TJDEC MODELLING OF CLOSURE OF UNDERGROUND OPENINGS

Abstract

Assessment of stresses and closure of openings are complex engineering problems and form the most important aspects in designing the underground structures. Distinct Element Method is one of the popular methods used in assessing the stresses and closure behaviour of underground openings. In the present work, closure behaviour of three underground openings has been studied through distinct element modelling, Universal Distinct Element Code (UDEC) has been used for this purpose. The underground openings belong to Vishnugad Pipalkoti Hydro-Electric Project in the state of Uttarakhand. The site is composed of joited rock mass at differet elevations with three sets of joits. The analysis of closure has been carried out for power house cavern (127m x20.3m x50in), transformer hall (1 12m x 16m x 24.5m) and surge tank (120m x l 2mx27m). The UDEC modelling has been carried out for four cases namely i. All the three cavities are excavated at a time in one stage considering a boundary size of 220m x300m ii. All the three cavities are excavated at a time in one stage considering a boundary size of 760m x980m iii. All the three cavities are excavated one by one in three stages considering a boundary size of 220m x 300m iv. All the three cavities are excavated in sequential order in fifteen stages considering a boundary size of 220m x 300m Finally the deformations and stresses obtained from UDEC analysis for each of the above cases has been compared with results obtained from the empirical and analytical methods.