Characterizing uplift load capacity of micropiles embedded in soil and rock considering inclined installation conditions

Abstract

In this study, the uplift load-carrying behavior of inclined micropiles (MP) embedded in various soil-rock layer conditions was investigated. For this purpose, a series of model load tests and finite element analyses were performed. The focus was given on the effects of MP inclination angle (θ) and rock-embedded ratio (Zr/L). For MPs in rock, the uplift load capacity (Qu,θ) was highest when vertically installed and decreased with increasing θ. The Qu,θ of MPs embedded in soil-rock mixed layers increased with Zr/L and decreased with increasing θ. Marked increases in Qu,θ were observed for Zr/L larger than 0.6 for all θs. As MPs inclination increased, the load-carrying mechanism shifted from the frictional resistance towards the passive resistance. The MPs inclined configuration caused less mobilization of the frictional resistance within the rock-embedded zone while producing the passive resistance within the upper soil zone. This explained the reductions in Qu,θ with increasing θ for MPs with the rock-embedded condition.