Impact of Antecedent Moisture Conditions on Power Pole Response during Ice Storm Loading

Failure of power poles during ice storms routinely disrupts the power distribution network, which is costly and can lead to loss of life. Such events are exacerbated by climate change, of which the effects on the power pole distribution network are two-fold. Firstly, climate change is causing more extreme weather and influencing the frequency and occurrence of extreme events. Secondly, drought and excessive rainfall events change the soil moisture; hence, the soil suction increases or decreases affecting the overturning stability of the poles. The role and seasonality of soil moisture content and suction are not routinely considered in the evaluation of power pole systems. This paper evaluates the role of antecedent moisture conditions and soil suction on the behavior of power poles during ice storm loading. The research expands on the current body of research by incorporating soil-structure interaction in the analysis. Analyses were carried out in the commercial software LPILE using p- y curves modified to incorporate the effects of soil suction. Modification to the p-y curves was completed using the concept of apparent cohesion. The variation in soil suction with depth along the embedded portion of the power pole is also considered in the analysis. To incorporate these effects, unsaturated seepage analysis was completed using the commercial software PLAXIS LE Groundwater for the study soils. The seepage analysis used past daily recorded precipitation for a testbed. The study found that while the groundline deflection is impacted by including soil and soil moisture conditions in the analysis. The maximum bending moment developed in the power poles was governed by the above ground loading, wind, and ice, and was not significantly impacted by soil conditions.