OCCURRENCE AND HAZARD ASSESSMENT ON LOESS LANDSLIDE OF GAOLANSHAN IN LANZHOU
Yin Yueping ① Zhang Zuochen ① Li Zhiheng ② Zhang Shuqiao ② Yu Jiandu ②(① China Geological Survey,Beijing 100035; ② Gansu Bureau of Geology Exploration,Lanzhou 730000)
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.