Abstract:To obtain a thorough understanding of the controlling effect for debris flow mitigation by herringbone water-sediment separation structure (HWSSS), systematic experimental researches was conducted. First, based on the characteristic of HWSSS, theoretical analyses on the substance and energy regulation functions and related evaluating parameters were proposed. The results show that the HWSSS exerts different sieving functions to different grain size classes of the sediments. The coarse sediment (diameter larger than grid opening width D) separation ratio was within the range of 0.8~1.0. The fine sediment (diameter smaller than grid opening width) separation ratio can be well expressed by a power function with the relative grid opening width (D/d_fm). The empirical formulas for calculating the total sediment separation rate by single structure (P_t) and multiple structure system (P_t(k)) were both developed. Generally, the separated sediments by HWSSS had a good sorting property, providing a possibility for the construction reuse. The density and velocity of discharged fluent, with smaller average diameter of solid particle and less sediment volume, were decreased. The theoretical calculation formula for the debris flow density after HWSSS regulating was also developed and verified by test data. All results are of great use in optimal design for HWSSS and developing series HWSSS system for debris flow mitigation.