Transition from acceleration waves to strong discontinuities in fluid-saturated solids: Drained versus undrained behaviour

摘要

The evolution of compression waves propagating in a fluid-saturated granular solid is considered. The pore fluid is assumed to consist of a liquid with a small amount of free gas. The stiffness of such a solid increases with increasing pressure. This property leads to the transformation of continuous compression waves into shock fronts after a finite time of propagation. The aim of the study is to calculate the critical distance covered by a continuous wave before it loses continuity. Critical distances are calculated for weak discontinuities (acceleration waves) propagating into a quiescent region. In numerical examples, the pressure dependence of the stiffness is taken in a form typical of granular solids. Emphasis is placed on the influence of free gas in the pore fluid and the permeability of the skeleton. Comparison of locally undrained and drained behaviour reveals that the drained model with low permeability turns out to be misleading for the calculation of the critical distance of a compression wave.