Stability Mechanism Analysis Of High Loess Excavation Slopes

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.