Optimization of support system for desilting chambers of Nathpa Jhakri hydroelectric project using discontinuum modeling

摘要

Stress analysis using numerical modeling is widely accepted for design of underground excavations due to their ability to incorporate most of the complexities and their reliability to produce realistic information. This paper presents the results of stress analysis carried out to bring out the effect of Adlt-II. The effect of discontinuities and the intersection of Adit-II with chambers were brought out in these studies. Actual jointing details like dip, dip direction and locations supplied by the project authorities were simulated In the analysis explicitly. The shotcrete and rock bolts were able to reduce the deformations to a small extent only as the existing support system was inadequate. Strengthening of the support systems in the walls of the chambers may be required near the Adit -II junctions to an extent of 20m on either side of the Adit -II walls. As the additional support system consisting of cable anchors has little effect, longer, bolts of 12m length were recommended. As seen from the performance of the bolts, majority of the yielded bolts exist in the vicinity of Adit -II region. The spacing of the bolts may be reduced to 1.2 m on either direction to reduce their percentage of failure.