Study On Design Methodology And Key Technologies Of Railway Tunnels In Low Mountains And Hills

There is a wide range of low mountains and hills in southern China.The low mountains and hills is a combination of slopes composed of a variety of rock types.It is rich in water resources and has continuous low hills.Under the geological and topographic features of the low mountains and hills,the railways are usually along with the river and the mountain built straightly.Therefore,a large number of railway tunnels have been built in the low mountains and hills with many special geologic areas and special terrain areas.Because of the large number of tunnels in the special terrain areas,it is of great practical significance to study the issues concerning the construction of tunnels in the areas with obvious features.Relying on the tunnels of the New Built Jiujiang-Quzhou Railway,this paper has studied three special geologic areas.The details are as follows:(1)Karst development section.Based on the characteristics of karst development in the engineering area,this paper adopts the numerical experiment method to analyze the mechanical properties of surrounding rocks of karst development and the effects of karst development on basic grading indicators of surrounding rocks were clarified.On this basis,the classification method of karst rock is established through data investigation.(2)Shallow buried section of gully zone.According to the characteristics of geological terrain and relevant regulations,the load calculation methods and structural design methods for retaining arch structures and tunnel structures are given.The key construction procedures for concealed backfilling and concealed excavation methods are analyzed,and the related construction techniques are summarized.(3)The opencut tunnel of the entrance of the Mountain-Adjacent tunnels.According to the characteristics of Geology and topography,combined with the standard calculation formula of unsymmetrical loading tunnel,the load calculation method and structural design method of single pressure opencut tunnel are presented.The theoretical analysis of longitudinal thrust of longitudinal section side slope is carried out,and the calculation method of shear stress of opencut tunnel structure is given,and the structural requirements of the structure are analyzed.The related construction technologies are summarized.