For how long will a structure settle? 2

[WWTEng]

I presume that this an open ended question but generally speaking, would you think that a building that has been around for 6-7 years has nearly as much as it could?

Thank you.

 

[drawoh]

WWTEng,

How long did it take to fix the leaning tower of Piza?

Or have they?

--
JHG

 

[WWTEng]

@ drawoh : I saw that coming

 

[Eldorado]

In my part of the country the expansive clays never stop moving. Two years ago we had an extremely wet year after about 6 years of drought and any building on the expansive soils was moving. THe more site improvements, the less the movement, but they moved. There are some buildings built on limestone. For these buildings there is little movement even on a properly prepared pad of fill 5' thick.

For a building built 6 to 7 years ago on a properly prepared pad not located on expansive soils, I wouldn't expect significant movement if the fill was less than 5'. If you use the 1% settlement rule, that's about 5/8". Obviously, if there is a substantial amount of fill and for steep sloped fill sites, settlement will be more dramatic and may take longer to taper off.

If the building was built on a deep excavation (perhaps 25' or more), you may exhibit a rebound of the over-consolidate soils and that could take a very long time to stabilize. I have seen the soil at the bottom of parking garages constructed after removing large quantities of overburden "grow" for many years.

 

[cvg]

re: leaning tower of Pisa, subsidence and settlement are not really the same thing. and expansion of clay soils isn't either. normal long term consolidation (settlement) under a building foundation should not take more than a few years. other factors such as depth of cut or fill, fluctuating groundwater levels, leaking pipes, earthquake, subsidence, collapsing alluvial soils, land sliding and fissuring all might cause additional ground movement but are not typical.

 

[Ron]

The soil conditions will dictate how long the settlement will continue. As an example, the Palace of Fine Arts Cultural Center in Mexico City has settled over 15 feet (that's feet, not inches) since its construction about a hundred years ago.

Consolidation settlement often takes many, many years to reach a tolerable level of continued settlement (often settlement will continue but decline in its rate when primary settlement is complete and secondary settlement takes over).

Look at the geotech report (assuming there is one...if not, get one!) and post a soil profile for us to see (along with your column loads).

 

[cvg]

Mexico City is subsiding due to drawdown of the aquifers causing everything in the basin to drop in elevation. this is not normal settlement / consolidation due to construction of a building. the subsidence occurs over the entire region and everything is snking. New Orleans is another example of this phenomena
Parts of Phoenix Arizona have settled over 17 feet in the last 60 years. this has caused drainage courses to reverse direction and created ground fissures. It was caused by overpumping, not by foundation loads.