干湿交替对砂岩力学特性影响的试验研究

由于地下水位的升降等原因,岩体经常处于干湿交替状态,这对岩体工程的长期稳定性不利。以红砂岩为研究对象,进行了干燥-饱水干湿交替作用后的常规单轴和三轴压缩试验研究,获得了砂岩应力-应变曲线,分析了其变形破坏特征。相对于没有经过干湿交替作用的干燥试件,经过不同次数的干燥-饱水交替作用后,砂岩的弹性模量、单轴和三轴抗压强度、黏聚力、内摩擦角等都有不同程度的降低。各力学指标的总体变化趋势是在第1次饱水之后均有较大幅度的下降,此后,随着干湿交替作用次数增加其降低的幅度逐渐减小,干湿交替作用使岩石的延性增强。在围压作用下,砂岩的峰值强度均随着围压的增大而增大,干燥试件强度的围压效应要比多次干湿交替作用后的试件显著。

Experimental study of mechanical properties of sandstone under cyclic drying and wetting

Cyclic wetting and drying usually occurs in rockmass for some reasons such as water level variation, which is fairly harmful for its long term safety. A series of uniaxial and triaxial compression experimental tests on sandstone under cyclic drying and wetting have been carried out. The corresponding complete stress-strain curves are obtained; and characteristics of deformation and failure are analyzed. Compared with the dry specimens, elastic modulus, cohesion, internal friction angle, uniaxial and triaxial compressive strengths of the specimens under “dry-saturation” cycling are all decreased to some degree. The general trend is that all mechanical indices have a relatively sharp decline after the first time saturated with water; and thereafter, decrease gradually followed by an increase in cycling times. The rock samples become more ductile under cyclic drying and wetting. Sandstone peak strength increases along with the increasing of confining pressure. The effect of confining pressure on peak strength is greater for dry specimens than for “dry-saturation” cycling specimens.