High cutting slopes with nearly horizontal soft-hard alternant strata are widely distributed in three gorges reservoir area, the soft and hard rocks are mainly mud stone and sandstone of Jurassic system. Sliding failure of this kind of slope is also the main geo-hazards in this area. Firstly, this paper analyzed the impact of topography, water as well as the differential weathering and combination characteristics of soft and hard rocks etc. on the sliding failure of slopes; secondly, sliding failure modes of this kind of slope were classified into four types including circular sliding, sliding along the extroversion structural surface, sliding along the mudded intercalation and wedge sliding, they were analyzed combined with case study. And lastly, support methods against the certain failure mode were put forward. The research results are significant to the support and treatment of high cutting slopes in Three gorges area.

Jinoping No.1 is a dominant reservoir cascade hydropower station which locates at the downstream of Yalong river. The underground powerhouse locates at the right bank of the dam, lithology is marble that belongs to the second member of Zagunao group. It is constructed at region with very complicated geological conditions and high geo-stress. Concrete cracking, spalling and steel buckling and bending occurred at the downstream crown after supporting. This paper analysed the causes of deformation and failure through geological analysis and numerical simulation, and concluded that deformation and failure mainly occurred at the region where the quality of surrounding rock belongs to Ⅲ1 and had nothing to do with the unstable block cut by cracks; stress field of surrounding rock varied continueously with the proceeding of successive excavation of underground powerhouse, so the compressive stress and shear stress concentration occurred which caused the compression and shear failure of downstream crown and made it bending to the free face. It is significant to the further enforcement of this project and to the research on other similar underground caverns theoretically and practically.

The indexes to determine the swelling potential of swelling rocks are still not unified. A series of testing results of swelling rocks of Zhangjiakou showed that: the dry saturated water absorption and the specific area of swelling rock are all correlated linearly with the content of smectite and the correlation coefficient can be reached to 87% and 96% respectively; however, content of the montmorillonite and free expansive ratio is in nonlinear correlation, which indicated that the free expansive ratio, the dry saturated water absorption and specific area can all reflect the characters of mineral components in swelling rocks. However, the liquid limit and the plasticity index were all in linear correlation with the montmorillonite content, but value of them were lower than practical ones, so they can not be suitable indexes to determine the expansibility of swelling rocks. The larger the free swelling ratio was, the larger the expensive ratio under no load was, but they have no good correlations which indicated that the properties of swelling rocks was complex, as a result it is defective tightness to determine the swelling potential only by mineral components. The swelling force and the expansive ratio under no load were also in linear correlation, which meant they can all characterize the swelling characters of swelling rocks. The lager the dry saturated water absorption was, the poorer the durability was, but the dry saturated water absorption can not reflect the disintegrative totally. Through comprehensive analysis, we took the dry saturated water absorption, coefficient of disintegrative and swelling force as the indexes to determine the swelling potential of swelling rocks.