Most recent tunnel designs rely on more thorough analyses of the intricate rock interactions. The three principal techniques for excavating rock tunneling are drill-and-blast for complete or partial cross-sections, TBM only for circular cross-sections with full faces, and road header for small portions. Tunnel-boring machines (TBM) are being utilized to excavate an increasing number of tunnels. Newer studies have demonstrated that subterranean structures such as tunnels produce a variety of consequences during and after ground shaking, challenging the long-held belief that they are among the most earthquake-resistant structures. Consequently, engineering assessment has become crucial for these unique structures from both the geotechnical and structural engineering standpoints. The designer should evaluate the underground structure's safety to ensure it can sustain various applied loads, considering both seismic loads and temporary and permanent static loads. This paper investigates how adding elastic, soft material between a circular tunnel and the surrounding rock affects seismic response. To conduct the study, Midas/GTS-NX was used to model the TBM tunnel and the nearby rock using the finite element (F.E.) method to simulate the soil-tunnel interactions. A time-history analysis of the El Centro (1940) earthquake was used to calculated the stresses accumulated in the tunnels during seismic episodes. Peak ground accelerations of 0.10-0.30 g, relative to the tunnel axis, were used for excitation. The analysis utilized a time step of 0.02 s, and the duration of the seismic event was set at 10 s. Numerical models were developed to represent tunnels passing through rock, with the traditional grout pea gravel vs. isolation layer. A parametric study determined how isolation material characteristics like shear modulus, Poisson's ratio, and unit weight affect tunnel-induced stresses. In the meantime, this paper details the effects of various seismic isolation materials, such as geofoam, foam concrete, and silicon-based isolation material, to improve protection against seismic shaking. The analysis's findings are discussed, and how seismic isolation affects these important structures' performance and safety requirements is explained.

Earthquake is one of the most critical hazard that damage buildings all over the world. Earthquake can result in ground shaking, soil liquefaction, damages, or even leads to complete collapse of buildings. So, buildings must be built to withstand the effect of earthquake so as to secure living conditions. Isolation method emerged as one of the efficient techniques for reducing the severe effects of earthquake. This project proposes a promising seismic isolation method by analysing different isolation method. A variety of isolation materials are available in order to reduce the seismic impact on buildings. This study investigated the efficiency of isolation materials such as polyurethane (PU) foam, coir fibre polyester composite, and geomembrane on seismic effect. In order to study the effectiveness of different isolation materials, seismic responses such as maximum roof acceleration, storey displacement, drift, and base shear of G+4 building was analysed using linear analysis by ANSYS software. Thus, this work aimed to propose the best suitable position of the most effective isolation material that reduces the seismic energy transferred. On other hand the use of this isolation method can provide an economic way to reduce the seismic energy transferred.