An experimental study of the creep characteristics of loess landslide sliding zone soil with different water content
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摘要:
黄土斜坡在受到降雨、人工灌溉、河流水浸润等作用后容易发生蠕变，最终发生滑坡，有时甚至会造成灾难性事故。以往研究中对不同含水率下黄土滑坡滑带土的蠕变性质研究较少，更缺乏定量化的规律分析。以榆林市色草湾村黄土滑坡滑带土为例，进行了一系列三轴蠕变试验，得到了黄土不同含水率下（w=10%、12%、14%、16%、18%，w表示含水率）的应力-应变-时间曲线与应力-应变等时曲线，分析了含水率对黄土蠕变特性的影响，并利用等时曲线法求取了黄土的长期强度，得出如下结论：（1）含水率越大，样品蠕变破坏所需的偏应力越小，轴向应变也越大，含水率增大后自由水厚度增大，土颗粒间胶结程度减小，且水膜会对土颗粒起润滑作用易于其错动滑移；（2）含水率越大，施加每级荷载后样品蠕变曲线达到稳定状态所需时间越长，水分的增加会使土体结构完整性降低，在应力的作用下土体内部结构调整相对缓慢，固结和蠕变过程中孔隙水压力消散需要的时间也越长；（3）通过分析黄土试样蠕变破坏表面形态发现，含水率较小时，蠕变破坏后的试样有明显的剪切破坏面，当试样含水率越大时，越容易发生横向鼓胀，表现出塑性破坏特征，表明含水率较大时，水的软化作用大于水对于土体的裂隙扩展作用；（4）引入了黄土长期强度折损率，揭示了不同含水率下黄土滑坡滑带土的长期强度与长期强度折损率的规律。研究成果可为黄土滑坡的长期稳定性分析提供参考依据。
Abstract:Loess slopes are often prone to creeping after being subjected to rainfall, artificial irrigation, river water infiltration, etc. Eventually a landslide occurred, even causing a catastrophic accident. There are few studies on the creep properties of loess landslide soil under different water content in the existing literature, and there is a lack of quantitative analysis of the law. A series of triaxial creep tests of sliding zone soil of loess landslide in the Secaowan Village, Yulin City have been carried. The stress-strain-time curves and isochronous stress-strain curves with different water contents (w=10%, 12%, 14%, 16%, 18%, w represents the water content) are obtained and the influence of water content on the creep characteristics of loess is analyzed as well. The long-term strength of loess is obtained by using the isochronous curve method. The research results show that (1) When the water content of the sample is larger, the deviator stress required for the creep failure of the sample is smaller, and the axial strain is larger. This phenomenon can be explained by the electric double layer theory as follows: The thickness of free water increases, the degree of cementation among soil particles decreases, and the water film will lubricate the soil particles and make them easy to slip. (2) When the water content of the sample is larger, the time required for the creep strain to reach a stable state after each level of load is applied is longer. This phenomenon can be explained as follows: The increase of loess moisture reduces the structural integrity of the soil, and the adjustment of the internal structure of the soil is relatively slow under the action of stress. Therefore, it takes a longer time for the pore water pressure to dissipate during consolidation and creep. (3) By analyzing the surface morphology of the creep failure of the loess sample, it is found that when the water content is small, the sample after the creep failure has an obvious shear failure surface. When the water content of the sample is larger, the lateral swelling is more likely to occur, showing the characteristics of plastic failure, and indicating that when the moisture content is larger, the softening effect of water is greater than the effect of water on the crack expansion of the soil. (4) The long-term strength loss rate of loess is introduced. It reveals the law of long-term strength and long-term strength loss rate of loess landslide soil under different water content. The research results can provide a reference for the long-term stability analysis of loess landslides.
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Key words:
- loess landslide /
- sliding zone soil /
- creep /
- water content /
- long-term strength
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表 1 蠕变试验偏应力加载方案
Table 1. Deviator stress loading scheme for creep tests
w/% q/kPa 10 150.0，187.5，212.5，250.0，287.5，300.0 12 150.0，175.0，212.5，237.5，262.5，287.5 14 137.5，162.5，187.5，225.0，250.0，262.5 16 125.0，150.0，175.0，200.0，225.0，237.5 18 112.5，150.0，162.5，187.5，212.5，225.0 
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表 2 黄土不同含水率下瞬时强度与长期强度
Table 2. Instantaneous strength and long-term strength of loess sample with different water content
w/% qf/kPa q'/kPa Q/% 10 312.5 282 9.8 12 300.0 260 13.3 14 275.0 235 14.5 16 250.0 194 22.4 18 237.5 171 28.0
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