Research On Construction Mechanics For Highspeed Railway Tunnel With Shallow-Depth And Large-Section In Dachen Railway

The paper studies associate to the Baoshiyan tunnel and Jiaxianggou tunnel of Dachen railway engineering items. In order to master the mechanical behavior of surrounding rock and lining support in shallow-depth large-section tunnel when tunneling, and provide scientific laws for safty construct in shallow-depth large -section tunnel.By means of theory analysis,monitoring measurement insite and numerical modelling,the paper explore the charcators of compression force of surrounding rock and displacement in Dachen railway shallow-depth large-section tunnel, and find out slack scope of surrounding rock, analyse the stress and stain of surrounding rock in stage two and stage three stress status. The paper avail some laws of stree and strain of surrounding rock: x dirction normal stress is the main stress in crown and invert, y dirction normal stress is the main stress in side wall, maximal shear stress generate in the 45°direction, maximal strain is 0.0027.Get the value scope of lateral pressure coefficient in tunnel site is 0.5～0.75.plastic zone and limit strain possiblely create at side wall like "ear" or" X". At the same time make stability estimation of surrounding rock, express the working conditions of surrounding rock after tunnering, master the force condition of support structure, select proper support methods in specific geological conditions, the paper analyse behavior of surrounding rock by displacement,axial force of bolt and intreral force of lining according to monitoring measurement and information feedback. Got the laws of relative displacement,speed rate of displacement in shallow-depth large-seciton railway tunnel; calculated the bolt which 2.5m in length 25mm in diameter and 100×100cm in spacing can favor the support requirement, found out the laws of axial force of bolt relative to the depth and terrain feature in shallow-depth tunnel and inner force of primary lining is much bigger in corner of arch, and properly raise the thickness in corner of arch; secondary lining is a meams to keep safey reserve, designed thickness is conservative,thickness in 40cm can favor the lining support in inner force.