surcharge estimating
surcharge estimating
(OP)
Hello
I have to perform e sheet pile design for an excavation.
The building to be retained is a 3 storey r/c structure with pad foundations.
Dimensions of the existing building in plan 9x32 m. The sheet pile wall will be along its long dimesion (32 m).
Anyone has any idea for calculating the surcharge loads coming from the pads?
In the previous designs I have had, the existing building foundation (to be retained)had been strip footing, which allowed me to restrict the design in 1 m pile wall.
Is this case different because of the concentrated loads coming from pads?
Thanks in advance
I have to perform e sheet pile design for an excavation.
The building to be retained is a 3 storey r/c structure with pad foundations.
Dimensions of the existing building in plan 9x32 m. The sheet pile wall will be along its long dimesion (32 m).
Anyone has any idea for calculating the surcharge loads coming from the pads?
In the previous designs I have had, the existing building foundation (to be retained)had been strip footing, which allowed me to restrict the design in 1 m pile wall.
Is this case different because of the concentrated loads coming from pads?
Thanks in advance






RE: surcharge estimating
RE: surcharge estimating
Actually our office deals regularly with these projects.
We get the geotechnical report from a licensed geotech but the surcharge evaluating is our issue.
As I mentioned, the cases when the existing foundation is a strip foundation or even a mat foundation is clear because the loads are treated either uniform or surface loading respectively.
Even in this case the concentrated load can be converted into uniform (conservatively) which has been our practice.
I am interested for any more detailed method concerning pad foundations.
I'm focusing in the "Boussinesq" concentrated load pressure
RE: surcharge estimating
RE: surcharge estimating
RE: surcharge estimating
In the past I have done a simple trial wedge analysis and then converted the loads from active to at-rest since that is the soil condition you are working with.
RE: surcharge estimating
I personally like the "conservativeness" of the geotechnic designs.
Not to mention that the discuss focuses on the "plane deformation state", or 2d calculation.
Anyway, I will try to make a 3d model of the soil in
SAP 2000 modeling as solid(just for fun).
The question is at defining "E" (deformation module).
RE: surcharge estimating
Sometimes you will need to underpin the existing footing and choose a rigid earth retention solution like a tiedback slurry wall.
As a quick guide, however, you may use 250 psf uniform surcharge for every 1 story of RC building. Attached are the surcharge charts to estimate your actual lateral stresses.
RE: surcharge estimating
Anyway, the analysis methods we've been using so far allow the soil yielding.
On the other side,we monitor the max. deflection of the sheet pile not to overpass the allowable value.
I don't think if it's anything wrong with that.
RE: surcharge estimating
As FixedEarth said, this may be an underpinning job rather than a sheeting job. Don't forget any required lateral support for underpinning.
www.PeirceEngineering.com
RE: surcharge estimating
RE: surcharge estimating
As a curiosity, I did a quick check on lateral stresses of 750 psf uniform loading near a 30 ft excavation and then compared it to a wall line footing of 8k/ft and isolated column load of 100 kips at a distance of 10 and 20 ft respectively. Guess what--the earth thrust values are within 15% of each other.
As you stated, if you limit the deflection then that ofcourse would help. However, if you have to dewater the bottom of the excavation and you have granular soils & other nearby structures, be extra cautious with soil settlement effects.