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Abstract The piping channel expansion in double-layer dike foundation is determined by the characteristics of particles in sand layer，water flow in the channel and the seepage force in the surface of the channel. By analyzing the mechanical balance of the particles in the surface of the channel and introducing some formulae of river dynamics as well as considering the relative exposure degree of the particles，fluctuating velocity，criteria of the particles? incipient motion and flow characteristics，the critical condition of piping channel expansion is proposed. Two sand box model experiments were done to study the combination impacts of the flow and seepage force on channel expansion. And the one-dimensional seepage experiment has proved that the hydraulic gradient near the overflow surface is much less than average gradient. It shows the rationality of the effective ratio between the actual and calculated seepage forces. Based on the experiments，a finite element method which is controlled by the critical condition of the stability of channel?s surface is built. It was used to simulate the expansion of piping channel. By comparing the calculated results and the experimental results，it is shown the proposed methods are reasonable.
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Received: 20 May 2013
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2013, Vol. 32 
