FOUNDATION DESIGN WITH MODERATE LIQUEFACTION POTENTIAL 2

[BTStructural]

Hello,

I have a three story, mixed use wood-framed project I'm working on in a relatively high seismic area where the soil is a sandy soil and water table is at 7'. Building will be built over a crawlspace. The soils engineer stated that the liquefaction potential would be moderate here based on these conditions and recommended no isolated pad footings but that continuous footings be used to help reduce differential settlement in case of liquefaction from a seismic event. The rub here is that, in my mind, to span over compromised soil locations you should design the foundation more like an expansive foundation with the slab above/connecting all of the tie-beams. The soils engineer has told the owner this isn't necessary and the owner naturally doesn't want to spend the extra money. Do I keep the slab above the tie-beams or just go with what the soils engineer said?

 

[BAretired]

Follow your instincts.

BA

 

[MotorCity]

You should talk to the geotechnical engineer to express your concern. I would be curious how the geotechnical expects the foundation to be supported by soil that has liquefied. At some point, it becomes risk vs reward.....you will want to document that the owner is betting against foundation failure due to liquefaction.

 

[rowingengineer]

What is the use of the slab, if a carpark sounds ok, if a use area I would expect a bit more. We mostly work to the NZ codes and they have some good info in this area.