Study On The Mechanics Characteristic Of Railway Tunnel Newiy-Fashioned Portal

In China, traditional portal of railway tunnel can be sorted as three types-origin, modified and special types, inclusive of 16 kinds on basis of the characteristic of terrain, basically they are of end wall and post type. With greater investment on railway infrastructures, the old-fashioned portal has become outdated in respect of engineering environment-nursing, landscaping, aesthetics and sustainable development, correspondingly it needs innovations. In recent years, highway tunnel has witnessed great breakthrough and innovations, such as bamboo-truncating type, dark glass type etc. It blends some theories, principles and views of architecture, horticulture and aesthetic into portal design with the achievement of aesthetic effects. Therefore, the study on brand-new types of railway tunnel is of great value. It should not any seek goals of aesthetic effect and environment keeping, more importantly ensure its functionality. Many years so far it is qualitatively regarded that tunnel portal stress is under complex 3-dimensional state, and it is designed according to standard draft. While the brand-new types of portal has no standard draft for reference, as a result, the study on stress characteristics of brand-new portal is of essential importance.In this paper it first suggests 3 types of brand-new portal to be investigated in the light of landscaping and environment nursing, namely up or down bamboo-truncating portal and arc retaining wall portal. Indoors model test employing similarity materials and mainly considering V-class surrounding rock is carried out respectively in respect of single track and double track so that the characteristics of ground pressure, structural stress of portal and internal force distribution in various case of slope and dead-weight stress field can be investigated. The main characteristics are as follows:l.The stress characteristic of lining of entrance corresponds with that of shell structure.2.The ground pressure and lining stress of lining of entrance increases as gradient of up-slope increases.3.Stress concentration occurs in jointed area of arc retaining wall and tunnel body.4.The characteristics of stress distribution in entrance structure prove that spatial effect occurs within certain length.Finally, FEM analysis is done to verify the reliability of model test. As a result, it can be used as reference for brand-new railway tunnel portal design.