Development and Application of Methodology for Quantification of Overbreaks in Hard Rock Tunnel Construction

Објеката

Тип
Рад у часопису
Верзија рада
објављена верзија
Језик
енглески
Креатор
Zoran Berisavljević, Dragoljub Bajić, Vojkan Jovičić
Извор
Applied Sciences
Издавач
MDPI
Датум издавања
2023
Сажетак
A methodology for determining overbreaks in hard rock tunnel construction using the drill-and-blast technique is presented in this paper. The methodology was developed for and applied to crystalline medium- to thick-bedded limestone, but it can be used in any jointed hard rock mass. Overbreaks are inevitable in hard rock tunnelling in a low-confinement environment (shallow tunnels up to several hundred meters deep) as a result of wedge failures along unfavourably oriented discontinuities caused by blasting. It is widely accepted in engineering practise that overbreaks will be inevitable even if smooth contour blasting is applied. If not controlled, overbreaks can result in extreme financial and time costs; and determining, predicting, and mitigating them is the key to successful tunnel construction in hard rock. Technological overbreaks, which are caused by the inappropriate use of drill-and-blast excavation, are not easily distinguished from the inevitable overbreaks dictated by the geological conditions with which they interfere and overlap. A methodology was developed with the aim of distinguishing the two causes of overbreaks, which can be applied in any phase of tunnel construction for evaluation or mitigation. The analysis of key inputs, including geological face mapping, shear strength tests along discontinuities of the rock mass, and their spatial orientation relative to tunnel advancement and survey overbreak measurements, is presented in this paper. Due to the stochastic and statistical nature of the problem, a probabilistic concept was also applied as part of the method so that the probability of failure around unprotected tunnel sections could be determined. The so-called stability criterion is introduced to distinguish between stable and unstable sections in terms of the probabilistic safety factor. The quantification of overbreaks, including the threshold value distinguishing technological from geological overbreaks, is proposed. The application of the methodology, demonstrated on an 8.1 km long section of a 12 km long pressure tunnel in hard rock, is presented in the paper.
Број
13
doi
10.3390/app13031379
issn
2076-3417
Subject
hard rock, drill-and-blast, geological overbreak, technological overbreak, stability criterion, discontinuity orientation, tunnel construction
Шира категорија рада
M20
Ужа категорија рада
М22
Права
Отворени приступ
Лиценца
All rights reserved
Формат
.pdf
Медија
applsci-13-01379.pdf

Zoran Berisavljević, Dragoljub Bajić, Vojkan Jovičić. "Development and Application of Methodology for Quantification of Overbreaks in Hard Rock Tunnel Construction" in Applied Sciences, MDPI (2023). https://doi.org/10.3390/app13031379

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