In this study, attempts were made to use sandy soil as the main raw material in making unfired bricks. e sprayed-cured brick specimens were tested for compressive and flexural strength, rate of water absorption, percentage of voids, bulk density, freezing/thawing, and water immersion resistance. In addition, the microstructures of the specimens were also studied using scanning electron microscope (SEM) and X-ray diffraction (XRD) technique. e test results show that unfired brick specimens with the addition of ground-granulated blast-furnace slag (GGBS) tend to achieve better mechanical properties when compared with the specimens that added cement alone, with GGBS correcting particle size distribution and contributing to the pozzolanic reactions and the pore-filling effects. e test specimens with the appropriate addition of cement, GGBS, quicklime, and gypsum are dense and show a low water absorption rate, a low percentage of voids, and an excellent freezing/thawing and water immersion resistance. e SEM observation and XRD analysis verify the formation of hydrate products C-S-H and ettringite, providing a better explanation of the mechanical and physical behavior and durability of the derived unfired bricks. e results obtained suggest that there is a technical approach for the high-efficient comprehensive utilization of sandy soil and provide increased economic and environmental benefits.

The riverbanks in the Lower Jingjiang Reach are mostly composite ones with fine sand overlain by cohesive clay, thus when the sandy layer is undermined due to rapid erosion, the cohesive upper layer generates a cantilever and is prone to beam failure. In this study, the formula of critical width of cantilever failure was improved considering the hydraulic effects. The formula of accumulated width of failed blocks at bank foot was deduced. A collapse analysis model of composite banks was subsequently proposed, and the collapse process of a typical bank slope was simulated using the model. The conclusions include: The cantilever failure of composite riverbanks is more prone to occur during the period of water level decline than that of water level rise. The critical width of cantilever decreases with the dropping of river level, the weakening of the supporting role of river water and the enhancement of the overturning effect of groundwater. The thicker the cohesive layer is, the greater the decrement of its critical overhang width is as river level decline. The protective effect of failed blocks accumulated at bank foot reduces its erosion distance, the more times the bank collapse takes place, the greater the impact is.

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Abstract.To study the influence of pile-soil interaction on the seismic behavior of PHC piles, this paper takes the PHC pile in the soft clay as the research object, which is simulated by fiber beam element, and the pile-soil interaction is simulated by using equivalent embedded method and p-y soft clay soil spring which is under cyclic load, respectively. The seismic behavior index of pile foundation under limit state is obtained through applying the horizontal cyclic load on the pile top. The research shows that, with the different depth of pile, the hysteretic energy dissipation index and the displacement ductility factor obtained by the equivalent embedded model are about 2.2~2.5 times and 1.1~1.4 times of the p-y curve model respectively. While the yield strength and ultimate strength obtained by the p-y curve model are larger than those obtained by equivalent embedded method.

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