帕隆藏布流域冰碛物斜坡结构及稳定性评价方法

Moraine slope structure in Parlung Zangbo River Basin and its stability evaluation method

帕隆藏布流域是我国海洋性冰川最重要的发育区,大量的冰碛物形成了数量众多的松散堆积体,孕育着密集的地质灾害。通过大量案例调查及现场测试工作,总结出冰碛物堆积体斜坡3种不同的斜坡结构及其可能发生的破坏方式,包括浅表冰碛层降雨蠕滑型、较厚冲洪积物覆于冰碛层之上的水岩作用控制型以及冰碛层夹湖相沉积差异风化型。针对研究区最常见的浅层破坏模式,以测窗法面含石率及泥沙含量来描述宽级配特征,以超重型动力触探锤击数表示固结程度,以坡长与高度对数比表示地形要素,考虑植被覆盖及松散层厚度影响,采用最小二乘曲线拟合,建立并验证了稳定性计算公式。通过对公式的实用化进行探索,得到不同冰碛物斜坡高度所对应的坡度值,当冰碛物斜坡高度小于10 m时,坡度可达70°以上。

The Parlung Zangbo River Basin is the largest region of oceanic glaciers in China,where a large amount of moraine form substantial loose deposits and numerous geological hazards develop.Through a lot of case investigation and field tests,three different slope structures of moraine deposits and their possible failure modes are summarized,i.e.,the rainfall-caused creep failure of shallow moraine,the water-rock interaction controlling failure of moraine layer covered with thicker alluvial deposits,differential weathering failure of moraine layer intermingled with lake deposits.In view of the shallow failure mode,most common shallow in the study area,the characteristics of wide gradation are described by the stone content and sediment content in per unit area by sampling window method,the consolidation degree is expressed by the hamming number of super-heavy dynamic penetration test,and the topographic elements are represented by the logarithmic ratio of slope length to height,so the stability calculation formula is established and verified by the least square curve with the consideration on the influence of vegetation cover and loose layer thickness.By practicality analysis of the formula,the slope values corresponding to the different moraine slope height are obtained.When the moraine slope height is less than 10 m,the slope can reach more than 70°.