soil pressures from a nearby structure? 1

[mats12]

Im dealing with a new house and a garage next to it. Garage also has basement, but house doesnt.
Garage and house are seperated by dilatation (5 cm). House foundation is on RC slab (slab on grade).

Im wondering... since house is next to garage - i should design a garage concrete basement wall (25 cm thick) on soil pressures + pressures from the nearby object (house). Is this correct?

contact pressures under grade on slab is cca 70 kN/m2. Lets say soil coefficient is ko = 0,5. Does that mean I have to consider 70 x 0,5 = 35 kN/m2 pressure on the concrete wall?

 

[Ron]

Yes

 

[mats12]

tnx, how far should structure 1 be away from structure 2 so you dont have to consicer such pressures? maybe 45 degrees? what happens to pressures then - do they dissipate?

Tnx for elaboration.

 

[Nor Cal SE]

This isn't an exact science, but I would say an offset equaling a 1-to-1 horizontal-to-vertical ratio or greater would be sufficient to consider the adjacent structure as not having impact on your retaining wall. For instance, if your retaining wall extends 12 feet into the soil, then I would say 12-ft or greater lateral distance from that retaining wall to the nearby structure's wall would suffice to assume no adjacent structure influence.

This is of course a generalization. Geotech engineers might have additional thoughts that account for soil type, etc.