SETTLEMENT OF FOOTINGS ON NON-PLASTIC SOILS USING FIELD TEST DATA

Abstract

The settlement of footings on non-plastic soils such as sands and silts is generally based on the results of field tests rather than laboratory tests because of the great difficulty in getting the undisturbed samples. The estimation of settlements in such soils are done by semi-empirical methods. In view of the highly conservative design rules that are widely accepted, many foundations on sands are undoubtedly overdesigned. In order to achieve more economical design, it is therefore necessary that the design, methods be continuously reevaluated by the indipendent study to the degree that is possible. The present work is concerned with a comparitive study of estimation of • settlement of footings on non-plastic soils using cone penetration tests, standard penetration test and plate load test at different locations within the University Campus. Assuming some typical data, results are obtained for settlement estimation by various methods such as De Beer and Marten (1957), Sclunertmann (1978) and IS Code method. The actual field observations were made by plate load test. The settlement computed by De Beer and Marten method gives conservative values in comparison with schmertmann method for different net foundation pressure and width of foundation. The trend of the pressure - settlement curves obtained by schmertmann method is reverse in comparison with De Beer and Marten method. The results from plate load test are less in comparison with schmertmann method. The IS Code method over estimates the magnitude of settlement in the case of loose and medium dense sands. The settlement ratio by Terzaghi-Peck relation gives conservative value in comparison with Bjerrum and Eggestad and Arnold method. Correlation between cone resistance, and standard -penetration resistance, standard penetration resistance and Dyanmic cone penetration resistance are also established