Drought Risk Assessment in Yunnan Province of China Based on Wavelet Analysis

A wavelet transform technique was used to analyze the precipitation data for nearly 60 years (1954–2012) in Yunnan Province of China. The wavelet coefficients and the variance yield of wavelet were calculated. The results showed that, in nearly 60 years, the spring precipitation increased slightly; however, the linear trend of other seasonal and annual precipitations showed a reducing trend. Seasonal and annual precipitation had the characteristics of multiple time scales. Different time scales showed the different cyclic alternating patterns. Overall, in the next period of time, different seasons and the annual precipitation will be in the periods of precipitation-reduced oscillation; high drought disaster risks may occur in Yunnan province. Particularly, by analyzing large area of severe drought of Yunnan province in 2009–2012, the predicted results of wavelet were verified. The results may provide a scientific basis for guiding agricultural production and the drought prevention work for Yunnan Province and other places of China

Research on the Penetration of Spudcan Foundation for Mobile Jack-Up Platform

[Introduction] The spudcan foundation is the key structure of the mobile jack-up platform, which displaces surrounding soil during its penetrating installation. In order to ensure the safety in the application of mobile jack-up platform to the offshore wind power installation works, it is particularly important to research the evolution of surrounding soil flow mechanism during spudcan penetration, and to evaluate the penetration resistance of spudcan reliably. [Method] The coupling Euler-Lagrange (CEL) method was used in this research to simualte the process of spudcan penetration under several typical seabed geological conditions (homogeneous and heterogeneous clay, sand, "clay-sand-clay" and "clay (hard)-sand (soft) and clay (hard)"), and to analyze the differences of penetration mechanisms. [Result] The simulation results show that in the process of spudcan penetration, the soil flow mechanism and penetration resistance of spudcan are closely related to the strength characteristics of seabed soil, while the friction coefficient of the interface between spudcan and seabed soil has little effect on the penetration mechanism and resistance. [Conclusion] From comparision with the results calculated in accordance current design specifications, the method combining large deformation finite element analysis and industry code design should be recommended to be applied in engineering design practice, as to provide a better basis for the assessment of punch-through risk and the prediction of penetrating depth in the process of spudcan penetration