DHARMSTRESS DISTRIBUTION IN SOIL 389
10.14 A strip load of considerable length and 1.5 m width transmits a pressure of 150 kN/m^2 to the
underlying soil. Determine the maximum principal stress at 0.75 m depth below the footing, if
the point lies (i) directly below the centre of the footing, and (ii) directly below the edge of the
footing. What is the absolute maximum shear stress and where does it occur?
10.15 A circular footing of 1.5 m radius transmits a uniform pressure of 90 kN/m^2. Calculate the verti-
cal stress at a point 1.5 m directly beneath its centre.
10.16 A rectangular area 4 m × 6 m carries a uniformly distributed load of 100 kN/m^2 at the ground
surface. Estimate the vertical pressure at a depth of 6 m vertically below the centre and also
below a corner of the loaded area. Compare the results with those obtained by an equivalent
point load method and also by dividing the loaded area into four equal parts and treating the
load from each as a point load. (S.V.U.—B.Tech. (Part-Time)—Sept., 1983)
10.17 A 4.5 m square foundation exerts a uniform pressure of 180 kN/m^2 on a soil. Determine the
vertical stress increment at a point 3 m below the foundation and 3.75 m from its centre along
one of the axes of symmetry.
10.18 The plan of a foundation is shown in Fig. 10.28 (a). The uniform pressure on the soil is 45 kN/m^2.
Determine the vertical stress increment due to the foundation at a depth of 4 m below the point
A.
2m
1m
A4m 4m 4m3m3m(a) (b)
Fig. 10.28 Plan of loaded area (Prob. 10.18)
[Hint: In order to obtain a set of rectangles whose corners meet at a point, a part of the area is
sometimes included twice and later a correction is applied. For this problem, the area must be
divided into six rectangles, as shown in Fig. 10.28 (b). The effect of the shaded portion is included
twice and must therefore be subtracted once).
10.19 A ring foundation is of 3 m external diameter and 2.00 m internal diameter. It transmits a
uniform pressure of 90 kN/m^2. Calculate the vertical stress at a depth of 1.5 m directly beneath
the centre of the loaded area.