持续强降雨条件下黄土-红层地区输电线路塔基场地稳定性分析

Stability Analysis of Transmission Line Tower Foundation Site in Loess-Red Bed Area under Continuous Heavy Rain

特殊岩土复合地貌区域输电线路塔基在极端降雨天气极易出现塔基不稳定问题。通过对临夏地区黄土-红层二元结构斜坡上塔基持续强降雨后出现的病害调查,发现黄土-红层斜坡构成的建筑场地地基稳定性主要受以下因素影响,即地貌人工改造,黄土-红层的特殊岩土工程性质,持续强降雨对岩土特性劣化,坡体渗流场的变化等。研究表明临夏地区黄土-红层斜坡以浅层破坏为主,具有蠕变塌滑特征。持续强降雨导致二元结构斜坡出现平行坡面渗流与土层基岩界面渗流。在考虑饱和状态下土层参数及渗流场的影响时,斜坡稳定系数远小于1,因此在气候变暖极端天气增多的大气候条件下,输电线路工程应考虑暴雨重现期和降雨持时的影响,塔基基础应嵌入红层以下一定深度,设计应当考虑浅层土体水平变形,或采用其他工程措施抵消水平应力。

The instability of the tower base of transmission line in the special soil-rock complex landform area is easy to occur in extreme rainfall weather.Through the investigation of the diseases that appeared after continuous heavy rainfall on the tower foundation on the loess-red layer dual structure slope in Linxia area,it is found that the stability of the building site composed of loess-red beds slope is mainly affected by the following factors:artificial transformation of geomorphology,special geotechnical engineering properties of loess-red beds-slope,deterioration of rock and soil characteristics by continuous heavy rainfall,the change of the seepage field of the slope,etc.The study shows that the loess-red beds slope in Linxia area is dominated by shallow failure,with creep-slump characteristics.Continuous heavy rainfall results in parallel slope seepage with dual structure and soil bedrock interface seepage.The slope stability coefficient is much less than 1 when considering the influence of soil parameters in saturated state and seepage.Therefore,the heavy rain recurrence period and rainfall holding time should be taken into account in the transmission line project under the condition of increasing extreme climate.The tower foundation should be embedded in a certain depth below the red beds layer,and the horizontal deformation of shallow soil should be considered in the design,or other engineering measures should be adopted to counteract the horizontal stress.