Two dimensional analysis are carried out to provide new findings on the Twin Tunnel wall thickness optimization. It finds the wall thickness of tunnel openings which is prepared at varying width between twin tunnel in the modelling Phase-II software. The analysis is based on residual and peak parameters of rock mass properties. The overburden depth, extraction ratio and factor of safety are considered for model analysis. It focuses on Elasto-Plastic rock masses with non-linear failure criteria and non-associated flow laws. The rock properties are assigned in residual and peak values in Mohrs columns failure criteria.Empirical and analytical methods are used for support design that is required by induced stresses and displacement. The support system is designed based on empirical as well as data from the Phase II simulation. The rock mass properties are assigned through RMR and Q-system and the result is similar with the design model.

Er. Krishna Murari Chaulagain has completed M.Sc. in Geo technical Engineering, from IOE Central Campus, Pulchowk Lalitpur, Nepal in 2013. Since then he has been working in Governmental organization and private consultancies as a Civil/Geo-technical Engineer. He has completed his Master thesis related to Twin Tunnel underground Structures.