Reliability assessment of basal-heave for excavations in clay

Evaluation of basal stability is important in the design of braced excavation in clay.Up to now,approaches to excavation design have always been essentially quantitative,i.e.,with single values assigned of the mechanical properties of soils and with a single factor estimating the safety of the design,regardless of both the uncertainties pertaining to the calculation procedures and/or variability of the soil properties.This study adopts different basal-heave stability analysis methods of Terzaghi,Taiwan's architecture code and Shanghai standard code for design of excavation engineering.The results highlight the inconsistency in the relationship between the factor of safety and the underlying level of risk,depending on the degree of uncertainty of either damage risk or design parameters.Larger factor of safety does not necessarily imply a smaller level of risk.