Analysis of Underwater Melting Process and Leakage Plugging Performance of Phase-Change Materials.

Leakage is a high-incidence disease of embankment dams, and efficiently addressing this disease guarantees the safe operation of dams. Underwater leakage self-priming plugging technology is a new technology that utilizes the melting and solidifying characteristics of phase-change materials and the negative pressure in the leakage entry area to accurately plug the leakage. However, little is yet known about the underwater melting process of phase-change materials and how their characteristics influence the plugging effect. In this study, three kinds of phase-change materials, namely, paraffin, rosin, and stearic acid, were used to conduct underwater leakage self-priming plugging tests, observe and analyze the underwater melting process, and compare the plugging effects. The results showed that the underwater melting process of phase-change materials exhibited different plugging window periods depending on their melting points, specific heat capacities, and mobilities, which were the main factors affecting their plugging effects. In the final plugging stage, paraffin had the best plugging effect, but the material strength was low; rosin had good plugging compactness, but the fluidity performance was poor, and the material effective utilization was low; stearic acid had a low melting point but dispersed easily. Therefore, a blocking material with a suitable blocking window period can be produced by adjusting the material properties accordingly for an improved blocking effect.

The role of metal compounds in dynamically regulating alkali infiltration during pickling of preserved eggs.

This study was conducted to investigate the dynamic regulation of alkali infiltration by different metal compounds during the pickling of preserved eggs. With the increased pickling time, the alkalinity of the pickling solution decreased, while the pH of preserved egg white increased firstly, then decreased, and finally increased again. The metal ions corresponding to the added metal compounds (CuSO4, CuSO4/ZnSO4 and PbO) underwent a complex migration with pickling time, and their content gradually increased in eggshell and yolk, but showed complex changes in egg white. The addition of metal compounds could produce a plugging effect. The main components of the black spots on eggshells of preserved eggs pickled by CuSO4, CuSO4/ZnSO4, and PbO were Cu2S, Cu2S/ZnS and PbS, respectively. In short, different metal compounds were combined with H2S to form insoluble compounds to block eggshell stomata, mesh pores and corrosion pores, thereby dynamically regulating the penetration of alkali.

Numerical investigation of soil plugging effect inside sleeve of cast-in-place piles driven by vibratory hammers in clays.

During driving sleeve of cast-in-place piles by vibratory hammers, soils were squeezed into sleeve and then soil plugging was formed. The physic-mechanical properties of the soil plug have direct influence on the load transmission between the sleeve wall and soil plug. Nevertheless, the researches on this issue are insufficient. In this study, finite element and infinite element coupling model was introduced, through the commercial code ABAQUS, to simulate the full penetration process of the sleeve driven from the ground surface to the desired depth by applying vibratory hammers. The research results indicated that the cyclic shearing action decreases both in soil shear strength and in granular cementation force when the sleeve is driven by vibratory hammers, which leads to a partially plugged mode of the soil plug inside the sleeve. Accordingly, the penetration resistance of sleeve driven by vibratory hammers is the smallest compared to those by other installation methods. When driving the sleeve, the annular soil arches forming in the soil plug at sleeve end induce a significant rise in the internal shaft resistance. Moreover, the influence of vibration frequencies, sleeve diameters, and soil layer properties on the soil plug was investigated in detail, and at the same time improved formulas were brought forward to describe the soil plug resistance inside vibratory driven sleeve.