Intelligent back analysis of displacements using precedent type analysis for tunneling

Abstract

Abstract Based on comprehensive monitored data obtained from typical tunnel projects, and by using engineering experiences of experts together with numerical modeling results, the precedent type analysis (PTA) technique developed was for back-analyzing in situ stress and elastic modulus of rock masses surrounding tunnels. Then, the PTA is used as a supporting technique in the method of intelligent back analysis (IBA). The IBA method can integrate the mechanism analysis with experimental identification. Such integration is based on ‘certainty factors’, and is implemented with the computer program BMP90 with a global inference engine. The program BMP90 can solve a series of back analysis problems—such as identifying potential problems to be encountered during back analysis, assessing the strategy to be adopted, selecting criteria for back analysis, and ensuring convergence of back analysis results. Based on the engineering applications to approximately 100 tunnel projects in China, it is found that the IBA method supported by the PTA technique can be successfully applied to tunnel projects, i.e. back-analyzing the lateral in situ stress factor (λ), and the elastic modulus ( E ) of rock masses. The method of IBA supported by PTA and its application to a tunnel project are presented in this paper.