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成都地铁区间盾构隧道所处地层主要为典型富水砂卵石地层,盾构施工引起的地层损失在地下水、地面荷载等影响下很容易形成滞后沉降,导致地表发生塌陷。针对成都地铁1号线一期工程建设经验,总结了砂卵石地层滞后沉降形成的原因,同时,采用颗粒分析软件PFC2D,从细观层面对砂卵石地层中滞后沉降的发展形成过程进行模拟,分析隧道埋深、地层空洞位置等因素对滞后沉降的影响。研究表明,砂卵石地层的特殊工程地质性质是滞后沉降形成的根本原因,盾构施工工艺是关键影响因素。细观研究表明,地层损失导致在隧道两侧上方约45°方向出现两条破碎带,形成三角形的松散区域,洞周地层应力发生显著变化。隧道埋深直接影响滞后沉降是否发生,地层空洞方位对滞后沉降的发生区域有重要影响。
The stratum of the shield tunnel in Chengdu Subway is mainly composed of typical water-rich sand and gravel stratum. The formation loss caused by shield construction is easy to form a delayed settlement under the influence of groundwater and ground load, resulting in the collapse of the ground surface. According to the construction experience of the first phase project of Chengdu Metro Line 1, the reasons for the formation of lag settlement in sand-gravel formation are summarized. At the same time, the formation and evolution of lag settlement in sand-gravel formation are simulated and analyzed by the particle analysis software PFC2D Tunnel depth, the location of stratum and other factors on the impact of lag subsidence. The research shows that the special engineering geology of sand-gravel stratum is the fundamental reason for the formation of lag subsidence. The shield construction technology is the key factor. Mesoscale studies show that the formation loss causes two fractures to appear in the direction of about 45 ° above both sides of the tunnel, forming a triangle-shaped loose area with significant stress changes in the stratum. The depth of the tunnel directly affects the occurrence of lag subsidence, and the location of formation cavities has an important influence on the occurrence of lag subsidence.