This special issue contains papers based on contributions submitted to the 54th US Rock Mechanics/Geomechanics Symposium. Although the 2020 symposium, originally scheduled to be held in Golden, CO, was ultimately canceled due to the COVID-19 pandemic, the symposium proceedings were published as a compilation of over 400 papers. The technical reviews conducted as part of the regular symposium process were used to identify outstanding papers for invitation to submit to this Special Issue. Invited authors expanded their original conference papers prior to submission to Rock Mechanics and Rock Engineering. Additional peer-review and revision according to the standard Rock Mechanics and Rock Engineering editorial process has ensured that the contributions are of the highest possible quality.

The 30 papers included in this Special Issue reflect the diversity and breadth of knowledge of ARMA’s membership and symposium attendees. Approximately half of the papers cover topics directly relevant to Civil, Mining, and Petroleum applications, with the remainder being more fundamental or interdisciplinary in nature. The papers cover a number of different thematic areas:

  • Site Characterization: Papers cover best practices for structural domaining based on mapping data (Carter et al.), and approaches for considering rock bridges in slope stability analysis (Elmo et al.)

  • Experimental Methods and Analytical Models: Papers cover experimental analyses of proppant in the context of hydraulic fracturing (Alagoz et al.; Bandara et al.), a novel dynamic indentation test (Hampton et al.), the application of fiber optic sensing for strain measurement during compression testing (Hegger et al.), new data processing protocols for direct shear testing (Packulak et al.), permeability evolution during confined Brazilian testing (Hagengruber et al.), elastodynamic property evaluation (Manogharan et al.), and the development of models for heterogeneous salt behavior (Azabou et al.) and microcrack growth in brittle rocks (Sisodiya & Zhang)

  • Structures and Geohazards: Papers cover volcanic slope instability (Wallace et al.), rock block stability assessment (Alejano et al.; Zhang et al.), demonstration of methods for prediction of tunneling conditions (Gangrade et al.; Pandit & Babu), and evaluation of the relationship between long-term excavation damage and rock fabric (Diederichs & Day)

  • Machine Learning: Papers cover the prediction of tunnel liner yield using machine learning (Morgenroth et al.) and the integration of numerical models and machine learning (Furtney et al.)

  • Numerical Studies: Papers cover bonded block modeling of small-scale (Justo et al.) and large-scale (Sunkpal & Sherizadeh), the effect of damping in distinct element method simulations (Sinha et al.) and modeling of fracture initiation (Garg et al.)

  • Hydraulic Fracturing and Unconventionals: Papers cover approaches for fracture complexity mapping (Li et al.) and anisotropic rock characterization (Sassen & Abell) as well as stress interference in multilayer unconventional reservoirs (Pei & Sepehrnoori)

  • Borehole Stability: Papers cover the development of a semi-analytical method for modeling borehole breakout (Setiawan & Zimmerman) and evaluation of the influence of natural fractures on borehole stability (Weijermars et al.)

  • Geothermal Systems: Papers cover analysis of in situ flowback data (Xing et al.) and simulation of coupled processes in fractured systems (Hu & Rutqvist)

This special issue would not have been produced without the contributions of countless individuals to the ARMA symposium and Rock Mechanics and Rock Engineering review processes. Special thanks are due to the 2020 ARMA Symposium technical committee and the Rock Mechanics and Rock Engineering editorial team.