Question

Determine the net allowable load and gross allowable load for a square footing 2m side, 1m deep. Assume FOS = 3y = 18kn/m, 0 = 25, C = 15KN/m?.​

Answer 1

Answer:

Q.No.1- A square footing of 2.5m by 2.5m is built in a homogeneous bed of sand of unit weight of 20 kN/m3 and an angle of shearing resistance of 36". The depth of the base of the footing is 1.5m below the ground surface. Calculate the safe load that can be carried by a footing with a f.o.s of 3 against complete shear failure. Use Terzaghi's analysis.

Solution

Given that

B=2.5m

D= 1.5m

y= 20 kN/m3

Ø=36,

Since the soil is dense, the footing is likely to fail by general shear failure. From table, the values of bearing capacity factors are:

Nc=65.4, Nq= 49.4, Ny=54

G = yD Also, o =

Since, c= 0,

Or,

qf = y D Nq + .04y B Ny

qnf = y D (Nq - 1) + 0.4 y B Ny

= 20 * 1.5(49.4 - 1) + 0.4 * 20 * 2.5 * 54

= 2532 kN/m3