滑带土蠕变过程及微观结构演化分析

滑带土的蠕变过程与微观结构密切相关，前人对滑带土的蠕变性质及微观结构做了大量研究，但对土体在蠕变过程中因时间效应发生的微观结构变化研究较少。本文选取延安二庄科北区滑坡滑带土为研究对象，采用直剪蠕变试验研究了滑带土的蠕变特性，用环境扫描电子显微镜对蠕变过程中不同阶段的土样进行SEM图像扫描，并对其微观结构孔隙特征进行定量分析。结果表明：滑带土样在400 kPa正应力荷载下具有明显蠕变特性，每一级剪应力加载均出现衰减蠕变和稳态蠕变阶段；当剪应力值达到255 kPa后，试样发生蠕变破坏，且滑带土样在蠕变过程中由于时间效应发生了塑性破坏。在每一级加载后，土样剪应变率均逐渐减小并最终趋于稳定；在各级剪应力加载后的衰减蠕变阶段，随着加载剪应力的增大，剪应变率也增大；蠕变过程中，土样的孔隙数逐渐减少，土颗粒重新定位排列，孔隙定向性增强，趋向于长条形的孔隙越来越多，孔隙轮廓越来越光滑，但圆形度越来越差。随着蠕变破坏的发生，在蠕变过程中形成的结构被迅速破坏，孔隙定向性减弱，数目急剧增加。

Creep process and the microstructural evolution of sliding -zone soil

Creep behavior of slip zone soil is closely related to its microstructure. The creeping properties and microstructures of sliding soil have been studied a lot before, but few studies have been made on the microstructure changes in the process of soil in the process of creep due to time effect. In this paper, the sliding zone soil of the Erzhuangke north landslide is selected as the research object, and the creep characteristics of the sliding zone soil are examined by direct shear creep test. SEM image scanning and quantitative analyses of soil samples at different stages in the creep process are conducted by environmental scanning electron microscope. The results show that the slip zone soil sample has obvious creep characteristics under 400 kPa positive stress load, and every level of shear stress loading has attenuation creep and steady -state creep stage, when the shear stress value reaches 255 kPa, the specimen is creeped and destroyed by the transition soil in the process of creep due to the time effect. After loading at each stage, the soil -like shear strain rate is gradually reduced and eventually stabilized, and in the attenuation creep ingressated after shear stress load at all levels, the shear strain rate increases with the increase of loading shear stress. In the process of creep, the number of pores in the soil sample decreases gradually, and the soil particles are repositioned and arranged. As a result, the directivity of pores is enhanced, more and more elongated pores tend to be formed, and the contour of pores becomes smoother, but the roundness becomes worse. With the occurrence of creep failure, the structure formed in the creep process is rapidly destroyed, the directivity of soil structure is weakened, and the number of pores increases sharply.