Soil Deformation around Prestressing Bed

[JohnRwals]

Hello!

Recently I found crack lines along the contact surface between concrete foundation
and soil around the stressing concrete block after prestressing force, 1000kips, was applied.
First I thought this was failure around prestressing beam line.
But, this could be elastic response of soil.
Isn't it normal to see this gap/crack open and close
as the prestressing force is applied and released?
Or, shouldn't this happen at all because soil/foundation should be stable?
I am asking this question because I am not familiar soil mechanics.
This seems to be typical ELASTIC soil reaction to the huge force rather than the beginning of failure.

Thanks for your time!

JRW

 

[KootK]

Or, shouldn't this happen at all because soil/foundation should be stable?

Everything deforms under load, including the soil.

This seems to be typical ELASTIC soil reaction to the huge force rather than the beginning of failure.

Note that the response of soil to load is very rarely elastic. There is usually both non-linearity of response and permanent set.

Based on the information provided, I don't have the ability to say whether or not the observed movement represents a problem.

 

[JohnRwals]

Let's assume 10'x10'x5'(depth) concrete blocks are used to resist prestressing force.
As prestressing force is applied and released repeatedly, I can sometimes see 1/8" wide crack lines along the interface between concrete blocks and soil.
In fact, I can see cracks only when applied prestressing force is very large.
My question is whether this system is acceptable as long as cracks are within 'reasonable' width.
In my opinion, this problem is not failure but mainly related with elastic soil response.
Therefore, as long as cracks are not exacerbated, I think this prestressing system is stable.

Any advice?

JRW

 

[HTURKAK]

If we assume 10'x10'x5'(depth) concrete blocks,

The wt of block = 10' x 10' x 5' x 145 lb/ft3 = 72 kips

Total Resistance assuming friction factor 0.4 and passive thrust 15 kips/ ft 2

Fhr= 72 X0.4+50X15=780 Kips << prestressing force= 1000kips

If you can provide more accurate data together with a section for both abutments you may get better responds..






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