Abstract
Hansbo’s flow model for one-dimensional consolidation analysis of saturated clay has been widely recognized as being the most representative for soft soils. Many studies have used the model to examine the characteristics of soil under various conditions. However, very few studies have considered soil under cyclic loading. In this study, using a Hansbo’s flow model and assuming known characteristics for soft clay deformation and rebound and recompression of soil, the one-dimensional consolidation model of soft clay under cyclic loading is established. A FlexPDE solution scheme with excess pore pressure u and void ratio e as variables is also given. The reliability of the proposed method is verified by comparing the obtained results with existing results. On this basis, the consolidation characteristics of soft clay foundations under unilateral drainage and cyclic loading are studied. The effects of soil rebound and recompression characteristics, Hansbo’s flow parameters, cyclic loading period, and cyclic loading form on the consolidation characteristics of soft clay foundation are analyzed. The results show that under cyclic loading, the effective stress, void ratio, and average consolidation degree of the foundation all present a cyclic state and gradually enter a stable cyclic state with the increase in cycles. The peak of effective stress lags behind the peak of cyclic load. The rebound and recompression characteristics of soil have little effect on the effective stress of soil but a great effect on the void ratio. In contrast to its characteristic under linear loading, the average consolidation degree of the foundation under cyclic loading finally enters a stable cyclic state. The results of the analysis can be used as a reference in the analysis of real life highways, railways, subway tunnels built on soft soil foundations subjected to periodic cyclic loading.
Highlights
Introduction e traditional Terzaghi consolidation theory, which states that when stress is applied to a porous material, it is opposed by the fluid pressure filling the pores in the material, is based on the assumption that the soil skeleton is characterized by linear elasticity, small strain, and Darcy’s flow. e mathematical form of the theory is simple and it is easy to obtain the analytical solution. us, it is widely used in practical engineering
Ere are two ways to define the average degree of consolidation, that is, average consolidation degree Up defined by excess pore pressure u and the average consolidation degree Us defined by surface settlement st, as follows: H0 (q(t) − u)
It can be seen from the figure that there are some similarities and differences between the average consolidation degree Up defined by excess pore pressure u and the average consolidation degree Us defined by surface settlement st
Summary
We consider a saturated soft clay layer of thickness H0. We assume that the soft clay has been consolidated under the action of soil weight and original uniform load qp. A uniformly distributed cyclic loading (q(t)) is applied on the top of the soft clay layer. Soil gradually begins consolidating under the uniform cyclic loading. Erefore, the following assumptions are made to establish an analytical model for the flow and aforementioned consolidation of the soft clay foundation. Hansbo’s flow model parameters (m and i1) remain constant in the consolidation process. (3) Nonlinear deformation and flow law of soft soil can be expressed in the classical form as e − lgσ′ and e − lgK [4].
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