Compressive Load-Carrying Behavior of Inclined Micropiles Installed in Soil and Rock Layers

Micropiles are an effective option to enhance the load-carrying performance of buildings and infrastructure. In this study, the compressive load capacity and load-carrying mechanism of inclined micropiles in soil and rock layers were investigated experimentally and analytically. A series of model load tests was conducted using model micropiles and rock specimens. The finite element analyses were performed for inclined micropiles in various soil-rock layer configurations. Vertical micropiles in rock exhibited the highest load-carrying capacity whereas inclined conditions were not beneficial. For the rock-mounted condition, the base capacity dominated the total load capacity when the inclination was lower than 15 degrees. For partially and fully rock-embedded conditions, the main load-carrying component was the skin friction and virtually no load was transferred to the micropile base. Micropile inclination caused less mobilization of skin friction within the rock-embedded zone. Instead, the passive resistance within the upper sand layer dominated the overall load capacity, which explained decreasing load capacity with increasing inclination for a rock-embedded condition.