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6. A structural engineer has hired you to design square concrete unembedded footings for a building, based only on capacity. Each footing will hold an axial load of 215 kN. Your technicians have conducted lab tests on specimens sampled from the site, and they report the following profile: a 0.6m thick sand layer over a 7mthick gravel layer (the gravel layer lies over rock). The lab report reveals that the friction angle of the sand is37 degrees, and that of the gravel is 42 degrees. Determine the size of one of the footings, in meters, such that the short term factor of safety against a capacity failure is as close to 3 as possible, but still larger than 3and smaller than 3.2. Express your answer with a resolution of 0.1 meters. That is, values of B of 1.2, 2.3,3.4m, etc., for example, are acceptable, whereas B values of 1.21, 2.32, 3.43m, etc., for example, are not.Check your answer with this one: Answer: B = 1.4m (FS = 3.15).

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