Fractal characteristics of pore structure and nonlinear deterioration mechanism of weakly cemented siltstone under alkaline water effect
Weakly cemented rocks have significant strength decline when exposed to groundwa-ter,frequently resulting in roof weighting anomaly and caving disasters in western coalfields in China.Based on the coal measure geology and hydrological settings of Hami coalfields in Xin-jiang Uygur Autonomous Region,the paper investigates the impact of alkaline pH levels and immersion durations on the micro-structure and pore fractal dimension of weakly cemented siltstone using SEM and digital processing techniques,determines the relationship from pore fractal dimension and porosity to uniaxial compressive strength(UCS)and tensile strength,establishing a nonlinear dynamic model to characterize the strength degradation due to alkaline erosion.The results show that:1)Mineral particles become morphologically rounded and loos-ened with alkalinity increase,and the enlargement in porosity and pore fractal dimension grad-ually slows with immersion.2)The UCS and tensile strength of eroded weakly cemented silt-stone are influenced by the pore structure morphology and distribution,featuring a negative correlation to pore fractal dimension,then to porosity.The rock brittleness is decreased due to alkaline erosion.3)A nonlinear dynamic model that incorporates pore fractal dimension,po-rosity,and UCS as descriptors is established utilizing the time series values of these descriptors as specific solutions.The pore fractal dimension,porosity,and UCS calculated via the nonlinear model show a good agreement with experimental results,and the error ranges are 2.37％-2.64％,2.38％-4.57％,3.48％-8.12％,respectively.The model is able to assess the porosity and strength parameters of weakly cemented rocks exposed to alkaline erosion over time.
alkaline erosionweakly cemented siltstoneporositypore fractal dimensionnonlinear model
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