大变形隧道初期支护受力特征及对策研究

Study of the Force Characteristics of the Primary Support in a Tunnel with Large Deformation and Related Countermeasures

由于隧址区岩体具有大变形效应,渝利铁路大梁隧道在初期支护施作后拱腰、拱脚等部位相继出现喷混凝土开裂、剥落、掉块等现象。为了保证隧道结构安全,采用现场测试(解除应力测试和松动圈测试)、数值模拟(试算/正演计算)等方法对该段支护结构的受力特征进行了研究,并提出了相应的对策措施。结果表明:在此地质条件下,初期支护配筋为6.36 cm^2时,结构将产生破坏(最大弯矩处安全系数为1.0),而实际配筋只有5.07 cm^2,所以初期支护内的配筋(格栅钢架)不能满足工程实际需要,必须调整类似地质条件的支护参数才能保证隧道整体稳定性;同时研究获得的松动圈范围为2.29 m,与地质雷达的松动圈测试结果相吻合,验证了该方法的可行性及结果的准确性。

Concrete cracking, spalling, and rock falls occurred at both tunnel haunch and feet in the Daliang tunnel of the Chongqin-Lichuan railway because of the large deformation effect of the surrounding rock. Considering the safety of the tunnel, site tests （a stress relief test and a loose circle test） and numerical simulations （trial and positive calculation） were performed in order to study the characteristics of the support structure and put forth corresponding countermeasures. The results showed that under this geological condition, the primary support structure will be destroyed when the amount of reinforcement is less than 6.36em2 （the safety index under the largest moments is The actual amount of reinforcement is only 5.07cm2 in the Daliang tunnel, which does not meet the requirement and must he adjusted. The study also found that the scope of a loose circle is 2.29m, which coincides with the result obtained by the geological radar; this testifies to the feasibility and correctness of this method