Stiffness considering embedment and native soil

The soil stiffness is based on the width of the trench, the embedment material and trench wall material, their densities or percent compaction. As explained in an earlier blog

E' = Sc . E'b
 Sc values can be obtained from the above table or the above graph or with the following formula

This enables us to obtain the value of E' the soil stiffness ,duly taking into account the native soil stiffness and embedment or backfilling soil stiffness.This is the most important factor for determining deflection of flexible pipes,particularly those which do not have a high pipe stiffness.
The important finding in the last decade is to consider stiffness of the soil in which the trench is dug and that of the soil in which the pipe is embedded.It is also clear that it may not be worthwhile to increase compaction beyond a point as it is expensive and it may be better to borrow and replace the soil..
We will consider these issues in detail after we deal with live loads and soil loads.
However by requests from many sources we are first moving to deal with the subject of how intermittent supply can be converted into  continuous supply.