Cyclic Loading Induced Sliding Instability of Rock Joint

Mairaj Soomro

The presence of joints and fractures can dramatically affect the mechanical behaviour of a rock mass by providing planes of weakness across which frictional sliding can occur. Structures designed in or on a fractured rock mass are often subjected to dynamic stresses induced by moving loads, seismic events, or mining activities. Thus, an accurate account of the behaviour of a discontinuous rock mass requires a realistic model for the tribological behaviour of discontinuities to evaluate the time-dependent shear behaviour of rock joints subjected to repeated loading for long-term stability assessments of jointed rock slopes, tunnels, and foundations. Therefore, a systematic cyclic triaxial series of test on replicated rough rock joint was carried out, and results clearly highlight the strength attenuation as a function of joint degradation with respect to the number of loading cycles, and a reduction in shear stiffness and enhanced ductility was observed. The experimental results also indicate that the onset of instability of a rock joint is suppressed with increase in confining pressure and number of loading cycles until the normalized shear deformation increases beyond a threshold value of critical shear strain. Based on the rigorous analyses of the experimental results, a rational classification of Joint Sliding Potential (JSP) of rock joint was proposed to characterize the induced instability potential of rock joint under cyclic loading.

About the speaker

Mairaj Soomro Senior Engineer, Subsidence Advisory NSW

Mairaj Soomro is a Senior Engineer with Subsidence Advisory NSW, where he provides expert engineering input on coal mining related surface subsidence. He has over 8 years’ experience as a geotechnical practitioner and academic in civil and mining engineering in Australia and overseas. He finished his PhD on Rock Joint Engineering from the University of Wollongong last year, focusing on the experimental and analytical behaviour of rock mass with advanced geotechnical laboratory experiments and field applications. Before joining the Subsidence Advisory NSW, he worked as a consulting geotechnical engineer and was involved in projects covering aspects from site investigations, numerical modelling and design, field monitoring, slope stabilization, and construction phase supervision.

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