Influence of topography on in situ stress parameter at the proposed powerhouse sites of Rupaligad re-regulating project, Nepal

摘要

In-situ stress parameters of the rock mass are one of the vital inputs for the design of any large underground openings. In general, the in-situ stress magnitude and orientation are influenced by topography, and major geological structures like folds, faults and intrusions. These structures bring about local heterogeneities in rocks, thus leading to change in orientation of stress trajectories. In this paper we would like to present a case study about the influence of topography/valley on in situ stress measurements carried out at a hydroelectric project site. The stress measurements were carried out by HTPF method on both left and right banks of the river at the proposed powerhouse sites. The test site/borehole location of left bank is in close proximity to valley compared to its counterpart. The (in-situ stress) major horizontal principal stress direction of the rock mass is N 20° and N 130° at right and left banks respectively. It is inferred that the horizontal stresses might have been relaxed due to the absence of influence of topography on the right bank whereas the direction of in-situ stress tensor at the left bank might be perturbed by topography due to the close proximity of the valley.