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Oil spills may occur during exploitation and transportation or can result from accidents in oil pipelines or tanks. Such spills may cause environmental and ecological problems than can lead to changes in the mechanical properties of the affected soil. A series of cyclic triaxial tests was conducted to evaluate the effects of oil contamination on the liquefaction potential of sands and silty sands. The specimens were prepared by adding silt to Firouzkooh sand at ratios of 15, 30, 35 and 40%, mixed with crude oil (contents of 4, 8 and 12%). The results indicated that the liquefaction potential increases with an increase in silt content until a silt content of 35%, when the liquefaction potential starts to decrease. It was also found that, up to 30% silt content, the silt controls the liquefaction behaviour. Furthermore, when oil contamination exceeds 8%, the liquefaction resistance starts to decline.

Overtopping is known as one the most important reasons for the failure of earth dams. In some cases, it has resulted in heavy damages and losses. Therefore, enhancing the safety of earth dams against overtopping has received much attention in the past four decades. In this paper, at first, the overtopping phenomena and its destructive consequences will be introduced. Then, overtopping failure mechanism of embankments will be described. Finally, different types of protection systems for stabilization of earth dams against overtopping will be presented. These include timber cribs, riprap and gabions, reinforced earth, roller compacted concrete, and the precast concrete blocks.

Using wedge-shaped concrete blocks (WSCB) to protect earth dams against overtopping has received much attention in recent years. The aim of this study is to assess the pattern of the infiltrated flow through the WSCBs system into the downstream shell of the earth dam. Moreover, its effects on the downstream slope stability are investigated using the finite-element analysis. A typical zoned earth overflow dam with the WSCB spillway is modelled. For this case study, the effects of depth and duration of overtopping as well as the permeability coefficient of the shell materials on the water infiltration pattern and the downstream safety factor are studied. The results show that if the permeability coefficient of shell materials is more than 10−3 cm/s, even for overflow with shallow depths, the infiltration rate and the extent of the saturated region will rapidly increase. Consequently, the safety factors will significantly decrease for such cases. However, if the materials with permeability coefficient less t...

Permanent ground deformation is one of the most damaging hazards for continuous buried lifelines. In this paper, numerical models using a Finite Element Method (FEM) were developed to analyze the buried High-Density Polyethylene (HDPE) pipelines subjected to the normal fault motions. The numerical predictions, were compared with those from ASCE Guidelines and with the experimental results obtained from geotechnical centrifuge tests. Moreover, the paper focuses on the effects of the design parameters such as, pipe diameter and thickness, pipeline burial depth, friction angle and density of the soil surrounding the pipe on the maximum bending strain as well as bending strain distribution along the pipeline. The results show that numerical models using a finite element method could produce reasonable predictions. However, the maximum predicted bending strains from the ASCE Guidelines are larger than those from experiments. The pipe deformation mechanisms are also significantly influenced by variation in burial depth, pipe surface characteristics, and backfill type.

Roller Compacted Concrete (RCC) has become a popular method for providing spillway and overtopping protection for earthen dams. So far, some studies were performed on the effects of RCC protection against hydraulic forces and erosion. The purpose of the present numerical investigation is to study the effect of interaction between downstream RCC spillway and embankment dam during steady-state seepage flow and overtopping over spillway. For this purpose, a zoned embankment dam with broad-crested spillway on its downstream slope is modeled using finite element numerical modeling. The results show that interaction between the dam body and RCC spillway ends up with increasing the factor of safety (FOS) of downstream slope during steady-state seepage. This factor does not decrease during overtopping conditions.