隧道出入口平面线形一致性

针对现行公路隧道设计规范对隧道进出口处平面线形一致性缺乏明确判别标准,提出了方向盘冻结3s导致的行车轨迹同原有路线的偏移值作为线形一致性的控制性指标,控制阈值取0.2m.对3种不同设计条件下的隧道线形一致性进行分析,发现缓和曲线参数是影响平面线形一致性的重要指标.通过理论推导给出不同设计条件下隧道进出口平面线形一致性的判别标准,使设计者能在保证线形安全的前提下对隧道进出口平面线形进行灵活设计和评价.应用该研究成果对龙庆高速公路某隧道洞口的线形一致性进行了分析,提出了相应的改进建议.

Consistency of Horizontal Alignment at Tunnel Entrance and Exit Zone

Current code of tunnel design lacks specific criterion for judging horizontal alignment at entrance and exit zone of highway tunnel. After 3-second freezing of steer wheel, the deviation of the track from desired path is proposed to evaluation the consistency of horizontal alignment at tunnel entrance and exit, and the control threshold is 0.2m. All design conditions can be generalized to three cases, which are studied carefully. Spiral curve parameter is found as a significant design index to guarantee the consistency. Then the equations for derivation calculation in different cases are deduced, and the suggested design indexes of the horizontal alignment at the tunnel entrance and exit zone are proposed, which help designer to bring more flexible productions. The research result is applied to analyze the consistency of the horizontal alignment of a tunnel of Longquan-Qingyuan expressway, and then the appropriate improving recommendation is proposed.