Studying of the wall cylindrical rigidity influence on the stress-strain state of the tank during local settlement

The article numerically researched the stress-strain state of the tank RVS-20000 at the settlement zone is located near the tank wall. A numerical model of the tank was developed in accordance with the actual geometric dimensions, taking into account all structural elements of the structure and the maximum operating loads. When modeling local settlement to account for the spatial work of the soil, the model of the Pasternak soil base was used. The stress-strain state calculation of the tank was performed at values of the radius of the drawdown zone from 1 to 10 m. The choice of this interval is due to the fact that in more than 92 % of cases, tanks with local bottom settlements fall within this range of values.The dependences of the maximum acting stresses in the wall of the internal combustion engine on the position of the inhomogeneity area in the soil base are established. The boundary of the zone of action of the edge effect from the tank wall is established. If the center of the heterogeneity area is located in this zone, it is necessary to conduct additional analysis of the tank metal structures stress-strain state when assigning the maximum settlement.

Diversity and Distribution of Riparian Arthropods in the Drawdown Zone of China’s Three Gorges Reservoir

Riparian zones are interesting habitats as they are important transitional zones between terrestrial and aquatic ecosystems, but highly threatened by human disturbances. They support a high arthropod diversity as they experience periodic flooding disturbance and sharp environmental gradients. Their associated arthropod fauna are of high conservation value. Nevertheless, their arthropod diversity remains largely unknown, and its distribution pattern along elevational gradients is poorly understood. Few data are available on the effects of flood regimes and other factors in determining riparian arthropod communities. In this study, we investigated the diversity and distribution of riparian arthropods along an elevational gradient and determined the major factors structuring the arthropod communities in the drawdown zone of the Three Gorges Reservoir, China. Significant compositional and structural changes of riparian arthropod communities were observed along the test elevational gradient. The abundance and richness of riparian arthropods increased with elevation. The relative abundance of predators decreased with elevation, whereas the saprovores and omnivores showed an upward trend along the elevational gradient. Redundancy analysis showed that there were significant interactions between the flood regimes, plant communities, and soil conditions. Among these environmental factors studied, flood duration was the main factor in structuring the riparian arthropod communities. Conservation and restoration strategies should consider flood duration in the operation of large reservoirs because riparian arthropods are particularly sensitive to flood regimes.

Patterns of plant species richness along the drawdown zone of the Three Gorges Reservoir 5 years after submergence

This study was conducted to understand the patterns of plant species richness in the Three Gorges Reservoir after 5 years after 175 m submergence. We hypothesized that hygrophyte and xerophyte species would show different species richness patterns, which was tested by collecting species composition and environmental variable data in 50 m long and 5 m wide transects in the drawdown zone from 145 m to 180 m. Xerophyte species richness (XSR) was highest in the middle of the drawdown zone, whereas hygrophyte species showed a continuous downward trend from 145 m to 180 m. Correlation analyses showed that the flooding period was significantly negatively correlated with the total species richness (TSR), XSR, and hygrophyte species richness (HSR). The TSR and XSR showed a significant positive correlation with soil type and a significant negative correlation with available K. HSR was significantly correlated with soil type and negatively correlated with ammonium N.