 1Status of tunnelling.pdf (Size: 158.86 KB / Downloads: 71) Abstract A considerable amount of tunnelling work has been going on in India for hydroelectric, irrigation, roads and railways projects. Most of these projects are located away from urban areas. The use of tunnelling for urban utilities, such as water supply, sewerage disposal and metro rail has recently begun. A few projects have been completed and some are under construction in metropolises such as Mumbai, Calcutta and Delhi. The present status of tunnelling and its future potential in India is highlighted in the paper with emphasis on tunnelling projects for hydro-power developments, as this sector presently has maximum underground construction activity in India. The tunnelling technologies f Introduction Tunnels and underground openings have been used since pre-historic times. The earliest examples of underground structures in India were in the form of dwelling pits cut into the compacted loess deposits in Kashmir around 3000 BC and 500 BC. This was brought to notice by the Archaeological Survey of India ŽASI. during excavations in 1960. Dwellings belonging to 1600 BC were also noticed at Nagarjuna Konda, in Andhra Pradesh State. The world’s most beautiful and elaborate rock tunnels, the rock temples in Maharashtra State, cut out of the hardest rock and having a length of a few kilometers, indicate ancient experiences in engineering by humans. Water supply project in Mumbai There are two major service reservoirs in Mumbai city for the supply of drinking water to the most thickly populated areas of central and southern Mumbai. One is located at Malabar hill on the west side, and the other at Bhandarwada hill on the east side of the Mumbai city. It was necessary to bring more fresh water to these reservoirs due to increasing demand. It was decided to excavate a tunnel for supplying the water to the reservoirs. Tunnel boring machines were procured with a view to eliminate the blasting and consequent ground vibrations. In Mumbai, the rock strata is found at 611 m below the ground surface. The rock type is predominantly volcanic breccia and basalt. The compressive strength of rock is generally in the range of 1770 MPa and elastics modulus ranges between 0.7 and 1.5105 kgcm2. In order to augment the water supply to Malabar hill and Bhandarwada hill reservoirs, the following three tunnel alignments were proposed. Tunnelling technology The Indian practice of providing steel rib supports for large caverns, which was followed for quite a long period until the 1980s, is being given a ‘farewell’ with the more frequent adoption of the latest technology of rock bolts and shotcrete. Since the 1990s, tunnel construction in India has followed the trends of international practices. This applies to all spheres of tunnelling activities with excavation, supporting and lining. Hydraulically operated drilling jumbos with two booms and three booms Žbesides multiple booms. have been introduced in drilling at Chamera project and being widely used in other projects such as Uri, Dulhasti, Ranganadi and Nathpa-Jhakri. In addition to the empirical approach, state-of-the-art technologies, such as numerical modelling, have been used for design purposes, which provides a better understanding of the rock mass behaviour around the excavated underground openings. In a few cases, continuous deformation measurements are carried out to verify the results of numerical and empirical approaches and to carry out ‘back analysis’. Instrumentationmonitoring From the stage of no instrumentation, underground construction projects in India have reached a stage where instrumentation has become mandatory. Various monitoring instruments such as tape extensometers, borehole extensometers, load cells, pressure cells and piezometers are being developed indigenously. Conclusions India has been facing challenging geological conditions during tunnelling in Himalaya. Thus, India has earned precious experience of tunnelling through squeezing grounds, intra-thrust zones, water charged rock masses and wide faults, etc. Today, India can take up challenging underground construction projects at an economical cost. There is an urgent need to boost underground space technology to save our world culture from all |
Reference: http://seminarprojects.com/Thread-status-of-tunnelling-and-underground-construction-activities-and-technologies#ixzz2J2FSudpW
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