超长联络通道冻结温度场发展规律及其对隧道变形的影响

为获得超长联络通道冻结过程对盾构隧道及周边地层的影响,以福州地铁2号线紫阳站—五里亭站区间冻结联络通道为工程背景,采用ANSYS有限元软件对长65.8 m的超长联络通道、盾构隧道及周边土层在双侧冻结过程中的温度场及位移场进行分析。结果表明:在积极冻结期前21 d,冻结管交叉区域的冻结壁扩散平均速率快,达到57 mm/d,后29 d平均速率只有27.6 mm/d;积极冻结期喇叭口附近区域存在宽10 m、高2.5 m的变形集中区,对地面产生变形影响最大;冻结对盾构隧道拱肩水平位移和拱脚竖向变形具有显著的影响,积极冻结期结束,拱肩的水平位移比盾构隧道右侧墙大85%,拱脚竖向位移比拱顶大45%。同时,结构变形及变形增长速率随冻结时间增加而增加。因此,建议应合理控制积极冻结时间及冻结方式,以确保建(构)筑物的安全。

Development of Freezing Temperature Field of Extra-long Connecting Aisle and Its Impact on Tunnel Deformation

To probe into the influence of super long connecting passage on shield tunnel and surrounding strata in active freezing process, we examined the temperature field and displacement field of the 65.8 meters long cross passage, the shield tunnel and surrounding soil layer by using ANSYS with the frozen connecting channel between Ziyang station and Wuliting station of Fuzhou Metro Line 2 as engineering background. Results suggest that in the first 21 days of the active freezing, the average rate of frozen wall diffusion at the cross section of freezing pipe amounted to 57 mm/d, while in the last 29 days the average rate was only 27.6 mm/d; in the active freezing period, we observed a deformation concentration area of 10 meters in width and 2.5 meters in height near the bell mouth, which had a greatest impact on ground deformation. Freezing had a significant impact on the horizontal displacement of the arch shoulder and the vertical deformation of the arch foot. In the end of the active freezing period, the horizontal displacement of the arch shoulder was 85% larger than that of the right wall of the shield tunnel, and the vertical displacement of the arch foot was 45% larger than that of the arch crown. In addition, the structural deformation value and deformation growth rate both increased with the elongation of freezing time. Therefore, we suggested controlling the active freezing time and method reasonably to ensure the safety of buildings (structures).