Lateral stress on Vertical settlement of soil

[kushtian]

Hi,

Can someone suggest me to some 'specific' literature where the effects of lateral stresses on vertical settlement have been discussed?

Thanks in advance.

 

[BigH]

Might want to check out three-dimensional consolidation . . . I remember a number of books that had 3-D - one, in particular involved a guy named Lee and it was published in the early 1970s. However:

http://www.math.purdue.edu/~santos/research/mi_modelo_con_jose/biot_JAP_1941_consolidation.pdf

 

[kushtian]

Thanks BigH.

I actually found the answer by analyzing this paper: Handy, Richard L. "Does lateral stress really influence settlement?." Journal of geotechnical and geoenvironmental engineering 127.7 (2001): 623-626.

But the funny thing this conception is probably wrong here. Without pore-water change we can't have settlement change.

 

[fattdad]

I guess to the extent that there is lateral stress away from the vertically loaded area, there remains a component of vertical stress. Clearly the vertical stresses adjacent to the loaded area will trigger some vertical consolidation (compression if elastic).

If you just consider the vector, then you could approximate the settlement along the vector line using 1-D (or elastic) theory. You will likely get the magnitude correct, but may overstate the time, as Cv is likely isotropic and the length of the drainage path is uncertain.

Just a few thoughts. . .

f-d

ípapß gordo ainÆt no madre flaca!

 

[BigHarvey]

Interesting subject !

The answer is certainly yes both for consolidation and for elastic compression.

On the consolidation aspect, it is a fact that in vacuum consolidation, surcharge due to the void is far more efficient than a classical fill surcharge. What is the difference between the two ? Void is isotropic and fill surcharge isn't. Nobody dared investigate it up to now...

A "normal" "elastic" soil will show horizontal stress = vertical stress x 0.5. When you apply a ground improvement technique to these granular soils they will show the 0.5 ratio go ut to 3 or 4 (you can observe a decrease of the FR when performing CPT although the nature of the soil has not changed during the process of mass compaction !)and you often observe settlements far lower than those calculated. Hence there must be some influence of the lateral stress not on the settlements but on the settlement computation methods !

Nice subject for a thesis ! What do you think BigH ?

 

[kushtian]

Hi BigHarvey,

I don't think lateral stress, alone, can change the vertical settlement. If you put lateral stress, it will densify the soil and certainly rise the pore water pressure up. I have modeled it with a finite element soft. Showed no change in settlement.

 

[fattdad]

errata: I said, "as Cv is likely isotropic and the length of the drainage path is uncertain." Meant, Cv is likely anisotropic.

Carry on. . .

f-d

ípapß gordo ainÆt no madre flaca!

 

[BigH]

Intuitively, the lateral stress must influence the amount of vertical settlement. As BigHarvey pointed out, ground improvements increase the "locked-in" lateral stresses - compaction with a large vibratory roller will increase the normally accepted 0.5 to over 0.7 or more. For a material to decrease in vertical "thickness" it has to expand in the horizontal directions as well. The larger the horizontal stress - at rest or "locked-in" - the more resistance it has to being squeezed - picture a soil, one having relative density of, say, 50% and the other of 85% - certainly, you would expect that the settlement under the footing in the latter case would be less than the former. This also manifests itself in compression testing. It is well known that when a lateral confining pressure is added (triaxial) compared to the "open air" test, the strength will be higher. While this might be construed for cohesionless soils, it would also apply to cohesive soils - think normally consolidated vs lightly overconsolidated to heavily overconsolidated soils (where you, Kushtian, might actually have negative porepressures develope).

Again, I would relate back to 3-D consolidation theory . . . BigHarvey - going for a Ph.D? or double?

 

[BigHarvey]

BigH, I must say I would love it just to pick the golf class which I missed because of a conflicting soil dynamics or rock mechanics class timetable during my NU time ! As a contractor I can spend enough money on research projects who help me to continue finding this profession fantastic