砂土地层盾构隧道超近距离下穿既有隧道变形控制技术研究

Study on Deformation Control Technology of Shield Tunnel Passing under an Existing Tunnel at Ultra-close Distance in Sand Layer

为研究砂土地层中盾构隧道超近距离下穿既有隧道变形控制措施,以西安地铁盾构区间隧道下穿地铁1号线出入段工程为依托,通过资料调研、数值模拟、现场试验和监控测量等方法,对既有隧道加固措施、盾构对地层适应性、掘进参数、隧道变形进行研究。结果表明:砂土地层盾构隧道超近距离下穿既有隧道,应对盾构进行专门设计,扩大刀盘开口率,配备专门的膨润土拌制和膨化系统,并避免在下穿影响范围内停机;数值计算和试掘进试验结果,盾构施工参数土仓压力为0.1 MPa,注浆压力为0.22 MPa,推力为10 000 kN,出土量为51 m^3/环,注浆量5~6 m^3/环;通过现场监测,盾构下穿过程中,既有地铁隧道轨道最大沉降及高差分别为6 mm和0.8 mm,符合规范要求,确保了地铁的安全运营,变形控制措施对既有地铁隧道作用十分显著。

In order to study the deformation control measures of the shield tunnel in sand layer passing under the existing tunnel at the extremely distance, this paper studies the existing tunnel reinforcement measures, the adaptability of the shield structure to the formation, tunneling parameters and tunnel deformation by means of data investigation, numerical simulation, field test and monitoring measurement based on the project of the Xi’an Metro shield tunnel passing through the No. 1 line. The results show that the shield tunnel undercrossing the existing tunnel at extremely distance in sand layer should be specially designed, and the opening rate of the shield cutter should be expanded, special bentonite mixing and expansion system should be equipped, and machine halt should be avoided within the scope of construction. Numerical calculations and experimental excavation test results show that the shield soil pressure is 0.1 MPa, grouting pressure is 0.22 MPa, shield thrust is 10 000 kN, unearthed amount is 51 m^3 per segment, grouting amount is 5~6 m^3 per segment. On-site monitoring indicates that the maximum settlement and height difference of the existing subway tunnel tracks are about 6 mm and 0.8 mm respectively, which meet the requirements of the specifications and ensure the safe operation of the subway. The above deformation control measures have good control effect on the deformation of existing subway tunnels.