The mechanics and physical properties of rock in near-surface (~100 m) environments plays a pivotal role in regulating surface processes (e.g. weathering and subsequent erosion), as well as in the long-term performance of engineered structures (e.g. tunnels, caverns, cut slopes, and historic buildings). To date, however, the vast majority of studies directed toward assessing the role of rock mechanics in regulating surface processes, or modes of structural degradation, have focused on external loading processes and/or critical material strength (i.e. compressive strength, tensile strength). Little attention has been given to subcritical processes – governed by different geomechanical ‘rules’ than those of critical fracture, and also perhaps more relevant to environmental forcing. The formulation of traditional approaches implicitly assumes mechanical properties vary only in response to critical loading or accumulated strain, and therefore almost never account for the physical effects associated with combinations and repeated cyclic alterations of temperature, humidity, pore fluid chemistry, and subcritical stress. Recent studies have demonstrated the role such factors play in determining the behavior of both intact and fractured rock over time spans ranging from several hours to millions of years. These studies highlight the requirement for more careful consideration of both the physics of underlying processes, and observation of resulting behaviors across the breadth of natural and engineered rock settings.

This session aims to bring together members of engineering, geomorphology, geophysical and rock physics communities in order to gain new, multidisciplinary insight into how subcritical cracking, rock fatigue and associated progressive rock damage 1) may influence rock degradation, weathering and erosion 2) may respond to relatively low magnitude stresses like those of Earth’s surface 3) and may be affected by environmental conditions (moisture, temperature or chemistry) comparable to Earth’s surface. We hope to attract a wide range of geomechanical, geomorphological, weathering and engineering research from either natural or engineered (tunneling, building stone preservation etc.) settings. Approaches may include field observations or geophysical instrumentation studies of fracture, laboratory experiments, and numerical modeling. In sum, we hope this session will provide new insight and a better predictability of processes and feedbacks between stress, environment and subcritical cracking and its effects.