A preknowledge of the stress distribution at points of high stress concentration helps the design engineers in evolving a safe and economical design of costly civil engineering structures. To study the mode of variation in boundary stresses around machine hall cavity due to sequence of gradual excavation, and the effect on boundary stresses around machine hall cavity due to provision of other adjacent cavities, the two dimensional photoelastic method, boundary element method and non linear finite element technique (with sequential excavation) have been used and the results obtained.


Une preconnaissance de la distribution de la contrainte a des endroits de la concentration elevee de la contrainte. aide les ingenieurs dans leurs efforts de developper un dessein sauf et economique des structures couteuses du genie civil. Afin detudier le mode de variation dans les contraintes aux limites autour de la cavite de la salle de machine a cause de 1 excavation graduelle, et I effet sur les contraintes aux limites autour la cavite de la salle de machine du a la presence des cavites contigues, la methods photoelastique bi dimensionelle, la methode de 1 element de la limite et la technique de l element fini non lineaire (avec l excavation consecutive) ont ete utilisees et les resultats obtenus.

AUSZUG Der Konstrkteur der von der Beanspruchungsverteilung an der Stellen der Hoch konzentration (von Beanspruchung) im voraus Bescheid weiss, ist in einer gunstigeren Lage eine sichere Bauart fur die kostspieligen Baustrukture zu entwerfen. Umdie Art und Weise von der Anderung der an der Maschinenhalle herum herrschenden Randbeanspruchungen zu untersuchen, sind die folgenden Verfahren angewendet worden: Zweidimetlsionale Photoelastischenmethode, Randelement Methode, Nichtlineare Finitelementen technique (mit stufenweisen Ausgrabungen).


Most of our water resources, particularly the hydroelectric potential lie in the Himalayan region. The topography in this region is such that most of the projects have unavoidable elements of underground excavations. Underground cavities are constructed either in rock medium for power house, water conductor system in the form of tunnels or in concrete under dam for drainage, inspection, dewatering, instrumentation, etc. For the design, stress analysis of underground cavities in a virgin stress field due to load and geometrical discontinuity is very essential. Pre knowledge of stress distribution at points of high stress concentration helps the design engineer in evolving a safe and economical design of costly water resource structures. Various stress analysis techniques such as Photoelastic Method, Boundary Element Method, Finite Element Method, Dynamic Relaxation Method, Displacement Discontinuity Method, can be viably used for the solution of the problem. All the methods give a reasonable approximation to the elastic stress field around the cavities provided that the limitations associated with each method are carefully observed.

The usefulness of 2 D Boundary Element Method, 2 D linear Finite Element Method and Photo elastic Technique for the estimation of stesses around

(Figure in full paper)

openings with particular reference to Tehri Power House for designing shape of underground (Machine hall) cavity have been discussed in the paper.

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