Geotechnical Evaluation of Lakhwar Underground Powerhouse, Uttrakhand Himalaya, India
The stability of underground excavations is dependent on the conditions of rock mass, in situ stress and distribution pattern of structural discontinuities of the area. This chapter discusses the stability status of the Lakhwar underground powerhouse in H
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Geotechnical Evaluation of Lakhwar Underground Powerhouse, Uttrakhand Himalaya, India R. Anbalagan, Sujata Parida, and K. Lakshmanan
Abstract The stability of underground excavations is dependent on the conditions of rock mass, in situ stress and distribution pattern of structural discontinuities of the area. This chapter discusses the stability status of the Lakhwar underground powerhouse in Himalaya using RMR and Q System to predict rock load and support requirements. Boundary Element Method (BEM) has been used to examine the stress distribution around the machine hall cavity to estimate the stability. In addition, the stability of the powerhouse has also been studied. Based on these analyses, suggestions on suitable support system for the power house are made.
13.1
Introduction
The underground space technology has gained greater importance in the recent times to overcome the problems of space and to accommodate strategically important projects. Designing and constructing large underground openings such as powerhouse cavities are always difficult in the seismically active Himalayan terrain which is characterized by high in situ stresses. The overall stability of the underground openings is dependent on a number of factors including, but not limited to, the conditions of rock mass, in situ stresses, stiffness of support, size and shape of cavity, method of construction and sequence of construction. Rock mass condition and its possible behavior during excavation help in calculating the stability of the cavity and the rock load. The in situ stresses also play an important role in the stability of an underground opening. The main factor in the design of underground openings is to help the rock mass to support itself.
R. Anbalagan • S. Parida (*) • K. Lakshmanan Department of Earth Sciences, IIT-Roorkee, Roorkee, Uttrakhand, India e-mail: [email protected] Mu. Ramkumar (ed.), On a Sustainable Future of the Earth’s Natural Resources, Springer Earth System Sciences, DOI 10.1007/978-3-642-32917-3_13, # Springer-Verlag Berlin Heidelberg 2013
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Fig. 13.1 Location of the study area
The Lakhwar dam is under construction in the lower reaches of Yamuna River (Fig. 13.1). It envisages the construction of a 204 m high concrete gravity dam (30 310 0600 :77 560 1500 ) near Lakhwar village (Sharma et al. 1999) with an underground powerhouse of 300 MW of installed capacity (Fig. 13.2). The powerhouse cavity has the dimensions of 46 m (height), 20 m (width) and 130 m (length) to accommodate the turbines and generators. The axis of the machine hall cavity is aligned in N60 W – S60 E direction, which is nearly parallel to the dam axis.
13.2
Geological Setting
The rocks exposed at the Lakhwar dam site and underground powerhouse are dolerites, which intruded the country rock consisting of phyllites, slates and quartzites of Chandpur Formation. The dolerites are dark green in color and coarse to medium grained, which become fine grained close to contacts of country rocks. The dolerites ar
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