大断面小净距隧道断面优化及其设计参数研究

对于大跨度小净距隧道而言,合理扁平率及双洞间距的设计对于节约成本,提高隧道线形规划具有至关重要的作用,因此,优化大跨度小净距隧道的扁平率及其间距是隧道设计施工面临的关键问题。以某双洞8车道隧道施工为研究背景,通过数值模拟及理论分析,对断面优化及其设计参数进行了深入研究。研究结果表明:随着高宽比的增加,拱顶位移逐渐减少,水平收敛逐渐增大,在高宽比为2.0时达到理想状态,这个时候的拱顶位移和水平收敛基本相同,此时断面有利于开挖。当高宽比取理想高宽比2.0时,这时应力较均匀,是开挖的理想断面,同时考虑行车通行的建筑界限,取高宽比为0.6333是合理的。隧洞埋深对塑性半径和周边位移的影响极大;弹性范围内的支护阻力与隧洞变形成正比;塑性半径随着围岩强度的增加而减小。

Section Optimization and Design Parameters Study on Large-Spanned Small-spaced Twin-tube Tunnel

As to large-spanned small-spaced twin-tube tunnel,the design of reasonable flattening ratio and the clear distance between the two tube plays a important role on cost saving and geometric shape planning.Therefore,optimizing the flattening ratio and the twin-tube distance of large-spanned small-spaced twin-tube tunnels is the key problem in tunnel design and construction.The article took the construction of a eight-lane twin-tube tunnel as an example and studied the cross-section and design parameters optimization by theoretical analysis and numerical modeling.The research results show that: the vault displacement decreases gradually and the level convergence increases gradually with the aspect ratio increases.And when the aspect ratio is 2.0,it is the ideal state that the vault displacement and the level convergence is basically the same,and that the stresses are more uniform,beneficial to excavation.However,considering the requirement of tunnel clearance of vehicular traffic,taking an aspect ratio of 0.6333 is reasonable.In addition,tunnel buried depth has a great impact on the plastic radius and peripheral displacement;the support resistance is proportional to tunnel deformation within the elastic range;the plastic radius decreases with the increase of surrounding rock strength.