砂岩蠕变特性及蠕变力学模型研究

应力水平对岩石蠕变特性有很大的影响。通过对砂岩单轴蠕变试验研究表明:当加载应力远小于屈服应力时,应变速率持续衰减最终保持恒定,只产生蠕变的第1,2阶段,试件不会破坏,属于稳定型蠕变;当加载应力大于或小于但接近于屈服应力时,应变速率先衰减后加速增长,蠕变的3个阶段都产生了,在蠕变第3阶段产生了轴向方向的3条裂纹,最终裂纹扩展贯通而破坏,破坏形式为张性拉裂破坏,属于非稳定型蠕变。实验说明,屈服应力是岩石产生极非稳定型蠕变的一个临界值。根据加载应力水平产生的蠕变差异,建立了砂岩的经验本构模型和蠕变力学模型,为岩体工程建设提供借鉴与参考。

Study on creep behaviour of sandstone and its mechanical models

Creep of rock could be influenced by a few factors and the stress states had great influence on the rheological characters of soft rock.The uniaxial compressive creep test on sand stone showed that,when the stress was considerably less than yield stress,the decreasing strain rate approached to a final steady value.In this case the creep was named stable creep and only got to the phase 1 and 2 without damage.On the other hand,when the stress was close to the yield stress,the strain rate decreased at the beginning,then accelerated to increase.Crack appeared and spread in the 3rd phase of the creeping process.The destructing pattern is tensive crack,which belonged to unsteady creeping.It was shown that yield stress was a critical value to cause unsteady creeping.An emperical constitutive model and the creep stress model were established according to the differences of creep induced by the stress level.