Abstract: The sandy grainmucky soil is a special structured lacustrine deposited soil with fine sand lenses from Dongting Lake. The dynamic strength envelope of Dongting sandy grainmucky soi samples was experimental studied by using DDS70 dynamic triaxial testing device. The effect of confining pressure and applied cyclic axial frequency on the dynamic strength was evaluated. Throughout the investigation, the following conclusions are obtained: 1) The dynamic cohesion and dynamic internal friction angle values decrease the number of cyclic stress; 2) The sample strength decreases rapidly at the small number of cyclic stress and after the cyclic stress number reaches a certain value, dynamic strength decrease slowly with the increase of number of cycles; 3) under the same cyclic number, the higher the frequency and the confining pressure, the higher the dynamic cohesion and the dynamic internal friction angle.

Key words: sandy grainmucky soil, dynamic triaxial shear tests, confining pressure, frequency, dynamic strength