灰岩三轴高温后效流变特性及长期强度研究

Study of triaxial rheological property and long-term strength of limestone after high temperature

流变特性是岩石的变形特征之一,长期强度作为岩石流变特性重要的强度指标也越来越受到工程建设的重视。开展了高温后灰岩三轴蠕变试验,首先采用高温前后岩样纵波波速的变化引入热损伤因子D,量化岩石热损伤,然后分别采用等时曲线法、过渡蠕变法和稳态蠕变速率法进行了灰岩蠕变长期强度分析,并提出一种改进的稳态蠕变速率曲线切线法。结果表明,基于波速的热损伤因子能较为准确地量化温度对灰岩性质的影响;热损伤因子与灰岩经历高温后的长期强度呈现高度相关性,确定灰岩的温度阈值在380℃附近,低于此温度表现为灰岩性质强化效应,高于此温度表现为损伤效应;提出的稳态蠕变速率曲线切线法对于灰岩的长期强度预测较为准确,与实际情况相符;各温度下岩样蠕变破坏形态均表现为剪切破坏,亚裂纹逐渐由与主剪切面平行转为垂直扩展。

Rheological property is one of the deformation characteristics of rock; and great importance shall be attached to the long-term strength of the rock mass among mechanical properties in most geotechnical engineering. According to the triaxial creep test of limestone after high temperature, a thermal damage factor based on longitudinal wave velocity is introduced to quantify the thermal effect on the rock mass, and a series of observations are used including isochronal curves of strain method, transient creep method and steady creep rate method to predict the long-term strength of limestone and put forward an improved method of steady-state creep rate curve-tangent method. The results show that the thermal damage factor which based on wave velocity can quantify the thermal effect accurately; and the thermal damage factor shows a close correlation with the long-term strength. The limestone threshold temperature is 380 determined in this tests; lower than which the property of limestone shows a reinforcement effect and beyond which shows a damage effect. The steady-state creep rate curve-tangent method predicting the long-term strength of limestone is much accurate and consistent with the actual situation. The failure modes of limestone at different temperatures are characterized by shear failure; and the sub-crack transforms gradually from the parallel to the main shear plane to the irregular extension. © 2016, Science Press. All right reserved.