Abstract

The Kachchh region, located in the highest seismicity belt of peninsular India, has undergone continuous tectonism along regional faults since Mesozoic times. The Kaswati dam, situated between two asymmetrical domes, witnessed a Mw 7.6 earthquake in 2001. The present investigation was carried out around the dam site to assess the cause of geotechnical hazards (ground motion amplification, soil liquefaction, landslide and surface ruptures) that occurred during the earthquake. Analyses of the spatial distribution of discontinuities, their relationship with deformed litho-units and different parameters of discontinuities (i.e. spacing, orientation, persistence, aperture, roughness, filling and weathering) were undertaken to characterize rock mass properties and seepage over time. Measured joint frequency, joint volume, block volume and block shape factor provide quantified data on the degree of jointing, shape and size of the block, Rock Quality Designation, Rock Mass Rating, Geological Strength Index and hydraulic aperture. The coefficient of permeability was determined from rock discontinuities to estimate the amount of seepage of water through rock joints. Rock mass characterization and water retention capacity were measured via an indirect method, which might be useful during the preliminary study of site characterization and produce accurate results at very low cost.

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