水力梯度对滤层细颗粒输移规律影响试验研究OA

In actual engineering projects,dynamic changes in the head difference between the upstream and downstream of embankment reservoirs(including amplitude changes and reciprocating fluctuations)exacerbate the risk of filter layer soil permeability instability.The particle transport mechanism requires further in-depth study.Using a self-developed large-scale permeameter,non-cohesive yellow sand was used as the base material and river pebbles as the filter material.Under the premise of keeping the composition of the filter and base materials unchanged,the effects of different pressure amplitudes and varying pressurization methods on the transport behavior of fine particles in the filter layer were investigated.The results indicate that as the amplitude of the head difference increases,seepage failure occurs in advance,and the anti-seepage capacity of the protected soil decreases.The critical hydraulic gradient and failure hydraulic gradient decrease,with their boundary becoming blurred,leading to a weakened anti-seepage capacity of the system.The larger the head difference,the lower the hydraulic gradient required for particle initiation and transport,making seepage failure more likely to occur.As the amplitude of the cyclic head difference increases,the system stability decreases,and particles are more likely to initiate and transport outside the filter layer.Even if no failure occurs under a steady head,a larger cyclic head amplitude may still induce instability and accelerate particle transport.The larger the amplitude,the shorter the seepage failure process,the more sudden the failure,and the greater the difficulty in prevention.Sudden rises or drops,or significant fluctuations in water level hinder the dissipation of water pressure,leading to the accumulation of excess pore water pressure,which weakens the effective stress of the soil and reduces system stability.Under the same head difference amplitude,cyclic head effects further weaken the anti-seepage capacity of the base-filter system,with the impact intensifying as the amplitude increases,thereby raising the risk of system instability.