Numerical simulation of rock failure under static and dynamic loading by splitting test of circular ring

Significance 

Tensile and shear fracture are the two main failure modes for rock and rock-like materials. Since its discovery, the Brazilian test has been extensively used to obtain tensile strength and also measure the toughness of brittle material such as rocks despite the various shortcomings inherent to it. Over the years, the fracture process of brittle materials has been a critical issue in fracture mechanics. As a consequence, this topic has been widely researched where experimental, analytical, and numerical approaches have all been employed to study the failure processes of rocks and rock like materials. Generally, it has been noted that numerical based methods better capture the transition from continuum to a dis-continuum state. Even better, several of these techniques can be integrated into a single tool hence offering a more profound solution to the fracture problem, for example, the integration of finite element method and discrete element method. Therefore, this provides the opportunity to integrate other techniques and observe the suitability of the generated results.

Central South University researchers in China, Professor Xibing Li and Fan Feng (PhD Student) and Professor Diyuan Li investigated the failure mode and strength characteristics of brittle hard rocks under static and dynamic loading by the simulation scheme. They choose to adopt the approach combining the finite element method and the discrete element method, named ELFEN, to simulate and investigate the failure process of a typical hard rock under static and dynamic splitting ring tests. Their work is currently published in the research journal, Engineering Fracture Mechanics.

They commenced their research work by first validating the FDEM software through simulations of Brazilian disk test under static loading. Next, they studied the failure of circular ring specimens under static and dynamic loading, with the ratio of internal to external diameter of the specimen groups varying from 0.1 to 0.6, with increments of 0.1. Afterwards, they introduced a rational load value so as to calculate the tensile strength of circular rock ring specimens under the splitting ring test. Lastly, they compared the numerical results obtained from their technique to previous experimental data, and found a good agreement between the numerical and experimental results.

They commenced their research work by first validating the FDEM software through simulations of Brazilian disk test under static loading. Next, they studied the failure of circular ring specimens under static and dynamic loading, with the ratio of internal to external diameter of the specimen groups varying from 0.1 to 0.6, with increments of 0.1. Afterwards, they introduced a rational load value so as to calculate the tensile strength of circular rock ring specimens under the splitting ring test. Lastly, they compared the numerical results obtained from their technique to previous experimental data, and found a good agreement between the numerical and experimental results.

The authors observed that under the static loading, with the increase in internal diameter, the failure mode was transformed from diametrical splitting to four-fan-shaped failure. The researchers also noted that under the dynamic loading, four-fan-shaped failure also occurred from geometric axial symmetry to axial asymmetry, which meant that, with increasing internal diameter, the tensile cracks along the horizontal diametrical direction gradually deviated toward the top loading platen. Overall, it was seen that the peak load of the circular ring had a descending trend with the increase in internal diameter under both loading conditions.

The study successfully employed the FDEM approach (ELFEN) to model the fracture process and failure characteristics of Carrara marble specimens by the splitting ring test, including both static and dynamic loading conditions. Generally, the numerical results obtained showed that the ratio of internal to external diameters and loading conditions were the main factors that affected the final failure modes and tensile strengths of the circular rock ring specimens. Altogether, the FDEM approach is an effective and convenient way to study the failure processes of rocks or rock-like materials.

Numerical simulation of rock failure under static and dynamic loading by splitting test of circular ring, Advances in Engineering
Numerical simulation of rock failure under static and dynamic loading by splitting test of circular ring
Numerical simulation of rock failure under static and dynamic loading by splitting test of circular ring, Advances in Engineering
Numerical simulation of rock failure under static and dynamic loading by splitting test of circular ring

About the author

Xibing Li obtained his PhD from Central South University, Changsha, China in 1992. Dr. Li is a Professor of Rock Dynamics and Mining Engineering at the Central South University, China. As the principal investigator, he has been in charge of over ten national research projects, such as the National Science Foundation for Distinguished Young Scholars, Cheung Kong Scholars Program, State Key Program of the National Natural Science Foundation, and State Key Development Program for Basic Research (973).

He proposed an innovative approach based on SHPB system with half sine wave loading. Considering the mechanical state of deep mining, he proposed a coupled static-dynamic loading theory and developed associated system. To date, he has published about 200 scientific papers on rock failure mechanisms and mining engineering, and he is the author of ten books of rock mechanics and mining engineering.

Profile : Professor, School of Resources and Safety Engineering, Central South University, Changsha, China

Email : [email protected]

About the author

Fan Feng is currently a PhD student in School of Resources and Safety Engineering, Central South University, Changsha, China. He is selected as a joint PhD student (visiting scholar) to study in Mining Engineering Department, Colorado School of Mines, CO, USA from 2017 to 2018.

His research interests involves numerical simulations of hard rock failure based on FEM/DEM method, slabbing and spiltting failure in deep mining engineering, true-triaxial loading and unloading of hard rocks, and rock burst mechanism and prevention in underground mining and tunneling projects. He has published more than 10 journal papers and 4 registered patents.
Profile : PhD student, School of Resources and Safety Engineering, Central South University, Changsha, China

Email : [email protected]

About the author

Diyuan Li obtained his PhD from Central South University, Changsha, China in 2010. Dr. Li is a Professor of Geotechnical and Mining Engineering at the Central South University, China. As the principal investigator, he has been in charge of two projects supported by National Natural Science Foundation of China and a project supported by Program for New Century Excellent Talents in University. Dr. Li has been a jointed PhD student at the Norwegian University of Science and Technology in 2007 – 2009 and a post-doc research fellow at the Nanyang Technological University, Singapore in 2011 – 2012. He has completed an Endeavour Australia Cheung Kong Research Fellowship in 2017 at the Monash University in Australia.

His research interests include rock mechanics for deep mining engineering, rock dynamics and rock fracture mechanics. He has published 60+ articles in high profile journals.
Profile : Professor, School of Resources and Safety Engineering, Central South University, Changsha, China

Email : [email protected]

Reference

Xibing Li, Fan Feng, Diyuan Li. Numerical simulation of rock failure under static and dynamic loading by splitting test of circular ring. Engineering Fracture Mechanics, volume 188 (2018) pages 184–201.

Go To Engineering Fracture Mechanics

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