东川铁路岔河偏压-滑坡隧道勘察治理

Investigation and Treatment of Chahe Unsymmetrical Pressure-landslide Tunnel of Dongchuan Railway

研究目的:岔河隧道为傍山隧道,隧道拱腰及拱顶纵向开裂掉块,边墙纵向开裂外移侵限,危及行车安全。隧道区具备地形和地质偏压条件,隧洞裂缝有明显偏压裂缝特征;勘探揭示山顶连续拉张裂缝,隧洞边墙存在水平纵向剪裂。查明隧道病害原因,正确评价稳定性,预测病害发展趋势,关系整治工程方案和整治工程成败。研究结论:岔河隧道病害是由地形偏压和地质构造偏压复合作用造成并发展为滑坡隧道的典型案例。地形、坡体特殊的地质结构构造、各岩土层的地质特性,决定坡体容易形成偏压,沿层面和高角度断层面形成软弱滑动带,是滑坡形成的内因。河流侧蚀作用、降雨下渗,特别是构造运动及地震作用引发的F1高角度正断层上盘的间歇性下降运动,是滑坡发生发展重要的外在触发原因。按勘察结论和措施建议进行综合整治,可达到预期效果。

Research purposes： The Chahe Tunnel is a hillside tunnel. The arch waist and vault of the tunnel cracked longitudinally with the block off. The sidewall cracked longitudinally and moved outside to exceed the boundary, and it endangered the traffic safety. As the tunnel area was featured with the topographic and geological conditions of unsymmetrical pressure, the tunnel cracks were also featured with the obvious unsymmetrical pressure. The investigation revealed that the continuous stretched and fractures happened on the mountain peak and the horizontal shearing cracks happened on the sidewall of the tunnel. To identify the reasons for the tunnel disaster, correctly evaluate the stability and predict the disaster development trend were crucial to the success of the its treatment. Research conclusions： The Chahe tunnel was a typical case that the tunnel became and developed into a landslide tunnel due to the joint effects of the unsymmetrical pressures of terrain and the geological structure. The special terrain and the slope geological structures and the geological characteristics of each soil layer made the slope easily to be pressured unsymmetrically. The soft and weak sliding zone formed along the bedding surface and the high - angle fault surface were the internal factors of the landslide formation. The river erosion, the rain infiltration and especially the intermittent declining movement of the hanging side of the F1 high - angle normal fault caused by the structure movement and seismic action were the important external triggering factors for the formation and development of landslide. The respected treatment effect can be achieved by doing the comprehensive treatments according to the investigation conclusions and suggestions.