Question 5.1: The depth of water in a well is 3 m. Below the bottom of the...

The formula for the submerged unit weight is

Since the soil is saturated,

For sand, \gamma_{b}=\frac{9.81(2.64-1)}{1+0.25 \times 2.64}=9.7 kN / m ^{3}

For clay, \gamma_{b}=\frac{9.81(2.70-1)}{1+0.20 \times 2.70}=10.83 kN / m ^{3}

Pressure at point A

(i) Total pressure =3 \times 9.7(\text { sand })+6 \times 9.81=29.1+58.9=88 kN / m ^{2}

(ii) Effective pressure =3 \times 9.7=29.1 kN / m ^{2}

(iii) Pore water pressure =6 \times 9.81=58.9 kN / m ^{2}

Pressure at point B

(i) Total pressure =5 \times 9.7+2 \times 10.83+10 \times 9.81=168.3 kN / m ^{2}

(ii) Intergranular pressure =5 \times 9.7+2 \times 10.83=70.2 kN / m ^{2}

(iii) Pore water pressure =10 \times 9.81=98.1 kN / m ^{2}