Experimental Study of Laterally Loaded Model Steel Piles in Two-Layers Soil System

This paper presents the results of laboratory model tests conducted to study the behavior of laterally-loaded model steel piles installed in a two layered soil system. Loose sand above clay deposit (case#1) and clay above loose sand deposit (case#2). For each case the interest was being on the thickness of the upper soil layer. The soil layers consisted of medium stiff clay which was imported from the Blue Nile river side and the loose sand was imported from North-west of Omdurman-Khartoum state. These tests were performed at the Faculty of Engineering, University of Khartoum in Sudan. The pile response is presented in terms of load-deflection curves, bending moment, shear force and soil pressure profiles and the load-maximum moments curves. The load-deflection curves are generally nonlinear for the two cases. For case#1, The ultimate lateral pile capacity decrease with increasing the thickness of sand layer above clay deposit and for case#2, the ultimate lateral pile capacity increases with increasing the thickness of the clay layer above sand deposit. The point of maximum moment and the point of zero shear force occurs at the same depth below the soil surface for both cases. The maximum bending moment occurs at a depth of 0.31L below the soil surface for both cases (L is the embedded length of the pile). It is noted that the deflection is dominant in estimating lateral pile capacity in layered soil system. Moreover it is important to consider the bending moment and the shear force, specially in the upper zones of the soil. Since the formulation of the soil in nature is in form of layers of different thicknesses and characteristics, it is important to make more researches on the effects of soil layering system on pile behavior.