Analysis on time-dependent deformation of landslide based on creep characteristics of weathered red mudstone: A case study of the Luobao landslide in Tianshui of Gansu Province
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摘要:
风化红层泥岩蠕变是我国黄土高原区边坡变形失稳的重要原因之一。选取天水市雒堡村巨型多级旋转滑坡，利用KTL全自动三轴仪和基于连续介质力学的离散单元方法（CDEM）数值模拟手段，开展了风化红层泥岩蠕变本构模型和滑坡时效变形研究。通过0.1～0.7 MPa不同围压下的分级加载蠕变试验，揭示了风化红层泥岩试样瞬时弹性变形、衰减蠕变和稳态蠕变三阶段的蠕变行为；同一围压下，轴向变形量随应力水平的增大而增大，且增长速率也逐渐增大；同一应力水平下，轴向变形量随围压的增大而增大，且增长速率也缓慢增大。拟合建立了试样Burgers蠕变本构模型方程。在此基础上，通过数值模拟揭示了自重应力下1 a尺度的滑体时效变形特征：约98.6%的变形发生在60 d内，随后进入稳态蠕变阶段；滑体水平位移量由浅及深逐渐减小，变形主要集中在后缘Ⅰ级滑体，最大位移约54.1 cm，滑坡变形模式表现为推移式；剪应变主要位于每一级滑体后缘滑带陡-缓转折处，最大剪应变约0.23 %，但未整体贯通，总体处于较稳定状态。
Abstract:Creep of weathered red mudstone is one of the important reasons inducing slope deformation and instability in loess plateau of China. Creep constitutive model of weathered red mudstone and time-dependent deformation characteristics of landslide were performed by using the KTL automatic triaxial instrument and CDEM, in giant -scale multiple rotational landslide of Luobao village in Tianshui City. Under different confining pressures between 0.1−0.7 MPa, the stepwise-loading creep tests on weathered red mudstone samples was performed. The creep process and creep characteristics were analyzed. The results show that the samples have experienced instantaneous elastic deformation stage, attenuation creep stage and steady creep stage. Under the same confining pressure, the increment of elastic deformation varies with different stress levels. The increasing rate of deformation is also increased gradually. At a certain stress level, the final creep of the samples under different confining pressures increases gradually with the increase of confining pressures. The increasing rate of deformation is increased slowly. The fitting results show that Burgers creep constitutive model is in high coincidence with the experimental data. On this basis, time-dependent deformation characteristics and the pattern at 1-year scale under gravity stress were revealed by numerical simulation. The results show that almost 95% of deformation occurred within 60 days, and then it entered the steady creep stage. The horizontal displacement of the slide mass decreases with the increase of the depth. The deformation is mainly concentrated on the slide mass Ⅰ, the maximum displacement is about 54.1 cm. The landslide shows a thrust load-caused deformation pattern. Shear strain occurs at the steep-slow junction of the trailing part of each slidemass, the maximum shear strain is about 0.23%, but no transfixion occurred. The whole slope is stable.
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Key words:
- red mudstone /
- landslide /
- creep /
- Burgers model /
- time-dependent deformation /
- Tianshui
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表 1 泥岩基本物性参数
Table 1. Basic physical parameters of mudstone
参数 干密度/（g·cm−3） 湿密度/（g·cm−3） 颗粒密度/（g·cm−3） 孔隙率/% 软化系数 数值 2.13～2.34 2.17～2.36 2.59～2.74 10.8～22.0 0.3～0.97（0.70*） 注：*为均值。 
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表 2 岩土体物理力学参数
Table 2. Physical and mechanical parameters of rock and soil mass
序号 材料 密度
/（g·cm−3）弹性模量
/MPa泊松比 黏聚力
/kPa内摩擦角
/（°）1 滑体 2.08 171.0 0.25 15.0 32 2 滑带土 2.00 106.0 0.26 10.0 23 3 黄土 1.60 56.2 0.28 36.4 25 4 泥岩 2.13 1920.0 0.20 5130.0 34
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表 3 滑坡滑体及滑带土蠕变参数
Table 3. Creep parameters of landslide deposits and the sliding body
序号 材料 
/MPa
/（MPa·h）
/MPa
/（MPa·h）1 滑体 68.4 342000 68.4 300 2 滑带土 40.6 176000 40.6 85 注：表中变量参照式（2）变量解释。
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