Structural Analysis of Tunnel using FEA

: Tunnels are typically built for transportation, such as roads, railways, or canals, but they can also be used for other purposes, such as mining, sewerage, or water supply. Tunnels allow us to travel safely and efficiently through difficult terrain, and they provide us with access to essential resources such as water and energy. The objective of current research is to evaluate the structural characteristics of tunnel structure under geo-mechanical loading conditions. The structural analysis of tunnel is conducted using techniques of FEA. The CAD modelling and FEA simulation of tunnel is conducted using ANSYS simulation package. The shear stress, normal stress and deformation data are generated. From the generated data, the critical regions are identified and the lateral zone of tunnel is one of them. This region is likely to induce damage in the form of crack.

Niyirora et. al. [3] (2022) the analytical approach has been widely adopted to investigate the interaction mechanism between surrounding rock and linings for tunnels in rheo-logical rock.
The author obtained closed-form solutions of a deep-buried circular tunnel considering the sequential installation of linings [4] Zhang et. al. [5] (2021) proposed a linear degradation model for the primary lining in order to evaluate the mechanical characteristics of the secondary lining throughout its lifespan. A set of numerical simulation models was developed to investigate the mechanical behavior of the secondary lining, taking into consideration the deterioration of the sprayed concrete lining.
Degradation was deemed to have occurred when there was a gradual decrease in the Young's modulus of the sprayed concrete lining.
Barros et. al. [6] (2020) This research contributes to the advancement of our understanding regarding the evaluation of tunnel safety in the long run. The limitations of the prescribed analytical framework necessitate further discussion, as it has been excessively simplified in specific domains. In this study, the rheological behavior of soft rock is characterized using the Burgers model, which accounts for the temporal dynamics of the encompassing rock.
Deme et. al. [7] (2020) The present study introduces an innovative methodology for the quantitative assessment of tunnel stability in rock masses with joints. The proposed strategy is founded upon a variation of the traditional finite element approach. The revised approach considers the interrelationships among joint orientation, joint spacing, joint strength, and tunnel stability. The comparison between field measurements and numerical analysis is being made.
The results indicate the efficacy of this distinct methodology in forecasting the stability of tunnels in rock masses that are characterized by joints.
Qiu et. al. [8] (2017) The present study introduces an innovative method for forecasting tunnel distortion. The approach integrates principles from the finite element technique, albeit with notable modifications. The revised approach incorporates considerations pertaining to the Bassan et. al. [9] (2016) This study aims to examine the impact of groundwater on the structural stability of tunnels. The utilization of a numerical model is employed by the authors to replicate the process of tunnelling through soil that is imbued with moisture. The model incorporates factors such as soil deformation, seepage pressure, and groundwater circulation. The outcomes of the simulation bring into focus the potential influence of groundwater on the stability of tunnels.
The authors argue that the incorporation of groundwater considerations is imperative in the planning and implementation of tunnel construction in moist soil environments.

OBJECTIVES
The objective of current research is to evaluate the structural characteristics of tunnel structure under geo-mechanical loading conditions. The structural analysis of tunnel is conducted using techniques of FEA. The CAD modelling and FEA simulation of tunnel is conducted using ANSYS simulation package.

METHODOLOGY
The structural analysis of tunnel is conducted using techniques of FEM which involves different  After discretization, the tunnel model is applied with loads and boundary conditions. The base of tunnel domain structure is applied with fixed support and with gravitational load. The material definition is defined for tunnel lining with M30 concrete and domain is defined with rock mass.

RESULTS AND DISCUSSION
The FEA simulation is conducted on tunnel with computational domain to determine total deformation, normal stress and shear stress.
. The total deformation plot is generated for computational domain comprising of earth and tunnel

Figure 5: Total deformation plot on tunnel domain
lining. The deformation plot shows higher magnitude at the top most region of tunnel structure.
The deformation at this region is nearly 335mm which reduces towards the tunnel lining structure. The normal stress distribution plot is generated for tunnel domain as shown in figure 8 above.
The topmost region of tunnel lining has tensile normal stress with magnitude of 1.53MPa and side faces of tunnel lining has compressive normal stress with magnitude of 28.2MPa. The normal stress distribution plot (vertical direction) is generated for tunnel subjected to both geotechnical and traffic loads. The induced normal stress is in both tensile and compressive. The side surface of tunnel experiences compressive normal stress with magnitude of 40.46MPa whereas the top surface experiences tensile normal stress wherein the magnitude is more than 2MPa.  The tunnel can be inspected using intelligent inspection robots. These robots comprise of cameras which can capture images of high resolution and can identify any possible failures/cracks/fracture.
The tunnels can be constructed using more energy efficient and sustainable materials. The use of green construction materials in tunnel would reduce the impact on environment and enhance sustainability.