reinforced specimens. The percent improvement increases with the fiber content up to a threshold value of 1.25% and differs depending on the magnitude of the water content used in compaction in reference to the optimum moisture content of the matrix clay.