Experimental Study On Phase Number Of Debris Flow

As a natural disaster phenomenon,debris flow poses a great threat to the ecological environment,economic development and people's life safety in the region.Its theoretical research is an important way for people to recognize,predict and manage debris flow disaster.At present,abundant achievements have been made in the theoretical research of debris flow movement model.However,the application of debris flow movement model is greatly limited due to the fact that scholars have not reached a unified understanding of the phase of debris flow.The phase theory of debris flow is the theoretical basis for constructing debris flow movement model,and is also an important basis for studying the definition and classification of debris flow.Therefore,the phase number of debris flow needs to be further studied.This paper takes the original deposits of debris flow as the research object,comprehensively adopts the methods of field investigation,literature review,and indoor experiment to discuss the interaction characteristics between the solid phase and the liquid phase of the debris flow and the material characteristics,and then studies the phase theory of the debris flow,which provides a new reference and guiding significance for the theory of debris flow,and the following conclusions are drawn:(1)The slope rheological experiment shows that,affected by the slurry-forming properties of the debris,the wide-graded debris materials with different particle compositions correspond to different slurry-forming ranges.This range can be used as a reflection of the slurry-forming properties of the debris and the classification of debris flow,and is the density interval of the formation of debris flow.(2)The measurement of excess pore water pressure shows that the low dissipation rate of the high excess pore water pressure in the debris flow body can provide upward supporting force for debris flow particles,which is the key reason for the high speed and long distance migration of debris flow in the low gradient gully bed.Meanwhile,the characteristics of low dissipation rate of excess pore pressure and strong maintenance ability in debris flow make debris flow different from the typical two-phase flow such as sediment-laden flow,flood flow and particle flow.(3)The measurement experiment of excess pore water pressure,the permeability experiment and the particle grading analysis show that the debris flow is well graded and the degree of inter-particle interlocking is good.Additionally,the presence of viscous particles makes the mud films adhere to the surfaces of particles,and the spaces between the particles are filled with fine particles,forming a structure supporting large particles and small spaces that can be easily blocked by fine particles and forming a structural framework capable of supporting large particles and tiny spaces that can be easily blocked by the fine debris,which is conducive to debris trapping the pore fluids and maintaining high pore water pressure.Under the combined action of excess pore water pressure and yield stress,the gravel,the pebbles and even some boulder particles in the debris flow are randomly dispersed in the matrix,and there is no obvious relative movement between them and the surrounding matrix.In short,the transported objects and the transporting medium are one and the same.