Bearing Capacity of Circular Foundation on Sand of Limited Thickness under Inclined Loading

Laboratory model test results for the ultimate bearing capacity of a circular surface foundation of diameter B supported by a dense sand layer of limited thickness (H) and subjected to inclined loading have been presented. For these tests, the H/B ratio for the sand layer was varied as 0.3, 0.5, 1.0, 2.0, 3.0, and 5.5 (which is considered large depth for sand). The load inclination (alpha) to the model foundation with respect to the vertical was kept at 0 degrees, 5 degrees, 10 degrees, and 20 degrees. For a given load inclination, the average inclined ultimate load per unit area, q(u(H/B, alpha/phi)), decreases with the increase in H/B. The ultimate average inclined load per unit area becomes constant [i.e.q(u(alpha/phi))] beyond a critical value of (H/B) approximate to (H/B)(cr). For the tests (H/B)(cr) was about 3. Based on the model test results, an empirical nondimensional reduction factor, R, has been developed to estimate the average inclined ultimate load per unit area at a given H/B(<= 3) from that obtained for the case at larger H/B[i.e.R = q(u(H/B, alpha/phi))/q(u(alpha/phi)) = f (H/B, alpha/phi)].