Abstract：Velocity in debris flow is one of the most important parameters for dynamic analysis and design of debris flow control works. In order to investigate the velocity profile along flow depth for particle phase and liquid phase in debris flows, the mixture of two organic liquids (Acrylic acid Polymers and ethyl acetate) was used to monitor the high viscosity of debris flow. The glass beads with uniform particle size were used as solid phase in debris flows. Both particle and liquid velocity components were investigated by PIV (Particle Image Velocimetry) measurement system under the condition of sediment flows and debris flows, respectively. The Takahashi model for the particle velocity distribution in debris flows was employed to calibrate the experimental results obtained by former researchers and measured by PIV measurement system in the experiments. The results indicated that the mixture liquid with higher viscosity produced a more uniform distribution of the particles along the flow depth. The experimental data measured by PIV system were in good agreement with the ones calculated by Takahashi model in debris flows (u/us>0.3). However, the data did not match the formers’ ones in sediment flows. It indicated that the shape of particle velocity profile along flow depth was mainly determined by the fluid viscosity and the uniformity of particles distributed in the flows.
