Spatial distribution characteristics and influence factor analysis of landslides —case study of the Hanwang area in Qinba Mountains

Abstract

The geological hazards of landslides in Hanwang Town, Ziyang County, Ankang City, Shaanxi Province, have emerged, yet the current understanding of the spatial distribution characteristics and influencing factors of landslides in this area remains unclear. Combining the results of remote sensing interpretation and field investigation, seven influencing factors, namely, elevation, slope direction, slope gradient, distance from rivers, distance from faults, engineering geologic lithology, and distance from roads, are selected for the study, and the distribution characteristics of landslides in each influencing factor and the influence of the resolution of Digital Elevation Model (DEM) on the results are statistically and analytically analysed. Furthermore, two high-risk landslides within the study area were subjected to comprehensive analysis, integrating the findings from drilling and other field investigations, in order to examine their deformation mechanisms. Based on this analysis, the following conclusions were derived: (1) There are 34 landslides in the study area, mainly small earth landslides, with a distribution density of 0.42/km2, threatening 414 people and property of about 55.87 million yuan. (2)The landslides in the study area are easy to occur in the <400 m elevation range, the landslides are developed in all slope directions, the gradient is mainly concentrated in the range of 10°–40°, the distribution density of the landslides is higher in the closer distance from the river and the faults (0–200 m), the landslide prone strata are mainly the softer and weaker metamorphic rocks, and the landslides are mainly around roads. (3) The resolution of the DEM should be selected based on the specific conditions of the study area, the requirements of the investigation, and the scale of the landslide. Opting for an appropriate DEM resolution is advantageous for understanding the patterns of landslides and conducting risk assessments in the region. (4) The Zhengjiabian landslide is a traction Landslide. The landslide body is a binary structure of gravel soil and slate weathering layer, and the damage process can be divided into three stages:①damage to the leading edge and stress release; ②continuous creep and cracking; ③rainfall infiltration and damage. The predominant slope material in the Brickyard landslide comprises clay, and the landslide is triggered by a combination of the traction effect resulting from excavation at the slope's base and the nudging effect caused by the stacking load of the brick factory. Additionally, the Brickyard landslide exhibits persistent creep deformation. The results of the study provide a certain scientific basis for disaster prevention and mitigation in the Hanwang Township area.