Plate load tests to analyze the load-settlement response of shallow foundations on sand beds reinforced with micropiles

Micropiles can act as structural support for a new foundation and sustainable solution for existing foundations with advantages such as high load-carrying capacity and use in in situ conditions. Installing micropiles around the footing at some distance from the footing edge could turn out to be extremely helpful for existing distressed foundations where improvement is needed. An experimental investigation is carried out on a laboratory model square footing in the ongoing study, placed on sand, with micropiles driven around the footing. A parametric study focusing on the effect of the slenderness ratio of the micropiles, the state of sand beds, the micropile spacing ratio (S/b), and the micropile edge distance ratio (E-D/d) are analyzed. The results demonstrate that the micropiles can appreciably improve the footing's settlement characteristics and load-bearing capacity when placed around it. The load-carrying capacity shows some appreciable increase by increasing the slenderness ratio of micropiles, but increasing the slenderness ratio beyond 20 is insignificant. For unreinforced footing, a denser form of sand was found more advantageous in terms of bearing capacity, while as for reinforced footing, micropiles provided maximum improvement for medium-density sand. The improvement in bearing capacity is approximately 22.2% when the spacing ratio is reduced from 0.5 to 0.3. Also, for an edge distance ratio of 3, the improvement in the bearing capacity ratio is 76% higher than that of unreinforced footing. Multivariate linear regression showed a strong correlation between the experimental and predicted bearing capacity ratio.