Behavior of micropiles in layered soils

Micropiles are replacement piles (cast-in-place) with a diameter less than 300 mm. Micropile installation can be vertically or with different angles from vertical and is qualified to withstand various types of loads (axial and lateral). The axial capacity of micropiles generates and relies on the bond that is developed between the gravity-grouted micropiles (Type A) or post-grouted micropiles (Type B, or C or D) and the soil. In this study, a model of micropiles Type A was developed and implemented using gravity grouting. A 2D finite elements method was used as an approach to represent, analysis, and assessment of the ultimate capacity of the micropiles in different layered soils. In this project, several factors were studied such as the penetration ratio of micropiles in the second layer, cohesion, and friction angles of soils. The results indicated that an increase in the penetration ratio causes an increase in the ultimate capacity in case the second layer is clay or sand. However, the incremental in the case of sand is less than the incremental in clay soil. This belongs to the fact that the micropiles ultimate capacity is only de-pendent on the shaft resistance more than the end bearing because of the small diameter of micropiles.