Univ., Diss--Neuchâtel.

The underwater mining has increased in the recent years and the growing awareness of the potential impacts on the environment, as results of increasing the encroachment on the marine environment. Therefore, the debate has increased about how to protect this environment by using the scientific research that\'s relevant to the various environmental effects and developing the equipment used in dredging. There is a wide diversity of underwater mining equipments, such as continuous and non-continuous dredging which used for production of sand, gravel, alluvial deposits and raw material. There are a relation between increasingly dredging activities in the recent years and their impacts on the aquatic environment. These impacts are causes by changes in the topography of the sea floor such as turbidity, noise and other environmental impacts. Today, there is an international framework of legislation which has been developed for dredging projects. This contains rules and regulations which must be followed by mining companies and have to implemented by national authorities. The European countries also develop their legislation to control on the dredged material which deposit on land and sea. This legislation is constantly changing related to scientific knowledge and increasing the implementation frameworks. Also, the people become more sensitive to emissions that have a negative attitude towards dredging in the neighborhood. In addition, dredging techniques give rise to objections, which eventually led to think in more environmentally-friendly production methods. After that, the use of dredger is the only alternative in some project. The question is what are the true benefits of these techniques and what is the relation between possible improvements and technological potential as well as the costs. Therefore, it is intended to assess mining techniques in the context of their environmental impact and the costs. There are many systematic approaches which have been used for evaluation and determination of the environmental performances of different dredging equipment, techniques and procedures. Moreover, the new future developments and latest proposals in the dredging industry have been presented. Also, the new proposal to reduce the turbidity and suspended material effect which is the most important environmental impacts during dredging operations has presented. This research work gives a description of underwater mining techniques and different way of evaluating the dredging equipment’s in term of environmental, economic and social aspects. Also, this work presents two different methods of evaluation. The first approach is the statistical analyses method by using the modern Fuzzy evaluation concept. The second slant is a mathematical accounting method by using the information from the Egyptian case study, in order to reach the most environmental-friendly dredging techniques by taking into account the economic and social point of views. The final evaluation showed that the suction and bucket ladder dredger are the best choices. The assessment was made after comparing many parameters such as performance, characteristics, working depth, soil types and project area. Also, this work presents two different new practices for extraction of the underwater placer deposits which occur on the Egyptian Mediterranean coast. The first technique uses floating processing unit in the in situ area, which gets the extracted material and treated it to reduce the transportation costs. The second technique has divided the working area to many stages which make the suction dredger used also for transporting the material into the beach. The pipeline will be the best method of transportation by using the power of suction, which reduce also the transportation costs and also avoid the environmental effects.

The underwater mining has increased in the recent years and the growing awareness of the potential impacts on the environment, as results of increasing the encroachment on the marine environment. Therefore, the debate has increased about how to protect this environment by using the scientific research that\'s relevant to the various environmental effects and developing the equipment used in dredging. There is a wide diversity of underwater mining equipments, such as continuous and non-continuous dredging which used for production of sand, gravel, alluvial deposits and raw material. There are a relation between increasingly dredging activities in the recent years and their impacts on the aquatic environment. These impacts are causes by changes in the topography of the sea floor such as turbidity, noise and other environmental impacts. Today, there is an international framework of legislation which has been developed for dredging projects. This contains rules and regulations which must be followed by mining companies and have to implemented by national authorities. The European countries also develop their legislation to control on the dredged material which deposit on land and sea. This legislation is constantly changing related to scientific knowledge and increasing the implementation frameworks. Also, the people become more sensitive to emissions that have a negative attitude towards dredging in the neighborhood. In addition, dredging techniques give rise to objections, which eventually led to think in more environmentally-friendly production methods. After that, the use of dredger is the only alternative in some project. The question is what are the true benefits of these techniques and what is the relation between possible improvements and technological potential as well as the costs. Therefore, it is intended to assess mining techniques in the context of their environmental impact and the costs. There are many systematic approaches which have been used for evaluation and determination of the environmental performances of different dredging equipment, techniques and procedures. Moreover, the new future developments and latest proposals in the dredging industry have been presented. Also, the new proposal to reduce the turbidity and suspended material effect which is the most important environmental impacts during dredging operations has presented. This research work gives a description of underwater mining techniques and different way of evaluating the dredging equipment’s in term of environmental, economic and social aspects. Also, this work presents two different methods of evaluation. The first approach is the statistical analyses method by using the modern Fuzzy evaluation concept. The second slant is a mathematical accounting method by using the information from the Egyptian case study, in order to reach the most environmental-friendly dredging techniques by taking into account the economic and social point of views. The final evaluation showed that the suction and bucket ladder dredger are the best choices. The assessment was made after comparing many parameters such as performance, characteristics, working depth, soil types and project area. Also, this work presents two different new practices for extraction of the underwater placer deposits which occur on the Egyptian Mediterranean coast. The first technique uses floating processing unit in the in situ area, which gets the extracted material and treated it to reduce the transportation costs. The second technique has divided the working area to many stages which make the suction dredger used also for transporting the material into the beach. The pipeline will be the best method of transportation by using the power of suction, which reduce also the transportation costs and also avoid the environmental effects.

The thesis is devoted to determining the parameters of the bucket to increase productivity of dredgers while mining deep-water organic-mineral sediments. It was achieved by increasing the fill factor through determining the rational geometrical parameters of the bucket. Analytical dependencies of the rational height and length of the bucket on the cutting parameters and physical-and-mechanical properties of the excavated sediments were determined. Expressions for defining forces while digging plasticity water-saturated soils were developed. Experimental investigations of the process of digging deep-water organic-mineral sediments in laboratory conditions and in the real conditions of operating single-bucket dredger in the Black Sea at the depth of 1885 m were carried out. The technique for calculation of the bucket\'s parameters was developed.

The thesis is devoted to determining the parameters of the bucket to increase productivity of dredgers while mining deep-water organic-mineral sediments. It was achieved by increasing the fill factor through determining the rational geometrical parameters of the bucket. Analytical dependencies of the rational height and length of the bucket on the cutting parameters and physical-and-mechanical properties of the excavated sediments were determined. Expressions for defining forces while digging plasticity water-saturated soils were developed. Experimental investigations of the process of digging deep-water organic-mineral sediments in laboratory conditions and in the real conditions of operating single-bucket dredger in the Black Sea at the depth of 1885 m were carried out. The technique for calculation of the bucket\'s parameters was developed.