Design a shallow foundation

Design a shallow foundation (its shape, dimension and placement) in the soil site shown below. The sand above the water table has a unit weight of 17 kN/m² and below the water table its saturated unit weight is 19 kN/m, its angle of friction is Ⓡ = 25°. The clay layer has a saturated unit weight of 20 kN/mº, its cohesion is 20 kN/m2 and angle of friction is 30°. The Poisson's ratio and modulus of elasticity for the sand are 0.25 and 20 MN/m², respectively; for the clay, they are 0.3 and 30 MN/m². The clay is an overly consolidated clay with a compression index Cc = 0.26 and its recompression index can be estimated as Cr = 0.2Cc, its pre-consolidation stress is 160 kPa and its original void ratio is 1.2. The foundation is supposed to support a dead load of 500 kN and a live load of 400 kN. 1 m V 1 m sand 4 m clay Rock • Use the Load Resistance Factor Design (LRFD) method for strength requirement, based on AASHTO's LRFD recommendations. • The service requirement is that the allowable settlement should not exceed 50 mm.