Scale-model investigation of brittle tunnel failure using a true-triaxial device
type: CreativeWork
description: Brittle instabilities in tunnel excavation have led to severe consequences such as spalling, violent rock ejection or rock burst, and tunnel collapse. Detached rocks from the tunnel boundary not only compromise the structural integrity of tunnels but also pose significant safety risks to personnel and construction equipment, disrupting the operations. Over the past decades, in-situ studies and laboratory tests have contributed to understanding the brittle failure mechanisms. However, the factors contributing to the progression and extent of brittle failure damage remain not fully understood, limiting the predictive and preventive capabilities. This dissertation aims to improve the understanding of tunnel brittle instabilities through laboratory experiments. The research focused on (1) developing an analog brittle rock model, (2) performing a series of tunnel model tests using a true-triaxial cell, a mock miniature tunnel boring machine (TBM), and acoustic emission (AE) monitoring, and (3) proposing more robust analytical methods and predictive models for brittle failures. The analog rock was designed to mimic the brittle behavior of sedimentary rock while maintaining a low uniaxial compressive strength (UCS). This combination of weak and brittle response was vital, as it allowed for using a lower-capacity true-triaxial loading apparatus and enabled large specimens, making it accessible to observe and document the progressive failure inside the excavated tunnel. The true-triaxial setup and mock miniature TBM allowed for realistic tunneling simulations, capturing unloading stress paths and face support behavior. Damage progression observation and post-mortem investigation provide detailed identification of damage mechanisms around the tunnel boundary, such as surficial spalling and damage zone development, as a V-shaped notch formed from progressive shear fracturing and resembled brittle-to-ductile transition. Real-time data on microcracking progression was captured u…
abstract: Brittle instabilities in tunnel excavation have led to severe consequences such as spalling, violent rock ejection or rock burst, and tunnel collapse. Detached rocks from the tunnel boundary not only compromise the structural integrity of tunnels but also pose significant safety risks to personnel and construction equipment, disrupting the operations. Over the past decades, in-situ studies and laboratory tests have contributed to understanding the brittle failure mechanisms. However, the factors contributing to the progression and extent of brittle failure damage remain not fully understood, limiting the predictive and preventive capabilities. This dissertation aims to improve the understanding of tunnel brittle instabilities through laboratory experiments. The research focused on (1) developing an analog brittle rock model, (2) performing a series of tunnel model tests using a true-triaxial cell, a mock miniature tunnel boring machine (TBM), and acoustic emission (AE) monitoring, and (3) proposing more robust analytical methods and predictive models for brittle failures. The analog rock was designed to mimic the brittle behavior of sedimentary rock while maintaining a low uniaxial compressive strength (UCS). This combination of weak and brittle response was vital, as it allowed for using a lower-capacity true-triaxial loading apparatus and enabled large specimens, making it accessible to observe and document the progressive failure inside the excavated tunnel. The true-triaxial setup and mock miniature TBM allowed for realistic tunneling simulations, capturing unloading stress paths and face support behavior. Damage progression observation and post-mortem investigation provide detailed identification of damage mechanisms around the tunnel boundary, such as surficial spalling and damage zone development, as a V-shaped notch formed from progressive shear fracturing and resembled brittle-to-ductile transition. Real-time data on microcracking progression was captured u…
author: Wibisono, Doandy Yonathan
language: eng
language: English
keywords: brittle-to-ductile transition, geotechnical hazard, predictive models for brittle failure, rock mechanics, true-triaxial testing, tunnel brittle instabilities
date published: 2024
date modified: 2026-07-24T01:43:19Z
provider: Colorado School of Mines
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Colorado School of Mines. Arthur Lakes Library

PropertyValue
property ID: Handle
value: https://hdl.handle.net/11124/180409