Compose a 2500 words essay on Labour Based Road Construction Methods. Needs to be plagiarism free!
When initially planning such a project it should be assessed whether building materials like gravel, sand, and water are available at distances close to the work site. Facilities for future maintenance are also deciding criteria. The reduction in a number of accidents and also the total economic development of the region due to the construction of this road also need to be considered.
The Pit method involves creating holes in existing walls and inserting needle beams with bearing plates through these holes resting on crib supports. The excavation is done to the new level and filled with concrete. (Singh Bharat and Gupta DL, 1999)
(i) Gravity walls which resists overturning by virtue of its entire mass. Walls of this type are economical for heights up to 2 to 3m. The base width should be 0.40 to 0.65 times the overall height. The flat face should be given a slight backward slope of 1 in 24 to account for the forward push that would inevitably follow. This combined effect provides the best counter for earth pressure. Vertical joints should be located in concrete walls at distance of 20m. ( Day Robert W, 2006)
(ii) Cantilever walls which depend on the resistance to withstand bending moment of the cantilevered slab about its base. These are suited for heights between 4.5m to 6m. The width used is between 0.4 to 0.65 times overall height. The wall thickness for single layer reinforcement is 150mm and 230mm for front and back reinforcement. Expansion joints are to be provided to account for the thermal expansion and the resulting movement. Spacing’s between 20m to 30 m are considered for British conditions.
(iii) Counterfort walls prevent overturning of the walls by the reactive force exerted by the earth located behind the wall.