Geotechnical assessment of a deep surge pool foundation – a case study

Foundation floor geological mapping of a deep surge pool is essential and has to be studied and documented for credible geologic interpretations. Rock is usually recognized as the best foundation material. However, design engineers should be aware of the dangers associated with heterogeneity and unfavourable rock conditions since over-stressing a rock foundation may result in large differential settlements or perhaps sudden failure. To evaluate the design foundation parameters for surge pool of Mahatma Gandhi Kalwakurthi Lift Irrigation Scheme (MGKLIS) stage II, engineering geological mapping on 1:200 scale was carried out after the final excavation and before first pore of concrete. All the discontinuities in the rock mass with the zone of influence of the foundation has been identified and mapped. Classification of rock mass using Rock Mass Rating of Bieniawski has been done. Bearing capacity of foundation was evaluated based on the rock type and Rock Mass Rating. The primary purpose of these investigations was to provide a permanent record of conditions during the excavation and recommend suitable engineering measures for the improvement of foundation. This permanent foundation record will assist in making better interpretation of post-construction foundation instrumentation data.