IJBTT

Back Analysis of Rock Support and Final-Lining Recommendation for Rock Class C1 of a Tunnel

Back Analysis of Rock Support and Final-Lining Recommendation for Rock Class C1 of a Tunnel
	© 2023 by IJETT Journal
	Volume-71 Issue-1
	Year of Publication : 2023
	Author : Arun Kumar, M. Sunil Singh
	DOI : 10.14445/22315381/IJETT-V71I1P208

How to Cite?

Arun Kumar, M. Sunil Singh, "Back Analysis of Rock Support and Final-Lining Recommendation for Rock Class C1 of a Tunnel," International Journal of Engineering Trends and Technology, vol. 71, no. 1, pp. 79-93, 2023. Crossref, https://doi.org/10.14445/22315381/IJETT-V71I1P208

Abstract
This paper provides recommendations for the rock support system and final lining of the tunnel along the Mumbai – Nagpur expressway using actual field data obtained from geotechnical investigation and PHASE2 software for numerical analysis and validation. Being a real-time study of an ongoing project, this may be a help to various researchers and consultants working in the field of tunnel support systems.Instrumentation data has been utilized for back analysis in order to determine the rock mass parameters to be considered in the numerical back analysis. The classification has been defined as per Class C1 with respect to the RMR value encountered at the site.Based upon the validated rock mass parameters, numerical analyses have been carried out for C1 for different rock covers using PHASE2 software. For Class C1, analysis has been carried out for rock cover of 12m and 25m min and max, respectively. It was observed that deformations in all the cases are small and are much smaller than the permissible convergence in the tunnel, which is taken as 0.5% of the tunnel span,i.e. 89.05mm. The maximum Axial force in a Rock bolt for a 25m cover is approximately 7% and for a 12m cover is approximately 30% of the capacity of a rock bolt. Also, the rock bolts are well outside the plastic zone in each case. Hence the provided rock bolts are safe and adequate for this case. The proposed final rock support is 25mm dia 4000mm long @ 2500mm c/c Rock bolt (Staggered)at the north end of the tunnel and 50 mm PFRS on the south end.

Keywords
Class C1, PHASE 2 software, RMR value, Rock class, Rock bolt.

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