Search

The HT ht value versus time of clays is shown in Fig. When the HT ht value is equal to 100%, it means the strength of soil has recovered its original intact shear strength. The regained strength of YS-1 clay is also considerable, and the value of HT ht is greater than 40% after 2 months. By contrast, the HT ht of YS-2 and ES-2 clays in the corresponding deep layer is much lower (see Table 1 in the original paper). [Extracted from the article]

Thixotropy is a very important and unique property of soft clay in engineering, which has been drawing more and more attention in recent years. This study investigated the thixotropic strength recovery of representative marine clays in different sites of offshore China. The microstructure changes of clay during thixotropy were observed using scanning electron microscopy, and then related microscopic characteristics were analyzed. Probability entropy, Ep , is proposed as a new indicator based on the statistics of the alteration of diameter and orientation of particles or aggregates. The results show that thixotropy had significant effect on the strength increase for all the offshore Chinese clays that were tested, but their strength regain with time varied between the different sites. Some good correlations were developed between the thixotropy strength ratio and index parameters, particularly for water content, plasticity index, liquidity index, and sensitivity. The microstructural evolution of the clay tested during thixotropy was characterized by the change in both the diameter and the arrangement of particles or aggregates. The probability entropy was proved to quantitatively describe and analyze the microstructural evolution during thixotropy of clay, and its value increases with time. This new indicator could help to provide deeper insight into the thixotropic mechanism of clay. [ABSTRACT FROM AUTHOR]

This paper presents an investigation on the microstructural evolution alongside the strength degradation of the soft marine soil under T-bar cyclic penetration. The marine soil that was recovered from the seabed in deep-water areas in the South China Sea can be representative of the characteristics of typical soft marine clay in this water area. The microstructure of clayed soils is characterized by particle-constituted aggregates and interaggregate pores, which is commonly considered to predominate the strength of soils. To quantitatively capture the evolving microstructural characteristics of the soil during loading, a new indicator (i.e., probability entropy, H) is proposed based on statistics of the alteration in aggregate size and orientation of the soil. With the aid of the new indicator, the soil microstructural evolution is further evaluated and associated with strength degradation during the continuous T-bar cyclic loading course. In addition, through a comparison between the intact marine soil samples and reconstituted ones, the effect of microstructural cementation of marine soil is examined on the shearing strength during the cyclic loading. The two types of soil samples show a significantly different evolving trend of microstructure. The probability entropy of intact soil decreases, while that of reconstituted soil increases. Thus, the intact soil exhibits a higher probability degree of entropy change than does the reconstituted soil. This result may provide a plausible explanation for the difference in strength between the intact soils and reconstituted ones, even if they have been subjected to the same consolidation stress condition. The novel quantitative method to evaluate the soil microstructure can be further applied to understand the mechanism of strength degradation of soft marine soils. This will provide a deeper insight to the engineering properties of those marine soils, which will facilitate a precise design for practical offshore foundations in deep waters. [ABSTRACT FROM AUTHOR]

In this study, the accumulated plastic strain (APS) of granite residual soil under cyclic loads is investigated by a series of undrained cyclic triaxial tests. Granite residual soil is a special kind of soil that is widely distributed in areas of rapid economic development. Owing to a lack of understanding of the cyclic deformation of granite residual soil, the effects of several essential stress conditions, such as cyclic shear amplitude, initial static deviatoric stress, and effective consolidation stress, are explored and analyzed on the APS growth with loading cycles. The cyclic loads represent the typical traffic load acting on the foundations of subgrade works. Based on the results of tests under various stress conditions, a simple and easily adopted accumulated plastic strain growth (APSG) model is correlated to predict the evolution of APS with loading cycle number. Through comparing the results of separate tests, the APSG model is validated and exhibits its ability to predict the accumulated plastic behavior with satisfactory accuracy. Furthermore, the APS growth with a loading cycle is examined under various stress conditions by the APSG model. The influences of those important stress factors on the APS behavior can be successfully described by two often-used parameters in soil dynamics, that is, cyclic stress ratio and static deviatoric stress ratio, which are involved in the APSG model. As a result, the characteristics of plastic deformation of granite residual soil under cyclic loading conditions can be further analyzed by the new model. Although this model is easy to adopt with some accuracy, a more powerful model based on rigorous theory is still needs to be developed in the future. The finding of this study will provide a deeper insight into the cyclic loading behavior of granite residual soils that are often encountered in the subgrade of traffic engineering in China. [ABSTRACT FROM AUTHOR]