A Numerical Modelling Approach to Assess Deformations of Horseshoe Cavern on Account of Rock Mass Characteristics and Discontinuities

Caverns are massive underground openings excavated for purposes like defense installations and nuclear waste disposal which becomes challenging for weak strata consisting of fractured rock masses and may result in future calamities. This study is dedicated to ascertain stability of a horseshoe cavern in different types of granitic rock masses as well as fractured rocks. Two different types of granitic formations are accounted and displacements obtained along cavern periphery have been illustrated in the preliminary part of this study. An increment in vertical displacement at the crown of 260% and lateral displacement of almost 170% for both walls were observed for moderately weathered rock. Further, implications due to orientation and frequency of joint sets on the displacements incurred has also been explored. This study acquires its novelty by considering combinations of joint sets with varying spacings for investigating their implications on cavern walls. Presence of discontinuities depicted that horizontal joint spaced closely increased the deformation magnitude which reduced with decrement in joint frequency. Subsequently, along with horizontal joints at 4m interval, vertical and oblique joints sets were also incorporated at different frequencies. Consideration of vertical joints at 2m spacing with horizontal joints resulted in 313.2% increase in vertical displacement at cavern crown as well as 340% and 363% increase in lateral deformation at the left and right wall, respectively in comparison to intact rock. In case of oblique joints spaced at 2m with horizontal joints, increment in vertical deformation at the crown proliferated to 329% in comparison to intact rock.