兰州皋兰山黄土滑坡特征及灾度评估研究

皋兰山滑坡是西北地区非常典型的黄土滑坡,由3个次级滑坡构成,形成条件可概括为:新构造作用促使皋兰山强烈隆起,形成高达200～300m以上陡峻的自然斜坡,平均坡度在33.7°,临空条件好;构成斜坡的基岩为泥岩,其上覆盖很厚的黄土层,泥岩表面风化、破碎严重,不透水,黄土垂直节理发育,有利于地表水的渗入,在黄土与泥岩的接触面构成抗剪强度低值带;在地下水对下部软弱层侵润作用下,其抗剪强度大大降低;地震是促使滑坡产生的突发因素;同时,由于斜坡前缘建房开挖边坡及公园建设加载和绿化灌溉等,导致坡体稳定性明显降低,出现失稳破坏。通过野外勘查和位移监测及稳定性计算表明:目前滑坡总体上处于稳定状态,局部滑坡体复活变形迹象渐趋明显,其中变形最严重的是位于斜坡中下部并紧邻市区的Ⅰ3滑坡、Ⅰ4滑坡和Ⅲ滑坡。文章还对滑坡潜在损失进行了初步评估,并提出了防治方案和建议。

OCCURRENCE AND HAZARD ASSESSMENT ON LOESS LANDSLIDE OF GAOLANSHAN IN LANZHOU

The Gaolanshan Landslide is located on the northern slope of the Mt. Gaolan adjacent to downtown of Lanzhou City and of railway hub. It is a largest one of the landslides in the region, with the volume of 20.56×10 ⁶ m ³ and multiple activities. Since the human activities, such as slope-cutting and plant irrigation, are recently intensifying, the landslide becomes active and damages houses and road nearby. The Mt. Gaolan is quite steep, 600m high and with 33.7° slope in average. The landslide body is in the high place and there is a wide space in front that threatens severely the city. This is a typical loess landslide, consisted of three sub-landslides. Under the circumstances of steep Mt. Gaolan controlled by neo-tectonic uplift, the slope was covered by huge thick loess. The main causes are as follows. The vertical fractures are commonly distributed that provides an easy way to water seepage. The seismic activity is strong and frequent, the earthquake intensity is greater than Ⅷ degree in the mountain area. The unreasonable human activity, such as slope-cutting, overload, water-ponds, plant irrigation in slope is becoming a key factor to induce a sliding. The monitor presents the deep movement along sliding surface and the stability of complete body is decreasing, especially Ⅰ ³,Ⅰ ⁴ and Ⅲ sub-landslide. On the base of the hazard assessment of landslide, a comprehensive stabilized program is suggested.