不同相对密实度含软岩堆石料的蠕变特性研究
Creep behavior of rockfill with soft rock under different relative densities
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摘要: 软岩作为高土石坝的筑坝材料时,易产生较大的蠕变变形,对高土石坝的长期稳定十分不利。因此有必要开展含软岩堆石料的蠕变特性研究。利用大型压缩仪,对不同相对密实度的含软岩堆石料进行了单轴蠕变试验,探讨了相对密实度对堆石料蠕变特性的影响。随着相对密实度增大,堆石料的轴向蠕变应变减小;随着轴向压力增大,相对密实度对轴向蠕变应变的影响程度提高。利用幂函数蠕变模型拟合轴向蠕变应变随时间变化的曲线,获得最终蠕变应变和衰减指数。探讨其与轴向压力的函数关系,得出两者分别与轴向压力满足双曲线函数和幂函数关系,建立了考虑轴向压力的单轴蠕变模型。由蠕变模型参数随相对密实度的变化可知,相对密实度对衰减指数的影响很小。依据模型中与最终蠕变应变相关的一个参数和相对密实度呈良好的线性关系,建立了同时考虑轴向压力和相对密实度的单轴蠕变模型,并讨论了模型各参数的物理意义。Abstract: When soft rock is used as the dam embankment materials for high earth-rock dams, large creep deformation may occur, which is very unfavorable to the long-term stability of high earth-rock dams. Therefore, it is necessary to study the creep characteristics of rockfill with soft rock. The uniaxial creep tests are carried out on rockfill with soft rock under different relative densities by using a large odemeter, and the influences of relative density on creep characteristics of rockfill are discussed. The axial creep strain of rockfill decreases as the increase in the relative density. With the increase in the axial pressure, the influences of the relative density on the axial creep strain are more significant. The creep model of power function is used to fit the change curves of the axial creep strain with time. The attenuation index and the final creep strain are obtained. The functional relationship among the final creep strain, the attenuation index and axial pressure is discussed. It is found that the final creep strain and the attenuation index meet the hyperbolic function and power function relationship with the axial pressure, respectively, and a uniaxial creep model considering axial pressure is proposed. The relationship between the parameters of the creep model and the relative density shows that the relative density has small effects on the attenuation index. Based on a good linear relationship between the parameter related to the final creep strain in the model and the relative density, a uniaxial creep model related to both the axial pressure and the relative density is proposed, and the physical significance of each parameter of the model is discussed.