坝基岩体软弱夹层饱水劣化剪切蠕变特性及本构模型

Shear creep characteristics and constitutive model of saturated and degraded dam foundation rock with weak interlayer

坝基岩体软弱夹层蠕变特性对大坝安全和稳定性极为重要,在介绍向家坝水电站坝基岩体软弱夹层发育情况的基础上,选取代表性的软弱夹层取样开展剪切蠕变试验,通过分析饱水时长对软弱夹层蠕变特性的影响规律,引入损伤变量建立非线性损伤蠕变本构模型。结果表明:1)坝基岩体软弱夹层具有明显的蠕变行为,饱水时长对坝基岩体软弱夹层蠕变特性具有显著影响,随着饱水时长的增加,蠕变变形量由1.489~2.931 mm逐渐增加,长期强度由518.34~171.52 kPa呈指数降低趋势;2)坝基岩体软弱夹层饱水劣化机理为:高孔隙度为水分子提供良好的运移通道——长期饱水作用溶解可溶性盐——颗粒骨架调整导致微观结构改变——蠕变变形增加、长期强度降低;3)改进的Burgers模型能够准确描述饱水作用下坝基岩体软弱夹层的剪切蠕变行为。研究成果希望能为岩体蠕变力学本构模型研究提供参考依据。

The creep characteristics of the soft interlayer of the dam foundation rock are extremely important to the safety and stability of the dam.Based on the introduction of the development of the soft interlayer of the dam foundation rock of the Xiangjiaba Hydropower Station,a representative sample of the soft interlayer was selected to carry out the shear creep test.Analyze the influence of the duration of water saturation on the creep characteristics of weak interlayers,and introduce damage variables to establish a nonlinear damage creep constitutive model.The results show that:1)The soft interlayer of the dam foundation rock has obvious creep behavior,and the duration of saturation has a significant impact on the creep characteristics of the soft interlayer of the dam foundation rock.With the increase of the duration of saturation,the amount of creep deformation varies from 1.489 mm to 2.931 mm Gradually increase,the long-term strength shows an exponential decrease trend from 518.34-171.52 kPa;2)The weak interlayer of the dam foundation rock body is saturated with water and the degradation mechanism is:high porosity provides a good migration channel for water molecules—long-term saturation to dissolve soluble salts—The adjustment of the particle skeleton leads to changes in the microstructure—increased creep deformation and reduced long-term strength;3)The improved Burgers model can accurately describe the shear creep behavior of the soft interlayer of the dam foundation rock under saturation.The research results are hoped to provide a reference for the study of constitutive models of rock mass creep mechanics.