1. Atwo-pole 60 Hz induction motor has a slip of2%on full load. The full-load speed is (a) 58.8 r/s (b) 3528 r/min (c) 60 r/s (d) 2880 r/min 2.The….

## calculate the average vertical stress increase in the soil layer below the center of the footing from z = 0 to 5B.

Vertical stress increase problem. As shown in Figure 3.27, a square spread footing is designed to support a column. The load on the column , including the foundation weight, is 600 kN. The dimensions of the foundation are B × B = 1.2 m × 1.2 m, and the foundation embedment is Df = 0.6 m. The subsoil is homogeneous silty sand with bulk unit weight of 18 kN/m³. Use the following methods to determine the vertical stress increases at z = 0, z = 2.5B, and z = 5B, and calculate the average vertical stress increase in the soil layer below the center of the footing from z = 0 to 5B. Note that z starts from the bottom of the foundation.

(1) Boussinesq method.

(2) Poulos and Davis method.

(3) 2:1 method.