3D ANALYSIS OF THE SEISMIC BEHAVIOR OF INCLINED MICROPILES-Paper

Paper

Pdf Summary

The study uses three-dimensional finite-difference modeling in FLAC to examine the seismic response of inclined micropile groups. The models include 10 m-long, 10 cm-diameter micropiles at inclinations of 70°, 80° and 90°, subjected to a one-directional representation of the 1978 Tabas earthquake. The numerical approach was compared with experimental data, with the authors reporting good agreement. The paper describes the soil as elastoplastic in its modeling approach, although the numerical-analysis section states that elastic soil was assumed.<br /><br />Results indicate strong interaction between the soil and micropiles. Compared with vertical piles, inclined micropiles are reported to improve soil performance under seismic loading and reduce displacement. The displacement ratios reported for the two pile-group configurations range from 0.41 at 70° to 0.44 at 90°. Increasing the angle also increases axial loads and shear forces. The largest positive bending moments occur at the greatest inclination, while negative bending moments increase more slowly. The two pile-group layouts show broadly similar response patterns.<br /><br />The authors conclude that inclined micropiles can help control earthquake-induced loads and improve foundation stability, but their design must account for the changes in axial force, shear and bending moment associated with inclination.

Keywords

three-dimensional finite-difference modeling

FLAC

inclined micropiles

seismic response

soil-structure interaction

Tabas earthquake

pile group

displacement reduction

bending moment

foundation stability