Pipes are often buried under the ground and placed in trenches that are backfilled. The weight of the pipe, the weight of backfill and the superimposed traffic loads if any, will then be transferred to the pipe. This will produce compressive stresses in the pipe material when the pipe is empty and there is no internal pressure to counteract these loads and the material may fail in compression if it exceeds the allowable compressive stress of the pipe material. The pipe should be checked for this possible failure. It is not a big problem for water pipelines, because such pipes are generally not laid very deep. Moreover, the steel pipes, the reinforced concrete pipes, and the cast iron pipes that are commonly used for transporting water are quite good in compression. The stresses produced due to external loadings, at present can be evaluated by using certain empirical formulae, as given below:
These formulae are based on the experiments carried out by
Marston, etc. at Lowa State College in the U.S.A.
a)
For pipes resting on or projecting above
the undisturbed ground in cohesion-less soil and cover with fills the
external load likely to come per unit length of pipe (W) is given
by : W = Cp. ¥.(D.D)
where Cp=a
coefficient, whose…
PLEASE FOLLOW THE BELOW FIGURES AND TABLES FOR FURTHER UNDERSTANDING THE STANDARD DEPTH OF EXCAVATION DEPTH FOR LAYING OF WATER SUPPLY PIPELINE ADJOINING ROADS:
- 1st figure will tell you about pipes resting on or projecting above the underground in cohesion-less soil
- 2nd image shows flexible pipes buried in narrow trenches
- 3rd image shows the rigid pipes buried in narrow trenches and thoroughly compacted with cohesion-less fills.
