Document Type : Research Article
Geotechnical engineering department, Faculty of civil engineering, Iran University of Science and Technology (IUST), Tehran, Iran
Most of the recent studies that have focused on the micropile group have been limited to a specific soil type. However, bearing capacity of micropile groups has not been considered in none of these studies. This study concerned three dimensional numerical modeling of loose sand, medium sand, silty clay and soft clay improved by micropile group. The bearing capacity of 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 (S/B) in soil. Despite the use of only shear failure criterion in FHWA Code, allowable settlement criterion was also considered in this study. In fact, a novel approach was presented to estimate bearing capacity of 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 micropile group in all four soils will decrease with increasing micropile length. On fact, The unit length bearing capacity of micropile group and the overall bearing capacity of micropile group in all four soils will decrease with increasing spacing of micropiles. Of course, with increasing micropile length, the unit length bearing capacity will decrease at a lower rate than overall bearing capacity. According to the simulation results, a punch failure occurred in the micropile group.