Comparison of field loading test results of bored piles with bearing capacity analysis based on various standards

Abstract

AbstractICA Construction (Ictas ‐ Astaldi JV) is the general contractor of the WHSD ring road project in St. Petersburg and Section 7 & 8 of M11 Motorway project, which will be the toll highway between St. Petersburg and Moscow. WHSD ring road that has been constructed by ICA Construction passes through nearshore and offshore areas on viaducts and there are also two cable stayed bridges on the alignment. As a part of M11 motorway project, several bridges have been constructed overpassing various rivers. Since, all these structures have deep foundation systems, several axial pile loading tests have been performed on both projects. Soil in the vicinity of St. Petersburg consists of soft to medium dense silty, partially sandy clay layers at top levels. These layers are followed by Cambrian aged hard clay layers. In Russian Federation and some Eastern European countries, bored pile design is based on SNIP norms. In norms like AASHTO or Eurocode, pile bearing capacity calculations consider both contribution of the tip resistance and skin friction. On the contrary, in SNIP norms contribution of the skin friction to pile bearing capacity is very limited. Therefore, piles are generally extended to deep bearing layers. For piles where large axial bearing capacities are required, base enlargement is applied. In this paper, axial pile bearing capacities in the scope of the above mentioned projects are calculated based on SNIP, AASHTO LRFD and Eurocode 7, respectively and the calculated values are compared with the pile bearing capacities obtained from field tests. Total number of axial pile load tests gives the possibility to make a statistical comparison. Results of axial pile load tests have revealed that especially the bearing capacities calculated in accordance with SNIP norms underestimates bearing capacities of bored piles erected in clayey soils.