Numerical Modelling for Ground Improvement of Batter Micropiles on Liquefiable Soils

The micropiles are widely used in the ground improvement for the liquefiable foundation. However, seismic behavior of batter micropile is not fully understood up to now because the behaviors of micropiles during earthquake are significantly influenced by the nonlinear characteristics of liquefiable soils and soil-pile interaction. Herein the influences of pile inclination and earthquake intensity on seismic response of micropile group on liquefiable soils were investigated by means of an effective stress analysis method. The numerical predications in the simulation model with intensity of 0.1, 0.2 0.3 g, frequency of 2 Hz input sine wave and pile inclination of 15° to the vertical axis, show that the stronger input motion intensity results in higher responses at the micropile top. But in the El Centro earthquake motion model with the pile inclination of 0°, 15°, 25° to the vertical axis, the maximum lateral displacements and maximum bending moments along micropile length decrease with increase of the micropile inclination, the relative micropile-soil lateral displacement increased. The deflection along the micropile in two type models both decreases with increasing the buried depth. The lateral soil-pile relative displacements in liquefiable soils are much more complicated than in non-liquefiable soils. The batter micropile leads to a reduction of bending moment in the micropiles, and accelerations and deflection at pile top.