大厚度黄土地层拓宽路基浸水破坏机制

Immersion Damage Mechanism of Widening Roadbed in Collapsible Loess with Great Thickness

摘要:

为研究大厚度湿陷性黄土地层浸水湿陷条件下拓宽路基变形破坏特性，基于长安大学土工离心机，安装了降雨浸水系统和位移量测系统，开展与实际应力相一致的离心模型试验，并根据试验结果探讨了湿陷性黄土地层拓宽路基的浸水破坏模式.试验结果表明：拓宽路基荷载影响下，新路基以及部分老路堤会产生新的沉降，最大沉降值出现在拓宽路基形心处，进而产生新旧路基间的不协调变形；持续降雨将会在拓宽路基坡脚处产生雨水入渗，入渗将诱发大厚度湿陷性黄土层内部产生非均匀湿陷，这会导致新旧路基体产生不同程度的湿陷突变，在湿陷突变所产生的差异沉降的作用下，路基边坡首先出现裂缝，进而在新旧路基拼接带处也出现裂缝，最终面临因地基整体增湿失稳所带来的更为严重的路基路面塌陷、滑移等问题.

Abstract:

In order to study the wetting failure mode and mechanism of widening subgrade in selfcollapsible loess areas, the rain system and deformation field test system were installed in geotechnical centrifuge of Chang’an University. The centrifugal modal test consistent with the actual stress was conducted using the undisturbed collapsible loess. The settlement law of widening roadbed flooded by rainfall was studied and the damage mode of widening roadbed was analyzed according to the test results. The test results show that the foundation under widening roadbed producea a large settlement under the action of gravity load whose largest value appears in widening roadbed centroid place, resulting in a poor coordination deformation between new and old roadbed. The local instability of the foundation under widening roadbed caused by continuous rainfall poses a great threat to the safety of the upper widening roadbed. The formation of widening roadbed is a gradual process: First is the emergence of the collapsible caves. Next, appear the cracks in toe. Fanally comes the large deformation caused by the wetting toes which gives rise to the damage of pavement even landslide.