DEFORMATION BEHAVIOUR OF INTERSECTING TUNNELS

Abstract

Underground structures are utilized for carrying water, oil, natural gas and, also for transportation. The increased complexity of underground structure due to rising infrastructure demand generates a new problem of intersection of new tunnels with existing operational tunnel. This creates a critical zone at the intersection whose design is complex. The deformation in tunnels depends on various types of loading (static, dynamic or impact load), geological properties of the ground and, the support system installed. In the present study, the extent of deformation experienced in the intersection area of tunnel under the effect of static loading is studied. Numerical analysis of tunnel intersection behavior using 3D numerical analysis software was done. Then numerical values were validated with the physical modeling values. Experimental simulations have also been carried out to investigate the deformation behavior of the proposed tunnel intersecting with the existing tunnel under static load conditions. The main target is to explore the deformation behavior at the interface and evaluate the impact of new tunnel on the existing tunnel. The advanced compression testing facility was used to determine the deformation. Based on the ease of availability and feasibility, model material had been selected for experimental investigation. Physical and Numerical analysis of real life world problem of Chenani Nashri tunnel intersection is performed in this study. Numerical analysis indicated that maximum displacement occurred at the crown and invert region of the intersecting tunnel, with displacement values of 0.0055m and 0.004m respectively.Experimental investigations conducted using 2000KN compression testing machine integrated with PZT sensor and Oscilloscope yields value of 0.0038m at the crown and 0.0035m at the invert. Numerical analysis results and experimental analysis shows that the portal of the intersecting tunnels shows 37.5% and 25.71% less deformation than the invert at the intersection respectively. The main tunnel portal experiences more deformation than the intersecting tunnel portal by 10.71% numerically. Single tunnel shows nearly symmetric deformation while intersecting tunnels do not. From the results it can be v concluded that experimental and numerical modeling results have variation of around 4-30%.