关键词: 北京地铁, 单洞双线隧道, 盾构, 下穿, 群桩响应, 复合锚杆桩, 防护, 数值模拟

Abstract:

During the construction of the running tunnel from Gaojiayuan Station to Wangjing  Station on Line 14 of Beijing Metro, the 10 mdiameter shield passes  close to the existing foundation piles of a bridge of the airport transit line. In this paper, the response of the existing bridge piles to the tunneling is simulated, the variation of the deformation and internal force of the existing piles caused by the tunneling are analyzed, so as to reduce the impact on the existing piles caused by shield tunneling. Results show that after the shield passes, the bending deformation and internal force of the existing piles have obvious changes. And the isolation mechanism of composite anchor piles is also studied. The result shows that the front piles have isolation effect, therefore the impact on the rear piles caused by the tunneling is not so serious. The following countermeasures are adopted: several rows of anchor piles are installed to achieve bigger isolation rigidity; grouting is made for the surrounding soils; casing is installed to reduce the impact on the environment.

Key words: Beijing Metro, doubletrack Metro tunnel, shield, passing close to existing foundation piles, response of existing piles, composite anchor pile, protection, numerical simulation