含粗粒滑带土剪切带演化及空间展布规律研究

Experimental study on the development process and spatial distribution of shear band of coarse-grained sliding zone soil

对含不同强度粗颗粒的滑带土进行了可视化中型直剪试验,通过竖直置入铝丝观察剪切后铝丝变形情况获取剪切破坏带的空间信息,并建立了剪切带空间曲面方程。通过粒子图像测速(particle image velocimetry,PIV)技术对可视面处二维剪切带信息进行提取,并与剪切试验得到的空间曲面方程的边界外推值进行对比,证明了空间曲面方程与PIV技术能够描述剪切带特征。然后通过PIV技术对不同剪切总位移与某一剪切位移下短时间内相对位移规律进行了分析。最后分析了预制损伤与粗颗粒强度对剪切带特征的影响。研究结果表明,剪切带形状为两端薄中间厚的带状,可采用高斯曲面方程对剪切带轮廓进行拟合。剪切带在发展过程中经历压密、自由损伤、损伤沿固定路径发展与剪切带贯通4个阶段,损伤使得剪切带发展各阶段前移,粗颗粒强度会对局部剪切带变形产生较大影响而对整体剪切带的变形影响较小。该研究成果对于揭示滑坡剪切带形成与演变规律从而设计合理的边坡防治方案具有重要意义。

In this study,a visual medium-scale direct shear test is carried out on the sliding zone soil with different coarse particle strengths.The spatial information of the shear band is obtained by placing a vertical aluminum wire to observe its deformation after shearing,and the spatial surface equation of the shear band is established.Particle image velocimetry(PIV)technology is used to extract and compare the 2D shear band information at the visible surface with the boundary extrapolation value of the space surface equation obtained from the test,demonstrating that the spatial surface equation and PIV technology can describe the characteristics of shear band.Then,PIV technology is used to analyze the evolution rule of shear band under different total and specific displacements.Finally,the influence of prefabricated damage and coarse particle strength on shear band characteristics was analyzed.Results show that the thickness of shear band presents a distribution pattern of narrow ends and wide middle,and its shape can be fitted by Gaussian surface equation.The shear band undergoes four stages during its development:compaction,free damage,damage development,and penetration.Damage causes early development of shear bands at various stages.Furthermore,coarse particle strength exerts a greater effect on the deformation of local shear bands and a smaller effect on the overall shear band.These findings hold significant implications for elucidating the formation and evolution of landslide shear bands and designing a rational slope control plan.