Use of a line of piles to prevent damages induced by tunnel excavations

Buildings founded in proximity to shallow tunnels under construction may be damaged by the ground displacements induced by tunneling. This is a matter of concern for design, and a variety of protective interventions are currently adopted to prevent such damages. Among these, rows of piles or jet-grouting columns are widely diffused. In this paper, the effectiveness of a simple row of piles is computed by means of three-dimensional (3D) finite-element (FE) analyses, thus allowing the investigation of the relationship between performance and some simple geometrical parameters, such as the spacing among the piles. The results of centrifuge tests are reported and used as a benchmark. The potential damage has been quantified in this work, taking into account both the settlement profile and the horizontal strain induced at the ground surface by tunneling. It is shown that although the settlement reduction is significant only for very small spacing (s ¼ 2–3 pile diameters), even largely spaced piles (s ¼ 5–6 pile diameters) are useful to prevent damage to buildings because of the significant reduction of the average horizontal strain.