Micropile group behaviour subjected to lateral loading

Micropiles are suitable for underpinning and seismic retrofitting of structures. It is specially suitable for low head room area and can easily access congested areas where it is difficult to construct conventional piles. Its two basic functions are structural support and soil reinforcement. Literature review showed contradictory group effects on micropile behaviour subjected to vertical and lateral loading. This study is to investigate the response of micropile groups subjected to lateral load installed in loose sand (relative density 30%), in medium dense sand (relative density 50%) and in dense sand (relative density 80%). The group behaviour is found to be a function of the state of the sand, spacing of the micropile groups and length-to-diameter (L/D) ratio. Ultimate lateral resistances of micropile groups are maximum at 2D spacing in loose sand and in medium dense sand. In dense sand, maximum lateral resistance is observed in 6D spacing. Overall, it was observed that groups with higher L/D ratio had positive group effects. Modes of failure of the micropile groups are found to be a function of the length-to-diameter ratio and relative density of the sand.