Studying the effects of gypsum karst cavities in tunneling

Abu Dhabi is expecting a huge growth over the next 20 years and is planning a massive integrated transportation system, including several modes of transportation to ensure that Abu Dhabi becomes a sustainable city on a global scale. Most of these structures are expected to encounter difficult ground conditions, which are a concern for construction both at the surface and underground. This study focuses on a ground hazard common in Abu Dhabi, gypsum dissolution and karst formation, and its impacts on subsurface infrastructure development. Numerical simulations to study the effect of gypsum cavities on tunneling are conducted using the finite element analyses with the PLAXIS 2D software and the geologic and construction data from the construction of the Strategic Tunneling Enhancement Programme (STEP) tunnels, in Abu Dhabi, UAE. Results of the analyses are presented graphically in charts that show the tunnel lining bending moment as functions of the tunnel geometry, cavity characteristics, construction parameters and properties of the ground. These graphs allow one to identify the most critical scenarios for tunneling through ground where cavities are present.