Creep Behavior in Brittle Rock Systems

Creep in brittle rocks denotes the progressive, time-dependent deformation that occurs under sustained load, even when stresses are below the instantaneous strength. Laboratory experiments and field observations alike reveal a characteristic three-phase evolution: an initial decelerating primary creep, a near-steady secondary creep, and an accelerating tertiary creep that culminates in failure. At the microscale, this behaviour is mediated by subcritical crack growth, crack coalescence and, in some lithologies, pressure solution at grain contacts. Heterogeneity in mineralogy, porosity and pre-existing discontinuities governs the spatial distribution of damage and localises deformation. Time-dependent strength may exceed short-term peak strength by tens of per cent, with implications for the stability of tunnels, slopes, nuclear waste repositories and CO₂ storage sites. Advances in acoustic emission monitoring, high-resolution imaging and numerical modelling have improved understanding of damage thresholds and the interplay between mechanical and chemical processes. Crucially, fluid presence can accelerate creep via stress corrosion or slow crack sealing, while temperature influences viscous contributions in mixed brittle-ductile regimes. Recognition of these mechanisms underpins more reliable risk assessment and design of engineering structures in cold regions, mining excavations and deep geological settings.

Research from Nature Portfolio

Recent studies have employed graded loading and acoustic emission monitoring to elucidate how weak layer orientation controls creep rupture. Experiments on composite rock masses with varied dip angles identified three damage stages—initial accumulation, acceleration and destruction—and demonstrated a transition from tensile to shear-slip failure as inclination increases. Complementary work on fissured red sandstone under triaxial creep has quantified how stress ratio and fissure dip affect elastic, visco-elastic and visco-plastic strains. Results show non-linear increases in steady-state creep rates with loading, a fissure-angle-dependent long-term strength and a marked permeability drop followed by a sudden rise at tertiary creep, highlighting the coupling between deformation and fluid pathways.

Creep Behavior in Brittle Rock Systems publication trend

The graph below shows the total number of articles in creep behavior in brittle rock systems across all publications each year (not limited to Nature Index journals).

Technical terms

Creep: Time-dependent irreversible deformation of rock under constant stress.

Subcritical crack growth: Slow extension of microcracks driven by stress corrosion below critical fracture intensity.

Pressure solution: The dissolution of mineral at grain contacts under stress, resulting in compaction over time.

Acoustic emission: Transient elastic waves generated by microfracture events within the rock mass.

Long-term strength: The maximum stress a rock can sustain over an extended period under a constant load.

References

1. Damage characteristics of weak rocks with different dip angles during creep. Scientific Reports (2023).
2. Creep and permeability evolution behavior of red sandstone containing a single fissure under a confining pressure of 30 MPa. Scientific Reports (2020).
3. Mechanisms of time‐dependent deformation in porous limestone. Journal of Geophysical Research: Solid Earth (2014).
4. Elastic Anisotropy Reversal During Brittle Creep in Shale. Geophysical Research Letters (2017).
5. Creep of CarbFix basalt: influence of rock–fluid interaction. Solid Earth (SE) (2022).