Abstract: For the multiformity, complexity of the slide zone clay and unequal of the shear strength parameters in the Three Gorges Reservoir area, the main factors affecting the shear strength parameters including geological representation, specimen size, test number, stress level are reseached, especially for the unequally shattered clay and silty clay, those factors may bring out much more influence. The characters of the slide zone are changed with the different places. The two groups test between the different places and the same characters of the slide zone show that the shear area should be no less than 2 500 cm2, otherwise the shear strength parameters (c, ?) are much unequal. The three groups tests in the same place, 5 or 6 points a group, show that the shear strength parameters (c, ?) have 0.5-1.0 time difference, and show that the test number in a group should be no less than 5 points; the contrast test under the different moisture content shows that the moisture content is more, and the parameters (c, ?) is littler. For the unequal characters of the shattered clay and silty clay, the granules diameters and content of the crushed stone also affect the shear strength. So, tester must sechedule reasonable test scheme according to code, project character, and environment of the slide zone, analyze the parameters according to macroscopical characters of slide zone and actual conditon of test point, then put forward proposition parameters.

Key words: Three Gorges Reservoir area, slide zone clay, parameters of shear strength, influencing factors