分级加载条件下岩石流变特性的试验研究

以红砂岩为例,采用重力加载式流变仪,在分级加载条件下对岩石的蠕变特性进行了单轴压缩蠕变试验研究,重点观察和分析了蠕变条件下岩石的弹性模量和泊松比的变形效应,同时对其他时效变形特点进行了分析。试验结果表明,侧向稳定蠕变阶段的应力门槛值低于轴向稳定蠕变的应力门槛值;侧向蠕变有明显的加速蠕变阶段,且比轴向加速蠕变阶段出现得早,而轴向蠕变的第三阶段则不太明显,一经出现试样随即破坏。在单体分级加载条件下,受蠕变的影响,随应力水平和变形量的增加,岩石的瞬时弹性模量有明显的增大,泊松比的变化则更为显著。

Experimental study on creep properties of rocks under stepwise loading

The creep behavior of rocks was investigated by many researchers.The time dependent behavior and strain-rate effect of elastic modulus were also studied by some authors.The lateral creep properties of rocks and deformation effect of elastic modulus of rocks,under creep condition however,were important for constitutive model and still have not been paid enough attention.In this paper,the lateral creep properties and strain effect of modulus under creep condition were experimentally studied using specimens made of red sandstone rock under step load with the developed gravitation style rock creep test machine.The test results showed that the lateral stress threshold of the second period was less than that of the axial stress threshold,the third period of lateral creep was obvious but not for axial one.The turning point of the third period of lateral creep appeared earlier than that of axial creep.Due to creep deformation,the instantaneous elastic modulus and the Poisson's ratio increased obviously with deformation.