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Tandon R.S.,National Geotechnical Facility | Gupta V.,National Geotechnical Facility | Gupta V.,Wadia Institute of Himalayan Geology
Bulletin of Engineering Geology and the Environment | Year: 2014

Various rock types-including highly deformed to undeformed quartzites, granites, granitic gneisses, gneisses, metabasics (meta-amphibolites and meta-dolerite), and dolomites-collected from different formations of the Lesser and Higher Himalayas were tested to evaluate correlations between the uniaxial compressive strength (UCS) and the point load test (PLI), Schmidt hammer rebound (SHR) value, and compressional wave velocity (Vp). Various equations between UCS and PLI, SHR, and Vp were obtained using regression analysis. It was found that there is high scatter in the data when all lithologies are considered together, whereas this scatter is reduced when the lithologies are considered individually. This was attributed to wide variations in the mineralogical and textural characteristics of different rocks. Furthermore, it was also noted that quartzites exhibit high scatter in their data points, even though they are monomineralic. Thin section studies revealed that different microfabrics have been produced in the quartzites, due to the actions of different deformational phases during tectonic activity in the area. Therefore, it is necessary to treat deformed and undeformed rocks separately when deriving such equations. © 2014 Springer-Verlag Berlin Heidelberg.

Tandon R.S.,National Geotechnical Facility | Gupta V.,Wadia Institute of Himalayan Geology | Sen K.,Wadia Institute of Himalayan Geology
Journal of Earth System Science | Year: 2015

The present contribution summarizes the results of a study focusing on the influence of quartz microstructures on the seismic wave velocities in the quartzites of the Garhwal Himalaya. Quartzites being monomineralic were chosen for the present study so as to nullify the effect of other mineral constituents on the seismic velocity. Samples were collected from different tectonic settings of the Higher and Lesser Himalayas which are separated from one another by the major tectonic zone ‘Main Central Thrust’ (MCT). These are mainly Pandukeshwar quartzite, Tapovan quartzite and Berinag quartzite. The samples of Berinag quartzite were collected from near the klippen and the thrust, termed as Alaknanda Thrust. The vast differences in microstructures and associated seismic wave velocities have been noted in different quartzites. It has also been observed that quartzites of the MCT zone and Alaknanda Thrust have higher seismic velocities. This is because of their coarse-grained nature of the rocks as evidenced by the strong positive relation between seismic velocities and grain area. The coarsening is either due to the operation of grain boundary migration and grain area reduction process or high aspect ratio/shape preferred orientation. The quartzites located around Nandprayag Klippen have undergone static recrystallization and exhibit the lowest seismic wave velocities. © Indian Academy of Sciences.

Gupta V.,Wadia Institute of Himalayan Geology | Tandon R.S.,National Geotechnical Facility
Bulletin of Engineering Geology and the Environment | Year: 2014

The transportation route between Chamoli and Badrinath in Uttarakhand is mainly a pilgrimage route to the famous Badrinath temple, at an elevation of ~3,100 m asl. It is estimated that some two to three million vehicles use this road annually, particularly between May and October. The Lesser and Higher Himalayan rocks exposed at 23 localities along the transportation corridor contain numerous joints. In view of their orientation, blocks of rock of varying sizes are susceptible to falling, endangering the vehicular traffic and the numerous village settlements along the route. In this study, kinematic rockfall hazard analysis was carried out for all the 23 localities where in situ rocks are observed. The results of the analyses were evaluated and the areas classified as of low, moderate, or high hazard. © 2014 Springer-Verlag Berlin Heidelberg.

