Causes and Stability Evaluation of a Large Landslide in Nanjing

Abstract

Through the geological survey in the field, the development characteristics of landslide landslides are systematically analyzed. Through the simulation of the influence of different factors on the stability, it is determined that the main reason for the sliding of the landslide is the heavy rainfall and the slope cutting, which reveals the geological origin and mechanical origin of the landslide body. The limit equilibrium theory is used to analyze the stability and residual sliding force of different potential sliding surfaces. For the three-row anchored anti-slide pile + profile prestressed frame anchor cable + drainage system emergency reinforcement measures adopted by the owner, the stability factor of the landslide body is demonstrated after emergency reinforcement. The research shows that although the corresponding reinforcement measures are taken, the landslide body still does not meet the safety requirements, and further deep reinforcement measures must be taken for treatment. The research results provide a theoretical basis for the reinforcement design of the landslide body. Introduction Landslide hazard is one of the most widespread geological hazards in steep slope area The number of landslides accounts for more than 70% of the total disasters, and the casualties caused by large landslides account for about 70% of the total casualties [1]. Landslide prevention and control engineering research has also become one of the hot spots in engineering research [2]. Since 1982, more than 70 landslides, avalanches and mudslides have occurred on both sides of the reservoir area. [3]. In June 2015, due to heavy rainfall, a large-scale landslide occurred on the south side of a mountain in Nanjing, which brought great security risks to the ecological security of the scenic spot and the Alila Hotel under construction, therefore it is necessary to conduct engineering geological research on the affected areas. Engineering Geological Conditions of Landslides Meteorology and Hydrology The rainfall in Nanjing is abundant. The annual precipitation is 1200mm, the annual average precipitation is 1106mm, and the season with the most precipitation is July, with 494.5mm; the season with the least precipitation is February, with only 7.7mm. The precipitation in June measured by the Nanjing National Climate Observatory in 2016 has reached 625.5mm, which not only far exceeds the June historical record, but also broke the historical record of July 1931. Topography The landslide body is located in the south branch of the western section of the hills of Ningzhen. It belongs to the Yangqiugang landform of Ningzhen, the low hilly and landform unit, and the terrain is undulating. The trend of the mountain is generally northwest-south-east, and the mountain vegetation is flourishing. The elevation of the east and west peaks is 247.5m and 201.6m. There is an east-west ridge on the top of the mountain, which is slightly saddle-shaped. 177 Physical and Mechanical Indicators of Each Rock Layer According to the indoor test, the shear strength indexes of each rock and soil body of the landslide body are shown in Table 1. Table 1. Shear strength index of soil (standard value). Name Consolidated quick shear Saturated shear Slow shear Residual shear