The stresses induced by a surface load on a loose horizontal sand (ɸ = 30o) layer were found to be σv = 6.0 kPa, τv = 1.6 kPa, σh = 3.7 kPa, and τh = -1.6 kPa. By means of Mohr circles, determine if such a state of stress is safe. If so, what is the factor of safety? Use FS = τff(available) / τf(applied) for the definition of factor of safety.

N B 0 Horizontal The stresses shown in the figure are applied at a point in a dry clayey sand soil mass. A= 50 kPa and B= 125 kPa The shear strength parameters of the clayey sand are: c'= 9kPa and p'=29° 0=30° a) The value of the shear stress, T, is slowly increased. What value would cause shear failure at this point (in kPa)? b) At failure, what angle does the failure plane make with the horizontal (in degrees)?