[/indent]A square foundation supports a column load of 800 kN. The soil beneath the footing is generally homogeneous. If the foundation bearing pressure from this load is reduced from 400 kPa to 100 kPa (the column load remaining constant), the change in stress at a depth of 3 m below the foundation center will be most nearly:D. an increase in stress of 20 kPa

A. a decrease in stress of 20 kPa

B. a decrease in stress of 10 kPa

C. an increase in stress of 10 kPa

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One of my old concrete design books references ACI-15.2.2 as a possible reference for sizing footings. Any help in locating a document that explains that formula would be appreciated. Thanks.