差异沉降条件下黄土拓宽路基协调机制模型试验研究

MODEL EXPERIMENTAL STUDY OF LOESS WIDENED EMBANKMENT COORDINATION MECHANISM UNDER CONDITIONS OF DIFFERENTIAL SETTLEMENT

以黄土地区高速公路拓宽工程为研究背景,借助大型地基沉降模拟试验平台,实现拓宽路基荷载下地基沉降变形的人为模拟,开展几何相似比为1∶1的足尺模型试验,建立路基内部土体及加筋材料变形监测系统,分析新老地基差异沉降条件下路基内部土体及加筋体的响应机制。试验结果表明:拓宽路基荷载作用下,随着地基差异沉降的增加,路基内部土体是一个不断变形协调过程,当地基差异沉降S达到9 cm时,路基与路面结构层出现脱空;新老路基拼接段铺设土工材料能使松散土体形成板结复合体,土工材料能够增强新老路基的整体稳定性和力学特性,土体填料更容易形成自拱效应;土工格栅能一定程度上消解新老路基间的差异沉降。随着新老地基差异沉降的增加,土体内部筋材受力不均匀且筋材内部相应产生了交替拉压应变,应变整体呈现增加的趋势,当新老地基差异沉降达到16 cm时,土工格栅拉压应变趋于稳定,土工格栅拉伸或压缩极限变化量仅为2 mm,远小于土工格栅破坏极限。

Aiming to study the loess area highway widening project,based on the large-scale foundation settlement simulation test platform,a scale test with the geometry similarity ratio of 1∶1 is carried out;and the roadbed internal soil and the reinforcing material deformation monitoring systems is also established to analyze the response mechanism of internal soil and reinforcement of the roadbed constructed under the conditions of old and new foundation differential settlements. The results show that:under the widened embankment load,the roadbed internal soil experiences a constant process of deformation and coordination with the increasing foundation differential settlement. When the differential settlement S reaches to 9 cm,subgrade and pavement layer appear a slight void. Laying the geotextile material on old and new roadbed splicing segment can lead loose soil to form the compaction complex,which can enhance the overall stability and mechanical properties of roadbed soil and easily form the arch effect. Besides,the geogrid can digest the settlement between new and old roadbed in a certain degree,but the effect is limited. The geogrid inside the soil plays a coordination role in the subgrade soil deformation. The reinforcement force is not uniform and the corresponding alternating of tension and compression strain appears. With the increasing foundation differential settlement,strain show a increasing trend as a whole. When the differential settlement S between old and new foundation reaches to 16 cm,tension and compression strain of geogrid tend to be stable. The ultimate amount of geogrid tensile or compression changes only 2 mm,far less than the destruction limit of geogrid.