Effect of water saturation on the strength of sandstones: experimental investigation and statistical analysis

Sandstones are widespread on the earth and are often damaged by water. Although there is a consensus that the strength of sandstones will decrease when they are in contact with water, the intrinsic properties controlling the water-weakening mechanism of sandstones are not completely clear. In this study, the uniaxial compression strength (UCS), point load index (PLI), and Brazilian tensile strength (BTS) of four clay-bearing sandstones with water saturation from 0 to 100% were measured by experiments. The results showed that a remarkable strength loss occurred when the water saturation increased from 0 to 60% similar to 80%, and then, the reduction rate slowed dramatically. Therefore, the critical water saturation level at which considerable strength loss due to the water-weakening effect is produced is 60 similar to 80%. In addition, the strength loss law caused by increasing water saturation satisfied both the exponential decay function and logarithmic decay function. The multiple linear regression method was used to model the relationship between the intrinsic properties and UCS loss caused by water-weakening effects considering the effect of water saturation. The porosity, elastic modulus and clay mineral content were automatically selected by the best subset regression as the main intrinsic properties controlling the water-weakening degree of sandstones. In addition, the critical water saturation level and the role that clay minerals play in the water-weakening effects of sandstones were comprehensively discussed. This study contributes to a better understanding of the water-weakening mechanism and provides a better strength estimation model for sandstones with different water saturation levels.

Automated summary

Sandstones are easily damaged by water, and the strength loss is most significant when the water saturation is between 60% and 80%. The study identifies porosity, elastic modulus, and clay mineral content as the main intrinsic properties controlling the water-weakening degree of sandstones.