【作者】 李彦兴；

【导师】 邵生俊；

【作者基本信息】 西安理工大学 ， 环境工程， 2004， 硕士

【摘要】 本文就黄土挖方高边坡工程问题，首先在三轴仪上考虑边坡开挖过程应力条件的变化，进行了Q₃、Q₂黄土不同含水量条件下围压卸荷、等p剪切及轴向加载三种应力路径的试验。研究表明，原状黄土含水量不同、固结围压不同、应力路径不同、应力应变曲线亦显著不同，可以由软化弹塑性模型、理想弹塑性模型或双曲线弹性模型描述。进而，整理分析了不同模型共同含有的初始切线模量、泊松比及强度指标，并根据初始切线模量变化规律揭示了黄土结构损伤特性。其次，在试验研究的基础上，应用能够反映黄土挖方边坡大、小主应力减小变化的围压卸荷剪切应力应变模型，将挖方边坡区分为路堑边坡和削坡，通过数值模拟开挖过程分析了坡高、坡型、坡比及地层含水量变化对边坡稳定性的影响。结果表明，地层含水量在12.0％～18.0％变化范围内，各种挖方边坡稳定性均随湿度的增大而显著降低；路堑边坡的稳定性随综合坡比的增大而降低，但削坡受自然坡比影响，随综合坡比的增大其稳定性基本不变；坡高30m的路堑边坡稳定性因坡型改变而有明显变化，且单一坡比多级马道型边坡的稳定性较上缓下陡平台型边坡的稳定性差，但坡高50m的路堑边坡稳定性因坡型变化而基本不变；当坡高、坡型、地层条件相同时，路堑边坡的稳定性较削坡的稳定性差。最后，就有限元法、强度折减法和极限平衡法，自然边坡与挖方边坡，围压卸荷应力路径模型分析与轴向加荷应力路径模型分析进行了比较讨论。表明有限元法、强度折减法、极限平衡法得出的安全系数依次降低；依据强度折减法分析，相同条件下，挖方边坡的安全系数较自然边坡的安全系数小；依据有限元西安理工大学硕士学位论文法分析，轴向加荷应力路径模型确定的安全系数较围压卸荷应力路径模型确定的安全系数小。更多还原

【Abstract】 The stability mechanism of high loess excavation slopes is discussed in this paper. First ,considering the change of stress conditions in excavation slopes by means of triaxial equipment, the triaxial tests of three kinds of stress paths of Q3 and Q2 loess, including lateral unloading, keeping mean normal stress changeless and conventional axial loading, is carried out under different water content and consolidation stress conditions. The results indicate that stress-strain curves with different water contents, consolidation stresses and stress paths are evidently dissimilar, which are correspondingly described with softening elastic-plastic model, ideal elastic-plastic model and hyperbolic elastic model. Further more, on the basis of analysis of triaxial tests, the initial elastic modulus, Poisson’s ratio and strength index included in differ models is analyzed, and the damage characteristics of Q3 loess is indicated on the basis of changing of the initial elastic modulus. Secondly, on the basis of mechanic properties analysis, applying the stress-strain model of lateral unloading which can reflect the decrease change of principal stress state in the excavation progress of slope, dividing excavations slope into cutting slope and sharpen slope, numerical simulation is respectively carried through in order to analyze the impact of changing of slope type, slope height and stratum water content on the slope stability. The result indicates that slope stability reduces notably with the humidity increasing in the condition of the water content of stratum froml2. 0% to 18%. with synthesize sloperatio increasing, the stability of cutting slopes decreases, but the stability of sharpen slope affected by natural slopes ratio changes rarely, the stability of cutting slope that height is 30m is change notably due to slope type, whose single slope ratio with madao is inferior to the slope that upper ratio is less than lower ratio with platform in middle part. But the stability of cutting slope with 50m height is little change with the slope type change. With same stratum, slope height, slope type, the cutting slope is inferior to the sharpen slope in stability. At last, the finite element method, the strength reduction method and limit equilibrium method, nature slopes and excavation slopes, lateral stress unloading model and axial loading model are analyzed and discussed relatively. The paper points out the factor of safety by means of finite element method, the strength reduction method and limit equilibrium method decreases in turn. According to analysis of the strength reduction method, the stability of the cutting slope is less than the stability of nature slope. According to the results by the finite element method, the factor of safety calculated by axial loading stress-strain model is less than the factor of safety by lateral unloading stress-strain model.更多还原