拓宽黄土路基湿化破坏机制模型试验研究

 为研究拓宽黄土路基浸水湿化破坏机制与模式，在土工离心机上设计并安装位移量测系统，以西安—潼关高速公路拓宽工程为研究载体，建立与实际应力相符的离心试验模型；针对浸水湿化后黄土拓宽路基的沉降变形规律和破坏形式进行研究，基于试验结果开展高填方黄土路堤破坏机制的讨论。研究结果表明，拓宽路基坡脚处高含水量对拓宽黄土路基稳定性影响极为显著，在地下水位较浅处的地带，强降雨天气或地下水位骤升所引起的拓宽路基荷载下黄土地基的局部失稳会极大威胁上部拓宽路基的安全，浸水破坏滑裂面的形成是一个渐进破坏过程。由于地基局部湿软，抗剪强度降低，地基的起始剪切破坏发生于老路坡脚处，一旦产生过大的变形量将会引起整个路基自上而下的滑移。地基破坏时的滑动面近似为圆弧状，建议采用裂隙圆弧法对拓宽荷载下地基进行稳定性评价。试验结果还表明，新老路基拼接带土体中的加筋材料起到裹附作用，可增强路基的板结效果，形成有效的土拱效应，这样就充分利用路堤填料本身的刚度，调整地基的沉降变形。

MODEL EXPERIMENTAL RESEARCH ON WETTING DAMAGE MECHANISM OF WIDENING LOESS ROADBED

To study the wetting mechanism of widening loess roadbed and its failure modes，the deformation measurement system is installed on geotechnical centrifuge. To achieve the actual stress with the loess embankment broadening，the Xi¢an—Tongguan Expressway is adopted. The results show that the widening embankment slope toe with high water content will influence loess roadbed stability in the zone with shallow water level. During the heavy rainfall or the sudden jump of the water level under the embankment load，the local loess soil instability will greatly threaten the safety of the widened embankment，and the flooding-damaged formation of slip surface is a progressive failure process. Due to local swampy ground and low shear strength，initial shear failure of foundation will occur on the old road slope once the foot of the wetting slope causes excessive distortion generated by the global body from top to bottom of the slip slope. The sliding surface of loess roadbed is approximately circular shape，and the method for stability evaluation of the foundation under widening load is proposed using fissures arching. The results also show that the new and old roadbeds with reinforced materials in soils attached to the role can form an effective soil arching effect，they can make the best of embankment rigidity to adjust deformation of the foundation settlement.