卵石几何特性对其地层变形性能的影响

Influence of Cobble Geometrical Properties on Deformation Performance of Cobble Stratum

成都地铁1#线穿越区域为典型卵石地层,通过现场筛分实验及数字图像技术对卵石几何特性进行统计分析.地铁沿线卵石直径和扁平度平均值分别为38.23 mm和1.54,都近似服从截尾正态分布,卵石长轴与水平面的夹角平均为32.72°.通过数值实验研究了卵石几何特性对卵石地层等效弹性模量的影响,结果表明:随着卵石面积百分含量的增加,等效弹性模量增加;随着卵石主轴与水平面夹角的增加,等效弹性模量增加;随着卵石扁平度的增加,等效弹性模量减小.在应变均匀性假设的基础上,推导出等效弹性模量理论预测公式,理论分析与数值计算比较接近,可以用来初步判断卵石地层等效弹性模量.

The ground of Chengdu Metro Line No 1 alignment is typical cobble stratum and the cobble geometrical properties are analyzed statistically through on-the-site screening experiments and digital image technique method. Its average value of the diameter of the cobble of the Mtro Line No. 1 alignment is 38.23 mm and the average value of the length ratio between the longest axis and the shortest axis is 1.54. The average angle between the cobble long axis and horizontal direction is 32.72~. The cobble geometrical shape is assumed to be an ellipse. Based on the numerical modeling, the influence of cobble geometrical properties on the equivalent elastic modulus of cobble stratum was studied. The numerical results show that the equivalent elastic modulus increases with increasing of cobble percentage content. The equivalent elastic modulus increases with increasing of the angle between the cobble longest axis and horizontal direction. While the equivalent elastic modulus decreases with increasing of the length ratio between the longest axis and the shortest axis of cobble. On the basis of uniform strain assumption, analytic solutions are derived from the theoretical approach for equivalent elastic modulus. The analytic solutions were validated by the numerical modelling method. The results indicate that the equivalent elastic modulus derived from the theoretical and numerical model is closely matched. The analytic solutions are helpful for improving the understanding of deformation for such ground condition.