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Abstract Piping is a multiphase and multifield coupling phenomenon involving numerous complicated mechanical behaviors，such as pore water seepage，fine particle erosion and migration，and deformation of porous media. A new seepage-erosion-stress coupling piping test apparatus is developed to simulate the evolution of piping and study the mechanism. The new apparatus consists of a special funnel-shaped drainage system，a confining pressure system，an axial pressure system，a seepage pressure system and a data acquisition system. The funnel-shaped drainage system is specially designed to collect the eroded fine particles and water. The confining and axial pressure systems are used to simulate the triaxial stress state of specimen. The largest confining pressure is up to 2.0 MPa，and the largest axial load is about 30 kN(the diameter of specimen is 101 mm). The seepage pressure system provides the migration power of fine particles，which can realize a fast switch from high hydraulic head(200 m) to low hydraulic head(＜2 m). The data acquisition system can monitor the variations of pore pressure and settlement. The three experiments under different stress states indicate that the stress state has a great influence on the evolution of piping. The critical piping hydraulic gradient under isotropic compression is far higher than that under no confining pressure，and is slightly higher than that under triaxial compression. The new apparatus can simulate the evolution of piping，and monitor the evolution of meso-structure，geometric，hydraulic and mechanical characteristics，which will provide a credible tool for studying piping mechanism.
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Received: 28 May 2013
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2013, Vol. 32 
