Geotechnical input in embankment dam construction and the influence of geosynthetics in the overall design

Thesis (MEng)--Stellenbosch University, 2017.ENGLISH ABSTRACT: Dams have played an important part in history, with some of the earliest civilizations like the Egyptians and Mesopotamians, constructing some of the first ever. Early examples ranged from simplistic earth structures to dams being constructed from masonry and building ruble. Since then the field of dam construction has progressed to include a wide range of designs and uses varying from the norm of holding water for irrigation and human consumption. Earth dams have become one such wide spread design, as the reasoning behind its construction, lies in the abundance of material. And as such, it makes sense that earth embankments make up more than 60% of the worlds constructed dams. As the years has gone by, technology has advanced in many fields of today’s world. This is true for one such field synonymous with earth embankments, which is namely geosynthetics, with the earliest inclusion of these products in 1970. From early inclusions as filters, geosynthetics have been changed earth embankment construction drastically, providing key help in solving difficult soil conditions. Ultimately, it has been the study of soil itself that has held the answer to solving difficult soil conditions and have aided in the advancement of geosynthetics technology. Geotechnics, the study and engineering understanding of soil interaction, has thus been an area well worth studying. Using a farm near Stanford in the Western Cape, the influence of geotechnics and geosynthetics in embankment dams was investigated. This study was conducted to see how the field of earth embankment design, incorporates the information gained from the geotechnical understanding of soil and how geosynthetics have altered how we look at embankment problems. Areas of the design process where looked at where geotechnics was used before, during and after the construction of an embankment dam. These areas where further broken down as a desk study where elements such as various soil types, climate and the various parts of an embankment dam. The next step was assessing the onsite ground conditions and using the results that were gathered to design an appropriate dam. Although not built yet, geotechnical measuring instrumentation was looked at, to assess the design that was built, as well as the steps that had to be taken for site preparation. From site-specific materials, it was determined that a 13.4 meter high earth clay core embankment dam would be constructed on the specific farm site. The water would be stored at a height of 10.4m and the slope gradients would be 1:2 for the downstream slope and 1:3 for the upstream slope. The core would have slope of 2:1 and a cut-off trench with slopes of 1:1. Geosynthetics would be used as upslope protection, for wave erosion.AFRIKAANSE OPSOMMING: Geen opsomming beskikbaa