Browsing by Author "Dorfling, Johannes Adolf"
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- ItemThe feasibility of using sediments from the Theewaterskloof, Greater Brandvlei and Waterzicht Dams as construction materials(Stellenbosch : Stellenbosch University, 2019-12) Dorfling, Johannes Adolf; Fouche, Nanine; Day, Peter; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: Between 2014 and 2018, the Western Cape experienced the worst drought that the province has faced since 1904. The drought led to numerous water restrictions being applied by municipalities to regulate water use by their respective communities. From the exposed surfaces caused by the receding dam water levels, it was clear that thick layers of sediment have been deposited in the dams over the years, decreasing the storage capacities of these dams. The removal of these reservoir sediments will assist in maintaining optimal water storage capacity. The aim of this study was to determine the practical and economic feasibility of removing sediments out of the Western Cape's two largest dams namely the Theewaterskloof and Greater Brandvlei Dams as well as the smaller Waterzicht farm dam, and the possible use of these sediments as construction materials such as road building materials, fine aggregates, lightweight aggregates, bricks and landfill clay liners. Field investigations were conducted on the exposed dam surfaces of these three reservoirs. During this fieldwork, zones were demarcated based on sediment type and location and samples were gathered from each zone. Subsequently, laboratory analyses were performed on these samples to determine their engineering and chemical properties. These properties were used to classify each sample according to the Unified Soil Classification System (USCS) and related to the specific criteria for the various construction materials under investigation. The data from field analyses were used, together with sediment types, to determine the volume of each sediment zone. Where the sediments in a mapped zone were found suitable to be used as construction materials, cost models were prepared based on the type of construction material to be removed to estimate the removal cost per unit volume. Based on the laboratory results, two cost models for the two zones were calculated. These zones included the poorly graded sands (SP) from zone B5 of the Greater Brandvlei Dam that is suitable for use as fine aggregate and clayey sands (CS) of the Waterzicht Dam that can be used for landfill liners in Class B and Class C type landfills. Three samples from the Theewaterskloof Dam and one sample from the Greater Brandvlei Dam can be used as lower layers of the pavement or in construction of fills, however the low cost, low quality and abundance of such road materials made it not feasible to be recovered for road construction unless such construction occurs adjacent to the sediment zones. The methods used in the cost models for the removal of sediment from zone B includes dry excavation with and without sheet piling and dredging if the zone is submerged by an increase in dam levels. The removal costs for dry excavation without sheet piling and dredging methods were considered feasible if no more than five sediment removal units are used. For dry excavation to be feasible the minimum proportion of the sediment reserve to be removed ranges from 26% to 100% if one to five excavators are used respectively. The cost model created for removing clayey sands (CS) from the Waterzicht farm dam estimated that if 100% of the sediment reserve is removed, it will be feasible to use the sediment for compacted clay liners for Class B and Class C landfills if the transport distances are 1 km and 25 km respectively. From the cost models, it was concluded that the sediments from the Greater Brandvlei Dam and Waterzicht farm dam may be feasibly mined, however the volume estimations indicate that removal of these mapped sediments will result in only a minor increase in storage capacity and will have only a small impact on lessening the effects on future droughts.