Numerical and experimental analysis of cracked two adjacent tunnels

The tunnel-soil interaction problem is one of the complicatedinteractive problems especially, the two adjacent circular tunnelscontaining cracks. In order to predict a realistic tunnel performance, thetunnel and the surrounding soil medium properties are to be considered.Based on the finite and infinite element method, a computerprogram is developed to model the two tunnels-soil installation. The soilmediwn is represented by four node isoparametric quadrilateral linear andnon-linear strain elements and simulate the outer elements by infinite planestrain elements. The circular tunnels are represented by beam elements,which extended to simulate the cracked part and called beam element withcrack. In addition, a special interface element permits frictional sliding,separation, and rebonding of the tunnel-soil interface is used.In this study, many different parameters are considered, such as theeffect of the coefficient of friction between the soil and tunnels andpresence of cracks which has significant effect on the soil stress and lininginternal forces.By using the Duncan model to simulate nonlinear soil performanceand to detect the tension zones of soil, these zones of soil can be modified.A new type of elements is developed to simulate the modification in thetension zones of soil.In addition to the above parameters, the effect of distance betweenthe two tunnels, crack location, crack-lining depth ratio, case of loading,height of the ground surface over the tunnels and type of soil are