水压循环作用下砂岩损伤本构模型研究

针对三峡库区水位反复升降作用下岩体质量劣化易致边坡及地基失稳的问题,以三峡库区典型砂岩为研究对象,利用岩石全自动多功能三轴流变仪开展了不同水压循环作用次数下砂岩力学特性试验研究。结果表明:水压循环次数越多对砂岩试样造成的损伤越大;根据水压循环过程中岩体的应力应变关系曲线特征,借助损伤理论及Weibull概率密度函数,建立了考虑砂岩损伤效应的损伤统计本构模型。对比分析表明:该模型与试验曲线符合较好,能够较好的反映水压循环作用对砂岩的损伤效应;随着水压循环作用次数的增加,Weibull分布参数F和m均逐渐减小; F与围压之间呈指数关系,而m与围压之间呈负指数关系,揭示了水压循环作用下岩样宏观强度逐渐降低的特性。研究成果对库区边坡及地基在水压循环作用下的稳定分析具有一定的参考价值。

Study on damage constitutive model of sandstone under hydro-pressure cycle effect

Aiming at the problem of that the quality deterioration of rock mass is prone to cause the instabilities of slope and foun-dation under the effect of the repeated fluctuations of the water level within area of the Three Gorges Ｒeservoir， the experimentalstudy on the mechanical performance of sandstone under the effects from various numbers of hydro-pressure cycles is made withfull-automatic and multipurpose rock triaxial rheological apparatus by taking the typical sandstone in the area of the Three GorgesＲeservoir. The result shows that the more the numbers of hydro-pressure cycle are， the larger the damage to the sandstone sampleis to be. In accordance with the characteristics of stress-strain curve of the rock mass during the hydro-pressure cycle， the statisti-cal damage constitutive model with the consideration of the damage effect of the sandstone is established by means of the relevantdamage theory and Weibull probability density function. The comparative analysis indicates that the model is better coincided withthe experiment curve， and then can better reflect the effect from the hydro-pressure cycle on the damage of the sand stone. Following with the increase of the numbers of the hydro-pressure cycle， both Weibull distribution parameters———F and m are gradu-ally decreased. F exhibits an exponential relationship with confining pressure， while a negative exponential relationship is therebetween m and confining pressure， which reveals the behavior of the gradual decrease of the macroscopic strength of the rock sam-ple. The study result has a certain referential value for the stability analysis made on the slope and foundation under hydro-pres-sure cycle in reservoir area.