Recommended rock joints setting in 2D FEM simulations for engineering design of excavations created in jointed rockmass

ABSTRACT

Numerical modelling has became one of the most widely used design tools for evaluation of engineering responses in ground and support measures around excavations. Proper model setup for numerical analysis is important, especially for excavations created in blocky and massive rockmasses by including rock joints network in the model. Characterisation of rock joint such as spacing, length, persistent and shear strength may have a large influence on the mechanical behaviours of rockmass in terms of strength and deformation in rock engineering problems. Overview the current practice, no appropriate guidance is given assistant in setting up rock joints network in model for jointed rockmass analysis. To fill this gap, a recommended rock joints setting for a range of rockmass qualities in model analysis is proposed based on a comprehensive literature review on rock joints studies. Verification of the recommended rock joints setting is performed that two published case examples are used to examine the disparity in rock joints setting in the model and checked against the difference between the modelled results and as-constructed monitoring records. The verification demonstrates that a close agreement between the model result and as-constructed monitoring record could be obtained to minimise any potential over- or under-design practice.

KEYWORDS:

• Discontinuum
• joints
• justification
• modelling
• rockmass

Acknowledgments

The authors would like to thank for Dr. Mojtaba Rajabi providing invaluable recommendations on the preparation of this paper; and to thank for Mr. Terrance Tang and Mr. Phil Cai providing the original PHASE² model (that is presented in Kong et al. 2016) and monitoring records for the case example of the Express Rail Link project to allow for this case study comparison.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Availability of data

Data generated or analysed during this study are provided in full within the published article.

Additional information

Notes on contributors

Keith W.K. Kong

Keith received his BEng in Mining Engineering (major in Underground Mining) from Imperial College, London and MSc in Civil & Structural Engineering from The University of Hong Kong. He is a Fellow of Engineers Australia, The Institution of Civil Engineers (ICE) & The Institute of Materials, Minerals and Mining (IOM3) of UK and an UK Registered Ground Engineering Adviser. He has 27 years of diverse international experience predominantly in design, construction, site supervision and project management of various major civil and underground space projects in Australia, China, Dubai, Hong Kong, New Zealand, the Philippines, Singapore and South Africa; in particular, of his involvement in the design/construction of 46 tunnels and underground space projects with total length of more than 275 km and total excavated volume of more than 14 Mm³. He was a committee member of the Working Group on Cavern and Tunnel Engineering, Geotechnical Division of the Hong Kong Institution of Engineers’ between Aug 2016 and Apr 2019.

Jurij Karlovsek

Dr. Karlovsek is a Senior Lecturer and an expert in the field of Geotechnical Engineering, dedicated to advancing knowledge through research and fostering the development of the next generation of engineers. His comprehensive expertise spans various domains within Geotechnical Engineering, including Sustainable Underground Space Development, Information Modelling with a focus on BIM in Tunnelling, Employing Non-Destructive and Spatial techniques for Infrastructure Projects. Dr Karlovsek plays a pivotal role as an EAIT Faculty Lead and Co-Director at the Sustainable Infrastructure Research Hub, collaborating closely with the BEL Faculty. Additionally, he is the co-founder and area lead at the Infrastructure CoLab.