Engineering Properties And Forming Mechanism Of Emeishan Basalt Saporote

Emeishan basalt saprolite is also called the weathering Emeishan Basalt,it exists extensively in Southwest regions. Emeishan basalt saprolite is a special type of rock that lies between rocks and soil, it retained the original rocks, structure and structural feature, but the internal structure had already been cavity as a result of leaching solubilizes, Its strength is far less than the original rock, but stronger than the soil due to the residual strength. The particularity of saprolite indicated certain potential hazard to our infrastructure and geology condition, it has aroused wide attention from scholars, much research has been done on the engineering characteristics and microscopic mechanism of the saprolite. This paper studied on the Emeishan basalt saprolite in Xiao Li Mountain, Chenggong County, Kunming city. The physical, mechanical and hydrogical properties are tested by a series of soil test, the formation mechanism is analyzed by SEM、XRD and chemical analysis methods. The main results are as follows:1、Emeishan basalt saprolite retains the structure of parent rock,but it is the clay that is of tiny particles、low dry density、high porosity、semipermeability、high hygroscopicity。2、Relativing to dry density、void ratio、grain composition, compressibility of researchful Emeishan basalt saporote is at at a moderate to inferior level,that is relationship with its remaining frame. Compressibility is that:red soil> amygdaloidal basalt saporote> tight basalt saporote.3、Through stress-strain curve of Emeishan basalt saporote by the direct shear test,their failure pattern is brittle failure,there is a obvious peak,and then the curve start to be stabilazation.In the triaxial test, The failure pattern are brittle failure and plasticac failure.The dispersion degree of the Emeishan basalt saporote’s shear strength parameters is high by shear test, it’s because of its joint planes.4、In weathering process of Emeishan basalt, the change of chemical element is Si、Na and Ca enrichment and Fe and Al losing, the content of Fe2O3and ignition loss obviously increase. The all WPI are negative, strong weathering of Emeishan basalt is showed by the chemical index:SA、Kr、base/Al、CIW and CIA similarly. 5^Comparing the mineral composition of fresh basalt with its saporote’s,it’s show that the kaolinite and sericite forms from the feldspar dissolution.Trough observing SEM of fresh Emeishan basalt and its saporote,The profile of fresh Emeishan basalt is compact without gash nearly and The arrangement of plank form mineral is regular, but the Emeishan basalt saporote of the research area is of honeycomb structure、the mineral composition adhering to the surface、lots of physical crack and the ripe aggregates.