连拱隧道斜交正作进洞设计

Discussion of Vertical Making for Skew Portal in Highway Double-arched Tunnel

连拱隧道在复杂偏压地质条件下,可采用斜交正作洞口来降低边仰坡高度,但目前对其设计和施工关键技术的研究仍较少。文章以双溪口隧道出口为例,阐述了连拱隧道斜交正作洞口的设计情况,通过三维有限元分析,研究梯形套拱的施工力学响应,结果表明:梯形套拱处于明显的偏压状态,虚拟洞壁作用显著;为了降低套拱倾覆的风险,在设计上要对套拱成洞面的斜交角度加以限制,并宜在套拱长边侧设置有效的反压体以平衡由初期支护传递的水平推力;另外,施工中先开挖山体较低一侧对套拱受力更为有利。该研究成果在双溪口隧道得到成功应用,对类似条件下连拱隧道斜交进洞有借鉴意义。

Under the complex geological eccentric compression condition, the vertical angle was made for skew portal in twintunnel in order to reduce height of the side and face upward slope and ensure stabilization of the entrance. By the example of Shuangxikou tunnel, this paper described the design of vertical angle made for skew portal in twin-tunnel and analyzed the mechanical response of trapezium umbrella arch through numerical simulations. Some conclusions had been drawn. Since the eccentric compression of arch, the effect on the virtual tunnel wall was significant. To reduce the risk of arch overturning, the skew angle should be limited in design. At the same time, counterweight fill could be set on the long side of umbrella arch to balance the horizontal force which was transferred by initial supporting. In addition, excavating the lower side of the mountain was more favorable for the stress of umbrella arch. The experience and conclusions had been successfully applied in Shuangxikou tunnel, which could be taken as reference for design and construction of similar skew entrance in twin-tunnels.