工程措施对控制大跨度海底隧道结构变形的施工效果研究

Effects of Engineering Measures on Controlling the deformationsof Long-span Subsea Tunnel

厦门东通道翔安隧道是我国第一条海底隧道,隧道场区地质条件复杂,施工难度大。施工至今,多个区段的隧道结构变形都超过了预留变形量,为此施工单位采取了多种工程措施,有效地抑制了隧道的结构变形。文章首先基于厦门海底隧道的现场监测数据,分析了隧道结构发生异常变形的原因;然后通过数值模拟结果与实测数据的对比,研究了各工程措施在此类地质条件下的施工效果。研究认为:在施工过程中,采用锁脚锚管、仰拱注浆及井点降水可以有效地抑制初期支护变形,尤其是对洞内及地表同时进行井点降水时,隧道拱顶下沉量可以减小约50%,拱部塑性区范围也大幅度减小;变更临时支护结构参数和采用系统锚杆对控制隧道结构变形也有一定的作用,但是在此类地质条件下其效用不明显;另外,隧道断面的封闭时间和封闭距离对其结构变形影响很大,应尽快施作仰拱,使断面尽早封闭成环。

Xiamen east passage subsea tunnel is the first subsea tunnel in China which features complex geological conditions and difficulties in construction. Deformations on some sections of the tunnel structure exceeded the predicted values and some engineering measures were adopted to control them. Based on the field monitoring data of the tunnel, the paper analyzes the causes of structure deformations and investigates the effects of some engineering measures by numerical calculation. Results indicated that some measures against structure deformation, including setting locking anchor bars, grouting in inverted arch and dewatering can reduce the deformations of the tunnel support, especially dewatering can reduce the deformations up to 50% while the range of plastic zone in the ground will also be reduced to a large extent. Meanwhile, the effects of increasing stiffiness and strength of temporary support and systemic anchors are not obvious. The paper further points out, it is important to construct invert arch to control structure deformation.