Guidelines for the Design of Bored Concrete Piles in Expansive Soils of Sudan

This paper summarizes the outcome of a research program carried out in Sudan to provide guidelines for the design of bored concrete piles in expansive soils. Design parameters were developed. The parameters under consideration are the adhesion, bearing capacity and uplift factors. The first two factors were obtained from laboratory adhesion tests and full scale pile load tests while the third was obtained from model tests on small piles. Experiments showed that the adhesion factor was 0.45 for moisture content below the plastic limit and linearly increased with moisture above the plastic limit. The end bearing capacity factor was back calculated from instrumented full scale load tests and a value of 9 was attained. Uplift factor was found to be 0.2 from model pile tests.  The results of the full scale tests showed that the compressive axial capacity of  piles installed in expansive soil were significantly reduced by wetting. Accordingly, high value of factor of safety (minimum 4.0) is recommended for the design of piles in these soils.