Abstract: With the progressive of urbanization and the available land for the development becomes less and less. It is necessary to study the deformation of the deep excavation supporting structures in the complicated geotechnical conditions. This paper presents the evaluation results of the geotechnical and geological conditions for a deep excavation site in Sichuan. The process of the deep excavation supporting system was numerically analyzed. The results indicate that, before the excavation, the deformation of soils adjacent to the excavated area is mainly in the vertical direction under the gravity load. In the red clay lenses, horizontal deformation can be observed but the magnitude of the horizontal deformation is small. With the progress of the excavation, the horizontal deformation magnitude increases in at the excavation supporting structure, and the shear deformation along the red clay lenses increases. With squeezing of the weak red clay soil from the supporting structure and causes the instability of the supporting structure. Construction recommendations were also proposed based on the numerical evaluation results in the paper.

Key words: deep excavation, soft soil lenses, plastic flowtension crack, slope/w software, stability evaluation