不同含水率与静置时间下滩涂土壤流变特性试验.

This study aims to determine the rheological properties and structural stability of the beach soil for shellfish cultivation. A series of rheological tests were carried out on the beach soil with different water content and standing time using a rotary rheometer. A single-factor test was also conducted to explore the influence of water content and standing time on the rheological properties of the beach soil. The soil shear was then analyzed to determine the influence of water content and standing time on yield stress. At the same time, the numerical model was established for the yield stress, water content and resting time after the central composite design (CCD) test in the response surface method (RSM). A comparison was then made on the influence of water content and resting time on yield stress. Finally, the reliability and accuracy of the regression model were further verified to compare the error between the measured and the actual values. The results show as follows: 1) The shear stress gradually decreased with the increase of water content under the same shearing rate in the shearing process, whereas there was a gradual increase with the increase of standing time; In addition, the beach soil was characterized by the consolidation. The longer the static time was, the longer the solid-liquid transformation was, and the later the solid-liquid node was. The static time shared the greatest impact on the solid-liquid node in the early stage. The longer the static time was, the smaller the impact on the solid-liquid node was. 2) When the average shear stress and yield stress were at the shear rate of 10 - 60 s-1 under the same standing time, the overall shear stress of the tidal flat soil gradually decreased with the increase of water content, thus reducing the structural stability of the tidal flat soil. In addition, the overall shear stress of the tidal flat soil gradually increased under the same moisture content with the increase of static time, indicating the increase in the structural stability of tidal flat soil. The change rate of yield stress with the static time showed that there was a cut-off point of moisture content in the beach soil, which was between 64.5% and 67.0%. In the samples exceeding this moisture content cut-off point, the change rate of yield stress with the static time remained stable after the static time exceeded 31 h, where there was no fluctuation in the yield stress. The yield stress ranged from 2 240 to 4 380 Pa. In addition, the yield stress in the sample of 62.0%-69.5% was between the 0-53 h, and the yield stress between 62.0%-69.5% was between 1 870-5 410 Pa. 3) The P and R 2 values of numerical models were above 0.05, and 0.953 4, respectively, indicating the high reliability and accuracy. There was a more significant influence of water content on the yield stress, compared with the resting time. However, the interaction between water content and resting time shared no significant influence on the yield stress. The test verified that the measured yield stress was basically consistent with the predicted one, with an error of less than 15.0%. The rheological properties of beach soil can be better characterized as well. The findings can provide a strong reference for the research and optimization of beach shellfish harvesting machinery [ABSTRACT FROM AUTHOR]