下穿机场跑道大断面隧道施工对策及地层变形规律研究

北京首都国际机场T3与T2航站楼之间的单层双跨连拱浅埋暗挖大断面隧道垂直下穿机场跑道,采用超长管幕下十导洞分步暗挖法施工。通过对隧道施工地表变形进行分析,得出以下结论:1)新建隧道施工地表最大沉降值平均为9.28 mm,控制变形情况良好,采用超长管幕保护浅埋暗挖施工技术切实可行;2)3个断面变形拟合得到的确定调节系数平均为0.951,地表变形符合Peck公式;3)变形拟合得到的K值平均为1.903,为北京地区常规数值的3~6倍,管幕的存在对新建隧道施工引起的地层变形具有阻隔及扩散作用;4)变形拟合得到的Vl值平均为0.201%,略低于北京地区常规施工方法水平。

Study on Construction Countermeasures for and Ground Deformation Rule of Construction of Large Cross-section Tunnel Crossing underneath Existing Airport Runway

The tunnel between Terminal 3 and Terminal 2 of Beijing Capital International Airport is a large cross section single story double arch tunnel with shallow cover. The tunnel, which crosses underneath a runway of the airport, is constructed by means of 10 pilot sequential excavation method under the protection of long pipe roof. In the paper, the ground deformation caused by the tunnel construction is analyzed. Conclusions drawn are as follows: 1) The average of the maximum ground surface settlement caused by the tunnel construction is 9.28 mm, and the ground deformation has been brought under effective control, which shows that the application of the long pipe roof to protect the construction of the shallow tunnel is feasible; 2) The average of the adjustment coefficient obtained from the deformation fitting of three cross sections is 0.951, and the ground surface deformation is consistent with the Peck formula; 3) The average of the K value obtained from the deformation fitting is 1.903, which is 3~6 times the common value in Beijing; the pipe roof can barrier and diffuse the ground deformation caused by the construction of the tunnel; 4) The average of the Vl value obtained from the deformation fitting is 0.201%, which is slightly smaller than the common value in Beijing. 