I am carrying out a tunnel excavation analysis and between the soil excavation and the tunnel lining placed there is load relief before the lining is placed. How do I model this?
When the soil is excavated in order to place the lining restrain the nodes which lies in the interface for soils and lining in the step in which the excavation takes place. The reactions are equivalent to the support provided by the excavated soil. If the lining was placed then these forces are then transmitted to the lining. Modify the input file to include the reactions as Nodal forces in the same step in which the excavation is carried out. Then in the next step reduce the reactions by the proportion by which load relief is to be applied.
