Three-dimensional viscoelastic finite element analysis of large underground powerhouse

摘要

A three-dimensional viscoelastic finite element analysis is conducted on Longtan underground caves, adopting the Kelvin and 3-parameter viscoelasticity model with tandem spring components. The calculation results demonstrate: the surrounding rock of Longtan underground caves has distinct rheological properties; the rheological displacement accounts for a comparatively high proportion of the total shift, about 46%; the rheological stabilization time is about 240 days; during the early stage of excavation, the rheological deformation, which constitutes 45% of the total displacement in the initial 30 days and 75% in the preliminary 70 days, is quite obvious; the displacement increases slowly afterwards and tends to become steady in the main 240 days later. This proves that it is appropriate to conduct support between 30 to 50 days after completing excavation to enable the surrounding rock and the support body to bear 50% of the rheological displacement respectively, thus giving full play to the rock's inherent stability and making the support body be optimized and reliable. It is suggested that support should be conducted about 40 days after excavation, which provides scientific basis for support design.