Effect of an arch-type tunnel in the foundation soil on the seismic response of dikes

This report studies the dynamic response of the dikes due to earthquake loading when there is an arc-shaped tunnel in the foundation soil below it. The study is being carried out using the PLAXIS 2D software by comparing output such as the ground displacement, settlement and peak ground acceleration experienced by the soil model. The basis of comparison is through varying the sizes and the positioning of the tunnels, and applying the entire soil model to an input of earthquake acceleration data as the dynamic loading. The design of the symmetrical dike used, consisted of a crest width of 8m, height of 12m and a base width of 80m. The width of the entire soil model was set at 5 times that of the dike’s base width. The soil thickness is then set to 100m below the base of the dike. For the sizing factor, 3 tunnels of the same arc-shape but with different dimensions, will be incorporated into the simulation model. Their dimensions are 3m, 4.5m and 6m in diameter. As for the positioning factor, a total of 3 positions tested. The first position will be where the tunnel is placed right under the dike, with their centers aligned. The second position will be where the tunnel is placed slightly to the side of the center line right under the foot of the dike. The last position will be where the tunnel is placed further to the side away from the dike. The results from the study shows that the smallest size arch-type cavity in alignment with the center of a dike resulted in the highest horizontal displacement, velocity and acceleration within the soil profile. Thus, the existence of an arch-type tunnel within the underlying soil profile of a dike have great influences on seismic loading of the dike.Bachelor of Engineering (Civil