Geologic Hazard Investigation for Abu Dhabi

Abstract

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 and groundwater conditions, which are a concern for construction both at the surface and underground. A first step to manage the risks associated with this type of infrastructure is to manage the hazards and the risk associated with the ground conditions. This research focuses on the study of a particular ground hazard common in Abu Dhabi, gypsum dissolution and karst formation, and its impacts on infrastructure development. This is done through the development of two complementary tasks, and therefore the research includes two parts. Part 1 focuses on the development of an up-to-date geologic model in combination with a spatial inventory of karst-related features, based on an extensive field survey and spatial statistical analysis. This allowed us to organize available data, set up databases and catalogs of karst features and proposed a unified geologic classification for Abu Dhabi subsurface. The developed 3D geologic model and the spatial statistical analysis of the geologic data can serve as a tool for planning and construction of urban systems in Abu Dhabi. Part 2 of this research studies the effect of gypsum cavities on tunneling. Geologic and construction data from the Strategic tunneling Enhancement programme (STEP) tunnels, the largest pipeline infrastructure project in the GCC region, served as the basis for the study. To investigate this problem, finite element analyses using the software PLAXIS are conducted, where the size of the cavity, the location, and distance between the two openings is systematically varied. The simulations are conducted in different ground types cohesive, granular and mixed ground. Results of the analyses are presented graphically in charts that show the bending moment and surface deformations 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 the ground where cavities are present.

Date of Award	Dec 2017
Original language	American English