Performance Study of Skirt Depth on Settlement and Net Upward Pressure Distribution Characteristics of a Single Skirted Isolated Square Footing

Skirts in foundation are common feature in offshore structures. These plays an important role as a structural member in foundation and are generally being used underneath shallow foundations of offshore structures. They are being used over the years, due to their stability advantages. However, limited knowledge is available on the performance of the skirted footings, when it comes to their usages as conventional shallow foundations on routine structures in cohesive soils. In the present work study is being carried out to check the effectiveness of various Skirt depths (Ds) in improving the performance of Single Skirted Isolated Square Footing (SSISF) resting on cohesive soil, either by reducing the settlement or by minimizing the variation of Net Upward Soil Pressure (NUSP), average soil pressure, beneath the footing. Finite element modeling of SSISF has been done considering uniform soil pressure under the foundation. For the study nine observation points for three footing sizes with seven different skirt depths have been considered. The model is being prepared and analyzed by making use of software SAP2000 Vs.18. In the study two types of soils have been considered in which the Net Upward Soil Pressures are being restricted to 80KN/m2and 150KN/m2, respectively. A special case also has been considered in which the footing is crossing over the property line. One third length of footing is being resting on poor soil with maximum permissible net upward soil pressure as 80kN/m2 while remaining two third length is resting on better soil with maximum permissible net upward soil pressure as 150kN/m2. Results from the analysis shows that the increase in depth of skirt controls the average settlement of footing within permissible limit and minimizes variation of average soil pressure below the footing.