Analysis on evolution process and movement mechanism of the Luojiapo landslide in Heifangtai, Gansu Province

At 7:50 on April 29, 2015, a large-scale landslide occurred in Heifangtai, Yongjing County, Gansu Province, with a landslide volume of 126.88 × 10⁴ m³, destroying 14 houses and three factories, resulting in a direct economic loss of 54.6 million yuan. Based on a large number of geological investigations on the disaster site, combined with comprehensive investigation means such as remote sensing, three-dimensional laser scanning and on-site video monitoring data, this paper evolution and sliding characteristics of Luojiapo landslide in detail, and analyzes the high-speed remote mechanism of the landslide. The results show that Luojiapo landslide has gone through five stages and five sliding forms from the timeline: loess staggered debris flow, loess mudstone debris flow, loess debris flow, loess mudflow and loess staggered sliding. The landslide movement mode can be divided into two types: block debris flow and loess mud flow. The high-speed and long-distance formation mechanism of block debris flow is closely related to the “concave bed filling effect” of the previous landslide and the underlying surface soil with high water content. The research results have positive guiding significance for further deepening the understanding of the formation mechanism and risk control of high-speed and long-distance landslides in the Heifangtai area.