Civil, Structural and Geotechnical Engineering - Assignment Example

Civil (Structural and Geotechnical Engineering) Water is collected from roofs which are made of appr0priate materials including corrugated sheets that slope at an angle that allows flow of water to the gutters from where the water is directed into downpipes. The water from the downpipe is then directed to a filter from it is channeled to a tank (T, Oweis, A. Hachum. 2005). The first step of rainwater harvesting starts at the point of water being gathered by the roof and this calls for ensuring that the roofing materials in use need to meet the set standards set by the Australia government where emphasis is placed on having roofing materials that does not result to toxic water. The other characteristic of roofing materials is that they are supposed to be smooth and non-porous as this will also ensure drainage is efficient. (IE-NLC., 2006). The roof is supposed to be strong enough to be able to withstand the impact of heavy rainfall that is experienced in the area of water harvesting. The roofing is to meet roofing standards of Australia even when each roof has its own design. A trussed roof usually will be composed of rafters, struts, ceiling joists and the nail plates and this allows attachment of each corner as seen in figure 1. The recommended roof slope is 1:10 to 1:25 so as to achieve the desired water flow rate. Where drainage is slow the first flash water may not be adequate to rinse the roof and thus jeopardizing the quality of water. (T.W.D.B., 2005). The water will be collected from the catchment by being delivered to the gutters and through extension of the gutters the water will be delivered to the filter. Due to suitability of corrugated iron sheets, they can also be used in making of water storage owing to their strength and are being weather proof as a result of their coating class. There is need to adhere to the required design constraints so as to be able to produce appropriate roof design. There might be variation in the screws or fasteners which are to be embedded through the roof depending on whether the roof is metallic or wooden (Ramset, p.193). The Alluminium gutters with round bottom are recommended for use owing to their good performance because they are not vulnerable to rusting and also flow of water on these gutters is smooth without collection of debris that would otherwise block the gutter. (Mudrakartha, 2002). The gutters are to have a slope of 1 inch per hour with the design being such that it can accommodate a periodic storm intensity of 10 years with the gutter slope not going lower than 0.5% for about 2/3 of its entire length while the remaining length is to have a slope of at least 1%. The pipe connection from the gutter system to the filtration system is to have a slope of at least 1.5% with their size being able to take care of the maximum intensity (BIS-1742-1983, 1983). Supporting pillars will be placed at an interval of about 5 meters to ensure that the pipes do not break or sag significantly. Sand filter A sand filter is used in the water harvesting system in ensuring that water of the required quality is provided. The sand filter has the capability to filter up to . The filter has three compartments which are concentric to each other the inner is filled with pebbles, the one at the centre having course aggregate and the out one if filled with sand. The sump which is the which receives water is directly below the sand filter. There may be further treatment of the water at the sump before he water can be pumped to storage tanks (Dwivedi, 2009). Figure 1 Pipe sizing Water is pumped from the sump to the point of utilization at a high pressure and this this calls for having pipes made of materials of appropriate strength and dimension that will be economical at the same time being able to withstand the pressure (BIS-1742-1983, 1983). By use of Barlow’s formula the correct pipe dimension can be calculated Barlow’s formula: p = 2St/D Where, p= pressure of the water in the pipe, S= material strength, T= pipe wall thickness D= pipe outside diameter PVC with a material strength of 160psi (1111.612kpa) is used in this design Taking the head to be overcome by the pump to be about 32m, which is a combination the head due to elevation and friction and other minor losses. The pipe diameter to be used is calculated by choosing the desired velocity of water bearing in mind