Foundation floor mapping is essential for very important structures to provide permanent data set for geological interpretations. Prototype fast breeder reactor (PFBR) is being constructing at Kalpakkam, India. Nuclear Island Connected Building (NICB) is the main nuclear safety related structure of (PFBR), and is resting on a raft of 101.5 m 9 93 m size at about 20 m below the existing ground level. Geological floor mapping was prepared after the excavation. 2 m 9 2 m grids were used for sampling study and mapping of the walls and floor. The floor region of this raft foundation was seen to contain certain weathered zone with fractures of thickness of in the order of 2 m. No evidences of faulting/shearing were observed on the surface of the floor area. The entire floor area was made up of compact and sound rock mass. However, there were some isolated patches of soft weathered/altered rock and small fractures in the rock. The structural features observed during the mapping exercise indicated the need for consolidation grouting so that the entire floor area function as single rock mass. This foundation geological map will assist in making better interpretation of post-construction foundation instrumentation data.

Many engineering structures have to be founded deep into rock or on rocks, especially in a nuclear reactor site. Numerical finite-element and boundary-element analyses for studies of the stress and displacement distribution of any rock engineering projects are based on deformation parameters. Empirical relations are available to relate the rock mass deformation modulus to index properties, but the equations include some uncertainties relating to the variability of rock type and the heterogeneous nature of the rock masses. For important structures, site-specific parameters have to be evaluated to assess strains and stresses in rock due to various load combinations. Pressuremeter tests, cyclic plate load tests, uniaxial jack tests and seismic crosshole tests were conducted to evaluate in situ design parameters. The objective of this paper is to evaluate deformation parameters of a prototype fast breeder reactor from these in situ tests. For high strain deformation modulus, the pressuremeter modulus is comparable with the rock mass modulus obtained from laboratory results in association with rock quality designation. Crosshole tests results are used for evaluation of low strain modulus.