深部围岩流变特性试验研究及其模型辨识

采用分级增量循环加卸载方式,对湖南湘煤集团牛马司矿业公司水井头煤矿-300m东大巷二煤层底板粉砂岩进行了单轴蠕变特性试验,详细探讨了轴向蠕变变形特征,蠕变速率与时间和应力水平的关系,瞬时弹性模量和变形模量变化特征.试验结果表明,当应力水平低于岩石的长期强度时,粉砂岩只发生衰减蠕变,应力水平对蠕变速率变化的影响不明显；当应力水平高于岩石的长期强度时,岩石等速蠕变阶段明显.对流变试验数据进行深入分析的基础上,进行了流变模型辨识和基于最小二乘法的参数确定.根据不同应力水平下加卸载过程中岩石的蠕变特点,提出了采用改进的两原模型模拟岩石的蠕变特性.模型计算结果表明,改进后的西元模型既能够较好地描述低应力下的衰减蠕变,又能较精确地描述高应力下岩石的衰减蠕变和等速蠕变特性.

An experimental study of the creep properties of deep surrounding rocks and creep model identification

By means of stepwise incremental cycling loading and unloading,the experiment is conducted on uniaxial creep properties of siltstone at the floor of coal seam II in the eastern roadway beneath 300 m of the Shuijingtou coalmine of the Niumasi Mining Company of Hunan Xiangmei Group.The axial creep deformation properties are discribed in details in this paper.The relationship among creep rate,time and stress level is discussed.The properties of the instantaneous elastic modulus and the deformation modulus are explored.The test results show that the attenuation creep occurs and the creep rate is inconspicuously influenced by stress level when the stress level is lower than the long-term strength of siltstone.Constant rate creep occurs when the stress level is higher than the long-term strength of siltstone.Through scientific analysis of the experimental data,the creep model is identified and parameters of the model are determined based on the principle of least square.According to creep characteristics of rock under stepwise loading and unloading at different stress levels,a modified Nishihara model is established for simulating the creep characteristics.Calculation results show that the modified Nishihara model not only better describes attenuation creep under lower stress level,but also accurately describes attenuation creep and constant rate creep under higher stress levels.