Medium gauge plastic sheeting with 300 mm laps.The subgrade strength will decrease as moisture content increases so protection may be required if it is to left exposed for any length of time. Soil stabilisation methods such as the use of cement, bituminous materials or chemicals.
Compacting subgrade to a high dry density.Removal of poor material in cuttings and replacing with selected fill.The strength of the subgrade can be achieved by using the following techniques: The required thickness of the pavement is determined by the subgrade strength, so it is desirable to make the subgrade as strong as possible. Subsoil drainage should be provided to deal with seepage through pavements and verges, from higher ground and a result of the seasonal rise and fall of the water table. Sand drains alongside the road are used to intercept ground water. Sand wicks are sand-filled boreholes beneath the road embankment that give greater stability to the soil by decreasing the length that water has to travel in a drainage path, so dissipating water pressure.
#Merge town buildings pictures full
If the cost of full or partial excavation of subsoil is uneconomical and would be likely to result in consolidation, sand wicks or sand drains may be used. Most earthworks are formed by cut-and-fill, and the type of ‘fill’ material must be considered, not only in terms of its physical properties, but on the conditions in which it is to be used, and the methods of compaction.ĭepending on its quality, compressible subsoil may be removed or stabilised. It is essential that the strength of the subgrade is tested prior to earthwork beginning. Below the formation level, the soil is known as the ‘ subgrade’. This is usually done using a tractor shovel, grader or bulldozer. It involves the removal of topsoil, along with any vegetation, before scraping and grading the area to the finished ‘formation level’.
Junctions, hammer heads, turning bays and intersecting curves are laid out in a similar manner.Įarthwork is one of the major works involved in road construction. The line operator moves the string up or down until the bubble is centred. The level of each profile board is controlled using a line level which is a short spirit level hung from a nylon string. By placing the traveller in the sight-line between two level boards, it can be seen whether or not the excavation has been carried out to correct levels and adjusted accordingly. A profile board with a fixed height, called the traveller, is used for controlling the excavated levels between these profile boards.
#Merge town buildings pictures series
A series of boards that show the exact level 1 metre above the completed construction level are placed at intervals along the proposed line of the road. This is carried out following the dimensions specified in layout drawings.Ī commonly used setting out procedure is the profile board method. Very broadly, the construction of roads can be described by three processes:
Modern roads tend to be constructed using asphalt and/or concrete. Road construction techniques were gradually improved by the study of road traffic, stone thickness, road alignment, and slope gradients, developing to use stones that were laid in a regular, compact design, and covered with smaller stones to produce a solid layer. The first Roman roads were stone paved, built in North Africa and Europe for military operations. The methods of constructing roads have changed a lot since the first roads were built around 4,000 BC – made of stone and timber. 5 Related articles on Designing Buildings.
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