非饱和原状黄土浸水前后地基承载力测试研究

Research on subgrade bearing capacity for unsaturated intact loess before and after immersion

针对湿陷性黄土地区公路建设中的地基承载力问题,以兰州南绕城某立交上更新统湿陷性黄土为研究对象,开展了浸水前、后土体浅层平板载荷试验与静力触探测试,结合土体物理指标变化,分析了浸水前后黄土地基承载力的损失规律。研究结果表明,原状黄土地基破坏形式为典型的整体剪切破坏,地基承载力特征值可达165k Pa,与陇西地区新黄土地基承载力经验回归关系式较吻合;浸水后由于土体软化,破坏形式更趋近于局部剪切破坏,承载力特征值约为85k Pa。静力触探测试成果表明,浸水后黄土地基的承载力损失百分比与含水率均随深度增加而减小,地表处承载力损失最大,达58%,6m以内损失率约为20%~50%,6~10m深度范围内损失率随深度增加由50%降为25%。

Considering the problem of foundation bearing capacity for highway construction in collapsible loess area,and taking the Pleistocene series collapsible loess at certain interchange in south Lanzhou as the study example,the shallow plate loading tests and the static penetration tests before and after the immersion are carried out to analyze the bearing capacity loss law of the collapsible loess before and after the immersion combined with soil physical indexes. The results show that the damage form of the collapsible loess in the study area is typical overall shear failure before the immersion,and the foundation bearing capacity characteristic value is 165 k Pa,which is accord with the foundation bearing capacity results from the experience regression equation of the new loess located in west Gansu area. Due to soil softening,the damage form is closer to the local shear failure after immersion,and the bearing capacity characteristic value is about 85 k Pa. On the basis of the static penetration test results,the changes with depth of the bearing capacity loss percentage and the moisture content of loess after immersion are almost the same,both decreasing with the increase of depth. The loss rate at ground surface is the most which is 58%,the loss rate within 6m is about 20% ~ 50% and the loss rate with depth 6 ~ 10 m drops from 50% to 25%.