Parametric Study on Analysis and Design of Permanently Anchored Secant Pile Wall for Earthquake Loading

Due to space limitations in urban areas, deep excavation in to the ground has become a common practice worldwide. Among the conventional retaining support systems, this study is focused on secant pile walls. The secant pile methodology comprised the formation of overlapping concrete piles. The overlap between the piles is achieved to prevent soil and ground water ingress. The analysis of these deep excavations involved consideration of soil parameters, deformation, interaction of soil and retaining configuration. It is difficult to precisely describe the nonlinear system using traditional analysis. Thus, in order to accurately describe the behavior of the anchored secant pile for earthquake loading, 3D finite element simulation was applied. The analysis for 20m excavation step in the fourth stage, showed incremental lateral displacement was 0.0552E-3m and total displacement was 0.114E-3m. The analysis indicated that the displacement induced in the ground increased with excavation depth. As the excavation depth increased, the unbalanced forces increased resulting to increase in stresses and displacement. Increase in pile diameter reduced displacement of the pile and with 1400mm pile diameter, the maximum displacement occurs at the wall; zero displacement , this was due to increase in structural stiffness. In addition, the modulus of deformability of the soil has great importance in the settlement of the soil. It is visible that when the thickness of the wall increases, the horizontal and vertical displacement near the wall increases. Decreasing the horizontal and vertical spacing of the anchors increased stiffness of the anchor per unit width. With high anchor stiffness, displacement occurs near the excavation surface thus, reducing the displacement of the wall.