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# help me understand this graph for reducing surface load on pipeline

## help me understand this graph for reducing surface load on pipeline

(OP)
This graph shows how ground pressure is reduced when you add steel mat on the ground surface.

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.

### RE: help me understand this graph for reducing surface load on pipeline

#### Quote (AskTooMuch ....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?)

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

#### Quote (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.)

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 ..

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