The respected Comrade
"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 consolidation analysis is one of the important factors for assuring the safety and regular working of buildings and structures which are built on the ground with soft soils such as clay and mud.
Until now most researches have been done on one-dimensional consolidation of unsaturated soils under the regular cyclic loads and one of saturated soils under different types of cyclic loads. If we go through earlier investigations, we could find that most researchers performed investigations on consolidation behavior of saturated soils under cyclic loads and unsaturated soils subjected to simple time-dependent loadings, but little research has been done on consolidation behavior of unsaturated soils under various complicated cyclic loadings.
We performed the investigation on one-dimensional consolidation behavior of unsaturated soils under cyclic loads such as trapezoidal, rectangular and triangular cyclic loadings based on the consolidation theory proposed by Fredlund and Hasan to promote the investigation on the consolidation behavior of unsaturated soils.
Firstly, we derived the analytical solutions for one-dimensional consolidation of unsaturated soils under various cyclic loadings based on the theory. To derive the solutions, we made five assumptions: (1) The flows of air and water phase are continuous and independent. (2) The soil particles and water phase are incompressible. (3) The effects of temperature change, air diffusing through water and air dissolving in the water, and the movement of vapor are ignored. (4) The coefficients of permeability and volume change for both air and water phases remain constant during the consolidation process. (5) The deformation takes place only along the vertical direction.
We derived the analytical solutions for one-dimensional consolidation of unsaturated soils under cyclic trapezoidal, rectangular and triangular cyclic loadings based from these assumptions.
The proposed solutions are degenerated into the existing solutions for unsaturated soils under constant and ramp loadings. By comparing with the earlier investigations, the proposed solutions are reliable and more general for one-dimensional consolidation of soils from unsaturated to saturated states under time-dependent loading.
Secondly, we performed a comprehensive parametric study to investigate the effects of different parameters on one-dimensional consolidation of unsaturated soils under various cyclic loadings.
The results showed that the coefficients ratio of permeability for air phase and water phase has sufficient effects on consolidation of the unsaturated soil layer under cyclic loadings. The dissipation rates of excess pore water and air pressures increase with the fluctuation when the coefficients ratio of permeability increases. And under cyclic loadings, the dissipation process of excess pore pressures does not complete after a long time, but rather continues oscillating with a certain amplitude. Thus, neglecting the effect of cyclic loadings may result in overestimated settlement and cannot consider the continuous volume change.
And the cyclic loading parameters, for example, the period of loading, the rate of loading increment or decrement, the rest period of loading and so on, have considerable impacts on consolidation of unsaturated soil. The longer the period of loading, the bigger the amplitude of fluctuation in the dissipation rates of excess pore water and air pressures and the higher the rate of loading increment or decrement is, the faster the dissipation rates of excess pore pressures are.
Our results were published as an essay under the title of ''One-dimensional consolidation analysis of unsaturated soils under cyclic loadings'' (https://doi.org/10.1155/2020/7285323) in the Journal ''Shock and Vibration''.