基底脱空条件下铁路隧道行车安全性分析

结合大瑶山隧道基底病害,在混凝土塑性损伤本构模型基础上,建立隧道-围岩相互作用动力计算模型,研究基底脱空对铁路隧道行车安全的影响。结果表明:随隧道基底脱空距离增加,隧道底部结构动力响应和损伤增大,且脱空距离超过一定深度后变化加剧;对于内侧单边脱空、两侧对称脱空和中间扩展脱空方式,当脱空距离分别达60、60、180cm时,需采取限速、加固等措施保证隧道行车安全。各脱空方式中,以两端向中间脱空方式所受影响最大。在该脱空方式下,当脱空距离从0cm增加到90cm时,底部结构竖向位移最大增幅达1.5倍;加速度最大增幅达17.2倍;主应力最大增幅达3.2倍;损伤值最大增幅达1.4倍。当脱空距离达120cm时,底部结构已发生破坏。可见,基底脱空对结构稳定和受力极为不利,将加剧结构损伤破坏。研究结果可为铁路隧道行车安全性评价和基底脱空整治提供参考。

Running Safety in Railway Tunnel with Base Voids

In view of base diseases of the Dayaoshan Tunnel and on the basis of the plasticity damage constitutive model of concrete,the dynamic calculation model for interaction between tunnel structure and surrounding rock was established to study the influence of base voids on the running safety of vehicles in a railway tunnel.The results indicate as follows: The dynamic responses and damages of the tunnel base structure increase with increasing of the tunnel base void distances,which intensifies when the voids distance goes beyond a certain depth;when unilateral voids on the inner side,symmetrical voids on both sides and extended voids in the middle occur and their distances reach 60 cm,60 cm and 180 cm respectively,speed limiting and reinforcement measures should be taken to guarantee the running safety in tunnels;of all types of base voids,the voids developing from both ends to the centre exert most serious influence,i.e.,when the void distance grows from 0 cm to 90 cm,the base structure possesses the maximum increment of vertical displacement as 1.5 times,that of acceleration as 17.2 times,that of principal stress as 3.2 times and that of damage as 1.4 times;when the void distance reaches 120 cm,damage was done to the base structure.The results provide useful reference to traffic safety evaluation and treatment base void in tunnels.