No abstract

No abstract

On May 12, 2008, a strong earthquake with a magnitude of 8.0 (Ms) struck Wenchuan town, in the eastern Sichuan area of west China. Following the earthquake on May 18, the Southwest Jiaotong University organized a damage survey team and dispatched it to the affected area for the investigation into the damage and collection of information and data. This paper outlines the findings of this investigation on the earthquake disaster to mountain tunnels and geotechnical engineering. The systematic investigation, involving geological conditions, design documents, construction and maintenance records of the tunnels, has been conducted and the degree of damage to investigated tunnels has been assessed according to the width and length of cracks, the stability of the slope above the tunnel, and the condition of the groundwater inrush. The results show that the major damage of the mountain tunnels was mainly concentrated in the tunnel portals due to widespread landslides and rockfalls, and the inner part of investigated tunnels suffered moderate damages mainly due to fault displacements. It is hoped that the information shared herein could enhance the outstanding of seismic behavior of mountain tunnels and improve seismic design and construction procedures. damage investigation, wenchuan earthquake, mountain tunnels, ground failures

As a core component of ac drive electric locomotive, performance of inverter-fed motor directly influences the stability and reliability of locomotive running. However, insulation early failures occur frequently. Presently, polyimide film, as a special type of engineering plastic film, widely applied in turn to turn insulation and turn to ground insulation of inverter-fed motors is a kind of basic insulating material. This paper investigates charge transport mechanism and space charge characteristics of polyimide films based on measuring and comparing space charge accumulation threshold field between corona-resistant and common polyimide films and analyzing the effect of temperature on space charge distribution. The results reveal that space charge accumulation threshold field of corona-resistant polyimide film is higher than that of common polyimide film; the adding of nano-particles effectively increases dielectric properties of corona-resistant film. Additionally, raising temperature promotes the electrode injecting charge and increases the charge energy and conductivity which gradually enhances space charge number and extends trapping position into the bulk, closely related to polyimide film insulation aging and breakdown which is an important characteristic.

No abstract