Dynamic and probabilistic multi-class prediction of tunnel squeezing intensity

Yu Chen, Tianbin Li, Peng Zeng, Junjie Ma, Edoardo Patelli, Ben Edwards

Research output: Contribution to journalArticle

Abstract

Tunnel squeezing is a time-dependent process that typically occurs in weak or over-stressed rock masses, significantly influencing the budget and time of tunnel construction. This paper presents a new framework to probabilistically predict the potential squeezing intensity and to dynamically update the prediction during construction based on the sequentially revealed ground information. An extensively well-documented database, which contains quantitative data from 154 squeezing sections with 95 unpublished inventories is established. A Decision Tree method is employed to train a probabilistic multi-classification model to predict the tunnel squeezing intensity. The trained classifier is then integrated with a Markovian geologic model, which features embedded Bayesian updating procedures, to achieve a dynamic prediction on the state probabilities of the geologic parameter within the model and the resulting squeezing intensity during excavation. An under-construction tunnel case—Miyaluo #3 tunnel—is used to illustrate the proposed framework. Results show that the Decision Tree classifier, as opposed to other black-box models, is easy to be interpreted. It provides reliable predictive accuracy while leading to insights into the understanding of the squeezing problem. The strength-stress ratio (SSR) is suggested to be the most important factor. Moreover, the implementation of the updating procedures is efficient since only a simple field test (e.g. Point Load index or Schmidt rebound index) is required. Multiple rounds of predictions within the updating process allow different levels of prediction, for example long-range, short-term, or immediate, to be extracted as useful information towards the decision-making of construction operations. Therefore, this framework can serve as a pragmatic tool to assist the selection of optimal primary-support and other construction strategies based on the potential squeezing risk.

Original languageEnglish
Pages (from-to)3521-3542
Number of pages22
JournalRock Mechanics and Rock Engineering
Volume53
Issue number8
Early online date17 May 2020
DOIs
Publication statusE-pub ahead of print - 17 May 2020

Keywords

  • Bayesian updating
  • decision tree
  • dynamic prediction
  • Markov process
  • multi-classification
  • tunnel squeezing

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  • Cite this

    Chen, Y., Li, T., Zeng, P., Ma, J., Patelli, E., & Edwards, B. (2020). Dynamic and probabilistic multi-class prediction of tunnel squeezing intensity. Rock Mechanics and Rock Engineering, 53(8), 3521-3542. https://doi.org/10.1007/s00603-020-02138-8