Principles of Rock Mechanics were employed for solving engineering problems in the areas of water resources development projects and mining industry. Excavation for large sized tunnels and underground power houses, particularly in the Himalayan region presented many complex geotechnical problems. The area was characterised by numerous and continuous thrust and shear zones, squeezing grounds, toxic gases and ground water movements. Field and laboratory tests and in-situ measurements were carried out in an attempt to understand the rock mass behaviour. Some typical cases are described. In the mining industry, longwall and knife edge methods were used. Surface movements and the behaviour of different materials were studied.
Les principes de la mecanique de roches ont ete utilises pour resoudre les problèmes mecaniques qui se posent dans les amenagements hydrauliques et dans l'industrie minière. L'excavation pour la construction des galeries et des centrales hydroelectriques souterraines de grandes dimensions,particulièrement dans la region de l'Himalaya, posait un grand nombre de problèmes geotechniques. Cette zone est caracterisee par de nombreuses failles anormales et zones de cisaillement continues, le tassement du sol, des gaz toxiques et le mouvement de la nappe phreatique. Les examens sur place et dans le laboratoire ainsi que les mesures "in-situ" ont ete effectues dans le but d'expliquer les comportements de la masse rocheuse. Plusieurs cas ont ete presentes. Dans l'industrie minière, les methodes de longwall et de couteau de balance ont ete utilisees. Le mouvement de surface et le comportement des differents materiaux de remblayage ont ete etudies.
Die Grundsatze der Gebirgsmechanik wurden zur Lösung der technischen Aufgaben auf dem Gebiet der Entwicklungsprojekte fuer Wasserhaushalt und Bergbauindustrie angewandt. Der Ausbruch grosser Stollen und unterirdischer Kraftwerke, besonders im Gebiet des Himalaya, stellte viele komplexe geotechnische Probleme. Das Gebiet war durch zahlreiche aktive Ueberschiebungs- und Scherzonen, drueckendes Gebirge, Giftgase und Grundwasser gekennzeichnet. Feld- und Laborversuche und in situ Messungen wurden durchgefuehrt, um das Verhalten des Gebirges zu verstehen. Einige typische Falle sind beschrieben. In der Bergbauindustrie wurden Strebbau- und Messerschneidemethoden verwendet. Die Oberflachenbewegungen und das Verhalten von verschiedenen Ersatzmaterialien wurden untersucht.
Various situations where principles of rock mechanics have been employed for solving engineering problems in India can broadly be classified into two categories Viz water resources and mining. Some of the details of such problems and the experience gained in the process of tackling them are indicated below.
Due to exploitation of favourable sites in the past years, river valley projects all over the world are now being constructed at incompetent sites. Most of these sites are inherently weak and would have been rejected a few years back. One such example is the Himalayan region in India where some of the most difficult projects involving high rockfill dams, tunnels and underground powerhouses are under construction. This region of the youngest mountains in the world, is characterised by the presence of numerous and continuous belts of thrusts and shear zones, problems of squeezing grounds, active stresses due to high overburden and tectonic activity, hot water springs, toxic gases, ground water movements and very weak and friable rocks forming ridges and valleys. While the construction of every project in the Himalayan region is an experience in itself, brief details of two of the typical projects are given below.
The project, located in the foothills of the Himalayas in Uttar Pradesh, one of the northern States of India, is being constructed in four stages. Stage I: Construction of a barrage a cross river Yamuna at Dak Pathar and construction of two run-of-the-river type surface powerhouses exploiting the falls through the power channel. This part of the construction is over. Stage II: This stage is being executed in two parts. Part 1: Construction of a dam across river Tons - a tributory to Yamuna - and a 6,25 km long, 7 m diameter tunnel leading to an underground powerhouse at Chhibro for generating 240 MW. This part of the construction is over. Part 2: A 5,91 km long tunnel between the underground powerhouse at Chhibro and a surface powerhouse at Khodri, short circuiting a loop of river Yamuna. Most of the construction works of this stage are over excepting about one kilometer of tunnelling. Fig 2 shows a layout plan of stage II of the project. Stage III: A high rock fill dam at Kishau, which is yet to be constructed. Stage IV: A barrage across river Assan and generation of power through drop in the power channel. Interesting and challenging problems from the geotechnical engineering View-point were met with during the execution of Stage II of the project. The first part of the tunnel from the dam to the underground powerhouse passed through comparatively harder rocks and was completed in time despite some difficult situations.
