Experimental and Numerical Studies on Load-Carrying Capacities of Encased Micropiles with Perforated Configuration under Axial and Lateral Loadings

In this study, the axial and lateral load-carrying behavior of encased micropile (MP) with perforated configuration was investigated. The perforated casing adopted in this study was a casing with holes on the casing surface to increase the frictional and bending resistances. Experimental tests and finite-element (FE) analyses were performed to characterize the interface friction and the effect of the perforated casing, considering the inclined condition of MP. The experimental tests showed that the interface friction angle of the perforated casing was close to the sand friction angle, whereas that of the smooth-surface casing was nearly half of the sand friction angle. The frictional characteristics of the smooth and perforated casings obtained from the experimental tests were used in the FE analysis. The perforated casing was sufficiently effective to maintain the reinforcing effect of the casing on the lateral load capacity. The axial load capacity of MP with the perforated casing was 22.4% higher than that with the conventional smooth casing. A similar improvement was observed for inclined MPs. It was indicated that the perforated casing was beneficial for both axial and lateral loading capacities.