help me understand this graph for reducing surface load on pipeline

[AskTooMuch]

This graph shows how ground pressure is reduced when you add steel mat on the ground surface.
I downloaded this from CEPA website.

If I have 80 psi load and I add 1" steel mat on the surface, it will become just 38 psi (on the surface) for soil with 150psi modulus of elasticity (E').
Am I right with my understanding?

Why is the ground pressure bigger as soil E' becomes higher?
For same example above, for 1" steel mat, E'=1000 psi, 80 psi ground pressure didn't reduce at all.

 

[HTURKAK]

Yes!! ...you are right !!...


The slab in this case steel slab will bridge the trench and the load is distributed with a similar concept of beams on elastic foundation. In order to obtain more evenly load distribution, steel plate stiffness shall be higher than the soil . Notice that , for increased slab thickness , you get better soil stresses.

If this is for road crossing, you may consider also to provide a space at the top of trench say 25 mm , or the last soil layer will not be so compacted for the road crossing zone ..