A Model of Stress-Damage-Permeability Relationship of Weakly Cemented Rocks under Triaxial Compressive Conditions

Abstract

To unravel the permeability variation mechanism of weakly cemented rocks (WCR), the paper conducted triaxial permeability tests on weakly cemented sandstones (WCS) collected from the Jurassic formation in northwest China. The paper identified the correlation of WCS permeability versus porosity, cementation structure, and mineral composition, further developing a model to characterize the WCS stress–damage–permeability relationship. The research indicated that the WCS permeability was initially high due to the naturally high porosity, large pore diameter, and loose particle cementation, thus favoring a significant decline as pore convergence in the compaction stage. In the residual stage, kaolinite and montmorillonite minerals disintegrated into water and narrowed fractures, causing a slight permeability increase from the initial to the maximum and residual stages. The WCS matrix fracturing was phenomenologically accompanied by clay mineral disintegration. By assuming that the matrix can be compressed, jointed, and fractured, the paper defined a damage variable D and accordingly developed a stress–damage–permeability relationship model that incorporated matrix compression, jointing, and fracturing. The model can describe the WCS permeability regime regarding the high initial permeability and slight difference of the maximum and residual permeabilities versus the initial.

Study on Permeability Evolution Law of Rock Mass under Mining Stress

“…Teng et al developed a permeability correction model for muddy sandstone under coupling fluid mechanics conditions, revealing the correlation between the permeability of muddy sandstone and effective stress (including external stress and pore pressure) [24]. Zhang et al conducted triaxial permeability tests to investigate the correlation between the permeability of weakly cemented sandstone and porosity, cementation structure and mineral composition and further advanced a model establishing the relationship between stress, damage and permeability for weakly cemented sandstone [25].…”