For Problems $1-4,$ refer to Figure $1.$ The site consists of $8$ ft of sand overlying $4$ ft of clay. The groundwater level is $4$ ft below the ground surface. Point A is located $2$ ft below the sand layer and is within the clay layer. A footing for a proposed building is to be constructed. The footing will be $5$ ft by $5$ ft at a depth of $2$ ft below the ground surface and the load on the footing is $400$ kips $.$ Point A is located below the center of the footing.

Figure $1.$ Subsurface conditions with building footing for Problems $1-4.$

$1.$ Determine the total stress, pore water pressure, and effective stress at Point A before excavation and construction of the footing.

$2.$ Determine the vertical stress increase at Point $\backslash ($ A $\backslash )$ due to the footing load using the procedure based on vertical stress at the corner of a rectangular loaded area.

$3.$ Determine the vertical stress increase at Point $\backslash ($ A $\backslash )$ due to the footing load using the procedure based on vertical stress at the center of a rectangular loaded area.

$4.$ Determine the vertical stress increase at Point $\backslash ($ A $\backslash )$ due to the footing load using the $\backslash (2$: $1\backslash )$ method.

For Problems $2-4,$ Caution: In most stress distribution solutions, z is the depth below the loaded area $($footing$)$ not depth from ground surface!