Reliability Analysis of Foundation Settlement in Nigeria Based on Standard Penetration Test Results: Fid-Bau Portal

Reliability Analysis of Foundation Settlement in Nigeria Based on Standard Penetration Test Results

Bunyamin, Salahudeen A. / Thomas, Ijimdiya S. / Adrian, Eberemu O. / Kolawole, Osinubi J.

Safety and reliability of building infrastructure is a major concern for many state and federal agencies in Nigeria. In an effort to harmonize with structural codes, geotechnical design codes around the world are beginning to migrate towards reliability-based design (RBD). The study aimed to develop the methodology to assist in the process of calibration with focus on standard penetration test (SPT) data obtained from 4,181 test holes (i.e., 37,629 data sets) distributed over Nigeria using Donut hammer equipment. Foundation settlements were determined at depths of 0.6, 2.1, 3.6, 5.1, 6.6, 8.1, 9.6, 11.1 and 12.6 m for applied foundation pressures of 50, 100, 200, 300 and 500 kN/m². Reliability analysis, expressed in the form of reliability index (β) and probability of failure (P_f) was performed for foundation settlement using First Order Reliability Method (FORM) in MATLAB. The footings were analysed for a 25 mm allowable settlement value as recommended in Eurocode 7. For SPT N-values with coefficient of variation (COV) of 10%, 20%, 26%, 30%, 40%, 50% and 60 %, the sensitivity results indicate that the applied foundation pressure and COV of SPT N-value significantly affected the magnitude of foundation settlements. Based on the output of this study, target reliability index (β_T) of 3.15 and target probability of failure (P_fT) of 0.0789% and the use of COV value of 30% of SPT N-value based on the Burland and Burbidge method (instead of the conventional 26% value) for SLS design is recommended for RBD of footings total settlement on soils in Nigeria.