Geological and geotechnical investigations of Loharinag-Pala Hydroelectric Project,Garhwal Himalaya,Uttarakhand   总被引：1，自引：0，他引：1  

Ajay K. Naithani  A. K. Bhatt  K. S. Krishna Murthy 《Journal of the Geological Society of India》2009,73(6):821-836

The project area, forming a part of Bhagirathi valley, exposed rocks classed as central Himalayan crystallines and are medium to high grade metamorphics. The rock types exposed are feldspathic gneisses, quartz-biotite schists, garnet-biotite schist, biotite gneisses, migmatites and amphibolites. To design the rock support for the underground structures of desilting chambers, HRT, surge shaft, pressure shafts, power house, TRT and for the foundations of barrage and intake of desilting chambers, rock mass classifications was attempted following the methods of Bieniawski Rock Mass Rating (RMR) Classification and Tunnelling Quality Index (Q) of Barton et al. RMR technique involves collection of data on rock strength, RQD (%), spacing of discontinuities, condition of discontinuities and groundwater condition, while the ‘Q’ involves collection of data on RQD (%), joint set numbers (Jn), joint roughness number (Jr), joint alternation number (Ja), joint water reduction factor (Jw) and stress reduction factors (SRF). The permeability test in the overburden was done by the constant head method, while in the bed rock portion conducted by packer test. The result indicates that the rock masses of the area fall under the good, fair and poor rock quality. Augen gneiss of power house area is coming under the category of moderately strong rock as proved by deformability characteristics and strength parameter. On the basis of above study recommendations have been made for the proper and safe construction of the project components.  相似文献   

Shear wave velocity structure of the upper mantle under the NW Indian Ocean     

A. Manglik   《Journal of Geodynamics》2002,34(5)

Shear wave velocity structure of the NW Indian ocean is analysed by using fundamental mode Rayleigh wave dispersion data of 67 events occurred during 1990–98 at the central Indian Ridge and Carlsberg Ridge and recorded at Hyderabad Geoscope station (HYB). These events provide a dense coverage of the NW Indian ocean and Chagos-Laccadive Ridge (CLR) in the back-azimuthal range of 192–253° with respect to HYB. The dispersion curves, corrected for continental and young ocean paths, indicate large variations in the shear wave velocity structure of the region. The group velocities along the CLR path support a typical aseismic ridge-type structure. However, the central region bounded between the Central Indian Ridge and India in the back-azimuth of 206–234° indicates a decrease in the group velocity by 0.1 km/s. Inversion of these data sets indicates presence of aseismic-ridge type lithospheric structure for CLR, a thin lithosphere and high velocity block in the depth range of 125–200 km for the central region, and a continental-type lithospheric structure for the northern-most part of the Indian ocean. It is inferred that the dynamic state of the upper mantle in this region has been significantly perturbed during the recent geological past.  相似文献   

Rheological thickness and strength of the Indian continental lithosphere     

A Manglik  R N Singh 《Journal of Earth System Science》1992,101(4):339-345

The estimates of rheological thickness and total lithospheric strength for the Indian continental lithosphere have been obtained based on the representative rheological properties of upper crust, lower crust and upper mantle, and some of the available heat flow and heat generation data. The rheological thickness, computed at different locations in the Indian shield, shows lateral variation ranging from 79km in the southern part to 65 km in the northern part for a strain rate of 10^-14 s^-1. The total strength of the continental lithosphere is of the order of 10¹³ Nm^-1 for the same value of strain rate and decreases northward. The computations carried out for a range of strain rates show an increase in the rheological thickness and strength of the lithosphere with increasing strain rate. These results would be important in understanding the flexural response of the Indian continental lithosphere to surface and subsurface loading, and response to tectonic forces acting on it.  相似文献   

A moving boundary solution for solidification of lava lake and magma intrusion in the presence of time-varying contact temperature     

Ajay Manglik 《Journal of Earth System Science》2005,114(2):169-176

During the solidification of a lava lake heat is released convectively from the top surface as well as conductively into the country rock from the base, leading to non-uniform solidification. The upper solidified layer grows at a faster rate than the lower solidified layer. Similarly, solidification of magma intrusion within the crust is also non-uniform due to the presence of thermal gradient in the crust. Available analytical solution for solidification of a melt layer assumes only symmetric cooling about the centre of the layer. In the present work a moving boundary solution for thermal evolution and non-uniform solidification of a melt layer incorporating time-varying contact temperature conditions at both of its boundaries is developed. The solution is obtained by using the Fourier spectral approach in the space domain and a modified finite difference scheme in the time domain, and is validated with available analytical solutions for simple cases and a semi-analytical solution for the case involving temperature gradient in the country rock. This solution can be used to analyse solidification of lava lakes and magma intrusions experiencing time-dependent temperature variation at their contacts with the country rock.  相似文献   

Rapid visual screening of different housing typologies in Himachal Pradesh,India     

Ajay Kumar  Sreerama  Rajaram  Chenna  Mishra  Shashank  Pradeep Kumar  Ramancharla  Karnath  Anoop 《Natural Hazards》2017,85(3):1851-1875

Natural Hazards - Methods capable of assessing the vulnerability of houses for future earthquakes are of fundamental importance for the safety and development of an area. As the detailed assessment...  相似文献   

Hydro-climatological changes in the Colorado River Basin over a century     

Ajay Kalra  Soumya Sagarika  Pratik Pathak  Sajjad Ahmad 《水文科学杂志》2017,62(14):2280-2296

This study evaluates changes in streamflow, temperature and precipitation over a time span of 105 years (1906–2010) in the Colorado River Basin (CRB). Monthly precipitation and temperature data for 29 climate divisions, and streamflow data for 29 naturalized gauges were analyzed. Two variations of the Mann-Kendall test, considering lag-1 auto correlation and long-term persistence, and the Pettitt test were employed to assess trends and shifts, respectively. Results indicated that streamflow increased during the winter–spring months and decreased during the summer– autumn period. Decreasing trends in winter precipitation were identified over snow-dominated regions in the upper basin. Significant increases in temperature were detected over several months. Major shifts were noticed in 1964, 1968 and in the late 1920s. Increasing temperature while decreasing streamflow and precipitation were noticed after major shifts in the 1930s, and these shifts coincided with coupled phases of El Niño Southern Oscillation and Pacific Decadal Oscillation.