The Experimental Study Of Preferential Flow Induced By The Bioturbation On The Tidal Flat Of Yellow River Estuary

There are lots of zoobenthos on the tidal flat sediments of Yellow River Estuary, because of the distribution of biological species and quantity are great different, so there are differences in the nature of the tidal flat sediment. Nowadays,the properties of sediments changed by bioturbation have been concerned by International Geosphere and Biosphere Plan (IGBP), especially the problems about the bioturbation and hydrodynamic coupling led to the tidal flat sediment flow differences. When the water inflows the soil that is disturbed by the caves, small pores have no time to absorb all water and the part of the water infiltrates rapidly along the biological caves that have strong permeability, then the preferential flow is produced. The preferential flow accelerates the migration of pollutants in the sediment and influences the marine environment; increases the drainage capacity and permeability of tidal flat sediments, and affects the pore water pressure dissipated, stress and strain analysis, liquefaction of the sea-bed stability, so studying the preferential flow by the biological caves is trigger meaningful.In this paper, on the basis of large amounts of field tests and indoor simulation tests, with early study results, to study the preferential flow induced by the biological caves on the tidal flat of the Yellow River Estuary. The research contents include following aspects:(1) Field and laboratory simulation seepage test of tidal flat sediments induced by the biological caves, through high-density resistance method and the method of tracer, setting different infiltration method and different infiltration solution that has different conductivities, to monitor the apparent resistance changes of the sediment induced by the biological caves, investigate the seepage of the tracer, and study the effects caused by the seepage. In addition, it proves that the method for measuring the seepage is feasible.(2) Indoor seepage test of the tidal flat sediments under simulation of wave, setting the two soil samples, one has biological caves, and the other has no biological caves. Monitor their response to simulated wave action and the pore water pressure changes with time; discuss the seepage of the two soil samples, and analysis different physical properties and mechanical targets impacted by different seepage.This paper comes to the following conclusions:(1) The tracer and high-density resistance method for detecting the preferential flow is practicable.(2) Field tests show that: biological caves increase its porosity and the drainage channels, tracer infiltrates rapidly through biological caves, cause preferential flow phenomenon at the districts that have biological caves.(3) Laboratory simulation seepage test of tidal flat sediments induced by the biological caves show that: The biological caves become the pathways of the preferential flow and they increase the infiltration coefficient of the sediment, seepage in the small pores is weak. When we anti-wash leach the soil with relatively high resistance solution, there are high resistance zones around the biological caves; we find that the preferential flow greatly affects the tracer migration in the soil. Biological caves have become the pathways of the fine-grained soil migration in the soil, and the burrows have the dual effects of increasing water content and decreasing water for the surrounding matrix. It also changes the basic properties of the soil around the biological caves, such as density, water content, grain size, strength, and electrical conductivity, etc.(4) Indoor seepage test of the tidal flat sediments under simulation of wave shows that: There are high-value areas of the pore water pressure in the two soil samples, but there is preferential flow in the soil sample which has biological caves, change the response to wave action, and reduce the commutation of pore water pressure. The fine particles in the lower part of the caves increase opportunities to be brought to surface by the preferential flow and the content of fine particles are relatively larger of the surface soil; cave improved upward drainage capacity, making the moisture of the surface soil and strength of the bottom soil increase.