Reliability analysis of 640 m long soil retaining wall for an embedded highway construction

A reliability analysis of 640 m long retaining wall for an embedded highway has been carried out. The soil profile at the site mainly consists of alternation of three cohesive and cohesionless soil layers. The soil investigations have been conducted by the borings (SPT N-values) of about 100 m interval. It was found that the most dominant source of uncertainty to control the performance of the retaining wall is the thickness of the soil layers which are different from a section to another. The layers thicknesses are modeled as correlated random processes whose thicknesses are known at the location of the borings. The thickness of a layer at a certain location is estimated by Co-Kriging method and the conditional simulation based on it with quantified uncertainty. The design calculation model error is also evaluated by comparing the calculated results with laboratory model experiment results and actual site measurements. The response surfaces of the performance of the retaining wall as a function of layer thicknesses and soil property variations are obtained by extensive design calculations of the retaining wall. Finally, the reliability evaluation of the retaining wall along the excavation has been carried out by Monte Carlo Simulation (MCS). The final result takes into account the spatial variability of soil properties both soil mechanical property variation and the layer thicknesses, the statistical estimation error due to sparse soil investigations, and design calculation model errors. The quantitative contributions of each component are also presented.