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We compared the catalytic effects of two polymers (soluble starch and apple pectin) on the flocculation of kaolinite suspension. Moreover, the relationship between the zeta potential value and the time when kaolin particle sedimentation occurred was verified, and the mechanism of flocculation was analyzed. Additionally, a constitutive model was proposed to simulate the non-ideal sedimentation of clay particles in an aqueous system under constant gravity. This model not only considers the inhomogeneity of the solute but also simulates the change in clay concentration with time during the deposition process. This model proposes a decay constant (α) and sedimentation coefficient (s). The model can also be used to calculate the instantaneous sedimentation rate of the clay suspensions at any time and any depth for the settling cylinder. These sedimentary characteristics were simulated by adopting the established deposition model. The results show that the model is capable of predicting the time required for the complete sedimentation of particles in the aqueous system, suggesting the feasibility of engineering wastewater treatment, site dredging, etc.

This study reports a group of field tests on cyclically loaded piles installed in soft clay in Huzhou, China. Two 29.5 m long pipe piles were instrumented with transducers to measure the accumulated settlement at the pile-head, the pore water pressure and total pressure at the pile-soil interface, and axial load at the pile end, respectively. The major objective of the field testing is to gain a better understanding of the evolution of the pile-head settlement and the effective stress at the pile-soil interface. The results of cyclic loading tests under different combinations of static load and cyclic load are discussed with reference to changes in the pile capacity, the permanent settlement, and the radial stresses. It is found that the permanent settlement of piles can be characterized as quickly stabilized (QS), progressively developing (PD), and dramatically failed (DF) patterns. Under low-level loading (QS pattern), the pile-shaft earth pressure is nearly undisturbed, final gains in effective stress are observed due to slight dissipation of pore pressure. For intermediate-level loading (PD pattern), significant reductions in pore pressure, earth pressure, and effective stress are observed after cyclic loading. Regarding high-level loading (DF pattern), the quick accumulation of pore water pressure leads to a slight increase in earth pressure, resulting in a continuous decrease in effective stress.

This study presents a field investigation on the evolution of the effective stress, the shaft friction at the pile-soil interface and the pile-end base resistance of a 29.5-m-long prestressed concrete pipe pile in soft clay under static and cyclic loadings (with a large number of 50 000 cycles). The results indicate that under low-level cyclic loading (CLR ≤ 0.2; CLR refers to the ratio of cyclic load amplitude to the ultimate capacity), the pore water pressure at the pile-soil interface accumulates initially with the number of cycles, followed by gradual dissipation after reaching its maximum value. The effective stress decreases initially and then increases again. The shaft friction is observed to increase after cyclic loading. Due to axial load redistribution, the base resistance decreases with the number of cycles. When the pile is imposed to high-level cyclic loading (CLR ≥ 0.5), the pore water pressure at the pile-soil interface keeps accumulating while the effective stress continues to decrease consequently, leading to the degradation in shaft friction. The base resistance increases as a result of axial load redistribution. In particular, the effects of the static load level and the cyclic load level on the variations of shaft friction are analyzed.

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