Abstract
This study investigates water-sand bursting disasters associated with fractured rock that affect safe mining in the mining areas of Western China. A broken rock water-sand seepage rheological test device was developed, and rheological tests were conducted on multiple groups of broken rock samples with single-stage axial loading and different load levels. When the rheology of each group of broken rock samples was stable, water-sand mixed fluid was injected into the samples at a certain pressure gradient to conduct water-sand seepage tests on broken rock masses. It was found that when the porosity of a fractured rock mass is within a certain range, the water-sand mixed fluid does not completely pass through the fractured rock mass and some sand particles are filtered by the fractured rock sample. There is an exponential relationship between the sand breaking ability and the sand filtration ability of fractured rock and its initial porosity, and the permeability of fractured rock decreases by a certain extent after sand filtration. However, for different load levels, when the flow through a fractured rock mass tends to be stable, the final porosity of the fractured rock mass decreases exponentially with axial compression. Based on the classical Kelvin rheological model and the basic theory of fractional calculus, a new fractional rheological model has been proposed and the rheological parameters under different load levels were fitted to the model. The new fractional rheological model is better able to describe the rheological characteristics of broken mudstone.
Highlights
The removal of underground coal in China’s western coal mining regions results in the formation of a goaf
An experimental study on the water-sand seepage characteristics of fractured rock under rheological action was conducted: (1) Creep-time characteristic plots were obtained by conducting axial compression experiments on several groups of broken mudstone samples
Based on fractional calculus and a three-parameter model, a fractional Kelvin model was connected in series with an Abel dashpot to form a new rheological model
Summary
The removal of underground coal in China’s western coal mining regions results in the formation of a goaf. Changes in volume are much larger [25], resulting in changes in the porosity of broken rock and the surrounding rock space These are crucial factors to consider [26] when addressing problems related to water and sand inrush in western coal mines. This paper adopts the fractional parameter α to represent equivalent changes in the relationship between elastic modulus and coefficient of viscosity It replaces a Newton dashpot with an Abel dashpot based on a saturated broken mudstone compaction rheological experiment, and a new rheological model is obtained via a fractional Kelvin model connected in series to a three-parameter model using a combination theory. This study provides a reference for safe mining in China’s western coal mines
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