(1. Key Laboratory of Mechanics on Disaster and Environment in Western China，Ministry of Education，Lanzhou University，Lanzhou，Gansu 730000，China；2. School of Civil Engineering and Mechanics，Lanzhou University，Lanzhou，Gansu 730000，China；3. Geological Hazards Institute，Gansu Academy of Sciences，Lanzhou，Gansu 730000，China)
Abstract：Mudstone is a kind of soft rocks containing abundant clay minerals. The physical and mechanical properties change drastically when mudstone encounters water. Studies on the green and red mudstones from Tianshui，Gansu province were carried out. The experiment results show that the green mudstone contains more clay，while the red one has more primary minerals. The main clay mineral in both types of mudstones is illite，and there are less kaolinite and little montmorillonite. When the two kinds of mudstones interact with water，a lot of Na+，K+， but little Ca2+ are dissolved out. As a result，the thickness of the bound water membrane increases，the attraction between the electrically charged molecules decreases，the adhesion force diminishes and the minerals are much easier to be eroded. The results also indicate that under the condition of high water content，shear strength parameters of both mudstones change with the variation of water content and dry density，but the shear strength of green mudstone is better than the red. When the water content increases to 25%，the shear strength of red mudstone declines dramatically. And when the water content is over 30%，both type of mudstones almost lose the shear strength.
2016, Vol. 35 
