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% ~ 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 ~ 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.

砂岩在地球上分布广泛，经常被水破坏。尽管人们普遍认为砂岩与水接触后强度会降低，但控制砂岩弱水机制的内在性质并不完全清楚。本研究通过实验测量了4种含水饱和度为0～100%的含粘土砂岩的单轴抗压强度（UCS）、点荷载指数（PLI）和巴西抗拉强度（BTS）。结果表明，当含水饱和度从0增加到60%~80%时，强度损失明显，随后降低速度显着减慢。因此，由于弱水效应而产生相当大的强度损失的临界含水饱和度为60～80%。此外，含水饱和度增加引起的强度损失规律同时满足指数衰减函数和对数衰减函数。考虑含水饱和度的影响，采用多元线性回归方法模拟了本征性质与弱水效应引起的UCS损失之间的关系。通过最佳子集回归自动选择孔隙度、弹性模量和粘土矿物含量作为控制砂岩弱水程度的主要内在性质。此外，还对临界含水饱和度水平以及粘土矿物在砂岩弱水作用中的作用进行了全面讨论。