Stability Analysis of Rock-Socketed Piles on Inclined Slope: Case Study on Conveyor Belt Foundations of Dangote Cement, Ethiopia

This study was carried out the stability analysis of rock-socketed pile on inclined slope at Dangote Cement (Ethiopia) around C1-12A, C1-13A and C1-14A Conveyor Belt foundation. The Conveyor foundations were founded on the natural inclined slope which passes through rugged topography and faces frequent slope stability problems. The study identified and analyzed the stability of slope by determining the geological and geotechnical properties of materials which compose the critical slope section. Detailed field work was done to collect a sample for laboratory tests such as moisture content, grain size analysis, Atterberg limit, compaction test and direct shear test. Based on the field manifestations and secondary data from different sources the critical slope section was identified for stability analyses. The slope stability analysis was made by three-dimensional finite element method, Rocscience based RS3 software. The slope stability analyses in terms of safety factor for both dry and saturated condition were analyzed. The analyzed results showed that, for saturated conveyor belt with rock-socketed pile, the factor of safety was 1.648 and stable. Even though, the factor of safety was stable, it was deducted from 3.698 for dry condition to 1.648 for saturated condition. Therefore, the stability of rock-socketed pile on inclined slope was highly depending on the raising of ground water table in the rainy season. Based on the identified slope stability governing factors, the proper drainage system such as surface drainage (i.e. furrows and ditches) which can prevent infiltration of rainfall and flood into the slope and subsurface drainage (i.e. horizontal and inclined drain pipe) which reduce the raising of groundwater was recommended. The stability of pile foundation in terms of bearing capacity, settlement, lateral resistance and pull-out capacity of grouped pile were analyzed using RSPile software and hand calculations. The analyzed results showed that, the pile foundation was safe against bearing capacity and uplift failure. The maximum displacement of grouped pile was less than the maximum permissible displacement and the maximum lateral deflection was less than the permissible lateral deflection allowed for grouped pile.