大跨连拱隧道上穿既有地铁隧道施工影响分析

Analysis on Construction Influence of Long-span Multi-arch Tunnel through Existing Subway Tunnel

摘要:

针对小净距条件下的大跨度双连拱隧道施工影响规律问题，首先对施工技术难点进行分析，并阐述应对措施，其次，选用ABAQUS软件对大跨度双连拱隧道小净距上穿既有地铁隧道进行数值模拟，分析地表沉降规律、开挖对既有隧道结构变形影响及新建隧道衬砌结构变形规律，结果表明：（1）双连拱隧道开挖引起的地表沉降是由中导洞、左洞和右洞分别独立开挖引起的地表沉降的结果叠加，开挖完成后，地表最大沉降为5.6 mm；（2）开挖引起的既有地铁隧道变形左线较右线大，但均未超过规定值10 mm；（3）新建隧道拱顶沉降大致可分为激增阶段、缓增阶段和稳定阶段，其中，拱顶沉降的激增阶段为施工的关键阶段，风险也最高，应提高监测频率。

Abstract:

In view of the influence law of construction of long-span double-arch tunnel under the condition of small clear distance, the technical difficulties of construction are analyzed and the countermeasures are set forth. Then, ABAQUS software is used to numerically simulate the long-span double-arch tunnel through the existing subway tunnel in small clear distance. The surface settlement law, the influence of excavation on the existing tunnel structure deformation and the lining structure deformation law of the new tunnel are analyzed. The results show that: (1) The surface settlement caused by the excavation of the double-arch tunnel is the superposition of the surface settlement caused by the independent excavation of the middle guide tunnel, the left tunnel and the right tunnel. And the maximum surface settlement is 5.6 mm after the completion of excavation. (2) The existing subway tunnel deformation caused by excavation is larger on the left line than on the right line, but all do not exceed the specified value of 10 mm. (3) The vault settlement of new tunnel can be roughly divided into the surge stage， slow increase stage and stable stage, in which the surge stage of vault settlement is the key stage of construction with the highest risk. Therefore, the monitoring frequency should be improved.