岩石流变特性及长期强度的试验研究

EXPERIMENTAL STUDY ON RHEOLOGY PROPERTIES AND LONG-TERM STRENGTH OF ROCKS

研制重力驱动偏心轮式杠杆扩力加载式流变仪,其扩力比稳定在120,误差在4‰以内,可实现任意长时间的恒定加载,满足流变试验的要求。应用该流变仪,对红砂岩的蠕变特性进行单轴压缩蠕变试验研究,重点观察和分析岩石横向蠕变规律与轴向蠕变规律的差异,并根据试验结果对岩石长期强度的确定进行分析。试验结果表明,横向稳定蠕变阶段的应力阈值低于轴向稳定蠕变阶段的应力阈值;横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;轴向蠕变的第三阶段则不太明显,且一经出现试样随即破坏。根据试验结果,考虑岩石蠕变的“岩石的长期强度”应根据岩石进入横向稳定蠕变的阈值应力来确定,这样确定的“岩石长期强度”值要比根据岩石进入轴向稳定蠕变的阈值应力确定的“岩石长期强度”值小19%～35%。这一结论对考虑蠕变稳定性的岩土工程设计具有重要的指导意义。

The gravitation level style rock rheology test machine was developed by the authors. Its scale-up ratio is 120 and the error is less than 0.4%. Load may keep stable in any time（e.g, long-term） to meet the requirements of rock theology test. The theology properties and stress effects of creep moduli under creep conditions were experimentally studied by using specimens of red sandstone under step load with the gravitational style rock theology test machine. The differences between axial and lateral creep properties and long-term strength of rock were specially observed and analyzed. The experimental result shows that the lateral stress threshold of the second creep stage is less than that of axial stress threshold. There is an obvious accelerated stage in the lateral creep course~ and the accelerated stage in lateral creep course appears earlier than that in the axial creep course~ but the third stage of the axial creep is not obvious and the rock specimen will be damaged as soon as the third stage appears. According to the experimental result, the long-term strength of rocks should be determined in terms of lateral stress threshold of second creep stage of the rock： so the determined long-term strength value is less 19% - 35% than that determined in terms of axial stress threshold of the second creep stage of the rocks. There is an important directive meaning for this result to account for the creep stability in the geotechnical engineering fields.