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

被引:10
作者
Berisavljevic, Zoran [1 ]
Bajic, Dragoljub [1 ]
Jovicic, Vojkan [2 ]
机构
[1] Univ Belgrade, Fac Min & Geol, Belgrade 11000, Serbia
[2] Univ Ljubljana, Fac Civil & Geodet Engn, Ljubljana 1000, Slovenia
来源
APPLIED SCIENCES-BASEL | 2023年 / 13卷 / 03期
关键词
hard rock; drill-and-blast; geological overbreak; technological overbreak; stability criterion; discontinuity orientation; tunnel construction; STRENGTH;
D O I
10.3390/app13031379
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
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.
引用
收藏
页数:26
相关论文
共 33 条
[1]  
[Anonymous], 2007, The complete ISRM Suggested Mehtods for Rock Characterization, Testing, and Monitoring: 1974-2006
[2]  
Aziznejad S., 2015, P 11 INT S ROCK FRAG, P377
[3]  
BARTON N, 1990, ROCK JOINTS, P603
[4]   SHEAR-STRENGTH OF ROCK AND ROCK JOINTS [J].
BARTON, N .
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, 1976, 13 (09) :255-279
[5]  
Barton N., 1982, P 23 US ROCK MECH S, P739
[6]  
Bieniawski Z.T., 1974, Proceedings of the 3rd Congress, V2, P27
[7]  
Bieniawski ZT, 1989, ENG ROCK MASS CLASSI
[8]  
Buocz I., 2014, Pollack Period, V9, P139, DOI [10.1556/Pollack.9.2014.3.15, DOI 10.1556/POLLACK.9.2014.3.15]
[9]   XG Boost Algorithm to Simultaneous Prediction of Rock Fragmentation and Induced Ground Vibration Using Unique Blast Data [J].
Chandrahas, N. Sri ;
Choudhary, Bhanwar Singh ;
Teja, M. Vishnu ;
Venkataramayya, M. S. ;
Prasad, N. S. R. Krishna .
APPLIED SCIENCES-BASEL, 2022, 12 (10)
[10]  
Danell R.E., 1997, FRAGBLAST, V1, P27, DOI [10.1080/13855149709408388, DOI 10.1080/13855149709408388]