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为了研究试样壁厚对空心扭剪试验中扭剪应力分布不均匀的影响,从假设土体为线弹性角度对空心扭剪试样横截面上扭剪应力的分布规律进行了理论推导,同时采用邓肯E-ν模型对不同壁厚的5组空心圆柱试样的扭剪过程进行三维有限元模拟,分析了在试验中以扭剪应力平均值和主应力轴旋转角平均值代替真实值所产生的误差与试样壁厚的关系。结果表明,外径相同的试样,壁厚越厚,横截面上的扭剪应力和主应力轴旋转角沿半径方向的分布越不均匀;利用试验中常用的扭剪应力平均值和主应力旋转角平均值代替真实值会产生误差,且误差随着壁厚的增大而增大;若将扭剪应力平均相对误差和主应力轴旋转角最大相对误差控制在10%以内,则内外径比不小于0.7,建议空心扭剪试样的尺寸取为外半径70mm、壁厚20mm、高度250mm。
In order to study the effect of sample wall thickness on the distribution of torsional shear stress in hollow torsional shear test, the distribution of torsional shear stress on the cross-section of hollow torsional shear specimen is assumed to be derived theoretically from the point of view of linear elasticity. The Duncan E-ν model was used to simulate the torsional shear process of five hollow cylinder specimens with different wall thicknesses. Three-dimensional finite element simulation was carried out. The average value of torsional shear stress and principal stress axis rotation angle were substituted for the true value The relationship between the error generated and the sample wall thickness. The results show that the thicker the wall thickness, the more uneven the distribution of the torsional shear stress and the rotation angle of the principal stress axis in the radial direction of the specimens with the same outer diameter. By using the average torsional shear stress and the principal stress If the average relative error of the torsional shear stress and the maximum relative error of the rotation angle of the principal stress axis are within 10%, the inner and outer diameters Ratio of not less than 0.7, the proposed hollow torsion shear specimen size is taken as the outer radius of 70mm, wall thickness 20mm, height 250mm.