Abstract
This study aims to analyze the level of geotechnical risks and predict the advance rate in rock Tunnel Boring Machine (TBM) tunnelling, using a multi-stage fuzzy logic modelling. Twelve parameters, affecting the geotechnical hazard scenario occurrence, which were clustered into five groups, were used as input parameters and the risk level was used as an output parameter. Also, based on the relation between the risk levels and advance rates, a predictive model for advance rate prediction was proposed. To validate the performance of modelling carried out, data from 58 geological zones in section two of the Zagros tunnel, Iran were used. The obtained results showed that by using the fuzzy logic- based model, in most zones, the risk levels estimated are in good agreement with field observations. Moreover, as expected, the high coefficient of determination (R2) of 0.91 between the risk level estimated and the average advance rate achieved in 58 analyzed zones, confirms the ability of the model proposed to predict the level of geotechnical risks. Furthermore, R2= 0.93, Root Mean Square Error (RMSE) of 0.62 and Variance Accounted For (VAF) of 97.51 between the measured and predicted advance rates show the good performance of the new predictive model developed for the advance rate estimation.
Highlights
While tunnel driving, there might be a considerable potential of geotechnical risks due to facing different hazard scenarios such as muddy conditions, fault zones, squeezing, instability, water inflow, mixed ground, gas inflow, which threaten the achievement of the advance rates, costs, and the planned schedule
A methodology based on the Rock Engineering Systems (RES) concept; first introduced by Hudson in 1992, for assessing geotechnical hazards for Tunnel Boring Machine (TBM) tunnelling was proposed by Benardos and Kaliampakos in 2004
Geotechnical risk analyses are of prime importance as they are the main source of risks imposed on the tunnelling process
Summary
There might be a considerable potential of geotechnical risks due to facing different hazard scenarios such as muddy conditions, fault zones, squeezing, instability, water inflow, mixed ground, gas inflow, which threaten the achievement of the advance rates, costs, and the planned schedule. To reduce the risk of facing such hazard scenarios in TBM tunnelling, it is required to evaluate areas which may endanger the operation of tunnelling and to identify the risk level associated with such hazard scenarios. Risk assessment has been one of the key issues in the field of geotechnical engineering. The concept of risk and risk analysis in rock engineering was introduced by Einstein in 1996. A methodology based on the Rock Engineering Systems (RES) concept; first introduced by Hudson in 1992, for assessing geotechnical hazards for TBM tunnelling was proposed by Benardos and Kaliampakos in 2004. The main objective is to propose a fuzzy logic model for the prediction of the level of geotechnical risks in rock TBM tunnelling. The results of this research work may be used for the prediction of risk levels before tunnel driving
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