Browsing by Author "Dangwal, V."

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    Numerical Analysis of a Collapsed Tunnel: A case study from NW Himalaya, India
    (Springer, 2022) Srivastav, A.; Pandey, V.H.R.; Kainthola, A.; Singh, P.K.; Dangwal, V.; Singh, T.N.
    The present research explores the effect of various support system on deformation in a shallow tunnel from North-Western Himalaya, India. The deformation measurements assessed through field investigation were utilized to simulate the pre-existing and the present ground scenario, and furthermore in the evaluation of elastic parameters such as Young�s modulus and Poisson�s ratio through finite element back analysis. Back-analysed model predicted a Young�s modulus of 32�MPa and Poisson�s ratio of 0.3. Afterwards, the effect on the deformation of surrounding groundmass for unexcavated and the present condition were numerically ascribed at three different stages of excavation. The numerical application of forepoling and steel liners showed a marked reduction in the tunnel deformation. The combined effect of applied support methods was also enumerated and compared with individual stabilization method. This assessment may aid engineers and planners working in similar geological conditions, by making the excavation safer, stable and economical. � 2021, Indian Geotechnical Society.
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    Parametric Study of Influence of Groundwater and Joint Spacing on Stability of a High Overburden Tunnel
    (Springer Science and Business Media Deutschland GmbH, 2022) Srivastav, A.; Kainthola, Ashutosh; Dangwal, V.; Singh, T.N.
    In a complex terrane, excavation engineers have to take into account various problems and challenges. Himalaya is rugged with highly undulating topography, major discontinuous boundaries, extremely heterogenous lithology and complex subsurface water system, which makes the excavation process more troublesome in it. Groundwater decreases the strength of the rock mass through increase in pore-water pressure and decrease in effective stresses. The Present research is based on estimation of influence of groundwater and discontinuity spacing on tunnel stability through field deformation and numerical simulation. The study site is part of Rishikesh-Karnaprayag railway project in Uttarakhand Himalaya. The tunnel has the diameter of 7.8�m with the overburden depth of 200�m. Sandstone rocks surrounding the excavation boundary belong to Mandhali formation. Initially, numerical model was simulated using the properties of discontinuities exposed at the tunnel phase and the mean properties of Borehole log data nearest to the excavation site. Afterward, deformation is calibrated at different water pressure heads and various discontinuity spacings. The variation in deformation is significant with variation in groundwater pressure and discontinuity spacing and reveals the importance of these parameters during underground excavation and stability assessment. � 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.