Hi allor, I saw your answer to the question "Flac Simulation Tunnel lining" dated on 09-15-2009. My tunnel section is about square (11ftx13 ft) and overburden is 10 ft. It is underneath a 12" concrete building foundation. I used flac 2D to model the tunnel and get the design loading for the steel rib set and the reinforced concrete tunnel structure. I have questions about how to control the intermediate settlement after installing the steel rib set. What is the criteria, such as 1 inch settlement or 0.5 inch settlement? The tunnel also used pipe roof reinforcement to prevent the soil from falling above. If you have any books regarding the steel rib set, such as roof column connection details, invert strut and column details, I would be very appreciated. Thanks.