Uplift performance of helical piles with cement injection in residual soils

Helical piles have been widely used in Brazil to resist uplift forces of transmission line towers due to certain advantages compared with other foundations, such as resistance to both compressive and tensile loads, easy transport to remote sites, possibility of installation at batter angles, rapid installation with small equipment, and no need for concrete and form-work. However, in some sites the appropriate soil layer for the installation of the pile helices is too deep or too hard to be penetrated. In these cases, the use of helical foundations is not economically and (or) technically viable. One possible solution for this problem is to install the pile in a soil with low bearing capacity improved with cement injection. To evaluate the applicability of a soil-treatment method for helical piles, two different procedures of injection were tested in typical Brazilian residual soils of different geologic origin. For this investigation, 41 multi-helix piles (15 conventional piles and 26 with cement injection) were installed and submitted to tensile loading tests. The results reveal that both techniques can improve the tension capacity and produce a stiffer load-displacement response of helical piles under uplift loads.