IISER MOHALI

Abstract: India is experiencing a period of significant infrastructure development, particularly in key sectors like railways, highways, and hydropower. However, most of the projects specially in hilly terrain face inordinate delays in completion due to various constraints resulting in cost overrun. Often the time and cost overrun in completion of projects are explained by a term "geological surprise or geological uncertainties" which refers to sudden occurrence of extraordinary adverse geological conditions during construction which were not anticipated at the time of investigation. Construction of projects especially in the Himalayas has been a challenging task due to complex geological conditions. Extremely rugged, densely forested, and inaccessible topography provide limited scope for investigation and more assumptions/projections are made, which finally becomes a cause of concern due to occurrence of geological uncertainties. Conventional exploration techniques like drilling/drifting are expensive and time- consuming and provide limited information. On the other hand geophysical techniques can provide geological information in a very fast and economic way. Utilizing the advanced geophysical techniques along with comprehensive geological mapping can be very helpful in minimizing geological uncertainties.
New age geophysical techniques are fast, economical and capable of providing finer details and continuous coverage of the investigated area. In the last two decades, development in software and hardware have considerably improved the reliability and applicability of geophysical techniques and also facilitated in generation of 3D models of subsurface conditions in complex geological environment. These techniques are being utilized successfully to resolve some of the critical geological issues in most of major construction projects. Some of the new age technologies are:
• Electrical Resistivity Tomography (ERT)
• Seismic Refraction Tomography (SRT)
• Seismic Tomography
• MASW ( Multi Spectral Analysis of Surface Wave)
• GPR ( Ground Penetration Radar)
• TEM ( Transient Electromagnetic)
New age geophysical investigation techniques have come up recently to bridge the gaps and proved to be effective in more accurate prognosis of sub surface geological condition down to considerable depth. The above geophysical investigation techniques are cost effective, and can provide continuous coverage of large areas in a very quick time. These techniques are extremely useful in developing more accurate sub surface geological model of the any project components.
In the present talk details of the new age geophysical techniques and some interesting case studies are discussed.