岩体载荷蠕变试验方法研究

STUDY OF METHODOLOGY OF PLATE-LOADING CREEP TEST OF ROCK MASS

由于试件尺寸效应以及试验边界条件与工程岩体工作状态的差异,室内流变试验结果难以准确反映工程岩体流变性质,一些重大水电工程实施了现场岩体蠕变试验,其中现场载荷蠕变试验采用较多,但该试验方法存在一些不完善之处,建议采用五参量广义Kelvin模型描述岩体蠕变特征,并采用一级加载方式进行试验,且荷载水平应与工程荷载相一致。推导岩体载荷蠕变试验五参量广义Kelvin蠕变公式,并验证恒载时间t=0,t→∞时,蠕变公式与弹性变形公式的统一性。最后,给出工程试验实例,采用非线性最小二乘曲线拟合法反演蠕变模型及其参数。反演结果表明,五参量广义Kelvin模型蠕变公式与试验曲线的相关性较好,明显优于三参量广义Kelvin模型。

Laboratory results can hardly reflect the rheological properties of engineering rock mass because of the size-effect of samples and the difference between test conditions and work state of engineering rock mass; so in-situ creep tests were carried out in some important hydropower projects; and the in-situ plate-loading creep test is applied more often. But in the test method, there exist some shortages, so it is suggested that the generalized five-parameter Kelvin model can be accepted to describe the rheological properties of rock mass; and the single-stage loading manner with load level being consistent with engineering load is suggested. The creep deformation equation based on generalized five- parameter Kelvin model of rock mass under plate-load is deduced; and it is found that the results agree with elastic deformation equation when t = 0 or t→∞. Finally, test examples, of which creep model and its parameters are inversed using nonlinear least squares curve fitting method, are given to demonstrate that the magnitude of the correlation between generalized five-parameter Kelvin model and test curves is superior to that of generalized three-parameter Kelvin model.