Experimental Study on Mechanical and Strain Localisation Behaviour of Sandstone Under Seepage-Stress Coupling

In this study, the effects on the mechanical and seepage behaviour of sandstone were analysed using triaxial compression tests under various confining and seepage pressure conditions. Three-dimensional digital image correlation and scanning electron microscopy were used to monitor the strain localisation behaviour and microstructure of the sandstone under various conditions. The results show that the peak stress and peak permeability of sandstone are more sensitive to the confining pressure factor than to the seepage pressure factor. The amount of axial strain in the strain field was apparent and the sample became severely compressed as the confining pressure decreased. However, according to the statistical results of the axial strain values at the onset of localisation, the influence of the seepage pressure is more significant. The effect of seepage on the microstructure of the sandstone fracture surface mainly comprises the erosion of mineral debris produced by damage, which is marginally affected by the confining pressure. The results of this study can enhance the understanding of the role of water in the mechanical and strain localisation behaviour of sandstone. A three-dimensional digital image correlation (3D-DIC) method was used to observe the strain field of sample surface in the triaxial compression tests.The mechanisms of confining and seepage pressure on the mechanical and seepage behaviours of sandstone were studied.The effects of seepage pressure on strain localisation characteristics were analysed.