Embedment Depths of Transmission Poles in Sands and Clays: A Monte Carlo Simulation Approach

The embedment depth of transmission poles in various types of cohesionless and cohesive soils is examined. The analytical process combines the closed-form solution of Broms with Monte Carlo Simulation of random soil properties to develop probability distributions of embedment depths. Six types of sands (loose, medium and dense, both moist and submerged) and six types of clays (ranging from very soft to stiff to hard) are considered. Pole heights above ground ranged from 41 feet (12.5 m) to 68 feet (20.7 m). Loading on pole top corresponded to ANSI class loads. A statistical assessment indicated that the embedment depths in both sands and clays are best described by a three-parameter log-normal distribution. Mean values of embedment calculated using the log-normal distribution are compared with those from the Rule of Thumb estimates that are commonly used by engineers. It is inferred that even for uniform soils, especially submerged sands and the softer clays, embedment depths are underestimated with conventional methods. On the other hand, our investigation suggests that for moist sands and stiff clays, the embedment depths that are commonly used are overestimated. Suggestions for future extensions of this study are made.