Research on landslide stability under different water content conditions based on the dynamic residual strength
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摘要:
长时降雨会引起斜坡发生累进性破坏，在此过程中，滑带土将随含水率的变化达到不同含水状态下的残余强度。传统应变软化模型不能准确表达这一变化过程中滑带土残余强度的动态特征， 而引入动态残余强度的应变软化模型能更加真实地模拟含水率变化时滑坡稳定性的发展。基于此，文章对四川中江县垮梁子滑坡开展了野外调查工作，通过现场竖井获取滑带土，采用环剪试验研究了滑带土力学参数与含水率的关系，在此基础上建立了基于动态残余强度的应变软化模型，模拟了垮梁子滑坡在滑带土处于不同含水率阶段的发展情况。结果表明：含水率的增加使得滑带土抗剪性能显著衰减，峰值及残余抗剪强度呈近乎线性降低，残余强度参数则表现出三次函数型衰减特征。应用基于残余强度参数衰减规律建立的应变软化模型模拟了垮梁子滑坡的变形破坏过程，结果表明在滑带土含水率低于20%时，斜坡仅在前缘局部产生塑性区；当含水率达到22%时，斜坡中上部开始产生塑性区及未贯通滑动面；当含水率达到24%时，塑性区趋于贯通，滑坡进入加速变形状态，并于坡表产生张拉裂缝；当含水率达到26%时，滑坡处于失稳状态，坡表张拉塑性区及破坏面的发展与滑坡现状破坏特征高度吻合。该成果可为相关滑坡的稳定性研究提供一定的理论依据。
Abstract:Long-term rainfall causes progressive damage to a slope. In this process, the slip zone soil will reach the residual strength under different water-containing states with the change of water content. The traditional strain softening model cannot accurately express the dynamic characteristics of the residual strength of the slip zone soil during this change, resulting in difficulty to get close to reality in the simulation of the landslide development process. The strain softening model that involves the dynamic residual strength can more realistically simulate the development of the stability of the landslide when the water content changes. Based on this, the field investigation was carried out on the Kualiangzi landslide in Zhongjiang County in Sichuan, and the slip zone soil was obtained through the on-site shaft. The ring shear test is used to study the relationship between the mechanical parameters of the slip zone soil and the water content, and a strain softening model based on the dynamic residual strength is established to simulate the development of the Kualiangzi landslide when the slip zone soil is at different water content stages. The evolution process of the landslide through the evolution of the plastic zone and the sliding surface is analyzed and compared with the current failure characteristics. The research results show that the increase of water content makes the shear resistance of slip zone soil attenuate significantly, the peak and residual shear strength decrease almost linearly, and the residual strength parameters show the characteristics of cubic attenuation. The strain softening model established based on the attenuation law of residual strength parameters simulates the deformation and failure process of the Kualiangzi landslide. It is found that when the water content of the slip zone soil is less than 20%, the slope only produces a plastic zone at the front edge; when the water content reaches 22%, a plastic zone and a non-penetrated sliding surface begin to appear in the middle and upper parts of the slope; when the water content of the slip zone soil reaches 24%, the plastic zone tends to penetrate, the landslide enters a state of accelerated deformation, and tensile cracks are generated on the slope surface; when the water content reaches 26%, the landslide is in a state of instability, and the development of the tensile plastic zone and failure surface of the slope is highly consistent with the current failure characteristics of the landslide. The results can provide a certain theoretical basis for the stability study of related landslides.
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Key words:
- dynamic residual strength /
- moisture content /
- strain softening /
- slope stability /
- numerical simulation
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表 1 滑带土抗剪强度参数
Table 1. Shear strength parameters of the slip zone soil
拟合公式 含水率 峰值抗剪强度参数 残余抗剪强度参数 cp φp cr φr y=a+bx 18% 33.67 14.06 23.06 11.33 20% 25.04 11.12 21.06 8.92 22% 20.33 8.24 16.40 7.38 24% 14.59 4.52 12.46 3.91 26% 7.99 4.31 7.69 3.45 
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表 2 各岩土层物理力学参数
Table 2. Physical and mechanical parameters of the rock and soil layer
地层
代号γ/(kN·m−3) E/MPa μ σt0/kPa c0/kPa cr1/kP cri/kPa φ0/(°) φr1/(°) φri/(°) 
Ⅰ 22.50 45 0.3 35 65 25.2 25.20 31.5 18.50 18.50 0.008 0.02 0.002 λ 19.50 15 0.34 0 35.77 23.40 3.19 14.98 11.51 3.30 0.008 0.02 0.002 Ⅲ 23.50 2.2×104 0.26 110 1200 1200 1200 42 42 42 0.008 0.02 0.002
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