Reliability Based Design of Base Heave Stability in Wide Excavations

Base heave stability is an important issue for excavations in clay. Many design equations for base heave stability are simplified for ease of use and typically have a conservative bias for design safety. In this study, three popular base heave design equations are calibrated based upon real case histories with wide excavation. It is found that modified Terzaghi's method is nearly unbiased, while Bjerrum and Eide's and slip circle methods are obviously biased to the conservative side. The model uncertainty associated with Bjerrum and Eide's method is the lowest, while that associated with the slip circle method is the highest. The reliability levels for the design code regulations are verified, and reliability-based design charts are provided. The conclusions can be applied for reliability-based design of base heave stability for wide excavations in clay.