Analytical solutions are presented for the consolidation of a semi-infinite stratum and a finite soil layer with an impeding layer located on the surface subjected to a vertical point loading. The Laplace transform and the Hankel transform are used with respect to time and the radial coordinate, respectively. Solutions of other distributed loadings, including the circular loading, can be easily obtained by integrating those of the point loading. The consolidation degree, excess pore water pressure, vertical total stress, and the shear stress of the consolidating layer are analyzed in this study. The consolidation rate decreases with the increase in the thickness of the impeding layer. Stresses of the consolidating layer vary during the consolidation due to the coupling of the excess pore water dissipation and the soil skeleton deformation. Further, the Mandel-Cryer effect is also analyzed in this study.
Silica nano-particles are suspended in the colloidal silica and can be induced to gradually gel after the PH value changes. Thus colloidal silica can be utilized to rapidly seep through loose calcareous sand, and the silicon gel is gradually formed to bond sand particles. However, based on observation by scanning electron microscope(SEM), there are a lot of microcracks in the silica gel, which reduces the strength of the sand-gel composite. Therefore, in order to suppress crack growth, wood fibers are dispersed in the colloidal silica which still can seep through calcareous sand. 18 silicon-gel stabilized sand samples were prepared for tri-axial tests, where the concentration of colloidal silica is 20%, and wood fiber concentrations are 0%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, respectively. The results show that:(1) there exists an optimum ratio of wood fiber to colloidal silica, that is, as the concentration of wood fiber increases, the strength represented by the peak value of deviator stress rises first and then falls; (2) there are opposite trends between the two strength parameters, internal friction angle and cohesion, that is, when the wood fiber concentration is 0.04%, the cohesion reaches the maximum value and the internal friction angle reaches the minimum value; (3) The photos by SEM show that, there are wood fibers on the inner wall of the crack in the silica gel, which may reduce the extent of crack propagation and contribute to the strength of stabilized sand samples.
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