The underground facilities are used for a wide range of civil and military applications (railways, highways and material storage). These structures are constructed in different possible ground conditions ranging from soft ground to massive jointed rock. Generally, the loads on tunnels consist of both static (overburden) and dynamic (blast, earthquake and traffic) loads. Therefore, the support system is usually designed to resist all transient loads developed during construction activities as well as the short-term ground loads.
Therefore, in the present work an attempt is made to simulate the in-situ condition through the physical modeling, to understand the tunnel deformation behavior by varying overburden thickness in soft rocks. The model material is selected on the basis of engineering properties of the different mix proportions of PoP, sand and clay (UCS, elastic modulus and Poisson's ratio), and the Plaster of Paris (PoP) mixed with sand and some percent of clay (50% PoP, 40% Badarpur sand, and 10% Kaolinite) is selected for physical modeling, as the PoP alone shows brittle behavior. It is interpreted that the height of overburden and thickness of lining are critical factors in correlating degree of fracture and damage to the tunnel—lining. Further, the deformation and degree of damage is determined for lined and unlined material and hence controlling the fracture in the existing conditions.
