Role of In-situ Stress parameters for the design of underground pump house at various lift irrigation packages of Kaleshwaram Project Dr. B.R. Ambedkar Pranahita, Chevella Sujala Sravanthi Scheme, Telangana

The magnitude and direction of In-situ stress plays a vital role in designing the underground caverns and-structures. In general, the stability of the underground structure gets enhanced if the long axis of the cavern-is oriented along or sub-parallel to the maximum principal stress direction. Besides this, the distribution of-stresses affects the shape, size, excavation sequence & orientation of the cavern. It is indispensable that-the shape of the cavern should be selected to minimize the stress concentration especially in the region-of high stresses (Hoek et. al, 1980). Moreover, the layout of the underground complex should be planned-in such a way to avoid any geological disturbances propagating from one cavern to the adjoining one. This paper discusses about the In-situ stress investigations carried out at various packages of Kaleshwaram lift irrigation project which is a multi-purpose irrigation project on the Godavari River in Kaleshwaram, Bhoopalpally, Telangana, India. This is one of the world’s largest multi-stage lift irrigation projects start at the confluence point of Pranahita and Godavari Rivers. The Project is divided into ‘7’ links and ‘28’ packages along with eight pumping stations located 150 metres underground covering about 500 km of 13 districts and a canal network of about 1,800 km in Telangana state. The stress measurements were very much required as an input parameter to design the underground pump house complex that was being constructed at each package of this irrigation scheme wherever it was proposed underground. Stress tensors were determined by “Hydraulic fracturing method” inside NX size borehole up to the required depth where the crown of the pump house encounters from the surface. Results were evaluated by using most sophisticated technique replacing the classical theory. The determined ‘k’ value (ratio of horizontal/vertical stress magnitude) indicates the stress condition of the area, thereby also suggesting the orientation of cavern for maximum stability. These parameters are utilized as required inputs for further stability of the pump houses with the help of numerical modelling analysis.