叠落式暗挖与盾构隧道施工的变形控制

Deformation Control of Overlapped Bored Tunnel and Shield Tunnel Construction

叠落隧道施工会对地层产生多次扰动,较之单线隧道地层变形机制更加复杂,对变形的准确预测并采取可靠的控制措施是隧道安全施工的重要保证。依托某地铁区间叠落式暗挖与盾构隧道工程,首先采用数值模拟分析了叠落式暗挖与盾构隧道地层变形特性;根据数值分析的结果从地层超前加固、开挖方法、支护结构等方面制订了地层变形的控制措施,使地层变形在控制标准范围内;实际施工中采用给出的控制措施来控制地层变形,保证了工程施工安全,取得了较好的实施效果,并通过现场试验对此进行了验证。研究结果表明:暗挖隧道(上行)施工产生的地表沉降明显大于盾构隧道(下行)开挖,两洞施工结束后的地表沉降最大值位于暗挖隧道拱顶上方;对本工程不同开挖顺序产生的地表变形而言,"先上后下"施工产生的地表最大沉降值及沉降影响范围均大于"先下后上"施工,工程实际中可采用"先下后上"的施工顺序;监测数据表明将暗挖隧道作为地层变形控制重点,通过对暗挖隧道采取超前注浆,可有效控制地表变形,减小两隧道开挖的地表影响范围,说明在暗挖隧道中采用超前注浆可作为叠落式暗挖与盾构隧道修建过程中的重要安全控制措施。研究结果可为类似隧道工程的设计、施工提供一定参考。

As the strata may be disturbed several times during construction of overlapped tunnel, the ground deformation mechanism of overlapped tunnel is more complex compared with single tunnel. To predict the ground deformation accurately and to take reliable control measures is an important guarantee for tunnel safe construction. Relying on the overlapped bored tunnel and shield tunnel project in a certain subway section, the ground deformation properties cause by overlapped bored tunneling and shield tunneling are studied by numerical simulation at first. According to the numerical simulation result, the measures for controlling ground deformation are formulated from the aspects of ground pre-reinforcement, excavation method and supporting structure, so that the ground deformation can be controlled within the standard range. In the actual construction, the control measures are taken to control the ground deformation which ensured construction safety and achieved good implementation effect, and the effectiveness is verified by field test. The research result shows that （1） the ground surface deformation caused by bored tunneling （upper tunneling） is obviously larger than that caused by shield tunneling （lower tunneling）, and the largest settlement point located at the vault top of the bored tunnel after excavation of the both tunnels; （2） for the surface deformation caused by different excavation sequences in this project, the value of largest settlement and influence scope at the surface are smaller in the case of first lower tunnel excavation and then upper tunnel excavation, which can be used in the engineering practice; （3） the field test data shows that setting the bored tunnel excavation as the focus of deformation control is feasible. The settlement and the surface influence range of the 2 tunnel excavation can be reduced by using pre-grouting in the bored tunnel, showing that pre-grouting in bored tunnel can be an important safety control measure during construction of overlapping bored tunnel and shield tunnel. The research result can provide a reference for the design and construction of similar tunnel projects.