Assessing dynamic responses of micropiles with different casing configurations using shaking table tests

In this study, the dynamic load response and seismic resistance of micropile (MP) installed with different casing configurations were investigated using shaking table tests. Focus was given on the seismic reinforcing effect of perforated casing (PC), as an optimized casing type, compared to conventional casing (CC) and uncased (UC) condition. A series of shaking table tests were conducted for model MPs with various casing and loading conditions. From the shaking table tests, it was shown that the dynamic properties and seismic performance of PC MP was similar enough to those of CC MP. The values of natural frequency (ω_n), damping ratio (ξ), maximum acceleration (a_max), and maximum bending moment (BM_max) obtained from the tests were compared for MPs with different casing conditions. Compared to UC MP, CC and PC MPs showed 19 % higher level of ω_n with an increase in ξ. The values of a_max for PC and CC MPs were lower than for UC MP, while the values of BM_max were all similar. The results of this study showed that perforated casing benefits for enhancing the seismic performances in a similar level to conventional casing.