Model pile testing in carbonate sediments of the Red Sea

Abstract

This paper presents the results of an experimental program of model piles in carbonate soil from the Red Sea. Direct and triaxial shear tests of the soil indicated very high effective angles of friction. These angles were greatly affected by confining pressures and relative densities. Results of model pile tests with and without applied surcharge pressures showed early peak frictional resistances for different relative densities. The peaks were stronger in the former case and followed by strain softening down to "stable" residual values. These residual values were found to be comparable with limiting values of friction predicted on the basis of limiting compressibility indices. Also, it was noticed that at the beginning of penetration, most of the applied load was taken by end bearing, but frictional share increased with further penetration until it took more than 50% of the load. Calculated values of the lateral soil pressure coefficient, Ks, showed a continuous decrease with penetration and it stabilized at deeper depths. Statistical correlations were found to relate Ks with the L/D ratio and surcharge pressure. Key words: ocean soil, sand, shear strength, pile, model test, bearing capacity, friction, uplift, active and passive earth pressures.