Gupta V.,Wadia Institute of Himalayan Geology | Bhasin R.K.,Norwegian Geotechnical Institute | Kaynia A.M.,Norwegian Geotechnical Institute | Chauhan V.K.,Wadia Institute of Himalayan Geology | And 3 more authors.
Geomatics, Natural Hazards and Risk | Year: 2015

Finite element analysis of failed slope of the Surabhi Resort landslide located in the Mussoorie township, Garhwal Himalaya has been carried out using shear strength reduction technique. Two slope models viz. debris and rock mass were taken into consideration in this study and have been analysed for possible failure of slope in future. Critical strength reduction factor (SRF) for the failed slope is observed to be 0.28 and 0.83 for the debris and rock mass model, respectively. A low SRF value of the slope revealed significant progressive displacement in the zone of detachment. This has also been evidenced in the form of cracks in the building of Surabhi Resort and presence of subsidence zones in the Mussoorie International School. These results are consistent with the study carried out by other workers using different approach. © 2015 Taylor & Francis

Gupta V.,Wadia Institute of Himalayan Geology | Nautiyal H.,Wadia Institute of Himalayan Geology | Kumar V.,Wadia Institute of Himalayan Geology | Jamir I.,Wadia Institute of Himalayan Geology | Tandon R.S.,National Geotechnical Facility
Natural Hazards | Year: 2016

Garhwal Himalaya has witnessed extreme climatic conditions in the form of incessant rainfall during June 15–17, 2013, generating numerous primary as well as secondary landslide hazards due to flooding event in the Bhagirathi River. This was probably the second highest flood after the 1978 flood in the area. The paper documents the spatial distribution of landslides and its consequences in the lower reaches of the Bhagirathi Valley between Bhatwari and Uttarkashi. It has been observed that within a stretch of 28 km in the study area, the river gradient is highly variable ranging from 3.6 to 66.6 m/km and is marked by three major knick points. These knick points are well correlated with the disposition of thrusts and a fault present in the area. An inventory of 23 active landslides has been prepared. Based on these knick points, the entire area has been divided into four zones. The area between Bhatwari and Ganeshpur is marked by the zone of transportation and between Ganeshpur and Uttarkashi, the zone of deposition of river sediments. It has been estimated that there is an average aggradation of about 0.5 m/year in the Bhagirathi River around Uttarkashi. Further, the huge volume of material deposited in the river around Uttarkashi township is posing serious threat to the slope stability on either banks of river. This calls for an urgent need for the formulation of policy for dredging the material from riverbed in order to maintain the continuous and uninterrupted flow of water during high discharge, in order to mitigate the problems of slope stability along the course of the river. © 2015, Springer Science+Business Media Dordrecht.

Gupta V.,Wadia Institute of Himalayan Geology | Bhasin R.K.,Norwegian Geotechnical Institute | Kaynia A.M.,Norwegian Geotechnical Institute | Tandon R.S.,National Geotechnical Facility | Venkateshwarlu B.,National Geotechnical Facility
Natural Hazards | Year: 2016

Nainital township located in the Kumaun Lesser Himalaya is known to be vulnerable to landslides since past, and it has been reported that half of the area of the township is covered with debris generated by landslide. A disastrous landslide in the Rais Hotel locality on the right side of the Balia Nala struck during September 2014 after the excessive rainfall. Geologically, the area dominantly comprises limestone with shale and slate which are highly crushed and weathered due to the presence of the Nainital Lake Fault that extends into Balia Nala as Balia Nala Fault. Ground-penetrating radar study depicts that these rocks are overlain by thin debris cover of the order of 5–10 m. The geotechnical studies confirm these rocks and the overlying soil as having very low strength. The landslide has triggered because of the excessive rainfall in the area. It has been observed that rainfall in the area has increased since 2010. An increase in more than 100 % intensity of rainfall during the monsoon from an average 33 mm per day (1995–2013) to 68 mm per day in 2014 is the main triggering factor for the initiation of landslide. The area has been continuously monitored for the last more than 3 years, as the distress in the area has been reported in the form of development of cracks. In order to prevent further sliding, immediate measures have to be taken to channelise water on both sides of the hill slopes so that the ingress of water into the slope is minimum. © 2015, Springer Science+Business Media Dordrecht.

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