干湿-冻融循环下延吉膨胀岩的力学特性及其应力-应变归一化

为了研究干湿、冻融和干湿-冻融循环作用对延吉膨胀岩的应力-应变关系、体变特性、抗剪强度的影响，开展了一系列的固结排水剪切试验。结果表明：未循环试样的应力-应变关系曲线表现为稳定型或弱应变软化型，3种环境作用后试样应力-应变关系曲线呈现出一定的应变软化特性，剪胀明显，而且围压越小、循环次数越高的试样软化和剪胀的程度越高；随着循环次数的增加，3种环境作用下试样的黏聚力急剧减小，而内摩擦角略有增加；干湿-冻融循环作用下试样的应力-应变关系软化程度最高，剪胀最显著，试样的黏聚力降低的幅度最大。基于Konder双曲线模型，对循环处理前后试样的应力-应变特性进行归一化分析，建立了考虑干湿-冻融循环次数和围压影响，能同时描述应变软化型和硬化型的应力-应变关系式，并对不同干湿-冻融循环次数试样的应力-应变曲线进行预测，预测值与实测值较为接近，预测效果较好。

Mechanical properties and normalized stress-strain behaviour of Yanji swelling rock under wetting-drying-freezing-thawing cycles

Consolidated and drained triaxial shear tests were conducted on Yanji swelling rock to investigate the effects of wetting-drying, freezing-thawing and wetting-drying-freezing-thawing cycles on the stress-strain behaviour, volumetric strain and shear strength of Yanji swelling rock samples. The test results indicate that the stress-strain behaviour of samples before cyclic treatments appears to be strain-hardening, while the samples after cyclic treatments show strain-softening behaviour and more evident shear dilation. Additionally, the effects induced by cyclic treatments are more pronounced with increasing number of cycles and decreasing confining pressure. As the number of cycles increases, the cohesion of samples significantly decrease but the internal friction angle slightly increases. It can also be seen that the samples subjected to wetting-drying-freezing-thawing cycles suffer greater alterations in mechanical properties compared with those subject to separate wetting-drying and freezing-thawing cycles. Subsequently, a stress-strain formula considering the effect of wetting-drying-freezing-thawing cycles and confining pressure is presented based on Konder hyperbolic function, which can describe both strain-hardening and strain-softening behaviours. A comparison between the predicted and measured values verifies that this model can well predict aforementioned stress-strain behaviours.