Large strain consolidation of dredged slurries considering clogging effect with coupled vertical–radial flow

Abstract

Dredged slurries improved by vacuum preloading methods were found to be still weak generally after the pore water drainage finished. Three reasons, including nonuniform consolidation, soil particles migration and blockage of the drain filter, have been proposed to explain the failure. Thus, finding out the principle factor is essential for modifying the vacuum improvement method effectively. In this paper, a large strain consolidation model with coupled vertical–radial flow is built to investigate the effects of the three factors. Blockage at the drain and clogging in the soil is found to be the main factors. Besides, the clogging in the soil shows a significant influence on the distribution of pore water pressure along the radius. Then, the consolidation behaviors and variations of water drainage direction are also analyzed under different upper boundary conditions compared to the results from a laboratory test. On that base, the hard shell boundary is found to be better in simulating the upper boundary conditions in the membrane system.

Appendix I

To simplify the equations, reduced coordinates system is used in the solution as the volume of soil particles is constant in the consolidation. Then, the governing equations are transferred to

$$\left( {1 + e} \right)\frac{\partial }{\partial r}\left[ {A\frac{\partial e}{{\partial r}}} \right] + B\frac{\partial e}{{\partial r}} + \frac{\partial }{\partial z}\left( {C\frac{\partial e}{{\partial z}}} \right) + D\frac{\partial e}{{\partial z}} = \frac{\partial e}{{\partial t}}$$

(A.1)

where

$$\begin{gathered} 0 \le r \le r_{{\text{w}}} : \, A = - \frac{{k_{{\text{w}}} }}{{\gamma_{{\text{w}}} }}\frac{{{\text{d}}\sigma^{\prime}}}{{{\text{d}}e}},B = \frac{{\left( {1 + e} \right)}}{r}A,C = \frac{{k_{{\text{w}}} }}{{\gamma_{{\text{w}}} \left( {1 + e} \right)}}\frac{{{\text{d}}\sigma^{\prime}}}{{{\text{d}}e}},D = \left( {1 - G_{{\text{s}}} } \right)k_{{\text{w}}} \frac{{\text{d}}}{{{\text{d}}e}}\left[ {\frac{1}{1 + e}} \right] \hfill \\ r_{{\text{w}}} \le r \le r_{{\text{c}}} : \, A = - \frac{{k_{{{\text{ch}}}} }}{{\gamma_{{\text{w}}} }}\frac{{{\text{d}}\sigma^{\prime}}}{{{\text{d}}e}},B = \frac{{\left( {1 + e} \right)}}{r}A,C = \frac{{k_{{{\text{cv}}}} }}{{\gamma_{{\text{w}}} \left( {1 + e} \right)}}\frac{{{\text{d}}\sigma^{\prime}}}{{{\text{d}}e}},D = \left( {1 - G_{{\text{s}}} } \right)\frac{{\text{d}}}{{{\text{d}}e}}\left[ {k_{{{\text{cv}}}} \frac{1}{1 + e}} \right] \hfill \\ r_{{\text{c}}} \le r \le r_{{\text{e}}} : \, A = - \frac{{k_{{\text{h}}} }}{{\gamma_{{\text{w}}} }}\frac{{{\text{d}}\sigma^{\prime}}}{{{\text{d}}e}},B = \frac{{\left( {1 + e} \right)}}{r}A,C = \frac{{k_{{\text{v}}} }}{{\gamma_{{\text{w}}} \left( {1 + e} \right)}}\frac{{{\text{d}}\sigma^{\prime}}}{{{\text{d}}e}},D = \left( {1 - G_{{\text{s}}} } \right)\frac{{\text{d}}}{{{\text{d}}e}}\left[ {k_{{\text{v}}} \frac{1}{1 + e}} \right] \hfill \\ \end{gathered}$$