Landslide Susceptibility Assessment And Evaluation Of Weathering Intensity Of Basalt In Western Guizhou

Basalt is widely distributed in southwest China, which is characterized by big thickness and strongly weathered. The weathered basalt has a loose structure and it is water-sensitive. These special physical and mechanical properties often lead to landslides, causing threat to people’s lives and property, as well as to transportation, industrial and agricultural facilities. Therefore, study on the typical characteristics of landslides in basalt region, as well as scientific evaluation and prediction of landslide susceptibility can provide the basis for landslide monitoring and forecasting, which has important practical significance.The work presented in this paper aimed to assess landslide susceptibility and evaluate weathering intensity of basalt rock mass, in western Guizhou. The specific contents are as follows:(1) Databases of the landslide-conditioning factors and landslide inventory were built, acoording to the avaliable data. A total of eleven landslide-conditioning factors including elevation, slope gradient, slope aspect, slope position, rock formations, faults, average annual rainfall, normalized difference vegetation index (NDVI), land cover types, rivers and roads were considered. The spatial distribution of landslides in different settings was observed.(2) GIS-based binary logistic regression model was applied to find the best-fitting predictive model that describes the relationship between landslides and a set of conditioning factors. Rock formations, average annual rainfall, elevation, land cover types, slope position, NDVI, slope aspect and slope gradient was selected as the major landslide-conditioning factors.(3) Spatial prediction of landslide probability for the study area was calculated based on the grid-based logistic regression model. A landslide susceptibility map was produced by clustering the probabilities. The study area was divided into five zones showing different landslide susceptibility levels. The high and very high susceptive zones cover an area of7873.72km2, accounting for27.58%of the total area, while83.23%of historical landslide are located within the region. Satisfactory agreement was obtained between the susceptibility map and the existing data on landslide locations It revealed that the assessment is accurate, and the binary logistic regression model is applicable to assess slope stability in the region.(4) A road hazard map was produced by overlaying the road map with the landslide susceptibility map. Such map provides useful information for road management and landslide prevention and mitigation work.(5) Mineralogical and chemical analysis was made on samples from different weathered layers of basalt along the Bijie to Weining Expressway to discuss the influences of weathering on the mineral and chemical compositions. In terms of the mineral characteristics, it is found that feldspar content decreased with increasing weathering intensity.Therefore, secondary alteration of feldspar can be taken as a sign of the weathering intensity. In terms of the chemical characteristics, it is found that the WPI chemical weathering indices showed obvious monotonicity sensitivity on weathering intensity, and it can be used for classification of weathering intensity.(6) Indices for evaluating the weathering intensity of basalt were selected based on standards for engineering classification of rock masses and relevant researches. The extenics model was applied to conduct quantitative classification of the weathering intensity of basalt.Landslides in basalt are important landslide types in the study area. Therefore, it is of theoretical and practical significance for landslide hazard assessment and evaluation of weathering intensity of basalt rocks masses. Besides, the research findings can provide a reference for other similar regions.