隧道式锚碇与上覆隧道相互作用的力学性能研究

Research on the Mechanical Properties of the Interaction between Compound Tunnel Anchorage and Overlying Tunnel

采用三维显式有限差分程序（FLAC^3D）,对南溪长江大桥泸州岸隧道式锚碇及上覆公路隧道各施工过程进行数值模拟,研究不同工序下各施工阶段支护结构的内力响应以及围岩体的应力场与位移场分布规律等力学行为。结果表明,锚碇与隧道的相互作用影响区域集中在锚室前端及上覆隧道洞口段范围内,且影响程度随两者之间距离的增大迅速减小;在设计主缆荷载作用下,上覆隧道洞口段发生向上位移,但量值相对较小,对隧道受力影响不大;复合锚碇体系的力学响应主要集中在锚固段始端3.5-4.0 m以及锚塞体与岩体接触面1.5-2.5 m附近区域;施工过程中应对隧道及锚室入口等浅层区域岩体、锚室及锚塞体开挖空间侧墙与拱腰等部位岩体进行加固;从岩体塑性区发展及支护结构受力状况来看,先建锚碇后修隧道的工序更加合理。

The numerical analysis was conducted on the construction sequences of the tunnel anchorage and overlaying highway tunnel located at Luzhou bank side of Nanxi Yangtze River Bridge. The analysis was performed by a three dimensional explicit finite-difference program （FLAC^3D）. This study included the stress response in the supporting structure under different construction sequences, the distribution of the stress field and the displacement field in the surrounding rock mass. The results show that the interaction zone between the anchorage and tunnel is in the forward part of tunnel anchorage room and the tunnel portal section of the overlaying tunnel. With an increase of the distance into the tunnel, the interaction rapidly diminishes. Under the design load for the main cable of suspension bridge, the tunnel portal section of the overlaying tunnel moves upward slightly. This movement has negligible effect on the stress distribution of the tunnel. The mechanical response of the compound tunnel anchorage is mainly located in 3.5-4.0 m distance to the beginning of anchoring part and 1.5-2.5 m range adjacent to the interface between the anchoring body and the surrounding rock. The following rock zone should be consolidated under construction such as the shallow buried layer rock nearby the tunnel portal section and the entrance of anchorage room, the side wall and the arch sides of the anchorage room and anchorage body. Based on the plastic zones development in surrounding rock and the stress distribution in supporting structure, the construction of tunnel anchorage prior to the overlaying tunnel is a much more practical and reasonable sequence.