A New Correlation to Estimate Bearing Capacity of Micropile Groups

Most of the recent studies that have focused on the micropile group have been limited to a specific soil type. However, the bearing capacity of micropile groups has not been considered in any of these studies. This study concerned three-dimensional numerical modeling of loose sand, medium sand, silty clay, and soft clay improved by the micropile group. The bearing capacity of the micropile group was estimated by 3D numerical modeling. The micropile group was modeled using spacing to diameter ratio (S/D) and the ratio of micropile length to cap width of micropile (L/B) in soil. Despite the use of only the shear failure criterion in the FHWA Code, the allowable settlement criterion was also considered in this study. A novel approach was presented to estimate the bearing capacity of the micropile group in which a new concept known as “unit length bearing capacity” has been used for the first time. The results demonstrated that in all four soils studied, the unit length bearing capacity of the group will decrease with increasing micropile length. In addition, the settlement of the micropile group in all four soils will decrease with increasing micropile length. The unit length bearing capacity of the micropile group and the overall bearing capacity of the micropile group in all four soils will decrease with an increasing spacing of micropiles. Of course, with increasing micropile length, the unit length bearing capacity will decrease at a slower rate than the overall bearing capacity. According to the simulation results, a punching failure occurred in the micropile group.