基于BOTDA的削坡作用下边坡破坏过程模型试验研究∗

在众多诱发滑坡的因素中,人工削坡引发的边坡失稳现象十分普遍。采用布里渊光时域分析技术(以下简称BOTDA 技术),通过模型试验和数值模拟分析,对削坡作用下的边坡变形机理及其演化过程进行了研究。由于传感光缆与土体之间的耦合性直接影响着监测结果的准确性,首先通过不同围压作用下的拉拔试验,掌握了传感光缆与土体耦合变形关系。然后,设计了坡顶加载试验模型,通过在水平向和竖直向植入传感光缆,实现对边坡模型在削坡作用下土体内部变形场的分布式监测。试验结果表明:水平和竖直向传感光缆监测到的应变异常区域与潜在滑动面位置相吻合,并被数值模拟所证实;在 BOTDA 监测数据的基础上提出了边坡模型水平特征最大应变值与安全系数之间的经验公式,对削坡作用下的边坡稳定性状态进行了评价,进而可对边坡失稳做出预警。

Model Test Research on Slope Failure Process under Slope Cutting Based on BOTDA Technology

Among other factors,artificial slope cutting is one of the most common triggering factors oflandslide. In this paper,a series of model tests and numerical simulation have been conducted to inves?tigate the failure mechanism and evolution process of the slope under slope cutting. As the coupling be?tween sensing cables and soil directly affects the accuracy of monitoring results. Firstly,a new pullout apparatus is designed and the coupling deformation relationship between sensing cables and soil isacquired through pull-out tests under different confining pressures. According to the pull-out tests,asurcharge loading test model was designed. Strain-sensing cables that can capture the strains at differ?ent positions of the model slope were embedded in the soil mass. The measurement data of the cutslope were analyzed. It can be found that an abnormal strain-field area obtained by horizontal and verti?cal sensors coordinated with the location of the potential slip surface. This is verified by a comparisonbetween the measurements of the cables and numerical simulation results. Based on the BOTDA da?ta,an empirical relationship is explored between the horizontal characteristic maximum strain and thesafety factor to estimate the slope stability condition and perform early-warning of landslide under theaction of slope cutting. The conclusions drawn in this study are of great significance to stability evalua?tion of artificial cut slopes.