北京地铁敞口式盾构掘进对砂层土体扰动规律研究

敞口式盾构在砂层掘进时会扰动周围土体,易引起地层坍塌.以北京地铁6号线2期敞口式盾构施工段为工程背景,阐述了国内首台挤压式敞口盾构机机体构造及开挖工序,通过地表沉降和地中水平位移监测,研究了盾构掘进对砂层的扰动特征.结合盾构掘进参数分析,探讨了减少土体扰动的控制措施.研究表明,盾构接近测孔区阶段,土体变形规律最复杂;通过和刚脱离测孔区阶段是土层变形控制的重要环节;盾构隧道轴线两侧1.5倍洞径范围内是土体扰动主要区域.所得结论可为砂土地层敞口式盾构施工地层位移控制提供可鉴参考.

Soil Disturbance of Beijing Subway Constructed by Open-Face Shield Tunneling Method in Sandy Stratum

The open-face shield tunneling the sand stratum can affect the surrounding soil and may cause collapse with excessive deformation. Based on the open-face shield construction of NO.2 Beijing’s Metro of Line 6， the structure and the comprehensive excavation system of the domestic first open-face shield was explained. The law of disturbance was analyzed by monitoring subsidence and horizontal displacements of the soil. Some measures to reduce soil disturbance were also presented. Results showed that the deformation law of the soil is the most complicated when the shield approaches to the monitoring holes. It is important to have a good control on the soil deformation when the shield is passing through and leaving monitoring holes. The range of the disturbance area can be 1.5 times the hole diameter from the shield. The conclusion can be used as a reference for controlling the deformation induced by shield construction in sandy stratum.