Work

Multiscale characteristics and cracking behavior in reservoir sandstone under dry-wet cycles: Insights from NMR, AE and SEM

Year: 2026

Type: article

Abstract: The periodic water-level fluctuations in the hydro-fluctuation belt of the Three Gorges reservoir diminish the mechanical properties of the reservoir rock mass, leading to slope instability and associated geological disasters. To investigate the multiscale characteristics and cracking behavior of sandstone under hydromechanical loading, here we conducted a series of dry-wet cyclic experiments, synchronized with acoustic emission (AE), nuclear magnetic resonance (NMR). The results show that the early warning points are primarily identified using the variance of AE parameters. According to the evolution of RA (rise time/amplitude) and AF (AE count/duration time), the tensile microcracks become pronounced as the number of dry-wet cycles increases. When the number of dry-wet cycle increases from 0 to 30, the proportion of tensile cracks increases substantially from 31.05% to 48.93%, signifying a transition in the failure mode from shear-dominated to a tensile-shear mixed one. The porosity of the sandstone increases exponentially with the number of dry-wet cycles. The T 2 spectrum evolves from unimodal to bimodal, thereby enhancing the structural heterogeneity of the pore network. This phenomenon is accompanied by a significant reorganization of the pore structure, with the proportion of micropores decreasing from 8.09% to 0.24% and that of macropores increasing from 50.78% to 65.30%. At a low number of cycles, the damage is characterized by the formation of dissolution pits and isolated microcracks on mineral surfaces. In contrast, the interparticle cementation is significantly weakened, resulting in the generation of large amounts of debris. In addition, the microcracks further propagate and coalesce into macroscopic fractures.

Source: Scientific Reports

DOI: 10.1038/s41598-026-46226-1

Authors: Pei He, Ruide Lei, Pengcheng Zhao, Ye Zhang, Linsen Zhou, Dong Wang

Institutions: Ministry of Natural Resources, Chongqing Institute of Geology and Mineral Resources, Sichuan University of Science and Engineering

Language: English

Topic: Rock Mechanics and Modeling

Subfield: Mechanics of Materials

Field: Engineering

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,690

Funders: National Natural Science Foundation of China, China Postdoctoral Science Foundation, China Three Gorges University