Keynote speakers

Charlie Chunlin Li

About

Dr. Charlie C. Li is a professor of rock mechanics for mining and civil engineering at the NTNU Norwegian University of Science and Technology, Norway. After his high education in engineering geology and rock mechanics, Dr. Li worked as a research fellow at the Luleå University of Technology, Sweden, and then as a ground control engineer in the Kristineberg mine, Sweden, for more than ten years. 

He was appointed as the professor of rock mechanics at NTNU in 2004. He worked in part-time as the Chief Technology Officer of Dynamic Rock Support AS to commercialize his invention of the D-Bolt in 2009-2013. His expertise is in stability assessment of underground spaces and ground control. His interests are ground support, rock bolting, rock anchoring, and rockburst. He published a book entitled “Rockbolting – Principles and Applications” in 2017. He published more than 100 scientific articles. Professor Li is a member of the Norwegian Academy of Technological Sciences. He was the ISRM Vice President for Europe in the period of 2015-2019.

Abstract

A study of the arching effect, bond strength and rock mass failure around rock ancestors

Rock anchors of high load capacity are used to provide, among others, resistance to dam overturning, restraint against slope sliding, and reinforcement of excavated abutments and tower foundations. The basic principle for rock anchor dimensioning has not been changed since the 1970s. Little progress has been made in the criteria for rock anchoring design. The knowledge in the failure mode of the rock mass around rock anchors is still very limited, which leads to uncertainties in rock anchor dimensioning. A research program was implemented in 2020-2024, aiming to study the arching effect in the rock mass under the anchor load, the bond strength between the anchor and the rock mass, and the role of the rock mass strength in the load-bearing capacity of the rock anchor through full-scale field tests, laboratory block models and discontinuous numerical modelling. 

The field tests showed that the bond strength was approximately 20% of the UCS (uniaxial compressive strength) of the grout in the anchor-grout interface, but only 5% of the UCS of the rock in the grout-rock interface. It also showed that the ultimate load of the rock anchor against the conic failure in the rock mass is many times higher than the weight of the failure cone. Load-bearing arches were clearly observed in the images of Digital Image Correlation in the laboratory block models. The full-scale tests, the laboratory block model tests, and the results of the UDEC numerical modelling in the project will be presented in the keynote. 

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