Investigating The Behavior Of Retaining Wall Nailed For Deep Foundation Excavation In Clay Soil Type By Finite Element Analysis

Abstract

Urbanization is one of the major driving forces behind the formation of today’s land use systems. In order to decrease the land use for urban areas, basements are constructing widely. The excavation is deep for the basements and it induces lateral displacement in the soil mass. When the soil displaces more than allowable displacement failure will occur. Soil nailing stabilization method is practicing now a days in the developed world. The objective of this research was to conduct parametric study on soil nailed deep excavation wall. This parametric study was conducted to evaluate the effect of nail spacing, nail inclination, surcharge and depth on the lateral displacement and to compare the maximum lateral displacement of nailed wall and only diaphram wall supported face for two (6m), three (9 m) and four (12 m) basements using FEM based software (plaxis 2D.v8.2) for static loading in case of Addis Ababa (clay major soil). The soil properties needed for the analysis were found from SPT correlations which were collected from organizations. The results show that there was influence of nail geometry (spacing and inclination), surcharge and depth on the maximum lateral displacement of excavation wall face. However, depth had significant effect when the surcharge was greater than 50 kPa. Excavation depth of 6 m was not capable of carrying load for more than 155.6 kPa which corresponds to maximum lateral displacement of 12mm. The 9-m depth of excavation can support a surcharge of up to 225 kPa which corresponds to the maximum lateral displacement of 18mm. The 12 m depth of excavation can carry a load of up to 286 kPa which corresponds to maximum lateral displacement of 24mm, but not more since they displace greater than the allowable displacement. The maximum lateral displacement increases with increase in the nail inclination and nail spacing. At 6 m the excavation depth can carry load up to 118 kPa without nailing (only diaphragm wall). At 9 m the excavation depth can carry load up to 130 kPa without nailing (only diaphragm wall). At 12 m the excavation depth can carry load up to 142.7 kPa without nailing (only diaphragm wall supported)