Predicting hard rock TBM performance using a multiple regression analysis of RMR classification system

Abstract

This study is to develop a practical empirical model based on a database compiled from 38 tunnel sections along the Karaj water conveyance tunnel for estimating TBM performance with emphasis on Field Penetration Index (FPI). A multiple linear regression correlating FPI with basic RMR input parameters and three additional parameters including tunnel depth, Elastic modulus and the angle between tunnel axis and discontinuity planes was presented. Analysis of the first developed model showed that Alpha angle, tunnel depth and groundwater condition must be excluded from the model because of their poor correlation with FPI. Analyzing the new model by elimination of these parameters resulted in creating a new predictive model with no significant multi-collinearity between independent variables. The comparison between the predicted and actual measured FPIs showed high strength of correlation with coefficient of 0.84. This paper discusses previous works in this area, reviews the available data from Karaj tunnel project, methodology for analysis, and introduces a convenient empirical predictive model for TBM performance. © 2011 ARMA, American Rock Mechanics Association.