毛细屏障在黄土路基干裂防控中的应用及设计参数影响分析  

Use of Capillary Barrier to Prevent Loess Subgrade Desiccation and Its Design Parameters

作　　者：黄沛[1] 张亚国[1] 杨西京 高引龙 王幼博 HUANG Pei;ZHANG Ya-guo;YANG Xi-jing;GAO Yin-long;WANG You-bo(School of Civil Engineering,Chang'an University,Xi'an 710061,Shaanxi,China)

机构地区：[1]长安大学建筑工程学院,陕西西安710061

出　　处：《中国公路学报》2024年第6期207-216,共10页China Journal of Highway and Transport

基　　金：国家自然科学基金项目(42072311,42041006)。

摘　　要：黏性土路基在长期干旱气候条件下易出现干缩开裂的现象,针对该问题提出利用毛细屏障盖层(Capillary Barrier Cover,CBC)代替防渗土工膜或注浆帷幕等传统工程措施来维持路基水分场的稳定。通过开展黄土路基物理模型试验对该方法的有效性进行验证,并基于非饱和土力学理论对其内在机理进行分析。物理模型试验结果表明:在持续15 d的高温(35℃~50℃)天气下,无毛细屏障盖层一侧的路基中观测点含水率下降了4.6%~7.9%,且路基顶部和斜坡位置均发生了干缩开裂;与之相比,铺设毛细屏障盖层一侧的路基对应位置处含水率仅下降了1.0%~2.0%,路基水分场均匀且无任何开裂现象;同时,由于细粒土层的隔热保温效应,铺设毛细屏障盖层侧的路基温度场较未铺设一侧总体低5.5℃;这说明毛细屏障盖层能够对路基水温场进行调控,有效地抑制路基中水分的蒸发。在此基础上,建立了与路基物理模型相对应的有限元数值模型,分析了毛细屏障盖层主要设计参数对其性能的影响规律。数值模型试验结果表明:随着盖层系统中粗粒土和细粒土厚度的增加,路基蒸发失水量均有所降低,但前者影响更为显著;当粗粒土层厚度增加40 mm时,路基各测点含水率降幅为1.7%~4.5%,而细粒土层增加同样厚度引起的变化不到1.0%;此外,毛细屏障盖层中土体的初始含水状态对路基水分场变化影响不大,实际工程设计中可从土体是否便于压实的角度来考虑其含水率取值。Clay subgrades are prone to desiccation cracking after long-term droughts.A capillary barrier cover(CBC)is proposed instead of traditional engineering methods,such as anti-seepage membranes and waterproof curtains,to maintain moisture stability in subgrades.Physical model tests were conducted to verify the effectiveness of the proposed approach.The working mechanism of the CBC in a drought environment was analyzed based on unsaturated soil mechanics principles.The results show that after 15 days of continuous drying(35℃-50℃),the water content of the subgrade without CBC decreases by 4.6%-7.9%,and cracks appear at the top surface and slope of the subgrade owing to shrinkage.The water content only decreases by 1.0%-2.0%in the subgrade with CBC,where no cracks develop.The temperature at the side with CBC is 5.5℃lower than that at the side without CBC.This demonstrates that the CBC can effectively adjust the moisture and temperature of the subgrade and limit moisture evaporation.Corresponding numerical tests were conducted to investigate the effects of the design parameters on the CBC performance.It was found that an increase in fine-and coarse-grained particles,particularly the latter,could decrease the evaporation of subgrade moisture.A 40 mm increment in the coarse-grained layer thickness decreases the water evaporation at each observed point by 1.7%-4.5%,whereas the same increment in the fine-grained layer thickness induces a decrease of less than 1%.In addition,the numerical results show that the initial water contents of the fine-and coarse-grained soil layers minimally influence the performance of the CBC,which can be determined by the required degree of compaction in practice.

关 键 词：路基工程 黄土路基 干缩开裂 毛细屏障 水分场稳定 设计参数 

分 类 号：U416[交通运输工程—道路与铁道工程]