The weakly cemented sandstone is the host rock in the Cretaceous and Jurassic strata with low intensity, high water-bearing capacity and sensitivity to disturbance. In order to investigate the influence of temperature and confining pressure on the permeability of weakly cemented sandstone, scanning electron microscope were used to characterize microstructure of the particles, a series of triaxial creep tests were performed on coarse sandstone, medium sandstone and fine sandstone separately, and the effect of particle size on the permeability of sandstone was also analyzed. The results indicate that the increase of confining pressure led to the plastic deformation between the rock particles, that permeability was irreversible as the confining pressure changed, and that the permeability reduction rate of coarse sandstone was lower than that of fine sandstone. The sensitivity of weakly cemented sandstone to temperature and confining pressure increased as the sizes of the particles decreased, and the effect on permeability was more obvious.
The performance and durability of concrete is always affected by atmospheric conditions, chemical ions and mechanical loads, which reduce its bearing capacity, leading to the occurrence of accidents. Macrosynthetic fibre-reinforced concrete, as an alternative material, is used to improve the corrosion resistance of underground structures. In this study, accelerated corrosion tests were designed to investigate the change in compressive strength, elastic modulus and fracture toughness of concrete soaked in sulfate environment. Microscopic monitoring techniques, including scanning electron microscopy and energy-dispersive X-ray spectroscopy, were adopted to find changes in the structure. Compared to macrosynthetic fibre-reinforced concrete and ordinary concrete soaked in sulfate corrosion environment, the results indicated that macrosynthetic fibre improved the structure compactness of concrete; the losses of elastic moduli and compressive strength of the specimens soaked in sulfate were reduced. The maximum crack initiation load of macrosynthetic fibre-reinforced concrete was enhanced. Through microstructure monitoring, it is found that macrosynthetic steel fibre contributes to a remarkable improvement in the fracture resistance of concrete.
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