Impact of Arch Geometry on Subsurface Settlement Prediction due to Tunnelling in Sand Considering Soil Arching

The present study investigates the effects of different shapes of arch to predict the subsurface settlement due to tunnelling in sand, considering soil arching. Most of the available analytical models considering soil arching for predicting the tunnelling-induced subsurface settlement are developed for circular shape of arch. In the present study, the subsurface settlement is also determined considering parabolic and catenary shape of arch. In addition, the procedure to calculate the vertical and horizontal stress in the frictional arch zone is developed based on the catenary-shaped trajectory of major principal stress. The results of the present study are compared with the field measurements to identify the proper shape of the arch for predicting the tunnelling-induced subsurface settlement. It is found that the shape of the arch can affect the tunnelling-induced settlements in relatively shallow depths. At shallow depths, the circular arch case shows slightly higher amount of settlement at the tunnel centerline than the parabolic and catenary arch cases.