Cyclic Wetting-Drying Effects on Rock Mechanical Properties

Cycles of wetting and drying profoundly influence the strength, stiffness and durability of rock materials across a variety of geological settings. Repeated infiltration and evaporation induce mineral dissolution, clay swelling and progressive microcrack formation, leading to reductions in uniaxial compressive strength, tensile strength and elastic modulus. Pore networks evolve, coalescing into larger voids and increasing porosity, which in turn accelerates moisture transport and further mechanical degradation. Acoustic emission monitoring reveals a shift from brittle fracture towards more ductile failure modes as cycles accumulate. These processes have global significance for reservoir slopes, open-pit mines, tunnels and cultural-heritage sites, where water level fluctuations and seasonal humidity changes threaten long-term stability. Understanding the coupled hydro-mechanical and chemical mechanisms is essential for predicting service life, designing mitigation measures and preserving critical infrastructure.

Research from Nature Portfolio

Recent studies have illuminated the mesostructural evolution of a slightly weathered red-bed soft rock subjected to cyclic water-level fluctuations simulating reservoir drawdown and replenishment. Detailed analysis by scanning electron microscopy and digital image processing showed that within a dozen cycles the average and maximum pore radii increased by more than 40 % and 100 % respectively, while overall porosity rose by over a quarter. Pore shapes transformed from oblate to more elongated forms, and the fractal dimension of the pore network increased, indicating greater structural complexity. A porosity evolution model was developed, offering a predictive tool for evaluating progressive damage under cyclical hydro-mechanical loading.

Research from all publishers

A recent laboratory-scale review of water–rock interaction experiments has synthesised observations on strength weakening under varying water contents, immersion durations and wetting-drying cycles. Results confirm that rock mass strength declines most steeply in early cycles, with acoustic emission activity and infrared radiation intensity diminishing in parallel. Comparative analysis of microscopic techniques underscored the importance of multi-scale imaging to characterise pore evolution and recommended extending studies to long-term immersion conditions to better reflect field timescales.

An experimental investigation into clay-bearing sandstone examined the impact of repeated wetting-drying on tensile behaviour and microstructure. Tensile strength decreased markedly with increasing cycles, with greater loss in samples of higher clay content. Crack initiation and propagation were delayed as cycles accumulated, signifying reduced stiffness and enhanced ductility. Acoustic emission records supported this trend, while microstructural analysis attributed weakening to frictional reduction between grains, chemical corrosion of clay minerals and the progressive development of microcracks.

A comparative study of sandstone and mudstone subjected to controlled wetting-drying revealed logarithmic declines in both elastic modulus and uniaxial compressive strength over successive cycles. Mudstone exhibited faster degradation than sandstone, correlating with higher water adsorption. The relationships between mechanical parameters and cycle number were well described by logarithmic fits, while linear correlations emerged between property loss and porosity increase, yielding practical degradation laws for engineering analyses.

Cyclic Wetting-Drying Effects on Rock Mechanical Properties publication trend

The graph below shows the total number of articles in cyclic wetting-drying effects on rock mechanical properties across all publications each year (not limited to Nature Index journals).

Technical terms

Uniaxial compressive strength: The maximum axial stress a rock specimen sustains under one-dimensional loading before failure.

Tensile strength: The resistance of a rock to fracture under tensile loading, often measured via indirect tests.

Elastic modulus: A measure of rock stiffness, defined as the slope of the stress–strain curve in the elastic deformation region.

Porosity: The volume fraction of void spaces within a rock, governing its fluid storage and transport properties.

Acoustic emission: Transient elastic waves generated by the rapid release of energy from microcrack formation or frictional slip in rock.

Fractal dimension: A numerical index describing the complexity of pore or crack networks, with higher values indicating more intricate structures.

References

1. Strength weakening and its micromechanism in water–rock interaction, a short review in laboratory tests. International Journal of Coal Science & Technology (2023).
2. Impact of water–rock interaction on the pore structures of red-bed soft rock. Scientific Reports (2021).
3. Effect of cyclic wetting–drying on tensile mechanical behavior and microstructure of clay-bearing sandstone. International Journal of Coal Science & Technology (2021).
4. Effects of Cyclic Wetting-Drying Conditions on Elastic Modulus and Compressive Strength of Sandstone and Mudstone. Processes (2018).