Towards a limit state design specification for reinforced soil walls

To achieve economy, reinforced soil wall projects undertaken by the Roads and Traffic Authority of New South Wales have been based on Design and Construct Contracts. This changing environment has prompted the RTA to develop a Limit State Design Specification which provides a rational and equitable framework for specialist contractors to produce designs with consistent safety margins for a range of conditions. Due to the complexities of this exercise, this design specification only covers reinforced soil walls with vertical or near-vertical facing. Calibration studies have been conducted to assess parameters that have significant impact on the cost of constructing reinforced soil walls. Reliability analyses were conducted to ensure that the partial factor on soil shear strength can lead to a consistent reliability. The potential problems of using a statistical definition of characteristic values are addressed.