BACK ANALYSIS OF THE NON-ELASTIC DEFORMATIONAL BEHAVIOR OF GROUND MATERIALS

Abstract

The observational method has become common in geotechnical engineering practices such as tunnelling or underground excavations. The most important point for successful employment of the observational method is not only to evaluate results of field measurements as accurately and promptly as possible, but also to use the findings of the evaluation to re-design and monitor further construction procedures. Back analysis is a rational approach for quantitative interpretation of the results of field measurements. However, care has to be taken in selecting a material model to assure the uniqueness of the final results. In this paper, a method of back analysis is proposed, taking into consideration effects of non-elastic strains, and assuming that the stability of tunnels can be monitored by strain-based safety criterion. The method is simple. It does not require the pre-assumption of a material model, and it can account for the non-linear deformation associated with plasticity, creep, or that caused by blasting. The method was applied to interpret the data obtained from a umaxial compression test, a model test, and an actual tunnel under construction. The results show that the proposed analysis method could explain non-linear deformational behavior of a different nature.