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为了研究在定向剪切应力路径下击实黄土的各向异性对其强度和变形特性的影响,利用空心圆柱扭剪仪对击实黄土进行了沿不同主应力轴方向的定向剪切试验,重点探讨中主应力系数b、主应力方向角?对剪切过程中击实黄土强度和变形的影响。试验结果表明,随着主应力方向角的增加,强度呈现出先减小后增大的变化规律,说明击实黄土存在显著的各向异性。在不同b值条件下,广义剪应力–应变曲线的割线模量在0°~30°随着?角增加而降低,在60°以后逐渐增大。通过分析广义剪应力–剪应变曲线变化规律和已有的研究成果,建议采用峰值广义剪应力作为定向剪切下击实黄土的破坏标准;当广义剪应变达到15%仍未出现广义剪应力峰值时,取15%广义剪应变对应的广义剪应力作为击实黄土的破坏标准。击实黄土各向异性特性还表现在b=0.5时各主应力方向上的强度较b=0.0时的强度低。
In order to study the effect of anisotropy of compacted loess on the strength and deformation properties under directional shear stress path, directional shear test of compacted loess along different principal stress axes was conducted by hollow cylindrical torsional shear tester. The influence of main stress coefficient b, main stress direction angle? On the strength and deformation of compacted loess during shearing is discussed. The experimental results show that with the increase of the direction angle of principal stress, the variation of strength decreases first and then increases, indicating that there is significant anisotropy of compacted loess. Under different b values, the secant modulus of the generalized shear stress-strain curve decreases with the increase of the angle from 0 ° to 30 ° and gradually increases after 60 °. By analyzing the law of generalized shear stress-shear strain curve and the existing research results, it is suggested that the generalized shear stress peak be used as the criterion for failure of compacted loess under directed shear. When the generalized shear strain reaches 15%, the generalized shear stress peak , Take the generalized shearing stress corresponding to a generalized shear strain of 15% as the criterion for the destruction of compacted loess. Computation of the anisotropy of loess also shows that the strength of each principal stress direction is lower than that of b = 0.0 for b = 0.5.