The aim of this thesis is the geological and geotechnical investigation of the Huangtupo landslide in China. The area of research is located in the Hubei province in the county of Badong, which is situated about 100 km upstream of the Three-Gorges-Dam at the Yangtse River. The emphasis is on clay mineralogy and its influence on the slope stability. The samples were taken from the fault zone of the Huangtupo slope, and were analysed via the X-Ray diffraction test. The safety factor of slopes can be calculated by the ratio between the resisting and driving forces. Usually the resisting force is strongly influenced by the clay minerals.strongly influence on the weathering and erosion. During several very difficult tests, the results depicted that especially the clay minerals are primarily responsible for the mechanical properties of rocks, because of their specific characteristics such as swelling capacity, absorption of water and plasticity. However, the results of the X-Ray diffraction test showed that the samples contained more than 90% Illit, a three layer swelling clay mineral, which has negative impact of the slope stability. The mechanical parameters obtained by laboratory tests. The of stability analysis and the technical documentation of the parameters are discussed in thesis of Christine Schönberger.