Several cone penetration tests have been conducted at a site underlain by a young, normally
consolidated silica sand deposit. Based on these tests, an engineer has developed the following
design soil profile:
This soil has an average unit weight of 18.1 kN/m3 above the groundwater table and 20.8 kN/m3 below. The groundwater table is at a depth of 3.1 m. An office building with a parking structure
is to be built at this site with ASD column loads of 400 to 1,500 kN and service loads of 380
to 1,100 kN. Square footings are to be used at a depth of 1 m. Using these data, create design
charts for both serviceability and ultimate limit states using ASD with a factor of safety of 2.5
and a design life of 50 years.
Hint: In a homogeneous soil, the critical shear surface for a bearing capacity failure extends
to a depth of approximately B below the bottom of the footing. See Chapter 4 for a correlation
between qc
in this zone and f′.