that very high speed result to high friction losses and very low speed would mean un economical design (LRHF, 2001). For this design a pipe velocity of 1.8m/s has been chosen and the expected discharge of the pump discharge is 3.5kg/s which translates to 0.0035m3/s. Cross section area of pipe  Area A= =0.55” Now applying Barlow’s formula and through substitution p = 2St/D t = 0.008m=0.3” The standard PVC pipe of ½”/0.84 will be appropriate. Storage tanks The design involves using 60000 liter plastic tanks being used and being laid on concrete slab. Plastic tanks of 60000l will be used in this system. The tanks will be laid on a concrete slab. The soil at the point where the tank is laid has a capacity of 240 kpa/m2. When the tank is filled with water force generated =60000x9.81=588600pa=588.6kpa In order for the tank to be accommodated by the soil area of slab required =  The tank is cylindrical in shape having a base area diameter of 3.5m The base area of tank =  Providing a slab of 10m2 The factor of safety will be =  Wind pressure calculations Tank height =  Surface area subjected to wind= With a wind speed in the approximated to 45.96km/hr= 12.77m/s The corresponding pressure using the pressure wind velocity chart =100pa Total force acting on the tank = 2180.5pa The force 2.1805kpa is acting at a 2/3 of the height of the tank. Taking the total weight of tank as to be 10.5kn Moment caused by wind =  Restoring moment from total weight of tank =  Therefore the factor of safety against toppling =  Excavation and fill works will be a very important aspect of the project bearing in mind that there will be introduction of water pumps. A number of design factors will play vital roles in shaping of earthwork with the design of pipes calling for careful planning (Gold Coast City Council p.5).With the elevations of the site being known, in addition there is need for discussion with surveyor with regards to the neighboring terrain so as to establish the exact points of laying the pipes. Before commencing on the earthworks it will be necessary to test the surrounding soil. Earthwork clearing needs to be minimized in conformation to the current regulations that have been put in councils. The clearing of trees is to be dedicated to the council as it is well placed to minimize disturbances that could result from this activity. References BIS-1742-1983 (1983). Sizing of RW Pipes for Roof Drainage Bureau of Indian Standards, New Delhi. CGWB. 2000. Guide on Artificial Recharge to Ground Water prepared by Central Ground Water Board, Ministry of Water Resources, Government of India, New Delhi. May. Dwivedi A. K. (2009). Domestic rooftop water harvesting- a case study. ARPN Journal of Engineering and Applied Sciences Gold Coast City Council(2005). Land Development Guidelines. Policy 11, Section 3 – Engineering Infastructure – Design Requirements. Gold Coast Planning Scheme Policies. Viewed 22nd October 2014. IE-NLC. (2006). Rain Water Harvesting and Water Management Proceedings of 22nd National Convention of Environmental Engineers, 11-12 November 2006, Organized by Institution of Engineers (India) Nagpur Local Centre, November. JAHMCO (2014). Float valves and switches. . Retrieved on 10th October 2014 From LRHF.(2001). A Report Domestic Roof Water Harvesting and Water Security in the Humid Tropics prepared by Lanka Rainwater Harvesting Forum under Domestic Roof Water Harvesting in the Humid Tropic, June. Mudrakartha and Chopade.(2002). Srinivas Mudrakartha and Shashikant Chopade Closing the Demand Supply gap through Rain Water Harvesting-A Case Study of Sargasan, Gujrat, India, Paper Submitted to-International Symposium on Artificial Recharge (ISAR-4), Adelaide, Australia, September. Rainwaterharvesting.org (2014). Components of a rainwater harvesting system. Retrieved on 10th October 2014 From< http://www.rainwaterharvesting.org/Urban/Components.htm> Ramset. (1997). Construction Industry Cataloge. Ramset Fasteners (AUST) Pty Limited, Croydon North, Victoria, Australia. Issue B. T, Oweis, A. Hachum. (2005). Water Harvesting and Supplemental irrigation for improved water productivity of dry farming systems in West Asia and North Africa. Agriculture Water Management. Brisbane Australia. Viewed 22nd October 2014. T.W.D.B. (2005). A Manual prepared by Texas Water Development Board Texas Manual on Rainwater Harvesting Texas Water Development Board, Austin, Texas, Third Edition. Read More