Time-variant reliability of retaining walls and calibration of partial factors

A methodology for the time-variant reliability analysis of geotechnical structures, particularly retaining walls, is presented. Calculation of the reliability of a wall, at any time during its lifetime, is enabled through the consideration of the degradation of soil shear strength parameters with time. In addition, the effects of spatial variability and model uncertainty are accounted for. Following an initial application with regard to British and European design standards, the methodology is extended in order to enable the calibration of partial factors for design to Eurocode 7. It is concluded that the values recommended for these factors are excessively high, at least for temporary structures that should be designed to withstand loads for just a few years. Therefore, a procedure for calculating reduced values of the partial factors that correspond to an appropriate safety level is further proposed.