Experimental Investigation of Square Footing Resting on Sand over Gypseous Soils

Abstract

This study included (40) tests of loading a square footing (100*100 mm) resting on two layered soils (sand over gypseous soils) using a steel box with the dimensions of (900*900*500 mm). Gypseous soil was brought from Tikrit-University with gypsum content 61%. The tests were divided into two groups. The first groups included (4) tests for gypseous soil only by using the field and maximum densities (14.5, 18.75 kN/m3) respectively, without soaking and with soaking where gypseous soil lost a great value of its resistance. The second group included (36) tests of loading two layers of soil by replacing a layer of gypseous soil by sandy soil with relative density (30%, 60%, and 80%) and depths (B/2, B and 3/2 B). The results showed that the replacement process gave an improvement in the bearing capacity when the gypseous soil was compacted to field density and soaked with a relative density of sand (80%) while the other cases did not have any improvement. The results of loading the two layers of soil also show that the soaking of gypseous soil under the sandy layer affects on the resistance of sand through reducing it especially when the depth of sand was (B/2) this effect decreased gradually with increase in the depth of the sandy layer.

Keywords

• shallow foundation
• two layers of soil
• gypseous soil
• sandy soil