Application of numerical back analysis for determination of soil mass specifications during tunnel construction

摘要

Geotechnical parameters play key roles in constructing and developing civil engineering projects, especially underground structures. One of the conventional methods to evaluate the tunnels' behavior and safety is applying a back-analysis method to assess the displacement amount during the construction of different parts of the tunnel. Applying this method and using displacement values obtained by tunnel monitoring, the estimated values of geotechnical parameters may converge to their real values. The present study was conducted to improve the estimation accuracy of geotechnical parameters for the tunnel route of Karaj (located 36 km west of Tehran, Iran) subway using the alternative univariate back analysis in FLAC3D software and modifying tunnel maintenance requirements, accordingly. The results showed that the use of geotechnical parameters extracted using back analysis lead to a more accurate design of the tunnel. Overall, through the applied back analysis, it is possible to reduce the shotcrete thickness of some subway stations up to 43% and obtain an optimum design.