Cemented soil allowable bearing pressure 2

[m1208]

Hi:
I am working on an old project and they have classified the soil as "Cemented Soil" under the foundation of the building. Table No. 29-B of the Uniform Building Code does not list the "Cemented Soil" in the table. I was wondering what soil class I can use for the allowable foundation pressure.

 

[BUGGAR]

Depends on the cement content. Find the original specs.

 

[oldestguy]

Get some undisturbed samples and test for unconfined compressive lengths. That's usually the allowable bearing strength with a nice safety factor.

 

[r13]

Are you engaged to perform building alteration, or addition? It is great if you know the original allowable bearing strength, but may not be necessary with help from an experienced geotechnical engineer. Depends on the age of the building, and its weight, the soil below footing has already densified to an extent, which provides a source of additional strength, which can be utilized for additional weight. Talk to a geotechnical engineer, you need one anyway.

 

[cvg]

is this caliche or cement treated soil?
if caliche, I would be hesitant to rely on it unless you know the depth and extent and quality

 

[geomane]

The cement treated soil may have been used just to improve the upper 12-18 inches due to moisture problems or some other issue encountered during construction. Depending on the size of your footing, the bearing pressure exerted by the footing, and the depth of the cement treated soil layer, you may need to investigate the allowable bearing pressure of the soil beneath the cement treated layer. Need to to check bearing capacity for a punching shear failure if the cement treated layer is thin. Settlement potential should also be checked.

 

[EireChch]

I dont think this is a man made created cemented soil as others are thinking.

We encounter (naturally) cemented soil all the time. SPTs are generally in the order of 50+. When we switch to coring and take samples for UCS, the UCS is generally just at or less than 0.6MPa, which BS would class as a soil.

Review the logs to confirm SPT values as an absolute minimum but taking an allowable bearing pressure for a dense granular soil should be fine.

And again, at the end of the day the allowable bearing pressure should (in most cases) be based on the settlement criteria being met.