Micropiles Performance Based Design: Evaluation of Current Design Methods Applied to Puerto Rico Soils

Abstract

Micropiles have been used mainly as foundation support elements to resist static and seismic loads. The use of micropiles have been increased not only in locations with poor soil conditions, but also in congested areas and those requiring a less obtrusive presence than other installation methods may provide. This investigation reviewed results from tension tests performed on different soil scenarios and compared results of ultimate capacity with tension results. Comparison between actual capacity versus design values showed micropiles underestimation on micropiles installed in rock, opposed to an overestimation when installed in cohesive soils. Economic impact of overestimation has been approximated to 12% increment, based on one of the cases studied on this investigation. On the overestimation on rock anchors, further investigation is needed to determine the economic impact. This initial step into defining soil to grout bonding of micropiles for Puerto Rico soils sets place for more detailed investigations, targeted to provide better design values, hence reducing cost impacts on the construction phase of this elements. Key Terms - Foundation, Geotechnical Capacity, Grout to Ground Bond, Micropile, Tension Tests.