Friday, 10 December 2010

Survey and Testing:

Survey for road or for existing road is a must. It is already brought out that water is the worst enemy of road after construction. Survey would make the engineer know filling and cutting needed at every spot so water won't accumulate on the road.
Also engineer can make best use of available earth for filling low area with earth obtained from cutting high area. Construction of every part of road including storm water drainage can be constructed ideally.
Testing of earth in the area of road and construction material would ensure best use of available material is made. Clay testing is the most important. After all load and vibrations of traffic are borne by the clay. Clay may be in layers and all layers may not have same properties. Hence, clay in each of the layers should be tested separately. Ideal clay is which doesn't absorb water. Next quality is which absorbs some water but doesn't swell. In practice this condition hardly exists except when road is constructed over plain hard rock. Even sand absorbs water and swells. A compromise is needed based on locally available clay. However, under no circumstances less than disintegrated rock (murrum in local language) should be allowed in road construction. Black cotton soil is the worst material for road construction. Every citizen can understand and test soil using transparent glass and water. Method is simple and like this. Take a few glasses, separate for each type of clay and one more for washed and dried sand. Fill all glasses with clay to approximately half of their capacity. Mark the level of clay with marking pen. Ensure level is same and clay is compacted to the extent there is no void. Place all on a table and fill with water. Leave this for approximately 24 hours. When one returns to check the result in increase in lever of clay would be noticed. This increase is different for different clay. Clay which swells the least is the best among the samples.
Basic reason for bad condition of road (road in potholes) during rainy season is use of bad clay in formation and various layers of road. Formation is the lowest part of the road. It may be formed by cutting and filling. Cutting provided better formation as the top earth is generlly low quality. Even in low areas cutting becomes necessary due to bad quality of existing earth. Before work starts on road testing of clay at this level should be undertaken and if satisfactory road construction should start.

No comments:

Popular Posts