Dr. Hesham El Naggar2026-08-042026-08-04https://dspace.academy.edu.ly/handle/123456789/2468The main objectives of this research are to investigate the performance of single and micropiles group installed in cohesionless soil and study the effect of increasing the drill bit/ hollow bar (Db/Dh) ratio from 2.25 which presents the common practice to 3. The results should be of value for both practitioners and researchers. Furthermore, the mechanical properties of neat grout and various reinforced grouts were investigated to study the visibility of increasing the performance of micropile under lateral loading.Hollow bar micropiles (HBMP) have gained wide acceptance due to their efficient load transfer mechanism, which facilitates carrying considerable relative load in compression and tension, and small installation equipment, which allows installation in sites with limited access. The HBMP is commonly constructed using a drill bit/ hollow bar diameter ratio (Db/Dh) of around 2, and they are typically designed as type B micropiles as classified by the Federal Highway Administration (FHWA), even though they are constructed differently. Thus, this thesis presents the results of laboratory and field testing programs as well as three-dimensional nonlinear finite element analyses that were conducted to investigate the performance of single and groups of HBMP.Hollow Bar Micropiles in Sand