Investigation of micropile group efficiency and grout column to steel ratio

微型桩应用广泛，包括用于现有基础托换和抗震加固的小容量微型桩，以及用于新结构的大容量基础。中空钢筋微型桩还有一个额外的优势，因为它们提供了快速安装和高度地基改善。目前，空心钢筋微型桩的施工仅限于钻头与空心筋直径之比小于等于2.5，这限制了微型桩的直径，从而限制了微型桩的承载能力。此外，微型桩被成组使用来支撑结构荷载。大量的实验和数值研究工作已经评估了桩间距对群体行为和效率的影响，但结果

Micropiles are used in various applications, including small capacity micropiles used for underpinning and seismic retrofitting of existing foundations, and high capacity foundations for new structures. Hollow bar micropiles have an added advantage as they provide fast installation with a high degree of ground improvement. The current practice for construction of hollow bar micropiles is limited to drilling bit/hollow bar diameter ratio of 2.5 or less, which limits the diameter of the micropile and hence its capacity. Additionally, micropiles are used in groups to support structural loads. Considerable research efforts, experimental and numerical, have evaluated the influence of pile spacing on group behavior and efficiency, yet the outcome