Several recent studies have investigated failure mechanisms for cast iron water pipes. These studies have primarily focused on the adverse effects of corrosion, frost, reactive backfill, and earthquakes. It appears that leaking pressure pipes can produce erosion voids under the buried structure. In this paper, a parametric study employing three-dimensional finite-element analyses is used to examine buried, continuous, cast iron water pipes. The objective is to understand the effect of such erosion voids on the stability of buried cast iron pipes and the longitudinal soil-pipe interaction. The results of the finite-element analyses demonstrate that the radial (σR) and the axial stresses (σA) are low compared with the hoop stresses (σθ), and the peak tension is always in the hoop direction. As a result of the high hoop stresses induced by the nonuniform bedding support, longitudinal fractures are likely to occur in the pipe, which may consequently cause pipe failure.

In this study, the uses of alum sludge (AS) as hydraulic barrier (HB) layer and daily cover (DC) material were investigated using two-dimensional finite element analysis. In the analyses, typical landfill geometries were carried out for two different side-slope steepness (2H:1V and 3H:1V), two different HB materials (compacted clay (CC) and AS) and four different DC scenarios (no DC, sand (S), compost, and AS), two landfill heights (20 m and 30 m) and two different municipal solid waste decomposition conditions (freshly disposed waste and old waste), and the effects of these variables on the displacements, and factor of safety (FS) values were investigated. For all the cases studied, FS values higher than 1.5 were obtained which indicated that the landfills were stable against sliding, and the displacement values were within the limits reported in the literature. The results of the finite element analysis also showed that AS used as HB and DC material yielded compatible results with the ones for the CC and S, which are widely used materials as HB and DC in landfills, respectively. Therefore, it can be said that, considering its low hydraulic conductivity, high shear strength, high contaminant removal abilities, and easy availability at no cost, AS can be used as an efficient alternative HB and DC material for landfills.