Internal erosion of chemically reinforced granular materials: A granulometric approach

SummaryInternal erosion (IE) of chemically reinforced granular materials results in dislodgement of particles from their rigid skeleton due to seepage stresses. Whether or not these particles can be dislodged and flushed out by seepage depends on (i) the amount of binding agent used to reinforce the granular matrix, (ii) the structure of pore network and (iii) severity of seepage stresses. Results of IE tests are presented for compacted-sand reinforced with increasing amounts of silica gel. The silica gel is a binding agent that permits low-permeability materials reinforcement. IE tests provided information about eroded particles, macro/micro-structural changes and indicators of ongoing IE mechanisms. For instance, data highlighted the existence of up to three IE stages. This includes flushing of movable particles, binder removal and subsequent releases then self-filtering of fine particles within the rigid skeleton. From the careful monitorings of effluent particles (in terms of concentrations and sizes), it was possible to gauge the dynamics of binder removal. Besides, it was also possible to follow changes in dimensions of the smallest constriction that drives travel distances of dislodged particles.

► Internal erosion in reinforced compacted sand columns exhibited three stages.
► Binder then fines removal increased the instability of the matrix of coarse grains.
► The instability could be traced by the sudden releases of fines into the effluent.
► Mass losses were the sum of dynamic releases and filtering of eroded fines.
► The granulometry of eroded particles depicted the dimensions of constrictions.