Study On The Grouts Diffusion Mechanism Of Shield Tunnel Back-filled Grouts Based On Filtration

As a key process of shield method, the research indiffusion mechanism of back-filled grouting contributes to controlling grouting parameters reasonably when shield tunnel is constructing. Moreover, it would help constructor to raise efficient of grouting, decrease stratum settlement sufficiently, make sure better impermeable ability after construction, and so on. However, most previous studiesussually simplified soil and grouts into homogeneoussingle-phase media and the interaction between soil pore and solid-liquid in grouts is ignored. As a consequence, the results of studies by this way were inaccurate. Combining with the features of shield method, this papermainly focused on diffusion process of grouts at penetration stage and compaction stage, and the diffusion mechanism of back-filled grouting is researched through theoreticalmethod and simulative method.Hemisphere model and cylindricality model were built, considering the filtration effect of backfilled grouting in shied tunnel construction.Through these two moldes, the expressions of soil porosity, volume fraction of grouts solid particle anddistribution of grouting pressure were deduced.On the basis of volume fraction of grouts solid particle, the conception of effective diffusion radius of grouts was put forward, so that the effection of grouting could be evaluated in theoretical way to some extent.Eventually, grouting effection was analyzed through engineering cases. The results show that these two models of penetration diffusion adapt to the calculation of back-filled grouting in sand.Hemisphere compaction model and cylindricality compaction model were built, considering the filterpressing effect of backfilled grouting in shied tunnel construction.The expression of pressure distruction on segments caused by grouting was modified. Combining the expression of pressure distruction and engineering cases, the grouting parameters were analyzed.Hemisphere numerical model was built by finite element software named COMSOL Multiphysics, considering the filtration effect of backfilled grouting in shied tunnel construction. And the soil porosity, grouts dynamic viscosity, effective diffusion radius of grouts and time history and 2-dimension distribution of grouting pressure. The results show that the conclusions gained from numerical models and theoretical models were uniform.Finally, the existing problems and the further direction of this reseach were discussed briefly.