季节性冻融作用及其对斜坡土体强度的影响——以甘肃永靖黑方台地区为例

Seasonal freeze-thaw action and its effect on the slope soil strength in Heifangtai area, Gansu Province

季节性冻土地区黄土斜坡冬春交际常发生崩塌、滑坡等地质灾害,造成了严重的生命财产损失。位于甘肃省永靖县的黄土台塬——黑方台为典型的季节性冻土地区,其3月份黄土滑坡灾害高发。通过对滑坡体的野外调查、原位监测,分析了该地区的冻融作用特征及其对斜坡土体强度的影响,证实了该地区表层土体存在显著的冻融循环作用,总结了斜坡体受冻融作用影响的宏观表现和受气温影响的斜坡表层黄土地温变化过程。在此基础上设计开展了黄土室内力学性质试验,分析了不同初始含水率对冻结黄土三轴抗剪强度参数的影响,对比分析了黄土与冻结黄土的三轴抗剪强度参数变化。由天然和饱和2种状态下的黄土经历15次冻融循环后的直剪实验得出冻融循环作用对黄土强度影响较大的结论。该结果可为冻融期黄土斜坡稳定性分析提供参考。

Geological hazards of landslides and collapses often occur in loess slopes of seasonal frozen soil areas when winter alternates with spring, which causes serious loss of life and property. Heifangtai loess tableland of Yongjing County in Gansu Province is a typical seasonal frozen soil area, where the loess landslides hazards occur very frequently in March. The characteristics of the freeze-thaw action and its effect on slope soil strength were analyzed through field investigation and in-situ measurement. The authors confirmed the very obvious existence of freeze-thaw cycle action in Heifangtai area, summed up the macroeconomic performance of slopes affected by the freeze-thaw action, and analyzed the variation process of ground temperature in slope surface loess affected by air temperature. On such a basis, laboratory tests of loess mechanical properties were designed. The triaxial shear strength parameters of frozen loess in different initial moistures were analyzed in comparison with things of loess. Through the direct shear tests of natural loess and saturated loess which both experienced 15 freeze-thaw cycles, the authors have reached the conclusion that the freeze-thaw action had a great effect on loess strength. The results will provide references for stability analysis of loess slope induced by the freeze-thaw action.