Nonlinear radial consolidation analysis of soft soil with vertical drains under cyclic loadings


The respected Comrade Kim Jong Un said:

"Scientific research institutions in the sector of land administration and environmental conservation should conduct dynamic scientific research in line with the demands of building a thriving country, so as to solve fully, promptly and at a high standard the scientific and technological problems arising in land administration and environmental conservation."

The analysis of consolidation is one of the important issues in ensuring the safe operation of various structures on soft soils. In most coastal areas, the soils beneath many structures are highly compressible and may be subjected to complicated cyclic loadings.

The consolidation behavior of the soft soil under cyclic loadings is very complex and has been studied for many years. In the past decades, a lot of scholars have conducted research on one-dimensional consolidation of soft soil subjected to cyclic loadings based on either the linear consolidation theory or the nonlinear consolidation theory. Some scholars studied one-dimensional consolidation of a clay layer under haversine cyclic loading on the basis of some assumptions. And another scholars derived analytical solutions for one-dimensional nonlinear consolidation of a saturated soil with variable compressibility and permeability under various cyclic loadings. Analytical solutions for one-dimensional consolidation of unsaturated soils under cyclic loadings were also presented.

Vertical drains are widely used for improving soft soil and many researchers have investigated the radial consolidation behavior of the soil with vertical drains under cyclic loadings.

Although there are many studies on one-dimensional consolidation of the soil under cyclic loadings, research on radial consolidation under cyclic loadings are very limited, and any analytical solutions have hardly ever been proposed for nonlinear radial consolidation of the soil with vertical drains subjected to cyclic loadings with the consideration of variable compressibility and permeability.

That is why we derived analytical solutions for nonlinear radial consolidation under various cyclic loadings and investigated nonlinear radial consolidation behavior of the soil under various cyclic loadings.

At first we presented the mathematical model and governing equation for nonlinear radial consolidation of the soil with vertical drains subjected to time-dependent loadings and derived analytical solutions for nonlinear radial consolidation under cyclic loadings.

In order to derive the analytical solutions, the main assumptions are summarized as follows: (1) The soil layer is staturated and homogeneous and the soil particles and pore water are incompressible. (2) Only the radial flow of pore water is considered and Darcy's law is valid for the water flow. (3) Both the loading and the settlement occure only in the vertical direction, while the soil and the vertical drain have an equal strain at any depth. The effect of the drain resistance was neglected.

The effects of different parameters on non-linear radial consolidation behavior under different types of cyclic loadings are investigated. The results show that under cyclic loadings, both the dissipation rate of excess pore water pressure and the settlement rate slow down when Cc(compression index)/Ck(permeability index) increases. The dissipation rate increases when maximum loading increases in case of Cc/Ck<1 but decreases with the increase in the maximum loading in the case of Cc/Ck>1, whereas the settlement rate increases with the increase in the maximum loading in all cases of Cc/Ck<1 and Cc/Ck>1. The higher the rate of loading increment or decrement is, the faster the dissipation rate and the settlement rate are.

Our research results were published as an essay under the title of ''Nonlinear Radial Consolidation Analysis of Soft Soil with Vertical Drains under Cyclic Loadings'' (https:/ in the Journal ''Shock and Vibration''.